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Date:      Mon, 7 Jan 2002 12:43:42 -0700
From:      Nate Williams <nate@yogotech.com>
To:        Daniel Eischen <eischen@pcnet1.pcnet.com>
Cc:        Nate Williams <nate@yogotech.com>, Dan Eischen <eischen@vigrid.com>, Peter Wemm <peter@wemm.org>, Archie Cobbs <archie@dellroad.org>, Alfred Perlstein <bright@mu.org>, arch@FreeBSD.ORG
Subject:   Re: Request for review: getcontext, setcontext, etc
Message-ID:  <15417.64110.441186.451573@caddis.yogotech.com>
In-Reply-To: <Pine.SUN.3.91.1020107142404.812B-100000@pcnet1.pcnet.com>
References:  <15417.62807.556838.947343@caddis.yogotech.com> <Pine.SUN.3.91.1020107142404.812B-100000@pcnet1.pcnet.com>

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> > > Sure, you can always save the FP context, but you can't really
> > > conditionally save it without changing the interface for these
> > > functions or adding another set of functions that save the FP
> > > context.
> > 
> > The reason for conditionally saving it is because it would allow the
> > most flexibility in the future.
> > 
> > > The FP context is what I'm most unsure about.
> > > I'm not familiar with the FPU, but is there any state that
> > > needs to be saved across the getcontext call?
> > 
> > Nope, but you need to be able to get the FPU context saved in setcontext.
> 
> Well, that's what I mean.  If somewhere else in the application
> there was a setcontext that returned to the getcontext above...

I think I understand what you are asking.  Are you asking if there is
application specific context that needs to be saved, such as GC state or
somesuch?  Or, am I truly confused?

> What I'm asking is, is there any FP state (other than the FP
> control word which does get saved/restored), from before the
> getcontext call that needs to be reloaded after the call, or
> does the compiler assume that state may have been changed
> by the call itself?

????

> What happens if the getcontext call above gets replaced by
> another function call that does more FP stuff?

In restrospect, I don't believe we switch contexts w/out a thread
switch, so it may be adequate to only worry FP context during signals.


Nate

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