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8291966: SwitchBootstrap.typeSwitch could be faster
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Reviewed-by: asotona
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@lahodaj
lahodaj committed Jun 5, 2023
1 parent db0857d commit 9be5769
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Showing 2 changed files with 182 additions and 87 deletions.
262 changes: 175 additions & 87 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
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2017, 2021, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2017, 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
Expand Down Expand Up @@ -27,16 +27,17 @@

import java.lang.Enum.EnumDesc;
import java.lang.invoke.CallSite;
import java.lang.invoke.ConstantBootstraps;
import java.lang.invoke.ConstantCallSite;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.util.List;
import java.util.Objects;
import java.util.stream.Stream;
import jdk.internal.access.SharedSecrets;
import jdk.internal.vm.annotation.Stable;

import static java.util.Objects.requireNonNull;
import jdk.internal.vm.annotation.Stable;

/**
* Bootstrap methods for linking {@code invokedynamic} call sites that implement
Expand All @@ -50,18 +51,38 @@ public class SwitchBootstraps {

private SwitchBootstraps() {}

private static final Object SENTINEL = new Object();
private static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup();

private static final MethodHandle DO_TYPE_SWITCH;
private static final MethodHandle DO_ENUM_SWITCH;
private static final MethodHandle INSTANCEOF_CHECK;
private static final MethodHandle INTEGER_EQ_CHECK;
private static final MethodHandle OBJECT_EQ_CHECK;
private static final MethodHandle ENUM_EQ_CHECK;
private static final MethodHandle NULL_CHECK;
private static final MethodHandle IS_ZERO;
private static final MethodHandle CHECK_INDEX;
private static final MethodHandle MAPPED_ENUM_LOOKUP;

static {
try {
DO_TYPE_SWITCH = LOOKUP.findStatic(SwitchBootstraps.class, "doTypeSwitch",
MethodType.methodType(int.class, Object.class, int.class, Object[].class));
DO_ENUM_SWITCH = LOOKUP.findStatic(SwitchBootstraps.class, "doEnumSwitch",
MethodType.methodType(int.class, Enum.class, int.class, Object[].class,
MethodHandles.Lookup.class, Class.class, ResolvedEnumLabels.class));
INSTANCEOF_CHECK = MethodHandles.permuteArguments(LOOKUP.findVirtual(Class.class, "isInstance",
MethodType.methodType(boolean.class, Object.class)),
MethodType.methodType(boolean.class, Object.class, Class.class), 1, 0);
INTEGER_EQ_CHECK = LOOKUP.findStatic(SwitchBootstraps.class, "integerEqCheck",
MethodType.methodType(boolean.class, Object.class, Integer.class));
OBJECT_EQ_CHECK = LOOKUP.findStatic(Objects.class, "equals",
MethodType.methodType(boolean.class, Object.class, Object.class));
ENUM_EQ_CHECK = LOOKUP.findStatic(SwitchBootstraps.class, "enumEqCheck",
MethodType.methodType(boolean.class, Object.class, EnumDesc.class, MethodHandles.Lookup.class, ResolvedEnumLabel.class));
NULL_CHECK = LOOKUP.findStatic(Objects.class, "isNull",
MethodType.methodType(boolean.class, Object.class));
IS_ZERO = LOOKUP.findStatic(SwitchBootstraps.class, "isZero",
MethodType.methodType(boolean.class, int.class));
CHECK_INDEX = LOOKUP.findStatic(Objects.class, "checkIndex",
MethodType.methodType(int.class, int.class, int.class));
MAPPED_ENUM_LOOKUP = LOOKUP.findStatic(SwitchBootstraps.class, "mappedEnumLookup",
MethodType.methodType(int.class, Enum.class, MethodHandles.Lookup.class,
Class.class, EnumDesc[].class, EnumMap.class));
}
catch (ReflectiveOperationException e) {
throw new ExceptionInInitializerError(e);
Expand Down Expand Up @@ -134,7 +155,8 @@ public static CallSite typeSwitch(MethodHandles.Lookup lookup,
labels = labels.clone();
Stream.of(labels).forEach(SwitchBootstraps::verifyLabel);

