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llvm-mirror/lib/CodeGen/MachineOutliner.cpp
Djordje Todorovic f63712851c [CSInfo] Use isCandidateForCallSiteEntry() when updating the CSInfo 
Use the isCandidateForCallSiteEntry().
This should mostly be an NFC, but there are some parts ensuring
the moveCallSiteInfo() and copyCallSiteInfo() operate with call site
entry candidates (both Src and Dest should be the call site entry
candidates).

Differential Revision: https://reviews.llvm.org/D74122
2020-02-10 10:03:14 +01:00

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//===---- MachineOutliner.cpp - Outline instructions -----------*- 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
//
//===----------------------------------------------------------------------===//
///
/// \file
/// Replaces repeated sequences of instructions with function calls.
///
/// This works by placing every instruction from every basic block in a
/// suffix tree, and repeatedly querying that tree for repeated sequences of
/// instructions. If a sequence of instructions appears often, then it ought
/// to be beneficial to pull out into a function.
///
/// The MachineOutliner communicates with a given target using hooks defined in
/// TargetInstrInfo.h. The target supplies the outliner with information on how
/// a specific sequence of instructions should be outlined. This information
/// is used to deduce the number of instructions necessary to
///
/// * Create an outlined function
/// * Call that outlined function
///
/// Targets must implement
/// * getOutliningCandidateInfo
/// * buildOutlinedFrame
/// * insertOutlinedCall
/// * isFunctionSafeToOutlineFrom
///
/// in order to make use of the MachineOutliner.
///
/// This was originally presented at the 2016 LLVM Developers' Meeting in the
/// talk "Reducing Code Size Using Outlining". For a high-level overview of
/// how this pass works, the talk is available on YouTube at
///
/// https://www.youtube.com/watch?v=yorld-WSOeU
///
/// The slides for the talk are available at
///
/// http://www.llvm.org/devmtg/2016-11/Slides/Paquette-Outliner.pdf
///
/// The talk provides an overview of how the outliner finds candidates and
/// ultimately outlines them. It describes how the main data structure for this
/// pass, the suffix tree, is queried and purged for candidates. It also gives
/// a simplified suffix tree construction algorithm for suffix trees based off
/// of the algorithm actually used here, Ukkonen's algorithm.
///
/// For the original RFC for this pass, please see
///
/// http://lists.llvm.org/pipermail/llvm-dev/2016-August/104170.html
///
/// For more information on the suffix tree data structure, please see
/// https://www.cs.helsinki.fi/u/ukkonen/SuffixT1withFigs.pdf
///
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineOutliner.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Mangler.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <functional>
#include <tuple>
#include <vector>
#define DEBUG_TYPE "machine-outliner"
using namespace llvm;
using namespace ore;
using namespace outliner;
STATISTIC(NumOutlined, "Number of candidates outlined");
STATISTIC(FunctionsCreated, "Number of functions created");
// Set to true if the user wants the outliner to run on linkonceodr linkage
// functions. This is false by default because the linker can dedupe linkonceodr
// functions. Since the outliner is confined to a single module (modulo LTO),
// this is off by default. It should, however, be the default behaviour in
// LTO.
static cl::opt<bool> EnableLinkOnceODROutlining(
"enable-linkonceodr-outlining", cl::Hidden,
cl::desc("Enable the machine outliner on linkonceodr functions"),
cl::init(false));
namespace {
/// Represents an undefined index in the suffix tree.
const unsigned EmptyIdx = -1;
/// A node in a suffix tree which represents a substring or suffix.
///
/// Each node has either no children or at least two children, with the root
/// being a exception in the empty tree.
///
/// Children are represented as a map between unsigned integers and nodes. If
/// a node N has a child M on unsigned integer k, then the mapping represented
/// by N is a proper prefix of the mapping represented by M. Note that this,
/// although similar to a trie is somewhat different: each node stores a full
/// substring of the full mapping rather than a single character state.
///
/// Each internal node contains a pointer to the internal node representing
/// the same string, but with the first character chopped off. This is stored
/// in \p Link. Each leaf node stores the start index of its respective
/// suffix in \p SuffixIdx.
struct SuffixTreeNode {
/// The children of this node.
///
/// A child existing on an unsigned integer implies that from the mapping
/// represented by the current node, there is a way to reach another
/// mapping by tacking that character on the end of the current string.
DenseMap<unsigned, SuffixTreeNode *> Children;
/// The start index of this node's substring in the main string.
unsigned StartIdx = EmptyIdx;
/// The end index of this node's substring in the main string.
///
/// Every leaf node must have its \p EndIdx incremented at the end of every
/// step in the construction algorithm. To avoid having to update O(N)
/// nodes individually at the end of every step, the end index is stored
/// as a pointer.
unsigned *EndIdx = nullptr;
/// For leaves, the start index of the suffix represented by this node.
///
/// For all other nodes, this is ignored.
unsigned SuffixIdx = EmptyIdx;
/// For internal nodes, a pointer to the internal node representing
/// the same sequence with the first character chopped off.
///
/// This acts as a shortcut in Ukkonen's algorithm. One of the things that
/// Ukkonen's algorithm does to achieve linear-time construction is
/// keep track of which node the next insert should be at. This makes each
/// insert O(1), and there are a total of O(N) inserts. The suffix link
/// helps with inserting children of internal nodes.
///
/// Say we add a child to an internal node with associated mapping S. The
/// next insertion must be at the node representing S - its first character.
/// This is given by the way that we iteratively build the tree in Ukkonen's
/// algorithm. The main idea is to look at the suffixes of each prefix in the
/// string, starting with the longest suffix of the prefix, and ending with
/// the shortest. Therefore, if we keep pointers between such nodes, we can
/// move to the next insertion point in O(1) time. If we don't, then we'd
/// have to query from the root, which takes O(N) time. This would make the
/// construction algorithm O(N^2) rather than O(N).
SuffixTreeNode *Link = nullptr;
/// The length of the string formed by concatenating the edge labels from the
/// root to this node.
unsigned ConcatLen = 0;
/// Returns true if this node is a leaf.
bool isLeaf() const { return SuffixIdx != EmptyIdx; }
/// Returns true if this node is the root of its owning \p SuffixTree.
bool isRoot() const { return StartIdx == EmptyIdx; }
/// Return the number of elements in the substring associated with this node.
size_t size() const {
// Is it the root? If so, it's the empty string so return 0.
if (isRoot())
return 0;
assert(*EndIdx != EmptyIdx && "EndIdx is undefined!");
// Size = the number of elements in the string.
// For example, [0 1 2 3] has length 4, not 3. 3-0 = 3, so we have 3-0+1.
return *EndIdx - StartIdx + 1;
}
SuffixTreeNode(unsigned StartIdx, unsigned *EndIdx, SuffixTreeNode *Link)
: StartIdx(StartIdx), EndIdx(EndIdx), Link(Link) {}
SuffixTreeNode() {}
};
/// A data structure for fast substring queries.
