[patch][0/5] powerpc: Add support to fully comply with IEEE-754 standard

[Kumar Gala]

On Jan 12, 2007, at 2:09 AM, Zhu Ebony-r57400 wrote:

>  Hi Kumar,
>
>> -----Original Message-----
>> From: Kumar Gala [mailto:galak at kernel.crashing.org]
>> Sent: 2007年1月12日 14:42
>> To: Zhu Ebony-r57400
>> Cc: paulus at samba.org; linuxppc-dev at ozlabs.org
>> Subject: Re: [patch][0/5] powerpc: Add support to fully
>> comply with IEEE-754 standard
>>
>>
>> On Jan 11, 2007, at 11:19 PM, Zhu Ebony-r57400 wrote:
>>
>>> Hi Paul,
>>>
>>> This series of patch add support to fully comply with IEEE-754
>>> standard for E500/E500v2 core when hardware floating point
>> compiling
>>> is used.
>>>
>>> Ebony
>>
>> Here are some general comments:
>> * We should be able to support math-emu (as it stands) and
>> the fixup handling [you break math-emu]
>
> I don't think I break the math-emu. I think the codes I added have
> no impact to the existing math-emu.

This snippet of code breaks it from math-emu/sfp-machine.h

>> +#ifdef CONFIG_SPE
>> +#define __FPU_FPSCR	(current->thread.spefscr)
>> +#else
>>  #define __FPU_FPSCR	(current->thread.fpscr.val)
>> +#endif

By doing this if I want 'classic FP' emulation as well as the IEEE  
fixup my fpscr for classic emu will not be updated properly.

>
>> * Copyrights / header comments should give credit to the orig
>> math- emu code
> I'd like to do this, but in most handler codes, I can't find  
> copyright information
> of the orig authors. I think the math-emu code comes from glibc. In  
> the
> sigfpe_handler.c, I gave credit to the orig author.

I think a comment is sufficient stating this is take from the math- 
emu code.

>> * Why isn't there any handling of SPEFloatingPointRound exceptions?
>
> I think the SPEFloatingPointRound exception is not necessary to  
> handle if we
> handle floating point exception this way.

I dont believe this, you'll have to explain if this is really true.   
But, I'm almost sure that if the RND mode is set to +/-inf and we do  
an operation that is within the normal bounds that should round we  
will NOT get one of the other exceptions.

- k