diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TClass.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TClass.java
index c4c43d061..676a9edf0 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TClass.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TClass.java
@@ -41,7 +41,7 @@ import org.teavm.classlib.java.lang.reflect.TModifier;
 import org.teavm.dependency.PluggableDependency;
 import org.teavm.interop.Address;
 import org.teavm.interop.DelegateTo;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.interop.Unmanaged;
 import org.teavm.jso.core.JSArray;
 import org.teavm.platform.Platform;
@@ -210,7 +210,7 @@ public class TClass<T> extends TObject implements TAnnotatedElement {
     }
 
     @GeneratedBy(ClassGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     private static native void createMetadata();
 
     public TField[] getFields() throws TSecurityException {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TClassLoader.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TClassLoader.java
index d9c59910b..c7e1acd72 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TClassLoader.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TClassLoader.java
@@ -19,7 +19,7 @@ import java.io.ByteArrayInputStream;
 import java.io.InputStream;
 import org.teavm.backend.javascript.spi.InjectedBy;
 import org.teavm.classlib.impl.Base64Impl;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.jso.JSBody;
 import org.teavm.jso.JSIndexer;
 import org.teavm.jso.JSObject;
@@ -69,7 +69,7 @@ public abstract class TClassLoader extends TObject {
     private static native String resourceToString(JSObject resource);
 
     @InjectedBy(ClassLoaderNativeGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     private static native ResourceContainer supplyResources();
 
     interface ResourceContainer extends JSObject {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TDouble.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TDouble.java
index 8ff43cb61..ef7f44a21 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TDouble.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TDouble.java
@@ -16,11 +16,11 @@
 package org.teavm.classlib.java.lang;
 
 import org.teavm.backend.javascript.spi.InjectedBy;
-import org.teavm.interop.DoesNotModifyStaticFields;
 import org.teavm.interop.Import;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.jso.JSBody;
 
-@DoesNotModifyStaticFields
+@NoSideEffects
 public class TDouble extends TNumber implements TComparable<TDouble> {
     public static final double POSITIVE_INFINITY = 1 / 0.0;
     public static final double NEGATIVE_INFINITY = -POSITIVE_INFINITY;
@@ -210,7 +210,7 @@ public class TDouble extends TNumber implements TComparable<TDouble> {
         return (int) (h >>> 32) ^ (int) h;
     }
 
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native int compare(double a, double b);
 
     @Override
@@ -228,18 +228,22 @@ public class TDouble extends TNumber implements TComparable<TDouble> {
 
     @JSBody(params = "v", script = "return isNaN(v);")
     @Import(module = "teavm", name = "isnan")
+    @NoSideEffects
     public static native boolean isNaN(double v);
 
     @JSBody(script = "return NaN;")
     @Import(module = "teavm", name = "TeaVM_getNaN")
+    @NoSideEffects
     private static native double getNaN();
 
     @JSBody(params = "v", script = "return !isFinite(v);")
     @Import(module = "teavm", name = "isinf")
+    @NoSideEffects
     public static native boolean isInfinite(double v);
 
     @JSBody(params = "v", script = "return isFinite(v);")
     @Import(module = "teavm", name = "isfinite")
+    @NoSideEffects
     public static native boolean isFinite(double v);
 
     public static long doubleToRawLongBits(double value) {
@@ -248,10 +252,12 @@ public class TDouble extends TNumber implements TComparable<TDouble> {
 
     @InjectedBy(DoubleGenerator.class)
     @Import(name = "teavm_reinterpretDoubleToLong")
+    @NoSideEffects
     public static native long doubleToLongBits(double value);
 
     @InjectedBy(DoubleGenerator.class)
     @Import(name = "teavm_reinterpretLongToDouble")
+    @NoSideEffects
     public static native double longBitsToDouble(long bits);
 
     public static String toHexString(double d) {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TFloat.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TFloat.java
index 1d71b8059..16600faaf 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TFloat.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TFloat.java
@@ -15,8 +15,8 @@
  */
 package org.teavm.classlib.java.lang;
 
-import org.teavm.interop.DoesNotModifyStaticFields;
 import org.teavm.interop.Import;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.jso.JSBody;
 
 public class TFloat extends TNumber implements TComparable<TFloat> {
@@ -92,18 +92,22 @@ public class TFloat extends TNumber implements TComparable<TFloat> {
 
     @JSBody(params = "v", script = "return isNaN(v);")
     @Import(module = "teavm", name = "isnan")
+    @NoSideEffects
     public static native boolean isNaN(float v);
 
