wasm gc: basic implementation of WeakReference

core/src/main/java/org/teavm/backend/wasm/gc/WasmGCDependencies.java

@@ -35,6 +35,7 @@ public class WasmGCDependencies {
         contributeMathUtils();
         contributeExceptionUtils();
         contributeInitializerUtils();
+        analyzer.addDependencyListener(new WasmGCReferenceQueueDependency());
     }
 
     public void contributeStandardExports() {

core/src/main/java/org/teavm/backend/wasm/gc/WasmGCReferenceQueueDependency.java

@@ -0,0 +1,44 @@
+/*
+ *  Copyright 2024 konsoletyper.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.backend.wasm.gc;
+
+import org.teavm.dependency.AbstractDependencyListener;
+import org.teavm.dependency.DependencyAgent;
+import org.teavm.dependency.DependencyNode;
+import org.teavm.dependency.MethodDependency;
+
+public class WasmGCReferenceQueueDependency extends AbstractDependencyListener {
+    private DependencyNode valueNode;
+
+    @Override
+    public void started(DependencyAgent agent) {
+        valueNode = agent.createNode();
+    }
+
+    @Override
+    public void methodReached(DependencyAgent agent, MethodDependency method) {
+        if (method.getMethod().getOwnerName().equals("java.lang.ref.WeakReference")) {
+            switch (method.getMethod().getName()) {
+                case "<init>":
+                    method.getVariable(1).connect(valueNode);
+                    break;
+                case "get":
+                    valueNode.connect(method.getResult());
+                    break;
+            }
+        }
+    }
+}

core/src/main/java/org/teavm/backend/wasm/generate/gc/classes/WasmGCClassGenerator.java

@@ -1118,6 +1118,10 @@ public class WasmGCClassGenerator implements WasmGCClassInfoProvider, WasmGCInit
         if (classReader.getParent() != null) {
             fillClassFields(fields, classReader.getParent());
         }
+        if (className.equals("java.lang.ref.WeakReference")) {
+            var field = new WasmField(WasmType.Reference.EXTERN.asStorage(), "nativeRef");
+            fields.add(field);
+        } else {
             for (var field : classReader.getFields()) {
                 if (className.equals("java.lang.Object") && field.getName().equals("monitor")) {
                     continue;
@@ -1133,6 +1137,7 @@ public class WasmGCClassGenerator implements WasmGCClassInfoProvider, WasmGCInit
                         names.forMemberField(field.getReference()));
                 fields.add(wasmField);
             }
+        }
         if (className.equals("java.lang.Class")) {
             var cls = classSource.get("java.lang.Class");
             classFlagsOffset = fields.size();

core/src/main/java/org/teavm/backend/wasm/generate/gc/classes/WasmGCClassInfoProvider.java

@@ -26,6 +26,7 @@ public interface WasmGCClassInfoProvider {
     int MONITOR_FIELD_OFFSET = 1;
     int CUSTOM_FIELD_OFFSETS = 2;
     int ARRAY_DATA_FIELD_OFFSET = 2;
+    int WEAK_REFERENCE_OFFSET = 2;
 
     WasmGCClassInfo getClassInfo(ValueType type);
 

core/src/main/java/org/teavm/backend/wasm/generators/gc/WasmGCCustomGenerators.java

@@ -15,6 +15,8 @@
  */
 package org.teavm.backend.wasm.generators.gc;
 
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.WeakReference;
 import java.lang.reflect.Array;
 import java.util.HashMap;
 import java.util.List;
@@ -41,6 +43,7 @@ public class WasmGCCustomGenerators implements WasmGCCustomGeneratorProvider {
         fillStringPool();
         fillSystem();
         fillArray();
+        fillWeakReference();
         for (var entry : generators.entrySet()) {
             add(entry.getKey(), entry.getValue());
         }
@@ -68,6 +71,14 @@ public class WasmGCCustomGenerators implements WasmGCCustomGeneratorProvider {
         add(new MethodReference(Array.class, "newInstanceImpl", Class.class, int.class, Object.class), arrayGenerator);
     }
 
+    private void fillWeakReference() {
+        var generator = new WeakReferenceGenerator();
+        add(new MethodReference(WeakReference.class, "<init>", Object.class, ReferenceQueue.class,
+                void.class), generator);
+        add(new MethodReference(WeakReference.class, "get", Object.class), generator);
+        add(new MethodReference(WeakReference.class, "clear", void.class), generator);
+    }
+
     @Override
     public WasmGCCustomGenerator get(MethodReference method) {
         var result = generators.get(method);

core/src/main/java/org/teavm/backend/wasm/generators/gc/WeakReferenceGenerator.java

