[flang][openacc] Make async clause behavior homogenous (llvm#136610)

The `async` clause was not handed in a similar way on `serial`,
`parallel` and `kernels` directive. This patches updates the `ACC.td`
file and the flang semantic to make it homogenous.

Author: clementval

flang/lib/Semantics/check-acc-structure.cpp

@@ -374,7 +374,6 @@ void AccStructureChecker::Leave(const parser::OpenACCCacheConstruct &x) {
 
 // Clause checkers
 CHECK_SIMPLE_CLAUSE(Auto, ACCC_auto)
-CHECK_SIMPLE_CLAUSE(Async, ACCC_async)
 CHECK_SIMPLE_CLAUSE(Attach, ACCC_attach)
 CHECK_SIMPLE_CLAUSE(Bind, ACCC_bind)
 CHECK_SIMPLE_CLAUSE(Capture, ACCC_capture)
@@ -444,6 +443,12 @@ void AccStructureChecker::CheckMultipleOccurrenceInDeclare(
   CheckMultipleOccurrenceInDeclare(objectList, clause);
 }
 
+void AccStructureChecker::Enter(const parser::AccClause::Async &c) {
+  llvm::acc::Clause crtClause = llvm::acc::Clause::ACCC_async;
+  CheckAllowed(crtClause);
+  CheckAllowedOncePerGroup(crtClause, llvm::acc::Clause::ACCC_device_type);
+}
+
 void AccStructureChecker::Enter(const parser::AccClause::Create &c) {
   CheckAllowed(llvm::acc::Clause::ACCC_create);
   const auto &modifierClause{c.v};

flang/test/Semantics/OpenACC/acc-kernels.f90

@@ -37,6 +37,17 @@ program openacc_kernels_validity
   !$acc kernels async(async1)
   !$acc end kernels
 
+  !ERROR: At most one ASYNC clause can appear on the KERNELS directive or in group separated by the DEVICE_TYPE clause
+  !$acc kernels async(async1) async(2)
+  !$acc end kernels
+
+  !$acc kernels async(async1) device_type(multicore) async(2) ! ok
+  !$acc end kernels
+
+  !ERROR: At most one ASYNC clause can appear on the KERNELS directive or in group separated by the DEVICE_TYPE clause
+  !$acc kernels async(async1) device_type(multicore) async(2) async(3)
+  !$acc end kernels
+
   !$acc kernels wait(wait1)
   !$acc end kernels
 

flang/test/Semantics/OpenACC/acc-parallel.f90

@@ -34,6 +34,17 @@ program openacc_parallel_validity
   !$acc parallel async(1)
   !$acc end parallel
 
+  !ERROR: At most one ASYNC clause can appear on the PARALLEL directive or in group separated by the DEVICE_TYPE clause
+  !$acc parallel async(1) async(2)
+  !$acc end parallel
+
+  !$acc parallel async(1) device_type(nvidia) async(3)
+  !$acc end parallel
+
+  !ERROR: At most one ASYNC clause can appear on the PARALLEL directive or in group separated by the DEVICE_TYPE clause
+  !$acc parallel async(1) device_type(nvidia) async(2) async(3)
+  !$acc end parallel
+
   !$acc parallel async(async1)
   !$acc end parallel
 

flang/test/Semantics/OpenACC/acc-serial.f90

@@ -52,10 +52,17 @@ program openacc_serial_validity
   !$acc serial async(1)
   !$acc end serial
 
-  !ERROR: At most one ASYNC clause can appear on the SERIAL directive
+  !ERROR: At most one ASYNC clause can appear on the SERIAL directive or in group separated by the DEVICE_TYPE clause
   !$acc serial async(1) async(2)
   !$acc end serial
 
+  !ERROR: At most one ASYNC clause can appear on the SERIAL directive or in group separated by the DEVICE_TYPE clause
+  !$acc serial async(1) device_type(nvidia) async(2) async(4)
+  !$acc end serial
+
+  !$acc serial async(1) device_type(nvidia) async(2)
+  !$acc end serial
+
   !$acc serial async(async1)
   !$acc end serial
 

llvm/include/llvm/Frontend/OpenACC/ACC.td

@@ -325,7 +325,8 @@ def ACC_Declare : Directive<"declare"> {
 
 // 2.5.3
 def ACC_Kernels : Directive<"kernels"> {
-  let allowedClauses = [VersionedClause<ACCC_Attach>,
+  let allowedClauses = [VersionedClause<ACCC_Async>,
+                        VersionedClause<ACCC_Attach>,
                         VersionedClause<ACCC_Copy>,
                         VersionedClause<ACCC_Copyin>,
                         VersionedClause<ACCC_Copyout>,
@@ -338,8 +339,7 @@ def ACC_Kernels : Directive<"kernels"> {
                         VersionedClause<ACCC_DevicePtr>,
                         VersionedClause<ACCC_VectorLength>,
                         VersionedClause<ACCC_Wait>];
-  let allowedOnceClauses = [VersionedClause<ACCC_Async>,
-                            VersionedClause<ACCC_Default>,
+  let allowedOnceClauses = [VersionedClause<ACCC_Default>,
                             VersionedClause<ACCC_If>,
                             VersionedClause<ACCC_Self>];
   let association = AS_Block;
@@ -380,27 +380,23 @@ def ACC_Parallel : Directive<"parallel"> {
 def ACC_Serial : Directive<"serial"> {
   // Spec line 950-951: clause is as for the parallel construct except that the
   // num_gangs, num_workers, and vector_length clauses are not permitted.
-  let allowedClauses = [
-    VersionedClause<ACCC_Attach>,
-    VersionedClause<ACCC_Copy>,
-    VersionedClause<ACCC_Copyin>,
-    VersionedClause<ACCC_Copyout>,
-    VersionedClause<ACCC_Create>,
-    VersionedClause<ACCC_DevicePtr>,
-    VersionedClause<ACCC_DeviceType>,
-    VersionedClause<ACCC_NoCreate>,
-    VersionedClause<ACCC_Present>,
-    VersionedClause<ACCC_Private>,
-    VersionedClause<ACCC_FirstPrivate>,
-    VersionedClause<ACCC_Reduction>,
-    VersionedClause<ACCC_Wait>
-  ];
-  let allowedOnceClauses = [
-    VersionedClause<ACCC_Async>,
-    VersionedClause<ACCC_Default>,
-    VersionedClause<ACCC_If>,
-    VersionedClause<ACCC_Self>
-  ];
+  let allowedClauses = [VersionedClause<ACCC_Async>,
+                        VersionedClause<ACCC_Attach>,
+                        VersionedClause<ACCC_Copy>,
+                        VersionedClause<ACCC_Copyin>,
+                        VersionedClause<ACCC_Copyout>,
+                        VersionedClause<ACCC_Create>,
+                        VersionedClause<ACCC_DevicePtr>,
+                        VersionedClause<ACCC_DeviceType>,
+                        VersionedClause<ACCC_NoCreate>,
+                        VersionedClause<ACCC_Present>,
+                        VersionedClause<ACCC_Private>,
+                        VersionedClause<ACCC_FirstPrivate>,
+                        VersionedClause<ACCC_Reduction>,
+                        VersionedClause<ACCC_Wait>];
+  let allowedOnceClauses = [VersionedClause<ACCC_Default>,
+                            VersionedClause<ACCC_If>,
+                            VersionedClause<ACCC_Self>];
   let association = AS_Block;
   let category = CA_Executable;
 }