Commit 03a96f4e authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Merging r310190: 

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r310190 | ctopper | 2017-08-05 16:34:44 -0700 (Sat, 05 Aug 2017) | 18 lines

[X86] Enable isel to use the PAUSE instruction even when SSE2 is disabled

Summary:
On older processors this instruction encoding is treated as a NOP.

MSVC doesn't disable intrinsics based on features the way clang/gcc does. Because the PAUSE instruction encoding doesn't crash older processors, some software out there uses these intrinsics without checking for SSE2.

This change also seems to also be consistent with gcc behavior.

Fixes PR34079

Reviewers: RKSimon, zvi

Reviewed By: RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D36361
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llvm-svn: 310293
parent 6e83d91d

llvm/lib/Target/X86/X86InstrSSE.td

+1 −2
Original line number Diff line number Diff line
@@ -3697,8 +3697,7 @@ let SchedRW = [WriteNop] in { 
// Pause. This "instruction" is encoded as "rep; nop", so even though it

// was introduced with SSE2, it's backward compatible.

def PAUSE : I<0x90, RawFrm, (outs), (ins),

              "pause", [(int_x86_sse2_pause)], IIC_SSE_PAUSE>,

              OBXS, Requires<[HasSSE2]>;

              "pause", [(int_x86_sse2_pause)], IIC_SSE_PAUSE>, OBXS;

}



let SchedRW = [WriteFence] in {

llvm/test/CodeGen/X86/pause.ll

0 → 100644
+15 −0
Original line number Diff line number Diff line 
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py

; RUN: llc < %s -disable-peephole -mtriple=i386-apple-darwin -mattr=-sse -show-mc-encoding | FileCheck %s

; RUN: llc < %s -disable-peephole -mtriple=i386-apple-darwin -mattr=-avx,+sse2 -show-mc-encoding | FileCheck %s

; RUN: llc < %s -disable-peephole -mtriple=i386-apple-darwin -mattr=+avx2 -show-mc-encoding | FileCheck %s

; RUN: llc < %s -disable-peephole -mtriple=i386-apple-darwin -mcpu=skx -show-mc-encoding | FileCheck %s



define void @test_x86_sse2_pause() {

; CHECK-LABEL: test_x86_sse2_pause:

; CHECK:       ## BB#0:

; CHECK-NEXT:    pause ## encoding: [0xf3,0x90]

; CHECK-NEXT:    retl ## encoding: [0xc3]

  tail call void @llvm.x86.sse2.pause()

  ret void

}

declare void @llvm.x86.sse2.pause() nounwind