diff options
| author | Feng Jiang <jiangfeng@kylinos.cn> | 2026-01-25 21:09:58 -0700 |
|---|---|---|
| committer | Paul Walmsley <pjw@kernel.org> | 2026-02-09 15:27:33 -0700 |
| commit | 18be4ca5cb4e5a86833de97d331f5bc14a6c5a6d (patch) | |
| tree | 47e35ff53c678798ffb96b03d8e72405a350ccd7 | |
| parent | 098921ec6818291d98bd3a4002c9dfbe2e75aac2 (diff) | |
riscv: lib: optimize strlen loop efficiency
Optimize the generic strlen implementation by using a pre-decrement
pointer. This reduces the loop body from 4 instructions to 3 and
eliminates the unconditional jump ('j').
Old loop (4 instructions, 2 branches):
1: lbu t0, 0(t1); beqz t0, 2f; addi t1, t1, 1; j 1b
New loop (3 instructions, 1 branch):
1: addi t1, t1, 1; lbu t0, 0(t1); bnez t0, 1b
This change improves execution efficiency and reduces branch pressure
for systems without the Zbb extension.
Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn>
Link: https://patch.msgid.link/20251218032614.57356-1-jiangfeng@kylinos.cn
Signed-off-by: Paul Walmsley <pjw@kernel.org>
| -rw-r--r-- | arch/riscv/lib/strlen.S | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/arch/riscv/lib/strlen.S b/arch/riscv/lib/strlen.S index eb4d2b7ed22b..e7736ccda514 100644 --- a/arch/riscv/lib/strlen.S +++ b/arch/riscv/lib/strlen.S @@ -21,13 +21,11 @@ SYM_FUNC_START(strlen) * Clobbers: * t0, t1 */ - mv t1, a0 + addi t1, a0, -1 1: - lbu t0, 0(t1) - beqz t0, 2f addi t1, t1, 1 - j 1b -2: + lbu t0, 0(t1) + bnez t0, 1b sub a0, t1, a0 ret |