diff --git a/classlib/src/main/java/org/teavm/classlib/impl/text/DoubleAnalyzer.java b/classlib/src/main/java/org/teavm/classlib/impl/text/DoubleAnalyzer.java
new file mode 100644
index 000000000..fa3f51aff
--- /dev/null
+++ b/classlib/src/main/java/org/teavm/classlib/impl/text/DoubleAnalyzer.java
@@ -0,0 +1,197 @@
+/*
+ *  Copyright 2018 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.classlib.impl.text;
+
+import java.util.Arrays;
+
+public final class DoubleAnalyzer {
+    private DoubleAnalyzer() {
+    }
+
+    private static final int MAX_ABS_DEC_EXP = 330;
+    public static final int DECIMAL_PRECISION = 18;
+    public static final long DOUBLE_MAX_POS = 100000000000000000L;
+    private static long[] mantissa10Table = new long[MAX_ABS_DEC_EXP * 2];
+    private static int[] exp10Table = new int[MAX_ABS_DEC_EXP * 2];
+
+    static {
+        long decimalMantissaOne = 8000000000000000000L;
+
+        long mantissa = decimalMantissaOne;
+        long remainder = 0;
+        int exponent = 1023;
+
+        for (int i = 0; i < MAX_ABS_DEC_EXP; ++i) {
+            mantissa10Table[i + MAX_ABS_DEC_EXP] = Long.divideUnsigned(mantissa, 80);
+            exp10Table[i + MAX_ABS_DEC_EXP] = exponent;
+
+            mantissa = Long.divideUnsigned(mantissa, 10);
+            remainder = Long.remainderUnsigned(mantissa, 10);
+            while (mantissa <= decimalMantissaOne && (mantissa & (1L << 63)) == 0) {
+                mantissa <<= 1;
+                exponent++;
+                remainder <<= 1;
+            }
+            mantissa += remainder / 10;
+        }
+
+        long maxMantissa = Long.MAX_VALUE / 10;
+        mantissa = decimalMantissaOne;
+        exponent = 1023;
+        for (int i = 0; i < MAX_ABS_DEC_EXP; ++i) {
+            long nextMantissa = mantissa;
+            int shift = 0;
+            while (nextMantissa > maxMantissa) {
+                nextMantissa >>= 1;
+                shift++;
+                exponent--;
+            }
+
+            nextMantissa *= 10;
+            if (shift > 0) {
+                long shiftedOffPart = mantissa & ((1 << shift) - 1);
+                nextMantissa += (shiftedOffPart * 10) >> shift;
+            }
+            mantissa = nextMantissa;
+
+            mantissa10Table[MAX_ABS_DEC_EXP - i - 1] = Long.divideUnsigned(mantissa, 80);
+            exp10Table[MAX_ABS_DEC_EXP - i - 1] = exponent;
+        }
+    }
+
+    public static void analyze(double d, Result result) {
+        long bits = Double.doubleToLongBits(d);
+        result.sign = (bits & (1L << 63)) != 0;
+        long mantissa = bits & ((1L << 52) - 1);
+        int exponent = (int) (bits >> 52) & ((1 << 11) - 1);
+        if (mantissa == 0 && exponent == 0) {
+            result.mantissa = 0;
+            result.exponent = 0;
+            return;
+        }
+
+        int errorShift = 0;
+        if (exponent == 0) {
+            mantissa <<= 1;
+            while ((mantissa & (1L << 52)) == 0) {
+                mantissa <<= 1;
+                exponent--;
+                ++errorShift;
+            }
+        } else {
+            mantissa |= 1L << 52;
+        }
+
+        int decExponent = Arrays.binarySearch(exp10Table, exponent);
+        if (decExponent < 0) {
+            decExponent = -decExponent - 2;
+        }
+        int binExponentCorrection = exponent - exp10Table[decExponent];
+        int mantissaShift = 12 + binExponentCorrection;
+
+        long decMantissa = mulAndShiftRight(mantissa, mantissa10Table[decExponent], mantissaShift);
+        if (decMantissa >= 1000000000000000000L) {
+            ++decExponent;
+            binExponentCorrection = exponent - exp10Table[decExponent];
+            mantissaShift = 12 + binExponentCorrection;
+            decMantissa = mulAndShiftRight(mantissa, mantissa10Table[decExponent], mantissaShift);
+        }
+
+        long error = mantissa10Table[decExponent] >>> (63 - mantissaShift - errorShift);
+        long upError = (error + 1) >> 1;
+        long downError = error >> 1;
