[flang][OpenMP] Move handling of OpenMP symbol flags to OpenMP.cpp (#75523)

The function `instantiateVariable` in Bridge.cpp has the following code:
```
  if (var.getSymbol().test(
          Fortran::semantics::Symbol::Flag::OmpThreadprivate))
    Fortran::lower::genThreadprivateOp(*this, var);

  if (var.getSymbol().test(
          Fortran::semantics::Symbol::Flag::OmpDeclareTarget))
    Fortran::lower::genDeclareTargetIntGlobal(*this, var);
```

Implement `handleOpenMPSymbolProperties` in OpenMP.cpp, move the above
code there, and have `instantiateVariable` call this function instead.

This would further separate OpenMP-related details into OpenMP.cpp.

Author: kparzysz

flang/include/flang/Lower/OpenMP.h

@@ -58,6 +58,13 @@ void genOpenMPConstruct(AbstractConverter &, Fortran::lower::SymMap &,
                         const parser::OpenMPConstruct &);
 void genOpenMPDeclarativeConstruct(AbstractConverter &, pft::Evaluation &,
                                    const parser::OpenMPDeclarativeConstruct &);
+/// Symbols in OpenMP code can have flags (e.g. threadprivate directive)
+/// that require additional handling when lowering the corresponding
+/// variable. Perform such handling according to the flags on the symbol.
+/// The variable \p var is required to have a `Symbol`.
+void genOpenMPSymbolProperties(AbstractConverter &converter,
+                               const pft::Variable &var);
+
 int64_t getCollapseValue(const Fortran::parser::OmpClauseList &clauseList);
 void genThreadprivateOp(AbstractConverter &, const pft::Variable &);
 void genDeclareTargetIntGlobal(AbstractConverter &, const pft::Variable &);

flang/lib/Lower/Bridge.cpp

@@ -4201,15 +4201,8 @@ class FirConverter : public Fortran::lower::AbstractConverter {
   void instantiateVar(const Fortran::lower::pft::Variable &var,
                       Fortran::lower::AggregateStoreMap &storeMap) {
     Fortran::lower::instantiateVariable(*this, var, localSymbols, storeMap);
-    if (var.hasSymbol()) {
-      if (var.getSymbol().test(
-              Fortran::semantics::Symbol::Flag::OmpThreadprivate))
-        Fortran::lower::genThreadprivateOp(*this, var);
-
-      if (var.getSymbol().test(
-              Fortran::semantics::Symbol::Flag::OmpDeclareTarget))
-        Fortran::lower::genDeclareTargetIntGlobal(*this, var);
-    }
+    if (var.hasSymbol())
+      genOpenMPSymbolProperties(*this, var);
   }
 
   /// Where applicable, save the exception state and halting and rounding

flang/lib/Lower/OpenMP.cpp

@@ -3542,6 +3542,19 @@ void Fortran::lower::genOpenMPDeclarativeConstruct(
     converter.genEval(e);
 }
 
+void Fortran::lower::genOpenMPSymbolProperties(
+    Fortran::lower::AbstractConverter &converter,
+    const Fortran::lower::pft::Variable &var) {
+  assert(var.hasSymbol() && "Expecting Symbol");
+  const Fortran::semantics::Symbol &sym = var.getSymbol();
+
+  if (sym.test(Fortran::semantics::Symbol::Flag::OmpThreadprivate))
+    Fortran::lower::genThreadprivateOp(converter, var);
+
+  if (sym.test(Fortran::semantics::Symbol::Flag::OmpDeclareTarget))
+    Fortran::lower::genDeclareTargetIntGlobal(converter, var);
+}
+
 int64_t Fortran::lower::getCollapseValue(
     const Fortran::parser::OmpClauseList &clauseList) {
   for (const Fortran::parser::OmpClause &clause : clauseList.v) {