Henri Verbeet <[email protected]> writes: > Something like the following may be faster: > > static const int bit_pos[] = > { > 0x00, 0x01, 0x0e, 0x02, 0x0f, 0x1b, 0x12, 0x03, > 0x1e, 0x10, 0x1c, 0x16, 0x18, 0x13, 0x0a, 0x04, > 0x1f, 0x0d, 0x1a, 0x11, 0x1d, 0x15, 0x17, 0x09, > 0x0c, 0x19, 0x14, 0x08, 0x0b, 0x07, 0x06, 0x05, > }; > const unsigned int c = 0x7dc4d65; > return bit_pos[((x & -x) * c) >> 27]; > > I'd expect that mostly due to eliminating the branches and the > implicit shift & mask operations in something like "y.c[1]".
Maybe, but there's no point. This is just a fallback implementation for broken platforms, any platform that we care about should never use this. -- Alexandre Julliard [email protected]
