[flang][openacc] Add clause validity tests for the update directive

[clementval]

Summary

Add couple of clause validity tests for the update directive and check for
the restriction where at least self, host or device clause must appear on the directive.

[sameeranjoshi]

Looks Good Thanks.

[clementval]

Rebase

[clementval]

Revert to previous version after a bad rebase/update

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

program openacc_clause_validity
 
   !ERROR: At least one of DEFAULT_ASYNC, DEVICE_NUM, DEVICE_TYPE clause must appear on the SET directive
   !$acc set
 
   !ERROR: At least one of ATTACH, COPY, COPYIN, COPYOUT, CREATE, DEFAULT, DEVICEPTR, NO_CREATE, PRESENT clause must appear on the DATA directive
   !$acc data
   !$acc end data
 
-  !$acc data copyin(i)
+  !$acc data copy(aa) if(.true.)
+  !$acc end data
+
+  !$acc data copy(aa) if(ifCondition)
+  !$acc end data
+
+  !$acc data copy(aa, bb, cc)
+  !$acc end data
+
+  !$acc data copyin(aa) copyin(readonly: bb) copyout(cc)
+  !$acc end data
+
+  !$acc data copyin(readonly: aa, bb) copyout(zero: cc)
+  !$acc end data
+
+  !$acc data create(aa, bb(:,:)) create(zero: cc(:,:))
+  !$acc end data
+
+  !$acc data no_create(aa) present(bb, cc)
+  !$acc end data
+
+  !$acc data deviceptr(aa) attach(bb, cc)
+  !$acc end data
+
+  !$acc data copy(aa, bb) default(none)
+  !$acc end data
+
+  !$acc data copy(aa, bb) default(present)
+  !$acc end data
+
+  !ERROR: At most one DEFAULT clause can appear on the DATA directive
+  !$acc data copy(aa, bb) default(none) default(present)
+  !$acc end data
+
+  !ERROR: At most one IF clause can appear on the DATA directive
+  !$acc data copy(aa) if(.true.) if(ifCondition)
   !$acc end data
 
   !$acc data copyin(i)
   !ERROR: Unmatched PARALLEL directive
   !$acc end parallel
 
   !$acc update self(a, f) host(g) device(h)
 

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

 //===----------------------------------------------------------------------===//
 
 // 2.12
 def ACC_Atomic : Directive<"atomic"> {}
 
 // 2.6.5
 def ACC_Data : Directive<"data"> {
   let allowedOnceClauses = [
-    VersionedClause<ACCC_If>
+    VersionedClause<ACCC_If>,
+    VersionedClause<ACCC_Default>
   ];
   let requiredClauses = [
     VersionedClause<ACCC_Attach>,
     VersionedClause<ACCC_Copy>,
     VersionedClause<ACCC_Copyin>,
     VersionedClause<ACCC_Copyout>,
     VersionedClause<ACCC_Create>,
     VersionedClause<ACCC_Default>,