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/*-
* Copyright (c) 2023 The FreeBSD Foundation
*
* This software was developed by Robert Clausecker <fuz@FreeBSD.org>
* under sponsorship from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ''AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE
*/
#include <machine/asm.h>
#include "amd64_archlevel.h"
#define ALIGN_TEXT .p2align 4,0x90 /* 16-byte alignment, nop filled */
.weak memchr
.set memchr, __memchr
ARCHFUNCS(__memchr)
ARCHFUNC(__memchr, scalar)
ARCHFUNC(__memchr, baseline)
ENDARCHFUNCS(__memchr)
ARCHENTRY(__memchr, scalar)
test %rdx, %rdx # empty input?
je .Lnomatch
lea (, %rdi, 8), %ecx
add %rdi, %rdx # pointer to end of buffer
and $~7, %rdi # align to 8 bytes
mov (%rdi), %rax # load first word
movzbl %sil, %esi # clear stray high bits
movabs $0x0101010101010101, %r8
imul %r8, %rsi # replicate char 8 times
/* compute head and tail masks */
mov %r8, %r10
movabs $0x8080808080808080, %r9
shl %cl, %r10 # 0x01 where string head is
lea (, %rdx, 8), %ecx
xor %r8, %r10 # 0x01 where it is not
neg %r8 # negate 01..01 so we can use lea
mov %r9, %r11
xor %rsi, %rax # str ^ c (0x00 where str[i] == c)
neg %ecx
or %r10, %rax # except before the string
shr %cl, %r11 # 0x80 where string tail is
add $8, %rdi # advance to next 8 bytes
cmp %rdx, %rdi # end of buffer reached during head?
jae .Ltail # and go to tail-processing code
/* main loop, unrolled twice */
ALIGN_TEXT
0: lea (%rax, %r8, 1), %rcx # (str ^ c) - 0x01..01
not %rax # ~(str ^ c)
and %r9, %rax # ((str^c) - 0x01..01) & ~(str^c)
and %rcx, %rax # not including junk bytes
jnz .Lmatch
mov (%rdi), %rax
add $8, %rdi
xor %rsi, %rax # str ^ c
cmp %rdx, %rdi
jae .Ltail
lea (%rax, %r8, 1), %rcx # (str ^ c) - 0x01..01
not %rax # ~(str ^ c)
and %r9, %rax # ((str^c) - 0x01..01) & ~(str^c)
and %rcx, %rax # not including junk bytes
jnz .Lmatch
mov (%rdi), %rax
add $8, %rdi
xor %rsi, %rax # str ^ c
cmp %rdx, %rdi
jb 0b
.Ltail: lea (%rax, %r8, 1), %rcx # (str ^ c) - 0x01..01
not %rax # ~(str ^ c)
and %r11, %rax # ((str^c) - 0x01..01) & ~(str^c)
and %rcx, %rax # not including junk bytes or bytes past buffer
jz .Lnomatch
.Lmatch:
tzcnt %rax, %rax # first match
shr $3, %eax # scale from bit to byte index
lea -8(%rdi, %rax), %rax # pointer to found c
ret
/* no match found */
.Lnomatch:
xor %eax, %eax # return null pointer
ret
ARCHEND(__memchr, scalar)
ARCHENTRY(__memchr, baseline)
test %rdx, %rdx # empty input?
je .Lnomatchb
movd %esi, %xmm2
mov %edi, %ecx
add %rdi, %rdx # pointer to end of buffer
and $~0x1f, %rdi # align to 32 bytes
movdqa (%rdi), %xmm0 # load first 32 bytes
movdqa 16(%rdi), %xmm1
punpcklbw %xmm2, %xmm2 # c -> cc
mov $-1, %r9d
shl %cl, %r9d # mask with zeroes before the string
punpcklwd %xmm2, %xmm2 # cc -> cccc
mov $-1, %r8d
xor %ecx, %ecx
sub %edx, %ecx # edx = -ecx
shr %cl, %r8d # bytes in tail that are part of the buffer
pshufd $0, %xmm2, %xmm2 # cccc -> cccccccccccccccc
add $32, %rdi # advance to next 32 bytes
mov $-1, %eax
cmp %rdx, %rdi # end of buffer reached during head?
cmovae %r8d, %eax # if yes, do combined head/tail processing
and %r9d, %eax # mask of bytes in head part of string
/* process head */
pcmpeqb %xmm2, %xmm1
pcmpeqb %xmm2, %xmm0
pmovmskb %xmm1, %esi
pmovmskb %xmm0, %ecx
shl $16, %esi
or %esi, %ecx # locations of matches
and %ecx, %eax # any match inside buffer?
jnz .Lprecisematchb
cmp %rdx, %rdi # did the buffer end here?
jae .Lnomatchb # if yes we are done
/* main loop */
ALIGN_TEXT
0: movdqa (%rdi), %xmm0 # load next string chunk
movdqa 16(%rdi), %xmm1
add $32, %rdi
cmp %rdx, %rdi # ready for main loop?
jae .Ltailb
pcmpeqb %xmm2, %xmm0
pcmpeqb %xmm2, %xmm1
por %xmm1, %xmm0 # match in either half?
pmovmskb %xmm0, %eax
test %eax, %eax
jz 0b
.Lmatchb:
pcmpeqb -32(%rdi), %xmm2 # redo comparison of first 16 bytes
pmovmskb %xmm1, %ecx
pmovmskb %xmm2, %eax
shl $16, %ecx
or %ecx, %eax # location of matches
.Lprecisematchb:
tzcnt %eax, %eax # find location of match
lea -32(%rdi, %rax, 1), %rax # point to matching byte
ret
.Ltailb:
pcmpeqb %xmm2, %xmm1
pcmpeqb %xmm2, %xmm0
pmovmskb %xmm1, %edx
pmovmskb %xmm0, %eax
shl $16, %edx
or %edx, %eax # location of matches
and %r8d, %eax # mask out matches beyond buffer
bsf %eax, %edx # location of match
lea -32(%rdi, %rdx, 1), %rdx # pointer to match (if any)
cmovnz %rdx, %rax # point to match if present,
ret # else null pointer
.Lnomatchb:
xor %eax, %eax # return null pointer
ret
ARCHEND(__memchr, baseline)
.section .note.GNU-stack,"",%progbits
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