RFR: 8255150: Add utility methods to check long indexes and ranges [v2]
Dean Long
dlong at openjdk.java.net
Fri Nov 6 00:02:58 UTC 2020
On Thu, 5 Nov 2020 15:47:31 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 ten commits:
>
> - Jorn's comments
> - Update headers and add intrinsic to Graal test ignore list
> - move compiler test and add bug to test
> - non x86_64 arch support
> - c2 test case
> - intrinsic
> - Use overloads of method names.
>
> Simplify internally to avoid overload resolution
> issues, leverging List<Number> for the exception
> mapper.
> - Vladimir's comments
> - checkLongIndex
C2 changes look good, except for new code block in inline_preconditions_checkIndex could use a comment.
src/hotspot/share/opto/library_call.cpp line 1015:
> 1013: Deoptimization::Action_make_not_entrant);
> 1014: }
> 1015:
A comment here explaining what the code below is doing would be helpful.
-------------
Changes requested by dlong (Reviewer).
PR: https://git.openjdk.java.net/jdk/pull/1003
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