On Wed, 1 Feb 2023 14:20:05 GMT, Jatin Bhateja <jbhat...@openjdk.org> wrote:
>> src/jdk.incubator.vector/share/classes/jdk/incubator/vector/AbstractMask.java
>> line 236:
>>
>>> 234: } else if (offset >= limit) {
>>> 235: return vectorSpecies().maskAll(false);
>>> 236: } else if (limit - offset >= length()) {
>>
>> Can you move this else if check at the top, this is the most general case
>> appearing in the loop and hence two extra uncommon trap jumps before it for
>> special cases may penalize this.
>
> Your patch re-organized the code to take care of following cases :-
> 1. offset < 0 : Still falling over to old code.
> 2. offset >= limit : Special case optimized
> 3. (limit - offset) >= length : Most general case.
> 4. Partial in range check : New intrinsic, existing java side
> implementation in checkIndex0 is also composed of intrinsified calls,
> infrequently taken paths will anyways lead to uncommon traps.
>
> Have you tried introducing just case 3 (first) and then case 2 in existing
> indexInRange implementation.
> Thanks for the review @jatin-bhateja !
>
> > Have you tried introducing just case 3 (first) and then case 2 in existing
> > indexInRange implementation.
>
> Yes, I tried with this way as well, together with the performance testing
> compared with current version. The result is:
>
> 1. For cases that the array size is aligned with the vector size, the
> performance is almost the same with each other.
> 2. For cases that the array size is not aligned (which needs the masked
> operation), the performance with current version can improve about 5%~6%
> compared with the way as you suggested. But the improvement is limited to the
> cases with smaller vector size, whose tail loop size is bigger.
>
> So, adding the new intrinsic has no side effect for me, except for the more
> complex java side code and one additional intrinsic.
Another benefit is the code change will be simpler, that almost all the files
except the `AbstractMask.java` do not need to be changed. I will make the
modification and rerun the benchmarks to decide whether it's necessary to add
the new intrinsics. Thanks!
-------------
PR: https://git.openjdk.org/jdk/pull/12064
