Re: CVS commit: src/sys/arch/pmax/stand/common

[Simon Burge <simonb%NetBSD.org@localhost>]

Matt Thomas wrote:

> On Nov 25, 2010, at 9:00 AM, Antti Kantee wrote:
> 
> > On Fri Nov 26 2010 at 01:50:11 +0900, Izumi Tsutsui wrote:
> >> but shouldn't we fix stub first, then discuss pros and blah of the change?
> >> Current binaries have not worked at all on MIPS1 since the last December.
> > 
> > Like I said, I don't have strong feelings about this.
> > 
> > If you want to fix stubs, go for it!
> > (there's no need for a discussion after that, anyway, since the issue
> > is decided and fixed)
> 
> Please don't.  I've changed the mips1 syscall handler to save t0-t2
> just like the mips3+ handler does.

Why is it necessary to save three extra regs for every syscall, when
only two syscalls actually use t0?  Callers of the syscalls don't expect
t0-t3 to be saved.

Also, why go to the effort of saving t0-t2 and not t3 as well?  Surely
that violates POLA?

Cheers,
Simon.