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).
This patch implements the UnscheduledSuccs counter in DGNode. It counts
the number of unscheduled successors and is used by the scheduler to
determine when a node is ready.
This patch moves:
- Utils::isStackSaveOrRestoreIntrinsic()
- Utils::isMemIntrinsic()
- Utils::isMemDepCandidate()
to DGNode because they no longer require LLVM IR access and are used
only by the DAG.
This patch implements the MemDGNode class for DAG nodes that are
candidates
for memory dependencies. These nodes form a chain that is accessible by
`getPrevNode()` and `getNextNode()`.
It also implements a builder class that creates MemDGNode intervals from
Instructions.
