On Sat, 4 May 2024 19:35:21 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 incrementally with one additional
> commit since the last revision:
>
> Rearrange; add lambdas for clarity
src/hotspot/cpu/x86/stubGenerator_x86_64_string.cpp line 1082:
> 1080: // noMatch - label bound outside to jump to if there is no match
> 1081: // haystack - the address of the first byte of the haystack
> 1082: // hsLen - the sizeof the haystack
Good to specify if the size (size of needle) and hsLen (size of haystack) is
in bytes or elements.
src/hotspot/cpu/x86/stubGenerator_x86_64_string.cpp line 1149:
> 1147:
> 1148: if (size == (isU ? 2 : 1)) {
> 1149: __ vpmovmskb(eq_mask, cmp_0, Assembler::AVX_256bit);
vpmovmskb is being done twice if doEarlyBailout is set to 1 (the setting we
have currently).
If it helps to simplify, we could assume that doEarlyBailout is always set to 1
and remove this configurability.
src/hotspot/cpu/x86/stubGenerator_x86_64_string.cpp line 1174:
> 1172: #define lastMask rTmp
> 1173: __ vpmovmskb(lastMask, cmp_k, Assembler::AVX_256bit);
> 1174: __ shrq(lastMask);
did you mean to shift the lastMask by shiftVal here?
src/hotspot/cpu/x86/stubGenerator_x86_64_string.cpp line 1185:
> 1183: if (size > (isU ? 4 : 2)) {
> 1184: if (doEarlyBailout) {
> 1185: __ testl(eq_mask, eq_mask);
The masks are 32 bit as we are comparing max 32 byes (256 bits) at a time. So
we could consistently do either andl, testl, shrl or andq, testq, shrq.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1593225178
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1593225488
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1593227487
PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1593229554
