[Flang][OpenMP] Remove TODO for shared and two values of default clause

Shared is the default behaviour in the IR, so no handling is required.
Default clause with shared or none do not require any handling since
Shared is the default behaviour in the IR and None is only required
for semantic checks.

This patch is carved out from D123930 to remove couple of false TODOs.

Reviewed By: peixin, shraiysh

Differential Revision: https://reviews.llvm.org/D128797

Co-authored-by: Nimish Mishra <neelam.nimish@gmail.com>

flang/lib/Lower/OpenMP.cpp

@@ -611,6 +611,21 @@ genOMP(Fortran::lower::AbstractConverter &converter,
                std::get_if<Fortran::parser::OmpClause::Copyin>(&clause.u)) {
       // Privatisation and copyin clauses are handled elsewhere.
       continue;
+    } else if (std::get_if<Fortran::parser::OmpClause::Shared>(&clause.u)) {
+      // Shared is the default behavior in the IR, so no handling is required.
+      continue;
+    } else if (const auto &defaultClause =
+                   std::get_if<Fortran::parser::OmpClause::Default>(
+                       &clause.u)) {
+      if ((defaultClause->v.v ==
+           Fortran::parser::OmpDefaultClause::Type::Shared) ||
+          (defaultClause->v.v ==
+           Fortran::parser::OmpDefaultClause::Type::None)) {
+        // Default clause with shared or none do not require any handling since
+        // Shared is the default behavior in the IR and None is only required
+        // for semantic checks.
+        continue;
+      }
     } else if (std::get_if<Fortran::parser::OmpClause::Threads>(&clause.u)) {
       // Nothing needs to be done for threads clause.
       continue;