311 lines
11 KiB
C
311 lines
11 KiB
C
|
//===- BasicAliasAnalysis.h - Stateless, local Alias Analysis ---*- 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
|
||
|
|
/// This is the interface for LLVM's primary stateless and local alias analysis.
|
||
|
|
///
|
||
|
|
//===----------------------------------------------------------------------===//
|
||
|
|
|
||
|
|
#ifndef LLVM_ANALYSIS_BASICALIASANALYSIS_H
|
||
|
|
#define LLVM_ANALYSIS_BASICALIASANALYSIS_H
|
||
|
|
|
||
|
|
#include "llvm/ADT/DenseMap.h"
|
||
|
|
#include "llvm/ADT/Optional.h"
|
||
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
||
|
|
#include "llvm/ADT/SmallVector.h"
|
||
|
|
#include "llvm/Analysis/AliasAnalysis.h"
|
||
|
|
#include "llvm/IR/PassManager.h"
|
||
|
|
#include "llvm/Pass.h"
|
||
|
|
#include <algorithm>
|
||
|
|
#include <cstdint>
|
||
|
|
#include <memory>
|
||
|
|
#include <utility>
|
||
|
|
|
||
|
|
namespace llvm {
|
||
|
|
|
||
|
|
struct AAMDNodes;
|
||
|
|
class APInt;
|
||
|
|
class AssumptionCache;
|
||
|
|
class BasicBlock;
|
||
|
|
class DataLayout;
|
||
|
|
class DominatorTree;
|
||
|
|
class Function;
|
||
|
|
class GEPOperator;
|
||
|
|
class LoopInfo;
|
||
|
|
class PHINode;
|
||
|
|
class SelectInst;
|
||
|
|
class TargetLibraryInfo;
|
||
|
|
class PhiValues;
|
||
|
|
class Value;
|
||
|
|
|
||
|
|
/// This is the AA result object for the basic, local, and stateless alias
|
||
|
|
/// analysis. It implements the AA query interface in an entirely stateless
|
||
|
|
/// manner. As one consequence, it is never invalidated due to IR changes.
|
||
|
|
/// While it does retain some storage, that is used as an optimization and not
|
||
|
|
/// to preserve information from query to query. However it does retain handles
|
||
|
|
/// to various other analyses and must be recomputed when those analyses are.
|
||
|
|
class BasicAAResult : public AAResultBase<BasicAAResult> {
|
||
|
|
friend AAResultBase<BasicAAResult>;
|
||
|
|
|
||
|
|
const DataLayout &DL;
|
||
|
|
const Function &F;
|
||
|
|
const TargetLibraryInfo &TLI;
|
||
|
|
AssumptionCache &AC;
|
||
|
|
DominatorTree *DT;
|
||
|
|
LoopInfo *LI;
|
||
|
|
PhiValues *PV;
|
||
|
|
|
||
|
|
public:
|
||
|
|
BasicAAResult(const DataLayout &DL, const Function &F,
|
||
|
|
const TargetLibraryInfo &TLI, AssumptionCache &AC,
|
||
|
|
DominatorTree *DT = nullptr, LoopInfo *LI = nullptr,
|
||
|
|
PhiValues *PV = nullptr)
|
||
|
|
: AAResultBase(), DL(DL), F(F), TLI(TLI), AC(AC), DT(DT), LI(LI), PV(PV)
|
||
|
|
{}
|
||
|
|
|
||
|
|
BasicAAResult(const BasicAAResult &Arg)
|
||
|
|
: AAResultBase(Arg), DL(Arg.DL), F(Arg.F), TLI(Arg.TLI), AC(Arg.AC),
|
||
|
|
DT(Arg.DT), LI(Arg.LI), PV(Arg.PV) {}
|
||
|
|
BasicAAResult(BasicAAResult &&Arg)
|
||
|
|
: AAResultBase(std::move(Arg)), DL(Arg.DL), F(Arg.F), TLI(Arg.TLI),
|
||
|
|
AC(Arg.AC), DT(Arg.DT), LI(Arg.LI), PV(Arg.PV) {}
|
||
|
|
|
||
|
|
/// Handle invalidation events in the new pass manager.
