Progress on liveness analysis.

Compute basic blocks and their predecessors, necessary for backward flow
analysis.  This is a work in progress and isn't yet enabled.

(When enabled, verification takes 20% longer, so there's some room for
improvement on performance.)

Also, this changes the "generate register maps" setting to be enabled
by default, and allows a "no" prefix on -Xgenregmap to disable it.

Bug 2534655

Change-Id: Id2e8512f53fc454ce2184879ab663ed7121274b6
11 files changed