Re: [PATCH v1 2/2] x86: Optimize strchr-evex.S

[Noah Goldstein <goldstein.w.n@gmail.com>]

On Fri, Apr 23, 2021 at 1:03 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Wed, Apr 21, 2021 at 05:39:53PM -0400, Noah Goldstein wrote:
> > No bug. This commit optimizes strlen-evex.S. The optimizations are
> > mostly small things such as save an ALU in the alignment process,
> > saving a few instructions in the loop return. The one significant
> > change is saving 2 instructions in the 4x loop. test-strchr,
> > test-strchrnul, test-wcschr, and test-wcschrnul are all passing.
> >
> > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > ---
> >  sysdeps/x86_64/multiarch/strchr-evex.S | 388 ++++++++++++++-----------
> >  1 file changed, 214 insertions(+), 174 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/multiarch/strchr-evex.S b/sysdeps/x86_64/multiarch/strchr-evex.S
> > index ddc86a7058..7cd111e96c 100644
> > --- a/sysdeps/x86_64/multiarch/strchr-evex.S
> > +++ b/sysdeps/x86_64/multiarch/strchr-evex.S
> > @@ -24,23 +24,26 @@
> >  #  define STRCHR     __strchr_evex
> >  # endif
> >
> > -# define VMOVU               vmovdqu64
> > -# define VMOVA               vmovdqa64
> > +# define VMOVU       vmovdqu64
> > +# define VMOVA       vmovdqa64
>
> These changes aren't needed.

Fixed.

