[Mlir-commits] [mlir] [mlir][Interfaces] Add `mustProgress` interface method + folding pattern (PR #179039)

[Matthias Springer]

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@@ -351,6 +351,18 @@ def RegionBranchOpInterface : OpInterface<"RegionBranchOpInterface"> {
       (ins "::mlir::Type":$lhs, "::mlir::Type":$rhs), [{}],
       /*defaultImplementation=*/[{ return lhs == rhs; }]
     >,
+    InterfaceMethod<[{
+        Region branch ops that "must progress" are required to terminate (i.e.,
+        not loop infinitely between their regions) or interact with the
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matthias-springer wrote:

I'd say "program termination" is an observable side effect.

I updated the documentation to also mention that the next op must be reached. This allows us to perform more aggressive dead code elimination, e.g., clearing out basic blocks that end with an `ub.unreachable` (which was discussed [here](https://github.com/llvm/llvm-project/pull/169873#discussion_r2570988454)).

https://github.com/llvm/llvm-project/pull/179039