Reland "[flang] add option to generate runtime type info as external (llvm#145901)" (llvm#2923)

Author: ronlieb

flang/include/flang/Evaluate/tools.h

@@ -1585,6 +1585,7 @@ bool IsExtensibleType(const DerivedTypeSpec *);
 bool IsSequenceOrBindCType(const DerivedTypeSpec *);
 bool IsBuiltinDerivedType(const DerivedTypeSpec *derived, const char *name);
 bool IsBuiltinCPtr(const Symbol &);
+bool IsFromBuiltinModule(const Symbol &);
 bool IsEventType(const DerivedTypeSpec *);
 bool IsLockType(const DerivedTypeSpec *);
 bool IsNotifyType(const DerivedTypeSpec *);

flang/include/flang/Lower/LoweringOptions.def

@@ -66,5 +66,9 @@ ENUM_LOWERINGOPT(RepackArraysWhole, unsigned, 1, 0)
 /// If true, CUDA Fortran runtime check is inserted.
 ENUM_LOWERINGOPT(CUDARuntimeCheck, unsigned, 1, 0)
 
+/// If true, do not generate definition for runtime type info global objects of
+/// derived types defined in other compilation units.
+ENUM_LOWERINGOPT(SkipExternalRttiDefinition, unsigned, 1, 0)
+
 #undef LOWERINGOPT
 #undef ENUM_LOWERINGOPT

flang/include/flang/Optimizer/CodeGen/CodeGen.h

@@ -39,6 +39,9 @@ struct FIRToLLVMPassOptions {
   // that such programs would crash at runtime if the derived type descriptors
   // are required by the runtime, so this is only an option to help debugging.
   bool ignoreMissingTypeDescriptors = false;
+  // Similar to ignoreMissingTypeDescriptors, but generate external declaration
+  // for the missing type descriptor globals instead.
+  bool skipExternalRttiDefinition = false;
 
   // Generate TBAA information for FIR types and memory accessing operations.
   bool applyTBAA = false;

flang/include/flang/Optimizer/Passes/CommandLineOpts.h

@@ -32,6 +32,19 @@ extern llvm::cl::opt<std::size_t> arrayStackAllocationThreshold;
 /// generated by the frontend.
 extern llvm::cl::opt<bool> ignoreMissingTypeDescriptors;
 
+/// Shared option in tools to only generate rtti static object definitions for
+/// derived types defined in the current compilation unit. Derived type
+/// descriptor object for types defined in other objects will only be declared
+/// as external. This also changes the linkage of rtti objects defined in the
+/// current compilation unit from linkonce_odr to external so that unused rtti
+/// objects are retained and can be accessed from other compilation units. This
+/// is an experimental option to explore compilation speed improvements and is
+/// an ABI breaking change because of the linkage change.
+/// It will also require linking against module file objects of modules defining
+/// only types (even for trivial types without type bound procedures, which
+/// differs from most compilers).
+extern llvm::cl::opt<bool> skipExternalRttiDefinition;
+
 /// Default optimization level used to create Flang pass pipeline is O0.
 extern llvm::OptimizationLevel defaultOptLevel;
 

flang/include/flang/Optimizer/Support/Utils.h

@@ -35,32 +35,6 @@ inline std::int64_t toInt(mlir::arith::ConstantOp cop) {
       .getSExtValue();
 }
 
-// Reconstruct binding tables for dynamic dispatch.
-using BindingTable = llvm::DenseMap<llvm::StringRef, unsigned>;
-using BindingTables = llvm::DenseMap<llvm::StringRef, BindingTable>;
-
-inline void buildBindingTables(BindingTables &bindingTables,
-                               mlir::ModuleOp mod) {
-
-  // The binding tables are defined in FIR after lowering inside fir.type_info
-  // operations. Go through each binding tables and store the procedure name and
-  // binding index for later use by the fir.dispatch conversion pattern.
-  for (auto typeInfo : mod.getOps<fir::TypeInfoOp>()) {
-    unsigned bindingIdx = 0;
-    BindingTable bindings;
-    if (typeInfo.getDispatchTable().empty()) {
-      bindingTables[typeInfo.getSymName()] = bindings;
-      continue;
-    }
-    for (auto dtEntry :
-         typeInfo.getDispatchTable().front().getOps<fir::DTEntryOp>()) {
-      bindings[dtEntry.getMethod()] = bindingIdx;
-      ++bindingIdx;
-    }
-    bindingTables[typeInfo.getSymName()] = bindings;
-  }
-}
-
 // Translate front-end KINDs for use in the IR and code gen.
 inline std::vector<fir::KindTy>
 fromDefaultKinds(const Fortran::common::IntrinsicTypeDefaultKinds &defKinds) {

flang/include/flang/Semantics/runtime-type-info.h

@@ -38,6 +38,10 @@ RuntimeDerivedTypeTables BuildRuntimeDerivedTypeTables(SemanticsContext &);
 /// to describe other derived types at runtime in flang descriptor.
 constexpr char typeInfoBuiltinModule[]{"__fortran_type_info"};
 
