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/* Placeholder function, not used by any processor at the moment.
Copyright (C) 2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/* UNUSED. Exists purely as reference implementation. */
#include <isa-level.h>
#if ISA_SHOULD_BUILD (4)
# include <sysdep.h>
# ifdef USE_AS_WCSLEN
# define VPCMPEQ vpcmpeqd
# define VPTESTN vptestnmd
# define VPMINU vpminud
# define CHAR_SIZE 4
# else
# define VPCMPEQ vpcmpeqb
# define VPTESTN vptestnmb
# define VPMINU vpminub
# define CHAR_SIZE 1
# endif
# define PAGE_SIZE 4096
# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
.section SECTION(.text),"ax",@progbits
/* Aligning entry point to 64 byte, provides better performance for
one vector length string. */
ENTRY_P2ALIGN (STRLEN, 6)
# ifdef USE_AS_STRNLEN
/* Check zero length. */
test %RSI_LP, %RSI_LP
jz L(ret_max)
# ifdef __ILP32__
/* Clear the upper 32 bits. */
movl %esi, %esi
# endif
# endif
movl %edi, %eax
vpxorq %VMM_128(0), %VMM_128(0), %VMM_128(0)
sall $20, %eax
cmpl $((PAGE_SIZE - VEC_SIZE) << 20), %eax
ja L(page_cross)
/* Compare [w]char for null, mask bit will be set for match. */
VPCMPEQ (%rdi), %VMM(0), %k0
# ifdef USE_AS_STRNLEN
KMOV %k0, %VRCX
/* Store max length in rax. */
mov %rsi, %rax
/* If rcx is 0, rax will have max length. We can not use VRCX
and VRAX here for evex256 because, upper 32 bits may be
undefined for ecx and eax. */
bsfq %rcx, %rax
cmp $CHAR_PER_VEC, %rax
ja L(align_more)
cmpq %rax, %rsi
cmovb %esi, %eax
# else
KMOV %k0, %VRAX
test %VRAX, %VRAX
jz L(align_more)
bsf %VRAX, %VRAX
# endif
ret
/* At this point vector max length reached. */
# ifdef USE_AS_STRNLEN
.p2align 4,,3
L(ret_max):
movq %rsi, %rax
ret
# endif
L(align_more):
mov %rdi, %rax
/* Align rax to VEC_SIZE. */
andq $-VEC_SIZE, %rax
# ifdef USE_AS_STRNLEN
movq %rdi, %rdx
subq %rax, %rdx
# ifdef USE_AS_WCSLEN
shr $2, %VRDX
# endif
/* At this point rdx contains [w]chars already compared. */
leaq -CHAR_PER_VEC(%rsi, %rdx), %rdx
/* At this point rdx contains number of w[char] needs to go.
Now onwards rdx will keep decrementing with each compare. */
# endif
/* Loop unroll 4 times for 4 vector loop. */
VPCMPEQ VEC_SIZE(%rax), %VMM(0), %k0
subq $-VEC_SIZE, %rax
KMOV %k0, %VRCX
test %VRCX, %VRCX
jnz L(ret_vec_x1)
# ifdef USE_AS_STRNLEN
subq $CHAR_PER_VEC, %rdx
jbe L(ret_max)
# endif
VPCMPEQ VEC_SIZE(%rax), %VMM(0), %k0
KMOV %k0, %VRCX
test %VRCX, %VRCX
jnz L(ret_vec_x2)
# ifdef USE_AS_STRNLEN
subq $CHAR_PER_VEC, %rdx
jbe L(ret_max)
# endif
VPCMPEQ (VEC_SIZE * 2)(%rax), %VMM(0), %k0
KMOV %k0, %VRCX
test %VRCX, %VRCX
jnz L(ret_vec_x3)
# ifdef USE_AS_STRNLEN
subq $CHAR_PER_VEC, %rdx
jbe L(ret_max)
# endif
VPCMPEQ (VEC_SIZE * 3)(%rax), %VMM(0), %k0
KMOV %k0, %VRCX
test %VRCX, %VRCX
jnz L(ret_vec_x4)
# ifdef USE_AS_STRNLEN
subq $CHAR_PER_VEC, %rdx
jbe L(ret_max)
/* Save pointer before 4 x VEC_SIZE alignment. */
movq %rax, %rcx
