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[CFLAA] Move the graph builder out from CFLSteens. NFC.

Browse Source 
Patch by Jia Chen.

Differential Revision: http://reviews.llvm.org/D22022

llvm-svn: 274958
This commit is contained in:
George Burgess IV 2016-07-09 02:54:42 +00:00
parent 933c3ab5a9
commit cd8bf7e395
5 changed files with 459 additions and 422 deletions
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11
include/llvm/Analysis/CFLAndersAliasAnalysis.h
View File

@ -21,12 +21,23 @@
namespace llvm {
namespace cflaa {
struct AliasSummary;
}
class CFLAndersAAResult : public AAResultBase<CFLAndersAAResult> {
friend AAResultBase<CFLAndersAAResult>;
public:
explicit CFLAndersAAResult();
/// \brief Get the alias summary for the given function
/// Return nullptr if the summary is not found or not available
const cflaa::AliasSummary *getAliasSummary(Function &Fn) {
// Dummy implementation
return nullptr;
}
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB) {
// Dummy implementation
return AAResultBase::alias(LocA, LocB);

8
include/llvm/Analysis/CFLSteensAliasAnalysis.h
View File

@ -29,6 +29,10 @@ namespace llvm {
class TargetLibraryInfo;
namespace cflaa {
struct AliasSummary;
}
class CFLSteensAAResult : public AAResultBase<CFLSteensAAResult> {
friend AAResultBase<CFLSteensAAResult>;
class FunctionInfo;
@ -52,6 +56,10 @@ public:
/// Returns the appropriate entry from the cache.
const Optional<FunctionInfo> &ensureCached(Function *Fn);
/// \brief Get the alias summary for the given function
/// Return nullptr if the summary is not found or not available
const cflaa::AliasSummary *getAliasSummary(Function &Fn);
AliasResult query(const MemoryLocation &LocA, const MemoryLocation &LocB);
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB) {

13
lib/Analysis/AliasAnalysisSummary.h
View File

@ -36,6 +36,7 @@
#define LLVM_ANALYSIS_ALIASANALYSISSUMMARY_H
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/IR/CallSite.h"
#include <bitset>
@ -96,6 +97,9 @@ AliasAttrs getExternallyVisibleAttrs(AliasAttrs);
// Function summary related stuffs
//===----------------------------------------------------------------------===//
/// The maximum number of arguments we can put into a summary.
static unsigned MaxSupportedArgsInSummary = 50;
/// We use InterfaceValue to describe parameters/return value, as well as
/// potential memory locations that are pointed to by parameters/return value,
/// of a function.
@ -129,6 +133,15 @@ struct ExternalAttribute {
AliasAttrs Attr;
};
/// AliasSummary is just a collection of ExternalRelation and ExternalAttribute
struct AliasSummary {
// RetParamRelations is a collection of ExternalRelations.
SmallVector<ExternalRelation, 8> RetParamRelations;
// RetParamAttributes is a collection of ExternalAttributes.
SmallVector<ExternalAttribute, 8> RetParamAttributes;
};
/// This is the result of instantiating InterfaceValue at a particular callsite
struct InstantiatedValue {
Value *Val;

409
lib/Analysis/CFLGraph.h
View File

@ -17,6 +17,9 @@
#include "AliasAnalysisSummary.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/Instructions.h"
namespace llvm {
namespace cflaa {
@ -144,6 +147,412 @@ public:
bool empty() const { return NodeImpls.empty(); }
std::size_t size() const { return NodeImpls.size(); }
};
///\brief A builder class used to create CFLGraph instance from a given function
/// The CFL-AA that uses this builder must provide its own type as a template
/// argument. This is necessary for interprocedural processing: CFLGraphBuilder
/// needs a way of obtaining the summary of other functions when callinsts are
/// encountered.
/// As a result, we expect the said CFL-AA to expose a getAliasSummary() public
/// member function that takes a Function& and returns the corresponding summary
/// as a const AliasSummary*.
template <typename CFLAA> class CFLGraphBuilder {
// Input of the builder
CFLAA &Analysis;
const TargetLibraryInfo &TLI;
// Output of the builder
CFLGraph Graph;
SmallVector<Value *, 4> ReturnedValues;
// Auxiliary structures used by the builder
SmallVector<InstantiatedRelation, 8> InstantiatedRelations;
SmallVector<InstantiatedAttr, 8> InstantiatedAttrs;
// Helper class
/// Gets the edges our graph should have, based on an Instruction*
class GetEdgesVisitor : public InstVisitor<GetEdgesVisitor, void> {
CFLAA &AA;
const TargetLibraryInfo &TLI;
CFLGraph &Graph;
SmallVectorImpl<Value *> &ReturnValues;
SmallVectorImpl<InstantiatedRelation> &InstantiatedRelations;
SmallVectorImpl<InstantiatedAttr> &InstantiatedAttrs;
static bool hasUsefulEdges(ConstantExpr *CE) {
// ConstantExpr doesn't have terminators, invokes, or fences, so only
// needs
// to check for compares.
return CE->getOpcode() != Instruction::ICmp &&
CE->getOpcode() != Instruction::FCmp;
}
// Returns possible functions called by CS into the given SmallVectorImpl.
