wasm gc: support resources

classlib/src/main/java/org/teavm/classlib/impl/console/Console.java

@@ -16,8 +16,8 @@
 package org.teavm.classlib.impl.console;
 
 import org.teavm.backend.c.intrinsic.RuntimeInclude;
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
 import org.teavm.backend.wasm.runtime.WasmSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.classlib.PlatformDetector;
 import org.teavm.interop.Address;
 import org.teavm.interop.Import;

classlib/src/main/java/org/teavm/classlib/impl/console/JSStderrPrintStream.java

@@ -15,7 +15,7 @@
  */
 package org.teavm.classlib.impl.console;
 
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.classlib.PlatformDetector;
 import org.teavm.jso.JSBody;
 

classlib/src/main/java/org/teavm/classlib/impl/console/JSStdoutPrintStream.java

@@ -15,7 +15,7 @@
  */
 package org.teavm.classlib.impl.console;
 
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.classlib.PlatformDetector;
 import org.teavm.jso.JSBody;
 

classlib/src/main/java/org/teavm/classlib/java/lang/TObject.java

@@ -15,7 +15,7 @@
  */
 package org.teavm.classlib.java.lang;
 
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.classlib.PlatformDetector;
 import org.teavm.dependency.PluggableDependency;
 import org.teavm.interop.Address;

core/src/main/java/org/teavm/backend/wasm/WasmGCModuleGenerator.java

@@ -29,7 +29,7 @@ import org.teavm.backend.wasm.model.expression.WasmGetGlobal;
 import org.teavm.backend.wasm.model.expression.WasmGetLocal;
 import org.teavm.backend.wasm.model.expression.WasmSetGlobal;
 import org.teavm.backend.wasm.runtime.StringInternPool;
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.model.MethodReference;
 import org.teavm.model.ValueType;
 

core/src/main/java/org/teavm/backend/wasm/WasmGCTarget.java

@@ -39,6 +39,7 @@ import org.teavm.backend.wasm.render.WasmBinaryVersion;
 import org.teavm.backend.wasm.render.WasmBinaryWriter;
 import org.teavm.backend.wasm.runtime.StringInternPool;
 import org.teavm.backend.wasm.transformation.gc.BaseClassesTransformation;
+import org.teavm.backend.wasm.transformation.gc.ClassLoaderResourceTransformation;
 import org.teavm.dependency.DependencyAnalyzer;
 import org.teavm.dependency.DependencyListener;
 import org.teavm.interop.Platforms;
@@ -119,7 +120,8 @@ public class WasmGCTarget implements TeaVMTarget, TeaVMWasmGCHost {
     @Override
     public List<ClassHolderTransformer> getTransformers() {
         return List.of(
-                new BaseClassesTransformation()
+                new BaseClassesTransformation(),
+                new ClassLoaderResourceTransformation()
         );
     }
 
@@ -167,7 +169,8 @@ public class WasmGCTarget implements TeaVMTarget, TeaVMWasmGCHost {
     public void emit(ListableClassHolderSource classes, BuildTarget buildTarget, String outputName) throws IOException {
         var module = new WasmModule();
         var customGenerators = new WasmGCCustomGenerators(classes, controller.getServices(),
-                customGeneratorFactories, customCustomGenerators);
+                customGeneratorFactories, customCustomGenerators,
+                controller.getProperties());
         var intrinsics = new WasmGCIntrinsics(classes, controller.getServices(), intrinsicFactories, customIntrinsics);
         var declarationsGenerator = new WasmGCDeclarationsGenerator(
                 module,
@@ -218,6 +221,7 @@ public class WasmGCTarget implements TeaVMTarget, TeaVMWasmGCHost {
         }
 
         moduleGenerator.generate();
+        customGenerators.contributeToModule(module);
         adjustModuleMemory(module);
 
         emitWasmFile(module, buildTarget, outputName);