|
||
|
|
bool invalidate(Function &Fn, const PreservedAnalyses &PA,
|
||
|
|
FunctionAnalysisManager::Invalidator &Inv);
|
||
|
|
|
||
|
|
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
|
||
|
|
AAQueryInfo &AAQI);
|
||
|
|
|
||
|
|
ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc,
|
||
|
|
AAQueryInfo &AAQI);
|
||
|
|
|
||
|
|
ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2,
|
||
|
|
AAQueryInfo &AAQI);
|
||
|
|
|
||
|
|
/// Chases pointers until we find a (constant global) or not.
|
||
|
|
bool pointsToConstantMemory(const MemoryLocation &Loc, AAQueryInfo &AAQI,
|
||
|
|
bool OrLocal);
|
||
|
|
|
||
|
|
/// Get the location associated with a pointer argument of a callsite.
|
||
|
|
ModRefInfo getArgModRefInfo(const CallBase *Call, unsigned ArgIdx);
|
||
|
|
|
||
|
|
/// Returns the behavior when calling the given call site.
|
||
|
|
FunctionModRefBehavior getModRefBehavior(const CallBase *Call);
|
||
|
|
|
||
|
|
/// Returns the behavior when calling the given function. For use when the
|
||
|
|
/// call site is not known.
|
||
|
|
FunctionModRefBehavior getModRefBehavior(const Function *Fn);
|
||
|
|
|
||
|
|
private:
|
||
|
|
// A linear transformation of a Value; this class represents ZExt(SExt(V,
|
||
|
|
// SExtBits), ZExtBits) * Scale + Offset.
|
||
|
|
struct VariableGEPIndex {
|
||
|
|
// An opaque Value - we can't decompose this further.
|
||
|
|
const Value *V;
|
||
|
|
|
||
|
|
// We need to track what extensions we've done as we consider the same Value
|
||
|
|
// with different extensions as different variables in a GEP's linear
|
||
|
|
// expression;
|
||
|
|
// e.g.: if V == -1, then sext(x) != zext(x).
|
||
|
|
unsigned ZExtBits;
|
||
|
|
unsigned SExtBits;
|
||
|
|
|
||
|
|
APInt Scale;
|
||
|
|
|
||
|
|
// Context instruction to use when querying information about this index.
|
||
|
|
const Instruction *CxtI;
|
||
|
|
|
||
|
|
bool operator==(const VariableGEPIndex &Other) const {
|
||
|
|
return V == Other.V && ZExtBits == Other.ZExtBits &&
|
||
|
|
SExtBits == Other.SExtBits && Scale == Other.Scale;
|
||
|
|
}
|
||
|
|
|
||
|
|
bool operator!=(const VariableGEPIndex &Other) const {
|
||
|
|
return !operator==(Other);
|
||
|
|
}
|
||
|
|
|
||
|
|
void dump() const {
|
||
|
|
print(dbgs());
|
||
|
|
dbgs() << "\n";
|
||
|
|
}
|
||
|
|
void print(raw_ostream &OS) const {
|
||
|
|
OS << "(V=" << V->getName()
|
||
|
|
<< ", zextbits=" << ZExtBits
|
||
|
|
<< ", sextbits=" << SExtBits
|
||
|
|
<< ", scale=" << Scale << ")";
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
// Represents the internal structure of a GEP, decomposed into a base pointer,
|
||
|
|
// constant offsets, and variable scaled indices.
|
||
|
|
struct DecomposedGEP {
|
||
|
|
// Base pointer of the GEP
|
||
|
|
const Value *Base;
|
||
|
|
// Total constant offset from base.
|
||
|
|
APInt Offset;
|
||
|
|
// Scaled variable (non-constant) indices.
|
||
|
|
SmallVector<VariableGEPIndex, 4> VarIndices;
|
||
|
|
// Is GEP index scale compile-time constant.
|
||
|
|
bool HasCompileTimeConstantScale;
|
||
|
|
|
||
|
|
void dump() const {
|
||
|
|
print(dbgs());
|
||
|
|
dbgs() << "\n";
|
||
|
|
}
|
||
|
|
void print(raw_ostream &OS) const {
|
||
|
|
OS << "(DecomposedGEP Base=" << Base->getName()
|
||
|
|
<< ", Offset=" << Offset
|
||
|
|
<< ", VarIndices=[";
|
||
|
|
for (size_t i = 0; i < VarIndices.size(); i++) {
|
||
|
|
if (i != 0)
|
||
|
|
OS << ", ";
|
||
|
|
VarIndices[i].print(OS);
|
||
|
|
}
|
||
|
|
OS << "], HasCompileTimeConstantScale=" << HasCompileTimeConstantScale
|
||
|
|
<< ")";
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
/// Tracks phi nodes we have visited.
