In the discussion of `8355177: Speed up StringBuilder::append(char[]) via
Unsafe::copyMemory` (https://github.com/openjdk/jdk/pull/24773
<https://github.com/openjdk/jdk/pull/24773 >), @liach (Chen Liang) suggested
reusing the StringUTF16::putCharsSB method introduced in PR #24773 instead of
the Intrinsic implementation in the StringUTF16::toBytes method.
Original:
```java
@IntrinsicCandidate
public static byte[] toBytes(char[] value, int off, int len) {
byte[] val = newBytesFor(len);
for (int i = 0; i < len; i++) {
putChar(val, i, value[off]);
off++;
}
return val;
}
```
After:
```java
public static byte[] toBytes(char[] value, int off, int len) {
byte[] val = (byte[])
Unsafe.getUnsafe().allocateUninitializedArray(byte.class, newBytesLength(len));
putCharsSB(val, 0, value, off, off + len);
return val;
}
```
This replacement does not degrade performance. Running
StringConstructor.newStringFromCharsMixedBegin verified that performance is
consistent with the original on x64 and slightly improved on aarch64.
The implementation after replacing the Intrinsic implementation removed 100
lines of C++ code, leaving only Java and Unsafe code, no Intrinsic or C++ code,
which makes the code more maintainable.
I've submitted a draft PR https://github.com/openjdk/jdk/pull/26553
<https://github.com/openjdk/jdk/pull/26553 > , please give me some feedback.
-
Shaojin Wen
