On Thu, 11 Jan 2024 23:06:32 GMT, Scott Gibbons <sgibb...@openjdk.org> wrote:

>> Re-write the IndexOf code without the use of the pcmpestri instruction, only 
>> using AVX2 instructions.  This change accelerates String.IndexOf on average 
>> 1.3x for AVX2.  The benchmark numbers:
>> 
>> 
>> Benchmark                                                   Score            
>> Latest          
>> StringIndexOf.advancedWithMediumSub   343.573                317.934         
>> 0.925375393x
>> StringIndexOf.advancedWithShortSub1    1039.081              1053.96         
>> 1.014319384x
>> StringIndexOf.advancedWithShortSub2        55.828            110.541         
>> 1.980027943x
>> StringIndexOf.constantPattern                        9.361           11.906  
>>         1.271872663x
>> StringIndexOf.searchCharLongSuccess          4.216           4.218           
>> 1.000474383x
>> StringIndexOf.searchCharMediumSuccess        3.133           3.216           
>> 1.02649218x
>> StringIndexOf.searchCharShortSuccess 3.76                    3.761           
>> 1.000265957x
>> StringIndexOf.success                                        9.186           
>> 9.713           1.057369911x
>> StringIndexOf.successBig                           14.341            46.343  
>>         3.231504079x
>> StringIndexOfChar.latin1_AVX2_String   6220.918              12154.52        
>>         1.953814533x
>> StringIndexOfChar.latin1_AVX2_char     5503.556              5540.044        
>>         1.006629895x
>> StringIndexOfChar.latin1_SSE4_String   6978.854              6818.689        
>>         0.977049957x
>> StringIndexOfChar.latin1_SSE4_char     5657.499              5474.624        
>>         0.967675646x
>> StringIndexOfChar.latin1_Short_String          7132.541              
>> 6863.359                0.962260014x
>> StringIndexOfChar.latin1_Short_char  16013.389             16162.437         
>> 1.009307711x
>> StringIndexOfChar.latin1_mixed_String          7386.123            14771.622 
>>         1.999915517x
>> StringIndexOfChar.latin1_mixed_char    9901.671              9782.245        
>>         0.987938803
>
> 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 1228:

> 1226:     result = _gvn.transform(new ProjNode(call, TypeFunc::Parms));
> 1227:   } else {
> 1228:     result = make_indexOf_node(src_start, src_count, tgt_start, 
> tgt_count,

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.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1453223658

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