>
> >
> >  # ifdef USE_AS_WCSCHR
> >  #  define VPBROADCAST        vpbroadcastd
> >  #  define VPCMP              vpcmpd
> >  #  define VPMINU     vpminud
> >  #  define CHAR_REG   esi
> > -#  define SHIFT_REG  r8d
> > +#  define SHIFT_REG  ecx
> > +#  define CHAR_SIZE  4
> >  # else
> >  #  define VPBROADCAST        vpbroadcastb
> >  #  define VPCMP              vpcmpb
> >  #  define VPMINU     vpminub
> >  #  define CHAR_REG   sil
> > -#  define SHIFT_REG  ecx
> > +#  define SHIFT_REG  edx
> > +#  define CHAR_SIZE  1
> >  # endif
> >
> > +
>
> No need to add a blank line here.
Fixed.
>
> >  # define XMMZERO     xmm16
> >
> >  # define YMMZERO     ymm16
> > @@ -56,23 +59,20 @@
> >
> >  # define VEC_SIZE 32
> >  # define PAGE_SIZE 4096
> > +# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
> >
> >       .section .text.evex,"ax",@progbits
> >  ENTRY (STRCHR)
> > -     movl    %edi, %ecx
> > -# ifndef USE_AS_STRCHRNUL
> > -     xorl    %edx, %edx
> > -# endif
> > -
> >       /* Broadcast CHAR to YMM0.      */
> > -     VPBROADCAST %esi, %YMM0
> > -
> > +     VPBROADCAST     %esi, %YMM0
> > +     movl    %edi, %eax
> > +     andl    $(PAGE_SIZE - 1), %eax
> >       vpxorq  %XMMZERO, %XMMZERO, %XMMZERO
> >
> > -     /* Check if we cross page boundary with one vector load.  */
> > -     andl    $(PAGE_SIZE - 1), %ecx
> > -     cmpl    $(PAGE_SIZE - VEC_SIZE), %ecx
> > -     ja  L(cross_page_boundary)
> > +     /* Check if we cross page boundary with one vector load. Otherwise
> > +        it is safe to use an unaligned load.  */
> > +     cmpl    $(PAGE_SIZE - VEC_SIZE), %eax
> > +     ja      L(cross_page_boundary)
> >
> >       /* Check the first VEC_SIZE bytes. Search for both CHAR and the
> >          null bytes.  */
> > @@ -83,251 +83,291 @@ ENTRY (STRCHR)
> >       VPMINU  %YMM2, %YMM1, %YMM2
> >       /* Each bit in K0 represents a CHAR or a null byte in YMM1.  */
> >       VPCMP   $0, %YMMZERO, %YMM2, %k0
> > -     ktestd  %k0, %k0
> > -     jz      L(more_vecs)
> >       kmovd   %k0, %eax
> > +     testl   %eax, %eax
> > +     jz      L(aligned_more)
> >       tzcntl  %eax, %eax
> > -     /* Found CHAR or the null byte.  */
> >  # ifdef USE_AS_WCSCHR
> >       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    (%rdi, %rax, 4), %rax
> > +     leaq    (%rdi, %rax, CHAR_SIZE), %rax
> >  # else
> >       addq    %rdi, %rax
> >  # endif
> >  # ifndef USE_AS_STRCHRNUL
> > -     cmp (%rax), %CHAR_REG
> > -     cmovne  %rdx, %rax
> > +     /* Found CHAR or the null byte.  */
> > +     cmp     (%rax), %CHAR_REG
> > +     jne     L(zero)
> >  # endif
> >       ret
> >
> > -     .p2align 4
> > -L(more_vecs):
> > -     /* Align data for aligned loads in the loop.  */
> > -     andq    $-VEC_SIZE, %rdi
> > -L(aligned_more):
> > -
> > -     /* Check the next 4 * VEC_SIZE.  Only one VEC_SIZE at a time
> > -        since data is only aligned to VEC_SIZE.      */
> > -     VMOVA   VEC_SIZE(%rdi), %YMM1
> > -     addq    $VEC_SIZE, %rdi
> > -
> > -     /* Leaves only CHARS matching esi as 0.  */
> > -     vpxorq  %YMM1, %YMM0, %YMM2
> > -     VPMINU  %YMM2, %YMM1, %YMM2
> > -     /* Each bit in K0 represents a CHAR or a null byte in YMM1.  */
> > -     VPCMP   $0, %YMMZERO, %YMM2, %k0
> > -     kmovd   %k0, %eax
> > -     testl   %eax, %eax
> > -     jnz     L(first_vec_x0)
> > -
> > -     VMOVA   VEC_SIZE(%rdi), %YMM1
> > -     /* Leaves only CHARS matching esi as 0.  */
> > -     vpxorq  %YMM1, %YMM0, %YMM2
> > -     VPMINU  %YMM2, %YMM1, %YMM2
> > -     /* Each bit in K0 represents a CHAR or a null byte in YMM1.  */
> > -     VPCMP   $0, %YMMZERO, %YMM2, %k0
> > -     kmovd   %k0, %eax
> > -     testl   %eax, %eax
> > -     jnz     L(first_vec_x1)
> > -
> > -     VMOVA   (VEC_SIZE * 2)(%rdi), %YMM1
> > -     /* Leaves only CHARS matching esi as 0.  */
> > -     vpxorq  %YMM1, %YMM0, %YMM2
> > -     VPMINU  %YMM2, %YMM1, %YMM2
> > -     /* Each bit in K0 represents a CHAR or a null byte in YMM1.  */
> > -     VPCMP   $0, %YMMZERO, %YMM2, %k0
> > -     kmovd   %k0, %eax
> > -     testl   %eax, %eax
> > -     jnz     L(first_vec_x2)
> > -
> > -     VMOVA   (VEC_SIZE * 3)(%rdi), %YMM1
> > -     /* Leaves only CHARS matching esi as 0.  */
> > -     vpxorq  %YMM1, %YMM0, %YMM2
> > -     VPMINU  %YMM2, %YMM1, %YMM2
> > -     /* Each bit in K0 represents a CHAR or a null byte in YMM1.  */
> > -     VPCMP   $0, %YMMZERO, %YMM2, %k0
