Initial implementation of JITLink - A replacement for RuntimeDyld.

Summary:

JITLink is a jit-linker that performs the same high-level task as RuntimeDyld:
it parses relocatable object files and makes their contents runnable in a target
process.

JITLink aims to improve on RuntimeDyld in several ways:

(1) A clear design intended to maximize code-sharing while minimizing coupling.

RuntimeDyld has been developed in an ad-hoc fashion for a number of years and
this had led to intermingling of code for multiple architectures (e.g. in
RuntimeDyldELF::processRelocationRef) in a way that makes the code more
difficult to read, reason about, extend. JITLink is designed to isolate
format and architecture specific code, while still sharing generic code.

(2) Support for native code models.

RuntimeDyld required the use of large code models (where calls to external
functions are made indirectly via registers) for many of platforms due to its
restrictive model for stub generation (one "stub" per symbol). JITLink allows
arbitrary mutation of the atom graph, allowing both GOT and PLT atoms to be
added naturally.

(3) Native support for asynchronous linking.

JITLink uses asynchronous calls for symbol resolution and finalization: these
callbacks are passed a continuation function that they must call to complete the
linker's work. This allows for cleaner interoperation with the new concurrent
ORC JIT APIs, while still being easily implementable in synchronous style if
asynchrony is not needed.

To maximise sharing, the design has a hierarchy of common code:

(1) Generic atom-graph data structure and algorithms (e.g. dead stripping and
 |  memory allocation) that are intended to be shared by all architectures.
 |
 + -- (2) Shared per-format code that utilizes (1), e.g. Generic MachO to
       |  atom-graph parsing.
       |
       + -- (3) Architecture specific code that uses (1) and (2). E.g.
                JITLinkerMachO_x86_64, which adds x86-64 specific relocation
                support to (2) to build and patch up the atom graph.

To support asynchronous symbol resolution and finalization, the callbacks for
these operations take continuations as arguments:

  using JITLinkAsyncLookupContinuation =
      std::function<void(Expected<AsyncLookupResult> LR)>;

  using JITLinkAsyncLookupFunction =
      std::function<void(const DenseSet<StringRef> &Symbols,
                         JITLinkAsyncLookupContinuation LookupContinuation)>;

  using FinalizeContinuation = std::function<void(Error)>;

  virtual void finalizeAsync(FinalizeContinuation OnFinalize);

In addition to its headline features, JITLink also makes other improvements:

  - Dead stripping support: symbols that are not used (e.g. redundant ODR
    definitions) are discarded, and take up no memory in the target process
    (In contrast, RuntimeDyld supported pointer equality for weak definitions,
    but the redundant definitions stayed resident in memory).

  - Improved exception handling support. JITLink provides a much more extensive
    eh-frame parser than RuntimeDyld, and is able to correctly fix up many
    eh-frame sections that RuntimeDyld currently (silently) fails on.

  - More extensive validation and error handling throughout.

This initial patch supports linking MachO/x86-64 only. Work on support for
other architectures and formats will happen in-tree.

Differential Revision: https://reviews.llvm.org/D58704

llvm-svn: 358818

include/llvm/ExecutionEngine/JITLink/JITLink.h

@@ -0,0 +1,919 @@
+//===------------ JITLink.h - JIT linker functionality ----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Contains generic JIT-linker types.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_JITLINK_JITLINK_H
+#define LLVM_EXECUTIONENGINE_JITLINK_JITLINK_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/ExecutionEngine/JITSymbol.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/Memory.h"
+#include "llvm/Support/MemoryBuffer.h"
+
+#include <map>
+#include <string>
+#include <system_error>
+
+namespace llvm {
+namespace jitlink {
+
+/// Base class for errors originating in JIT linker, e.g. missing relocation
+/// support.
+class JITLinkError : public ErrorInfo<JITLinkError> {
+public:
+  static char ID;
+
+  JITLinkError(Twine ErrMsg) : ErrMsg(ErrMsg.str()) {}
+
+  void log(raw_ostream &OS) const override;
+  const std::string &getErrorMessage() const { return ErrMsg; }
+  std::error_code convertToErrorCode() const override;
+
+private:
+  std::string ErrMsg;
+};
+
+/// Manages allocations of JIT memory.
+///
+/// Instances of this class may be accessed concurrently from multiple threads
+/// and their implemetations should include any necessary synchronization.
+class JITLinkMemoryManager {
+public:
+  using ProtectionFlags = sys::Memory::ProtectionFlags;
+
+  class SegmentRequest {
+  public:
+    SegmentRequest() = default;
+    SegmentRequest(size_t ContentSize, unsigned ContentAlign,
+                   uint64_t ZeroFillSize, unsigned ZeroFillAlign)
+        : ContentSize(ContentSize), ZeroFillSize(ZeroFillSize),
+          ContentAlign(ContentAlign), ZeroFillAlign(ZeroFillAlign) {}
+    size_t getContentSize() const { return ContentSize; }
+    unsigned getContentAlignment() const { return ContentAlign; }
+    uint64_t getZeroFillSize() const { return ZeroFillSize; }
+    unsigned getZeroFillAlignment() const { return ZeroFillAlign; }
+
+  private:
+    size_t ContentSize = 0;
+    uint64_t ZeroFillSize = 0;
+    unsigned ContentAlign = 0;
+    unsigned ZeroFillAlign = 0;
+  };
+
+  using SegmentsRequestMap = DenseMap<unsigned, SegmentRequest>;
+
+  using FinalizeContinuation = std::function<void(Error)>;
+
+  /// Represents an allocation created by the memory manager.
+  ///
+  /// An allocation object is responsible for allocating and owning jit-linker
+  /// working and target memory, and for transfering from working to target
+  /// memory.
+  ///
+  class Allocation {
+  public:
+    virtual ~Allocation();
+
+    /// Should return the address of linker working memory for the segment with
+    /// the given protection flags.
+    virtual MutableArrayRef<char> getWorkingMemory(ProtectionFlags Seg) = 0;
+
+    /// Should return the final address in the target process where the segment
+    /// will reside.
+    virtual JITTargetAddress getTargetMemory(ProtectionFlags Seg) = 0;
+
+    /// Should transfer from working memory to target memory, and release
+    /// working memory.
+    virtual void finalizeAsync(FinalizeContinuation OnFinalize) = 0;
+
+    /// Should deallocate target memory.
+    virtual Error deallocate() = 0;
+  };
+
+  virtual ~JITLinkMemoryManager();
+
+  /// Create an Allocation object.
+  virtual Expected<std::unique_ptr<Allocation>>
+  allocate(const SegmentsRequestMap &Request) = 0;
+};
+
+// Forward declare the Atom class.
+class Atom;
+
+/// Edge class. Represents both object file relocations, as well as layout and
+/// keep-alive constraints.
+class Edge {
+public:
+  using Kind = uint8_t;
+
+  using GenericEdgeKind = enum : Kind {
+    Invalid,                    // Invalid edge value.
+    FirstKeepAlive,             // Keeps target alive. Offset/addend zero.
+    KeepAlive = FirstKeepAlive, // Tag first edge kind that preserves liveness.
+    LayoutNext,                 // Layout constraint. Offset/Addend zero.
+    FirstRelocation             // First architecture specific relocation.
+  };
+
+  using OffsetT = uint32_t;
+  using AddendT = int64_t;
+
+  Edge(Kind K, OffsetT Offset, Atom &Target, AddendT Addend)
+      : Target(&Target), Offset(Offset), Addend(Addend), K(K) {}
+
+  OffsetT getOffset() const { return Offset; }
+  Kind getKind() const { return K; }
+  void setKind(Kind K) { this->K = K; }
+  bool isRelocation() const { return K >= FirstRelocation; }
+  Kind getRelocation() const {
+    assert(isRelocation() && "Not a relocation edge");
+    return K - FirstRelocation;
+  }
+  bool isKeepAlive() const { return K >= FirstKeepAlive; }
+  Atom &getTarget() const { return *Target; }
+  void setTarget(Atom &Target) { this->Target = &Target; }
+  AddendT getAddend() const { return Addend; }
+  void setAddend(AddendT Addend) { this->Addend = Addend; }
+
+private:
+  Atom *Target;
+  OffsetT Offset;
+  AddendT Addend;
+  Kind K = 0;
+};
+
+using EdgeVector = std::vector<Edge>;
+
+const StringRef getGenericEdgeKindName(Edge::Kind K);
+
+/// Base Atom class. Used by absolute and undefined atoms.
+class Atom {
+  friend class AtomGraph;
+
+protected:
+  /// Create a named (as yet unresolved) atom.
+  Atom(StringRef Name)
+      : Name(Name), IsDefined(false), IsLive(false), ShouldDiscard(false),
+        IsGlobal(false), IsAbsolute(false), IsCallable(false),
+        IsExported(false), IsWeak(false), HasLayoutNext(false),
+        IsCommon(false) {}
+
+  /// Create an absolute symbol atom.
+  Atom(StringRef Name, JITTargetAddress Address)
+      : Name(Name), Address(Address), IsDefined(true), IsLive(false),
+        ShouldDiscard(false), IsGlobal(false), IsAbsolute(false),
+        IsCallable(false), IsExported(false), IsWeak(false),
+        HasLayoutNext(false), IsCommon(false) {}
+
+public:
+  /// Returns true if this atom has a name.
+  bool hasName() const { return Name != StringRef(); }
+
+  /// Returns the name of this atom.
+  StringRef getName() const { return Name; }
+
+  /// Returns the current target address of this atom.
+  /// The initial target address (for atoms that have one) will be taken from
+  /// the input object file's virtual address space. During the layout phase
+  /// of JIT linking the atom's address will be updated to point to its final
+  /// address in the JIT'd process.
+  JITTargetAddress getAddress() const { return Address; }
+
+  /// Set the current target address of this atom.
+  void setAddress(JITTargetAddress Address) { this->Address = Address; }
+
+  /// Returns true if this is a defined atom.
+  bool isDefined() const { return IsDefined; }
+
+  /// Returns true if this atom is marked as live.
+  bool isLive() const { return IsLive; }
+
+  /// Mark this atom as live.
+  ///
+  /// Note: Only defined and absolute atoms can be marked live.
+  void setLive(bool IsLive) {
+    assert((IsDefined || IsAbsolute || !IsLive) &&
+           "Only defined and absolute atoms can be marked live");
+    this->IsLive = IsLive;
+  }
+
+  /// Returns true if this atom should be discarded during pruning.
+  bool shouldDiscard() const { return ShouldDiscard; }
+
+  /// Mark this atom to be discarded.
+  ///
+  /// Note: Only defined and absolute atoms can be marked live.
+  void setShouldDiscard(bool ShouldDiscard) {
+    assert((IsDefined || IsAbsolute || !ShouldDiscard) &&
+           "Only defined and absolute atoms can be marked live");
+    this->ShouldDiscard = ShouldDiscard;
+  }
+
+  /// Returns true if this definition is global (i.e. visible outside this
+  /// linkage unit).
+  ///
+  /// Note: This is distict from Exported, which means visibile outside the
+  /// JITDylib that this graph is being linked in to.
+  bool isGlobal() const { return IsGlobal; }
+
+  /// Mark this atom as global.
+  void setGlobal(bool IsGlobal) { this->IsGlobal = IsGlobal; }
+
+  /// Returns true if this atom represents an absolute symbol.
+  bool isAbsolute() const { return IsAbsolute; }
+
+  /// Returns true if this atom is known to be callable.
+  ///
+  /// Primarily provided for easy interoperability with ORC, which uses the
+  /// JITSymbolFlags::Common flag to identify symbols that can be interposed
+  /// with stubs.
+  bool isCallable() const { return IsCallable; }
+
+  /// Mark this atom as callable.
+  void setCallable(bool IsCallable) {
+    assert((IsDefined || IsAbsolute || !IsCallable) &&
+           "Callable atoms must be defined or absolute");
+    this->IsCallable = IsCallable;
+  }
+
+  /// Returns true if this atom should appear in the symbol table of a final
+  /// linked image.
+  bool isExported() const { return IsExported; }
+
+  /// Mark this atom as exported.
+  void setExported(bool IsExported) {
+    assert((!IsExported || ((IsDefined || IsAbsolute) && hasName())) &&
+           "Exported atoms must have names");
+    this->IsExported = IsExported;
+  }
+
+  /// Returns true if this is a weak symbol.
+  bool isWeak() const { return IsWeak; }
+
+  /// Mark this atom as weak.
+  void setWeak(bool IsWeak) { this->IsWeak = IsWeak; }
+
+private:
+  StringRef Name;
+  JITTargetAddress Address = 0;
+
+  bool IsDefined : 1;
+  bool IsLive : 1;
+  bool ShouldDiscard : 1;
+
+  bool IsGlobal : 1;
+  bool IsAbsolute : 1;
+  bool IsCallable : 1;
+  bool IsExported : 1;
+  bool IsWeak : 1;
+
+protected:
+  // These flags only make sense for DefinedAtom, but we can minimize the size
+  // of DefinedAtom by defining them here.
+  bool HasLayoutNext : 1;
+  bool IsCommon : 1;
+};
+
+// Forward declare DefinedAtom.
+class DefinedAtom;
+
+raw_ostream &operator<<(raw_ostream &OS, const Atom &A);
+void printEdge(raw_ostream &OS, const Atom &FixupAtom, const Edge &E,
+               StringRef EdgeKindName);
+
+/// Represents an object file section.
+class Section {
+  friend class AtomGraph;
+
+private:
+  Section(StringRef Name, sys::Memory::ProtectionFlags Prot, unsigned Ordinal,
+          bool IsZeroFill)
+      : Name(Name), Prot(Prot), Ordinal(Ordinal), IsZeroFill(IsZeroFill) {}
+
+  using DefinedAtomSet = DenseSet<DefinedAtom *>;
+
+public:
+  using atom_iterator = DefinedAtomSet::iterator;
+  using const_atom_iterator = DefinedAtomSet::const_iterator;
+
+  ~Section();
+  StringRef getName() const { return Name; }
+  sys::Memory::ProtectionFlags getProtectionFlags() const { return Prot; }
+  unsigned getSectionOrdinal() const { return Ordinal; }
+  size_t getNextAtomOrdinal() { return ++NextAtomOrdinal; }
+
+  bool isZeroFill() const { return IsZeroFill; }
+
+  /// Returns an iterator over the atoms in the section (in no particular
+  /// order).
+  iterator_range<atom_iterator> atoms() {
+    return make_range(DefinedAtoms.begin(), DefinedAtoms.end());
+  }
+
+  /// Returns an iterator over the atoms in the section (in no particular
+  /// order).
+  iterator_range<const_atom_iterator> atoms() const {
+    return make_range(DefinedAtoms.begin(), DefinedAtoms.end());
+  }
+
+  /// Return the number of atoms in this section.
+  DefinedAtomSet::size_type atoms_size() { return DefinedAtoms.size(); }
+
+  /// Return true if this section contains no atoms.
+  bool atoms_empty() const { return DefinedAtoms.empty(); }
+
+private:
+  void addAtom(DefinedAtom &DA) {
+    assert(!DefinedAtoms.count(&DA) && "Atom is already in this section");
+    DefinedAtoms.insert(&DA);
+  }
+
+  void removeAtom(DefinedAtom &DA) {
+    assert(DefinedAtoms.count(&DA) && "Atom is not in this section");
+    DefinedAtoms.erase(&DA);
+  }
+
+  StringRef Name;
+  sys::Memory::ProtectionFlags Prot;
+  unsigned Ordinal = 0;
+  unsigned NextAtomOrdinal = 0;
+  bool IsZeroFill = false;
+  DefinedAtomSet DefinedAtoms;
+};
+
+/// Defined atom class. Suitable for use by defined named and anonymous
+/// atoms.
+class DefinedAtom : public Atom {
+  friend class AtomGraph;
+
+private:
+  DefinedAtom(Section &Parent, JITTargetAddress Address, uint32_t Alignment)
+      : Atom("", Address), Parent(Parent), Ordinal(Parent.getNextAtomOrdinal()),
+        Alignment(Alignment) {}
+
+  DefinedAtom(Section &Parent, StringRef Name, JITTargetAddress Address,
+              uint32_t Alignment)
+      : Atom(Name, Address), Parent(Parent),
+        Ordinal(Parent.getNextAtomOrdinal()), Alignment(Alignment) {}
+
+public:
+  using edge_iterator = EdgeVector::iterator;
+
+  Section &getSection() const { return Parent; }
+
+  uint64_t getSize() const { return Size; }
+
+  StringRef getContent() const {
+    assert(!Parent.isZeroFill() && "Trying to get content for zero-fill atom");
+    assert(Size <= std::numeric_limits<size_t>::max() &&
+           "Content size too large");
+    return {ContentPtr, Size};
+  }
+  void setContent(StringRef Content) {
+    assert(!Parent.isZeroFill() && "Calling setContent on zero-fill atom?");
+    ContentPtr = Content.data();
+    Size = Content.size();
+  }
+
+  bool isZeroFill() const { return Parent.isZeroFill(); }
+
+  void setZeroFill(uint64_t Size) {
+    assert(Parent.isZeroFill() && !ContentPtr &&
+           "Can't set zero-fill length of a non zero-fill atom");
+    this->Size = Size;
+  }
+
+  uint64_t getZeroFillSize() const {
+    assert(Parent.isZeroFill() &&
+           "Can't get zero-fill length of a non zero-fill atom");
+    return Size;
+  }
+
+  uint32_t getAlignment() const { return Alignment; }
+
+  bool hasLayoutNext() const { return HasLayoutNext; }
+  void setLayoutNext(DefinedAtom &Next) {
+    assert(!HasLayoutNext && "Atom already has layout-next constraint");
+    HasLayoutNext = true;
+    Edges.push_back(Edge(Edge::LayoutNext, 0, Next, 0));
+  }
+  DefinedAtom &getLayoutNext() {
+    assert(HasLayoutNext && "Atom does not have a layout-next constraint");
+    DefinedAtom *Next = nullptr;
+    for (auto &E : edges())
+      if (E.getKind() == Edge::LayoutNext) {
+        assert(E.getTarget().isDefined() &&
+               "layout-next target atom must be a defined atom");
+        Next = static_cast<DefinedAtom *>(&E.getTarget());
+        break;
+      }
+    assert(Next && "Missing LayoutNext edge");
+    return *Next;
+  }
+
+  bool isCommon() const { return IsCommon; }
+
+  void addEdge(Edge::Kind K, Edge::OffsetT Offset, Atom &Target,
+               Edge::AddendT Addend) {
+    assert(K != Edge::LayoutNext &&
+           "Layout edges should be added via addLayoutNext");
+    Edges.push_back(Edge(K, Offset, Target, Addend));
+  }
+
+  iterator_range<edge_iterator> edges() {
+    return make_range(Edges.begin(), Edges.end());
+  }
+  size_t edges_size() const { return Edges.size(); }
+  bool edges_empty() const { return Edges.empty(); }
+
+  unsigned getOrdinal() const { return Ordinal; }
+
+private:
+  void setCommon(uint64_t Size) {
+    assert(ContentPtr == 0 && "Atom already has content?");
+    IsCommon = true;
+    setZeroFill(Size);
+  }
+
+  EdgeVector Edges;
+  uint64_t Size = 0;
+  Section &Parent;
+  const char *ContentPtr = nullptr;
+  unsigned Ordinal = 0;
+  uint32_t Alignment = 0;
+};
+
+class AtomGraph {
+private:
+  using SectionList = std::vector<std::unique_ptr<Section>>;
+  using AddressToAtomMap = std::map<JITTargetAddress, DefinedAtom *>;
+  using NamedAtomMap = DenseMap<StringRef, Atom *>;
+  using ExternalAtomSet = DenseSet<Atom *>;
+
+public:
+  using external_atom_iterator = ExternalAtomSet::iterator;
+
+  using section_iterator = pointee_iterator<SectionList::iterator>;
+  using const_section_iterator = pointee_iterator<SectionList::const_iterator>;
+
+  template <typename SecItrT, typename AtomItrT, typename T>
+  class defined_atom_iterator_impl
+      : public iterator_facade_base<
+            defined_atom_iterator_impl<SecItrT, AtomItrT, T>,
+            std::forward_iterator_tag, T> {
+  public:
+    defined_atom_iterator_impl() = default;
+
+    defined_atom_iterator_impl(SecItrT SI, SecItrT SE)
+        : SI(SI), SE(SE),
+          AI(SI != SE ? SI->atoms().begin() : Section::atom_iterator()) {
+      moveToNextAtomOrEnd();
+    }
+
+    bool operator==(const defined_atom_iterator_impl &RHS) const {
+      return (SI == RHS.SI) && (AI == RHS.AI);
+    }
+
+    T operator*() const {
+      assert(AI != SI->atoms().end() && "Dereferencing end?");
+      return *AI;
+    }
+
+    defined_atom_iterator_impl operator++() {
+      ++AI;
+      moveToNextAtomOrEnd();
+      return *this;
+    }
+
+  private:
+    void moveToNextAtomOrEnd() {
+      while (SI != SE && AI == SI->atoms().end()) {
+        ++SI;
+        if (SI == SE)
+          AI = Section::atom_iterator();
+        else
+          AI = SI->atoms().begin();
+      }
+    }
+
+    SecItrT SI, SE;
+    AtomItrT AI;
+  };
+
+  using defined_atom_iterator =
+      defined_atom_iterator_impl<section_iterator, Section::atom_iterator,
+                                 DefinedAtom *>;
+
+  using const_defined_atom_iterator =
+      defined_atom_iterator_impl<const_section_iterator,
+                                 Section::const_atom_iterator,
+                                 const DefinedAtom *>;
+
+  AtomGraph(std::string Name, unsigned PointerSize,
+            support::endianness Endianness)
+      : Name(std::move(Name)), PointerSize(PointerSize),
+        Endianness(Endianness) {}
+
+  /// Returns the name of this graph (usually the name of the original
+  /// underlying MemoryBuffer).
+  const std::string &getName() { return Name; }
+
+  /// Returns the pointer size for use in this graph.
+  unsigned getPointerSize() const { return PointerSize; }
+
+  /// Returns the endianness of atom-content in this graph.
+  support::endianness getEndianness() const { return Endianness; }
+
+  /// Create a section with the given name, protection flags, and alignment.
+  Section &createSection(StringRef Name, sys::Memory::ProtectionFlags Prot,
+                         bool IsZeroFill) {
+    std::unique_ptr<Section> Sec(
+        new Section(Name, Prot, Sections.size(), IsZeroFill));
+    Sections.push_back(std::move(Sec));
+    return *Sections.back();
+  }
+
+  /// Add an external atom representing an undefined symbol in this graph.
+  Atom &addExternalAtom(StringRef Name) {
+    assert(!NamedAtoms.count(Name) && "Duplicate named atom inserted");
+    Atom *A = reinterpret_cast<Atom *>(
+        AtomAllocator.Allocate(sizeof(Atom), alignof(Atom)));
+    new (A) Atom(Name);
+    ExternalAtoms.insert(A);
+    NamedAtoms[Name] = A;
+    return *A;
+  }
+
+  /// Add an external atom representing an absolute symbol.
+  Atom &addAbsoluteAtom(StringRef Name, JITTargetAddress Addr) {
+    assert(!NamedAtoms.count(Name) && "Duplicate named atom inserted");
+    Atom *A = reinterpret_cast<Atom *>(
+        AtomAllocator.Allocate(sizeof(Atom), alignof(Atom)));
+    new (A) Atom(Name, Addr);
+    AbsoluteAtoms.insert(A);
+    NamedAtoms[Name] = A;
+    return *A;
+  }
+
+  /// Add an anonymous defined atom to the graph.
+  ///
+  /// Anonymous atoms have content but no name. They must have an address.
+  DefinedAtom &addAnonymousAtom(Section &Parent, JITTargetAddress Address,
+                                uint32_t Alignment) {
+    DefinedAtom *A = reinterpret_cast<DefinedAtom *>(
+        AtomAllocator.Allocate(sizeof(DefinedAtom), alignof(DefinedAtom)));
+    new (A) DefinedAtom(Parent, Address, Alignment);
+    Parent.addAtom(*A);
+    getAddrToAtomMap()[A->getAddress()] = A;
+    return *A;
+  }
+
+  /// Add a defined atom to the graph.
+  ///
+  /// Allocates and constructs a DefinedAtom instance with the given parent,
+  /// name, address, and alignment.
+  DefinedAtom &addDefinedAtom(Section &Parent, StringRef Name,
+                              JITTargetAddress Address, uint32_t Alignment) {
+    assert(!NamedAtoms.count(Name) && "Duplicate named atom inserted");
+    DefinedAtom *A = reinterpret_cast<DefinedAtom *>(
+        AtomAllocator.Allocate(sizeof(DefinedAtom), alignof(DefinedAtom)));
+    new (A) DefinedAtom(Parent, Name, Address, Alignment);
+    Parent.addAtom(*A);
+    getAddrToAtomMap()[A->getAddress()] = A;
+    NamedAtoms[Name] = A;
+    return *A;
+  }
+
+  /// Add a common symbol atom to the graph.
+  ///
+  /// Adds a common-symbol atom to the graph with the given parent, name,
+  /// address, alignment and size.
+  DefinedAtom &addCommonAtom(Section &Parent, StringRef Name,
+                             JITTargetAddress Address, uint32_t Alignment,
+                             uint64_t Size) {
+    assert(!NamedAtoms.count(Name) && "Duplicate named atom inserted");
+    DefinedAtom *A = reinterpret_cast<DefinedAtom *>(
+        AtomAllocator.Allocate(sizeof(DefinedAtom), alignof(DefinedAtom)));
+    new (A) DefinedAtom(Parent, Name, Address, Alignment);
+    A->setCommon(Size);
+    Parent.addAtom(*A);
+    NamedAtoms[Name] = A;
+    return *A;
+  }
+
+  iterator_range<section_iterator> sections() {
+    return make_range(section_iterator(Sections.begin()),
+                      section_iterator(Sections.end()));
+  }
+
+  iterator_range<external_atom_iterator> external_atoms() {
+    return make_range(ExternalAtoms.begin(), ExternalAtoms.end());
+  }
+
+  iterator_range<external_atom_iterator> absolute_atoms() {
+    return make_range(AbsoluteAtoms.begin(), AbsoluteAtoms.end());
+  }
+
+  iterator_range<defined_atom_iterator> defined_atoms() {
+    return make_range(defined_atom_iterator(Sections.begin(), Sections.end()),
+                      defined_atom_iterator(Sections.end(), Sections.end()));
+  }
+
+  iterator_range<const_defined_atom_iterator> defined_atoms() const {
+    return make_range(
+        const_defined_atom_iterator(Sections.begin(), Sections.end()),
+        const_defined_atom_iterator(Sections.end(), Sections.end()));
+  }
+
+  /// Returns the atom with the given name, which must exist in this graph.
+  Atom &getAtomByName(StringRef Name) {
+    auto I = NamedAtoms.find(Name);
+    assert(I != NamedAtoms.end() && "Name not in NamedAtoms map");
+    return *I->second;
+  }
+
+  /// Returns the atom with the given name, which must exist in this graph and
+  /// be a DefinedAtom.
+  DefinedAtom &getDefinedAtomByName(StringRef Name) {
+    auto &A = getAtomByName(Name);
+    assert(A.isDefined() && "Atom is not a defined atom");
+    return static_cast<DefinedAtom &>(A);
+  }
+
+  /// Search for the given atom by name.
+  /// Returns the atom (if found) or an error (if no atom with this name
+  /// exists).
+  Expected<Atom &> findAtomByName(StringRef Name) {
+    auto I = NamedAtoms.find(Name);
+    if (I == NamedAtoms.end())
+      return make_error<JITLinkError>("No atom named " + Name);
+    return *I->second;
+  }
+
+  /// Search for the given defined atom by name.
+  /// Returns the defined atom (if found) or an error (if no atom with this
+  /// name exists, or if one exists but is not a defined atom).
+  Expected<DefinedAtom &> findDefinedAtomByName(StringRef Name) {
+    auto I = NamedAtoms.find(Name);
+    if (I == NamedAtoms.end())
+      return make_error<JITLinkError>("No atom named " + Name);
+    if (!I->second->isDefined())
+      return make_error<JITLinkError>("Atom " + Name +
+                                      " exists but is not a "
+                                      "defined atom");
+    return static_cast<DefinedAtom &>(*I->second);
+  }
+
+  /// Returns the atom covering the given address, or an error if no such atom
+  /// exists.
+  ///
+  /// Returns null if no atom exists at the given address.
+  DefinedAtom *getAtomByAddress(JITTargetAddress Address) {
+    refreshAddrToAtomCache();
+
+    // If there are no defined atoms, bail out early.
+    if (AddrToAtomCache->empty())
+      return nullptr;
+
+    // Find the atom *after* the given address.
+    auto I = AddrToAtomCache->upper_bound(Address);
+
+    // If this address falls before any known atom, bail out.
+    if (I == AddrToAtomCache->begin())
+      return nullptr;
+
+    // The atom we're looking for is the one before the atom we found.
+    --I;
+
+    // Otherwise range check the atom that was found.
+    assert(!I->second->getContent().empty() && "Atom content not set");
+    if (Address >= I->second->getAddress() + I->second->getContent().size())
+      return nullptr;
+
+    return I->second;
+  }
+
+  /// Like getAtomByAddress, but returns an Error if the given address is not
+  /// covered by an atom, rather than a null pointer.
+  Expected<DefinedAtom &> findAtomByAddress(JITTargetAddress Address) {
+    if (auto *DA = getAtomByAddress(Address))
+      return *DA;
+    return make_error<JITLinkError>("No atom at address " +
+                                    formatv("{0:x16}", Address));
+  }
+
+  // Remove the given external atom from the graph.
+  void removeExternalAtom(Atom &A) {
+    assert(!A.isDefined() && !A.isAbsolute() && "A is not an external atom");
+    assert(ExternalAtoms.count(&A) && "A is not in the external atoms set");
+    ExternalAtoms.erase(&A);
+    A.~Atom();
+  }
+
+  /// Remove the given absolute atom from the graph.
+  void removeAbsoluteAtom(Atom &A) {
+    assert(A.isAbsolute() && "A is not an absolute atom");
+    assert(AbsoluteAtoms.count(&A) && "A is not in the absolute atoms set");
+    AbsoluteAtoms.erase(&A);
+    A.~Atom();
+  }
+
+  /// Remove the given defined atom from the graph.
+  void removeDefinedAtom(DefinedAtom &DA) {
+    if (AddrToAtomCache) {
+      assert(AddrToAtomCache->count(DA.getAddress()) &&
+             "Cache exists, but does not contain atom");
+      AddrToAtomCache->erase(DA.getAddress());
+    }
+    if (DA.hasName()) {
+      assert(NamedAtoms.count(DA.getName()) && "Named atom not in map");
+      NamedAtoms.erase(DA.getName());
+    }
+    DA.getSection().removeAtom(DA);
+    DA.~DefinedAtom();
+  }
+
+  /// Invalidate the atom-to-address map.
+  void invalidateAddrToAtomMap() { AddrToAtomCache = None; }
+
+  /// Dump the graph.
+  ///
+  /// If supplied, the EdgeKindToName function will be used to name edge
+  /// kinds in the debug output. Otherwise raw edge kind numbers will be
+  /// displayed.
+  void dump(raw_ostream &OS,
+            std::function<StringRef(Edge::Kind)> EdegKindToName =
+                std::function<StringRef(Edge::Kind)>());
+
+private:
+  AddressToAtomMap &getAddrToAtomMap() {
+    refreshAddrToAtomCache();
+    return *AddrToAtomCache;
+  }
+
+  const AddressToAtomMap &getAddrToAtomMap() const {
+    refreshAddrToAtomCache();
+    return *AddrToAtomCache;
+  }
+
+  void refreshAddrToAtomCache() const {
+    if (!AddrToAtomCache) {
+      AddrToAtomCache = AddressToAtomMap();
+      for (auto *DA : defined_atoms())
+        (*AddrToAtomCache)[DA->getAddress()] = const_cast<DefinedAtom *>(DA);
+    }
+  }
+
+  // Put the BumpPtrAllocator first so that we don't free any of the atoms in
+  // it until all of their destructors have been run.
+  BumpPtrAllocator AtomAllocator;
+
+  std::string Name;
+  unsigned PointerSize;
+  support::endianness Endianness;
+  SectionList Sections;
+  NamedAtomMap NamedAtoms;
+  ExternalAtomSet ExternalAtoms;
+  ExternalAtomSet AbsoluteAtoms;
+  mutable Optional<AddressToAtomMap> AddrToAtomCache;
+};
+
+/// A function for mutating AtomGraphs.
+using AtomGraphPassFunction = std::function<Error(AtomGraph &)>;
+
+/// A list of atom graph passes.
+using AtomGraphPassList = std::vector<AtomGraphPassFunction>;
+
+/// An atom graph pass configuration, consisting of a list of pre-prune,
+/// post-prune, and post-fixup passes.
+struct PassConfiguration {
+
+  /// Pre-prune passes.
+  ///
+  /// These passes are called on the graph after it is built, and before any
+  /// atoms have been pruned.
+  ///
+  /// Notable use cases: Marking atoms live or should-discard.
+  AtomGraphPassList PrePrunePasses;
+
+  /// Post-prune passes.
+  ///
+  /// These passes are called on the graph after dead and should-discard atoms
+  /// have been removed, but before fixups are applied.
+  ///
+  /// Notable use cases: Building GOT, stub, and TLV atoms.
+  AtomGraphPassList PostPrunePasses;
+
+  /// Post-fixup passes.
+  ///
+  /// These passes are called on the graph after atom contents has been copied
+  /// to working memory, and fixups applied.
+  ///
+  /// Notable use cases: Testing and validation.
+  AtomGraphPassList PostFixupPasses;
+};
+
+/// A JITLinkMemoryManager that allocates in-process memory.
+class InProcessMemoryManager : public JITLinkMemoryManager {
+public:
+  Expected<std::unique_ptr<Allocation>>
+  allocate(const SegmentsRequestMap &Request) override;
+};
+
+/// A map of symbol names to resolved addresses.
+using AsyncLookupResult = DenseMap<StringRef, JITEvaluatedSymbol>;
+
+/// A function to call with a resolved symbol map (See AsyncLookupResult) or an
+/// error if resolution failed.
+using JITLinkAsyncLookupContinuation =
+    std::function<void(Expected<AsyncLookupResult> LR)>;
+
+/// An asynchronous symbol lookup. Performs a search (possibly asynchronously)
+/// for the given symbols, calling the given continuation with either the result
+/// (if the lookup succeeds), or an error (if the lookup fails).
+using JITLinkAsyncLookupFunction =
+    std::function<void(const DenseSet<StringRef> &Symbols,
+                       JITLinkAsyncLookupContinuation LookupContinuation)>;
+
+/// Holds context for a single jitLink invocation.
+class JITLinkContext {
+public:
+  /// Destroy a JITLinkContext.
+  virtual ~JITLinkContext();
+
+  /// Return the MemoryManager to be used for this link.
+  virtual JITLinkMemoryManager &getMemoryManager() = 0;
+
+  /// Returns a StringRef for the object buffer.
+  /// This method can not be called once takeObjectBuffer has been called.
+  virtual MemoryBufferRef getObjectBuffer() const = 0;
+
+  /// Notify this context that linking failed.
+  /// Called by JITLink if linking cannot be completed.
+  virtual void notifyFailed(Error Err) = 0;
+
+  /// Called by JITLink to resolve external symbols. This method is passed a
+  /// lookup continutation which it must call with a result to continue the
+  /// linking process.
+  virtual void lookup(const DenseSet<StringRef> &Symbols,
+                      JITLinkAsyncLookupContinuation LookupContinuation) = 0;
+
+  /// Called by JITLink once all defined atoms in the graph have been assigned
+  /// their final memory locations in the target process. At this point he
+  /// atom graph can be, inspected to build a symbol table however the atom
+  /// content will not generally have been copied to the target location yet.
+  virtual void notifyResolved(AtomGraph &G) = 0;
+
+  /// Called by JITLink to notify the context that the object has been
+  /// finalized (i.e. emitted to memory and memory permissions set). If all of
+  /// this objects dependencies have also been finalized then the code is ready
+  /// to run.
+  virtual void
+  notifyFinalized(std::unique_ptr<JITLinkMemoryManager::Allocation> A) = 0;
+
+  /// Called by JITLink prior to linking to determine whether default passes for
+  /// the target should be added. The default implementation returns true.
+  /// If subclasses override this method to return false for any target then
+  /// they are required to fully configure the pass pipeline for that target.
+  virtual bool shouldAddDefaultTargetPasses(const Triple &TT) const;
+
+  /// Returns the mark-live pass to be used for this link. If no pass is
+  /// returned (the default) then the target-specific linker implementation will
+  /// choose a conservative default (usually marking all atoms live).
+  /// This function is only called if shouldAddDefaultTargetPasses returns true,
+  /// otherwise the JITContext is responsible for adding a mark-live pass in
+  /// modifyPassConfig.
+  virtual AtomGraphPassFunction getMarkLivePass(const Triple &TT) const;
+
+  /// Called by JITLink to modify the pass pipeline prior to linking.
+  /// The default version performs no modification.
+  virtual Error modifyPassConfig(const Triple &TT, PassConfiguration &Config);
+};
+
+/// Marks all atoms in a graph live. This can be used as a default, conservative
+/// mark-live implementation.
+Error markAllAtomsLive(AtomGraph &G);
+
+/// Basic JITLink implementation.
+///
+/// This function will use sensible defaults for GOT and Stub handling.
+void jitLink(std::unique_ptr<JITLinkContext> Ctx);
+
+} // end namespace jitlink
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_JITLINK_JITLINK_H

