[v3,2/3] x86: Optimize memchr-avx2.S

  No bug. This commit optimizes memchr-avx2.S. The optimizations include
replacing some branches with cmovcc, avoiding some branches entirely
in the less_4x_vec case, making the page cross logic less strict,
asaving a few instructions the in loop return loop. test-memchr,
test-rawmemchr, and test-wmemchr are all passing.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
---
 sysdeps/x86_64/multiarch/memchr-avx2.S | 425 ++++++++++++++-----------
 1 file changed, 247 insertions(+), 178 deletions(-)
  

On Mon, May 3, 2021 at 6:58 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> No bug. This commit optimizes memchr-avx2.S. The optimizations include
> replacing some branches with cmovcc, avoiding some branches entirely
> in the less_4x_vec case, making the page cross logic less strict,
> asaving a few instructions the in loop return loop. test-memchr,
> test-rawmemchr, and test-wmemchr are all passing.
>
> Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> ---
>  sysdeps/x86_64/multiarch/memchr-avx2.S | 425 ++++++++++++++-----------
>  1 file changed, 247 insertions(+), 178 deletions(-)
>
> diff --git a/sysdeps/x86_64/multiarch/memchr-avx2.S b/sysdeps/x86_64/multiarch/memchr-avx2.S
> index 1fcb1c350f..0d8758e3e7 100644
> --- a/sysdeps/x86_64/multiarch/memchr-avx2.S
> +++ b/sysdeps/x86_64/multiarch/memchr-avx2.S
> @@ -26,8 +26,22 @@
>
>  # ifdef USE_AS_WMEMCHR
>  #  define VPCMPEQ      vpcmpeqd
> +#  define VPBROADCAST  vpbroadcastd
> +#  define CHAR_SIZE    4
>  # else
>  #  define VPCMPEQ      vpcmpeqb
> +#  define VPBROADCAST  vpbroadcastb
> +#  define CHAR_SIZE    1
> +# endif
> +
> +# ifdef USE_AS_RAWMEMCHR
> +#  define ERAW_PTR_REG ecx
> +#  define RRAW_PTR_REG rcx
> +#  define ALGN_PTR_REG rdi
> +# else
> +#  define ERAW_PTR_REG edi
> +#  define RRAW_PTR_REG rdi
> +#  define ALGN_PTR_REG rcx
>  # endif
>
>  # ifndef VZEROUPPER
> @@ -39,6 +53,7 @@
>  # endif
>
>  # define VEC_SIZE 32
> +# define PAGE_SIZE 4096
>
>         .section SECTION(.text),"ax",@progbits
>  ENTRY (MEMCHR)
> @@ -47,295 +62,349 @@ ENTRY (MEMCHR)
>         test    %RDX_LP, %RDX_LP
>         jz      L(null)
>  # endif
> -       movl    %edi, %ecx
> -       /* Broadcast CHAR to YMM0.  */
> -       vmovd   %esi, %xmm0
>  # ifdef USE_AS_WMEMCHR
>         shl     $2, %RDX_LP
> -       vpbroadcastd %xmm0, %ymm0
>  # else
>  #  ifdef __ILP32__
>         /* Clear the upper 32 bits.  */
>         movl    %edx, %edx
>  #  endif
> -       vpbroadcastb %xmm0, %ymm0
>  # endif
> +       /* Broadcast CHAR to YMMMATCH.  */
> +       vmovd   %esi, %xmm0
> +       VPBROADCAST %xmm0, %ymm0
>         /* Check if we may cross page boundary with one vector load.  */
> -       andl    $(2 * VEC_SIZE - 1), %ecx
> -       cmpl    $VEC_SIZE, %ecx
> -       ja      L(cros_page_boundary)
> +       movl    %edi, %eax
> +       andl    $(PAGE_SIZE - 1), %eax
