/* memcmp/wmemcmp optimized with AVX2.
Copyright (C) 2017-2018 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
<http://www.gnu.org/licenses/>. */
#if IS_IN (libc)
/* memcmp/wmemcmp is implemented as:
1. For size from 2 to 7 bytes, load as big endian with movbe and bswap
to avoid branches.
2. Use overlapping compare to avoid branch.
3. Use vector compare when size >= 4 bytes for memcmp or size >= 8
bytes for wmemcmp.
4. If size is 8 * VEC_SIZE or less, unroll the loop.
5. Compare 4 * VEC_SIZE at a time with the aligned first memory
area.
6. Use 2 vector compares when size is 2 * VEC_SIZE or less.
7. Use 4 vector compares when size is 4 * VEC_SIZE or less.
8. Use 8 vector compares when size is 8 * VEC_SIZE or less. */
# include <sysdep.h>
# ifndef MEMCMP
# define MEMCMP __memcmp_avx2_movbe
# endif
# ifdef USE_AS_WMEMCMP
# define VPCMPEQ vpcmpeqd
# else
# define VPCMPEQ vpcmpeqb
# endif
# ifndef VZEROUPPER
# define VZEROUPPER vzeroupper
# endif
# define VEC_SIZE 32
# define VEC_MASK ((1 << VEC_SIZE) - 1)
/* Warning!
wmemcmp has to use SIGNED comparison for elements.
memcmp has to use UNSIGNED comparison for elemnts.
*/
.section .text.avx,"ax",@progbits
ENTRY (MEMCMP)
# ifdef USE_AS_WMEMCMP
shl $2, %rdx
# endif
cmpq $VEC_SIZE, %rdx
jb L(less_vec)
/* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */
vmovdqu (%rsi), %ymm2
VPCMPEQ (%rdi), %ymm2, %ymm2
vpmovmskb %ymm2, %eax
subl $VEC_MASK, %eax
jnz L(first_vec)
cmpq $(VEC_SIZE * 2), %rdx
jbe L(last_vec)
VPCMPEQ %ymm0, %ymm0, %ymm0
/* More than 2 * VEC. */
cmpq $(VEC_SIZE * 8), %rdx
ja L(more_8x_vec)
cmpq $(VEC_SIZE * 4), %rdx
jb L(last_4x_vec)
/* From 4 * VEC to 8 * VEC, inclusively. */
vmovdqu (%rsi), %ymm1
VPCMPEQ (%rdi), %ymm1, %ymm1
vmovdqu VEC_SIZE(%rsi), %ymm2
VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2
vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3
VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3
vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4
VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4
vpand %ymm1, %ymm2, %ymm5
vpand %ymm3, %ymm4, %ymm6
vpand %ymm5, %ymm6, %ymm5
vptest %ymm0, %ymm5
jnc L(4x_vec_end)
leaq -(4 * VEC_SIZE)(%rdi, %rdx), %rdi
leaq -(4 * VEC_SIZE)(%rsi, %rdx), %rsi
vmovdqu (%rsi), %ymm1
VPCMPEQ (%rdi), %ymm1, %ymm1
vmovdqu VEC_SIZE(%rsi), %ymm2
VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2
vpand %ymm2, %ymm1, %ymm5
vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3
VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3
vpand %ymm3, %ymm5, %ymm5
vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4
VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4
vpand %ymm4, %ymm5, %ymm5
vptest %ymm0, %ymm5
jnc L(4x_vec_end)
xorl %eax, %eax
VZEROUPPER
ret
.p2align 4
L(last_2x_vec):
/* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */
vmovdqu (%rsi), %ymm2
VPCMPEQ (%rdi), %ymm2, %ymm2
