Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
> 
>>Jan Kiszka wrote:
>>
>>>Gilles Chanteperdrix wrote:
>>>
>>>
>>>>Jan Kiszka wrote:
>>>>
>>>>
>>>>>Jan Kiszka wrote:
>>>>>
>>>>>
>>>>>
>>>>>>Gilles Chanteperdrix wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>>So, Ok, I will try to do something for x86 (either reduce the numbers of
>>>>>>>registers used by the C code, or reduce the assembly to the bare
>>>>>>>minimum). But, please, pick my generic implementation of llmulshft, it
>>>>>>>was carefully written.
>>>>>>
>>>>>>Yes, it is the better choice for 32 bit archs (my previous tests didn't
>>>>>>reflect the usage in Xenomai truely, redoing them made my generic
>>>>>>version fall behind yours). Will include it.
>>>>>
>>>>>Done, see -v6. Then I added that two-liner for x86_64 rthal_llmulshft,
>>>>>fixed the BITS_PER_LONG bug, and enabled generic-based support for ARM
>>>>>(testing welcome!).
>>>>>
>>>>>At this chance: My series now also includes rthal_llimd for x86_64,
>>>>>another two-liner.
>>>>
>>>>v6 is not in the download area.
>>>>
>>>
>>>Mpf, forgot to press "update". Done.
>>
>>Ok, I agree with the fast-tsc-to-ns patch: I could not get gcc to
>>generate code with less moves on x86 (which is, for me, if it was still
>>needed, yet another proof that these register moves are harmless).
> 
> 
> No question -- from the average performance POV.
> 
> 
>>However, I do not agree with the x86_64 llimd: it will not work if m is
>>greater than 2G, that is why we implement llimd in terms of ullimd on
>>other architectures.
>>
> 
> 
> Please help me, I don't see it yet:
> 
> m is 32 bit and gets extended to 64 bit without considering any sign (as
> it should be). Then we multiply 64x64 bit signed, but we know for sure
> that the second multiplier is always positive. Same for division. Basic
> tests ((-1*1000000000)/2 vs. (-1*3000000000)/2) confirmed this on the
> target.

No, you are right. It works.

-- 
                                                 Gilles Chanteperdrix

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