Wasm: add parser for own debug information

core/src/main/java/org/teavm/backend/wasm/debug/DebugClassesBuilder.java

@@ -24,6 +24,7 @@ public class DebugClassesBuilder extends DebugSectionBuilder implements DebugCla
     private ObjectIntMap<String> classes = new ObjectIntHashMap<>();
 
     public DebugClassesBuilder(DebugPackages packages, DebugStrings strings) {
+        super(DebugConstants.SECTION_CLASSES);
         this.packages = packages;
         this.strings = strings;
     }

core/src/main/java/org/teavm/backend/wasm/debug/DebugConstants.java

@@ -25,4 +25,11 @@ public final class DebugConstants {
     public static final int LOC_FILE = 3;
     public static final int LOC_PTR = 4;
     public static final int LOC_USER = 10;
+
+    public static final String SECTION_STRINGS = "teavm_str";
+    public static final String SECTION_FILES = "teavm_file";
+    public static final String SECTION_PACKAGES = "teavm_pkg";
+    public static final String SECTION_CLASSES = "teavm_cls";
+    public static final String SECTION_METHODS = "teavm_mtd";
+    public static final String SECTION_LINES = "teavm_line";
 }

core/src/main/java/org/teavm/backend/wasm/debug/DebugFilesBuilder.java

@@ -24,6 +24,7 @@ public class DebugFilesBuilder extends DebugSectionBuilder implements DebugFiles
     private ObjectIntMap<FileData> fileMap = new ObjectIntHashMap<>();
 
     public DebugFilesBuilder(DebugStrings strings) {
+        super(DebugConstants.SECTION_FILES);
         this.strings = strings;
     }
 

core/src/main/java/org/teavm/backend/wasm/debug/DebugInfoBuilder.java

@@ -62,19 +62,19 @@ public class DebugInfoBuilder {
 
     public List<WasmCustomSection> build() {
         var result = new ArrayList<WasmCustomSection>();
-        addSection(result, "teavm_str", strings);
-        addSection(result, "teavm_file", files);
-        addSection(result, "teavm_pkg", packages);
-        addSection(result, "teavm_classes", classes);
-        addSection(result, "teavm_methods", methods);
-        addSection(result, "teavm_line", lines);
+        addSection(result, strings);
+        addSection(result, files);
+        addSection(result, packages);
+        addSection(result, classes);
+        addSection(result, methods);
+        addSection(result, lines);
         return result;
     }
 
-    private void addSection(List<WasmCustomSection> sections, String name, DebugSectionBuilder builder) {
+    private void addSection(List<WasmCustomSection> sections, DebugSectionBuilder builder) {
         if (builder.isEmpty()) {
             return;
         }
-        sections.add(new WasmCustomSection(name, builder.build()));
+        sections.add(new WasmCustomSection(builder.name(), builder.build()));
     }
 }

core/src/main/java/org/teavm/backend/wasm/debug/DebugLinesBuilder.java

@@ -30,6 +30,7 @@ public class DebugLinesBuilder extends DebugSectionBuilder implements DebugLines
     private Deque<State> states = new ArrayDeque<>();
 
     public DebugLinesBuilder(DebugFiles files, DebugMethods methods) {
+        super(DebugConstants.SECTION_LINES);
         this.files = files;
         this.methods = methods;
     }
@@ -45,8 +46,8 @@ public class DebugLinesBuilder extends DebugSectionBuilder implements DebugLines
     @Override
     public void location(String file, int line) {
         if (Objects.equals(file, this.file) && this.ptr != lastWrittenPtr && this.line != line) {
-            if (this.ptr - lastWrittenPtr < 32 && Math.abs(this.line - line) <= 3) {
-                blob.writeByte(DebugConstants.LOC_USER + 32 * (this.ptr - lastWrittenPtr) + (line - this.line) + 3);
+            if (this.ptr - lastWrittenPtr < 32 && Math.abs(line - this.line) <= 3) {
+                blob.writeByte(DebugConstants.LOC_USER + (this.ptr - lastWrittenPtr) + 32 * (line - this.line + 3));
                 this.line = line;
                 lastWrittenPtr = ptr;
                 return;

core/src/main/java/org/teavm/backend/wasm/debug/DebugMethodsBuilder.java

@@ -25,6 +25,7 @@ public class DebugMethodsBuilder extends  DebugSectionBuilder implements DebugMe
     private ObjectIntMap<MethodReference> methods = new ObjectIntHashMap<>();
 
     public DebugMethodsBuilder(DebugClasses classes, DebugStrings strings) {
+        super(DebugConstants.SECTION_METHODS);
         this.classes = classes;
         this.strings = strings;
     }

core/src/main/java/org/teavm/backend/wasm/debug/DebugPackagesBuilder.java

@@ -24,6 +24,7 @@ public class DebugPackagesBuilder extends DebugSectionBuilder implements DebugPa
     private ObjectIntMap<PackageInfo> packages = new ObjectIntHashMap<>();
 
     public DebugPackagesBuilder(DebugStrings strings) {
+        super(DebugConstants.SECTION_PACKAGES);
         this.strings = strings;
     }
 

core/src/main/java/org/teavm/backend/wasm/debug/DebugSectionBuilder.java

@@ -19,12 +19,21 @@ import org.teavm.backend.wasm.blob.BinaryDataConsumer;
 import org.teavm.backend.wasm.blob.Blob;
 
 public class DebugSectionBuilder {
+    private String name;
     protected Blob blob = new Blob();
 