include/llvm/ExecutionEngine/JITLink/JITLink_EHFrameSupport.h

@@ -0,0 +1,42 @@
+//===----- JITLink_EHFrameSupport.h - JITLink eh-frame utils ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// EHFrame registration support for JITLink.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_JITLINK_JITLINK_EHFRAMESUPPORT_H
+#define LLVM_EXECUTIONENGINE_JITLINK_JITLINK_EHFRAMESUPPORT_H
+
+#include "llvm/ADT/Triple.h"
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+#include "llvm/ExecutionEngine/JITSymbol.h"
+#include "llvm/Support/Error.h"
+
+namespace llvm {
+namespace jitlink {
+
+/// Registers all FDEs in the given eh-frame section with the current process.
+Error registerEHFrameSection(const void *EHFrameSectionAddr);
+
+/// Deregisters all FDEs in the given eh-frame section with the current process.
+Error deregisterEHFrameSection(const void *EHFrameSectionAddr);
+
+/// Creates a pass that records the address of the EH frame section. If no
+/// eh-frame section is found, it will set EHFrameAddr to zero.
+///
+/// Authors of JITLinkContexts can use this function to register a post-fixup
+/// pass that records the address of the eh-frame section. This address can
+/// be used after finalization to register and deregister the frame.
+AtomGraphPassFunction createEHFrameRecorderPass(const Triple &TT,
+                                                JITTargetAddress &EHFrameAddr);
+
+} // end namespace jitlink
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_JITLINK_JITLINK_EHFRAMESUPPORT_H

include/llvm/ExecutionEngine/JITLink/JITLink_MachO.h

@@ -0,0 +1,30 @@
+//===--- JITLink_MachO.h - Generic JIT link function for MachO --*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic jit-link functions for MachO.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_JITLINK_JITLINK_MACHO_H
+#define LLVM_EXECUTIONENGINE_JITLINK_JITLINK_MACHO_H
+
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+
+namespace llvm {
+namespace jitlink {
+
+/// jit-link the given ObjBuffer, which must be a MachO object file.
+///
+/// Uses conservative defaults for GOT and stub handling based on the target
+/// platform.
+void jitLink_MachO(std::unique_ptr<JITLinkContext> Ctx);
+
+} // end namespace jitlink
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_JITLINK_JITLINK_MACHO_X86_64_H

include/llvm/ExecutionEngine/JITLink/JITLink_MachO_x86_64.h

@@ -0,0 +1,63 @@
+//===--- JITLink_MachO_x86_64.h - JIT link functions for MachO --*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// jit-link functions for MachO/x86-64.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_JITLINK_JITLINK_MACHO_X86_64_H
+#define LLVM_EXECUTIONENGINE_JITLINK_JITLINK_MACHO_X86_64_H
+
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+
+namespace llvm {
+namespace jitlink {
+
+namespace MachO_x86_64_Edges {
+
+enum MachOX86RelocationKind : Edge::Kind {
+  Branch32 = Edge::FirstRelocation,
+  Pointer64,
+  Pointer64Anon,
+  PCRel32,
+  PCRel32Minus1,
+  PCRel32Minus2,
+  PCRel32Minus4,
+  PCRel32Anon,
+  PCRel32Minus1Anon,
+  PCRel32Minus2Anon,
+  PCRel32Minus4Anon,
+  PCRel32GOTLoad,
+  PCRel32GOT,
+  PCRel32TLV,
+  Delta32,
+  Delta64,
+  NegDelta32,
+  NegDelta64,
+};
+
+} // namespace MachO_x86_64_Edges
+
+/// jit-link the given object buffer, which must be a MachO x86-64 object file.
+///
+/// If PrePrunePasses is empty then a default mark-live pass will be inserted
+/// that will mark all exported atoms live. If PrePrunePasses is not empty, the
+/// caller is responsible for including a pass to mark atoms as live.
+///
+/// If PostPrunePasses is empty then a default GOT-and-stubs insertion pass will
+/// be inserted. If PostPrunePasses is not empty then the caller is responsible
+/// for including a pass to insert GOT and stub edges.
+void jitLink_MachO_x86_64(std::unique_ptr<JITLinkContext> Ctx);
+
+/// Return the string name of the given MachO x86-64 edge kind.
+StringRef getMachOX86RelocationKindName(Edge::Kind R);
+
+} // end namespace jitlink
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_JITLINK_JITLINK_MACHO_X86_64_H

include/llvm/ExecutionEngine/JITSymbol.h

@@ -55,7 +55,7 @@ template <typename T> JITTargetAddress pointerToJITTargetAddress(T *Ptr) {
 class JITSymbolFlags {
 public:
   using UnderlyingType = uint8_t;
-  using TargetFlagsType = uint64_t;
+  using TargetFlagsType = uint8_t;
 
   enum FlagNames : UnderlyingType {
     None = 0,
@@ -83,7 +83,7 @@ public:
   /// Construct a JITSymbolFlags instance from the given flags and target
   ///        flags.
   JITSymbolFlags(FlagNames Flags, TargetFlagsType TargetFlags)
-    : Flags(Flags), TargetFlags(TargetFlags) {}
+      : TargetFlags(TargetFlags), Flags(Flags) {}
 
   /// Implicitly convert to bool. Returs true if any flag is set.
   explicit operator bool() const { return Flags != None || TargetFlags != 0; }
@@ -167,8 +167,8 @@ public:
   fromObjectSymbol(const object::SymbolRef &Symbol);
 
 private:
-  FlagNames Flags = None;
   TargetFlagsType TargetFlags = 0;
+  FlagNames Flags = None;
 };
 
 inline JITSymbolFlags operator&(const JITSymbolFlags &LHS,

include/llvm/ExecutionEngine/Orc/Core.h

@@ -174,7 +174,7 @@ public:
   /// Note: The returned flags may have transient flags (Lazy, Materializing)
   /// set. These should be stripped with JITSymbolFlags::stripTransientFlags
   /// before using.
-  const SymbolFlagsMap &getSymbols() { return SymbolFlags; }
+  const SymbolFlagsMap &getSymbols() const { return SymbolFlags; }
 
   /// Returns the names of any symbols covered by this
   /// MaterializationResponsibility object that have queries pending. This

include/llvm/ExecutionEngine/Orc/ExecutionUtils.h

@@ -217,25 +217,26 @@ public:
 
   /// Create a DynamicLibrarySearchGenerator that searches for symbols in the
   /// given sys::DynamicLibrary.
+  ///
   /// If the Allow predicate is given then only symbols matching the predicate
-  /// will be searched for in the DynamicLibrary. If the predicate is not given
-  /// then all symbols will be searched for.
-  DynamicLibrarySearchGenerator(sys::DynamicLibrary Dylib, const DataLayout &DL,
+  /// will be searched for. If the predicate is not given then all symbols will
+  /// be searched for.
+  DynamicLibrarySearchGenerator(sys::DynamicLibrary Dylib, char GlobalPrefix,
                                 SymbolPredicate Allow = SymbolPredicate());
 
   /// Permanently loads the library at the given path and, on success, returns
   /// a DynamicLibrarySearchGenerator that will search it for symbol definitions
   /// in the library. On failure returns the reason the library failed to load.
   static Expected<DynamicLibrarySearchGenerator>
-  Load(const char *FileName, const DataLayout &DL,
+  Load(const char *FileName, char GlobalPrefix,
        SymbolPredicate Allow = SymbolPredicate());
 
   /// Creates a DynamicLibrarySearchGenerator that searches for symbols in
   /// the current process.
   static Expected<DynamicLibrarySearchGenerator>
-  GetForCurrentProcess(const DataLayout &DL,
+  GetForCurrentProcess(char GlobalPrefix,
                        SymbolPredicate Allow = SymbolPredicate()) {
-    return Load(nullptr, DL, std::move(Allow));
+    return Load(nullptr, GlobalPrefix, std::move(Allow));
   }
 
   SymbolNameSet operator()(JITDylib &JD, const SymbolNameSet &Names);

include/llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h

@@ -0,0 +1,134 @@
+//===-- ObjectLinkingLayer.h - JITLink-based jit linking layer --*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Contains the definition for an JITLink-based, in-process object linking
+// layer.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_ORC_OBJECTLINKINGLAYER_H
+#define LLVM_EXECUTIONENGINE_ORC_OBJECTLINKINGLAYER_H
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+#include "llvm/ExecutionEngine/JITSymbol.h"
+#include "llvm/ExecutionEngine/Orc/Core.h"
+#include "llvm/ExecutionEngine/Orc/Layer.h"
+#include "llvm/Support/Error.h"
+#include <algorithm>
+#include <cassert>
+#include <functional>
+#include <list>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace llvm {
+
+namespace object {
+class ObjectFile;
+} // namespace object
+
+namespace orc {
+
+class ObjectLinkingLayerJITLinkContext;
+
+class ObjectLinkingLayer : public ObjectLayer {
+  friend class ObjectLinkingLayerJITLinkContext;
+
+public:
+  /// Function object for receiving object-loaded notifications.
+  using NotifyLoadedFunction = std::function<void(VModuleKey)>;
+
+  /// Function object for receiving finalization notifications.
+  using NotifyEmittedFunction = std::function<void(VModuleKey)>;
+
+  /// Function object for modifying PassConfiguration objects.
+  using ModifyPassConfigFunction =
+      std::function<void(const Triple &TT, jitlink::PassConfiguration &Config)>;
+
+  /// Construct an ObjectLinkingLayer with the given NotifyLoaded,
+  ///        and NotifyEmitted functors.
+  ObjectLinkingLayer(
+      ExecutionSession &ES, jitlink::JITLinkMemoryManager &MemMgr,
+      NotifyLoadedFunction NotifyLoaded = NotifyLoadedFunction(),
+      NotifyEmittedFunction NotifyEmitted = NotifyEmittedFunction(),
+      ModifyPassConfigFunction ModifyPassConfig = ModifyPassConfigFunction());
+
+  /// Emit the object.
+  void emit(MaterializationResponsibility R,
+            std::unique_ptr<MemoryBuffer> O) override;
+
+  /// Instructs this ObjectLinkingLayer instance to override the symbol flags
+  /// found in the AtomGraph with the flags supplied by the
+  /// MaterializationResponsibility instance. This is a workaround to support
+  /// symbol visibility in COFF, which does not use the libObject's
+  /// SF_Exported flag. Use only when generating / adding COFF object files.
+  ///
+  /// FIXME: We should be able to remove this if/when COFF properly tracks
+  /// exported symbols.
+  ObjectLinkingLayer &
+  setOverrideObjectFlagsWithResponsibilityFlags(bool OverrideObjectFlags) {
+    this->OverrideObjectFlags = OverrideObjectFlags;
+    return *this;
+  }
+
+  /// If set, this ObjectLinkingLayer instance will claim responsibility
+  /// for any symbols provided by a given object file that were not already in
+  /// the MaterializationResponsibility instance. Setting this flag allows
+  /// higher-level program representations (e.g. LLVM IR) to be added based on
+  /// only a subset of the symbols they provide, without having to write
+  /// intervening layers to scan and add the additional symbols. This trades
+  /// diagnostic quality for convenience however: If all symbols are enumerated
+  /// up-front then clashes can be detected and reported early (and usually
+  /// deterministically). If this option is set, clashes for the additional
+  /// symbols may not be detected until late, and detection may depend on
+  /// the flow of control through JIT'd code. Use with care.
+  ObjectLinkingLayer &
+  setAutoClaimResponsibilityForObjectSymbols(bool AutoClaimObjectSymbols) {
+    this->AutoClaimObjectSymbols = AutoClaimObjectSymbols;
+    return *this;
+  }
+
+private:
+  using AllocPtr = std::unique_ptr<jitlink::JITLinkMemoryManager::Allocation>;
+
+  class ObjectResources {
+  public:
+    ObjectResources() = default;
+    ObjectResources(AllocPtr Alloc, JITTargetAddress EHFrameAddr);
+    ObjectResources(ObjectResources &&Other);
+    ObjectResources &operator=(ObjectResources &&Other);
+    ~ObjectResources();
+
+  private:
+    AllocPtr Alloc;
+    JITTargetAddress EHFrameAddr = 0;
+  };
+
+  void notifyFinalized(ObjectResources OR) {
+    ObjResources.push_back(std::move(OR));
+  }
+
+  mutable std::mutex LayerMutex;
+  jitlink::JITLinkMemoryManager &MemMgr;
+  NotifyLoadedFunction NotifyLoaded;
+  NotifyEmittedFunction NotifyEmitted;
+  ModifyPassConfigFunction ModifyPassConfig;
+  bool OverrideObjectFlags = false;
+  bool AutoClaimObjectSymbols = false;
+  std::vector<ObjectResources> ObjResources;
+};
+
+} // end namespace orc
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_ORC_OBJECTLINKINGLAYER_H

include/llvm/Support/Memory.h

@@ -18,6 +18,10 @@
 #include <system_error>
 
 namespace llvm {
+
+// Forward declare raw_ostream: it is used for debug dumping below.
+class raw_ostream;
+
 namespace sys {
 
   /// This class encapsulates the notion of a memory block which has an address
@@ -141,7 +145,14 @@ namespace sys {
     MemoryBlock M;
   };
 
-}
-}
+#ifndef NDEBUG
+  /// Debugging output for Memory::ProtectionFlags.
+  raw_ostream &operator<<(raw_ostream &OS, const Memory::ProtectionFlags &PF);
+
+  /// Debugging output for MemoryBlock.
+  raw_ostream &operator<<(raw_ostream &OS, const MemoryBlock &MB);
+#endif // ifndef NDEBUG
+  }    // end namespace sys
+  }    // end namespace llvm
 
 #endif

lib/ExecutionEngine/CMakeLists.txt

@@ -19,6 +19,7 @@ if(BUILD_SHARED_LIBS)
 endif()
 
 add_subdirectory(Interpreter)
+add_subdirectory(JITLink)
 add_subdirectory(MCJIT)
 add_subdirectory(Orc)
 add_subdirectory(RuntimeDyld)

lib/ExecutionEngine/JITLink/CMakeLists.txt

@@ -0,0 +1,11 @@
+add_llvm_library(LLVMJITLink
+  JITLink.cpp
+  JITLinkGeneric.cpp
+  JITLink_EHFrameSupport.cpp
+  JITLink_MachO.cpp
+  JITLink_MachO_x86_64.cpp
+  MachOAtomGraphBuilder.cpp
+
+  DEPENDS
+  intrinsics_gen
+  )

lib/ExecutionEngine/JITLink/JITLink.cpp

@@ -0,0 +1,261 @@
+//===------------- JITLink.cpp - Core Run-time JIT linker APIs ------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+
+#include "llvm/BinaryFormat/Magic.h"
+#include "llvm/ExecutionEngine/JITLink/JITLink_MachO.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Process.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+using namespace llvm::object;
+
+#define DEBUG_TYPE "jitlink"
+
+namespace {
+
+enum JITLinkErrorCode { GenericJITLinkError = 1 };
+
+// FIXME: This class is only here to support the transition to llvm::Error. It
+// will be removed once this transition is complete. Clients should prefer to
+// deal with the Error value directly, rather than converting to error_code.
+class JITLinkerErrorCategory : public std::error_category {
+public:
+  const char *name() const noexcept override { return "runtimedyld"; }
+
+  std::string message(int Condition) const override {
+    switch (static_cast<JITLinkErrorCode>(Condition)) {
+    case GenericJITLinkError:
+      return "Generic JITLink error";
+    }
+    llvm_unreachable("Unrecognized JITLinkErrorCode");
+  }
+};
+
+static ManagedStatic<JITLinkerErrorCategory> JITLinkerErrorCategory;
+
+} // namespace
+
+namespace llvm {
+namespace jitlink {
+
+char JITLinkError::ID = 0;
+
+void JITLinkError::log(raw_ostream &OS) const { OS << ErrMsg << "\n"; }
+
+std::error_code JITLinkError::convertToErrorCode() const {
+  return std::error_code(GenericJITLinkError, *JITLinkerErrorCategory);
+}
+
+JITLinkMemoryManager::~JITLinkMemoryManager() = default;
+
+JITLinkMemoryManager::Allocation::~Allocation() = default;
+
+const StringRef getGenericEdgeKindName(Edge::Kind K) {
+  switch (K) {
+  case Edge::Invalid:
+    return "INVALID RELOCATION";
+  case Edge::KeepAlive:
+    return "Keep-Alive";
+  case Edge::LayoutNext:
+    return "Layout-Next";
+  default:
+    llvm_unreachable("Unrecognized relocation kind");
+  }
+}
+
+raw_ostream &operator<<(raw_ostream &OS, const Atom &A) {
+  OS << "<";
+  if (A.getName().empty())
+    OS << "anon@" << format("0x%016" PRIx64, A.getAddress());
+  else
+    OS << A.getName();
+  OS << " [";
+  if (A.isDefined()) {
+    auto &DA = static_cast<const DefinedAtom &>(A);
+    OS << " section=" << DA.getSection().getName();
+    if (DA.isLive())
+      OS << " live";
+    if (DA.shouldDiscard())
+      OS << " should-discard";
+  } else
+    OS << " external";
+  OS << " ]>";
+  return OS;
+}
+
+void printEdge(raw_ostream &OS, const Atom &FixupAtom, const Edge &E,
+               StringRef EdgeKindName) {
+  OS << "edge@" << formatv("{0:x16}", FixupAtom.getAddress() + E.getOffset())
+     << ": " << FixupAtom << " + " << E.getOffset() << " -- " << EdgeKindName
+     << " -> " << E.getTarget() << " + " << E.getAddend();
+}
+
+Section::~Section() {
+  for (auto *DA : DefinedAtoms)
+    DA->~DefinedAtom();
+}
+
+void AtomGraph::dump(raw_ostream &OS,
+                     std::function<StringRef(Edge::Kind)> EdgeKindToName) {
+  if (!EdgeKindToName)
+    EdgeKindToName = [](Edge::Kind K) { return StringRef(); };
+
+  OS << "Defined atoms:\n";
+  for (auto *DA : defined_atoms()) {
+    OS << "  " << format("0x%016" PRIx64, DA->getAddress()) << ": " << *DA
+       << "\n";
+    for (auto &E : DA->edges()) {
+      OS << "    ";
+      StringRef EdgeName = (E.getKind() < Edge::FirstRelocation
+                                ? getGenericEdgeKindName(E.getKind())
+                                : EdgeKindToName(E.getKind()));
+
+      if (!EdgeName.empty())
+        printEdge(OS, *DA, E, EdgeName);
+      else {
+        auto EdgeNumberString = std::to_string(E.getKind());
+        printEdge(OS, *DA, E, EdgeNumberString);
+      }
+      OS << "\n";
+    }
+  }
+
+  OS << "Absolute atoms:\n";
+  for (auto *A : absolute_atoms())
+    OS << "  " << format("0x%016" PRIx64, A->getAddress()) << ": " << *A
+       << "\n";
+
+  OS << "External atoms:\n";
+  for (auto *A : external_atoms())
+    OS << "  " << format("0x%016" PRIx64, A->getAddress()) << ": " << *A
+       << "\n";
+}
+
+Expected<std::unique_ptr<JITLinkMemoryManager::Allocation>>
+InProcessMemoryManager::allocate(const SegmentsRequestMap &Request) {
+
+  using AllocationMap = DenseMap<unsigned, sys::MemoryBlock>;
+
+  // Local class for allocation.
+  class IPMMAlloc : public Allocation {
+  public:
+    IPMMAlloc(AllocationMap SegBlocks) : SegBlocks(std::move(SegBlocks)) {}
+    MutableArrayRef<char> getWorkingMemory(ProtectionFlags Seg) override {
+      assert(SegBlocks.count(Seg) && "No allocation for segment");
+      return {static_cast<char *>(SegBlocks[Seg].base()),
+              SegBlocks[Seg].size()};
+    }
+    JITTargetAddress getTargetMemory(ProtectionFlags Seg) override {
+      assert(SegBlocks.count(Seg) && "No allocation for segment");
+      return reinterpret_cast<JITTargetAddress>(SegBlocks[Seg].base());
+    }
+    void finalizeAsync(FinalizeContinuation OnFinalize) override {
+      OnFinalize(applyProtections());
+    }
+    Error deallocate() override {
+      for (auto &KV : SegBlocks)
+        if (auto EC = sys::Memory::releaseMappedMemory(KV.second))
+          return errorCodeToError(EC);
+      return Error::success();
+    }
+
+  private:
+    Error applyProtections() {
+      for (auto &KV : SegBlocks) {
+        auto &Prot = KV.first;
+        auto &Block = KV.second;
+        if (auto EC = sys::Memory::protectMappedMemory(Block, Prot))
+          return errorCodeToError(EC);
+        if (Prot & sys::Memory::MF_EXEC)
+          sys::Memory::InvalidateInstructionCache(Block.base(), Block.size());
+      }
+      return Error::success();
+    }
+
+    AllocationMap SegBlocks;
+  };
+
+  AllocationMap Blocks;
+  const sys::Memory::ProtectionFlags ReadWrite =
+      static_cast<sys::Memory::ProtectionFlags>(sys::Memory::MF_READ |
+                                                sys::Memory::MF_WRITE);
+
+  for (auto &KV : Request) {
+    auto &Seg = KV.second;
+
+    if (Seg.getContentAlignment() > sys::Process::getPageSize())
+      return make_error<StringError>("Cannot request higher than page "
+                                     "alignment",
+                                     inconvertibleErrorCode());
+
+    if (sys::Process::getPageSize() % Seg.getContentAlignment() != 0)
+      return make_error<StringError>("Page size is not a multiple of "
+                                     "alignment",
+                                     inconvertibleErrorCode());
+
+    uint64_t ZeroFillStart =
+        alignTo(Seg.getContentSize(), Seg.getZeroFillAlignment());
+    uint64_t SegmentSize = ZeroFillStart + Seg.getZeroFillSize();
+
+    std::error_code EC;
+    auto SegMem =
+        sys::Memory::allocateMappedMemory(SegmentSize, nullptr, ReadWrite, EC);
+
+    if (EC)
+      return errorCodeToError(EC);
+
+    // Zero out the zero-fill memory.
+    bzero(static_cast<char *>(SegMem.base()) + ZeroFillStart,
+          Seg.getZeroFillSize());
+
+    // Record the block for this segment.
+    Blocks[KV.first] = std::move(SegMem);
+  }
+  return std::unique_ptr<InProcessMemoryManager::Allocation>(
+      new IPMMAlloc(std::move(Blocks)));
+}
+
+JITLinkContext::~JITLinkContext() {}
+
+bool JITLinkContext::shouldAddDefaultTargetPasses(const Triple &TT) const {
+  return true;
+}
+
+AtomGraphPassFunction JITLinkContext::getMarkLivePass(const Triple &TT) const {
+  return AtomGraphPassFunction();
+}
+
+Error JITLinkContext::modifyPassConfig(const Triple &TT,
+                                       PassConfiguration &Config) {
+  return Error::success();
+}
+
+Error markAllAtomsLive(AtomGraph &G) {
+  for (auto *DA : G.defined_atoms())
+    DA->setLive(true);
+  return Error::success();
+}
+
+void jitLink(std::unique_ptr<JITLinkContext> Ctx) {
+  auto Magic = identify_magic(Ctx->getObjectBuffer().getBuffer());
+  switch (Magic) {
+  case file_magic::macho_object:
+    return jitLink_MachO(std::move(Ctx));
+  default:
+    Ctx->notifyFailed(make_error<JITLinkError>("Unsupported file format"));
+  };
+}
+
+} // end namespace jitlink
+} // end namespace llvm

