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

Message ID 20210503225832.4042137-2-goldstein.w.n@gmail.com
State New
Headers show
Series
  • Untitled series #37441
Related show

Commit Message

No bug. This commit optimizes memchr-evex.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,
saving some ALU in the alignment process, and most importantly
increasing ILP in the 4x 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-evex.S | 547 +++++++++++++++----------
 1 file changed, 322 insertions(+), 225 deletions(-)

-- 
2.29.2

Comments

On Mon, May 3, 2021 at 6:58 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>

> No bug. This commit optimizes memchr-evex.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,

> saving some ALU in the alignment process, and most importantly

> increasing ILP in the 4x 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-evex.S | 547 +++++++++++++++----------

>  1 file changed, 322 insertions(+), 225 deletions(-)

>

> diff --git a/sysdeps/x86_64/multiarch/memchr-evex.S b/sysdeps/x86_64/multiarch/memchr-evex.S

> index 6dd5d67b90..81d5cd6486 100644

> --- a/sysdeps/x86_64/multiarch/memchr-evex.S

> +++ b/sysdeps/x86_64/multiarch/memchr-evex.S

> @@ -26,14 +26,28 @@

>

>  # ifdef USE_AS_WMEMCHR

>  #  define VPBROADCAST  vpbroadcastd

> -#  define VPCMP                vpcmpd

> -#  define SHIFT_REG    r8d

> +#  define VPMINU       vpminud

> +#  define VPCMP        vpcmpd

> +#  define VPCMPEQ      vpcmpeqd

> +#  define CHAR_SIZE    4

>  # else

>  #  define VPBROADCAST  vpbroadcastb

> -#  define VPCMP                vpcmpb

> -#  define SHIFT_REG    ecx

> +#  define VPMINU       vpminub

> +#  define VPCMP        vpcmpb

> +#  define VPCMPEQ      vpcmpeqb

> +#  define CHAR_SIZE    1

>  # endif

>

> +# ifdef USE_AS_RAWMEMCHR

> +#  define RAW_PTR_REG  rcx

> +#  define ALGN_PTR_REG rdi

> +# else

> +#  define RAW_PTR_REG  rdi

> +#  define ALGN_PTR_REG rcx

> +# endif

> +

> +# define XMMZERO       xmm23

> +# define YMMZERO       ymm23

>  # define XMMMATCH      xmm16

>  # define YMMMATCH      ymm16

>  # define YMM1          ymm17

> @@ -44,6 +58,8 @@

>  # define YMM6          ymm22

>

>  # define VEC_SIZE 32

> +# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)

> +# define PAGE_SIZE 4096

>

>         .section .text.evex,"ax",@progbits

>  ENTRY (MEMCHR)

> @@ -51,11 +67,7 @@ ENTRY (MEMCHR)

>         /* Check for zero length.  */

>         test    %RDX_LP, %RDX_LP

>         jz      L(zero)

> -# endif

> -       movl    %edi, %ecx

> -# ifdef USE_AS_WMEMCHR

> -       shl     $2, %RDX_LP

> -# else

> +

>  #  ifdef __ILP32__

>         /* Clear the upper 32 bits.  */

>         movl    %edx, %edx

> @@ -64,318 +76,403 @@ ENTRY (MEMCHR)

>         /* Broadcast CHAR to YMMMATCH.  */

>         VPBROADCAST %esi, %YMMMATCH

>         /* 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.  */

> -       VPCMP   $0, (%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> -       testl   %eax, %eax

> -

> +       VPCMP   $0, (%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %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)

> +       /* If length < CHAR_PER_VEC handle special.  */

> +       cmpq    $CHAR_PER_VEC, %rdx

> +       jbe     L(first_vec_x0)

> +# endif

> +       testl   %eax, %eax

> +       jz      L(aligned_more)

> +       tzcntl  %eax, %eax

> +# ifdef USE_AS_WMEMCHR

> +       /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

> +       leaq    (%rdi, %rax, CHAR_SIZE), %rax

>  # else

> -       jnz     L(first_vec_x0)

> +       addq    %rdi, %rax

>  # endif

> -

> -       /* Align data for aligned loads in the loop.  */

> -       addq    $VEC_SIZE, %rdi

> -       andl    $(VEC_SIZE - 1), %ecx

> -       andq    $-VEC_SIZE, %rdi

> +       ret

>

>  # ifndef USE_AS_RAWMEMCHR

> -       /* Adjust length.  */

> -       addq    %rcx, %rdx

> -

> -       subq    $(VEC_SIZE * 4), %rdx

> -       jbe     L(last_4x_vec_or_less)

> -# endif

> -       jmp     L(more_4x_vec)

> +L(zero):

> +       xorl    %eax, %eax

> +       ret

>

> +       .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, CHAR_SIZE), %rax

> +       cmovle  %rcx, %rax

> +       ret

> +# else

> +       /* NB: first_vec_x0 is 17 bytes which will leave

> +          cross_page_boundary (which is relatively cold) close enough

> +          to ideal alignment. So only realign L(cross_page_boundary) if

> +          rawmemchr.  */

>         .p2align 4

> -L(cros_page_boundary):

> -       andl    $(VEC_SIZE - 1), %ecx

> +# endif

> +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. ALGN_PTR_REG is rcx for memchr and rdi

