134 lines
2.2 KiB
ArmAsm
134 lines
2.2 KiB
ArmAsm
/* 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 strlen(const char *s) */
|
|
SYM_FUNC_START(strlen)
|
|
|
|
ALTERNATIVE("nop", "j strlen_zbb", 0, RISCV_ISA_EXT_ZBB, CONFIG_RISCV_ISA_ZBB)
|
|
|
|
/*
|
|
* Returns
|
|
* a0 - string length
|
|
*
|
|
* Parameters
|
|
* a0 - String to measure
|
|
*
|
|
* Clobbers:
|
|
* t0, t1
|
|
*/
|
|
mv t1, a0
|
|
1:
|
|
lbu t0, 0(t1)
|
|
beqz t0, 2f
|
|
addi t1, t1, 1
|
|
j 1b
|
|
2:
|
|
sub a0, t1, a0
|
|
ret
|
|
|
|
/*
|
|
* Variant of strlen using the ZBB extension if available
|
|
*/
|
|
#ifdef CONFIG_RISCV_ISA_ZBB
|
|
strlen_zbb:
|
|
|
|
#ifdef CONFIG_CPU_BIG_ENDIAN
|
|
# define CZ clz
|
|
# define SHIFT sll
|
|
#else
|
|
# define CZ ctz
|
|
# define SHIFT srl
|
|
#endif
|
|
|
|
.option push
|
|
.option arch,+zbb
|
|
|
|
/*
|
|
* Returns
|
|
* a0 - string length
|
|
*
|
|
* Parameters
|
|
* a0 - String to measure
|
|
*
|
|
* Clobbers
|
|
* t0, t1, t2, t3
|
|
*/
|
|
|
|
/* Number of irrelevant bytes in the first word. */
|
|
andi t2, a0, SZREG-1
|
|
|
|
/* Align pointer. */
|
|
andi t0, a0, -SZREG
|
|
|
|
li t3, SZREG
|
|
sub t3, t3, t2
|
|
slli t2, t2, 3
|
|
|
|
/* Get the first word. */
|
|
REG_L t1, 0(t0)
|
|
|
|
/*
|
|
* Shift away the partial data we loaded to remove the irrelevant bytes
|
|
* preceding the string with the effect of adding NUL bytes at the
|
|
* end of the string's first word.
|
|
*/
|
|
SHIFT t1, t1, t2
|
|
|
|
/* Convert non-NUL into 0xff and NUL into 0x00. */
|
|
orc.b t1, t1
|
|
|
|
/* Convert non-NUL into 0x00 and NUL into 0xff. */
|
|
not t1, t1
|
|
|
|
/*
|
|
* Search for the first set bit (corresponding to a NUL byte in the
|
|
* original chunk).
|
|
*/
|
|
CZ t1, t1
|
|
|
|
/*
|
|
* The first chunk is special: compare against the number
|
|
* of valid bytes in this chunk.
|
|
*/
|
|
srli a0, t1, 3
|
|
bgtu t3, a0, 2f
|
|
|
|
/* Prepare for the word comparison loop. */
|
|
addi t2, t0, SZREG
|
|
li t3, -1
|
|
|
|
/*
|
|
* Our critical loop is 4 instructions and processes data in
|
|
* 4 byte or 8 byte chunks.
|
|
*/
|
|
.p2align 3
|
|
1:
|
|
REG_L t1, SZREG(t0)
|
|
addi t0, t0, SZREG
|
|
orc.b t1, t1
|
|
beq t1, t3, 1b
|
|
|
|
not t1, t1
|
|
CZ t1, t1
|
|
srli t1, t1, 3
|
|
|
|
/* Get number of processed bytes. */
|
|
sub t2, t0, t2
|
|
|
|
/* Add number of characters in the first word. */
|
|
add a0, a0, t2
|
|
|
|
/* Add number of characters in the last word. */
|
|
add a0, a0, t1
|
|
2:
|
|
ret
|
|
|
|
.option pop
|
|
#endif
|
|
SYM_FUNC_END(strlen)
|
|
SYM_FUNC_ALIAS(__pi_strlen, strlen)
|