C: add setting to generate code with lots of assertions

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

@@ -17,8 +17,8 @@ package org.teavm.classlib.java.lang;
 
 import java.io.PrintStream;
 import java.io.PrintWriter;
+import org.teavm.classlib.PlatformDetector;
 import org.teavm.classlib.java.util.TArrays;
-import org.teavm.interop.DelegateTo;
 import org.teavm.interop.Remove;
 import org.teavm.interop.Rename;
 import org.teavm.interop.Superclass;
@@ -101,15 +101,12 @@ public class TThrowable extends RuntimeException {
     }
 
     @Override
-    @DelegateTo("fillInStackTraceLowLevel")
     public Throwable fillInStackTrace() {
-        return this;
+        if (PlatformDetector.isLowLevel()) {
-    }
+            int stackSize = ExceptionHandling.callStackSize() - 1;
-
+            stackTrace = new TStackTraceElement[stackSize];
-    private TThrowable fillInStackTraceLowLevel() {
+            ExceptionHandling.fillStackTrace((StackTraceElement[]) (Object) stackTrace);
-        int stackSize = ExceptionHandling.callStackSize() - 1;
+        }
-        stackTrace = new TStackTraceElement[stackSize];
-        ExceptionHandling.fillStackTrace((StackTraceElement[]) (Object) stackTrace);
         return this;
     }
 

core/src/main/java/org/teavm/backend/c/CTarget.java

@@ -64,6 +64,7 @@ import org.teavm.backend.c.intrinsic.Intrinsic;
 import org.teavm.backend.c.intrinsic.IntrinsicContext;
 import org.teavm.backend.c.intrinsic.IntrinsicFactory;
 import org.teavm.backend.c.intrinsic.LongIntrinsic;
+import org.teavm.backend.c.intrinsic.MemoryTraceIntrinsic;
 import org.teavm.backend.c.intrinsic.MutatorIntrinsic;
 import org.teavm.backend.c.intrinsic.PlatformClassIntrinsic;
 import org.teavm.backend.c.intrinsic.PlatformClassMetadataIntrinsic;
@@ -340,6 +341,7 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
         intrinsics.add(new PlatformClassIntrinsic());
         intrinsics.add(new PlatformClassMetadataIntrinsic());
         intrinsics.add(new GCIntrinsic());
+        intrinsics.add(new MemoryTraceIntrinsic());
         intrinsics.add(new MutatorIntrinsic());
         intrinsics.add(new ExceptionHandlingIntrinsic());
         intrinsics.add(new FunctionIntrinsic(characteristics, exportDependencyListener.getResolvedMethods()));
@@ -356,9 +358,11 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
         generators.add(new ReferenceQueueGenerator());
 
         stringPool = new SimpleStringPool();
+        boolean vmAssertions = Boolean.parseBoolean(System.getProperty("teavm.c.vmAssertions", "false"));
         GenerationContext context = new GenerationContext(vtableProvider, characteristics,
                 controller.getDependencyInfo(), stringPool, nameProvider, controller.getDiagnostics(), classes,
-                intrinsics, generators, asyncMethods::contains, buildTarget, incremental, longjmpUsed);
+                intrinsics, generators, asyncMethods::contains, buildTarget, incremental, longjmpUsed,
+                vmAssertions);
 
         BufferedCodeWriter runtimeWriter = new BufferedCodeWriter(false);
         BufferedCodeWriter runtimeHeaderWriter = new BufferedCodeWriter(false);
@@ -371,6 +375,9 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
         if (longjmpUsed) {
             runtimeHeaderWriter.println("#define TEAVM_USE_SETJMP 1");
         }
+        if (vmAssertions) {
+            runtimeHeaderWriter.println("#define TEAVM_MEMORY_TRACE 1");
+        }
         emitResource(runtimeHeaderWriter, "runtime.h");
 
         ClassGenerator classGenerator = new ClassGenerator(context, tagRegistry, decompiler,

core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java

@@ -319,6 +319,16 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         }
     }
 
+    private void visitReference(Expr expr) {
+        if (context.isVmAssertions()) {
+            writer.print("TEAVM_VERIFY(");
+        }
+        expr.acceptVisitor(this);
+        if (context.isVmAssertions()) {
+            writer.print(")");
+        }
+    }
+
     @Override
     public void visit(UnaryExpr expr) {
         pushLocation(expr.getLocation());
@@ -337,7 +347,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
                 break;
             case LENGTH:
                 writer.print("TEAVM_ARRAY_LENGTH(");
-                expr.getOperand().acceptVisitor(this);
+                visitReference(expr.getOperand());
                 writer.print(")");
                 break;
             case NULL_CHECK: {
@@ -347,7 +357,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
                     withCallSite();
                 }
                 writer.print("teavm_nullCheck(");
-                expr.getOperand().acceptVisitor(this);
+                visitReference(expr.getOperand());
                 writer.print(")");
                 if (needParenthesis) {
                     writer.print(")");
@@ -412,7 +422,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
     public void visit(SubscriptExpr expr) {
         pushLocation(expr.getLocation());
         writer.print("TEAVM_ARRAY_AT(");
-        expr.getArray().acceptVisitor(this);
+        visitReference(expr.getArray());
         writer.print(", ").print(getArrayType(expr.getType())).print(", ");
         expr.getIndex().acceptVisitor(this);
         writer.print(")");
@@ -604,7 +614,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         } else {
             receiver = allocTemporaryVariable(CVariableType.PTR);
             writer.print("((").print(receiver).print(" = ");
-            arguments.get(0).acceptVisitor(this);
+            visitReference(arguments.get(0));
             writer.print("), ");
             closingParenthesis = true;
         }
@@ -811,8 +821,18 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         if (qualified != null) {
             ClassReader cls = context.getClassSource().get(field.getClassName());
             writer.print("TEAVM_FIELD(");
+
+            boolean shouldVerify = context.isVmAssertions()
+                    && context.getCharacteristics().isManaged(field.getClassName());
+            if (shouldVerify) {
+                writer.print("TEAVM_VERIFY(");
+            }
             qualified.acceptVisitor(this);
+            if (shouldVerify) {
+                writer.print(")");
+            }
             writer.print(", ");
+
             if (cls != null && isNative(cls)) {
                 InteropUtil.processInclude(cls.getAnnotations(), includes);
                 InteropUtil.printNativeReference(writer, cls);
@@ -919,7 +939,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
     public void visit(InstanceOfExpr expr) {
         pushLocation(expr.getLocation());
         writer.print("teavm_instanceof(");
-        expr.getExpr().acceptVisitor(this);
+        visitReference(expr.getExpr());
         includes.includeType(expr.getType());
         writer.print(", ").print(names.forSupertypeFunction(expr.getType())).print(")");
         popLocation(expr.getLocation());
@@ -945,7 +965,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         }
 
         writer.print("teavm_checkcast(");
-        expr.getValue().acceptVisitor(this);
+        visitReference(expr.getValue());
         includes.includeType(expr.getTarget());
         writer.print(", ").print(names.forSupertypeFunction(expr.getTarget())).print(")");
 

core/src/main/java/org/teavm/backend/c/generate/CodeGenerator.java

@@ -108,6 +108,15 @@ public class CodeGenerator {
 
     private void generateLocals(MethodNode methodNode, int[] temporaryCount, IntContainer spilledVariables) {
         int start = methodNode.getReference().parameterCount() + 1;
+
+        for (int i = 0; i < start; ++i) {
+            if (spilledVariables.contains(i)) {
+                VariableNode variableNode = methodNode.getVariables().get(i);
+                localsWriter.print("volatile ").printType(variableNode.getType()).print(" teavm_spill_")
+                        .print(String.valueOf(i)).println(";");
+            }
+        }
+
         for (int i = start; i < methodNode.getVariables().size(); ++i) {
             VariableNode variableNode = methodNode.getVariables().get(i);
             if (variableNode.getType() == null) {