> +          for rawmemchr.  */

> +       andq    $-VEC_SIZE, %ALGN_PTR_REG

> +       VPCMP   $0, (%ALGN_PTR_REG), %YMMMATCH, %k0

> +       kmovd   %k0, %r8d

>  # ifdef USE_AS_WMEMCHR

> -       /* NB: Divide shift count by 4 since each bit in K1 represent 4

> +       /* NB: Divide shift count by 4 since each bit in K0 represent 4

>            bytes.  */

> -       movl    %ecx, %SHIFT_REG

> -       sarl    $2, %SHIFT_REG

> +       sarl    $2, %eax

> +# endif

> +# ifndef USE_AS_RAWMEMCHR

> +       movl    $(PAGE_SIZE / CHAR_SIZE), %esi

> +       subl    %eax, %esi

>  # endif

> -       andq    $-VEC_SIZE, %rdi

> -       VPCMP   $0, (%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> -       /* Remove the leading bytes.  */

> -       sarxl   %SHIFT_REG, %eax, %eax

> -       testl   %eax, %eax

> -       jz      L(aligned_more)

> -       tzcntl  %eax, %eax

>  # ifdef USE_AS_WMEMCHR

> -       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

> -       sall    $2, %eax

> +       andl    $(CHAR_PER_VEC - 1), %eax

>  # endif

> +       /* Remove the leading bytes.  */

> +       sarxl   %eax, %r8d, %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

> +       testl   %eax, %eax

> +       jz      L(cross_page_continue)

> +       tzcntl  %eax, %eax

> +# ifdef USE_AS_WMEMCHR

> +       /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

> +       leaq    (%RAW_PTR_REG, %rax, CHAR_SIZE), %rax

> +# else

> +       addq    %RAW_PTR_REG, %rax

>  # endif

> -       addq    %rdi, %rax

> -       addq    %rcx, %rax

>         ret

>

>         .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

> +       leaq    VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax

> +       ret

>

> -       /* Check the end of data.  */

> -       subq    %rcx, %rdx

> -       jbe     L(zero)

> -# endif

> +       .p2align 4

> +L(first_vec_x2):

> +       tzcntl  %eax, %eax

> +       leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax

> +       ret

>

> -       addq    $VEC_SIZE, %rdi

> +       .p2align 4

> +L(first_vec_x3):

> +       tzcntl  %eax, %eax

> +       leaq    (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax

> +       ret

>

> -# 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

> +       leaq    (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax

> +       ret

>

> -L(more_4x_vec):

> +       .p2align 5

> +L(aligned_more):

>         /* Check the first 4 * VEC_SIZE.  Only one VEC_SIZE at a time

>            since data is only aligned to VEC_SIZE.  */

> -       VPCMP   $0, (%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> -       testl   %eax, %eax

> -       jnz     L(first_vec_x0)

>

> -       VPCMP   $0, VEC_SIZE(%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> +# ifndef USE_AS_RAWMEMCHR

> +       /* Align data to VEC_SIZE.  */

> +L(cross_page_continue):

> +       xorl    %ecx, %ecx

> +       subl    %edi, %ecx

> +       andq    $-VEC_SIZE, %rdi

> +       /* esi is for adjusting length to see if near the end.  */

> +       leal    (VEC_SIZE * 5)(%rdi, %rcx), %esi

> +#  ifdef USE_AS_WMEMCHR

> +       /* NB: Divide bytes by 4 to get the wchar_t count.  */

> +       sarl    $2, %esi

> +#  endif

> +# else

> +       andq    $-VEC_SIZE, %rdi

> +L(cross_page_continue):

> +# endif

> +       /* Load first VEC regardless.  */

> +       VPCMP   $0, (VEC_SIZE)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %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)

>

> -       VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> +       VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %eax

>         testl   %eax, %eax

>         jnz     L(first_vec_x2)

>

> -       VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> +       VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %eax

>         testl   %eax, %eax

>         jnz     L(first_vec_x3)

>

> -       addq    $(VEC_SIZE * 4), %rdi

> +       VPCMP   $0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %eax

> +       testl   %eax, %eax

> +       jnz     L(first_vec_x4)

> +

>

>  # ifndef USE_AS_RAWMEMCHR

> -       subq    $(VEC_SIZE * 4), %rdx

> -       jbe     L(last_4x_vec_or_less)

> -# endif

> +       /* Check if at last CHAR_PER_VEC * 4 length.  */

> +       subq    $(CHAR_PER_VEC * 4), %rdx

> +       jbe     L(last_4x_vec_or_less_cmpeq)

> +       addq    $VEC_SIZE, %rdi

>

> -       /* Align data to 4 * VEC_SIZE.  */

> -       movq    %rdi, %rcx

> -       andl    $(4 * VEC_SIZE - 1), %ecx

> +       /* Align data to VEC_SIZE * 4 for the loop and readjust length.

> +        */

> +#  ifdef USE_AS_WMEMCHR

> +       movl    %edi, %ecx

>         andq    $-(4 * VEC_SIZE), %rdi

> -

> -# ifndef USE_AS_RAWMEMCHR

> -       /* Adjust length.  */

> +       andl    $(VEC_SIZE * 4 - 1), %ecx

> +       /* NB: Divide bytes by 4 to get the wchar_t count.  */

> +       sarl    $2, %ecx

>         addq    %rcx, %rdx

> +#  else

> +       addq    %rdi, %rdx

> +       andq    $-(4 * VEC_SIZE), %rdi

> +       subq    %rdi, %rdx

> +#  endif

> +# else

> +       addq    $VEC_SIZE, %rdi

> +       andq    $-(4 * VEC_SIZE), %rdi

>  # endif

>

> +       vpxorq  %XMMZERO, %XMMZERO, %XMMZERO

> +

> +       /* Compare 4 * VEC at a time forward.  */

>         .p2align 4

>  L(loop_4x_vec):

