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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18664 91177308-0d34-0410-b5e6-96231b3b80d8
195 lines
7.5 KiB
C++
195 lines
7.5 KiB
C++
//===- AliasAnalysis.cpp - Generic Alias Analysis Interface Implementation -==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the generic AliasAnalysis interface which is used as the
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// common interface used by all clients and implementations of alias analysis.
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//
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// This file also implements the default version of the AliasAnalysis interface
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// that is to be used when no other implementation is specified. This does some
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// simple tests that detect obvious cases: two different global pointers cannot
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// alias, a global cannot alias a malloc, two different mallocs cannot alias,
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// etc.
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//
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// This alias analysis implementation really isn't very good for anything, but
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// it is very fast, and makes a nice clean default implementation. Because it
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// handles lots of little corner cases, other, more complex, alias analysis
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// implementations may choose to rely on this pass to resolve these simple and
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// easy cases.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/Instructions.h"
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#include "llvm/Target/TargetData.h"
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#include <iostream>
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using namespace llvm;
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// Register the AliasAnalysis interface, providing a nice name to refer to.
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namespace {
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RegisterAnalysisGroup<AliasAnalysis> Z("Alias Analysis");
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}
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//===----------------------------------------------------------------------===//
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// Default chaining methods
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//===----------------------------------------------------------------------===//
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AliasAnalysis::AliasResult
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AliasAnalysis::alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size) {
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assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
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return AA->alias(V1, V1Size, V2, V2Size);
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}
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void AliasAnalysis::getMustAliases(Value *P, std::vector<Value*> &RetVals) {
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assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
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return AA->getMustAliases(P, RetVals);
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}
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bool AliasAnalysis::pointsToConstantMemory(const Value *P) {
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assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
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return AA->pointsToConstantMemory(P);
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}
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bool AliasAnalysis::doesNotAccessMemory(Function *F) {
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assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
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return AA->doesNotAccessMemory(F);
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}
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bool AliasAnalysis::onlyReadsMemory(Function *F) {
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assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
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return doesNotAccessMemory(F) || AA->onlyReadsMemory(F);
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}
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bool AliasAnalysis::hasNoModRefInfoForCalls() const {
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assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
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return AA->hasNoModRefInfoForCalls();
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}
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void AliasAnalysis::deleteValue(Value *V) {
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assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
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AA->deleteValue(V);
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}
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void AliasAnalysis::copyValue(Value *From, Value *To) {
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assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
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AA->copyValue(From, To);
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}
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AliasAnalysis::ModRefResult
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AliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
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// FIXME: we can do better.
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assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
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return AA->getModRefInfo(CS1, CS2);
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}
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//===----------------------------------------------------------------------===//
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// AliasAnalysis non-virtual helper method implementation
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//===----------------------------------------------------------------------===//
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AliasAnalysis::ModRefResult
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AliasAnalysis::getModRefInfo(LoadInst *L, Value *P, unsigned Size) {
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return alias(L->getOperand(0), TD->getTypeSize(L->getType()),
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P, Size) ? Ref : NoModRef;
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}
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AliasAnalysis::ModRefResult
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AliasAnalysis::getModRefInfo(StoreInst *S, Value *P, unsigned Size) {
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// If the stored address cannot alias the pointer in question, then the
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// pointer cannot be modified by the store.
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if (!alias(S->getOperand(1), TD->getTypeSize(S->getOperand(0)->getType()),
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P, Size))
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return NoModRef;
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// If the pointer is a pointer to constant memory, then it could not have been
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// modified by this store.
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return pointsToConstantMemory(P) ? NoModRef : Mod;
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}
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AliasAnalysis::ModRefResult
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AliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
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ModRefResult Mask = ModRef;
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if (Function *F = CS.getCalledFunction())
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if (onlyReadsMemory(F)) {
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if (doesNotAccessMemory(F)) return NoModRef;
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Mask = Ref;
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}
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if (!AA) return Mask;
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// If P points to a constant memory location, the call definitely could not
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// modify the memory location.
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if ((Mask & Mod) && AA->pointsToConstantMemory(P))
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Mask = Ref;
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return ModRefResult(Mask & AA->getModRefInfo(CS, P, Size));
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}
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// AliasAnalysis destructor: DO NOT move this to the header file for
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// AliasAnalysis or else clients of the AliasAnalysis class may not depend on
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// the AliasAnalysis.o file in the current .a file, causing alias analysis
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// support to not be included in the tool correctly!
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//
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AliasAnalysis::~AliasAnalysis() {}
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/// setTargetData - Subclasses must call this method to initialize the
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/// AliasAnalysis interface before any other methods are called.
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///
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void AliasAnalysis::InitializeAliasAnalysis(Pass *P) {
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TD = &P->getAnalysis<TargetData>();
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AA = &P->getAnalysis<AliasAnalysis>();
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}
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// getAnalysisUsage - All alias analysis implementations should invoke this
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// directly (using AliasAnalysis::getAnalysisUsage(AU)) to make sure that
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// TargetData is required by the pass.
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void AliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<TargetData>(); // All AA's need TargetData.
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AU.addRequired<AliasAnalysis>(); // All AA's chain
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}
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/// canBasicBlockModify - Return true if it is possible for execution of the
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/// specified basic block to modify the value pointed to by Ptr.
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///
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bool AliasAnalysis::canBasicBlockModify(const BasicBlock &BB,
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const Value *Ptr, unsigned Size) {
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return canInstructionRangeModify(BB.front(), BB.back(), Ptr, Size);
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}
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/// canInstructionRangeModify - Return true if it is possible for the execution
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/// of the specified instructions to modify the value pointed to by Ptr. The
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/// instructions to consider are all of the instructions in the range of [I1,I2]
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/// INCLUSIVE. I1 and I2 must be in the same basic block.
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///
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bool AliasAnalysis::canInstructionRangeModify(const Instruction &I1,
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const Instruction &I2,
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const Value *Ptr, unsigned Size) {
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assert(I1.getParent() == I2.getParent() &&
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"Instructions not in same basic block!");
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BasicBlock::iterator I = const_cast<Instruction*>(&I1);
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BasicBlock::iterator E = const_cast<Instruction*>(&I2);
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++E; // Convert from inclusive to exclusive range.
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for (; I != E; ++I) // Check every instruction in range
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if (getModRefInfo(I, const_cast<Value*>(Ptr), Size) & Mod)
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return true;
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return false;
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}
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// Because of the way .a files work, we must force the BasicAA implementation to
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// be pulled in if the AliasAnalysis classes are pulled in. Otherwise we run
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// the risk of AliasAnalysis being used, but the default implementation not
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// being linked into the tool that uses it.
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//
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namespace llvm {
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extern void BasicAAStub();
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}
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static IncludeFile INCLUDE_BASICAA_CPP((void*)&BasicAAStub);
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