core/src/main/java/org/teavm/backend/c/generate/GenerationContext.java

@@ -45,12 +45,13 @@ public class GenerationContext {
     private BuildTarget buildTarget;
     private boolean incremental;
     private boolean longjmp;
+    private boolean vmAssertions;
 
     public GenerationContext(VirtualTableProvider virtualTableProvider, Characteristics characteristics,
             DependencyInfo dependencies, StringPool stringPool, NameProvider names, Diagnostics diagnostics,
             ClassReaderSource classSource, List<Intrinsic> intrinsics, List<Generator> generators,
             Predicate<MethodReference> asyncMethods, BuildTarget buildTarget, boolean incremental,
-            boolean longjmp) {
+            boolean longjmp, boolean vmAssertions) {
         this.virtualTableProvider = virtualTableProvider;
         this.characteristics = characteristics;
         this.dependencies = dependencies;
@@ -64,6 +65,7 @@ public class GenerationContext {
         this.buildTarget = buildTarget;
         this.incremental = incremental;
         this.longjmp = longjmp;
+        this.vmAssertions = vmAssertions;
     }
 
     public void addIntrinsic(Intrinsic intrinsic) {
@@ -131,4 +133,8 @@ public class GenerationContext {
     public boolean isLongjmp() {
         return longjmp;
     }
+
+    public boolean isVmAssertions() {
+        return vmAssertions;
+    }
 }

core/src/main/java/org/teavm/backend/c/intrinsic/MemoryTraceIntrinsic.java

@@ -0,0 +1,40 @@
+/*
+ *  Copyright 2019 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.c.intrinsic;
+
+import org.teavm.ast.InvocationExpr;
+import org.teavm.model.MethodReference;
+import org.teavm.runtime.MemoryTrace;
+
+public class MemoryTraceIntrinsic implements Intrinsic {
+    @Override
+    public boolean canHandle(MethodReference method) {
+        return method.getClassName().equals(MemoryTrace.class.getName());
+    }
+
+    @Override
+    public void apply(IntrinsicContext context, InvocationExpr invocation) {
+        context.writer().print("teavm_gc_").print(invocation.getMethod().getName()).print("(");
+        if (!invocation.getArguments().isEmpty()) {
+            context.emit(invocation.getArguments().get(0));
+            for (int i = 1; i < invocation.getArguments().size(); ++i) {
+                context.writer().print(", ");
+                context.emit(invocation.getArguments().get(i));
+            }
+        }
+        context.writer().print(")");
+    }
+}

core/src/main/java/org/teavm/backend/c/util/GCVisualizer.java

@@ -0,0 +1,185 @@
+/*
+ *  Copyright 2019 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.c.util;
+
+import java.awt.image.BufferedImage;
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.List;
+import javax.imageio.ImageIO;
+
+public final class GCVisualizer {
+    private static final int WIDTH = 1024;
+    private static final int LINE_HEIGHT = 4;
+    private static final int GAP_SIZE = 1;
+    private static final int GC_GAP_SIZE = 3;
+
+    private GCVisualizer() {
+    }
+
+    public static void main(String[] args) throws IOException {
+        if (args.length != 2) {
+            System.err.println("Two arguments (input, ouput) expected");
+            System.exit(1);
+        }
+
+        List<Line> lines = readData(args[0]);
+        BufferedImage bitmap = createBitmap(lines);
+        writeBitmap(bitmap, args[1]);
+    }
+
+    private static List<Line> readData(String fileName) throws IOException {
+        List<Line> lines = new ArrayList<>();
+        try (BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(fileName),
+                StandardCharsets.UTF_8))) {
+            while (true) {
+                String fileLine = reader.readLine();
+                if (fileLine == null) {
+                    break;
+                }
+
+                int charIndex = fileLine.indexOf(':');
+                if (charIndex < 0) {
+                    continue;
+                }
+
+                String kind = fileLine.substring(0, charIndex);
+                if (kind.equals("start") || lines.isEmpty()) {
+                    lines.add(new Line());
+                }
+                Line line = lines.get(lines.size() - 1);
+
+                int[] array;
+                switch (kind) {
+                    case "start":
+                        array = line.start;
+                        break;
+                    case "sweep":
+                        array = line.sweep;
+                        break;
+                    case "defrag":
+                        array = line.defrag;
+                        break;
+                    default:
+                        continue;
+                }
+
+                charIndex = fileLine.indexOf(' ', charIndex);
+                if (charIndex < 0) {
+                    continue;
+                }
+                charIndex++;
+
+                for (int i = 0; i < array.length; ++i) {
+                    int next = fileLine.indexOf(' ', charIndex);
+                    if (next < 0) {
+                        next = fileLine.length();
+                    }
+
+                    try {
+                        array[i] = Integer.parseInt(fileLine.substring(charIndex, next));
+                    } catch (NumberFormatException e) {
+                        // do nothing
+                    }
+
+                    if (next == fileLine.length()) {
+                        break;
+                    }
+                    charIndex = next + 1;
+                }
+            }
+        }
+
+        return lines;
+    }
+
+    private static BufferedImage createBitmap(List<Line> lines) {
+        int height = lines.size() * (3 * (GAP_SIZE + LINE_HEIGHT) + GC_GAP_SIZE);
+        int[] data = new int[WIDTH * height];
+
+        int offset = 0;
+        for (Line line : lines) {
+            offset = renderComponent(data, line.start, offset, 0, 0, 255);
+            offset = renderComponent(data, line.sweep, offset, 0, 255, 0);
+            offset = renderComponent(data, line.defrag, offset, 255, 0, 0);
+            renderLine(data, offset, GC_GAP_SIZE, 0, 0, 0);
+            offset += WIDTH * GC_GAP_SIZE;
+        }
+
+        BufferedImage image = new BufferedImage(WIDTH, height, BufferedImage.TYPE_INT_ARGB);
+        image.setRGB(0, 0, WIDTH, height, data, 0, WIDTH);
+        return image;
+    }
+
+    private static int renderComponent(int[] data, int[] array, int offset, int r, int g, int b) {
+        renderArray(data, array, offset, r, g, b);
+        offset += LINE_HEIGHT * WIDTH;
+        renderLine(data, offset, GAP_SIZE, 0, 0, 0);
+        offset += GAP_SIZE * WIDTH;
+        return offset;
+    }
+
+    private static void renderArray(int[] data, int[] array, int offset, int r, int g, int b) {
+        for (int i = 0; i < WIDTH; ++i) {
+            int start = array.length * i / WIDTH;
+            int end = array.length * (i + 1) / WIDTH;
+            int total = 0;
+            for (int j = start; j < end; ++j) {
+                total += array[j];
+            }
+            double rate = total / (4096.0 * (end - start));
+            int pixelR = makeColorComponent(r, rate);
+            int pixelG = makeColorComponent(g, rate);
+            int pixelB = makeColorComponent(b, rate);
+
+            int pixelOffset = offset;
+            int pixel = (255 << 24) | ((pixelR & 255) << 16) | ((pixelG & 255) << 8) | (pixelB & 255);
+            for (int j = 0; j < LINE_HEIGHT; ++j) {
+                data[pixelOffset] = pixel;
+                pixelOffset += WIDTH;
+            }
+            offset++;
+        }
+    }
+
+    private static void renderLine(int[] data, int offset, int height, int r, int g, int b) {
+        int count = height * WIDTH;
+        int pixel = (255 << 24) | ((r & 255) << 16) | ((g & 255) << 8) | (b & 255);
+        for (int i = 0; i < count; ++i) {
+            data[offset++] = pixel;
+        }
+    }
+
+    private static int makeColorComponent(int c, double rate) {
+        int r = (int) (c * rate + 255 * (1 - rate));
+        return Math.min(Math.max(r, 0), 255);
+    }
+
+    private static void writeBitmap(BufferedImage image, String fileName) throws IOException {
+        ImageIO.write(image, "png", new File(fileName));
+    }
+
+    static class Line {
+        int[] start = new int[4096];
+        int[] sweep = new int[4096];
+        int[] defrag = new int[4096];
+    }
+}

