Extending constraints using register subclasses

[Jamie Prescott]

> From: Andrew Pinski <pinskia@gmail.com>

> To: Jamie Prescott <jpresss@yahoo.com>
> Cc: gcc@gcc.gnu.org
> Sent: Saturday, May 16, 2009 8:04:59 AM
> Subject: Re: Extending constraints using register subclasses
> 
> On Sat, May 16, 2009 at 7:57 AM, Jamie Prescott wrote:
> > Now I managed to have the approach based on register subclasses working. The 
> above
> > works too, but I somehow found it less clear and more "global" than inline 
> assembly
> > constraints.
> 
> It is not global as the register variables don't escape out of the
> scope.  If you use them in inline functions, it makes them less global
> and also easier to read too.

And how would you cleanly solve a case like this?

int swi_open_file(char const *path, int mode)
{
    int error;

    asm ("swi 32\n\t" : "=r0" (error) : "r0" (path), "r1" (mode));

    return error;
}


- Jamie