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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 | /* 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 strncmp(const char *cs, const char *ct, size_t count) */ SYM_FUNC_START(strncmp) ALTERNATIVE("nop", "j strncmp_zbb", 0, RISCV_ISA_EXT_ZBB, CONFIG_RISCV_ISA_ZBB) /* * Returns * a0 - comparison result, value like strncmp * * Parameters * a0 - string1 * a1 - string2 * a2 - number of characters to compare * * Clobbers * t0, t1, t2 */ li t2, 0 1: beq a2, t2, 2f lbu t0, 0(a0) lbu t1, 0(a1) addi a0, a0, 1 addi a1, a1, 1 bne t0, t1, 3f addi t2, t2, 1 bnez t0, 1b 2: li a0, 0 ret 3: /* * strncmp only needs to return (< 0, 0, > 0) values * not necessarily -1, 0, +1 */ sub a0, t0, t1 ret /* * Variant of strncmp using the ZBB extension if available */ #ifdef CONFIG_RISCV_ISA_ZBB strncmp_zbb: .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. */ #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: 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 #endif SYM_FUNC_END(strncmp) |