RS6000 call pattern clobbers
Mon Feb 26 18:42:00 GMT 2007
> > Do you remember why you wrote the call patterns this way? Was
> > there a problem with reload and clobbers of hard registers in a register
> > class containing a single register or some other historical quirk?
> I think the former. I no longer remember the details, but if you had
> a clobber of a hard reg, there were a number of things that such a hard
> reg couldn't be used for (this is where the details are murky) and in order
> to avoid that problem a match_scratch was used to delay the explicit hard
> register usage as long as possible.
Actually, this depended on SMALL_REGISTER_CLASSES. If the target was not
marked has having SMALL_REGISTER_CLASSES, any explicitly used hard register
would not be used for register and/or spill allocations anywhere in the
More information about the Gcc