+    protected DebugSectionBuilder(String name) {
+        this.name = name;
+    }
+
     public void read(BinaryDataConsumer consumer) {
         blob.newReader(consumer).readRemaining();
     }
 
+    public String name() {
+        return name;
+    }
+
     public byte[] build() {
         return blob.toArray();
     }

core/src/main/java/org/teavm/backend/wasm/debug/DebugStringsBuilder.java

@@ -22,6 +22,10 @@ import java.nio.charset.StandardCharsets;
 public class DebugStringsBuilder extends DebugSectionBuilder implements DebugStrings {
     private ObjectIntMap<String> strings = new ObjectIntHashMap<>();
 
+    public DebugStringsBuilder() {
+        super(DebugConstants.SECTION_STRINGS);
+    }
+
     @Override
     public int stringPtr(String str) {
         var result = strings.getOrDefault(str, -1);

core/src/main/java/org/teavm/backend/wasm/debug/info/ClassInfo.java

@@ -0,0 +1,27 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public abstract class ClassInfo {
+    public abstract PackageInfo pkg();
+
+    public abstract String name();
+
+    public String fullName() {
+        var pkg = pkg();
+        return pkg != null ? pkg.fullName() + "." + name() : name();
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/FileInfo.java

@@ -0,0 +1,27 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public abstract class FileInfo {
+    public abstract FileInfo parent();
+
+    public abstract String name();
+
+    public String fullName() {
+        var parent = this.parent();
+        return parent != null ? parent.fullName() + "/" + name() : name();
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/InliningLocation.java

@@ -0,0 +1,34 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public class InliningLocation {
+    private Location location;
+    private MethodInfo method;
+
+    public InliningLocation(Location location, MethodInfo method) {
+        this.location = location;
+        this.method = method;
+    }
+
+    public Location location() {
+        return location;
+    }
+
+    public MethodInfo method() {
+        return method;
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/InstructionLocation.java

@@ -0,0 +1,34 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public class InstructionLocation {
+    private int address;
+    private Location location;
+
+    public InstructionLocation(int address, Location location) {
+        this.address = address;
+        this.location = location;
+    }
+
+    public int address() {
+        return address;
+    }
+
+    public Location location() {
+        return location;
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfo.java

@@ -0,0 +1,60 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+import java.io.PrintStream;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import org.teavm.common.CollectionUtil;
+
+public class LineInfo {
+    private LineInfoSequence[] sequences;
+    private List<? extends LineInfoSequence> sequenceList;
+
+    public LineInfo(LineInfoSequence[] sequences) {
+        this.sequences = sequences.clone();
+        sequenceList = Collections.unmodifiableList(Arrays.asList(this.sequences));
+    }
+
+    public List<? extends LineInfoSequence> sequences() {
+        return sequenceList;
+    }
+
+    public LineInfoSequence find(int address) {
+        var index = CollectionUtil.binarySearch(sequenceList, address, LineInfoSequence::endAddress);
+        if (index < 0) {
+            index = -index - 1;
+        }
+        if (index >= sequenceList.size()) {
+            return null;
+        }
+        var sequence = sequenceList.get(index);
+        return address >= sequence.startAddress() ? sequence : null;
+    }
+
+    public void dump(PrintStream out) {
+        for (var i = 0; i < sequences.length; ++i) {
+            var sequence = sequences[i];
+            out.println("Sequence " + i + ": " + sequence.method().fullName() + " [" + sequence.startAddress() + ".."
+                    + sequence.endAddress() + ")");
+            for (var location : sequence.unpack().locations()) {
+                out.println("  at " + location.address() + " " + location.location().file().fullName() + ":"
+                        + location.location().line());
+            }
+        }
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfoCommand.java

@@ -0,0 +1,30 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public abstract class LineInfoCommand {
+    private int address;
+
+    public LineInfoCommand(int address) {
+        this.address = address;
+    }
+
+    public int address() {
+        return address;
+    }
+
+    public abstract void acceptVisitor(LineInfoCommandVisitor visitor);
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfoCommandExecutor.java

@@ -0,0 +1,54 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public class LineInfoCommandExecutor implements LineInfoCommandVisitor {
+    private FileInfo file;
+    private int line = 1;
+    private int address;
+    private InliningLocation inliningLocation;
+
+    public InstructionLocation createLocation() {
+        return file != null ? new InstructionLocation(address, new Location(file, line, inliningLocation)) : null;
+    }
+
+    @Override
+    public void visit(LineInfoEnterCommand command) {
+        address = command.address();
+        inliningLocation = new InliningLocation(new Location(file, line, inliningLocation), command.method());
+        file = null;
+        line = 1;
+    }
+
+    @Override
+    public void visit(LineInfoExitCommand command) {
+        address = command.address();
+        inliningLocation = inliningLocation.location().inlining();
+    }
+
+    @Override
+    public void visit(LineInfoFileCommand command) {
+        address = command.address();
+        file = command.file();
+        line = command.line();
+    }
+
+    @Override
+    public void visit(LineInfoLineCommand command) {
+        address = command.address();
+        line = command.line();
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfoCommandVisitor.java

@@ -0,0 +1,26 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public interface LineInfoCommandVisitor {
+    void visit(LineInfoEnterCommand command);
+
+    void visit(LineInfoExitCommand command);
+
+    void visit(LineInfoFileCommand command);
+
+    void visit(LineInfoLineCommand command);
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfoEnterCommand.java

