On Wed, 28 Aug 2024 22:59:20 GMT, Shaojin Wen <s...@openjdk.org> wrote:
>> src/java.base/share/classes/jdk/internal/classfile/impl/StackMapGenerator.java
>> line 1060:
>>
>>> 1058: if (desc == CD_void) throw new AssertionError("Should
>>> not reach here");
>>> 1059: Type type;
>>> 1060: if (desc instanceof PrimitiveClassDescImpl) {
>>
>> Can we use `desc.isPrimitive()`?
>
> I have tried isPrimitive(). The codeSize of the virtual function call
> isPrimitive() is 2 bytes larger than instanceof. The performance of
> instanceof should be better. But isPrimitive() is a public API and easier to
> understand. If you think isPrimitive is better, I think it's OK too.
ClassDesc {
default boolean isPrimitive() {
return descriptorString().length() == 1;
}
}
Using isPrimitive will result in three virtual function calls,
isPrimitive/descriptorString/length. C2 can be optimized inline, but one more
reference access to descriptorString is necessary. Considering the possible
slowdown caused by cache miss, can we keep using instanceof?
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/20756#discussion_r1735388215