+/// Name of the builtin derived type in __fortran_type_inf that is used for
+/// derived type descriptors.
+constexpr char typeDescriptorTypeName[]{"derivedtype"};
+
 /// Name of the bindings descriptor component in the DerivedType type of the
 /// __Fortran_type_info module
 constexpr char bindingDescCompName[]{"binding"};

flang/lib/Evaluate/tools.cpp

@@ -2334,6 +2334,11 @@ bool IsBuiltinCPtr(const Symbol &symbol) {
   return false;
 }
 
+bool IsFromBuiltinModule(const Symbol &symbol) {
+  const Scope &scope{symbol.GetUltimate().owner()};
+  return IsSameModule(&scope, scope.context().GetBuiltinsScope());
+}
+
 bool IsIsoCType(const DerivedTypeSpec *derived) {
   return IsBuiltinDerivedType(derived, "c_ptr") ||
       IsBuiltinDerivedType(derived, "c_funptr");

flang/lib/Frontend/CompilerInvocation.cpp

@@ -14,6 +14,7 @@
 #include "flang/Frontend/CodeGenOptions.h"
 #include "flang/Frontend/PreprocessorOptions.h"
 #include "flang/Frontend/TargetOptions.h"
+#include "flang/Optimizer/Passes/CommandLineOpts.h"
 #include "flang/Semantics/semantics.h"
 #include "flang/Support/Fortran-features.h"
 #include "flang/Support/OpenMP-features.h"
@@ -1807,6 +1808,7 @@ void CompilerInvocation::setLoweringOptions() {
   // Lower TRANSPOSE as a runtime call under -O0.
   loweringOpts.setOptimizeTranspose(codegenOpts.OptimizationLevel > 0);
   loweringOpts.setUnderscoring(codegenOpts.Underscoring);
+  loweringOpts.setSkipExternalRttiDefinition(skipExternalRttiDefinition);
 
   const Fortran::common::LangOptions &langOptions = getLangOpts();
   loweringOpts.setIntegerWrapAround(langOptions.getSignedOverflowBehavior() ==

flang/lib/Lower/Bridge.cpp

@@ -263,6 +263,7 @@ class TypeInfoConverter {
   }
 
   void createTypeInfo(Fortran::lower::AbstractConverter &converter) {
+    createTypeInfoForTypeDescriptorBuiltinType(converter);
     while (!registeredTypeInfoA.empty()) {
       currentTypeInfoStack = &registeredTypeInfoB;
       for (const TypeInfo &info : registeredTypeInfoA)
@@ -278,10 +279,22 @@ class TypeInfoConverter {
 private:
   void createTypeInfoOpAndGlobal(Fortran::lower::AbstractConverter &converter,
                                  const TypeInfo &info) {
-    Fortran::lower::createRuntimeTypeInfoGlobal(converter, info.symbol.get());
+    if (!converter.getLoweringOptions().getSkipExternalRttiDefinition())
+      Fortran::lower::createRuntimeTypeInfoGlobal(converter, info.symbol.get());
     createTypeInfoOp(converter, info);
   }
 
+  void createTypeInfoForTypeDescriptorBuiltinType(
+      Fortran::lower::AbstractConverter &converter) {
+    if (registeredTypeInfoA.empty())
+      return;
+    auto builtinTypeInfoType = llvm::cast<fir::RecordType>(
+        converter.genType(registeredTypeInfoA[0].symbol.get()));
+    converter.getFirOpBuilder().createTypeInfoOp(
+        registeredTypeInfoA[0].loc, builtinTypeInfoType,
+        /*parentType=*/fir::RecordType{});
+  }
+
   void createTypeInfoOp(Fortran::lower::AbstractConverter &converter,
                         const TypeInfo &info) {
     fir::RecordType parentType{};

