Fix PR5258, jump-threading creating invalid PHIs.

When an incoming value for a PHI is updated, we must also updated all other
incoming values for the same BB to match, otherwise we create invalid PHIs.

llvm-svn: 84638

1 files changed, 10 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/SSAUpdater.cpp b/llvm/lib/Transforms/Utils/SSAUpdater.cpp
index ee2f37b26cc..ed9c0ee6c70 100644
--- a/llvm/lib/Transforms/Utils/SSAUpdater.cpp
+++ b/llvm/lib/Transforms/Utils/SSAUpdater.cpp
@@ -178,10 +178,18 @@ Value *SSAUpdater::GetValueInMiddleOfBlock(BasicBlock *BB) {
 void SSAUpdater::RewriteUse(Use &U) {
   Instruction *User = cast<Instruction>(U.getUser());
   BasicBlock *UseBB = User->getParent();
-  if (PHINode *UserPN = dyn_cast<PHINode>(User))
+  PHINode *UserPN = dyn_cast<PHINode>(User);
+  if (UserPN)
     UseBB = UserPN->getIncomingBlock(U);
 
-  U.set(GetValueInMiddleOfBlock(UseBB));
+  Value *V = GetValueInMiddleOfBlock(UseBB);
+  U.set(V);
+  if (UserPN) {
+    // Incoming value from the same BB must be consistent
+    for (unsigned i=0;i<UserPN->getNumIncomingValues();i++)
+      if (UserPN->getIncomingBlock(i) == UseBB)
+        UserPN->setIncomingValue(i, V);
+  }
 }