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

@@ -18,7 +18,7 @@ package org.teavm.backend.wasm.gc;
 import java.util.Arrays;
 import java.util.List;
 import org.teavm.backend.wasm.WasmRuntime;
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.dependency.DependencyAnalyzer;
 import org.teavm.model.MethodReference;
 
@@ -37,6 +37,7 @@ public class WasmGCDependencies {
         contributeInitializerUtils();
         contributeString();
         analyzer.addDependencyListener(new WasmGCReferenceQueueDependency());
+        analyzer.addDependencyListener(new WasmGCResourceDependency());
     }
 
     public void contributeStandardExports() {

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

@@ -0,0 +1,39 @@
+/*
+ *  Copyright 2024 Alexey Andreev.
+ *
+ *  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.backend.wasm.runtime.gc.WasmGCResources;
+import org.teavm.dependency.AbstractDependencyListener;
+import org.teavm.dependency.DependencyAgent;
+import org.teavm.dependency.MethodDependency;
+import org.teavm.model.MethodReference;
+
+public class WasmGCResourceDependency extends AbstractDependencyListener {
+    private static final MethodReference ACQUIRE_METHOD = new MethodReference(WasmGCResources.class,
+            "acquireResources", WasmGCResources.Resource[].class);
+
+    @Override
+    public void methodReached(DependencyAgent agent, MethodDependency method) {
+        if (method.getMethod().getReference().equals(ACQUIRE_METHOD)) {
+            var create = agent.linkMethod(new MethodReference(WasmGCResources.class,
+                    "create", String.class, int.class, int.class, WasmGCResources.Resource.class));
+            create.propagate(1, agent.getType("java.lang.String"));
+            create.use();
+            method.getResult().propagate(agent.getType("[" + WasmGCResources.Resource.class.getName()));
+            method.getResult().getArrayItem().propagate(agent.getType(WasmGCResources.Resource.class.getName()));
+        }
+    }
+}

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

@@ -76,7 +76,7 @@ import org.teavm.backend.wasm.model.expression.WasmStructNew;
 import org.teavm.backend.wasm.model.expression.WasmStructNewDefault;
 import org.teavm.backend.wasm.model.expression.WasmStructSet;
 import org.teavm.backend.wasm.runtime.StringInternPool;
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.dependency.DependencyInfo;
 import org.teavm.model.ClassHierarchy;
 import org.teavm.model.ClassReader;

core/src/main/java/org/teavm/backend/wasm/generate/gc/methods/WasmGCGenerationContext.java

@@ -34,7 +34,7 @@ import org.teavm.backend.wasm.generate.gc.strings.WasmGCStringProvider;
 import org.teavm.backend.wasm.model.WasmFunction;
 import org.teavm.backend.wasm.model.WasmModule;
 import org.teavm.backend.wasm.model.WasmTag;
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.model.ClassHierarchy;
 import org.teavm.model.ClassReaderSource;
 import org.teavm.model.ElementModifier;

core/src/main/java/org/teavm/backend/wasm/generate/gc/methods/WasmGCMethodGenerator.java

@@ -52,6 +52,7 @@ import org.teavm.model.CallLocation;
 import org.teavm.model.ClassHierarchy;
 import org.teavm.model.ElementModifier;
 import org.teavm.model.ListableClassHolderSource;
+import org.teavm.model.ListableClassReaderSource;
 import org.teavm.model.MethodHolder;
 import org.teavm.model.MethodReader;
 import org.teavm.model.MethodReference;
@@ -353,6 +354,16 @@ public class WasmGCMethodGenerator implements BaseWasmFunctionRepository {
     }
 
     private WasmGCCustomGeneratorContext customGeneratorContext = new WasmGCCustomGeneratorContext() {
+        @Override
+        public ClassLoader classLoader() {
+            return classLoader;
+        }
+
+        @Override
+        public ListableClassReaderSource classes() {
+            return classes;
+        }
+
         @Override
         public WasmModule module() {
             return module;
@@ -387,5 +398,15 @@ public class WasmGCMethodGenerator implements BaseWasmFunctionRepository {
         public BaseWasmFunctionRepository functions() {
             return WasmGCMethodGenerator.this;
         }
+
+        @Override
+        public Diagnostics diagnostics() {
+            return diagnostics;
+        }
+
+        @Override
+        public WasmGCStringProvider strings() {
+            return context.strings();
+        }
     };
 }

core/src/main/java/org/teavm/backend/wasm/generate/gc/strings/WasmGCStringPool.java