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

@@ -52,6 +52,7 @@ import org.teavm.backend.wasm.intrinsics.FunctionIntrinsic;
 import org.teavm.backend.wasm.intrinsics.GCIntrinsic;
 import org.teavm.backend.wasm.intrinsics.IntegerIntrinsic;
 import org.teavm.backend.wasm.intrinsics.LongIntrinsic;
+import org.teavm.backend.wasm.intrinsics.MemoryTraceIntrinsic;
 import org.teavm.backend.wasm.intrinsics.MutatorIntrinsic;
 import org.teavm.backend.wasm.intrinsics.ObjectIntrinsic;
 import org.teavm.backend.wasm.intrinsics.PlatformClassIntrinsic;
@@ -355,6 +356,7 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
         context.addIntrinsic(new ObjectIntrinsic());
         context.addIntrinsic(new ConsoleIntrinsic());
         context.addGenerator(new ArrayGenerator());
+        context.addIntrinsic(new MemoryTraceIntrinsic());
 
         IntrinsicFactoryContext intrinsicFactoryContext = new IntrinsicFactoryContext();
         for (WasmIntrinsicFactory additionalIntrinsicFactory : additionalIntrinsics) {

core/src/main/java/org/teavm/backend/wasm/intrinsics/MemoryTraceIntrinsic.java

@@ -0,0 +1,35 @@
+/*
+ *  Copyright 2019 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.intrinsics;
+
+import org.teavm.ast.InvocationExpr;
+import org.teavm.backend.wasm.model.expression.WasmDrop;
+import org.teavm.backend.wasm.model.expression.WasmExpression;
+import org.teavm.backend.wasm.model.expression.WasmInt32Constant;
+import org.teavm.model.MethodReference;
+import org.teavm.runtime.MemoryTrace;
+
+public class MemoryTraceIntrinsic implements WasmIntrinsic {
+    @Override
+    public boolean isApplicable(MethodReference methodReference) {
+        return methodReference.getClassName().equals(MemoryTrace.class.getName());
+    }
+
+    @Override
+    public WasmExpression apply(InvocationExpr invocation, WasmIntrinsicManager manager) {
+        return new WasmDrop(new WasmInt32Constant(0));
+    }
+}

core/src/main/java/org/teavm/model/lowlevel/Characteristics.java

@@ -17,6 +17,7 @@ package org.teavm.model.lowlevel;
 
 import com.carrotsearch.hppc.ObjectByteHashMap;
 import com.carrotsearch.hppc.ObjectByteMap;
+import org.teavm.interop.Address;
 import org.teavm.interop.Function;
 import org.teavm.interop.StaticInit;
 import org.teavm.interop.Structure;
@@ -83,6 +84,10 @@ public class Characteristics {
         return result != 0;
     }
 
+    public boolean isManaged(String className) {
+        return !isStructure(className) && !isFunction(className) && !className.equals(Address.class.getName());
+    }
+
     public boolean isManaged(MethodReference methodReference) {
         byte result = isManaged.getOrDefault(methodReference, (byte) -1);
         if (result < 0) {

core/src/main/java/org/teavm/runtime/ExceptionHandling.java

@@ -132,7 +132,6 @@ public final class ExceptionHandling {
         return size + 1;
     }
 
-    @Unmanaged
     public static void fillStackTrace(StackTraceElement[] target) {
         Address stackFrame = ShadowStack.getStackTop();
         int index = 0;

core/src/main/java/org/teavm/runtime/GC.java

@@ -34,7 +34,7 @@ public final class GC {
     static int freeMemory = (int) availableBytes();
     static RuntimeReference firstWeakReference;
 
-    static RelocationBlock lastRelocationTarget;
+    static RelocationBlock lastRelocationBlock;
 
     static native Address gcStorageAddress();
 
@@ -65,76 +65,72 @@ public final class GC {
         currentChunkPointer = gcStorageAddress().toStructure();
         currentChunkPointer.value = currentChunk;
         freeChunks = 1;
-        getAvailableChunkIfPossible(0);
     }
 
     public static RuntimeObject alloc(int size) {
         FreeChunk current = currentChunk;
         Address next = current.toAddress().add(size);
         if (!next.add(Structure.sizeOf(FreeChunk.class)).isLessThan(currentChunkLimit)) {
-            getAvailableChunk(size);
+            getNextChunk(size);
             current = currentChunk;
-            next = currentChunk.toAddress().add(size);
+            next = current.toAddress().add(size);
         }
-        int freeSize = current.size;
+        currentChunk = next.toStructure();
-        freeSize -= size;
-        if (freeSize > 0) {
-            currentChunk = next.toStructure();
-            currentChunk.size = freeSize;
-        } else {
-            freeMemory -= size;
-            getAvailableChunkIfPossible(currentChunk.size + 1);
-        }
-        currentChunk.classReference = 0;
         freeMemory -= size;
+        MemoryTrace.allocate(current.toAddress(), size);
         return current.toAddress().toStructure();
     }
 
-    private static void getAvailableChunk(int size) {
+    private static void getNextChunk(int size) {
-        if (getAvailableChunkIfPossible(size)) {
+        if (getNextChunkIfPossible(size)) {
             return;
         }
         collectGarbage();
-        if (!getAvailableChunkIfPossible(size)) {
+        if (currentChunk.size < size && !getNextChunkIfPossible(size)) {
             ExceptionHandling.printStack();
             outOfMemory();
         }
     }
 
-    private static boolean getAvailableChunkIfPossible(int size) {
+    private static boolean getNextChunkIfPossible(int size) {
-        if (freeChunks == 0) {
-            return false;
-        }
         while (true) {
-            if (currentChunk.toAddress().add(size) == currentChunkLimit) {
+            if (currentChunk.toAddress().isLessThan(currentChunkLimit)) {
-                break;
+                currentChunk.classReference = 0;
-            }
+                currentChunk.size = (int) (currentChunkLimit.toLong() - currentChunk.toAddress().toLong());
-            if (currentChunk.toAddress().add(size + Structure.sizeOf(FreeChunk.class)).isLessThan(currentChunkLimit)) {
-                break;
             }
             if (--freeChunks == 0) {
                 return false;
             }
-            freeMemory -= currentChunk.size;
             currentChunkPointer = Structure.add(FreeChunkHolder.class, currentChunkPointer, 1);
             currentChunk = currentChunkPointer.value;
-            currentChunkLimit = currentChunk.toAddress().add(currentChunk.size);
+            if (currentChunk.size >= size) {
+                currentChunkLimit = currentChunk.toAddress().add(currentChunk.size);
+                break;
+            }
+            freeMemory -= currentChunk.size;
         }
         return true;
     }
 
     public static void collectGarbage() {
+        MemoryTrace.gcStarted();
         mark();
         processReferences();
         sweep();
+        MemoryTrace.sweepCompleted();
         defragment();
-        sortFreeChunks();
+        MemoryTrace.defragCompleted();
+        //sortFreeChunks();
         updateFreeMemory();
+        currentChunk = currentChunkPointer.value;
+        currentChunkLimit = currentChunk.toAddress().add(currentChunk.size);
     }
 
     private static void mark() {
+        MemoryTrace.initMark();
         firstWeakReference = null;
-        Allocator.fillZero(regionsAddress().toAddress(), regionMaxCount() * Structure.sizeOf(Region.class));
+        int regionsCount = (int) ((availableBytes() - 1) / regionSize()) + 1;
+        Allocator.fillZero(regionsAddress().toAddress(), regionsCount * Structure.sizeOf(Region.class));
 
