[llvm] 0e89ff8 - [X86] SimplifyDemandedBits - only narrow a broadcast source if we only have one use.

[Roman Lebedev via llvm-commits]

Thanks!

On Mon, Sep 20, 2021 at 12:54 AM Simon Pilgrim via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
>
>
> Author: Simon Pilgrim
> Date: 2021-09-19T22:53:30+01:00
> New Revision: 0e89ff8195e994e5051f19669e1044d47120ac06
>
> URL: https://github.com/llvm/llvm-project/commit/0e89ff8195e994e5051f19669e1044d47120ac06
> DIFF: https://github.com/llvm/llvm-project/commit/0e89ff8195e994e5051f19669e1044d47120ac06.diff
>
> LOG: [X86] SimplifyDemandedBits - only narrow a broadcast source if we only have one use.
>
> Helps with the regression noted on D109065 - don't truncate a broadcast source if the source has multiple uses.
>
> Added:
>
>
> Modified:
>     llvm/lib/Target/X86/X86ISelLowering.cpp
>     llvm/test/CodeGen/X86/oddshuffles.ll
>
> Removed:
>
>
>
> ################################################################################
> diff  --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
> index 3187c41a4ab1..3520bbfe1983 100644
> --- a/llvm/lib/Target/X86/X86ISelLowering.cpp
> +++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
> @@ -40381,7 +40381,8 @@ bool X86TargetLowering::SimplifyDemandedBitsForTargetNode(
>      // Don't attempt this on AVX512 as it might affect broadcast folding.
>      // TODO: Should we attempt this for i32/i16 splats? They tend to be slower.
>      if ((BitWidth == 64) && SrcVT.isScalarInteger() && !Subtarget.hasAVX512() &&
> -        OriginalDemandedBits.countLeadingZeros() >= (BitWidth / 2)) {
> +        OriginalDemandedBits.countLeadingZeros() >= (BitWidth / 2) &&
> +        Src->hasOneUse()) {
>        MVT NewSrcVT = MVT::getIntegerVT(BitWidth / 2);
>        SDValue NewSrc =
>            TLO.DAG.getNode(ISD::TRUNCATE, SDLoc(Src), NewSrcVT, Src);
>
> diff  --git a/llvm/test/CodeGen/X86/oddshuffles.ll b/llvm/test/CodeGen/X86/oddshuffles.ll
> index 0a3ddb81d345..b7f7321a8d3d 100644
> --- a/llvm/test/CodeGen/X86/oddshuffles.ll
> +++ b/llvm/test/CodeGen/X86/oddshuffles.ll
> @@ -2261,13 +2261,10 @@ define <16 x i32> @splat_v3i32(<3 x i32>* %ptr) {
>  ;
>  ; AVX1-LABEL: splat_v3i32:
>  ; AVX1:       # %bb.0:
> -; AVX1-NEXT:    movq (%rdi), %rax
> -; AVX1-NEXT:    vmovq %rax, %xmm0
> -; AVX1-NEXT:    vxorps %xmm1, %xmm1, %xmm1
> -; AVX1-NEXT:    vblendps {{.*#+}} ymm0 = ymm1[0],ymm0[1],ymm1[2,3,4,5,6,7]
> -; AVX1-NEXT:    vmovd %eax, %xmm2
> -; AVX1-NEXT:    vpshufd {{.*#+}} xmm2 = xmm2[0,0,0,0]
> -; AVX1-NEXT:    vblendps {{.*#+}} ymm1 = ymm1[0,1],ymm2[2],ymm1[3,4,5,6,7]
> +; AVX1-NEXT:    vmovddup {{.*#+}} xmm1 = mem[0,0]
> +; AVX1-NEXT:    vxorps %xmm2, %xmm2, %xmm2
> +; AVX1-NEXT:    vblendps {{.*#+}} ymm0 = ymm2[0],ymm1[1],ymm2[2,3,4,5,6,7]
> +; AVX1-NEXT:    vblendps {{.*#+}} ymm1 = ymm2[0,1],ymm1[2],ymm2[3,4,5,6,7]
>  ; AVX1-NEXT:    retq
>  ;
>  ; AVX2-SLOW-LABEL: splat_v3i32:
> @@ -2289,13 +2286,10 @@ define <16 x i32> @splat_v3i32(<3 x i32>* %ptr) {
>  ;
>  ; XOP-LABEL: splat_v3i32:
>  ; XOP:       # %bb.0:
> -; XOP-NEXT:    movq (%rdi), %rax
> -; XOP-NEXT:    vmovq %rax, %xmm0
> -; XOP-NEXT:    vxorps %xmm1, %xmm1, %xmm1
> -; XOP-NEXT:    vblendps {{.*#+}} ymm0 = ymm1[0],ymm0[1],ymm1[2,3,4,5,6,7]
> -; XOP-NEXT:    vmovd %eax, %xmm2
> -; XOP-NEXT:    vpshufd {{.*#+}} xmm2 = xmm2[0,0,0,0]
> -; XOP-NEXT:    vblendps {{.*#+}} ymm1 = ymm1[0,1],ymm2[2],ymm1[3,4,5,6,7]
> +; XOP-NEXT:    vmovddup {{.*#+}} xmm1 = mem[0,0]
> +; XOP-NEXT:    vxorps %xmm2, %xmm2, %xmm2
> +; XOP-NEXT:    vblendps {{.*#+}} ymm0 = ymm2[0],ymm1[1],ymm2[2,3,4,5,6,7]
> +; XOP-NEXT:    vblendps {{.*#+}} ymm1 = ymm2[0,1],ymm1[2],ymm2[3,4,5,6,7]
>  ; XOP-NEXT:    retq
>    %1 = load <3 x i32>, <3 x i32>* %ptr, align 1
>    %2 = shufflevector <3 x i32> %1, <3 x i32> undef, <16 x i32> <i32 0, i32 1, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
>
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits