diff --git a/teavm-core/src/main/java/org/teavm/debugging/CallFrame.java b/teavm-core/src/main/java/org/teavm/debugging/CallFrame.java
index 59d55fc3f..20edbe8c4 100644
--- a/teavm-core/src/main/java/org/teavm/debugging/CallFrame.java
+++ b/teavm-core/src/main/java/org/teavm/debugging/CallFrame.java
@@ -15,18 +15,26 @@
  */
 package org.teavm.debugging;
 
+import org.teavm.model.MethodReference;
+
 /**
  *
  * @author Alexey Andreev
  */
 public class CallFrame {
     private SourceLocation location;
+    private MethodReference method;
 
-    CallFrame(SourceLocation location) {
+    CallFrame(SourceLocation location, MethodReference method) {
         this.location = location;
+        this.method = method;
     }
 
     public SourceLocation getLocation() {
         return location;
     }
+
+    public MethodReference getMethod() {
+        return method;
+    }
 }
diff --git a/teavm-core/src/main/java/org/teavm/debugging/DebugInformation.java b/teavm-core/src/main/java/org/teavm/debugging/DebugInformation.java
index 3d207156b..a1a4ba273 100644
--- a/teavm-core/src/main/java/org/teavm/debugging/DebugInformation.java
+++ b/teavm-core/src/main/java/org/teavm/debugging/DebugInformation.java
@@ -16,7 +16,6 @@
 package org.teavm.debugging;
 
 import java.util.*;
-import org.teavm.model.MethodDescriptor;
 import org.teavm.model.MethodReference;
 
 /**
@@ -24,31 +23,31 @@ import org.teavm.model.MethodReference;
  * @author Alexey Andreev
  */
 public class DebugInformation {
-    List<String> fileNames = new ArrayList<>();
-    Map<String, Integer> fileNameMap = new HashMap<>();
-    List<String> classNames = new ArrayList<>();
-    Map<String, Integer> classNameMap = new HashMap<>();
-    List<MethodDescriptor> methods = new ArrayList<>();
-    Map<MethodDescriptor, Integer> methodMap = new HashMap<>();
-    List<FileDescription> fileDescriptions = new ArrayList<>();
+    String[] fileNames;
+    Map<String, Integer> fileNameMap;
+    FileDescription[] fileDescriptions;
+    // TODO: for less memory consumption replace with two arrays + custom binary search
     GeneratedLocation[] fileNameKeys;
     int[] fileNameValues;
-    GeneratedLocation[] classKeys;
-    int[] classValues;
-    GeneratedLocation[] methodKeys;
-    int[] methodValues;
     GeneratedLocation[] lineNumberKeys;
     int[] lineNumberValues;
 
-    public Collection<GeneratedLocation> getGeneratedLocations(String fileName, int lineNumber) {
+    public Collection<GeneratedLocation> getGeneratedLocations(String fileName, int line) {
         Integer fileIndex = fileNameMap.get(fileName);
         if (fileIndex == null) {
             return Collections.emptyList();
         }
-        FileDescription description = fileDescriptions.get(lineNumber);
-        return lineNumber < description.generatedLocations.length ?
-                Arrays.asList(description.generatedLocations[lineNumber]) :
-                Collections.<GeneratedLocation>emptyList();
+        FileDescription description = fileIndex >= 0 ? fileDescriptions[fileIndex] : null;
+        if (description == null) {
+            return null;
+        }
+        GeneratedLocation[] locations = line < description.generatedLocations.length ?
+                description.generatedLocations[line] : null;
+        return locations != null ? Arrays.asList(locations) : Collections.<GeneratedLocation>emptyList();
+    }
+
+    public Collection<GeneratedLocation> getGeneratedLocations(SourceLocation sourceLocation) {
+        return getGeneratedLocations(sourceLocation.getFileName(), sourceLocation.getLine());
     }
 
     public SourceLocation getSourceLocation(int line, int column) {
@@ -57,18 +56,35 @@ public class DebugInformation {
 
     public SourceLocation getSourceLocation(GeneratedLocation generatedLocation) {
         String fileName = componentByKey(fileNameKeys, fileNameValues, fileNames, generatedLocation);
-        String className = componentByKey(classKeys, classValues, classNames, generatedLocation);
-        MethodDescriptor method = componentByKey(methodKeys, methodValues, methods, generatedLocation);
         int lineNumberIndex = indexByKey(lineNumberKeys, generatedLocation);
         int lineNumber = lineNumberIndex >= 0 ? lineNumberValues[lineNumberIndex] : -1;
-        return new SourceLocation(fileName, lineNumber, new MethodReference(className, method));
+        return new SourceLocation(fileName, lineNumber);
     }
 
-    private <T> T componentByKey(GeneratedLocation[] keys, int[] valueIndexes, List<T> values,
+    public MethodReference getMethodAt(String fileName, int line) {
+        if (line < 0) {
+            return null;
+        }
+        Integer fileIndex = fileNameMap.get(fileName);
+        if (fileIndex == null) {
+            return null;
+        }
+        FileDescription description = fileDescriptions[fileIndex];
+        if (description == null) {
+            return null;
+        }
+        return line < description.methodMap.length ? description.methodMap[line] : null;
+    }
+
+    public MethodReference getMethodAt(SourceLocation sourceLocation) {
+        return getMethodAt(sourceLocation.getFileName(), sourceLocation.getLine());
+    }
+
+    private <T> T componentByKey(GeneratedLocation[] keys, int[] valueIndexes, T[] values,
             GeneratedLocation location) {
         int keyIndex = indexByKey(keys, location);
         int valueIndex = keyIndex >= 0 ? valueIndexes[keyIndex] : -1;
-        return valueIndex >= 0 ? values.get(valueIndex) : null;
+        return valueIndex >= 0 ? values[valueIndex] : null;
     }
 
     private int indexByKey(GeneratedLocation[] keys, GeneratedLocation location) {
@@ -76,7 +92,8 @@ public class DebugInformation {
         return index >= 0 ? index : -index - 2;
     }
 
-    class FileDescription {
+    static class FileDescription {
         GeneratedLocation[][] generatedLocations;
+        MethodReference[] methodMap;
     }
 }
diff --git a/teavm-core/src/main/java/org/teavm/debugging/DebugInformationBuilder.java b/teavm-core/src/main/java/org/teavm/debugging/DebugInformationBuilder.java
index c43f18799..9abfd8ccf 100644
--- a/teavm-core/src/main/java/org/teavm/debugging/DebugInformationBuilder.java
+++ b/teavm-core/src/main/java/org/teavm/debugging/DebugInformationBuilder.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.debugging;
 
+import java.util.*;
 import org.teavm.codegen.LocationProvider;
 import org.teavm.model.MethodReference;
 
@@ -24,6 +25,15 @@ import org.teavm.model.MethodReference;
  */
 public class DebugInformationBuilder implements DebugInformationEmitter {
     private LocationProvider locationProvider;
+    private DebugInformation debugInformation;
+    private List<String> fileNames = new ArrayList<>();
+    private Map<String, Integer> fileNameMap = new HashMap<>();
+    private List<Entry> fileNameEntries = new ArrayList<>();
+    private List<Entry> lineNumberEntries = new ArrayList<>();
+    private MethodReference currentMethod;
+    private String currentFileName;
+    private int currentLine;
+    private List<FileDescriptionProto> fileDescriptions = new ArrayList<>();
 
     public LocationProvider getLocationProvider() {
         return locationProvider;
@@ -33,18 +43,111 @@ public class DebugInformationBuilder implements DebugInformationEmitter {
         this.locationProvider = locationProvider;
     }
 
-    @Override
-    public void emitFile(String fileName) {
+    private GeneratedLocation getGeneratedLocation() {
+        return new GeneratedLocation(locationProvider.getLine(), locationProvider.getColumn());
+    }
 
