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/*
* Copyright (c) 2023, 2024 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
.weak memccpy
.set memccpy, __memccpy
ARCHFUNCS(__memccpy)
ARCHFUNC(__memccpy, scalar)
ARCHFUNC(__memccpy, baseline)
ENDARCHFUNCS(__memccpy)
ARCHENTRY(__memccpy, scalar)
push %rbp # establish stack frame
mov %rsp, %rbp
push %rax # dummy push for alignment
push %rbx
push %rdi
push %rsi
mov %rsi, %rdi
mov %edx, %esi
mov %rcx, %rdx
mov %rcx, %rbx
call CNAME(__memchr) # ptr = memchr(src, c, len)
pop %rsi
pop %rdi
lea 1(%rax), %rdx
sub %rsi, %rdx # size = ptr - src + 1
mov %rbx, %rcx
lea (%rdi, %rdx, 1), %rbx # res = dest + size
test %rax, %rax # if (ptr == NULL)
cmovz %rcx, %rdx # size = len
cmovz %rax, %rbx # res = NULL
call CNAME(memcpy)
mov %rbx, %rax # return (res)
pop %rbx
leave
ret
ARCHEND(__memccpy, scalar)
ARCHENTRY(__memccpy, baseline)
sub $1, %rcx # RCX refers to last character in buffer
jb .L0 # go to special code path if len was 0
movd %edx, %xmm4
mov %rcx, %rdx
punpcklbw %xmm4, %xmm4 # c -> cc
mov %esi, %ecx
punpcklwd %xmm4, %xmm4 # cc -> cccc
mov %rsi, %r9 # stash a copy of the source pointer for later
pshufd $0, %xmm4, %xmm4 # cccc -> cccccccccccccccc
and $~0xf, %rsi
movdqa %xmm4, %xmm1
pcmpeqb (%rsi), %xmm1 # c found in head?
and $0xf, %ecx
mov $-1, %eax
pmovmskb %xmm1, %r8d
lea -32(%rcx), %r11
shl %cl, %eax # mask of bytes in the string
add %rdx, %r11 # distance from alignment boundary - 32
jnc .Lrunt # jump if buffer length is 32 or less
and %r8d, %eax
jz 0f # match (or induced match) found?
/* match in first chunk */
tzcnt %eax, %edx # where is c?
sub %ecx, %edx # ... from the beginning of the string?
lea 1(%rdi, %rdx, 1), %rax # return value
jmp .L0116
0: movdqa 16(%rsi), %xmm3 # load second string chunk
movdqu (%r9), %xmm2 # load unaligned string head
movdqa %xmm4, %xmm1
pcmpeqb %xmm3, %xmm1 # c found in second chunk?
/* process second chunk */
pmovmskb %xmm1, %eax
test %eax, %eax
jz 0f
/* match in second chunk */
tzcnt %eax, %edx # where is c?
sub $16, %ecx
sub %ecx, %edx # adjust for alignment offset
lea 1(%rdi, %rdx, 1), %rax # return value
jmp .L0132
/* c not found in second chunk: prepare for main loop */
0: movdqa 32(%rsi), %xmm0 # load next string chunk
movdqa %xmm4, %xmm1
movdqu %xmm2, (%rdi) # deposit head into buffer
sub %rcx, %rdi # adjust RDI to correspond to RSI
mov %r11, %rdx
movdqu %xmm3, 16(%rdi) # deposit second chunk
sub %rsi, %rdi # express RDI as distance from RSI
add $32, %rsi # advance RSI past first two chunks
sub $16, %rdx # enough left for another round?
jb 1f
/* main loop unrolled twice */
ALIGN_TEXT
0: pcmpeqb %xmm0, %xmm1 # c encountered?
pmovmskb %xmm1, %eax
test %eax, %eax
jnz 3f
movdqu %xmm0, (%rsi, %rdi)
movdqa 16(%rsi), %xmm0 # load next string chunk
movdqa %xmm4, %xmm1
cmp $16, %rdx # more than a full chunk left?
jb 2f
add $32, %rsi # advance pointers to next chunk
pcmpeqb %xmm0, %xmm1 # c encountered?
