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Utils: Keep distinct MDNodes distinct in MapMetadata()

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Create new copies of distinct `MDNode`s instead of following the
uniquing `MDNode` logic.

Just like self-references (or other cycles), `MapMetadata()` creates a
new node.  In practice most calls use `RF_NoModuleLevelChanges`, in
which case nothing is duplicated anyway.

Part of PR22111.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225476 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith
2015-01-08 22:42:30 +00:00
parent f416d72973
commit 3408708548
3 changed files with 64 additions and 0 deletions
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14
lib/Transforms/Utils/ValueMapper.cpp
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@ -212,6 +212,20 @@ static Metadata *MapMetadataImpl(const Metadata *MD, ValueToValueMapTy &VM,
if (Flags & RF_NoModuleLevelChanges)
return mapToSelf(VM, MD);
// Distinct nodes are always recreated.
if (Node->isDistinct()) {
// Create the node first so it's available for cyclical references.
SmallVector<Metadata *, 4> EmptyOps(Node->getNumOperands());
MDNode *NewMD = MDNode::getDistinct(Node->getContext(), EmptyOps);
mapToMetadata(VM, Node, NewMD);
// Fix the operands.
for (unsigned I = 0, E = Node->getNumOperands(); I != E; ++I)
NewMD->replaceOperandWith(I, getMappedOp(Node->getOperand(I)));
return NewMD;
}
// Create a dummy node in case we have a metadata cycle.
MDNodeFwdDecl *Dummy = MDNode::getTemporary(Node->getContext(), None);
mapToMetadata(VM, Node, Dummy);