///
/// Suffix trees represent the suffixes of their input strings in their leaves.
/// A suffix tree is a type of compressed trie structure where each node
/// represents an entire substring rather than a single character. Each leaf
/// of the tree is a suffix.
///
/// A suffix tree can be seen as a type of state machine where each state is a
/// substring of the full string. The tree is structured so that, for a string
/// of length N, there are exactly N leaves in the tree. This structure allows
/// us to quickly find repeated substrings of the input string.
///
/// In this implementation, a "string" is a vector of unsigned integers.
/// These integers may result from hashing some data type. A suffix tree can
/// contain 1 or many strings, which can then be queried as one large string.
///
/// The suffix tree is implemented using Ukkonen's algorithm for linear-time
/// suffix tree construction. Ukkonen's algorithm is explained in more detail
/// in the paper by Esko Ukkonen "On-line construction of suffix trees. The
/// paper is available at
///
/// https://www.cs.helsinki.fi/u/ukkonen/SuffixT1withFigs.pdf
class SuffixTree {
public:
/// Each element is an integer representing an instruction in the module.
ArrayRef<unsigned> Str;
/// A repeated substring in the tree.
struct RepeatedSubstring {
/// The length of the string.
unsigned Length;
/// The start indices of each occurrence.
std::vector<unsigned> StartIndices;
};
private:
/// Maintains each node in the tree.
SpecificBumpPtrAllocator<SuffixTreeNode> NodeAllocator;
/// The root of the suffix tree.
///
/// The root represents the empty string. It is maintained by the
/// \p NodeAllocator like every other node in the tree.
SuffixTreeNode *Root = nullptr;
/// Maintains the end indices of the internal nodes in the tree.
///
/// Each internal node is guaranteed to never have its end index change
/// during the construction algorithm; however, leaves must be updated at
/// every step. Therefore, we need to store leaf end indices by reference
/// to avoid updating O(N) leaves at every step of construction. Thus,
/// every internal node must be allocated its own end index.
BumpPtrAllocator InternalEndIdxAllocator;
/// The end index of each leaf in the tree.
unsigned LeafEndIdx = -1;
/// Helper struct which keeps track of the next insertion point in
/// Ukkonen's algorithm.
struct ActiveState {
/// The next node to insert at.
SuffixTreeNode *Node = nullptr;
/// The index of the first character in the substring currently being added.
unsigned Idx = EmptyIdx;
/// The length of the substring we have to add at the current step.
unsigned Len = 0;
};
/// The point the next insertion will take place at in the
/// construction algorithm.
ActiveState Active;
/// Allocate a leaf node and add it to the tree.
///
/// \param Parent The parent of this node.
/// \param StartIdx The start index of this node's associated string.
/// \param Edge The label on the edge leaving \p Parent to this node.
///
/// \returns A pointer to the allocated leaf node.
SuffixTreeNode *insertLeaf(SuffixTreeNode &Parent, unsigned StartIdx,
unsigned Edge) {
assert(StartIdx <= LeafEndIdx && "String can't start after it ends!");
SuffixTreeNode *N = new (NodeAllocator.Allocate())
SuffixTreeNode(StartIdx, &LeafEndIdx, nullptr);
Parent.Children[Edge] = N;
return N;
}
/// Allocate an internal node and add it to the tree.
///
/// \param Parent The parent of this node. Only null when allocating the root.
/// \param StartIdx The start index of this node's associated string.
/// \param EndIdx The end index of this node's associated string.
/// \param Edge The label on the edge leaving \p Parent to this node.
///
/// \returns A pointer to the allocated internal node.
SuffixTreeNode *insertInternalNode(SuffixTreeNode *Parent, unsigned StartIdx,
unsigned EndIdx, unsigned Edge) {
assert(StartIdx <= EndIdx && "String can't start after it ends!");
assert(!(!Parent && StartIdx != EmptyIdx) &&
"Non-root internal nodes must have parents!");
unsigned *E = new (InternalEndIdxAllocator) unsigned(EndIdx);
SuffixTreeNode *N =
new (NodeAllocator.Allocate()) SuffixTreeNode(StartIdx, E, Root);
if (Parent)
Parent->Children[Edge] = N;
return N;
}
/// Set the suffix indices of the leaves to the start indices of their
/// respective suffixes.
void setSuffixIndices() {
// List of nodes we need to visit along with the current length of the
// string.
std::vector<std::pair<SuffixTreeNode *, unsigned>> ToVisit;
// Current node being visited.
SuffixTreeNode *CurrNode = Root;
// Sum of the lengths of the nodes down the path to the current one.
unsigned CurrNodeLen = 0;
ToVisit.push_back({CurrNode, CurrNodeLen});
while (!ToVisit.empty()) {
std::tie(CurrNode, CurrNodeLen) = ToVisit.back();
ToVisit.pop_back();
CurrNode->ConcatLen = CurrNodeLen;
for (auto &ChildPair : CurrNode->Children) {
assert(ChildPair.second && "Node had a null child!");
ToVisit.push_back(
{ChildPair.second, CurrNodeLen + ChildPair.second->size()});
}
// No children, so we are at the end of the string.
if (CurrNode->Children.size() == 0 && !CurrNode->isRoot())
CurrNode->SuffixIdx = Str.size() - CurrNodeLen;
}
}
/// Construct the suffix tree for the prefix of the input ending at
/// \p EndIdx.
///
/// Used to construct the full suffix tree iteratively. At the end of each
/// step, the constructed suffix tree is either a valid suffix tree, or a
/// suffix tree with implicit suffixes. At the end of the final step, the
/// suffix tree is a valid tree.
///
/// \param EndIdx The end index of the current prefix in the main string.
/// \param SuffixesToAdd The number of suffixes that must be added
/// to complete the suffix tree at the current phase.
///
/// \returns The number of suffixes that have not been added at the end of
/// this step.
unsigned extend(unsigned EndIdx, unsigned SuffixesToAdd) {
SuffixTreeNode *NeedsLink = nullptr;
while (SuffixesToAdd > 0) {
// Are we waiting to add anything other than just the last character?
if (Active.Len == 0) {
// If not, then say the active index is the end index.
Active.Idx = EndIdx;
}
assert(Active.Idx <= EndIdx && "Start index can't be after end index!");
// The first character in the current substring we're looking at.
unsigned FirstChar = Str[Active.Idx];
// Have we inserted anything starting with FirstChar at the current node?
if (Active.Node->Children.count(FirstChar) == 0) {
// If not, then we can just insert a leaf and move too the next step.
insertLeaf(*Active.Node, EndIdx, FirstChar);
// The active node is an internal node, and we visited it, so it must
// need a link if it doesn't have one.
if (NeedsLink) {
NeedsLink->Link = Active.Node;
NeedsLink = nullptr;
}
} else {
// There's a match with FirstChar, so look for the point in the tree to
// insert a new node.
