diff options
Diffstat (limited to 'lib/find_last_bit.c')
| -rw-r--r-- | lib/find_last_bit.c | 36 |
1 files changed, 14 insertions, 22 deletions
diff --git a/lib/find_last_bit.c b/lib/find_last_bit.c index 91ca09fbf6f9..3e3be40c6a6e 100644 --- a/lib/find_last_bit.c +++ b/lib/find_last_bit.c @@ -4,6 +4,9 @@ * Written by Rusty Russell <rusty@rustcorp.com.au> * (Inspired by David Howell's find_next_bit implementation) * + * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease + * size and improve performance, 2015. + * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version @@ -11,37 +14,26 @@ */ #include <linux/bitops.h> +#include <linux/bitmap.h> #include <linux/export.h> -#include <asm/types.h> -#include <asm/byteorder.h> +#include <linux/kernel.h> #ifndef find_last_bit unsigned long find_last_bit(const unsigned long *addr, unsigned long size) { - unsigned long words; - unsigned long tmp; - - /* Start at final word. */ - words = size / BITS_PER_LONG; + if (size) { + unsigned long val = BITMAP_LAST_WORD_MASK(size); + unsigned long idx = (size-1) / BITS_PER_LONG; - /* Partial final word? */ - if (size & (BITS_PER_LONG-1)) { - tmp = (addr[words] & (~0UL >> (BITS_PER_LONG - - (size & (BITS_PER_LONG-1))))); - if (tmp) - goto found; - } + do { + val &= addr[idx]; + if (val) + return idx * BITS_PER_LONG + __fls(val); - while (words) { - tmp = addr[--words]; - if (tmp) { -found: - return words * BITS_PER_LONG + __fls(tmp); - } + val = ~0ul; + } while (idx--); } - - /* Not found */ return size; } EXPORT_SYMBOL(find_last_bit); |