[Flang][OpenMP] WIP: Add frontend support for declare variant

Support is added for parsing and semantics. Lowering will emit a TODO error.

append_args clause and use of interop inside have some overlap with #120584.

Author: kiranchandramohan

flang/include/flang/Parser/dump-parse-tree.h

@@ -480,6 +480,13 @@ class ParseTreeDumper {
   NODE(parser, OldParameterStmt)
   NODE(parser, OmpTypeSpecifier)
   NODE(parser, OmpTypeNameList)
+  NODE(parser, OmpAdjustArgsClause)
+  NODE(OmpAdjustArgsClause, OmpAdjustOp)
+  NODE_ENUM(OmpAdjustArgsClause::OmpAdjustOp, Value)
+  NODE(parser, OmpInteropType)
+  NODE_ENUM(OmpInteropType, Value)
+  NODE(parser, OmpAppendArgsClause)
+  NODE(OmpAppendArgsClause, OmpAppendOp)
   NODE(parser, OmpLocator)
   NODE(parser, OmpLocatorList)
   NODE(parser, OmpReductionSpecifier)
@@ -693,6 +700,7 @@ class ParseTreeDumper {
   NODE(parser, OpenMPCriticalConstruct)
   NODE(parser, OpenMPDeclarativeAllocate)
   NODE(parser, OpenMPDeclarativeConstruct)
+  NODE(parser, OmpDeclareVariantDirective)
   NODE(parser, OpenMPDeclareReductionConstruct)
   NODE(parser, OpenMPDeclareSimdConstruct)
   NODE(parser, OpenMPDeclareTargetConstruct)

flang/include/flang/Parser/parse-tree.h

@@ -3974,6 +3974,15 @@ struct OmpAbsentClause {
   WRAPPER_CLASS_BOILERPLATE(OmpAbsentClause, OmpDirectiveList);
 };
 
+struct OmpAdjustArgsClause {
+  TUPLE_CLASS_BOILERPLATE(OmpAdjustArgsClause);
+  struct OmpAdjustOp {
+    ENUM_CLASS(Value, Nothing, NeedDevicePtr)
+    WRAPPER_CLASS_BOILERPLATE(OmpAdjustOp, Value);
+  };
+  std::tuple<OmpAdjustOp, OmpObjectList> t;
+};
+
 // Ref: [5.0:135-140], [5.1:161-166], [5.2:264-265]
 //
 // affinity-clause ->
@@ -4017,6 +4026,22 @@ struct OmpAllocateClause {
   std::tuple<MODIFIERS(), OmpObjectList> t;
 };
 
+
+// InteropType -> target || targetsync
+struct OmpInteropType {
+  ENUM_CLASS(Value, Target, TargetSync)
+  WRAPPER_CLASS_BOILERPLATE(OmpInteropType, Value);
+};
+
+struct OmpAppendArgsClause {
+  struct OmpAppendOp {
+    WRAPPER_CLASS_BOILERPLATE(
+        OmpAppendOp, std::list<OmpInteropType>);
+  };
+  WRAPPER_CLASS_BOILERPLATE(
+      OmpAppendArgsClause, std::list<OmpAppendOp>);
+};
+
 // Ref: [5.2:216-217 (sort of, as it's only mentioned in passing)
 // AT(compilation|execution)
 struct OmpAtClause {
@@ -4625,6 +4650,13 @@ struct OmpBlockDirective {
   CharBlock source;
 };
 
+
+struct OmpDeclareVariantDirective {
+  TUPLE_CLASS_BOILERPLATE(OmpDeclareVariantDirective);
+  CharBlock source;
+  std::tuple<Verbatim, std::optional<Name>, Name, OmpClauseList> t;
+};
+
 // 2.10.6 declare-target -> DECLARE TARGET (extended-list) |
 //                          DECLARE TARGET [declare-target-clause[ [,]
 //                                          declare-target-clause]...]
@@ -4703,7 +4735,7 @@ struct OpenMPDeclarativeConstruct {
   std::variant<OpenMPDeclarativeAllocate, OpenMPDeclarativeAssumes,
       OpenMPDeclareMapperConstruct, OpenMPDeclareReductionConstruct,
       OpenMPDeclareSimdConstruct, OpenMPDeclareTargetConstruct,
-      OpenMPThreadprivate, OpenMPRequiresConstruct, OpenMPUtilityConstruct,
+      OmpDeclareVariantDirective, OpenMPThreadprivate, OpenMPRequiresConstruct, OpenMPUtilityConstruct,
       OmpMetadirectiveDirective>
       u;
 };

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -3126,6 +3126,13 @@ static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
   TODO(converter.getCurrentLocation(), "OpenMP ASSUMES declaration");
 }
 
