[flang-commits] [flang] [flang] Represent use statement in fir. (PR #168106)

[Abid Qadeer via flang-commits]

================
@@ -226,6 +226,95 @@ static mlir::FlatSymbolRefAttr gatherComponentInit(
   return mlir::FlatSymbolRefAttr::get(mlirContext, name);
 }
 
+/// Emit fir.use_stmt operations for USE statements in the given scope
+static void
+emitUseStatementsFromScope(Fortran::lower::AbstractConverter &converter,
+                           mlir::OpBuilder &builder, mlir::Location loc,
+                           const Fortran::semantics::Scope &scope) {
+  mlir::MLIRContext *context = builder.getContext();
+
+  for (const auto &preservedStmt : scope.preservedUseStmts()) {
+
+    auto getMangledName = [&](const std::string &localName) -> std::string {
+      Fortran::parser::CharBlock charBlock{localName.data(), localName.size()};
+      const auto *sym = scope.FindSymbol(charBlock);
+      if (!sym)
+        return "";
+
+      const auto &ultimateSym = sym->GetUltimate();
+
+      // Skip cases which can cause mangleName to fail.
+      if (ultimateSym.has<Fortran::semantics::DerivedTypeDetails>())
+        return "";
+
+      if (const auto *generic =
+              ultimateSym.detailsIf<Fortran::semantics::GenericDetails>()) {
+        if (!generic->specific())
+          return "";
+      }
+
+      return converter.mangleName(ultimateSym);
+    };
+
+    mlir::StringAttr moduleNameAttr =
+        mlir::StringAttr::get(context, preservedStmt.moduleName);
+
+    llvm::SmallVector<mlir::Attribute> onlySymbolAttrs;
+    llvm::SmallVector<mlir::Attribute> renameAttrs;
+
+    switch (preservedStmt.kind) {
+    case Fortran::semantics::PreservedUseStmt::Kind::UseOnly:
+      // USE mod, ONLY: list
+      for (const auto &name : preservedStmt.onlyNames) {
+        std::string mangledName = getMangledName(name);
+        if (!mangledName.empty())
+          onlySymbolAttrs.push_back(
+              mlir::FlatSymbolRefAttr::get(context, mangledName));
+      }
+      // Handle renames within ONLY clause
+      for (const auto &local : preservedStmt.renames) {
+        std::string mangledName = getMangledName(local);
+        if (!mangledName.empty()) {
+          auto localAttr = mlir::StringAttr::get(context, local);
+          auto symbolRef = mlir::FlatSymbolRefAttr::get(context, mangledName);
+          renameAttrs.push_back(
+              fir::UseRenameAttr::get(context, localAttr, symbolRef));
+        }
+      }
+      break;
+
+    case Fortran::semantics::PreservedUseStmt::Kind::UseRenames:
+      // USE mod, renames (import all with some renames)
+      for (const auto &local : preservedStmt.renames) {
+        std::string mangledName = getMangledName(local);
+        if (!mangledName.empty()) {
+          auto localAttr = mlir::StringAttr::get(context, local);
+          auto symbolRef = mlir::FlatSymbolRefAttr::get(context, mangledName);
+          renameAttrs.push_back(
+              fir::UseRenameAttr::get(context, localAttr, symbolRef));
+        }
+      }
+      break;
+
+    case Fortran::semantics::PreservedUseStmt::Kind::UseAll:
+      // USE mod (import all, no renames)
+      break;
+    }
----------------
abidh wrote:

I have simplified the code as suggested. Please let me know if you have any other comments.

https://github.com/llvm/llvm-project/pull/168106