[flang] Explicitly map host associated symbols

[clementval]

Summary

Explicitly map host associated symbols in DoConcurrent with shared
locality-spec, clauses in OpenMP/OpenACC. The mapping of host-assoc
symbols is set to their parent SymbolBox. This is achieved through
a new interface function in the AbstractConverter.

This was already upstream for OpenMP.

This patch is part of the upstreaming effort from fir-dev branch.

Co-authored-by: Kiran Chandramohan <[e-mail]>

[PeteSteinfeld]

All builds and tests correctly and looks good.

flang/lib/Lower/OpenACC.cpp

 getDesignatorNameIfDataRef(const Fortran::parser::Designator &designator) {
   const auto *dataRef = std::get_if<Fortran::parser::DataRef>(&designator.u);
   return dataRef ? std::get_if<Fortran::parser::Name>(&dataRef->u) : nullptr;
 }
 
 static void genObjectList(const Fortran::parser::AccObjectList &objectList,
                           Fortran::lower::AbstractConverter &converter,
                           llvm::SmallVectorImpl<mlir::Value> &operands) {
+  auto addOperands = [&](Fortran::lower::SymbolRef sym) {
+    const auto variable = converter.getSymbolAddress(sym);
+    // TODO: Might need revisiting to handle for non-shared clauses
+    if (variable) {
+      operands.push_back(variable);
+    } else {
+      if (const auto *details =
+              sym->detailsIf<Fortran::semantics::HostAssocDetails>())
+        operands.push_back(converter.getSymbolAddress(details->symbol()));
+    }
+  };
+
   for (const auto &accObject : objectList.v) {
-    std::visit(
-        Fortran::common::visitors{
+    std::visit(Fortran::common::visitors{
                    [&](const Fortran::parser::Designator &designator) {
-              if (const auto *name = getDesignatorNameIfDataRef(designator)) {
-                const auto variable = converter.getSymbolAddress(*name->symbol);
-                operands.push_back(variable);
+                     if (const auto *name =
+                             getDesignatorNameIfDataRef(designator)) {
+                       addOperands(*name->symbol);
                      }
                    },
                    [&](const Fortran::parser::Name &name) {
-              const auto variable = converter.getSymbolAddress(*name.symbol);
-              operands.push_back(variable);
+                     addOperands(*name.symbol);
                    }},
                accObject.u);
   }
 }
 
 template <typename Clause>
 static void genObjectListWithModifier(
     const Clause *x, Fortran::lower::AbstractConverter &converter,
     Fortran::parser::AccDataModifier::Modifier mod,
     llvm::SmallVectorImpl<mlir::Value> &operandsWithModifier,