| 1 | /* SPDX-License-Identifier: GPL-2.0-only */
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| 2 |
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| 3 | |
| 4 | |
| 5 | |
| 6 | |
| 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_CFG("nop", "j strcmp_zbb", 0, RISCV_ISA_EXT_ZBB,
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| 12 | IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB))
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| 13 |
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| 14 | /*
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| 15 | * Returns
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| 16 | * a0 - comparison result, value like strcmp
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| 17 | *
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| 18 | * Parameters
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| 19 | * a0 - string1
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| 20 | * a1 - string2
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| 21 | *
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| 22 | * Clobbers
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| 23 | * t0, t1
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| 24 | */
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| 25 | 1:
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| 26 | lbu t0, 0(a0)
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| 27 | lbu t1, 0(a1)
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| 28 | addi a0, a0, 1
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| 29 | addi a1, a1, 1
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| 30 | bne t0, t1, 2f
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| 31 | bnez t0, 1b
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| 32 | li a0, 0
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| 33 | ret
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| 34 | 2:
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| 35 | /*
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| 36 | * strcmp only needs to return (< 0, 0, > 0) values
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| 37 | * not necessarily -1, 0, +1
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| 38 | */
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| 39 | sub a0, t0, t1
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| 40 | ret
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| 41 |
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| 42 | /*
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| 43 | * Variant of strcmp using the ZBB extension if available.
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| 44 | * The code was published as part of the bitmanip manual
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| 45 | * in Appendix A.
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| 46 | */
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| 47 | |
| 48 | strcmp_zbb:
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| 49 |
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| 50 | .option push
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| 51 | .option arch,+zbb
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| 52 |
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| 53 | /*
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| 54 | * Returns
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| 55 | * a0 - comparison result, value like strcmp
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| 56 | *
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| 57 | * Parameters
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| 58 | * a0 - string1
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| 59 | * a1 - string2
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| 60 | *
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| 61 | * Clobbers
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| 62 | * t0, t1, t2, t3, t4
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| 63 | */
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| 64 |
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| 65 | or t2, a0, a1
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| 66 | li t4, -1
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| 67 | and t2, t2, SZREG-1
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| 68 | bnez t2, 3f
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| 69 |
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| 70 | /* Main loop for aligned string. */
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| 71 | .p2align 3
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| 72 | 1:
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| 73 | REG_L t0, 0(a0)
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| 74 | REG_L t1, 0(a1)
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| 75 | orc.b t3, t0
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| 76 | bne t3, t4, 2f
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| 77 | addi a0, a0, SZREG
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| 78 | addi a1, a1, SZREG
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| 79 | beq t0, t1, 1b
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| 80 |
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| 81 | /*
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| 82 | * Words don't match, and no null byte in the first
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| 83 | * word. Get bytes in big-endian order and compare.
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| 84 | */
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| 85 | #ifndef CONFIG_CPU_BIG_ENDIAN
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| 86 | rev8 t0, t0
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| 87 | rev8 t1, t1
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| 88 | #endif
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| 89 |
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| 90 | /* Synthesize (t0 >= t1) ? 1 : -1 in a branchless sequence. */
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| 91 | sltu a0, t0, t1
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| 92 | neg a0, a0
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| 93 | ori a0, a0, 1
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| 94 | ret
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| 95 |
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| 96 | 2:
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| 97 | /*
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| 98 | * Found a null byte.
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| 99 | * If words don't match, fall back to simple loop.
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| 100 | */
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| 101 | bne t0, t1, 3f
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| 102 |
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| 103 | /* Otherwise, strings are equal. */
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| 104 | li a0, 0
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| 105 | ret
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| 106 |
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| 107 | /* Simple loop for misaligned strings. */
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| 108 | .p2align 3
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| 109 | 3:
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| 110 | lbu t0, 0(a0)
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| 111 | lbu t1, 0(a1)
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| 112 | addi a0, a0, 1
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| 113 | addi a1, a1, 1
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| 114 | bne t0, t1, 4f
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| 115 | bnez t0, 3b
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| 116 |
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| 117 | 4:
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| 118 | sub a0, t0, t1
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| 119 | ret
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| 120 |
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| 121 | .option pop
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| 122 | |
| 123 | SYM_FUNC_END(strcmp)
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| 124 | SYM_FUNC_ALIAS(__pi_strcmp, strcmp)
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| 125 | EXPORT_SYMBOL(strcmp)
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