> -       /* Compare 4 * VEC at a time forward.  */

> -       VPCMP   $0, (%rdi), %YMMMATCH, %k1

> -       VPCMP   $0, VEC_SIZE(%rdi), %YMMMATCH, %k2

> -       kord    %k1, %k2, %k5

> -       VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k3

> -       VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k4

> -

> -       kord    %k3, %k4, %k6

> -       kortestd %k5, %k6

> -       jnz     L(4x_vec_end)

> -

> -       addq    $(VEC_SIZE * 4), %rdi

> -

> +       /* It would be possible to save some instructions using 4x VPCMP

> +          but bottleneck on port 5 makes it not woth it.  */

> +       VPCMP   $4, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k1

> +       /* xor will set bytes match esi to zero.  */

> +       vpxorq  (VEC_SIZE * 5)(%rdi), %YMMMATCH, %YMM2

> +       vpxorq  (VEC_SIZE * 6)(%rdi), %YMMMATCH, %YMM3

> +       VPCMP   $0, (VEC_SIZE * 7)(%rdi), %YMMMATCH, %k3

> +       /* Reduce VEC2 / VEC3 with min and VEC1 with zero mask.  */

> +       VPMINU  %YMM2, %YMM3, %YMM3 {%k1} {z}

> +       VPCMP   $0, %YMM3, %YMMZERO, %k2

>  # ifdef USE_AS_RAWMEMCHR

> -       jmp     L(loop_4x_vec)

> +       subq    $-(VEC_SIZE * 4), %rdi

> +       kortestd %k2, %k3

> +       jz      L(loop_4x_vec)

>  # else

> -       subq    $(VEC_SIZE * 4), %rdx

> +       kortestd %k2, %k3

> +       jnz     L(loop_4x_vec_end)

> +

> +       subq    $-(VEC_SIZE * 4), %rdi

> +

> +       subq    $(CHAR_PER_VEC * 4), %rdx

>         ja      L(loop_4x_vec)

>

> +       /* Fall through into less than 4 remaining vectors of length case.

> +        */

> +       VPCMP   $0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %eax

> +       addq    $(VEC_SIZE * 3), %rdi

> +       .p2align 4

>  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)

> -

> -       VPCMP   $0, (%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> +       /* Check if first VEC contained match.  */

>         testl   %eax, %eax

> -       jnz     L(first_vec_x0)

> +       jnz     L(first_vec_x1_check)

>

> -       VPCMP   $0, VEC_SIZE(%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> -       testl   %eax, %eax

> -       jnz     L(first_vec_x1)

> +       /* If remaining length > CHAR_PER_VEC * 2.  */

> +       addl    $(CHAR_PER_VEC * 2), %edx

> +       jg      L(last_4x_vec)

>

> -       VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> -       testl   %eax, %eax

> +L(last_2x_vec):

> +       /* If remaining length < CHAR_PER_VEC.  */

> +       addl    $CHAR_PER_VEC, %edx

> +       jle     L(zero_end)

>

> -       jnz     L(first_vec_x2_check)

> -       subl    $VEC_SIZE, %edx

> -       jle     L(zero)

> +       /* Check VEC2 and compare any match with remaining length.  */

> +       VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %eax

> +       tzcntl  %eax, %eax

> +       cmpl    %eax, %edx

> +       jbe     L(set_zero_end)

> +       leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax

> +L(zero_end):

> +       ret

>

> -       VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> -       testl   %eax, %eax

>

> -       jnz     L(first_vec_x3_check)

> +       .p2align 4

> +L(first_vec_x1_check):

> +       tzcntl  %eax, %eax

> +       /* Adjust length.  */

> +       subl    $-(CHAR_PER_VEC * 4), %edx

> +       /* Check if match within remaining length.  */

> +       cmpl    %eax, %edx

> +       jbe     L(set_zero_end)

> +       /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

> +       leaq    VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax

> +       ret

> +L(set_zero_end):

>         xorl    %eax, %eax

>         ret

>

>         .p2align 4

> -L(last_2x_vec):

> -       addl    $(VEC_SIZE * 2), %edx

> -       VPCMP   $0, (%rdi), %YMMMATCH, %k1

> +L(loop_4x_vec_end):

> +# endif

> +       /* rawmemchr will fall through into this if match was found in

> +          loop.  */

> +

> +       /* k1 has not of matches with VEC1.  */

>         kmovd   %k1, %eax

> -       testl   %eax, %eax

> +# ifdef USE_AS_WMEMCHR

> +       subl    $((1 << CHAR_PER_VEC) - 1), %eax

> +# else

> +       incl    %eax

> +# endif

> +       jnz     L(last_vec_x1_return)

>

> -       jnz     L(first_vec_x0_check)

> -       subl    $VEC_SIZE, %edx

> -       jle     L(zero)

> +       VPCMP   $0, %YMM2, %YMMZERO, %k0

> +       kmovd   %k0, %eax

> +       testl   %eax, %eax

> +       jnz     L(last_vec_x2_return)

>

> -       VPCMP   $0, VEC_SIZE(%rdi), %YMMMATCH, %k1

> -       kmovd   %k1, %eax

> +       kmovd   %k2, %eax

>         testl   %eax, %eax

> -       jnz     L(first_vec_x1_check)

> -       xorl    %eax, %eax

> -       ret

> +       jnz     L(last_vec_x3_return)

>

> -       .p2align 4

> -L(first_vec_x0_check):

