On Mon, 16 Oct 2023 15:00:42 GMT, Shaojin Wen <d...@openjdk.org> wrote:
>> I submitted PR #15555 before, and there were too many changes. I split it
>> into multiple PRs with small changes. This one is one of them.
>>
>> this PR removed the duplicate code for getChars in
>> BigDecimal#StringBuilderHelper, i also make performance faster.
>> Please review and don't hesitate to critique my approach and patch.
>
> Shaojin Wen has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Use StringConcatFactory.makeConcatWithConstants
Good, narrows it down to what's going on in `prepend(long, byte[], String)`.
Might boil down to `System.arraycopy`. This method might not be optimized for
tiny arrays on all platforms. Specializing for single-char case:
diff --git a/src/java.base/share/classes/java/lang/String.java
b/src/java.base/share/classes/java/lang/String.java
index 9b19d7e2ac1..6eb70925dab 100644
--- a/src/java.base/share/classes/java/lang/String.java
+++ b/src/java.base/share/classes/java/lang/String.java
@@ -4723,7 +4723,11 @@ static void repeatCopyRest(byte[] buffer, int offset,
int limit, int copied) {
*/
void getBytes(byte[] dst, int dstBegin, byte coder) {
if (coder() == coder) {
- System.arraycopy(value, 0, dst, dstBegin << coder, value.length);
+ if (value.length == 1) {
+ dst[(dstBegin << coder)] = value[0];
+ } else {
+ System.arraycopy(value, 0, dst, dstBegin << coder,
value.length);
+ }
} else { // this.coder == LATIN && coder == UTF16
StringLatin1.inflate(value, 0, dst, dstBegin, value.length);
}
.. seem to help the JIT do the right thing consistently, too:
Benchmark Mode Cnt Score Error Units
BigDecimals.testSmallToEngineeringString avgt 50 11,757 ± 0,480 ns/op
-------------
PR Comment: https://git.openjdk.org/jdk/pull/16006#issuecomment-1764787645
