[vector] java doc for iota()

[Viswanathan, Sandhya]

Hi Yang,

We need advice from John on partial wrapping and the 256-element vector length.

Best Regards,
Sandhya

-----Original Message-----
From: Yang Zhang (Arm Technology China) <Yang.Zhang at arm.com> 
Sent: Wednesday, November 13, 2019 2:42 AM
To: Viswanathan, Sandhya <sandhya.viswanathan at intel.com>; 'Paul Sandoz' <paul.sandoz at oracle.com>
Cc: 'panama-dev at openjdk.java.net' <panama-dev at openjdk.java.net>
Subject: RE: [vector] java doc for iota()

Hi Sandhya

>There is mention of partial wrapping in java doc of fromValues in VectorShuffle.java:
>     *
>     * <p> For each shuffle lane, where {@code N} is the shuffle lane
>     * index, the {@code N}th index value is validated
>     * against the species {@code VLENGTH}, and (if invalid)
>     * is partially wrapped to an exceptional index in the
>     * range {@code [-VLENGTH..-1]}.
Why the exceptional index is in the range [-VLENGTH..-1] in partially wrapping? Is it meaningful?

In VectorShuffle, Internal representation reorder is byte data. But for AArch64 SVE, maximum length of byte vector is 256(2048/8 bytes).  If [-VLENGTH..-1] of reorder is unused, we can reinterpret them as [128, 255] in AArch64 backend.

Regards
Yang

IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.