From 4002a1b6f1cb7c7db7965bd281fb29664fd6c816 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 28 Oct 2008 05:49:35 +0000
Subject: [PATCH] Fix a nasty miscompilation of 176.gcc on linux/x86 where we
 synthesized a memset using 16-byte XMM stores, but where the stack
 realignment code didn't work.  Until it does (PR2962) disable use of xmm regs
 in memcpy and memset formation for linux and other targets with
 insufficiently aligned stacks.

This is part of PR2888



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58317 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp            | 13 +++++++----
 .../X86/2008-10-27-StackRealignment.ll        | 22 +++++++++++++++++++
 2 files changed, 31 insertions(+), 4 deletions(-)
 create mode 100644 test/CodeGen/X86/2008-10-27-StackRealignment.ll

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 3dbedba7b96..a10f8a8daaf 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -850,10 +850,15 @@ unsigned X86TargetLowering::getByValTypeAlignment(const Type *Ty) const {
 MVT
 X86TargetLowering::getOptimalMemOpType(uint64_t Size, unsigned Align,
                                        bool isSrcConst, bool isSrcStr) const {
-  if ((isSrcConst || isSrcStr) && Subtarget->hasSSE2() && Size >= 16)
-    return MVT::v4i32;
-  if ((isSrcConst || isSrcStr) && Subtarget->hasSSE1() && Size >= 16)
-    return MVT::v4f32;
+  // FIXME: This turns off use of xmm stores for memset/memcpy on targets like
+  // linux.  This is because the stack realignment code can't handle certain
+  // cases like PR2962.  This should be removed when PR2962 is fixed.
+  if (Subtarget->getStackAlignment() >= 16) {
+    if ((isSrcConst || isSrcStr) && Subtarget->hasSSE2() && Size >= 16)
+      return MVT::v4i32;
+    if ((isSrcConst || isSrcStr) && Subtarget->hasSSE1() && Size >= 16)
+      return MVT::v4f32;
+  }
   if (Subtarget->is64Bit() && Size >= 8)
     return MVT::i64;
   return MVT::i32;
diff --git a/test/CodeGen/X86/2008-10-27-StackRealignment.ll b/test/CodeGen/X86/2008-10-27-StackRealignment.ll
new file mode 100644
index 00000000000..d8b0e706d2a
--- /dev/null
+++ b/test/CodeGen/X86/2008-10-27-StackRealignment.ll
@@ -0,0 +1,22 @@
+; Linux doesn't support stack realignment for functions with allocas (PR2888).
+; Until it does, we shouldn't use movaps to access the stack.  On targets with
+; sufficiently aligned stack (e.g. darwin) we should.
+
+; RUN: llvm-as < %s | llc -mtriple=i386-pc-linux-gnu -mcpu=yonah | not grep movaps
+; RUN: llvm-as < %s | llc -mtriple=i686-apple-darwin9 -mcpu=yonah | grep movaps | count 2
+
+
+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-f80:32:32"
+target triple = "i386-pc-linux-gnu"
+  
+define void @foo(i32 %t) nounwind {
+  %tmp1210 = alloca i8, i32 32, align 4
+  call void @llvm.memset.i64(i8* %tmp1210, i8 0, i64 32, i32 4)
+  
+  %x = alloca i8, i32 %t
+  call void @dummy(i8* %x)
+  ret void
+}
+
+declare void @dummy(i8* %x)
+declare void @llvm.memset.i64(i8*, i8, i64, i32) nounwind