@@ -0,0 +1,34 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public class LineInfoEnterCommand extends LineInfoCommand {
+    private MethodInfo method;
+
+    public LineInfoEnterCommand(int address, MethodInfo method) {
+        super(address);
+        this.method = method;
+    }
+
+    public MethodInfo method() {
+        return method;
+    }
+
+    @Override
+    public void acceptVisitor(LineInfoCommandVisitor visitor) {
+        visitor.visit(this);
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfoExitCommand.java

@@ -0,0 +1,27 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public class LineInfoExitCommand extends LineInfoCommand {
+    public LineInfoExitCommand(int address) {
+        super(address);
+    }
+
+    @Override
+    public void acceptVisitor(LineInfoCommandVisitor visitor) {
+        visitor.visit(this);
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfoFileCommand.java

@@ -0,0 +1,40 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public class LineInfoFileCommand extends LineInfoCommand {
+    private FileInfo file;
+    private int line;
+
+    public LineInfoFileCommand(int address, FileInfo file, int line) {
+        super(address);
+        this.file = file;
+        this.line = line;
+    }
+
+    public FileInfo file() {
+        return file;
+    }
+
+    public int line() {
+        return line;
+    }
+
+    @Override
+    public void acceptVisitor(LineInfoCommandVisitor visitor) {
+        visitor.visit(this);
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfoLineCommand.java

@@ -0,0 +1,34 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public class LineInfoLineCommand extends LineInfoCommand {
+    private int line;
+
+    public LineInfoLineCommand(int address, int line) {
+        super(address);
+        this.line = line;
+    }
+
+    public int line() {
+        return line;
+    }
+
+    @Override
+    public void acceptVisitor(LineInfoCommandVisitor visitor) {
+        visitor.visit(this);
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfoSequence.java

@@ -0,0 +1,63 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+public class LineInfoSequence {
+    private int startAddress;
+    private int endAddress;
+    private MethodInfo method;
+    private LineInfoCommand[] commands;
+    private List<LineInfoCommand> commandList;
+
+    public LineInfoSequence(int startAddress, int endAddress, MethodInfo method, LineInfoCommand[] commands) {
+        this.startAddress = startAddress;
+        this.endAddress = endAddress;
+        this.method = method;
+        this.commands = commands.clone();
+        commandList = Collections.unmodifiableList(Arrays.asList(this.commands));
+    }
+
+    public int startAddress() {
+        return startAddress;
+    }
+
+    public int endAddress() {
+        return endAddress;
+    }
+
+    public MethodInfo method() {
+        return method;
+    }
+
+    public List<? extends LineInfoCommand> commands() {
+        return commandList;
+    }
+
+    public LineInfoUnpackedSequence unpack() {
+        var commandExecutor = new LineInfoCommandExecutor();
+        var locations = new ArrayList<InstructionLocation>();
+        for (var command : commands) {
+            command.acceptVisitor(commandExecutor);
+            locations.add(commandExecutor.createLocation());
+        }
+        return new LineInfoUnpackedSequence(startAddress, endAddress, method, locations);
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/LineInfoUnpackedSequence.java

@@ -0,0 +1,61 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+import java.util.List;
+import org.teavm.common.CollectionUtil;
+
+public class LineInfoUnpackedSequence {
+    private int startAddress;
+    private int endAddress;
+    private MethodInfo method;
+    private List<? extends InstructionLocation> locations;
+
+    LineInfoUnpackedSequence(int startAddress, int endAddress, MethodInfo method,
+            List<? extends InstructionLocation> locations) {
+        this.startAddress = startAddress;
+        this.endAddress = endAddress;
+        this.method = method;
+        this.locations = locations;
+    }
+
+    public int startAddress() {
+        return startAddress;
+    }
+
+    public int endAddress() {
+        return endAddress;
+    }
+
+    public MethodInfo method() {
+        return method;
+    }
+
+    public List<? extends InstructionLocation> locations() {
+        return locations;
+    }
+
+    public InstructionLocation find(int address) {
+        if (address < startAddress || address >= endAddress) {
+            return null;
+        }
+        var index = CollectionUtil.binarySearch(locations, address, InstructionLocation::address);
+        if (index < 0) {
+            index = -index;
+        }
+        return locations.get(Math.min(locations.size() - 1, index));
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/Location.java

@@ -0,0 +1,40 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public class Location {
+    private FileInfo file;
+    private int line;
+    private InliningLocation inlining;
+
+    public Location(FileInfo file, int line, InliningLocation inlining) {
+        this.file = file;
+        this.line = line;
+        this.inlining = inlining;
+    }
+
+    public FileInfo file() {
+        return file;
+    }
+
+    public int line() {
+        return line;
+    }
+
+    public InliningLocation inlining() {
+        return inlining;
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/MethodInfo.java

@@ -0,0 +1,26 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public abstract class MethodInfo {
+    public abstract ClassInfo cls();
+
+    public abstract String name();
+
+    public String fullName() {
+        return cls().fullName() + "." + name();
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/info/PackageInfo.java

@@ -0,0 +1,27 @@
+/*
+ *  Copyright 2022 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.debug.info;
+
+public abstract class PackageInfo {
+    public abstract PackageInfo parent();
+
+    public abstract String name();
+
+    public final String fullName() {
+        var parent = this.parent();
+        return parent != null ? parent.fullName() + "." + name() : name();
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/BlobReader.java

@@ -0,0 +1,26 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+class BlobReader {
+    private byte[] data;
+
+    public BlobReader(byte[] data) {
+        this.data = data;
+    }
+
+
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/DebugClassParser.java

