[Mlir-commits] [mlir] [mlir] MLIR-QUERY slice-matchers implementation (PR #115670)

[Denzel-Brian Budii]

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@@ -363,8 +366,267 @@ struct RecursivePatternMatcher {
   std::tuple<OperandMatchers...> operandMatchers;
 };
 
+/// Fills `backwardSlice` with the computed backward slice (i.e.
+/// all the transitive defs of op)
+///
+/// The implementation traverses the def chains in postorder traversal for
+/// efficiency reasons: if an operation is already in `backwardSlice`, no
+/// need to traverse its definitions again. Since use-def chains form a DAG,
+/// this terminates.
+///
+/// Upon return to the root call, `backwardSlice` is filled with a
+/// postorder list of defs. This happens to be a topological order, from the
+/// point of view of the use-def chains.
+///
+/// Example starting from node 8
+/// ============================
+///
+///    1       2      3      4
+///    |_______|      |______|
+///    |   |             |
+///    |   5             6
+///    |___|_____________|
+///      |               |
+///      7               8
+///      |_______________|
+///              |
+///              9
+///
+/// Assuming all local orders match the numbering order:
+///    {1, 2, 5, 3, 4, 6}
+///
+
+class BackwardSliceMatcher {
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chios202 wrote:

Yes, implementations would be better in a .cpp file 

https://github.com/llvm/llvm-project/pull/115670