> +       cmpl    $(PAGE_SIZE - VEC_SIZE), %eax
> +       ja      L(cross_page_boundary)
>
>         /* Check the first VEC_SIZE bytes.  */
> -       VPCMPEQ (%rdi), %ymm0, %ymm1
> +       VPCMPEQ (%rdi), %ymm0, %ymm1
>         vpmovmskb %ymm1, %eax
> -       testl   %eax, %eax
> -
>  # ifndef USE_AS_RAWMEMCHR
> -       jnz     L(first_vec_x0_check)
> -       /* Adjust length and check the end of data.  */
> -       subq    $VEC_SIZE, %rdx
> -       jbe     L(zero)
> -# else
> -       jnz     L(first_vec_x0)
> +       /* If length < CHAR_PER_VEC handle special.  */
> +       cmpq    $VEC_SIZE, %rdx
> +       jbe     L(first_vec_x0)
>  # endif
> -
> -       /* Align data for aligned loads in the loop.  */
> -       addq    $VEC_SIZE, %rdi
> -       andl    $(VEC_SIZE - 1), %ecx
> -       andq    $-VEC_SIZE, %rdi
> +       testl   %eax, %eax
> +       jz      L(aligned_more)
> +       tzcntl  %eax, %eax
> +       addq    %rdi, %rax
> +       VZEROUPPER_RETURN
>
>  # ifndef USE_AS_RAWMEMCHR
> -       /* Adjust length.  */
> -       addq    %rcx, %rdx
> +       .p2align 5
> +L(first_vec_x0):
> +       /* Check if first match was before length.  */
> +       tzcntl  %eax, %eax
> +       xorl    %ecx, %ecx
> +       cmpl    %eax, %edx
> +       leaq    (%rdi, %rax), %rax
> +       cmovle  %rcx, %rax
> +       VZEROUPPER_RETURN
>
> -       subq    $(VEC_SIZE * 4), %rdx
> -       jbe     L(last_4x_vec_or_less)
> +L(null):
> +       xorl    %eax, %eax
> +       ret
>  # endif
> -       jmp     L(more_4x_vec)
> -
>         .p2align 4
> -L(cros_page_boundary):
> -       andl    $(VEC_SIZE - 1), %ecx
> -       andq    $-VEC_SIZE, %rdi
> -       VPCMPEQ (%rdi), %ymm0, %ymm1
> +L(cross_page_boundary):
> +       /* Save pointer before aligning as its original value is necessary
> +          for computer return address if byte is found or adjusting length
> +          if it is not and this is memchr.  */
> +       movq    %rdi, %rcx
> +       /* Align data to VEC_SIZE - 1. ALGN_PTR_REG is rcx for memchr and
> +          rdi for rawmemchr.  */
> +       orq     $(VEC_SIZE - 1), %ALGN_PTR_REG
> +       VPCMPEQ -(VEC_SIZE - 1)(%ALGN_PTR_REG), %ymm0, %ymm1
>         vpmovmskb %ymm1, %eax
> +# ifndef USE_AS_RAWMEMCHR
> +       /* Calculate length until end of page (length checked for a
> +          match).  */
> +       leaq    1(%ALGN_PTR_REG), %rsi
> +       subq    %RRAW_PTR_REG, %rsi
> +# endif
>         /* Remove the leading bytes.  */
> -       sarl    %cl, %eax
> -       testl   %eax, %eax
> -       jz      L(aligned_more)
> -       tzcntl  %eax, %eax
> +       sarxl   %ERAW_PTR_REG, %eax, %eax
>  # ifndef USE_AS_RAWMEMCHR
>         /* Check the end of data.  */
> -       cmpq    %rax, %rdx
> -       jbe     L(zero)
> +       cmpq    %rsi, %rdx
> +       jbe     L(first_vec_x0)
>  # endif
> -       addq    %rdi, %rax
> -       addq    %rcx, %rax
> +       testl   %eax, %eax
> +       jz      L(cross_page_continue)
