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* Re: [PATCH v2] x86: Improve vec generation in memset-vec-unaligned-erms.S
       [not found]     ` <CAFUsyfJKX5V0sCBzkY1gDuCHyEyQRgxsCKo13SJsJmb=1vYY=g@mail.gmail.com>
@ 2022-05-04  5:46       ` Sunil Pandey
  0 siblings, 0 replies; only message in thread
From: Sunil Pandey @ 2022-05-04  5:46 UTC (permalink / raw)
  To: Noah Goldstein, Libc-stable Mailing List; +Cc: H.J. Lu, GNU C Library

On Sun, Feb 6, 2022 at 7:48 PM Noah Goldstein via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On Sun, Feb 6, 2022 at 10:29 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Sat, Feb 5, 2022 at 10:54 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > >
> > > No bug.
> > >
> > > Split vec generation into multiple steps. This allows the
> > > broadcast in AVX2 to use 'xmm' registers for the L(less_vec)
> > > case. This saves an expensive lane-cross instruction and removes
> > > the need for 'vzeroupper'.
> > >
> > > For SSE2 replace 2x 'punpck' instructions with zero-idiom 'pxor' for
> > > byte broadcast.
> > >
> > > Results for memset-avx2 small (geomean of N = 20 benchset runs).
> > >
> > > size, New Time, Old Time, New / Old
> > >    0,    4.100,    3.831,     0.934
> > >    1,    5.074,    4.399,     0.867
> > >    2,    4.433,    4.411,     0.995
> > >    4,    4.487,    4.415,     0.984
> > >    8,    4.454,    4.396,     0.987
> > >   16,    4.502,    4.443,     0.987
> > >
> > > All relevant string/wcsmbs tests are passing.
> > > ---
> > >  sysdeps/x86_64/memset.S                       |  21 ++-
> > >  .../multiarch/memset-avx2-unaligned-erms.S    |  18 +-
> > >  .../multiarch/memset-avx512-unaligned-erms.S  |  18 +-
> > >  .../multiarch/memset-evex-unaligned-erms.S    |  18 +-
> > >  .../multiarch/memset-vec-unaligned-erms.S     | 164 +++++++++++-------
> > >  5 files changed, 152 insertions(+), 87 deletions(-)
> > >
> > > diff --git a/sysdeps/x86_64/memset.S b/sysdeps/x86_64/memset.S
> > > index 65c09bd0ac..ccf036be53 100644
> > > --- a/sysdeps/x86_64/memset.S
> > > +++ b/sysdeps/x86_64/memset.S
> > > @@ -28,17 +28,22 @@
> > >  #define VMOVU     movups
> > >  #define VMOVA     movaps
> > >
> > > -#define MEMSET_VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> > > +# define MEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > >    movd d, %xmm0; \
> > > -  movq r, %rax; \
> > > -  punpcklbw %xmm0, %xmm0; \
> > > -  punpcklwd %xmm0, %xmm0; \
> > > -  pshufd $0, %xmm0, %xmm0
> > > +  pxor %xmm1, %xmm1; \
> > > +  pshufb %xmm1, %xmm0; \
> > > +  movq r, %rax
> > >
> > > -#define WMEMSET_VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> > > +# define WMEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > >    movd d, %xmm0; \
> > > -  movq r, %rax; \
> > > -  pshufd $0, %xmm0, %xmm0
> > > +  pshufd $0, %xmm0, %xmm0; \
> > > +  movq r, %rax
> > > +
> > > +# define MEMSET_VDUP_TO_VEC0_HIGH()
> > > +# define MEMSET_VDUP_TO_VEC0_LOW()
> > > +
> > > +# define WMEMSET_VDUP_TO_VEC0_HIGH()
> > > +# define WMEMSET_VDUP_TO_VEC0_LOW()
> > >
> > >  #define SECTION(p)             p
> > >
> > > diff --git a/sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S
> > > index 1af668af0a..c0bf2875d0 100644
> > > --- a/sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S
> > > +++ b/sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S