+        if (mantissa == (1L << 52)) {
+            downError >>= 2;
+        }
+
+        long lowerPos = findLowerDistanceToZero(decMantissa, downError);
+        long upperPos = findUpperDistanceToZero(decMantissa, upError);
+        if (lowerPos > upperPos) {
+            decMantissa = (decMantissa / lowerPos) * lowerPos;
+        } else if (lowerPos < upperPos) {
+            decMantissa = (decMantissa / upperPos) * upperPos + upperPos;
+        } else {
+            decMantissa = ((decMantissa + upperPos / 2) / upperPos) * upperPos;
+        }
+
+        if (decMantissa >= 1000000000000000000L) {
+            decExponent++;
+            decMantissa /= 10;
+        }
+
+        result.mantissa = decMantissa;
+        result.exponent = decExponent - MAX_ABS_DEC_EXP;
+    }
+
+    private static long findLowerDistanceToZero(long mantissa, long error) {
+        long pos = 10;
+        while (pos <= error) {
+            pos *= 10;
+        }
+        long mantissaRight = mantissa % pos;
+        if (mantissaRight >= error / 2) {
+            pos /= 10;
+        }
+        return pos;
+    }
+
+    private static long findUpperDistanceToZero(long mantissa, long error) {
+        long pos = 1;
+        while (pos <= error) {
+            pos *= 10;
+        }
+        long mantissaRight = mantissa % pos;
+        if (pos - mantissaRight > error / 2) {
+            pos /= 10;
+        }
+        return pos;
+    }
+
+    // Multiply two longs and shft result right by 64-shift bits.
+    private static long mulAndShiftRight(long a, long b, int shift) {
+        long a1 = a & 0xFFFF;
+        long a2 = (a >>> 16) & 0xFFFF;
+        long a3 = (a >>> 32) & 0xFFFF;
+        long a4 = (a >>> 48) & 0xFFFF;
+
+        long b1 = b & 0xFFFF;
+        long b2 = (b >>> 16) & 0xFFFF;
+        long b3 = (b >>> 32) & 0xFFFF;
+        long b4 = (b >>> 48) & 0xFFFF;
+
+        long cm = b3 * a1 + b2 * a2 + b1 * a3;
+        long c0 = b4 * a1 + b3 * a2 + b2 * a3 + b1 * a4;
+        long c1 = b4 * a2 + b3 * a3 + b2 * a4;
+        long c2 = b4 * a3 + b3 * a4;
+        long c3 = b4 * a4;
+
+        long c = (c3 << (32 + shift)) + (c2 << (16 + shift)) + (c1 << shift);
+        if (shift <= 16) {
+            c += c0 >>> (16 - shift);
+        } else {
+            c += c0 << (shift - 16);
+        }
+        c += cm >>> (32 - shift);
+
+        return c;
+    }
+
+    public static class Result {
+        public long mantissa;
+        public int exponent;
+        public boolean sign;
+    }
+}
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/LongNativeGenerator.java b/classlib/src/main/java/org/teavm/classlib/java/lang/LongNativeGenerator.java
index 851654e29..3cf532086 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/LongNativeGenerator.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/LongNativeGenerator.java
@@ -28,6 +28,17 @@ public class LongNativeGenerator implements Generator {
             case "compare":
                 writer.append("return Long_compare(").append(context.getParameterName(1)).append(", ")
                         .append(context.getParameterName(2)).append(");").softNewLine();
+                context.useLongLibrary();
+                break;
+            case "divideUnsigned":
+                writer.append("return Long_udiv(").append(context.getParameterName(1)).append(", ")
+                        .append(context.getParameterName(2)).append(");").softNewLine();
+                context.useLongLibrary();
+                break;
+            case "remainderUnsigned":
+                writer.append("return Long_urem(").append(context.getParameterName(1)).append(", ")
+                        .append(context.getParameterName(2)).append(");").softNewLine();
+                context.useLongLibrary();
                 break;
         }
     }
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
index 5d29f9f4f..a22294e82 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
@@ -15,31 +15,27 @@
  */
 package org.teavm.classlib.java.lang;
 