SuffixTreeNode *NextNode = Active.Node->Children[FirstChar];
unsigned SubstringLen = NextNode->size();
// Is the current suffix we're trying to insert longer than the size of
// the child we want to move to?
if (Active.Len >= SubstringLen) {
// If yes, then consume the characters we've seen and move to the next
// node.
Active.Idx += SubstringLen;
Active.Len -= SubstringLen;
Active.Node = NextNode;
continue;
}
// Otherwise, the suffix we're trying to insert must be contained in the
// next node we want to move to.
unsigned LastChar = Str[EndIdx];
// Is the string we're trying to insert a substring of the next node?
if (Str[NextNode->StartIdx + Active.Len] == LastChar) {
// If yes, then we're done for this step. Remember our insertion point
// and move to the next end index. At this point, we have an implicit
// suffix tree.
if (NeedsLink && !Active.Node->isRoot()) {
NeedsLink->Link = Active.Node;
NeedsLink = nullptr;
}
Active.Len++;
break;
}
// The string we're trying to insert isn't a substring of the next node,
// but matches up to a point. Split the node.
//
// For example, say we ended our search at a node n and we're trying to
// insert ABD. Then we'll create a new node s for AB, reduce n to just
// representing C, and insert a new leaf node l to represent d. This
// allows us to ensure that if n was a leaf, it remains a leaf.
//
// | ABC ---split---> | AB
// n s
// C / \ D
// n l
// The node s from the diagram
SuffixTreeNode *SplitNode =
insertInternalNode(Active.Node, NextNode->StartIdx,
NextNode->StartIdx + Active.Len - 1, FirstChar);
// Insert the new node representing the new substring into the tree as
// a child of the split node. This is the node l from the diagram.
insertLeaf(*SplitNode, EndIdx, LastChar);
// Make the old node a child of the split node and update its start
// index. This is the node n from the diagram.
NextNode->StartIdx += Active.Len;
SplitNode->Children[Str[NextNode->StartIdx]] = NextNode;
// SplitNode is an internal node, update the suffix link.
if (NeedsLink)
NeedsLink->Link = SplitNode;
NeedsLink = SplitNode;
}
// We've added something new to the tree, so there's one less suffix to
// add.
SuffixesToAdd--;
if (Active.Node->isRoot()) {
if (Active.Len > 0) {
Active.Len--;
Active.Idx = EndIdx - SuffixesToAdd + 1;
}
} else {
// Start the next phase at the next smallest suffix.
Active.Node = Active.Node->Link;
}
}
return SuffixesToAdd;
}
public:
/// Construct a suffix tree from a sequence of unsigned integers.
///
/// \param Str The string to construct the suffix tree for.
SuffixTree(const std::vector<unsigned> &Str) : Str(Str) {
Root = insertInternalNode(nullptr, EmptyIdx, EmptyIdx, 0);
Active.Node = Root;
// Keep track of the number of suffixes we have to add of the current
// prefix.
unsigned SuffixesToAdd = 0;
// Construct the suffix tree iteratively on each prefix of the string.
// PfxEndIdx is the end index of the current prefix.
// End is one past the last element in the string.
for (unsigned PfxEndIdx = 0, End = Str.size(); PfxEndIdx < End;
PfxEndIdx++) {
SuffixesToAdd++;
LeafEndIdx = PfxEndIdx; // Extend each of the leaves.
SuffixesToAdd = extend(PfxEndIdx, SuffixesToAdd);
}
// Set the suffix indices of each leaf.
assert(Root && "Root node can't be nullptr!");
setSuffixIndices();
}
/// Iterator for finding all repeated substrings in the suffix tree.
struct RepeatedSubstringIterator {
private:
/// The current node we're visiting.
SuffixTreeNode *N = nullptr;
/// The repeated substring associated with this node.
RepeatedSubstring RS;
/// The nodes left to visit.
std::vector<SuffixTreeNode *> ToVisit;
/// The minimum length of a repeated substring to find.
/// Since we're outlining, we want at least two instructions in the range.
/// FIXME: This may not be true for targets like X86 which support many
/// instruction lengths.
const unsigned MinLength = 2;
/// Move the iterator to the next repeated substring.
void advance() {
// Clear the current state. If we're at the end of the range, then this
// is the state we want to be in.
RS = RepeatedSubstring();
N = nullptr;
// Each leaf node represents a repeat of a string.
std::vector<SuffixTreeNode *> LeafChildren;
// Continue visiting nodes until we find one which repeats more than once.
while (!ToVisit.empty()) {
SuffixTreeNode *Curr = ToVisit.back();
ToVisit.pop_back();
LeafChildren.clear();
// Keep track of the length of the string associated with the node. If
// it's too short, we'll quit.
unsigned Length = Curr->ConcatLen;
// Iterate over each child, saving internal nodes for visiting, and
// leaf nodes in LeafChildren. Internal nodes represent individual
// strings, which may repeat.
for (auto &ChildPair : Curr->Children) {
// Save all of this node's children for processing.
if (!ChildPair.second->isLeaf())
ToVisit.push_back(ChildPair.second);
// It's not an internal node, so it must be a leaf. If we have a
// long enough string, then save the leaf children.
else if (Length >= MinLength)
LeafChildren.push_back(ChildPair.second);
}
// The root never represents a repeated substring. If we're looking at
// that, then skip it.
if (Curr->isRoot())
continue;
// Do we have any repeated substrings?
if (LeafChildren.size() >= 2) {
// Yes. Update the state to reflect this, and then bail out.
N = Curr;
RS.Length = Length;
for (SuffixTreeNode *Leaf : LeafChildren)
RS.StartIndices.push_back(Leaf->SuffixIdx);
break;
}
}
// At this point, either NewRS is an empty RepeatedSubstring, or it was
// set in the above loop. Similarly, N is either nullptr, or the node
// associated with NewRS.
}
public:
/// Return the current repeated substring.
RepeatedSubstring &operator*() { return RS; }
RepeatedSubstringIterator &operator++() {
advance();
return *this;
}
RepeatedSubstringIterator operator++(int I) {
RepeatedSubstringIterator It(*this);
advance();
return It;
}
bool operator==(const RepeatedSubstringIterator &Other) {
return N == Other.N;
}
bool operator!=(const RepeatedSubstringIterator &Other) {
return !(*this == Other);
}
RepeatedSubstringIterator(SuffixTreeNode *N) : N(N) {
// Do we have a non-null node?
if (N) {
// Yes. At the first step, we need to visit all of N's children.
// Note: This means that we visit N last.
ToVisit.push_back(N);
advance();
}
}
};
typedef RepeatedSubstringIterator iterator;
iterator begin() { return iterator(Root); }
iterator end() { return iterator(nullptr); }
};
/// Maps \p MachineInstrs to unsigned integers and stores the mappings.
struct InstructionMapper {
/// The next available integer to assign to a \p MachineInstr that
/// cannot be outlined.
