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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 <machine/param.h>
#include "amd64_archlevel.h"
#define ALIGN_TEXT .p2align 4,0x90 /* 16-byte alignment, nop filled */
.weak strcspn
.set strcspn, __strcspn
ARCHFUNCS(__strcspn)
ARCHFUNC(__strcspn, scalar)
NOARCHFUNC
ARCHFUNC(__strcspn, x86_64_v2)
ENDARCHFUNCS(__strcspn)
ARCHENTRY(__strcspn, scalar)
push %rbp # align stack to enable function call
mov %rsp, %rbp
sub $256, %rsp # allocate space for lookup table
/* check for special cases */
movzbl (%rsi), %eax # first character in the set
test %eax, %eax
jz .Lstrlen
movzbl 1(%rsi), %edx # second character in the set
test %edx, %edx
jz .Lstrchr
/* no special case matches -- prepare lookup table */
xor %r8d, %r8d
mov $28, %ecx
0: mov %r8, (%rsp, %rcx, 8)
mov %r8, 8(%rsp, %rcx, 8)
mov %r8, 16(%rsp, %rcx, 8)
mov %r8, 24(%rsp, %rcx, 8)
sub $4, %ecx
jnc 0b
add $2, %rsi
movb $1, (%rsp, %rax, 1) # register first chars in set
movb $1, (%rsp, %rdx, 1)
mov %rdi, %rax # a copy of the source to iterate over
/* process remaining chars in set */
ALIGN_TEXT
0: movzbl (%rsi), %ecx
movb $1, (%rsp, %rcx, 1)
test %ecx, %ecx
jz 1f
movzbl 1(%rsi), %ecx
movb $1, (%rsp, %rcx, 1)
test %ecx, %ecx
jz 1f
add $2, %rsi
jmp 0b
/* find match */
ALIGN_TEXT
1: movzbl (%rax), %ecx
cmpb $0, (%rsp, %rcx, 1)
jne 2f
movzbl 1(%rax), %ecx
cmpb $0, (%rsp, %rcx, 1)
jne 3f
movzbl 2(%rax), %ecx
cmpb $0, (%rsp, %rcx, 1)
jne 4f
movzbl 3(%rax), %ecx
add $4, %rax
cmpb $0, (%rsp, %rcx, 1)
je 1b
sub $3, %rax
4: dec %rdi
3: inc %rax
2: sub %rdi, %rax # number of characters preceding match
leave
ret
/* set is empty, degrades to strlen */
.Lstrlen:
leave
jmp CNAME(strlen)
/* just one character in set, degrades to strchr */
.Lstrchr:
mov %rdi, (%rsp) # stash a copy of the string
mov %eax, %esi # find the character in the set
call CNAME(strchrnul)
sub (%rsp), %rax # length of prefix before match
leave
ret
ARCHEND(__strcspn, scalar)
/*
* This kernel uses pcmpistri to do the heavy lifting.
* We provide five code paths, depending on set size:
*
* 0: call strlen()
* 1: call strchr()
* 2--16: one pcmpistri per 16 bytes of input
* 17--32: two pcmpistri per 16 bytes of input
* >=33: fall back to look up table
*/
ARCHENTRY(__strcspn, x86_64_v2)
push %rbp
mov %rsp, %rbp
sub $256, %rsp
/* check for special cases */
movzbl (%rsi), %eax
test %eax, %eax # empty string?
jz .Lstrlenv2
cmpb $0, 1(%rsi) # single character string?
jz .Lstrchrv2
/* find set size and copy up to 32 bytes to (%rsp) */
mov %esi, %ecx
and $~0xf, %rsi # align set pointer
movdqa (%rsi), %xmm0
pxor %xmm1, %xmm1
and $0xf, %ecx # amount of bytes rsi is past alignment
xor %edx, %edx
pcmpeqb %xmm0, %xmm1 # end of string reached?
movdqa %xmm0, 32(%rsp) # transfer head of set to stack
pmovmskb %xmm1, %eax
shr %cl, %eax # clear out junk before string
test %eax, %eax # end of set reached?
