llvm-6502/lib/Analysis/AliasAnalysis.cpp
Duncan Sands 5d84afdc83 Commit 44487 broke bootstrap of llvm-gcc-4.2. It is
not yet clear why, but in the meantime work around the
problem by making less use of readnone/readonly info.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44626 91177308-0d34-0410-b5e6-96231b3b80d8
2007-12-05 21:03:28 +00:00

225 lines
8.7 KiB
C++

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