RFR(S) JDK-8205528: Base64 Encode Algorithm using AVX512 Instructions

[Vladimir Kozlov]

On 6/22/18 3:58 PM, Paul Sandoz wrote:
> Hi Smita,
> 
> I am ok with it if Vladimir is :-) One slight concern is this may be biasing towards the x86 implementation of the intrinsic.

Looking on code and it will be a lot of changes in Base64.java. I am 
concern about that late in JDK 11.

I think we should keep duplicated code for x86 intrinsic as Smita 
suggested. And we can return to this when/if we intrinsify Decoder too.

> I dunno if an int[] table is as useful for an AARCH64 intrinsic.

We should ask RH to check.

But I think SPARC is better operating on 32-bit values than 16-bit (at 
least it was issue before).

Vladimir

> 
> Paul.
> 
>> On Jun 22, 2018, at 3:25 PM, Kamath, Smita <smita.kamath at intel.com> wrote:
>>
>> Hi Paul,
>>
>> I can change the Java arrays(toBase64URL and toBase64) to int[] and use them in the intrinsic if it is acceptable. Please let me know.
>>
>> Thanks,
>> Smita
>>
>> -----Original Message-----
>> From: Paul Sandoz [mailto:paul.sandoz at oracle.com]
>> Sent: Friday, June 22, 2018 3:18 PM
>> To: Kamath, Smita <smita.kamath at intel.com>
>> Cc: Vladimir Kozlov <vladimir.kozlov at oracle.com>; hotspot compiler <hotspot-compiler-dev at openjdk.java.net>
>> Subject: Re: RFR(S) JDK-8205528: Base64 Encode Algorithm using AVX512 Instructions
>>
>>
>>
>>> On Jun 22, 2018, at 3:00 PM, Kamath, Smita <smita.kamath at intel.com> wrote:
>>>> Looks like you changed all need place to implement intrinsic.
>>>> One question so: why you have own copy of base64 charsets and not using one in library:
>>>>
>>>>        private int encode0(byte[] src, int off, int end, byte[] dst) {
>>>>            char[] base64 = isURL ? toBase64URL : toBase64;
>>>>
>>>
>>> Yes, especially if we converted those from char[] to byte[] (which might also improve the C2 generated code) and pass the selected byte[] to the intrinsic.
>>> Smita>>  I need an integer array in order to use vpgatherdd instruction with vector index. Vpgather instruction works on 32 bit array and so I need to define base64 charset in a 32 bit array.
>>>
>>
>> Thanks, I also saw your reply to Vladimir and see why you need this [*]. We could still unify leveraging a Java int[] array at the expense of extra space required on non-intrisified platforms. IMHO the less stub code and the more Java code the better with regards to maintenance.
>>
>>
>>> Naming wise for the Java methods here are some suggestions:
>>>
>>> generateImplEncode -> encodeBlockWithBoundsCheck  implEncode ->
>>> encodeBlock
>>>
>>> Also can generateImplEncode be private?
>>> Smita>> I'll make these changes and send an updated webrev.
>>>
>>
>> Ok.
>>
>>
>>> Further. is there is a need to perform bounds checks in generateImplEncode given the public methods calling encode will, i presume, have dominating checks?
>>> Smita>> The check is not required. I'll retain encodeBlock and remove encodeBlockWithBoundsCheck.
>>>
>>
>> Ok.
>>
>> Thanks,
>> Paul.
>>
>> [*] On AVX-512 it's tempting to explore permute/rearrange operations on bytes, if there are any such instructions, since the translation array of bytes (toBase64URL or toBase64) fits neatly into one z register, or for AVX-2 in two y registers if some masked variant, based on ranges, is possible.
>