@@ -36,7 +36,7 @@ import org.teavm.backend.wasm.model.expression.WasmStructNewDefault;
 import org.teavm.backend.wasm.model.expression.WasmStructSet;
 import org.teavm.backend.wasm.render.WasmBinaryWriter;
 import org.teavm.backend.wasm.runtime.StringInternPool;
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.dependency.DependencyInfo;
 import org.teavm.model.MethodReference;
 

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

@@ -25,7 +25,7 @@ import org.teavm.backend.wasm.model.expression.WasmGetLocal;
 import org.teavm.backend.wasm.model.expression.WasmIsNull;
 import org.teavm.backend.wasm.model.expression.WasmStructGet;
 import org.teavm.backend.wasm.model.expression.WasmThrow;
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.model.MethodReference;
 
 public class ClassGenerators implements WasmGCCustomGenerator {

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

@@ -20,10 +20,17 @@ import org.teavm.backend.wasm.WasmFunctionTypes;
 import org.teavm.backend.wasm.generate.gc.WasmGCNameProvider;
 import org.teavm.backend.wasm.generate.gc.classes.WasmGCClassInfoProvider;
 import org.teavm.backend.wasm.generate.gc.classes.WasmGCTypeMapper;
+import org.teavm.backend.wasm.generate.gc.strings.WasmGCStringProvider;
 import org.teavm.backend.wasm.model.WasmModule;
 import org.teavm.backend.wasm.model.WasmTag;
+import org.teavm.diagnostics.Diagnostics;
+import org.teavm.model.ListableClassReaderSource;
 
 public interface WasmGCCustomGeneratorContext {
+    ClassLoader classLoader();
+
+    ListableClassReaderSource classes();
+
     WasmModule module();
 
     WasmFunctionTypes functionTypes();
@@ -37,4 +44,8 @@ public interface WasmGCCustomGeneratorContext {
     BaseWasmFunctionRepository functions();
 
     WasmTag exceptionTag();
+
+    Diagnostics diagnostics();
+
+    WasmGCStringProvider strings();
 }

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

@@ -21,8 +21,11 @@ import java.lang.reflect.Array;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Properties;
 import org.teavm.backend.wasm.generate.gc.methods.WasmGCCustomGeneratorProvider;
-import org.teavm.backend.wasm.runtime.WasmGCSupport;
+import org.teavm.backend.wasm.model.WasmModule;
+import org.teavm.backend.wasm.runtime.gc.WasmGCResources;
+import org.teavm.backend.wasm.runtime.gc.WasmGCSupport;
 import org.teavm.common.ServiceRepository;
 import org.teavm.model.ClassReaderSource;
 import org.teavm.model.MethodReference;
@@ -32,24 +35,32 @@ public class WasmGCCustomGenerators implements WasmGCCustomGeneratorProvider {
     private Map<MethodReference, Container> generators = new HashMap<>();
     private ClassReaderSource classes;
     private ServiceRepository services;
+    private WasmGCResourcesGenerator resourcesGenerator;
 
     public WasmGCCustomGenerators(ClassReaderSource classes, ServiceRepository services,
             List<WasmGCCustomGeneratorFactory> factories,
-            Map<MethodReference, WasmGCCustomGenerator> generators) {
+            Map<MethodReference, WasmGCCustomGenerator> generators,
+            Properties properties) {
         this.factories = List.copyOf(factories);
         this.classes = classes;
         this.services = services;
+        resourcesGenerator = new WasmGCResourcesGenerator(properties);
         fillClass();
         fillStringPool();
         fillSystem();
         fillArray();
         fillWeakReference();
         fillString();
+        fillResources();
         for (var entry : generators.entrySet()) {
             add(entry.getKey(), entry.getValue());
         }
     }
 
