Fix performance regression.

Rationale:
One "improvement" overlooked in the previous CL hoists
a try-test out of the optimization to make sure we don't
change HIR when not needed. However, the try-test may
affect the outcome of the test, so that was bad, bad!

Bug: 64091002
Test: test-art-host
Change-Id: Icf5f73e7cbeb209ee5fa5f6c1bef64fe127bb2fd