[flang][Driver] Support -gsplit-dwarf. (#160540)

This flags enables the compiler to generate most of the debug
information in a separate file which can be useful for executable size
and link times. Clang already supports this flag.
 
I have tried to follow the logic of the clang implementation where
possible. Some functions were moved where they could be used by both
clang and flang. The `addOtherOptions` was renamed to `addDebugOptions`
to better reflect its purpose.

Clang also set the `splitDebugFilename` field of the `DICompileUnit` in
the IR when this option is present. That part is currently missing from
this patch and will come in a follow-up PR.

1 files changed, 6 insertions, 0 deletions

diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 09b5173..81610ed 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -160,6 +160,12 @@ static bool parseDebugArgs(Fortran::frontend::CodeGenOptions &opts,
     opts.DwarfVersion =
         getLastArgIntValue(args, clang::driver::options::OPT_dwarf_version_EQ,
                            /*Default=*/0, diags);
+    if (const llvm::opt::Arg *a =
+            args.getLastArg(clang::driver::options::OPT_split_dwarf_file))
+      opts.SplitDwarfFile = a->getValue();
+    if (const llvm::opt::Arg *a =
+            args.getLastArg(clang::driver::options::OPT_split_dwarf_output))
+      opts.SplitDwarfOutput = a->getValue();
   }
   return true;
 }