From owner-freebsd-amd64@FreeBSD.ORG  Tue Jul 17 15:27:38 2012
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Date: Wed, 18 Jul 2012 01:27:29 +1000 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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Cc: freebsd-amd64@FreeBSD.org
Subject: Re: amd64/169927: siginfo, si_code for fpe errors when error occurs
 using the SSE math processor
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On Wed, 18 Jul 2012, Bruce Evans wrote:

> On Tue, 17 Jul 2012, Konstantin Belousov wrote:
>> ...
>> +	status =3D mxcsr & 0x3f;
>> +	control =3D (mxcsr >> 16) & 0x3f;
>> +	return (fpetable[status & (~control | 0x40)]);
>
> The 0x40 bit doesn't exist in the mxcsr status and ORing it in here has
> no effect.  Replace the last 3 lines by:
>
> 	return (fpetable[(status & (control >> 16)) & 0x3f];

Change status and control to mxcsr here, and remove the status and control
variables.

> ..
> So I still want a single kernel exception handle that merges the statuses.

Merge the independent statuses modified by their independent controls:

   	return (fpetable[(fpsw & ((~fpcw & 0x3f) | 0x40)) |
 	    ((mxcsr & (mxcsr >> 16)) & 0x3f)]);

Use the same trap handler that reads all these statuses and controls.

Bruce