From b061c4bc44caf62a16adad6047cda60785c2d0a4 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Mon, 31 Mar 2008 20:32:52 +0000
Subject: [PATCH] Fix a DAGCombiner optimization to respect volatile
 qualification.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48994 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/DAGCombiner.cpp |  3 ++-
 test/CodeGen/X86/pr2182.ll               | 24 ++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/X86/pr2182.ll

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 9f44c6a728f..4eccb815e3b 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4387,7 +4387,8 @@ SDOperand DAGCombiner::visitLOAD(SDNode *N) {
   // value.
   // TODO: Handle store large -> read small portion.
   // TODO: Handle TRUNCSTORE/LOADEXT
-  if (LD->getExtensionType() == ISD::NON_EXTLOAD) {
+  if (LD->getExtensionType() == ISD::NON_EXTLOAD &&
+      !LD->isVolatile()) {
     if (ISD::isNON_TRUNCStore(Chain.Val)) {
       StoreSDNode *PrevST = cast<StoreSDNode>(Chain);
       if (PrevST->getBasePtr() == Ptr &&
diff --git a/test/CodeGen/X86/pr2182.ll b/test/CodeGen/X86/pr2182.ll
new file mode 100644
index 00000000000..f65725db8bd
--- /dev/null
+++ b/test/CodeGen/X86/pr2182.ll
@@ -0,0 +1,24 @@
+; RUN: llvm-as < %s | llc | grep {addl	\$3, (%eax)} | count 4
+; PR2182
+
+target datalayout =
+"e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin8"
+@x = weak global i32 0          ; <i32*> [#uses=8]
+
+define void @loop_2() nounwind  {
+entry:
+        %tmp = volatile load i32* @x, align 4           ; <i32> [#uses=1]
+        %tmp1 = add i32 %tmp, 3         ; <i32> [#uses=1]
+        volatile store i32 %tmp1, i32* @x, align 4
+        %tmp.1 = volatile load i32* @x, align 4         ; <i32> [#uses=1]
+        %tmp1.1 = add i32 %tmp.1, 3             ; <i32> [#uses=1]
+        volatile store i32 %tmp1.1, i32* @x, align 4
+        %tmp.2 = volatile load i32* @x, align 4         ; <i32> [#uses=1]
+        %tmp1.2 = add i32 %tmp.2, 3             ; <i32> [#uses=1]
+        volatile store i32 %tmp1.2, i32* @x, align 4
+        %tmp.3 = volatile load i32* @x, align 4         ; <i32> [#uses=1]
+        %tmp1.3 = add i32 %tmp.3, 3             ; <i32> [#uses=1]
+        volatile store i32 %tmp1.3, i32* @x, align 4
+        ret void
+}