// Returns true if targets found, false otherwise.
static bool getPossibleTargets(CallSite CS,
SmallVectorImpl<Function *> &Output) {
if (auto *Fn = CS.getCalledFunction()) {
Output.push_back(Fn);
return true;
}
// TODO: If the call is indirect, we might be able to enumerate all
// potential
// targets of the call and return them, rather than just failing.
return false;
}
void addNode(Value *Val) {
assert(Val != nullptr);
if (!Graph.addNode(Val))
return;
if (isa<GlobalValue>(Val)) {
Graph.addAttr(Val, getGlobalOrArgAttrFromValue(*Val));
// Currently we do not attempt to be smart on globals
InstantiatedAttrs.push_back(
InstantiatedAttr{InstantiatedValue{Val, 1}, getAttrUnknown()});
} else if (auto CExpr = dyn_cast<ConstantExpr>(Val))
if (hasUsefulEdges(CExpr))
visitConstantExpr(CExpr);
}
void addNodeWithAttr(Value *Val, AliasAttrs Attr) {
addNode(Val);
Graph.addAttr(Val, Attr);
}
void addEdge(Value *From, Value *To, EdgeType Type) {
assert(From != nullptr && To != nullptr);
if (!From->getType()->isPointerTy() || !To->getType()->isPointerTy())
return;
addNode(From);
if (To != From)
addNode(To);
Graph.addEdge(From, To, Type);
}
public:
GetEdgesVisitor(CFLGraphBuilder &Builder)
: AA(Builder.Analysis), TLI(Builder.TLI), Graph(Builder.Graph),
ReturnValues(Builder.ReturnedValues),
InstantiatedRelations(Builder.InstantiatedRelations),
InstantiatedAttrs(Builder.InstantiatedAttrs) {}
void visitInstruction(Instruction &) {
llvm_unreachable("Unsupported instruction encountered");
}
void visitReturnInst(ReturnInst &Inst) {
if (auto RetVal = Inst.getReturnValue()) {
if (RetVal->getType()->isPointerTy()) {
addNode(RetVal);
ReturnValues.push_back(RetVal);
}
}
}
void visitPtrToIntInst(PtrToIntInst &Inst) {
auto *Ptr = Inst.getOperand(0);
addNodeWithAttr(Ptr, getAttrEscaped());
}
void visitIntToPtrInst(IntToPtrInst &Inst) {
auto *Ptr = &Inst;
addNodeWithAttr(Ptr, getAttrUnknown());
}
void visitCastInst(CastInst &Inst) {
auto *Src = Inst.getOperand(0);
addEdge(Src, &Inst, EdgeType::Assign);
}
void visitBinaryOperator(BinaryOperator &Inst) {
auto *Op1 = Inst.getOperand(0);
auto *Op2 = Inst.getOperand(1);
addEdge(Op1, &Inst, EdgeType::Assign);
addEdge(Op2, &Inst, EdgeType::Assign);
}
void visitAtomicCmpXchgInst(AtomicCmpXchgInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = Inst.getNewValOperand();
addEdge(Ptr, Val, EdgeType::Dereference);
}
void visitAtomicRMWInst(AtomicRMWInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = Inst.getValOperand();
addEdge(Ptr, Val, EdgeType::Dereference);
}
void visitPHINode(PHINode &Inst) {
for (Value *Val : Inst.incoming_values())
addEdge(Val, &Inst, EdgeType::Assign);
}
void visitGetElementPtrInst(GetElementPtrInst &Inst) {
auto *Op = Inst.getPointerOperand();
addEdge(Op, &Inst, EdgeType::Assign);
}
void visitSelectInst(SelectInst &Inst) {
// Condition is not processed here (The actual statement producing
// the condition result is processed elsewhere). For select, the
// condition is evaluated, but not loaded, stored, or assigned
// simply as a result of being the condition of a select.
auto *TrueVal = Inst.getTrueValue();
auto *FalseVal = Inst.getFalseValue();
addEdge(TrueVal, &Inst, EdgeType::Assign);
addEdge(FalseVal, &Inst, EdgeType::Assign);
}
void visitAllocaInst(AllocaInst &Inst) { Graph.addNode(&Inst); }
void visitLoadInst(LoadInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = &Inst;
addEdge(Val, Ptr, EdgeType::Reference);
}
void visitStoreInst(StoreInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = Inst.getValueOperand();
addEdge(Ptr, Val, EdgeType::Dereference);
}
void visitVAArgInst(VAArgInst &Inst) {
// We can't fully model va_arg here. For *Ptr = Inst.getOperand(0), it
// does
// two things:
// 1. Loads a value from *((T*)*Ptr).