+import org.teavm.classlib.impl.text.DoubleAnalyzer;
 import org.teavm.classlib.java.io.TSerializable;
 import org.teavm.classlib.java.util.TArrays;
 
 class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequence {
     static class Constants {
-        private static float[] powersOfTen = { 1E1f, 1E2f, 1E4f, 1E8f, 1E16f, 1E32f };
-        private static double[] doublePowersOfTen = { 1E1, 1E2, 1E4, 1E8, 1E16, 1E32, 1E64, 1E128, 1E256 };
-        private static float[] negPowersOfTen = { 1E-1f, 1E-2f, 1E-4f, 1E-8f, 1E-16f, 1E-32f };
-        private static double[] negDoublePowersOfTen = { 1E-1, 1E-2, 1E-4, 1E-8, 1E-16, 1E-32,
-                1E-64, 1E-128, 1E-256 };
-        private static int[] intPowersOfTen = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000,
+        static float[] powersOfTen = { 1E1f, 1E2f, 1E4f, 1E8f, 1E16f, 1E32f };
+        static float[] negPowersOfTen = { 1E-1f, 1E-2f, 1E-4f, 1E-8f, 1E-16f, 1E-32f };
+        static int[] intPowersOfTen = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000,
                 1000000000 };
-        private static long[] longPowersOfTen = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000,
+        static long[] longPowersOfTen = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000,
                 1000000000, 10000000000L, 100000000000L, 1000000000000L, 10000000000000L, 100000000000000L,
                 1000000000000000L, 10000000000000000L, 100000000000000000L, 1000000000000000000L };
-        private static final long[] longLogPowersOfTen = { 1, 10, 100, 10000, 100000000, 10000000000000000L, };
+        static final long[] longLogPowersOfTen = { 1, 10, 100, 10000, 100000000, 10000000000000000L, };
 
-        private static final int FLOAT_DECIMAL_PRECISION = 7;
-        private static final int DOUBLE_DECIMAL_PRECISION = 16;
-        private static final float FLOAT_DECIMAL_FACTOR = 1E6f;
-        private static final double DOUBLE_DECIMAL_FACTOR = 1E15;
-        private static final int FLOAT_MAX_EXPONENT = 38;
-        private static final int DOUBLE_MAX_EXPONENT = 308;
-        private static final int FLOAT_MAX_POS = 1000000;
-        private static final long DOUBLE_MAX_POS = 1000000000000000L;
+        static final int FLOAT_DECIMAL_PRECISION = 7;
+        static final float FLOAT_DECIMAL_FACTOR = 1E6f;
+        static final int FLOAT_MAX_EXPONENT = 38;
+        static final int FLOAT_MAX_POS = 1000000;
+
+        static final DoubleAnalyzer.Result doubleAnalysisResult = new DoubleAnalyzer.Result();
     }
 
     char[] buffer;
@@ -388,58 +384,22 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
             buffer[target++] = 'y';
             return this;
         }
+
+        DoubleAnalyzer.Result number = Constants.doubleAnalysisResult;
+        DoubleAnalyzer.analyze(value, number);
+        long mantissa = number.mantissa;
+        int exp = number.exponent;
+        boolean negative = number.sign;
+        int intPart = 1;
+
         // Get absolute value
-        boolean negative = false;
         int sz = 1; // Decimal point always included
-        if (value < 0) {
-            negative = true;
-            value = -value;
+        if (negative) {
             ++sz; // including '-' sign of mantissa
         }
 
