RFR: 8340710: Optimize DirectClassBuilder::build

[Chen Liang]

On Sun, 22 Sep 2024 05:30:43 GMT, Shaojin Wen <swen at openjdk.org> wrote:

> Do some refactoring so that the code can be inlined by the C1/C2 optimizer.
> 
> 1. DirectClassBuilder::build codeSize 361 -> 315
> 2. DirectCodeBuilder::writeExceptionHandlers codeSize 183 -> 31
> 3. BufWriterImpl::writeIndex codeSize 62 -> 37 (forceinline)
> 4. BufWriterImpl::writeU2 (forceinline)
> 5. Util::writeAttributes codSize 45 -> 40 (forceinline)
> 6. Util::writeList codSize 47 -> 42 (forceinline)

src/java.base/share/classes/jdk/internal/classfile/impl/BufWriterImpl.java line 99:

> 97:     }
> 98: 
> 99:     void writeMagic(int minorVersion, int majorVersion) {

Can we use `writeLong(((long) MAGIC_NUMBER) << 32 | minorVersion << 16 | majorVersion);`?

src/java.base/share/classes/jdk/internal/classfile/impl/BufWriterImpl.java line 99:

> 97:     }
> 98: 
> 99:     void writeMagic(int minorVersion, int majorVersion) {

Can we call this `writeHeader` as this writes both the magic and the version?

src/java.base/share/classes/jdk/internal/classfile/impl/Util.java line 256:

> 254:         int size = list.size();
> 255:         buf.writeU2(size);
> 256:         for (int i = 0; i < size; i++) {

👍 Manual loop unrolling is good for startup

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PR Review Comment: https://git.openjdk.org/jdk/pull/21118#discussion_r1770556482
PR Review Comment: https://git.openjdk.org/jdk/pull/21118#discussion_r1770670377
PR Review Comment: https://git.openjdk.org/jdk/pull/21118#discussion_r1770556848