[flang][openmp]Add UserReductionDetails and use in DECLARE REDUCTION

flang/include/flang/Semantics/symbol.h

@@ -30,6 +30,8 @@ class raw_ostream;
 }
 namespace Fortran::parser {
 struct Expr;
+struct OpenMPDeclareReductionConstruct;
+struct OmpMetadirectiveDirective;
 }
 
 namespace Fortran::semantics {
@@ -728,14 +730,48 @@ class GenericDetails {
 };
 llvm::raw_ostream &operator<<(llvm::raw_ostream &, const GenericDetails &);
 
+// Used for OpenMP DECLARE REDUCTION, it holds the information
+// needed to resolve which declaration (there could be multiple
+// with the same name) to use for a given type.
+class UserReductionDetails {
+public:
+  using TypeVector = std::vector<const DeclTypeSpec *>;
+  using DeclInfo = std::variant<const parser::OpenMPDeclareReductionConstruct *,
+      const parser::OmpMetadirectiveDirective *>;
+  using DeclVector = std::vector<DeclInfo>;
+
+  UserReductionDetails() = default;
+
+  void AddType(const DeclTypeSpec &type) { typeList_.push_back(&type); }
+  const TypeVector &GetTypeList() const { return typeList_; }
+
+  bool SupportsType(const DeclTypeSpec &type) const {
+    // We have to compare the actual type, not the pointer, as some
+    // types are not guaranteed to be the same object.
+    for (auto t : typeList_) {
+      if (*t == type) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  void AddDecl(const DeclInfo &decl) { declList_.emplace_back(decl); }
+  const DeclVector &GetDeclList() const { return declList_; }
+
+private:
+  TypeVector typeList_;
+  DeclVector declList_;
+};
+
 class UnknownDetails {};
 
 using Details = std::variant<UnknownDetails, MainProgramDetails, ModuleDetails,
     SubprogramDetails, SubprogramNameDetails, EntityDetails,
     ObjectEntityDetails, ProcEntityDetails, AssocEntityDetails,
     DerivedTypeDetails, UseDetails, UseErrorDetails, HostAssocDetails,
     GenericDetails, ProcBindingDetails, NamelistDetails, CommonBlockDetails,
-    TypeParamDetails, MiscDetails>;
+    TypeParamDetails, MiscDetails, UserReductionDetails>;
 llvm::raw_ostream &operator<<(llvm::raw_ostream &, const Details &);
 std::string DetailsToString(const Details &);
 

flang/lib/Parser/unparse.cpp

@@ -3368,4 +3368,12 @@ template void Unparse<Program>(llvm::raw_ostream &, const Program &,
 template void Unparse<Expr>(llvm::raw_ostream &, const Expr &,
     const common::LangOptions &, Encoding, bool, bool, preStatementType *,
     AnalyzedObjectsAsFortran *);
+
+template void Unparse<parser::OpenMPDeclareReductionConstruct>(
+    llvm::raw_ostream &, const parser::OpenMPDeclareReductionConstruct &,
+    const common::LangOptions &, Encoding, bool, bool, preStatementType *,
+    AnalyzedObjectsAsFortran *);
+template void Unparse<parser::OmpMetadirectiveDirective>(llvm::raw_ostream &,
+    const parser::OmpMetadirectiveDirective &, const common::LangOptions &,
+    Encoding, bool, bool, preStatementType *, AnalyzedObjectsAsFortran *);
 } // namespace Fortran::parser

flang/lib/Semantics/assignment.cpp

@@ -43,6 +43,7 @@ class AssignmentContext {
   void Analyze(const parser::PointerAssignmentStmt &);
   void Analyze(const parser::ConcurrentControl &);
   int deviceConstructDepth_{0};
+  SemanticsContext &context() { return context_; }
 
 private:
   bool CheckForPureContext(const SomeExpr &rhs, parser::CharBlock rhsSource);
@@ -218,8 +219,17 @@ void AssignmentContext::PopWhereContext() {
 