> > > @@ -10,15 +10,18 @@
> > >  # define VMOVU     vmovdqu
> > >  # define VMOVA     vmovdqa
> > >
> > > -# define MEMSET_VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> > > +# define MEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > >    vmovd d, %xmm0; \
> > > -  movq r, %rax; \
> > > -  vpbroadcastb %xmm0, %ymm0
> > > +  movq r, %rax;
> > >
> > > -# define WMEMSET_VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> > > -  vmovd d, %xmm0; \
> > > -  movq r, %rax; \
> > > -  vpbroadcastd %xmm0, %ymm0
> > > +# define WMEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > > +  MEMSET_SET_VEC0_AND_SET_RETURN(d, r)
> > > +
> > > +# define MEMSET_VDUP_TO_VEC0_HIGH() vpbroadcastb %xmm0, %ymm0
> > > +# define MEMSET_VDUP_TO_VEC0_LOW() vpbroadcastb %xmm0, %xmm0
> > > +
> > > +# define WMEMSET_VDUP_TO_VEC0_HIGH() vpbroadcastd %xmm0, %ymm0
> > > +# define WMEMSET_VDUP_TO_VEC0_LOW() vpbroadcastd %xmm0, %xmm0
> > >
> > >  # ifndef SECTION
> > >  #  define SECTION(p)           p##.avx
> > > @@ -30,5 +33,6 @@
> > >  #  define WMEMSET_SYMBOL(p,s)  p##_avx2_##s
> > >  # endif
> > >
> > > +# define USE_XMM_LESS_VEC
> > >  # include "memset-vec-unaligned-erms.S"
> > >  #endif
> > > diff --git a/sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S
> > > index f14d6f8493..5241216a77 100644
> > > --- a/sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S
> > > +++ b/sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S
> > > @@ -15,13 +15,19 @@
> > >
> > >  # define VZEROUPPER
> > >
> > > -# define MEMSET_VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> > > -  movq r, %rax; \
> > > -  vpbroadcastb d, %VEC0
> > > +# define MEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > > +  vpbroadcastb d, %VEC0; \
> > > +  movq r, %rax
> > >
> > > -# define WMEMSET_VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> > > -  movq r, %rax; \
> > > -  vpbroadcastd d, %VEC0
> > > +# define WMEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > > +  vpbroadcastd d, %VEC0; \
> > > +  movq r, %rax
> > > +
> > > +# define MEMSET_VDUP_TO_VEC0_HIGH()
> > > +# define MEMSET_VDUP_TO_VEC0_LOW()
> > > +
> > > +# define WMEMSET_VDUP_TO_VEC0_HIGH()
> > > +# define WMEMSET_VDUP_TO_VEC0_LOW()
> > >
> > >  # define SECTION(p)            p##.evex512
> > >  # define MEMSET_SYMBOL(p,s)    p##_avx512_##s
> > > diff --git a/sysdeps/x86_64/multiarch/memset-evex-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-evex-unaligned-erms.S
> > > index 64b09e77cc..6370021506 100644
> > > --- a/sysdeps/x86_64/multiarch/memset-evex-unaligned-erms.S
> > > +++ b/sysdeps/x86_64/multiarch/memset-evex-unaligned-erms.S
> > > @@ -15,13 +15,19 @@
> > >
> > >  # define VZEROUPPER
> > >
> > > -# define MEMSET_VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> > > -  movq r, %rax; \
> > > -  vpbroadcastb d, %VEC0
> > > +# define MEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > > +  vpbroadcastb d, %VEC0; \
> > > +  movq r, %rax
> > >
> > > -# define WMEMSET_VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> > > -  movq r, %rax; \
> > > -  vpbroadcastd d, %VEC0
> > > +# define WMEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > > +  vpbroadcastd d, %VEC0; \
> > > +  movq r, %rax
> > > +
> > > +# define MEMSET_VDUP_TO_VEC0_HIGH()
> > > +# define MEMSET_VDUP_TO_VEC0_LOW()