> +       tzcntl  %eax, %eax
> +       addq    %RRAW_PTR_REG, %rax
>  L(return_vzeroupper):
>         ZERO_UPPER_VEC_REGISTERS_RETURN
>
>         .p2align 4
> -L(aligned_more):
> -# ifndef USE_AS_RAWMEMCHR
> -        /* Calculate "rdx + rcx - VEC_SIZE" with "rdx - (VEC_SIZE - rcx)"
> -          instead of "(rdx + rcx) - VEC_SIZE" to void possible addition
> -          overflow.  */
> -       negq    %rcx
> -       addq    $VEC_SIZE, %rcx
> +L(first_vec_x1):
> +       tzcntl  %eax, %eax
> +       incq    %rdi
> +       addq    %rdi, %rax
> +       VZEROUPPER_RETURN
>
> -       /* Check the end of data.  */
> -       subq    %rcx, %rdx
> -       jbe     L(zero)
> -# endif
> +       .p2align 4
> +L(first_vec_x2):
> +       tzcntl  %eax, %eax
> +       addq    $(VEC_SIZE + 1), %rdi
> +       addq    %rdi, %rax
> +       VZEROUPPER_RETURN
> +
> +       .p2align 4
> +L(first_vec_x3):
> +       tzcntl  %eax, %eax
> +       addq    $(VEC_SIZE * 2 + 1), %rdi
> +       addq    %rdi, %rax
> +       VZEROUPPER_RETURN
>
> -       addq    $VEC_SIZE, %rdi
>
> -# ifndef USE_AS_RAWMEMCHR
> -       subq    $(VEC_SIZE * 4), %rdx
> -       jbe     L(last_4x_vec_or_less)
> -# endif
> +       .p2align 4
> +L(first_vec_x4):
> +       tzcntl  %eax, %eax
> +       addq    $(VEC_SIZE * 3 + 1), %rdi
> +       addq    %rdi, %rax
> +       VZEROUPPER_RETURN
>
> -L(more_4x_vec):
> +       .p2align 4
> +L(aligned_more):
>         /* Check the first 4 * VEC_SIZE.  Only one VEC_SIZE at a time
>            since data is only aligned to VEC_SIZE.  */
> -       VPCMPEQ (%rdi), %ymm0, %ymm1
> -       vpmovmskb %ymm1, %eax
> -       testl   %eax, %eax
> -       jnz     L(first_vec_x0)
>
> -       VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
> +# ifndef USE_AS_RAWMEMCHR
> +L(cross_page_continue):
> +       /* Align data to VEC_SIZE - 1.  */
> +       xorl    %ecx, %ecx
> +       subl    %edi, %ecx
> +       orq     $(VEC_SIZE - 1), %rdi
> +       /* esi is for adjusting length to see if near the end.  */
> +       leal    (VEC_SIZE * 4 + 1)(%rdi, %rcx), %esi
> +# else
> +       orq     $(VEC_SIZE - 1), %rdi
> +L(cross_page_continue):
> +# endif
> +       /* Load first VEC regardless.  */
> +       VPCMPEQ 1(%rdi), %ymm0, %ymm1
>         vpmovmskb %ymm1, %eax
> +# ifndef USE_AS_RAWMEMCHR
> +       /* Adjust length. If near end handle specially.  */
> +       subq    %rsi, %rdx
> +       jbe     L(last_4x_vec_or_less)
> +# endif
>         testl   %eax, %eax
>         jnz     L(first_vec_x1)
>
> -       VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1
> +       VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
>         vpmovmskb %ymm1, %eax
>         testl   %eax, %eax
>         jnz     L(first_vec_x2)
>
> -       VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm1
> +       VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1
>         vpmovmskb %ymm1, %eax
