Fix a subtle iterator invalidation bug in a recursive algorithm.

llvm-svn: 40776

1 files changed, 7 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index 2384e59ca0e..1f3ecfa2b19 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -726,19 +726,21 @@ Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig,
                                bool top_level) { 
                                  
   // If we have already computed this value, return the previously computed val.
-  Value *&V = Phis[BB];
+  Value *V = Phis[BB];
   if (V && ! top_level) return V;
   
   BasicBlock* singlePred = BB->getSinglePredecessor();
-  if (singlePred)
-    return V = GetValueForBlock(singlePred, orig, Phis);
-  
+  if (singlePred) {
+    V = GetValueForBlock(singlePred, orig, Phis);
+    Phis[BB] = V;
+    return V;
+  }
   // Otherwise, the idom is the loop, so we need to insert a PHI node.  Do so
   // now, then get values to fill in the incoming values for the PHI.
   PHINode *PN = new PHINode(orig->getType(), orig->getName()+".rle",
                             BB->begin());
   PN->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB)));
-  V = PN;
+  Phis[BB] = PN;
   
   bool all_same = true;
   Value* first = 0;