> > -     ktestd  %k0, %k0
> > -     jz      L(prep_loop_4x)
> > -
> > -     kmovd   %k0, %eax
> > +     /* .p2align 5 helps keep performance more consistent if ENTRY()
> > +        alignment % 32 was either 16 or 0. As well this makes the
> > +        alignment % 32 of the loop_4x_vec fixed which makes tuning it
> > +        easier.  */
> > +     .p2align 5
> > +L(first_vec_x3):
> >       tzcntl  %eax, %eax
> > +# ifndef USE_AS_STRCHRNUL
> >       /* Found CHAR or the null byte.  */
> > -# ifdef USE_AS_WCSCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    (VEC_SIZE * 3)(%rdi, %rax, 4), %rax
> > -# else
> > -     leaq    (VEC_SIZE * 3)(%rdi, %rax), %rax
> > +     cmp     (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %CHAR_REG
> > +     jne     L(zero)
> >  # endif
> > +     /* NB: Multiply sizeof char type (1 or 4) to get the number of
> > +        bytes.  */
> > +     leaq    (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
> > +     ret
> > +
> >  # ifndef USE_AS_STRCHRNUL
> > -     cmp (%rax), %CHAR_REG
> > -     cmovne  %rdx, %rax
> > -# endif
> > +L(zero):
> > +     xorl    %eax, %eax
> >       ret
> > +# endif
> >
> >       .p2align 4
> > -L(first_vec_x0):
> > +L(first_vec_x4):
> > +# ifndef USE_AS_STRCHRNUL
> > +     /* Check to see if first match was CHAR (k0) or null (k1).  */
> > +     kmovd   %k0, %eax
> >       tzcntl  %eax, %eax
> > -     /* Found CHAR or the null byte.  */
> > -# ifdef USE_AS_WCSCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    (%rdi, %rax, 4), %rax
> > +     kmovd   %k1, %ecx
> > +     /* bzhil will not be 0 if first match was null.  */
> > +     bzhil   %eax, %ecx, %ecx
> > +     jne     L(zero)
> >  # else
> > -     addq    %rdi, %rax
> > -# endif
> > -# ifndef USE_AS_STRCHRNUL
> > -     cmp (%rax), %CHAR_REG
> > -     cmovne  %rdx, %rax
> > +     /* Combine CHAR and null matches.  */
> > +     kord    %k0, %k1, %k0
> > +     kmovd   %k0, %eax
> > +     tzcntl  %eax, %eax
> >  # endif
> > +     /* NB: Multiply sizeof char type (1 or 4) to get the number of
> > +        bytes.  */
> > +     leaq    (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
> >       ret
> >
> >       .p2align 4
> >  L(first_vec_x1):
> >       tzcntl  %eax, %eax
> > -     /* Found CHAR or the null byte.  */
> > -# ifdef USE_AS_WCSCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    VEC_SIZE(%rdi, %rax, 4), %rax
> > -# else
> > -     leaq    VEC_SIZE(%rdi, %rax), %rax
> > -# endif
> >  # ifndef USE_AS_STRCHRNUL
> > -     cmp (%rax), %CHAR_REG
> > -     cmovne  %rdx, %rax
> > +     /* Found CHAR or the null byte.  */
> > +     cmp     (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %CHAR_REG
> > +     jne     L(zero)
> > +
> >  # endif
> > +     /* NB: Multiply sizeof char type (1 or 4) to get the number of
> > +        bytes.  */
> > +     leaq    (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %rax
> >       ret
> >
> >       .p2align 4
> >  L(first_vec_x2):
> > +# ifndef USE_AS_STRCHRNUL
> > +     /* Check to see if first match was CHAR (k0) or null (k1).  */
> > +     kmovd   %k0, %eax
> >       tzcntl  %eax, %eax
> > -     /* Found CHAR or the null byte.  */
> > -# ifdef USE_AS_WCSCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    (VEC_SIZE * 2)(%rdi, %rax, 4), %rax
> > +     kmovd   %k1, %ecx
> > +     /* bzhil will not be 0 if first match was null.  */
> > +     bzhil   %eax, %ecx, %ecx
> > +     jne     L(zero)
> >  # else
> > -     leaq    (VEC_SIZE * 2)(%rdi, %rax), %rax
> > -# endif
> > -# ifndef USE_AS_STRCHRNUL
> > -     cmp (%rax), %CHAR_REG
> > -     cmovne  %rdx, %rax
> > +     /* Combine CHAR and null matches.  */
> > +     kord    %k0, %k1, %k0
> > +     kmovd   %k0, %eax
> > +     tzcntl  %eax, %eax
> >  # endif
> > +     /* NB: Multiply sizeof char type (1 or 4) to get the number of
> > +        bytes.  */
> > +     leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> >       ret
> >
> > -L(prep_loop_4x):
> > -     /* Align data to 4 * VEC_SIZE.  */
> > +     .p2align 4
> > +L(aligned_more):
> > +     /* Align data to VEC_SIZE.  */
> > +     andq    $-VEC_SIZE, %rdi
> > +L(cross_page_continue):
> > +     /* Check the next 4 * VEC_SIZE.  Only one VEC_SIZE at a time since
> > +        data is only aligned to VEC_SIZE. Use two alternating methods for
> > +        checking VEC to balance latency and port contention.  */
>
> Please limit lines to 72 columns.
>