> +       kmovd   %k3, %eax

>         tzcntl  %eax, %eax

> -# ifdef USE_AS_WMEMCHR

> -       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

> -       sall    $2, %eax

> +# ifdef USE_AS_RAWMEMCHR

> +       leaq    (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax

> +# else

> +       leaq    (VEC_SIZE * 7)(%rdi, %rax, CHAR_SIZE), %rax

>  # endif

> -       /* Check the end of data.  */

> -       cmpq    %rax, %rdx

> -       jbe     L(zero)

> -       addq    %rdi, %rax

>         ret

>

>         .p2align 4

> -L(first_vec_x1_check):

> +L(last_vec_x1_return):

>         tzcntl  %eax, %eax

> -# ifdef USE_AS_WMEMCHR

> -       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

> -       sall    $2, %eax

> -# endif

> -       /* Check the end of data.  */

> -       cmpq    %rax, %rdx

> -       jbe     L(zero)

> -       addq    $VEC_SIZE, %rax

> +# ifdef USE_AS_RAWMEMCHR

> +#  ifdef USE_AS_WMEMCHR

> +       /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

> +       leaq    (%rdi, %rax, CHAR_SIZE), %rax

> +#  else

>         addq    %rdi, %rax

> -       ret

> -

> -       .p2align 4

> -L(first_vec_x2_check):

> -       tzcntl  %eax, %eax

> -# ifdef USE_AS_WMEMCHR

> -       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

> -       sall    $2, %eax

> +#  endif

> +# else

> +       /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

> +       leaq    (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax

>  # endif

> -       /* Check the end of data.  */

> -       cmpq    %rax, %rdx

> -       jbe     L(zero)

> -       addq    $(VEC_SIZE * 2), %rax

> -       addq    %rdi, %rax

>         ret

>

>         .p2align 4

> -L(first_vec_x3_check):

> +L(last_vec_x2_return):

>         tzcntl  %eax, %eax

> -# ifdef USE_AS_WMEMCHR

> -       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

> -       sall    $2, %eax

> +# ifdef USE_AS_RAWMEMCHR

> +       /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

> +       leaq    VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax

> +# else

> +       /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

> +       leaq    (VEC_SIZE * 5)(%rdi, %rax, CHAR_SIZE), %rax

>  # endif

> -       /* Check the end of data.  */

> -       cmpq    %rax, %rdx

> -       jbe     L(zero)

> -       addq    $(VEC_SIZE * 3), %rax

> -       addq    %rdi, %rax

>         ret

>

>         .p2align 4

> -L(zero):

> -       xorl    %eax, %eax

> -       ret

> -# endif

> -

> -       .p2align 4

> -L(first_vec_x0):

> +L(last_vec_x3_return):

>         tzcntl  %eax, %eax

> -# ifdef USE_AS_WMEMCHR

> -       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

> -       leaq    (%rdi, %rax, 4), %rax

> +# ifdef USE_AS_RAWMEMCHR

> +       /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

> +       leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax

>  # else

> -       addq    %rdi, %rax

> +       /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

> +       leaq    (VEC_SIZE * 6)(%rdi, %rax, CHAR_SIZE), %rax

>  # endif

>         ret

>

> +

> +# ifndef USE_AS_RAWMEMCHR

> +L(last_4x_vec_or_less_cmpeq):

> +       VPCMP   $0, (VEC_SIZE * 5)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %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    $(CHAR_PER_VEC * 2), %edx

> +       jle     L(last_2x_vec)

> +

>         .p2align 4

> -L(first_vec_x1):

> +L(last_4x_vec):

> +       VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %eax

> +       testl   %eax, %eax

> +       jnz     L(last_vec_x2)

> +

> +

> +       VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %eax

> +       /* Create mask for possible matches within remaining length.  */

> +#  ifdef USE_AS_WMEMCHR

> +       movl    $((1 << (CHAR_PER_VEC * 2)) - 1), %ecx

> +       bzhil   %edx, %ecx, %ecx

> +#  else

> +       movq    $-1, %rcx

> +       bzhiq   %rdx, %rcx, %rcx

> +#  endif

> +       /* Test matches in data against length match.  */

> +       andl    %ecx, %eax

> +       jnz     L(last_vec_x3)

> +

> +       /* if remaining length <= CHAR_PER_VEC * 3 (Note this is after

> +          remaining length was found to be > CHAR_PER_VEC * 2.  */

> +       subl    $CHAR_PER_VEC, %edx

> +       jbe     L(zero_end2)

> +

> +

> +       VPCMP   $0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0

> +       kmovd   %k0, %eax

> +       /* Shift remaining length mask for last VEC.  */

> +#  ifdef USE_AS_WMEMCHR

> +       shrl    $CHAR_PER_VEC, %ecx

> +#  else

> +       shrq    $CHAR_PER_VEC, %rcx

> +#  endif

> +       andl    %ecx, %eax

> +       jz      L(zero_end2)

>         tzcntl  %eax, %eax

> -# ifdef USE_AS_WMEMCHR

> -       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

> -       leaq    VEC_SIZE(%rdi, %rax, 4), %rax

> -# else

> -       addq    $VEC_SIZE, %rax

> -       addq    %rdi, %rax

> -# endif

> +       leaq    (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax

> +L(zero_end2):

>         ret

>

> -       .p2align 4

> -L(first_vec_x2):

> +L(last_vec_x2):

