[PATCH] Fix rounding bug in emulation for double floatoperating

[Kumar Gala]

On Dec 14, 2007, at 12:06 AM, Zang Roy-r61911 wrote:

> On Fri, 2007-12-14 at 13:46, Kumar Gala wrote:
>>>> When I run this on a G5 (w/HW FP) I get:
>>>>
>>>> dmul 3fe0000000000000 * 1 = 0 expected 0 (PASS)
>>>> dmul bfe0000000000000 * 1 = 8000000000000000 expected 0 (PASS)
>>>> dmul 8000000000000001 * bfe0000000000000 = 0 expected 0 (PASS)
>>>>
>>>> ddiv 1 / 4000000000000000 = 0 expected 0 (PASS)
>>>>
>>>> and on the 85xx w/FP emu:
>>>>
>>>> dmul 3fe0000000000000 * 1 = 0 expected 0 (PASS)
>>>> dmul bfe0000000000000 * 1 = 8000000000000000 expected 0 (PASS)
>>>> dmul 8000000000000001 * bfe0000000000000 = 0 expected 0 (PASS)
>>>>
>>>> ddiv 1 / 4000000000000000 = 0 expected 0 (PASS)
>>>>
>>>> Maybe I'm missing where the error is.
>>> I am missing ...
>>> It is supposed to run based on previous IEEE 754 patch.
>>> http://ozlabs.org/pipermail/linuxppc-dev/2007-February/031351.html
>>
>> I'd really like to see to see a testcase show the issue with "classic
>> FP emu" on a 85xx system.
> I can understand.
> You know, For a 85xx system without the previous patch or other
> 'classic' powerpc, it is hard to trigger this issue. Although I  
> believe
> it is a problem fixed up.
> Do you have any idea?

maybe I'm missing it, but can we not do the same operation w/classic  
FP that you are doing w/SPE fp?

is this in standard rounding mode, etc?

- k