lib/ExecutionEngine/JITLink/JITLinkGeneric.cpp

@@ -0,0 +1,464 @@
+//===--------- JITLinkGeneric.cpp - Generic JIT linker utilities ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic JITLinker utility class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "JITLinkGeneric.h"
+#include "JITLink_EHFrameSupportImpl.h"
+
+#include "llvm/Support/BinaryStreamReader.h"
+#include "llvm/Support/MemoryBuffer.h"
+
+#define DEBUG_TYPE "jitlink"
+
+namespace llvm {
+namespace jitlink {
+
+JITLinkerBase::~JITLinkerBase() {}
+
+void JITLinkerBase::linkPhase1(std::unique_ptr<JITLinkerBase> Self) {
+
+  // Build the atom graph.
+  if (auto GraphOrErr = buildGraph(Ctx->getObjectBuffer()))
+    G = std::move(*GraphOrErr);
+  else
+    return Ctx->notifyFailed(GraphOrErr.takeError());
+  assert(G && "Graph should have been created by buildGraph above");
+
+  // Prune and optimize the graph.
+  if (auto Err = runPasses(Passes.PrePrunePasses, *G))
+    return Ctx->notifyFailed(std::move(Err));
+
+  LLVM_DEBUG({
+    dbgs() << "Atom graph \"" << G->getName() << "\" pre-pruning:\n";
+    dumpGraph(dbgs());
+  });
+
+  prune(*G);
+
+  LLVM_DEBUG({
+    dbgs() << "Atom graph \"" << G->getName() << "\" post-pruning:\n";
+    dumpGraph(dbgs());
+  });
+
+  // Run post-pruning passes.
+  if (auto Err = runPasses(Passes.PostPrunePasses, *G))
+    return Ctx->notifyFailed(std::move(Err));
+
+  // Sort atoms into segments.
+  layOutAtoms();
+
+  // Allocate memory for segments.
+  if (auto Err = allocateSegments(Layout))
+    return Ctx->notifyFailed(std::move(Err));
+
+  // Notify client that the defined atoms have been assigned addresses.
+  Ctx->notifyResolved(*G);
+
+  auto ExternalSymbols = getExternalSymbolNames();
+
+  // We're about to hand off ownership of ourself to the continuation. Grab a
+  // pointer to the context so that we can call it to initiate the lookup.
+  //
+  // FIXME: Once callee expressions are defined to be sequenced before argument
+  // expressions (c++17) we can simplify all this to:
+  //
+  // Ctx->lookup(std::move(UnresolvedExternals),
+  //             [Self=std::move(Self)](Expected<AsyncLookupResult> Result) {
+  //               Self->linkPhase2(std::move(Self), std::move(Result));
+  //             });
+  //
+  // FIXME: Use move capture once we have c++14.
+  auto *TmpCtx = Ctx.get();
+  auto *UnownedSelf = Self.release();
+  auto Phase2Continuation =
+      [UnownedSelf](Expected<AsyncLookupResult> LookupResult) {
+        std::unique_ptr<JITLinkerBase> Self(UnownedSelf);
+        UnownedSelf->linkPhase2(std::move(Self), std::move(LookupResult));
+      };
+  TmpCtx->lookup(std::move(ExternalSymbols), std::move(Phase2Continuation));
+}
+
+void JITLinkerBase::linkPhase2(std::unique_ptr<JITLinkerBase> Self,
+                               Expected<AsyncLookupResult> LR) {
+  // If the lookup failed, bail out.
+  if (!LR)
+    return Ctx->notifyFailed(LR.takeError());
+
+  // Assign addresses to external atoms.
+  applyLookupResult(*LR);
+
+  LLVM_DEBUG({
+    dbgs() << "Atom graph \"" << G->getName() << "\" before copy-and-fixup:\n";
+    dumpGraph(dbgs());
+  });
+
+  // Copy atom content to working memory and fix up.
+  if (auto Err = copyAndFixUpAllAtoms(Layout, *Alloc))
+    return Ctx->notifyFailed(std::move(Err));
+
+  LLVM_DEBUG({
+    dbgs() << "Atom graph \"" << G->getName() << "\" after copy-and-fixup:\n";
+    dumpGraph(dbgs());
+  });
+
+  if (auto Err = runPasses(Passes.PostFixupPasses, *G))
+    return Ctx->notifyFailed(std::move(Err));
+
+  // FIXME: Use move capture once we have c++14.
+  auto *UnownedSelf = Self.release();
+  auto Phase3Continuation = [UnownedSelf](Error Err) {
+    std::unique_ptr<JITLinkerBase> Self(UnownedSelf);
+    UnownedSelf->linkPhase3(std::move(Self), std::move(Err));
+  };
+
+  Alloc->finalizeAsync(std::move(Phase3Continuation));
+}
+
+void JITLinkerBase::linkPhase3(std::unique_ptr<JITLinkerBase> Self, Error Err) {
+  if (Err)
+    return Ctx->notifyFailed(std::move(Err));
+  Ctx->notifyFinalized(std::move(Alloc));
+}
+
+Error JITLinkerBase::runPasses(AtomGraphPassList &Passes, AtomGraph &G) {
+  for (auto &P : Passes)
+    if (auto Err = P(G))
+      return Err;
+  return Error::success();
+}
+
+void JITLinkerBase::layOutAtoms() {
+  // Group sections by protections, and whether or not they're zero-fill.
+  for (auto &S : G->sections()) {
+
+    // Skip empty sections.
+    if (S.atoms_empty())
+      continue;
+
+    auto &SL = Layout[S.getProtectionFlags()];
+    if (S.isZeroFill())
+      SL.ZeroFillSections.push_back(SegmentLayout::SectionLayout(S));
+    else
+      SL.ContentSections.push_back(SegmentLayout::SectionLayout(S));
+  }
+
+  // Sort sections within the layout by ordinal.
+  {
+    auto CompareByOrdinal = [](const SegmentLayout::SectionLayout &LHS,
+                               const SegmentLayout::SectionLayout &RHS) {
+      return LHS.S->getSectionOrdinal() < RHS.S->getSectionOrdinal();
+    };
+    for (auto &KV : Layout) {
+      auto &SL = KV.second;
+      std::sort(SL.ContentSections.begin(), SL.ContentSections.end(),
+                CompareByOrdinal);
+      std::sort(SL.ZeroFillSections.begin(), SL.ZeroFillSections.end(),
+                CompareByOrdinal);
+    }
+  }
+
+  // Add atoms to the sections.
+  for (auto &KV : Layout) {
+    auto &SL = KV.second;
+    for (auto *SIList : {&SL.ContentSections, &SL.ZeroFillSections}) {
+      for (auto &SI : *SIList) {
+        std::vector<DefinedAtom *> LayoutHeads;
+        LayoutHeads.reserve(SI.S->atoms_size());
+
+        // First build the list of layout-heads (i.e. "heads" of layout-next
+        // chains).
+        DenseSet<DefinedAtom *> AlreadyLayedOut;
+        for (auto *DA : SI.S->atoms()) {
+          if (AlreadyLayedOut.count(DA))
+            continue;
+          LayoutHeads.push_back(DA);
+          while (DA->hasLayoutNext()) {
+            auto &Next = DA->getLayoutNext();
+            AlreadyLayedOut.insert(&Next);
+            DA = &Next;
+          }
+        }
+
+        // Now sort the list of layout heads by address.
+        std::sort(LayoutHeads.begin(), LayoutHeads.end(),
+                  [](const DefinedAtom *LHS, const DefinedAtom *RHS) {
+                    return LHS->getAddress() < RHS->getAddress();
+                  });
+
+        // Now populate the SI.Atoms field by appending each of the chains.
+        for (auto *DA : LayoutHeads) {
+          SI.Atoms.push_back(DA);
+          while (DA->hasLayoutNext()) {
+            auto &Next = DA->getLayoutNext();
+            SI.Atoms.push_back(&Next);
+            DA = &Next;
+          }
+        }
+      }
+    }
+  }
+
+  LLVM_DEBUG({
+    dbgs() << "Segment ordering:\n";
+    for (auto &KV : Layout) {
+      dbgs() << "  Segment "
+             << static_cast<sys::Memory::ProtectionFlags>(KV.first) << ":\n";
+      auto &SL = KV.second;
+      for (auto &SIEntry :
+           {std::make_pair(&SL.ContentSections, "content sections"),
+            std::make_pair(&SL.ZeroFillSections, "zero-fill sections")}) {
+        auto &SIList = *SIEntry.first;
+        dbgs() << "    " << SIEntry.second << ":\n";
+        for (auto &SI : SIList) {
+          dbgs() << "      " << SI.S->getName() << ":\n";
+          for (auto *DA : SI.Atoms)
+            dbgs() << "        " << *DA << "\n";
+        }
+      }
+    }
+  });
+}
+
+Error JITLinkerBase::allocateSegments(const SegmentLayoutMap &Layout) {
+
+  // Compute segment sizes and allocate memory.
+  LLVM_DEBUG(dbgs() << "JIT linker requesting: { ");
+  JITLinkMemoryManager::SegmentsRequestMap Segments;
+  for (auto &KV : Layout) {
+    auto &Prot = KV.first;
+    auto &SegLayout = KV.second;
+
+    // Calculate segment content size.
+    size_t SegContentSize = 0;
+    for (auto &SI : SegLayout.ContentSections) {
+      assert(!SI.S->atoms_empty() && "Sections in layout must not be empty");
+      assert(!SI.Atoms.empty() && "Section layouts must not be empty");
+      for (auto *DA : SI.Atoms) {
+        SegContentSize = alignTo(SegContentSize, DA->getAlignment());
+        SegContentSize += DA->getSize();
+      }
+    }
+
+    // Get segment content alignment.
+    unsigned SegContentAlign = 1;
+    if (!SegLayout.ContentSections.empty())
+      SegContentAlign =
+          SegLayout.ContentSections.front().Atoms.front()->getAlignment();
+
+    // Calculate segment zero-fill size.
+    uint64_t SegZeroFillSize = 0;
+    for (auto &SI : SegLayout.ZeroFillSections) {
+      assert(!SI.S->atoms_empty() && "Sections in layout must not be empty");
+      assert(!SI.Atoms.empty() && "Section layouts must not be empty");
+      for (auto *DA : SI.Atoms) {
+        SegZeroFillSize = alignTo(SegZeroFillSize, DA->getAlignment());
+        SegZeroFillSize += DA->getSize();
+      }
+    }
+
+    // Calculate segment zero-fill alignment.
+    uint32_t SegZeroFillAlign = 1;
+    if (!SegLayout.ZeroFillSections.empty())
+      SegZeroFillAlign =
+          SegLayout.ZeroFillSections.front().Atoms.front()->getAlignment();
+
+    if (SegContentSize == 0)
+      SegContentAlign = SegZeroFillAlign;
+
+    if (SegContentAlign % SegZeroFillAlign != 0)
+      return make_error<JITLinkError>("First content atom alignment does not "
+                                      "accommodate first zero-fill atom "
+                                      "alignment");
+
+    Segments[Prot] = {SegContentSize, SegContentAlign, SegZeroFillSize,
+                      SegZeroFillAlign};
+
+    LLVM_DEBUG({
+      dbgs() << (&KV == &*Layout.begin() ? "" : "; ")
+             << static_cast<sys::Memory::ProtectionFlags>(Prot) << ": "
+             << SegContentSize << " content bytes (alignment "
+             << SegContentAlign << ") + " << SegZeroFillSize
+             << " zero-fill bytes (alignment " << SegZeroFillAlign << ")";
+    });
+  }
+  LLVM_DEBUG(dbgs() << " }\n");
+
+  if (auto AllocOrErr = Ctx->getMemoryManager().allocate(Segments))
+    Alloc = std::move(*AllocOrErr);
+  else
+    return AllocOrErr.takeError();
+
+  LLVM_DEBUG({
+    dbgs() << "JIT linker got working memory:\n";
+    for (auto &KV : Layout) {
+      auto Prot = static_cast<sys::Memory::ProtectionFlags>(KV.first);
+      dbgs() << "  " << Prot << ": "
+             << (const void *)Alloc->getWorkingMemory(Prot).data() << "\n";
+    }
+  });
+
+  // Update atom target addresses.
+  for (auto &KV : Layout) {
+    auto &Prot = KV.first;
+    auto &SL = KV.second;
+
+    JITTargetAddress AtomTargetAddr =
+        Alloc->getTargetMemory(static_cast<sys::Memory::ProtectionFlags>(Prot));
+
+    for (auto *SIList : {&SL.ContentSections, &SL.ZeroFillSections})
+      for (auto &SI : *SIList)
+        for (auto *DA : SI.Atoms) {
+          AtomTargetAddr = alignTo(AtomTargetAddr, DA->getAlignment());
+          DA->setAddress(AtomTargetAddr);
+          AtomTargetAddr += DA->getSize();
+        }
+  }
+
+  return Error::success();
+}
+
+DenseSet<StringRef> JITLinkerBase::getExternalSymbolNames() const {
+  // Identify unresolved external atoms.
+  DenseSet<StringRef> UnresolvedExternals;
+  for (auto *DA : G->external_atoms()) {
+    assert(DA->getAddress() == 0 &&
+           "External has already been assigned an address");
+    assert(DA->getName() != StringRef() && DA->getName() != "" &&
+           "Externals must be named");
+    UnresolvedExternals.insert(DA->getName());
+  }
+  return UnresolvedExternals;
+}
+
+void JITLinkerBase::applyLookupResult(AsyncLookupResult Result) {
+  for (auto &KV : Result) {
+    Atom &A = G->getAtomByName(KV.first);
+    assert(A.getAddress() == 0 && "Atom already resolved");
+    A.setAddress(KV.second.getAddress());
+  }
+
+  assert(llvm::all_of(G->external_atoms(),
+                      [](Atom *A) { return A->getAddress() != 0; }) &&
+         "All atoms should have been resolved by this point");
+}
+
+void JITLinkerBase::dumpGraph(raw_ostream &OS) {
+  assert(G && "Graph is not set yet");
+  G->dump(dbgs(), [this](Edge::Kind K) { return getEdgeKindName(K); });
+}
+
+void prune(AtomGraph &G) {
+  std::vector<DefinedAtom *> Worklist;
+  DenseMap<DefinedAtom *, std::vector<Edge *>> EdgesToUpdate;
+
+  // Build the initial worklist from all atoms initially live.
+  for (auto *DA : G.defined_atoms()) {
+    if (!DA->isLive() || DA->shouldDiscard())
+      continue;
+
+    for (auto &E : DA->edges()) {
+      if (!E.getTarget().isDefined())
+        continue;
+
+      auto &EDT = static_cast<DefinedAtom &>(E.getTarget());
+
+      if (EDT.shouldDiscard())
+        EdgesToUpdate[&EDT].push_back(&E);
+      else if (E.isKeepAlive() && !EDT.isLive())
+        Worklist.push_back(&EDT);
+    }
+  }
+
+  // Propagate live flags to all atoms reachable from the initial live set.
+  while (!Worklist.empty()) {
+    DefinedAtom &NextLive = *Worklist.back();
+    Worklist.pop_back();
+
+    assert(!NextLive.shouldDiscard() &&
+           "should-discard nodes should never make it into the worklist");
+
+    // If this atom has already been marked as live, or is marked to be
+    // discarded, then skip it.
+    if (NextLive.isLive())
+      continue;
+
+    // Otherwise set it as live and add any non-live atoms that it points to
+    // to the worklist.
+    NextLive.setLive(true);
+
+    for (auto &E : NextLive.edges()) {
+      if (!E.getTarget().isDefined())
+        continue;
+
+      auto &EDT = static_cast<DefinedAtom &>(E.getTarget());
+
+      if (EDT.shouldDiscard())
+        EdgesToUpdate[&EDT].push_back(&E);
+      else if (E.isKeepAlive() && !EDT.isLive())
+        Worklist.push_back(&EDT);
+    }
+  }
+
+  // Collect atoms to remove, then remove them from the graph.
+  std::vector<DefinedAtom *> AtomsToRemove;
+  for (auto *DA : G.defined_atoms())
+    if (DA->shouldDiscard() || !DA->isLive())
+      AtomsToRemove.push_back(DA);
+
+  LLVM_DEBUG(dbgs() << "Pruning atoms:\n");
+  for (auto *DA : AtomsToRemove) {
+    LLVM_DEBUG(dbgs() << "  " << *DA << "... ");
+
+    // Check whether we need to replace this atom with an external atom.
+    //
+    // We replace if all of the following hold:
+    //   (1) The atom is marked should-discard,
+    //   (2) it is live, and
+    //   (3) it has edges pointing to it.
+    //
+    // Otherwise we simply delete the atom.
+    bool ReplaceWithExternal = DA->isLive() && DA->shouldDiscard();
+    std::vector<Edge *> *EdgesToUpdateForDA = nullptr;
+    if (ReplaceWithExternal) {
+      auto ETUItr = EdgesToUpdate.find(DA);
+      if (ETUItr == EdgesToUpdate.end())
+        ReplaceWithExternal = false;
+      else
+        EdgesToUpdateForDA = &ETUItr->second;
+    }
+
+    G.removeDefinedAtom(*DA);
+
+    if (ReplaceWithExternal) {
+      assert(EdgesToUpdateForDA &&
+             "Replacing atom: There should be edges to update");
+
+      auto &ExternalReplacement = G.addExternalAtom(DA->getName());
+      for (auto *EdgeToUpdate : *EdgesToUpdateForDA)
+        EdgeToUpdate->setTarget(ExternalReplacement);
+      LLVM_DEBUG(dbgs() << "replaced with " << ExternalReplacement << "\n");
+    } else
+      LLVM_DEBUG(dbgs() << "deleted\n");
+  }
+
+  // Finally, discard any absolute symbols that were marked should-discard.
+  {
+    std::vector<Atom *> AbsoluteAtomsToRemove;
+    for (auto *A : G.absolute_atoms())
+      if (A->shouldDiscard() || A->isLive())
+        AbsoluteAtomsToRemove.push_back(A);
+    for (auto *A : AbsoluteAtomsToRemove)
+      G.removeAbsoluteAtom(*A);
+  }
+}
+
+} // end namespace jitlink
+} // end namespace llvm

lib/ExecutionEngine/JITLink/JITLinkGeneric.h

@@ -0,0 +1,246 @@
+//===------ JITLinkGeneric.h - Generic JIT linker utilities -----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic JITLinker utilities. E.g. graph pruning, eh-frame parsing.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
+#define LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
+
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+
+#define DEBUG_TYPE "jitlink"
+
+namespace llvm {
+
+class MemoryBufferRef;
+
+namespace jitlink {
+
+/// Base class for a JIT linker.
+///
+/// A JITLinkerBase instance links one object file into an ongoing JIT
+/// session. Symbol resolution and finalization operations are pluggable,
+/// and called using continuation passing (passing a continuation for the
+/// remaining linker work) to allow them to be performed asynchronously.
+class JITLinkerBase {
+public:
+  JITLinkerBase(std::unique_ptr<JITLinkContext> Ctx, PassConfiguration Passes)
+      : Ctx(std::move(Ctx)), Passes(std::move(Passes)) {
+    assert(this->Ctx && "Ctx can not be null");
+  }
+
+  virtual ~JITLinkerBase();
+
+protected:
+  struct SegmentLayout {
+    using SectionAtomsList = std::vector<DefinedAtom *>;
+    struct SectionLayout {
+      SectionLayout(Section &S) : S(&S) {}
+
+      Section *S;
+      SectionAtomsList Atoms;
+    };
+
+    using SectionLayoutList = std::vector<SectionLayout>;
+
+    SectionLayoutList ContentSections;
+    SectionLayoutList ZeroFillSections;
+  };
+
+  using SegmentLayoutMap = DenseMap<unsigned, SegmentLayout>;
+
+  // Phase 1:
+  //   1.1: Build atom graph
+  //   1.2: Run pre-prune passes
+  //   1.2: Prune graph
+  //   1.3: Run post-prune passes
+  //   1.4: Sort atoms into segments
+  //   1.5: Allocate segment memory
+  //   1.6: Identify externals and make an async call to resolve function
+  void linkPhase1(std::unique_ptr<JITLinkerBase> Self);
+
+  // Phase 2:
+  //   2.1: Apply resolution results
+  //   2.2: Fix up atom contents
+  //   2.3: Call OnResolved callback
+  //   2.3: Make an async call to transfer and finalize memory.
+  void linkPhase2(std::unique_ptr<JITLinkerBase> Self,
+                  Expected<AsyncLookupResult> LookupResult);
+
+  // Phase 3:
+  //   3.1: Call OnFinalized callback, handing off allocation.
+  void linkPhase3(std::unique_ptr<JITLinkerBase> Self, Error Err);
+
+  // Build a graph from the given object buffer.
+  // To be implemented by the client.
+  virtual Expected<std::unique_ptr<AtomGraph>>
+  buildGraph(MemoryBufferRef ObjBuffer) = 0;
+
+  // For debug dumping of the atom graph.
+  virtual StringRef getEdgeKindName(Edge::Kind K) const = 0;
+
+private:
+  // Run all passes in the given pass list, bailing out immediately if any pass
+  // returns an error.
+  Error runPasses(AtomGraphPassList &Passes, AtomGraph &G);
+
+  // Copy atom contents and apply relocations.
+  // Implemented in JITLinker.
+  virtual Error
+  copyAndFixUpAllAtoms(const SegmentLayoutMap &Layout,
+                       JITLinkMemoryManager::Allocation &Alloc) const = 0;
+
+  void layOutAtoms();
+  Error allocateSegments(const SegmentLayoutMap &Layout);
+  DenseSet<StringRef> getExternalSymbolNames() const;
+  void applyLookupResult(AsyncLookupResult LR);
+
+  void dumpGraph(raw_ostream &OS);
+
+  std::unique_ptr<JITLinkContext> Ctx;
+  PassConfiguration Passes;
+  std::unique_ptr<AtomGraph> G;
+  SegmentLayoutMap Layout;
+  std::unique_ptr<JITLinkMemoryManager::Allocation> Alloc;
+};
+
+template <typename LinkerImpl> class JITLinker : public JITLinkerBase {
+public:
+  using JITLinkerBase::JITLinkerBase;
+
+  /// Link constructs a LinkerImpl instance and calls linkPhase1.
+  /// Link should be called with the constructor arguments for LinkerImpl, which
+  /// will be forwarded to the constructor.
+  template <typename... ArgTs> static void link(ArgTs &&... Args) {
+    auto L = llvm::make_unique<LinkerImpl>(std::forward<ArgTs>(Args)...);
+
+    // Ownership of the linker is passed into the linker's doLink function to
+    // allow it to be passed on to async continuations.
+    //
+    // FIXME: Remove LTmp once we have c++17.
+    // C++17 sequencing rules guarantee that function name expressions are
+    // sequenced before arguments, so L->linkPhase1(std::move(L), ...) will be
+    // well formed.
+    auto &LTmp = *L;
+    LTmp.linkPhase1(std::move(L));
+  }
+
+private:
+  const LinkerImpl &impl() const {
+    return static_cast<const LinkerImpl &>(*this);
+  }
+
+  Error
+  copyAndFixUpAllAtoms(const SegmentLayoutMap &Layout,
+                       JITLinkMemoryManager::Allocation &Alloc) const override {
+    LLVM_DEBUG(dbgs() << "Copying and fixing up atoms:\n");
+    for (auto &KV : Layout) {
+      auto &Prot = KV.first;
+      auto &SegLayout = KV.second;
+
+      auto SegMem = Alloc.getWorkingMemory(
+          static_cast<sys::Memory::ProtectionFlags>(Prot));
+      char *LastAtomEnd = SegMem.data();
+      char *AtomDataPtr = nullptr;
+
+      LLVM_DEBUG({
+        dbgs() << "  Processing segment "
+               << static_cast<sys::Memory::ProtectionFlags>(Prot) << " [ "
+               << (const void *)SegMem.data() << " .. "
+               << (const void *)((char *)SegMem.data() + SegMem.size())
+               << " ]\n    Processing content sections:\n";
+      });
+
+      for (auto &SI : SegLayout.ContentSections) {
+        LLVM_DEBUG(dbgs() << "    " << SI.S->getName() << ":\n");
+        for (auto *DA : SI.Atoms) {
+          AtomDataPtr = LastAtomEnd;
+
+          // Align.
+          AtomDataPtr += alignmentAdjustment(AtomDataPtr, DA->getAlignment());
+          LLVM_DEBUG({
+            dbgs() << "      Bumped atom pointer to "
+                   << (const void *)AtomDataPtr << " to meet alignment of "
+                   << DA->getAlignment() << "\n";
+          });
+
+          // Zero pad up to alignment.
+          LLVM_DEBUG({
+            if (LastAtomEnd != AtomDataPtr)
+              dbgs() << "      Zero padding from " << (const void *)LastAtomEnd
+                     << " to " << (const void *)AtomDataPtr << "\n";
+          });
+          while (LastAtomEnd != AtomDataPtr)
+            *LastAtomEnd++ = 0;
+
+          // Copy initial atom content.
+          LLVM_DEBUG({
+            dbgs() << "      Copying atom " << *DA << " content, "
+                   << DA->getContent().size() << " bytes, from "
+                   << (const void *)DA->getContent().data() << " to "
+                   << (const void *)AtomDataPtr << "\n";
+          });
+          memcpy(AtomDataPtr, DA->getContent().data(), DA->getContent().size());
+
+          // Copy atom data and apply fixups.
+          LLVM_DEBUG(dbgs() << "      Applying fixups.\n");
+          for (auto &E : DA->edges()) {
+
+            // Skip non-relocation edges.
+            if (!E.isRelocation())
+              continue;
+
+            // Dispatch to LinkerImpl for fixup.
+            if (auto Err = impl().applyFixup(*DA, E, AtomDataPtr))
+              return Err;
+          }
+
+          // Point the atom's content to the fixed up buffer.
+          DA->setContent(StringRef(AtomDataPtr, DA->getContent().size()));
+
+          // Update atom end pointer.
+          LastAtomEnd = AtomDataPtr + DA->getContent().size();
+        }
+      }
+
+      // Zero pad the rest of the segment.
+      LLVM_DEBUG({
+        dbgs() << "    Zero padding end of segment from "
+               << (const void *)LastAtomEnd << " to "
+               << (const void *)((char *)SegMem.data() + SegMem.size()) << "\n";
+      });
+      while (LastAtomEnd != SegMem.data() + SegMem.size())
+        *LastAtomEnd++ = 0;
+    }
+
+    return Error::success();
+  }
+};
+
+/// Dead strips and replaces discarded definitions with external atoms.
+///
+/// Finds the set of nodes reachable from any node initially marked live
+/// (nodes marked should-discard are treated as not live, even if they are
+/// reachable). All nodes not marked as live at the end of this process,
+/// are deleted. Nodes that are live, but marked should-discard are replaced
+/// with external atoms and all edges to them are re-written.
+void prune(AtomGraph &G);
+
+Error addEHFrame(AtomGraph &G, Section &EHFrameSection,
+                 StringRef EHFrameContent, JITTargetAddress EHFrameAddress,
+                 Edge::Kind FDEToCIERelocKind, Edge::Kind FDEToTargetRelocKind);
+
+} // end namespace jitlink
+} // end namespace llvm
+
+#undef DEBUG_TYPE // "jitlink"
+
+#endif // LLVM_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H

