[OpenMP][Flang] Emit default declare mappers implicitly for derived types

This patch adds support to emit default declare mappers for implicit mapping of derived types when not supplied by user. This especially helps tackle mapping of allocatables of derived types.
This supports nested derived types as well.

Author: TIFitis

flang/lib/Lower/OpenMP/ClauseProcessor.cpp

@@ -1102,23 +1102,30 @@ void ClauseProcessor::processMapObjects(
 
   auto getDefaultMapperID = [&](const omp::Object &object,
                                 std::string &mapperIdName) {
-    if (!mlir::isa<mlir::omp::DeclareMapperOp>(
-            firOpBuilder.getRegion().getParentOp())) {
-      const semantics::DerivedTypeSpec *typeSpec = nullptr;
-
-      if (object.sym()->owner().IsDerivedType())
-        typeSpec = object.sym()->owner().derivedTypeSpec();
-      else if (object.sym()->GetType() &&
-               object.sym()->GetType()->category() ==
-                   semantics::DeclTypeSpec::TypeDerived)
-        typeSpec = &object.sym()->GetType()->derivedTypeSpec();
-
-      if (typeSpec) {
-        mapperIdName = typeSpec->name().ToString() + ".omp.default.mapper";
-        if (auto *sym = converter.getCurrentScope().FindSymbol(mapperIdName))
-          mapperIdName = converter.mangleName(mapperIdName, sym->owner());
-      }
+    const semantics::DerivedTypeSpec *typeSpec = nullptr;
+
+    if (object.sym()->GetType() && object.sym()->GetType()->category() ==
+                                       semantics::DeclTypeSpec::TypeDerived)
+      typeSpec = &object.sym()->GetType()->derivedTypeSpec();
+    else if (object.sym()->owner().IsDerivedType())
+      typeSpec = object.sym()->owner().derivedTypeSpec();
+
+    if (typeSpec) {
+      mapperIdName = typeSpec->name().ToString() + ".omp.default.mapper";
+      if (auto *sym = converter.getCurrentScope().FindSymbol(mapperIdName))
+        mapperIdName = converter.mangleName(mapperIdName, sym->owner());
+      else
+        mapperIdName =
+            converter.mangleName(mapperIdName, *typeSpec->GetScope());
     }
+
+    // Make sure we don't return a mapper to self
+    llvm::StringRef parentOpName;
+    if (auto declMapOp = mlir::dyn_cast<mlir::omp::DeclareMapperOp>(
+            firOpBuilder.getRegion().getParentOp()))
+      parentOpName = declMapOp.getSymName();
+    if (mapperIdName == parentOpName)
+      mapperIdName = "";
   };
 
   // Create the mapper symbol from its name, if specified.

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -2348,6 +2348,124 @@ genSingleOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
       queue, item, clauseOps);
 }
 