>         tzcntl  %eax, %eax

> -# ifdef USE_AS_WMEMCHR

> -       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

> -       leaq    (VEC_SIZE * 2)(%rdi, %rax, 4), %rax

> -# else

> -       addq    $(VEC_SIZE * 2), %rax

> -       addq    %rdi, %rax

> -# endif

> +       leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax

>         ret

>

>         .p2align 4

> -L(4x_vec_end):

> -       kmovd   %k1, %eax

> -       testl   %eax, %eax

> -       jnz     L(first_vec_x0)

> -       kmovd   %k2, %eax

> -       testl   %eax, %eax

> -       jnz     L(first_vec_x1)

> -       kmovd   %k3, %eax

> -       testl   %eax, %eax

> -       jnz     L(first_vec_x2)

> -       kmovd   %k4, %eax

> -       testl   %eax, %eax

> -L(first_vec_x3):

> +L(last_vec_x3):

>         tzcntl  %eax, %eax

> -# ifdef USE_AS_WMEMCHR

> -       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

> -       leaq    (VEC_SIZE * 3)(%rdi, %rax, 4), %rax

> -# else

> -       addq    $(VEC_SIZE * 3), %rax

> -       addq    %rdi, %rax

> -# endif

> +       leaq    (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax

>         ret

> +# endif

>

>  END (MEMCHR)

>  #endif

> --

> 2.29.2

>


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

Patch

diff --git a/sysdeps/x86_64/multiarch/memchr-evex.S b/sysdeps/x86_64/multiarch/memchr-evex.S
index 6dd5d67b90..81d5cd6486 100644
--- a/sysdeps/x86_64/multiarch/memchr-evex.S
+++ b/sysdeps/x86_64/multiarch/memchr-evex.S
@@ -26,14 +26,28 @@ 
 
 # ifdef USE_AS_WMEMCHR
 #  define VPBROADCAST	vpbroadcastd
-#  define VPCMP		vpcmpd
-#  define SHIFT_REG	r8d
+#  define VPMINU	vpminud
+#  define VPCMP	vpcmpd
+#  define VPCMPEQ	vpcmpeqd
+#  define CHAR_SIZE	4
 # else
 #  define VPBROADCAST	vpbroadcastb
-#  define VPCMP		vpcmpb
-#  define SHIFT_REG	ecx
+#  define VPMINU	vpminub
+#  define VPCMP	vpcmpb
+#  define VPCMPEQ	vpcmpeqb
+#  define CHAR_SIZE	1
 # endif
 
+# ifdef USE_AS_RAWMEMCHR
+#  define RAW_PTR_REG	rcx
+#  define ALGN_PTR_REG	rdi
+# else
+#  define RAW_PTR_REG	rdi
+#  define ALGN_PTR_REG	rcx
+# endif
+
+# define XMMZERO	xmm23
+# define YMMZERO	ymm23
 # define XMMMATCH	xmm16
 # define YMMMATCH	ymm16
 # define YMM1		ymm17
@@ -44,6 +58,8 @@ 
 # define YMM6		ymm22
 
 # define VEC_SIZE 32
+# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
+# define PAGE_SIZE 4096
 
 	.section .text.evex,"ax",@progbits
 ENTRY (MEMCHR)
@@ -51,11 +67,7 @@  ENTRY (MEMCHR)
 	/* Check for zero length.  */
 	test	%RDX_LP, %RDX_LP
 	jz	L(zero)
-# endif
-	movl	%edi, %ecx
-# ifdef USE_AS_WMEMCHR
-	shl	$2, %RDX_LP
-# else
+
 #  ifdef __ILP32__
 	/* Clear the upper 32 bits.  */
 	movl	%edx, %edx
@@ -64,318 +76,403 @@  ENTRY (MEMCHR)
 	/* Broadcast CHAR to YMMMATCH.  */
 	VPBROADCAST %esi, %YMMMATCH
 	/* 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.  */
-	VPCMP	$0, (%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
-	testl	%eax, %eax
-
+	VPCMP	$0, (%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %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)
+	/* If length < CHAR_PER_VEC handle special.  */
+	cmpq	$CHAR_PER_VEC, %rdx
+	jbe	L(first_vec_x0)
+# endif
+	testl	%eax, %eax
+	jz	L(aligned_more)
+	tzcntl	%eax, %eax
+# ifdef USE_AS_WMEMCHR
+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
+	leaq	(%rdi, %rax, CHAR_SIZE), %rax
 # else
-	jnz	L(first_vec_x0)
+	addq	%rdi, %rax
 # endif
-
-	/* Align data for aligned loads in the loop.  */
-	addq	$VEC_SIZE, %rdi
-	andl	$(VEC_SIZE - 1), %ecx
-	andq	$-VEC_SIZE, %rdi
+	ret
 
 # ifndef USE_AS_RAWMEMCHR
-	/* Adjust length.  */
-	addq	%rcx, %rdx
-
-	subq	$(VEC_SIZE * 4), %rdx
-	jbe	L(last_4x_vec_or_less)
-# endif
-	jmp	L(more_4x_vec)
+L(zero):
+	xorl	%eax, %eax
+	ret
 