lib/ExecutionEngine/JITLink/JITLink_EHFrameSupport.cpp

@@ -0,0 +1,537 @@
+//===-------- JITLink_EHFrameSupport.cpp - JITLink eh-frame utils ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "JITLink_EHFrameSupportImpl.h"
+
+#include "llvm/BinaryFormat/Dwarf.h"
+
+#define DEBUG_TYPE "jitlink"
+
+namespace llvm {
+namespace jitlink {
+
+EHFrameParser::EHFrameParser(AtomGraph &G, Section &EHFrameSection,
+                             StringRef EHFrameContent,
+                             JITTargetAddress EHFrameAddress,
+                             Edge::Kind FDEToCIERelocKind,
+                             Edge::Kind FDEToTargetRelocKind)
+    : G(G), EHFrameSection(EHFrameSection), EHFrameContent(EHFrameContent),
+      EHFrameAddress(EHFrameAddress),
+      EHFrameReader(EHFrameContent, G.getEndianness()),
+      FDEToCIERelocKind(FDEToCIERelocKind),
+      FDEToTargetRelocKind(FDEToTargetRelocKind) {}
+
+Error EHFrameParser::atomize() {
+  while (!EHFrameReader.empty()) {
+    size_t RecordOffset = EHFrameReader.getOffset();
+
+    LLVM_DEBUG({
+      dbgs() << "Processing eh-frame record at "
+             << format("0x%016" PRIx64, EHFrameAddress + RecordOffset)
+             << " (offset " << RecordOffset << ")\n";
+    });
+
+    size_t CIELength = 0;
+    uint32_t CIELengthField;
+    if (auto Err = EHFrameReader.readInteger(CIELengthField))
+      return Err;
+
+    // Process CIE length/extended-length fields to build the atom.
+    //
+    // The value of these fields describe the length of the *rest* of the CIE
+    // (not including data up to the end of the field itself) so we have to
+    // bump CIELength to include the data up to the end of the field: 4 bytes
+    // for Length, or 12 bytes (4 bytes + 8 bytes) for ExtendedLength.
+    if (CIELengthField == 0) // Length 0 means end of __eh_frame section.
+      break;
+
+    // If the regular length field's value is 0xffffffff, use extended length.
+    if (CIELengthField == 0xffffffff) {
+      uint64_t CIEExtendedLengthField;
+      if (auto Err = EHFrameReader.readInteger(CIEExtendedLengthField))
+        return Err;
+      if (CIEExtendedLengthField > EHFrameReader.bytesRemaining())
+        return make_error<JITLinkError>("CIE record extends past the end of "
+                                        "the __eh_frame section");
+      if (CIEExtendedLengthField + 12 > std::numeric_limits<size_t>::max())
+        return make_error<JITLinkError>("CIE record too large to process");
+      CIELength = CIEExtendedLengthField + 12;
+    } else {
+      if (CIELengthField > EHFrameReader.bytesRemaining())
+        return make_error<JITLinkError>("CIE record extends past the end of "
+                                        "the __eh_frame section");
+      CIELength = CIELengthField + 4;
+    }
+
+    LLVM_DEBUG(dbgs() << "  length: " << CIELength << "\n");
+
+    // Add an atom for this record.
+    CurRecordAtom = &G.addAnonymousAtom(
+        EHFrameSection, EHFrameAddress + RecordOffset, G.getPointerSize());
+    CurRecordAtom->setContent(EHFrameContent.substr(RecordOffset, CIELength));
+
+    // Read the CIE Pointer.
+    size_t CIEPointerAddress = EHFrameAddress + EHFrameReader.getOffset();
+    uint32_t CIEPointer;
+    if (auto Err = EHFrameReader.readInteger(CIEPointer))
+      return Err;
+
+    // Based on the CIE pointer value, parse this as a CIE or FDE record.
+    if (CIEPointer == 0) {
+      if (auto Err = processCIE())
+        return Err;
+    } else {
+      if (auto Err = processFDE(CIEPointerAddress, CIEPointer))
+        return Err;
+    }
+
+    EHFrameReader.setOffset(RecordOffset + CIELength);
+  }
+
+  return Error::success();
+}
+
+Expected<EHFrameParser::AugmentationInfo>
+EHFrameParser::parseAugmentationString() {
+  AugmentationInfo AugInfo;
+  uint8_t NextChar;
+  uint8_t *NextField = &AugInfo.Fields[0];
+
+  if (auto Err = EHFrameReader.readInteger(NextChar))
+    return std::move(Err);
+
+  while (NextChar != 0) {
+    switch (NextChar) {
+    case 'z':
+      AugInfo.AugmentationDataPresent = true;
+      break;
+    case 'e':
+      if (auto Err = EHFrameReader.readInteger(NextChar))
+        return std::move(Err);
+      if (NextChar != 'h')
+        return make_error<JITLinkError>("Unrecognized substring e" +
+                                        Twine(NextChar) +
+                                        " in augmentation string");
+      AugInfo.EHDataFieldPresent = true;
+      break;
+    case 'L':
+    case 'P':
+    case 'R':
+      *NextField++ = NextChar;
+      break;
+    default:
+      return make_error<JITLinkError>("Unrecognized character " +
+                                      Twine(NextChar) +
+                                      " in augmentation string");
+    }
+
+    if (auto Err = EHFrameReader.readInteger(NextChar))
+      return std::move(Err);
+  }
+
+  return std::move(AugInfo);
+}
+
+Expected<JITTargetAddress> EHFrameParser::readAbsolutePointer() {
+  static_assert(sizeof(JITTargetAddress) == sizeof(uint64_t),
+                "Result must be able to hold a uint64_t");
+  JITTargetAddress Addr;
+  if (G.getPointerSize() == 8) {
+    if (auto Err = EHFrameReader.readInteger(Addr))
+      return std::move(Err);
+  } else if (G.getPointerSize() == 4) {
+    uint32_t Addr32;
+    if (auto Err = EHFrameReader.readInteger(Addr32))
+      return std::move(Err);
+    Addr = Addr32;
+  } else
+    llvm_unreachable("Pointer size is not 32-bit or 64-bit");
+  return Addr;
+}
+
+Error EHFrameParser::processCIE() {
+  // Use the dwarf namespace for convenient access to pointer encoding
+  // constants.
+  using namespace dwarf;
+
+  LLVM_DEBUG(dbgs() << "  Record is CIE\n");
+
+  /// Reset state for the new CIE.
+  MostRecentCIE = CurRecordAtom;
+  LSDAFieldPresent = false;
+
+  uint8_t Version = 0;
+  if (auto Err = EHFrameReader.readInteger(Version))
+    return Err;
+
+  if (Version != 0x01)
+    return make_error<JITLinkError>("Bad CIE version " + Twine(Version) +
+                                    " (should be 0x01) in eh-frame");
+
+  auto AugInfo = parseAugmentationString();
+  if (!AugInfo)
+    return AugInfo.takeError();
+
+  // Skip the EH Data field if present.
+  if (AugInfo->EHDataFieldPresent)
+    if (auto Err = EHFrameReader.skip(G.getPointerSize()))
+      return Err;
+
+  // Read and sanity check the code alignment factor.
+  {
+    uint64_t CodeAlignmentFactor = 0;
+    if (auto Err = EHFrameReader.readULEB128(CodeAlignmentFactor))
+      return Err;
+    if (CodeAlignmentFactor != 1)
+      return make_error<JITLinkError>("Unsupported CIE code alignment factor " +
+                                      Twine(CodeAlignmentFactor) +
+                                      " (expected 1)");
+  }
+
+  // Read and sanity check the data alignment factor.
+  {
+    int64_t DataAlignmentFactor = 0;
+    if (auto Err = EHFrameReader.readSLEB128(DataAlignmentFactor))
+      return Err;
+    if (DataAlignmentFactor != -8)
+      return make_error<JITLinkError>("Unsupported CIE data alignment factor " +
+                                      Twine(DataAlignmentFactor) +
+                                      " (expected -8)");
+  }
+
+  // Skip the return address register field.
+  if (auto Err = EHFrameReader.skip(1))
+    return Err;
+
+  uint64_t AugmentationDataLength = 0;
+  if (auto Err = EHFrameReader.readULEB128(AugmentationDataLength))
+    return Err;
+
+  uint32_t AugmentationDataStartOffset = EHFrameReader.getOffset();
+
+  uint8_t *NextField = &AugInfo->Fields[0];
+  while (uint8_t Field = *NextField++) {
+    switch (Field) {
+    case 'L': {
+      LSDAFieldPresent = true;
+      uint8_t LSDAPointerEncoding;
+      if (auto Err = EHFrameReader.readInteger(LSDAPointerEncoding))
+        return Err;
+      if (LSDAPointerEncoding != (DW_EH_PE_pcrel | DW_EH_PE_absptr))
+        return make_error<JITLinkError>(
+            "Unsupported LSDA pointer encoding " +
+            formatv("{0:x2}", LSDAPointerEncoding) + " in CIE at " +
+            formatv("{0:x16}", CurRecordAtom->getAddress()));
+      break;
+    }
+    case 'P': {
+      uint8_t PersonalityPointerEncoding = 0;
+      if (auto Err = EHFrameReader.readInteger(PersonalityPointerEncoding))
+        return Err;
+      if (PersonalityPointerEncoding !=
+          (DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4))
+        return make_error<JITLinkError>(
+            "Unspported personality pointer "
+            "encoding " +
+            formatv("{0:x2}", PersonalityPointerEncoding) + " in CIE at " +
+            formatv("{0:x16}", CurRecordAtom->getAddress()));
+      uint32_t PersonalityPointerAddress;
+      if (auto Err = EHFrameReader.readInteger(PersonalityPointerAddress))
+        return Err;
+      break;
+    }
+    case 'R': {
+      uint8_t FDEPointerEncoding;
+      if (auto Err = EHFrameReader.readInteger(FDEPointerEncoding))
+        return Err;
+      if (FDEPointerEncoding != (DW_EH_PE_pcrel | DW_EH_PE_absptr))
+        return make_error<JITLinkError>(
+            "Unsupported FDE address pointer "
+            "encoding " +
+            formatv("{0:x2}", FDEPointerEncoding) + " in CIE at " +
+            formatv("{0:x16}", CurRecordAtom->getAddress()));
+      break;
+    }
+    default:
+      llvm_unreachable("Invalid augmentation string field");
+    }
+  }
+
+  if (EHFrameReader.getOffset() - AugmentationDataStartOffset >
+      AugmentationDataLength)
+    return make_error<JITLinkError>("Read past the end of the augmentation "
+                                    "data while parsing fields");
+
+  return Error::success();
+}
+
+Error EHFrameParser::processFDE(JITTargetAddress CIEPointerAddress,
+                                uint32_t CIEPointer) {
+  LLVM_DEBUG(dbgs() << "  Record is FDE\n");
+
+  // Sanity check the CIE pointer: if this is an FDE it must be proceeded by
+  // a CIE.
+  if (MostRecentCIE == nullptr)
+    return make_error<JITLinkError>("__eh_frame must start with CIE, not "
+                                    "FDE");
+
+  LLVM_DEBUG({
+    dbgs() << "  CIE pointer: "
+           << format("0x%016" PRIx64, CIEPointerAddress - CIEPointer) << "\n";
+  });
+
+  // Verify that this FDE's CIE pointer points to the most recent CIE entry.
+  if (CIEPointerAddress - CIEPointer != MostRecentCIE->getAddress())
+    return make_error<JITLinkError>("__eh_frame FDE's CIE Pointer does not "
+                                    "point at the most recent CIE");
+
+  // The CIEPointer looks good. Add a relocation.
+  CurRecordAtom->addEdge(FDEToCIERelocKind,
+                         CIEPointerAddress - CurRecordAtom->getAddress(),
+                         *MostRecentCIE, 0);
+
+  // Read and sanity check the PC-start pointer and size.
+  JITTargetAddress PCBeginAddress = EHFrameAddress + EHFrameReader.getOffset();
+
+  auto PCBeginDelta = readAbsolutePointer();
+  if (!PCBeginDelta)
+    return PCBeginDelta.takeError();
+
+  JITTargetAddress PCBegin = PCBeginAddress + *PCBeginDelta;
+  LLVM_DEBUG({
+    dbgs() << "  PC begin: " << format("0x%016" PRIx64, PCBegin) << "\n";
+  });
+
+  auto *TargetAtom = G.getAtomByAddress(PCBegin);
+
+  if (!TargetAtom)
+    return make_error<JITLinkError>("FDE PC-begin " +
+                                    formatv("{0:x16}", PCBegin) +
+                                    " does not point at atom");
+
+  if (TargetAtom->getAddress() != PCBegin)
+    return make_error<JITLinkError>(
+        "FDE PC-begin " + formatv("{0:x16}", PCBegin) +
+        " does not point to start of atom at " +
+        formatv("{0:x16}", TargetAtom->getAddress()));
+
+  LLVM_DEBUG(dbgs() << "  FDE target: " << *TargetAtom << "\n");
+
+  // The PC-start pointer and size look good. Add relocations.
+  CurRecordAtom->addEdge(FDEToTargetRelocKind,
+                         PCBeginAddress - CurRecordAtom->getAddress(),
+                         *TargetAtom, 0);
+
+  // Add a keep-alive relocation from the function to the FDE to ensure it is
+  // not dead stripped.
+  TargetAtom->addEdge(Edge::KeepAlive, 0, *CurRecordAtom, 0);
+
+  // Skip over the PC range size field.
+  if (auto Err = EHFrameReader.skip(G.getPointerSize()))
+    return Err;
+
+  if (LSDAFieldPresent) {
+    uint64_t AugmentationDataSize;
+    if (auto Err = EHFrameReader.readULEB128(AugmentationDataSize))
+      return Err;
+    if (AugmentationDataSize != G.getPointerSize())
+      return make_error<JITLinkError>("Unexpected FDE augmentation data size "
+                                      "(expected " +
+                                      Twine(G.getPointerSize()) + ", got " +
+                                      Twine(AugmentationDataSize) + ")");
+    JITTargetAddress LSDAAddress = EHFrameAddress + EHFrameReader.getOffset();
+    auto LSDADelta = readAbsolutePointer();
+    if (!LSDADelta)
+      return LSDADelta.takeError();
+
+    JITTargetAddress LSDA = LSDAAddress + *LSDADelta;
+
+    auto *LSDAAtom = G.getAtomByAddress(LSDA);
+
+    if (!LSDAAtom)
+      return make_error<JITLinkError>("FDE LSDA " + formatv("{0:x16}", LSDA) +
+                                      " does not point at atom");
+
+    if (LSDAAtom->getAddress() != LSDA)
+      return make_error<JITLinkError>(
+          "FDE LSDA " + formatv("{0:x16}", LSDA) +
+          " does not point to start of atom at " +
+          formatv("{0:x16}", LSDAAtom->getAddress()));
+
+    LLVM_DEBUG(dbgs() << "  FDE LSDA: " << *LSDAAtom << "\n");
+
+    // LSDA looks good. Add relocations.
+    CurRecordAtom->addEdge(FDEToTargetRelocKind,
+                           LSDAAddress - CurRecordAtom->getAddress(), *LSDAAtom,
+                           0);
+  }
+
+  return Error::success();
+}
+
+Error addEHFrame(AtomGraph &G, Section &EHFrameSection,
+                 StringRef EHFrameContent, JITTargetAddress EHFrameAddress,
+                 Edge::Kind FDEToCIERelocKind,
+                 Edge::Kind FDEToTargetRelocKind) {
+  return EHFrameParser(G, EHFrameSection, EHFrameContent, EHFrameAddress,
+                       FDEToCIERelocKind, FDEToTargetRelocKind)
+      .atomize();
+}
+
+// Determine whether we can register EH tables.
+#if (defined(__GNUC__) && !defined(__ARM_EABI__) && !defined(__ia64__) &&      \
+     !defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__))
+#define HAVE_EHTABLE_SUPPORT 1
+#else
+#define HAVE_EHTABLE_SUPPORT 0
+#endif
+
+#if HAVE_EHTABLE_SUPPORT
+extern "C" void __register_frame(const void *);
+extern "C" void __deregister_frame(const void *);
+
+Error registerFrameWrapper(const void *P) {
+  __register_frame(P);
+  return Error::success();
+}
+
+Error deregisterFrameWrapper(const void *P) {
+  __deregister_frame(P);
+  return Error::success();
+}
+
+#else
+
+// The building compiler does not have __(de)register_frame but
+// it may be found at runtime in a dynamically-loaded library.
+// For example, this happens when building LLVM with Visual C++
+// but using the MingW runtime.
+static Error registerFrameWrapper(const void *P) {
+  static void((*RegisterFrame)(const void *)) = 0;
+
+  if (!RegisterFrame)
+    *(void **)&RegisterFrame =
+        llvm::sys::DynamicLibrary::SearchForAddressOfSymbol("__register_frame");
+
+  if (RegisterFrame) {
+    RegisterFrame(P);
+    return Error::success();
+  }
+
+  return make_error<JITLinkError>("could not register eh-frame: "
+                                  "__register_frame function not found");
+}
+
+static void deregisterFrameWrapper(const void *P) {
+  static void((*DeregisterFrame)(const void *)) = 0;
+
+  if (!DeregisterFrame)
+    *(void **)&DeregisterFrame =
+        llvm::sys::DynamicLibrary::SearchForAddressOfSymbol(
+            "__deregister_frame");
+
+  if (DeregisterFrame) {
+    DeregisterFrame(P);
+    return Error::success();
+  }
+
+  return make_error<JITLinkError>("could not deregister eh-frame: "
+                                  "__deregister_frame function not found");
+}
+#endif
+
+#ifdef __APPLE__
+
+template <typename HandleFDEFn>
+Error walkAppleEHFrameSection(const char *const SectionStart,
+                              HandleFDEFn HandleFDE) {
+  const char *CurCFIRecord = SectionStart;
+  uint64_t Size = *reinterpret_cast<const uint32_t *>(CurCFIRecord);
+
+  while (Size != 0) {
+    const char *OffsetField = CurCFIRecord + (Size == 0xffffffff ? 12 : 4);
+    if (Size == 0xffffffff)
+      Size = *reinterpret_cast<const uint64_t *>(CurCFIRecord + 4) + 12;
+    else
+      Size += 4;
+    uint32_t Offset = *reinterpret_cast<const uint32_t *>(OffsetField);
+    if (Offset != 0)
+      if (auto Err = HandleFDE(CurCFIRecord))
+        return Err;
+
+    LLVM_DEBUG({
+      dbgs() << "Registering eh-frame section:\n";
+      dbgs() << "Processing " << (Offset ? "FDE" : "CIE") << " @"
+             << (void *)CurCFIRecord << ": [";
+      for (unsigned I = 0; I < Size; ++I)
+        dbgs() << format(" 0x%02" PRIx8, *(CurCFIRecord + I));
+      dbgs() << " ]\n";
+    });
+    CurCFIRecord += Size;
+
+    Size = *reinterpret_cast<const uint32_t *>(CurCFIRecord);
+  }
+
+  return Error::success();
+}
+
+#endif // __APPLE__
+
+Error registerEHFrameSection(const void *EHFrameSectionAddr) {
+#ifdef __APPLE__
+  // On Darwin __register_frame has to be called for each FDE entry.
+  return walkAppleEHFrameSection(static_cast<const char *>(EHFrameSectionAddr),
+                                 registerFrameWrapper);
+#else
+  // On Linux __register_frame takes a single argument:
+  // a pointer to the start of the .eh_frame section.
+
+  // How can it find the end? Because crtendS.o is linked
+  // in and it has an .eh_frame section with four zero chars.
+  return registerFrameWrapper(EHFrameSectionAddr);
+#endif
+}
+
+Error deregisterEHFrameSection(const void *EHFrameSectionAddr) {
+#ifdef __APPLE__
+  return walkAppleEHFrameSection(static_cast<const char *>(EHFrameSectionAddr),
+                                 deregisterFrameWrapper);
+#else
+  return deregisterFrameWrapper(EHFrameSectionAddr);
+#endif
+}
+
+AtomGraphPassFunction createEHFrameRecorderPass(const Triple &TT,
+                                                JITTargetAddress &EHFrameAddr) {
+  const char *EHFrameSectionName = nullptr;
+  if (TT.getObjectFormat() == Triple::MachO)
+    EHFrameSectionName = "__eh_frame";
+  else
+    EHFrameSectionName = ".eh_frame";
+
+  auto RecordEHFrame = [EHFrameSectionName,
+                        &EHFrameAddr](AtomGraph &G) -> Error {
+    // Search for a non-empty eh-frame and record the address of the first atom
+    // in it.
+    JITTargetAddress Addr = 0;
+    for (auto &S : G.sections())
+      if (S.getName() == EHFrameSectionName && !S.atoms_empty()) {
+        Addr = (*S.atoms().begin())->getAddress();
+        break;
+      }
+
+    EHFrameAddr = Addr;
+    return Error::success();
+  };
+
+  return RecordEHFrame;
+}
+
+} // end namespace jitlink
+} // end namespace llvm

lib/ExecutionEngine/JITLink/JITLink_EHFrameSupportImpl.h

@@ -0,0 +1,66 @@
+//===----- JITLink_EHFrameSupport.h - JITLink eh-frame utils ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// EHFrame registration support for JITLink.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_EXECUTIONENGINE_JITLINK_JITLINK_EHFRAMESUPPORTIMPL_H
+#define LLVM_LIB_EXECUTIONENGINE_JITLINK_JITLINK_EHFRAMESUPPORTIMPL_H
+
+#include "llvm/ExecutionEngine/JITLink/JITLink_EHFrameSupport.h"
+
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+#include "llvm/Support/BinaryStreamReader.h"
+
+namespace llvm {
+namespace jitlink {
+
+/// A generic parser for eh-frame sections.
+///
+/// Adds atoms representing CIE and FDE entries, using the given FDE-to-CIE and
+/// FDEToTarget relocation kinds.
+class EHFrameParser {
+public:
+  EHFrameParser(AtomGraph &G, Section &EHFrameSection, StringRef EHFrameContent,
+                JITTargetAddress EHFrameAddress, Edge::Kind FDEToCIERelocKind,
+                Edge::Kind FDEToTargetRelocKind);
+  Error atomize();
+
+private:
+  struct AugmentationInfo {
+    bool AugmentationDataPresent = false;
+    bool EHDataFieldPresent = false;
+    uint8_t Fields[4] = {0x0, 0x0, 0x0, 0x0};
+  };
+
+  Expected<AugmentationInfo> parseAugmentationString();
+  Expected<JITTargetAddress> readAbsolutePointer();
+  Error processCIE();
+  Error processFDE(JITTargetAddress CIEPointerAddress, uint32_t CIEPointer);
+
+  AtomGraph &G;
+  Section &EHFrameSection;
+  StringRef EHFrameContent;
+  JITTargetAddress EHFrameAddress;
+  BinaryStreamReader EHFrameReader;
+  DefinedAtom *CurRecordAtom = nullptr;
+  DefinedAtom *MostRecentCIE = nullptr;
+  bool LSDAFieldPresent = false;
+  Edge::Kind FDEToCIERelocKind;
+  Edge::Kind FDEToTargetRelocKind;
+};
+
+Error addEHFrame(AtomGraph &G, Section &EHFrameSection,
+                 StringRef EHFrameContent, JITTargetAddress EHFrameAddress,
+                 Edge::Kind FDEToCIERelocKind, Edge::Kind FDEToTargetRelocKind);
+
+} // end namespace jitlink
+} // end namespace llvm
+
+#endif // LLVM_LIB_EXECUTIONENGINE_JITLINK_JITLINK_EHFRAMESUPPORTIMPL_H

lib/ExecutionEngine/JITLink/JITLink_MachO.cpp

@@ -0,0 +1,73 @@
+//===------------ JITLink.cpp - Run-time JIT linker for MachO -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/JITLink/JITLink_MachO.h"
+
+#include "llvm/BinaryFormat/MachO.h"
+#include "llvm/ExecutionEngine/JITLink/JITLink_MachO_x86_64.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/MemoryBuffer.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "jitlink"
+
+namespace llvm {
+namespace jitlink {
+
+void jitLink_MachO(std::unique_ptr<JITLinkContext> Ctx) {
+
+  // We don't want to do full MachO validation here. Just parse enough of the
+  // header to find out what MachO linker to use.
+
+  StringRef Data = Ctx->getObjectBuffer().getBuffer();
+  if (Data.size() < 4) {
+    Ctx->notifyFailed(make_error<JITLinkError>("Truncated MachO buffer"));
+    return;
+  }
+
+  uint32_t Magic;
+  memcpy(&Magic, Data.data(), sizeof(uint32_t));
+  LLVM_DEBUG({
+    dbgs() << "jitLink_MachO: magic = " << format("0x%08" PRIx32, Magic)
+           << "\n";
+  });
+
+  if (Magic == MachO::MH_MAGIC || Magic == MachO::MH_CIGAM) {
+    Ctx->notifyFailed(
+        make_error<JITLinkError>("MachO 32-bit platforms not supported"));
+    return;
+  } else if (Magic == MachO::MH_MAGIC_64 || Magic == MachO::MH_CIGAM_64) {
+    MachO::mach_header_64 Header;
+
+    memcpy(&Header, Data.data(), sizeof(MachO::mach_header_64));
+    if (Magic == MachO::MH_CIGAM_64)
+      swapStruct(Header);
+
+    LLVM_DEBUG({
+      dbgs() << "jitLink_MachO: cputype = "
+             << format("0x%08" PRIx32, Header.cputype)
+             << ", cpusubtype = " << format("0x%08" PRIx32, Header.cpusubtype)
+             << "\n";
+    });
+
+    switch (Header.cputype) {
+    case MachO::CPU_TYPE_X86_64:
+      return jitLink_MachO_x86_64(std::move(Ctx));
+    }
+    Ctx->notifyFailed(make_error<JITLinkError>("MachO-64 CPU type not valid"));
+    return;
+  }
+
+  Ctx->notifyFailed(make_error<JITLinkError>("MachO magic not valid"));
+}
+
+} // end namespace jitlink
+} // end namespace llvm

