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/* __memcmpeq optimized with EVEX.
Copyright (C) 2017-2021 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/>. */
#if IS_IN (libc)
/* __memcmpeq is implemented as:
1. Use ymm vector compares when possible. The only case where
vector compares is not possible for when size < VEC_SIZE
and loading from either s1 or s2 would cause a page cross.
2. Use xmm vector compare when size >= 8 bytes.
3. Optimistically compare up to first 4 * VEC_SIZE one at a
to check for early mismatches. Only do this if its guranteed the
work is not wasted.
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 MEMCMPEQ
# define MEMCMPEQ __memcmpeq_evex
# endif
# define VMOVU_MASK vmovdqu8
# define VMOVU vmovdqu64
# define VPCMP vpcmpub
# define VPTEST vptestmb
# define VEC_SIZE 32
# define PAGE_SIZE 4096
# define YMM0 ymm16
# define YMM1 ymm17
# define YMM2 ymm18
# define YMM3 ymm19
# define YMM4 ymm20
# define YMM5 ymm21
# define YMM6 ymm22
.section .text.evex, "ax", @progbits
ENTRY_P2ALIGN (MEMCMPEQ, 6)
# ifdef __ILP32__
/* Clear the upper 32 bits. */
movl %edx, %edx
# endif
cmp $VEC_SIZE, %RDX_LP
/* Fall through for [0, VEC_SIZE] as its the hottest. */
ja L(more_1x_vec)
/* Create mask of bytes that are guranteed to be valid because
of length (edx). Using masked movs allows us to skip checks for
page crosses/zero size. */
movl $-1, %ecx
bzhil %edx, %ecx, %ecx
kmovd %ecx, %k2
/* Use masked loads as VEC_SIZE could page cross where length
(edx) would not. */
VMOVU_MASK (%rsi), %YMM2{%k2}
VPCMP $4,(%rdi), %YMM2, %k1{%k2}
kmovd %k1, %eax
ret
L(last_1x_vec):
VMOVU -(VEC_SIZE * 1)(%rsi, %rdx), %YMM1
VPCMP $4, -(VEC_SIZE * 1)(%rdi, %rdx), %YMM1, %k1
kmovd %k1, %eax
L(return_neq0):
ret
.p2align 4
L(more_1x_vec):
/* From VEC + 1 to 2 * VEC. */
VMOVU (%rsi), %YMM1
/* Use compare not equals to directly check for mismatch. */
VPCMP $4,(%rdi), %YMM1, %k1
kmovd %k1, %eax
testl %eax, %eax
jnz L(return_neq0)
cmpq $(VEC_SIZE * 2), %rdx
jbe L(last_1x_vec)
/* Check second VEC no matter what. */
VMOVU VEC_SIZE(%rsi), %YMM2
VPCMP $4, VEC_SIZE(%rdi), %YMM2, %k1
kmovd %k1, %eax
testl %eax, %eax
jnz L(return_neq0)
/* Less than 4 * VEC. */
cmpq $(VEC_SIZE * 4), %rdx
jbe L(last_2x_vec)
/* Check third and fourth VEC no matter what. */
VMOVU (VEC_SIZE * 2)(%rsi), %YMM3
VPCMP $4,(VEC_SIZE * 2)(%rdi), %YMM3, %k1
kmovd %k1, %eax
testl %eax, %eax
jnz L(return_neq0)
VMOVU (VEC_SIZE * 3)(%rsi), %YMM4
VPCMP $4,(VEC_SIZE * 3)(%rdi), %YMM4, %k1
kmovd %k1, %eax
testl %eax, %eax
jnz L(return_neq0)
/* Go to 4x VEC loop. */
cmpq $(VEC_SIZE * 8), %rdx
ja L(more_8x_vec)
/* Handle remainder of size = 4 * VEC + 1 to 8 * VEC without any
branches. */
VMOVU -(VEC_SIZE * 4)(%rsi, %rdx), %YMM1