@@ -0,0 +1,68 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+import java.util.ArrayList;
+import org.teavm.backend.wasm.debug.DebugConstants;
+import org.teavm.backend.wasm.debug.info.ClassInfo;
+import org.teavm.backend.wasm.debug.info.PackageInfo;
+
+public class DebugClassParser extends DebugSectionParser {
+    private DebugStringParser strings;
+    private DebugPackageParser packages;
+    private ClassInfoImpl[] classes;
+
+    public DebugClassParser(DebugStringParser strings, DebugPackageParser packages) {
+        super(DebugConstants.SECTION_CLASSES, strings, packages);
+        this.strings = strings;
+        this.packages = packages;
+    }
+
+    public ClassInfo getClass(int ptr) {
+        return classes[ptr];
+    }
+
+    @Override
+    protected void doParse() {
+        var classes = new ArrayList<ClassInfoImpl>();
+        while (ptr < data.length) {
+            var pkg = packages.getPackage(readLEB());
+            var name = strings.getString(readLEB());
+            classes.add(new ClassInfoImpl(pkg, name));
+        }
+        this.classes = classes.toArray(new ClassInfoImpl[0]);
+    }
+
+    private static class ClassInfoImpl extends ClassInfo {
+        private PackageInfo pkg;
+        private String name;
+
+        ClassInfoImpl(PackageInfo pkg, String name) {
+            this.pkg = pkg;
+            this.name = name;
+        }
+
+        @Override
+        public PackageInfo pkg() {
+            return pkg;
+        }
+
+        @Override
+        public String name() {
+            return name;
+        }
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/DebugFileParser.java

@@ -0,0 +1,83 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+import java.util.ArrayList;
+import org.teavm.backend.wasm.debug.DebugConstants;
+import org.teavm.backend.wasm.debug.info.FileInfo;
+
+public class DebugFileParser extends DebugSectionParser {
+    private DebugStringParser strings;
+    private FileInfoImpl[] files;
+
+    public DebugFileParser(DebugStringParser strings) {
+        super(DebugConstants.SECTION_FILES, strings);
+        this.strings = strings;
+    }
+
+    public FileInfo getFile(int index) {
+        return index > 0 ? files[index - 1] : null;
+    }
+
+    @Override
+    protected void doParse() {
+        var builders = new ArrayList<FileBuilder>();
+        while (ptr < data.length) {
+            var parent = readLEB();
+            var nameIndex = readLEB();
+            var name = (nameIndex & 1) == 0
+                    ? strings.getString(nameIndex >>> 1)
+                    : strings.getString(nameIndex >>> 1) + "." + strings.getString(readLEB());
+            builders.add(new FileBuilder(parent, name));
+        }
+        this.files = new FileInfoImpl[builders.size()];
+        for (var i = 0; i < files.length; ++i) {
+            files[i] = new FileInfoImpl(builders.get(i).name);
+        }
+        for (var i = 0; i < files.length; ++i) {
+            files[i].parent = getFile(builders.get(i).parent);
+        }
+    }
+
+    private static class FileInfoImpl extends FileInfo {
+        private FileInfo parent;
+        private final String name;
+
+        private FileInfoImpl(String name) {
+            this.name = name;
+        }
+
+        @Override
+        public FileInfo parent() {
+            return parent;
+        }
+
+        @Override
+        public String name() {
+            return name;
+        }
+    }
+
+    private static class FileBuilder {
+        int parent;
+        String name;
+
+        FileBuilder(int parent, String name) {
+            this.parent = parent;
+            this.name = name;
+        }
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/DebugInfoParser.java

