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bef64bcb94
Add an assembly implementation of strrchr() for RISC-V. This implementation minimizes instruction count and avoids unnecessary memory access to the stack. The performance benefits are most visible on small workloads (1-16 bytes) where the architectural savings in function overhead outweigh the execution time of the scan loop. Benchmark results (QEMU TCG, rv64): Length | Original (MB/s) | Optimized (MB/s) | Improvement -------|-----------------|------------------|------------ 1 B | 20 | 21 | +5.0% 7 B | 111 | 120 | +8.1% 16 B | 189 | 199 | +5.3% 512 B | 361 | 382 | +5.8% 4096 B | 388 | 391 | +0.8% Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn> Tested-by: Joel Stanley <joel@jms.id.au> Link: https://patch.msgid.link/20260130025018.172925-9-jiangfeng@kylinos.cn Signed-off-by: Paul Walmsley <pjw@kernel.org>
38 lines
624 B
ArmAsm
38 lines
624 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 *strrchr(const char *s, int c) */
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SYM_FUNC_START(strrchr)
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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 seaerch for
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*
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* Returns
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* a0 - Address of last occurrence of 'c' or 0
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*
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* Clobbers
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* t0, t1
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*/
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andi a1, a1, 0xff
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mv t1, a0
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li a0, 0
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1:
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lbu t0, 0(t1)
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bne t0, a1, 2f
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mv a0, t1
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2:
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addi t1, t1, 1
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bnez t0, 1b
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ret
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SYM_FUNC_END(strrchr)
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SYM_FUNC_ALIAS_WEAK(__pi_strrchr, strrchr)
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EXPORT_SYMBOL(strrchr)
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