RFR: 8248188: Add IntrinsicCandidate and API for Base64 decoding [v12]

[Corey Ashford]

On Mon, 26 Oct 2020 19:27:59 GMT, Paul Murphy <github.com+12972156+pmur at openjdk.org> wrote:

>> Because the bytes are displayed e15..e8, instead of the other way around, it's hard to follow.  As an example, consider just the last four bytes of the table, but displayed in the reverse order:
>> 
>> 00||b0:0..5    00||b0:6..7||b1:0..3    00||b1:4..7||b2:0..1    00||b2:2..7
>> 
>> After vpextd with bit select pattern 00111111 for all bytes:
>> 
>> b0:0..5||b0:6..7    b1:0..3||1:4..7    b2:0..1||b2:2..7
>> =
>> b0:0..7    b1:0..7    b2:0..7
>> 
>> Should I reverse the order of this table with a comment at the top, to explain the reason for the reversal?  It seems like a good idea.
>
> Since you are operating on doublewords here, expressing this as operations on a doubleword instead of bytes would be more intuitive here.  I think the lane mappings for little endian are what throw me off.

Are you satisfied with the recent changes to the comments?

-------------

PR: https://git.openjdk.java.net/jdk/pull/293