> > > +
> > > +# define WMEMSET_VDUP_TO_VEC0_HIGH()
> > > +# define WMEMSET_VDUP_TO_VEC0_LOW()
> > >
> > >  # define SECTION(p)            p##.evex
> > >  # define MEMSET_SYMBOL(p,s)    p##_evex_##s
> > > diff --git a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
> > > index 1e0511c79a..1b502b78e4 100644
> > > --- a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
> > > +++ b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
> > > @@ -58,8 +58,10 @@
> > >  #ifndef MOVQ
> > >  # if VEC_SIZE > 16
> > >  #  define MOVQ                         vmovq
> > > +#  define MOVD                         vmovd
> > >  # else
> > >  #  define MOVQ                         movq
> > > +#  define MOVD                         movd
> > >  # endif
> > >  #endif
> > >
> > > @@ -72,9 +74,17 @@
> > >  #if defined USE_WITH_EVEX || defined USE_WITH_AVX512
> > >  # define END_REG       rcx
> > >  # define LOOP_REG      rdi
> > > +# define LESS_VEC_REG  rax
> > >  #else
> > >  # define END_REG       rdi
> > >  # define LOOP_REG      rdx
> > > +# define LESS_VEC_REG  rdi
> > > +#endif
> > > +
> > > +#ifdef USE_XMM_LESS_VEC
> > > +# define XMM_SMALL     1
> > > +#else
> > > +# define XMM_SMALL     0
> > >  #endif
> > >
> > >  #define PAGE_SIZE 4096
> > > @@ -110,8 +120,12 @@ END_CHK (WMEMSET_CHK_SYMBOL (__wmemset_chk, unaligned))
> > >
> > >  ENTRY (WMEMSET_SYMBOL (__wmemset, unaligned))
> > >         shl     $2, %RDX_LP
> > > -       WMEMSET_VDUP_TO_VEC0_AND_SET_RETURN (%esi, %rdi)
> > > -       jmp     L(entry_from_bzero)
> > > +       WMEMSET_SET_VEC0_AND_SET_RETURN (%esi, %rdi)
> > > +       WMEMSET_VDUP_TO_VEC0_LOW()
> > > +       cmpq    $VEC_SIZE, %rdx
> > > +       jb      L(less_vec_no_vdup)
> > > +       WMEMSET_VDUP_TO_VEC0_HIGH()
> > > +       jmp     L(entry_from_wmemset)
> > >  END (WMEMSET_SYMBOL (__wmemset, unaligned))
> > >  #endif
> > >
> > > @@ -123,7 +137,7 @@ END_CHK (MEMSET_CHK_SYMBOL (__memset_chk, unaligned))
> > >  #endif
> > >
> > >  ENTRY (MEMSET_SYMBOL (__memset, unaligned))
> > > -       MEMSET_VDUP_TO_VEC0_AND_SET_RETURN (%esi, %rdi)
> > > +       MEMSET_SET_VEC0_AND_SET_RETURN (%esi, %rdi)
> > >  # ifdef __ILP32__
> > >         /* Clear the upper 32 bits.  */
> > >         mov     %edx, %edx
> > > @@ -131,6 +145,8 @@ ENTRY (MEMSET_SYMBOL (__memset, unaligned))
> > >  L(entry_from_bzero):
> > >         cmpq    $VEC_SIZE, %rdx
> > >         jb      L(less_vec)
> > > +       MEMSET_VDUP_TO_VEC0_HIGH()
> > > +L(entry_from_wmemset):
> > >         cmpq    $(VEC_SIZE * 2), %rdx
> > >         ja      L(more_2x_vec)
> > >         /* From VEC and to 2 * VEC.  No branch when size == VEC_SIZE.  */
> > > @@ -179,27 +195,27 @@ END_CHK (MEMSET_CHK_SYMBOL (__memset_chk, unaligned_erms))
> > >  # endif
> > >
> > >  ENTRY_P2ALIGN (MEMSET_SYMBOL (__memset, unaligned_erms), 6)
> > > -       MEMSET_VDUP_TO_VEC0_AND_SET_RETURN (%esi, %rdi)
> > > +       MEMSET_SET_VEC0_AND_SET_RETURN (%esi, %rdi)
> > >  # ifdef __ILP32__
> > >         /* Clear the upper 32 bits.  */
> > >         mov     %edx, %edx
> > >  # endif
> > >         cmp     $VEC_SIZE, %RDX_LP
> > >         jb      L(less_vec)
> > > +       MEMSET_VDUP_TO_VEC0_HIGH ()
> > >         cmp     $(VEC_SIZE * 2), %RDX_LP
> > >         ja      L(stosb_more_2x_vec)
> > > -       /* From VEC and to 2 * VEC.  No branch when size == VEC_SIZE.