+    public void contributeToModule(WasmModule module) {
+        resourcesGenerator.writeModule(module);
+    }
+
     private void fillClass() {
         var classGenerators = new ClassGenerators();
         add(new MethodReference(Class.class, "isAssignableFrom", Class.class, boolean.class), classGenerators);
@@ -85,6 +96,11 @@ public class WasmGCCustomGenerators implements WasmGCCustomGeneratorProvider {
         add(new MethodReference(String.class, "intern", String.class), generator);
     }
 
+    private void fillResources() {
+        add(new MethodReference(WasmGCResources.class, "acquireResources", WasmGCResources.Resource[].class),
+                resourcesGenerator);
+    }
+
     @Override
     public WasmGCCustomGenerator get(MethodReference method) {
         var result = generators.get(method);

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

@@ -0,0 +1,174 @@
+/*
+ *  Copyright 2024 Alexey Andreev.
+ *
+ *  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.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedHashSet;
+import java.util.Properties;
+import java.util.ServiceLoader;
+import org.teavm.backend.wasm.generate.TemporaryVariablePool;
+import org.teavm.backend.wasm.generate.gc.methods.WasmGCGenerationUtil;
+import org.teavm.backend.wasm.model.WasmFunction;
+import org.teavm.backend.wasm.model.WasmGlobal;
+import org.teavm.backend.wasm.model.WasmLocal;
+import org.teavm.backend.wasm.model.WasmMemorySegment;
+import org.teavm.backend.wasm.model.WasmModule;
+import org.teavm.backend.wasm.model.WasmType;
+import org.teavm.backend.wasm.model.expression.WasmCall;
+import org.teavm.backend.wasm.model.expression.WasmExpression;
+import org.teavm.backend.wasm.model.expression.WasmGetGlobal;
+import org.teavm.backend.wasm.model.expression.WasmGetLocal;
+import org.teavm.backend.wasm.model.expression.WasmInt32Constant;
+import org.teavm.backend.wasm.model.expression.WasmIntBinary;
+import org.teavm.backend.wasm.model.expression.WasmIntBinaryOperation;
+import org.teavm.backend.wasm.model.expression.WasmIntType;
+import org.teavm.backend.wasm.runtime.gc.WasmGCResources;
+import org.teavm.classlib.ResourceSupplier;
+import org.teavm.classlib.ResourceSupplierContext;
+import org.teavm.model.CallLocation;
+import org.teavm.model.ListableClassReaderSource;
+import org.teavm.model.MethodReference;
+import org.teavm.model.ValueType;
+
+public class WasmGCResourcesGenerator implements WasmGCCustomGenerator {
+    private Properties properties;
+    private ByteArrayOutputStream resources = new ByteArrayOutputStream();
+    private WasmGlobal baseGlobal;
+
+    public WasmGCResourcesGenerator(Properties properties) {
+        this.properties = properties;
+    }
+
+    public void writeModule(WasmModule module) {
+        if (resources.size() == 0) {
+            return;
+        }
+
+        var segment = new WasmMemorySegment();
+        if (!module.getSegments().isEmpty()) {
+            var lastSegment = module.getSegments().get(module.getSegments().size() - 1);
+            segment.setOffset(lastSegment.getOffset() + lastSegment.getLength());
+        }
+        segment.setData(resources.toByteArray());
+        module.getSegments().add(segment);
+        baseGlobal.setInitialValue(new WasmInt32Constant(segment.getOffset()));
+    }
+
+    @Override
+    public void apply(MethodReference method, WasmFunction function, WasmGCCustomGeneratorContext context) {
+        var supplierContext = new SupplierContextImpl(context.classLoader(), context.classes(), properties);
+        var resourceSet = new LinkedHashSet<String>();
+        for (var supplier : ServiceLoader.load(ResourceSupplier.class, context.classLoader())) {
+            var resources = supplier.supplyResources(supplierContext);
+            if (resources != null) {
+                resourceSet.addAll(Arrays.asList(resources));
+            }
+        }