>         testl   %eax, %eax
>         jnz     L(first_vec_x3)
>
> -       addq    $(VEC_SIZE * 4), %rdi
> +       VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1
> +       vpmovmskb %ymm1, %eax
> +       testl   %eax, %eax
> +       jnz     L(first_vec_x4)
>
>  # ifndef USE_AS_RAWMEMCHR
> +       /* Check if at last VEC_SIZE * 4 length.  */
>         subq    $(VEC_SIZE * 4), %rdx
> -       jbe     L(last_4x_vec_or_less)
> -# endif
> -
> -       /* Align data to 4 * VEC_SIZE.  */
> -       movq    %rdi, %rcx
> -       andl    $(4 * VEC_SIZE - 1), %ecx
> -       andq    $-(4 * VEC_SIZE), %rdi
> -
> -# ifndef USE_AS_RAWMEMCHR
> -       /* Adjust length.  */
> +       jbe     L(last_4x_vec_or_less_cmpeq)
> +       /* Align data to VEC_SIZE * 4 - 1 for the loop and readjust
> +          length.  */
> +       incq    %rdi
> +       movl    %edi, %ecx
> +       orq     $(VEC_SIZE * 4 - 1), %rdi
> +       andl    $(VEC_SIZE * 4 - 1), %ecx
>         addq    %rcx, %rdx
> +# else
> +       /* Align data to VEC_SIZE * 4 - 1 for loop.  */
> +       incq    %rdi
> +       orq     $(VEC_SIZE * 4 - 1), %rdi
>  # endif
>
> +       /* Compare 4 * VEC at a time forward.  */
>         .p2align 4
>  L(loop_4x_vec):
> -       /* Compare 4 * VEC at a time forward.  */
> -       VPCMPEQ (%rdi), %ymm0, %ymm1
> -       VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm2
> -       VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm3
> -       VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm4
> -
> +       VPCMPEQ 1(%rdi), %ymm0, %ymm1
> +       VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm2
> +       VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm3
> +       VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm4
>         vpor    %ymm1, %ymm2, %ymm5
>         vpor    %ymm3, %ymm4, %ymm6
>         vpor    %ymm5, %ymm6, %ymm5
>
> -       vpmovmskb %ymm5, %eax
> -       testl   %eax, %eax
> -       jnz     L(4x_vec_end)
> -
> -       addq    $(VEC_SIZE * 4), %rdi
> -
> +       vpmovmskb %ymm5, %ecx
>  # ifdef USE_AS_RAWMEMCHR
> -       jmp     L(loop_4x_vec)
> +       subq    $-(VEC_SIZE * 4), %rdi
> +       testl   %ecx, %ecx
> +       jz      L(loop_4x_vec)
>  # else
> -       subq    $(VEC_SIZE * 4), %rdx
> -       ja      L(loop_4x_vec)
> +       testl   %ecx, %ecx
> +       jnz     L(loop_4x_vec_end)
>
> -L(last_4x_vec_or_less):
> -       /* Less than 4 * VEC and aligned to VEC_SIZE.  */
> -       addl    $(VEC_SIZE * 2), %edx
> -       jle     L(last_2x_vec)
> +       subq    $-(VEC_SIZE * 4), %rdi
>
> -       VPCMPEQ (%rdi), %ymm0, %ymm1
> -       vpmovmskb %ymm1, %eax
> -       testl   %eax, %eax
> -       jnz     L(first_vec_x0)
> +       subq    $(VEC_SIZE * 4), %rdx
> +       ja      L(loop_4x_vec)
>
> -       VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
> +       /* Fall through into less than 4 remaining vectors of length case.
