The TransactionAcceptOrRevert pass is the final pass in the Sandbox
Vectorizer's default pass pipeline. It's job is to check the cost
before/after vectorization and accept or revert the IR to its original
state.
Since we are now starting the transaction in BottomUpVec, tests that run
a custom pipeline need to accept the transaction. This is done with the
help of the TransactionAlwaysAccept pass (tr-accept).