lib/ExecutionEngine/JITLink/JITLink_MachO_x86_64.cpp

@@ -0,0 +1,621 @@
+//===------- JITLink_MachO_x86_64.cpp - JIT linker functionality ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// MachO jit-link implementation.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/JITLink/JITLink_MachO_x86_64.h"
+
+#include "MachOAtomGraphBuilder.h"
+
+#define DEBUG_TYPE "jitlink"
+
+using namespace llvm;
+using namespace llvm::jitlink;
+using namespace llvm::jitlink::MachO_x86_64_Edges;
+
+namespace {
+
+class MachOAtomGraphBuilder_x86_64 : public MachOAtomGraphBuilder {
+public:
+  MachOAtomGraphBuilder_x86_64(const object::MachOObjectFile &Obj)
+      : MachOAtomGraphBuilder(Obj),
+        NumSymbols(Obj.getSymtabLoadCommand().nsyms) {
+    addCustomAtomizer("__eh_frame", [this](MachOSection &EHFrameSection) {
+      return addEHFrame(getGraph(), EHFrameSection.getGenericSection(),
+                        EHFrameSection.getContent(),
+                        EHFrameSection.getAddress(), NegDelta32, Delta64);
+    });
+  }
+
+private:
+  static Expected<MachOX86RelocationKind>
+  getRelocationKind(const MachO::relocation_info &RI) {
+    switch (RI.r_type) {
+    case MachO::X86_64_RELOC_UNSIGNED:
+      if (!RI.r_pcrel && RI.r_length == 3)
+        return RI.r_extern ? Pointer64 : Pointer64Anon;
+      break;
+    case MachO::X86_64_RELOC_SIGNED:
+      if (RI.r_pcrel && RI.r_length == 2)
+        return RI.r_extern ? PCRel32 : PCRel32Anon;
+      break;
+    case MachO::X86_64_RELOC_BRANCH:
+      if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
+        return Branch32;
+      break;
+    case MachO::X86_64_RELOC_GOT_LOAD:
+      if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
+        return PCRel32GOTLoad;
+      break;
+    case MachO::X86_64_RELOC_GOT:
+      if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
+        return PCRel32GOT;
+      break;
+    case MachO::X86_64_RELOC_SUBTRACTOR:
+      // SUBTRACTOR must be non-pc-rel, extern, with length 2 or 3.
+      // Initially represent SUBTRACTOR relocations with 'Delta<W>'. They may
+      // be turned into NegDelta<W> by parsePairRelocation.
+      if (!RI.r_pcrel && RI.r_extern) {
+        if (RI.r_length == 2)
+          return Delta32;
+        else if (RI.r_length == 3)
+          return Delta64;
+      }
+      break;
+    case MachO::X86_64_RELOC_SIGNED_1:
+      if (RI.r_pcrel && RI.r_length == 2)
+        return RI.r_extern ? PCRel32Minus1 : PCRel32Minus1Anon;
+      break;
+    case MachO::X86_64_RELOC_SIGNED_2:
+      if (RI.r_pcrel && RI.r_length == 2)
+        return RI.r_extern ? PCRel32Minus2 : PCRel32Minus2Anon;
+      break;
+    case MachO::X86_64_RELOC_SIGNED_4:
+      if (RI.r_pcrel && RI.r_length == 2)
+        return RI.r_extern ? PCRel32Minus4 : PCRel32Minus4Anon;
+      break;
+    case MachO::X86_64_RELOC_TLV:
+      if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
+        return PCRel32TLV;
+      break;
+    }
+
+    return make_error<JITLinkError>("Unsupported x86-64 relocation kind");
+  }
+
+  Expected<Atom &> findAtomBySymbolIndex(const MachO::relocation_info &RI) {
+    auto &Obj = getObject();
+    if (RI.r_symbolnum >= NumSymbols)
+      return make_error<JITLinkError>("Symbol index out of range");
+    auto SymI = Obj.getSymbolByIndex(RI.r_symbolnum);
+    auto Name = SymI->getName();
+    if (!Name)
+      return Name.takeError();
+    return getGraph().getAtomByName(*Name);
+  }
+
+  MachO::relocation_info
+  getRelocationInfo(const object::relocation_iterator RelItr) {
+    MachO::any_relocation_info ARI =
+        getObject().getRelocation(RelItr->getRawDataRefImpl());
+    MachO::relocation_info RI;
+    memcpy(&RI, &ARI, sizeof(MachO::relocation_info));
+    return RI;
+  }
+
+  using PairRelocInfo = std::tuple<MachOX86RelocationKind, Atom *, uint64_t>;
+
+  // Parses paired SUBTRACTOR/UNSIGNED relocations and, on success,
+  // returns the edge kind and addend to be used.
+  Expected<PairRelocInfo>
+  parsePairRelocation(DefinedAtom &AtomToFix, Edge::Kind SubtractorKind,
+                      const MachO::relocation_info &SubRI,
+                      JITTargetAddress FixupAddress, const char *FixupContent,
+                      object::relocation_iterator &UnsignedRelItr,
+                      object::relocation_iterator &RelEnd) {
+    using namespace support;
+
+    assert(((SubtractorKind == Delta32 && SubRI.r_length == 2) ||
+            (SubtractorKind == Delta64 && SubRI.r_length == 3)) &&
+           "Subtractor kind should match length");
+    assert(SubRI.r_extern && "SUBTRACTOR reloc symbol should be extern");
+    assert(!SubRI.r_pcrel && "SUBTRACTOR reloc should not be PCRel");
+
+    if (UnsignedRelItr == RelEnd)
+      return make_error<JITLinkError>("x86_64 SUBTRACTOR without paired "
+                                      "UNSIGNED relocation");
+
+    auto UnsignedRI = getRelocationInfo(UnsignedRelItr);
+
+    if (SubRI.r_address != UnsignedRI.r_address)
+      return make_error<JITLinkError>("x86_64 SUBTRACTOR and paired UNSIGNED "
+                                      "point to different addresses");
+
+    if (SubRI.r_length != UnsignedRI.r_length)
+      return make_error<JITLinkError>("length of x86_64 SUBTRACTOR and paired "
+                                      "UNSIGNED reloc must match");
+
+    auto FromAtom = findAtomBySymbolIndex(SubRI);
+    if (!FromAtom)
+      return FromAtom.takeError();
+
+    // Read the current fixup value.
+    uint64_t FixupValue = 0;
+    if (SubRI.r_length == 3)
+      FixupValue = *(const ulittle64_t *)FixupContent;
+    else
+      FixupValue = *(const ulittle32_t *)FixupContent;
+
+    // Find 'ToAtom' using symbol number or address, depending on whether the
+    // paired UNSIGNED relocation is extern.
+    Atom *ToAtom = nullptr;
+    if (UnsignedRI.r_extern) {
+      // Find target atom by symbol index.
+      if (auto ToAtomOrErr = findAtomBySymbolIndex(UnsignedRI))
+        ToAtom = &*ToAtomOrErr;
+      else
+        return ToAtomOrErr.takeError();
+    } else {
+      if (auto ToAtomOrErr = getGraph().findAtomByAddress(FixupValue))
+        ToAtom = &*ToAtomOrErr;
+      else
+        return ToAtomOrErr.takeError();
+      FixupValue -= ToAtom->getAddress();
+    }
+
+    MachOX86RelocationKind DeltaKind;
+    Atom *TargetAtom;
+    uint64_t Addend;
+    if (&AtomToFix == &*FromAtom) {
+      TargetAtom = ToAtom;
+      DeltaKind = (SubRI.r_length == 3) ? Delta64 : Delta32;
+      Addend = FixupValue + (FixupAddress - FromAtom->getAddress());
+      // FIXME: handle extern 'from'.
+    } else if (&AtomToFix == ToAtom) {
+      TargetAtom = &*FromAtom;
+      DeltaKind = (SubRI.r_length == 3) ? NegDelta64 : NegDelta32;
+      Addend = FixupValue - (FixupAddress - ToAtom->getAddress());
+    } else {
+      // AtomToFix was neither FromAtom nor ToAtom.
+      return make_error<JITLinkError>("SUBTRACTOR relocation must fix up "
+                                      "either 'A' or 'B'");
+    }
+
+    return PairRelocInfo(DeltaKind, TargetAtom, Addend);
+  }
+
+  Error addRelocations() override {
+    using namespace support;
+    auto &G = getGraph();
+    auto &Obj = getObject();
+
+    for (auto &S : Obj.sections()) {
+
+      JITTargetAddress SectionAddress = S.getAddress();
+
+      for (auto RelItr = S.relocation_begin(), RelEnd = S.relocation_end();
+           RelItr != RelEnd; ++RelItr) {
+
+        MachO::relocation_info RI = getRelocationInfo(RelItr);
+
+        // Sanity check the relocation kind.
+        auto Kind = getRelocationKind(RI);
+        if (!Kind)
+          return Kind.takeError();
+
+        // Find the address of the value to fix up.
+        JITTargetAddress FixupAddress = SectionAddress + (uint32_t)RI.r_address;
+
+        LLVM_DEBUG({
+          dbgs() << "Processing relocation at "
+                 << format("0x%016" PRIx64, FixupAddress) << "\n";
+        });
+
+        // Find the atom that the fixup points to.
+        DefinedAtom *AtomToFix = nullptr;
+        {
+          auto AtomToFixOrErr = G.findAtomByAddress(FixupAddress);
+          if (!AtomToFixOrErr)
+            return AtomToFixOrErr.takeError();
+          AtomToFix = &*AtomToFixOrErr;
+        }
+
+        if (FixupAddress + (1 << RI.r_length) >
+            AtomToFix->getAddress() + AtomToFix->getContent().size())
+          return make_error<JITLinkError>(
+              "Relocation content extends past end of fixup atom");
+
+        // Get a pointer to the fixup content.
+        const char *FixupContent = AtomToFix->getContent().data() +
+                                   (FixupAddress - AtomToFix->getAddress());
+
+        // The target atom and addend will be populated by the switch below.
+        Atom *TargetAtom = nullptr;
+        uint64_t Addend = 0;
+
+        switch (*Kind) {
+        case Branch32:
+        case PCRel32:
+        case PCRel32GOTLoad:
+        case PCRel32GOT:
+          if (auto TargetAtomOrErr = findAtomBySymbolIndex(RI))
+            TargetAtom = &*TargetAtomOrErr;
+          else
+            return TargetAtomOrErr.takeError();
+          Addend = *(const ulittle32_t *)FixupContent;
+          break;
+        case Pointer64:
+          if (auto TargetAtomOrErr = findAtomBySymbolIndex(RI))
+            TargetAtom = &*TargetAtomOrErr;
+          else
+            return TargetAtomOrErr.takeError();
+          Addend = *(const ulittle64_t *)FixupContent;
+          break;
+        case Pointer64Anon: {
+          JITTargetAddress TargetAddress = *(const ulittle64_t *)FixupContent;
+          if (auto TargetAtomOrErr = G.findAtomByAddress(TargetAddress))
+            TargetAtom = &*TargetAtomOrErr;
+          else
+            return TargetAtomOrErr.takeError();
+          Addend = TargetAddress - TargetAtom->getAddress();
+          break;
+        }
+        case PCRel32Minus1:
+        case PCRel32Minus2:
+        case PCRel32Minus4:
+          if (auto TargetAtomOrErr = findAtomBySymbolIndex(RI))
+            TargetAtom = &*TargetAtomOrErr;
+          else
+            return TargetAtomOrErr.takeError();
+          Addend = *(const ulittle32_t *)FixupContent +
+                   (1 << (*Kind - PCRel32Minus1));
+          break;
+        case PCRel32Anon: {
+          JITTargetAddress TargetAddress =
+              FixupAddress + 4 + *(const ulittle32_t *)FixupContent;
+          if (auto TargetAtomOrErr = G.findAtomByAddress(TargetAddress))
+            TargetAtom = &*TargetAtomOrErr;
+          else
+            return TargetAtomOrErr.takeError();
+          Addend = TargetAddress - TargetAtom->getAddress();
+          break;
+        }
+        case PCRel32Minus1Anon:
+        case PCRel32Minus2Anon:
+        case PCRel32Minus4Anon: {
+          JITTargetAddress Delta = 1 << (*Kind - PCRel32Minus1Anon);
+          JITTargetAddress TargetAddress =
+              FixupAddress + 4 + Delta + *(const ulittle32_t *)FixupContent;
+          if (auto TargetAtomOrErr = G.findAtomByAddress(TargetAddress))
+            TargetAtom = &*TargetAtomOrErr;
+          else
+            return TargetAtomOrErr.takeError();
+          Addend = TargetAddress - TargetAtom->getAddress();
+          break;
+        }
+        case Delta32:
+        case Delta64: {
+          // We use Delta32/Delta64 to represent SUBTRACTOR relocations.
+          // parsePairRelocation handles the paired reloc, and returns the
+          // edge kind to be used (either Delta32/Delta64, or
+          // NegDelta32/NegDelta64, depending on the direction of the
+          // subtraction) along with the addend.
+          auto PairInfo =
+              parsePairRelocation(*AtomToFix, *Kind, RI, FixupAddress,
+                                  FixupContent, ++RelItr, RelEnd);
+          if (!PairInfo)
+            return PairInfo.takeError();
+          std::tie(*Kind, TargetAtom, Addend) = *PairInfo;
+          assert(TargetAtom && "No target atom from parsePairRelocation?");
+          break;
+        }
+        default:
+          llvm_unreachable("Special relocation kind should not appear in "
+                           "mach-o file");
+        }
+
+        LLVM_DEBUG({
+          Edge GE(*Kind, FixupAddress - AtomToFix->getAddress(), *TargetAtom,
+                  Addend);
+          printEdge(dbgs(), *AtomToFix, GE,
+                    getMachOX86RelocationKindName(*Kind));
+          dbgs() << "\n";
+        });
+        AtomToFix->addEdge(*Kind, FixupAddress - AtomToFix->getAddress(),
+                           *TargetAtom, Addend);
+      }
+    }
+    return Error::success();
+  }
+
+  unsigned NumSymbols = 0;
+};
+
+class MachOInPlaceGOTAndStubsBuilder {
+public:
+  MachOInPlaceGOTAndStubsBuilder(AtomGraph &G) : G(G) {}
+
+  void run() {
+    // We're going to be adding new atoms, but we don't want to iterate over
+    // the newly added ones, so just copy the existing atoms out.
+    std::vector<DefinedAtom *> DAs(G.defined_atoms().begin(),
+                                   G.defined_atoms().end());
+
+    for (auto *DA : DAs)
+      for (auto &E : DA->edges())
+        if (E.getKind() == PCRel32GOT || E.getKind() == PCRel32GOTLoad)
+          fixGOTEdge(E);
+        else if (E.getKind() == Branch32 && !E.getTarget().isDefined())
+          fixExternalBranchEdge(E);
+  }
+
+  Atom &getGOTEntryAtom(Atom &Target) {
+    assert(!Target.getName().empty() &&
+           "GOT load edge cannot point to anonymous target");
+
+    auto GOTEntryI = GOTEntries.find(Target.getName());
+
+    // Build the entry if it doesn't exist.
+    if (GOTEntryI == GOTEntries.end()) {
+      // Build a GOT section if we don't have one already.
+      if (!GOTSection)
+        GOTSection = &G.createSection("$__GOT", sys::Memory::MF_READ, false);
+
+      auto &GOTEntryAtom = G.addAnonymousAtom(*GOTSection, 0x0, 8);
+      GOTEntryAtom.setContent(
+          StringRef(reinterpret_cast<const char *>(NullGOTEntryContent), 8));
+      GOTEntryAtom.addEdge(Pointer64, 0, Target, 0);
+      GOTEntryI =
+          GOTEntries.insert(std::make_pair(Target.getName(), &GOTEntryAtom))
+              .first;
+    }
+
+    assert(GOTEntryI != GOTEntries.end() && "Could not get GOT entry atom");
+    return *GOTEntryI->second;
+  }
+
+  void fixGOTEdge(Edge &E) {
+    assert((E.getKind() == PCRel32GOT || E.getKind() == PCRel32GOTLoad) &&
+           "Not a GOT edge?");
+    auto &GOTEntryAtom = getGOTEntryAtom(E.getTarget());
+    E.setKind(PCRel32);
+    E.setTarget(GOTEntryAtom);
+    // Leave the edge addend as-is.
+  }
+
+  Atom &getStubAtom(Atom &Target) {
+    assert(!Target.getName().empty() &&
+           "Branch edge can not point to an anonymous target");
+    auto StubI = Stubs.find(Target.getName());
+
+    if (StubI == Stubs.end()) {
+      // Build a Stubs section if we don't have one already.
+      if (!StubsSection) {
+        auto StubsProt = static_cast<sys::Memory::ProtectionFlags>(
+            sys::Memory::MF_READ | sys::Memory::MF_EXEC);
+        StubsSection = &G.createSection("$__STUBS", StubsProt, false);
+      }
+
+      auto &StubAtom = G.addAnonymousAtom(*StubsSection, 0x0, 2);
+      StubAtom.setContent(
+          StringRef(reinterpret_cast<const char *>(StubContent), 6));
+
+      // Re-use GOT entries for stub targets.
+      auto &GOTEntryAtom = getGOTEntryAtom(Target);
+      StubAtom.addEdge(PCRel32, 2, GOTEntryAtom, 0);
+
+      StubI = Stubs.insert(std::make_pair(Target.getName(), &StubAtom)).first;
+    }
+
+    assert(StubI != Stubs.end() && "Count not get stub atom");
+    return *StubI->second;
+  }
+
+  void fixExternalBranchEdge(Edge &E) {
+    assert(E.getKind() == Branch32 && "Not a Branch32 edge?");
+    assert(E.getAddend() == 0 && "Branch32 edge has non-zero addend?");
+    E.setTarget(getStubAtom(E.getTarget()));
+  }
+
+  AtomGraph &G;
+  DenseMap<StringRef, DefinedAtom *> GOTEntries;
+  DenseMap<StringRef, DefinedAtom *> Stubs;
+  static const uint8_t NullGOTEntryContent[8];
+  static const uint8_t StubContent[6];
+  Section *GOTSection = nullptr;
+  Section *StubsSection = nullptr;
+};
+
+const uint8_t MachOInPlaceGOTAndStubsBuilder::NullGOTEntryContent[8] = {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+const uint8_t MachOInPlaceGOTAndStubsBuilder::StubContent[6] = {
+    0xFF, 0x25, 0x00, 0x00, 0x00, 0x00};
+} // namespace
+
+namespace llvm {
+namespace jitlink {
+
+class MachOJITLinker_x86_64 : public JITLinker<MachOJITLinker_x86_64> {
+  friend class JITLinker<MachOJITLinker_x86_64>;
+
+public:
+  MachOJITLinker_x86_64(std::unique_ptr<JITLinkContext> Ctx,
+                        PassConfiguration PassConfig)
+      : JITLinker(std::move(Ctx), std::move(PassConfig)) {}
+
+private:
+  StringRef getEdgeKindName(Edge::Kind R) const override {
+    return getMachOX86RelocationKindName(R);
+  }
+
+  Expected<std::unique_ptr<AtomGraph>>
+  buildGraph(MemoryBufferRef ObjBuffer) override {
+    auto MachOObj = object::ObjectFile::createMachOObjectFile(ObjBuffer);
+    if (!MachOObj)
+      return MachOObj.takeError();
+    return MachOAtomGraphBuilder_x86_64(**MachOObj).buildGraph();
+  }
+
+  static Error targetOutOfRangeError(const Edge &E) {
+    std::string ErrMsg;
+    {
+      raw_string_ostream ErrStream(ErrMsg);
+      ErrStream << "Target \"" << E.getTarget() << "\" out of range";
+    }
+    return make_error<JITLinkError>(std::move(ErrMsg));
+  }
+
+  Error applyFixup(DefinedAtom &A, const Edge &E, char *AtomWorkingMem) const {
+    using namespace support;
+
+    char *FixupPtr = AtomWorkingMem + E.getOffset();
+    JITTargetAddress FixupAddress = A.getAddress() + E.getOffset();
+
+    switch (E.getKind()) {
+    case Branch32:
+    case PCRel32:
+    case PCRel32Anon: {
+      int64_t Value =
+          E.getTarget().getAddress() - (FixupAddress + 4) + E.getAddend();
+      if (Value < std::numeric_limits<int32_t>::min() ||
+          Value > std::numeric_limits<int32_t>::max())
+        return targetOutOfRangeError(E);
+      *(little32_t *)FixupPtr = Value;
+      break;
+    }
+    case Pointer64:
+    case Pointer64Anon: {
+      uint64_t Value = E.getTarget().getAddress() + E.getAddend();
+      *(ulittle64_t *)FixupPtr = Value;
+      break;
+    }
+    case PCRel32Minus1:
+    case PCRel32Minus2:
+    case PCRel32Minus4: {
+      int Delta = 4 + (1 << (E.getKind() - PCRel32Minus1));
+      int64_t Value =
+          E.getTarget().getAddress() - (FixupAddress + Delta) + E.getAddend();
+      if (Value < std::numeric_limits<int32_t>::min() ||
+          Value > std::numeric_limits<int32_t>::max())
+        return targetOutOfRangeError(E);
+      *(little32_t *)FixupPtr = Value;
+      break;
+    }
+    case PCRel32Minus1Anon:
+    case PCRel32Minus2Anon:
+    case PCRel32Minus4Anon: {
+      int Delta = 4 + (1 << (E.getKind() - PCRel32Minus1Anon));
+      int64_t Value =
+          E.getTarget().getAddress() - (FixupAddress + Delta) + E.getAddend();
+      if (Value < std::numeric_limits<int32_t>::min() ||
+          Value > std::numeric_limits<int32_t>::max())
+        return targetOutOfRangeError(E);
+      *(little32_t *)FixupPtr = Value;
+      break;
+    }
+    case Delta32:
+    case Delta64:
+    case NegDelta32:
+    case NegDelta64: {
+      int64_t Value;
+      if (E.getKind() == Delta32 || E.getKind() == Delta64)
+        Value = E.getTarget().getAddress() - FixupAddress + E.getAddend();
+      else
+        Value = FixupAddress - E.getTarget().getAddress() + E.getAddend();
+
+      if (E.getKind() == Delta32 || E.getKind() == NegDelta32) {
+        if (Value < std::numeric_limits<int32_t>::min() ||
+            Value > std::numeric_limits<int32_t>::max())
+          return targetOutOfRangeError(E);
+        *(little32_t *)FixupPtr = Value;
+      } else
+        *(little64_t *)FixupPtr = Value;
+      break;
+    }
+    default:
+      llvm_unreachable("Unrecognized edge kind");
+    }
+
+    return Error::success();
+  }
+
+  uint64_t NullValue = 0;
+};
+
+void jitLink_MachO_x86_64(std::unique_ptr<JITLinkContext> Ctx) {
+  PassConfiguration Config;
+  Triple TT("x86_64-apple-macosx");
+
+  if (Ctx->shouldAddDefaultTargetPasses(TT)) {
+    // Add a mark-live pass.
+    if (auto MarkLive = Ctx->getMarkLivePass(TT))
+      Config.PrePrunePasses.push_back(std::move(MarkLive));
+    else
+      Config.PrePrunePasses.push_back(markAllAtomsLive);
+
+    // Add an in-place GOT/Stubs pass.
+    Config.PostPrunePasses.push_back([](AtomGraph &G) -> Error {
+      MachOInPlaceGOTAndStubsBuilder(G).run();
+      return Error::success();
+    });
+  }
+
+  if (auto Err = Ctx->modifyPassConfig(TT, Config))
+    return Ctx->notifyFailed(std::move(Err));
+
+  // Construct a JITLinker and run the link function.
+  MachOJITLinker_x86_64::link(std::move(Ctx), std::move(Config));
+}
+
+StringRef getMachOX86RelocationKindName(Edge::Kind R) {
+  switch (R) {
+  case Branch32:
+    return "Branch32";
+  case Pointer64:
+    return "Pointer64";
+  case Pointer64Anon:
+    return "Pointer64Anon";
+  case PCRel32:
+    return "PCRel32";
+  case PCRel32Minus1:
+    return "PCRel32Minus1";
+  case PCRel32Minus2:
+    return "PCRel32Minus2";
+  case PCRel32Minus4:
+    return "PCRel32Minus4";
+  case PCRel32Anon:
+    return "PCRel32Anon";
+  case PCRel32Minus1Anon:
+    return "PCRel32Minus1Anon";
+  case PCRel32Minus2Anon:
+    return "PCRel32Minus2Anon";
+  case PCRel32Minus4Anon:
+    return "PCRel32Minus4Anon";
+  case PCRel32GOTLoad:
+    return "PCRel32GOTLoad";
+  case PCRel32GOT:
+    return "PCRel32GOT";
+  case PCRel32TLV:
+    return "PCRel32TLV";
+  case Delta32:
+    return "Delta32";
+  case Delta64:
+    return "Delta64";
+  case NegDelta32:
+    return "NegDelta32";
+  case NegDelta64:
+    return "NegDelta64";
+  default:
+    return getGenericEdgeKindName(static_cast<Edge::Kind>(R));
+  }
+}
+
+} // end namespace jitlink
+} // end namespace llvm

lib/ExecutionEngine/JITLink/LLVMBuild.txt

@@ -0,0 +1,21 @@
+;===----- ./lib/ExecutionEngine/JTILink/LLVMBuild.txt ----------*- Conf -*--===;
+;
+; Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+; See https://llvm.org/LICENSE.txt for license information.
+; SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+;
+;===------------------------------------------------------------------------===;
+;
+; This is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+;   http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[component_0]
+type = Library
+name = JITLink
+parent = ExecutionEngine
+required_libraries = Object Support

lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.cpp

@@ -0,0 +1,289 @@
+//=--------- MachOAtomGraphBuilder.cpp - MachO AtomGraph builder ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic MachO AtomGraph buliding code.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MachOAtomGraphBuilder.h"
+
+#define DEBUG_TYPE "jitlink"
+
+namespace llvm {
+namespace jitlink {
+
+MachOAtomGraphBuilder::~MachOAtomGraphBuilder() {}
+
+Expected<std::unique_ptr<AtomGraph>> MachOAtomGraphBuilder::buildGraph() {
+  if (auto Err = parseSections())
+    return std::move(Err);
+
+  if (auto Err = addAtoms())
+    return std::move(Err);
+
+  if (auto Err = addRelocations())
+    return std::move(Err);
+
+  return std::move(G);
+}
+
+MachOAtomGraphBuilder::MachOAtomGraphBuilder(const object::MachOObjectFile &Obj)
+    : Obj(Obj),
+      G(llvm::make_unique<AtomGraph>(Obj.getFileName(), getPointerSize(Obj),
+                                     getEndianness(Obj))) {}
+
+void MachOAtomGraphBuilder::addCustomAtomizer(StringRef SectionName,
+                                              CustomAtomizeFunction Atomizer) {
+  assert(!CustomAtomizeFunctions.count(SectionName) &&
+         "Custom atomizer for this section already exists");
+  CustomAtomizeFunctions[SectionName] = std::move(Atomizer);
+}
+
+unsigned
+MachOAtomGraphBuilder::getPointerSize(const object::MachOObjectFile &Obj) {
+  return Obj.is64Bit() ? 8 : 4;
+}
+
+support::endianness
+MachOAtomGraphBuilder::getEndianness(const object::MachOObjectFile &Obj) {
+  return Obj.isLittleEndian() ? support::little : support::big;
+}
+
+MachOAtomGraphBuilder::MachOSection &MachOAtomGraphBuilder::getCommonSection() {
+  if (!CommonSymbolsSection) {
+    auto Prot = static_cast<sys::Memory::ProtectionFlags>(
+        sys::Memory::MF_READ | sys::Memory::MF_WRITE);
+    auto &GenericSection = G->createSection("<common>", Prot, true);
+    CommonSymbolsSection = MachOSection(GenericSection);
+  }
+  return *CommonSymbolsSection;
+}
+
+Error MachOAtomGraphBuilder::parseSections() {
+  for (auto &SecRef : Obj.sections()) {
+    assert((SecRef.getAlignment() <= std::numeric_limits<uint32_t>::max()) &&
+           "Section alignment does not fit in 32 bits");
+
+    StringRef Name;
+    if (auto EC = SecRef.getName(Name))
+      return errorCodeToError(EC);
+
+    StringRef Content;
+
+    // If this is a virtual section, leave its content empty.
+    if (!SecRef.isVirtual()) {
+      if (auto EC = SecRef.getContents(Content))
+        return errorCodeToError(EC);
+      if (Content.size() != SecRef.getSize())
+        return make_error<JITLinkError>("Section content size does not match "
+                                        "declared size for " +
+                                        Name);
+    }
+
+    unsigned SectionIndex = SecRef.getIndex() + 1;
+
+    LLVM_DEBUG({
+      dbgs() << "Adding section " << Name << ": "
+             << format("0x%016" PRIx64, SecRef.getAddress())
+             << ", size: " << Content.size()
+             << ", align: " << SecRef.getAlignment() << "\n";
+    });
+
+    // FIXME: Get real section permissions
+    // How, exactly, on MachO?
+    sys::Memory::ProtectionFlags Prot;
+    if (SecRef.isText())
+      Prot = static_cast<sys::Memory::ProtectionFlags>(sys::Memory::MF_READ |
+                                                       sys::Memory::MF_EXEC);
+    else
+      Prot = static_cast<sys::Memory::ProtectionFlags>(sys::Memory::MF_READ |
+                                                       sys::Memory::MF_WRITE);
+
+    auto &GenericSection = G->createSection(Name, Prot, SecRef.isBSS());
+    if (SecRef.isVirtual())
+      Sections[SectionIndex] =
+          MachOSection(GenericSection, SecRef.getAddress(),
+                       SecRef.getAlignment(), SecRef.getSize());
+    Sections[SectionIndex] = MachOSection(GenericSection, SecRef.getAddress(),
+                                          SecRef.getAlignment(), Content);
+  }
+
+  return Error::success();
+}
+
+// Adds atoms with identified start addresses (but not lengths) for all named
+// atoms.
+// Also, for every section that contains named atoms, but does not have an
+// atom at offset zero of that section, constructs an anonymous atom covering
+// that range.
+Error MachOAtomGraphBuilder::addNonCustomAtoms() {
+  using AddrToAtomMap = std::map<JITTargetAddress, DefinedAtom *>;
+  DenseMap<MachOSection *, AddrToAtomMap> SecToAtoms;
+
+  DenseMap<MachOSection *, unsigned> FirstOrdinal;
+
+  for (auto SymI = Obj.symbol_begin(), SymE = Obj.symbol_end(); SymI != SymE;
+       ++SymI) {
+    object::SymbolRef Sym(SymI->getRawDataRefImpl(), &Obj);
+
+    auto Name = Sym.getName();
+    if (!Name)
+      return Name.takeError();
+
+    auto Addr = Sym.getAddress();
+    if (!Addr)
+      return Addr.takeError();
+
+    auto SymType = Sym.getType();
+    if (!SymType)
+      return SymType.takeError();
+
+    auto Flags = Sym.getFlags();
+
+    if (Flags & object::SymbolRef::SF_Undefined) {
+      LLVM_DEBUG(dbgs() << "Adding undef atom \"" << *Name << "\"\n");
+      G->addExternalAtom(*Name);
+      continue;
+    } else if (Flags & object::SymbolRef::SF_Absolute) {
+      LLVM_DEBUG(dbgs() << "Adding absolute \"" << *Name << "\" addr: "
+                        << format("0x%016" PRIx64, *Addr) << "\n");
+      auto &A = G->addAbsoluteAtom(*Name, *Addr);
+      A.setGlobal(Flags & object::SymbolRef::SF_Global);
+      A.setExported(Flags & object::SymbolRef::SF_Exported);
+      A.setWeak(Flags & object::SymbolRef::SF_Weak);
+      continue;
+    } else if (Flags & object::SymbolRef::SF_Common) {
+      LLVM_DEBUG({
+        dbgs() << "Adding common \"" << *Name
+               << "\" addr: " << format("0x%016" PRIx64, *Addr) << "\n";
+      });
+      auto &A =
+          G->addCommonAtom(getCommonSection().getGenericSection(), *Name, *Addr,
+                           std::max(Sym.getAlignment(), 1U),
+                           Obj.getCommonSymbolSize(Sym.getRawDataRefImpl()));
+      A.setGlobal(Flags & object::SymbolRef::SF_Global);
+      A.setExported(Flags & object::SymbolRef::SF_Exported);
+      continue;
+    }
+
+    LLVM_DEBUG(dbgs() << "Adding defined atom \"" << *Name << "\"\n");
+
+    // This atom is neither undefined nor absolute, so it must be defined in
+    // this object. Get its section index.
+    auto SecItr = Sym.getSection();
+    if (!SecItr)
+      return SecItr.takeError();
+
+    uint64_t SectionIndex = (*SecItr)->getIndex() + 1;
+
+    LLVM_DEBUG(dbgs() << "  to section index " << SectionIndex << "\n");
+
+    auto SecByIndexItr = Sections.find(SectionIndex);
+    if (SecByIndexItr == Sections.end())
+      return make_error<JITLinkError>("Unrecognized section index in macho");
+
+    auto &Sec = SecByIndexItr->second;
+
+    auto &A = G->addDefinedAtom(Sec.getGenericSection(), *Name, *Addr,
+                                std::max(Sym.getAlignment(), 1U));
+
+    A.setGlobal(Flags & object::SymbolRef::SF_Global);
+    A.setExported(Flags & object::SymbolRef::SF_Exported);
+    A.setWeak(Flags & object::SymbolRef::SF_Weak);
+
+    A.setCallable(*SymType & object::SymbolRef::ST_Function);
+
+    LLVM_DEBUG({
+      dbgs() << "  Added " << *Name
+             << " addr: " << format("0x%016" PRIx64, *Addr)
+             << ", align: " << A.getAlignment()
+             << ", section: " << Sec.getGenericSection().getName() << "\n";
+    });
+
+    auto &SecAtoms = SecToAtoms[&Sec];
+    SecAtoms[A.getAddress() - Sec.getAddress()] = &A;
+  }
+
+  // Add anonymous atoms.
+  for (auto &KV : Sections) {
+    auto &S = KV.second;
+
+    // Skip empty sections.
+    if (S.empty())
+      continue;
+
+    // Skip sections with custom handling.
+    if (CustomAtomizeFunctions.count(S.getName()))
+      continue;
+
+    auto SAI = SecToAtoms.find(&S);
+
+    // If S is not in the SecToAtoms map then it contained no named atom. Add
+    // one anonymous atom to cover the whole section.
+    if (SAI == SecToAtoms.end()) {
+      SecToAtoms[&S][0] = &G->addAnonymousAtom(
+          S.getGenericSection(), S.getAddress(), S.getAlignment());
+      continue;
+    }
+
+    // Otherwise, check whether this section had an atom covering offset zero.
+    // If not, add one.
+    auto &SecAtoms = SAI->second;
+    if (!SecAtoms.count(0))
+      SecAtoms[0] = &G->addAnonymousAtom(S.getGenericSection(), S.getAddress(),
+                                         S.getAlignment());
+  }
+
+  LLVM_DEBUG(dbgs() << "MachOGraphBuilder setting atom content\n");
+
+  // Set atom contents.
+  for (auto &KV : SecToAtoms) {
+    auto &S = *KV.first;
+    auto &SecAtoms = KV.second;
+
+    // Iterate the atoms in reverse order and set up their contents.
+    JITTargetAddress LastAtomAddr = S.getSize();
+    for (auto I = SecAtoms.rbegin(), E = SecAtoms.rend(); I != E; ++I) {
+      auto Offset = I->first;
+      auto &A = *I->second;
+      LLVM_DEBUG({
+        dbgs() << "  " << A << " to [ " << S.getAddress() + Offset << " .. "
+               << S.getAddress() + LastAtomAddr << " ]\n";
+      });
+      if (S.isZeroFill())
+        A.setZeroFill(LastAtomAddr - Offset);
+      else
+        A.setContent(S.getContent().substr(Offset, LastAtomAddr - Offset));
+      LastAtomAddr = Offset;
+    }
+  }
+
+  return Error::success();
+}
+
+Error MachOAtomGraphBuilder::addAtoms() {
+  // Add all named atoms.
+  if (auto Err = addNonCustomAtoms())
+    return Err;
+
+  // Process special sections.
+  for (auto &KV : Sections) {
+    auto &S = KV.second;
+    auto HI = CustomAtomizeFunctions.find(S.getGenericSection().getName());
+    if (HI != CustomAtomizeFunctions.end()) {
+      auto &Atomize = HI->second;
+      if (auto Err = Atomize(S))
+        return Err;
+    }
+  }
+
+  return Error::success();
+}
+
+} // end namespace jitlink
+} // end namespace llvm

lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.h

@@ -0,0 +1,119 @@
+//===----- MachOAtomGraphBuilder.h - MachO AtomGraph builder ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic MachO AtomGraph building code.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LIB_EXECUTIONENGINE_JITLINK_MACHOATOMGRAPHBUILDER_H
+#define LIB_EXECUTIONENGINE_JITLINK_MACHOATOMGRAPHBUILDER_H
+
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+
+#include "JITLinkGeneric.h"
+
+#include "llvm/Object/MachO.h"
+
+namespace llvm {
+namespace jitlink {
+
+class MachOAtomGraphBuilder {
+public:
+  virtual ~MachOAtomGraphBuilder();
+  Expected<std::unique_ptr<AtomGraph>> buildGraph();
+
+protected:
+  using OffsetToAtomMap = std::map<JITTargetAddress, DefinedAtom *>;
+
+  class MachOSection {
+  public:
+    MachOSection() = default;
+
+    /// Create a MachO section with the given content.
+    MachOSection(Section &GenericSection, JITTargetAddress Address,
+                 unsigned Alignment, StringRef Content)
+        : Address(Address), GenericSection(&GenericSection),
+          ContentPtr(Content.data()), Size(Content.size()),
+          Alignment(Alignment) {}
+
+    /// Create a zero-fill MachO section with the given size.
+    MachOSection(Section &GenericSection, JITTargetAddress Address,
+                 unsigned Alignment, size_t ZeroFillSize)
+        : Address(Address), GenericSection(&GenericSection), Size(ZeroFillSize),
+          Alignment(Alignment) {}
+
+    /// Create a section without address, content or size (used for common
+    /// symbol sections).
+    MachOSection(Section &GenericSection) : GenericSection(&GenericSection) {}
+
+    Section &getGenericSection() const {
+      assert(GenericSection && "Section is null");
+      return *GenericSection;
+    }
+
+    StringRef getName() const {
+      assert(GenericSection && "No generic section attached");
+      return GenericSection->getName();
+    }
+
+    bool isZeroFill() const { return !ContentPtr; }
+
+    bool empty() const { return getSize() == 0; }
+
+    size_t getSize() const { return Size; }
+
+    StringRef getContent() const {
+      assert(ContentPtr && "getContent() called on zero-fill section");
+      return {ContentPtr, Size};
+    }
+
+    JITTargetAddress getAddress() const { return Address; }
+
+    unsigned getAlignment() const { return Alignment; }
+
+  private:
+    JITTargetAddress Address = 0;
+    Section *GenericSection = nullptr;
+    const char *ContentPtr = nullptr;
+    size_t Size = 0;
+    unsigned Alignment = 0;
+  };
+
+  using CustomAtomizeFunction = std::function<Error(MachOSection &S)>;
+
+  MachOAtomGraphBuilder(const object::MachOObjectFile &Obj);
+
+  AtomGraph &getGraph() const { return *G; }
+
+  const object::MachOObjectFile &getObject() const { return Obj; }
+
+  void addCustomAtomizer(StringRef SectionName, CustomAtomizeFunction Atomizer);
+
+  virtual Error addRelocations() = 0;
+
+private:
+  static unsigned getPointerSize(const object::MachOObjectFile &Obj);
+  static support::endianness getEndianness(const object::MachOObjectFile &Obj);
+
+  MachOSection &getCommonSection();
+
+  Error parseSections();
+  Error addNonCustomAtoms();
+  Error addAtoms();
+
+  const object::MachOObjectFile &Obj;
+  std::unique_ptr<AtomGraph> G;
+  DenseMap<unsigned, MachOSection> Sections;
+  StringMap<CustomAtomizeFunction> CustomAtomizeFunctions;
+  Optional<MachOSection> CommonSymbolsSection;
+};
+
+} // end namespace jitlink
+} // end namespace llvm
+
+#endif // LIB_EXECUTIONENGINE_JITLINK_MACHOATOMGRAPHBUILDER_H

lib/ExecutionEngine/LLVMBuild.txt

@@ -15,7 +15,8 @@
 ;===------------------------------------------------------------------------===;
 
