RFR: 8248188: Add IntrinsicCandidate and API for Base64 decoding [v2]

[Roger Riggs]

On Mon, 5 Oct 2020 21:45:06 GMT, CoreyAshford <github.com+51754783+CoreyAshford at openjdk.org> wrote:

>> Core Libs changes and the test look fine.
>
> 8248188: Add IntrinsicCandidate and API for Base64 decoding, add Power64LE intrinsic implementation.
> 
> This patch set encompasses the following commits:
> 
> Adds a new intrinsic candidate to the java.lang.Base64 class - decodeBlock(), and provides a flexible API for the
> intrinsic. The API is similar to the existing encodeBlock intrinsic.
> Adds the code in HotSpot to check and martial the new intrinsic's arguments to the arch-specific intrinsic
> implementation.
> Adds a Power64LE-specific implementation of the decodeBlock intrinsic.
> 
> Adds a JMH microbenchmark for both Base64 encoding and encoding.
> 
> Enhances the JTReg hotspot intrinsic "TestBase64.java" regression test to more fully test both decoding and encoding.

fyi, there is no need to do a rebase.  The preferred way is to do a merge.
When the changes are integrated, all of the individual commits are squashed to create a single commit.

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