Enhance `ResourceParsingClassHierarchyResolver.getClassInfo` to use `ClassReaderImpl` to improve performance. Previously this method inflated and stored all UTF-8 entries in the constant pool and later accessed the array of strings to try finding the name of the superclass. `ClassReaderImpl` instead stores constant pool offsets and later lazily reads/inflates UTF8 entries as needed.
I’ve ran all tier 1 tests and tests within `test/jdk/jdk/classfile` on the latest version of this change, and they all pass. I ran some informal performance testing to see if these changes led to any improvement. I created a .class file with several thousand unique strings in a String array to deliberately enlarge the number of UTF-8 entries in the constant pool. I then benchmarked the performance of running a process nearly identical to `ClassHierarchyInfoTest.testClassLoaderParsingResolver` on this custom class over 200 runs using JMH. The results are as follows. | Version | Avg Time (ns/op) | Δ vs Before | |--------|------------------:|-------------| | **Before** | 1,483,671.539 ± 3,477.744 | — | | **After** | 1,380,064.517 ± 3,482.434 | ≈ 7.0% faster | ------------- Commit messages: - JDK-8350938 Changes: https://git.openjdk.org/jdk/pull/28458/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28458&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8350938 Stats: 28 lines in 1 file changed: 3 ins; 19 del; 6 mod Patch: https://git.openjdk.org/jdk/pull/28458.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28458/head:pull/28458 PR: https://git.openjdk.org/jdk/pull/28458