     @JSBody(params = "v", script = "return !isFinite(v);")
     @Import(module = "teavm", name = "isinf")
+    @NoSideEffects
     public static native boolean isInfinite(float v);
 
     @JSBody(params = "v", script = "return isFinite(v);")
     @Import(module = "teavm", name = "isfinite")
+    @NoSideEffects
     public static native boolean isFinite(float v);
 
     @JSBody(script = "return NaN;")
     @Import(module = "teavm", name = "TeaVM_getNaN")
+    @NoSideEffects
     private static native float getNaN();
 
     public static float parseFloat(TString string) throws TNumberFormatException {
@@ -238,7 +242,7 @@ public class TFloat extends TNumber implements TComparable<TFloat> {
         return isInfinite(value);
     }
 
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native int compare(float f1, float f2);
 
     @Override
@@ -252,10 +256,12 @@ public class TFloat extends TNumber implements TComparable<TFloat> {
 
     @JSBody(params = "value", script = "return $rt_floatToIntBits(value);")
     @Import(name = "teavm_reinterpretFloatToInt")
+    @NoSideEffects
     public static native int floatToIntBits(float value);
 
     @JSBody(params = "bits", script = "return $rt_intBitsToFloat(bits);")
     @Import(name = "teavm_reinterpretIntToFloat")
+    @NoSideEffects
     public static native float intBitsToFloat(int bits);
 
     public static String toHexString(float f) {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TInteger.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TInteger.java
index 7f1daf576..b407aaaf0 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TInteger.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TInteger.java
@@ -17,7 +17,7 @@ package org.teavm.classlib.java.lang;
 
 import static org.teavm.classlib.impl.IntegerUtil.toUnsignedLogRadixString;
 import org.teavm.backend.javascript.spi.InjectedBy;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 
 public class TInteger extends TNumber implements TComparable<TInteger> {
     public static final int SIZE = 32;
@@ -252,7 +252,7 @@ public class TInteger extends TNumber implements TComparable<TInteger> {
         return compare(value, other.value);
     }
 
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native int compare(int x, int y);
 
     public static int numberOfLeadingZeros(int i) {
@@ -358,10 +358,10 @@ public class TInteger extends TNumber implements TComparable<TInteger> {
     }
 
     @InjectedBy(IntegerNativeGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native int divideUnsigned(int dividend, int divisor);
 
     @InjectedBy(IntegerNativeGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native int remainderUnsigned(int dividend, int divisor);
 }
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TLong.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TLong.java
index 6bf0dc5aa..8c38bae93 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TLong.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TLong.java
@@ -17,7 +17,7 @@ package org.teavm.classlib.java.lang;
 
 import static org.teavm.classlib.impl.IntegerUtil.toUnsignedLogRadixString;
 import org.teavm.backend.javascript.spi.GeneratedBy;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 
 public class TLong extends TNumber implements TComparable<TLong> {
     public static final long MIN_VALUE = -0x8000000000000000L;
@@ -213,7 +213,7 @@ public class TLong extends TNumber implements TComparable<TLong> {
         return other instanceof TLong && ((TLong) other).value == value;
     }
 
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native int compare(long a, long b);
 
     @Override
@@ -353,10 +353,10 @@ public class TLong extends TNumber implements TComparable<TLong> {
     }
 
     @GeneratedBy(LongNativeGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native long divideUnsigned(long dividend, long divisor);
 
     @GeneratedBy(LongNativeGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native long remainderUnsigned(long dividend, long divisor);
 }
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TMath.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TMath.java
index 1a3f47647..8f11261f8 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TMath.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TMath.java
@@ -16,10 +16,10 @@
 package org.teavm.classlib.java.lang;
 
 import org.teavm.backend.javascript.spi.GeneratedBy;
-import org.teavm.interop.DoesNotModifyStaticFields;
 import org.teavm.interop.Import;
+import org.teavm.interop.NoSideEffects;
 
-@DoesNotModifyStaticFields
+@NoSideEffects
 public final class TMath extends TObject {
     public static final double E = 2.71828182845904523536;
     public static final double PI = 3.14159265358979323846;
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TObject.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TObject.java
index 48bdb11bc..e54364c60 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TObject.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TObject.java
@@ -21,7 +21,7 @@ import org.teavm.interop.Address;
 import org.teavm.interop.Async;
 import org.teavm.interop.AsyncCallback;
 import org.teavm.interop.DelegateTo;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.interop.Rename;
 import org.teavm.interop.Structure;
 import org.teavm.interop.Superclass;
@@ -273,7 +273,7 @@ public class TObject {
     }
 