+static mlir::FlatSymbolRefAttr
+genImplicitDefaultDeclareMapper(lower::AbstractConverter &converter,
+                                mlir::Location loc, fir::RecordType recordType,
+                                llvm::StringRef mapperNameStr) {
+  fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
+  lower::StatementContext stmtCtx;
+
+  // Save current insertion point before moving to the module scope to create
+  // the DeclareMapperOp
+  mlir::OpBuilder::InsertionGuard guard(firOpBuilder);
+
+  firOpBuilder.setInsertionPointToStart(converter.getModuleOp().getBody());
+  auto declMapperOp = firOpBuilder.create<mlir::omp::DeclareMapperOp>(
+      loc, mapperNameStr, recordType);
+  auto &region = declMapperOp.getRegion();
+  firOpBuilder.createBlock(&region);
+  auto mapperArg = region.addArgument(firOpBuilder.getRefType(recordType), loc);
+
+  auto declareOp =
+      firOpBuilder.create<hlfir::DeclareOp>(loc, mapperArg, /*uniq_name=*/"");
+
+  const auto genBoundsOps = [&](mlir::Value mapVal,
+                                llvm::SmallVectorImpl<mlir::Value> &bounds) {
+    fir::ExtendedValue extVal =
+        hlfir::translateToExtendedValue(mapVal.getLoc(), firOpBuilder,
+                                        hlfir::Entity{mapVal},
+                                        /*contiguousHint=*/true)
+            .first;
+    fir::factory::AddrAndBoundsInfo info = fir::factory::getDataOperandBaseAddr(
+        firOpBuilder, mapVal, /*isOptional=*/false, mapVal.getLoc());
+    bounds = fir::factory::genImplicitBoundsOps<mlir::omp::MapBoundsOp,
+                                                mlir::omp::MapBoundsType>(
+        firOpBuilder, info, extVal,
+        /*dataExvIsAssumedSize=*/false, mapVal.getLoc());
+  };
+
+  // Return a reference to the contents of a derived type with one field.
+  // Also return the field type.
+  const auto getFieldRef =
+      [&](mlir::Value rec,
+          unsigned index) -> std::tuple<mlir::Value, mlir::Type> {
+    auto recType = mlir::dyn_cast<fir::RecordType>(
+        fir::unwrapPassByRefType(rec.getType()));
+    auto [fieldName, fieldTy] = recType.getTypeList()[index];
+    mlir::Value field = firOpBuilder.create<fir::FieldIndexOp>(
+        loc, fir::FieldType::get(recType.getContext()), fieldName, recType,
+        fir::getTypeParams(rec));
+    return {firOpBuilder.create<fir::CoordinateOp>(
+                loc, firOpBuilder.getRefType(fieldTy), rec, field),
+            fieldTy};
+  };
+
+  mlir::omp::DeclareMapperInfoOperands clauseOps;
+  llvm::SmallVector<llvm::SmallVector<int64_t>> memberPlacementIndices;
+  llvm::SmallVector<mlir::Value> memberMapOps;
+
+  llvm::omp::OpenMPOffloadMappingFlags mapFlag =
+      llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_TO |
+      llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_FROM |
+      llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_IMPLICIT;
+  mlir::omp::VariableCaptureKind captureKind =
+      mlir::omp::VariableCaptureKind::ByRef;
+  int64_t index = 0;
+
+  // Populate the declareMapper region with the map information.
+  for (const auto &[memberName, memberType] :
+       mlir::dyn_cast<fir::RecordType>(recordType).getTypeList()) {
+    auto [ref, type] = getFieldRef(declareOp.getBase(), index);
+    mlir::FlatSymbolRefAttr mapperId;
+    if (auto recType = mlir::dyn_cast<fir::RecordType>(memberType)) {
+      std::string mapperIdName =
+          recType.getName().str() + ".omp.default.mapper";
+      if (auto *sym = converter.getCurrentScope().FindSymbol(mapperIdName))
+        mapperIdName = converter.mangleName(mapperIdName, sym->owner());
+      else if (auto *sym = converter.getCurrentScope().FindSymbol(memberName))
+        mapperIdName = converter.mangleName(mapperIdName, sym->owner());
+
+      if (converter.getModuleOp().lookupSymbol(mapperIdName))
+        mapperId = mlir::FlatSymbolRefAttr::get(&converter.getMLIRContext(),
+                                                mapperIdName);
+      else
+        mapperId = genImplicitDefaultDeclareMapper(converter, loc, recType,
+                                                   mapperIdName);
+    }
+
+    llvm::SmallVector<mlir::Value> bounds;
+    genBoundsOps(ref, bounds);
+    mlir::Value mapOp = createMapInfoOp(
+        firOpBuilder, loc, ref, /*varPtrPtr=*/mlir::Value{}, "", bounds,
+        /*members=*/{},
+        /*membersIndex=*/mlir::ArrayAttr{},
+        static_cast<
+            std::underlying_type_t<llvm::omp::OpenMPOffloadMappingFlags>>(
+            mapFlag),
+        captureKind, ref.getType(), /*partialMap=*/false, mapperId);
+    memberMapOps.emplace_back(mapOp);
+    memberPlacementIndices.emplace_back(llvm::SmallVector<int64_t>{index++});
+  }
+
+  llvm::SmallVector<mlir::Value> bounds;
+  genBoundsOps(declareOp.getOriginalBase(), bounds);
+  mlir::omp::MapInfoOp mapOp = createMapInfoOp(
+      firOpBuilder, loc, declareOp.getOriginalBase(),
+      /*varPtrPtr=*/mlir::Value(), /*name=*/"", bounds, memberMapOps,
+      firOpBuilder.create2DI64ArrayAttr(memberPlacementIndices),
+      static_cast<std::underlying_type_t<llvm::omp::OpenMPOffloadMappingFlags>>(
+          mapFlag),
+      captureKind, declareOp.getType(0),
+      /*partialMap=*/true);
+
+  clauseOps.mapVars.emplace_back(mapOp);
+
+  firOpBuilder.create<mlir::omp::DeclareMapperInfoOp>(loc, clauseOps.mapVars);
+  // declMapperOp->dumpPretty();
+  return mlir::FlatSymbolRefAttr::get(&converter.getMLIRContext(),
+                                      mapperNameStr);
+}
+
 static mlir::omp::TargetOp
 genTargetOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
             lower::StatementContext &stmtCtx,
@@ -2420,15 +2538,26 @@ genTargetOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
       name << sym.name().ToString();
 
