egcs-971031, sparc-sun-solaris2.5 new bootstrap failure

[Joern Rennecke]

>   > >  Thu Nov  6 18:27:36 1997  Jim Wilson  <wilson@cygnus.com>
>   > >
>   > >  	* flags.h (flag_rerun_loop_opt): Declare.
>   > >       * loop.c (invariant_p, case LABEL_REF): Check
>   > >  	flag_rerun_loop_opt.
>   > >       * toplev.c (flag_rerum_loop_opt): Delete static.
>   > 
>   > Ah, that means that Jeff implemented rerun-loop-opt slightly  
>   > differently from the way g77 had it; we *did* have an externally  
>   > visible flag -frerun-loop-opt.
> We always had a user visible -frerun-loop-opt option.
> 
> I believe Jim was referring to the variable itself -- it was static
> in toplev.c, but needed to be external so that loop.c could peek at
> it.

I wonder if that was actually the most appropriate patch; the comment
in invariant_p says that the information is still not as good as we'd
like to have.

Why not add a new argument to loop_optimize, so that
rest_of_compilation can exactly tell it if there will be an subsequent
loop unrolling.  loop_optimize could then store this information in a
variable static to loop.c .