     @DelegateTo("hashCodeLowLevelImpl")
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     private static native int hashCodeLowLevel(TObject obj);
 
     @Unmanaged
@@ -282,7 +282,7 @@ public class TObject {
     }
 
     @DelegateTo("setHashCodeLowLevelImpl")
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     private static native void setHashCodeLowLevel(TObject obj, int value);
 
     @Unmanaged
@@ -303,7 +303,7 @@ public class TObject {
     }
 
     @DelegateTo("identityOrMonitorLowLevel")
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     private native int identityOrMonitor();
 
     private static int identityOrMonitorLowLevel(RuntimeObject object) {
@@ -311,7 +311,7 @@ public class TObject {
     }
 
     @DelegateTo("setIdentityLowLevel")
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     native void setIdentity(int id);
 
     private static void setIdentityLowLevel(RuntimeObject object, int id) {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TString.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
index bc4383ac7..2afc65212 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
@@ -30,7 +30,7 @@ import org.teavm.classlib.java.util.TFormatter;
 import org.teavm.classlib.java.util.TLocale;
 import org.teavm.classlib.java.util.regex.TPattern;
 import org.teavm.dependency.PluggableDependency;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 
 public class TString extends TObject implements TSerializable, TComparable<TString>, TCharSequence {
     public static final TComparator<TString> CASE_INSENSITIVE_ORDER = (o1, o2) -> o1.compareToIgnoreCase(o2);
@@ -628,7 +628,7 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
 
     @GeneratedBy(StringNativeGenerator.class)
     @PluggableDependency(StringNativeGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public native TString intern();
 
     public boolean matches(String regex) {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TSystem.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TSystem.java
index 23641bc7a..820140a30 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TSystem.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TSystem.java
@@ -25,8 +25,8 @@ import org.teavm.classlib.java.io.TPrintStream;
 import org.teavm.classlib.java.lang.reflect.TArray;
 import org.teavm.interop.Address;
 import org.teavm.interop.DelegateTo;
-import org.teavm.interop.DoesNotModifyStaticFields;
 import org.teavm.interop.Import;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.interop.Unmanaged;
 import org.teavm.runtime.Allocator;
 import org.teavm.runtime.GC;
@@ -104,7 +104,7 @@ public final class TSystem extends TObject {
 
     @GeneratedBy(SystemNativeGenerator.class)
     @DelegateTo("doArrayCopyLowLevel")
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     private static native void doArrayCopy(Object src, int srcPos, Object dest, int destPos, int length);
 
     @Unmanaged
@@ -126,7 +126,7 @@ public final class TSystem extends TObject {
 
     @DelegateTo("currentTimeMillisLowLevel")
     @GeneratedBy(SystemNativeGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native long currentTimeMillis();
 
     private static long currentTimeMillisLowLevel() {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/reflect/TArray.java b/classlib/src/main/java/org/teavm/classlib/java/lang/reflect/TArray.java
index 604064eef..76825dda8 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/reflect/TArray.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/reflect/TArray.java
@@ -24,7 +24,7 @@ import org.teavm.classlib.java.lang.TNullPointerException;
 import org.teavm.classlib.java.lang.TObject;
 import org.teavm.dependency.PluggableDependency;
 import org.teavm.interop.DelegateTo;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.interop.Unmanaged;
 import org.teavm.platform.PlatformClass;
 import org.teavm.runtime.Allocator;
@@ -36,7 +36,7 @@ public final class TArray extends TObject {
     @GeneratedBy(ArrayNativeGenerator.class)
     @PluggableDependency(ArrayNativeGenerator.class)
     @DelegateTo("getLengthLowLevel")
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     public static native int getLength(TObject array) throws TIllegalArgumentException;
 
     @SuppressWarnings("unused")
@@ -65,7 +65,7 @@ public final class TArray extends TObject {
 
     @GeneratedBy(ArrayNativeGenerator.class)
     @DelegateTo("newInstanceLowLevel")
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     private static native TObject newInstanceImpl(PlatformClass componentType, int length);
 
     @SuppressWarnings("unused")
@@ -92,11 +92,11 @@ public final class TArray extends TObject {
 
     @GeneratedBy(ArrayNativeGenerator.class)
     @PluggableDependency(ArrayNativeGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     private static native TObject getImpl(TObject array, int index);
 
