-fuse-caller-save - Collect register usage information

[Eric Botcazou]

> This is the updated version of the previously approved patch
> submitted here (http://gcc.gnu.org/ml/gcc-patches/2013-03/msg01320.html ).
> The changes are:
> - using a new hook call_fusage_contains_non_callee_clobbers,
> - incorporating minor review comments from Richard Sandiford
>    ( http://gcc.gnu.org/ml/gcc-patches/2014-04/msg01436.html ).
> 
> As part of the fuse-caller-save patch series, bootstrapped and reg-tested on
> x86_64, and build and reg-tested on MIPS.
> 
> Eric, non-cgraph part OK for trunk?

I think we should consider creating a new rule: for every target hook added, 
another must be first removed...

So this call_fusage_contains_non_callee_clobbers is essentially only a stop 
gap measure for the ports that haven't been changed yet?  If so, please add a 
??? comment at the beginning of collect_fn_hard_reg_usage:

  /* ??? To be removed when all the ports have been fixed.  */
  if (!targetm.call_fusage_contains_non_callee_clobbers)

and invoke collect_fn_hard_reg_usage from rest_of_handle_final only when 
flag_use_caller_save is true.

Why do you need to retest them in get_call_reg_set_usage and get_call_fndecl?

-- 
Eric Botcazou