RFR: 8309254: Implement fast-path for ASCII-compatible CharsetEncoders on RISC-V [v2]

[Yanhong Zhu]

On Thu, 1 Jun 2023 07:24:09 GMT, Dingli Zhang <dzhang at openjdk.org> wrote:

>> [JDK-8274242](https://bugs.openjdk.org/browse/JDK-8274242) propose to extend the x86 ISO-8859-1 encoding intrinsic to work 
>> also for ASCII-compatible encodings, which helps speeding up various 
>> CharsetEncoders. Implementing a similar intrinsic should be considered on 
>> RISC-V as well.
>> 
>> The instruct log with -XX:+PrintOptoAssembly output looks like:
>> 
>> 06e +   Encode ISO array R12, R11, R13 -> R10 # KILL R12, R11, R13, R7, V0-V3
>> 
>> 
>> ## Testing:
>> qemu w/ UseRVV:
>> - [x] Tier1 tests (release)
>> - [x] Tier2 tests (release)
>> - [x] Tier3 tests (release)
>> - [x] test/hotspot/jtreg/compiler/intrinsics/string/TestEncodeIntrinsics.java
>
> Dingli Zhang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add missing space

Looks good.

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Marked as reviewed by yzhu (Author).

PR Review: https://git.openjdk.org/jdk/pull/14256#pullrequestreview-1454827974