| 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
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| 2 | |
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| 3 | #include <linux/linkage.h> |
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| 4 | #include <asm/asm.h> |
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| 5 | #include <asm/alternative-macros.h> |
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| 6 | #include <asm/hwcap.h> |
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| 7 | |
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| 8 | /* int strcmp(const char *cs, const char *ct) */ |
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| 9 | SYM_FUNC_START(strcmp) |
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| 10 | |
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| 11 | ALTERNATIVE("nop" , "j strcmp_zbb" , 0, RISCV_ISA_EXT_ZBB, CONFIG_RISCV_ISA_ZBB) |
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| 12 | |
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| 13 | /* |
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| 14 | * Returns |
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| 15 | * a0 - comparison result, value like strcmp |
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| 16 | * |
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| 17 | * Parameters |
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| 18 | * a0 - string1 |
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| 19 | * a1 - string2 |
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| 20 | * |
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| 21 | * Clobbers |
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| 22 | * t0, t1 |
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| 23 | */ |
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| 24 | 1: |
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| 25 | lbu t0, 0(a0) |
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| 26 | lbu t1, 0(a1) |
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| 27 | addi a0, a0, 1 |
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| 28 | addi a1, a1, 1 |
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| 29 | bne t0, t1, 2f |
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| 30 | bnez t0, 1b |
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| 31 | li a0, 0 |
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| 32 | ret |
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| 33 | 2: |
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| 34 | /* |
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| 35 | * strcmp only needs to return (< 0, 0, > 0) values |
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| 36 | * not necessarily -1, 0, +1 |
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| 37 | */ |
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| 38 | sub a0, t0, t1 |
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| 39 | ret |
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| 40 | |
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| 41 | /* |
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| 42 | * Variant of strcmp using the ZBB extension if available. |
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| 43 | * The code was published as part of the bitmanip manual |
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| 44 | * in Appendix A. |
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| 45 | */ |
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| 46 | #ifdef CONFIG_RISCV_ISA_ZBB |
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| 47 | strcmp_zbb: |
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| 48 | |
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| 49 | .option push |
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| 50 | .option arch,+zbb |
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| 51 | |
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| 52 | /* |
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| 53 | * Returns |
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| 54 | * a0 - comparison result, value like strcmp |
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| 55 | * |
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| 56 | * Parameters |
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| 57 | * a0 - string1 |
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| 58 | * a1 - string2 |
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| 59 | * |
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| 60 | * Clobbers |
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| 61 | * t0, t1, t2, t3, t4 |
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| 62 | */ |
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| 63 | |
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| 64 | or t2, a0, a1 |
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| 65 | li t4, -1 |
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| 66 | and t2, t2, SZREG-1 |
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| 67 | bnez t2, 3f |
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| 68 | |
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| 69 | /* Main loop for aligned string. */ |
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| 70 | .p2align 3 |
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| 71 | 1: |
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| 72 | REG_L t0, 0(a0) |
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| 73 | REG_L t1, 0(a1) |
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| 74 | orc.b t3, t0 |
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| 75 | bne t3, t4, 2f |
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| 76 | addi a0, a0, SZREG |
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| 77 | addi a1, a1, SZREG |
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| 78 | beq t0, t1, 1b |
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| 79 | |
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| 80 | /* |
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| 81 | * Words don't match, and no null byte in the first |
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| 82 | * word. Get bytes in big-endian order and compare. |
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| 83 | */ |
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| 84 | #ifndef CONFIG_CPU_BIG_ENDIAN |
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| 85 | rev8 t0, t0 |
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| 86 | rev8 t1, t1 |
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| 87 | #endif |
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| 88 | |
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| 89 | /* Synthesize (t0 >= t1) ? 1 : -1 in a branchless sequence. */ |
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| 90 | sltu a0, t0, t1 |
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| 91 | neg a0, a0 |
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| 92 | ori a0, a0, 1 |
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| 93 | ret |
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| 94 | |
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| 95 | 2: |
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| 96 | /* |
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| 97 | * Found a null byte. |
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| 98 | * If words don't match, fall back to simple loop. |
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| 99 | */ |
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| 100 | bne t0, t1, 3f |
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| 101 | |
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| 102 | /* Otherwise, strings are equal. */ |
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| 103 | li a0, 0 |
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| 104 | ret |
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| 105 | |
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| 106 | /* Simple loop for misaligned strings. */ |
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| 107 | .p2align 3 |
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| 108 | 3: |
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| 109 | lbu t0, 0(a0) |
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| 110 | lbu t1, 0(a1) |
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| 111 | addi a0, a0, 1 |
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| 112 | addi a1, a1, 1 |
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| 113 | bne t0, t1, 4f |
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| 114 | bnez t0, 3b |
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| 115 | |
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| 116 | 4: |
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| 117 | sub a0, t0, t1 |
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| 118 | ret |
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| 119 | |
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| 120 | .option pop |
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| 121 | #endif |
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| 122 | SYM_FUNC_END(strcmp) |
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| 123 | |
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