///
/// Set to -3 for compatability with \p DenseMapInfo<unsigned>.
unsigned IllegalInstrNumber = -3;
/// The next available integer to assign to a \p MachineInstr that can
/// be outlined.
unsigned LegalInstrNumber = 0;
/// Correspondence from \p MachineInstrs to unsigned integers.
DenseMap<MachineInstr *, unsigned, MachineInstrExpressionTrait>
InstructionIntegerMap;
/// Correspondence between \p MachineBasicBlocks and target-defined flags.
DenseMap<MachineBasicBlock *, unsigned> MBBFlagsMap;
/// The vector of unsigned integers that the module is mapped to.
std::vector<unsigned> UnsignedVec;
/// Stores the location of the instruction associated with the integer
/// at index i in \p UnsignedVec for each index i.
std::vector<MachineBasicBlock::iterator> InstrList;
// Set if we added an illegal number in the previous step.
// Since each illegal number is unique, we only need one of them between
// each range of legal numbers. This lets us make sure we don't add more
// than one illegal number per range.
bool AddedIllegalLastTime = false;
/// Maps \p *It to a legal integer.
///
/// Updates \p CanOutlineWithPrevInstr, \p HaveLegalRange, \p InstrListForMBB,
/// \p UnsignedVecForMBB, \p InstructionIntegerMap, and \p LegalInstrNumber.
///
/// \returns The integer that \p *It was mapped to.
unsigned mapToLegalUnsigned(
MachineBasicBlock::iterator &It, bool &CanOutlineWithPrevInstr,
bool &HaveLegalRange, unsigned &NumLegalInBlock,
std::vector<unsigned> &UnsignedVecForMBB,
std::vector<MachineBasicBlock::iterator> &InstrListForMBB) {
// We added something legal, so we should unset the AddedLegalLastTime
// flag.
AddedIllegalLastTime = false;
// If we have at least two adjacent legal instructions (which may have
// invisible instructions in between), remember that.
if (CanOutlineWithPrevInstr)
HaveLegalRange = true;
CanOutlineWithPrevInstr = true;
// Keep track of the number of legal instructions we insert.
NumLegalInBlock++;
// Get the integer for this instruction or give it the current
// LegalInstrNumber.
InstrListForMBB.push_back(It);
MachineInstr &MI = *It;
bool WasInserted;
DenseMap<MachineInstr *, unsigned, MachineInstrExpressionTrait>::iterator
ResultIt;
std::tie(ResultIt, WasInserted) =
InstructionIntegerMap.insert(std::make_pair(&MI, LegalInstrNumber));
unsigned MINumber = ResultIt->second;
// There was an insertion.
if (WasInserted)
LegalInstrNumber++;
UnsignedVecForMBB.push_back(MINumber);
// Make sure we don't overflow or use any integers reserved by the DenseMap.
if (LegalInstrNumber >= IllegalInstrNumber)
report_fatal_error("Instruction mapping overflow!");
assert(LegalInstrNumber != DenseMapInfo<unsigned>::getEmptyKey() &&
"Tried to assign DenseMap tombstone or empty key to instruction.");
assert(LegalInstrNumber != DenseMapInfo<unsigned>::getTombstoneKey() &&
"Tried to assign DenseMap tombstone or empty key to instruction.");
return MINumber;
}
/// Maps \p *It to an illegal integer.
///
/// Updates \p InstrListForMBB, \p UnsignedVecForMBB, and \p
/// IllegalInstrNumber.
///
/// \returns The integer that \p *It was mapped to.
unsigned mapToIllegalUnsigned(
MachineBasicBlock::iterator &It, bool &CanOutlineWithPrevInstr,
std::vector<unsigned> &UnsignedVecForMBB,
std::vector<MachineBasicBlock::iterator> &InstrListForMBB) {
// Can't outline an illegal instruction. Set the flag.
CanOutlineWithPrevInstr = false;
// Only add one illegal number per range of legal numbers.
if (AddedIllegalLastTime)
return IllegalInstrNumber;
// Remember that we added an illegal number last time.
AddedIllegalLastTime = true;
unsigned MINumber = IllegalInstrNumber;
InstrListForMBB.push_back(It);
UnsignedVecForMBB.push_back(IllegalInstrNumber);
IllegalInstrNumber--;
assert(LegalInstrNumber < IllegalInstrNumber &&
"Instruction mapping overflow!");
assert(IllegalInstrNumber != DenseMapInfo<unsigned>::getEmptyKey() &&
"IllegalInstrNumber cannot be DenseMap tombstone or empty key!");
assert(IllegalInstrNumber != DenseMapInfo<unsigned>::getTombstoneKey() &&
"IllegalInstrNumber cannot be DenseMap tombstone or empty key!");
return MINumber;
}
/// Transforms a \p MachineBasicBlock into a \p vector of \p unsigneds
/// and appends it to \p UnsignedVec and \p InstrList.
///
/// Two instructions are assigned the same integer if they are identical.
/// If an instruction is deemed unsafe to outline, then it will be assigned an
/// unique integer. The resulting mapping is placed into a suffix tree and
/// queried for candidates.
///
/// \param MBB The \p MachineBasicBlock to be translated into integers.
/// \param TII \p TargetInstrInfo for the function.
void convertToUnsignedVec(MachineBasicBlock &MBB,
const TargetInstrInfo &TII) {
unsigned Flags = 0;
// Don't even map in this case.
if (!TII.isMBBSafeToOutlineFrom(MBB, Flags))
return;
// Store info for the MBB for later outlining.
MBBFlagsMap[&MBB] = Flags;
MachineBasicBlock::iterator It = MBB.begin();
// The number of instructions in this block that will be considered for
// outlining.
unsigned NumLegalInBlock = 0;
// True if we have at least two legal instructions which aren't separated
// by an illegal instruction.
bool HaveLegalRange = false;
// True if we can perform outlining given the last mapped (non-invisible)
// instruction. This lets us know if we have a legal range.
bool CanOutlineWithPrevInstr = false;
// FIXME: Should this all just be handled in the target, rather than using
// repeated calls to getOutliningType?
std::vector<unsigned> UnsignedVecForMBB;
std::vector<MachineBasicBlock::iterator> InstrListForMBB;
for (MachineBasicBlock::iterator Et = MBB.end(); It != Et; ++It) {
// Keep track of where this instruction is in the module.
switch (TII.getOutliningType(It, Flags)) {
case InstrType::Illegal:
mapToIllegalUnsigned(It, CanOutlineWithPrevInstr, UnsignedVecForMBB,
InstrListForMBB);
break;
case InstrType::Legal:
mapToLegalUnsigned(It, CanOutlineWithPrevInstr, HaveLegalRange,
NumLegalInBlock, UnsignedVecForMBB, InstrListForMBB);
break;
case InstrType::LegalTerminator:
mapToLegalUnsigned(It, CanOutlineWithPrevInstr, HaveLegalRange,
NumLegalInBlock, UnsignedVecForMBB, InstrListForMBB);
// The instruction also acts as a terminator, so we have to record that
// in the string.
mapToIllegalUnsigned(It, CanOutlineWithPrevInstr, UnsignedVecForMBB,
InstrListForMBB);
break;
case InstrType::Invisible:
// Normally this is set by mapTo(Blah)Unsigned, but we just want to
// skip this instruction. So, unset the flag here.
