RFR: 8269725: AArch64: Add VectorMask query implementation for NEON [v3]

[Xiaohong Gong]

On Fri, 9 Jul 2021 08:26:05 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Xiaohong Gong has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Remove the begining "negr" for "firsttrue,lasttrue"
>
> src/hotspot/cpu/aarch64/aarch64_neon.ad line 5381:
> 
>> 5379:     Label FIRST_TRUE_INDEX;
>> 5380: 
>> 5381:     // Move the lower 64-bits to a general register and check whether the
> 
> "64 bits". No hyphen.

Fixed, thanks!

> src/hotspot/cpu/aarch64/aarch64_neon_ad.m4 line 2319:
> 
>> 2317: 
>> 2318:     // Move the lower 64-bits to a general register and check whether the
>> 2319:     // value is zero.
> 
> These comments aren't very helpful. I can tell that this moves the lower 64-bits to a general register and checks whether the value is zero by reading the instructions. Your comments should say why, not how.
> In reviewing this patch I had to search through the Java source to find out. It's "Returns the index of the first mask lane that is set in a mask of 16 bytes. Returns 16 (VLENGTH) if none of them are set."

Hi @theRealAph , I'v modified the comments in the latest commits. Could you please take a look at it again? Thanks so much!

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PR: https://git.openjdk.java.net/jdk/pull/4699