// 2. Increments (stores to) *Ptr by some target-specific amount.
// For now, we'll handle this like a landingpad instruction (by placing
// the
// result in its own group, and having that group alias externals).
addNodeWithAttr(&Inst, getAttrUnknown());
}
static bool isFunctionExternal(Function *Fn) {
return !Fn->hasExactDefinition();
}
bool tryInterproceduralAnalysis(CallSite CS,
const SmallVectorImpl<Function *> &Fns) {
assert(Fns.size() > 0);
if (CS.arg_size() > MaxSupportedArgsInSummary)
return false;
// Exit early if we'll fail anyway
for (auto *Fn : Fns) {
if (isFunctionExternal(Fn) || Fn->isVarArg())
return false;
// Fail if the caller does not provide enough arguments
assert(Fn->arg_size() <= CS.arg_size());
if (!AA.getAliasSummary(*Fn))
return false;
}
for (auto *Fn : Fns) {
auto Summary = AA.getAliasSummary(*Fn);
assert(Summary != nullptr);
auto &RetParamRelations = Summary->RetParamRelations;
for (auto &Relation : RetParamRelations) {
auto IRelation = instantiateExternalRelation(Relation, CS);
if (IRelation.hasValue())
InstantiatedRelations.push_back(*IRelation);
}
auto &RetParamAttributes = Summary->RetParamAttributes;
for (auto &Attribute : RetParamAttributes) {
auto IAttr = instantiateExternalAttribute(Attribute, CS);
if (IAttr.hasValue())
InstantiatedAttrs.push_back(*IAttr);
}
}
return true;
}
void visitCallSite(CallSite CS) {
auto Inst = CS.getInstruction();
// Make sure all arguments and return value are added to the graph first
for (Value *V : CS.args())
addNode(V);
if (Inst->getType()->isPointerTy())
addNode(Inst);
// Check if Inst is a call to a library function that
// allocates/deallocates
// on the heap. Those kinds of functions do not introduce any aliases.
// TODO: address other common library functions such as realloc(),
// strdup(),
// etc.
if (isMallocLikeFn(Inst, &TLI) || isCallocLikeFn(Inst, &TLI) ||
isFreeCall(Inst, &TLI))
return;
// TODO: Add support for noalias args/all the other fun function
// attributes
// that we can tack on.
SmallVector<Function *, 4> Targets;
if (getPossibleTargets(CS, Targets))
if (tryInterproceduralAnalysis(CS, Targets))
return;
// Because the function is opaque, we need to note that anything
// could have happened to the arguments (unless the function is marked
// readonly or readnone), and that the result could alias just about
// anything, too (unless the result is marked noalias).
if (!CS.onlyReadsMemory())
for (Value *V : CS.args()) {
if (V->getType()->isPointerTy()) {
// The argument itself escapes.
addNodeWithAttr(V, getAttrEscaped());
// The fate of argument memory is unknown. Note that since
// AliasAttrs
// is transitive with respect to dereference, we only need to
// specify
// it for the first-level memory.
InstantiatedAttrs.push_back(
InstantiatedAttr{InstantiatedValue{V, 1}, getAttrUnknown()});
}
}
if (Inst->getType()->isPointerTy()) {
auto *Fn = CS.getCalledFunction();
if (Fn == nullptr || !Fn->doesNotAlias(0))
// No need to call addNodeWithAttr() since we've added Inst at the
// beginning of this function and we know it is not a global.
Graph.addAttr(Inst, getAttrUnknown());
}
}
/// Because vectors/aggregates are immutable and unaddressable, there's
/// nothing we can do to coax a value out of them, other than calling
/// Extract{Element,Value}. We can effectively treat them as pointers to
/// arbitrary memory locations we can store in and load from.
void visitExtractElementInst(ExtractElementInst &Inst) {
auto *Ptr = Inst.getVectorOperand();
auto *Val = &Inst;
addEdge(Val, Ptr, EdgeType::Reference);
}
void visitInsertElementInst(InsertElementInst &Inst) {
auto *Vec = Inst.getOperand(0);
auto *Val = Inst.getOperand(1);
addEdge(Vec, &Inst, EdgeType::Assign);
addEdge(&Inst, Val, EdgeType::Dereference);
}
void visitLandingPadInst(LandingPadInst &Inst) {
// Exceptions come from "nowhere", from our analysis' perspective.
