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/* SPDX-License-Identifier: GPL-2.0-only */
#include <linux/linkage.h>
#include <asm/asm.h>
#include <asm/alternative-macros.h>
#include <asm/hwcap.h>
/* int strcmp(const char *cs, const char *ct) */
SYM_FUNC_START(strcmp)
ALTERNATIVE("nop", "j strcmp_zbb", 0, RISCV_ISA_EXT_ZBB, CONFIG_RISCV_ISA_ZBB)
/*
* Returns
* a0 - comparison result, value like strcmp
*
* Parameters
* a0 - string1
* a1 - string2
*
* Clobbers
* t0, t1
*/
1:
lbu t0, 0(a0)
lbu t1, 0(a1)
addi a0, a0, 1
addi a1, a1, 1
bne t0, t1, 2f
bnez t0, 1b
li a0, 0
ret
2:
/*
* strcmp only needs to return (< 0, 0, > 0) values
* not necessarily -1, 0, +1
*/
sub a0, t0, t1
ret
/*
* Variant of strcmp using the ZBB extension if available.
* The code was published as part of the bitmanip manual
* in Appendix A.
*/
#ifdef CONFIG_RISCV_ISA_ZBB
strcmp_zbb:
.option push
.option arch,+zbb
/*
* Returns
* a0 - comparison result, value like strcmp
*
* Parameters
* a0 - string1
* a1 - string2
*
* Clobbers
* t0, t1, t2, t3, t4
*/
or t2, a0, a1
li t4, -1
and t2, t2, SZREG-1
bnez t2, 3f
/* Main loop for aligned string. */
.p2align 3
1:
REG_L t0, 0(a0)
REG_L t1, 0(a1)
orc.b t3, t0
bne t3, t4, 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.
*/
#ifndef CONFIG_CPU_BIG_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:
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
.option pop
#endif
SYM_FUNC_END(strcmp)
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