[Flang][OpenMP][Sema] Add semantics checks for REQUIRES directive

[skatrak]

Summary

This patch adds semantics checks for REQUIRES directives appearing after other directives that are affected by them. In particular, it adds checks for device constructs appearing after device-related REQUIRES directives and for the atomic_default_mem_order clause appearing after atomic operations where the memory order is not explicitly specified.

This is patch 2/5 of a series splitting D149337 to simplify review.

Depends on D157710.

[kiranchandramohan]

LG.

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

403

Nit: Add a comment here that this for combined constructs having target and loop.

801

Nit: Add a comment here on why this is required.

1210–1211

Nit: Not related to this patch, but for ease of recollection, add a comment saying that there are two forms of declare target (one with clauses and the other without).

3032–3033

3040

[skatrak]

Address nit comments and update unit tests.

flang/lib/Semantics/check-omp-structure.h

private:
   void CheckSharedBindingInOuterContext(
       const parser::OmpObjectList &ompObjectList);
   const parser::OmpObjectList *GetOmpObjectList(const parser::OmpClause &);
   void CheckPredefinedAllocatorRestriction(const parser::CharBlock &source,
       const parser::OmpObjectList &ompObjectList);
   void CheckPredefinedAllocatorRestriction(
       const parser::CharBlock &source, const parser::Name &name);
   bool isPredefinedAllocator{false};
+
+  void CheckAllowedRequiresClause(llvmOmpClause clause);
+  bool deviceConstructFound_{false};
+  bool atomicDirectiveDefaultOrderFound_{false};
+
   void EnterDirectiveNest(const int index) { directiveNest_[index]++; }
   void ExitDirectiveNest(const int index) { directiveNest_[index]--; }
   int GetDirectiveNest(const int index) { return directiveNest_[index]; }
   template <typename D> void CheckHintClause(D *, D *);
 
   enum directiveNestType {
     SIMDNest,
     TargetBlockOnlyTeams,
     TargetNest,
     LastType
   };
   int directiveNest_[LastType + 1] = {0};
 };
 } // namespace Fortran::semantics
 #endif // FORTRAN_SEMANTICS_CHECK_OMP_STRUCTURE_H_

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

if (const auto &endLoopDir{
     CheckMatching<parser::OmpLoopDirective>(beginDir, endDir);
   }
 
   PushContextAndClauseSets(beginDir.source, beginDir.v);
   if (llvm::omp::allSimdSet.test(GetContext().directive)) {
     EnterDirectiveNest(SIMDNest);
   }
 
+  // Combined target loop constructs are target device constructs. Keep track of
+  // whether any such construct has been visited to later check that REQUIRES
+  // directives for target-related options don't appear after them.
+  if (llvm::omp::allTargetSet.test(beginDir.v)) {
+    deviceConstructFound_ = true;
+  }
+
   if (beginDir.v == llvm::omp::Directive::OMPD_do) {
     // 2.7.1 do-clause -> private-clause |
     //                    firstprivate-clause |
     //                    lastprivate-clause |
     //                    linear-clause |
     //                    reduction-clause |
     //                    schedule-clause |
     //                    collapse-clause |
if (GetContext().directive == llvm::omp::Directive::OMPD_teams &&
       context_.Say(GetContextParent().directiveSource,
           "TARGET construct with nested TEAMS region contains statements or "
           "directives outside of the TEAMS construct"_err_en_US);
     }
   }
 
   CheckNoBranching(block, beginDir.v, beginDir.source);
 
+  // Target block constructs are target device constructs. Keep track of
+  // whether any such construct has been visited to later check that REQUIRES
+  // directives for target-related options don't appear after them.
+  if (llvm::omp::allTargetSet.test(beginDir.v)) {
+    deviceConstructFound_ = true;
+  }
+
   switch (beginDir.v) {
   case llvm::omp::Directive::OMPD_target:
     if (CheckTargetBlockOnlyTeams(block)) {
       EnterDirectiveNest(TargetBlockOnlyTeams);
     }
     break;
   case llvm::omp::OMPD_workshare:
   case llvm::omp::OMPD_parallel_workshare:
common::visit(
         },
         ompObject.u);
   }
 }
 
