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Sort the incoming values in PHI nodes to match the predecessor order.

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This helps expose duplicate PHIs, which will make it easier for them
to be eliminated.

llvm-svn: 85623
This commit is contained in:
Dan Gohman 2009-10-30 22:22:22 +00:00
parent ad6c6a3d33
commit 82139ffc65
1 changed files with 19 additions and 0 deletions
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19
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -10980,6 +10980,25 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
}
}
}
// Sort the PHI node operands to match the pred iterator order. This will
// help identical PHIs be eliminated by other passes. Other passes shouldn't
// depend on this for correctness however.
unsigned i = 0;
for (pred_iterator PI = pred_begin(PN.getParent()),
PE = pred_end(PN.getParent()); PI != PE; ++PI, ++i)
if (PN.getIncomingBlock(i) != *PI) {
unsigned j = PN.getBasicBlockIndex(*PI);
Value *VA = PN.getIncomingValue(i);
BasicBlock *BBA = PN.getIncomingBlock(i);
Value *VB = PN.getIncomingValue(j);
BasicBlock *BBB = PN.getIncomingBlock(j);
PN.setIncomingBlock(i, BBB);
PN.setIncomingValue(i, VB);
PN.setIncomingBlock(j, BBA);
PN.setIncomingValue(j, VA);
}
return 0;
}