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diff --git a/memory/build/Utils.h b/memory/build/Utils.h
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+++ b/memory/build/Utils.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef Utils_h
+#define Utils_h
+
+#include <type_traits>
+
+#include "mozilla/CheckedInt.h"
+#include "mozilla/TemplateLib.h"
+
+// Helper for log2 of powers of 2 at compile time.
+template <size_t N>
+struct Log2 : mozilla::tl::CeilingLog2<N> {
+  using mozilla::tl::CeilingLog2<N>::value;
+  static_assert(1ULL << value == N, "Number is not a power of 2");
+};
+#define LOG2(N) Log2<N>::value
+
+enum class Order {
+  eLess = -1,
+  eEqual = 0,
+  eGreater = 1,
+};
+
+// Compare two integers. Returns whether the first integer is Less,
+// Equal or Greater than the second integer.
+template <typename T>
+Order CompareInt(T aValue1, T aValue2) {
+  static_assert(std::is_integral_v<T>, "Type must be integral");
+  if (aValue1 < aValue2) {
+    return Order::eLess;
+  }
+  if (aValue1 > aValue2) {
+    return Order::eGreater;
+  }
+  return Order::eEqual;
+}
+
+// Compare two addresses. Returns whether the first address is Less,
+// Equal or Greater than the second address.
+template <typename T>
+Order CompareAddr(T* aAddr1, T* aAddr2) {
+  return CompareInt(uintptr_t(aAddr1), uintptr_t(aAddr2));
+}
+
+// User-defined literals to make constants more legible
+constexpr size_t operator"" _KiB(unsigned long long int aNum) {
+  return size_t(aNum) * 1024;
+}
+
+constexpr size_t operator"" _KiB(long double aNum) {
+  return size_t(aNum * 1024);
+}
+
+constexpr size_t operator"" _MiB(unsigned long long int aNum) {
+  return size_t(aNum) * 1024_KiB;
+}
+
+constexpr size_t operator"" _MiB(long double aNum) {
+  return size_t(aNum * 1024_KiB);
+}
+
+constexpr double operator""_percent(long double aPercent) {
+  return double(aPercent) / 100;
+}
+
+// Helper for (fast) comparison of fractions without involving divisions or
+// floats.
+class Fraction {
+ public:
+  explicit constexpr Fraction(size_t aNumerator, size_t aDenominator)
+      : mNumerator(aNumerator), mDenominator(aDenominator) {}
+
+  MOZ_IMPLICIT constexpr Fraction(long double aValue)
+      // We use an arbitrary power of two as denominator that provides enough
+      // precision for our use case.
+      : mNumerator(aValue * 4096), mDenominator(4096) {}
+
+  inline bool operator<(const Fraction& aOther) const {
+#ifndef MOZ_DEBUG
+    // We are comparing A / B < C / D, with all A, B, C and D being positive
+    // numbers. Multiplying both sides with B * D, we have:
+    // (A * B * D) / B < (C * B * D) / D, which can then be simplified as
+    // A * D < C * B. When can thus compare our fractions without actually
+    // doing any division.
+    // This however assumes the multiplied quantities are small enough not
+    // to overflow the multiplication. We use CheckedInt on debug builds
+    // to enforce the assumption.
+    return mNumerator * aOther.mDenominator < aOther.mNumerator * mDenominator;
+#else
+    mozilla::CheckedInt<size_t> numerator(mNumerator);
+    mozilla::CheckedInt<size_t> denominator(mDenominator);
+    // value() asserts when the multiplication overflowed.
+    size_t lhs = (numerator * aOther.mDenominator).value();
+    size_t rhs = (aOther.mNumerator * denominator).value();
+    return lhs < rhs;
+#endif
+  }
+
+  inline bool operator>(const Fraction& aOther) const { return aOther < *this; }
+
+  inline bool operator>=(const Fraction& aOther) const {
+    return !(*this < aOther);
+  }
+
+  inline bool operator<=(const Fraction& aOther) const {
+    return !(*this > aOther);
+  }
+
+  inline bool operator==(const Fraction& aOther) const {
+#ifndef MOZ_DEBUG
+    // Same logic as operator<
+    return mNumerator * aOther.mDenominator == aOther.mNumerator * mDenominator;
+#else
+    mozilla::CheckedInt<size_t> numerator(mNumerator);
+    mozilla::CheckedInt<size_t> denominator(mDenominator);
+    size_t lhs = (numerator * aOther.mDenominator).value();
+    size_t rhs = (aOther.mNumerator * denominator).value();
+    return lhs == rhs;
+#endif
+  }
+
+  inline bool operator!=(const Fraction& aOther) const {
+    return !(*this == aOther);
+  }
+
+ private:
+  size_t mNumerator;
+  size_t mDenominator;
+};
+
+#endif