[NFC] Make LazyLocalGraph even lazier (#6919)

Do not even construct the Flower helper class until we actually need it.
This avoids even scanning the function and building the internal CFG if
we never get any API call that needs it.

This speeds up LICM by 50% (as now we never construct the CFG if we
don't find a loop), and Stack IR-enabled binary writing by 10% (as many
functions do not have locals in positions that can be optimized using
LocalGraph).

This moves |locations| from the base class to LocalGraph. It is not
needed in the lazy version, so that makes sense for now (we can't keep
it in the base, as then it would need to be mutable, which only makes
sense for laziness).

0 files changed, 0 insertions, 0 deletions