AddedIllegalLastTime = false;
break;
}
}
// Are there enough legal instructions in the block for outlining to be
// possible?
if (HaveLegalRange) {
// After we're done every insertion, uniquely terminate this part of the
// "string". This makes sure we won't match across basic block or function
// boundaries since the "end" is encoded uniquely and thus appears in no
// repeated substring.
mapToIllegalUnsigned(It, CanOutlineWithPrevInstr, UnsignedVecForMBB,
InstrListForMBB);
InstrList.insert(InstrList.end(), InstrListForMBB.begin(),
InstrListForMBB.end());
UnsignedVec.insert(UnsignedVec.end(), UnsignedVecForMBB.begin(),
UnsignedVecForMBB.end());
}
}
InstructionMapper() {
// Make sure that the implementation of DenseMapInfo<unsigned> hasn't
// changed.
assert(DenseMapInfo<unsigned>::getEmptyKey() == (unsigned)-1 &&
"DenseMapInfo<unsigned>'s empty key isn't -1!");
assert(DenseMapInfo<unsigned>::getTombstoneKey() == (unsigned)-2 &&
"DenseMapInfo<unsigned>'s tombstone key isn't -2!");
}
};
/// An interprocedural pass which finds repeated sequences of
/// instructions and replaces them with calls to functions.
///
/// Each instruction is mapped to an unsigned integer and placed in a string.
/// The resulting mapping is then placed in a \p SuffixTree. The \p SuffixTree
/// is then repeatedly queried for repeated sequences of instructions. Each
/// non-overlapping repeated sequence is then placed in its own
/// \p MachineFunction and each instance is then replaced with a call to that
/// function.
struct MachineOutliner : public ModulePass {
static char ID;
/// Set to true if the outliner should consider functions with
/// linkonceodr linkage.
bool OutlineFromLinkOnceODRs = false;
/// Set to true if the outliner should run on all functions in the module
/// considered safe for outlining.
/// Set to true by default for compatibility with llc's -run-pass option.
/// Set when the pass is constructed in TargetPassConfig.
bool RunOnAllFunctions = true;
StringRef getPassName() const override { return "Machine Outliner"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<MachineModuleInfoWrapperPass>();
AU.addPreserved<MachineModuleInfoWrapperPass>();
AU.setPreservesAll();
ModulePass::getAnalysisUsage(AU);
}
MachineOutliner() : ModulePass(ID) {
initializeMachineOutlinerPass(*PassRegistry::getPassRegistry());
}
/// Remark output explaining that not outlining a set of candidates would be
/// better than outlining that set.
void emitNotOutliningCheaperRemark(
unsigned StringLen, std::vector<Candidate> &CandidatesForRepeatedSeq,
OutlinedFunction &OF);
/// Remark output explaining that a function was outlined.
void emitOutlinedFunctionRemark(OutlinedFunction &OF);
/// Find all repeated substrings that satisfy the outlining cost model by
/// constructing a suffix tree.
///
/// If a substring appears at least twice, then it must be represented by
/// an internal node which appears in at least two suffixes. Each suffix
/// is represented by a leaf node. To do this, we visit each internal node
/// in the tree, using the leaf children of each internal node. If an
/// internal node represents a beneficial substring, then we use each of
/// its leaf children to find the locations of its substring.
///
/// \param Mapper Contains outlining mapping information.
/// \param[out] FunctionList Filled with a list of \p OutlinedFunctions
/// each type of candidate.
void findCandidates(InstructionMapper &Mapper,
std::vector<OutlinedFunction> &FunctionList);
/// Replace the sequences of instructions represented by \p OutlinedFunctions
/// with calls to functions.
///
/// \param M The module we are outlining from.
/// \param FunctionList A list of functions to be inserted into the module.
/// \param Mapper Contains the instruction mappings for the module.
bool outline(Module &M, std::vector<OutlinedFunction> &FunctionList,
InstructionMapper &Mapper, unsigned &OutlinedFunctionNum);
/// Creates a function for \p OF and inserts it into the module.
MachineFunction *createOutlinedFunction(Module &M, OutlinedFunction &OF,
InstructionMapper &Mapper,
unsigned Name);
/// Calls 'doOutline()'.
bool runOnModule(Module &M) override;
/// Construct a suffix tree on the instructions in \p M and outline repeated
/// strings from that tree.
bool doOutline(Module &M, unsigned &OutlinedFunctionNum);
/// Return a DISubprogram for OF if one exists, and null otherwise. Helper
/// function for remark emission.
DISubprogram *getSubprogramOrNull(const OutlinedFunction &OF) {
for (const Candidate &C : OF.Candidates)
if (MachineFunction *MF = C.getMF())
if (DISubprogram *SP = MF->getFunction().getSubprogram())
return SP;
return nullptr;
}
/// Populate and \p InstructionMapper with instruction-to-integer mappings.
/// These are used to construct a suffix tree.
void populateMapper(InstructionMapper &Mapper, Module &M,
MachineModuleInfo &MMI);
/// Initialize information necessary to output a size remark.
/// FIXME: This should be handled by the pass manager, not the outliner.
/// FIXME: This is nearly identical to the initSizeRemarkInfo in the legacy
/// pass manager.
void initSizeRemarkInfo(const Module &M, const MachineModuleInfo &MMI,
StringMap<unsigned> &FunctionToInstrCount);
/// Emit the remark.
// FIXME: This should be handled by the pass manager, not the outliner.
void
emitInstrCountChangedRemark(const Module &M, const MachineModuleInfo &MMI,
const StringMap<unsigned> &FunctionToInstrCount);
};
} // Anonymous namespace.
char MachineOutliner::ID = 0;
namespace llvm {
ModulePass *createMachineOutlinerPass(bool RunOnAllFunctions) {
MachineOutliner *OL = new MachineOutliner();
OL->RunOnAllFunctions = RunOnAllFunctions;
return OL;
}
} // namespace llvm
INITIALIZE_PASS(MachineOutliner, DEBUG_TYPE, "Machine Function Outliner", false,
false)
void MachineOutliner::emitNotOutliningCheaperRemark(
unsigned StringLen, std::vector<Candidate> &CandidatesForRepeatedSeq,
OutlinedFunction &OF) {
// FIXME: Right now, we arbitrarily choose some Candidate from the
// OutlinedFunction. This isn't necessarily fixed, nor does it have to be.