 void OmpStructureChecker::Leave(const parser::OpenMPDeclareTargetConstruct &x) {
   const auto &dir{std::get<parser::Verbatim>(x.t)};
   const auto &spec{std::get<parser::OmpDeclareTargetSpecifier>(x.t)};
+  // Handle both forms of DECLARE TARGET.
+  // - Extended list: It behaves as if there was an ENTER/TO clause with the
+  //   list of objects as argument. It accepts no explicit clauses.
+  // - With clauses.
   if (const auto *objectList{parser::Unwrap<parser::OmpObjectList>(spec.u)}) {
+    deviceConstructFound_ = true;
     CheckSymbolNames(dir.source, *objectList);
     CheckIsVarPartOfAnotherVar(dir.source, *objectList);
     CheckThreadprivateOrDeclareTargetVar(*objectList);
   } else if (const auto *clauseList{
                  parser::Unwrap<parser::OmpClauseList>(spec.u)}) {
+    bool toClauseFound{false}, deviceTypeClauseFound{false};
     for (const auto &clause : clauseList->v) {
-      if (const auto *toClause{std::get_if<parser::OmpClause::To>(&clause.u)}) {
-        CheckSymbolNames(dir.source, toClause->v);
-        CheckIsVarPartOfAnotherVar(dir.source, toClause->v);
-        CheckThreadprivateOrDeclareTargetVar(toClause->v);
-      } else if (const auto *linkClause{
-                     std::get_if<parser::OmpClause::Link>(&clause.u)}) {
-        CheckSymbolNames(dir.source, linkClause->v);
-        CheckIsVarPartOfAnotherVar(dir.source, linkClause->v);
-        CheckThreadprivateOrDeclareTargetVar(linkClause->v);
+      common::visit(
+          common::visitors{
+              [&](const parser::OmpClause::To &toClause) {
+                toClauseFound = true;
+                CheckSymbolNames(dir.source, toClause.v);
+                CheckIsVarPartOfAnotherVar(dir.source, toClause.v);
+                CheckThreadprivateOrDeclareTargetVar(toClause.v);
+              },
+              [&](const parser::OmpClause::Link &linkClause) {
+                CheckSymbolNames(dir.source, linkClause.v);
+                CheckIsVarPartOfAnotherVar(dir.source, linkClause.v);
+                CheckThreadprivateOrDeclareTargetVar(linkClause.v);
+              },
+              [&](const parser::OmpClause::DeviceType &deviceTypeClause) {
+                deviceTypeClauseFound = true;
+                if (deviceTypeClause.v.v !=
+                    parser::OmpDeviceTypeClause::Type::Host) {
+                  // Function / subroutine explicitly marked as runnable by the
+                  // target device.
+                  deviceConstructFound_ = true;
+                }
+              },
+              [&](const auto &) {},
+          },
+          clause.u);
+
+      if (toClauseFound && !deviceTypeClauseFound) {
+        deviceConstructFound_ = true;
       }
     }
   }
   dirContext_.pop_back();
 }
 
 void OmpStructureChecker::Enter(const parser::OpenMPExecutableAllocate &x) {
   isPredefinedAllocator = true;
auto checkForValidMemoryOrderClause =
         }
       };
   if (leftHandClauseList) {
     checkForValidMemoryOrderClause(leftHandClauseList);
   }
   if (rightHandClauseList) {
     checkForValidMemoryOrderClause(rightHandClauseList);
   }
+  if (numMemoryOrderClause == 0) {
+    atomicDirectiveDefaultOrderFound_ = true;
+  }
 }
 
 void OmpStructureChecker::Enter(const parser::OpenMPAtomicConstruct &x) {
   common::visit(
       common::visitors{
           [&](const parser::OmpAtomic &atomicConstruct) {
             const auto &dir{std::get<parser::Verbatim>(atomicConstruct.t)};
             PushContextAndClauseSets(

 
 void OmpStructureChecker::Enter(const parser::OmpClause &x) {
   SetContextClause(x);
 }
 