+    @Override
+    public void emitLocation(String fileName, int line) {
+        Integer fileIndex;
+        if (fileName != null) {
+            fileIndex = fileNameMap.get(fileName);
+            if (fileIndex == null) {
+                fileIndex = fileNames.size();
+                fileNames.add(fileName);
+                fileNameMap.put(fileName, fileIndex);
+                fileDescriptions.add(new FileDescriptionProto());
+            }
+        } else {
+            fileIndex = -1;
+        }
+        if (currentFileName != fileName) {
+            fileNameEntries.add(new Entry(getGeneratedLocation(), fileIndex));
+        }
+        if (currentLine != line) {
+            lineNumberEntries.add(new Entry(getGeneratedLocation(), line));
+        }
+        if (fileName != null && line >= 0 && (currentFileName != fileName || currentLine != line)) {
+            FileDescriptionProto fileDesc = fileDescriptions.get(fileIndex);
+            fileDesc.setMethod(line, currentMethod);
+            fileDesc.addGeneratedLocation(line, getGeneratedLocation());
+        }
     }
 
     @Override
     public void emitMethod(MethodReference method) {
-
+        currentMethod = method;
     }
 
-    @Override
-    public void emitLineNumber(String lineNumber) {
+    public DebugInformation getDebugInformation() {
+        if (debugInformation == null) {
+            debugInformation = new DebugInformation();
 
+            debugInformation.fileNames = fileNames.toArray(new String[0]);
+            debugInformation.fileNameMap = new HashMap<>(fileNameMap);
+
+            debugInformation.fileNameKeys = new GeneratedLocation[fileNameEntries.size()];
+            debugInformation.fileNameValues = new int[fileNameEntries.size()];
+            int index = 0;
+            for (Entry entry : fileNameEntries) {
+                debugInformation.fileNameKeys[index] = entry.key;
+                debugInformation.fileNameValues[index] = entry.value;
+                index++;
+            }
+
+            debugInformation.lineNumberKeys = new GeneratedLocation[lineNumberEntries.size()];
+            debugInformation.lineNumberValues = new int[lineNumberEntries.size()];
+            index = 0;
+            for (Entry entry : lineNumberEntries) {
+                debugInformation.lineNumberKeys[index] = entry.key;
+                debugInformation.lineNumberValues[index] = entry.value;
+                index++;
+            }
+
+            debugInformation.fileDescriptions = new DebugInformation.FileDescription[fileDescriptions.size()];
+            index = 0;
+            for (FileDescriptionProto fileDescProto : fileDescriptions) {
+                DebugInformation.FileDescription fileDesc = new DebugInformation.FileDescription();
+                debugInformation.fileDescriptions[index++] = fileDesc;
+                fileDesc.methodMap = fileDescProto.methodMap.toArray(new MethodReference[0]);
+                fileDesc.generatedLocations = new GeneratedLocation[fileDescProto.generatedLocations.size()][];
+                for (int i = 0; i < fileDescProto.generatedLocations.size(); ++i) {
+                    fileDesc.generatedLocations[i] = fileDescProto.generatedLocations.get(index)
+                            .toArray(new GeneratedLocation[0]);
+                }
+            }
+        }
+        return debugInformation;
+    }
+
+    static class FileDescriptionProto {
+        List<List<GeneratedLocation>> generatedLocations = new ArrayList<>();
+        List<MethodReference> methodMap = new ArrayList<>();
+
+        void addGeneratedLocation(int line, GeneratedLocation location) {
+            if (line >= generatedLocations.size()) {
+                generatedLocations.addAll(Collections.<List<GeneratedLocation>>nCopies(
+                        line - generatedLocations.size() + 1, null));
+            }
+            List<GeneratedLocation> existingLocations = generatedLocations.get(line);
+            existingLocations.add(location);
+        }
+
+        void setMethod(int line, MethodReference method) {
+            if (line >= methodMap.size()) {
+                methodMap.addAll(Collections.<MethodReference>nCopies(line - methodMap.size() + 1, null));
+            }
+            methodMap.set(line, method);
+        }
+    }
+
+    static class Entry {
+        GeneratedLocation key;
+        int value;
+
+        public Entry(GeneratedLocation key, int value) {
+            this.key = key;
+            this.value = value;
+        }
     }
 }
diff --git a/teavm-core/src/main/java/org/teavm/debugging/DebugInformationEmitter.java b/teavm-core/src/main/java/org/teavm/debugging/DebugInformationEmitter.java
index 718a48b5d..c22a846a4 100644
--- a/teavm-core/src/main/java/org/teavm/debugging/DebugInformationEmitter.java
+++ b/teavm-core/src/main/java/org/teavm/debugging/DebugInformationEmitter.java
@@ -22,9 +22,7 @@ import org.teavm.model.MethodReference;
  * @author Alexey Andreev
  */
 public interface DebugInformationEmitter {
-    void emitFile(String fileName);
+    void emitLocation(String fileName, int line);
 