// We should probably sort these by function name or something to make sure
// the remarks are stable.
Candidate &C = CandidatesForRepeatedSeq.front();
MachineOptimizationRemarkEmitter MORE(*(C.getMF()), nullptr);
MORE.emit([&]() {
MachineOptimizationRemarkMissed R(DEBUG_TYPE, "NotOutliningCheaper",
C.front()->getDebugLoc(), C.getMBB());
R << "Did not outline " << NV("Length", StringLen) << " instructions"
<< " from " << NV("NumOccurrences", CandidatesForRepeatedSeq.size())
<< " locations."
<< " Bytes from outlining all occurrences ("
<< NV("OutliningCost", OF.getOutliningCost()) << ")"
<< " >= Unoutlined instruction bytes ("
<< NV("NotOutliningCost", OF.getNotOutlinedCost()) << ")"
<< " (Also found at: ";
// Tell the user the other places the candidate was found.
for (unsigned i = 1, e = CandidatesForRepeatedSeq.size(); i < e; i++) {
R << NV((Twine("OtherStartLoc") + Twine(i)).str(),
CandidatesForRepeatedSeq[i].front()->getDebugLoc());
if (i != e - 1)
R << ", ";
}
R << ")";
return R;
});
}
void MachineOutliner::emitOutlinedFunctionRemark(OutlinedFunction &OF) {
MachineBasicBlock *MBB = &*OF.MF->begin();
MachineOptimizationRemarkEmitter MORE(*OF.MF, nullptr);
MachineOptimizationRemark R(DEBUG_TYPE, "OutlinedFunction",
MBB->findDebugLoc(MBB->begin()), MBB);
R << "Saved " << NV("OutliningBenefit", OF.getBenefit()) << " bytes by "
<< "outlining " << NV("Length", OF.getNumInstrs()) << " instructions "
<< "from " << NV("NumOccurrences", OF.getOccurrenceCount())
<< " locations. "
<< "(Found at: ";
// Tell the user the other places the candidate was found.
for (size_t i = 0, e = OF.Candidates.size(); i < e; i++) {
R << NV((Twine("StartLoc") + Twine(i)).str(),
OF.Candidates[i].front()->getDebugLoc());
if (i != e - 1)
R << ", ";
}
R << ")";
MORE.emit(R);
}
void MachineOutliner::findCandidates(
InstructionMapper &Mapper, std::vector<OutlinedFunction> &FunctionList) {
FunctionList.clear();
SuffixTree ST(Mapper.UnsignedVec);
// First, find all of the repeated substrings in the tree of minimum length
// 2.
std::vector<Candidate> CandidatesForRepeatedSeq;
for (auto It = ST.begin(), Et = ST.end(); It != Et; ++It) {
CandidatesForRepeatedSeq.clear();
SuffixTree::RepeatedSubstring RS = *It;
unsigned StringLen = RS.Length;
for (const unsigned &StartIdx : RS.StartIndices) {
unsigned EndIdx = StartIdx + StringLen - 1;
// Trick: Discard some candidates that would be incompatible with the
// ones we've already found for this sequence. This will save us some
// work in candidate selection.
//
// If two candidates overlap, then we can't outline them both. This
// happens when we have candidates that look like, say
//
// AA (where each "A" is an instruction).
//
// We might have some portion of the module that looks like this:
// AAAAAA (6 A's)
//
// In this case, there are 5 different copies of "AA" in this range, but
// at most 3 can be outlined. If only outlining 3 of these is going to
// be unbeneficial, then we ought to not bother.
//
// Note that two things DON'T overlap when they look like this:
// start1...end1 .... start2...end2
// That is, one must either
// * End before the other starts
// * Start after the other ends
if (std::all_of(
CandidatesForRepeatedSeq.begin(), CandidatesForRepeatedSeq.end(),
[&StartIdx, &EndIdx](const Candidate &C) {
return (EndIdx < C.getStartIdx() || StartIdx > C.getEndIdx());
})) {
// It doesn't overlap with anything, so we can outline it.
// Each sequence is over [StartIt, EndIt].
// Save the candidate and its location.
MachineBasicBlock::iterator StartIt = Mapper.InstrList[StartIdx];
MachineBasicBlock::iterator EndIt = Mapper.InstrList[EndIdx];
MachineBasicBlock *MBB = StartIt->getParent();
CandidatesForRepeatedSeq.emplace_back(StartIdx, StringLen, StartIt,
EndIt, MBB, FunctionList.size(),
Mapper.MBBFlagsMap[MBB]);
}
}
// We've found something we might want to outline.
// Create an OutlinedFunction to store it and check if it'd be beneficial
// to outline.
if (CandidatesForRepeatedSeq.size() < 2)
continue;
// Arbitrarily choose a TII from the first candidate.
// FIXME: Should getOutliningCandidateInfo move to TargetMachine?
const TargetInstrInfo *TII =
CandidatesForRepeatedSeq[0].getMF()->getSubtarget().getInstrInfo();
OutlinedFunction OF =
TII->getOutliningCandidateInfo(CandidatesForRepeatedSeq);
// If we deleted too many candidates, then there's nothing worth outlining.
// FIXME: This should take target-specified instruction sizes into account.
if (OF.Candidates.size() < 2)
continue;
// Is it better to outline this candidate than not?
if (OF.getBenefit() < 1) {
emitNotOutliningCheaperRemark(StringLen, CandidatesForRepeatedSeq, OF);
continue;
}
FunctionList.push_back(OF);
}
}
MachineFunction *MachineOutliner::createOutlinedFunction(
Module &M, OutlinedFunction &OF, InstructionMapper &Mapper, unsigned Name) {
// Create the function name. This should be unique.
// FIXME: We should have a better naming scheme. This should be stable,
// regardless of changes to the outliner's cost model/traversal order.
std::string FunctionName = ("OUTLINED_FUNCTION_" + Twine(Name)).str();
// Create the function using an IR-level function.
LLVMContext &C = M.getContext();
Function *F = Function::Create(FunctionType::get(Type::getVoidTy(C), false),
Function::ExternalLinkage, FunctionName, M);
// NOTE: If this is linkonceodr, then we can take advantage of linker deduping
// which gives us better results when we outline from linkonceodr functions.
F->setLinkage(GlobalValue::InternalLinkage);
F->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
// FIXME: Set nounwind, so we don't generate eh_frame? Haven't verified it's
// necessary.
// Set optsize/minsize, so we don't insert padding between outlined
// functions.
F->addFnAttr(Attribute::OptimizeForSize);
F->addFnAttr(Attribute::MinSize);
// Include target features from an arbitrary candidate for the outlined
// function. This makes sure the outlined function knows what kinds of
// instructions are going into it. This is fine, since all parent functions
// must necessarily support the instructions that are in the outlined region.
