Re: [PR41276, PR41307] don't leak VALUEs into VAR_LOCATION NOTEs

[Jakub Jelinek <jakub at redhat dot com>]

On Wed, Sep 09, 2009 at 09:46:07AM +0200, Eric Botcazou wrote:
> > Here's what I'm testing.  Ok to install if it passes regtesting?
> 
> I think it must be specified whether the return value of the callback is 
> expanded again or not.  With this latest patch it would be for VALUEs but 
> wouldn't for SUBREGs; any possibility to unify that either way?

To me it looks like for VALUEs we expand them twice:

1) the only way how vt_expand_loc_callback returns non-NULL is through:
      result = cselib_expand_value_rtx_cb (loc->loc, regs, max_depth,
                                           vt_expand_loc_callback, vars);
      result = check_wrap_constant (GET_MODE (loc->loc), result);
      if (result)
        break;

and then

2)          result = evd->callback (orig, evd->regs_active, max_depth,
                                    evd->callback_arg);
            if (result == orig)
              result = NULL;
            else if (result)
              result = cselib_expand_value_rtx_1 (result, evd, max_depth);

I wonder what the cselib_expand_value_rtx_1 call is for.  If we dropped
this, the return value from the callback wouldn't be expanded again in any
case.

	Jakub