RFR: 8320448: Accelerate IndexOf using AVX2 [v20]

[Sandhya Viswanathan]

On Fri, 17 May 2024 23:47:45 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:
> 
>   Addressing lots of comments.  Interim commit.

src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 4737:

> 4735:     bind(COMPARE_BYTE);
> 4736:   } else {
> 4737:     lea(ary1, Address(ary1, expand_ary2 ? 4 : 2));

This change is not required. expand_ary2 code doesn't come here.

src/hotspot/cpu/x86/stubGenerator_x86_64_string.cpp line 1233:

> 1231:   __ andq(eq_mask, rTmp);
> 1232: 
> 1233:   __ testl(eq_mask, eq_mask);

Mismatch of operation size q vs l: andq and testl.

src/hotspot/cpu/x86/stubGenerator_x86_64_string.cpp line 1623:

> 1621:     ////////////////////////////////////////////////////////////////////////////////////////
> 1622:     //
> 1623:     // Small haystack (<32 bytes) switch

This should be <= 32 bytes.

src/hotspot/cpu/x86/stubGenerator_x86_64_string.cpp line 1709:

> 1707:     //  XMM_BYTE_K - last element of needle, broadcast
> 1708:     //
> 1709:     //  The haystack is >= 32 bytes

Should this be > 32 bytes?

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

PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1609023624
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1609043720
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1609160143
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1609163535