         Address staticRoots = Mutator.getStaticGCRoots();
         int staticCount = staticRoots.getInt();
@@ -172,6 +168,7 @@ public final class GC {
                 continue;
             }
             object.classReference |= RuntimeObject.GC_MARKED;
+            MemoryTrace.mark(object.toAddress());
 
             long offset = object.toAddress().toLong() - heapAddress().toLong();
             Region region = Structure.add(Region.class, regionsAddress(), (int) (offset /  regionSize()));
@@ -211,9 +208,9 @@ public final class GC {
 
     private static void markWeakReference(RuntimeReference object) {
         if (object.queue != null) {
-            mark(object.queue);
+            enqueueMark(object.queue);
             if (object.next != null && object.object != null) {
-                mark(object.object);
+                enqueueMark(object);
             }
         }
         if (object.next == null && object.object != null) {
@@ -225,7 +222,7 @@ public final class GC {
     private static void markReferenceQueue(RuntimeReferenceQueue object) {
         RuntimeReference reference = object.first;
         while (reference != null) {
-            mark(reference);
+            enqueueMark(object);
             reference = reference.next;
         }
     }
@@ -238,9 +235,7 @@ public final class GC {
                 layout = layout.add(2);
                 int fieldOffset = layout.getShort();
                 RuntimeObject reference = object.toAddress().add(fieldOffset).getAddress().toStructure();
-                if (reference != null && !isMarked(reference)) {
+                enqueueMark(reference);
-                    MarkQueue.enqueue(reference);
-                }
             }
         }
     }
@@ -252,13 +247,17 @@ public final class GC {
         Address base = Address.align(array.toAddress().add(RuntimeArray.class, 1), Address.sizeOf());
         for (int i = 0; i < array.size; ++i) {
             RuntimeObject reference = base.getAddress().toStructure();
-            if (reference != null && !isMarked(reference)) {
+            enqueueMark(reference);
-                MarkQueue.enqueue(reference);
-            }
             base = base.add(Address.sizeOf());
         }
     }
 
+    private static void enqueueMark(RuntimeObject object) {
+        if (object != null && !isMarked(object)) {
+            MarkQueue.enqueue(object);
+        }
+    }
+
     private static void processReferences() {
         RuntimeReference reference = firstWeakReference;
         while (reference != null) {
@@ -297,16 +296,23 @@ public final class GC {
             if (!object.toAddress().isLessThan(currentRegionEnd)) {
                 int currentRegionIndex = (int) ((object.toAddress().toLong() - heapAddress().toLong()) / regionSize());
                 Region currentRegion = Structure.add(Region.class, regionsAddress(), currentRegionIndex);
-                while (currentRegion.start == 0) {
+                if (currentRegion.start == 0) {
-                    if (++currentRegionIndex == regionsCount) {
+                    if (lastFreeSpace == null) {
-                        object = limit.toStructure();
+                        lastFreeSpace = object;
-                        break loop;
                     }
-                    currentRegion = Structure.add(Region.class, regionsAddress(), currentRegionIndex);
+
+                    do {
+                        if (++currentRegionIndex == regionsCount) {
+                            object = limit.toStructure();
+                            break loop;
+                        }
+                        currentRegion = Structure.add(Region.class, regionsAddress(), currentRegionIndex);
+                    } while (currentRegion.start == 0);
+
+                    Address newRegionStart = heapAddress().add(currentRegionIndex * regionSize());
+                    object = newRegionStart.add(currentRegion.start - 1).toStructure();
+                    currentRegionEnd = newRegionStart.add(regionSize());
                 }
-                Address newRegionStart = heapAddress().add(currentRegionIndex * regionSize());
-                object = newRegionStart.add(currentRegion.start - 1).toStructure();
-                currentRegionEnd = newRegionStart.add(regionSize());
             }
 
             int tag = object.classReference;
@@ -329,6 +335,7 @@ public final class GC {
                 if (lastFreeSpace != null) {
                     lastFreeSpace.classReference = 0;
                     lastFreeSpace.size = (int) (object.toAddress().toLong() - lastFreeSpace.toAddress().toLong());
+                    MemoryTrace.free(lastFreeSpace.toAddress(), lastFreeSpace.size);
                     freeChunkPtr.value = lastFreeSpace;
                     freeChunkPtr = Structure.add(FreeChunkHolder.class, freeChunkPtr, 1);
                     freeChunks++;
@@ -348,6 +355,7 @@ public final class GC {
             int freeSize = (int) (object.toAddress().toLong() - lastFreeSpace.toAddress().toLong());
             lastFreeSpace.classReference = 0;
             lastFreeSpace.size = freeSize;
+            MemoryTrace.free(lastFreeSpace.toAddress(), lastFreeSpace.size);
             freeChunkPtr.value = lastFreeSpace;
             freeChunkPtr = Structure.add(FreeChunkHolder.class, freeChunkPtr, 1);
             freeChunks++;
@@ -381,8 +389,8 @@ public final class GC {
                 RuntimeObject obj = stackRootsPtr.getAddress().toStructure();
                 if (!obj.toAddress().isLessThan(relocationThreshold)) {
                     obj.classReference |= RuntimeObject.GC_MARKED;
-                    stackRootsPtr = stackRootsPtr.add(Address.sizeOf());
                 }
+                stackRootsPtr = stackRootsPtr.add(Address.sizeOf());
             }
         }
     }
@@ -397,12 +405,14 @@ public final class GC {
         FreeChunk freeChunk = currentChunkPointer.value;
         FreeChunk object = freeChunk.toAddress().add(freeChunk.size).toStructure();
 
-        RelocationBlock relocationTarget = Structure.add(FreeChunkHolder.class, currentChunkPointer, freeChunks)
+        RelocationBlock relocationBlock = Structure.add(FreeChunkHolder.class, currentChunkPointer, freeChunks)
                 .toAddress().toStructure();
-        relocationTarget.start = freeChunk.toAddress();
+        Address relocationTarget = freeChunk.toAddress();
-        relocationTarget.current = relocationTarget.start;
+        relocationBlock.start = relocationTarget;
-        relocationTarget.end = limit;
+        relocationBlock.end = limit;
-        RelocationBlock lastRelocationTarget = relocationTarget;
+        relocationBlock.count = 0;
+        RelocationBlock lastRelocationBlock = relocationBlock;
+        int countInCurrentRelocationBlock = 0;
 
