On Mon, 26 Jul 2021 08:22:28 GMT, Сергей Цыпанов
<github.com+10835776+stsypa...@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 with a new target base due to a
> merge or a rebase. The pull request now contains three commits:
>
> - Merge branch 'master' into 8270160
> - Merge branch 'master' into 8270160
>
> # Conflicts:
> # src/java.base/share/classes/java/lang/StringLatin1.java
> - 8270160: Remove redundant bounds check from AbstractStringBuilder.charAt()
src/java.base/share/classes/java/lang/AbstractStringBuilder.java line 227:
> 225: private void ensureCapacityInternal(int minimumCapacity) {
> 226: // overflow-conscious code
> 227: int oldCapacity = capacity();
This doesn't seem related to the intent of the patch, and might distort startup
profiles a bit.
src/java.base/share/classes/java/lang/AbstractStringBuilder.java line 352:
> 350: @Override
> 351: public char charAt(int index) {
> 352: checkIndex(index, count);
This is good and harmonizes with the implementation in `String`.
src/java.base/share/classes/java/lang/StringLatin1.java line 47:
> 45: public static char charAt(byte[] value, int index) {
> 46: checkIndex(index, value.length);
> 47: return getChar(value, index);
Seems unrelated to the gist of the patch, and again might skew startup profiles.
-------------
PR: https://git.openjdk.java.net/jdk/pull/4738