@@ -0,0 +1,282 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.teavm.backend.wasm.debug.info.LineInfo;
+import org.teavm.common.Promise;
+
+public class DebugInfoParser {
+    private static final int WASM_HEADER_SIZE = 8;
+    private DebugInfoReader reader;
+    private int pos;
+    private int posBefore;
+    private byte[] buffer = new byte[256];
+    private int posInBuffer;
+    private int bufferLimit;
+    private int currentLEB;
+    private int currentLEBShift;
+    private boolean eof;
+    private int bytesInLEB;
+    private int sectionCode;
+    private List<byte[]> chunks = new ArrayList<>();
+    private Map<String, DebugSectionParser> sectionParsers = new HashMap<>();
+    private DebugLinesParser lines;
+
+    public DebugInfoParser(DebugInfoReader reader) {
+        this.reader = reader;
+
+        var strings = addSection(new DebugStringParser());
+        var files = addSection(new DebugFileParser(strings));
+        var packages = addSection(new DebugPackageParser(strings));
+        var classes = addSection(new DebugClassParser(strings, packages));
+        var methods = addSection(new DebugMethodParser(strings, classes));
+        lines = addSection(new DebugLinesParser(files, methods));
+    }
+
+    private <T extends DebugSectionParser> T addSection(T section) {
+        sectionParsers.put(section.name(), section);
+        return section;
+    }
+
+    public LineInfo getLineInfo() {
+        return lines.getLineInfo();
+    }
+
+    public Promise<Void> parse() {
+        return parseHeader().thenAsync(v -> parseSections());
+    }
+
+    private Promise<Void> parseHeader() {
+        return fillAtLeast(16).thenVoid(v -> {
+            if (remaining() < WASM_HEADER_SIZE) {
+                error("Invalid WebAssembly header");
+            }
+            if (readInt32() != 0x6d736100) {
+                error("Invalid WebAssembly magic number");
+            }
+            if (readInt32() != 1) {
+                error("Unsupported WebAssembly version");
+            }
+        });
+    }
+
+    private Promise<Void> parseSections() {
+        return readLEB().thenAsync(n -> {
+            if (n == null) {
+                return Promise.VOID;
+            }
+            sectionCode = n;
+            return continueParsingSection().thenAsync(v -> parseSections());
+        });
+    }
+
+    private Promise<Void> continueParsingSection() {
+        return requireLEB("Unexpected end of file reading section length").thenAsync(sectionSize -> {
+            if (sectionCode == 0) {
+                return parseSection(pos + sectionSize);
+            } else {
+                return skip(sectionSize, "Error skipping section " + sectionCode + " of size " + sectionSize);
+            }
+        });
+    }
+
+    private Promise<Void> parseSection(int limit) {
+        return readString("Error reading custom section name").thenAsync(name -> {
+            var sectionParser = sectionParsers.get(name);
+            System.out.println("Section '" + name + "': " + (sectionParser != null ? "parsed" : "unknown"));
+            if (sectionParser != null) {
+                return readBytes(limit - pos, "Error reading section '" + name + "' content")
+                        .thenVoid(sectionParser::parse);
+            } else {
+                return skip(limit - pos, "Error skipping section '" + name + "'");
+            }
+        });
+    }
+
+    private Promise<String> readString(String error) {
+        return readBytes(error).then(b -> new String(b, StandardCharsets.UTF_8));
+    }
+
+    private Promise<byte[]> readBytes(String error) {
+        return requireLEB(error + ": error parsing size")
+                .thenAsync(size -> readBytes(size, error + ": error reading content"));
+    }
+
+    private Promise<byte[]> readBytes(int count, String error) {
+        return readBytesImpl(count, error).then(v -> {
+            var result = new byte[count];
+            var i = 0;
+            for (var chunk : chunks) {
+                System.arraycopy(chunk, 0, result, i, chunk.length);
+                i += chunk.length;
+            }
+            chunks.clear();
+            return result;
+        });
+    }
+
+    private Promise<Void> readBytesImpl(int count, String error) {
+        posBefore = pos;
+        var min = Math.min(count, remaining());
+        var chunk = new byte[min];
+        System.arraycopy(buffer, posInBuffer, chunk, 0, min);
+        chunks.add(chunk);
+        pos += min;
+        posInBuffer += min;
+        if (count > min) {
+            if (eof) {
+                error(error);
+            }
+            return fill().thenAsync(x -> readBytesImpl(count - min, error));
+        } else {
+            return Promise.VOID;
+        }
+    }
+
+    private Promise<Integer> requireLEB(String errorMessage) {
+        return readLEB().then(n -> {
+            if (n == null) {
+                error(errorMessage);
+            }
+            return n;
+        });
+    }
+
+    private Promise<Integer> readLEB() {
+        posBefore = pos;
+        currentLEB = 0;
+        bytesInLEB = 0;
+        currentLEBShift = 0;
+        return continueLEB();
+    }
+
+    private Promise<Integer> continueLEB() {
+        while (posInBuffer < bufferLimit) {
+            var b = buffer[posInBuffer++];
+            ++pos;
+            ++bytesInLEB;
+            var digit = b & 0x7F;
+            if (((digit << currentLEBShift) >> currentLEBShift) != digit) {
+                error("LEB represents too big number");
+            }
+            currentLEB |= digit << currentLEBShift;
+            if ((b & 0x80) == 0) {
+                return Promise.of(currentLEB);
+            }
+            currentLEBShift += 7;
+        }
+        return fill().thenAsync(bytesRead -> {
+            if (eof) {
+                if (bytesInLEB > 0) {
+                    error("Unexpected end of file reached reading LEB");
+                }
+                return Promise.of(null);
+            } else {
+                return continueLEB();
+            }
+        });
+    }
+
+    private int readInt32() {
+        posBefore = pos;
+        var result = (buffer[posInBuffer] & 255)
+                | ((buffer[posInBuffer + 1] & 255) << 8)
+                | ((buffer[posInBuffer + 2] & 255) << 16)
+                | ((buffer[posInBuffer + 3] & 255) << 24);
+        posInBuffer += 4;
+        pos += 4;
+        return result;
+    }
+
+    private int remaining() {
+        return bufferLimit - posInBuffer;
+    }
+
+    private Promise<Void> skip(int bytes, String error) {
+        if (bytes <= remaining()) {
+            posInBuffer += bytes;
+            pos += bytes;
+            return Promise.VOID;
+        } else {
+            posBefore = pos;
+            pos += remaining();
+            bytes -= remaining();
+            posInBuffer = 0;
+            bufferLimit = 0;
+            return skipImpl(bytes, error);
+        }
+    }
+
+    private Promise<Void> skipImpl(int bytes, String error) {
+        return reader.skip(bytes).thenAsync(bytesSkipped -> {
+            if (bytesSkipped < 0) {
+                error(error);
+            }
+            pos += bytesSkipped;
+            return bytes > bytesSkipped ? skipImpl(bytes - bytesSkipped, error) : Promise.VOID;
+        });
+    }
+
+    private Promise<Void> fillAtLeast(int least) {
+        return fill().thenAsync(x -> fillAtLeastImpl(least));
+    }
+
+    private Promise<Void> fillAtLeastImpl(int least) {
+        if (eof || least <= remaining()) {
+            return Promise.VOID;
+        }
+        return reader.read(buffer, bufferLimit, Math.min(least, buffer.length - bufferLimit))
+                .thenAsync(bytesRead -> {
+                    if (bytesRead < 0) {
+                        eof = true;
+                    } else {
+                        bufferLimit += bytesRead;
+                    }
+                    return fillAtLeastImpl(least);
+                });
+    }
+
+    private Promise<Void> fill() {
+        return readNext(buffer.length - remaining());
+    }
+
+    private Promise<Void> readNext(int bytes) {
+        if (eof) {
+            return Promise.VOID;
+        }
+        if (posInBuffer > 0 && posInBuffer < bufferLimit) {
+            System.arraycopy(buffer, posInBuffer, buffer, 0, bufferLimit - posInBuffer);
+        }
+        bufferLimit -= posInBuffer;
+        posInBuffer = 0;
+        return reader.read(buffer, bufferLimit, bytes).thenVoid(bytesRead -> {
+            if (bytesRead < 0) {
+                eof = true;
+            } else {
+                bufferLimit += bytesRead;
+            }
+        });
+    }
+
+    private void error(String message) {
+        throw new ParseException(message, posBefore);
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/DebugInfoReader.java