+	.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, CHAR_SIZE), %rax
+	cmovle	%rcx, %rax
+	ret
+# else
+	/* NB: first_vec_x0 is 17 bytes which will leave
+	   cross_page_boundary (which is relatively cold) close enough
+	   to ideal alignment. So only realign L(cross_page_boundary) if
+	   rawmemchr.  */
 	.p2align 4
-L(cros_page_boundary):
-	andl	$(VEC_SIZE - 1), %ecx
+# endif
+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. ALGN_PTR_REG is rcx for memchr and rdi
+	   for rawmemchr.  */
+	andq	$-VEC_SIZE, %ALGN_PTR_REG
+	VPCMP	$0, (%ALGN_PTR_REG), %YMMMATCH, %k0
+	kmovd	%k0, %r8d
 # ifdef USE_AS_WMEMCHR
-	/* NB: Divide shift count by 4 since each bit in K1 represent 4
+	/* NB: Divide shift count by 4 since each bit in K0 represent 4
 	   bytes.  */
-	movl	%ecx, %SHIFT_REG
-	sarl	$2, %SHIFT_REG
+	sarl	$2, %eax
+# endif
+# ifndef USE_AS_RAWMEMCHR
+	movl	$(PAGE_SIZE / CHAR_SIZE), %esi
+	subl	%eax, %esi
 # endif
-	andq	$-VEC_SIZE, %rdi
-	VPCMP	$0, (%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
-	/* Remove the leading bytes.  */
-	sarxl	%SHIFT_REG, %eax, %eax
-	testl	%eax, %eax
-	jz	L(aligned_more)
-	tzcntl	%eax, %eax
 # ifdef USE_AS_WMEMCHR
-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
-	sall	$2, %eax
+	andl	$(CHAR_PER_VEC - 1), %eax
 # endif
+	/* Remove the leading bytes.  */
+	sarxl	%eax, %r8d, %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
+	testl	%eax, %eax
+	jz	L(cross_page_continue)
+	tzcntl	%eax, %eax
+# ifdef USE_AS_WMEMCHR
+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
+	leaq	(%RAW_PTR_REG, %rax, CHAR_SIZE), %rax
+# else
+	addq	%RAW_PTR_REG, %rax
 # endif
-	addq	%rdi, %rax
-	addq	%rcx, %rax
 	ret
 
 	.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
+	leaq	VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax
+	ret
 
-	/* Check the end of data.  */
-	subq	%rcx, %rdx
-	jbe	L(zero)
-# endif
+	.p2align 4
+L(first_vec_x2):
+	tzcntl	%eax, %eax
+	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
+	ret
 
-	addq	$VEC_SIZE, %rdi
+	.p2align 4
+L(first_vec_x3):
+	tzcntl	%eax, %eax
+	leaq	(VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
+	ret
 
-# 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
+	leaq	(VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
+	ret
 
-L(more_4x_vec):
+	.p2align 5
+L(aligned_more):
 	/* Check the first 4 * VEC_SIZE.  Only one VEC_SIZE at a time
 	   since data is only aligned to VEC_SIZE.  */
-	VPCMP	$0, (%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
-	testl	%eax, %eax
-	jnz	L(first_vec_x0)
 
-	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
+# ifndef USE_AS_RAWMEMCHR
+	/* Align data to VEC_SIZE.  */
+L(cross_page_continue):
+	xorl	%ecx, %ecx
+	subl	%edi, %ecx
+	andq	$-VEC_SIZE, %rdi
+	/* esi is for adjusting length to see if near the end.  */
+	leal	(VEC_SIZE * 5)(%rdi, %rcx), %esi
+#  ifdef USE_AS_WMEMCHR
+	/* NB: Divide bytes by 4 to get the wchar_t count.  */
+	sarl	$2, %esi
+#  endif
+# else
+	andq	$-VEC_SIZE, %rdi
+L(cross_page_continue):
+# endif
+	/* Load first VEC regardless.  */
+	VPCMP	$0, (VEC_SIZE)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %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)
 
-	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
+	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %eax
 	testl	%eax, %eax
 	jnz	L(first_vec_x2)
 
-	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
+	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %eax
 	testl	%eax, %eax
 	jnz	L(first_vec_x3)
 
-	addq	$(VEC_SIZE * 4), %rdi
+	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %eax
+	testl	%eax, %eax
+	jnz	L(first_vec_x4)
+
 
 # ifndef USE_AS_RAWMEMCHR
-	subq	$(VEC_SIZE * 4), %rdx
-	jbe	L(last_4x_vec_or_less)
-# endif
+	/* Check if at last CHAR_PER_VEC * 4 length.  */
+	subq	$(CHAR_PER_VEC * 4), %rdx
+	jbe	L(last_4x_vec_or_less_cmpeq)
+	addq	$VEC_SIZE, %rdi
 
-	/* Align data to 4 * VEC_SIZE.  */
-	movq	%rdi, %rcx
-	andl	$(4 * VEC_SIZE - 1), %ecx
+	/* Align data to VEC_SIZE * 4 for the loop and readjust length.
+	 */
+#  ifdef USE_AS_WMEMCHR
+	movl	%edi, %ecx
 	andq	$-(4 * VEC_SIZE), %rdi
-
-# ifndef USE_AS_RAWMEMCHR
-	/* Adjust length.  */
+	andl	$(VEC_SIZE * 4 - 1), %ecx
+	/* NB: Divide bytes by 4 to get the wchar_t count.  */
+	sarl	$2, %ecx
 	addq	%rcx, %rdx
+#  else
+	addq	%rdi, %rdx
+	andq	$-(4 * VEC_SIZE), %rdi
+	subq	%rdi, %rdx
+#  endif
+# else
+	addq	$VEC_SIZE, %rdi
+	andq	$-(4 * VEC_SIZE), %rdi
 # endif
 
