🚀 go-pugleaf

The sparc.h file contains the following definition:

/* Nonzero means that we should generate code using a flat register window
   model, i.e. no save/restore instructions are generated, in the most
   efficient manner.  This code is not compatible with normal sparc code.  */
/* This is not a user selectable option yet, because it requires changes
   that are not yet switchable via command line arguments.  */
#define TARGET_FRW (target_flags & 256)

If I remove some comments a few lines further down, I can then compile with the
-mfrw command-line option and generate code that contains no save or restore
instructions.  Compiling simple "hello world" and dhrystone programs seems to work
with this switch enabled.

My question is, why is this "not a user selectable option"?  Is there some subtle
problem with code generated with this switch enabled?  I know that to get
sensible answers, I should compile the libraries with the same options.  Is there
anything else?

--Phil.