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bitops: provide an inline implementation of find_first_bit

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find_first_bit has started to be used heavily in TCG code. The current
implementation based on find_next_bit is not optimal and can't be
optimized be the compiler if the bit array has a fixed size, which is
the case most of the time.

This new implementation does not use find_next_bit and is yet small
enough to be inlined.

Cc: Corentin Chary <corentin.chary@gmail.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Aurelien Jarno 2013-12-21 01:15:21 +01:00
parent 2edaf21b93
commit 739b7a9075
1 changed files with 11 additions and 1 deletions
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12
include/qemu/bitops.h
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@ -157,7 +157,17 @@ unsigned long find_next_zero_bit(const unsigned long *addr,
static inline unsigned long find_first_bit(const unsigned long *addr,
unsigned long size)
{
return find_next_bit(addr, size, 0);
unsigned long result, tmp;
for (result = 0; result < size; result += BITS_PER_LONG) {
tmp = *addr++;
if (tmp) {
result += ctzl(tmp);
return result < size ? result : size;
}
}
/* Not found */
return size;
}
/**