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8354899: Reduce overhead associated with type switches #24705

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7c76e52
8354899: Reduce overhead associated with type switches
liach Apr 16, 2025
cbc3fd3
Fix adding potentially unbound labels
liach Apr 17, 2025
5f929a4
Merge branch 'master' of https://github.com/openjdk/jdk into fix/swit…
liach Apr 22, 2025
2c17dd1
Rollback classfile boot speed changes
liach Apr 22, 2025
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45 changes: 34 additions & 11 deletions src/java.base/share/classes/java/lang/runtime/SwitchBootstraps.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,8 @@

import java.lang.Enum.EnumDesc;
import java.lang.classfile.CodeBuilder;
import java.lang.classfile.attribute.StackMapFrameInfo;
import java.lang.classfile.attribute.StackMapTableAttribute;
import java.lang.constant.ClassDesc;
import java.lang.constant.ConstantDesc;
import java.lang.constant.MethodTypeDesc;
Expand All @@ -48,6 +50,7 @@
import java.lang.classfile.Label;
import java.lang.classfile.instruction.SwitchCase;

import jdk.internal.classfile.impl.DirectCodeBuilder;
import jdk.internal.constant.ClassOrInterfaceDescImpl;
import jdk.internal.constant.ConstantUtils;
import jdk.internal.constant.MethodTypeDescImpl;
Expand Down Expand Up @@ -103,6 +106,13 @@ private SwitchBootstraps() {}
private static final MethodType MT_TYPE_SWITCH = MethodType.methodType(int.class,
Object.class,
int.class);
private static final List<StackMapFrameInfo.VerificationTypeInfo> TYPE_SWITCH_LOCALS = List.of(
StackMapFrameInfo.ObjectVerificationTypeInfo.of(CD_Object), StackMapFrameInfo.SimpleVerificationTypeInfo.INTEGER
);
private static final List<StackMapFrameInfo.VerificationTypeInfo> TYPE_SWITCH_EXTRA_LOCALS = List.of(
StackMapFrameInfo.ObjectVerificationTypeInfo.of(CD_Object), StackMapFrameInfo.SimpleVerificationTypeInfo.INTEGER,
StackMapFrameInfo.ObjectVerificationTypeInfo.of(CD_BiPredicate), StackMapFrameInfo.ObjectVerificationTypeInfo.of(CD_List)
);

private static class StaticHolders {
private static final MethodHandle MAPPED_ENUM_SWITCH;
Expand Down Expand Up @@ -482,8 +492,11 @@ private static Consumer<CodeBuilder> generateTypeSwitchSkeleton(Class<?> selecto
int ENUM_CACHE = 2;
int EXTRA_CLASS_LABELS = 3;

var locals = enumDescs == null && extraClassLabels == null ? TYPE_SWITCH_LOCALS : TYPE_SWITCH_EXTRA_LOCALS;

return cb -> {
// Objects.checkIndex(RESTART_IDX, labelConstants + 1)
var stackMapFrames = new ArrayList<StackMapFrameInfo>(labelConstants.length * 2);
cb.iload(RESTART_IDX)
.loadConstant(labelConstants.length + 1)
.invokestatic(CD_Objects, "checkIndex", CHECK_INDEX_DESCRIPTOR)
Expand All @@ -494,9 +507,12 @@ private static Consumer<CodeBuilder> generateTypeSwitchSkeleton(Class<?> selecto
.iconst_m1()
.ireturn()
.labelBinding(nonNullLabel);
stackMapFrames.add(StackMapFrameInfo.of(nonNullLabel, locals, List.of()));
if (labelConstants.length == 0) {
cb.loadConstant(0)
.ireturn();
.ireturn()
.with(StackMapTableAttribute.of(stackMapFrames));
DirectCodeBuilder.withMaxs(cb, 2, locals.size()); // checkIndex uses 2
return;
}
cb.iload(RESTART_IDX);
Expand All @@ -509,6 +525,7 @@ private static Consumer<CodeBuilder> generateTypeSwitchSkeleton(Class<?> selecto
for (int idx = labelConstants.length - 1; idx >= 0; idx--) {
Object currentLabel = labelConstants[idx];
Label target = cb.newLabel();
stackMapFrames.add(StackMapFrameInfo.of(target, locals, List.of()));
Label next;
if (lastLabel == null) {
next = dflt;
Expand Down Expand Up @@ -541,7 +558,7 @@ private static Consumer<CodeBuilder> generateTypeSwitchSkeleton(Class<?> selecto
} else if (!unconditionalExactnessCheck(Wrapper.asPrimitiveType(selectorType), classLabel)) {
// Integer i = ... or int i = ...
// o instanceof float
Label notNumber = cb.newLabel();
Label notNumber = cb.newLabel(); // this label may end up unbound
cb.aload(SELECTOR_OBJ)
.instanceOf(CD_Number);
if (selectorType == long.class || selectorType == float.class || selectorType == double.class ||
Expand Down Expand Up @@ -570,8 +587,9 @@ private static Consumer<CodeBuilder> generateTypeSwitchSkeleton(Class<?> selecto
"intValue",
MethodTypeDesc.of(CD_int))
.goto_(compare)
.labelBinding(notNumber)
.aload(SELECTOR_OBJ)
.labelBinding(notNumber);
stackMapFrames.add(StackMapFrameInfo.of(notNumber, locals, List.of()));
cb.aload(SELECTOR_OBJ)
.instanceOf(CD_Character)
.ifeq(next)
.aload(SELECTOR_OBJ)
Expand All @@ -580,6 +598,7 @@ private static Consumer<CodeBuilder> generateTypeSwitchSkeleton(Class<?> selecto
"charValue",
MethodTypeDesc.of(CD_char))
.labelBinding(compare);
stackMapFrames.add(StackMapFrameInfo.of(compare, locals, List.of(StackMapFrameInfo.SimpleVerificationTypeInfo.INTEGER)));
}

