In order to reduce our reliance on __builtin_{ffs, clz, ctz, popcount},
this commit removes all calls to these functions and replaces them with
the equivalent functions in AK/BuiltinWrappers.h.
Since it's possible to determine where the small zones will start to
occur for each PhysicalRegion, we can use arithmetic so that the call
time for both large and small zones is identical.
Most of the time, we will be freeing physical pages within the
full-sized zones. We can do some simple math to find the right zone
immediately instead of looping through the zones, checking each one.
We still do loop through the slack/remainder zones at the end.
There's probably an even nicer way to solve this, but this is already a
nice improvement. :^)
