Re: question regarding asm()

[dtm at waterw dot com]

I do believe that you really can't do what you desire.  You can 
kinda fake it though, by saying what registers you want particular
variables to be in beforehand:

	register int myvar asm("10");	// r10 on gcc for linux-ppc

-David

On Wed, 8 Oct 1997, Marc Lehmann wrote:

> Sorry to post this question again, but my last e-mail was definitely ignored,
> and the documentation still is wrong.... (And I still have no idea
> how, for example, kernel people are supposed to tell gcc NOT to
> use some registers in an asm that are used in an asm...)
> 
> ----- Forwarded message from Marc Lehmann -----
> 
> David Edelsohn wrote:
> >	Clobber just means that GCC cannot make assumptions about the
> >register after the call, not before.
> 
> That's what I expected, but the docs seems to sugest otherwise..
> 
> >You explicitly use r9 and r10 in your pattern but never tell GCC.  The
> >pattern should list r9 and r10 as
> 
> It's not "my" pattern, it is taken as an example from the gcc info files, so
> the documentation is wrong and should be fixed.
> 
> >inputs so that GCC knows not to touch them.  In fact you should leave the
> >destinations as open register but make those required inputs so that GCC
> >fills them in during register allocation.
> 
> The problem is that one cannot on all ports of gcc select
> specific registers as input (in that case, r9), but
> only register classes.
> 
> How am I supposed to tell gcc that (say..) register r13 is NOT to be used as
> input in an asm when the target machine has no constraint specificly for
> r13? (on the x86 you have almost one class per reg, so that's not a problem,
> but this is not true for %ebp... there is NO way to tell gcc NOT to use %ebp
> as an input operand, or do I miss sth.?)
> 
>       -----==-
>       ----==-- _
>       ---==---(_)__  __ ____  __       Marc Lehmann
>       --==---/ / _ \/ // /\ \/ /       pcg@goof.com
>       -=====/_/_//_/\_,_/ /_/\_\
>     The choice of a GNU generation
> 
> ----- End of forwarded message from Marc Lehmann -----
>