Crossing BBs is not currently supported by the structures of the
vectorizer. This patch fixes instances where this was happening,
including:
- a walk of use-def operands that updates the UnscheduledSuccs counter,
- the dead instruction removal is now done per BB,
- the scheduler, which will reject bundles that cross BBs.
This patch adds support for re-scheduling already scheduled
instructions. For now this will clear and rebuild the DAG, and will
reschedule the code using the new DAG.
This patch implements a ready-list-based scheduler that operates on
DependencyGraph.
It is used by the sandbox vectorizer to test the legality of vectorizing
a group of instrs.
SchedBundle is a helper container, containing all DGNodes that
correspond to the instructions that we are attempting to schedule with
trySchedule(Instrs).