 [common]
-subdirectories = Interpreter MCJIT RuntimeDyld IntelJITEvents OProfileJIT Orc PerfJITEvents
+subdirectories = Interpreter MCJIT JITLink RuntimeDyld IntelJITEvents
+                 OProfileJIT Orc PerfJITEvents
 
 [component_0]
 type = Library

lib/ExecutionEngine/Orc/CMakeLists.txt

@@ -11,6 +11,7 @@ add_llvm_library(LLVMOrcJIT
   Layer.cpp
   LLJIT.cpp
   NullResolver.cpp
+  ObjectLinkingLayer.cpp
   ObjectTransformLayer.cpp
   OrcABISupport.cpp
   OrcCBindings.cpp

lib/ExecutionEngine/Orc/Core.cpp

@@ -26,17 +26,17 @@ namespace {
 
 #ifndef NDEBUG
 
-cl::opt<bool> PrintHidden("debug-orc-print-hidden", cl::init(false),
+cl::opt<bool> PrintHidden("debug-orc-print-hidden", cl::init(true),
                           cl::desc("debug print hidden symbols defined by "
                                    "materialization units"),
                           cl::Hidden);
 
-cl::opt<bool> PrintCallable("debug-orc-print-callable", cl::init(false),
+cl::opt<bool> PrintCallable("debug-orc-print-callable", cl::init(true),
                             cl::desc("debug print callable symbols defined by "
                                      "materialization units"),
                             cl::Hidden);
 
-cl::opt<bool> PrintData("debug-orc-print-data", cl::init(false),
+cl::opt<bool> PrintData("debug-orc-print-data", cl::init(true),
                         cl::desc("debug print data symbols defined by "
                                  "materialization units"),
                         cl::Hidden);
@@ -1051,9 +1051,11 @@ void JITDylib::notifyFailed(const SymbolNameSet &FailedSymbols) {
 void JITDylib::setSearchOrder(JITDylibSearchList NewSearchOrder,
                               bool SearchThisJITDylibFirst,
                               bool MatchNonExportedInThisDylib) {
-  if (SearchThisJITDylibFirst && NewSearchOrder.front().first != this)
-    NewSearchOrder.insert(NewSearchOrder.begin(),
-                          {this, MatchNonExportedInThisDylib});
+  if (SearchThisJITDylibFirst) {
+    if (NewSearchOrder.empty() || NewSearchOrder.front().first != this)
+      NewSearchOrder.insert(NewSearchOrder.begin(),
+                            {this, MatchNonExportedInThisDylib});
+  }
 
   ES.runSessionLocked([&]() { SearchOrder = std::move(NewSearchOrder); });
 }
@@ -1450,77 +1452,55 @@ JITDylib::JITDylib(ExecutionSession &ES, std::string Name)
 
 Error JITDylib::defineImpl(MaterializationUnit &MU) {
   SymbolNameSet Duplicates;
-  SymbolNameSet MUDefsOverridden;
+  std::vector<SymbolStringPtr> ExistingDefsOverridden;
+  std::vector<SymbolStringPtr> MUDefsOverridden;
 
-  struct ExistingDefOverriddenEntry {
-    SymbolMap::iterator ExistingDefItr;
-    JITSymbolFlags NewFlags;
-  };
-  std::vector<ExistingDefOverriddenEntry> ExistingDefsOverridden;
-
-  for (auto &KV : MU.getSymbols()) {
+  for (const auto &KV : MU.getSymbols()) {
     assert(!KV.second.isLazy() && "Lazy flag should be managed internally.");
     assert(!KV.second.isMaterializing() &&
            "Materializing flags should be managed internally.");
 
-    SymbolMap::iterator EntryItr;
-    bool Added;
+    auto I = Symbols.find(KV.first);
 
-    auto NewFlags = KV.second;
-    NewFlags |= JITSymbolFlags::Lazy;
-
-    std::tie(EntryItr, Added) = Symbols.insert(
-        std::make_pair(KV.first, JITEvaluatedSymbol(0, NewFlags)));
-
-    if (!Added) {
+    if (I != Symbols.end()) {
       if (KV.second.isStrong()) {
-        if (EntryItr->second.getFlags().isStrong() ||
-            (EntryItr->second.getFlags() & JITSymbolFlags::Materializing))
+        if (I->second.getFlags().isStrong() ||
+            I->second.getFlags().isMaterializing())
           Duplicates.insert(KV.first);
-        else
-          ExistingDefsOverridden.push_back({EntryItr, NewFlags});
+        else {
+          assert(I->second.getFlags().isLazy() &&
+                 !I->second.getFlags().isMaterializing() &&
+                 "Overridden existing def should be in the Lazy state");
+          ExistingDefsOverridden.push_back(KV.first);
+        }
       } else
-        MUDefsOverridden.insert(KV.first);
+        MUDefsOverridden.push_back(KV.first);
     }
   }
 
-  if (!Duplicates.empty()) {
-    // We need to remove the symbols we added.
-    for (auto &KV : MU.getSymbols()) {
-      if (Duplicates.count(KV.first))
-        continue;
-
-      bool Found = false;
-      for (const auto &EDO : ExistingDefsOverridden)
-        if (EDO.ExistingDefItr->first == KV.first)
-          Found = true;
-
-      if (!Found)
-        Symbols.erase(KV.first);
-    }
-
-    // FIXME: Return all duplicates.
+  // If there were any duplicate definitions then bail out.
+  if (!Duplicates.empty())
     return make_error<DuplicateDefinition>(**Duplicates.begin());
-  }
 
-  // Update flags on existing defs and call discard on their materializers.
-  for (auto &EDO : ExistingDefsOverridden) {
-    assert(EDO.ExistingDefItr->second.getFlags().isLazy() &&
-           !EDO.ExistingDefItr->second.getFlags().isMaterializing() &&
-           "Overridden existing def should be in the Lazy state");
+  // Discard any overridden defs in this MU.
+  for (auto &S : MUDefsOverridden)
+    MU.doDiscard(*this, S);
 
-    EDO.ExistingDefItr->second.setFlags(EDO.NewFlags);
+  // Discard existing overridden defs.
+  for (auto &S : ExistingDefsOverridden) {
 
-    auto UMII = UnmaterializedInfos.find(EDO.ExistingDefItr->first);
+    auto UMII = UnmaterializedInfos.find(S);
     assert(UMII != UnmaterializedInfos.end() &&
            "Overridden existing def should have an UnmaterializedInfo");
-
-    UMII->second->MU->doDiscard(*this, EDO.ExistingDefItr->first);
+    UMII->second->MU->doDiscard(*this, S);
   }
 
-  // Discard overridden symbols povided by MU.
-  for (auto &Sym : MUDefsOverridden)
-    MU.doDiscard(*this, Sym);
+  // Finally, add the defs from this MU.
+  for (auto &KV : MU.getSymbols()) {
+    auto NewFlags = KV.second;
+    NewFlags |= JITSymbolFlags::Lazy;
+    Symbols[KV.first] = JITEvaluatedSymbol(0, NewFlags);
+  }
 
   return Error::success();
 }

lib/ExecutionEngine/Orc/ExecutionUtils.cpp

@@ -178,18 +178,19 @@ Error LocalCXXRuntimeOverrides::enable(JITDylib &JD,
 }
 
 DynamicLibrarySearchGenerator::DynamicLibrarySearchGenerator(
-    sys::DynamicLibrary Dylib, const DataLayout &DL, SymbolPredicate Allow)
+    sys::DynamicLibrary Dylib, char GlobalPrefix, SymbolPredicate Allow)
     : Dylib(std::move(Dylib)), Allow(std::move(Allow)),
-      GlobalPrefix(DL.getGlobalPrefix()) {}
+      GlobalPrefix(GlobalPrefix) {}
 
 Expected<DynamicLibrarySearchGenerator>
-DynamicLibrarySearchGenerator::Load(const char *FileName, const DataLayout &DL,
+DynamicLibrarySearchGenerator::Load(const char *FileName, char GlobalPrefix,
                                     SymbolPredicate Allow) {
   std::string ErrMsg;
   auto Lib = sys::DynamicLibrary::getPermanentLibrary(FileName, &ErrMsg);
   if (!Lib.isValid())
     return make_error<StringError>(std::move(ErrMsg), inconvertibleErrorCode());
-  return DynamicLibrarySearchGenerator(std::move(Lib), DL, std::move(Allow));
+  return DynamicLibrarySearchGenerator(std::move(Lib), GlobalPrefix,
+                                       std::move(Allow));
 }
 
 SymbolNameSet DynamicLibrarySearchGenerator::
@@ -209,7 +210,8 @@ operator()(JITDylib &JD, const SymbolNameSet &Names) {
     if (HasGlobalPrefix && (*Name).front() != GlobalPrefix)
       continue;
 
-    std::string Tmp((*Name).data() + (HasGlobalPrefix ? 1 : 0), (*Name).size());
+    std::string Tmp((*Name).data() + HasGlobalPrefix,
+                    (*Name).size() - HasGlobalPrefix);
     if (void *Addr = Dylib.getAddressOfSymbol(Tmp.c_str())) {
       Added.insert(Name);
       NewSymbols[Name] = JITEvaluatedSymbol(

lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp

@@ -0,0 +1,382 @@
+//===------- ObjectLinkingLayer.cpp - JITLink backed ORC ObjectLayer ------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/ExecutionEngine/JITLink/JITLink_EHFrameSupport.h"
+
+#include <vector>
+
+#define DEBUG_TYPE "orc"
+
+using namespace llvm;
+using namespace llvm::jitlink;
+using namespace llvm::orc;
+
+namespace llvm {
+namespace orc {
+
+class ObjectLinkingLayerJITLinkContext final : public JITLinkContext {
+public:
+  ObjectLinkingLayerJITLinkContext(ObjectLinkingLayer &Layer,
+                                   MaterializationResponsibility MR,
+                                   std::unique_ptr<MemoryBuffer> ObjBuffer)
+      : Layer(Layer), MR(std::move(MR)), ObjBuffer(std::move(ObjBuffer)) {}
+
+  JITLinkMemoryManager &getMemoryManager() override { return Layer.MemMgr; }
+
+  MemoryBufferRef getObjectBuffer() const override {
+    return ObjBuffer->getMemBufferRef();
+  }
+
+  void notifyFailed(Error Err) override {
+    Layer.getExecutionSession().reportError(std::move(Err));
+    MR.failMaterialization();
+  }
+
+  void lookup(const DenseSet<StringRef> &Symbols,
+              JITLinkAsyncLookupContinuation LookupContinuation) override {
+
+    JITDylibSearchList SearchOrder;
+    MR.getTargetJITDylib().withSearchOrderDo(
+        [&](const JITDylibSearchList &JDs) { SearchOrder = JDs; });
+
+    auto &ES = Layer.getExecutionSession();
+
+    SymbolNameSet InternedSymbols;
+    for (auto &S : Symbols)
+      InternedSymbols.insert(ES.intern(S));
+
+    // OnResolve -- De-intern the symbols and pass the result to the linker.
+    // FIXME: Capture LookupContinuation by move once we have c++14.
+    auto SharedLookupContinuation =
+        std::make_shared<JITLinkAsyncLookupContinuation>(
+            std::move(LookupContinuation));
+    auto OnResolve = [SharedLookupContinuation](Expected<SymbolMap> Result) {
+      if (!Result)
+        (*SharedLookupContinuation)(Result.takeError());
+      else {
+        AsyncLookupResult LR;
+        for (auto &KV : *Result)
+          LR[*KV.first] = KV.second;
+        (*SharedLookupContinuation)(std::move(LR));
+      }
+    };
+
+    ES.lookup(
+        SearchOrder, std::move(InternedSymbols), std::move(OnResolve),
+        // OnReady:
+        [&ES](Error Err) { ES.reportError(std::move(Err)); },
+        // RegisterDependencies:
+        [this](const SymbolDependenceMap &Deps) {
+          registerDependencies(Deps);
+        });
+  }
+
+  void notifyResolved(AtomGraph &G) override {
+    auto &ES = Layer.getExecutionSession();
+
+    SymbolFlagsMap ExtraSymbolsToClaim;
+    bool AutoClaim = Layer.AutoClaimObjectSymbols;
+
+    SymbolMap InternedResult;
+    for (auto *DA : G.defined_atoms())
+      if (DA->hasName() && DA->isGlobal()) {
+        auto InternedName = ES.intern(DA->getName());
+        JITSymbolFlags Flags;
+
+        if (DA->isExported())
+          Flags |= JITSymbolFlags::Exported;
+        if (DA->isWeak())
+          Flags |= JITSymbolFlags::Weak;
+        if (DA->isCallable())
+          Flags |= JITSymbolFlags::Callable;
+        if (DA->isCommon())
+          Flags |= JITSymbolFlags::Common;
+
+        InternedResult[InternedName] =
+            JITEvaluatedSymbol(DA->getAddress(), Flags);
+        if (AutoClaim && !MR.getSymbols().count(InternedName)) {
+          assert(!ExtraSymbolsToClaim.count(InternedName) &&
+                 "Duplicate symbol to claim?");
+          ExtraSymbolsToClaim[InternedName] = Flags;
+        }
+      }
+
+    for (auto *A : G.absolute_atoms())
+      if (A->hasName()) {
+        auto InternedName = ES.intern(A->getName());
+        JITSymbolFlags Flags;
+        Flags |= JITSymbolFlags::Absolute;
+        if (A->isWeak())
+          Flags |= JITSymbolFlags::Weak;
+        if (A->isCallable())
+          Flags |= JITSymbolFlags::Callable;
+        InternedResult[InternedName] =
+            JITEvaluatedSymbol(A->getAddress(), Flags);
+        if (AutoClaim && !MR.getSymbols().count(InternedName)) {
+          assert(!ExtraSymbolsToClaim.count(InternedName) &&
+                 "Duplicate symbol to claim?");
+          ExtraSymbolsToClaim[InternedName] = Flags;
+        }
+      }
+
+    if (!ExtraSymbolsToClaim.empty())
+      if (auto Err = MR.defineMaterializing(ExtraSymbolsToClaim))
+        return notifyFailed(std::move(Err));
+
+    MR.resolve(InternedResult);
+
+    if (Layer.NotifyLoaded)
+      Layer.NotifyLoaded(MR.getVModuleKey());
+  }
+
+  void notifyFinalized(
+      std::unique_ptr<JITLinkMemoryManager::Allocation> A) override {
+
+    if (EHFrameAddr) {
+      // If there is an eh-frame then try to register it.
+      if (auto Err = registerEHFrameSection((void *)EHFrameAddr)) {
+        Layer.getExecutionSession().reportError(std::move(Err));
+        MR.failMaterialization();
+        return;
+      }
+    }
+
+    MR.emit();
+    Layer.notifyFinalized(
+        ObjectLinkingLayer::ObjectResources(std::move(A), EHFrameAddr));
+  }
+
+  AtomGraphPassFunction getMarkLivePass(const Triple &TT) const override {
+    return [this](AtomGraph &G) { return markResponsibilitySymbolsLive(G); };
+  }
+
+  Error modifyPassConfig(const Triple &TT, PassConfiguration &Config) override {
+    // Add passes to mark duplicate defs as should-discard, and to walk the
+    // atom graph to build the symbol dependence graph.
+    Config.PrePrunePasses.push_back(
+        [this](AtomGraph &G) { return markSymbolsToDiscard(G); });
+    Config.PostPrunePasses.push_back(
+        [this](AtomGraph &G) { return computeNamedSymbolDependencies(G); });
+
+    Config.PostFixupPasses.push_back(
+        createEHFrameRecorderPass(TT, EHFrameAddr));
+
+    if (Layer.ModifyPassConfig)
+      Layer.ModifyPassConfig(TT, Config);
+
+    return Error::success();
+  }
+
+private:
+  using AnonAtomNamedDependenciesMap =
+      DenseMap<const DefinedAtom *, SymbolNameSet>;
+
+  Error markSymbolsToDiscard(AtomGraph &G) {
+    auto &ES = Layer.getExecutionSession();
+    for (auto *DA : G.defined_atoms())
+      if (DA->isWeak() && DA->hasName()) {
+        auto S = ES.intern(DA->getName());
+        auto I = MR.getSymbols().find(S);
+        if (I == MR.getSymbols().end())
+          DA->setShouldDiscard(true);
+      }
+
+    for (auto *A : G.absolute_atoms())
+      if (A->isWeak() && A->hasName()) {
+        auto S = ES.intern(A->getName());
+        auto I = MR.getSymbols().find(S);
+        if (I == MR.getSymbols().end())
+          A->setShouldDiscard(true);
+      }
+
+    return Error::success();
+  }
+
+  Error markResponsibilitySymbolsLive(AtomGraph &G) const {
+    auto &ES = Layer.getExecutionSession();
+    for (auto *DA : G.defined_atoms())
+      if (DA->hasName() &&
+          MR.getSymbols().count(ES.intern(DA->getName())))
+        DA->setLive(true);
+    return Error::success();
+  }
+
+  Error computeNamedSymbolDependencies(AtomGraph &G) {
+    auto &ES = MR.getTargetJITDylib().getExecutionSession();
+    auto AnonDeps = computeAnonDeps(G);
+
+    for (auto *DA : G.defined_atoms()) {
+
+      // Skip anonymous and non-global atoms: we do not need dependencies for
+      // these.
+      if (!DA->hasName() || !DA->isGlobal())
+        continue;
+
+      auto DAName = ES.intern(DA->getName());
+      SymbolNameSet &DADeps = NamedSymbolDeps[DAName];
+
+      for (auto &E : DA->edges()) {
+        auto &TA = E.getTarget();
+
+        if (TA.hasName())
+          DADeps.insert(ES.intern(TA.getName()));
+        else {
+          assert(TA.isDefined() && "Anonymous atoms must be defined");
+          auto &DTA = static_cast<DefinedAtom &>(TA);
+          auto I = AnonDeps.find(&DTA);
+          if (I != AnonDeps.end())
+            for (auto &S : I->second)
+              DADeps.insert(S);
+        }
+      }
+    }
+
+    return Error::success();
+  }
+
+  AnonAtomNamedDependenciesMap computeAnonDeps(AtomGraph &G) {
+
+    auto &ES = MR.getTargetJITDylib().getExecutionSession();
+    AnonAtomNamedDependenciesMap DepMap;
+
+    // For all anonymous atoms:
+    // (1) Add their named dependencies.
+    // (2) Add them to the worklist for further iteration if they have any
+    //     depend on any other anonymous atoms.
+    struct WorklistEntry {
+      WorklistEntry(DefinedAtom *DA, DenseSet<DefinedAtom *> DAAnonDeps)
+          : DA(DA), DAAnonDeps(std::move(DAAnonDeps)) {}
+
+      DefinedAtom *DA = nullptr;
+      DenseSet<DefinedAtom *> DAAnonDeps;
+    };
+    std::vector<WorklistEntry> Worklist;
+    for (auto *DA : G.defined_atoms())
+      if (!DA->hasName()) {
+        auto &DANamedDeps = DepMap[DA];
+        DenseSet<DefinedAtom *> DAAnonDeps;
+
+        for (auto &E : DA->edges()) {
+          auto &TA = E.getTarget();
+          if (TA.hasName())
+            DANamedDeps.insert(ES.intern(TA.getName()));
+          else {
+            assert(TA.isDefined() && "Anonymous atoms must be defined");
+            DAAnonDeps.insert(static_cast<DefinedAtom *>(&TA));
+          }
+        }
+
+        if (!DAAnonDeps.empty())
+          Worklist.push_back(WorklistEntry(DA, std::move(DAAnonDeps)));
+      }
+
+    // Loop over all anonymous atoms with anonymous dependencies, propagating
+    // their respective *named* dependencies. Iterate until we hit a stable
+    // state.
+    bool Changed;
+    do {
+      Changed = false;
+      for (auto &WLEntry : Worklist) {
+        auto *DA = WLEntry.DA;
+        auto &DANamedDeps = DepMap[DA];
+        auto &DAAnonDeps = WLEntry.DAAnonDeps;
+
+        for (auto *TA : DAAnonDeps) {
+          auto I = DepMap.find(TA);
+          if (I != DepMap.end())
+            for (const auto &S : I->second)
+              Changed |= DANamedDeps.insert(S).second;
+        }
+      }
+    } while (Changed);
+
+    return DepMap;
+  }
+
+  void registerDependencies(const SymbolDependenceMap &QueryDeps) {
+    for (auto &NamedDepsEntry : NamedSymbolDeps) {
+      auto &Name = NamedDepsEntry.first;
+      auto &NameDeps = NamedDepsEntry.second;
+      SymbolDependenceMap SymbolDeps;
+
+      for (const auto &QueryDepsEntry : QueryDeps) {
+        JITDylib &SourceJD = *QueryDepsEntry.first;
+        const SymbolNameSet &Symbols = QueryDepsEntry.second;
+        auto &DepsForJD = SymbolDeps[&SourceJD];
+
+        for (const auto &S : Symbols)
+          if (NameDeps.count(S))
+            DepsForJD.insert(S);
+
+        if (DepsForJD.empty())
+          SymbolDeps.erase(&SourceJD);
+      }
+
+      MR.addDependencies(Name, SymbolDeps);
+    }
+  }
+
+  ObjectLinkingLayer &Layer;
+  MaterializationResponsibility MR;
+  std::unique_ptr<MemoryBuffer> ObjBuffer;
+  DenseMap<SymbolStringPtr, SymbolNameSet> NamedSymbolDeps;
+  JITTargetAddress EHFrameAddr = 0;
+};
+
+ObjectLinkingLayer::ObjectLinkingLayer(
+    ExecutionSession &ES, JITLinkMemoryManager &MemMgr,
+    NotifyLoadedFunction NotifyLoaded, NotifyEmittedFunction NotifyEmitted,
+    ModifyPassConfigFunction ModifyPassConfig)
+    : ObjectLayer(ES), MemMgr(MemMgr), NotifyLoaded(std::move(NotifyLoaded)),
+      NotifyEmitted(std::move(NotifyEmitted)),
+      ModifyPassConfig(std::move(ModifyPassConfig)) {}
+
+void ObjectLinkingLayer::emit(MaterializationResponsibility R,
+                              std::unique_ptr<MemoryBuffer> O) {
+  assert(O && "Object must not be null");
+  jitLink(llvm::make_unique<ObjectLinkingLayerJITLinkContext>(
+      *this, std::move(R), std::move(O)));
+}
+
+ObjectLinkingLayer::ObjectResources::ObjectResources(
+    AllocPtr Alloc, JITTargetAddress EHFrameAddr)
+    : Alloc(std::move(Alloc)), EHFrameAddr(EHFrameAddr) {}
+
+ObjectLinkingLayer::ObjectResources::ObjectResources(ObjectResources &&Other)
+    : Alloc(std::move(Other.Alloc)), EHFrameAddr(Other.EHFrameAddr) {
+  Other.EHFrameAddr = 0;
+}
+
+ObjectLinkingLayer::ObjectResources &
+ObjectLinkingLayer::ObjectResources::operator=(ObjectResources &&Other) {
+  std::swap(Alloc, Other.Alloc);
+  std::swap(EHFrameAddr, Other.EHFrameAddr);
+  return *this;
+}
+
+ObjectLinkingLayer::ObjectResources::~ObjectResources() {
+  const char *ErrBanner =
+      "ObjectLinkingLayer received error deallocating object resources:";
+
+  assert((EHFrameAddr == 0 || Alloc) &&
+         "Non-null EHFrameAddr must have an associated allocation");
+
+  if (EHFrameAddr)
+    if (auto Err = deregisterEHFrameSection((void *)EHFrameAddr))
+      logAllUnhandledErrors(std::move(Err), llvm::errs(), ErrBanner);
+
+  if (Alloc)
+    if (auto Err = Alloc->deallocate())
+      logAllUnhandledErrors(std::move(Err), llvm::errs(), ErrBanner);
+}
+
+} // End namespace orc.
+} // End namespace llvm.

lib/ExecutionEngine/RuntimeDyld/RTDyldMemoryManager.cpp

@@ -47,7 +47,7 @@ extern "C" void __deregister_frame(void *);
 // it may be found at runtime in a dynamically-loaded library.
 // For example, this happens when building LLVM with Visual C++
 // but using the MingW runtime.
-void __register_frame(void *p) {
+static void __register_frame(void *p) {
   static bool Searched = false;
   static void((*rf)(void *)) = 0;
 
@@ -60,7 +60,7 @@ void __register_frame(void *p) {
     rf(p);
 }
 
-void __deregister_frame(void *p) {
+static void __deregister_frame(void *p) {
   static bool Searched = false;
   static void((*df)(void *)) = 0;
 

lib/Support/Memory.cpp

@@ -15,6 +15,10 @@
 #include "llvm/Config/llvm-config.h"
 #include "llvm/Support/Valgrind.h"
 
+#ifndef NDEBUG
+#include "llvm/Support/raw_ostream.h"
+#endif // ifndef NDEBUG
+
 // Include the platform-specific parts of this class.
 #ifdef LLVM_ON_UNIX
 #include "Unix/Memory.inc"
@@ -22,3 +26,28 @@
 #ifdef _WIN32
 #include "Windows/Memory.inc"
 #endif
+
+#ifndef NDEBUG
+
+namespace llvm {
+namespace sys {
+
+raw_ostream &operator<<(raw_ostream &OS, const Memory::ProtectionFlags &PF) {
+  assert((PF & ~(Memory::MF_READ | Memory::MF_WRITE | Memory::MF_EXEC)) == 0 &&
+         "Unrecognized flags");
+
+  return OS << (PF & Memory::MF_READ ? 'R' : '-')
+            << (PF & Memory::MF_WRITE ? 'W' : '-')
+            << (PF & Memory::MF_EXEC ? 'X' : '-');
+}
+
+raw_ostream &operator<<(raw_ostream &OS, const MemoryBlock &MB) {
+  return OS << "[ " << MB.base() << " .. "
+            << (void *)((char *)MB.base() + MB.size()) << " ] (" << MB.size()
+            << " bytes)";
+}
+
+} // end namespace sys
+} // end namespace llvm
+
+#endif // ifndef NDEBUG

test/ExecutionEngine/JITLink/MachO_x86-64_relocations.s

@@ -0,0 +1,203 @@
+# RUN: rm -rf %t && mkdir -p %t
+# RUN: llvm-mc -triple=x86_64-apple-macosx10.9 -filetype=obj -o %t/test_x86-64.o %s
+# RUN: llvm-jitlink -noexec -define-abs external_data=0xdeadbeef -define-abs external_func=0xcafef00d -check=%s %t/test_x86-64.o
+
+        .section        __TEXT,__text,regular,pure_instructions
+
+        .align  4, 0x90
+Lanon_func:
+        retq
+
+        .globl  named_func
+        .align  4, 0x90
+named_func:
+        xorq    %rax, %rax
+        retq
+
+# Check X86_64_RELOC_BRANCH handling with a call to a local function.
+#
+# jitlink-check: decode_operand(test_local_call, 0) = named_func - next_pc(test_local_call)
+        .globl  test_local_call
+        .align  4, 0x90
+test_local_call:
+        callq   named_func
+        retq
+
+        .globl  _main
+        .align  4, 0x90
+_main:
+        retq
+
+# Check X86_64_RELOC_GOTPCREL handling with a load from an external symbol.
+# Validate both the reference to the GOT entry, and also the content of the GOT
+# entry.
+#
+# jitlink-check: decode_operand(test_gotld, 4) = got_addr(test_x86-64.o, external_data) - next_pc(test_gotld)
+# jitlink-check: *{8}(got_addr(test_x86-64.o, external_data)) = external_data
+        .globl  test_gotld
+        .align  4, 0x90
+test_gotld:
+        movq    external_data@GOTPCREL(%rip), %rax
+        retq
+
+# Check that calls to external functions trigger the generation of stubs and GOT
+# entries.
+#
+# jitlink-check: decode_operand(test_external_call, 0) = stub_addr(test_x86-64.o, external_func) - next_pc(test_external_call)
+# jitlink-check: *{8}(got_addr(test_x86-64.o, external_func)) = external_func
+        .globl  test_external_call
+        .align  4, 0x90
+test_external_call:
+        callq   external_func
+        retq
+
+# Check signed relocation handling:
+#
+# X86_64_RELOC_SIGNED / Extern -- movq address of linker global
+# X86_64_RELOC_SIGNED1 / Extern -- movb immediate byte to linker global
+# X86_64_RELOC_SIGNED2 / Extern -- movw immediate word to linker global
+# X86_64_RELOC_SIGNED4 / Extern -- movl immediate long to linker global
+#
+# X86_64_RELOC_SIGNED / Anon -- movq address of linker private into register
+# X86_64_RELOC_SIGNED1 / Anon -- movb immediate byte to linker private
+# X86_64_RELOC_SIGNED2 / Anon -- movw immediate word to linker private
+# X86_64_RELOC_SIGNED4 / Anon -- movl immediate long to linker private
+signed_reloc_checks:
+        .globl signed
+# jitlink-check: decode_operand(signed, 4) = named_data - next_pc(signed)
+signed:
+        movq named_data(%rip), %rax
+
+        .globl signed1
+# jitlink-check: decode_operand(signed1, 3) = named_data - next_pc(signed1)
+signed1:
+        movb $0xAA, named_data(%rip)
+
+        .globl signed2
+# jitlink-check: decode_operand(signed2, 3) = named_data - next_pc(signed2)
+signed2:
+        movw $0xAAAA, named_data(%rip)
+
+        .globl signed4
+# jitlink-check: decode_operand(signed4, 3) = named_data - next_pc(signed4)
+signed4:
+        movl $0xAAAAAAAA, named_data(%rip)
+
+        .globl signedanon
+# jitlink-check: decode_operand(signedanon, 4) = section_addr(test_x86-64.o, __data) - next_pc(signedanon)
+signedanon:
+        movq Lanon_data(%rip), %rax
+
+        .globl signed1anon
+# jitlink-check: decode_operand(signed1anon, 3) = section_addr(test_x86-64.o, __data) - next_pc(signed1anon)
+signed1anon:
+        movb $0xAA, Lanon_data(%rip)
+
+        .globl signed2anon
+# jitlink-check: decode_operand(signed2anon, 3) = section_addr(test_x86-64.o, __data) - next_pc(signed2anon)
+signed2anon:
+        movw $0xAAAA, Lanon_data(%rip)
+
+        .globl signed4anon
+# jitlink-check: decode_operand(signed4anon, 3) = section_addr(test_x86-64.o, __data) - next_pc(signed4anon)
+signed4anon:
+        movl $0xAAAAAAAA, Lanon_data(%rip)
+
+
+
+        .section        __DATA,__data
+
+# Storage target for non-extern X86_64_RELOC_SIGNED_(1/2/4) relocs.
+        .p2align  3
+Lanon_data:
+        .quad   0x1111111111111111
+
+# Check X86_64_RELOC_SUBTRACTOR Quad/Long in anonymous storage with anonymous minuend
+# Only the form "LA: .quad LA - B + C" is tested. The form "LA: .quad B - LA + C" is
+# invalid because the minuend can not be local.
+#
+# Note: +8 offset in expression below to accounts for sizeof(Lanon_data).
+# jitlink-check: *{8}(section_addr(test_x86-64.o, __data) + 8) = (section_addr(test_x86-64.o, __data) + 8) - named_data + 2
+        .p2align  3
+Lanon_minuend_quad:
+        .quad Lanon_minuend_quad - named_data + 2
+
+# Note: +16 offset in expression below to accounts for sizeof(Lanon_data) + sizeof(Lanon_minuend_long).
+# jitlink-check: *{4}(section_addr(test_x86-64.o, __data) + 16) = ((section_addr(test_x86-64.o, __data) + 16) - named_data + 2)[31:0]
+        .p2align  2
+Lanon_minuend_long:
+        .long Lanon_minuend_long - named_data + 2
+
+
+# Named quad storage target (first named atom in __data).
+        .globl named_data
+        .p2align  3
+named_data:
+        .quad   0x2222222222222222
+
+# Check X86_64_RELOC_UNSIGNED / extern handling by putting the address of a
+# local named function in a pointer variable.
+#
+# jitlink-check: *{8}named_func_addr = named_func
+        .globl  named_func_addr
+        .p2align  3
+named_func_addr:
+        .quad   named_func
+
+# Check X86_64_RELOC_UNSIGNED / non-extern handling by putting the address of a
+# local anonymous function in a pointer variable.
+#
+# jitlink-check: *{8}anon_func_addr = section_addr(test_x86-64.o, __text)
+        .globl  anon_func_addr
+        .p2align  3
+anon_func_addr:
+        .quad   Lanon_func
+
+# X86_64_RELOC_SUBTRACTOR Quad/Long in named storage with anonymous minuend
+#
+# jitlink-check: *{8}minuend_quad1 = section_addr(test_x86-64.o, __data) - minuend_quad1 + 2
+# Only the form "B: .quad LA - B + C" is tested. The form "B: .quad B - LA + C" is
+# invalid because the minuend can not be local.
+        .globl  minuend_quad1
+        .p2align  3
+minuend_quad1:
+        .quad Lanon_data - minuend_quad1 + 2
+
+# jitlink-check: *{4}minuend_long1 = (section_addr(test_x86-64.o, __data) - minuend_long1 + 2)[31:0]
+        .globl  minuend_long1
+        .p2align  2
+minuend_long1:
+        .long Lanon_data - minuend_long1 + 2
+
+# Check X86_64_RELOC_SUBTRACTOR Quad/Long in named storage with minuend and subtrahend.
+# Both forms "A: .quad A - B + C" and "A: .quad B - A + C" are tested.
+#
+# Check "A: .quad B - A + C".
+# jitlink-check: *{8}minuend_quad2 = (named_data - minuend_quad2 + 2)
+        .globl  minuend_quad2
+        .p2align  3
+minuend_quad2:
+        .quad named_data - minuend_quad2 + 2
+
+# Check "A: .long B - A + C".
+# jitlink-check: *{4}minuend_long2 = (named_data - minuend_long2 + 2)[31:0]
+        .globl  minuend_long2
+        .p2align  2
+minuend_long2:
+        .long named_data - minuend_long2 + 2
+
+# Check "A: .quad A - B + C".
+# jitlink-check: *{8}minuend_quad3 = (minuend_quad3 - named_data + 2)
+        .globl  minuend_quad3
+        .p2align  3
+minuend_quad3:
+        .quad minuend_quad3 - named_data + 2
+
+# Check "A: .long B - A + C".
+# jitlink-check: *{4}minuend_long3 = (minuend_long3 - named_data + 2)[31:0]
+        .globl  minuend_long3
+        .p2align  2
+minuend_long3:
+        .long minuend_long3 - named_data + 2
+
+.subsections_via_symbols