+
+        var descriptors = new ArrayList<ResourceDescriptor>();
+        var location = new CallLocation(new MethodReference(ClassLoader.class,
+                "getResourceAsStream", String.class, InputStream.class));
+        for (var resource : resourceSet) {
+            try (var input = context.classLoader().getResourceAsStream(resource)) {
+                if (input == null) {
+                    context.diagnostics().error(location, "Resource not found: " + resource);
+                } else {
+                    var start = resources.size();
+                    input.transferTo(resources);
+                    var end = resources.size();
+                    descriptors.add(new ResourceDescriptor(resource, start, end));
+                }
+            } catch (IOException e) {
+                context.diagnostics().error(location, "Error occurred reading resource '" + resource + "'");
+            }
+        }
+
+        if (!descriptors.isEmpty()) {
+            baseGlobal = new WasmGlobal(context.names().topLevel("teavm@resourcesBaseAddress"),
+                    WasmType.INT32, new WasmInt32Constant(0));
+            context.module().globals.add(baseGlobal);
+
+            var genUtil = new WasmGCGenerationUtil(context.classInfoProvider(), new TemporaryVariablePool(function));
+            var local = new WasmLocal(context.typeMapper().mapType(ValueType.parse(WasmGCResources.Resource[].class)));
+            function.add(local);
+            var constructor = context.functions().forStaticMethod(new MethodReference(WasmGCResources.class,
+                    "create", String.class, int.class, int.class, WasmGCResources.Resource.class));
+
+            genUtil.allocateArrayWithElements(
+                    ValueType.parse(WasmGCResources.Resource.class),
+                    () -> {
+                        var items = new ArrayList<WasmExpression>();
+                        for (var descriptor : descriptors) {
+                            var name = context.strings().getStringConstant(descriptor.name);
+                            var offset = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.ADD,
+                                    new WasmGetGlobal(baseGlobal), new WasmInt32Constant(descriptor.address));
+                            var end = new WasmInt32Constant(descriptor.end - descriptor.address);
+                            items.add(new WasmCall(constructor, new WasmGetGlobal(name.global), offset, end));
+                        }
+                        return items;
+                    },
+                    null,
+                    local,
+                    function.getBody()
+            );
+            function.getBody().add(new WasmGetLocal(local));
+        }
+    }
+
+    private static class ResourceDescriptor {
+        String name;
+        int address;
+        int end;
+
+        ResourceDescriptor(String name, int address, int end) {
+            this.name = name;
+            this.address = address;
+            this.end = end;
+        }
+    }
+
+    static class SupplierContextImpl implements ResourceSupplierContext {
+        private ClassLoader classLoader;
+        private ListableClassReaderSource classSource;
+        private Properties properties;
+
+        SupplierContextImpl(ClassLoader classLoader, ListableClassReaderSource classSource,
+                Properties properties) {
+            this.classLoader = classLoader;
+            this.classSource = classSource;
+            this.properties = properties;
+        }
+
+        @Override
+        public ClassLoader getClassLoader() {
+            return classLoader;
+        }
+
+        @Override
+        public ListableClassReaderSource getClassSource() {
+            return classSource;
+        }
+
+        @Override
+        public Properties getProperties() {
+            return properties;
+        }
+    }
+}