+static void genOMP(
+    lower::AbstractConverter &converter, lower::SymMap &symTable,
+    semantics::SemanticsContext &semaCtx, lower::pft::Evaluation &eval,
+    const parser::OmpDeclareVariantDirective &declareVariantDirective) {
+  TODO(converter.getCurrentLocation(), "OpenMPDeclareVariantDirective");
+}
+
 static void genOMP(
     lower::AbstractConverter &converter, lower::SymMap &symTable,
     semantics::SemanticsContext &semaCtx, lower::pft::Evaluation &eval,

flang/lib/Parser/openmp-parsers.cpp

@@ -550,6 +550,17 @@ TYPE_PARSER(sourced(construct<OmpToClause::Modifier>(
 TYPE_PARSER(sourced(construct<OmpWhenClause::Modifier>( //
     Parser<OmpContextSelector>{})))
 
+TYPE_PARSER(construct<OmpInteropType>(
+    "TARGETSYNC" >> pure(OmpInteropType::Value::TargetSync) ||
+    "TARGET" >> pure(OmpInteropType::Value::Target)))
+
+TYPE_PARSER(construct<OmpAppendArgsClause::OmpAppendOp>(
+    "INTEROP" >> parenthesized(nonemptyList(Parser<OmpInteropType>{}))))
+
+TYPE_PARSER(construct<OmpAdjustArgsClause::OmpAdjustOp>(
+    "NOTHING" >> pure(OmpAdjustArgsClause::OmpAdjustOp::Value::Nothing) ||
+    "NEED_DEVICE_PTR" >> pure(OmpAdjustArgsClause::OmpAdjustOp::Value::NeedDevicePtr)))
+
 // --- Parsers for clauses --------------------------------------------
 
 /// `MOBClause` is a clause that has a
@@ -569,12 +580,19 @@ static inline MOBClause makeMobClause(
   }
 }
 
+TYPE_PARSER(construct<OmpAdjustArgsClause>(
+    (Parser<OmpAdjustArgsClause::OmpAdjustOp>{} / ":"),
+    Parser<OmpObjectList>{}))
+
 // [5.0] 2.10.1 affinity([aff-modifier:] locator-list)
 //              aff-modifier: interator-modifier
 TYPE_PARSER(construct<OmpAffinityClause>(
     maybe(nonemptyList(Parser<OmpAffinityClause::Modifier>{}) / ":"),
     Parser<OmpObjectList>{}))
 
+TYPE_PARSER(construct<OmpAppendArgsClause>(
+    parenthesized(nonemptyList(Parser<OmpAppendArgsClause::OmpAppendOp>{}))))
+
 // 2.15.3.1 DEFAULT (PRIVATE | FIRSTPRIVATE | SHARED | NONE)
 TYPE_PARSER(construct<OmpDefaultClause::DataSharingAttribute>(
     "PRIVATE" >> pure(OmpDefaultClause::DataSharingAttribute::Private) ||
@@ -808,6 +826,8 @@ TYPE_PARSER("ABSENT" >> construct<OmpClause>(construct<OmpClause::Absent>(
                             parenthesized(Parser<OmpAbsentClause>{}))) ||
     "ACQUIRE" >> construct<OmpClause>(construct<OmpClause::Acquire>()) ||
     "ACQ_REL" >> construct<OmpClause>(construct<OmpClause::AcqRel>()) ||
+    "ADJUST_ARGS" >> construct<OmpClause>(construct<OmpClause::AdjustArgs>(
+                  parenthesized(Parser<OmpAdjustArgsClause>{}))) ||
     "AFFINITY" >> construct<OmpClause>(construct<OmpClause::Affinity>(
                       parenthesized(Parser<OmpAffinityClause>{}))) ||
     "ALIGN" >> construct<OmpClause>(construct<OmpClause::Align>(
@@ -816,6 +836,8 @@ TYPE_PARSER("ABSENT" >> construct<OmpClause>(construct<OmpClause::Absent>(
                      parenthesized(Parser<OmpAlignedClause>{}))) ||
     "ALLOCATE" >> construct<OmpClause>(construct<OmpClause::Allocate>(
                       parenthesized(Parser<OmpAllocateClause>{}))) ||
+    "APPEND_ARGS" >> construct<OmpClause>(construct<OmpClause::AppendArgs>(
+                  parenthesized(Parser<OmpAppendArgsClause>{}))) ||
     "ALLOCATOR" >> construct<OmpClause>(construct<OmpClause::Allocator>(
                        parenthesized(scalarIntExpr))) ||
     "AT" >> construct<OmpClause>(construct<OmpClause::At>(
@@ -1209,6 +1231,11 @@ TYPE_PARSER(construct<OmpInitializerClause>(
     construct<OmpInitializerClause>(Parser<OmpInitializerExpr>{}) ||
     construct<OmpInitializerClause>(Parser<OmpInitializerProc>{})))
 