-        // Split into decimal mantissa and decimal exponent
-        int exp = 0;
-        long mantissa = 0;
-        int intPart = 1;
-        int digits = 0;
-        if (value >= 1) {
-            int bit = 256;
-            exp = 0;
-            double digit = 1;
-            for (int i = Constants.doublePowersOfTen.length - 1; i >= 0; --i) {
-                if ((exp | bit) <= Constants.DOUBLE_MAX_EXPONENT && Constants.doublePowersOfTen[i] * digit <= value) {
-                    digit *= Constants.doublePowersOfTen[i];
-                    exp |= bit;
-                }
-                bit >>= 1;
-            }
-            mantissa = (long) (((value / digit) * Constants.DOUBLE_DECIMAL_FACTOR) + 0.5);
-        } else {
-            int bit = 256;
-            exp = 0;
-            double digit = 1;
-            for (int i = Constants.negDoublePowersOfTen.length - 1; i >= 0; --i) {
-                if ((exp | bit) <= 324 && Constants.negDoublePowersOfTen[i] * digit * 10 > value) {
-                    exp |= bit;
-                    if (exp == 324) {
-                        value /= Constants.negDoublePowersOfTen[i];
-                    } else {
-                        digit *= Constants.negDoublePowersOfTen[i];
-                    }
-                }
-                bit >>= 1;
-            }
-            exp = -exp;
-            mantissa = (long) (((value * Constants.DOUBLE_MAX_POS) / digit) + 0.5);
-
-            while (mantissa >= 10000000000000000L) {
-                mantissa /= 10;
-                exp--;
-            }
-        }
-
         // Remove trailing zeros
-        digits = Constants.DOUBLE_DECIMAL_PRECISION;
+        int digits = DoubleAnalyzer.DECIMAL_PRECISION;
         int zeros = trailingDecimalZeros(mantissa);
         if (zeros > 0) {
             digits -= zeros;
@@ -482,7 +442,7 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
         if (negative) {
             buffer[target++] = '-';
         }
-        long pos = Constants.DOUBLE_MAX_POS;
+        long pos = DoubleAnalyzer.DOUBLE_MAX_POS;
         for (int i = 0; i < digits; ++i) {
             int intDigit;
             if (pos > 0) {
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 0ed37ccf3..65cad8dba 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
@@ -243,9 +243,11 @@ public class TDouble extends TNumber implements TComparable<TDouble> {
     }
 
     @InjectedBy(DoubleGenerator.class)
+    @Import(name = "teavm_reinterpretDoubleToLong")
     public static native long doubleToLongBits(double value);
 
     @InjectedBy(DoubleGenerator.class)
+    @Import(name = "teavm_reinterpretLongToDouble")
     public static native double longBitsToDouble(long bits);
 
     public static TString 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 9e9a0ee9f..96fa205cf 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
@@ -247,9 +247,11 @@ public class TFloat extends TNumber implements TComparable<TFloat> {
     }
 
     @JSBody(params = "value", script = "return $rt_floatToIntBits(value);")
+    @Import(name = "teavm_reinterpretFloatToInt")
     public static native int floatToIntBits(float value);
 
     @JSBody(params = "bits", script = "return $rt_intBitsToFloat(bits);")
+    @Import(name = "teavm_reinterpretIntToFloat")
     public static native float intBitsToFloat(int bits);
 
     public static TString toHexString(float f) {
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 bc75c942b..db6c138bc 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
@@ -16,6 +16,7 @@
 package org.teavm.classlib.java.lang;
 
 import static org.teavm.classlib.impl.IntegerUtil.toUnsignedLogRadixString;
+import org.teavm.backend.javascript.spi.GeneratedBy;
 
 public class TLong extends TNumber implements TComparable<TLong> {
     public static final long MIN_VALUE = -0x8000000000000000L;
@@ -348,4 +349,10 @@ public class TLong extends TNumber implements TComparable<TLong> {
     public static int signum(long i) {
         return (int) ((i >> 63) | (-i >>> 63));
     }
+
+    @GeneratedBy(LongNativeGenerator.class)
+    public static native long divideUnsigned(long dividend, long divisor);
+
+    @GeneratedBy(LongNativeGenerator.class)
+    public static native long remainderUnsigned(long dividend, long divisor);
 }
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 eec71f071..18727c4bc 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
@@ -43,7 +43,7 @@ public final class TSystem extends TObject {
 
