From 61ff1af76f4887bb7c555e4d0b8a7eeb73b05086 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Sat, 17 Dec 2016 15:03:24 +0100 Subject: [PATCH] use lookup table for malloc bin index instead of float conversion float conversion is slow and big on soft-float targets. The lookup table increases code size a bit on most hard float targets (and adds 60byte rodata), performance can be a bit slower because of position independent data access and cpu internal state dependence (cache, extra branches), but the overall effect should be minimal (common, small size allocations should be unaffected). --- src/malloc/malloc.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c index b90636cc..c38c46fe 100644 --- a/src/malloc/malloc.c +++ b/src/malloc/malloc.c @@ -111,19 +111,29 @@ static int first_set(uint64_t x) #endif } +static const unsigned char bin_tab[60] = { + 32,33,34,35,36,36,37,37,38,38,39,39, + 40,40,40,40,41,41,41,41,42,42,42,42,43,43,43,43, + 44,44,44,44,44,44,44,44,45,45,45,45,45,45,45,45, + 46,46,46,46,46,46,46,46,47,47,47,47,47,47,47,47, +}; + static int bin_index(size_t x) { x = x / SIZE_ALIGN - 1; if (x <= 32) return x; + if (x < 512) return bin_tab[x/8-4]; if (x > 0x1c00) return 63; - return ((union { float v; uint32_t r; }){(int)x}.r>>21) - 496; + return bin_tab[x/128-4] + 16; } static int bin_index_up(size_t x) { x = x / SIZE_ALIGN - 1; if (x <= 32) return x; - return ((union { float v; uint32_t r; }){(int)x}.r+0x1fffff>>21) - 496; + x--; + if (x < 512) return bin_tab[x/8-4] + 1; + return bin_tab[x/128-4] + 17; } #if 0 -- 2.25.1