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- implemented instcombine of phi (X, X, X) -> X

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3397 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-08-20 15:35:35 +00:00
parent dce9427985
commit f02c46834a
1 changed files with 12 additions and 1 deletions
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13
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -594,10 +594,21 @@ Instruction *InstCombiner::visitCastInst(CastInst &CI) {
//
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
// If the PHI node only has one incoming value, eliminate the PHI node...
if (PN.getNumIncomingValues() == 0)
return ReplaceInstUsesWith(PN, Constant::getNullValue(PN.getType()));
if (PN.getNumIncomingValues() == 1)
return ReplaceInstUsesWith(PN, PN.getIncomingValue(0));
// Otherwise if all of the incoming values are the same for the PHI, replace
// the PHI node with the incoming value.
//
Value *InVal = PN.getIncomingValue(0);
for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i)
if (PN.getIncomingValue(i) != InVal)
return 0; // Not the same, bail out.
return 0;
// All of the incoming values are the same, replace the PHI node now.
return ReplaceInstUsesWith(PN, InVal);
}