 AssignmentChecker::~AssignmentChecker() {}
 
+SemanticsContext &AssignmentChecker::context() {
+  return context_.value().context();
+}
+
 AssignmentChecker::AssignmentChecker(SemanticsContext &context)
     : context_{new AssignmentContext{context}} {}
+
+void AssignmentChecker::Enter(
+    const parser::OpenMPDeclareReductionConstruct &x) {
+  context().set_location(x.source);
+}
 void AssignmentChecker::Enter(const parser::AssignmentStmt &x) {
   context_.value().Analyze(x);
 }

flang/lib/Semantics/assignment.h

@@ -37,6 +37,7 @@ class AssignmentChecker : public virtual BaseChecker {
 public:
   explicit AssignmentChecker(SemanticsContext &);
   ~AssignmentChecker();
+  void Enter(const parser::OpenMPDeclareReductionConstruct &x);
   void Enter(const parser::AssignmentStmt &);
   void Enter(const parser::PointerAssignmentStmt &);
   void Enter(const parser::WhereStmt &);
@@ -54,6 +55,8 @@ class AssignmentChecker : public virtual BaseChecker {
   void Enter(const parser::OpenACCLoopConstruct &);
   void Leave(const parser::OpenACCLoopConstruct &);
 
+  SemanticsContext &context();
+
 private:
   common::Indirection<AssignmentContext> context_;
 };

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

@@ -8,6 +8,7 @@
 
 #include "check-omp-structure.h"
 #include "definable.h"
+#include "resolve-names-utils.h"
 #include "flang/Evaluate/check-expression.h"
 #include "flang/Evaluate/expression.h"
 #include "flang/Evaluate/type.h"
@@ -3520,6 +3521,17 @@ bool OmpStructureChecker::CheckReductionOperator(
         break;
       }
     }
+    // User-defined operators are OK if there has been a declared reduction
+    // for that. We mangle those names to store the user details.
+    if (const auto *definedOp{std::get_if<parser::DefinedOpName>(&dOpr.u)}) {
+      std::string mangled{MangleDefinedOperator(definedOp->v.symbol->name())};
+      const Scope &scope{definedOp->v.symbol->owner()};
+      if (const Symbol *symbol{scope.FindSymbol(mangled)}) {
+        if (symbol->detailsIf<UserReductionDetails>()) {
+          return true;
+        }
+      }
+    }
     context_.Say(source, "Invalid reduction operator in %s clause."_err_en_US,
         parser::ToUpperCaseLetters(getClauseName(clauseId).str()));
     return false;
@@ -3533,8 +3545,7 @@ bool OmpStructureChecker::CheckReductionOperator(
       valid =
           llvm::is_contained({"max", "min", "iand", "ior", "ieor"}, realName);
       if (!valid) {
-        auto *misc{name->symbol->detailsIf<MiscDetails>()};
-        valid = misc && misc->kind() == MiscDetails::Kind::ConstructName;
+        valid = name->symbol->detailsIf<UserReductionDetails>();
       }
     }
     if (!valid) {
@@ -3614,8 +3625,20 @@ void OmpStructureChecker::CheckReductionObjects(
   }
 }
 