       mlir::FlatSymbolRefAttr mapperId;
-      if (sym.GetType()->category() == semantics::DeclTypeSpec::TypeDerived) {
+      if (sym.GetType()->category() == semantics::DeclTypeSpec::TypeDerived &&
+          defaultMaps.empty()) {
         auto &typeSpec = sym.GetType()->derivedTypeSpec();
         std::string mapperIdName =
             typeSpec.name().ToString() + ".omp.default.mapper";
         if (auto *sym = converter.getCurrentScope().FindSymbol(mapperIdName))
           mapperIdName = converter.mangleName(mapperIdName, sym->owner());
+        else
+          mapperIdName =
+              converter.mangleName(mapperIdName, *typeSpec.GetScope());
+
         if (converter.getModuleOp().lookupSymbol(mapperIdName))
           mapperId = mlir::FlatSymbolRefAttr::get(&converter.getMLIRContext(),
                                                   mapperIdName);
+        else
+          mapperId = genImplicitDefaultDeclareMapper(
+              converter, loc,
+              mlir::cast<fir::RecordType>(
+                  converter.genType(sym.GetType()->derivedTypeSpec())),
+              mapperIdName);
       }
 
       fir::factory::AddrAndBoundsInfo info =
@@ -4039,6 +4168,7 @@ genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
   ClauseProcessor cp(converter, semaCtx, clauses);
   cp.processMap(loc, stmtCtx, clauseOps);
   firOpBuilder.create<mlir::omp::DeclareMapperInfoOp>(loc, clauseOps.mapVars);
+  // declMapperOp->dumpPretty();
 }
 
 static void

flang/lib/Optimizer/OpenMP/MapInfoFinalization.cpp

@@ -377,7 +377,7 @@ class MapInfoFinalizationPass
                                    getDescriptorMapType(mapType, target)),
             op.getMapCaptureTypeAttr(), /*varPtrPtr=*/mlir::Value{}, newMembers,
             newMembersAttr, /*bounds=*/mlir::SmallVector<mlir::Value>{},
-            /*mapperId*/ mlir::FlatSymbolRefAttr(), op.getNameAttr(),
+            op.getMapperIdAttr(), op.getNameAttr(),
             /*partial_map=*/builder.getBoolAttr(false));
     op.replaceAllUsesWith(newDescParentMapOp.getResult());
     op->erase();