Fixed.

> > +
> > +     /* This method has higher latency but has better port
> > +        distribution.  */
> > +     VMOVA   (VEC_SIZE)(%rdi), %YMM1
> > +     /* Leaves only CHARS matching esi as 0.  */
> > +     vpxorq  %YMM1, %YMM0, %YMM2
> > +     VPMINU  %YMM2, %YMM1, %YMM2
> > +     /* Each bit in K0 represents a CHAR or a null byte in YMM1.  */
> > +     VPCMP   $0, %YMMZERO, %YMM2, %k0
> > +     kmovd   %k0, %eax
> > +     testl   %eax, %eax
> > +     jnz     L(first_vec_x1)
> > +
> > +     /* This method has higher latency but has better port
> > +        distribution.  */
> > +     VMOVA   (VEC_SIZE * 2)(%rdi), %YMM1
> > +     /* Each bit in K0 represents a CHAR in YMM1.  */
> > +     VPCMP   $0, %YMM1, %YMM0, %k0
> > +     /* Each bit in K1 represents a CHAR in YMM1.  */
> > +     VPCMP   $0, %YMM1, %YMMZERO, %k1
> > +     kortestd        %k0, %k1
> > +     jnz     L(first_vec_x2)
> > +
> > +     VMOVA   (VEC_SIZE * 3)(%rdi), %YMM1
> > +     /* Leaves only CHARS matching esi as 0.  */
> > +     vpxorq  %YMM1, %YMM0, %YMM2
> > +     VPMINU  %YMM2, %YMM1, %YMM2
> > +     /* Each bit in K0 represents a CHAR or a null byte in YMM1.  */
> > +     VPCMP   $0, %YMMZERO, %YMM2, %k0
> > +     kmovd   %k0, %eax
> > +     testl   %eax, %eax
> > +     jnz     L(first_vec_x3)
> > +
> > +     VMOVA   (VEC_SIZE * 4)(%rdi), %YMM1
> > +     /* Each bit in K0 represents a CHAR in YMM1.  */
> > +     VPCMP   $0, %YMM1, %YMM0, %k0
> > +     /* Each bit in K1 represents a CHAR in YMM1.  */
> > +     VPCMP   $0, %YMM1, %YMMZERO, %k1
> > +     kortestd        %k0, %k1
> > +     jnz     L(first_vec_x4)
> > +
> > +     /* Align data to VEC_SIZE * 4 for the loop.  */
> > +     addq    $VEC_SIZE, %rdi
> >       andq    $-(VEC_SIZE * 4), %rdi
> >
> >       .p2align 4
> >  L(loop_4x_vec):
> > -     /* Compare 4 * VEC at a time forward.  */
> > +     /* Check 4x VEC at a time. No penalty to imm32 offset with evex
> > +        encoding.  */
> >       VMOVA   (VEC_SIZE * 4)(%rdi), %YMM1
> >       VMOVA   (VEC_SIZE * 5)(%rdi), %YMM2
> >       VMOVA   (VEC_SIZE * 6)(%rdi), %YMM3
> >       VMOVA   (VEC_SIZE * 7)(%rdi), %YMM4
> >
> > -     /* Leaves only CHARS matching esi as 0.  */
> > +     /* For YMM1 and YMM3 use xor to set the CHARs matching esi to zero.  */
>
> Please limit lines to 72 columns.
>

Fixed.

> >       vpxorq  %YMM1, %YMM0, %YMM5
> > -     vpxorq  %YMM2, %YMM0, %YMM6
> > +     /* For YMM2 and YMM4 cmp not equals to CHAR and store result in k
> > +        register. Its possible to save either 1 or 2 instructions using cmp no
> > +        equals method for either YMM1 or YMM1 and YMM3 respectively but
> > +        bottleneck on p5 makes it no worth it.  */
>
> Please limit lines to 72 columns.
>

Fixed.

