This is the first of the 7 steps outlined in #75801. This PR explicitely
calls the SimplifyLoops pass. Directly following this pass should follow
the 6 others required to structurize the IR.
Running this pass could generate empty basic-blocks, which are implicit
fallthrough to the successor BB.
There was a specific condition in the SPIR-V ISel which handled implicit
fallthrough, but it couldn't work on empty basic-blocks. This commits
removes the old logic, and adds this new logic, which checks all
basic-blocks for implicit fallthroughs, including empty ones.
---------
Signed-off-by: Nathan Gauër <brioche@google.com>
a9ffc92fc4