tools/lli/lli.cpp

@@ -800,7 +800,8 @@ int runOrcLazyJIT(const char *ProgName) {
     return Dump(std::move(TSM), R);
   });
   J->getMainJITDylib().setGenerator(
-      ExitOnErr(orc::DynamicLibrarySearchGenerator::GetForCurrentProcess(DL)));
+      ExitOnErr(orc::DynamicLibrarySearchGenerator::GetForCurrentProcess(
+          DL.getGlobalPrefix())));
 
   orc::MangleAndInterner Mangle(J->getExecutionSession(), DL);
   orc::LocalCXXRuntimeOverrides CXXRuntimeOverrides;

tools/llvm-jitlink/CMakeLists.txt

@@ -0,0 +1,17 @@
+set(LLVM_LINK_COMPONENTS
+  ${LLVM_TARGETS_TO_BUILD}
+  ExecutionEngine
+  JITLink
+  MC
+  Object
+  OrcJIT
+  RuntimeDyld
+  Support
+  )
+
+add_llvm_tool(llvm-jitlink
+  llvm-jitlink.cpp
+  llvm-jitlink-macho.cpp
+  )
+
+export_executable_symbols(llvm-jitlink)

tools/llvm-jitlink/LLVMBuild.txt

@@ -0,0 +1,21 @@
+;===- ./tools/llvm-jitlink/LLVMBuild.txt -----------------------*- Conf -*--===;
+;
+; Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+; See https://llvm.org/LICENSE.txt for license information.
+; SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+;
+;===------------------------------------------------------------------------===;
+;
+; This is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+;   http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[component_0]
+type = Tool
+name = llvm-jitlink
+parent = Tools
+required_libraries = JITLink MC Object RuntimeDyld Support all-targets

tools/llvm-jitlink/llvm-jitlink-macho.cpp

@@ -0,0 +1,142 @@
+//===-- llvm-jitlink-macho.cpp -- MachO parsing support for llvm-jitlink --===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// .
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-jitlink.h"
+
+#include "llvm/Support/Error.h"
+#include "llvm/Support/Path.h"
+
+#define DEBUG_TYPE "llvm-jitlink"
+
+using namespace llvm;
+using namespace llvm::jitlink;
+
+static bool isMachOGOTSection(Section &S) { return S.getName() == "$__GOT"; }
+
+static bool isMachOStubsSection(Section &S) {
+  return S.getName() == "$__STUBS";
+}
+
+static Expected<Edge &> getFirstRelocationEdge(AtomGraph &G, DefinedAtom &DA) {
+  auto EItr = std::find_if(DA.edges().begin(), DA.edges().end(),
+                           [](Edge &E) { return E.isRelocation(); });
+  if (EItr == DA.edges().end())
+    return make_error<StringError>("GOT entry in " + G.getName() + ", \"" +
+                                       DA.getSection().getName() +
+                                       "\" has no relocations",
+                                   inconvertibleErrorCode());
+  return *EItr;
+}
+
+static Expected<Atom &> getMachOGOTTarget(AtomGraph &G, DefinedAtom &DA) {
+  auto E = getFirstRelocationEdge(G, DA);
+  if (!E)
+    return E.takeError();
+  auto &TA = E->getTarget();
+  if (!TA.hasName())
+    return make_error<StringError>("GOT entry in " + G.getName() + ", \"" +
+                                       DA.getSection().getName() +
+                                       "\" points to anonymous "
+                                       "atom",
+                                   inconvertibleErrorCode());
+  if (TA.isDefined() || TA.isAbsolute())
+    return make_error<StringError>(
+        "GOT entry \"" + TA.getName() + "\" in " + G.getName() + ", \"" +
+            DA.getSection().getName() + "\" does not point to an external atom",
+        inconvertibleErrorCode());
+  return TA;
+}
+
+static Expected<Atom &> getMachOStubTarget(AtomGraph &G, DefinedAtom &DA) {
+  auto E = getFirstRelocationEdge(G, DA);
+  if (!E)
+    return E.takeError();
+  auto &GOTA = E->getTarget();
+  if (!GOTA.isDefined() ||
+      !isMachOGOTSection(static_cast<DefinedAtom &>(GOTA).getSection()))
+    return make_error<StringError>("Stubs entry in " + G.getName() + ", \"" +
+                                       DA.getSection().getName() +
+                                       "\" does not point to GOT entry",
+                                   inconvertibleErrorCode());
+  return getMachOGOTTarget(G, static_cast<DefinedAtom &>(GOTA));
+}
+
+namespace llvm {
+
+Error registerMachOStubsAndGOT(Session &S, AtomGraph &G) {
+  auto FileName = sys::path::filename(G.getName());
+  if (S.FileInfos.count(FileName)) {
+    return make_error<StringError>("When -check is passed, file names must be "
+                                   "distinct (duplicate: \"" +
+                                       FileName + "\")",
+                                   inconvertibleErrorCode());
+  }
+
+  auto &FileInfo = S.FileInfos[FileName];
+  LLVM_DEBUG({
+    dbgs() << "Registering MachO file info for \"" << FileName << "\"\n";
+  });
+  for (auto &Sec : G.sections()) {
+    LLVM_DEBUG({
+      dbgs() << "  Section \"" << Sec.getName() << "\": "
+             << (Sec.atoms_empty() ? "empty. skipping." : "processing...")
+             << "\n";
+    });
+
+    // Skip empty sections.
+    if (Sec.atoms_empty())
+      continue;
+
+    if (FileInfo.SectionInfos.count(Sec.getName()))
+      return make_error<StringError>("Encountered duplicate section name \"" +
+                                         Sec.getName() + "\" in \"" + FileName +
+                                         "\"",
+                                     inconvertibleErrorCode());
+
+    bool isGOTSection = isMachOGOTSection(Sec);
+    bool isStubsSection = isMachOStubsSection(Sec);
+
+    auto &SectionInfo = FileInfo.SectionInfos[Sec.getName()];
+
+    auto *FirstAtom = *Sec.atoms().begin();
+    auto *LastAtom = FirstAtom;
+    for (auto *DA : Sec.atoms()) {
+      if (DA->getAddress() < FirstAtom->getAddress())
+        FirstAtom = DA;
+      if (DA->getAddress() > LastAtom->getAddress())
+        LastAtom = DA;
+      if (isGOTSection) {
+        if (auto TA = getMachOGOTTarget(G, *DA)) {
+          FileInfo.GOTEntryInfos[TA->getName()] = {DA->getContent(),
+                                                   DA->getAddress()};
+        } else
+          return TA.takeError();
+      } else if (isStubsSection) {
+        if (auto TA = getMachOStubTarget(G, *DA))
+          FileInfo.StubInfos[TA->getName()] = {DA->getContent(),
+                                               DA->getAddress()};
+        else
+          return TA.takeError();
+      } else if (DA->hasName() && DA->isGlobal())
+        S.SymbolInfos[DA->getName()] = {DA->getContent(), DA->getAddress()};
+    }
+    const char *StartAddr = FirstAtom->getContent().data();
+    const char *EndAddr =
+        LastAtom->getContent().data() + LastAtom->getContent().size();
+    SectionInfo.TargetAddress = FirstAtom->getAddress();
+    SectionInfo.Content = StringRef(StartAddr, EndAddr - StartAddr);
+  }
+
+  return Error::success();
+}
+
+} // end namespace llvm

tools/llvm-jitlink/llvm-jitlink.cpp

@@ -0,0 +1,529 @@
+//===- llvm-jitlink.cpp -- Command line interface/tester for llvm-jitlink -===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This utility provides a simple command line interface to the llvm jitlink
+// library, which makes relocatable object files executable in memory. Its
+// primary function is as a testing utility for the jitlink library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-jitlink.h"
+
+#include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDisassembler/MCDisassembler.h"
+#include "llvm/MC/MCInstPrinter.h"
+#include "llvm/MC/MCInstrInfo.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/Object/COFF.h"
+#include "llvm/Object/MachO.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/DynamicLibrary.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/TargetSelect.h"
+
+#include <list>
+#include <string>
+
+#include "dlfcn.h"
+
+#define DEBUG_TYPE "llvm-jitlink"
+
+using namespace llvm;
+using namespace llvm::jitlink;
+using namespace llvm::orc;
+
+static cl::list<std::string> InputFiles(cl::Positional, cl::OneOrMore,
+                                        cl::desc("input files"));
+
+static cl::opt<bool> NoExec("noexec", cl::desc("Do not execute loaded code"),
+                            cl::init(false));
+
+static cl::list<std::string>
+    CheckFiles("check", cl::desc("File containing verifier checks"),
+               cl::ZeroOrMore);
+
+static cl::opt<std::string>
+    EntryPointName("entry", cl::desc("Symbol to call as main entry point"),
+                   cl::init(""));
+
+static cl::list<std::string> JITLinkDylibs(
+    "jld", cl::desc("Specifies the JITDylib to be used for any subsequent "
+                    "input file arguments"));
+
+static cl::list<std::string>
+    Dylibs("dlopen", cl::desc("Dynamic libraries to load before linking"),
+           cl::ZeroOrMore);
+
+static cl::opt<bool>
+    NoProcessSymbols("no-process-syms",
+                     cl::desc("Do not resolve to llvm-jitlink process symbols"),
+                     cl::init(false));
+
+static cl::list<std::string>
+AbsoluteDefs("define-abs",
+             cl::desc("Inject absolute symbol definitions (syntax: <name>=<addr>)"),
+             cl::ZeroOrMore);
+
+static cl::opt<bool> ShowAddrs(
+    "show-addrs",
+    cl::desc("Print registered symbol, section, got and stub addresses"),
+    cl::init(false));
+
+static cl::opt<bool> ShowAtomGraph(
+    "show-graph",
+    cl::desc("Print the atom graph after fixups have been applied"),
+    cl::init(false));
+
+static cl::opt<bool> ShowSizes(
+                               "show-sizes",
+                               cl::desc("Show sizes: pre- and post-dead stripping, and allocations"),
+                               cl::init(false));
+
+ExitOnError ExitOnErr;
+
+namespace llvm {
+
+static raw_ostream &
+operator<<(raw_ostream &OS, const Session::MemoryRegionInfo &MRI) {
+  return OS << "target addr = " << format("0x%016" PRIx64, MRI.TargetAddress)
+            << ", content: " << (const void *)MRI.Content.data() << " -- "
+            << (const void *)(MRI.Content.data() + MRI.Content.size()) << " ("
+            << MRI.Content.size() << " bytes)";
+}
+
+static raw_ostream &
+operator<<(raw_ostream &OS, const Session::SymbolInfoMap &SIM) {
+  OS << "Symbols:\n";
+  for (auto &SKV : SIM)
+    OS << "  \"" << SKV.first() << "\" " << SKV.second << "\n";
+  return OS;
+}
+
+static raw_ostream &
+operator<<(raw_ostream &OS, const Session::FileInfo &FI) {
+  for (auto &SIKV : FI.SectionInfos)
+    OS << "  Section \"" << SIKV.first() << "\": " << SIKV.second << "\n";
+  for (auto &GOTKV : FI.GOTEntryInfos)
+    OS << "  GOT \"" << GOTKV.first() << "\": " << GOTKV.second << "\n";
+  for (auto &StubKV : FI.StubInfos)
+    OS << "  Stub \"" << StubKV.first() << "\": " << StubKV.second << "\n";
+  return OS;
+}
+
+static raw_ostream &
+operator<<(raw_ostream &OS, const Session::FileInfoMap &FIM) {
+  for (auto &FIKV : FIM)
+    OS << "File \"" << FIKV.first() << "\":\n" << FIKV.second;
+  return OS;
+}
+
+static uint64_t computeTotalAtomSizes(AtomGraph &G) {
+  uint64_t TotalSize = 0;
+  for (auto *DA : G.defined_atoms())
+    if (DA->isZeroFill())
+      TotalSize += DA->getZeroFillSize();
+    else
+      TotalSize += DA->getContent().size();
+  return TotalSize;
+}
+
+Session::Session(Triple TT)
+    : ObjLayer(ES, MemMgr, ObjectLinkingLayer::NotifyLoadedFunction(),
+               ObjectLinkingLayer::NotifyEmittedFunction(),
+               [this](const Triple &TT, PassConfiguration &PassConfig) {
+                 modifyPassConfig(TT, PassConfig);
+               }),
+      TT(std::move(TT)) {}
+
+void Session::dumpSessionInfo(raw_ostream &OS) {
+  OS << "Registered addresses:\n" << SymbolInfos << FileInfos;
+}
+
+void Session::modifyPassConfig(const Triple &FTT,
+                               PassConfiguration &PassConfig) {
+  if (!CheckFiles.empty())
+    PassConfig.PostFixupPasses.push_back([this](AtomGraph &G) {
+      if (TT.getObjectFormat() == Triple::MachO)
+        return registerMachOStubsAndGOT(*this, G);
+      return make_error<StringError>("Unsupported object format for GOT/stub "
+                                     "registration",
+                                     inconvertibleErrorCode());
+    });
+
+  if (ShowAtomGraph)
+    PassConfig.PostFixupPasses.push_back([](AtomGraph &G) -> Error {
+      outs() << "Atom graph post-fixup:\n";
+      G.dump(outs());
+      return Error::success();
+    });
+
+
+  if (ShowSizes) {
+    PassConfig.PrePrunePasses.push_back([this](AtomGraph &G) -> Error {
+        SizeBeforePruning += computeTotalAtomSizes(G);
+        return Error::success();
+      });
+    PassConfig.PostFixupPasses.push_back([this](AtomGraph &G) -> Error {
+        SizeAfterFixups += computeTotalAtomSizes(G);
+        return Error::success();
+      });
+  }
+
+}
+
+Expected<Session::FileInfo &> Session::findFileInfo(StringRef FileName) {
+  auto FileInfoItr = FileInfos.find(FileName);
+  if (FileInfoItr == FileInfos.end())
+    return make_error<StringError>("file \"" + FileName + "\" not recognized",
+                                   inconvertibleErrorCode());
+  return FileInfoItr->second;
+}
+
+Expected<Session::MemoryRegionInfo &>
+Session::findSectionInfo(StringRef FileName, StringRef SectionName) {
+  auto FI = findFileInfo(FileName);
+  if (!FI)
+    return FI.takeError();
+  auto SecInfoItr = FI->SectionInfos.find(SectionName);
+  if (SecInfoItr == FI->SectionInfos.end())
+    return make_error<StringError>("no section \"" + SectionName +
+                                       "\" registered for file \"" + FileName +
+                                       "\"",
+                                   inconvertibleErrorCode());
+  return SecInfoItr->second;
+}
+
+Expected<Session::MemoryRegionInfo &>
+Session::findStubInfo(StringRef FileName, StringRef TargetName) {
+  auto FI = findFileInfo(FileName);
+  if (!FI)
+    return FI.takeError();
+  auto StubInfoItr = FI->StubInfos.find(TargetName);
+  if (StubInfoItr == FI->StubInfos.end())
+    return make_error<StringError>("no stub for \"" + TargetName +
+                                       "\" registered for file \"" + FileName +
+                                       "\"",
+                                   inconvertibleErrorCode());
+  return StubInfoItr->second;
+}
+
+Expected<Session::MemoryRegionInfo &>
+Session::findGOTEntryInfo(StringRef FileName, StringRef TargetName) {
+  auto FI = findFileInfo(FileName);
+  if (!FI)
+    return FI.takeError();
+  auto GOTInfoItr = FI->GOTEntryInfos.find(TargetName);
+  if (GOTInfoItr == FI->GOTEntryInfos.end())
+    return make_error<StringError>("no GOT entry for \"" + TargetName +
+                                       "\" registered for file \"" + FileName +
+                                       "\"",
+                                   inconvertibleErrorCode());
+  return GOTInfoItr->second;
+}
+
+bool Session::isSymbolRegistered(StringRef SymbolName) {
+  return SymbolInfos.count(SymbolName);
+}
+
+Expected<Session::MemoryRegionInfo &>
+Session::findSymbolInfo(StringRef SymbolName, Twine ErrorMsgStem) {
+  auto SymInfoItr = SymbolInfos.find(SymbolName);
+  if (SymInfoItr == SymbolInfos.end())
+    return make_error<StringError>(ErrorMsgStem + ": symbol " + SymbolName +
+                                       " not found",
+                                   inconvertibleErrorCode());
+  return SymInfoItr->second;
+}
+
+} // end namespace llvm
+
+Error loadProcessSymbols(Session &S) {
+  std::string ErrMsg;
+  if (sys::DynamicLibrary::LoadLibraryPermanently(nullptr, &ErrMsg))
+    return make_error<StringError>(std::move(ErrMsg), inconvertibleErrorCode());
+
+  char GlobalPrefix = S.TT.getObjectFormat() == Triple::MachO ? '_' : '\0';
+  S.ES.getMainJITDylib().setGenerator(ExitOnErr(
+      orc::DynamicLibrarySearchGenerator::GetForCurrentProcess(GlobalPrefix)));
+
+  return Error::success();
+}
+
+Error loadDylibs() {
+  // FIXME: This should all be handled inside DynamicLibrary.
+  for (const auto &Dylib : Dylibs) {
+    if (!sys::fs::is_regular_file(Dylib))
+      return make_error<StringError>("\"" + Dylib + "\" is not a regular file",
+                                     inconvertibleErrorCode());
+    std::string ErrMsg;
+    if (sys::DynamicLibrary::LoadLibraryPermanently(Dylib.c_str(), &ErrMsg))
+      return make_error<StringError>(ErrMsg, inconvertibleErrorCode());
+  }
+
+  return Error::success();
+}
+
+Triple getFirstFileTriple() {
+  assert(!InputFiles.empty() && "InputFiles can not be empty");
+  auto ObjBuffer =
+      ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(InputFiles.front())));
+  auto Obj = ExitOnErr(
+      object::ObjectFile::createObjectFile(ObjBuffer->getMemBufferRef()));
+  return Obj->makeTriple();
+}
+
+Error loadObjects(Session &S) {
+
+  std::map<unsigned, JITDylib *> IdxToJLD;
+
+  // First, set up JITDylibs.
+  LLVM_DEBUG(dbgs() << "Creating JITDylibs...\n");
+  {
+    // Create a "main" JITLinkDylib.
+    auto &MainJD = S.ES.getMainJITDylib();
+    IdxToJLD[0] = &MainJD;
+    S.JDSearchOrder.push_back(&MainJD);
+    LLVM_DEBUG(dbgs() << "  0: " << MainJD.getName() << "\n");
+
+    // Add any extra JITLinkDylibs from the command line.
+    std::string JDNamePrefix("lib");
+    for (auto JLDItr = JITLinkDylibs.begin(), JLDEnd = JITLinkDylibs.end();
+         JLDItr != JLDEnd; ++JLDItr) {
+      auto &JD = S.ES.createJITDylib(JDNamePrefix + *JLDItr);
+      unsigned JDIdx =
+          JITLinkDylibs.getPosition(JLDItr - JITLinkDylibs.begin());
+      IdxToJLD[JDIdx] = &JD;
+      S.JDSearchOrder.push_back(&JD);
+      LLVM_DEBUG(dbgs() << "  " << JDIdx << ": " << JD.getName() << "\n");
+    }
+
+    // Set every dylib to link against every other, in command line order.
+    for (auto *JD : S.JDSearchOrder) {
+      JITDylibSearchList O;
+      for (auto *JD2 : S.JDSearchOrder) {
+        if (JD2 == JD)
+          continue;
+        O.push_back(std::make_pair(JD2, false));
+      }
+      JD->setSearchOrder(std::move(O));
+    }
+  }
+
+  // Load each object into the corresponding JITDylib..
+  LLVM_DEBUG(dbgs() << "Adding objects...\n");
+  for (auto InputFileItr = InputFiles.begin(), InputFileEnd = InputFiles.end();
+       InputFileItr != InputFileEnd; ++InputFileItr) {
+    unsigned InputFileArgIdx =
+        InputFiles.getPosition(InputFileItr - InputFiles.begin());
+    StringRef InputFile = *InputFileItr;
+    auto &JD = *std::prev(IdxToJLD.lower_bound(InputFileArgIdx))->second;
+    LLVM_DEBUG(dbgs() << "  " << InputFileArgIdx << ": \"" << InputFile
+                      << "\" to " << JD.getName() << "\n";);
+    auto ObjBuffer =
+        ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(InputFile)));
+    ExitOnErr(S.ObjLayer.add(JD, std::move(ObjBuffer)));
+  }
+
+  // Define absolute symbols.
+  LLVM_DEBUG(dbgs() << "Defining absolute symbols...\n");
+  for (auto AbsDefItr = AbsoluteDefs.begin(), AbsDefEnd = AbsoluteDefs.end();
+       AbsDefItr != AbsDefEnd; ++AbsDefItr) {
+    unsigned AbsDefArgIdx =
+      AbsoluteDefs.getPosition(AbsDefItr - AbsoluteDefs.begin());
+    auto &JD = *std::prev(IdxToJLD.lower_bound(AbsDefArgIdx))->second;
+
+    StringRef AbsDefStmt = *AbsDefItr;
+    size_t EqIdx = AbsDefStmt.find_first_of('=');
+    if (EqIdx == StringRef::npos)
+      return make_error<StringError>("Invalid absolute define \"" + AbsDefStmt +
+                                     "\". Syntax: <name>=<addr>",
+                                     inconvertibleErrorCode());
+    StringRef Name = AbsDefStmt.substr(0, EqIdx).trim();
+    StringRef AddrStr = AbsDefStmt.substr(EqIdx + 1).trim();
+
+    uint64_t Addr;
+    if (AddrStr.getAsInteger(0, Addr))
+      return make_error<StringError>("Invalid address expression \"" + AddrStr +
+                                     "\" in absolute define \"" + AbsDefStmt +
+                                     "\"",
+                                     inconvertibleErrorCode());
+    JITEvaluatedSymbol AbsDef(Addr, JITSymbolFlags::Exported);
+    if (auto Err = JD.define(absoluteSymbols({{S.ES.intern(Name), AbsDef}})))
+      return Err;
+
+    // Register the absolute symbol with the session symbol infos.
+    S.SymbolInfos[Name] = { StringRef(), Addr };
+  }
+
+  LLVM_DEBUG({
+    dbgs() << "Dylib search order is [ ";
+    for (auto *JD : S.JDSearchOrder)
+      dbgs() << JD->getName() << " ";
+    dbgs() << "]\n";
+  });
+
+  return Error::success();
+}
+
+Error runChecks(Session &S) {
+
+  auto TripleName = S.TT.str();
+  std::string ErrorStr;
+  const Target *TheTarget = TargetRegistry::lookupTarget("", S.TT, ErrorStr);
+  if (!TheTarget)
+    ExitOnErr(make_error<StringError>("Error accessing target '" + TripleName +
+                                          "': " + ErrorStr,
+                                      inconvertibleErrorCode()));
+
+  std::unique_ptr<MCSubtargetInfo> STI(
+      TheTarget->createMCSubtargetInfo(TripleName, "", ""));
+  if (!STI)
+    ExitOnErr(
+        make_error<StringError>("Unable to create subtarget for " + TripleName,
+                                inconvertibleErrorCode()));
+
+  std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
+  if (!MRI)
+    ExitOnErr(make_error<StringError>("Unable to create target register info "
+                                      "for " +
+                                          TripleName,
+                                      inconvertibleErrorCode()));
+
+  std::unique_ptr<MCAsmInfo> MAI(TheTarget->createMCAsmInfo(*MRI, TripleName));
+  if (!MAI)
+    ExitOnErr(make_error<StringError>("Unable to create target asm info " +
+                                          TripleName,
+                                      inconvertibleErrorCode()));
+
+  MCContext Ctx(MAI.get(), MRI.get(), nullptr);
+
+  std::unique_ptr<MCDisassembler> Disassembler(
+      TheTarget->createMCDisassembler(*STI, Ctx));
+  if (!Disassembler)
+    ExitOnErr(make_error<StringError>("Unable to create disassembler for " +
+                                          TripleName,
+                                      inconvertibleErrorCode()));
+
+  std::unique_ptr<MCInstrInfo> MII(TheTarget->createMCInstrInfo());
+
+  std::unique_ptr<MCInstPrinter> InstPrinter(
+      TheTarget->createMCInstPrinter(Triple(TripleName), 0, *MAI, *MII, *MRI));
+
+  auto IsSymbolValid = [&S](StringRef Symbol) {
+    return S.isSymbolRegistered(Symbol);
+  };
+
+  auto GetSymbolInfo = [&S](StringRef Symbol) {
+    return S.findSymbolInfo(Symbol, "Can not get symbol info");
+  };
+
+  auto GetSectionInfo = [&S](StringRef FileName, StringRef SectionName) {
+    return S.findSectionInfo(FileName, SectionName);
+  };
+
+  auto GetStubInfo = [&S](StringRef FileName, StringRef SectionName) {
+    return S.findStubInfo(FileName, SectionName);
+  };
+
+  auto GetGOTInfo = [&S](StringRef FileName, StringRef SectionName) {
+    return S.findGOTEntryInfo(FileName, SectionName);
+  };
+
+  RuntimeDyldChecker Checker(
+      IsSymbolValid, GetSymbolInfo, GetSectionInfo, GetStubInfo, GetGOTInfo,
+      S.TT.isLittleEndian() ? support::little : support::big,
+      Disassembler.get(), InstPrinter.get(), dbgs());
+
+  for (auto &CheckFile : CheckFiles) {
+    auto CheckerFileBuf =
+        ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(CheckFile)));
+    if (!Checker.checkAllRulesInBuffer("# jitlink-check:", &*CheckerFileBuf))
+      ExitOnErr(make_error<StringError>(
+          "Some checks in " + CheckFile + " failed", inconvertibleErrorCode()));
+  }
+
+  return Error::success();
+}
+
+static void dumpSessionStats(Session &S) {
+  if (ShowSizes)
+    outs() << "Total size of all atoms before pruning: " << S.SizeBeforePruning
+           << "\nTotal size of all atoms after fixups: " << S.SizeAfterFixups
+           << "\n";
+}
+
+static Expected<JITEvaluatedSymbol> getMainEntryPoint(Session &S) {
+
+  // First, if the entry point has not been set, set it to a sensible default
+  // for this process.
+  if (EntryPointName.empty()) {
+    if (S.TT.getObjectFormat() == Triple::MachO)
+      EntryPointName = "_main";
+    else
+      EntryPointName = "main";
+  }
+
+  return S.ES.lookup(S.JDSearchOrder, EntryPointName);
+}
+
+Expected<int> runEntryPoint(Session &S, JITEvaluatedSymbol EntryPoint) {
+  assert(EntryPoint.getAddress() && "Entry point address should not be null");
+
+  constexpr const char *JITProgramName = "<llvm-jitlink jit'd code>";
+  auto PNStorage = llvm::make_unique<char[]>(strlen(JITProgramName) + 1);
+  strcpy(PNStorage.get(), JITProgramName);
+
+  std::vector<const char *> EntryPointArgs;
+  EntryPointArgs.push_back(PNStorage.get());
+  EntryPointArgs.push_back(nullptr);
+
+  using MainTy = int (*)(int, const char *[]);
+  MainTy EntryPointPtr = reinterpret_cast<MainTy>(EntryPoint.getAddress());
+
+  return EntryPointPtr(EntryPointArgs.size() - 1, EntryPointArgs.data());
+}
+
+int main(int argc, char *argv[]) {
+  InitLLVM X(argc, argv);
+
+  InitializeAllTargetInfos();
+  InitializeAllTargetMCs();
+  InitializeAllDisassemblers();
+
+  cl::ParseCommandLineOptions(argc, argv, "llvm jitlink tool");
+  ExitOnErr.setBanner(std::string(argv[0]) + ": ");
+
+  Session S(getFirstFileTriple());
+
+  if (!NoProcessSymbols)
+    ExitOnErr(loadProcessSymbols(S));
+  ExitOnErr(loadDylibs());
+
+  ExitOnErr(loadObjects(S));
+
+  auto EntryPoint = ExitOnErr(getMainEntryPoint(S));
+
+  if (ShowAddrs)
+    S.dumpSessionInfo(outs());
+
+  ExitOnErr(runChecks(S));
+
+  dumpSessionStats(S);
+
+  if (NoExec)
+    return 0;
+
+  return ExitOnErr(runEntryPoint(S, EntryPoint));
+}

tools/llvm-jitlink/llvm-jitlink.h

@@ -0,0 +1,72 @@
+//===---- llvm-jitlink.h - Session and format-specific decls ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Utilities for remote-JITing with LLI.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TOOLS_LLVM_JITLINK_LLVM_JITLINK_H
+#define LLVM_TOOLS_LLVM_JITLINK_LLVM_JITLINK_H
+
+#include "llvm/ADT/Triple.h"
+#include "llvm/ExecutionEngine/Orc/Core.h"
+#include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
+#include "llvm/ExecutionEngine/RuntimeDyldChecker.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include <vector>
+
+namespace llvm {
+
+struct Session {
+  orc::ExecutionSession ES;
+  jitlink::InProcessMemoryManager MemMgr;
+  orc::ObjectLinkingLayer ObjLayer;
+  std::vector<orc::JITDylib *> JDSearchOrder;
+  Triple TT;
+
+  Session(Triple TT);
+  void dumpSessionInfo(raw_ostream &OS);
+  void modifyPassConfig(const Triple &FTT,
+                        jitlink::PassConfiguration &PassConfig);
+
+  using MemoryRegionInfo = RuntimeDyldChecker::MemoryRegionInfo;
+
+  struct FileInfo {
+    StringMap<MemoryRegionInfo> SectionInfos;
+    StringMap<MemoryRegionInfo> StubInfos;
+    StringMap<MemoryRegionInfo> GOTEntryInfos;
+  };
+
+  using SymbolInfoMap = StringMap<MemoryRegionInfo>;
+  using FileInfoMap = StringMap<FileInfo>;
+
+  Expected<FileInfo &> findFileInfo(StringRef FileName);
+  Expected<MemoryRegionInfo &> findSectionInfo(StringRef FileName,
+                                               StringRef SectionName);
+  Expected<MemoryRegionInfo &> findStubInfo(StringRef FileName,
+                                            StringRef TargetName);
+  Expected<MemoryRegionInfo &> findGOTEntryInfo(StringRef FileName,
+                                                StringRef TargetName);
+
+  bool isSymbolRegistered(StringRef Name);
+  Expected<MemoryRegionInfo &> findSymbolInfo(StringRef SymbolName,
+                                              Twine ErrorMsgStem);
+
+  SymbolInfoMap SymbolInfos;
+  FileInfoMap FileInfos;
+  uint64_t SizeBeforePruning = 0;
+  uint64_t SizeAfterFixups = 0;
+};
+
+Error registerMachOStubsAndGOT(Session &S, jitlink::AtomGraph &G);
+
+} // end namespace llvm
+
+#endif // LLVM_TOOLS_LLVM_JITLINK_LLVM_JITLINK_H

unittests/ExecutionEngine/CMakeLists.txt

@@ -12,6 +12,7 @@ add_llvm_unittest(ExecutionEngineTests
   ExecutionEngineTest.cpp
   )
 