@@ -0,0 +1,121 @@
+/*
+ *  Copyright 2024 konsoletyper.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.backend.wasm.generators.gc;
+
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.WeakReference;
+import org.teavm.backend.wasm.generate.gc.classes.WasmGCClassInfoProvider;
+import org.teavm.backend.wasm.model.WasmFunction;
+import org.teavm.backend.wasm.model.WasmLocal;
+import org.teavm.backend.wasm.model.WasmType;
+import org.teavm.backend.wasm.model.expression.WasmBlock;
+import org.teavm.backend.wasm.model.expression.WasmCall;
+import org.teavm.backend.wasm.model.expression.WasmGetLocal;
+import org.teavm.backend.wasm.model.expression.WasmNullBranch;
+import org.teavm.backend.wasm.model.expression.WasmNullCondition;
+import org.teavm.backend.wasm.model.expression.WasmNullConstant;
+import org.teavm.backend.wasm.model.expression.WasmReturn;
+import org.teavm.backend.wasm.model.expression.WasmStructGet;
+import org.teavm.backend.wasm.model.expression.WasmStructSet;
+import org.teavm.model.MethodReference;
+import org.teavm.model.ValueType;
+
+public class WeakReferenceGenerator implements WasmGCCustomGenerator {
+    private WasmFunction createWeakReferenceFunction;
+
+    @Override
+    public void apply(MethodReference method, WasmFunction function, WasmGCCustomGeneratorContext context) {
+        switch (method.getName()) {
+            case "<init>":
+                generateConstructor(context, function);
+                break;
+            case "get":
+                generateDeref(context, function);
+                break;
+            case "clear":
+                generateClear(context, function);
+                break;
+        }
+    }
+
+    private void generateConstructor(WasmGCCustomGeneratorContext context, WasmFunction function) {
+        var weakRefStruct = context.classInfoProvider().getClassInfo(WeakReference.class.getName()).getStructure();
+        var thisLocal = new WasmLocal(weakRefStruct.getReference(), "this");
+        var valueLocal = new WasmLocal(context.typeMapper().mapType(ValueType.parse(Object.class)), "value");
+        var queueLocal = new WasmLocal(context.typeMapper().mapType(ValueType.parse(ReferenceQueue.class)), "queue");
+        function.add(thisLocal);
+        function.add(valueLocal);
+        function.add(queueLocal);
+
+        var weakRefConstructor = getCreateWeakReferenceFunction(context);
+        var weakRef = new WasmCall(weakRefConstructor, new WasmGetLocal(valueLocal), new WasmGetLocal(thisLocal));
+        function.getBody().add(new WasmStructSet(weakRefStruct, new WasmGetLocal(thisLocal),
+                WasmGCClassInfoProvider.WEAK_REFERENCE_OFFSET, weakRef));
+    }
+
+    private void generateDeref(WasmGCCustomGeneratorContext context, WasmFunction function) {
+        var weakRefStruct = context.classInfoProvider().getClassInfo(WeakReference.class.getName()).getStructure();
+        var objectType = context.classInfoProvider().getClassInfo("java.lang.Object").getType();
+        var thisLocal = new WasmLocal(weakRefStruct.getReference(), "this");
+        function.add(thisLocal);
+
+        var block = new WasmBlock(false);
+        block.setType(WasmType.Reference.EXTERN);
+        var weakRef = new WasmStructGet(weakRefStruct, new WasmGetLocal(thisLocal),
+                WasmGCClassInfoProvider.WEAK_REFERENCE_OFFSET);
+        var br = new WasmNullBranch(WasmNullCondition.NOT_NULL, weakRef, block);
+        block.getBody().add(br);
+        block.getBody().add(new WasmReturn(new WasmNullConstant(objectType)));
+
+        function.getBody().add(new WasmCall(createDerefFunction(context), block));
+    }
+
+    private void generateClear(WasmGCCustomGeneratorContext context, WasmFunction function) {
+        var weakRefStruct = context.classInfoProvider().getClassInfo(WeakReference.class.getName()).getStructure();
+        var thisLocal = new WasmLocal(weakRefStruct.getReference(), "this");
+        function.add(thisLocal);
+
+        function.getBody().add(new WasmStructSet(weakRefStruct, new WasmGetLocal(thisLocal),
+                WasmGCClassInfoProvider.WEAK_REFERENCE_OFFSET, new WasmNullConstant(WasmType.Reference.EXTERN)));
+    }
+
+    private WasmFunction getCreateWeakReferenceFunction(WasmGCCustomGeneratorContext context) {
+        if (createWeakReferenceFunction == null) {
+            var function = new WasmFunction(context.functionTypes().of(
+                    WasmType.Reference.EXTERN,
+                    context.typeMapper().mapType(ValueType.parse(Object.class)),
+                    context.typeMapper().mapType(ValueType.parse(WeakReference.class))
+            ));
+            function.setName(context.names().topLevel("teavm@createWeakReference"));
+            function.setImportName("createWeakRef");
+            function.setImportModule("teavm");
+            context.module().functions.add(function);
+            createWeakReferenceFunction = function;
+        }
+        return createWeakReferenceFunction;
+    }
+
+    private WasmFunction createDerefFunction(WasmGCCustomGeneratorContext context) {
+        var function = new WasmFunction(context.functionTypes().of(
+                context.typeMapper().mapType(ValueType.parse(Object.class)),
+                WasmType.Reference.EXTERN));
+        function.setName(context.names().topLevel("teavm@deref"));
+        function.setImportName("deref");
+        function.setImportModule("teavm");
+        context.module().functions.add(function);
+        return function;
+    }
+}

core/src/main/java/org/teavm/backend/wasm/transformation/gc/BaseClassesTransformation.java

