1 files changed, 12 insertions, 6 deletions
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index 915871e3c2..09aff1b3b3 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -557,12 +557,12 @@ namespace {
     }
     
     /// removeFromLeaderTable - Scan the list of values corresponding to a given
-    /// value number, and remove the given value if encountered.
-    void removeFromLeaderTable(uint32_t N, Value *V, BasicBlock *BB) {
+    /// value number, and remove the given instruction if encountered.
+    void removeFromLeaderTable(uint32_t N, Instruction *I, BasicBlock *BB) {
       LeaderTableEntry* Prev = 0;
       LeaderTableEntry* Curr = &LeaderTable[N];
 
-      while (Curr->Val != V || Curr->BB != BB) {
+      while (Curr->Val != I || Curr->BB != BB) {
         Prev = Curr;
         Curr = Curr->Next;
       }
@@ -2021,9 +2021,15 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS, BasicBlock *Root) {
             DT->properlyDominates(cast<Instruction>(RHS)->getParent(), Root)) &&
            "Instruction doesn't dominate scope!");
 
-    // If value numbering later deduces that an instruction in the scope is equal
-    // to 'LHS' then ensure it will be turned into 'RHS'.
-    addToLeaderTable(LVN, RHS, Root);
+    // If value numbering later sees that an instruction in the scope is equal
+    // to 'LHS' then ensure it will be turned into 'RHS'.  In order to preserve
+    // the invariant that instructions only occur in the leader table for their
+    // own value number (this is used by removeFromLeaderTable), do not do this
+    // if RHS is an instruction (if an instruction in the scope is morphed into
+    // LHS then it will be turned into RHS by the next GVN iteration anyway, so
+    // using the leader table is about compiling faster, not optimizing better).
+    if (!isa<Instruction>(RHS))
+      addToLeaderTable(LVN, RHS, Root);
 
     // Replace all occurrences of 'LHS' with 'RHS' everywhere in the scope.  As
     // LHS always has at least one use that is not dominated by Root, this will