riscv: lib: add strnlen() implementation

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Add an optimized strnlen() implementation for RISC-V. This version
includes a generic optimization and a Zbb-powered optimization using
the 'orc.b' instruction, derived from the strlen() implementation.

Benchmark results (QEMU TCG, rv64):
  Length | Original (MB/s) | Optimized (MB/s) | Improvement
  -------|-----------------|------------------|------------
  16 B   | 179             | 309              | +72.6%
  512 B  | 347             | 1562             | +350.1%
  4096 B | 356             | 1878             | +427.5%

Suggested-by: Qingfang Deng <dqfext@gmail.com>
Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn>
Link: https://patch.msgid.link/20260130025018.172925-7-jiangfeng@kylinos.cn
Signed-off-by: Paul Walmsley <pjw@kernel.org>

...

This commit is contained in:

Feng Jiang 2026-04-03 19:28:47 -06:00 • committed by Paul Walmsley

parent e73bcb3708

commit 5ba15d419f

4 changed files with 172 additions and 1 deletions

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3

arch/riscv/include/asm/string.h

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1

arch/riscv/lib/Makefile

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164

arch/riscv/lib/strnlen.S

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arch/riscv/purgatory/Makefile

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