 // Following clauses do not have a separate node in parse-tree.h.
 CHECK_SIMPLE_CLAUSE(AcqRel, OMPC_acq_rel)
 CHECK_SIMPLE_CLAUSE(Acquire, OMPC_acquire)
-CHECK_SIMPLE_CLAUSE(AtomicDefaultMemOrder, OMPC_atomic_default_mem_order)
 CHECK_SIMPLE_CLAUSE(Affinity, OMPC_affinity)
 CHECK_SIMPLE_CLAUSE(Capture, OMPC_capture)
 CHECK_SIMPLE_CLAUSE(Default, OMPC_default)
 CHECK_SIMPLE_CLAUSE(Depobj, OMPC_depobj)
 CHECK_SIMPLE_CLAUSE(Destroy, OMPC_destroy)
 CHECK_SIMPLE_CLAUSE(Detach, OMPC_detach)
 CHECK_SIMPLE_CLAUSE(DeviceType, OMPC_device_type)
 CHECK_SIMPLE_CLAUSE(DistSchedule, OMPC_dist_schedule)
-CHECK_SIMPLE_CLAUSE(DynamicAllocators, OMPC_dynamic_allocators)
 CHECK_SIMPLE_CLAUSE(Exclusive, OMPC_exclusive)
 CHECK_SIMPLE_CLAUSE(Final, OMPC_final)
 CHECK_SIMPLE_CLAUSE(Flush, OMPC_flush)
 CHECK_SIMPLE_CLAUSE(From, OMPC_from)
 CHECK_SIMPLE_CLAUSE(Full, OMPC_full)
 CHECK_SIMPLE_CLAUSE(Hint, OMPC_hint)
 CHECK_SIMPLE_CLAUSE(InReduction, OMPC_in_reduction)
 CHECK_SIMPLE_CLAUSE(Inclusive, OMPC_inclusive)
 CHECK_SIMPLE_CLAUSE(Match, OMPC_match)
 CHECK_SIMPLE_CLAUSE(Nontemporal, OMPC_nontemporal)
 CHECK_SIMPLE_CLAUSE(Order, OMPC_order)
 CHECK_SIMPLE_CLAUSE(Read, OMPC_read)
-CHECK_SIMPLE_CLAUSE(ReverseOffload, OMPC_reverse_offload)
 CHECK_SIMPLE_CLAUSE(Threadprivate, OMPC_threadprivate)
 CHECK_SIMPLE_CLAUSE(Threads, OMPC_threads)
 CHECK_SIMPLE_CLAUSE(Inbranch, OMPC_inbranch)
 CHECK_SIMPLE_CLAUSE(IsDevicePtr, OMPC_is_device_ptr)
 CHECK_SIMPLE_CLAUSE(HasDeviceAddr, OMPC_has_device_addr)
 CHECK_SIMPLE_CLAUSE(Link, OMPC_link)
 CHECK_SIMPLE_CLAUSE(Indirect, OMPC_indirect)
 CHECK_SIMPLE_CLAUSE(Mergeable, OMPC_mergeable)
 CHECK_SIMPLE_CLAUSE(Nogroup, OMPC_nogroup)
 CHECK_SIMPLE_CLAUSE(Notinbranch, OMPC_notinbranch)
 CHECK_SIMPLE_CLAUSE(Nowait, OMPC_nowait)
 CHECK_SIMPLE_CLAUSE(Partial, OMPC_partial)
 CHECK_SIMPLE_CLAUSE(ProcBind, OMPC_proc_bind)
 CHECK_SIMPLE_CLAUSE(Release, OMPC_release)
 CHECK_SIMPLE_CLAUSE(Relaxed, OMPC_relaxed)
 CHECK_SIMPLE_CLAUSE(SeqCst, OMPC_seq_cst)
 CHECK_SIMPLE_CLAUSE(Simd, OMPC_simd)
 CHECK_SIMPLE_CLAUSE(Sizes, OMPC_sizes)
 CHECK_SIMPLE_CLAUSE(TaskReduction, OMPC_task_reduction)
 CHECK_SIMPLE_CLAUSE(To, OMPC_to)
-CHECK_SIMPLE_CLAUSE(UnifiedAddress, OMPC_unified_address)
-CHECK_SIMPLE_CLAUSE(UnifiedSharedMemory, OMPC_unified_shared_memory)
 CHECK_SIMPLE_CLAUSE(Uniform, OMPC_uniform)
 CHECK_SIMPLE_CLAUSE(Unknown, OMPC_unknown)
 CHECK_SIMPLE_CLAUSE(Untied, OMPC_untied)
 CHECK_SIMPLE_CLAUSE(UsesAllocators, OMPC_uses_allocators)
 CHECK_SIMPLE_CLAUSE(Update, OMPC_update)
 CHECK_SIMPLE_CLAUSE(Write, OMPC_write)
 CHECK_SIMPLE_CLAUSE(Init, OMPC_init)
 CHECK_SIMPLE_CLAUSE(Use, OMPC_use)
return common::visit(
             } else {
               return nullptr;
             }
           },
       },
       clause.u);
 }
 
