In a program that constructs a LifetimeRegion, the retain and release of
every ProgramLifetime class count references in the chunk that holds the
instance, once the process has created a region. Speed builds inline those
bodies into every use of an instance. A program that references
LifetimeRegion but never creates a region still carried the counting path
inline at every use, and its walks over ProgramLifetime graphs ran about
10% slower than the same program without the reference.
The flag test that skips counting is now marked likely, so the counting
path is laid out away from the callers' hot code. Programs that create
regions take the same path as before.
Chris Tate
ebbc3d4519