Ryotaro Kasuga 0d6a584f69 [MachinePipeliner] Add an abstract layer to manipulate Data Dependenc… (#109918) ...

…e Graph

In MachinePipeliner, a DAG class is used to represent the Data
Dependence Graph. Data Dependence Graph generally contains cycles, so
it's not appropriate to use DAG classes. In fact, some "hacks" are used
to express back-edges in the current implementation. This patch adds a
new class to provide a better interface for manipulating dependencies.
Our approach is as follows:

- To build the graph, we use the ScheduleDAGInstrs class as it is,
because it has powerful functions and the current implementation depends
heavily on it.
- After the graph construction is finished (i.e., during scheduling), we
use the new class DataDependenceGraph to manipulate the dependencies.

Since we don't change the dependencies during scheduling, the new class
only provides functions to read them. Also, this patch is just a
refactoring, i.e., scheduling results should not change with or without
this patch.

2024-12-24 10:02:15 +09:00

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