Status of fenv.h header and floating point environment support in newlib

Mon Feb 17 17:48:50 UTC 2020

Please stay on devel at . You get more help that way. I moved this back.

On Mon, Feb 17, 2020 at 10:31 AM Ayush Dwivedi <21cencturyayush at gmail.com>
wrote:

> Thank you Joel.
> I will add my name to the page you pointed out and start building my
> proposal as well. I think my first priority should be researching in depth
> about the floating point support (the registers and the FPU support) for
> the processors based on ARM. I think collecting the various BSD
> implementations sources for fenv is needed first. I found this FreeBSD
> implementation for the ARM architecture:
> https://github.com/freebsd/freebsd/blob/master/lib/msun/arm/fenv.h
> Thanks a lot for sharing the NetBSD implementation it's thorough :)
>

It may turn out they are the same code or close for a given architecture.
FreeBSD is #1 choice. NetBSD likely has more architectures.

Another place I remembered is https://musl.libc.org/. They appear to have
a lot of architectures.

I spot checked a few other projects that I could think of but they either
also
used the FreeBSD code or only supported x86 and arm.

> About proposal should I be building it starting today? Also can I send
> patches if I happen to implement anything irrespective of the fact that
> POSIX Compliance is a GSoC open project of RTEMS(as in contributing patches
> independently would they be taken in consideration for a review?)
>

Working on your proposal should be a top priority. If we don't get accepted
as a project or you don't finish your proposal, then we can accept you. :)

With that said, there are things to do as you work on the proposal.

Being able to build newlib independently is critical on this project.
Vaibhav
and I have scripts to ease that.

Eventually you will have to have a toolchain for each architecture you want
to address.

You should also consider that after the first couple of these, they will
get easier so
pick some other POSIX Compliance tickets that are interesting. This is
AFAIK the
only one that is per architecture though. The rest will be port/implement
some code
and write tests.

> I will start looking into PowerPC and MIPS implementations later on. If
> you have more implementations links and resources please share them with me
> if possible.
>

Look as you work on your proposal.

--joel

>
> Regards,
> Ayush Dwivedi
>
>
> On Mon 17 Feb, 2020, 9:06 PM Joel Sherrill, <joel at rtems.org> wrote:
>
>> Ayush please add yourself to  https://devel.rtems.org/wiki/GSoC/2020.
>>
>> Vaibhav.. we haven't asked others to add themselves to the table.
>> Please ping anyone we missed.
>>
>> On the fenv.h side, there are some basic guidelines on how to provide
>> the fenv functionality and subtleties from the POSIX requirements.
>>
>> First, the preferred origin of the implementation is another open source
>> project with FreeBSD and NetBSD being at the top of the list. For example,
>> here is the NetBSD implementation for the m68k:
>>
>> https://github.com/NetBSD/src/blob/trunk/sys/arch/m68k/include/fenv.h
>>
>> But there are differences between vanilla m68k and coldfire so that may
>> not support all CPU variations. Would have to be determined.
>>
>> I have not found a SPARC implementation with an appropriate license.
>> Jiri may have a better source.
>>
>> I would put ARM, PowerPC, and MIPS at the top of the desired list that we
>> should be able to find BSD implementations for. We don't have an aarch64
>> port yet but I wouldn't stop a GSoC student from adding it to newlib.
>> Just can't
>> be tested with RTEMS yet. Beyond that, architectures like the m68k where
>> it
>> is porting, not writing from scratch are priorities. Covering as many
>> architectures
>> that are popular with RTEMS is the goal. SPARC64 would be down the list
>> based on that.
>>
>> Next POSIX allows an implementation to not support much if it isn't there
>> in hardware.
>>
>>
>> https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/fenv.h.html#tag_13_12
>>
>>
>> The fact that an architecture may not support a feature is challenging to
>> testing.
>>
>> --joel
>>
>> On Mon, Feb 17, 2020 at 5:54 AM Jiri Gaisler <jiri at gaisler.se> wrote:
>>
>>>
>>> On 2/17/20 11:16 AM, Vaibhav Gupta wrote:
>>>
>>>
>>>
>>> On Mon, Feb 17, 2020, 3:07 PM Ayush Dwivedi <21cencturyayush at gmail.com>
>>> wrote:
>>>
>>>> Hello Joel,
>>>> This is regarding the open project #2966 POSIX-Compliance #2971( Add
>>>> fenv.h to newlib). The task is about adding the floating point environment
>>>> header to the newlib library but the source code of the library already has
>>>> the header with the listed function declarations and data struct as needed.
>>>> The implementations for the following architectures are available in the
>>>> newlib-cygwin repository:
>>>> >RISCV
>>>> >i386
>>>> >x86_64
>>>> As pointed out in the POSIX Compliance project sub-task page the
>>>> implementations for following architectures are yet to be added:
>>>> >ARM(software float implementation for this exists but no fenv
>>>> implementation)
>>>> >AArch64(software float implementation for this exists but no fenv
>>>> implementation)
>>>> >SPARC and SPARC64(directories for these architectures are missing from
>>>> libm/machine/ so no implementation of any sort)
>>>>
>>>> I would like to try and implement the functions declared in the header
>>>> using BSD libc of FreeBSD as reference for the ARM and SPARC architectures.
>>>>
>>>> Following is the output after running test for posix fenv
>>>> header(psxfenv01.exe) for SPARC using sparc-rtems5-sis and
>>>> sparc-rtems5-gdb.(The Test failed)
>>>>
>>> Yes because testsuite needs modifications and moreover fenv on SPARC is
>>> not yet supported. Since the support for RISCV and x86_64 is present, you
>>> can make a testsuite for them. You can use qemu for running riscv files.
>>>
>>> Note that sis (riscv-rtems5-sis) also supports RISCV32 using the griscv
>>> BSP in RTEMS.
>>>
>>> Jiri.
>>>
>>> _______________________________________________
>>> devel mailing list
>>> devel at rtems.org
>>> http://lists.rtems.org/mailman/listinfo/devel
>>
>>
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