Re: [Qemu-devel] [Consult] tilegx: About floating point instructions

[Chen Gang]

On 8/4/15 04:47, Chen Gang wrote:
> On 8/4/15 00:40, Richard Henderson wrote:
>> On 08/01/2015 02:47 AM, Chen Gang wrote:
>>> I am just adding floating point instructions (e.g. fsingle_add1),
>>> but for me, I can not find any details about them (the ISA
>>> documents only give a summary description, but not details), e.g.
>>
>> The tilegx splits the four/six cycle arithmetic into multiple
>> black-box instructions.  You need only really implement one of the
>> four, with the rest of them being implemented as nops or moves.
>>
>> Looking at what gcc produces gives the hints:
>>
>> fdouble_unpack_min   min, srca, srcb fdouble_unpack_max      max, srca,
>> srcb fdouble_add_flags       flg, srca, srcb fdouble_addsub          max, 
>> min, flg 
>> fdouble_pack1                dst, max, flg fdouble_pack2             dst, 
>> max, zero
>>
>> The unpack, addsub, and pack2 insns can be ignored, the add_flags
>> insn can perform the whole operation, the pack1 insn performs a move
>> from "flg" to "dst".
>>
>> Similarly for the single-precision:
>>
>> fsingle_add1         tmp, srca, srcb fsingle_addsub2         tmp, srca, srcb 
>> fsingle_pack1                flg, tmp fsingle_pack2          dst, tmp, flg
>>
>> The add1 insn performs the whole operation, the addsub2 and pack1
>> insns are ignored, and the pack2 insn is a move from tmp to dst.
>>

After check the tilegx.md completely, for me, we still need implement
each of them precisely, or we can not emulate all cases (e.g. muldf3).

But it doesn't matter. Based on tilegx.md, the summary contents in ISA
document, and your explanation, I guess, it is enough for me to finish
them. :-)

And still welcome additional information for it.

Thanks.

> 
> Thank you very much. I am just analyzing the template file (tilegx.md)
> and testsuite executable file (20000603-1.exe) for it. Your information
> is really valuable to me! :-)
> 
> And still welcome any additional information for it: especially related
> details documentations which should be more 'standard' than the third-
> party's implementation (e.g. gcc implementation).
> 
> 
> I shall try to let qemu tilegx support gcc testsuite successfully within
> this month.
> 
> 
> Thanks.
> 

-- 
Chen Gang

Open, share, and attitude like air, water, and life which God blessed