RFR: 8283667: [vectorapi] Vectorization for masked load with IOOBE with predicate feature [v2]

[Xiaohong Gong]

On Fri, 29 Apr 2022 21:34:13 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

>> Xiaohong Gong has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Rename the "usePred" to "offsetInRange"
>
> IIUC when the hardware does not support predicated loads then any false `offsetIntRange` value causes the load intrinsic to fail resulting in the fallback, so it would not be materially any different to the current behavior, just more uniformly implemented.
> 
> Why can't the intrinsic support the passing a boolean directly? Is it something to do with constants? If that is not possible I recommend creating named constant values and pass those all the way through rather than converting a boolean to an integer value. Then there is no need for a branch checking `offsetInRange`.
> 
> Might be better to hold off until the JEP is integrated and then update, since this will conflict (`byte[]` and `ByteBuffer` load methods are removed and `MemorySegment` load methods are added). You could prepare for that now by branching off `vectorIntrinsics`.

Thanks for your comments @PaulSandoz !

> IIUC when the hardware does not support predicated loads then any false `offsetIntRange` value causes the load intrinsic to fail resulting in the fallback, so it would not be materially any different to the current behavior, just more uniformly implemented.

Yes, it's true that this patch doesn't have any different to the hardware that does not support the predicated loads. It only benefits the predicated feature supported systems like ARM SVE and X86 AVX-512.

> Why can't the intrinsic support the passing a boolean directly? Is it something to do with constants? If that is not possible I recommend creating named constant values and pass those all the way through rather than converting a boolean to an integer value. Then there is no need for a branch checking offsetInRange.

Yeah, I agree that it's not good by adding a branch checking for `offsetInRange`. But actually I met the constant issue that passing the values all the way cannot guarantee the argument a constant in compiler at the compile time. Do you have any better idea to fixing this?

> Might be better to hold off until the JEP is integrated and then update, since this will conflict (byte[] and ByteBuffer load methods are removed and MemorySegment load methods are added). You could prepare for that now by branching off vectorIntrinsics.

Agree. Thanks!

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PR: https://git.openjdk.java.net/jdk/pull/8035