+static bool CheckSymbolSupportsType(const Scope &scope,
+    const parser::CharBlock &name, const DeclTypeSpec &type) {
+  if (const auto *symbol{scope.FindSymbol(name)}) {
+    if (const auto *reductionDetails{
+            symbol->detailsIf<UserReductionDetails>()}) {
+      return reductionDetails->SupportsType(type);
+    }
+  }
+  return false;
+}
+
 static bool IsReductionAllowedForType(
-    const parser::OmpReductionIdentifier &ident, const DeclTypeSpec &type) {
+    const parser::OmpReductionIdentifier &ident, const DeclTypeSpec &type,
+    const Scope &scope, SemanticsContext &context) {
   auto isLogical{[](const DeclTypeSpec &type) -> bool {
     return type.category() == DeclTypeSpec::Logical;
   }};
@@ -3635,27 +3658,40 @@ static bool IsReductionAllowedForType(
       case parser::DefinedOperator::IntrinsicOperator::Multiply:
       case parser::DefinedOperator::IntrinsicOperator::Add:
       case parser::DefinedOperator::IntrinsicOperator::Subtract:
-        return type.IsNumeric(TypeCategory::Integer) ||
+        if (type.IsNumeric(TypeCategory::Integer) ||
             type.IsNumeric(TypeCategory::Real) ||
-            type.IsNumeric(TypeCategory::Complex);
+            type.IsNumeric(TypeCategory::Complex))
+          return true;
+        break;
 
       case parser::DefinedOperator::IntrinsicOperator::AND:
       case parser::DefinedOperator::IntrinsicOperator::OR:
       case parser::DefinedOperator::IntrinsicOperator::EQV:
       case parser::DefinedOperator::IntrinsicOperator::NEQV:
-        return isLogical(type);
+        if (isLogical(type)) {
+          return true;
+        }
+        break;
 
       // Reduction identifier is not in OMP5.2 Table 5.2
       default:
         DIE("This should have been caught in CheckIntrinsicOperator");
         return false;
       }
-    }
-    return true;
+      parser::CharBlock name{MakeNameFromOperator(*intrinsicOp, context)};
+      return CheckSymbolSupportsType(scope, name, type);
+    } else if (const auto *definedOp{
+                   std::get_if<parser::DefinedOpName>(&dOpr.u)}) {
+      return CheckSymbolSupportsType(
+          scope, MangleDefinedOperator(definedOp->v.symbol->name()), type);
+    }
+    llvm_unreachable(
+        "A DefinedOperator is either a DefinedOpName or an IntrinsicOperator");
   }};
 
   auto checkDesignator{[&](const parser::ProcedureDesignator &procD) {
     const parser::Name *name{std::get_if<parser::Name>(&procD.u)};
+    CHECK(name && name->symbol);
     if (name && name->symbol) {
       const SourceName &realName{name->symbol->GetUltimate().name()};
       // OMP5.2: The type [...] of a list item that appears in a
@@ -3664,18 +3700,35 @@ static bool IsReductionAllowedForType(
         // IAND: arguments must be integers: F2023 16.9.100
         // IEOR: arguments must be integers: F2023 16.9.106
         // IOR: arguments must be integers: F2023 16.9.111
-        return type.IsNumeric(TypeCategory::Integer);
+        if (type.IsNumeric(TypeCategory::Integer)) {
+          return true;
+        }
       } else if (realName == "max" || realName == "min") {
         // MAX: arguments must be integer, real, or character:
         // F2023 16.9.135
         // MIN: arguments must be integer, real, or character:
         // F2023 16.9.141
-        return type.IsNumeric(TypeCategory::Integer) ||
-            type.IsNumeric(TypeCategory::Real) || isCharacter(type);
+        if (type.IsNumeric(TypeCategory::Integer) ||
+            type.IsNumeric(TypeCategory::Real) || isCharacter(type)) {
+          return true;
+        }
       }
+
+      // If we get here, it may be a user declared reduction, so check
+      // if the symbol has UserReductionDetails, and if so, the type is
+      // supported.
+      if (const auto *reductionDetails{
+              name->symbol->detailsIf<UserReductionDetails>()}) {
+        return reductionDetails->SupportsType(type);
+      }
+
+      // We also need to check for mangled names (max, min, iand, ieor and ior)
+      // and then check if the type is there.
+      parser::CharBlock mangledName{MangleSpecialFunctions(name->source)};
+      return CheckSymbolSupportsType(scope, mangledName, type);
     }
-    // TODO: user defined reduction operators. Just allow everything for now.
-    return true;
+    // Everything else is "not matching type".
+    return false;
   }};
 
