[flang] [llvm] [mlir] [Frontend][OpenMP] Refactor getLeafConstructs, add getCompoundConstruct (PR #87247)

[Sergio Afonso via llvm-commits]

================
@@ -1311,8 +1298,8 @@ static void genWsloopClauses(
   if (ReductionProcessor::doReductionByRef(clauseOps.reductionVars))
     clauseOps.reductionByRefAttr = firOpBuilder.getUnitAttr();
 
-  if (endClauses) {
-    ClauseProcessor ecp(converter, semaCtx, *endClauses);
+  if (!endClauses.empty()) {
----------------
skatrak wrote:

Nit: This check can be removed now.

https://github.com/llvm/llvm-project/pull/87247