1 files changed, 10 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/Utils/PredicateInfo.cpp b/llvm/lib/Transforms/Utils/PredicateInfo.cpp
index 978d5a2..371d9e6 100644
--- a/llvm/lib/Transforms/Utils/PredicateInfo.cpp
+++ b/llvm/lib/Transforms/Utils/PredicateInfo.cpp
@@ -260,9 +260,16 @@ bool PredicateInfoBuilder::stackIsInScope(const ValueDFSStack &Stack,
   // next to the defs they must go with so that we can know it's time to pop
   // the stack when we hit the end of the phi uses for a given def.
   const ValueDFS &Top = *Stack.back().V;
-  if (Top.LocalNum == LN_Last && Top.PInfo) {
-    if (!VDUse.U)
-      return false;
+  assert(Top.PInfo && "RenameStack should only contain predicate infos (defs)");
+  if (Top.LocalNum == LN_Last) {
+    if (!VDUse.U) {
+      assert(VDUse.PInfo && "A non-use VDUse should have a predicate info");
+      // We should reserve adjacent LN_Last defs for the same phi use.
+      return VDUse.LocalNum == LN_Last &&
+             // If the two phi defs have the same edge, they must be designated
+             // for the same succ BB.
+             getBlockEdge(Top.PInfo) == getBlockEdge(VDUse.PInfo);
+    }
     auto *PHI = dyn_cast<PHINode>(VDUse.U->getUser());
     if (!PHI)
       return false;