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adf5421339
Add an assembly implementation of strchr() for RISC-V. By eliminating stack frame management (prologue/epilogue) and optimizing the function entries, the assembly version provides significant relative gains for short strings where the fixed overhead of the C function is most prominent. As string length increases, performance converges with the generic C implementation. Benchmark results (QEMU TCG, rv64): Length | Original (MB/s) | Optimized (MB/s) | Improvement -------|-----------------|------------------|------------ 1 B | 21 | 22 | +4.8% 7 B | 113 | 121 | +7.1% 16 B | 195 | 202 | +3.6% 512 B | 376 | 389 | +3.5% 4096 B | 394 | 393 | -0.3% Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn> Tested-by: Joel Stanley <joel@jms.id.au> Link: https://patch.msgid.link/20260130025018.172925-8-jiangfeng@kylinos.cn Signed-off-by: Paul Walmsley <pjw@kernel.org>
36 lines
600 B
ArmAsm
36 lines
600 B
ArmAsm
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2025 Feng Jiang <jiangfeng@kylinos.cn>
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*/
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#include <linux/linkage.h>
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#include <asm/asm.h>
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/* char *strchr(const char *s, int c) */
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SYM_FUNC_START(strchr)
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/*
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* Parameters
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* a0 - The string to be searched
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* a1 - The character to search for
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*
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* Returns
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* a0 - Address of first occurrence of 'c' or 0
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*
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* Clobbers
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* t0
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*/
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andi a1, a1, 0xff
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1:
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lbu t0, 0(a0)
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beq t0, a1, 2f
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addi a0, a0, 1
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bnez t0, 1b
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li a0, 0
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2:
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ret
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SYM_FUNC_END(strchr)
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SYM_FUNC_ALIAS_WEAK(__pi_strchr, strchr)
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EXPORT_SYMBOL(strchr)
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