RFR: 8320448: Accelerate IndexOf using AVX2 [v48]

[Emanuel Peter]

On Wed, 29 May 2024 22:20:31 GMT, Scott Gibbons <sgibbons at 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 incrementally with one additional commit since the last revision:
> 
>   Remove duplicate vm.compiler2.enabled

test/jdk/java/lang/String/IndexOf.java line 35:

> 33:  * @requires vm.cpu.features ~= ".*avx2.*"
> 34:  * @requires vm.compiler2.enabled
> 35:  * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -Xcomp -XX:-TieredCompilation -XX:UseAVX=2 -XX:+UnlockDiagnosticVMOptions -XX:+EnableX86ECoreOpts IndexOf

Same here: why is the test AVX2 specific? Could other platforms not also be "tickled" in interesting ways with this test?

test/jdk/java/lang/StringBuffer/ECoreIndexOf.java line 29:

> 27:  * @requires vm.cpu.features ~= ".*avx2.*"
> 28:  * @requires vm.compiler2.enabled
> 29:  * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+EnableX86ECoreOpts -XX:UseAVX=2 -Xbatch -XX:-TieredCompilation -XX:CompileCommand=dontinline,ECoreIndexOf.indexOfKernel ECoreIndexOf

Does this test really need to be `avx2` specific? Does it even need to be C2 specific?
Or can this run on all platforms?

test/jdk/java/lang/StringBuffer/IndexOf.java line 188:

> 186:      }
> 187: 
> 188:  }

It looks like you just indented basically the whole file by 1 space. Why?

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PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1620019084
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1620016717
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1620013302