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Re: FPU support implementation question.
- To: Patrick O'Grady <patrick at softprocess dot com>
- Subject: Re: [ECOS] FPU support implementation question.
- From: Jonathan Larmour <jlarmour at redhat dot co dot uk>
- Date: Tue, 11 Apr 2000 18:13:43 +0100
- CC: ecos-discuss at sourceware dot cygnus dot com
- Organization: Red Hat UK Ltd.
- References: <Pine.BSF.4.10.10004110918190.66721-100000@plasticgrape.com>
Patrick O'Grady wrote:
>
> - Don't make it configurable. The hardware should only generate
> interrupts if you enable it (which should be always) AND when a thread
> tries to use the FPU... that way an application can enable or disable this
> mode automatically. My experience is that if you allow someone to
> configure it, they'll mess it up, and that two years later, when a
> customer says, 'well, I only want to perform one operation...' that you
> don't have to rebuild the OS...
I thought the configurability was going to be between "make it always save
the FPU state", and "make it save the FPU state lazily". No application
would stop working as a result, if that's what you mean.
But if it isn't what you mean, I would say that there *is* extra overhead
in using lazy FPU switches so even if it's the default, having an
alternative is A Good Thing.
Jifl
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