Re: [Qemu-devel] [PATCH v3] target/mips: Fix minor bug in FPU

[Alex Bennée]

Aleksandar Markovic <address@hidden> writes:

>>
>> From: Peter Maydell <address@hidden>
>> Subject: Re: [PATCH v3] target/mips: Fix minor bug in FPU
>>
>> On Tue, 19 Mar 2019 at 19:21, Aleksandar Markovic
>> <address@hidden> wrote:
>> >
>> > > From: Mateja Marjanovic <address@hidden>
>> > > Subject: [PATCH v3] target/mips: Fix minor bug in FPU
>> > >
>> > > From: Mateja Marjanovic <address@hidden>
>> > >
>> > > Wrong type of NaN was generated for IEEE 754-2008 by MADDF.<D|S> and
>> > > MSUBF.<D|S> instructions when the arguments were (inf, zero, nan) or
>> > > (zero, inf, nan).
>> > > These instructions were tested and the results match with the results
>> > > of the machine that has a MIPS64 r6 cpu.
>> > >
>> > > Signed-off-by: Mateja Marjanovic <address@hidden>
>> > > ---
>> >
>> > Mateja,
>> >
>> > The commit message is missing information on the reference source
>> > of information, that you placed in the cover letter. In my opinion, this is
>> > an important peace of information for anybody seeing and examining
>> > this patch in future, so please submit a new version of the patch as an
>> > isolated patch and updated commit message.
>>
>> If Alex is willing to edit the commit message in his tree
>> that would save Mateja from having to do another respin.
>>
>
> Sure, that would be a good option. Whoever (Alex or Mateja) modifies
> the patch, the commit message should please read: (I did some
> rearranging and editing)
>
>
> Wrong type of NaN was generated for IEEE 754-2008 by MADDF.<D|S> and
> MSUBF.<D|S> instructions when the arguments were (Inf, Zero, NaN) or
> (Zero, Inf, NaN).
>
> The if-else statement establishes if the system conforms to IEEE
> 754-1985 or IEEE 754-2008, and defines different behaviors depending
> on that. In case of IEEE 754-2008, in mentioned cases of inputs,
> <MADDF|MSUBF>.<D|S> returns the input value 'c' [2] (page 53) and
> raises floating point exception 'Invalid Operation' [1] (pages 349,
> 350).
>
> These scenarios were tested and the results in QEMU emulation match
> the results obtained on the machine that has a MIPS64R6 CPU.
>
> [1] MIPS Architecture for Programmers Volume II-a: The MIPS64
>     Instruction Set Reference Manual, Revision 6.06
> [2] MIPS Architecture for Programmers Volume IV-j: The MIPS64
>     SIMD Architecture Module, Revision 1.12
>
> Reviewed-by: Peter Maydell <address@hidden>
> Signed-off-by: Mateja Marjanovic <address@hidden>

I've updated the commit message, thanks.

--
Alex Bennée