> > +     VPCMP   $4, %YMM0, %YMM2, %k2
> >       vpxorq  %YMM3, %YMM0, %YMM7
> > -     vpxorq  %YMM4, %YMM0, %YMM8
> > -
> > -     VPMINU  %YMM5, %YMM1, %YMM5
> > -     VPMINU  %YMM6, %YMM2, %YMM6
> > -     VPMINU  %YMM7, %YMM3, %YMM7
> > -     VPMINU  %YMM8, %YMM4, %YMM8
> > -
> > -     VPMINU  %YMM5, %YMM6, %YMM1
> > -     VPMINU  %YMM7, %YMM8, %YMM2
> > -
> > -     VPMINU  %YMM1, %YMM2, %YMM1
> > -
> > -     /* Each bit in K0 represents a CHAR or a null byte.  */
> > -     VPCMP   $0, %YMMZERO, %YMM1, %k0
> > -
> > -     addq    $(VEC_SIZE * 4), %rdi
> > -
> > -     ktestd  %k0, %k0
> > +     VPCMP   $4, %YMM0, %YMM4, %k4
> > +
> > +     /* Use min to select all zeros (either from xor or end of string).  */
>
> Please limit lines to 72 columns.

Fixed.

>
> > +     VPMINU  %YMM1, %YMM5, %YMM1
> > +     VPMINU  %YMM3, %YMM7, %YMM3
> > +
> > +     /* Use min + zeromask to select for zeros. Since k2 and k4 will be
> > +        have 0 as positions that matched with CHAR which will set zero in
> > +        the corresponding destination bytes in YMM2 / YMM4.  */
>
> Please limit lines to 72 columns.

Fixed.

