SPARC Floating Point Support Changes

[Sebastian Huber]

On 08/05/15 15:48, Gedare Bloom wrote:
> To clarify, are you asking if SPARC user applications are manipulating
> the FSR in a function without saving it first and restoring it before
> returning?

No, you can do whatever you want with the FSR. What you cannot expect is 
that its value is preserved across a function call (this includes a 
context switch), e.g. it is volatile.

>
> On Fri, May 8, 2015 at 2:48 AM, Sebastian Huber
> <sebastian.huber at embedded-brains.de> wrote:
>> Hello,
>>
>> we work currently on an optimization for the SPARC floating point support.
>> See also:
>>
>> https://devel.rtems.org/ticket/2270
>>
>> We implement alternative (1). The floating point status register (FSR) is
>> volatile according to the SPARC ABI.
>>
>> https://lists.rtems.org/pipermail/devel/2015-May/011232.html
>>
>> We are not sure if this is honoured in the RTEMS applications in general.
>> Are there known uses cases which treat the FSR in a thread specific
>> non-volatile way? It would be beneficial to rely on a volatile only usage
>> since this would lead to a much simpler floating point context save/restore
>> code.
>>
>> --
>> Sebastian Huber, embedded brains GmbH
>>
>> Address : Dornierstr. 4, D-82178 Puchheim, Germany
>> Phone   : +49 89 189 47 41-16
>> Fax     : +49 89 189 47 41-09
>> E-Mail  : sebastian.huber at embedded-brains.de
>> PGP     : Public key available on request.
>>
>> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
>>
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-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at embedded-brains.de
PGP     : Public key available on request.

Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.