// So we place the instruction its own group, noting that said group may
// alias externals
addNodeWithAttr(&Inst, getAttrUnknown());
}
void visitInsertValueInst(InsertValueInst &Inst) {
auto *Agg = Inst.getOperand(0);
auto *Val = Inst.getOperand(1);
addEdge(Agg, &Inst, EdgeType::Assign);
addEdge(&Inst, Val, EdgeType::Dereference);
}
void visitExtractValueInst(ExtractValueInst &Inst) {
auto *Ptr = Inst.getAggregateOperand();
addEdge(&Inst, Ptr, EdgeType::Reference);
}
void visitShuffleVectorInst(ShuffleVectorInst &Inst) {
auto *From1 = Inst.getOperand(0);
auto *From2 = Inst.getOperand(1);
addEdge(From1, &Inst, EdgeType::Assign);
addEdge(From2, &Inst, EdgeType::Assign);
}
void visitConstantExpr(ConstantExpr *CE) {
switch (CE->getOpcode()) {
default:
llvm_unreachable("Unknown instruction type encountered!");
// Build the switch statement using the Instruction.def file.
#define HANDLE_INST(NUM, OPCODE, CLASS) \
case Instruction::OPCODE: \
this->visit##OPCODE(*(CLASS *)CE); \
break;
#include "llvm/IR/Instruction.def"
}
}
};
// Helper functions
// Determines whether or not we an instruction is useless to us (e.g.
// FenceInst)
static bool hasUsefulEdges(Instruction *Inst) {
bool IsNonInvokeRetTerminator = isa<TerminatorInst>(Inst) &&
!isa<InvokeInst>(Inst) &&
!isa<ReturnInst>(Inst);
return !isa<CmpInst>(Inst) && !isa<FenceInst>(Inst) &&
!IsNonInvokeRetTerminator;
}
void addArgumentToGraph(Argument &Arg) {
if (Arg.getType()->isPointerTy()) {
Graph.addNode(&Arg);
Graph.addAttr(&Arg, getGlobalOrArgAttrFromValue(Arg));
// Pointees of a formal parameter is known to the caller
InstantiatedAttrs.push_back(
InstantiatedAttr{InstantiatedValue{&Arg, 1}, getAttrCaller()});
}
}
// Given an Instruction, this will add it to the graph, along with any
// Instructions that are potentially only available from said Instruction
// For example, given the following line:
// %0 = load i16* getelementptr ([1 x i16]* @a, 0, 0), align 2
// addInstructionToGraph would add both the `load` and `getelementptr`
// instructions to the graph appropriately.
void addInstructionToGraph(Instruction &Inst) {
if (!hasUsefulEdges(&Inst))
return;
GetEdgesVisitor(*this).visit(Inst);
}
// Builds the graph needed for constructing the StratifiedSets for the given
// function
void buildGraphFrom(Function &Fn) {
for (auto &Bb : Fn.getBasicBlockList())
for (auto &Inst : Bb.getInstList())
addInstructionToGraph(Inst);
for (auto &Arg : Fn.args())
addArgumentToGraph(Arg);
}
public:
CFLGraphBuilder(CFLAA &Analysis, const TargetLibraryInfo &TLI, Function &Fn)
: Analysis(Analysis), TLI(TLI) {
buildGraphFrom(Fn);
}
const CFLGraph &getCFLGraph() const { return Graph; }
const SmallVector<Value *, 4> &getReturnValues() const {
return ReturnedValues;
}
const SmallVector<InstantiatedRelation, 8> &getInstantiatedRelations() const {
return InstantiatedRelations;
}
const SmallVector<InstantiatedAttr, 8> &getInstantiatedAttrs() const {
return InstantiatedAttrs;
}
};
}
}

440
lib/Analysis/CFLSteensAliasAnalysis.cpp
View File

@ -41,12 +41,9 @@
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
@ -71,425 +68,27 @@ CFLSteensAAResult::~CFLSteensAAResult() {}
/// Information we have about a function and would like to keep around.
class CFLSteensAAResult::FunctionInfo {
StratifiedSets<Value *> Sets;
// RetParamRelations is a collection of ExternalRelations.
SmallVector<ExternalRelation, 8> RetParamRelations;
// RetParamAttributes is a collection of ExternalAttributes.
