RFR: 8255150: Add utility methods to check long indexes and ranges [v7]

[Dean Long]

On Tue, 17 Nov 2020 08:33:20 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> This change add 3 new methods in Objects:
>> 
>> public static long checkIndex(long index, long length)
>> public static long checkFromToIndex(long fromIndex, long toIndex, long length)
>> public static long checkFromIndexSize(long fromIndex, long size, long length)
>> 
>> This mirrors the int utility methods that were added by JDK-8135248
>> with the same motivations.
>> 
>> As is the case with the int checkIndex(), the long checkIndex() method
>> is JIT compiled as an intrinsic. It allows the JIT to compile
>> checkIndex to an unsigned comparison and properly recognize it as
>> a range check that then becomes a candidate for the existing range check
>> optimizations. This has proven to be important for panama's
>> MemorySegment API and a prototype of this change (with some extra c2
>> improvements) showed that panama micro benchmark results improve
>> significantly.
>> 
>> This change includes:
>> 
>> - the API change
>> - the C2 intrinsic
>> - tests for the API and the C2 intrinsic
>> 
>> This is a joint work with Paul who reviewed and reworked the API change
>> and filled the CSR.
>
> Roland Westrelin has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 27 commits:
> 
>  - Merge branch 'master' of https://git.openjdk.java.net/jdk into JDK-8255150
>  - Merge branch 'master' into JDK-8255150
>  - Merge branch 'master' into JDK-8255150
>  - Merge branch 'master' of https://git.openjdk.java.net/jdk into JDK-8255150
>  - exclude compiler test when run with -Xcomp
>  - CastLL should define carry_depency
>  - intrinsic comments
>  - Jorn's comments
>  - Update headers and add intrinsic to Graal test ignore list
>  - move compiler test and add bug to test
>  - ... and 17 more: https://git.openjdk.java.net/jdk/compare/4553fa0b...feb32943

Marked as reviewed by dlong (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/1003