From 794c15dc71061d7c3cc6028fbe64eb30d0cdbb66 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Mon, 2 Nov 2009 04:37:17 +0000
Subject: [PATCH] fix a bug exposed by moving SRoA earlier which caused a crash
 building kc++

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85786 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Utils/PromoteMemoryToRegister.cpp         |  7 +++++-
 test/Transforms/Mem2Reg/crash.ll              | 23 ++++++++++++++++---
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/lib/Transforms/Utils/PromoteMemoryToRegister.cpp b/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
index b70276e255e..de6ad1dde58 100644
--- a/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+++ b/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();
diff --git a/test/Transforms/Mem2Reg/crash.ll b/test/Transforms/Mem2Reg/crash.ll
index ce795aaaca4..655549f7940 100644
--- a/test/Transforms/Mem2Reg/crash.ll
+++ b/test/Transforms/Mem2Reg/crash.ll
@@ -1,12 +1,12 @@
 ; RUN: opt < %s -mem2reg -S
 ; PR5023
 
-declare i32 @bar()
+declare i32 @test1f()
 
-define i32 @foo() {
+define i32 @test1() {
 entry:
   %whichFlag = alloca i32
-  %A = invoke i32 @bar()
+  %A = invoke i32 @test1f()
           to label %invcont2 unwind label %lpad86
 
 invcont2:
@@ -22,3 +22,20 @@ lpad86:
   
 }
 
+
+
+define i32 @test2() {
+entry:
+  %whichFlag = alloca i32
+  br label %bb15
+
+bb15:
+  %B = load i32* %whichFlag
+  ret i32 %B
+
+invcont2:
+  %C = load i32* %whichFlag
+  store i32 %C, i32* %whichFlag
+  br label %bb15
+}
+
-- 
2.34.1