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lahodajlahodaj
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8268766: Desugaring of pattern matching enum switch should be improved
Reviewed-by: mcimadamore, psandoz
1 parent 4f70759 commit fa08cc6

7 files changed

Lines changed: 426 additions & 138 deletions

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‎src/java.base/share/classes/java/lang/runtime/SwitchBootstraps.java‎

Lines changed: 129 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -26,12 +26,11 @@
2626
package java.lang.runtime;
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import java.lang.invoke.CallSite;
29+
import java.lang.invoke.ConstantBootstraps;
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import java.lang.invoke.ConstantCallSite;
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import java.lang.invoke.MethodHandle;
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import java.lang.invoke.MethodHandles;
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import java.lang.invoke.MethodType;
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import java.util.Arrays;
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import java.util.Objects;
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import java.util.stream.Stream;
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import jdk.internal.javac.PreviewFeature;
@@ -53,12 +52,15 @@ private SwitchBootstraps() {}
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private static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup();
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56-
private static final MethodHandle DO_SWITCH;
55+
private static final MethodHandle DO_TYPE_SWITCH;
56+
private static final MethodHandle DO_ENUM_SWITCH;
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5858
static {
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try {
60-
DO_SWITCH = LOOKUP.findStatic(SwitchBootstraps.class, "doSwitch",
60+
DO_TYPE_SWITCH = LOOKUP.findStatic(SwitchBootstraps.class, "doTypeSwitch",
6161
MethodType.methodType(int.class, Object.class, int.class, Object[].class));
62+
DO_ENUM_SWITCH = LOOKUP.findStatic(SwitchBootstraps.class, "doEnumSwitch",
63+
MethodType.methodType(int.class, Enum.class, int.class, Object[].class));
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}
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catch (ReflectiveOperationException e) {
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throw new ExceptionInInitializerError(e);
@@ -108,14 +110,13 @@ private SwitchBootstraps() {}
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* second parameter of type {@code int} and with {@code int} as its return type,
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* or if {@code labels} contains an element that is not of type {@code String},
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* {@code Integer} or {@code Class}.
111-
* @throws Throwable if there is any error linking the call site
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* @jvms 4.4.6 The CONSTANT_NameAndType_info Structure
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* @jvms 4.4.10 The CONSTANT_Dynamic_info and CONSTANT_InvokeDynamic_info Structures
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*/
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public static CallSite typeSwitch(MethodHandles.Lookup lookup,
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String invocationName,
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MethodType invocationType,
118-
Object... labels) throws Throwable {
119+
Object... labels) {
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if (invocationType.parameterCount() != 2
120121
|| (!invocationType.returnType().equals(int.class))
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|| invocationType.parameterType(0).isPrimitive()
@@ -126,7 +127,7 @@ public static CallSite typeSwitch(MethodHandles.Lookup lookup,
126127
labels = labels.clone();
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Stream.of(labels).forEach(SwitchBootstraps::verifyLabel);
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129-
MethodHandle target = MethodHandles.insertArguments(DO_SWITCH, 2, (Object) labels);
130+
MethodHandle target = MethodHandles.insertArguments(DO_TYPE_SWITCH, 2, (Object) labels);
130131
return new ConstantCallSite(target);
131132
}
132133

@@ -142,7 +143,7 @@ private static void verifyLabel(Object label) {
142143
}
143144
}
144145

145-
private static int doSwitch(Object target, int startIndex, Object[] labels) {
146+
private static int doTypeSwitch(Object target, int startIndex, Object[] labels) {
146147
if (target == null)
147148
return -1;
148149