core/src/main/java/org/teavm/backend/wasm/intrinsics/gc/WasmGCIntrinsics.java

@@ -23,6 +23,7 @@ import org.teavm.backend.wasm.WasmRuntime;
 import org.teavm.backend.wasm.generate.gc.methods.WasmGCIntrinsicProvider;
 import org.teavm.backend.wasm.model.expression.WasmIntType;
 import org.teavm.backend.wasm.runtime.StringInternPool;
+import org.teavm.backend.wasm.runtime.gc.WasmGCResources;
 import org.teavm.common.ServiceRepository;
 import org.teavm.model.ClassReaderSource;
 import org.teavm.model.MethodReference;
@@ -49,6 +50,7 @@ public class WasmGCIntrinsics implements WasmGCIntrinsicProvider {
         fillDouble();
         fillArray();
         fillString();
+        fillResources();
         for (var entry : customIntrinsics.entrySet()) {
             add(entry.getKey(), entry.getValue());
         }
@@ -156,6 +158,11 @@ public class WasmGCIntrinsics implements WasmGCIntrinsicProvider {
         add(new MethodReference(className, "setValue", ValueType.parse(String.class), ValueType.VOID), intrinsic);
     }
 
+    private void fillResources() {
+        var intrinsic = new WasmGCResourcesIntrinsic();
+        add(new MethodReference(WasmGCResources.class, "readSingleByte", int.class, int.class), intrinsic);
+    }
+
     private void add(MethodReference methodRef, WasmGCIntrinsic intrinsic) {
         intrinsics.put(methodRef, new IntrinsicContainer(intrinsic));
     }

core/src/main/java/org/teavm/backend/wasm/intrinsics/gc/WasmGCResourcesIntrinsic.java

@@ -0,0 +1,28 @@
+/*
+ *  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.intrinsics.gc;
+
+import org.teavm.ast.InvocationExpr;
+import org.teavm.backend.wasm.model.expression.WasmExpression;
+import org.teavm.backend.wasm.model.expression.WasmInt32Subtype;
+import org.teavm.backend.wasm.model.expression.WasmLoadInt32;
+
+public class WasmGCResourcesIntrinsic implements WasmGCIntrinsic {
+    @Override
+    public WasmExpression apply(InvocationExpr invocation, WasmGCIntrinsicContext context) {
+        return new WasmLoadInt32(1, context.generate(invocation.getArguments().get(0)), WasmInt32Subtype.UINT8);
+    }
+}

core/src/main/java/org/teavm/backend/wasm/runtime/gc/WasmGCResources.java

@@ -0,0 +1,94 @@
+/*
+ *  Copyright 2024 Alexey Andreev.
+ *
+ *  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.runtime.gc;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.HashMap;
+import java.util.Map;
+
+public final class WasmGCResources {
+    private static Map<String, Resource> resources = new HashMap<>();
+
+    private WasmGCResources() {
+    }
+
+    static {
+        for (var resource : acquireResources()) {
+            resources.put(resource.name, resource);
+        }
+    }
+
+    private static native Resource[] acquireResources();
+
+    private static Resource create(String name, int start, int length) {
+        return new Resource(name, start, start + length);
+    }
+
+    public static InputStream getResource(String name) {
+        var resource = resources.get(name);
+        if (resource == null) {
+            return null;
+        }
+        return new ResourceInputStream(resource.start, resource.end);
+    }
+
+    public static class Resource {
+        public final String name;
+        public final int start;
+        public final int end;
+
+        public Resource(String name, int start, int end) {
+            this.name = name;
+            this.start = start;
+            this.end = end;
+        }
+    }
+
+    public static final class ResourceInputStream extends InputStream {
+        private int address;
+        private int end;
+
+        private ResourceInputStream(int address, int end) {
+            this.address = address;
+            this.end = end;
+        }
+
+        @Override
+        public int read() throws IOException {
+            return address < end ? readSingleByte(address++) : -1;
+        }
+
+        @Override
+        public int read(byte[] b, int off, int len) throws IOException {
+            if (address >= end) {
+                return -1;
+            }
+            var bytesToRead = Math.min(len, end - address);
+            readBytes(b, off, bytesToRead, address);
+            address += bytesToRead;
+            return bytesToRead;
+        }
+    }
+
+    private static void readBytes(byte[] bytes, int off, int len, int fromAddress) {
+        for (int i = 0; i < len; ++i) {
+            bytes[i] = (byte) readSingleByte(fromAddress++);
+        }
+    }
+
+    private static native int readSingleByte(int address);
+}

