From 700843ec2c4cb4aa442377809c6ebb3ae3030c61 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Sun, 6 Jan 2013 19:00:15 +0000
Subject: [PATCH] Fix for PR14739. It's not safe to fold a load into a call
 across a store. Thanks to Nick Lewycky for the initial patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171665 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelDAGToDAG.cpp |  5 +++++
 test/CodeGen/X86/fold-call.ll      | 25 +++++++++++++++++++++----
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index c1eaa0e654c..935f9bd715f 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -420,6 +420,11 @@ static bool isCalleeLoad(SDValue Callee, SDValue &Chain, bool HasCallSeq) {
 
   if (!Chain.getNumOperands())
     return false;
+  // Since we are not checking for AA here, conservatively abort if the chain
+  // writes to memory. It's not safe to move the callee (a load) across a store.
+  if (isa<MemSDNode>(Chain.getNode()) &&
+      cast<MemSDNode>(Chain.getNode())->writeMem())
+    return false;
   if (Chain.getOperand(0).getNode() == Callee.getNode())
     return true;
   if (Chain.getOperand(0).getOpcode() == ISD::TokenFactor &&
diff --git a/test/CodeGen/X86/fold-call.ll b/test/CodeGen/X86/fold-call.ll
index 603e9ad66ca..35327faa648 100644
--- a/test/CodeGen/X86/fold-call.ll
+++ b/test/CodeGen/X86/fold-call.ll
@@ -1,10 +1,27 @@
-; RUN: llc < %s -march=x86 | not grep mov
-; RUN: llc < %s -march=x86-64 | not grep mov
+; RUN: llc < %s -march=x86 | FileCheck %s
+; RUN: llc < %s -march=x86-64 | FileCheck %s
 
-declare void @bar()
+; CHECK: test1
+; CHECK-NOT: mov
 
-define void @foo(i32 %i0, i32 %i1, i32 %i2, i32 %i3, i32 %i4, i32 %i5, void()* %arg) nounwind {
+declare void @bar()
+define void @test1(i32 %i0, i32 %i1, i32 %i2, i32 %i3, i32 %i4, i32 %i5, void()* %arg) nounwind {
 	call void @bar()
 	call void %arg()
 	ret void
 }
+
+; PR14739
+; CHECK: test2
+; CHECK: mov{{.*}} $0, ([[REGISTER:%[a-z]+]])
+; CHECK-NOT: jmp{{.*}} *([[REGISTER]])
+
+%struct.X = type { void ()* }
+define void @test2(%struct.X* nocapture %x) {
+entry:
+  %f = getelementptr inbounds %struct.X* %x, i64 0, i32 0
+  %0 = load void ()** %f
+  store void ()* null, void ()** %f
+  tail call void %0()
+  ret void
+}
-- 
2.34.1