RFR: 8238669: Long.divideUnsigned is extremely slow for certain values (Needs to be Intrinsic)

[Joe Darcy]

Hello,

I also suggest taking a look at the existing regression tests in

     test/jdk/java/lang/Long/Unsigned.java

to see if more cases should be added with the new algorithm. 
Potentially, the existing algorithm could retire to serve as a reference 
in the regression tests.

Thanks,

-Joe

On 9/2/2020 7:37 AM, Raffaello Giulietti wrote:
> Hi Brian,
>
> thanks for taking a look.
>
> I didn't write JMH benchmarks.
>
>
> Greetings
> Raffaello
>
>
>
> On 2020-09-02 16:25, Brian Burkhalter wrote:
>> Hi Raffaello,
>>
>> I can take a look. Did you write any (JMH?) microbenchmarks?
>>
>> Thanks,
>>
>> Brian
>>
>>> On Sep 2, 2020, at 5:52 AM, Raffaello Giulietti 
>>> <raffaello.giulietti at gmail.com 
>>> <mailto:raffaello.giulietti at gmail.com>> wrote:
>>>
>>> here's a patch for [1], which is currently unassigned. Anybody 
>>> willing to sponsor it?
>>>
>>> The fix is based on "Hacker's Delight" (2nd ed), section 9.3 and 
>>> makes use of longs only, no BigInteger, no garbage to collect. It is 
>>> faster and "greener" than the current code.
>>>
>>> Contrary to the dramatic plea in the subject, with this fix I think 
>>> there's no pressing need for an intrinsic.
>>>
>>> The fix should be back-portable to 11 and 8, where the methods first 
>>> appeared, but I only tried on a current changeset [2].
>>>
>>> Passes tier1.
>>>
>>> If anybody needs the fix as attachment, just let me know.
>>
>