ART: Add two extra DCE passes

Add two DCE passes to eliminate dead instructions left by:
- Loop optimization unrolling. After loop optimization, dead
  instructions are often left that, when removed can simplify the
  structure of the loop and remove basic blocks. This extra DCE pass
  creates an opportunity for the load store elimination pass to
  remove some loads/stores.
- The last instruction simplification pass.

Authors: Hari Limaye, Chris Jones

Test: 458-checker-instruct-simplification
Test: 530-checker-lse, 530-checker-lse-simd, 706-checker-scheduler
Test: test-art-target, test-art-host

Change-Id: I6e14cbfc3c320af5f507135a067bb7b5bc4df8f4
5 files changed