@@ -15,6 +15,7 @@
  */
 package org.teavm.backend.wasm.transformation.gc;
 
+import java.lang.ref.ReferenceQueue;
 import org.teavm.interop.Import;
 import org.teavm.model.AccessLevel;
 import org.teavm.model.AnnotationHolder;
@@ -24,6 +25,7 @@ import org.teavm.model.ClassHolderTransformer;
 import org.teavm.model.ClassHolderTransformerContext;
 import org.teavm.model.ElementModifier;
 import org.teavm.model.FieldReference;
+import org.teavm.model.MethodDescriptor;
 import org.teavm.model.MethodHolder;
 import org.teavm.model.MethodReference;
 import org.teavm.model.Program;
@@ -95,6 +97,19 @@ public class BaseClassesTransformation implements ClassHolderTransformer {
                     }
                 }
             }
+        } else if (cls.getName().equals("java.lang.ref.WeakReference")) {
+            var constructor = cls.getMethod(new MethodDescriptor("<init>", Object.class, ReferenceQueue.class,
+                    void.class));
+            constructor.getModifiers().add(ElementModifier.NATIVE);
+            constructor.setProgram(null);
+
+            var get = cls.getMethod(new MethodDescriptor("get", Object.class));
+            get.getModifiers().add(ElementModifier.NATIVE);
+            get.setProgram(null);
+
+            var clear = cls.getMethod(new MethodDescriptor("clear", void.class));
+            clear.getModifiers().add(ElementModifier.NATIVE);
+            clear.setProgram(null);
         }
     }
 

core/src/main/resources/org/teavm/backend/wasm/wasm-gc-runtime.js

@@ -16,10 +16,15 @@
 
 var TeaVM = TeaVM || {};
 TeaVM.wasm = function() {
+    let exports;
     function defaults(imports) {
         let stderr = "";
         let stdout = "";
-        let exports;
+        let finalizationRegistry = new FinalizationRegistry(heldValue => {
+            if (typeof exports.reportGarbageCollectedValue === "function") {
+                exports.reportGarbageCollectedValue(heldValue)
+            }
+        });
         imports.teavm = {
             putcharStderr(c) {
                 if (c === 10) {
@@ -40,8 +45,18 @@ TeaVM.wasm = function() {
             currentTimeMillis() {
                 return new Date().getTime();
             },
-            dateToString(timestamp, controller) {
+            dateToString(timestamp) {
                 return stringToJava(new Date(timestamp).toString());
+            },
+            createWeakRef(value, heldValue) {
+                let weakRef = new WeakRef(value);
+                if (heldValue !== null) {
+                    finalizationRegistry.register(value, heldValue)
+                }
+                return weakRef;
+            },
+            deref(weakRef) {
+                return weakRef.deref();
             }
         };
         imports.teavmMath = Math;
@@ -83,7 +98,6 @@ TeaVM.wasm = function() {
                 exports = instance.exports;
                 let javaArgs = exports.createStringArray(args.length);
                 for (let i = 0; i < args.length; ++i) {
-                    let arg = args[i];
                     exports.setToStringArray(javaArgs, i, stringToJava(args[i]));
                 }
                 try {

tests/src/test/java/org/teavm/classlib/java/lang/StringTest.java

@@ -322,7 +322,7 @@ public class StringTest {
     private String turkish = "istanbul";
 
     @Test
-    @SkipPlatform({ TestPlatform.C, TestPlatform.WEBASSEMBLY, TestPlatform.WASI })
+    @SkipPlatform({ TestPlatform.C, TestPlatform.WEBASSEMBLY, TestPlatform.WASI, TestPlatform.WEBASSEMBLY_GC })
     public void convertsCaseLocaled() {
         assertEquals(turkish, "İstanbul".toLowerCase(new Locale("tr", "TR")));
         assertEquals(common, "İstanbul".toLowerCase(Locale.US));

tests/src/test/java/org/teavm/classlib/java/util/WeakHashMapTest.java

@@ -51,7 +51,7 @@ import org.teavm.junit.TeaVMTestRunner;
 import org.teavm.junit.TestPlatform;
 
 @RunWith(TeaVMTestRunner.class)
-@SkipPlatform({TestPlatform.WEBASSEMBLY, TestPlatform.WASI})
+@SkipPlatform({TestPlatform.WEBASSEMBLY, TestPlatform.WASI, TestPlatform.WEBASSEMBLY_GC})
 public class WeakHashMapTest {
     static class MockMap<K, V> extends AbstractMap<K, V> {
         @Override