|
||
|
|
///
|
||
|
|
/// When interpret "Value" pointer equality as value equality we need to make
|
||
|
|
/// sure that the "Value" is not part of a cycle. Otherwise, two uses could
|
||
|
|
/// come from different "iterations" of a cycle and see different values for
|
||
|
|
/// the same "Value" pointer.
|
||
|
|
///
|
||
|
|
/// The following example shows the problem:
|
||
|
|
/// %p = phi(%alloca1, %addr2)
|
||
|
|
/// %l = load %ptr
|
||
|
|
/// %addr1 = gep, %alloca2, 0, %l
|
||
|
|
/// %addr2 = gep %alloca2, 0, (%l + 1)
|
||
|
|
/// alias(%p, %addr1) -> MayAlias !
|
||
|
|
/// store %l, ...
|
||
|
|
SmallPtrSet<const BasicBlock *, 8> VisitedPhiBBs;
|
||
|
|
|
||
|
|
/// Tracks instructions visited by pointsToConstantMemory.
|
||
|
|
SmallPtrSet<const Value *, 16> Visited;
|
||
|
|
|
||
|
|
static const Value *
|
||
|
|
GetLinearExpression(const Value *V, APInt &Scale, APInt &Offset,
|
||
|
|
unsigned &ZExtBits, unsigned &SExtBits,
|
||
|
|
const DataLayout &DL, unsigned Depth, AssumptionCache *AC,
|
||
|
|
DominatorTree *DT, bool &NSW, bool &NUW);
|
||
|
|
|
||
|
|
static DecomposedGEP
|
||
|
|
DecomposeGEPExpression(const Value *V, const DataLayout &DL,
|
||
|
|
AssumptionCache *AC, DominatorTree *DT);
|
||
|
|
|
||
|
|
static bool isGEPBaseAtNegativeOffset(const GEPOperator *GEPOp,
|
||
|
|
const DecomposedGEP &DecompGEP, const DecomposedGEP &DecompObject,
|
||
|
|
LocationSize ObjectAccessSize);
|
||
|
|
|
||
|
|
/// A Heuristic for aliasGEP that searches for a constant offset
|
||
|
|
/// between the variables.
|
||
|
|
///
|
||
|
|
/// GetLinearExpression has some limitations, as generally zext(%x + 1)
|
||
|
|
/// != zext(%x) + zext(1) if the arithmetic overflows. GetLinearExpression
|
||
|
|
/// will therefore conservatively refuse to decompose these expressions.
|
||
|
|
/// However, we know that, for all %x, zext(%x) != zext(%x + 1), even if
|
||
|
|
/// the addition overflows.