Candidate &FirstCand = OF.Candidates.front();
const Function &ParentFn = FirstCand.getMF()->getFunction();
if (ParentFn.hasFnAttribute("target-features"))
F->addFnAttr(ParentFn.getFnAttribute("target-features"));
BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
IRBuilder<> Builder(EntryBB);
Builder.CreateRetVoid();
MachineModuleInfo &MMI = getAnalysis<MachineModuleInfoWrapperPass>().getMMI();
MachineFunction &MF = MMI.getOrCreateMachineFunction(*F);
MachineBasicBlock &MBB = *MF.CreateMachineBasicBlock();
const TargetSubtargetInfo &STI = MF.getSubtarget();
const TargetInstrInfo &TII = *STI.getInstrInfo();
// Insert the new function into the module.
MF.insert(MF.begin(), &MBB);
for (auto I = FirstCand.front(), E = std::next(FirstCand.back()); I != E;
++I) {
MachineInstr *NewMI = MF.CloneMachineInstr(&*I);
NewMI->dropMemRefs(MF);
// Don't keep debug information for outlined instructions.
NewMI->setDebugLoc(DebugLoc());
MBB.insert(MBB.end(), NewMI);
}
TII.buildOutlinedFrame(MBB, MF, OF);
// Outlined functions shouldn't preserve liveness.
MF.getProperties().reset(MachineFunctionProperties::Property::TracksLiveness);
MF.getRegInfo().freezeReservedRegs(MF);
// If there's a DISubprogram associated with this outlined function, then
// emit debug info for the outlined function.
if (DISubprogram *SP = getSubprogramOrNull(OF)) {
// We have a DISubprogram. Get its DICompileUnit.
DICompileUnit *CU = SP->getUnit();
DIBuilder DB(M, true, CU);
DIFile *Unit = SP->getFile();
Mangler Mg;
// Get the mangled name of the function for the linkage name.
std::string Dummy;
llvm::raw_string_ostream MangledNameStream(Dummy);
Mg.getNameWithPrefix(MangledNameStream, F, false);
DISubprogram *OutlinedSP = DB.createFunction(
Unit /* Context */, F->getName(), StringRef(MangledNameStream.str()),
Unit /* File */,
0 /* Line 0 is reserved for compiler-generated code. */,
DB.createSubroutineType(DB.getOrCreateTypeArray(None)), /* void type */
0, /* Line 0 is reserved for compiler-generated code. */
DINode::DIFlags::FlagArtificial /* Compiler-generated code. */,
/* Outlined code is optimized code by definition. */
DISubprogram::SPFlagDefinition | DISubprogram::SPFlagOptimized);
// Don't add any new variables to the subprogram.
DB.finalizeSubprogram(OutlinedSP);
// Attach subprogram to the function.
F->setSubprogram(OutlinedSP);
// We're done with the DIBuilder.
DB.finalize();
}
return &MF;
}
bool MachineOutliner::outline(Module &M,
std::vector<OutlinedFunction> &FunctionList,
InstructionMapper &Mapper,
unsigned &OutlinedFunctionNum) {
bool OutlinedSomething = false;
// Sort by benefit. The most beneficial functions should be outlined first.
llvm::stable_sort(FunctionList, [](const OutlinedFunction &LHS,
const OutlinedFunction &RHS) {
return LHS.getBenefit() > RHS.getBenefit();
});
// Walk over each function, outlining them as we go along. Functions are
// outlined greedily, based off the sort above.
for (OutlinedFunction &OF : FunctionList) {
// If we outlined something that overlapped with a candidate in a previous
// step, then we can't outline from it.
erase_if(OF.Candidates, [&Mapper](Candidate &C) {
return std::any_of(
Mapper.UnsignedVec.begin() + C.getStartIdx(),
Mapper.UnsignedVec.begin() + C.getEndIdx() + 1,
[](unsigned I) { return (I == static_cast<unsigned>(-1)); });
});
// If we made it unbeneficial to outline this function, skip it.
if (OF.getBenefit() < 1)
continue;
// It's beneficial. Create the function and outline its sequence's
// occurrences.
OF.MF = createOutlinedFunction(M, OF, Mapper, OutlinedFunctionNum);
emitOutlinedFunctionRemark(OF);
FunctionsCreated++;
OutlinedFunctionNum++; // Created a function, move to the next name.
MachineFunction *MF = OF.MF;
const TargetSubtargetInfo &STI = MF->getSubtarget();
const TargetInstrInfo &TII = *STI.getInstrInfo();
// Replace occurrences of the sequence with calls to the new function.
for (Candidate &C : OF.Candidates) {
MachineBasicBlock &MBB = *C.getMBB();
MachineBasicBlock::iterator StartIt = C.front();
MachineBasicBlock::iterator EndIt = C.back();
// Insert the call.
auto CallInst = TII.insertOutlinedCall(M, MBB, StartIt, *MF, C);
// If the caller tracks liveness, then we need to make sure that
// anything we outline doesn't break liveness assumptions. The outlined
// functions themselves currently don't track liveness, but we should
// make sure that the ranges we yank things out of aren't wrong.
if (MBB.getParent()->getProperties().hasProperty(
MachineFunctionProperties::Property::TracksLiveness)) {
// Helper lambda for adding implicit def operands to the call
// instruction. It also updates call site information for moved
// code.
auto CopyDefsAndUpdateCalls = [&CallInst](MachineInstr &MI) {
for (MachineOperand &MOP : MI.operands()) {
// Skip over anything that isn't a register.
if (!MOP.isReg())
continue;
// If it's a def, add it to the call instruction.
if (MOP.isDef())
CallInst->addOperand(MachineOperand::CreateReg(
MOP.getReg(), true, /* isDef = true */
true /* isImp = true */));
}
if (MI.isCandidateForCallSiteEntry())
MI.getMF()->eraseCallSiteInfo(&MI);
};
// Copy over the defs in the outlined range.
// First inst in outlined range <-- Anything that's defined in this
// ... .. range has to be added as an
// implicit Last inst in outlined range <-- def to the call
// instruction. Also remove call site information for outlined block
// of code.
std::for_each(CallInst, std::next(EndIt), CopyDefsAndUpdateCalls);
}
// Erase from the point after where the call was inserted up to, and
// including, the final instruction in the sequence.
// Erase needs one past the end, so we need std::next there too.
MBB.erase(std::next(StartIt), std::next(EndIt));
// Keep track of what we removed by marking them all as -1.
std::for_each(Mapper.UnsignedVec.begin() + C.getStartIdx(),
Mapper.UnsignedVec.begin() + C.getEndIdx() + 1,
[](unsigned &I) { I = static_cast<unsigned>(-1); });
OutlinedSomething = true;
// Statistics.
