RFR: 8320448: Accelerate IndexOf using AVX2 [v51]

[Emanuel Peter]

On Thu, 30 May 2024 15:48:50 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:
> 
>   Fix bug number in tests

Ok, now it is good for me. But I would definately wait with integration for after the fork next week.

src/hotspot/cpu/x86/c2_stubGenerator_x86_64_string.cpp line 2:

> 1: /*
> 2:  * Copyright (c) 2023, 2024 Intel Corporation. All rights reserved.

Is the 2023 year intentional? I don't know your policy, so you can just ignore this ;)

src/hotspot/cpu/x86/c2_stubGenerator_x86_64_string.cpp line 334:

> 332:   // NUMBER_OF_CASES (currently 10) needle sizes for both big and small.  There are special
> 333:   // routines for handling needle sizes > NUMBER_OF_CASES (L_{big,small}CaseDefault).  These
> 334:   // cases use C@'s arrays_equals() to compare the needle to the haystack.  The small cases

Suggestion:

  // cases use C2's arrays_equals() to compare the needle to the haystack.  The small cases

Randomly spotted this.

src/hotspot/cpu/x86/c2_stubGenerator_x86_64_string.cpp line 773:

> 771:     // jae done
> 772:     //
> 773:     // Final index of start of needle @((16 - (ndlLen %16)) & 0xf) << 1

What is the meaning of the `@`? Maybe `at`. I'd use the same consistently

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

Marked as reviewed by epeter (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16753#pullrequestreview-2088739965
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1621015782
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1621017548
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1621019611