@@ -167,4 +168,124 @@ private static int doSwitch(Object target, int startIndex, Object[] labels) {
167168
return labels.length;
168169
}
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171+
/**
172+
* Bootstrap method for linking an {@code invokedynamic} call site that
173+
* implements a {@code switch} on a target of an enum type. The static
174+
* arguments are used to encode the case labels associated to the switch
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* construct, where each label can be encoded in two ways:
176+
* <ul>
177+
* <li>as a {@code String} value, which represents the name of
178+
* the enum constant associated with the label</li>
179+
* <li>as a {@code Class} value, which represents the enum type
180+
* associated with a type test pattern</li>
181+
* </ul>
182+
* <p>
183+
* The returned {@code CallSite}'s method handle will have
184+
* a return type of {@code int} and accepts two parameters: the first argument
185+
* will be an {@code Enum} instance ({@code target}) and the second
186+
* will be {@code int} ({@code restart}).
187+
* <p>
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* If the {@code target} is {@code null}, then the method of the call site
189+
* returns {@literal -1}.
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* <p>
191+
* If the {@code target} is not {@code null}, then the method of the call site
192+
* returns the index of the first element in the {@code labels} array starting from
193+
* the {@code restart} index matching one of the following conditions:
194+
* <ul>
195+
* <li>the element is of type {@code Class} that is assignable
196+
* from the target's class; or</li>
197+
* <li>the element is of type {@code String} and equals to the target
198+
* enum constant's {@link Enum#name()}.</li>
199+
* </ul>
200+
* <p>
201+
* If no element in the {@code labels} array matches the target, then
202+
* the method of the call site return the length of the {@code labels} array.
203+
*
204+
* @param lookup Represents a lookup context with the accessibility
205+
* privileges of the caller. When used with {@code invokedynamic},
206+
* this is stacked automatically by the VM.
207+
* @param invocationName unused
208+
* @param invocationType The invocation type of the {@code CallSite} with two parameters,
209+
* an enum type, an {@code int}, and {@code int} as a return type.
210+
* @param labels case labels - {@code String} constants and {@code Class} instances,
211+
* in any combination
212+
* @return a {@code CallSite} returning the first matching element as described above
213+
*
214+
* @throws NullPointerException if any argument is {@code null}
215+
* @throws IllegalArgumentException if any element in the labels array is null, if the
216+
* invocation type is not a method type whose first parameter type is an enum type,
217+
* second parameter of type {@code int} and whose return type is {@code int},
218+
* or if {@code labels} contains an element that is not of type {@code String} or
219+
* {@code Class} of the target enum type.
220+
* @jvms 4.4.6 The CONSTANT_NameAndType_info Structure
221+
* @jvms 4.4.10 The CONSTANT_Dynamic_info and CONSTANT_InvokeDynamic_info Structures
222+
*/
223+
public static CallSite enumSwitch(MethodHandles.Lookup lookup,
224+
String invocationName,
225+
MethodType invocationType,
226+
Object... labels) {
227+
if (invocationType.parameterCount() != 2
228+
|| (!invocationType.returnType().equals(int.class))
229+
|| invocationType.parameterType(0).isPrimitive()
230+
|| !invocationType.parameterType(0).isEnum()
231+
|| !invocationType.parameterType(1).equals(int.class))
232+
throw new IllegalArgumentException("Illegal invocation type " + invocationType);
233+
requireNonNull(labels);
234+
235+
labels = labels.clone();
236+
237+
Class<?> enumClass = invocationType.parameterType(0);
238+
labels = Stream.of(labels).map(l -> convertEnumConstants(lookup, enumClass, l)).toArray();
239+
240+
MethodHandle target =
241+
MethodHandles.insertArguments(DO_ENUM_SWITCH, 2, (Object) labels);
242+
target = target.asType(invocationType);
243+
244+
return new ConstantCallSite(target);
245+
}
246+
247+
private static <E extends Enum<E>> Object convertEnumConstants(MethodHandles.Lookup lookup, Class<?> enumClassTemplate, Object label) {
248+
if (label == null) {
249+
throw new IllegalArgumentException("null label found");
250+
}
251+
Class<?> labelClass = label.getClass();
252+
if (labelClass == Class.class) {
253+
if (label != enumClassTemplate) {
254+
throw new IllegalArgumentException("the Class label: " + label +
255+
", expected the provided enum class: " + enumClassTemplate);
256+
}
257+
return label;
258+
} else if (labelClass == String.class) {
259+
@SuppressWarnings("unchecked")
260+
Class<E> enumClass = (Class<E>) enumClassTemplate;
261+
try {
262+
return ConstantBootstraps.enumConstant(lookup, (String) label, enumClass);
263+
} catch (IllegalArgumentException ex) {
264+
return null;
265+
}
266+
} else {
267+
throw new IllegalArgumentException("label with illegal type found: " + labelClass +
268+
", expected label of type either String or Class");
269+
}
270+
}
271+
272+
private static int doEnumSwitch(Enum<?> target, int startIndex, Object[] labels) {
273+
if (target == null)
274+
return -1;
275+
276+
// Dumbest possible strategy
277+
Class<?> targetClass = target.getClass();
278+
for (int i = startIndex; i < labels.length; i++) {
279+
Object label = labels[i];
280+
if (label instanceof Class<?> c) {
281+
if (c.isAssignableFrom(targetClass))
282+
return i;
283+
} else if (label == target) {
284+
return i;
285+
}
286+
}
287+
288+
return labels.length;
289+
}
290+
170291
}

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