[flang][openacc] Disallow the zero modifier on the copyout clause with the declare directive

[clementval]

Summary

The OpenACC 3.3 specification does not allow the zero modifier
on the copyout clause used with the declare directive.

This is similar to D156703 for the create clause.

This might be missing piece in the spec but we disallow it until proven otherwise.

[razvanlupusoru]

Thank you for adding this check. This also seems like a possible unintentional omission from spec since it is supported in data clause.

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

if (modifier->v != parser::AccDataModifier::Modifier::Zero) {
       context_.Say(GetContext().clauseSource,
           "Only the ZERO modifier is allowed for the %s clause "
           "on the %s directive"_err_en_US,
           parser::ToUpperCaseLetters(
               llvm::acc::getOpenACCClauseName(llvm::acc::Clause::ACCC_copyout)
                   .str()),
           ContextDirectiveAsFortran());
     }
+    if (GetContext().directive == llvm::acc::Directive::ACCD_declare) {
+      context_.Say(GetContext().clauseSource,
+          "The ZERO modifier is not allowed for the %s clause "
+          "on the %s directive"_err_en_US,
+          parser::ToUpperCaseLetters(
+              llvm::acc::getOpenACCClauseName(llvm::acc::Clause::ACCC_copyout)
+                  .str()),
+          ContextDirectiveAsFortran());
+    }
   }
 }
 
 void AccStructureChecker::Enter(const parser::AccClause::Gang &g) {
   CheckAllowed(llvm::acc::Clause::ACCC_gang);
 
   if (g.v) {
     bool hasNum = false;

flang/test/Semantics/OpenACC/acc-declare-validity.f90

contains
   end function fct1
 
   subroutine sub2(cc)
     real(8), dimension(*) :: cc
     !ERROR: Assumed-size dummy arrays may not appear on the DECLARE directive
     !$acc declare present(cc)
   end subroutine sub2
 
+  subroutine sub3()
+    real :: aa(100)
+    !ERROR: The ZERO modifier is not allowed for the COPYOUT clause on the DECLARE directive
+    !$acc declare copyout(zero: aa)
+  end subroutine
+
 end module openacc_declare_validity