[flang-commits] [flang] [flang][lowering] Implement component-wise initialization for derived types (PR #187465)

[via flang-commits]

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@@ -812,6 +819,244 @@ mustBeDefaultInitializedAtRuntime(const Fortran::lower::pft::Variable &var) {
   return Fortran::lower::hasDefaultInitialization(sym);
 }
 
+namespace {
+/// Determines if \p sym represents a complex derived type.
+/// A derived type is considered complex if it contains allocatable, pointer,
+/// or procedure pointer components, or nested complex derived types.
+static bool isComplexDerivedType(const Fortran::semantics::Symbol &sym) {
+  const Fortran::semantics::DeclTypeSpec *declTy = sym.GetType();
+  if (!declTy || !declTy->AsDerived())
+    return false;
+  const Fortran::semantics::DerivedTypeSpec &derivedSpec = *declTy->AsDerived();
+  const Fortran::semantics::Scope *scope = derivedSpec.GetScope();
+  if (!scope)
+    return false;
+  const auto &typeDetails =
+      derivedSpec.typeSymbol().get<Fortran::semantics::DerivedTypeDetails>();
+  for (const auto &compName : typeDetails.componentNames()) {
+    auto iter = scope->find(compName);
+    if (iter == scope->cend())
+      continue;
+    const Fortran::semantics::Symbol &compSym = iter->second.get();
+    const auto *objDetails =
+        compSym.detailsIf<Fortran::semantics::ObjectEntityDetails>();
+    const auto *procDetails =
+        compSym.detailsIf<Fortran::semantics::ProcEntityDetails>();
+    if (Fortran::semantics::IsAllocatableOrPointer(compSym)) {
+      return true;
+    } else if (procDetails && procDetails->init().has_value()) {
+      return true;
+    } else if (objDetails && objDetails->init() && compSym.Rank() > 0) {
+      return true;
+    } else if (isComplexDerivedType(compSym)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/// Performs precise, component-wise initialization for \p derivedSpec,
+/// selectively generating IR only for components that require it.
+static void genDerivedTypeComponentInit(
+    Fortran::lower::AbstractConverter &converter, mlir::Location loc,
+    const Fortran::semantics::DerivedTypeSpec &derivedSpec,
+    mlir::Value baseAddr, fir::RecordType recTy) {
+  fir::FirOpBuilder &builder = converter.getFirOpBuilder();
+  const Fortran::semantics::Scope *scope = derivedSpec.GetScope();
+  if (!scope)
+    return;
+  const auto &typeDetails =
+      derivedSpec.typeSymbol().get<Fortran::semantics::DerivedTypeDetails>();
+  for (const auto &compName : typeDetails.componentNames()) {
+    auto scopeIter = scope->find(compName);
+    if (scopeIter == scope->cend())
+      continue;
+    const Fortran::semantics::Symbol &compSym = scopeIter->second.get();
+    const auto *objDetails =
+        compSym.detailsIf<Fortran::semantics::ObjectEntityDetails>();
+    const auto *procDetails =
+        compSym.detailsIf<Fortran::semantics::ProcEntityDetails>();
+    // Determine if the component requires initialization.
+    // Dynamic descriptors (pointers/allocatables) and explicitly initialized
+    // entities must be processed.
+    bool needsInit = Fortran::semantics::IsAllocatableOrPointer(compSym) ||
+                     (objDetails && objDetails->init()) ||
+                     (procDetails && procDetails->init().has_value());
+    if (!needsInit && !Fortran::lower::hasDefaultInitialization(compSym))
+      continue;
+    std::string name = converter.getRecordTypeFieldName(compSym);
+    mlir::Type compFirTy = recTy.getType(name);
+    if (!compFirTy)
+      continue;
+    // Compute the memory coordinate of the current component.
+    auto fieldIdx = builder.create<fir::FieldIndexOp>(
+        loc, fir::FieldType::get(recTy.getContext()), name, recTy,
+        mlir::ValueRange{});
+    auto compAddr =
+        builder.create<fir::CoordinateOp>(loc, builder.getRefType(compFirTy),
+                                          baseAddr, mlir::ValueRange{fieldIdx});
+
+    // Case A: Standard data components (ObjectEntityDetails).
+    if (objDetails) {
+      if (objDetails->init()) {
+        // Subcase A.1: Component has explicit initialization.
+        if (Fortran::semantics::IsPointer(compSym)) {
+          // Subcase A.1.1: Pointer with explicit target.
+          std::string globalName = fir::NameUniquer::doGenerated(
+              (converter.mangleName(derivedSpec) + fir::kNameSeparator + name +
+               fir::kNameSeparator + "init")
+                  .str());
+          fir::GlobalOp global = builder.getNamedGlobal(globalName);
+          if (!global) {
+            global = builder.createGlobal(loc, compFirTy, globalName,
+                                          builder.createInternalLinkage(),
+                                          mlir::Attribute{}, true);
----------------
jeanPerier wrote:

Practice in LLVM code is to spell out the argument names before passing literal (so `/*isConst=*/true` here)

https://github.com/llvm/llvm-project/pull/187465