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enhance FindAvailableLoadedValue to make use of AliasAnalysis

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if it has it.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60167 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-11-27 08:18:12 +00:00
parent 52c95856b4
commit ee6e10bc8e
1 changed files with 20 additions and 1 deletions
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21
lib/Transforms/Utils/BasicBlockUtils.cpp
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@ -20,6 +20,7 @@
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Target/TargetData.h"
#include <algorithm>
using namespace llvm;
@ -390,6 +391,13 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
unsigned MaxInstsToScan,
AliasAnalysis *AA) {
if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
// If we're using alias analysis to disambiguate get the size of *Ptr.
unsigned AccessSize = 0;
if (AA) {
const Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
AccessSize = AA->getTargetData().getTypeStoreSizeInBits(AccessTy);
}
while (ScanFrom != ScanBB->begin()) {
// Don't scan huge blocks.
@ -415,14 +423,25 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
isa<GlobalVariable>(SI->getOperand(1))))
continue;
// If we have alias analysis and it says the store won't modify the loaded
// value, ignore the store.
if (AA &&
(AA->getModRefInfo(SI, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
continue;
// Otherwise the store that may or may not alias the pointer, bail out.
++ScanFrom;
return 0;
}
// If this is some other instruction that may clobber Ptr, bail out.
if (Inst->mayWriteToMemory()) {
// If alias analysis claims that it really won't modify the load,
// ignore it.
if (AA &&
(AA->getModRefInfo(Inst, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
continue;
// May modify the pointer, bail out.
++ScanFrom;
return 0;