flang/lib/Lower/ConvertVariable.cpp

@@ -647,13 +647,19 @@ fir::GlobalOp Fortran::lower::defineGlobal(
 
 /// Return linkage attribute for \p var.
 static mlir::StringAttr
-getLinkageAttribute(fir::FirOpBuilder &builder,
+getLinkageAttribute(Fortran::lower::AbstractConverter &converter,
                     const Fortran::lower::pft::Variable &var) {
+  fir::FirOpBuilder &builder = converter.getFirOpBuilder();
   // Runtime type info for a same derived type is identical in each compilation
   // unit. It desired to avoid having to link against module that only define a
   // type. Therefore the runtime type info is generated everywhere it is needed
-  // with `linkonce_odr` LLVM linkage.
-  if (var.isRuntimeTypeInfoData())
+  // with `linkonce_odr` LLVM linkage (unless the skipExternalRttiDefinition
+  // option is set, in which case one will need to link against objects of
+  // modules defining types). Builtin objects rtti is always generated because
+  // the builtin module is currently not compiled or part of the runtime.
+  if (var.isRuntimeTypeInfoData() &&
+      (!converter.getLoweringOptions().getSkipExternalRttiDefinition() ||
+       Fortran::semantics::IsFromBuiltinModule(var.getSymbol())))
     return builder.createLinkOnceODRLinkage();
   if (var.isModuleOrSubmoduleVariable())
     return {}; // external linkage
@@ -673,7 +679,7 @@ static void instantiateGlobal(Fortran::lower::AbstractConverter &converter,
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
   std::string globalName = converter.mangleName(sym);
   mlir::Location loc = genLocation(converter, sym);
-  mlir::StringAttr linkage = getLinkageAttribute(builder, var);
+  mlir::StringAttr linkage = getLinkageAttribute(converter, var);
   fir::GlobalOp global;
   if (var.isModuleOrSubmoduleVariable()) {
     // A non-intrinsic module global is defined when lowering the module.
@@ -1265,7 +1271,7 @@ instantiateAggregateStore(Fortran::lower::AbstractConverter &converter,
   if (var.isGlobal()) {
     fir::GlobalOp global;
     auto &aggregate = var.getAggregateStore();
-    mlir::StringAttr linkage = getLinkageAttribute(builder, var);
+    mlir::StringAttr linkage = getLinkageAttribute(converter, var);
     if (var.isModuleOrSubmoduleVariable()) {
       // A module global was or will be defined when lowering the module. Emit
       // only a declaration if the global does not exist at that point.
@@ -2470,8 +2476,7 @@ void Fortran::lower::defineModuleVariable(
     AbstractConverter &converter, const Fortran::lower::pft::Variable &var) {
   // Use empty linkage for module variables, which makes them available
   // for use in another unit.
-  mlir::StringAttr linkage =
-      getLinkageAttribute(converter.getFirOpBuilder(), var);
+  mlir::StringAttr linkage = getLinkageAttribute(converter, var);
   if (!var.isGlobal())
     fir::emitFatalError(converter.getCurrentLocation(),
                         "attempting to lower module variable as local");
@@ -2606,10 +2611,9 @@ void Fortran::lower::createIntrinsicModuleGlobal(
 void Fortran::lower::createRuntimeTypeInfoGlobal(
     Fortran::lower::AbstractConverter &converter,
     const Fortran::semantics::Symbol &typeInfoSym) {
-  fir::FirOpBuilder &builder = converter.getFirOpBuilder();
   std::string globalName = converter.mangleName(typeInfoSym);
   auto var = Fortran::lower::pft::Variable(typeInfoSym, /*global=*/true);
-  mlir::StringAttr linkage = getLinkageAttribute(builder, var);
+  mlir::StringAttr linkage = getLinkageAttribute(converter, var);
   defineGlobal(converter, var, globalName, linkage);
 }
 

flang/lib/Optimizer/CodeGen/CodeGen.cpp

@@ -1332,6 +1332,56 @@ genCUFAllocDescriptor(mlir::Location loc,
       .getResult();
 }
 