   return common::visit(
@@ -3690,7 +3743,8 @@ void OmpStructureChecker::CheckReductionObjectTypes(
 
   for (auto &[symbol, source] : symbols) {
     if (auto *type{symbol->GetType()}) {
-      if (!IsReductionAllowedForType(ident, *type)) {
+      const auto &scope{context_.FindScope(symbol->name())};
+      if (!IsReductionAllowedForType(ident, *type, scope, context_)) {
         context_.Say(source,
             "The type of '%s' is incompatible with the reduction operator."_err_en_US,
             symbol->name());

flang/lib/Semantics/mod-file.cpp

@@ -894,6 +894,7 @@ void ModFileWriter::PutEntity(llvm::raw_ostream &os, const Symbol &symbol) {
           [&](const ObjectEntityDetails &) { PutObjectEntity(os, symbol); },
           [&](const ProcEntityDetails &) { PutProcEntity(os, symbol); },
           [&](const TypeParamDetails &) { PutTypeParam(os, symbol); },
+          [&](const UserReductionDetails &) { PutUserReduction(os, symbol); },
           [&](const auto &) {
             common::die("PutEntity: unexpected details: %s",
                 DetailsToString(symbol.details()).c_str());
@@ -1043,6 +1044,28 @@ void ModFileWriter::PutTypeParam(llvm::raw_ostream &os, const Symbol &symbol) {
   os << '\n';
 }
 
+void ModFileWriter::PutUserReduction(
+    llvm::raw_ostream &os, const Symbol &symbol) {
+  const auto &details{symbol.get<UserReductionDetails>()};
+  // The module content for a OpenMP Declare Reduction is the OpenMP
+  // declaration. There may be multiple declarations.
+  // Decls are pointers, so do not use a reference.
+  for (const auto decl : details.GetDeclList()) {
+    common::visit( //
+        common::visitors{//
+            [&](const parser::OpenMPDeclareReductionConstruct *d) {
+              Unparse(os, *d, context_.langOptions());
+            },
+            [&](const parser::OmpMetadirectiveDirective *m) {
+              Unparse(os, *m, context_.langOptions());
+            },
+            [&](const auto &) {
+              DIE("Unknown OpenMP DECLARE REDUCTION content");
+            }},
+        decl);
+  }
+}
+
 void PutInit(llvm::raw_ostream &os, const Symbol &symbol, const MaybeExpr &init,
     const parser::Expr *unanalyzed, SemanticsContext &context) {
   if (IsNamedConstant(symbol) || symbol.owner().IsDerivedType()) {

flang/lib/Semantics/mod-file.h

@@ -80,6 +80,7 @@ class ModFileWriter {
   void PutDerivedType(const Symbol &, const Scope * = nullptr);
   void PutDECStructure(const Symbol &, const Scope * = nullptr);
   void PutTypeParam(llvm::raw_ostream &, const Symbol &);
+  void PutUserReduction(llvm::raw_ostream &, const Symbol &);
   void PutSubprogram(const Symbol &);
   void PutGeneric(const Symbol &);
   void PutUse(const Symbol &);

flang/lib/Semantics/resolve-names-utils.h

@@ -146,5 +146,11 @@ struct SymbolAndTypeMappings;
 void MapSubprogramToNewSymbols(const Symbol &oldSymbol, Symbol &newSymbol,
     Scope &newScope, SymbolAndTypeMappings * = nullptr);
 
+parser::CharBlock MakeNameFromOperator(
+    const parser::DefinedOperator::IntrinsicOperator &op,
+    SemanticsContext &context);
+parser::CharBlock MangleSpecialFunctions(const parser::CharBlock &name);
+std::string MangleDefinedOperator(const parser::CharBlock &name);
+
 } // namespace Fortran::semantics
 #endif // FORTRAN_SEMANTICS_RESOLVE_NAMES_H_