         Address relocations = Structure.add(FreeChunk.class, freeChunk, 1).toAddress();
         Address relocationsLimit = freeChunk.toAddress().add(freeChunk.size);
@@ -411,36 +421,43 @@ public final class GC {
         objects: while (object.toAddress().isLessThan(limit)) {
             int size = objectSize(object);
             if (object.classReference != 0) {
-                if ((object.classReference & RuntimeObject.GC_MARKED) != 0
+                Address nextRelocationTarget = null;
-                        || !relocationTarget.start.isLessThan(object.toAddress())) {
+                boolean shouldRelocateObject = (object.classReference & RuntimeObject.GC_MARKED) == 0;
-                    if (!lastWasLocked) {
+                if (shouldRelocateObject) {
-                        lastRelocationTarget.end = object.toAddress();
-                        lastRelocationTarget = Structure.add(RelocationBlock.class, lastRelocationTarget, 1);
-                        lastRelocationTarget.end = limit;
-                        lastWasLocked = true;
-                    }
-                    lastRelocationTarget.start = object.toAddress().add(size);
-                    lastRelocationTarget.current = lastRelocationTarget.start;
-                    object.classReference &= ~RuntimeObject.GC_MARKED;
-                } else {
-                    lastRelocationTarget.end = object.toAddress().add(size);
-                    lastWasLocked = false;
-
-                    Address nextRelocationTarget;
                     while (true) {
-                        nextRelocationTarget = relocationTarget.current.add(size);
+                        nextRelocationTarget = relocationTarget.add(size);
-                        if (nextRelocationTarget.isLessThan(relocationTarget.end)) {
+                        if (!relocationBlock.end.isLessThan(nextRelocationTarget)) {
                             break;
                         }
 
-                        relocationTarget = Structure.add(RelocationBlock.class, relocationTarget, 1);
+                        RelocationBlock nextRelocationBlock = Structure.add(RelocationBlock.class, relocationBlock, 1);
-                        if (lastRelocationTarget.toAddress().isLessThan(relocationTarget.toAddress())) {
+                        if (nextRelocationBlock.start == object.toAddress()) {
-                            break objects;
+                            shouldRelocateObject = false;
+                            break;
                         }
+                        relocationBlock.count = countInCurrentRelocationBlock;
+                        countInCurrentRelocationBlock = 0;
+                        relocationBlock = nextRelocationBlock;
+                        relocationTarget = relocationBlock.start;
                     }
+                }
+
+                if (!shouldRelocateObject) {
+                    if (!lastWasLocked) {
+                        lastRelocationBlock.end = object.toAddress();
+                        lastRelocationBlock = Structure.add(RelocationBlock.class, lastRelocationBlock, 1);
+                        lastRelocationBlock.end = limit;
+                        lastWasLocked = true;
+                    }
+                    lastRelocationBlock.start = object.toAddress().add(size);
+                    lastRelocationBlock.count = 0;
+                    object.classReference &= ~RuntimeObject.GC_MARKED;
+                } else {
+                    lastWasLocked = false;
 
                     while (!relocations.add(Structure.sizeOf(Relocation.class)).isLessThan(relocationsLimit)) {
                         if (--freeChunks == 0) {
+                            lastRelocationBlock.end = object.toAddress();
                             break objects;
                         }
                         freeChunkPointer = Structure.add(FreeChunkHolder.class, freeChunkPointer, 1);
@@ -452,35 +469,37 @@ public final class GC {
                     Relocation relocation = relocations.toStructure();
                     relocation.classBackup = object.classReference;
                     relocation.sizeBackup = object.size;
-                    relocation.newAddress = relocationTarget.current;
+                    relocation.newAddress = relocationTarget;
+                    countInCurrentRelocationBlock++;
                     relocations = relocations.add(Structure.sizeOf(Relocation.class));
 
                     long targetAddress = relocation.toAddress().toLong();
                     object.classReference = (int) (targetAddress >>> 33) | RuntimeObject.GC_MARKED;
                     object.size = (int) (targetAddress >> 1);
-                    relocationTarget.current = nextRelocationTarget;
+                    relocationTarget = nextRelocationTarget;
                 }
             } else {
                 lastWasLocked = false;
-                lastRelocationTarget.end = object.toAddress().add(object.size);
             }
             object = object.toAddress().add(size).toStructure();
         }
 
+        relocationBlock.count = countInCurrentRelocationBlock;
+
         while (object.toAddress().isLessThan(limit)) {
             int size = objectSize(object);
             if (object.classReference != 0) {
                 object.classReference &= ~RuntimeObject.GC_MARKED;
             } else {
-                lastRelocationTarget = Structure.add(RelocationBlock.class, lastRelocationTarget, 1);
+                lastRelocationBlock = Structure.add(RelocationBlock.class, lastRelocationBlock, 1);
-                lastRelocationTarget.start = object.toAddress();
+                lastRelocationBlock.start = object.toAddress();
-                lastRelocationTarget.current = lastRelocationTarget.start;
+                lastRelocationBlock.count = 0;
-                lastRelocationTarget.end = lastRelocationTarget.start.add(size);
+                lastRelocationBlock.end = lastRelocationBlock.start.add(size);
             }
             object = object.toAddress().add(size).toStructure();
         }
 
-        GC.lastRelocationTarget = lastRelocationTarget;
+        GC.lastRelocationBlock = lastRelocationBlock;
     }
 
     private static void updatePointersFromStaticRoots() {
@@ -633,47 +652,44 @@ public final class GC {
         FreeChunk freeChunk = currentChunkPointer.value;
         FreeChunk object = freeChunk.toAddress().add(freeChunk.size).toStructure();
 
-        RelocationBlock relocationTarget = Structure.add(FreeChunkHolder.class, currentChunkPointer, freeChunks)
+        RelocationBlock relocationBlock = Structure.add(FreeChunkHolder.class, currentChunkPointer, freeChunks)
                 .toAddress().toStructure();
-        Address currentTarget = relocationTarget.start;
+        int countInRelocationBlock = relocationBlock.count;
+        Address relocationTarget = relocationBlock.start;
 
         Address blockTarget = null;
         Address blockSource = null;
         int blockSize = 0;
 
-        objects: while (object.toAddress().isLessThan(limit)) {
+        while (object.toAddress().isLessThan(limit)) {
             int size = objectSize(object);
             if ((object.classReference & RuntimeObject.GC_MARKED) != 0) {
                 object.classReference &= ~RuntimeObject.GC_MARKED;
 
-                Address nextRelocationTarget;
+                while (countInRelocationBlock == 0) {
-                while (true) {
-                    nextRelocationTarget = currentTarget.add(size);
-                    if (nextRelocationTarget.isLessThan(relocationTarget.end)) {
-                        break;
-                    }
-
                     if (blockSize != 0) {
                         Allocator.moveMemoryBlock(blockSource, blockTarget, blockSize);
+                        MemoryTrace.move(blockSource, blockTarget, blockSize);
                         blockSource = null;
                         blockSize = 0;
                     }
 
-                    relocationTarget = Structure.add(RelocationBlock.class, relocationTarget, 1);
+                    relocationBlock.start = relocationTarget;
-                    if (lastRelocationTarget.toAddress().isLessThan(relocationTarget.toAddress())) {
+                    relocationBlock = Structure.add(RelocationBlock.class, relocationBlock, 1);
-                        break objects;
+                    countInRelocationBlock = relocationBlock.count;
-                    }
+                    relocationTarget = relocationBlock.start;
-                    currentTarget = relocationTarget.start;
                 }
 
                 if (blockSource == null) {
                     blockSource = object.toAddress();
-                    blockTarget = currentTarget;
+                    blockTarget = relocationTarget;
                 }
-                currentTarget = nextRelocationTarget;
+                relocationTarget = relocationTarget.add(size);
                 blockSize += size;
+                --countInRelocationBlock;
             } else if (blockSource != null) {
                 Allocator.moveMemoryBlock(blockSource, blockTarget, blockSize);
+                MemoryTrace.move(blockSource, blockTarget, blockSize);
                 blockSource = null;
                 blockSize = 0;
             }
@@ -681,8 +697,10 @@ public final class GC {
             object = object.toAddress().add(size).toStructure();
         }
 
