rfc: clobber all call-saved registers

[Richard Earnshaw]

> On Jan  8, 2002, Richard Henderson <rth@redhat.com> wrote:
> 
> > (1) A header file somewhere in the testsuite that has a whole
> >     whale-load of ifdefs and chooses the correct asm statement,
> 
> > (2) A compiler builtin that generates the correct asm statement
> >     based on the contents of call_used[].
> 
> How about a new entry for the list already containing "cc" and
> "memory", acceptable in the clobbers of an extended asm?
> 
>   asm ("" : : : "call_used");
> 

Hmm, this might be useful as a way of safely allowing an asm to call a 
subroutine and ensure that the compiler clobbers all the correct registers 
at that point.

R.