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Add support for simplifying a load from a computed value to a load from a global when it

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is provable that they're equivalent.  This fixes PR4855.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112994 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2010-09-03 19:08:37 +00:00
parent ac53061464
commit 1593dd6779
3 changed files with 63 additions and 8 deletions
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40
lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
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@@ -21,8 +21,9 @@
#include "llvm/ADT/Statistic.h"
using namespace llvm;
STATISTIC(NumPhis, "Number of phis propagated");
STATISTIC(NumSelects, "Number of selects propagated");
STATISTIC(NumPhis, "Number of phis propagated");
STATISTIC(NumSelects, "Number of selects propagated");
STATISTIC(NumMemAccess, "Number of memory access targets propagated");
namespace {
class CorrelatedValuePropagation : public FunctionPass {
@@ -30,6 +31,7 @@ namespace {
bool processSelect(SelectInst *SI);
bool processPHI(PHINode *P);
bool processMemAccess(Instruction *I);
public:
static char ID;
@@ -54,6 +56,7 @@ Pass *llvm::createCorrelatedValuePropagationPass() {
bool CorrelatedValuePropagation::processSelect(SelectInst *S) {
if (S->getType()->isVectorTy()) return false;
if (isa<Constant>(S->getOperand(0))) return false;
Constant *C = LVI->getConstant(S->getOperand(0), S->getParent());
if (!C) return false;
@@ -97,6 +100,23 @@ bool CorrelatedValuePropagation::processPHI(PHINode *P) {
return Changed;
}
bool CorrelatedValuePropagation::processMemAccess(Instruction *I) {
Value *Pointer = 0;
if (LoadInst *L = dyn_cast<LoadInst>(I))
Pointer = L->getPointerOperand();
else
Pointer = cast<StoreInst>(I)->getPointerOperand();
if (isa<Constant>(Pointer)) return false;
Constant *C = LVI->getConstant(Pointer, I->getParent());
if (!C) return false;
++NumMemAccess;
I->replaceUsesOfWith(Pointer, C);
return true;
}
bool CorrelatedValuePropagation::runOnFunction(Function &F) {
LVI = &getAnalysis<LazyValueInfo>();
@@ -106,10 +126,18 @@ bool CorrelatedValuePropagation::runOnFunction(Function &F) {
bool BBChanged = false;
for (BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ) {
Instruction *II = BI++;
if (SelectInst *SI = dyn_cast<SelectInst>(II))
BBChanged |= processSelect(SI);
else if (PHINode *P = dyn_cast<PHINode>(II))
BBChanged |= processPHI(P);
switch (II->getOpcode()) {
case Instruction::Select:
BBChanged |= processSelect(cast<SelectInst>(II));
break;
case Instruction::PHI:
BBChanged |= processPHI(cast<PHINode>(II));
break;
case Instruction::Load:
case Instruction::Store:
BBChanged |= processMemAccess(II);
break;
}
}
// Propagating correlated values might leave cruft around.