[mlir][Interfaces] ValueBoundsOpInterface: Compute constant bounds

[springerm]

Summary

Add a helper function that computes a constant (int64_t) bound. The stopCondition is optional: If none is provided, the traversal continues until a constant bound could be computed.

Depends On: D145806

[springerm]

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[dcaballe]

mlir/lib/Interfaces/ValueBoundsOpInterface.cpp

356

nit: .

364

Did you finally add the option to make UB close? (I guess I'll figure it out :))

mlir/test/Dialect/Affine/value-bounds-reification.mlir

42

For cases where constant is not provided and there are multiple bounds, are we returning now the non-constant one?

88

Nit: What about introducing a test.reify_constant_bound instead?

[springerm]

mlir/lib/Interfaces/ValueBoundsOpInterface.cpp

364

Yes, it will be added as part of D146356.

mlir/test/Dialect/Affine/value-bounds-reification.mlir

42

No, we still return the constant one. That's a limitation of the FlatLinearConstraints implementation. (There's a TODO in there.)

The constant attribute here just says that the computed bound must be a constant. If it is not specified, the computed bound may be constant or not constant.