MethodHandle target = MethodHandles.insertArguments(DO_TYPE_SWITCH, 2, (Object) labels);
MethodHandle target = createMethodHandleSwitch(lookup, labels);

return new ConstantCallSite(target);
}

Expand All @@ -151,36 +173,81 @@ private static void verifyLabel(Object label) {
}
}

private static int doTypeSwitch(Object target, int startIndex, Object[] labels) {
Objects.checkIndex(startIndex, labels.length + 1);

if (target == null)
return -1;

// Dumbest possible strategy
Class<?> targetClass = target.getClass();
for (int i = startIndex; i < labels.length; i++) {
Object label = labels[i];
if (label instanceof Class<?> c) {
if (c.isAssignableFrom(targetClass))
return i;
} else if (label instanceof Integer constant) {
if (target instanceof Number input && constant.intValue() == input.intValue()) {
return i;
} else if (target instanceof Character input && constant.intValue() == input.charValue()) {
return i;
}
} else if (label instanceof EnumDesc<?> enumDesc) {
if (target.getClass().isEnum() &&
((Enum<?>) target).describeConstable().stream().anyMatch(d -> d.equals(enumDesc))) {
return i;
/*
* Construct test chains for labels inside switch, to handle switch repeats:
* switch (idx) {
* case 0 -> if (selector matches label[0]) return 0; else if (selector matches label[1]) return 1; else ...
* case 1 -> if (selector matches label[1]) return 1; else ...
* ...
* }
*/
private static MethodHandle createRepeatIndexSwitch(MethodHandles.Lookup lookup, Object[] labels) {
MethodHandle def = MethodHandles.dropArguments(MethodHandles.constant(int.class, labels.length), 0, Object.class);
MethodHandle[] testChains = new MethodHandle[labels.length];
List<Object> labelsList = List.of(labels).reversed();

for (int i = 0; i < labels.length; i++) {
MethodHandle test = def;
int idx = labels.length - 1;
List<Object> currentLabels = labelsList.subList(0, labels.length - i);

for (int j = 0; j < currentLabels.size(); j++, idx--) {
Object currentLabel = currentLabels.get(j);
if (j + 1 < currentLabels.size() && currentLabels.get(j + 1) == currentLabel) continue;
MethodHandle currentTest;
if (currentLabel instanceof Class<?>) {
currentTest = INSTANCEOF_CHECK;
} else if (currentLabel instanceof Integer) {
currentTest = INTEGER_EQ_CHECK;
} else if (currentLabel instanceof EnumDesc) {
currentTest = MethodHandles.insertArguments(ENUM_EQ_CHECK, 2, lookup, new ResolvedEnumLabel());
} else {
currentTest = OBJECT_EQ_CHECK;
}
} else if (label.equals(target)) {
return i;
test = MethodHandles.guardWithTest(MethodHandles.insertArguments(currentTest, 1, currentLabel),
MethodHandles.dropArguments(MethodHandles.constant(int.class, idx), 0, Object.class),
test);
}
testChains[i] = MethodHandles.dropArguments(test, 0, int.class);
}

return MethodHandles.tableSwitch(MethodHandles.dropArguments(def, 0, int.class), testChains);
}

