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Factor some code into a new FoldSingleEntryPHINodes method.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60501 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2008-12-03 19:44:02 +00:00
parent e96cc775e4
commit 29874e0dc6
6 changed files with 37 additions and 24 deletions
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18
lib/Transforms/Utils/BasicBlockUtils.cpp
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@ -54,6 +54,24 @@ void llvm::DeleteDeadBlock(BasicBlock *BB) {
BB->eraseFromParent();
}
/// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
/// any single-entry PHI nodes in it, fold them away. This handles the case
/// when all entries to the PHI nodes in a block are guaranteed equal, such as
/// when the block has exactly one predecessor.
void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) {
if (!isa<PHINode>(BB->begin()))
return;
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
if (PN->getIncomingValue(0) != PN)
PN->replaceAllUsesWith(PN->getIncomingValue(0));
else
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
PN->eraseFromParent();
}
}
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {