Fix 3113: If we have a dead cyclic PHI, replace the whole thing

with an undef.

llvm-svn: 59972

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
index a04ccfea361..b8664b0d4a1 100644
--- a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -206,7 +206,10 @@ void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
   if (DestBB->getSinglePredecessor()) {
     // If DestBB has single-entry PHI nodes, fold them.
     while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
-      PN->replaceAllUsesWith(PN->getIncomingValue(0));
+      Value *NewVal = PN->getIncomingValue(0);
+      // Replace self referencing PHI with undef, it must be dead.
+      if (NewVal == PN) NewVal = UndefValue::get(PN->getType());
+      PN->replaceAllUsesWith(NewVal);
       PN->eraseFromParent();
     }
 
@@ -569,6 +572,9 @@ static bool FindMaximalLegalAddressingMode(Value *Addr, const Type *AccessTy,
   if (Instruction *I = dyn_cast_or_null<Instruction>(AddrInst))
     AddrModeInsts.push_back(I);
 
+  if (AddrInst && !AddrInst->hasOneUse())
+    ;
+  else
   switch (Opcode) {
   case Instruction::PtrToInt:
     // PtrToInt is always a noop, as we know that the int type is pointer sized.