jnz 0f
movdqa 16(%rsi), %xmm0 # second chunk of the set
mov $16, %edx
sub %ecx, %edx # length of set preceding xmm0
pxor %xmm1, %xmm1
pcmpeqb %xmm0, %xmm1
movdqa %xmm0, 48(%rsp)
movdqu 32(%rsp, %rcx, 1), %xmm2 # head of set
pmovmskb %xmm1, %eax
test %eax, %eax
jnz 1f
movdqa 32(%rsi), %xmm0 # third chunk
add $16, %edx
pxor %xmm1, %xmm1
pcmpeqb %xmm0, %xmm1
movdqa %xmm0, 64(%rsp)
pmovmskb %xmm1, %eax
test %eax, %eax # still not done?
jz .Lgt32v2
0: movdqu 32(%rsp, %rcx, 1), %xmm2 # head of set
1: tzcnt %eax, %eax
add %eax, %edx # length of set (excluding NUL byte)
cmp $32, %edx # above 32 bytes?
ja .Lgt32v2
/*
* At this point we know that we want to use pcmpistri.
* one last problem obtains: the head of the string is not
* aligned and may cross a cacheline. If this is the case,
* we take the part before the page boundary and repeat the
* last byte to fill up the xmm register.
*/
mov %rdi, %rax # save original string pointer
lea 15(%rdi), %esi # last byte of the head
xor %edi, %esi
test $PAGE_SIZE, %esi # does the head cross a page?
jz 0f
/* head crosses page: copy to stack to fix up */
and $~0xf, %rax # align head pointer temporarily
movzbl 15(%rax), %esi # last head byte on the page
movdqa (%rax), %xmm0
movabs $0x0101010101010101, %r8
imul %r8, %rsi # repeated 8 times
movdqa %xmm0, (%rsp) # head word on stack
mov %rsi, 16(%rsp) # followed by filler (last byte x8)
mov %rsi, 24(%rsp)
mov %edi, %eax
and $0xf, %eax # offset of head from alignment
add %rsp, %rax # pointer to fake head
0: movdqu (%rax), %xmm0 # load head (fake or real)
lea 16(%rdi), %rax
and $~0xf, %rax # second 16 bytes of string (aligned)
1: cmp $16, %edx # 16--32 bytes?
ja .Lgt16v2
/* set is 2--16 bytes in size */
/* _SIDD_UBYTE_OPS|_SIDD_CMP_EQUAL_ANY|_SIDD_LEAST_SIGNIFICANT */
pcmpistri $0, %xmm0, %xmm2 # match in head?
jbe .Lheadmatchv2
ALIGN_TEXT
0: pcmpistri $0, (%rax), %xmm2
jbe 1f # match or end of string?
pcmpistri $0, 16(%rax), %xmm2
lea 32(%rax), %rax
ja 0b # match or end of string?
3: lea -16(%rax), %rax # go back to second half
1: jc 2f # jump if match found
movdqa (%rax), %xmm0 # reload string piece
pxor %xmm1, %xmm1
pcmpeqb %xmm1, %xmm0 # where is the NUL byte?
pmovmskb %xmm0, %ecx
tzcnt %ecx, %ecx # location of NUL byte in (%rax)
2: sub %rdi, %rax # offset of %xmm0 from beginning of string
add %rcx, %rax # prefix length before match/NUL
leave
ret
.Lheadmatchv2:
jc 2f # jump if match found
pxor %xmm1, %xmm1
pcmpeqb %xmm1, %xmm0
pmovmskb %xmm0, %ecx
tzcnt %ecx, %ecx # location of NUL byte
2: mov %ecx, %eax # prefix length before match/NUL
leave
ret
/* match in first set half during head */
.Lheadmatchv2first:
mov %ecx, %eax
pcmpistri $0, %xmm0, %xmm3 # match in second set half?
cmp %ecx, %eax # before the first half match?