+        relocationBlock.start = relocationTarget;
         if (blockSource != null) {
             Allocator.moveMemoryBlock(blockSource, blockTarget, blockSize);
+            MemoryTrace.move(blockSource, blockTarget, blockSize);
         }
     }
 
@@ -691,16 +709,16 @@ public final class GC {
         RelocationBlock relocationBlock = Structure.add(FreeChunkHolder.class, currentChunkPointer, freeChunks)
                 .toAddress().toStructure();
         freeChunks = 0;
-        while (!lastRelocationTarget.toAddress().isLessThan(relocationBlock.toAddress())) {
+        while (!lastRelocationBlock.toAddress().isLessThan(relocationBlock.toAddress())) {
-            if (!relocationBlock.current.isLessThan(relocationBlock.end)) {
+            if (relocationBlock.start.isLessThan(relocationBlock.end)) {
-                continue;
+                FreeChunk freeChunk = relocationBlock.start.toStructure();
+                freeChunk.size = (int) (relocationBlock.end.toLong() - relocationBlock.start.toLong());
+                freeChunk.classReference = 0;
+                MemoryTrace.assertFree(freeChunk.toAddress(), freeChunk.size);
+                freeChunkPointer.value = freeChunk;
+                freeChunkPointer = Structure.add(FreeChunkHolder.class, freeChunkPointer, 1);
+                freeChunks++;
             }
-            FreeChunk freeChunk = relocationBlock.current.toStructure();
-            freeChunk.size = (int) (relocationBlock.end.toLong() - relocationBlock.current.toLong());
-            freeChunk.classReference = 0;
-            freeChunkPointer.value = freeChunk;
-            freeChunkPointer = Structure.add(FreeChunkHolder.class, freeChunkPointer, 1);
-            freeChunks++;
             relocationBlock = Structure.add(RelocationBlock.class, relocationBlock, 1);
         }
     }
@@ -708,8 +726,6 @@ public final class GC {
     private static void sortFreeChunks() {
         currentChunkPointer = gcStorageAddress().toStructure();
         sortFreeChunks(0, freeChunks - 1);
-        currentChunk = currentChunkPointer.value;
-        currentChunkLimit = currentChunk.toAddress().add(currentChunk.size);
     }
 
     private static void updateFreeMemory() {

core/src/main/java/org/teavm/runtime/MemoryTrace.java

@@ -0,0 +1,43 @@
+/*
+ *  Copyright 2019 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.runtime;
+
+import org.teavm.interop.Address;
+
+public class MemoryTrace {
+    private MemoryTrace() {
+    }
+
+    public static native void allocate(Address address, int size);
+
+    public static native void free(Address address, int size);
+
+    public static native void assertFree(Address address, int size);
+
+    public static native void checkIsFree(Address address, int size);
+
+    public static native void initMark();
+
+    public static native void mark(Address address);
+
+    public static native void move(Address from, Address to, int size);
+
+    public static native void gcStarted();
+
+    public static native void sweepCompleted();
+
+    public static native void defragCompleted();
+}

core/src/main/java/org/teavm/runtime/RelocationBlock.java

@@ -19,7 +19,7 @@ import org.teavm.interop.Address;
 import org.teavm.interop.Structure;
 
 class RelocationBlock extends Structure {
+    int count;
     Address start;
-    Address current;
     Address end;
 }

core/src/main/resources/org/teavm/backend/c/runtime.c

@@ -23,6 +23,10 @@
 #endif
 
 void* teavm_gc_heapAddress = NULL;
+#ifdef TEAVM_MEMORY_TRACE
+    uint8_t* teavm_gc_heapMap = NULL;
+    uint8_t* teavm_gc_markMap = NULL;
+#endif
 
 TeaVM_StackFrame* teavm_stackTop = NULL;
 
@@ -107,37 +111,13 @@ void teavm_beforeInit() {
 }
 
 #ifdef __GNUC__
-void teavm_initHeap(int64_t heapSize) {
-    long workSize = (long) (heapSize / 16);
-    long regionsSize = (long) (heapSize / teavm_gc_regionSize);
 
-    long pageSize = sysconf(_SC_PAGE_SIZE);
+static void* teavm_virtualAlloc(int size) {
-    int heapPages = (int) ((heapSize + pageSize + 1) / pageSize * pageSize);
+    return mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
-    int workPages = (int) ((workSize + pageSize + 1) / pageSize * pageSize);
+}
-    int regionsPages = (int) ((regionsSize * 2 + pageSize + 1) / pageSize * pageSize);
 
-    teavm_gc_heapAddress = mmap(
+static long teavm_pageSize() {
-            NULL,
+    return sysconf(_SC_PAGE_SIZE);
-            heapPages,
-            PROT_READ | PROT_WRITE,
-            MAP_PRIVATE | MAP_ANONYMOUS,
-            0, 0);
-    teavm_gc_gcStorageAddress = mmap(
-            NULL,
-            workPages,
-            PROT_READ | PROT_WRITE,
-            MAP_PRIVATE | MAP_ANONYMOUS,
-            0, 0);
-    teavm_gc_regionsAddress = mmap(
-            NULL,
-            regionsPages,
-            PROT_READ | PROT_WRITE,
-            MAP_PRIVATE | MAP_ANONYMOUS,
-            0, 0);
-
-    teavm_gc_gcStorageSize = (int) workSize;
-    teavm_gc_regionMaxCount = regionsSize;
-    teavm_gc_availableBytes = heapSize;
 }
 
 int64_t teavm_currentTimeMillis() {
@@ -173,24 +153,10 @@ static void* teavm_virtualAlloc(int size) {
     #endif
 }
 
-void teavm_initHeap(int64_t heapSize) {
+static long teavm_pageSize() {
-    long workSize = (long) (heapSize / 16);
-    long regionsSize = (long) (heapSize / teavm_gc_regionSize);
-
     SYSTEM_INFO systemInfo;
     GetSystemInfo(&systemInfo);
-    long pageSize = systemInfo.dwPageSize;
+    return systemInfo.dwPageSize;
-    int heapPages = (int) ((heapSize + pageSize + 1) / pageSize * pageSize);
-    int workPages = (int) ((workSize + pageSize + 1) / pageSize * pageSize);
-    int regionsPages = (int) ((regionsSize * 2 + pageSize + 1) / pageSize * pageSize);
-
-    teavm_gc_heapAddress = teavm_virtualAlloc(heapPages);
-    teavm_gc_gcStorageAddress = teavm_virtualAlloc(workPages);
-    teavm_gc_regionsAddress = teavm_virtualAlloc(regionsPages);
-
-    teavm_gc_gcStorageSize = (int) workSize;
-    teavm_gc_regionMaxCount = regionsSize;
-    teavm_gc_availableBytes = heapSize;
 }
 
 int64_t teavm_currentTimeMillis() {
@@ -210,6 +176,31 @@ int64_t teavm_currentTimeNano() {
 }
 #endif
 
