X86: Enable SSE memory intrinsics even when stack alignment is less than 16 bytes.
The stack realignment code was fixed to work when there is stack realignment and
a dynamic alloca is present so this shouldn't cause correctness issues anymore.
Note that this also enables generation of AVX instructions for memset
under the assumptions:
- Unaligned loads/stores are always fast on CPUs supporting AVX
- AVX is not slower than SSE
We may need some tweaked heuristics if one of those assumptions turns out not to
be true.
Effectively reverts r58317. Part of PR2962.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167967 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 863379e..53a095f 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1362,18 +1362,14 @@
bool IsZeroVal,
bool MemcpyStrSrc,
MachineFunction &MF) const {
- // 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.
const Function *F = MF.getFunction();
if (IsZeroVal &&
!F->getFnAttributes().hasAttribute(Attributes::NoImplicitFloat)) {
if (Size >= 16 &&
(Subtarget->isUnalignedMemAccessFast() ||
((DstAlign == 0 || DstAlign >= 16) &&
- (SrcAlign == 0 || SrcAlign >= 16))) &&
- Subtarget->getStackAlignment() >= 16) {
- if (Subtarget->getStackAlignment() >= 32) {
+ (SrcAlign == 0 || SrcAlign >= 16)))) {
+ if (Size >= 32) {
if (Subtarget->hasAVX2())
return MVT::v8i32;
if (Subtarget->hasAVX())
@@ -1385,7 +1381,6 @@
return MVT::v4f32;
} else if (!MemcpyStrSrc && Size >= 8 &&
!Subtarget->is64Bit() &&
- Subtarget->getStackAlignment() >= 8 &&
Subtarget->hasSSE2()) {
// Do not use f64 to lower memcpy if source is string constant. It's
// better to use i32 to avoid the loads.