pow2roundup function
Rounds numbers <= 2^32 up to the nearest power of 2.
Implementation
@pragma('vm:prefer-inline')
@pragma('dart2js:tryInline')
int pow2roundup(int x) {
assert(x > 0, 'num must be positive');
--x;
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
x |= x >> 16;
return x + 1;
}