NumOutlined++;
}
}
LLVM_DEBUG(dbgs() << "OutlinedSomething = " << OutlinedSomething << "\n";);
return OutlinedSomething;
}
void MachineOutliner::populateMapper(InstructionMapper &Mapper, Module &M,
MachineModuleInfo &MMI) {
// Build instruction mappings for each function in the module. Start by
// iterating over each Function in M.
for (Function &F : M) {
// If there's nothing in F, then there's no reason to try and outline from
// it.
if (F.empty())
continue;
// There's something in F. Check if it has a MachineFunction associated with
// it.
MachineFunction *MF = MMI.getMachineFunction(F);
// If it doesn't, then there's nothing to outline from. Move to the next
// Function.
if (!MF)
continue;
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
if (!RunOnAllFunctions && !TII->shouldOutlineFromFunctionByDefault(*MF))
continue;
// We have a MachineFunction. Ask the target if it's suitable for outlining.
// If it isn't, then move on to the next Function in the module.
if (!TII->isFunctionSafeToOutlineFrom(*MF, OutlineFromLinkOnceODRs))
continue;
// We have a function suitable for outlining. Iterate over every
// MachineBasicBlock in MF and try to map its instructions to a list of
// unsigned integers.
for (MachineBasicBlock &MBB : *MF) {
// If there isn't anything in MBB, then there's no point in outlining from
// it.
// If there are fewer than 2 instructions in the MBB, then it can't ever
// contain something worth outlining.
// FIXME: This should be based off of the maximum size in B of an outlined
// call versus the size in B of the MBB.
if (MBB.empty() || MBB.size() < 2)
continue;
// Check if MBB could be the target of an indirect branch. If it is, then
// we don't want to outline from it.
if (MBB.hasAddressTaken())
continue;
// MBB is suitable for outlining. Map it to a list of unsigneds.
Mapper.convertToUnsignedVec(MBB, *TII);
}
}
}
void MachineOutliner::initSizeRemarkInfo(
const Module &M, const MachineModuleInfo &MMI,
StringMap<unsigned> &FunctionToInstrCount) {
// Collect instruction counts for every function. We'll use this to emit
// per-function size remarks later.
for (const Function &F : M) {
MachineFunction *MF = MMI.getMachineFunction(F);
// We only care about MI counts here. If there's no MachineFunction at this
// point, then there won't be after the outliner runs, so let's move on.
if (!MF)
continue;
FunctionToInstrCount[F.getName().str()] = MF->getInstructionCount();
}
}
void MachineOutliner::emitInstrCountChangedRemark(
const Module &M, const MachineModuleInfo &MMI,
const StringMap<unsigned> &FunctionToInstrCount) {
// Iterate over each function in the module and emit remarks.
// Note that we won't miss anything by doing this, because the outliner never
// deletes functions.
for (const Function &F : M) {
MachineFunction *MF = MMI.getMachineFunction(F);
// The outliner never deletes functions. If we don't have a MF here, then we
// didn't have one prior to outlining either.
if (!MF)
continue;
std::string Fname = std::string(F.getName());
unsigned FnCountAfter = MF->getInstructionCount();
unsigned FnCountBefore = 0;
// Check if the function was recorded before.
auto It = FunctionToInstrCount.find(Fname);
// Did we have a previously-recorded size? If yes, then set FnCountBefore
// to that.
if (It != FunctionToInstrCount.end())
FnCountBefore = It->second;
// Compute the delta and emit a remark if there was a change.
int64_t FnDelta = static_cast<int64_t>(FnCountAfter) -
static_cast<int64_t>(FnCountBefore);
if (FnDelta == 0)
continue;
MachineOptimizationRemarkEmitter MORE(*MF, nullptr);
MORE.emit([&]() {
MachineOptimizationRemarkAnalysis R("size-info", "FunctionMISizeChange",
DiagnosticLocation(), &MF->front());
R << DiagnosticInfoOptimizationBase::Argument("Pass", "Machine Outliner")
<< ": Function: "
<< DiagnosticInfoOptimizationBase::Argument("Function", F.getName())
<< ": MI instruction count changed from "
<< DiagnosticInfoOptimizationBase::Argument("MIInstrsBefore",
FnCountBefore)
<< " to "
<< DiagnosticInfoOptimizationBase::Argument("MIInstrsAfter",
FnCountAfter)
<< "; Delta: "
<< DiagnosticInfoOptimizationBase::Argument("Delta", FnDelta);
return R;
});
}
}
bool MachineOutliner::runOnModule(Module &M) {
// Check if there's anything in the module. If it's empty, then there's
// nothing to outline.
if (M.empty())
return false;
// Number to append to the current outlined function.
unsigned OutlinedFunctionNum = 0;
if (!doOutline(M, OutlinedFunctionNum))
return false;
return true;
}
bool MachineOutliner::doOutline(Module &M, unsigned &OutlinedFunctionNum) {
MachineModuleInfo &MMI = getAnalysis<MachineModuleInfoWrapperPass>().getMMI();
// If the user passed -enable-machine-outliner=always or
// -enable-machine-outliner, the pass will run on all functions in the module.
// Otherwise, if the target supports default outlining, it will run on all
// functions deemed by the target to be worth outlining from by default. Tell
// the user how the outliner is running.
LLVM_DEBUG({
dbgs() << "Machine Outliner: Running on ";
if (RunOnAllFunctions)
dbgs() << "all functions";
else
dbgs() << "target-default functions";
dbgs() << "\n";
});
// If the user specifies that they want to outline from linkonceodrs, set
// it here.
OutlineFromLinkOnceODRs = EnableLinkOnceODROutlining;
InstructionMapper Mapper;
// Prepare instruction mappings for the suffix tree.
populateMapper(Mapper, M, MMI);
std::vector<OutlinedFunction> FunctionList;
// Find all of the outlining candidates.
findCandidates(Mapper, FunctionList);
// If we've requested size remarks, then collect the MI counts of every
// function before outlining, and the MI counts after outlining.
// FIXME: This shouldn't be in the outliner at all; it should ultimately be
// the pass manager's responsibility.
// This could pretty easily be placed in outline instead, but because we
// really ultimately *don't* want this here, it's done like this for now
// instead.
// Check if we want size remarks.
bool ShouldEmitSizeRemarks = M.shouldEmitInstrCountChangedRemark();
StringMap<unsigned> FunctionToInstrCount;
if (ShouldEmitSizeRemarks)
initSizeRemarkInfo(M, MMI, FunctionToInstrCount);
// Outline each of the candidates and return true if something was outlined.
bool OutlinedSomething =
outline(M, FunctionList, Mapper, OutlinedFunctionNum);
// If we outlined something, we definitely changed the MI count of the
// module. If we've asked for size remarks, then output them.
// FIXME: This should be in the pass manager.
if (ShouldEmitSizeRemarks && OutlinedSomething)
emitInstrCountChangedRemark(M, MMI, FunctionToInstrCount);
return OutlinedSomething;
}
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