Fix an issue that Chris noticed, where local PRE was not properly instantiating

a new value numbering set after splitting a critical edge.  This increases
the number of instances of PRE on 403.gcc from ~60 to ~570.

llvm-svn: 60393

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index d1f413eea29..039d52029aa 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1299,6 +1299,7 @@ bool GVN::performPRE(Function& F) {
         
       if (isCriticalEdge(PREPred->getTerminator(), succNum)) {
         toSplit.push_back(std::make_pair(PREPred->getTerminator(), succNum));
+        Changed = true;
         continue;
       }
       
@@ -1361,10 +1362,14 @@ bool GVN::performPRE(Function& F) {
   }
   
   for (SmallVector<std::pair<TerminatorInst*, unsigned>, 4>::iterator
-       I = toSplit.begin(), E = toSplit.end(); I != E; ++I)
+       I = toSplit.begin(), E = toSplit.end(); I != E; ++I) {
     SplitCriticalEdge(I->first, I->second, this);
+    BasicBlock* NewBlock = I->first->getSuccessor(I->second);
+    localAvail[NewBlock] =
+             new ValueNumberScope(localAvail[I->first->getParent()]);
+  }
   
-  return Changed || toSplit.size();
+  return Changed;
 }
 
 // iterateOnFunction - Executes one iteration of GVN