> +        */
> +       VPCMPEQ (VEC_SIZE * 0 + 1)(%rdi), %ymm0, %ymm1
>         vpmovmskb %ymm1, %eax
> +       .p2align 4
> +L(last_4x_vec_or_less):
> +       /* Check if first VEC contained match.  */
>         testl   %eax, %eax
> -       jnz     L(first_vec_x1)
> +       jnz     L(first_vec_x1_check)
>
> -       VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1
> -       vpmovmskb %ymm1, %eax
> -       testl   %eax, %eax
> +       /* If remaining length > VEC_SIZE * 2.  */
> +       addl    $(VEC_SIZE * 2), %edx
> +       jg      L(last_4x_vec)
>
> -       jnz     L(first_vec_x2_check)
> -       subl    $VEC_SIZE, %edx
> -       jle     L(zero)
> +L(last_2x_vec):
> +       /* If remaining length < VEC_SIZE.  */
> +       addl    $VEC_SIZE, %edx
> +       jle     L(zero_end)
>
> -       VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm1
> +       /* Check VEC2 and compare any match with remaining length.  */
> +       VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
>         vpmovmskb %ymm1, %eax
> -       testl   %eax, %eax
> -
> -       jnz     L(first_vec_x3_check)
> -       xorl    %eax, %eax
> +       tzcntl  %eax, %eax
> +       cmpl    %eax, %edx
> +       jbe     L(set_zero_end)
> +       addq    $(VEC_SIZE + 1), %rdi
> +       addq    %rdi, %rax
> +L(zero_end):
>         VZEROUPPER_RETURN
>
>         .p2align 4
> -L(last_2x_vec):
> -       addl    $(VEC_SIZE * 2), %edx
> -       VPCMPEQ (%rdi), %ymm0, %ymm1
> +L(loop_4x_vec_end):
> +# endif
> +       /* rawmemchr will fall through into this if match was found in
> +          loop.  */
> +
>         vpmovmskb %ymm1, %eax
>         testl   %eax, %eax
> +       jnz     L(last_vec_x1_return)
>
> -       jnz     L(first_vec_x0_check)
> -       subl    $VEC_SIZE, %edx
> -       jle     L(zero)
> -
> -       VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
> -       vpmovmskb %ymm1, %eax
> +       vpmovmskb %ymm2, %eax
>         testl   %eax, %eax
> -       jnz     L(first_vec_x1_check)
> -       xorl    %eax, %eax
> -       VZEROUPPER_RETURN
> +       jnz     L(last_vec_x2_return)
>
> -       .p2align 4
> -L(first_vec_x0_check):
> -       tzcntl  %eax, %eax
> -       /* Check the end of data.  */
> -       cmpq    %rax, %rdx
> -       jbe     L(zero)
> +       vpmovmskb %ymm3, %eax
> +       /* Combine VEC3 matches (eax) with VEC4 matches (ecx).  */
> +       salq    $32, %rcx
> +       orq     %rcx, %rax
> +       tzcntq  %rax, %rax
> +# ifdef USE_AS_RAWMEMCHR
> +       subq    $(VEC_SIZE * 2 - 1), %rdi
> +# else
> +       subq    $-(VEC_SIZE * 2 + 1), %rdi
> +# endif
>         addq    %rdi, %rax
>         VZEROUPPER_RETURN
> +# ifndef USE_AS_RAWMEMCHR
>
>         .p2align 4
>  L(first_vec_x1_check):
>         tzcntl  %eax, %eax
> -       /* Check the end of data.  */
> -       cmpq    %rax, %rdx
> -       jbe     L(zero)
> -       addq    $VEC_SIZE, %rax
> +       /* Adjust length.  */
> +       subl    $-(VEC_SIZE * 4), %edx
> +       /* Check if match within remaining length.  */
> +       cmpl    %eax, %edx
> +       jbe     L(set_zero_end)
> +       incq    %rdi
>         addq    %rdi, %rax
>         VZEROUPPER_RETURN
> +       .p2align 4
> +L(set_zero_end):
> +       xorl    %eax, %eax
> +       VZEROUPPER_RETURN
> +# endif
>
>         .p2align 4
> -L(first_vec_x2_check):
> +L(last_vec_x1_return):
>         tzcntl  %eax, %eax
> -       /* Check the end of data.  */
> -       cmpq    %rax, %rdx
> -       jbe     L(zero)
