int func1( unsigned long long val )
{
return __builtin_ctzll( val );
}
int func2( unsigned long long val )
{
unsigned lo = (unsigned)val;
return lo ? __builtin_ctz(lo) : __builtin_ctz(unsigned(val>>32)) + 32;
}
func1 is more than 2 times slower than func2.
But it should be at least as fast as func2
__builtin_ctzll is not expanded inline like __builtin_ctz.
--
Summary: __builtin_ctzll slower than 2*__builtin_ctz
Product: gcc
Version: 4.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: joerg dot richter at pdv-fs dot de
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31695