@@ -0,0 +1,24 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+import org.teavm.common.Promise;
+
+public interface DebugInfoReader {
+    Promise<Integer> skip(int amount);
+
+    Promise<Integer> read(byte[] buffer, int offset, int count);
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/DebugLinesParser.java

@@ -0,0 +1,168 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.List;
+import org.teavm.backend.wasm.debug.DebugConstants;
+import org.teavm.backend.wasm.debug.info.FileInfo;
+import org.teavm.backend.wasm.debug.info.LineInfo;
+import org.teavm.backend.wasm.debug.info.LineInfoCommand;
+import org.teavm.backend.wasm.debug.info.LineInfoEnterCommand;
+import org.teavm.backend.wasm.debug.info.LineInfoExitCommand;
+import org.teavm.backend.wasm.debug.info.LineInfoFileCommand;
+import org.teavm.backend.wasm.debug.info.LineInfoLineCommand;
+import org.teavm.backend.wasm.debug.info.LineInfoSequence;
+import org.teavm.backend.wasm.debug.info.MethodInfo;
+
+public class DebugLinesParser extends DebugSectionParser {
+    private DebugFileParser files;
+    private DebugMethodParser methods;
+    private LineInfo lineInfo;
+    private List<LineInfoSequence> sequences = new ArrayList<>();
+    private List<LineInfoCommand> commands = new ArrayList<>();
+    private Deque<State> stateStack = new ArrayDeque<>();
+    private FileInfo file;
+    private int line = 1;
+    private int address;
+    private MethodInfo currentMethod;
+    private int sequenceStartAddress;
+
+    public DebugLinesParser(
+            DebugFileParser files,
+            DebugMethodParser methods
+    ) {
+        super(DebugConstants.SECTION_LINES, files, methods);
+        this.files = files;
+        this.methods = methods;
+    }
+
+    public LineInfo getLineInfo() {
+        return lineInfo;
+    }
+
+    @Override
+    protected void doParse() {
+        while (ptr < data.length) {
+            var cmd = data[ptr++] & 0xFF;
+            switch (cmd) {
+                case DebugConstants.LOC_START:
+                    start();
+                    break;
+                case DebugConstants.LOC_END:
+                    end();
+                    break;
+                case DebugConstants.LOC_LINE:
+                    moveToLine();
+                    break;
+                case DebugConstants.LOC_FILE:
+                    moveToFile();
+                    break;
+                case DebugConstants.LOC_PTR:
+                    advanceAddress();
+                    break;
+                default:
+                    if (cmd >= DebugConstants.LOC_USER) {
+                        specialCommand(cmd);
+                    } else {
+                        throw new IllegalStateException("Invalid command at " + ptr + ": " + cmd);
+                    }
+                    break;
+            }
+        }
+        lineInfo = new LineInfo(sequences.toArray(new LineInfoSequence[0]));
+        sequences = null;
+        commands = null;
+        stateStack = null;
+        currentMethod = null;
+    }
+
+    private void start() {
+        var method = methods.getMethod(readLEB());
+        if (currentMethod == null) {
+            currentMethod = method;
+            sequenceStartAddress = address;
+        } else {
+            stateStack.push(new State(file, line));
+            commands.add(new LineInfoEnterCommand(address, method));
+        }
+        file = null;
+        line = 1;
+    }
+
+    private void end() {
+        if (stateStack.isEmpty()) {
+            if (currentMethod != null) {
+                sequences.add(new LineInfoSequence(sequenceStartAddress, address, currentMethod,
+                        commands.toArray(new LineInfoCommand[0])));
+            }
+            commands.clear();
+            currentMethod = null;
+            file = null;
+            line = 1;
+        } else {
+            var state = stateStack.pop();
+            file = state.file;
+            line = state.line;
+            commands.add(new LineInfoExitCommand(address));
+        }
+    }
+
+    private void moveToLine() {
+        line = line + readSignedLEB();
+        if (currentMethod != null) {
+            commands.add(new LineInfoLineCommand(address, line));
+        }
+    }
+
+    private void moveToFile() {
+        file = files.getFile(readLEB());
+        line = 1;
+        if (ptr < data.length && data[ptr] == DebugConstants.LOC_LINE) {
+            ++ptr;
+            line = line + readSignedLEB();
+        }
+        if (currentMethod != null) {
+            commands.add(new LineInfoFileCommand(address, file, line));
+        }
+    }
+
+    private void advanceAddress() {
+        address += readLEB();
+    }
+
+    private void specialCommand(int cmd) {
+        cmd -= DebugConstants.LOC_USER;
+        address += cmd % 32;
+        cmd /= 32;
+        line += cmd - 3;
+        if (currentMethod != null) {
+            commands.add(new LineInfoFileCommand(address, file, line));
+        }
+    }
+
+    private static class State {
+        FileInfo file;
+        int line;
+
+        State(FileInfo file, int line) {
+            this.file = file;
+            this.line = line;
+        }
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/DebugMethodParser.java

