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/* SPDX-License-Identifier: GPL-2.0-only */
/* This code originates from Linux 5.19 */
/*
* Implement memmove(). This can handle overlap between src and dst.
*
* Input:
* rdi: dest
* rsi: src
* rdx: count
*
* Output:
* rax: dest
*/
.global memmove
memmove:
mov %rdi, %rax
/* Decide forward/backward copy mode */
cmp %rdi, %rsi
jge .Lmemmove_begin_forward
mov %rsi, %r8
add %rdx, %r8
cmp %rdi, %r8
jg 2f
/* Don't optimize for FSRM and ERMS like Linux */
.Lmemmove_begin_forward:
cmp $0x20, %rdx
jb 1f
/*
* movsq instruction have many startup latency
* so we handle small size by general register.
*/
cmp $680, %rdx
jb 3f
/*
* movsq instruction is only good for aligned case.
*/
cmpb %dil, %sil
je 4f
3:
sub $0x20, %rdx
/*
* We gobble 32 bytes forward in each loop.
*/
5:
sub $0x20, %rdx
movq 0*8(%rsi), %r11
movq 1*8(%rsi), %r10
movq 2*8(%rsi), %r9
movq 3*8(%rsi), %r8
leaq 4*8(%rsi), %rsi
movq %r11, 0*8(%rdi)
movq %r10, 1*8(%rdi)
movq %r9, 2*8(%rdi)
movq %r8, 3*8(%rdi)
leaq 4*8(%rdi), %rdi
jae 5b
addq $0x20, %rdx
jmp 1f
/*
* Handle data forward by movsq.
*/
.p2align 4
4:
movq %rdx, %rcx
movq -8(%rsi, %rdx), %r11
lea -8(%rdi, %rdx), %r10
shrq $3, %rcx
rep movsq
movq %r11, (%r10)
jmp 13f
.Lmemmove_end_forward:
/*
* Handle data backward by movsq.
*/
.p2align 4
7:
movq %rdx, %rcx
movq (%rsi), %r11
movq %rdi, %r10
leaq -8(%rsi, %rdx), %rsi
leaq -8(%rdi, %rdx), %rdi
shrq $3, %rcx
std
rep movsq
cld
movq %r11, (%r10)
jmp 13f
/*
* Start to prepare for backward copy.
*/
.p2align 4
2:
cmp $0x20, %rdx
jb 1f
cmp $680, %rdx
jb 6f
cmp %dil, %sil
je 7b
6:
/*
* Calculate copy position to tail.
*/
addq %rdx, %rsi
addq %rdx, %rdi
subq $0x20, %rdx
/*
* We gobble 32 bytes backward in each loop.
*/
8:
subq $0x20, %rdx
movq -1*8(%rsi), %r11
movq -2*8(%rsi), %r10
movq -3*8(%rsi), %r9
movq -4*8(%rsi), %r8
leaq -4*8(%rsi), %rsi
movq %r11, -1*8(%rdi)
movq %r10, -2*8(%rdi)
movq %r9, -3*8(%rdi)
movq %r8, -4*8(%rdi)
leaq -4*8(%rdi), %rdi
jae 8b
/*
* Calculate copy position to head.
*/
addq $0x20, %rdx
subq %rdx, %rsi
subq %rdx, %rdi
1:
cmpq $16, %rdx
jb 9f
/*
* Move data from 16 bytes to 31 bytes.
*/
movq 0*8(%rsi), %r11
movq 1*8(%rsi), %r10
movq -2*8(%rsi, %rdx), %r9
movq -1*8(%rsi, %rdx), %r8
movq %r11, 0*8(%rdi)
movq %r10, 1*8(%rdi)
movq %r9, -2*8(%rdi, %rdx)
movq %r8, -1*8(%rdi, %rdx)
jmp 13f
.p2align 4
9:
cmpq $8, %rdx
jb 10f
/*
* Move data from 8 bytes to 15 bytes.
*/
movq 0*8(%rsi), %r11
movq -1*8(%rsi, %rdx), %r10
movq %r11, 0*8(%rdi)
movq %r10, -1*8(%rdi, %rdx)
jmp 13f
10:
cmpq $4, %rdx
jb 11f
/*
* Move data from 4 bytes to 7 bytes.
*/
movl (%rsi), %r11d
movl -4(%rsi, %rdx), %r10d
movl %r11d, (%rdi)
movl %r10d, -4(%rdi, %rdx)
jmp 13f
11:
cmp $2, %rdx
jb 12f
/*
* Move data from 2 bytes to 3 bytes.
*/
movw (%rsi), %r11w
movw -2(%rsi, %rdx), %r10w
movw %r11w, (%rdi)
movw %r10w, -2(%rdi, %rdx)
jmp 13f
12:
cmp $1, %rdx
jb 13f
/*
* Move data for 1 byte.
*/
movb (%rsi), %r11b
movb %r11b, (%rdi)
13:
RET
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