VMOVU -(VEC_SIZE * 3)(%rsi, %rdx), %YMM2
addq %rdx, %rdi
/* Wait to load from s1 until addressed adjust due to
unlamination. */
/* vpxor will be all 0s if s1 and s2 are equal. Otherwise it
will have some 1s. */
vpxorq -(VEC_SIZE * 4)(%rdi), %YMM1, %YMM1
/* Ternary logic to xor -(VEC_SIZE * 3)(%rdi) with YMM2 while
oring with YMM1. Result is stored in YMM1. */
vpternlogd $0xde, -(VEC_SIZE * 3)(%rdi), %YMM1, %YMM2
VMOVU -(VEC_SIZE * 2)(%rsi, %rdx), %YMM3
vpxorq -(VEC_SIZE * 2)(%rdi), %YMM3, %YMM3
/* Or together YMM1, YMM2, and YMM3 into YMM3. */
VMOVU -(VEC_SIZE)(%rsi, %rdx), %YMM4
vpxorq -(VEC_SIZE)(%rdi), %YMM4, %YMM4
/* Or together YMM2, YMM3, and YMM4 into YMM4. */
vpternlogd $0xfe, %YMM2, %YMM3, %YMM4
/* Compare YMM4 with 0. If any 1s s1 and s2 don't match. */
VPTEST %YMM4, %YMM4, %k1
kmovd %k1, %eax
ret
.p2align 4
L(more_8x_vec):
/* Set end of s1 in rdx. */
leaq -(VEC_SIZE * 4)(%rdi, %rdx), %rdx
/* rsi stores s2 - s1. This allows loop to only update one
pointer. */
subq %rdi, %rsi
/* Align s1 pointer. */
andq $-VEC_SIZE, %rdi
/* Adjust because first 4x vec where check already. */
subq $-(VEC_SIZE * 4), %rdi
.p2align 4
L(loop_4x_vec):
VMOVU (%rsi, %rdi), %YMM1
vpxorq (%rdi), %YMM1, %YMM1
VMOVU VEC_SIZE(%rsi, %rdi), %YMM2
vpternlogd $0xde,(VEC_SIZE)(%rdi), %YMM1, %YMM2
VMOVU (VEC_SIZE * 2)(%rsi, %rdi), %YMM3
vpxorq (VEC_SIZE * 2)(%rdi), %YMM3, %YMM3
VMOVU (VEC_SIZE * 3)(%rsi, %rdi), %YMM4
vpxorq (VEC_SIZE * 3)(%rdi), %YMM4, %YMM4
vpternlogd $0xfe, %YMM2, %YMM3, %YMM4
VPTEST %YMM4, %YMM4, %k1
kmovd %k1, %eax
testl %eax, %eax
jnz L(return_neq2)
subq $-(VEC_SIZE * 4), %rdi
cmpq %rdx, %rdi
jb L(loop_4x_vec)
subq %rdx, %rdi
VMOVU (VEC_SIZE * 3)(%rsi, %rdx), %YMM4
vpxorq (VEC_SIZE * 3)(%rdx), %YMM4, %YMM4
/* rdi has 4 * VEC_SIZE - remaining length. */
cmpl $(VEC_SIZE * 3), %edi
jae L(8x_last_1x_vec)
/* Load regardless of branch. */
VMOVU (VEC_SIZE * 2)(%rsi, %rdx), %YMM3
/* Ternary logic to xor (VEC_SIZE * 2)(%rdx) with YMM3 while
oring with YMM4. Result is stored in YMM4. */
vpternlogd $0xf6,(VEC_SIZE * 2)(%rdx), %YMM3, %YMM4
cmpl $(VEC_SIZE * 2), %edi
jae L(8x_last_2x_vec)
VMOVU VEC_SIZE(%rsi, %rdx), %YMM2
vpxorq VEC_SIZE(%rdx), %YMM2, %YMM2
VMOVU (%rsi, %rdx), %YMM1
vpxorq (%rdx), %YMM1, %YMM1
vpternlogd $0xfe, %YMM1, %YMM2, %YMM4
L(8x_last_1x_vec):
L(8x_last_2x_vec):
VPTEST %YMM4, %YMM4, %k1
kmovd %k1, %eax
L(return_neq2):
ret
.p2align 4,, 8
L(last_2x_vec):
VMOVU -(VEC_SIZE * 2)(%rsi, %rdx), %YMM1
vpxorq -(VEC_SIZE * 2)(%rdi, %rdx), %YMM1, %YMM1
VMOVU -(VEC_SIZE * 1)(%rsi, %rdx), %YMM2
vpternlogd $0xde, -(VEC_SIZE * 1)(%rdi, %rdx), %YMM1, %YMM2
VPTEST %YMM2, %YMM2, %k1
kmovd %k1, %eax
ret
/* 1 Bytes from next cache line. */
END (MEMCMPEQ)
#endif
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