     @GeneratedBy(ArrayNativeGenerator.class)
     @PluggableDependency(ArrayNativeGenerator.class)
-    @DoesNotModifyStaticFields
+    @NoSideEffects
     private static native void setImpl(TObject array, int index, TObject value);
 }
diff --git a/core/src/main/java/org/teavm/backend/javascript/rendering/Renderer.java b/core/src/main/java/org/teavm/backend/javascript/rendering/Renderer.java
index 6165a5369..f1db7d080 100644
--- a/core/src/main/java/org/teavm/backend/javascript/rendering/Renderer.java
+++ b/core/src/main/java/org/teavm/backend/javascript/rendering/Renderer.java
@@ -379,7 +379,7 @@ public class Renderer implements RenderingManager {
         try {
             MethodReader clinit = classSource.get(cls.getName()).getMethod(CLINIT_METHOD);
 
-            if (clinit != null && context.isDynamicInitializer(cls.getName())) {
+            if (clinit != null) {
                 renderCallClinit(clinit, cls);
             }
             if (!cls.getClassHolder().getModifiers().contains(ElementModifier.INTERFACE)) {
diff --git a/core/src/main/java/org/teavm/model/analysis/ClassInitializerAnalysis.java b/core/src/main/java/org/teavm/model/analysis/ClassInitializerAnalysis.java
index 79ab1cddc..2ca9143f3 100644
--- a/core/src/main/java/org/teavm/model/analysis/ClassInitializerAnalysis.java
+++ b/core/src/main/java/org/teavm/model/analysis/ClassInitializerAnalysis.java
@@ -27,7 +27,7 @@ import java.util.Set;
 import org.teavm.dependency.DependencyInfo;
 import org.teavm.dependency.MethodDependencyInfo;
 import org.teavm.dependency.ValueDependencyInfo;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.model.BasicBlockReader;
 import org.teavm.model.ClassHierarchy;
 import org.teavm.model.ClassReader;
@@ -155,15 +155,7 @@ public class ClassInitializerAnalysis implements ClassInitializerInfo {
             InstructionAnalyzer reader = new InstructionAnalyzer(currentClass, methodInfo);
             ProgramReader program = method.getProgram();
             if (program == null) {
-                methodInfo.anyFieldModified = true;
-                if (method.getAnnotations().get(DoesNotModifyStaticFields.class.getName()) != null) {
-                    methodInfo.anyFieldModified = false;
-                } else {
-                    ClassReader containingClass = classes.get(method.getOwnerName());
-                    if (containingClass.getAnnotations().get(DoesNotModifyStaticFields.class.getName()) != null) {
-                        methodInfo.anyFieldModified = false;
-                    }
-                }
+                methodInfo.anyFieldModified = hasSideEffects(method);
             } else {
                 for (BasicBlockReader block : program.getBasicBlocks()) {
                     block.readAllInstructions(reader);
@@ -180,6 +172,18 @@ public class ClassInitializerAnalysis implements ClassInitializerInfo {
         return methodInfo;
     }
 
+    private boolean hasSideEffects(MethodReader method) {
+        if (method.getAnnotations().get(NoSideEffects.class.getName()) != null) {
+            return false;
+        }
+        ClassReader containingClass = classes.get(method.getOwnerName());
+        if (containingClass.getAnnotations().get(NoSideEffects.class.getName()) != null) {
+            return false;
+        }
+
+        return true;
+    }
+
     class InstructionAnalyzer extends AbstractInstructionReader {
         String currentClass;
         MethodInfo methodInfo;
diff --git a/core/src/main/java/org/teavm/vm/TeaVM.java b/core/src/main/java/org/teavm/vm/TeaVM.java
index c55fb8aed..d748faa85 100644
--- a/core/src/main/java/org/teavm/vm/TeaVM.java
+++ b/core/src/main/java/org/teavm/vm/TeaVM.java
@@ -75,7 +75,6 @@ import org.teavm.model.ValueType;
 import org.teavm.model.analysis.ClassInitializerAnalysis;
 import org.teavm.model.analysis.ClassInitializerInfo;
 import org.teavm.model.instructions.InitClassInstruction;
-import org.teavm.model.instructions.InvokeInstruction;
 import org.teavm.model.optimization.ArrayUnwrapMotion;
 import org.teavm.model.optimization.ClassInitElimination;
 import org.teavm.model.optimization.ConstantConditionElimination;
@@ -523,9 +522,9 @@ public class TeaVM implements TeaVMHost, ServiceRepository {
         BasicBlock block = program.basicBlockAt(0);
         Instruction first = block.getFirstInstruction();
         for (String className : classInitializerInfo.getInitializationOrder()) {
-            InvokeInstruction invoke = new InvokeInstruction();
-            invoke.setMethod(new MethodReference(className, "<clinit>", ValueType.VOID));
-            first.insertPrevious(invoke);
+            InitClassInstruction clinit = new InitClassInstruction();
+            clinit.setClassName(className);
+            first.insertPrevious(clinit);
         }
     }
 
