On Wed, 21 Aug 2024 20:25:07 GMT, Chen Liang <li...@openjdk.org> wrote:
> @cl4es discovered that Stack Map generation in ClassFile API uses > `componentType` and `arrayType` for `aaload` `aastore` instructions, which > are currently quite slow. We can split out array class descriptors from class > or interfaces to support faster `arrayType` and `componentType` operations. > > Tentative, as I currently have no way to measure the actual impact of this > patch on the startup performance; however, this made the `ClassDesc` > implementations much cleaner. Apparently, changing method `default`‑ness requires a CSR (even for fully sealed hierarchies), but I can’t find the PR where I was informed of this. -------------------------------------------------------------------------------- Using `return this instanceof <type>ClassDescImpl` might allow **C2** to better avoid megamorphic virtual invocations (see [GH‑17488]), but this needs to be benchmarked: [GH‑17488]: https://github.com/openjdk/jdk/pull/17488 src/java.base/share/classes/java/lang/constant/ClassDesc.java line 237: > 235: */ > 236: default boolean isArray() { > 237: return false; Suggestion: return this instanceof ArrayClassDescImpl; src/java.base/share/classes/java/lang/constant/ClassDesc.java line 246: > 244: */ > 245: default boolean isPrimitive() { > 246: return false; Suggestion: return this instanceof PrimitiveClassDescImpl; src/java.base/share/classes/java/lang/constant/ClassDesc.java line 255: > 253: */ > 254: default boolean isClassOrInterface() { > 255: return false; Suggestion: return this instanceof ReferenceClassDescImpl; ------------- PR Review: https://git.openjdk.org/jdk/pull/20665#pullrequestreview-2263259130 PR Review Comment: https://git.openjdk.org/jdk/pull/20665#discussion_r1732794261 PR Review Comment: https://git.openjdk.org/jdk/pull/20665#discussion_r1732794721 PR Review Comment: https://git.openjdk.org/jdk/pull/20665#discussion_r1732795070