@@ -0,0 +1,68 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+import java.util.ArrayList;
+import org.teavm.backend.wasm.debug.DebugConstants;
+import org.teavm.backend.wasm.debug.info.ClassInfo;
+import org.teavm.backend.wasm.debug.info.MethodInfo;
+
+public class DebugMethodParser extends DebugSectionParser {
+    private DebugStringParser strings;
+    private DebugClassParser classes;
+    private MethodInfoImpl[] methods;
+
+    public DebugMethodParser(DebugStringParser strings, DebugClassParser classes) {
+        super(DebugConstants.SECTION_METHODS);
+        this.strings = strings;
+        this.classes = classes;
+    }
+
+    public MethodInfo getMethod(int ptr) {
+        return methods[ptr];
+    }
+
+    @Override
+    protected void doParse() {
+        var methods = new ArrayList<MethodInfoImpl>();
+        while (ptr < data.length) {
+            var cls = classes.getClass(readLEB());
+            var name = strings.getString(readLEB());
+            methods.add(new MethodInfoImpl(cls, name));
+        }
+        this.methods = methods.toArray(new MethodInfoImpl[0]);
+    }
+
+    private static class MethodInfoImpl extends MethodInfo {
+        private ClassInfo cls;
+        private String name;
+
+        MethodInfoImpl(ClassInfo cls, String name) {
+            this.cls = cls;
+            this.name = name;
+        }
+
+        @Override
+        public ClassInfo cls() {
+            return cls;
+        }
+
+        @Override
+        public String name() {
+            return name;
+        }
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/DebugPackageParser.java

@@ -0,0 +1,78 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+import java.util.ArrayList;
+import org.teavm.backend.wasm.debug.DebugConstants;
+import org.teavm.backend.wasm.debug.info.PackageInfo;
+
+public class DebugPackageParser extends DebugSectionParser {
+    private DebugStringParser strings;
+    private PackageInfoImpl[] packages;
+
+    public DebugPackageParser(DebugStringParser strings) {
+        super(DebugConstants.SECTION_PACKAGES, strings);
+        this.strings = strings;
+    }
+
+    public PackageInfo getPackage(int index) {
+        return index == 0 ? null : packages[index - 1];
+    }
+
+    @Override
+    protected void doParse() {
+        var packageBuilders = new ArrayList<PackageBuilder>();
+        while (ptr < data.length) {
+            packageBuilders.add(new PackageBuilder(readLEB(), strings.getString(readLEB())));
+        }
+        packages = new PackageInfoImpl[packageBuilders.size()];
+        for (var i = 0; i < packages.length; ++i) {
+            packages[i] = new PackageInfoImpl(packageBuilders.get(i).name);
+        }
+        for (var i = 0; i < packages.length; ++i) {
+            packages[i].parent = getPackage(packageBuilders.get(i).parent);
+        }
+    }
+
+    private static class PackageInfoImpl extends PackageInfo {
+        private PackageInfo parent;
+        private String name;
+
+        PackageInfoImpl(String name) {
+            this.name = name;
+        }
+
+        @Override
+        public PackageInfo parent() {
+            return parent;
+        }
+
+        @Override
+        public String name() {
+            return name;
+        }
+    }
+
+    private static class PackageBuilder {
+        int parent;
+        String name;
+
+        PackageBuilder(int parent, String name) {
+            this.parent = parent;
+            this.name = name;
+        }
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/DebugSectionParser.java

@@ -0,0 +1,103 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.List;
+
+public abstract class DebugSectionParser {
+    private String name;
+    private List<DebugSectionParser> dependantSections = new ArrayList<>();
+    byte[] data;
+    int ptr;
+    private boolean ready;
+    private int unsatisfiedDependencies;
+
+    protected DebugSectionParser(String name, DebugSectionParser... dependencies) {
+        this.name = name;
+        for (var dependency : dependencies) {
+            dependency.dependantSections.add(this);
+        }
+        unsatisfiedDependencies = dependencies.length;
+    }
+
+    public String name() {
+        return name;
+    }
+
+    public boolean ready() {
+        return ready;
+    }
+
+    public void parse(byte[] data) {
+        this.data = data;
+        if (unsatisfiedDependencies == 0) {
+            parse();
+        }
+    }
+
+    private void parse() {
+        doParse();
+        ready = true;
+        data = null;
+        for (var dependant : dependantSections) {
+            if (--dependant.unsatisfiedDependencies == 0 && dependant.data != null) {
+                dependant.parse();
+            }
+        }
+    }
+
+    protected abstract void doParse();
+
+    protected int readLEB() {
+        var result = 0;
+        var shift = 0;
+        while (true) {
+            var b = data[ptr++];
+            result |= (b & 0x7F) << shift;
+            if ((b & 0x80) == 0) {
+                break;
+            }
+            shift += 7;
+        }
+        return result;
+    }
+
+    protected int readSignedLEB() {
+        var result = 0;
+        var shift = 0;
+        while (true) {
+            var b = data[ptr++];
+            result |= (b & 0x7F) << shift;
+            if ((b & 0x80) == 0) {
+                if ((b & 0x40) != 0) {
+                    result |= -1 << (shift + 7);
+                }
+                break;
+            }
+            shift += 7;
+        }
+        return result;
+    }
+
+    protected String readString() {
+        var length = readLEB();
+        var result = new String(data, ptr, length, StandardCharsets.UTF_8);
+        ptr += length;
+        return result;
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/DebugStringParser.java