> > > -        */
> > > -       VMOVU   %VEC(0), (%rax)
> > > -       VMOVU   %VEC(0), -VEC_SIZE(%rax, %rdx)
> > > +       /* From VEC and to 2 * VEC.  No branch when size == VEC_SIZE.  */
> > > +       VMOVU   %VEC(0), (%rdi)
> > > +       VMOVU   %VEC(0), (VEC_SIZE * -1)(%rdi, %rdx)
> > >         VZEROUPPER_RETURN
> > >  #endif
> > >
> > > -       .p2align 4,, 10
> > > +       .p2align 4,, 4
> > >  L(last_2x_vec):
> > >  #ifdef USE_LESS_VEC_MASK_STORE
> > > -       VMOVU   %VEC(0), (VEC_SIZE * 2 + LOOP_4X_OFFSET)(%rcx)
> > > -       VMOVU   %VEC(0), (VEC_SIZE * 3 + LOOP_4X_OFFSET)(%rcx)
> > > +       VMOVU   %VEC(0), (VEC_SIZE * -2)(%rdi, %rdx)
> > > +       VMOVU   %VEC(0), (VEC_SIZE * -1)(%rdi, %rdx)
> > >  #else
> > >         VMOVU   %VEC(0), (VEC_SIZE * -2)(%rdi)
> > >         VMOVU   %VEC(0), (VEC_SIZE * -1)(%rdi)
> > > @@ -212,6 +228,7 @@ L(last_2x_vec):
> > >  #ifdef USE_LESS_VEC_MASK_STORE
> > >         .p2align 4,, 10
> > >  L(less_vec):
> > > +L(less_vec_no_vdup):
> > >         /* Less than 1 VEC.  */
> > >  # if VEC_SIZE != 16 && VEC_SIZE != 32 && VEC_SIZE != 64
> > >  #  error Unsupported VEC_SIZE!
> > > @@ -262,28 +279,18 @@ L(stosb_more_2x_vec):
> > >         /* Fallthrough goes to L(loop_4x_vec). Tests for memset (2x, 4x]
> > >            and (4x, 8x] jump to target.  */
> > >  L(more_2x_vec):
> > > -
> > > -       /* Two different methods of setting up pointers / compare. The
> > > -          two methods are based on the fact that EVEX/AVX512 mov
> > > -          instructions take more bytes then AVX2/SSE2 mov instructions. As
> > > -          well that EVEX/AVX512 machines also have fast LEA_BID. Both
> > > -          setup and END_REG to avoid complex address mode. For EVEX/AVX512
> > > -          this saves code size and keeps a few targets in one fetch block.
> > > -          For AVX2/SSE2 this helps prevent AGU bottlenecks.  */
> > > -#if defined USE_WITH_EVEX || defined USE_WITH_AVX512
> > > -       /* If EVEX/AVX512 compute END_REG - (VEC_SIZE * 4 +
> > > -          LOOP_4X_OFFSET) with LEA_BID.  */
> > > -
> > > -       /* END_REG is rcx for EVEX/AVX512.  */
> > > -       leaq    -(VEC_SIZE * 4 + LOOP_4X_OFFSET)(%rdi, %rdx), %END_REG
> > > -#endif
> > > -
> > > -       /* Stores to first 2x VEC before cmp as any path forward will
> > > -          require it.  */
> > > -       VMOVU   %VEC(0), (%rax)
> > > -       VMOVU   %VEC(0), VEC_SIZE(%rax)
> > > +       /* Store next 2x vec regardless.  */
> > > +       VMOVU   %VEC(0), (%rdi)
> > > +       VMOVU   %VEC(0), (VEC_SIZE * 1)(%rdi)
> > >
> > >
> > > +       /* Two different methods of setting up pointers / compare. The two
> > > +          methods are based on the fact that EVEX/AVX512 mov instructions take
