RFR: 8270160: Remove redundant bounds check from AbstractStringBuilder.charAt() [v5]

[Claes Redestad]

On Mon, 2 Aug 2021 11:34:00 GMT, Сергей Цыпанов <github.com+10835776+stsypanov at openjdk.org> wrote:

>> `AbstractStringBuilder.charAt(int)` does bounds check before calling `charAt()` (for non-latin Strings):
>> 
>> @Override
>> public char charAt(int index) {
>>     checkIndex(index, count);
>>     if (isLatin1()) {
>>         return (char)(value[index] & 0xff);
>>     }
>>     return StringUTF16.charAt(value, index);
>> }
>> 
>> This can be improved by removing bounds check from ASB.charAt() in favour of one in String*.charAt(). This gives slight improvement:
>> 
>> before
>> Benchmark                           Mode  Cnt  Score   Error  Units
>> StringBuilderCharAtBenchmark.latin  avgt   50  2,827 ± 0,024  ns/op
>> StringBuilderCharAtBenchmark.utf    avgt   50  2,985 ± 0,020  ns/op
>> 
>> after
>> Benchmark                           Mode  Cnt  Score   Error  Units
>> StringBuilderCharAtBenchmark.latin  avgt   50  2,434 ± 0,004  ns/op
>> StringBuilderCharAtBenchmark.utf    avgt   50  2,631 ± 0,004  ns/op
>
> Сергей Цыпанов has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8270160 Revert irrelevant changes

Marked as reviewed by redestad (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/4738