+/// Get the address of the type descriptor global variable that was created by
+/// lowering for derived type \p recType.
+template <typename ModOpTy>
+static mlir::Value
+getTypeDescriptor(ModOpTy mod, mlir::ConversionPatternRewriter &rewriter,
+                  mlir::Location loc, fir::RecordType recType,
+                  const fir::FIRToLLVMPassOptions &options) {
+  std::string name =
+      options.typeDescriptorsRenamedForAssembly
+          ? fir::NameUniquer::getTypeDescriptorAssemblyName(recType.getName())
+          : fir::NameUniquer::getTypeDescriptorName(recType.getName());
+  mlir::Type llvmPtrTy = ::getLlvmPtrType(mod.getContext());
+  mlir::DataLayout dataLayout(mod);
+  if (auto global = mod.template lookupSymbol<fir::GlobalOp>(name))
+    return replaceWithAddrOfOrASCast(
+        rewriter, loc, fir::factory::getGlobalAddressSpace(&dataLayout),
+        fir::factory::getProgramAddressSpace(&dataLayout), global.getSymName(),
+        llvmPtrTy);
+  // The global may have already been translated to LLVM.
+  if (auto global = mod.template lookupSymbol<mlir::LLVM::GlobalOp>(name))
+    return replaceWithAddrOfOrASCast(
+        rewriter, loc, global.getAddrSpace(),
+        fir::factory::getProgramAddressSpace(&dataLayout), global.getSymName(),
+        llvmPtrTy);
+  // Type info derived types do not have type descriptors since they are the
+  // types defining type descriptors.
+  if (options.ignoreMissingTypeDescriptors ||
+      fir::NameUniquer::belongsToModule(
+          name, Fortran::semantics::typeInfoBuiltinModule))
+    return rewriter.create<mlir::LLVM::ZeroOp>(loc, llvmPtrTy);
+
+  if (!options.skipExternalRttiDefinition)
+    fir::emitFatalError(loc,
+                        "runtime derived type info descriptor was not "
+                        "generated and skipExternalRttiDefinition and "
+                        "ignoreMissingTypeDescriptors options are not set");
+
+  // Rtti for a derived type defined in another compilation unit and for which
+  // rtti was not defined in lowering because of the skipExternalRttiDefinition
+  // option. Generate the object declaration now.
+  auto insertPt = rewriter.saveInsertionPoint();
+  rewriter.setInsertionPoint(mod.getBody(), mod.getBody()->end());
+  mlir::LLVM::GlobalOp global = rewriter.create<mlir::LLVM::GlobalOp>(
+      loc, llvmPtrTy, /*constant=*/true, mlir::LLVM::Linkage::External, name,
+      mlir::Attribute());
+  rewriter.restoreInsertionPoint(insertPt);
+  return rewriter.create<mlir::LLVM::AddressOfOp>(loc, llvmPtrTy,
+                                                  global.getSymName());
+}
+
 /// Common base class for embox to descriptor conversion.
 template <typename OP>
 struct EmboxCommonConversion : public fir::FIROpConversion<OP> {
@@ -1444,41 +1494,6 @@ struct EmboxCommonConversion : public fir::FIROpConversion<OP> {
                        stride);
   }
 
