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diff --git a/clang-r353983/include/llvm/Support/CheckedArithmetic.h b/clang-r353983/include/llvm/Support/CheckedArithmetic.h
new file mode 100644
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+++ b/clang-r353983/include/llvm/Support/CheckedArithmetic.h
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+//==-- llvm/Support/CheckedArithmetic.h - Safe arithmetical operations *- C++ //
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains generic functions for operating on integers which
+// give the indication on whether the operation has overflown.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_CHECKEDARITHMETIC_H
+#define LLVM_SUPPORT_CHECKEDARITHMETIC_H
+
+#include "llvm/ADT/APInt.h"
+#include "llvm/ADT/Optional.h"
+
+#include <type_traits>
+
+namespace {
+
+/// Utility function to apply a given method of \c APInt \p F to \p LHS and
+/// \p RHS.
+/// \return Empty optional if the operation overflows, or result otherwise.
+template <typename T, typename F>
+typename std::enable_if<std::is_integral<T>::value && sizeof(T) * 8 <= 64,
+                        llvm::Optional<T>>::type
+checkedOp(T LHS, T RHS, F Op, bool Signed = true) {
+  llvm::APInt ALHS(/*BitSize=*/sizeof(T) * 8, LHS, Signed);
+  llvm::APInt ARHS(/*BitSize=*/sizeof(T) * 8, RHS, Signed);
+  bool Overflow;
+  llvm::APInt Out = (ALHS.*Op)(ARHS, Overflow);
+  if (Overflow)
+    return llvm::None;
+  return Signed ? Out.getSExtValue() : Out.getZExtValue();
+}
+}
+
+namespace llvm {
+
+/// Add two signed integers \p LHS and \p RHS.
+/// \return Optional of sum if no signed overflow occurred,
+/// \c None otherwise.
+template <typename T>
+typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type
+checkedAdd(T LHS, T RHS) {
+  return checkedOp(LHS, RHS, &llvm::APInt::sadd_ov);
+}
+
+/// Multiply two signed integers \p LHS and \p RHS.
+/// \return Optional of product if no signed overflow occurred,
+/// \c None otherwise.
+template <typename T>
+typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type
+checkedMul(T LHS, T RHS) {
+  return checkedOp(LHS, RHS, &llvm::APInt::smul_ov);
+}
+
+/// Multiply A and B, and add C to the resulting product.
+/// \return Optional of result if no signed overflow occurred,
+/// \c None otherwise.
+template <typename T>
+typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type
+checkedMulAdd(T A, T B, T C) {
+  if (auto Product = checkedMul(A, B))
+    return checkedAdd(*Product, C);
+  return llvm::None;
+}
+
+/// Add two unsigned integers \p LHS and \p RHS.
+/// \return Optional of sum if no unsigned overflow occurred,
+/// \c None otherwise.
+template <typename T>
+typename std::enable_if<std::is_unsigned<T>::value, llvm::Optional<T>>::type
+checkedAddUnsigned(T LHS, T RHS) {
+  return checkedOp(LHS, RHS, &llvm::APInt::uadd_ov, /*Signed=*/false);
+}
+
+/// Multiply two unsigned integers \p LHS and \p RHS.
+/// \return Optional of product if no unsigned overflow occurred,
+/// \c None otherwise.
+template <typename T>
+typename std::enable_if<std::is_unsigned<T>::value, llvm::Optional<T>>::type
+checkedMulUnsigned(T LHS, T RHS) {
+  return checkedOp(LHS, RHS, &llvm::APInt::umul_ov, /*Signed=*/false);
+}
+
+/// Multiply unsigned integers A and B, and add C to the resulting product.
+/// \return Optional of result if no unsigned overflow occurred,
+/// \c None otherwise.
+template <typename T>
+typename std::enable_if<std::is_unsigned<T>::value, llvm::Optional<T>>::type
+checkedMulAddUnsigned(T A, T B, T C) {
+  if (auto Product = checkedMulUnsigned(A, B))
+    return checkedAddUnsigned(*Product, C);
+  return llvm::None;
+}
+
+} // End llvm namespace
+
+#endif