Rewrite topological sort order and improve GVN.

Rewrite the topological sort order to include a full loop
before the blocks that go after the loop. Add a new iterator
class LoopRepeatingTopologicalSortIterator that differs from
the RepeatingTopologicalSortIterator by repeating only loops
and repeating them early. It returns to the loop head if the
head needs recalculation when we reach the end of the loop.

In GVN, use the new loop-repeating topological sort iterator
and for a loop head merge only the preceding blocks' LVNs
if we're not currently recalculating this loop.

Also fix LocalValueNumbering::InPlaceIntersectMaps() which
was keeping only the last element of the intersection, avoid
some unnecessary processing during LVN merge and add some
missing braces to MIRGraph::InferTypeAndSize().

Bug: 16398693

(cherry picked from 55fff044d3a4f7196098e25bab1dad106d9b54a2)

Change-Id: Id7bcd99c8abed1b7500b9ef723313d4c5fc6f1e8
16 files changed