Re: [Qemu-devel] [PATCH 2/6] softfloat: fix float{32, 64}_maybe_silence_nan() for MIPS

[Aurelien Jarno <aurelien@aurel32.net>]

Peter Maydell a écrit :
> On 3 January 2011 14:34, Aurelien Jarno <aurelien@aurel32.net> wrote:
>> On targets that define sNaN with the sNaN bit as one, simply clearing
>> this bit may correspond to an infinite value.
>>
>> Convert it to a default NaN if SNAN_BIT_IS_ONE, as it corresponds to
>> the MIPS implementation, the only emulated CPU with SNAN_BIT_IS_ONE.
>> When other CPU of this type are added, this might be updated to include
>> more cases.
> 
> This patch doesn't apply to master:
> 
>> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
>> ---
>>  fpu/softfloat-specialize.h |   12 ++++++------
>>  1 files changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
>> index f23bd6a..31481e7 100644
>> --- a/fpu/softfloat-specialize.h
>> +++ b/fpu/softfloat-specialize.h
>> @@ -107,13 +107,13 @@ int float32_is_signaling_nan( float32 a_ )
>>  float32 float32_maybe_silence_nan( float32 a_ )
>>  {
>>     if (float32_is_signaling_nan(a_)) {
>> -        bits32 a = float32_val(a_);
> 
> ...on master this line is
>         uint32_t a = float32_val(a_);
> 
> (different type) so the patch doesn't apply.

Oops, yes, my patch series should have started by a patch fixing types,
but i made a mistake selecting the commits to send. Will fix that in a v2.

> Other than that, looks OK. I think I'd like a comment somewhere
> along the lines of
> /* Rules for silencing a signaling NaN are target-specific. Typically
>  * targets with !SNAN_BIT_IS_ONE use the rule that the NaN
>  * is silenced by setting the bit. Targets where SNAN_BIT_IS_ONE
>  * must do something more complicated, because clearing the
>  * bit might turn a NaN into an infinity. This code is correct for
>  * MIPS but new targets might need something different.
>  */
> 
> Or you could have the #ifdefs be on TARGET_whatever so
> that it's clear (because it won't compile) that adding a new
> TARGET_FOO means you have to check behaviour in this
> area. But I don't feel very strongly about that.
> 

Ok, thanks for the review, will fix that.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net