Re: [Qemu-devel] [PATCH v2 0/2] softfloat tests based on berkeley's testfloat

[Alex Bennée]

Emilio G. Cota <address@hidden> writes:

> On Mon, Sep 10, 2018 at 12:26:58 +0100, Alex Bennée wrote:
>>
>> Emilio G. Cota <address@hidden> writes:
>>
>> > A few fixes since yesterday's v1:
>> >   https://lists.gnu.org/archive/html/qemu-devel/2018-09/msg00884.html
>> >
>> > - Convert copy_qemu_to_soft80 to qemu_to_soft80, just like the other
>> >   conversion functions
>> > - Set fp-test as the program name as reported by itself
>> > - Fix Makefile to include .d files so that dependencies are
>> >   properly tracked
>> > - Update commit log
>>
>> Just some general comments:
>>
>>  - I think this is a better way to go than the IBM test suite
>>  - I'm ambivalent about maintaining our fp-test.c in close alignment to
>>    softfloat unless we expect much upstreaming of changes.
>
> I don't think there'll be any, to be honest. They have a git repo but
> I doubt they'll take any patches. This was just a minimum attempt to
> get some tests working (I don't have a lot of time to work on this)
>
>>  - the coverage seems a bit low. Rebuilding everything with
>>    --enable-gcov and running -all1 -all2 I get:
>>
>>   tests/fp/fp-test.c - 53.5 % coverage 43.3 % branch coverage
>>   fpu/softfloat.c - 32.5 % coverage 25.1 % branch coverage
>>
>> But maybe I didn't pass enough options to fp-test? I could really do
>> with a --just-run-everything-and-summarise-failing-functions option so I
>> can then go through in more detail with fp-test fFOO_BAR.
>
> Yes right now to get better coverage you need to run it several times.
> After a few runs I got it to 58%, but still without testing some
> rounding modes. So considering we're coming from 0% coverage, I'd
> say coverage is pretty good!

I agree ;-)

>
> But yes, we should add a flag to just test -all.
>
> There are some functions that we are not testing yet though, but
> that can be fixed over time (we can add more tests to fp-test even
> though they're not in testfloat, such as testing flush-to-zero/
> denormals-are-zero, or the muladd variants that we have).
>
> I have basically no time left to work on this. What do you think about
> the following plan?
>
> 1. Have our own clones (forks) of testfloat/softfloat in qemu servers.
> 2. Add those as submodules
> 3. Add fp-test with as you said an -all flag that reports all
>    errors to get decent coverage.

Works for me.

> 4. Add hardfloat patches, with tests. This requires a small
>    change to testfloat:
>    https://github.com/cota/berkeley-testfloat-3/commit/ca9fa2ba05

It seems a shame to have our mirror of testfloat diverge but if it can't
be avoided I guess it will have to do. Couldn't we just zero the HW
flags in the wrapped up function? I may be misremembering but don't we
fall-back to softfloat code anyway if we have reached any limits that
trigger exception flags?

> I'd then leave adding further tests to increase coverage and fixing
> the existing bugs (prior to hardfloat) to someone else with
> more time/resources.

Agreed. I should have time to chase down the softfloat regressions once
I'm back from Connect after next week.

>
> Thanks,
>
>               Emilio


--
Alex Bennée