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host-utils: Simplify pow2ceil()

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Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1501148776-16890-4-git-send-email-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Markus Armbruster 2017-07-27 11:46:16 +02:00 committed by Dr. David Alan Gilbert
parent 43c64a093d
commit 362aaf1457
1 changed files with 13 additions and 8 deletions
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21
include/qemu/host-utils.h
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@ -381,18 +381,23 @@ static inline uint64_t pow2floor(uint64_t value)
return 0x8000000000000000ull >> clz64(value);
}
/* round up to the nearest power of 2 (0 if overflow) */
/*
* Return @value rounded up to the nearest power of two modulo 2^64.
* This is *zero* for @value > 2^63, so be careful.
*/
static inline uint64_t pow2ceil(uint64_t value)
{
uint8_t nlz = clz64(value);
int n = clz64(value - 1);
if (is_power_of_2(value)) {
return value;
if (!n) {
/*
* @value - 1 has no leading zeroes, thus @value - 1 >= 2^63
* Therefore, either @value == 0 or @value > 2^63.
* If it's 0, return 1, else return 0.
*/
return !value;
}
if (!nlz) {
return 0;
}
return 1ULL << (64 - nlz);
return 0x8000000000000000ull >> (n - 1);
}
/**