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When an MDNode changes to become identical to another MDNode, 

delete the MDNode that changed, rather than the other MDNode.
This is less work, because it doesn't require the changed node
to be re-inserted into the uniquing map and it doesn't require
the is-function-local flag to be recomputed. Also, it avoids
trouble when the existing node is part of a complicated
data structure.

llvm-svn: 114996
This commit is contained in:
Dan Gohman 2010-09-28 22:07:19 +00:00
parent a3181e2d79
commit 25a7bc9081
1 changed files with 4 additions and 5 deletions
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9
llvm/lib/VMCore/Metadata.cpp
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@ -339,15 +339,14 @@ void MDNode::replaceOperand(MDNodeOperand *Op, Value *To) {
// Now that the node is out of the folding set, get ready to reinsert it.
// First, check to see if another node with the same operands already exists
// in the set. If it doesn't exist, this returns the position to insert it.
// in the set. If so, then this node is redundant.
FoldingSetNodeID ID;
Profile(ID);
void *InsertPoint;
if (MDNode *N = pImpl->MDNodeSet.FindNodeOrInsertPos(ID, InsertPoint)) {
N->replaceAllUsesWith(this);
N->destroy();
N = pImpl->MDNodeSet.FindNodeOrInsertPos(ID, InsertPoint);
assert(N == 0 && "shouldn't be in the map now!"); (void)N;
replaceAllUsesWith(N);
destroy();
return;
}
// InsertPoint will have been set by the FindNodeOrInsertPos call.