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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 | /* 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) |