     public static TPrintStream out() {
         if (outCache == null) {
-            new TPrintStream(new TConsoleOutputStreamStdout(), false);
+            outCache = new TPrintStream(new TConsoleOutputStreamStdout(), false);
         }
         return outCache;
     }
diff --git a/core/src/main/java/org/teavm/backend/c/CTarget.java b/core/src/main/java/org/teavm/backend/c/CTarget.java
index e4b8433c7..52d1c8e79 100644
--- a/core/src/main/java/org/teavm/backend/c/CTarget.java
+++ b/core/src/main/java/org/teavm/backend/c/CTarget.java
@@ -49,6 +49,7 @@ import org.teavm.backend.c.intrinsic.FunctionIntrinsic;
 import org.teavm.backend.c.intrinsic.GCIntrinsic;
 import org.teavm.backend.c.intrinsic.Intrinsic;
 import org.teavm.backend.c.intrinsic.IntrinsicFactory;
+import org.teavm.backend.c.intrinsic.LongIntrinsic;
 import org.teavm.backend.c.intrinsic.MutatorIntrinsic;
 import org.teavm.backend.c.intrinsic.PlatformClassIntrinsic;
 import org.teavm.backend.c.intrinsic.PlatformClassMetadataIntrinsic;
@@ -234,6 +235,7 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
         intrinsics.add(new ExceptionHandlingIntrinsic());
         intrinsics.add(new FunctionIntrinsic(characteristics, exportDependencyListener.getResolvedMethods()));
         intrinsics.add(new RuntimeClassIntrinsic());
+        intrinsics.add(new LongIntrinsic());
 
         List<Generator> generators = new ArrayList<>();
         generators.add(new ArrayGenerator());
diff --git a/core/src/main/java/org/teavm/backend/c/intrinsic/LongIntrinsic.java b/core/src/main/java/org/teavm/backend/c/intrinsic/LongIntrinsic.java
new file mode 100644
index 000000000..3b7ed7a21
--- /dev/null
+++ b/core/src/main/java/org/teavm/backend/c/intrinsic/LongIntrinsic.java
@@ -0,0 +1,55 @@
+/*
+ *  Copyright 2018 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;
+
+public class LongIntrinsic implements Intrinsic {
+    @Override
+    public boolean canHandle(MethodReference method) {
+        if (!method.getClassName().equals(Long.class.getName())) {
+            return false;
+        }
+        switch (method.getName()) {
+            case "divideUnsigned":
+            case "remainderUnsigned":
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    @Override
+    public void apply(IntrinsicContext context, InvocationExpr invocation) {
+        switch (invocation.getMethod().getName()) {
+            case "divideUnsigned":
+                writeBinary(context, invocation, "/");
+                break;
+            case "remainderUnsigned":
+                writeBinary(context, invocation, "%");
+                break;
+        }
+    }
+
+    private void writeBinary(IntrinsicContext context, InvocationExpr invocation, String operation) {
+        context.writer().print("((int64_t) ((uint64_t) ");
+        context.emit(invocation.getArguments().get(0));
+        context.writer().print(" " + operation + " (uint64_t) ");
+        context.emit(invocation.getArguments().get(1));
+        context.writer().print("))");
+    }
+}
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 da3febc07..58ed9a0cf 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
@@ -1006,6 +1006,11 @@ public class Renderer implements RenderingManager {
         public String typeToClassString(ValueType type) {
             return context.typeToClsString(type);
         }
+
+        @Override
+        public void useLongLibrary() {
+            longLibraryUsed = true;
+        }
     }
 
     private void appendMonitor(StatementRenderer statementRenderer, MethodNode methodNode) throws IOException {
diff --git a/core/src/main/java/org/teavm/backend/javascript/spi/GeneratorContext.java b/core/src/main/java/org/teavm/backend/javascript/spi/GeneratorContext.java
index 826a651ed..a629820cd 100644
--- a/core/src/main/java/org/teavm/backend/javascript/spi/GeneratorContext.java
+++ b/core/src/main/java/org/teavm/backend/javascript/spi/GeneratorContext.java
@@ -43,4 +43,6 @@ public interface GeneratorContext extends ServiceRepository {
     Diagnostics getDiagnostics();
 