+void OmpStructureChecker::Enter(
+    const parser::OmpClause::AtomicDefaultMemOrder &x) {
+  CheckAllowedRequiresClause(llvm::omp::Clause::OMPC_atomic_default_mem_order);
+}
+
+void OmpStructureChecker::Enter(const parser::OmpClause::DynamicAllocators &x) {
+  CheckAllowedRequiresClause(llvm::omp::Clause::OMPC_dynamic_allocators);
+}
+
+void OmpStructureChecker::Enter(const parser::OmpClause::ReverseOffload &x) {
+  CheckAllowedRequiresClause(llvm::omp::Clause::OMPC_reverse_offload);
+}
+
+void OmpStructureChecker::Enter(const parser::OmpClause::UnifiedAddress &x) {
+  CheckAllowedRequiresClause(llvm::omp::Clause::OMPC_unified_address);
+}
+
+void OmpStructureChecker::Enter(
+    const parser::OmpClause::UnifiedSharedMemory &x) {
+  CheckAllowedRequiresClause(llvm::omp::Clause::OMPC_unified_shared_memory);
+}
+
+void OmpStructureChecker::CheckAllowedRequiresClause(llvmOmpClause clause) {
+  CheckAllowed(clause);
+
+  if (clause == llvm::omp::Clause::OMPC_atomic_default_mem_order) {
+    // Check that it does not appear after an atomic operation without memory
+    // order
+    if (atomicDirectiveDefaultOrderFound_) {
+      context_.Say(GetContext().clauseSource,
+          "REQUIRES directive with '%s' clause found lexically after atomic "
+          "operation without a memory order clause"_err_en_US,
+          parser::ToUpperCaseLetters(getClauseName(clause).str()));
+    }
+  } else {
+    // Check that it does not appear after a device construct
+    if (deviceConstructFound_) {
+      context_.Say(GetContext().clauseSource,
+          "REQUIRES directive with '%s' clause found lexically after device "
+          "construct"_err_en_US,
+          parser::ToUpperCaseLetters(getClauseName(clause).str()));
+    }
+  }
+}
+
 } // namespace Fortran::semantics

flang/test/Semantics/OpenMP/requires02.f90

+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! OpenMP Version 5.0
+! 2.4 Requires directive
+! All atomic_default_mem_order clauses in 'requires' directives must come
+! strictly before any atomic directives on which the memory_order clause is not
+! specified.
+
+subroutine f
+  integer :: a = 0
+  !$omp atomic
+  a = a + 1
+end subroutine f
+
+subroutine g
+  !ERROR: REQUIRES directive with 'ATOMIC_DEFAULT_MEM_ORDER' clause found lexically after atomic operation without a memory order clause
+  !$omp requires atomic_default_mem_order(relaxed)
+end subroutine g

flang/test/Semantics/OpenMP/requires03.f90

+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! OpenMP Version 5.0
+! 2.4 Requires directive
+! Target-related clauses in 'requires' directives must come strictly before any
+! device constructs, such as target regions.
+
+subroutine f
+  !$omp target
+  !$omp end target
+end subroutine f
+
+subroutine g
+  !ERROR: REQUIRES directive with 'DYNAMIC_ALLOCATORS' clause found lexically after device construct
+  !$omp requires dynamic_allocators
+  !ERROR: REQUIRES directive with 'REVERSE_OFFLOAD' clause found lexically after device construct
+  !$omp requires reverse_offload
+  !ERROR: REQUIRES directive with 'UNIFIED_ADDRESS' clause found lexically after device construct
+  !$omp requires unified_address
+  !ERROR: REQUIRES directive with 'UNIFIED_SHARED_MEMORY' clause found lexically after device construct
+  !$omp requires unified_shared_memory
+end subroutine g

flang/test/Semantics/OpenMP/requires04.f90

+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! OpenMP Version 5.0
+! 2.4 Requires directive
+! Target-related clauses in 'requires' directives must come strictly before any
+! device constructs, such as declare target with device_type=nohost|any.
+
+subroutine f
+  !$omp declare target device_type(nohost)
+end subroutine f
+
+subroutine g
+  !ERROR: REQUIRES directive with 'DYNAMIC_ALLOCATORS' clause found lexically after device construct
+  !$omp requires dynamic_allocators
+  !ERROR: REQUIRES directive with 'REVERSE_OFFLOAD' clause found lexically after device construct
+  !$omp requires reverse_offload
+  !ERROR: REQUIRES directive with 'UNIFIED_ADDRESS' clause found lexically after device construct
+  !$omp requires unified_address
+  !ERROR: REQUIRES directive with 'UNIFIED_SHARED_MEMORY' clause found lexically after device construct
+  !$omp requires unified_shared_memory
+end subroutine g

