fix a bug exposed by moving SRoA earlier which caused a crash building kc++

llvm-svn: 85786

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp b/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
index b70276e255e..de6ad1dde58 100644
--- a/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+++ b/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
@@ -749,7 +749,12 @@ void PromoteMem2Reg::RewriteSingleStoreAlloca(AllocaInst *AI,
     }
     
     // Otherwise, we *can* safely rewrite this load.
-    LI->replaceAllUsesWith(OnlyStore->getOperand(0));
+    Value *ReplVal = OnlyStore->getOperand(0);
+    // If the replacement value is the load, this must occur in unreachable
+    // code.
+    if (ReplVal == LI)
+      ReplVal = UndefValue::get(LI->getType());
+    LI->replaceAllUsesWith(ReplVal);
     if (AST && isa<PointerType>(LI->getType()))
       AST->deleteValue(LI);
     LI->eraseFromParent();