Add DCE check to test 458-checker-instruct-simplification

Follow-up to 9837caff9cbfb61e3dabc6fbecb398d4d659c017 by checking
that dead code is actually removed.

Test: make -j32 test-art-host
Change-Id: Ic7848be893c6fe5e65f5bcdd525597072bf67857
1 file changed