flang/test/Semantics/OpenMP/requires05.f90

+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! OpenMP Version 5.0
+! 2.4 Requires directive
+! Target-related clauses in 'requires' directives must come strictly before any
+! device constructs, such as declare target with 'to' clause and no device_type.
+
+subroutine f
+  !$omp declare target to(f)
+end subroutine f
+
+subroutine g
+  !ERROR: REQUIRES directive with 'DYNAMIC_ALLOCATORS' clause found lexically after device construct
+  !$omp requires dynamic_allocators
+  !ERROR: REQUIRES directive with 'REVERSE_OFFLOAD' clause found lexically after device construct
+  !$omp requires reverse_offload
+  !ERROR: REQUIRES directive with 'UNIFIED_ADDRESS' clause found lexically after device construct
+  !$omp requires unified_address
+  !ERROR: REQUIRES directive with 'UNIFIED_SHARED_MEMORY' clause found lexically after device construct
+  !$omp requires unified_shared_memory
+end subroutine g

flang/test/Semantics/OpenMP/requires06.f90

+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! OpenMP Version 5.0
+! 2.4 Requires directive
+! Target-related clauses in 'requires' directives must come strictly before any
+! device constructs, such as declare target with extended list.
+
+subroutine f
+  !$omp declare target (f)
+end subroutine f
+
+subroutine g
+  !ERROR: REQUIRES directive with 'DYNAMIC_ALLOCATORS' clause found lexically after device construct
+  !$omp requires dynamic_allocators
+  !ERROR: REQUIRES directive with 'REVERSE_OFFLOAD' clause found lexically after device construct
+  !$omp requires reverse_offload
+  !ERROR: REQUIRES directive with 'UNIFIED_ADDRESS' clause found lexically after device construct
+  !$omp requires unified_address
+  !ERROR: REQUIRES directive with 'UNIFIED_SHARED_MEMORY' clause found lexically after device construct
+  !$omp requires unified_shared_memory
+end subroutine g

flang/test/Semantics/OpenMP/requires07.f90

+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! OpenMP Version 5.0
+! 2.4 Requires directive
+! Target-related clauses in 'requires' directives must come strictly before any
+! device constructs, such as target parallel regions.
+
+subroutine f
+  !$omp target parallel
+  !$omp end target parallel
+end subroutine f
+
+subroutine g
+  !ERROR: REQUIRES directive with 'DYNAMIC_ALLOCATORS' clause found lexically after device construct
+  !$omp requires dynamic_allocators
+  !ERROR: REQUIRES directive with 'REVERSE_OFFLOAD' clause found lexically after device construct
+  !$omp requires reverse_offload
+  !ERROR: REQUIRES directive with 'UNIFIED_ADDRESS' clause found lexically after device construct
+  !$omp requires unified_address
+  !ERROR: REQUIRES directive with 'UNIFIED_SHARED_MEMORY' clause found lexically after device construct
+  !$omp requires unified_shared_memory
+end subroutine g

flang/test/Semantics/OpenMP/requires08.f90

+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! OpenMP Version 5.0
+! 2.4 Requires directive
+! Target-related clauses in 'requires' directives must come strictly before any
+! device constructs, such as target teams distribute parallel do loops.
+
+subroutine f
+  !$omp target teams distribute parallel do
+  do i=1, 10
+  end do
+  !$omp end target teams distribute parallel do
+end subroutine f
+
+subroutine g
+  !ERROR: REQUIRES directive with 'DYNAMIC_ALLOCATORS' clause found lexically after device construct
+  !$omp requires dynamic_allocators
+  !ERROR: REQUIRES directive with 'REVERSE_OFFLOAD' clause found lexically after device construct
+  !$omp requires reverse_offload
+  !ERROR: REQUIRES directive with 'UNIFIED_ADDRESS' clause found lexically after device construct
+  !$omp requires unified_address
+  !ERROR: REQUIRES directive with 'UNIFIED_SHARED_MEMORY' clause found lexically after device construct
+  !$omp requires unified_shared_memory
+end subroutine g