From d76232ff8be662b8851e975d13d59cad4bf423d3 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Mon, 7 Feb 2022 17:23:41 +0100 Subject: [PATCH] tools/nolibc/string: slightly simplify memmove() The direction test inside the loop was not always completely optimized, resulting in a larger than necessary function. This change adds a direction variable that is set out of the loop. Now the function is down to 48 bytes on x86, 32 on ARM and 68 on mips. It's worth noting that other approaches were attempted (including relying on the up and down functions) but they were only slightly beneficial on x86 and cost more on others. Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney --- tools/include/nolibc/string.h | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h index 6d8fad7..b831a02 100644 --- a/tools/include/nolibc/string.h +++ b/tools/include/nolibc/string.h @@ -50,14 +50,22 @@ void *_nolibc_memcpy_down(void *dst, const void *src, size_t len) static __attribute__((unused)) void *memmove(void *dst, const void *src, size_t len) { - ssize_t pos = (dst <= src) ? -1 : (long)len; - void *ret = dst; + size_t dir, pos; - while (len--) { - pos += (dst <= src) ? 1 : -1; - ((char *)dst)[pos] = ((char *)src)[pos]; + pos = len; + dir = -1; + + if (dst < src) { + pos = -1; + dir = 1; } - return ret; + + while (len) { + pos += dir; + ((char *)dst)[pos] = ((const char *)src)[pos]; + len--; + } + return dst; } /* must be exported, as it's used by libgcc on ARM */ -- 2.7.4