+	vpxorq	%XMMZERO, %XMMZERO, %XMMZERO
+
+	/* Compare 4 * VEC at a time forward.  */
 	.p2align 4
 L(loop_4x_vec):
-	/* Compare 4 * VEC at a time forward.  */
-	VPCMP	$0, (%rdi), %YMMMATCH, %k1
-	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k2
-	kord	%k1, %k2, %k5
-	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k3
-	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k4
-
-	kord	%k3, %k4, %k6
-	kortestd %k5, %k6
-	jnz	L(4x_vec_end)
-
-	addq	$(VEC_SIZE * 4), %rdi
-
+	/* It would be possible to save some instructions using 4x VPCMP
+	   but bottleneck on port 5 makes it not woth it.  */
+	VPCMP	$4, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k1
+	/* xor will set bytes match esi to zero.  */
+	vpxorq	(VEC_SIZE * 5)(%rdi), %YMMMATCH, %YMM2
+	vpxorq	(VEC_SIZE * 6)(%rdi), %YMMMATCH, %YMM3
+	VPCMP	$0, (VEC_SIZE * 7)(%rdi), %YMMMATCH, %k3
+	/* Reduce VEC2 / VEC3 with min and VEC1 with zero mask.  */
+	VPMINU	%YMM2, %YMM3, %YMM3 {%k1} {z}
+	VPCMP	$0, %YMM3, %YMMZERO, %k2
 # ifdef USE_AS_RAWMEMCHR
-	jmp	L(loop_4x_vec)
+	subq	$-(VEC_SIZE * 4), %rdi
+	kortestd %k2, %k3
+	jz	L(loop_4x_vec)
 # else
-	subq	$(VEC_SIZE * 4), %rdx
+	kortestd %k2, %k3
+	jnz	L(loop_4x_vec_end)
+
+	subq	$-(VEC_SIZE * 4), %rdi
+
+	subq	$(CHAR_PER_VEC * 4), %rdx
 	ja	L(loop_4x_vec)
 
+	/* Fall through into less than 4 remaining vectors of length case.
+	 */
+	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %eax
+	addq	$(VEC_SIZE * 3), %rdi
+	.p2align 4
 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)
-
-	VPCMP	$0, (%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
+	/* Check if first VEC contained match.  */
 	testl	%eax, %eax
-	jnz	L(first_vec_x0)
+	jnz	L(first_vec_x1_check)
 
-	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
-	testl	%eax, %eax
-	jnz	L(first_vec_x1)
+	/* If remaining length > CHAR_PER_VEC * 2.  */
+	addl	$(CHAR_PER_VEC * 2), %edx
+	jg	L(last_4x_vec)
 
-	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
-	testl	%eax, %eax
+L(last_2x_vec):
+	/* If remaining length < CHAR_PER_VEC.  */
+	addl	$CHAR_PER_VEC, %edx
+	jle	L(zero_end)
 
-	jnz	L(first_vec_x2_check)
-	subl	$VEC_SIZE, %edx
-	jle	L(zero)
+	/* Check VEC2 and compare any match with remaining length.  */
+	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %eax
+	tzcntl	%eax, %eax
+	cmpl	%eax, %edx
+	jbe	L(set_zero_end)
+	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
+L(zero_end):
+	ret
 
-	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
-	testl	%eax, %eax
 
-	jnz	L(first_vec_x3_check)
+	.p2align 4
+L(first_vec_x1_check):
+	tzcntl	%eax, %eax
+	/* Adjust length.  */
+	subl	$-(CHAR_PER_VEC * 4), %edx
+	/* Check if match within remaining length.  */
+	cmpl	%eax, %edx
+	jbe	L(set_zero_end)
+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
+	leaq	VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax
+	ret
+L(set_zero_end):
 	xorl	%eax, %eax
 	ret
 
 	.p2align 4
-L(last_2x_vec):
-	addl	$(VEC_SIZE * 2), %edx
-	VPCMP	$0, (%rdi), %YMMMATCH, %k1
+L(loop_4x_vec_end):
+# endif
+	/* rawmemchr will fall through into this if match was found in
+	   loop.  */
+
+	/* k1 has not of matches with VEC1.  */
 	kmovd	%k1, %eax
-	testl	%eax, %eax
+# ifdef USE_AS_WMEMCHR
+	subl	$((1 << CHAR_PER_VEC) - 1), %eax
+# else
+	incl	%eax
+# endif
+	jnz	L(last_vec_x1_return)
 
-	jnz	L(first_vec_x0_check)
-	subl	$VEC_SIZE, %edx
-	jle	L(zero)
+	VPCMP	$0, %YMM2, %YMMZERO, %k0
+	kmovd	%k0, %eax
+	testl	%eax, %eax
+	jnz	L(last_vec_x2_return)
 
-	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k1
-	kmovd	%k1, %eax
+	kmovd	%k2, %eax
 	testl	%eax, %eax
-	jnz	L(first_vec_x1_check)
-	xorl	%eax, %eax
-	ret
+	jnz	L(last_vec_x3_return)
 
-	.p2align 4
-L(first_vec_x0_check):
+	kmovd	%k3, %eax
 	tzcntl	%eax, %eax
-# ifdef USE_AS_WMEMCHR
-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
-	sall	$2, %eax
+# ifdef USE_AS_RAWMEMCHR
+	leaq	(VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
+# else
+	leaq	(VEC_SIZE * 7)(%rdi, %rax, CHAR_SIZE), %rax
 # endif
-	/* Check the end of data.  */
-	cmpq	%rax, %rdx
-	jbe	L(zero)
-	addq	%rdi, %rax
 	ret
 