vpmovmskb %ymm2, %eax
subl $VEC_MASK, %eax
jnz L(first_vec)
L(last_vec):
/* Use overlapping loads to avoid branches. */
leaq -VEC_SIZE(%rdi, %rdx), %rdi
leaq -VEC_SIZE(%rsi, %rdx), %rsi
vmovdqu (%rsi), %ymm2
VPCMPEQ (%rdi), %ymm2, %ymm2
vpmovmskb %ymm2, %eax
subl $VEC_MASK, %eax
jnz L(first_vec)
VZEROUPPER
ret
.p2align 4
L(first_vec):
/* A byte or int32 is different within 16 or 32 bytes. */
tzcntl %eax, %ecx
# ifdef USE_AS_WMEMCMP
xorl %eax, %eax
movl (%rdi, %rcx), %edx
cmpl (%rsi, %rcx), %edx
L(wmemcmp_return):
setl %al
negl %eax
orl $1, %eax
# else
movzbl (%rdi, %rcx), %eax
movzbl (%rsi, %rcx), %edx
sub %edx, %eax
# endif
VZEROUPPER
ret
# ifdef USE_AS_WMEMCMP
.p2align 4
L(4):
xorl %eax, %eax
movl (%rdi), %edx
cmpl (%rsi), %edx
jne L(wmemcmp_return)
ret
# else
.p2align 4
L(between_4_7):
/* Load as big endian with overlapping movbe to avoid branches. */
movbe (%rdi), %eax
movbe (%rsi), %ecx
shlq $32, %rax
shlq $32, %rcx
movbe -4(%rdi, %rdx), %edi
movbe -4(%rsi, %rdx), %esi
orq %rdi, %rax
orq %rsi, %rcx
subq %rcx, %rax
je L(exit)
sbbl %eax, %eax
orl $1, %eax
ret
.p2align 4
L(exit):
ret
.p2align 4
L(between_2_3):
/* Load as big endian to avoid branches. */
movzwl (%rdi), %eax
movzwl (%rsi), %ecx
shll $8, %eax
shll $8, %ecx
bswap %eax
bswap %ecx
movb -1(%rdi, %rdx), %al
movb -1(%rsi, %rdx), %cl
/* Subtraction is okay because the upper 8 bits are zero. */
subl %ecx, %eax
ret
.p2align 4
L(1):
movzbl (%rdi), %eax
movzbl (%rsi), %ecx
subl %ecx, %eax
ret
# endif
.p2align 4
L(zero):
xorl %eax, %eax
ret
.p2align 4
L(less_vec):
# ifdef USE_AS_WMEMCMP
/* It can only be 0, 4, 8, 12, 16, 20, 24, 28 bytes. */
cmpb $4, %dl
je L(4)
jb L(zero)
# else
cmpb $1, %dl
je L(1)
jb L(zero)
cmpb $4, %dl
jb L(between_2_3)
cmpb $8, %dl
jb L(between_4_7)
# endif
cmpb $16, %dl
jae L(between_16_31)
/* It is between 8 and 15 bytes. */
vmovq (%rdi), %xmm1
vmovq (%rsi), %xmm2
VPCMPEQ %xmm1, %xmm2, %xmm2
vpmovmskb %xmm2, %eax
subl $0xffff, %eax
jnz L(first_vec)
/* Use overlapping loads to avoid branches. */
leaq -8(%rdi, %rdx), %rdi
leaq -8(%rsi, %rdx), %rsi
vmovq (%rdi), %xmm1
vmovq (%rsi), %xmm2
VPCMPEQ %xmm1, %xmm2, %xmm2
vpmovmskb %xmm2, %eax
subl $0xffff, %eax
jnz L(first_vec)
ret
.p2align 4
L(between_16_31):
/* From 16 to 31 bytes. No branch when size == 16. */
vmovdqu (%rsi), %xmm2
VPCMPEQ (%rdi), %xmm2, %xmm2
vpmovmskb %xmm2, %eax
subl $0xffff, %eax
jnz L(first_vec)
/* Use overlapping loads to avoid branches. */
leaq -16(%rdi, %rdx), %rdi
leaq -16(%rsi, %rdx), %rsi
vmovdqu (%rsi), %xmm2
VPCMPEQ (%rdi), %xmm2, %xmm2
vpmovmskb %xmm2, %eax
subl $0xffff, %eax
jnz L(first_vec)
ret
.p2align 4
L(more_8x_vec):
/* More than 8 * VEC. Check the first VEC. */
vmovdqu (%rsi), %ymm2
VPCMPEQ (%rdi), %ymm2, %ymm2
vpmovmskb %ymm2, %eax
subl $VEC_MASK, %eax
jnz L(first_vec)
/* Align the first memory area for aligned loads in the loop.
