[flang][OpenMP] Add parsing support for detach clause

Author: NimishMishra

flang/include/flang/Parser/dump-parse-tree.h

@@ -507,6 +507,7 @@ class ParseTreeDumper {
   NODE_ENUM(OmpDefaultmapClause, ImplicitBehavior)
   NODE_ENUM(OmpDefaultmapClause, VariableCategory)
   NODE(parser, OmpDependClause)
+  NODE(parser, OmpDetachClause)
   NODE(OmpDependClause, InOut)
   NODE(OmpDependClause, Sink)
   NODE(OmpDependClause, Source)

flang/include/flang/Parser/parse-tree.h

@@ -3515,6 +3515,12 @@ struct OmpIfClause {
   std::tuple<std::optional<DirectiveNameModifier>, ScalarLogicalExpr> t;
 };
 
+// OpenMPv5.2 12.5.2 detach-clause -> DETACH (event-handle)
+struct OmpDetachClause {
+  WRAPPER_CLASS_BOILERPLATE(OmpDetachClause, OmpObject);
+  CharBlock source;
+};
+
 // 2.8.1 aligned-clause -> ALIGNED (variable-name-list[ : scalar-constant])
 struct OmpAlignedClause {
   TUPLE_CLASS_BOILERPLATE(OmpAlignedClause);

flang/lib/Parser/openmp-parsers.cpp

@@ -215,7 +215,7 @@ TYPE_PARSER(construct<OmpIfClause>(
         ":"),
     scalarLogicalExpr))
 
-// 2.15.3.6 REDUCTION (reduction-identifier: variable-name-list)
+// OpenMPv5.2 2.15.3.6 REDUCTION (reduction-identifier: variable-name-list)
 TYPE_PARSER(construct<OmpReductionOperator>(Parser<DefinedOperator>{}) ||
     construct<OmpReductionOperator>(Parser<ProcedureDesignator>{}))
 
@@ -298,6 +298,9 @@ TYPE_CONTEXT_PARSER("Omp LINEAR clause"_en_US,
         construct<OmpLinearClause>(construct<OmpLinearClause::WithoutModifier>(
             nonemptyList(name), maybe(":" >> scalarIntConstantExpr)))))
 
+// 12.5.2 detach-clause -> DETACH (event-handle)
+TYPE_PARSER(construct<OmpDetachClause>(Parser<OmpObject>{}))
+
 // 2.8.1 ALIGNED (list: alignment)
 TYPE_PARSER(construct<OmpAlignedClause>(
     Parser<OmpObjectList>{}, maybe(":" >> scalarIntConstantExpr)))
@@ -414,6 +417,8 @@ TYPE_PARSER(
                        parenthesized(Parser<OmpReductionClause>{}))) ||
     "IN_REDUCTION" >> construct<OmpClause>(construct<OmpClause::InReduction>(
                           parenthesized(Parser<OmpInReductionClause>{}))) ||
+    "DETACH" >> construct<OmpClause>(construct<OmpClause::Detach>(
+                    parenthesized(Parser<OmpDetachClause>{}))) ||
     "TASK_REDUCTION" >>
         construct<OmpClause>(construct<OmpClause::TaskReduction>(
             parenthesized(Parser<OmpReductionClause>{}))) ||

flang/lib/Parser/unparse.cpp

@@ -2131,6 +2131,7 @@ class UnparseVisitor {
     Put(":");
     Walk(std::get<OmpObjectList>(x.t));
   }
+  void Unparse(const OmpDetachClause &x) { Walk(x.v); }
   void Unparse(const OmpInReductionClause &x) {
     Walk(std::get<OmpReductionOperator>(x.t));
     Put(":");

flang/test/Parser/OpenMP/task.f90

@@ -0,0 +1,16 @@
+! RUN: %flang_fc1 -fdebug-dump-parse-tree -fopenmp -fopenmp-version=50  %s | FileCheck --ignore-case %s
+! RUN: %flang_fc1 -fdebug-unparse -fopenmp -fopenmp-version=50  %s | FileCheck --ignore-case --check-prefix="CHECK-UNPARSE" %s
+
+!CHECK: OmpBlockDirective -> llvm::omp::Directive = task
+!CHECK: OmpClauseList -> OmpClause -> Detach -> OmpDetachClause -> OmpObject -> Designator -> DataRef -> Name = 'event'
+
+!CHECK-UNPARSE: INTEGER(KIND=8_4) event
+!CHECK-UNPARSE: !$OMP TASK  DETACH(event)
+!CHECK-UNPARSE: !$OMP END TASK
+subroutine task_detach
+  use omp_lib
+  implicit none
+  integer(kind=omp_event_handle_kind) :: event
+  !$omp task detach(event)
+  !$omp end task
+end subroutine

llvm/include/llvm/Frontend/OpenMP/OMP.td

@@ -132,6 +132,7 @@ def OMPC_Destroy : Clause<"destroy"> {
 }
 def OMPC_Detach : Clause<"detach"> {
   let clangClass = "OMPDetachClause";
+  let flangClass = "OmpDetachClause";
 }
 def OMPC_Device : Clause<"device"> {
   let clangClass = "OMPDeviceClause";