> > > +          more bytes then AVX2/SSE2 mov instructions. As well that EVEX/AVX512
> > > +          machines also have fast LEA_BID. Both setup and END_REG to avoid complex
> > > +          address mode. For EVEX/AVX512 this saves code size and keeps a few
> > > +          targets in one fetch block. For AVX2/SSE2 this helps prevent AGU
> > > +          bottlenecks.  */
> > >  #if !(defined USE_WITH_EVEX || defined USE_WITH_AVX512)
> > >         /* If AVX2/SSE2 compute END_REG (rdi) with ALU.  */
> > >         addq    %rdx, %END_REG
> > > @@ -292,6 +299,15 @@ L(more_2x_vec):
> > >         cmpq    $(VEC_SIZE * 4), %rdx
> > >         jbe     L(last_2x_vec)
> > >
> > > +
> > > +#if defined USE_WITH_EVEX || defined USE_WITH_AVX512
> > > +       /* If EVEX/AVX512 compute END_REG - (VEC_SIZE * 4 + LOOP_4X_OFFSET) with
> > > +          LEA_BID.  */
> > > +
> > > +       /* END_REG is rcx for EVEX/AVX512.  */
> > > +       leaq    -(VEC_SIZE * 4 + LOOP_4X_OFFSET)(%rdi, %rdx), %END_REG
> > > +#endif
> > > +
> > >         /* Store next 2x vec regardless.  */
> > >         VMOVU   %VEC(0), (VEC_SIZE * 2)(%rax)
> > >         VMOVU   %VEC(0), (VEC_SIZE * 3)(%rax)
> > > @@ -355,65 +371,93 @@ L(stosb_local):
> > >         /* Define L(less_vec) only if not otherwise defined.  */
> > >         .p2align 4
> > >  L(less_vec):
> > > +       /* Broadcast esi to partial register (i.e VEC_SIZE == 32 broadcast to
> > > +          xmm). This is only does anything for AVX2.  */
> > > +       MEMSET_VDUP_TO_VEC0_LOW ()
> > > +L(less_vec_no_vdup):
> > >  #endif
> > >  L(cross_page):
> > >  #if VEC_SIZE > 32
> > >         cmpl    $32, %edx
> > > -       jae     L(between_32_63)
> > > +       jge     L(between_32_63)
> > >  #endif
> > >  #if VEC_SIZE > 16
> > >         cmpl    $16, %edx
> > > -       jae     L(between_16_31)
> > > +       jge     L(between_16_31)
> > > +#endif
> > > +#ifndef USE_XMM_LESS_VEC
> > > +       MOVQ    %XMM0, %rcx
> > >  #endif
> > > -       MOVQ    %XMM0, %rdi
> > >         cmpl    $8, %edx
> > > -       jae     L(between_8_15)
> > > +       jge     L(between_8_15)
> > >         cmpl    $4, %edx
> > > -       jae     L(between_4_7)
> > > +       jge     L(between_4_7)
> > >         cmpl    $1, %edx
> > > -       ja      L(between_2_3)
> > > -       jb      L(return)
> > > -       movb    %sil, (%rax)
> > > -       VZEROUPPER_RETURN
> > > +       jg      L(between_2_3)
> > > +       jl      L(between_0_0)
> > > +       movb    %sil, (%LESS_VEC_REG)
> > > +L(between_0_0):
> > > +       ret
> > >
> > > -       /* Align small targets only if not doing so would cross a fetch
> > > -          line.  */
> > > +       /* Align small targets only if not doing so would cross a fetch line.
