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Date: Thu, 8 Oct 2015 12:33:55 +0300
From: Konstantin Belousov <kostikbel@gmail.com>
To: Garrett Cooper <yaneurabeya@gmail.com>
Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>
Subject: Re: Comparing behavior of test-fesetenv.c on AMD Opterons and Intel
 Xeons: running FNSTENV on Opteron -- should it zero out __x87.__other?
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On Thu, Oct 08, 2015 at 02:14:12AM -0700, Garrett Cooper wrote:
> 
> > On Oct 8, 2015, at 01:06, Konstantin Belousov <kostikbel@gmail.com> wrote:
> > 
> >> On Thu, Oct 08, 2015 at 12:38:15AM -0700, Garrett Cooper wrote:
> 
> ...
> 
> >> Hi kib!
> >> 
> >> Ok -- that's what my gut was telling me when I was reading the spec, but I needed a second opinion. Interesting how Intel leaves the __other field alone and AMD [opterons] don't ;/..
> > 
> > Your statement does not make any sense.  Re-read what I tell above.
> > The __other field is not written by code, the code does not change
> > by the matter of being run on Intel or AMD processors.  It just happens
> > so that on one of your system the stack are seems to be zero, while on
> > another, it does not.
> 
> I thought __other corresponded to C0-C3 based on my read of the spec -- is that incorrect?

What are C0-C3 you reference ? I can only think about condition code
bits from the FPU status word which have that names, but the word is put
into the __status field of fenv_t.

And, what spec did you read ?