# endif
/* Align address to VEC_SIZE * 4 for loop. */
andq $-(VEC_SIZE * 4), %rax
# ifdef USE_AS_STRNLEN
subq %rax, %rcx
# ifdef USE_AS_WCSLEN
shr $2, %VRCX
# endif
/* rcx contains number of [w]char will be recompared due to
alignment fixes. rdx must be incremented by rcx to offset
alignment adjustment. */
addq %rcx, %rdx
/* Need jump as we don't want to add/subtract rdx for first
iteration of 4 x VEC_SIZE aligned loop. */
# endif
.p2align 4,,11
L(loop):
/* VPMINU and VPCMP combination provide better performance as
compared to alternative combinations. */
VMOVA (VEC_SIZE * 4)(%rax), %VMM(1)
VPMINU (VEC_SIZE * 5)(%rax), %VMM(1), %VMM(2)
VMOVA (VEC_SIZE * 6)(%rax), %VMM(3)
VPMINU (VEC_SIZE * 7)(%rax), %VMM(3), %VMM(4)
VPTESTN %VMM(2), %VMM(2), %k0
VPTESTN %VMM(4), %VMM(4), %k1
subq $-(VEC_SIZE * 4), %rax
KORTEST %k0, %k1
# ifndef USE_AS_STRNLEN
jz L(loop)
# else
jnz L(loopend)
subq $(CHAR_PER_VEC * 4), %rdx
ja L(loop)
mov %rsi, %rax
ret
# endif
L(loopend):
VPTESTN %VMM(1), %VMM(1), %k2
KMOV %k2, %VRCX
test %VRCX, %VRCX
jnz L(ret_vec_x1)
KMOV %k0, %VRCX
/* At this point, if k0 is non zero, null char must be in the
second vector. */
test %VRCX, %VRCX
jnz L(ret_vec_x2)
VPTESTN %VMM(3), %VMM(3), %k3
KMOV %k3, %VRCX
test %VRCX, %VRCX
jnz L(ret_vec_x3)
/* At this point null [w]char must be in the fourth vector so no
need to check. */
KMOV %k1, %VRCX
/* Fourth, third, second vector terminating are pretty much
same, implemented this way to avoid branching and reuse code
from pre loop exit condition. */
L(ret_vec_x4):
bsf %VRCX, %VRCX
subq %rdi, %rax
# ifdef USE_AS_WCSLEN
subq $-(VEC_SIZE * 3), %rax
shrq $2, %rax
addq %rcx, %rax
# else
leaq (VEC_SIZE * 3)(%rcx, %rax), %rax
# endif
# ifdef USE_AS_STRNLEN
cmpq %rsi, %rax
cmovnb %rsi, %rax
# endif
ret
L(ret_vec_x3):
bsf %VRCX, %VRCX
subq %rdi, %rax
# ifdef USE_AS_WCSLEN
subq $-(VEC_SIZE * 2), %rax
shrq $2, %rax
addq %rcx, %rax
# else
leaq (VEC_SIZE * 2)(%rcx, %rax), %rax
# endif
# ifdef USE_AS_STRNLEN
cmpq %rsi, %rax
cmovnb %rsi, %rax
# endif
ret
L(ret_vec_x2):
subq $-VEC_SIZE, %rax
L(ret_vec_x1):
bsf %VRCX, %VRCX
subq %rdi, %rax
# ifdef USE_AS_WCSLEN
shrq $2, %rax
# endif
addq %rcx, %rax
# ifdef USE_AS_STRNLEN
cmpq %rsi, %rax
cmovnb %rsi, %rax
# endif
ret
L(page_cross):
mov %rdi, %rax
movl %edi, %ecx
andl $(VEC_SIZE - 1), %ecx
# ifdef USE_AS_WCSLEN
sarl $2, %ecx
# endif
/* ecx contains number of w[char] to be skipped as a result
of address alignment. */
andq $-VEC_SIZE, %rax
VPCMPEQ (%rax), %VMM(0), %k0
KMOV %k0, %VRDX
/* Ignore number of character for alignment adjustment. */
shr %cl, %VRDX
# ifdef USE_AS_STRNLEN
jnz L(page_cross_end)
movl $CHAR_PER_VEC, %eax
sub %ecx, %eax
cmp %rax, %rsi
ja L(align_more)
# else
jz L(align_more)
# endif
L(page_cross_end):
bsf %VRDX, %VRAX
# ifdef USE_AS_STRNLEN
cmpq %rsi, %rax
cmovnb %esi, %eax
# endif
ret
END (STRLEN)
#endif
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