[mlir][SCF] Implement RegionBranchOpInterface on ExecuteRegionOp

This is needed for the BufferDeallocation pass.

Differential Revision: https://reviews.llvm.org/D121526

mlir/include/mlir/Dialect/SCF/SCFOps.td

@@ -56,7 +56,8 @@ def ConditionOp : SCF_Op<"condition", [
 // ExecuteRegionOp
 //===----------------------------------------------------------------------===//
 
-def ExecuteRegionOp : SCF_Op<"execute_region"> {
+def ExecuteRegionOp : SCF_Op<"execute_region", [
+    DeclareOpInterfaceMethods<RegionBranchOpInterface>]> {
   let summary = "operation that executes its region exactly once";
   let description = [{
     The `execute_region` operation is used to allow multiple blocks within SCF

mlir/lib/Dialect/SCF/SCF.cpp

@@ -236,6 +236,24 @@ void ExecuteRegionOp::getCanonicalizationPatterns(RewritePatternSet &results,
   results.add<SingleBlockExecuteInliner, MultiBlockExecuteInliner>(context);
 }
 
+/// Given the region at `index`, or the parent operation if `index` is None,
+/// return the successor regions. These are the regions that may be selected
+/// during the flow of control. `operands` is a set of optional attributes that
+/// correspond to a constant value for each operand, or null if that operand is
+/// not a constant.
+void ExecuteRegionOp::getSuccessorRegions(
+    Optional<unsigned> index, ArrayRef<Attribute> operands,
+    SmallVectorImpl<RegionSuccessor> &regions) {
+  // If the predecessor is the ExecuteRegionOp, branch into the body.
+  if (!index.hasValue()) {
+    regions.push_back(RegionSuccessor(&getRegion()));
+    return;
+  }
+
+  // Otherwise, the region branches back to the parent operation.
+  regions.push_back(RegionSuccessor(getResults()));
+}
+
 //===----------------------------------------------------------------------===//
 // ConditionOp
 //===----------------------------------------------------------------------===//