ValueMapper: Resolve cycles on the new nodes

Fix a major bug from r265456.  Although it's now much rarer, ValueMapper
sometimes has to duplicate cycles.  The
might-transitively-reference-a-temporary counts don't decrement on their
own when there are cycles, and you need to call MDNode::resolveCycles to
fix it.

r265456 was checking the input nodes to see if they were unresolved.
This is useless; they should never be unresolved.  Instead we should
check the output nodes and resolve cycles on them.

llvm-svn: 266258

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/ValueMapper.cpp b/llvm/lib/Transforms/Utils/ValueMapper.cpp
index 76875ec7385..772800c2e61 100644
--- a/llvm/lib/Transforms/Utils/ValueMapper.cpp
+++ b/llvm/lib/Transforms/Utils/ValueMapper.cpp
@@ -587,6 +587,7 @@ void MDNodeMapper::mapDistinctNodes() {
 
 void MDNodeMapper::mapUniquedNodes() {
   // Construct uniqued nodes, building forward references as necessary.
+  SmallVector<MDNode *, 16> CyclicNodes;
   for (auto *N : POT) {
     if (N->isDistinct())
       continue;
@@ -601,11 +602,12 @@ void MDNodeMapper::mapUniquedNodes() {
 
     TempMDNode ClonedN = D.Placeholder ? std::move(D.Placeholder) : N->clone();
     remapOperands(D, *ClonedN);
-    M.mapToMetadata(N, MDNode::replaceWithUniqued(std::move(ClonedN)));
+    CyclicNodes.push_back(MDNode::replaceWithUniqued(std::move(ClonedN)));
+    M.mapToMetadata(N, CyclicNodes.back());
   }
 
   // Resolve cycles.
-  for (auto *N : POT)
+  for (auto *N : CyclicNodes)
     if (!N->isResolved())
       N->resolveCycles();
 }