SmallVector<ExternalAttribute, 8> RetParamAttributes;
AliasSummary Summary;
public:
FunctionInfo(Function &Fn, const SmallVectorImpl<Value *> &RetVals,
StratifiedSets<Value *> S);
const StratifiedSets<Value *> &getStratifiedSets() const { return Sets; }
const SmallVectorImpl<ExternalRelation> &getRetParamRelations() const {
return RetParamRelations;
}
const SmallVectorImpl<ExternalAttribute> &getRetParamAttributes() const {
return RetParamAttributes;
}
const AliasSummary &getAliasSummary() const { return Summary; }
};
/// Try to go from a Value* to a Function*. Never returns nullptr.
static Optional<Function *> parentFunctionOfValue(Value *);
/// Returns possible functions called by the Inst* into the given
/// SmallVectorImpl. Returns true if targets found, false otherwise. This is
/// templated so we can use it with CallInsts and InvokeInsts.
static bool getPossibleTargets(CallSite, SmallVectorImpl<Function *> &);
const StratifiedIndex StratifiedLink::SetSentinel =
std::numeric_limits<StratifiedIndex>::max();
namespace {
/// The maximum number of arguments we can put into a summary.
LLVM_CONSTEXPR unsigned MaxSupportedArgsInSummary = 50;
/// StratifiedSets call for knowledge of "direction", so this is how we
/// represent that locally.
enum class Level { Same, Above, Below };
/// Gets the edges our graph should have, based on an Instruction*
class GetEdgesVisitor : public InstVisitor<GetEdgesVisitor, void> {
CFLSteensAAResult &AA;
const TargetLibraryInfo &TLI;
CFLGraph &Graph;
SmallVectorImpl<Value *> &ReturnValues;
SmallVectorImpl<InstantiatedRelation> &InstantiatedRelations;
SmallVectorImpl<InstantiatedAttr> &InstantiatedAttrs;
static bool hasUsefulEdges(ConstantExpr *CE) {
// ConstantExpr doesn't have terminators, invokes, or fences, so only needs
// to check for compares.
return CE->getOpcode() != Instruction::ICmp &&
CE->getOpcode() != Instruction::FCmp;
}
void addNode(Value *Val) {
assert(Val != nullptr);
if (!Graph.addNode(Val))
return;
if (isa<GlobalValue>(Val)) {
Graph.addAttr(Val, getGlobalOrArgAttrFromValue(*Val));
// Currently we do not attempt to be smart on globals
InstantiatedAttrs.push_back(
InstantiatedAttr{InstantiatedValue{Val, 1}, getAttrUnknown()});
} else if (auto CExpr = dyn_cast<ConstantExpr>(Val))
if (hasUsefulEdges(CExpr))
visitConstantExpr(CExpr);
}
void addNodeWithAttr(Value *Val, AliasAttrs Attr) {
addNode(Val);
Graph.addAttr(Val, Attr);
}
void addEdge(Value *From, Value *To, EdgeType Type) {
assert(From != nullptr && To != nullptr);
if (!From->getType()->isPointerTy() || !To->getType()->isPointerTy())
return;
addNode(From);
if (To != From)
addNode(To);
Graph.addEdge(From, To, Type);
}
public:
GetEdgesVisitor(CFLSteensAAResult &AA, const TargetLibraryInfo &TLI,
CFLGraph &Graph, SmallVectorImpl<Value *> &ReturnValues,
SmallVectorImpl<InstantiatedRelation> &InstantiatedRelations,
SmallVectorImpl<InstantiatedAttr> &InstantiatedAttrs)
: AA(AA), TLI(TLI), Graph(Graph), ReturnValues(ReturnValues),
InstantiatedRelations(InstantiatedRelations),
InstantiatedAttrs(InstantiatedAttrs) {}
void visitInstruction(Instruction &) {
llvm_unreachable("Unsupported instruction encountered");
}
void visitReturnInst(ReturnInst &Inst) {
if (auto RetVal = Inst.getReturnValue()) {
if (RetVal->getType()->isPointerTy()) {
addNode(RetVal);
ReturnValues.push_back(RetVal);
}
}
}
void visitPtrToIntInst(PtrToIntInst &Inst) {
auto *Ptr = Inst.getOperand(0);
addNodeWithAttr(Ptr, getAttrEscaped());
}
void visitIntToPtrInst(IntToPtrInst &Inst) {
auto *Ptr = &Inst;
addNodeWithAttr(Ptr, getAttrUnknown());
}
void visitCastInst(CastInst &Inst) {
auto *Src = Inst.getOperand(0);
addEdge(Src, &Inst, EdgeType::Assign);
}
void visitBinaryOperator(BinaryOperator &Inst) {
auto *Op1 = Inst.getOperand(0);
auto *Op2 = Inst.getOperand(1);
addEdge(Op1, &Inst, EdgeType::Assign);
addEdge(Op2, &Inst, EdgeType::Assign);
}
void visitAtomicCmpXchgInst(AtomicCmpXchgInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = Inst.getNewValOperand();
addEdge(Ptr, Val, EdgeType::Dereference);
}
void visitAtomicRMWInst(AtomicRMWInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = Inst.getValOperand();
addEdge(Ptr, Val, EdgeType::Dereference);
}
void visitPHINode(PHINode &Inst) {
for (Value *Val : Inst.incoming_values())
addEdge(Val, &Inst, EdgeType::Assign);
}
void visitGetElementPtrInst(GetElementPtrInst &Inst) {
auto *Op = Inst.getPointerOperand();
addEdge(Op, &Inst, EdgeType::Assign);
}
void visitSelectInst(SelectInst &Inst) {
// Condition is not processed here (The actual statement producing
// the condition result is processed elsewhere). For select, the
// condition is evaluated, but not loaded, stored, or assigned
// simply as a result of being the condition of a select.
