RFR: 8320448: Accelerate IndexOf using AVX2 [v7]

[Scott Gibbons]

On Tue, 16 Jan 2024 12:09:11 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Scott Gibbons has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 22 commits:
>> 
>>  - Merge branch 'openjdk:master' into indexof
>>  - Merge branch 'openjdk:master' into indexof
>>  - Addressing review comments.
>>  - Fix for JDK-8321599
>>  - Support UU IndexOf
>>  - Only use optimization when EnableX86ECoreOpts is true
>>  - Fix whitespace
>>  - Merge branch 'openjdk:master' into indexof
>>  - Comments; added exhaustive-ish test
>>  - Subtracting 0x10 twice.
>>  - ... and 12 more: https://git.openjdk.org/jdk/compare/8e12053e...3e58d0c2
>
> src/hotspot/share/opto/library_call.cpp line 1229:
> 
>> 1227:   } else {
>> 1228:     result = make_indexOf_node(src_start, src_count, tgt_start, tgt_count,
>> 1229:                                result_rgn, result_phi, ae);
> 
> Existing routines emits IR to handle following special cases.
> 
> tgt_cnt > src_cnt return -1
> tgt_cnt == 0 return 0.
> 
> Should we not be preserving those check before calling stub ?
> 
> As of now these checks are part of stub and doing them in JIT code will save call overhead.

Working on this.  Trying to develop my IR chops.  However, this is optimizing for a very small percentage of calls, so there will be unnoticable effect on overall performance.  There will only be savings for calls that have needle length == 0 (probably zero calls do this) or haystack length < needle length (maybe, but highly unlikely).

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PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1604010493