From 6eff75104e660bae5b28963190a6940eeecb7484 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Fri, 1 Oct 2010 05:51:02 +0000
Subject: [PATCH] fix PR8267 - Instcombine shouldn't optimizer away volatile
 memcpy's.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115296 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/InstCombine/InstCombineCalls.cpp |  7 ++++++-
 test/Transforms/InstCombine/memcpy.ll           | 15 ++++++++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 0ebe3b45589..ed078ec1c51 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -280,7 +280,8 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
 
     // memmove/cpy/set of zero bytes is a noop.
     if (Constant *NumBytes = dyn_cast<Constant>(MI->getLength())) {
-      if (NumBytes->isNullValue()) return EraseInstFromFunction(CI);
+      if (NumBytes->isNullValue())
+        return EraseInstFromFunction(CI);
 
       if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes))
         if (CI->getZExtValue() == 1) {
@@ -289,6 +290,10 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
           // alignment is sufficient.
         }
     }
+    
+    // No other transformations apply to volatile transfers.
+    if (MI->isVolatile())
+      return 0;
 
     // If we have a memmove and the source operation is a constant global,
     // then the source and dest pointers can't alias, so we can change this
diff --git a/test/Transforms/InstCombine/memcpy.ll b/test/Transforms/InstCombine/memcpy.ll
index 421156d7712..8a2e3aaad02 100644
--- a/test/Transforms/InstCombine/memcpy.ll
+++ b/test/Transforms/InstCombine/memcpy.ll
@@ -2,9 +2,18 @@
 
 declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32, i1) nounwind
 
-define void @test4(i8* %a) {
+define void @test1(i8* %a) {
         tail call void @llvm.memcpy.p0i8.p0i8.i32(i8* %a, i8* %a, i32 100, i32 1, i1 false)
         ret void
-}
-; CHECK: define void @test4
+; CHECK: define void @test1
 ; CHECK-NEXT: ret void
+}
+
+
+; PR8267
+define void @test2(i8* %a) {
+        tail call void @llvm.memcpy.p0i8.p0i8.i32(i8* %a, i8* %a, i32 100, i32 1, i1 true)
+        ret void
+; CHECK: define void @test2
+; CHECK-NEXT: call void @llvm.memcpy
+}