auto *TrueVal = Inst.getTrueValue();
auto *FalseVal = Inst.getFalseValue();
addEdge(TrueVal, &Inst, EdgeType::Assign);
addEdge(FalseVal, &Inst, EdgeType::Assign);
}
void visitAllocaInst(AllocaInst &Inst) { Graph.addNode(&Inst); }
void visitLoadInst(LoadInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = &Inst;
addEdge(Val, Ptr, EdgeType::Reference);
}
void visitStoreInst(StoreInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = Inst.getValueOperand();
addEdge(Ptr, Val, EdgeType::Dereference);
}
void visitVAArgInst(VAArgInst &Inst) {
// We can't fully model va_arg here. For *Ptr = Inst.getOperand(0), it does
// two things:
// 1. Loads a value from *((T*)*Ptr).
// 2. Increments (stores to) *Ptr by some target-specific amount.
// For now, we'll handle this like a landingpad instruction (by placing the
// result in its own group, and having that group alias externals).
addNodeWithAttr(&Inst, getAttrUnknown());
}
static bool isFunctionExternal(Function *Fn) {
return !Fn->hasExactDefinition();
}
bool tryInterproceduralAnalysis(CallSite CS,
const SmallVectorImpl<Function *> &Fns) {
assert(Fns.size() > 0);
if (CS.arg_size() > MaxSupportedArgsInSummary)
return false;
// Exit early if we'll fail anyway
for (auto *Fn : Fns) {
if (isFunctionExternal(Fn) || Fn->isVarArg())
return false;
// Fail if the caller does not provide enough arguments
assert(Fn->arg_size() <= CS.arg_size());
auto &MaybeInfo = AA.ensureCached(Fn);
if (!MaybeInfo.hasValue())
return false;
}
for (auto *Fn : Fns) {
auto &FnInfo = AA.ensureCached(Fn);
assert(FnInfo.hasValue());
auto &RetParamRelations = FnInfo->getRetParamRelations();
for (auto &Relation : RetParamRelations) {
auto IRelation = instantiateExternalRelation(Relation, CS);
if (IRelation.hasValue())
InstantiatedRelations.push_back(*IRelation);
}
auto &RetParamAttributes = FnInfo->getRetParamAttributes();
for (auto &Attribute : RetParamAttributes) {
auto IAttr = instantiateExternalAttribute(Attribute, CS);
if (IAttr.hasValue())
InstantiatedAttrs.push_back(*IAttr);
}
}
return true;
}
void visitCallSite(CallSite CS) {
auto Inst = CS.getInstruction();
// Make sure all arguments and return value are added to the graph first
for (Value *V : CS.args())
addNode(V);
if (Inst->getType()->isPointerTy())
addNode(Inst);
// Check if Inst is a call to a library function that allocates/deallocates
// on the heap. Those kinds of functions do not introduce any aliases.
// TODO: address other common library functions such as realloc(), strdup(),
// etc.
if (isMallocLikeFn(Inst, &TLI) || isCallocLikeFn(Inst, &TLI) ||
isFreeCall(Inst, &TLI))
return;
// TODO: Add support for noalias args/all the other fun function attributes
// that we can tack on.
SmallVector<Function *, 4> Targets;
if (getPossibleTargets(CS, Targets))
if (tryInterproceduralAnalysis(CS, Targets))
return;
// Because the function is opaque, we need to note that anything
// could have happened to the arguments (unless the function is marked
// readonly or readnone), and that the result could alias just about
// anything, too (unless the result is marked noalias).
if (!CS.onlyReadsMemory())
for (Value *V : CS.args()) {
if (V->getType()->isPointerTy()) {
// The argument itself escapes.
addNodeWithAttr(V, getAttrEscaped());
// The fate of argument memory is unknown. Note that since AliasAttrs
// is transitive with respect to dereference, we only need to specify
// it for the first-level memory.
InstantiatedAttrs.push_back(
InstantiatedAttr{InstantiatedValue{V, 1}, getAttrUnknown()});
}
}
if (Inst->getType()->isPointerTy()) {
auto *Fn = CS.getCalledFunction();
if (Fn == nullptr || !Fn->doesNotAlias(0))
// No need to call addNodeWithAttr() since we've added Inst at the
// beginning of this function and we know it is not a global.