 	.p2align 4
-L(first_vec_x1_check):
+L(last_vec_x1_return):
 	tzcntl	%eax, %eax
-# ifdef USE_AS_WMEMCHR
-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
-	sall	$2, %eax
-# endif
-	/* Check the end of data.  */
-	cmpq	%rax, %rdx
-	jbe	L(zero)
-	addq	$VEC_SIZE, %rax
+# ifdef USE_AS_RAWMEMCHR
+#  ifdef USE_AS_WMEMCHR
+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
+	leaq	(%rdi, %rax, CHAR_SIZE), %rax
+#  else
 	addq	%rdi, %rax
-	ret
-
-	.p2align 4
-L(first_vec_x2_check):
-	tzcntl	%eax, %eax
-# ifdef USE_AS_WMEMCHR
-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
-	sall	$2, %eax
+#  endif
+# else
+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
+	leaq	(VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
 # endif
-	/* Check the end of data.  */
-	cmpq	%rax, %rdx
-	jbe	L(zero)
-	addq	$(VEC_SIZE * 2), %rax
-	addq	%rdi, %rax
 	ret
 
 	.p2align 4
-L(first_vec_x3_check):
+L(last_vec_x2_return):
 	tzcntl	%eax, %eax
-# ifdef USE_AS_WMEMCHR
-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
-	sall	$2, %eax
+# ifdef USE_AS_RAWMEMCHR
+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
+	leaq	VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax
+# else
+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
+	leaq	(VEC_SIZE * 5)(%rdi, %rax, CHAR_SIZE), %rax
 # endif
-	/* Check the end of data.  */
-	cmpq	%rax, %rdx
-	jbe	L(zero)
-	addq	$(VEC_SIZE * 3), %rax
-	addq	%rdi, %rax
 	ret
 
 	.p2align 4
-L(zero):
-	xorl	%eax, %eax
-	ret
-# endif
-
-	.p2align 4
-L(first_vec_x0):
+L(last_vec_x3_return):
 	tzcntl	%eax, %eax
-# ifdef USE_AS_WMEMCHR
-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
-	leaq	(%rdi, %rax, 4), %rax
+# ifdef USE_AS_RAWMEMCHR
+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
+	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
 # else
-	addq	%rdi, %rax
+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
+	leaq	(VEC_SIZE * 6)(%rdi, %rax, CHAR_SIZE), %rax
 # endif
 	ret
 
+
+# ifndef USE_AS_RAWMEMCHR
+L(last_4x_vec_or_less_cmpeq):
+	VPCMP	$0, (VEC_SIZE * 5)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %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	$(CHAR_PER_VEC * 2), %edx
+	jle	L(last_2x_vec)
+
 	.p2align 4
-L(first_vec_x1):
+L(last_4x_vec):
+	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %eax
+	testl	%eax, %eax
+	jnz	L(last_vec_x2)
+
+
+	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %eax
+	/* Create mask for possible matches within remaining length.  */
+#  ifdef USE_AS_WMEMCHR
+	movl	$((1 << (CHAR_PER_VEC * 2)) - 1), %ecx
+	bzhil	%edx, %ecx, %ecx
+#  else
+	movq	$-1, %rcx
+	bzhiq	%rdx, %rcx, %rcx
+#  endif
+	/* Test matches in data against length match.  */
+	andl	%ecx, %eax
+	jnz	L(last_vec_x3)
+
+	/* if remaining length <= CHAR_PER_VEC * 3 (Note this is after
+	   remaining length was found to be > CHAR_PER_VEC * 2.  */
+	subl	$CHAR_PER_VEC, %edx
+	jbe	L(zero_end2)
+
+
+	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0
+	kmovd	%k0, %eax
+	/* Shift remaining length mask for last VEC.  */
+#  ifdef USE_AS_WMEMCHR
+	shrl	$CHAR_PER_VEC, %ecx
+#  else
+	shrq	$CHAR_PER_VEC, %rcx
+#  endif
+	andl	%ecx, %eax
+	jz	L(zero_end2)
 	tzcntl	%eax, %eax
-# ifdef USE_AS_WMEMCHR
-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
-	leaq	VEC_SIZE(%rdi, %rax, 4), %rax
-# else
-	addq	$VEC_SIZE, %rax
-	addq	%rdi, %rax
-# endif
+	leaq	(VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
+L(zero_end2):
 	ret
 
-	.p2align 4
-L(first_vec_x2):
+L(last_vec_x2):
 	tzcntl	%eax, %eax
-# ifdef USE_AS_WMEMCHR
-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
-	leaq	(VEC_SIZE * 2)(%rdi, %rax, 4), %rax
-# else
-	addq	$(VEC_SIZE * 2), %rax
-	addq	%rdi, %rax
-# endif
+	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
 	ret
 
 	.p2align 4
-L(4x_vec_end):
-	kmovd	%k1, %eax
-	testl	%eax, %eax
-	jnz	L(first_vec_x0)
-	kmovd	%k2, %eax
-	testl	%eax, %eax
-	jnz	L(first_vec_x1)
-	kmovd	%k3, %eax
-	testl	%eax, %eax
-	jnz	L(first_vec_x2)
-	kmovd	%k4, %eax
-	testl	%eax, %eax
-L(first_vec_x3):
+L(last_vec_x3):
 	tzcntl	%eax, %eax
-# ifdef USE_AS_WMEMCHR
-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
-	leaq	(VEC_SIZE * 3)(%rdi, %rax, 4), %rax
-# else
-	addq	$(VEC_SIZE * 3), %rax
-	addq	%rdi, %rax
-# endif
+	leaq	(VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
 	ret
+# endif
 
 END (MEMCHR)
 #endif