zyfeier commented on code in PR #8042: URL: https://github.com/apache/nuttx/pull/8042#discussion_r1064313975
########## libs/libc/machine/risc-v/gnu/arch_strcmp.S: ########## @@ -0,0 +1,184 @@ +/**************************************************************************** + * libs/libc/machine/risc-v/gnu/arch_strcmp.S + * + * Copyright (c) 2017 SiFive Inc. All rights reserved. + * + * This copyrighted material is made available to anyone wishing to use, + * modify, copy, or redistribute it subject to the terms and conditions + * of the FreeBSD License. This program is distributed in the hope that + * it will be useful, but WITHOUT ANY WARRANTY expressed or implied, + * including the implied warranties of MERCHANTABILITY or FITNESS FOR + * A PARTICULAR PURPOSE. A copy of this license is available at + * http://www.opensource.org/licenses. + * + ****************************************************************************/ + +#include "asm.h" + +.text +.globl strcmp +.type strcmp, @function +strcmp: + or a4, a0, a1 + li t2, -1 + and a4, a4, SZREG-1 + bnez a4, .Lmisaligned + +#if SZREG == 4 + li a5, 0x7f7f7f7f +#else + ld a5, mask +#endif + + .macro check_one_word i n + REG_L a2, \i*SZREG(a0) + REG_L a3, \i*SZREG(a1) + + and t0, a2, a5 + or t1, a2, a5 + add t0, t0, a5 + or t0, t0, t1 + + bne t0, t2, .Lnull\i + .if \i+1-\n + bne a2, a3, .Lmismatch + .else + add a0, a0, \n*SZREG + add a1, a1, \n*SZREG + beq a2, a3, .Lloop + # fall through to .Lmismatch + .endif + .endm + + .macro foundnull i n + .ifne \i + .Lnull\i: + add a0, a0, \i*SZREG + add a1, a1, \i*SZREG + .ifeq \i-1 + .Lnull0: + .endif + bne a2, a3, .Lmisaligned + li a0, 0 + ret + .endif + .endm + +.Lloop: + # examine full words at a time, favoring strings of a couple dozen chars +#if __riscv_xlen == 32 + check_one_word 0 5 + check_one_word 1 5 + check_one_word 2 5 + check_one_word 3 5 + check_one_word 4 5 +#else + check_one_word 0 3 + check_one_word 1 3 + check_one_word 2 3 +#endif + # backwards branch to .Lloop contained above + +.Lmismatch: + # words don't match, but a2 has no null byte. + +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ + +#if __riscv_xlen == 64 + sll a4, a2, 48 + sll a5, a3, 48 + bne a4, a5, .Lmismatch_upper + sll a4, a2, 32 + sll a5, a3, 32 + bne a4, a5, .Lmismatch_upper +#endif + sll a4, a2, 16 + sll a5, a3, 16 + bne a4, a5, .Lmismatch_upper + + srl a4, a2, 8*SZREG-16 + srl a5, a3, 8*SZREG-16 + sub a0, a4, a5 + and a1, a0, 0xff + bnez a1, 1f + ret + +.Lmismatch_upper: + srl a4, a4, 8*SZREG-16 + srl a5, a5, 8*SZREG-16 + sub a0, a4, a5 + and a1, a0, 0xff + bnez a1, 1f + ret + +1:and a4, a4, 0xff + and a5, a5, 0xff + sub a0, a4, a5 + ret + +#else + +#if __riscv_xlen == 64 + srl a4, a2, 48 + srl a5, a3, 48 + bne a4, a5, .Lmismatch_lower + srl a4, a2, 32 + srl a5, a3, 32 + bne a4, a5, .Lmismatch_lower +#endif + srl a4, a2, 16 + srl a5, a3, 16 + bne a4, a5, .Lmismatch_lower + + srl a4, a2, 8 + srl a5, a3, 8 + bne a4, a5, 1f + and a4, a2, 0xff + and a5, a3, 0xff +1:sub a0, a4, a5 + ret + +.Lmismatch_lower: + srl a2, a4, 8 + srl a3, a5, 8 + bne a2, a3, 1f + and a2, a4, 0xff + and a3, a5, 0xff +1:sub a0, a2, a3 + ret + +#endif + +.Lmisaligned: + # misaligned + lbu a2, 0(a0) + lbu a3, 0(a1) + add a0, a0, 1 + add a1, a1, 1 + bne a2, a3, 1f + bnez a2, .Lmisaligned + +1: + sub a0, a2, a3 + ret + + # cases in which a null byte was detected +#if __riscv_xlen == 32 Review Comment: __riscv_xlen is gcc predefined macros, it can work well too. Can't we use macros predefined by the compiler? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