Graph.addAttr(Inst, getAttrUnknown());
}
}
/// Because vectors/aggregates are immutable and unaddressable, there's
/// nothing we can do to coax a value out of them, other than calling
/// Extract{Element,Value}. We can effectively treat them as pointers to
/// arbitrary memory locations we can store in and load from.
void visitExtractElementInst(ExtractElementInst &Inst) {
auto *Ptr = Inst.getVectorOperand();
auto *Val = &Inst;
addEdge(Val, Ptr, EdgeType::Reference);
}
void visitInsertElementInst(InsertElementInst &Inst) {
auto *Vec = Inst.getOperand(0);
auto *Val = Inst.getOperand(1);
addEdge(Vec, &Inst, EdgeType::Assign);
addEdge(&Inst, Val, EdgeType::Dereference);
}
void visitLandingPadInst(LandingPadInst &Inst) {
// Exceptions come from "nowhere", from our analysis' perspective.
// So we place the instruction its own group, noting that said group may
// alias externals
addNodeWithAttr(&Inst, getAttrUnknown());
}
void visitInsertValueInst(InsertValueInst &Inst) {
auto *Agg = Inst.getOperand(0);
auto *Val = Inst.getOperand(1);
addEdge(Agg, &Inst, EdgeType::Assign);
addEdge(&Inst, Val, EdgeType::Dereference);
}
void visitExtractValueInst(ExtractValueInst &Inst) {
auto *Ptr = Inst.getAggregateOperand();
addEdge(&Inst, Ptr, EdgeType::Reference);
}
void visitShuffleVectorInst(ShuffleVectorInst &Inst) {
auto *From1 = Inst.getOperand(0);
auto *From2 = Inst.getOperand(1);
addEdge(From1, &Inst, EdgeType::Assign);
addEdge(From2, &Inst, EdgeType::Assign);
}
void visitConstantExpr(ConstantExpr *CE) {
switch (CE->getOpcode()) {
default:
llvm_unreachable("Unknown instruction type encountered!");
// Build the switch statement using the Instruction.def file.
#define HANDLE_INST(NUM, OPCODE, CLASS) \
case Instruction::OPCODE: \
visit##OPCODE(*(CLASS *)CE); \
break;
#include "llvm/IR/Instruction.def"
}
}
};
class CFLGraphBuilder {
// Input of the builder
CFLSteensAAResult &Analysis;
const TargetLibraryInfo &TLI;
// Output of the builder
CFLGraph Graph;
SmallVector<Value *, 4> ReturnedValues;
// Auxiliary structures used by the builder
SmallVector<InstantiatedRelation, 8> InstantiatedRelations;
SmallVector<InstantiatedAttr, 8> InstantiatedAttrs;
// Helper functions
// Determines whether or not we an instruction is useless to us (e.g.
// FenceInst)
static bool hasUsefulEdges(Instruction *Inst) {
bool IsNonInvokeRetTerminator = isa<TerminatorInst>(Inst) &&
!isa<InvokeInst>(Inst) &&
!isa<ReturnInst>(Inst);
return !isa<CmpInst>(Inst) && !isa<FenceInst>(Inst) &&
!IsNonInvokeRetTerminator;
}
void addArgumentToGraph(Argument &Arg) {
if (Arg.getType()->isPointerTy()) {
Graph.addNode(&Arg);
Graph.addAttr(&Arg, getGlobalOrArgAttrFromValue(Arg));
// Pointees of a formal parameter is known to the caller
InstantiatedAttrs.push_back(
InstantiatedAttr{InstantiatedValue{&Arg, 1}, getAttrCaller()});
}
}
// Given an Instruction, this will add it to the graph, along with any
// Instructions that are potentially only available from said Instruction
// For example, given the following line:
// %0 = load i16* getelementptr ([1 x i16]* @a, 0, 0), align 2
// addInstructionToGraph would add both the `load` and `getelementptr`
// instructions to the graph appropriately.
