diff --git a/AK/BuiltinWrappers.h b/AK/BuiltinWrappers.h
index 2ea6b68c025..81c27d58463 100644
--- a/AK/BuiltinWrappers.h
+++ b/AK/BuiltinWrappers.h
@@ -97,6 +97,24 @@ inline constexpr int count_leading_zeroes(IntType value)
 #endif
 }
 
+#ifdef __SIZEOF_INT128__
+// This is required for math.cpp internal_scalbn
+inline constexpr int count_leading_zeroes(unsigned __int128 value)
+{
+#    if defined(AK_COMPILER_CLANG) || defined(AK_COMPILER_GCC)
+    return (value > __UINT64_MAX__) ? __builtin_clzll(value >> 64) : 64 + __builtin_clzll(value);
+#    else
+    unsigned __int128 mask = (unsigned __int128)1 << 127;
+    int ret = 0;
+    while ((value & mask) == 0) {
+        ++ret;
+        mask >>= 1;
+    }
+    return ret;
+#    endif
+}
+#endif
+
 // The function will return the number of leading zeroes in the type. If
 // the given number is zero, this function will return the number of bits
 // in the IntType.
diff --git a/AK/FloatingPoint.h b/AK/FloatingPoint.h
index eeca5ea6b64..fea42d575cb 100644
--- a/AK/FloatingPoint.h
+++ b/AK/FloatingPoint.h
@@ -15,6 +15,26 @@ namespace AK {
 template<typename T>
 union FloatExtractor;
 
+#ifdef AK_HAS_FLOAT_128
+template<>
+union FloatExtractor<f128> {
+    static constexpr int mantissa_bits = 112;
+    static constexpr unsigned __int128 mantissa_max = (((unsigned __int128)1) << 112) - 1;
+    static constexpr int exponent_bias = 16383;
+    static constexpr int exponent_bits = 15;
+    static constexpr unsigned exponent_max = 32767;
+    struct {
+        unsigned __int128 mantissa : 112;
+        unsigned exponent : 15;
+        unsigned sign : 1;
+    };
+    f128 d;
+};
+// Validate that f128 and the FloatExtractor union are 128 bits.
+static_assert(sizeof(f128) == 16);
+static_assert(sizeof(FloatExtractor<f128>) == 16);
+#endif
+
 #ifdef AK_HAS_FLOAT_80
 template<>
 union FloatExtractor<f80> {
diff --git a/AK/IntegralMath.h b/AK/IntegralMath.h
index 415e485bf9d..4bf90181395 100644
--- a/AK/IntegralMath.h
+++ b/AK/IntegralMath.h
@@ -31,7 +31,7 @@ constexpr T ceil_log2(T x)
         return 0;
 
     T log = AK::log2(x);
-    log += (x & ((1 << (log - 1)) - 1)) != 0;
+    log += (x & ((((T)1) << (log - 1)) - 1)) != 0;
     return log;
 }