+// OpenMP 5.2: 7.5.4 Declare Variant directive
+TYPE_PARSER(sourced(construct<OmpDeclareVariantDirective>(
+    verbatim("DECLARE VARIANT"_tok),
+    "(" >> maybe(name / ":"), name / ")", Parser<OmpClauseList>{})))
+
 // 2.16 Declare Reduction Construct
 TYPE_PARSER(sourced(construct<OpenMPDeclareReductionConstruct>(
     verbatim("DECLARE REDUCTION"_tok),
@@ -1380,6 +1407,8 @@ TYPE_PARSER(
                                 Parser<OpenMPDeclareSimdConstruct>{}) ||
                             construct<OpenMPDeclarativeConstruct>(
                                 Parser<OpenMPDeclareTargetConstruct>{}) ||
+                            construct<OpenMPDeclarativeConstruct>(
+                                Parser<OmpDeclareVariantDirective>{}) ||
                             construct<OpenMPDeclarativeConstruct>(
                                 Parser<OpenMPDeclarativeAllocate>{}) ||
                             construct<OpenMPDeclarativeConstruct>(

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

@@ -1604,6 +1604,15 @@ void OmpStructureChecker::Leave(const parser::OpenMPDeclareSimdConstruct &) {
   dirContext_.pop_back();
 }
 
+void OmpStructureChecker::Enter(const parser::OmpDeclareVariantDirective &x) {
+  const auto &dir{std::get<parser::Verbatim>(x.t)};
+  PushContextAndClauseSets(dir.source, llvm::omp::Directive::OMPD_declare_variant);
+}
+
+void OmpStructureChecker::Leave(const parser::OmpDeclareVariantDirective &) {
+  dirContext_.pop_back();
+}
+
 void OmpStructureChecker::Enter(const parser::OpenMPDepobjConstruct &x) {
   const auto &dir{std::get<parser::Verbatim>(x.t)};
   PushContextAndClauseSets(dir.source, llvm::omp::Directive::OMPD_depobj);

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

@@ -96,6 +96,8 @@ class OmpStructureChecker
   void Enter(const parser::OmpEndSectionsDirective &);
   void Leave(const parser::OmpEndSectionsDirective &);
 
+  void Enter(const parser::OmpDeclareVariantDirective &);
+  void Leave(const parser::OmpDeclareVariantDirective &);
   void Enter(const parser::OpenMPDeclareSimdConstruct &);
   void Leave(const parser::OpenMPDeclareSimdConstruct &);
   void Enter(const parser::OpenMPDeclarativeAllocate &);

flang/lib/Semantics/resolve-names.cpp

@@ -1494,6 +1494,25 @@ class OmpVisitor : public virtual DeclarationVisitor {
     return true;
   }
 
+  bool Pre(const parser::OmpDeclareVariantDirective &x) {
+    AddOmpSourceRange(x.source);
+    auto FindSymbolOrError = [](parser::Name& procName) {
+      auto *symbol{FindSymbol(NonDerivedTypeScope(), procName)};
+      if (!symbol) {
+        context().Say(procName.source,
+            "Implicit subroutine declaration '%s' in !$OMP DECLARE VARIANT"_err_en_US,
+            procName.source);
+      }
+    };
+    auto &baseProcName = std::get<std::optional<parser::Name>>(x.t);
+    if (baseProcName) {
+      FindSymbolOrError(*baseProcName);
+    }
+    auto &varProcName = std::get<parser::Name>(x.t);
+    FindSymbolOrError(varProcName);
+    return true;
+  }
+
   bool Pre(const parser::OpenMPDeclareReductionConstruct &x) {
     AddOmpSourceRange(x.source);
     ProcessReductionSpecifier(

llvm/include/llvm/Frontend/OpenMP/OMP.td

@@ -43,6 +43,7 @@ def OMPC_AcqRel : Clause<"acq_rel"> {
   let clangClass = "OMPAcqRelClause";
 }
 def OMPC_AdjustArgs : Clause<"adjust_args"> {
+  let flangClass = "OmpAdjustArgsClause";
 }
 def OMPC_Affinity : Clause<"affinity"> {
   let clangClass = "OMPAffinityClause";
@@ -65,6 +66,7 @@ def OMPC_Allocator : Clause<"allocator"> {
   let flangClass = "ScalarIntExpr";
 }
 def OMPC_AppendArgs : Clause<"append_args"> {
+  let flangClass = "OmpAppendArgsClause";
 }
 def OMPC_At : Clause<"at"> {
   let clangClass = "OMPAtClause";
@@ -712,10 +714,10 @@ def OMP_EndDeclareTarget : Directive<"end declare target"> {
 }
 def OMP_DeclareVariant : Directive<"declare variant"> {
   let allowedClauses = [
-    VersionedClause<OMPC_Match>,
-  ];
-  let allowedExclusiveClauses = [
     VersionedClause<OMPC_AdjustArgs, 51>,
+  ];
+  let allowedOnceClauses = [
+    VersionedClause<OMPC_Match>,
     VersionedClause<OMPC_AppendArgs, 51>,
   ];
   let association = AS_Declaration;