The DAG maintains a chain of MemDGNodes that links together all the
nodes that may touch memroy.
Whenever a new instruction gets created we need to make sure that this
chain gets updated. If the new instruction touches memory then its
corresponding MemDGNode should be inserted into the chain.
This patch adds the callback registration logic in the DAG's constructor
and the corresponding deregistration logic in the destructor. It also
implements the code that makes sure that SchedBundle and DGNodes can be
safely destroyed in any order.
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.
When NewInterval is below DAGInterval we used to revisit instructions
already visited. This patch fixes this by separating the scan in two:
1. The full scan of the NewInterval, and
2. The cross-interval scan for DAGInterval.
This is further explained in the new description.
This patch implements `Interval::comesBefore(const Interval &Other)`
which returns true if this interval is strictly before Other in program
order. The function asserts that the intervals are disjoint.
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.
This patch converts InstrInterval class to a class template and renames
InstrInterval to Itnerval.
This change will allow us to reuse the Interval for dependency graph
nodes.