     String typeToClassString(ValueType type);
+
+    void useLongLibrary();
 }
diff --git a/core/src/main/java/org/teavm/backend/wasm/WasmTarget.java b/core/src/main/java/org/teavm/backend/wasm/WasmTarget.java
index dfd233525..d4bc95174 100644
--- a/core/src/main/java/org/teavm/backend/wasm/WasmTarget.java
+++ b/core/src/main/java/org/teavm/backend/wasm/WasmTarget.java
@@ -49,6 +49,7 @@ import org.teavm.backend.wasm.intrinsics.ExceptionHandlingIntrinsic;
 import org.teavm.backend.wasm.intrinsics.FloatIntrinsic;
 import org.teavm.backend.wasm.intrinsics.FunctionIntrinsic;
 import org.teavm.backend.wasm.intrinsics.GCIntrinsic;
+import org.teavm.backend.wasm.intrinsics.LongIntrinsic;
 import org.teavm.backend.wasm.intrinsics.MutatorIntrinsic;
 import org.teavm.backend.wasm.intrinsics.ObjectIntrinsic;
 import org.teavm.backend.wasm.intrinsics.PlatformClassIntrinsic;
@@ -343,6 +344,7 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
         context.addIntrinsic(new RuntimeClassIntrinsic());
         context.addIntrinsic(new FloatIntrinsic());
         context.addIntrinsic(new DoubleIntrinsic());
+        context.addIntrinsic(new LongIntrinsic());
         context.addIntrinsic(new ObjectIntrinsic());
         context.addGenerator(new ArrayGenerator());
 
diff --git a/core/src/main/java/org/teavm/backend/wasm/intrinsics/LongIntrinsic.java b/core/src/main/java/org/teavm/backend/wasm/intrinsics/LongIntrinsic.java
new file mode 100644
index 000000000..a05771c67
--- /dev/null
+++ b/core/src/main/java/org/teavm/backend/wasm/intrinsics/LongIntrinsic.java
@@ -0,0 +1,56 @@
+/*
+ *  Copyright 2018 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.WasmExpression;
+import org.teavm.backend.wasm.model.expression.WasmIntBinary;
+import org.teavm.backend.wasm.model.expression.WasmIntBinaryOperation;
+import org.teavm.backend.wasm.model.expression.WasmIntType;
+import org.teavm.model.MethodReference;
+
+public class LongIntrinsic implements WasmIntrinsic {
+    @Override
+    public boolean isApplicable(MethodReference methodReference) {
+        if (!methodReference.getClassName().equals(Long.class.getName())) {
+            return false;
+        }
+
+        switch (methodReference.getName()) {
+            case "divideUnsigned":
+            case "remainderUnsigned":
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    @Override
+    public WasmExpression apply(InvocationExpr invocation, WasmIntrinsicManager manager) {
+        switch (invocation.getMethod().getName()) {
+            case "divideUnsigned":
+                return new WasmIntBinary(WasmIntType.INT64, WasmIntBinaryOperation.DIV_UNSIGNED,
+                        manager.generate(invocation.getArguments().get(0)),
+                        manager.generate(invocation.getArguments().get(1)));
+            case "remainderUnsigned":
+                return new WasmIntBinary(WasmIntType.INT64, WasmIntBinaryOperation.REM_UNSIGNED,
+                        manager.generate(invocation.getArguments().get(0)),
+                        manager.generate(invocation.getArguments().get(1)));
+            default:
+                throw new AssertionError();
+        }
+    }
+}
diff --git a/core/src/main/resources/org/teavm/backend/c/runtime.c b/core/src/main/resources/org/teavm/backend/c/runtime.c
index a3accc499..f578aa4c2 100644
--- a/core/src/main/resources/org/teavm/backend/c/runtime.c
+++ b/core/src/main/resources/org/teavm/backend/c/runtime.c
@@ -273,4 +273,25 @@ static int32_t teavm_timeZoneOffset() {
 }
 