     void emitMethod(MethodReference method);
-
-    void emitLineNumber(String lineNumber);
 }
\ No newline at end of file
diff --git a/teavm-core/src/main/java/org/teavm/debugging/Debugger.java b/teavm-core/src/main/java/org/teavm/debugging/Debugger.java
index dbcaf7132..a080373c8 100644
--- a/teavm-core/src/main/java/org/teavm/debugging/Debugger.java
+++ b/teavm-core/src/main/java/org/teavm/debugging/Debugger.java
@@ -16,6 +16,7 @@
 package org.teavm.debugging;
 
 import java.util.*;
+import org.teavm.model.MethodReference;
 
 /**
  *
@@ -65,12 +66,14 @@ public class Debugger {
             return;
         }
         // TODO: lookup all locations that are "out of" the current location and create temporary breakpoints
+        javaScriptDebugger.stepOut();
     }
 
     public void stepOver() {
         if (!javaScriptDebugger.isSuspended()) {
             return;
         }
+        javaScriptDebugger.stepOver();
         // TODO: lookup all locations that are "after" the current location and create temporary breakpoints
     }
 
@@ -115,9 +118,10 @@ public class Debugger {
             boolean wasEmpty = false;
             for (JavaScriptCallFrame jsFrame : javaScriptDebugger.getCallStack()) {
                 SourceLocation loc = debugInformation.getSourceLocation(jsFrame.getLocation());
-                boolean empty = loc.getFileName() != null || loc.getMethod() != null  || loc.getLine() < 0;
+                boolean empty = loc == null || (loc.getFileName() == null && loc.getLine() < 0);
+                MethodReference method = !empty ? debugInformation.getMethodAt(loc) : null;
                 if (!empty || !wasEmpty) {
-                    frames.add(new CallFrame(loc));
+                    frames.add(new CallFrame(loc, method));
                 }
                 wasEmpty = empty;
             }
diff --git a/teavm-core/src/main/java/org/teavm/debugging/DummyDebugInformationEmitter.java b/teavm-core/src/main/java/org/teavm/debugging/DummyDebugInformationEmitter.java
index 43c6b20b1..38cff54b4 100644
--- a/teavm-core/src/main/java/org/teavm/debugging/DummyDebugInformationEmitter.java
+++ b/teavm-core/src/main/java/org/teavm/debugging/DummyDebugInformationEmitter.java
@@ -24,14 +24,10 @@ import org.teavm.model.MethodReference;
  */
 public class DummyDebugInformationEmitter implements DebugInformationEmitter {
     @Override
-    public void emitFile(String fileName) {
+    public void emitLocation(String fileName, int line) {
     }
 
     @Override
     public void emitMethod(MethodReference method) {
     }
-
-    @Override
-    public void emitLineNumber(String lineNumber) {
-    }
 }
diff --git a/teavm-core/src/main/java/org/teavm/debugging/SourceLocation.java b/teavm-core/src/main/java/org/teavm/debugging/SourceLocation.java
index 9be482085..28625420f 100644
--- a/teavm-core/src/main/java/org/teavm/debugging/SourceLocation.java
+++ b/teavm-core/src/main/java/org/teavm/debugging/SourceLocation.java
@@ -15,7 +15,6 @@
  */
 package org.teavm.debugging;
 
-import org.teavm.model.MethodReference;
 
 /**
  *
@@ -24,12 +23,10 @@ import org.teavm.model.MethodReference;
 public class SourceLocation {
     private String fileName;
     private int line;
-    private MethodReference method;
 
-    public SourceLocation(String fileName, int line, MethodReference method) {
+    public SourceLocation(String fileName, int line) {
         this.fileName = fileName;
         this.line = line;
-        this.method = method;
     }
 
     public String getFileName() {
@@ -39,8 +36,4 @@ public class SourceLocation {
     public int getLine() {
         return line;
     }
-
-    public MethodReference getMethod() {
-        return method;
-    }
 }