/*
* Construct code that maps the given selector and repeat index to a case label number:
* if (selector == null) return -1;
* else return "createRepeatIndexSwitch(labels)"
*/
private static MethodHandle createMethodHandleSwitch(MethodHandles.Lookup lookup, Object[] labels) {
MethodHandle mainTest;
MethodHandle def = MethodHandles.dropArguments(MethodHandles.constant(int.class, labels.length), 0, Object.class);
if (labels.length > 0) {
mainTest = createRepeatIndexSwitch(lookup, labels);
} else {
mainTest = MethodHandles.dropArguments(def, 0, int.class);
}
MethodHandle body =
MethodHandles.guardWithTest(MethodHandles.dropArguments(NULL_CHECK, 0, int.class),
MethodHandles.dropArguments(MethodHandles.constant(int.class, -1), 0, int.class, Object.class),
mainTest);
MethodHandle switchImpl =
MethodHandles.permuteArguments(body, MethodType.methodType(int.class, Object.class, int.class), 1, 0);
return withIndexCheck(switchImpl, labels.length);
}

private static boolean integerEqCheck(Object value, Integer constant) {
if (value instanceof Number input && constant.intValue() == input.intValue()) {
return true;
} else if (value instanceof Character input && constant.intValue() == input.charValue()) {
return true;
}

return labels.length;
return false;
}

private static boolean isZero(int value) {
return value == 0;
}

/**
Expand Down Expand Up @@ -254,28 +321,31 @@ public static CallSite enumSwitch(MethodHandles.Lookup lookup,
labels = labels.clone();

Class<?> enumClass = invocationType.parameterType(0);
Stream.of(labels).forEach(l -> validateEnumLabel(enumClass, l));
MethodHandle temporary =
MethodHandles.insertArguments(DO_ENUM_SWITCH, 2, labels, lookup, enumClass, new ResolvedEnumLabels());
temporary = temporary.asType(invocationType);
labels = Stream.of(labels).map(l -> convertEnumConstants(lookup, enumClass, l)).toArray();

return new ConstantCallSite(temporary);
}
MethodHandle target;
boolean constantsOnly = Stream.of(labels).allMatch(l -> enumClass.isAssignableFrom(EnumDesc.class));

private static <E extends Enum<E>> void validateEnumLabel(Class<?> enumClassTemplate, Object label) {
if (label == null) {
throw new IllegalArgumentException("null label found");
}
Class<?> labelClass = label.getClass();
if (labelClass == Class.class) {
if (label != enumClassTemplate) {
throw new IllegalArgumentException("the Class label: " + label +
", expected the provided enum class: " + enumClassTemplate);
}
} else if (labelClass != String.class) {
throw new IllegalArgumentException("label with illegal type found: " + labelClass +
", expected label of type either String or Class");
if (labels.length > 0 && constantsOnly) {
//If all labels are enum constants, construct an optimized handle for repeat index 0:
//if (selector == null) return -1
//else if (idx == 0) return mappingArray[selector.ordinal()]; //mapping array created lazily
//else return "createRepeatIndexSwitch(labels)"
MethodHandle body =
MethodHandles.guardWithTest(MethodHandles.dropArguments(NULL_CHECK, 0, int.class),
MethodHandles.dropArguments(MethodHandles.constant(int.class, -1), 0, int.class, Object.class),
MethodHandles.guardWithTest(MethodHandles.dropArguments(IS_ZERO, 1, Object.class),
createRepeatIndexSwitch(lookup, labels),
MethodHandles.insertArguments(MAPPED_ENUM_LOOKUP, 1, lookup, enumClass, labels, new EnumMap())));
target = MethodHandles.permuteArguments(body, MethodType.methodType(int.class, Object.class, int.class), 1, 0);
} else {
target = createMethodHandleSwitch(lookup, labels);
}

target = target.asType(invocationType);
target = withIndexCheck(target, labels.length);

return new ConstantCallSite(target);
}

private static <E extends Enum<E>> Object convertEnumConstants(MethodHandles.Lookup lookup, Class<?> enumClassTemplate, Object label) {
Expand All @@ -290,52 +360,70 @@ private static <E extends Enum<E>> Object convertEnumConstants(MethodHandles.Loo
}
return label;
} else if (labelClass == String.class) {
@SuppressWarnings("unchecked")
Class<E> enumClass = (Class<E>) enumClassTemplate;
try {
return ConstantBootstraps.enumConstant(lookup, (String) label, enumClass);
} catch (IllegalArgumentException ex) {
return null;
}
return EnumDesc.of(enumClassTemplate.describeConstable().get(), (String) label);
} else {
throw new IllegalArgumentException("label with illegal type found: " + labelClass +
", expected label of type either String or Class");
}
}

