[flang][openacc] Fix wait-argument for wait clause + add tests

[clementval]

Summary

This patch fix the usage of the wait-argument in a clause and add several tests and fix the unparsing of
the wait-argument.

flang/lib/Parser/openacc-parsers.cpp

TYPE_PARSER("AUTO" >> construct<AccClause>(construct<AccClause::Auto>()) ||
     "USE_DEVICE" >> construct<AccClause>(construct<AccClause::UseDevice>(
                         parenthesized(Parser<AccObjectList>{}))) ||
     "VECTOR_LENGTH" >> construct<AccClause>(construct<AccClause::VectorLength>(
                            parenthesized(scalarIntExpr))) ||
     "VECTOR" >>
         construct<AccClause>(construct<AccClause::Vector>(maybe(
             parenthesized(("LENGTH:" >> scalarIntExpr || scalarIntExpr))))) ||
     "WAIT" >> construct<AccClause>(construct<AccClause::Wait>(
-                  maybe(Parser<AccWaitArgument>{}))) ||
+                  maybe(parenthesized(Parser<AccWaitArgument>{})))) ||
     "WORKER" >>
         construct<AccClause>(construct<AccClause::Worker>(maybe(
             parenthesized(("NUM:" >> scalarIntExpr || scalarIntExpr))))) ||
     "WRITE" >> construct<AccClause>(construct<AccClause::Auto>()))
 
 TYPE_PARSER(
     construct<AccObject>(designator) || construct<AccObject>("/" >> name / "/"))
 
 TYPE_PARSER(construct<AccObjectList>(nonemptyList(Parser<AccObject>{})))
 
 TYPE_PARSER(construct<AccObjectListWithModifier>(
     maybe(Parser<AccDataModifier>{}), Parser<AccObjectList>{}))
 
-TYPE_PARSER(construct<AccWaitArgument>(
-    maybe("DEVNUM:" >> scalarIntExpr / ":"), nonemptyList(scalarIntExpr)))
+// 2.16.3 (2485) wait-argument is:
+//   [devnum : int-expr :] [queues :] int-expr-list
+TYPE_PARSER(construct<AccWaitArgument>(maybe("DEVNUM:" >> scalarIntExpr / ":"),
+    "QUEUES:" >> nonemptyList(scalarIntExpr) || nonemptyList(scalarIntExpr)))
 
 // 2.9 (1609) size-expr is one of:
 //   int-expr
 TYPE_PARSER(construct<AccSizeExpr>(scalarIntExpr) ||
     construct<AccSizeExpr>("*" >> maybe(scalarIntExpr)))
 TYPE_PARSER(construct<AccSizeExprList>(nonemptyList(Parser<AccSizeExpr>{})))
 
 // 2.9 (1607) gang-arg is one of:

flang/lib/Parser/unparse.cpp

void Unparse(const OpenACCCacheConstruct &x) {
     BeginOpenACC();
     Word("!$ACC ");
     Word("CACHE(");
     Walk(std::get<AccObjectListWithModifier>(x.t));
     Put(")");
     Put("\n");
     EndOpenACC();
   }
+  void Unparse(const AccWaitArgument &x) {
+    Walk("DEVNUM:", std::get<std::optional<ScalarIntExpr>>(x.t), ":");
+    Walk(std::get<std::list<ScalarIntExpr>>(x.t), ",");
+  }
   void Unparse(const OpenACCWaitConstruct &x) {
     BeginOpenACC();
     Word("!$ACC ");
     Word("WAIT(");
     Walk(std::get<std::optional<AccWaitArgument>>(x.t));
     Walk(std::get<AccClauseList>(x.t));
     Put(")");
     Put("\n");

flang/test/Semantics/acc-clause-validity.f90

program openacc_clause_validity
 
   !$acc serial loop
   do i = 1, N
     a(i) = 3.14
   end do
   !ERROR: Unmatched END PARALLEL LOOP directive
   !$acc end parallel loop
 
+  !$acc kernels wait(1, 2) async(3)
+  !$acc end kernels
+
+  !$acc kernels wait(queues: 1, 2) async(3)
+  !$acc end kernels
+
+  !$acc kernels wait(devnum: 1: 1, 2) async(3)
+  !$acc end kernels
+
+  !$acc kernels wait(devnum: 1: queues: 1, 2) async(3)
+  !$acc end kernels
+
+  !$acc wait(1)
+  !$acc wait(1, 2)
+
+  !$acc wait(queues: 1)
+  !$acc wait(queues: 1, 2)
+
+  !$acc wait(devnum: 1: 3)
+  !$acc wait(devnum: 1: 3, 4)
+
+  !$acc wait(devnum: 1: queues: 3)
+  !$acc wait(devnum: 1: queues: 3, 4)
+
  contains
 
    subroutine sub1(a)
      real :: a(:)
      !ERROR: At least one of GANG, SEQ, VECTOR, WORKER clause must appear on the ROUTINE directive
      !$acc routine
    end subroutine sub1
 
    subroutine sub2(a)
      real :: a(:)
      !ERROR: Clause NOHOST is not allowed after clause DEVICE_TYPE on the ROUTINE directive
      !$acc routine seq device_type(*) nohost
    end subroutine sub2
 
 end program openacc_clause_validity