RFR: 8306842: Classfile API performance improvements

[ExE Boss]

On Wed, 26 Apr 2023 15:04:50 GMT, Adam Sotona <asotona at openjdk.org> wrote:

> Following improvements implemented:
> - Switch over `String` replaced with switch single char
> - Binary search for frames in `StackMapGenerator`
> - `StackMapGenerator.rawHandlers` with pre-calculated offsets
> - `ClassEntry` is caching `ClassDesc` symbol
> - Caching of type symbols in `NameAndTypeEntry` and `MethodTypeEntry`
> - Caching `MethodTypeDesc` in `MethodInfo` implementations
> - `StackMapGenerator` and `Utils` delegating to cached `MethodTypeDesc` instead of custom parsing
> 
> No API change.
> 
> Benchmarks show stack map generation improved by 21% and code generation from symbols improved by 30%.
> 
> 
> Benchmark                     Mode  Cnt       Score       Error  Units
> GenerateStackMaps.benchmark  thrpt   10  407931.202 ± 13101.023  ops/s
> RebuildMethodBodies.shared   thrpt    4   10258.597 ±   383.699  ops/s
> RebuildMethodBodies.unshared thrpt    4    7224.543 ±   256.800  ops/s
> 
> 
> 
> Benchmark                     Mode  Cnt       Score      Error  Units
> GenerateStackMaps.benchmark  thrpt   10  495101.110 ± 2389.628  ops/s
> RebuildMethodBodies.shared    thrpt   4   13380.272 ±  810.113  ops/s
> RebuildMethodBodies.unshared  thrpt   4    9399.863 ±  557.060  ops/s

In order to avoid eager conversion of a `ClassDesc` to internal name, I suggest extending `AbstractPoolEntry.Utf8EntryImpl` with `State.CLASS_DESC`:

class AbstractPoolEntry.Utf8EntryImpl extends AbstractPoolEntry implements Utf8Entry {
	enum State { CLASS_DESC, ... }

	// Set in any state other than RAW or CLASS_DESC
	private int hash;
	// Set in any state other than RAW
	private int charLen;
	// Only set in CLASS_DESC state, must be an L-type Class descriptor
	private ClassDesc classDesc;

	Utf8EntryImpl(ConstantPool cpm, int index, ClassDesc cd) {
		super(cpm, Classfile.TAG_UTF8, index, 0);
		this.rawBytes = null;
		this.offset = 0;
		this.rawLen = 0;
		String descriptor = cd.descriptorString();
		if (cd.isArray()) {
			this.state = State.STRING;
			this.stringValue = descriptor;
			this.charLen = descriptor.length();
			this.hash = hashString(descriptor.hashCode());
		} else {
			assert cd.isClassOrInterface() : cd;
			this.state = State.CLASS_DESC;
			this.classDesc = cd;
			this.charLen = descriptor.length() - 2;
		}
	}

	private void inflateClassDesc() {
		String internalName = Utils.toInternalName(this.classDesc);
		assert this.charLen = internalName.length();
		this.stringValue = internalName;
		this.hash = hashString(internalName.hashCode());
		this.state = State.STRING;
	}

	@Override
	public Utf8EntryImpl clone(ConstantPoolBuilder cp) {
		if (cp.canWriteDirect(constantPool))
			return this;
		if (state = State.CLASS_DESC) {
			return (Utf8EntryImpl) cp.utf8Entry(classDesc);
		}
		return (state == State.STRING && rawBytes == null)
			? (Utf8EntryImpl) cp.utf8Entry(stringValue)
			: ((SplitConstantPool) cp).maybeCloneUtf8Entry(this);
	}

	@Override
	public int hashCode() {
		if (state == State.CLASS_DESC) {
			inflateClassDesc();
		}
		...
	}

	@Override
	public String toString() {
		if (state == State.CLASS_DESC) {
			inflateClassDesc();
		}
		...
	}

	@Override
	public char charAt(int index) {
		if (state == State.CLASS_DESC) {
			return classDesc.descriptorString()
				.charAt(Objects.checkIndex(index, charLen) + 1);
		}
		...
	}

	@Override
	public boolean equalsString(String s) {
		if (state == State.CLASS_DESC) {
			inflateClassDesc();
		}
		...
	}

	@Override
	public void writeTo(BufWriter pool) {
		if (rawBytes != null) {
			...
		}
		else {
			if (state == State.CLASS_DESC) {
				inflateClassDesc();
			}
			...
		}
	}
}

src/java.base/share/classes/jdk/internal/classfile/impl/AbstractPoolEntry.java line 586:

> 584:                 sym = Util.toClassDesc(asInternalName());
> 585:             }
> 586:             return sym;

Suggestion:

            var sym = this.sym;
            if (sym != null) {
                return sym;
            }
            return this.sym = Util.toClassDesc(asInternalName());

src/java.base/share/classes/jdk/internal/classfile/impl/AbstractPoolEntry.java line 988:

> 986:                 sym = MethodTypeDesc.ofDescriptor(descriptor().stringValue());
> 987:             }
> 988:             return sym;

Suggestion:

            var sym = this.sym;
            if (sym != null) {
                return sym;
            }
            return this.sym = MethodTypeDesc.ofDescriptor(descriptor().stringValue());

-------------

PR Comment: https://git.openjdk.org/jdk/pull/13671#issuecomment-1527967835
PR Review Comment: https://git.openjdk.org/jdk/pull/13671#discussion_r1178367689
PR Review Comment: https://git.openjdk.org/jdk/pull/13671#discussion_r1178369318