core/src/main/java/org/teavm/backend/wasm/runtime/gc/WasmGCSupport.java

@@ -13,7 +13,7 @@
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  */
-package org.teavm.backend.wasm.runtime;
+package org.teavm.backend.wasm.runtime.gc;
 
 import org.teavm.interop.Import;
 

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

@@ -0,0 +1,60 @@
+/*
+ *  Copyright 2024 Alexey Andreev.
+ *
+ *  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.transformation.gc;
+
+import java.io.InputStream;
+import org.teavm.backend.wasm.runtime.gc.WasmGCResources;
+import org.teavm.model.ClassHolder;
+import org.teavm.model.ClassHolderTransformer;
+import org.teavm.model.ClassHolderTransformerContext;
+import org.teavm.model.MethodDescriptor;
+import org.teavm.model.MethodHolder;
+import org.teavm.model.MethodReference;
+import org.teavm.model.Program;
+import org.teavm.model.instructions.ExitInstruction;
+import org.teavm.model.instructions.InvocationType;
+import org.teavm.model.instructions.InvokeInstruction;
+
+public class ClassLoaderResourceTransformation implements ClassHolderTransformer {
+    @Override
+    public void transformClass(ClassHolder cls, ClassHolderTransformerContext context) {
+        if (cls.getName().equals(ClassLoader.class.getName())) {
+            var method = cls.getMethod(new MethodDescriptor("getResourceAsStream", String.class, InputStream.class));
+            transformGetResourceAsStream(method);
+        }
+    }
+
+    private void transformGetResourceAsStream(MethodHolder method) {
+        var program = new Program();
+        program.createVariable();
+        var nameVar = program.createVariable();
+        var block = program.createBasicBlock();
+
+        var invoke = new InvokeInstruction();
+        invoke.setType(InvocationType.SPECIAL);
+        invoke.setMethod(new MethodReference(WasmGCResources.class, "getResource", String.class,
+                InputStream.class));
+        invoke.setArguments(nameVar);
+        invoke.setReceiver(program.createVariable());
+        block.add(invoke);
+
+        var exit = new ExitInstruction();
+        exit.setValueToReturn(invoke.getReceiver());
+        block.add(exit);
+
+        method.setProgram(program);
+    }
+}

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

@@ -19,8 +19,8 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
 import java.io.BufferedReader;
 import java.io.IOException;
-import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.teavm.junit.EachTestCompiledSeparately;
@@ -48,14 +48,14 @@ public class ClassLoaderTest {
     @Test
     @SkipPlatform({TestPlatform.C, TestPlatform.WEBASSEMBLY, TestPlatform.WASI})
     public void returnsNullForNonExistentResource() {
-        InputStream input = ClassLoader.getSystemClassLoader().getResourceAsStream("non-existent-resource.txt");
+        var input = ClassLoader.getSystemClassLoader().getResourceAsStream("non-existent-resource.txt");
         assertNull(input);
     }
 
     private static String loadResource(String name) {
-        ClassLoader classLoader = ClassLoader.getSystemClassLoader();
+        var classLoader = ClassLoader.getSystemClassLoader();
-        try (BufferedReader reader = new BufferedReader(new InputStreamReader(classLoader.getResourceAsStream(
+        try (var reader = new BufferedReader(new InputStreamReader(classLoader.getResourceAsStream(
-                "resources-for-test/" + name), "UTF-8"))) {
+                "resources-for-test/" + name), StandardCharsets.UTF_8))) {
             return reader.readLine();
         } catch (IOException e) {
             return "";