cmova %ecx, %eax # use the earlier match
leave
ret
.Lgt16v2:
movdqu 48(%rsp, %rcx, 1), %xmm3 # second part of set
/* set is 17--32 bytes in size */
pcmpistri $0, %xmm0, %xmm2 # match in first set half?
jb .Lheadmatchv2first
pcmpistri $0, %xmm0, %xmm3 # match in second set half or end of string?
jbe .Lheadmatchv2
ALIGN_TEXT
0: movdqa (%rax), %xmm0
pcmpistri $0, %xmm0, %xmm2
jb 4f # match in first set half?
pcmpistri $0, %xmm0, %xmm3
jbe 1f # match in second set half or end of string?
movdqa 16(%rax), %xmm0
add $32, %rax
pcmpistri $0, %xmm0, %xmm2
jb 3f # match in first set half?
pcmpistri $0, %xmm0, %xmm3
ja 0b # neither match in 2nd half nor string end?
/* match in second half or NUL */
lea -16(%rax), %rax # go back to second half
1: jc 2f # jump if match found
pxor %xmm1, %xmm1
pcmpeqb %xmm1, %xmm0 # where is the NUL byte?
pmovmskb %xmm0, %ecx
tzcnt %ecx, %ecx # location of NUL byte in (%rax)
2: sub %rdi, %rax # offset of %xmm0 from beginning of string
add %rcx, %rax # prefix length before match/NUL
leave
ret
/* match in first half */
3: sub $16, %rax # go back to second half
4: sub %rdi, %rax # offset of %xmm0 from beginning of string
mov %ecx, %edx
pcmpistri $0, %xmm0, %xmm3 # match in second set half?
cmp %ecx, %edx # before the first half match?
cmova %ecx, %edx # use the earlier match
add %rdx, %rax # return full ofset
leave
ret
/* set is empty, degrades to strlen */
.Lstrlenv2:
leave
jmp CNAME(strlen)
/* just one character in set, degrades to strchr */
.Lstrchrv2:
mov %rdi, (%rsp) # stash a copy of the string
mov %eax, %esi # find this character
call CNAME(strchrnul)
sub (%rsp), %rax # length of prefix before match
leave
ret
/* set is >=33 bytes in size */
.Lgt32v2:
xorps %xmm0, %xmm0
mov $256-64, %edx
/* clear out look up table */
0: movaps %xmm0, (%rsp, %rdx, 1)
movaps %xmm0, 16(%rsp, %rdx, 1)
movaps %xmm0, 32(%rsp, %rdx, 1)
movaps %xmm0, 48(%rsp, %rdx, 1)
sub $64, %edx
jnc 0b
add %rcx, %rsi # restore string pointer
mov %rdi, %rax # keep a copy of the string
/* initialise look up table */
ALIGN_TEXT
0: movzbl (%rsi), %ecx
movb $1, (%rsp, %rcx, 1)
test %ecx, %ecx
jz 1f
movzbl 1(%rsi), %ecx
movb $1, (%rsp, %rcx, 1)
test %ecx, %ecx
jz 1f
movzbl 2(%rsi), %ecx
movb $1, (%rsp, %rcx, 1)
test %ecx, %ecx
jz 1f
movzbl 3(%rsi), %ecx
movb $1, (%rsp, %rcx, 1)
test %ecx, %ecx
jz 1f
add $4, %rsi
jmp 0b
/* find match */
ALIGN_TEXT
1: movzbl (%rax), %ecx
cmpb $0, (%rsp, %rcx, 1)
jne 2f
movzbl 1(%rax), %ecx
cmpb $0, (%rsp, %rcx, 1)
jne 3f
movzbl 2(%rax), %ecx
cmpb $0, (%rsp, %rcx, 1)
jne 4f
movzbl 3(%rax), %ecx
add $4, %rax
cmpb $0, (%rsp, %rcx, 1)
je 1b
sub $3, %rax
4: dec %rdi
3: inc %rax
2: sub %rdi, %rax # number of characters preceding match
leave
ret
ARCHEND(__strcspn, x86_64_v2)
.section .note.GNU-stack,"",%progbits
|