+add_subdirectory(JITLink)
 add_subdirectory(Orc)
 
 # Include MCJIT tests only if native arch is a built JIT target.

unittests/ExecutionEngine/JITLink/CMakeLists.txt

@@ -0,0 +1,15 @@
+set(LLVM_LINK_COMPONENTS
+  ${LLVM_TARGETS_TO_BUILD}
+  JITLink
+  MC
+  Object
+  RuntimeDyld
+  Support
+  )
+
+add_llvm_unittest(JITLinkTests
+    JITLinkTestCommon.cpp
+    JITLinkTest_MachO_x86_64_Tests.cpp
+  )
+
+target_link_libraries(JITLinkTests PRIVATE LLVMTestingSupport)

unittests/ExecutionEngine/JITLink/JITLinkTestCommon.cpp

@@ -0,0 +1,232 @@
+//===------- JITLinkTestCommon.cpp - Common code for JITLink tests --------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "JITLinkTestCommon.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCParser/MCTargetAsmParser.h"
+#include "llvm/Support/TargetSelect.h"
+
+using namespace llvm::jitlink;
+namespace llvm {
+
+JITLinkTestCommon::TestResources::TestResources(StringRef AsmSrc,
+                                                StringRef TripleStr, bool PIC,
+                                                bool LargeCodeModel,
+                                                MCTargetOptions Options)
+    : ObjStream(ObjBuffer), Options(std::move(Options)) {
+  Triple TT(Triple::normalize(TripleStr));
+  initializeTripleSpecifics(TT);
+  initializeTestSpecifics(AsmSrc, TT, PIC, LargeCodeModel);
+}
+
+MemoryBufferRef
+JITLinkTestCommon::TestResources::getTestObjectBufferRef() const {
+  return MemoryBufferRef(StringRef(ObjBuffer.data(), ObjBuffer.size()),
+                         "Test object");
+}
+
+void JITLinkTestCommon::TestResources::initializeTripleSpecifics(Triple &TT) {
+  std::string Error;
+  TheTarget = TargetRegistry::lookupTarget("", TT, Error);
+
+  if (!TheTarget)
+    report_fatal_error(Error);
+
+  MRI.reset(TheTarget->createMCRegInfo(TT.getTriple()));
+  if (!MRI)
+    report_fatal_error("Could not build MCRegisterInfo for triple");
+
+  MAI.reset(TheTarget->createMCAsmInfo(*MRI, TT.getTriple()));
+  if (!MAI)
+    report_fatal_error("Could not build MCAsmInfo for triple");
+
+  MCII.reset(TheTarget->createMCInstrInfo());
+  if (!MCII)
+    report_fatal_error("Could not build MCInstrInfo for triple");
+
+  STI.reset(TheTarget->createMCSubtargetInfo(TT.getTriple(), "", ""));
+  if (!STI)
+    report_fatal_error("Could not build MCSubtargetInfo for triple");
+
+  DisCtx = llvm::make_unique<MCContext>(MAI.get(), MRI.get(), nullptr);
+  Dis.reset(TheTarget->createMCDisassembler(*STI, *DisCtx));
+
+  if (!Dis)
+    report_fatal_error("Could not build MCDisassembler");
+}
+
+void JITLinkTestCommon::TestResources::initializeTestSpecifics(
+    StringRef AsmSrc, const Triple &TT, bool PIC, bool LargeCodeModel) {
+  SrcMgr.AddNewSourceBuffer(MemoryBuffer::getMemBuffer(AsmSrc), SMLoc());
+  AsCtx = llvm::make_unique<MCContext>(MAI.get(), MRI.get(), &MOFI, &SrcMgr);
+  MOFI.InitMCObjectFileInfo(TT, PIC, *AsCtx, LargeCodeModel);
+
+  std::unique_ptr<MCCodeEmitter> CE(
+      TheTarget->createMCCodeEmitter(*MCII, *MRI, *AsCtx));
+  if (!CE)
+    report_fatal_error("Could not build MCCodeEmitter");
+
+  std::unique_ptr<MCAsmBackend> MAB(
+      TheTarget->createMCAsmBackend(*STI, *MRI, Options));
+  if (!MAB)
+    report_fatal_error("Could not build MCAsmBackend for test");
+
+  std::unique_ptr<MCObjectWriter> MOW(MAB->createObjectWriter(ObjStream));
+
+  MOS.reset(TheTarget->createMCObjectStreamer(
+      TT, *AsCtx, std::move(MAB), std::move(MOW), std::move(CE), *STI,
+      Options.MCRelaxAll, Options.MCIncrementalLinkerCompatible, false));
+
+  std::unique_ptr<MCAsmParser> MAP(
+      createMCAsmParser(SrcMgr, *AsCtx, *MOS, *MAI));
+  std::unique_ptr<MCTargetAsmParser> TAP(
+      TheTarget->createMCAsmParser(*STI, *MAP, *MCII, Options));
+
+  if (!TAP)
+    report_fatal_error("Could not build MCTargetAsmParser for test");
+
+  MAP->setTargetParser(*TAP);
+
+  if (MAP->Run(false))
+    report_fatal_error("Failed to parse test case");
+}
+
+JITLinkTestCommon::TestJITLinkContext::TestJITLinkContext(
+    TestResources &TR, TestCaseFunction TestCase)
+    : TR(TR), TestCase(std::move(TestCase)) {}
+
+JITLinkTestCommon::TestJITLinkContext &
+JITLinkTestCommon::TestJITLinkContext::setMemoryManager(
+    std::unique_ptr<JITLinkMemoryManager> MM) {
+  assert(!MemMgr && "Memory manager already set");
+  MemMgr = std::move(MM);
+  return *this;
+}
+
+JITLinkMemoryManager &
+JITLinkTestCommon::TestJITLinkContext::getMemoryManager() {
+  if (!MemMgr)
+    MemMgr = llvm::make_unique<InProcessMemoryManager>();
+  return *MemMgr;
+}
+
+MemoryBufferRef JITLinkTestCommon::TestJITLinkContext::getObjectBuffer() const {
+  return TR.getTestObjectBufferRef();
+}
+
+void JITLinkTestCommon::TestJITLinkContext::notifyFailed(Error Err) {
+  ADD_FAILURE() << "Unexpected failure: " << toString(std::move(Err));
+}
+
+void JITLinkTestCommon::TestJITLinkContext::lookup(
+    const DenseSet<StringRef> &Symbols,
+    JITLinkAsyncLookupContinuation LookupContinuation) {
+  jitlink::AsyncLookupResult LookupResult;
+  DenseSet<StringRef> MissingSymbols;
+  for (const auto &Symbol : Symbols) {
+    auto I = Externals.find(Symbol);
+    if (I != Externals.end())
+      LookupResult[Symbol] = I->second;
+    else
+      MissingSymbols.insert(Symbol);
+  }
+
+  if (MissingSymbols.empty())
+    LookupContinuation(std::move(LookupResult));
+  else {
+    std::string ErrMsg;
+    {
+      raw_string_ostream ErrMsgStream(ErrMsg);
+      ErrMsgStream << "Failed to resolve external symbols: [";
+      for (auto &Sym : MissingSymbols)
+        ErrMsgStream << " " << Sym;
+      ErrMsgStream << " ]\n";
+    }
+    LookupContinuation(
+        make_error<StringError>(std::move(ErrMsg), inconvertibleErrorCode()));
+  }
+}
+
+void JITLinkTestCommon::TestJITLinkContext::notifyResolved(AtomGraph &G) {
+  if (NotifyResolved)
+    NotifyResolved(G);
+}
+
+void JITLinkTestCommon::TestJITLinkContext::notifyFinalized(
+    std::unique_ptr<JITLinkMemoryManager::Allocation> A) {
+  if (NotifyFinalized)
+    NotifyFinalized(std::move(A));
+}
+
+Error JITLinkTestCommon::TestJITLinkContext::modifyPassConfig(
+    const Triple &TT, PassConfiguration &Config) {
+  if (TestCase)
+    Config.PostFixupPasses.push_back([&](AtomGraph &G) -> Error {
+      TestCase(G);
+      return Error::success();
+    });
+  return Error::success();
+}
+
+JITLinkTestCommon::JITLinkTestCommon() { initializeLLVMTargets(); }
+
+Expected<std::pair<MCInst, size_t>>
+JITLinkTestCommon::disassemble(const MCDisassembler &Dis,
+                               jitlink::DefinedAtom &Atom, size_t Offset) {
+  ArrayRef<uint8_t> InstBuffer(
+      reinterpret_cast<const uint8_t *>(Atom.getContent().data()) + Offset,
+      Atom.getContent().size() - Offset);
+
+  MCInst Inst;
+  uint64_t InstSize;
+  auto Status =
+      Dis.getInstruction(Inst, InstSize, InstBuffer, 0, nulls(), nulls());
+
+  if (Status != MCDisassembler::Success)
+    return make_error<StringError>("Could not disassemble instruction",
+                                   inconvertibleErrorCode());
+
+  return std::make_pair(Inst, InstSize);
+}
+
+Expected<int64_t>
+JITLinkTestCommon::decodeImmediateOperand(const MCDisassembler &Dis,
+                                          jitlink::DefinedAtom &Atom,
+                                          size_t OpIdx, size_t Offset) {
+  auto InstAndSize = disassemble(Dis, Atom, Offset);
+  if (!InstAndSize)
+    return InstAndSize.takeError();
+
+  if (OpIdx >= InstAndSize->first.getNumOperands())
+    return make_error<StringError>("Invalid operand index",
+                                   inconvertibleErrorCode());
+
+  auto &Op = InstAndSize->first.getOperand(OpIdx);
+
+  if (!Op.isImm())
+    return make_error<StringError>("Operand at index is not immediate",
+                                   inconvertibleErrorCode());
+
+  return Op.getImm();
+}
+
+bool JITLinkTestCommon::AreTargetsInitialized = false;
+
+void JITLinkTestCommon::initializeLLVMTargets() {
+  if (!AreTargetsInitialized) {
+    InitializeAllTargets();
+    InitializeAllTargetMCs();
+    InitializeAllAsmParsers();
+    InitializeAllAsmPrinters();
+    InitializeAllDisassemblers();
+    AreTargetsInitialized = true;
+  }
+}
+
+} // end namespace llvm

unittests/ExecutionEngine/JITLink/JITLinkTestCommon.h

@@ -0,0 +1,196 @@
+//===---- JITLinkTestCommon.h - Utilities for Orc Unit Tests ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Common utilities for JITLink unit tests.
+//
+//===----------------------------------------------------------------------===//
+
+
+#ifndef LLVM_UNITTESTS_EXECUTIONENGINE_JITLINK_JITLINKTESTCOMMON_H
+#define LLVM_UNITTESTS_EXECUTIONENGINE_JITLINK_JITLINKTESTCOMMON_H
+
+#include "llvm/ADT/Triple.h"
+#include "llvm/ExecutionEngine/JITLink/JITLink.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDisassembler/MCDisassembler.h"
+#include "llvm/MC/MCInstrInfo.h"
+#include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCObjectStreamer.h"
+#include "llvm/MC/MCParser/MCAsmParser.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/MC/MCTargetOptions.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/TargetRegistry.h"
+
+#include "gtest/gtest.h"
+
+namespace llvm {
+
+class JITLinkTestCommon {
+public:
+
+  class TestResources {
+  public:
+    TestResources(StringRef AsmSrc, StringRef TripleStr, bool PIC,
+                  bool LargeCodeModel, MCTargetOptions Options);
+
+    MemoryBufferRef getTestObjectBufferRef() const;
+
+    const MCDisassembler &getDisassembler() const { return *Dis; }
+
+  private:
+    void initializeTripleSpecifics(Triple &TT);
+    void initializeTestSpecifics(StringRef AsmSource, const Triple &TT,
+                                 bool PIC, bool LargeCodeModel);
+
+    const Target *TheTarget = nullptr;
+    SourceMgr SrcMgr;
+    SmallVector<char, 0> ObjBuffer;
+    raw_svector_ostream ObjStream;
+
+    MCTargetOptions Options;
+    std::unique_ptr<MCRegisterInfo> MRI;
+    std::unique_ptr<MCAsmInfo> MAI;
+    std::unique_ptr<MCInstrInfo> MCII;
+    std::unique_ptr<MCSubtargetInfo> STI;
+
+    MCObjectFileInfo MOFI;
+    std::unique_ptr<MCContext> AsCtx;
+    std::unique_ptr<MCStreamer> MOS;
+
+    std::unique_ptr<MCContext> DisCtx;
+    std::unique_ptr<const MCDisassembler> Dis;
+  };
+
+  class TestJITLinkContext : public jitlink::JITLinkContext {
+  public:
+    using TestCaseFunction = std::function<void(jitlink::AtomGraph &)>;
+
+    using NotifyResolvedFunction = std::function<void(jitlink::AtomGraph &G)>;
+
+    using NotifyFinalizedFunction = std::function<void(
+        std::unique_ptr<jitlink::JITLinkMemoryManager::Allocation>)>;
+
+    TestJITLinkContext(TestResources &TR, TestCaseFunction TestCase);
+
+    StringMap<JITEvaluatedSymbol> &externals() { return Externals; }
+
+    TestJITLinkContext &
+    setNotifyResolved(NotifyResolvedFunction NotifyResolved);
+
+    TestJITLinkContext &
+    setNotifyFinalized(NotifyFinalizedFunction NotifyFinalized);
+
+    TestJITLinkContext &
+    setMemoryManager(std::unique_ptr<jitlink::JITLinkMemoryManager> MM);
+
+    jitlink::JITLinkMemoryManager &getMemoryManager() override;
+
+    MemoryBufferRef getObjectBuffer() const override;
+
+    void notifyFailed(Error Err) override;
+
+    void
+    lookup(const DenseSet<StringRef> &Symbols,
+           jitlink::JITLinkAsyncLookupContinuation LookupContinuation) override;
+
+    void notifyResolved(jitlink::AtomGraph &G) override;
+
+    void notifyFinalized(
+        std::unique_ptr<jitlink::JITLinkMemoryManager::Allocation> A) override;
+
+    Error modifyPassConfig(const Triple &TT,
+                           jitlink::PassConfiguration &Config) override;
+
+  private:
+    TestResources &TR;
+    TestCaseFunction TestCase;
+    NotifyResolvedFunction NotifyResolved;
+    NotifyFinalizedFunction NotifyFinalized;
+    std::unique_ptr<MemoryBuffer> ObjBuffer;
+    std::unique_ptr<jitlink::JITLinkMemoryManager> MemMgr;
+    StringMap<JITEvaluatedSymbol> Externals;
+  };
+
+  JITLinkTestCommon();
+
+  std::unique_ptr<TestResources>
+  getTestResources(StringRef AsmSrc, StringRef Triple, bool PIC,
+                   bool LargeCodeModel, MCTargetOptions Options) const {
+    return llvm::make_unique<TestResources>(AsmSrc, Triple, PIC, LargeCodeModel,
+                                            std::move(Options));
+  }
+
+  template <typename T>
+  static Expected<T> readInt(jitlink::AtomGraph &G, jitlink::DefinedAtom &A,
+                             size_t Offset = 0) {
+    if (Offset + sizeof(T) > A.getContent().size())
+      return make_error<StringError>("Reading past end of atom content",
+                                     inconvertibleErrorCode());
+    return support::endian::read<T, 1>(A.getContent().data() + Offset,
+                                       G.getEndianness());
+  }
+
+  template <typename T>
+  static Expected<T> readInt(jitlink::AtomGraph &G, StringRef AtomName,
+                             size_t Offset = 0) {
+    auto DA = G.findDefinedAtomByName(AtomName);
+    if (!DA)
+      return DA.takeError();
+    return readInt<T>(G, *DA);
+  }
+
+  static Expected<std::pair<MCInst, size_t>>
+  disassemble(const MCDisassembler &Dis, jitlink::DefinedAtom &Atom,
+              size_t Offset = 0);
+
+  static Expected<int64_t> decodeImmediateOperand(const MCDisassembler &Dis,
+                                                  jitlink::DefinedAtom &Atom,
+                                                  size_t OpIdx,
+                                                  size_t Offset = 0);
+
+  static jitlink::Atom &atom(jitlink::AtomGraph &G, StringRef Name) {
+    return G.getAtomByName(Name);
+  }
+
+  static jitlink::DefinedAtom &definedAtom(jitlink::AtomGraph &G,
+                                           StringRef Name) {
+    return G.getDefinedAtomByName(Name);
+  }
+
+  static JITTargetAddress atomAddr(jitlink::AtomGraph &G, StringRef Name) {
+    return atom(G, Name).getAddress();
+  }
+
+  template <typename PredT>
+  static size_t countEdgesMatching(jitlink::DefinedAtom &DA,
+                                   const PredT &Pred) {
+    return std::count_if(DA.edges().begin(), DA.edges().end(), Pred);
+  }
+
+  template <typename PredT>
+  static size_t countEdgesMatching(jitlink::AtomGraph &G, StringRef Name,
+                                   const PredT &Pred) {
+    return countEdgesMatching(definedAtom(G, Name), Pred);
+  }
+
+private:
+
+  static bool AreTargetsInitialized;
+  void initializeLLVMTargets();
+
+  DenseMap<StringRef, JITEvaluatedSymbol> Externals;
+};
+
+} // end namespace llvm
+
+#endif

unittests/ExecutionEngine/JITLink/JITLinkTest_MachO_x86_64_Tests.cpp

@@ -0,0 +1,224 @@
+//===---- JITLinkTest_MachO_x86_64.cpp - Tests for JITLink MachO/x86-64 ---===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "JITLinkTestCommon.h"
+
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ExecutionEngine/JITLink/JITLink_MachO_x86_64.h"
+#include "llvm/Testing/Support/Error.h"
+
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace llvm::jitlink;
+using namespace llvm::jitlink::MachO_x86_64_Edges;
+
+namespace {
+
+class JITLinkTest_MachO_x86_64 : public JITLinkTestCommon,
+                                 public testing::Test {
+public:
+  using BasicVerifyGraphFunction =
+      std::function<void(AtomGraph &, const MCDisassembler &)>;
+
+  void runBasicVerifyGraphTest(StringRef AsmSrc, StringRef Triple,
+                               StringMap<JITEvaluatedSymbol> Externals,
+                               bool PIC, bool LargeCodeModel,
+                               MCTargetOptions Options,
+                               BasicVerifyGraphFunction RunGraphTest) {
+    auto TR = getTestResources(AsmSrc, Triple, PIC, LargeCodeModel,
+                               std::move(Options));
+
+    auto JTCtx = llvm::make_unique<TestJITLinkContext>(
+        *TR, [&](AtomGraph &G) { RunGraphTest(G, TR->getDisassembler()); });
+
+    JTCtx->externals() = std::move(Externals);
+
+    jitLink_MachO_x86_64(std::move(JTCtx));
+  }
+
+protected:
+  static void verifyIsPointerTo(AtomGraph &G, DefinedAtom &A, Atom &Target) {
+    EXPECT_EQ(A.edges_size(), 1U) << "Incorrect number of edges for pointer";
+    if (A.edges_size() != 1U)
+      return;
+    auto &E = *A.edges().begin();
+    EXPECT_EQ(E.getKind(), Pointer64)
+        << "Expected pointer to have a pointer64 relocation";
+    EXPECT_EQ(&E.getTarget(), &Target) << "Expected edge to point at target";
+    EXPECT_THAT_EXPECTED(readInt<uint64_t>(G, A), HasValue(Target.getAddress()))
+        << "Pointer does not point to target";
+  }
+
+  static void verifyGOTLoad(AtomGraph &G, DefinedAtom &A, Edge &E,
+                            Atom &Target) {
+    EXPECT_EQ(E.getAddend(), 0U) << "Expected GOT load to have a zero addend";
+    EXPECT_TRUE(E.getTarget().isDefined())
+        << "GOT entry should be a defined atom";
+    if (!E.getTarget().isDefined())
+      return;
+
+    verifyIsPointerTo(G, static_cast<DefinedAtom &>(E.getTarget()), Target);
+  }
+
+  static void verifyCall(const MCDisassembler &Dis, AtomGraph &G,
+                         DefinedAtom &Caller, Edge &E, Atom &Callee) {
+    EXPECT_EQ(E.getKind(), Branch32) << "Edge is not a Branch32";
+    EXPECT_EQ(E.getAddend(), 0U) << "Expected no addend on stub call";
+    EXPECT_EQ(&E.getTarget(), &Callee)
+        << "Edge does not point at expected callee";
+
+    JITTargetAddress FixupAddress = Caller.getAddress() + E.getOffset();
+    uint64_t PCRelDelta = Callee.getAddress() - (FixupAddress + 4);
+
+    EXPECT_THAT_EXPECTED(
+        decodeImmediateOperand(Dis, Caller, 0, E.getOffset() - 1),
+        HasValue(PCRelDelta));
+  }
+
+  static void verifyIndirectCall(const MCDisassembler &Dis, AtomGraph &G,
+                                 DefinedAtom &Caller, Edge &E, Atom &Callee) {
+    EXPECT_EQ(E.getKind(), PCRel32) << "Edge is not a PCRel32";
+    EXPECT_EQ(E.getAddend(), 0) << "Expected no addend on stub cal";
+    EXPECT_TRUE(E.getTarget().isDefined()) << "Target is not a defined atom";
+    if (!E.getTarget().isDefined())
+      return;
+    verifyIsPointerTo(G, static_cast<DefinedAtom &>(E.getTarget()), Callee);
+
+    JITTargetAddress FixupAddress = Caller.getAddress() + E.getOffset();
+    uint64_t PCRelDelta = E.getTarget().getAddress() - (FixupAddress + 4);
+
+    EXPECT_THAT_EXPECTED(
+        decodeImmediateOperand(Dis, Caller, 3, E.getOffset() - 2),
+        HasValue(PCRelDelta));
+  }
+
+  static void verifyCallViaStub(const MCDisassembler &Dis, AtomGraph &G,
+                                DefinedAtom &Caller, Edge &E, Atom &Callee) {
+    verifyCall(Dis, G, Caller, E, E.getTarget());
+
+    if (!E.getTarget().isDefined()) {
+      ADD_FAILURE() << "Edge target is not a stub";
+      return;
+    }
+
+    auto &StubAtom = static_cast<DefinedAtom &>(E.getTarget());
+    EXPECT_EQ(StubAtom.edges_size(), 1U)
+        << "Expected one edge from stub to target";
+
+    auto &StubEdge = *StubAtom.edges().begin();
+
+    verifyIndirectCall(Dis, G, static_cast<DefinedAtom &>(StubAtom), StubEdge,
+                       Callee);
+  }
+};
+
+} // end anonymous namespace
+
+// Test each operation on LegacyObjectTransformLayer.
+TEST_F(JITLinkTest_MachO_x86_64, BasicRelocations) {
+  runBasicVerifyGraphTest(
+      R"(
+            .section        __TEXT,__text,regular,pure_instructions
+            .build_version macos, 10, 14
+            .globl  _bar
+            .p2align        4, 0x90
+    _bar:
+            callq    _baz
+
+            .globl  _foo
+            .p2align        4, 0x90
+    _foo:
+            callq   _bar
+    _foo.1:
+            movq    _y@GOTPCREL(%rip), %rcx
+    _foo.2:
+            movq    _p(%rip), %rdx
+
+            .section        __DATA,__data
+            .globl  _x
+            .p2align        2
+    _x:
+            .long   42
+
+            .globl  _p
+            .p2align        3
+    _p:
+            .quad   _x
+
+    .subsections_via_symbols)",
+      "x86_64-apple-macosx10.14",
+      {{"_y", JITEvaluatedSymbol(0xdeadbeef, JITSymbolFlags::Exported)},
+       {"_baz", JITEvaluatedSymbol(0xcafef00d, JITSymbolFlags::Exported)}},
+      true, false, MCTargetOptions(),
+      [](AtomGraph &G, const MCDisassembler &Dis) {
+        // Name the atoms in the asm above.
+        auto &Baz = atom(G, "_baz");
+        auto &Y = atom(G, "_y");
+
+        auto &Bar = definedAtom(G, "_bar");
+        auto &Foo = definedAtom(G, "_foo");
+        auto &Foo_1 = definedAtom(G, "_foo.1");
+        auto &Foo_2 = definedAtom(G, "_foo.2");
+        auto &X = definedAtom(G, "_x");
+        auto &P = definedAtom(G, "_p");
+
+        // Check unsigned reloc for _p
+        {
+          EXPECT_EQ(P.edges_size(), 1U) << "Unexpected number of relocations";
+          EXPECT_EQ(P.edges().begin()->getKind(), Pointer64)
+              << "Unexpected edge kind for _p";
+          EXPECT_THAT_EXPECTED(readInt<uint64_t>(G, P),
+                               HasValue(X.getAddress()))
+              << "Unsigned relocation did not apply correctly";
+        }
+
+        // Check that _bar is a call-via-stub to _baz.
+        // This will check that the call goes to a stub, that the stub is an
+        // indirect call, and that the pointer for the indirect call points to
+        // baz.
+        {
+          EXPECT_EQ(Bar.edges_size(), 1U)
+              << "Incorrect number of edges for bar";
+          EXPECT_EQ(Bar.edges().begin()->getKind(), Branch32)
+              << "Unexpected edge kind for _bar";
+          verifyCallViaStub(Dis, G, Bar, *Bar.edges().begin(), Baz);
+        }
+
+        // Check that _foo is a direct call to _bar.
+        {
+          EXPECT_EQ(Foo.edges_size(), 1U)
+              << "Incorrect number of edges for foo";
+          EXPECT_EQ(Foo.edges().begin()->getKind(), Branch32);
+          verifyCall(Dis, G, Foo, *Foo.edges().begin(), Bar);
+        }
+
+        // Check .got load in _foo.1
+        {
+          EXPECT_EQ(Foo_1.edges_size(), 1U)
+              << "Incorrect number of edges for foo_1";
+          EXPECT_EQ(Foo_1.edges().begin()->getKind(), PCRel32);
+          verifyGOTLoad(G, Foo_1, *Foo_1.edges().begin(), Y);
+        }
+
+        // Check PCRel ref to _p in _foo.2
+        {
+          EXPECT_EQ(Foo_2.edges_size(), 1U)
+              << "Incorrect number of edges for foo_2";
+          EXPECT_EQ(Foo_2.edges().begin()->getKind(), PCRel32);
+
+          JITTargetAddress FixupAddress =
+              Foo_2.getAddress() + Foo_2.edges().begin()->getOffset();
+          uint64_t PCRelDelta = P.getAddress() - (FixupAddress + 4);
+
+          EXPECT_THAT_EXPECTED(decodeImmediateOperand(Dis, Foo_2, 4, 0),
+                               HasValue(PCRelDelta))
+              << "PCRel load does not reference expected target";
+        }
+      });
+}