|
||
|
|
bool
|
||
|
|
constantOffsetHeuristic(const SmallVectorImpl<VariableGEPIndex> &VarIndices,
|
||
|
|
LocationSize V1Size, LocationSize V2Size,
|
||
|
|
const APInt &BaseOffset, AssumptionCache *AC,
|
||
|
|
DominatorTree *DT);
|
||
|
|
|
||
|
|
bool isValueEqualInPotentialCycles(const Value *V1, const Value *V2);
|
||
|
|
|
||
|
|
void GetIndexDifference(SmallVectorImpl<VariableGEPIndex> &Dest,
|
||
|
|
const SmallVectorImpl<VariableGEPIndex> &Src);
|
||
|
|
|
||
|
|
AliasResult aliasGEP(const GEPOperator *V1, LocationSize V1Size,
|
||
|
|
const AAMDNodes &V1AAInfo, const Value *V2,
|
||
|
|
LocationSize V2Size, const AAMDNodes &V2AAInfo,
|
||
|
|
const Value *UnderlyingV1, const Value *UnderlyingV2,
|
||
|
|
AAQueryInfo &AAQI);
|
||
|
|
|
||
|
|
AliasResult aliasPHI(const PHINode *PN, LocationSize PNSize,
|
||
|
|
const AAMDNodes &PNAAInfo, const Value *V2,
|
||
|
|
LocationSize V2Size, const AAMDNodes &V2AAInfo,
|
||
|
|
AAQueryInfo &AAQI);
|
||
|
|
|
||
|
|
AliasResult aliasSelect(const SelectInst *SI, LocationSize SISize,
|
||
|
|
const AAMDNodes &SIAAInfo, const Value *V2,
|
||
|
|
LocationSize V2Size, const AAMDNodes &V2AAInfo,
|
||
|
|
AAQueryInfo &AAQI);
|
||
|
|
|
||
|
|
AliasResult aliasCheck(const Value *V1, LocationSize V1Size,
|
||
|
|
const AAMDNodes &V1AATag, const Value *V2,
|
||
|
|
LocationSize V2Size, const AAMDNodes &V2AATag,
|
||
|
|
AAQueryInfo &AAQI);
|
||
|
|
|
||
|
|
AliasResult aliasCheckRecursive(const Value *V1, LocationSize V1Size,
|
||
|
|
const AAMDNodes &V1AATag, const Value *V2,
|
||
|
|
LocationSize V2Size, const AAMDNodes &V2AATag,
|
||
|
|
AAQueryInfo &AAQI, const Value *O1,
|
||
|
|
const Value *O2);
|
||
|
|
};
|
||
|
|
|
||
|
|
/// Analysis pass providing a never-invalidated alias analysis result.
|
||
|
|
class BasicAA : public AnalysisInfoMixin<BasicAA> {
|
||
|
|
friend AnalysisInfoMixin<BasicAA>;
|
||
|
|
|
||
|
|
static AnalysisKey Key;
|
||
|
|
|
||
|
|
public:
|
||
|
|
using Result = BasicAAResult;
|
||
|
|
|
||
|
|
BasicAAResult run(Function &F, FunctionAnalysisManager &AM);
|
||
|
|
};
|
||
|
|
|
||
|
|
/// Legacy wrapper pass to provide the BasicAAResult object.
|
||
|
|
class BasicAAWrapperPass : public FunctionPass {
|
||
|
|
std::unique_ptr<BasicAAResult> Result;
|
||
|
|
|
||
|
|
virtual void anchor();
|
||
|
|
|
||
|
|
public:
|
||
|
|
static char ID;
|
||
|
|
|
||
|
|
BasicAAWrapperPass();
|
||
|
|
|
||
|
|
BasicAAResult &getResult() { return *Result; }
|
||
|
|
const BasicAAResult &getResult() const { return *Result; }
|
||
|
|
|
||
|
|
bool runOnFunction(Function &F) override;
|
||
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override;
|
||
|
|
};
|
||
|
|
|
||
|
|
FunctionPass *createBasicAAWrapperPass();
|
||
|
|
|
||
|
|
/// A helper for the legacy pass manager to create a \c BasicAAResult object
|
||
|
|
/// populated to the best of our ability for a particular function when inside
|
||
|
|
/// of a \c ModulePass or a \c CallGraphSCCPass.
|
||
|
|
BasicAAResult createLegacyPMBasicAAResult(Pass &P, Function &F);
|
||
|
|
|
||
|
|
/// This class is a functor to be used in legacy module or SCC passes for
|
||
|
|
/// computing AA results for a function. We store the results in fields so that
|
||
|
|
/// they live long enough to be queried, but we re-use them each time.
|
||
|
|
class LegacyAARGetter {
|
||
|
|
Pass &P;
|
||
|
|
Optional<BasicAAResult> BAR;
|
||
|
|
Optional<AAResults> AAR;
|
||
|
|
|
||
|
|
public:
|
||
|
|
LegacyAARGetter(Pass &P) : P(P) {}
|
||
|
|
AAResults &operator()(Function &F) {
|
||
|
|
BAR.emplace(createLegacyPMBasicAAResult(P, F));
|
||
|
|
AAR.emplace(createLegacyPMAAResults(P, F, *BAR));
|
||
|
|
return *AAR;
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
} // end namespace llvm
|
||
|
|
|
||
|
|
#endif // LLVM_ANALYSIS_BASICALIASANALYSIS_H
|