> -       addq    $(VEC_SIZE * 2), %rax
> +# ifdef USE_AS_RAWMEMCHR
> +       subq    $(VEC_SIZE * 4 - 1), %rdi
> +# else
> +       incq    %rdi
> +# endif
>         addq    %rdi, %rax
>         VZEROUPPER_RETURN
>
>         .p2align 4
> -L(first_vec_x3_check):
> +L(last_vec_x2_return):
>         tzcntl  %eax, %eax
> -       /* Check the end of data.  */
> -       cmpq    %rax, %rdx
> -       jbe     L(zero)
> -       addq    $(VEC_SIZE * 3), %rax
> +# ifdef USE_AS_RAWMEMCHR
> +       subq    $(VEC_SIZE * 3 - 1), %rdi
> +# else
> +       subq    $-(VEC_SIZE + 1), %rdi
> +# endif
>         addq    %rdi, %rax
>         VZEROUPPER_RETURN
>
> +# ifndef USE_AS_RAWMEMCHR
>         .p2align 4
> -L(zero):
> -       xorl    %eax, %eax
> -       jmp     L(return_vzeroupper)
> +L(last_4x_vec_or_less_cmpeq):
> +       VPCMPEQ (VEC_SIZE * 4 + 1)(%rdi), %ymm0, %ymm1
> +       vpmovmskb %ymm1, %eax
> +       subq    $-(VEC_SIZE * 4), %rdi
> +       /* Check first VEC regardless.  */
> +       testl   %eax, %eax
> +       jnz     L(first_vec_x1_check)
>
> +       /* If remaining length <= CHAR_PER_VEC * 2.  */
> +       addl    $(VEC_SIZE * 2), %edx
> +       jle     L(last_2x_vec)
>         .p2align 4
> -L(null):
> -       xorl    %eax, %eax
> -       ret
> -# endif
> +L(last_4x_vec):
> +       VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
> +       vpmovmskb %ymm1, %eax
> +       testl   %eax, %eax
> +       jnz     L(last_vec_x2_return)
>
> -       .p2align 4
> -L(first_vec_x0):
> -       tzcntl  %eax, %eax
> -       addq    %rdi, %rax
> -       VZEROUPPER_RETURN
> +       VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1
> +       vpmovmskb %ymm1, %eax
>
> -       .p2align 4
> -L(first_vec_x1):
> -       tzcntl  %eax, %eax
> -       addq    $VEC_SIZE, %rax
> -       addq    %rdi, %rax
> -       VZEROUPPER_RETURN
> +       /* Create mask for possible matches within remaining length.  */
> +       movq    $-1, %rcx
> +       bzhiq   %rdx, %rcx, %rcx
>
> -       .p2align 4
> -L(first_vec_x2):
> +       /* Test matches in data against length match.  */
> +       andl    %ecx, %eax
> +       jnz     L(last_vec_x3)
> +
> +       /* if remaining length <= VEC_SIZE * 3 (Note this is after
> +          remaining length was found to be > VEC_SIZE * 2.  */
> +       subl    $VEC_SIZE, %edx
> +       jbe     L(zero_end2)
> +
> +       VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1
> +       vpmovmskb %ymm1, %eax
> +       /* Shift remaining length mask for last VEC.  */
> +       shrq    $32, %rcx
> +       andl    %ecx, %eax
> +       jz      L(zero_end2)
>         tzcntl  %eax, %eax
> -       addq    $(VEC_SIZE * 2), %rax
> +       addq    $(VEC_SIZE * 3 + 1), %rdi
>         addq    %rdi, %rax
> +L(zero_end2):
>         VZEROUPPER_RETURN
>
>         .p2align 4
> -L(4x_vec_end):
> -       vpmovmskb %ymm1, %eax
> -       testl   %eax, %eax
> -       jnz     L(first_vec_x0)
> -       vpmovmskb %ymm2, %eax
> -       testl   %eax, %eax
> -       jnz     L(first_vec_x1)
> -       vpmovmskb %ymm3, %eax
> -       testl   %eax, %eax
> -       jnz     L(first_vec_x2)
> -       vpmovmskb %ymm4, %eax
> -       testl   %eax, %eax
> -L(first_vec_x3):
> +L(last_vec_x3):
>         tzcntl  %eax, %eax
> -       addq    $(VEC_SIZE * 3), %rax
> +       subq    $-(VEC_SIZE * 2 + 1), %rdi
>         addq    %rdi, %rax
>         VZEROUPPER_RETURN
> +# endif
>
>  END (MEMCHR)
>  #endif
> --
> 2.29.2
>

This is the patch I will push unless anyone has objections.