> > > +        */
> > >  #if VEC_SIZE > 32
> > >         .p2align 4,, SMALL_MEMSET_ALIGN(MOV_SIZE, RET_SIZE)
> > >         /* From 32 to 63.  No branch when size == 32.  */
> > >  L(between_32_63):
> > > -       VMOVU   %YMM0, (%rax)
> > > -       VMOVU   %YMM0, -32(%rax, %rdx)
> > > +       VMOVU   %YMM0, (%LESS_VEC_REG)
> > > +       VMOVU   %YMM0, -32(%LESS_VEC_REG, %rdx)
> > >         VZEROUPPER_RETURN
> > >  #endif
> > >
> > >  #if VEC_SIZE >= 32
> > > -       .p2align 4,, SMALL_MEMSET_ALIGN(MOV_SIZE, RET_SIZE)
> > > +       .p2align 4,, SMALL_MEMSET_ALIGN(MOV_SIZE, 1)
> > >  L(between_16_31):
> > >         /* From 16 to 31.  No branch when size == 16.  */
> > > -       VMOVU   %XMM0, (%rax)
> > > -       VMOVU   %XMM0, -16(%rax, %rdx)
> > > -       VZEROUPPER_RETURN
> > > +       VMOVU   %XMM0, (%LESS_VEC_REG)
> > > +       VMOVU   %XMM0, -16(%LESS_VEC_REG, %rdx)
> > > +       ret
> > >  #endif
> > >
> > > -       .p2align 4,, SMALL_MEMSET_ALIGN(3, RET_SIZE)
> > > +       /* Move size is 3 for SSE2, EVEX, and AVX512. Move size is 4 for AVX2.
> > > +        */
> > > +       .p2align 4,, SMALL_MEMSET_ALIGN(3 + XMM_SMALL, 1)
> > >  L(between_8_15):
> > >         /* From 8 to 15.  No branch when size == 8.  */
> > > -       movq    %rdi, (%rax)
> > > -       movq    %rdi, -8(%rax, %rdx)
> > > -       VZEROUPPER_RETURN
> > > +#ifdef USE_XMM_LESS_VEC
> > > +       MOVQ    %XMM0, (%rdi)
> > > +       MOVQ    %XMM0, -8(%rdi, %rdx)
> > > +#else
> > > +       movq    %rcx, (%LESS_VEC_REG)
> > > +       movq    %rcx, -8(%LESS_VEC_REG, %rdx)
> > > +#endif
> > > +       ret
> > >
> > > -       .p2align 4,, SMALL_MEMSET_ALIGN(2, RET_SIZE)
> > > +       /* Move size is 2 for SSE2, EVEX, and AVX512. Move size is 4 for AVX2.
> > > +        */
> > > +       .p2align 4,, SMALL_MEMSET_ALIGN(2 << XMM_SMALL, 1)
> > >  L(between_4_7):
> > >         /* From 4 to 7.  No branch when size == 4.  */
> > > -       movl    %edi, (%rax)
> > > -       movl    %edi, -4(%rax, %rdx)
> > > -       VZEROUPPER_RETURN
> > > +#ifdef USE_XMM_LESS_VEC
> > > +       MOVD    %XMM0, (%rdi)
> > > +       MOVD    %XMM0, -4(%rdi, %rdx)
> > > +#else
> > > +       movl    %ecx, (%LESS_VEC_REG)
> > > +       movl    %ecx, -4(%LESS_VEC_REG, %rdx)
> > > +#endif
> > > +       ret
> > >
> > > -       .p2align 4,, SMALL_MEMSET_ALIGN(3, RET_SIZE)
> > > +       /* 4 * XMM_SMALL for the third mov for AVX2.  */
> > > +       .p2align 4,, 4 * XMM_SMALL + SMALL_MEMSET_ALIGN(3, 1)
> > >  L(between_2_3):
> > >         /* From 2 to 3.  No branch when size == 2.  */
> > > -       movw    %di, (%rax)
> > > -       movb    %dil, -1(%rax, %rdx)
> > > -       VZEROUPPER_RETURN
> > > +#ifdef USE_XMM_LESS_VEC
> > > +       movb    %sil, (%rdi)
> > > +       movb    %sil, 1(%rdi)
> > > +       movb    %sil, -1(%rdi, %rdx)
> > > +#else
> > > +       movw    %cx, (%LESS_VEC_REG)
> > > +       movb    %sil, -1(%LESS_VEC_REG, %rdx)
> > > +#endif
> > > +       ret
> > >  END (MEMSET_SYMBOL (__memset, unaligned_erms))
> > > --
> > > 2.25.1
> > >
> >
> > LGTM.
> >
> > Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
> >
> > Thanks.
>
> Thanks pushed.
> >
> > --
> > H.J.

I would like to backport this patch to release branches.
Any comments or objections?

--Sunil

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