From a05c4c2bcae124d12f4e0ddaa6dce240e552463b Mon Sep 17 00:00:00 2001
From: Jakub Staszak <kubastaszak@gmail.com>
Date: Sun, 18 Oct 2015 19:34:10 +0000
Subject: [PATCH] Preserve CFG in MergedLoadStoreMotion. This fixes PR24426.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@250660 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Scalar/MergedLoadStoreMotion.cpp           |  1 +
 test/Transforms/GVN/pr24426.ll                 | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 test/Transforms/GVN/pr24426.ll

diff --git a/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp b/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
index 4161d6f7dd7..744ab4b9100 100644
--- a/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
+++ b/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
@@ -118,6 +118,7 @@ public:
 private:
   // This transformation requires dominator postdominator info
   void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
     AU.addRequired<TargetLibraryInfoWrapperPass>();
     AU.addRequired<AAResultsWrapperPass>();
     AU.addPreserved<GlobalsAAWrapperPass>();
diff --git a/test/Transforms/GVN/pr24426.ll b/test/Transforms/GVN/pr24426.ll
new file mode 100644
index 00000000000..76b190f8fc2
--- /dev/null
+++ b/test/Transforms/GVN/pr24426.ll
@@ -0,0 +1,18 @@
+; RUN: opt < %s -memcpyopt -mldst-motion -gvn -S | FileCheck %s
+
+declare void @check(i8)
+
+declare void @write(i8* %res)
+
+define void @test1() {
+  %1 = alloca [10 x i8]
+  %2 = bitcast [10 x i8]* %1 to i8*
+  call void @write(i8* %2)
+  %3 = load i8, i8* %2
+
+; CHECK-NOT: undef
+  call void @check(i8 %3)
+
+  ret void
+}
+
-- 
2.34.1