124 lines
2.0 KiB
ArmAsm
124 lines
2.0 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0-only */
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#include <linux/linkage.h>
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#include <asm/asm.h>
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#include <asm-generic/export.h>
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#include <asm/alternative-macros.h>
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#include <asm/errata_list.h>
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/* int strcmp(const char *cs, const char *ct) */
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SYM_FUNC_START(strcmp)
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ALTERNATIVE("nop", "j strcmp_zbb", 0, RISCV_ISA_EXT_ZBB, CONFIG_RISCV_ISA_ZBB)
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/*
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* Returns
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* a0 - comparison result, value like strcmp
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*
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* Parameters
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* a0 - string1
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* a1 - string2
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*
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* Clobbers
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* t0, t1
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*/
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1:
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lbu t0, 0(a0)
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lbu t1, 0(a1)
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addi a0, a0, 1
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addi a1, a1, 1
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bne t0, t1, 2f
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bnez t0, 1b
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li a0, 0
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ret
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2:
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/*
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* strcmp only needs to return (< 0, 0, > 0) values
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* not necessarily -1, 0, +1
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*/
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sub a0, t0, t1
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ret
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/*
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* Variant of strcmp using the ZBB extension if available.
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* The code was published as part of the bitmanip manual
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* in Appendix A.
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*/
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#ifdef CONFIG_RISCV_ISA_ZBB
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strcmp_zbb:
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.option push
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.option arch,+zbb
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/*
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* Returns
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* a0 - comparison result, value like strcmp
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*
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* Parameters
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* a0 - string1
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* a1 - string2
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*
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* Clobbers
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* t0, t1, t2, t3, t4
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*/
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or t2, a0, a1
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li t4, -1
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and t2, t2, SZREG-1
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bnez t2, 3f
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/* Main loop for aligned string. */
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.p2align 3
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1:
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REG_L t0, 0(a0)
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REG_L t1, 0(a1)
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orc.b t3, t0
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bne t3, t4, 2f
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addi a0, a0, SZREG
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addi a1, a1, SZREG
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beq t0, t1, 1b
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/*
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* Words don't match, and no null byte in the first
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* word. Get bytes in big-endian order and compare.
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*/
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#ifndef CONFIG_CPU_BIG_ENDIAN
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rev8 t0, t0
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rev8 t1, t1
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#endif
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/* Synthesize (t0 >= t1) ? 1 : -1 in a branchless sequence. */
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sltu a0, t0, t1
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neg a0, a0
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ori a0, a0, 1
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ret
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2:
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/*
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* Found a null byte.
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* If words don't match, fall back to simple loop.
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*/
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bne t0, t1, 3f
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/* Otherwise, strings are equal. */
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li a0, 0
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ret
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/* Simple loop for misaligned strings. */
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.p2align 3
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3:
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lbu t0, 0(a0)
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lbu t1, 0(a1)
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addi a0, a0, 1
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addi a1, a1, 1
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bne t0, t1, 4f
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bnez t0, 3b
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4:
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sub a0, t0, t1
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ret
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.option pop
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#endif
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SYM_FUNC_END(strcmp)
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