+static int teavm_pageCount(int64_t size, int64_t pageSize) {
+    return (int) ((size + pageSize + 1) / pageSize * pageSize);
+}
+
+void teavm_initHeap(int64_t heapSize) {
+    long workSize = (long) (heapSize / 16);
+    long regionsSize = (long) (heapSize / teavm_gc_regionSize) + 1;
+    long pageSize = teavm_pageSize();
+
+    teavm_gc_heapAddress = teavm_virtualAlloc(teavm_pageCount(heapSize, pageSize));
+    teavm_gc_gcStorageAddress = teavm_virtualAlloc(teavm_pageCount(workSize, pageSize));
+    teavm_gc_regionsAddress = teavm_virtualAlloc(teavm_pageCount(regionsSize * 2, pageSize));
+
+    #ifdef TEAVM_MEMORY_TRACE
+        int64_t heapMapSize = heapSize / sizeof(void*);
+        teavm_gc_heapMap = teavm_virtualAlloc(teavm_pageCount(heapMapSize, pageSize));
+        memset(teavm_gc_heapMap, 0, heapMapSize);
+        teavm_gc_markMap = teavm_virtualAlloc(teavm_pageCount(heapMapSize, pageSize));
+    #endif
+
+    teavm_gc_gcStorageSize = (int) workSize;
+    teavm_gc_regionMaxCount = regionsSize;
+    teavm_gc_availableBytes = heapSize;
+}
+
 #ifdef _MSC_VER
 #undef gmtime_r
 #undef localtime_r
@@ -606,3 +597,263 @@ void teavm_logchar(int32_t c) {
 	OutputDebugStringW(buffer);
 }
 #endif
+
+#ifdef TEAVM_MEMORY_TRACE
+
+void teavm_gc_assertSize(int32_t size) {
+    if (size % sizeof(void*) != 0) {
+        abort();
+    }
+}
+
+#endif
+
+void teavm_gc_allocate(void* address, int32_t size) {
+    #ifdef TEAVM_MEMORY_TRACE
+        teavm_gc_assertAddress(address);
+        teavm_gc_assertSize(size);
+
+        size /= sizeof(void*);
+        uint8_t* map = teavm_gc_heapMap + (((char*) address - (char*) teavm_gc_heapAddress) / sizeof(void*));
+
+        if (*map != 0) {
+            fprintf(stderr, "[GC] trying allocate at memory in use at: %d\n",
+                    (int) ((char*) address - (char*) teavm_gc_heapAddress));
+            abort();
+        }
+        *map++ = 1;
+
+        for (int32_t i = 1; i < size; ++i) {
+            if (*map != 0) {
+                fprintf(stderr, "[GC] trying allocate at memory in use at: %d\n",
+                        (int) ((char*) address - (char*) teavm_gc_heapAddress));
+                abort();
+            }
+            *map++ = 2;
+        }
+    #endif
+}
+
+void teavm_gc_free(void* address, int32_t size) {
+    #ifdef TEAVM_MEMORY_TRACE
+        teavm_gc_assertAddress(address);
+        teavm_gc_assertSize(size);
+
+        int32_t offset = (int32_t) (((char*) address - (char*) teavm_gc_heapAddress) / sizeof(void*));
+        uint8_t* markMap = teavm_gc_markMap + offset;
+        size /= sizeof(void*);
+        for (int32_t i = 0; i < size; ++i) {
+            if (markMap[i] != 0) {
+                fprintf(stderr, "[GC] trying to release reachable object at: %d\n",
+                        (int) ((char*) address - (char*) teavm_gc_heapAddress));
+                abort();
+            }
+        }
+
+        uint8_t* map = teavm_gc_heapMap + offset;
+        memset(map, 0, size);
+    #endif
+}
+
+void teavm_gc_assertFree(void* address, int32_t size) {
+    #ifdef TEAVM_MEMORY_TRACE
+        teavm_gc_assertAddress(address);
+        teavm_gc_assertSize(size);
+
+        int32_t offset = (int32_t) (((char*) address - (char*) teavm_gc_heapAddress) / sizeof(void*));
+        uint8_t* map = teavm_gc_heapMap + offset;
+        size /= sizeof(void*);
+        for (int32_t i = 0; i < size; ++i) {
+            if (map[i] != 0) {
+                fprintf(stderr, "[GC] memory supposed to be free at: %d\n",
+                        (int) ((char*) address - (char*) teavm_gc_heapAddress));
+                abort();
+            }
+        }
+    #endif
+}
+
+void teavm_gc_initMark() {
+    #ifdef TEAVM_MEMORY_TRACE
+        memset(teavm_gc_markMap, 0, teavm_gc_availableBytes / sizeof(void*));
+    #endif
+}
+
+#ifdef TEAVM_MEMORY_TRACE
+int32_t teavm_gc_objectSize(void* address) {
+    TeaVM_Class* cls = TEAVM_CLASS_OF(address);
+    if (cls->itemType == NULL) {
+        return cls->size;
+    }
+
+    int32_t itemSize = cls->itemType->flags & 2 ? cls->itemType->size : sizeof(void*);
+    TeaVM_Array* array = (TeaVM_Array*) address;
+    char* size = TEAVM_ALIGN((void*) sizeof(TeaVM_Array), itemSize);
+    size += array->size * itemSize;
+    size = TEAVM_ALIGN(size, sizeof(void*));
+    return (int32_t) (intptr_t) size;
+}
+#endif
+
+void teavm_gc_mark(void* address) {
+    #ifdef TEAVM_MEMORY_TRACE
+        if (address < teavm_gc_heapAddress
+                || (char*) address >= (char*) teavm_gc_heapAddress + teavm_gc_availableBytes) {
+            return;
+        }
+
+        teavm_gc_assertAddress(address);
+
+        int32_t offset = (int32_t) (((char*) address - (char*) teavm_gc_heapAddress) / sizeof(void*));
+        uint8_t* map = teavm_gc_heapMap + offset;
+        uint8_t* markMap = teavm_gc_markMap + offset;
+
+        int32_t size = teavm_gc_objectSize(address);
+        teavm_gc_assertSize(size);
+        size /= sizeof(void*);
+
+        if (*map++ != 1 || *markMap != 0) {
+            fprintf(stderr, "[GC] assertion failed marking object at: %d\n", (int) ((char*) address - (char*) teavm_gc_heapAddress));
+            abort();
+        }
+        *markMap++ = 1;
+
+        for (int32_t i = 1; i < size; ++i) {
+            if (*map++ != 2 || *markMap != 0) {
+                abort();
+            }
+            *markMap++ = 1;
+        }
+    #endif
+}
+
+void teavm_gc_move(void* from, void* to, int32_t size) {
+    #ifdef TEAVM_MEMORY_TRACE
+        teavm_gc_assertAddress(from);
+        teavm_gc_assertAddress(to);
+        teavm_gc_assertSize(size);
+
+        uint8_t* mapFrom = teavm_gc_heapMap + (((char*) from - (char*) teavm_gc_heapAddress) / sizeof(void*));
+        uint8_t* mapTo = teavm_gc_heapMap + (((char*) to - (char*) teavm_gc_heapAddress) / sizeof(void*));
+        size /= sizeof(void*);
+
+        if (mapFrom > mapTo) {
+            for (int32_t i = 0; i < size; ++i) {
+                if (mapFrom[i] == 0 || mapTo[i] != 0) {
+                    fprintf(stderr, "[GC] assertion failed moving object from: %d to %d\n",
+                        (int) ((char*) from - (char*) teavm_gc_heapAddress), (int) ((char*) to - (char*) teavm_gc_heapAddress));
+                    abort();
+                }
+                mapTo[i] = mapFrom[i];
+                mapFrom[i] = 0;
+            }
+        } else {
+            for (int32_t i = size - 1; i >= 0; --i) {
+                if (mapFrom[i] == 0 || mapTo[i] != 0) {
+                    abort();
+                }
+                mapTo[i] = mapFrom[i];
+                mapFrom[i] = 0;
+            }
+        }
+    #endif
+}
+
+#ifdef TEAVM_MEMORY_TRACE
+    static FILE* teavm_gc_traceFile = NULL;
+
+    static void teavm_writeHeapMemory(char* name) {
+        #ifdef TEAVM_GC_LOG
+            if (teavm_gc_traceFile == NULL) {
+                teavm_gc_traceFile = fopen("teavm-gc-trace.txt", "w");
+            }
+            FILE* file = teavm_gc_traceFile;
+            fprintf(file, "%s:", name);
+
+            int32_t numbers = 4096;
+            int64_t mapSize = teavm_gc_availableBytes / sizeof(void*);
+            for (int i = 0; i < numbers; ++i) {
+                int64_t start = mapSize * i / numbers;
+                int64_t end = mapSize * (i + 1) / numbers;
+                int count = 0;
+                for (int j = start; j < end; ++j) {
+                    if (teavm_gc_heapMap[j] != 0) {
+                        count++;
+                    }
+                }
+                int rate = count * 4096 / (end - start);
+                fprintf(file, " %d", rate);
+            }
+            fprintf(file, "\n");
+            fflush(file);
+        #endif
+    }
+
+    void teavm_gc_checkHeapConsistency() {
+        TeaVM_Object* obj = teavm_gc_heapAddress;
+        while ((char*) obj < (char*) teavm_gc_heapAddress + teavm_gc_availableBytes) {
+            int32_t size;
+            if (obj->header == 0) {
+                size = obj->hash;
+                teavm_gc_assertFree(obj, size);
+            } else {
+                teavm_verify(obj);
+                TeaVM_Class* cls = TEAVM_CLASS_OF(obj);
+                if (cls->itemType != NULL) {
+                    if (!(cls->itemType->flags & 2)) {
+                        char* offset = NULL;
+                        offset += sizeof(TeaVM_Array);
+                        offset = TEAVM_ALIGN(offset, sizeof(void*));
+                        void** data = (void**)((char*)obj + (uintptr_t)offset);
+                        int32_t size = ((TeaVM_Array*)obj)->size;
+                        for (int32_t i = 0; i < size; ++i) {
+                            teavm_verify(data[i]);
+                        }
+                    }
+                } else {
+                    while (cls != NULL) {
+                        int32_t kind = (cls->flags >> 7) & 7;
+                        if (kind == 1) {
+
+                        } else if (kind == 2) {
+
+                        } else {
+                            int16_t* layout = cls->layout;
+                            if (layout != NULL) {
+                                int16_t size = *layout++;
+                                for (int32_t i = 0; i < size; ++i) {
+                                    void** ptr = (void**) ((char*) obj + *layout++);
+                                    teavm_verify(*ptr);
+                                }
+                            }
+                        }
+
+                        cls = cls->superclass;
+                    }
+                }
+                size = teavm_gc_objectSize(obj);
+            }
+            obj = (TeaVM_Object*) ((char*) obj + size);
+        }
+    }
+#endif
+
+void teavm_gc_gcStarted() {
+    #ifdef TEAVM_MEMORY_TRACE
+        teavm_writeHeapMemory("start");
+        teavm_gc_checkHeapConsistency();
+    #endif
+}
+
+void teavm_gc_sweepCompleted() {
+    #ifdef TEAVM_MEMORY_TRACE
+        teavm_writeHeapMemory("sweep");
+        teavm_gc_checkHeapConsistency();
+    #endif
+}
+
+void teavm_gc_defragCompleted() {
+    #ifdef TEAVM_MEMORY_TRACE
+        teavm_writeHeapMemory("defrag");
+    #endif
+}

