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

llvm-svn: 58317

1 files changed, 9 insertions, 4 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 3dbedba7b96..a10f8a8daaf 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/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;