diff --git a/interop/core/src/main/java/org/teavm/interop/DoesNotModifyStaticFields.java b/interop/core/src/main/java/org/teavm/interop/NoSideEffects.java
similarity index 95%
rename from interop/core/src/main/java/org/teavm/interop/DoesNotModifyStaticFields.java
rename to interop/core/src/main/java/org/teavm/interop/NoSideEffects.java
index 1f4cbcc73..8496b7b2b 100644
--- a/interop/core/src/main/java/org/teavm/interop/DoesNotModifyStaticFields.java
+++ b/interop/core/src/main/java/org/teavm/interop/NoSideEffects.java
@@ -22,5 +22,5 @@ import java.lang.annotation.Target;
 
 @Retention(RetentionPolicy.RUNTIME)
 @Target({ ElementType.METHOD, ElementType.TYPE })
-public @interface DoesNotModifyStaticFields {
+public @interface NoSideEffects {
 }
diff --git a/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java b/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java
index 01a661188..7bd3a8fab 100644
--- a/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java
+++ b/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java
@@ -32,7 +32,7 @@ import org.mozilla.javascript.ast.FunctionNode;
 import org.teavm.backend.javascript.rendering.JSParser;
 import org.teavm.cache.IncrementalDependencyRegistration;
 import org.teavm.diagnostics.Diagnostics;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.interop.Sync;
 import org.teavm.jso.JSBody;
 import org.teavm.jso.JSByRef;
@@ -654,7 +654,9 @@ class JSClassProcessor {
             MethodHolder proxyMethod = new MethodHolder(proxyRef.getDescriptor());
             proxyMethod.getModifiers().add(ElementModifier.NATIVE);
             proxyMethod.getModifiers().add(ElementModifier.STATIC);
-            proxyMethod.getAnnotations().add(new AnnotationHolder(DoesNotModifyStaticFields.class.getName()));
+            if (method.getAnnotations().get(NoSideEffects.class.getName()) != null) {
+                proxyMethod.getAnnotations().add(new AnnotationHolder(NoSideEffects.class.getName()));
+            }
             boolean inline = repository.inlineMethods.contains(methodRef);
             AnnotationHolder generatorAnnot = new AnnotationHolder(inline
                     ? DynamicInjector.class.getName() : DynamicGenerator.class.getName());
diff --git a/platform/src/main/java/org/teavm/platform/Platform.java b/platform/src/main/java/org/teavm/platform/Platform.java
index 74f2b5a53..f1eff2919 100644
--- a/platform/src/main/java/org/teavm/platform/Platform.java
+++ b/platform/src/main/java/org/teavm/platform/Platform.java
@@ -21,6 +21,7 @@ import org.teavm.backend.javascript.spi.InjectedBy;
 import org.teavm.dependency.PluggableDependency;
 import org.teavm.interop.Address;
 import org.teavm.interop.DelegateTo;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.interop.PlatformMarker;
 import org.teavm.interop.PlatformMarkers;
 import org.teavm.interop.Unmanaged;
@@ -42,10 +43,12 @@ public final class Platform {
 
     @InjectedBy(PlatformGenerator.class)
     @Unmanaged
+    @NoSideEffects
     public static native PlatformObject getPlatformObject(Object obj);
 
     @GeneratedBy(PlatformGenerator.class)
     @PluggableDependency(PlatformGenerator.class)
+    @NoSideEffects
     public static native Object clone(Object obj);
 
     @DelegateTo("isInstanceLowLevel")
@@ -61,6 +64,7 @@ public final class Platform {
     }
 
     @JSBody(params = "object", script = "return typeof object === 'undefined';")
+    @NoSideEffects
     private static native boolean isUndefined(JSObject object);
 
     @DelegateTo("isAssignableLowLevel")
@@ -86,9 +90,11 @@ public final class Platform {
     @InjectedBy(PlatformGenerator.class)
     @PluggableDependency(PlatformGenerator.class)
     @Unmanaged
+    @NoSideEffects
     public static native Class<?> asJavaClass(PlatformObject obj);
 
