RFR: 8311220: Optimization for StringLatin UpperLower

[温绍锦]

On Mon, 3 Jul 2023 08:25:06 GMT, Glavo <duke at openjdk.org> wrote:

>> # Benchmark Result
>> 
>> 
>> sh make/devkit/createJMHBundle.sh
>> bash configure --with-jmh=build/jmh/jars
>> make test TEST="micro:java.lang.StringUpperLower.*"
>> 
>> 
>> 
>> ## 1. [aliyun_ecs_c8i.xlarge](https://help.aliyun.com/document_detail/25378.html#c8i)
>> * cpu : intel xeon sapphire rapids (x64)
>> 
>> ``` diff
>> -Benchmark                      Mode  Cnt   Score   Error  Units (baseline)
>> -StringUpperLower.lowerToLower  avgt   15  27.180 ± 0.017  ns/op
>> -StringUpperLower.lowerToUpper  avgt   15  47.196 ± 0.066  ns/op
>> -StringUpperLower.mixedToLower  avgt   15  32.307 ± 0.072  ns/op
>> -StringUpperLower.mixedToUpper  avgt   15  44.005 ± 0.414  ns/op
>> -StringUpperLower.upperToLower  avgt   15  32.310 ± 0.033  ns/op
>> -StringUpperLower.upperToUpper  avgt   15  42.053 ± 0.341  ns/op
>> 
>> +Benchmark                      Mode  Cnt   Score   Error  Units
>> +StringUpperLower.lowerToLower  avgt   15  16.976 ± 0.043  ns/op (+60.160)
>> +StringUpperLower.lowerToUpper  avgt   15  46.373 ± 0.086  ns/op (+1.77%)
>> +StringUpperLower.mixedToLower  avgt   15  32.018 ± 0.061  ns/op (+0.9%)
>> +StringUpperLower.mixedToUpper  avgt   15  42.019 ± 0.473  ns/op (+4.72%)
>> +StringUpperLower.upperToLower  avgt   15  32.052 ± 0.051  ns/op (+0.8%)
>> +StringUpperLower.upperToUpper  avgt   15  16.978 ± 0.190  ns/op (+47.69%)
>> 
>> 
>> ## 2. [aliyun_ecs_c8a.xlarge](https://help.aliyun.com/document_detail/25378.html#c8a)
>> * cpu : amd epc genoa (x64)
>> 
>> ``` diff
>> -Benchmark                      Mode  Cnt   Score   Error  Units (baseline)
>> -StringUpperLower.lowerToLower  avgt   15  22.164 ± 0.021  ns/op
>> -StringUpperLower.lowerToUpper  avgt   15  46.113 ± 0.047  ns/op
>> -StringUpperLower.mixedToLower  avgt   15  28.501 ± 0.037  ns/op
>> -StringUpperLower.mixedToUpper  avgt   15  38.782 ± 0.038  ns/op
>> -StringUpperLower.upperToLower  avgt   15  28.625 ± 0.162  ns/op
>> -StringUpperLower.upperToUpper  avgt   15  27.960 ± 0.038  ns/op
>> 
>> +Benchmark                      Mode  Cnt   Score   Error  Units
>> +StringUpperLower.lowerToLower  avgt   15  15.273 ± 0.012  ns/op (+45.18%)
>> +StringUpperLower.lowerToUpper  avgt   15  46.939 ± 0.037  ns/op (-1.75%)
>> +StringUpperLower.mixedToLower  avgt   15  27.978 ± 0.015  ns/op (+1.86%)
>> +StringUpperLower.mixedToUpper  avgt   15  38.120 ± 0.047  ns/op (+1.73%)
>> +StringUpperLower.upperToLower  avgt   15  27.994 ± 0.053  ns/op (+2.25%)
>> +StringUpperLower.upperToUpper  avgt   15  17.405 ± 0.006  ns/op (+60.64%)
>> 
>> 
>> 
>> ## 3. [aliyun_ecs_c8y.x...
>
> src/java.base/share/classes/java/lang/StringLatin1.java line 442:
> 
>> 440:             if (!canEncode(cp)) {                      // not a latin1 character
>> 441:                 return toLowerCaseEx(str, value, first, locale, false);
>> 442:             }
> 
> Suggestion:
> 
> 
> 
> I think this branch is unnecessary. All lowercase forms of Latin-1 characters can be encoded using Latin-1.

String str0 = new String(new byte[]{-75}, StandardCharsets.ISO_8859_1);
String str1 = str0.toUpperCase();

str0.coder is LATIN1
str1.coder is UTF16

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

PR Review Comment: https://git.openjdk.org/jdk/pull/14751#discussion_r1250542217