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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Taken from Linux arch/riscv/lib/strncmp.S
*/
#include <linux/linkage.h>
#include <asm/asm.h>
ENTRY(__strncmp)
WEAK(strncmp)
.option push
.option arch,+zbb
/*
* Returns
* a0 - comparison result, like strncmp
*
* Parameters
* a0 - string1
* a1 - string2
* a2 - number of characters to compare
*
* Clobbers
* t0, t1, t2, t3, t4, t5, t6
*/
or t2, a0, a1
li t5, -1
and t2, t2, SZREG-1
add t4, a0, a2
bnez t2, 3f
/* Adjust limit for fast-path. */
andi t6, t4, -SZREG
/* Main loop for aligned string. */
.p2align 3
1:
bge a0, t6, 3f
REG_L t0, 0(a0)
REG_L t1, 0(a1)
orc.b t3, t0
bne t3, t5, 2f
orc.b t3, t1
bne t3, t5, 2f
addi a0, a0, SZREG
addi a1, a1, SZREG
beq t0, t1, 1b
/*
* Words don't match, and no null byte in the first
* word. Get bytes in big-endian order and compare.
*/
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
rev8 t0, t0
rev8 t1, t1
#endif
/* Synthesize (t0 >= t1) ? 1 : -1 in a branchless sequence. */
sltu a0, t0, t1
neg a0, a0
ori a0, a0, 1
ret
2:
/*
* Found a null byte.
* If words don't match, fall back to simple loop.
*/
bne t0, t1, 3f
/* Otherwise, strings are equal. */
li a0, 0
ret
/* Simple loop for misaligned strings. */
.p2align 3
3:
bge a0, t4, 5f
lbu t0, 0(a0)
lbu t1, 0(a1)
addi a0, a0, 1
addi a1, a1, 1
bne t0, t1, 4f
bnez t0, 3b
4:
sub a0, t0, t1
ret
5:
li a0, 0
ret
.option pop
END(__strncmp)
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