     @JSBody(script = "return $rt_nextId();")
+    @NoSideEffects
     public static native int nextObjectId();
 
     public static <T> T newInstance(PlatformClass cls) {
@@ -100,6 +106,7 @@ public final class Platform {
     }
 
     @GeneratedBy(PlatformGenerator.class)
+    @NoSideEffects
     private static native void prepareNewInstance();
 
     @GeneratedBy(PlatformGenerator.class)
@@ -108,6 +115,7 @@ public final class Platform {
 
     @GeneratedBy(PlatformGenerator.class)
     @PluggableDependency(PlatformGenerator.class)
+    @NoSideEffects
     public static native PlatformClass lookupClass(String name);
 
     @PluggableDependency(PlatformGenerator.class)
@@ -133,6 +141,7 @@ public final class Platform {
     @GeneratedBy(PlatformGenerator.class)
     @PluggableDependency(PlatformGenerator.class)
     @DelegateTo("getEnumConstantsLowLevel")
+    @NoSideEffects
     public static native Enum<?>[] getEnumConstants(PlatformClass cls);
 
     private static Enum<?>[] getEnumConstantsLowLevel(PlatformClass cls) {
@@ -194,7 +203,6 @@ public final class Platform {
         Window.clearTimeout(id);
     }
 
-    @JSBody(script = "return [];")
     public static <T> PlatformQueue<T> createQueue() {
         if (isLowLevel()) {
             return new LowLevelQueue<>();
@@ -204,6 +212,7 @@ public final class Platform {
     }
 
     @JSBody(script = "return [];")
+    @NoSideEffects
     private static native  <T> PlatformQueue<T> createQueueJs();
 
     public static PlatformString stringFromCharCode(int charCode) {
diff --git a/platform/src/main/java/org/teavm/platform/plugin/MetadataProviderTransformer.java b/platform/src/main/java/org/teavm/platform/plugin/MetadataProviderTransformer.java
index 6f8d0a432..0d97359e2 100644
--- a/platform/src/main/java/org/teavm/platform/plugin/MetadataProviderTransformer.java
+++ b/platform/src/main/java/org/teavm/platform/plugin/MetadataProviderTransformer.java
@@ -18,7 +18,7 @@ package org.teavm.platform.plugin;
 import java.util.HashSet;
 import java.util.Set;
 import org.teavm.backend.javascript.spi.GeneratedBy;
-import org.teavm.interop.DoesNotModifyStaticFields;
+import org.teavm.interop.NoSideEffects;
 import org.teavm.model.AccessLevel;
 import org.teavm.model.AnnotationHolder;
 import org.teavm.model.AnnotationValue;
@@ -68,8 +68,8 @@ class MetadataProviderTransformer implements ClassHolderTransformer {
                 MetadataProviderNativeGenerator.class.getName())));
         createMethod.getAnnotations().add(genAnnot);
         ModelUtils.copyAnnotations(method.getAnnotations(), createMethod.getAnnotations());
-        if (createMethod.getAnnotations().get(DoesNotModifyStaticFields.class.getName()) == null) {
-            createMethod.getAnnotations().add(new AnnotationHolder(DoesNotModifyStaticFields.class.getName()));
+        if (createMethod.getAnnotations().get(NoSideEffects.class.getName()) == null) {
+            createMethod.getAnnotations().add(new AnnotationHolder(NoSideEffects.class.getName()));
         }
 
         AnnotationHolder refAnnot = new AnnotationHolder(MetadataProviderRef.class.getName());
diff --git a/tools/junit/src/main/java/org/teavm/junit/TeaVMTestConfiguration.java b/tools/junit/src/main/java/org/teavm/junit/TeaVMTestConfiguration.java
index bdb5ad0f4..f568ca8d1 100644
--- a/tools/junit/src/main/java/org/teavm/junit/TeaVMTestConfiguration.java
+++ b/tools/junit/src/main/java/org/teavm/junit/TeaVMTestConfiguration.java
@@ -37,7 +37,7 @@ interface TeaVMTestConfiguration<T extends TeaVMTarget> {
 
         @Override
         public void apply(TeaVM vm) {
-            vm.setOptimizationLevel(TeaVMOptimizationLevel.SIMPLE);
+            vm.setOptimizationLevel(TeaVMOptimizationLevel.ADVANCED);
         }
 
         @Override