@@ -0,0 +1,40 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+import java.util.ArrayList;
+import org.teavm.backend.wasm.debug.DebugConstants;
+
+public class DebugStringParser extends DebugSectionParser {
+    private String[] strings;
+
+    public DebugStringParser() {
+        super(DebugConstants.SECTION_STRINGS);
+    }
+
+    @Override
+    protected void doParse() {
+        var strings = new ArrayList<String>();
+        while (ptr < data.length) {
+            strings.add(readString());
+        }
+        this.strings = strings.toArray(new String[0]);
+    }
+
+    public String getString(int ref) {
+        return strings[ref];
+    }
+}

core/src/main/java/org/teavm/backend/wasm/debug/parser/ParseException.java

@@ -0,0 +1,27 @@
+/*
+ *  Copyright 2022 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.debug.parser;
+
+class ParseException extends RuntimeException {
+    final String message;
+    final int pos;
+
+    ParseException(String message, int pos) {
+        super("Error parsing at " + pos + ": " + message);
+        this.message = message;
+        this.pos = pos;
+    }
+}

core/src/main/java/org/teavm/common/CollectionUtil.java

@@ -0,0 +1,54 @@
+/*
+ *  Copyright 2022 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.common;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.function.Function;
+
+public final class CollectionUtil {
+    private CollectionUtil() {
+    }
+
+    public static <T, K extends Comparable<K>> int binarySearch(List<? extends T> list, K key,
+            Function<T, K> keyExtractor) {
+        return binarySearch(list, key, keyExtractor, Comparable::compareTo);
+    }
+
+    public static <T, K> int binarySearch(List<? extends T> list, K key, Function<T, K> keyExtractor,
+            Comparator<K> comparator) {
+        var l = 0;
+        var u = list.size() - 1;
+        while (true) {
+            var i = (l + u) / 2;
+            var t = keyExtractor.apply(list.get(i));
+            var cmp = comparator.compare(t, key);
+            if (cmp == 0) {
+                return i;
+            } else if (cmp > 0) {
+                l = i + i;
+                if (l > u) {
+                    return -i - 1;
+                }
+            } else {
+                u = i - 1;
+                if (u < l) {
+                    return -i;
+                }
+            }
+        }
+    }
+}

core/src/main/java/org/teavm/common/Promise.java

@@ -15,14 +15,17 @@
  */
 package org.teavm.common;
 
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
+import java.util.Queue;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
 public class Promise<T> {
+    private static ThreadLocal<Queue<Runnable>> processing = new ThreadLocal<>();
     public static final Promise<Void> VOID = Promise.of(null);
 
     private T value;
@@ -187,6 +190,7 @@ public class Promise<T> {
     }
 
     <S> void passValue(Function<? super T, S> f, Promise<? super S> target) {
+        runAction(() -> {
             if (state == State.COMPLETED) {
                 S next;
                 try {
@@ -199,17 +203,28 @@ public class Promise<T> {
             } else {
                 target.completeWithError(error);
             }
+        });
     }
 
     <S> void passValueAsync(Function<T, Promise<S>> f, Promise<S> target) {
+        runAction(() -> {
             if (state == State.COMPLETED) {
-            target.completeAsync(f.apply(value));
+                Promise<S> next;
+                try {
+                    next = f.apply(value);
+                } catch (Throwable e) {
+                    target.completeWithError(e);
+                    return;
+                }
+                target.completeAsync(next);
             } else {
                 target.completeWithError(error);
             }
+        });
     }
 
     <S> void passError(Function<Throwable, S> f, Promise<? super S> target) {
+        runAction(() -> {
             S next;
             try {
                 next = f.apply(error);
@@ -218,6 +233,7 @@ public class Promise<T> {
                 return;
             }
             target.complete(next);
+        });
     }
 
     void complete(T value) {
@@ -245,6 +261,7 @@ public class Promise<T> {
     }
 
     private void completeImpl(T value) {
+        runAction(() -> {
             state = State.COMPLETED;
             this.value = value;
 
@@ -260,6 +277,7 @@ public class Promise<T> {
                 }
             }
             catchList = null;
+        });
     }
 
     void completeWithError(Throwable e) {
@@ -270,6 +288,7 @@ public class Promise<T> {
     }
 
     void completeWithErrorImpl(Throwable e) {
+        runAction(() -> {
             state = State.ERRORED;
             this.error = e;
 
@@ -283,6 +302,22 @@ public class Promise<T> {
                 e.printStackTrace();
             }
             thenList = null;
+        });
+    }
+
+    private void runAction(Runnable action) {
+        var queue = processing.get();
+        if (queue != null) {
+            queue.add(action);
+        } else {
+            queue = new ArrayDeque<>();
+            queue.add(action);
+            processing.set(queue);
+            while (!queue.isEmpty()) {
+                queue.remove().run();
+            }
+            processing.remove();
+        }
     }
 
     enum State {