 static char* teavm_stringToC(void*);
-static inline void teavm_free(void*);
\ No newline at end of file
+static inline void teavm_free(void*);
+
+static inline int64_t teavm_reinterpretDoubleToLong(double v) {
+    union { int64_t longValue; double doubleValue; } conv;
+    conv.doubleValue = v;
+    return conv.longValue;
+}
+static inline double teavm_reinterpretLongToDouble(int64_t v) {
+    union { int64_t longValue; double doubleValue; } conv;
+    conv.longValue = v;
+    return conv.doubleValue;
+}
+static inline int32_t teavm_reinterpretFloatToInt(float v) {
+    union { int32_t intValue; float floatValue; } conv;
+    conv.floatValue = v;
+    return conv.intValue;
+}
+static inline float teavm_reinterpretIntToFloat(int32_t v) {
+    union { int32_t intValue; float floatValue; } conv;
+    conv.intValue = v;
+    return conv.floatValue;
+}
\ No newline at end of file
diff --git a/core/src/main/resources/org/teavm/backend/javascript/long.js b/core/src/main/resources/org/teavm/backend/javascript/long.js
index dfe58c1ab..d2c6af669 100644
--- a/core/src/main/resources/org/teavm/backend/javascript/long.js
+++ b/core/src/main/resources/org/teavm/backend/javascript/long.js
@@ -197,12 +197,24 @@ function Long_div(a, b) {
     }
     return Long_divRem(a, b)[0];
 }
+function Long_udiv(a, b) {
+    if (a.hi >= 0 && a.hi < Long_MAX_NORMAL && b.hi >= 0 && b.hi < Long_MAX_NORMAL) {
+        return Long_fromNumber(Long_toNumber(a) / Long_toNumber(b));
+    }
+    return Long_udivRem(a, b)[0];
+}
 function Long_rem(a, b) {
     if (Math.abs(a.hi) < Long_MAX_NORMAL && Math.abs(b.hi) < Long_MAX_NORMAL) {
         return Long_fromNumber(Long_toNumber(a) % Long_toNumber(b));
     }
     return Long_divRem(a, b)[1];
 }
+function Long_urem(a, b) {
+    if (a.hi >= 0 && a.hi < Long_MAX_NORMAL && b.hi >= 0 && b.hi < Long_MAX_NORMAL) {
+        return Long_fromNumber(Long_toNumber(a) / Long_toNumber(b));
+    }
+    return Long_udivRem(a, b)[1];
+}
 function Long_divRem(a, b) {
     if (b.lo === 0 && b.hi === 0) {
         throw new Error("Division by zero");
@@ -221,6 +233,17 @@ function Long_divRem(a, b) {
     q = new Long(q.lo, q.hi);
     return positive ? [q, a] : [Long_neg(q), Long_neg(a)];
 }
+function Long_udivRem(a, b) {
+    if (b.lo === 0 && b.hi === 0) {
+        throw new Error("Division by zero");
+    }
+    a = new LongInt(a.lo, a.hi, 0);
+    b = new LongInt(b.lo, b.hi, 0);
+    var q = LongInt_div(a, b);
+    a = new Long(a.lo, a.hi);
+    q = new Long(q.lo, q.hi);
+    return [q, a];
+}
 function Long_shiftLeft16(a) {
     return new Long(a.lo << 16, (a.lo >>> 16) | (a.hi << 16));
 }
diff --git a/tests/src/test/java/org/teavm/classlib/java/lang/StringBuilderTest.java b/tests/src/test/java/org/teavm/classlib/java/lang/StringBuilderTest.java
index 9f8f6c68b..a15f155bb 100644
--- a/tests/src/test/java/org/teavm/classlib/java/lang/StringBuilderTest.java
+++ b/tests/src/test/java/org/teavm/classlib/java/lang/StringBuilderTest.java
@@ -279,8 +279,8 @@ public class StringBuilderTest {
     @Test
     public void minDoubleAppended() {
         StringBuilder sb = new StringBuilder();
-        sb.append(2.2250738585072E-308);
-        assertEquals("2.2250738585072E-308", sb.toString());
+        sb.append(3E-308);
+        assertEquals("3.0E-308", sb.toString());
     }
 
     @Test