TypePairs typePair = TypePairs.of(Wrapper.asPrimitiveType(selectorType), classLabel);
Expand Down Expand Up @@ -648,18 +667,19 @@ private static Consumer<CodeBuilder> generateTypeSwitchSkeleton(Class<?> selecto
"intValue",
MethodTypeDesc.of(CD_int))
.goto_(compare)
.labelBinding(notNumber)
.aload(SELECTOR_OBJ)
.labelBinding(notNumber);
stackMapFrames.add(StackMapFrameInfo.of(notNumber, locals, List.of()));
cb.aload(SELECTOR_OBJ)
.instanceOf(CD_Character)
.ifeq(next)
.aload(SELECTOR_OBJ)
.checkcast(CD_Character)
.invokevirtual(CD_Character,
"charValue",
MethodTypeDesc.of(CD_char))
.labelBinding(compare)

.loadConstant(integerLabel)
.labelBinding(compare);
stackMapFrames.add(StackMapFrameInfo.of(compare, locals, List.of(StackMapFrameInfo.SimpleVerificationTypeInfo.INTEGER)));
cb.loadConstant(integerLabel)
.if_icmpne(next);
} else if ((caseLabel instanceof Long ||
caseLabel instanceof Float ||
Expand Down Expand Up @@ -688,9 +708,12 @@ private static Consumer<CodeBuilder> generateTypeSwitchSkeleton(Class<?> selecto
cb.loadConstant(idx)
.ireturn();
}
stackMapFrames.add(StackMapFrameInfo.of(dflt, locals, List.of()));
cb.labelBinding(dflt)
.loadConstant(labelConstants.length)
.ireturn();
.ireturn()
.with(StackMapTableAttribute.of(stackMapFrames));
DirectCodeBuilder.withMaxs(cb, 3, locals.size()); // enum labels use 3 stack, others use 2
};
}

Expand All @@ -702,7 +725,7 @@ private static MethodHandle generateTypeSwitch(MethodHandles.Lookup caller, Clas
List<EnumDesc<?>> enumDescs = addExtraInfo ? new ArrayList<>() : null;
List<Class<?>> extraClassLabels = addExtraInfo ? new ArrayList<>() : null;

byte[] classBytes = ClassFile.of().build(ConstantUtils.binaryNameToDesc(typeSwitchClassName(caller.lookupClass())),
byte[] classBytes = ClassFile.of(ClassFile.StackMapsOption.DROP_STACK_MAPS).build(ConstantUtils.binaryNameToDesc(typeSwitchClassName(caller.lookupClass())),
clb -> {
clb.withFlags(AccessFlag.FINAL, AccessFlag.SUPER, AccessFlag.SYNTHETIC)
.withMethodBody("typeSwitch",
Expand Down
13 changes: 11 additions & 2 deletions src/java.base/share/classes/jdk/internal/classfile/impl/DirectCodeBuilder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -48,10 +48,8 @@ public final class DirectCodeBuilder
extends AbstractDirectBuilder<CodeModel>
implements TerminalCodeBuilder {
private static final CharacterRange[] EMPTY_CHARACTER_RANGE = {};
private static final DeferredLabel[] EMPTY_LABEL_ARRAY = {};
private static final LocalVariable[] EMPTY_LOCAL_VARIABLE_ARRAY = {};
private static final LocalVariableType[] EMPTY_LOCAL_VARIABLE_TYPE_ARRAY = {};
private static final AbstractPseudoInstruction.ExceptionCatchImpl[] EMPTY_HANDLER_ARRAY = {};
private static final DeferredLabel[] EMPTY_DEFERRED_LABEL_ARRAY = {};

final List<AbstractPseudoInstruction.ExceptionCatchImpl> handlers = new ArrayList<>();
Expand All @@ -74,6 +72,9 @@ public final class DirectCodeBuilder
private DeferredLabel[] deferredLabels = EMPTY_DEFERRED_LABEL_ARRAY;
private int deferredLabelsCount = 0;

private int maxStackHint = -1;
private int maxLocalsHint = -1;

/* Locals management
lazily computed maxLocal = -1
first time: derive count from methodType descriptor (for new methods) & ACC_STATIC,
Expand Down Expand Up @@ -173,6 +174,12 @@ public MethodInfo methodInfo() {
return methodInfo;
}

public static void withMaxs(CodeBuilder cob, int stacks, int locals) {
var dcb = (DirectCodeBuilder) cob;
dcb.maxStackHint = stacks;
dcb.maxLocalsHint = locals;
}

private UnboundAttribute<CodeAttribute> content = null;

private void writeExceptionHandlers(BufWriterImpl buf) {
Expand Down Expand Up @@ -319,6 +326,8 @@ private void writeCounters(boolean codeMatch, BufWriterImpl buf) {
if (codeMatch) {
var originalAttribute = (CodeImpl) original;
buf.writeU2U2(originalAttribute.maxStack(), originalAttribute.maxLocals());
} else if (maxLocalsHint >= 0 && maxStackHint >= 0) {
buf.writeU2U2(maxStackHint, maxLocalsHint);
} else {
StackCounter cntr = StackCounter.of(DirectCodeBuilder.this, buf);
buf.writeU2U2(cntr.maxStack(), cntr.maxLocals());
Expand Down