private static int doEnumSwitch(Enum<?> target, int startIndex, Object[] unresolvedLabels,
MethodHandles.Lookup lookup, Class<?> enumClass,
ResolvedEnumLabels resolvedLabels) {
Objects.checkIndex(startIndex, unresolvedLabels.length + 1);
private static <T extends Enum<T>> int mappedEnumLookup(T value, MethodHandles.Lookup lookup, Class<T> enumClass, EnumDesc<?>[] labels, EnumMap enumMap) {
if (enumMap.map == null) {
T[] constants = SharedSecrets.getJavaLangAccess().getEnumConstantsShared(enumClass);
int[] map = new int[constants.length];
int ordinal = 0;

if (target == null)
return -1;
for (T constant : constants) {
map[ordinal] = labels.length;

if (resolvedLabels.resolvedLabels == null) {
resolvedLabels.resolvedLabels = Stream.of(unresolvedLabels)
.map(l -> convertEnumConstants(lookup, enumClass, l))
.toArray();
for (int i = 0; i < labels.length; i++) {
if (Objects.equals(labels[i].constantName(), constant.name())) {
map[ordinal] = i;
break;
}
}

ordinal++;
}
}
return enumMap.map[value.ordinal()];
}

private static boolean enumEqCheck(Object value, EnumDesc<?> label, MethodHandles.Lookup lookup, ResolvedEnumLabel resolvedEnum) {
if (resolvedEnum.resolvedEnum == null) {
Object resolved;

try {
Class<?> clazz = label.constantType().resolveConstantDesc(lookup);

Object[] labels = resolvedLabels.resolvedLabels;

// Dumbest possible strategy
Class<?> targetClass = target.getClass();
for (int i = startIndex; i < labels.length; i++) {
Object label = labels[i];
if (label instanceof Class<?> c) {
if (c.isAssignableFrom(targetClass))
return i;
} else if (label == target) {
return i;
if (value.getClass() != clazz) {
return false;
}

resolved = label.resolveConstantDesc(lookup);
} catch (IllegalArgumentException | ReflectiveOperationException ex) {
resolved = SENTINEL;
}

resolvedEnum.resolvedEnum = resolved;
}

return labels.length;
return value == resolvedEnum.resolvedEnum;
}

private static MethodHandle withIndexCheck(MethodHandle target, int labelsCount) {
MethodHandle checkIndex = MethodHandles.insertArguments(CHECK_INDEX, 1, labelsCount + 1);

return MethodHandles.filterArguments(target, 1, checkIndex);
}

private static final class ResolvedEnumLabel {
@Stable
public Object resolvedEnum;
}

private static final class ResolvedEnumLabels {
private static final class EnumMap {
@Stable
public Object[] resolvedLabels;
public int[] map;
}
}
7 changes: 7 additions & 0 deletions test/jdk/java/lang/runtime/SwitchBootstrapsTest.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,7 @@ public void testTypes() throws Throwable {
testType("", 0, 0, String.class, String.class, String.class);
testType("", 1, 1, String.class, String.class, String.class);
testType("", 2, 2, String.class, String.class, String.class);
testType("", 0, 0);
}

public void testEnums() throws Throwable {
Expand All @@ -131,6 +132,12 @@ public void testEnums() throws Throwable {
} catch (IllegalArgumentException ex) {
//OK
}
testEnum(E1.B, 0, 0, "B", "A");
testEnum(E1.A, 0, 1, "B", "A");
testEnum(E1.A, 0, 0, "A", "A", "B");
testEnum(E1.A, 1, 1, "A", "A", "B");
testEnum(E1.A, 2, 3, "A", "A", "B");
testEnum(E1.A, 0, 0);
}

public void testWrongSwitchTypes() throws Throwable {
Expand Down

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