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Handle X = phi Y --> X = Y

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2501 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-05-06 18:06:38 +00:00
parent fee97e83ce
commit 473945d1dc
1 changed files with 19 additions and 0 deletions
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19
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -19,6 +19,7 @@
#include "llvm/ConstantHandling.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/iPHINode.h"
#include "llvm/iOperators.h"
#include "llvm/Pass.h"
#include "llvm/Support/InstIterator.h"
@ -69,6 +70,7 @@ namespace {
Instruction *visitSetCondInst(BinaryOperator *I);
Instruction *visitShiftInst(Instruction *I);
Instruction *visitCastInst(CastInst *CI);
Instruction *visitPHINode(PHINode *PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst *GEP);
Instruction *visitMemAccessInst(MemAccessInst *MAI);
@ -412,6 +414,8 @@ static inline bool isEliminableCastOfCast(const CastInst *CI,
// CastInst simplification
//
Instruction *InstCombiner::visitCastInst(CastInst *CI) {
if (CI->use_empty()) return 0; // Don't fix dead instructions...
// If the user is casting a value to the same type, eliminate this cast
// instruction...
if (CI->getType() == CI->getOperand(0)->getType() && !CI->use_empty()) {
@ -436,6 +440,21 @@ Instruction *InstCombiner::visitCastInst(CastInst *CI) {
}
// PHINode simplification
//
Instruction *InstCombiner::visitPHINode(PHINode *PN) {
if (PN->use_empty()) return 0; // Don't fix dead instructions...
// If the PHI node only has one incoming value, eliminate the PHI node...
if (PN->getNumIncomingValues() == 1) {
AddUsesToWorkList(PN); // Add all modified instrs to worklist
PN->replaceAllUsesWith(PN->getIncomingValue(0));
return PN;
}
return 0;
}
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst *GEP) {
// Is it getelementptr %P, uint 0