core/src/main/resources/org/teavm/backend/c/runtime.h

@@ -75,13 +75,50 @@ typedef struct TeaVM_StackFrame {
 } TeaVM_StackFrame;
 
 extern void* teavm_gc_heapAddress;
-extern char *teavm_beforeClasses;
+extern void* teavm_gc_gcStorageAddress;
+extern int32_t teavm_gc_gcStorageSize;
+extern void* teavm_gc_regionsAddress;
+extern int32_t teavm_gc_regionSize;
+extern int32_t teavm_gc_regionMaxCount;
+extern int64_t teavm_gc_availableBytes;
+extern void*** teavm_gc_staticRoots;
+extern char* teavm_beforeClasses;
+
+#ifdef TEAVM_MEMORY_TRACE
+    extern uint8_t* teavm_gc_heapMap;
+    extern uint8_t* teavm_gc_markMap;
+#endif
 
 #define TEAVM_PACK_CLASS(cls) ((int32_t) ((uintptr_t) ((char*) (cls) - teavm_beforeClasses) >> 3))
 #define TEAVM_UNPACK_CLASS(cls) ((TeaVM_Class*) (teavm_beforeClasses + ((cls) << 3)))
 #define TEAVM_CLASS_OF(obj) (TEAVM_UNPACK_CLASS(((TeaVM_Object*) (obj))->header))
 #define TEAVM_AS(ptr, type) ((type*) (ptr))
 
+#ifdef TEAVM_MEMORY_TRACE
+    static inline void teavm_gc_assertAddress(void* address) {
+        if ((unsigned int) (uintptr_t) address % sizeof(void*) != 0) {
+            abort();
+        }
+    }
+
+    static inline void* teavm_verify(void* address) {
+        if (address >= teavm_gc_heapAddress
+                && (char*) address < (char*) teavm_gc_heapAddress + teavm_gc_availableBytes) {
+            teavm_gc_assertAddress(address);
+            uint8_t* map = teavm_gc_heapMap + (((char*) address - (char*) teavm_gc_heapAddress) / sizeof(void*));
+            if (*map != 1) {
+                abort();
+            }
+        }
+
+        return address;
+    }
+
+    #define TEAVM_VERIFY(ptr) teavm_verify(ptr)
+#else
+    #define TEAVM_VERIFY(ptr) ptr
+#endif
+
 #define TEAVM_VTABLE(obj, type) (TEAVM_AS(TEAVM_CLASS_OF(obj), type))
 #define TEAVM_METHOD(obj, type, method) (TEAVM_VTABLE(obj, type)->method)
 #define TEAVM_FIELD(ptr, type, name) (TEAVM_AS(ptr, type)->name)
@@ -181,14 +218,6 @@ static inline void* teavm_checkcast(void* obj, int32_t (*cls)(TeaVM_Class*)) {
 
 extern TeaVM_StackFrame* teavm_stackTop;
 
-extern void* teavm_gc_gcStorageAddress;
-extern int32_t teavm_gc_gcStorageSize;
-extern void* teavm_gc_regionsAddress;
-extern int32_t teavm_gc_regionSize;
-extern int32_t teavm_gc_regionMaxCount;
-extern int64_t teavm_gc_availableBytes;
-extern void*** teavm_gc_staticRoots;
-
 extern double teavm_rand();
 
 static inline float teavm_getNaN() {
@@ -434,4 +463,14 @@ inline static void* teavm_nullCheck(void* o) {
 #define TEAVM_JUMP_TO_FRAME(frame, id)
 #endif
 
-extern void* teavm_catchException();
+extern void* teavm_catchException();
+
+extern void teavm_gc_allocate(void* address, int32_t size);
+extern void teavm_gc_free(void* address, int32_t size);
+extern void teavm_gc_assertFree(void* address, int32_t size);
+extern void teavm_gc_initMark();
+extern void teavm_gc_mark(void* address);
+extern void teavm_gc_move(void* from, void* to, int32_t size);
+extern void teavm_gc_gcStarted();
+extern void teavm_gc_sweepCompleted();
+extern void teavm_gc_defragCompleted();