[llvm] r270378 - [x86, AVX] don't add a vzeroupper if that's what the code is already doing (PR27823)

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Sun May 22 15:22:47 2016
New Revision: 270378

URL: http://llvm.org/viewvc/llvm-project?rev=270378&view=rev
Log:
[x86, AVX] don't add a vzeroupper if that's what the code is already doing (PR27823)

This isn't the complete fix, but it handles the trivial examples of duplicate vzero* ops in PR27823:
https://llvm.org/bugs/show_bug.cgi?id=27823
...and amusingly, the bogus cases already exist as regression tests, so let's take this baby step.

We'll need to do more in the general case where there's legitimate AVX usage in the function + there's
already a vzero in the code.

Differential Revision: http://reviews.llvm.org/D20477


Modified:
    llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp
    llvm/trunk/test/CodeGen/X86/avx-intrinsics-fast-isel.ll
    llvm/trunk/test/CodeGen/X86/avx-intrinsics-x86.ll

Modified: llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp?rev=270378&r1=270377&r2=270378&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp Sun May 22 15:22:47 2016
@@ -192,6 +192,12 @@ void VZeroUpperInserter::processBasicBlo
     if ((!IsControlFlow || IsReturnFromX86INTR) && CurState == EXITS_DIRTY)
       continue;
 
+    // Ignore existing VZERO* instructions.
+    // FIXME: The existence of these instructions should be used to modify the
+    // current state and/or used when deciding whether we need to create a VZU.
+    if (MI->getOpcode() == X86::VZEROALL || MI->getOpcode() == X86::VZEROUPPER)
+      continue;
+
     if (hasYmmReg(MI)) {
       // We found a ymm-using instruction; this could be an AVX instruction,
       // or it could be control flow.

Modified: llvm/trunk/test/CodeGen/X86/avx-intrinsics-fast-isel.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/avx-intrinsics-fast-isel.ll?rev=270378&r1=270377&r2=270378&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/avx-intrinsics-fast-isel.ll (original)
+++ llvm/trunk/test/CodeGen/X86/avx-intrinsics-fast-isel.ll Sun May 22 15:22:47 2016
@@ -3736,13 +3736,11 @@ define void @test_mm256_zeroall() nounwi
 ; X32-LABEL: test_mm256_zeroall:
 ; X32:       # BB#0:
 ; X32-NEXT:    vzeroall
-; X32-NEXT:    vzeroupper
 ; X32-NEXT:    retl
 ;
 ; X64-LABEL: test_mm256_zeroall:
 ; X64:       # BB#0:
 ; X64-NEXT:    vzeroall
-; X64-NEXT:    vzeroupper
 ; X64-NEXT:    retq
   call void @llvm.x86.avx.vzeroall()
   ret void
@@ -3753,13 +3751,11 @@ define void @test_mm256_zeroupper() noun
 ; X32-LABEL: test_mm256_zeroupper:
 ; X32:       # BB#0:
 ; X32-NEXT:    vzeroupper
-; X32-NEXT:    vzeroupper
 ; X32-NEXT:    retl
 ;
 ; X64-LABEL: test_mm256_zeroupper:
 ; X64:       # BB#0:
 ; X64-NEXT:    vzeroupper
-; X64-NEXT:    vzeroupper
 ; X64-NEXT:    retq
   call void @llvm.x86.avx.vzeroupper()
   ret void

Modified: llvm/trunk/test/CodeGen/X86/avx-intrinsics-x86.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/avx-intrinsics-x86.ll?rev=270378&r1=270377&r2=270378&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/avx-intrinsics-x86.ll (original)
+++ llvm/trunk/test/CodeGen/X86/avx-intrinsics-x86.ll Sun May 22 15:22:47 2016
@@ -4755,7 +4755,6 @@ define void @test_x86_avx_vzeroall() {
 ; AVX-LABEL: test_x86_avx_vzeroall:
 ; AVX:       ## BB#0:
 ; AVX-NEXT:    vzeroall
-; AVX-NEXT:    vzeroupper
 ; AVX-NEXT:    retl
 ;
 ; AVX512VL-LABEL: test_x86_avx_vzeroall:
@@ -4772,7 +4771,6 @@ define void @test_x86_avx_vzeroupper() {
 ; AVX-LABEL: test_x86_avx_vzeroupper:
 ; AVX:       ## BB#0:
 ; AVX-NEXT:    vzeroupper
-; AVX-NEXT:    vzeroupper
 ; AVX-NEXT:    retl
 ;
 ; AVX512VL-LABEL: test_x86_avx_vzeroupper: