[Mlir-commits] [mlir] [mlir][Interfaces][NFC] Add `RegionBranchOpInterface` helper for forwarded values (PR #173981)

[Matthias Springer]

================
@@ -251,30 +251,16 @@ def RegionBranchOpInterface : OpInterface<"RegionBranchOpInterface"> {
            "::llvm::SmallVectorImpl<::mlir::RegionBranchPoint> &":$predecessors),
       [{}],
       /*defaultImplementation=*/[{
-        ::llvm::SmallVector<::mlir::RegionSuccessor> successors;
-        $_op.getSuccessorRegions(RegionBranchPoint::parent(),
-                                 successors);
-        if (llvm::any_of(successors, [&] (const RegionSuccessor & succ) {
+        auto op = cast<RegionBranchOpInterface>($_op.getOperation());
+        for (::mlir::RegionBranchPoint point : op.getAllRegionBranchPoints()) {
+          ::llvm::SmallVector<::mlir::RegionSuccessor> successors;
+          op.getSuccessorRegions(point, successors);
+          bool isPred = llvm::any_of(successors, [&] (const auto &succ) {
             return succ.getSuccessor() == successor.getSuccessor() ||
-              (succ.isParent() && successor.isParent());
-          }))
-          predecessors.push_back(RegionBranchPoint::parent());
-        for (Region &region : $_op->getRegions()) {
-          for (::mlir::Block &block : region) {
-            if (block.empty())
-              continue;
-            if (auto terminator =
-                    dyn_cast<RegionBranchTerminatorOpInterface>(block.back())) {
-              ::llvm::SmallVector<::mlir::RegionSuccessor> successors;
-              $_op.getSuccessorRegions(RegionBranchPoint(terminator),
-                                       successors);
-              if (llvm::any_of(successors, [&] (const RegionSuccessor & succ) {
-                  return succ.getSuccessor() == successor.getSuccessor() ||
-                    (succ.isParent() && successor.isParent());
----------------
matthias-springer wrote:

This line checks if the `succ` matches `successor` (the function parameter). We don't care about the successor inputs (they may not be populated), that's why we don't use `operator==`.

Technically, I think `succ.isParent() && successor.isParent()` is not needed because if the region successor is the parent op, `getSuccessor()` would return a `nullptr` region.

https://github.com/llvm/llvm-project/pull/173981