RFR: 8311932: Suboptimal compiled code of nested loop over memory segment [v2]

[Tobias Hartmann]

On Tue, 14 Nov 2023 12:38:41 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> To enable the elimination of long range checks, the loop that contains
>> the range checks is transformed into a loop nest and the range checks
>> are changed to operate on int values computed before the loop is
>> entered. This causes extra overhead out of loop and once, the range
>> checks are eliminated, can only pay off if the loop is executed for
>> long enough. This change disable the transformation if the trip count
>> computed from profile data is too low. This came up with a
>> MemorySegment API micro benchmarks and improves performance
>> significantly.
>
> Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   -XX:+TieredCompilation

Looks good to me. I've re-submitted testing and report back once it passed.

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Marked as reviewed by thartmann (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16650#pullrequestreview-1731462867