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lib/util: Add ctz64() and popcount64().

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Add raw_ctz64(), ctz64(), and popcount64() using builtins when
available.

Signed-off By: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
This commit is contained in:
Jarno Rajahalme
2013-11-18 09:28:44 -08:00
parent 481da12c8d
commit cc4c738e12
2 changed files with 95 additions and 10 deletions
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38
lib/util.h
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@@ -285,6 +285,10 @@ void ignore(bool x OVS_UNUSED);
/* Bitwise tests. */
int log_2_floor(uint32_t);
int log_2_ceil(uint32_t);
unsigned int popcount(uint32_t);
/* Returns the number of trailing 0-bits in 'n'. Undefined if 'n' == 0.
*
* This compiles to a single machine instruction ("bsf") with GCC on x86. */
@@ -301,6 +305,31 @@ raw_ctz(uint32_t n)
int raw_ctz(uint32_t n);
#endif
#if __GNUC__ >= 4
static inline int
raw_ctz64(uint64_t n)
{
return __builtin_ctzll(n);
}
static inline int
popcount64(uint64_t n)
{
return __builtin_popcountll(n);
}
#else
/* Defined using the 32-bit counterparts. */
static inline int
raw_ctz64(uint64_t n)
{
return (uint32_t)n ? raw_ctz(n) : 32 + raw_ctz(n >> 32);
}
static inline int
popcount64(uint64_t n)
{
return popcount(n) + popcount(n >> 32);
}
#endif
/* Returns the number of trailing 0-bits in 'n', or 32 if 'n' is 0. */
static inline int
ctz(uint32_t n)
@@ -308,9 +337,12 @@ ctz(uint32_t n)
return n ? raw_ctz(n) : 32;
}
int log_2_floor(uint32_t);
int log_2_ceil(uint32_t);
unsigned int popcount(uint32_t);
/* Returns the number of trailing 0-bits in 'n', or 64 if 'n' is 0. */
static inline int
ctz64(uint64_t n)
{
return n ? raw_ctz64(n) : 64;
}
/* Returns the rightmost 1-bit in 'x' (e.g. 01011000 => 00001000), or 0 if 'x'
* is 0. */