Compute how much the first memory area is misaligned. */
movq %rdi, %rcx
andl $(VEC_SIZE - 1), %ecx
/* Get the negative of offset for alignment. */
subq $VEC_SIZE, %rcx
/* Adjust the second memory area. */
subq %rcx, %rsi
/* Adjust the first memory area which should be aligned now. */
subq %rcx, %rdi
/* Adjust length. */
addq %rcx, %rdx
L(loop_4x_vec):
/* Compare 4 * VEC at a time forward. */
vmovdqu (%rsi), %ymm1
VPCMPEQ (%rdi), %ymm1, %ymm1
vmovdqu VEC_SIZE(%rsi), %ymm2
VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2
vpand %ymm2, %ymm1, %ymm5
vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3
VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3
vpand %ymm3, %ymm5, %ymm5
vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4
VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4
vpand %ymm4, %ymm5, %ymm5
vptest %ymm0, %ymm5
jnc L(4x_vec_end)
addq $(VEC_SIZE * 4), %rdi
addq $(VEC_SIZE * 4), %rsi
subq $(VEC_SIZE * 4), %rdx
cmpq $(VEC_SIZE * 4), %rdx
jae L(loop_4x_vec)
/* Less than 4 * VEC. */
cmpq $VEC_SIZE, %rdx
jbe L(last_vec)
cmpq $(VEC_SIZE * 2), %rdx
jbe L(last_2x_vec)
L(last_4x_vec):
/* From 2 * VEC to 4 * VEC. */
vmovdqu (%rsi), %ymm2
VPCMPEQ (%rdi), %ymm2, %ymm2
vpmovmskb %ymm2, %eax
subl $VEC_MASK, %eax
jnz L(first_vec)
addq $VEC_SIZE, %rdi
addq $VEC_SIZE, %rsi
vmovdqu (%rsi), %ymm2
VPCMPEQ (%rdi), %ymm2, %ymm2
vpmovmskb %ymm2, %eax
subl $VEC_MASK, %eax
jnz L(first_vec)
/* Use overlapping loads to avoid branches. */
leaq -(3 * VEC_SIZE)(%rdi, %rdx), %rdi
leaq -(3 * VEC_SIZE)(%rsi, %rdx), %rsi
vmovdqu (%rsi), %ymm2
VPCMPEQ (%rdi), %ymm2, %ymm2
vpmovmskb %ymm2, %eax
subl $VEC_MASK, %eax
jnz L(first_vec)
addq $VEC_SIZE, %rdi
addq $VEC_SIZE, %rsi
vmovdqu (%rsi), %ymm2
VPCMPEQ (%rdi), %ymm2, %ymm2
vpmovmskb %ymm2, %eax
subl $VEC_MASK, %eax
jnz L(first_vec)
VZEROUPPER
ret
.p2align 4
L(4x_vec_end):
vpmovmskb %ymm1, %eax
subl $VEC_MASK, %eax
jnz L(first_vec)
vpmovmskb %ymm2, %eax
subl $VEC_MASK, %eax
jnz L(first_vec_x1)
vpmovmskb %ymm3, %eax
subl $VEC_MASK, %eax
jnz L(first_vec_x2)
vpmovmskb %ymm4, %eax
subl $VEC_MASK, %eax
tzcntl %eax, %ecx
# ifdef USE_AS_WMEMCMP
xorl %eax, %eax
movl (VEC_SIZE * 3)(%rdi, %rcx), %edx
cmpl (VEC_SIZE * 3)(%rsi, %rcx), %edx
jmp L(wmemcmp_return)
# else
movzbl (VEC_SIZE * 3)(%rdi, %rcx), %eax
movzbl (VEC_SIZE * 3)(%rsi, %rcx), %edx
sub %edx, %eax
# endif
VZEROUPPER
ret
.p2align 4
L(first_vec_x1):
tzcntl %eax, %ecx
# ifdef USE_AS_WMEMCMP
xorl %eax, %eax
movl VEC_SIZE(%rdi, %rcx), %edx
cmpl VEC_SIZE(%rsi, %rcx), %edx
jmp L(wmemcmp_return)
# else
movzbl VEC_SIZE(%rdi, %rcx), %eax
movzbl VEC_SIZE(%rsi, %rcx), %edx
sub %edx, %eax
# endif
VZEROUPPER
ret
.p2align 4
L(first_vec_x2):
tzcntl %eax, %ecx
# ifdef USE_AS_WMEMCMP
xorl %eax, %eax
movl (VEC_SIZE * 2)(%rdi, %rcx), %edx
cmpl (VEC_SIZE * 2)(%rsi, %rcx), %edx
jmp L(wmemcmp_return)
# else
movzbl (VEC_SIZE * 2)(%rdi, %rcx), %eax
movzbl (VEC_SIZE * 2)(%rsi, %rcx), %edx
sub %edx, %eax
# endif
VZEROUPPER
ret
END (MEMCMP)
#endif