void addInstructionToGraph(Instruction &Inst) {
if (!hasUsefulEdges(&Inst))
return;
GetEdgesVisitor(Analysis, TLI, Graph, ReturnedValues, InstantiatedRelations,
InstantiatedAttrs)
.visit(Inst);
}
// Builds the graph needed for constructing the StratifiedSets for the given
// function
void buildGraphFrom(Function &Fn) {
for (auto &Bb : Fn.getBasicBlockList())
for (auto &Inst : Bb.getInstList())
addInstructionToGraph(Inst);
for (auto &Arg : Fn.args())
addArgumentToGraph(Arg);
}
public:
CFLGraphBuilder(CFLSteensAAResult &Analysis, const TargetLibraryInfo &TLI,
Function &Fn)
: Analysis(Analysis), TLI(TLI) {
buildGraphFrom(Fn);
}
const CFLGraph &getCFLGraph() const { return Graph; }
const SmallVector<Value *, 4> &getReturnValues() const {
return ReturnedValues;
}
const SmallVector<InstantiatedRelation, 8> &getInstantiatedRelations() const {
return InstantiatedRelations;
}
const SmallVector<InstantiatedAttr, 8> &getInstantiatedAttrs() const {
return InstantiatedAttrs;
}
};
}
//===----------------------------------------------------------------------===//
@ -514,18 +113,6 @@ static Optional<Function *> parentFunctionOfValue(Value *Val) {
return None;
}
static bool getPossibleTargets(CallSite CS,
SmallVectorImpl<Function *> &Output) {
if (auto *Fn = CS.getCalledFunction()) {
Output.push_back(Fn);
return true;
}
// TODO: If the call is indirect, we might be able to enumerate all potential
// targets of the call and return them, rather than just failing.
return false;
}
static Level directionOfEdgeType(EdgeType Weight) {
switch (Weight) {
case EdgeType::Reference:
@ -586,7 +173,8 @@ CFLSteensAAResult::FunctionInfo::FunctionInfo(
auto Itr = InterfaceMap.find(SetIndex);
if (Itr != InterfaceMap.end()) {
if (CurrValue != Itr->second)
RetParamRelations.push_back(ExternalRelation{CurrValue, Itr->second});
Summary.RetParamRelations.push_back(
ExternalRelation{CurrValue, Itr->second});
break;
}
@ -594,7 +182,7 @@ CFLSteensAAResult::FunctionInfo::FunctionInfo(
InterfaceMap.insert(std::make_pair(SetIndex, CurrValue));
auto ExternalAttrs = getExternallyVisibleAttrs(Link.Attrs);
if (ExternalAttrs.any())
RetParamAttributes.push_back(
Summary.RetParamAttributes.push_back(
ExternalAttribute{CurrValue, ExternalAttrs});
if (!Link.hasBelow())
@ -628,7 +216,7 @@ CFLSteensAAResult::FunctionInfo::FunctionInfo(
// Builds the graph + StratifiedSets for a function.
CFLSteensAAResult::FunctionInfo CFLSteensAAResult::buildSetsFrom(Function *Fn) {
CFLGraphBuilder GraphBuilder(*this, TLI, *Fn);
CFLGraphBuilder<CFLSteensAAResult> GraphBuilder(*this, TLI, *Fn);
StratifiedSetsBuilder<Value *> SetBuilder;
auto &Graph = GraphBuilder.getCFLGraph();
@ -721,6 +309,14 @@ CFLSteensAAResult::ensureCached(Function *Fn) {
return Iter->second;
}
const AliasSummary *CFLSteensAAResult::getAliasSummary(Function &Fn) {
auto &FunInfo = ensureCached(&Fn);
if (FunInfo.hasValue())
return &FunInfo->getAliasSummary();
else
return nullptr;
}
AliasResult CFLSteensAAResult::query(const MemoryLocation &LocA,
const MemoryLocation &LocB) {
auto *ValA = const_cast<Value *>(LocA.Ptr);
@ -793,8 +389,8 @@ ModRefInfo CFLSteensAAResult::getArgModRefInfo(ImmutableCallSite CS,
auto &MaybeInfo = ensureCached(const_cast<Function *>(CalledFunc));
if (!MaybeInfo.hasValue())
return MRI_ModRef;
auto &RetParamAttributes = MaybeInfo->getRetParamAttributes();
auto &RetParamRelations = MaybeInfo->getRetParamRelations();
auto &RetParamAttributes = MaybeInfo->getAliasSummary().RetParamAttributes;
auto &RetParamRelations = MaybeInfo->getAliasSummary().RetParamRelations;
bool ArgAttributeIsWritten =
std::any_of(RetParamAttributes.begin(), RetParamAttributes.end(),
@ -832,8 +428,8 @@ FunctionModRefBehavior CFLSteensAAResult::getModRefBehavior(const Function *F) {
auto &MaybeInfo = ensureCached(const_cast<Function *>(F));
if (!MaybeInfo.hasValue())
return FMRB_UnknownModRefBehavior;
auto &RetParamAttributes = MaybeInfo->getRetParamAttributes();
auto &RetParamRelations = MaybeInfo->getRetParamRelations();
auto &RetParamAttributes = MaybeInfo->getAliasSummary().RetParamAttributes;
auto &RetParamRelations = MaybeInfo->getAliasSummary().RetParamRelations;
// First, if any argument is marked Escpaed, Unknown or Global, anything may
// happen to them and thus we can't draw any conclusion.