pmovmskb %xmm1, %eax
test %eax, %eax
jnz 4f
movdqu %xmm0, -16(%rsi, %rdi)
movdqa (%rsi), %xmm0 # load next string chunk
movdqa %xmm4, %xmm1
sub $32, %rdx
jae 0b
1: sub $16, %rsi # undo second advancement
add $16, %edx
/* 1--16 bytes left in the buffer but string has not ended yet */
2: pcmpeqb %xmm1, %xmm0 # c encountered?
pmovmskb %xmm0, %r8d
mov %r8d, %ecx
bts %edx, %r8d # treat end of buffer as end of string
tzcnt %r8d, %r8d # find tail length
add %rsi, %rdi # restore RDI
movdqu 1(%rsi, %r8, 1), %xmm0 # load string tail
movdqu %xmm0, 1(%rdi, %r8, 1) # store string tail
lea 17(%rdi, %r8, 1), %rsi # return value if terminator encountered
xor %eax, %eax # return value if no terminator encountered
bt %r8d, %ecx # terminator encountered inside buffer?
cmovc %rsi, %rax # if yes, return pointer, else NULL
ret
4: sub $16, %rsi # undo second advancement
/* terminator found and buffer has not ended yet */
3: tzcnt %eax, %eax # find length of string tail
movdqu -15(%rsi, %rax, 1), %xmm0 # load string tail (incl. c)
add %rsi, %rdi # restore destination pointer
movdqu %xmm0, -15(%rdi, %rax, 1) # store string tail (incl. c)
lea 1(%rdi, %rax, 1), %rax # compute return value
ret
/* buffer is 1--32 bytes in size */
ALIGN_TEXT
.Lrunt: add $32, %r11d # undo earlier decrement
mov %r8d, %r10d # keep a copy of the original match mask
bts %r11d, %r8d # induce match at buffer end
and %ax, %r8w # is there a match in the first 16 bytes?
jnz 0f # if yes, skip looking at second chunk
pcmpeqb 16(%rsi), %xmm4 # check for match in second chunk
pmovmskb %xmm4, %r8d
shl $16, %r8d # place second chunk matches in bits 16--31
mov %r8d, %r10d # keep a copy of the original match mask
bts %r11d, %r8d # induce a match at buffer end
0: xor %eax, %eax # return value if terminator not found
tzcnt %r8d, %edx # find string/buffer length from alignment boundary
lea 1(%rdi, %rdx, 1), %r8 # return value if terminator found + rcx
sub %rcx, %r8
bt %edx, %r10d # was the terminator present?
cmovc %r8, %rax # if yes, return pointer, else NULL
sub %ecx, %edx # find actual string/buffer length
ALIGN_TEXT
.L0132: cmp $16, %rdx # at least 17 bytes to copy?
jb .L0116
/* copy 17--32 bytes */
movdqu (%r9), %xmm0 # load first 16 bytes
movdqu -15(%r9, %rdx, 1), %xmm1 # load last 16 bytes
movdqu %xmm0, (%rdi)
movdqu %xmm1, -15(%rdi, %rdx, 1)
ret
/* process strings of 1--16 bytes (rdx: min(buflen, srclen), rax: srclen) */
ALIGN_TEXT
.L0116: cmp $8, %rdx # at least 9 bytes to copy?
jae .L0916
cmp $4, %rdx # at least 5 bytes to copy?
jae .L0508
cmp $2, %rdx # at least 3 bytes to copy?
jae .L0304
/* copy one or two bytes */
movzbl (%r9), %ecx # load first byte from src
movzbl (%r9, %rdx, 1), %esi # load last byte from src
mov %cl, (%rdi) # deposit into destination
mov %sil, (%rdi, %rdx, 1)
ret
.L0304: movzwl (%r9), %ecx
movzwl -1(%r9, %rdx, 1), %esi
mov %cx, (%rdi)
mov %si, -1(%rdi, %rdx, 1)
ret
.L0508: mov (%r9), %ecx
mov -3(%r9, %rdx, 1), %esi
mov %ecx, (%rdi)
mov %esi, -3(%rdi, %rdx, 1)
ret
.L0916: mov (%r9), %rcx
mov -7(%r9, %rdx, 1), %rsi
mov %rcx, (%rdi)
mov %rsi, -7(%rdi, %rdx, 1)
ret
/* length zero destination: return null pointer */
.L0: xor %eax, %eax
ret
ARCHEND(__memccpy, baseline)
.section .note.GNU-stack,"",%progbits
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