>
> > +     VPMINU  %YMM1, %YMM2, %YMM2{%k2}{z}
> > +     VPMINU  %YMM3, %YMM4, %YMM4
> > +     VPMINU  %YMM2, %YMM4, %YMM4{%k4}{z}
> > +
> > +     VPCMP   $0, %YMMZERO, %YMM4, %k1
> > +     kmovd   %k1, %ecx
> > +     subq    $-(VEC_SIZE * 4), %rdi
> > +     testl   %ecx, %ecx
> >       jz      L(loop_4x_vec)
> >
> > -     /* Each bit in K0 represents a CHAR or a null byte in YMM1.  */
> > -     VPCMP   $0, %YMMZERO, %YMM5, %k0
> > +     VPCMP   $0, %YMMZERO, %YMM1, %k0
> >       kmovd   %k0, %eax
> >       testl   %eax, %eax
> > -     jnz     L(first_vec_x0)
> > +     jnz     L(last_vec_x1)
> >
> > -     /* Each bit in K1 represents a CHAR or a null byte in YMM2.  */
> > -     VPCMP   $0, %YMMZERO, %YMM6, %k1
> > -     kmovd   %k1, %eax
> > +     VPCMP   $0, %YMMZERO, %YMM2, %k0
> > +     kmovd   %k0, %eax
> >       testl   %eax, %eax
> > -     jnz     L(first_vec_x1)
> > -
> > -     /* Each bit in K2 represents a CHAR or a null byte in YMM3.  */
> > -     VPCMP   $0, %YMMZERO, %YMM7, %k2
> > -     /* Each bit in K3 represents a CHAR or a null byte in YMM4.  */
> > -     VPCMP   $0, %YMMZERO, %YMM8, %k3
> > +     jnz     L(last_vec_x2)
> >
> > +     VPCMP   $0, %YMMZERO, %YMM3, %k0
> > +     kmovd   %k0, %eax
> > +     /* Combine YMM3 matches (eax) with YMM4 matches (ecx).  */
> >  # ifdef USE_AS_WCSCHR
> > -     /* NB: Each bit in K2/K3 represents 4-byte element.  */
> > -     kshiftlw $8, %k3, %k1
> > +     sall    $8, %ecx
> > +     orl     %ecx, %eax
> > +     tzcntl  %eax, %eax
> >  # else
> > -     kshiftlq $32, %k3, %k1
> > +     salq    $32, %rcx
> > +     orq     %rcx, %rax
> > +     tzcntq  %rax, %rax
> >  # endif
> > +# ifndef USE_AS_STRCHRNUL
> > +     /* Check if match was CHAR or null.  */
> > +     cmp     (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %CHAR_REG
> > +     jne     L(zero_end)
> > +# endif
> > +     /* NB: Multiply sizeof char type (1 or 4) to get the number of
> > +        bytes.  */
> > +     leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> > +     ret
> >
> > -     /* Each bit in K1 represents a NULL or a mismatch.  */
> > -     korq    %k1, %k2, %k1
> > -     kmovq   %k1, %rax
> > +# ifndef USE_AS_STRCHRNUL
> > +L(zero_end):
> > +     xorl    %eax, %eax
> > +     ret
> > +# endif
> >
> > -     tzcntq  %rax, %rax
> > -# ifdef USE_AS_WCSCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    (VEC_SIZE * 2)(%rdi, %rax, 4), %rax
> > -# else
> > -     leaq    (VEC_SIZE * 2)(%rdi, %rax), %rax
> > +     .p2align 4
> > +L(last_vec_x1):
> > +     tzcntl  %eax, %eax
> > +# ifndef USE_AS_STRCHRNUL
> > +     /* Check if match was null.  */
> > +     cmp     (%rdi, %rax, CHAR_SIZE), %CHAR_REG
> > +     jne     L(zero_end)
> >  # endif
> > +     /* NB: Multiply sizeof char type (1 or 4) to get the number of
> > +        bytes.  */
> > +     leaq    (%rdi, %rax, CHAR_SIZE), %rax
> > +     ret
> > +
> > +     .p2align 4
> > +L(last_vec_x2):
> > +     tzcntl  %eax, %eax
> >  # ifndef USE_AS_STRCHRNUL
> > -     cmp (%rax), %CHAR_REG
> > -     cmovne  %rdx, %rax
> > +     /* Check if match was null.  */
> > +     cmp     (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %CHAR_REG
> > +     jne     L(zero_end)
> >  # endif
> > +     /* NB: Multiply sizeof char type (1 or 4) to get the number of
> > +        bytes.  */
> > +     leaq    (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %rax
> >       ret
> >
> >       /* Cold case for crossing page with first load.  */
> >       .p2align 4
> >  L(cross_page_boundary):
> > +     movq    %rdi, %rdx
> > +     /* Align rdi.  */
> >       andq    $-VEC_SIZE, %rdi
> > -     andl    $(VEC_SIZE - 1), %ecx
> > -
> >       VMOVA   (%rdi), %YMM1
> > -
> >       /* Leaves only CHARS matching esi as 0.  */
> >       vpxorq  %YMM1, %YMM0, %YMM2
> >       VPMINU  %YMM2, %YMM1, %YMM2
> >       /* Each bit in K0 represents a CHAR or a null byte in YMM1.  */
> >       VPCMP   $0, %YMMZERO, %YMM2, %k0
> >       kmovd   %k0, %eax
> > -     testl   %eax, %eax
> > -
> > +     /* Remove the leading bits.      */
> >  # ifdef USE_AS_WCSCHR
> > +     movl    %edx, %SHIFT_REG
> >       /* NB: Divide shift count by 4 since each bit in K1 represent 4
> >          bytes.  */
> > -     movl    %ecx, %SHIFT_REG
> > -     sarl    $2, %SHIFT_REG
> > +     sarl    $2, %SHIFT_REG
> > +     andl    $(CHAR_PER_VEC - 1), %SHIFT_REG
> >  # endif
> > -
> > -     /* Remove the leading bits.      */
> >       sarxl   %SHIFT_REG, %eax, %eax
> > +     /* If eax is zero continue.  */
> >       testl   %eax, %eax
> > -
> > -     jz      L(aligned_more)
> > +     jz      L(cross_page_continue)
> >       tzcntl  %eax, %eax
> > -     addq    %rcx, %rdi
> > +# ifndef USE_AS_STRCHRNUL
> > +     /* Check to see if match was CHAR or null.  */
> > +     cmp     (%rdx, %rax, CHAR_SIZE), %CHAR_REG
> > +     jne     L(zero_end)
> > +# endif
> >  # ifdef USE_AS_WCSCHR
> >       /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    (%rdi, %rax, 4), %rax
> > +     leaq    (%rdx, %rax, CHAR_SIZE), %rax
> >  # else
> > -     addq    %rdi, %rax
> > -# endif
> > -# ifndef USE_AS_STRCHRNUL
> > -     cmp (%rax), %CHAR_REG
> > -     cmovne  %rdx, %rax
> > +     addq    %rdx, %rax
> >  # endif
> >       ret
> >
> > --
> > 2.29.2
> >
>
> Thanks.
>
> H.J.