-  /// Get the address of the type descriptor global variable that was created by
-  /// lowering for derived type \p recType.
-  template <typename ModOpTy>
-  mlir::Value
-  getTypeDescriptor(ModOpTy mod, mlir::ConversionPatternRewriter &rewriter,
-                    mlir::Location loc, fir::RecordType recType) const {
-    std::string name =
-        this->options.typeDescriptorsRenamedForAssembly
-            ? fir::NameUniquer::getTypeDescriptorAssemblyName(recType.getName())
-            : fir::NameUniquer::getTypeDescriptorName(recType.getName());
-    mlir::Type llvmPtrTy = ::getLlvmPtrType(mod.getContext());
-    mlir::DataLayout dataLayout(mod);
-    if (auto global = mod.template lookupSymbol<fir::GlobalOp>(name)) {
-      return replaceWithAddrOfOrASCast(
-          rewriter, loc, fir::factory::getGlobalAddressSpace(&dataLayout),
-          fir::factory::getProgramAddressSpace(&dataLayout),
-          global.getSymName(), llvmPtrTy);
-    }
-    if (auto global = mod.template lookupSymbol<mlir::LLVM::GlobalOp>(name)) {
-      // The global may have already been translated to LLVM.
-      return replaceWithAddrOfOrASCast(
-          rewriter, loc, global.getAddrSpace(),
-          fir::factory::getProgramAddressSpace(&dataLayout),
-          global.getSymName(), llvmPtrTy);
-    }
-    // Type info derived types do not have type descriptors since they are the
-    // types defining type descriptors.
-    if (!this->options.ignoreMissingTypeDescriptors &&
-        !fir::NameUniquer::belongsToModule(
-            name, Fortran::semantics::typeInfoBuiltinModule))
-      fir::emitFatalError(
-          loc, "runtime derived type info descriptor was not generated");
-    return rewriter.create<mlir::LLVM::ZeroOp>(loc, llvmPtrTy);
-  }
-
   template <typename ModOpTy>
   mlir::Value populateDescriptor(mlir::Location loc, ModOpTy mod,
                                  fir::BaseBoxType boxTy, mlir::Type inputType,
@@ -1543,16 +1558,17 @@ struct EmboxCommonConversion : public fir::FIROpConversion<OP> {
           mlir::Type innerType = fir::unwrapInnerType(inputType);
           if (innerType && mlir::isa<fir::RecordType>(innerType)) {
             auto recTy = mlir::dyn_cast<fir::RecordType>(innerType);
-            typeDesc = getTypeDescriptor(mod, rewriter, loc, recTy);
+            typeDesc =
+                getTypeDescriptor(mod, rewriter, loc, recTy, this->options);
           } else {
             // Unlimited polymorphic type descriptor with no record type. Set
             // type descriptor address to a clean state.
             typeDesc = rewriter.create<mlir::LLVM::ZeroOp>(
                 loc, ::getLlvmPtrType(mod.getContext()));
           }
         } else {
-          typeDesc = getTypeDescriptor(mod, rewriter, loc,
-                                       fir::unwrapIfDerived(boxTy));
+          typeDesc = getTypeDescriptor(
+              mod, rewriter, loc, fir::unwrapIfDerived(boxTy), this->options);
         }
       }
       if (typeDesc)
@@ -3064,26 +3080,10 @@ struct TypeDescOpConversion : public fir::FIROpConversion<fir::TypeDescOp> {
     assert(mlir::isa<fir::RecordType>(inTy) && "expecting fir.type");
     auto recordType = mlir::dyn_cast<fir::RecordType>(inTy);
     auto module = typeDescOp.getOperation()->getParentOfType<mlir::ModuleOp>();
-    std::string typeDescName =
-        this->options.typeDescriptorsRenamedForAssembly
-            ? fir::NameUniquer::getTypeDescriptorAssemblyName(
-                  recordType.getName())
-            : fir::NameUniquer::getTypeDescriptorName(recordType.getName());
-    auto llvmPtrTy = ::getLlvmPtrType(typeDescOp.getContext());
-    if (auto global = module.lookupSymbol<mlir::LLVM::GlobalOp>(typeDescName)) {
-      replaceWithAddrOfOrASCast(rewriter, typeDescOp->getLoc(),
-                                global.getAddrSpace(),
-                                getProgramAddressSpace(rewriter),
-                                global.getSymName(), llvmPtrTy, typeDescOp);
-      return mlir::success();
-    } else if (auto global = module.lookupSymbol<fir::GlobalOp>(typeDescName)) {
-      replaceWithAddrOfOrASCast(rewriter, typeDescOp->getLoc(),
-                                getGlobalAddressSpace(rewriter),
-                                getProgramAddressSpace(rewriter),
-                                global.getSymName(), llvmPtrTy, typeDescOp);
-      return mlir::success();
-    }
-    return mlir::failure();
+    mlir::Value typeDesc = getTypeDescriptor(
+        module, rewriter, typeDescOp.getLoc(), recordType, this->options);
+    rewriter.replaceOp(typeDescOp, typeDesc);
+    return mlir::success();
   }
 };
 

flang/lib/Optimizer/Passes/CommandLineOpts.cpp

@@ -39,6 +39,12 @@ cl::opt<bool> ignoreMissingTypeDescriptors(
              "translating FIR to LLVM"),
     cl::init(false), cl::Hidden);
 
+cl::opt<bool> skipExternalRttiDefinition(
+    "skip-external-rtti-definition", llvm::cl::init(false),
+    llvm::cl::desc("do not define rtti static objects for types belonging to "
+                   "other compilation units"),
+    cl::Hidden);
+
 OptimizationLevel defaultOptLevel{OptimizationLevel::O0};
 
 codegenoptions::DebugInfoKind noDebugInfo{codegenoptions::NoDebugInfo};

flang/lib/Optimizer/Passes/Pipelines.cpp

@@ -108,6 +108,7 @@ void addFIRToLLVMPass(mlir::PassManager &pm,
                       const MLIRToLLVMPassPipelineConfig &config) {
   fir::FIRToLLVMPassOptions options;
   options.ignoreMissingTypeDescriptors = ignoreMissingTypeDescriptors;
+  options.skipExternalRttiDefinition = skipExternalRttiDefinition;
   options.applyTBAA = config.AliasAnalysis;
   options.forceUnifiedTBAATree = useOldAliasTags;
   options.typeDescriptorsRenamedForAssembly =