| //==-- 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 <optional> |
| #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> |
| std::enable_if_t<std::is_integral_v<T> && sizeof(T) * 8 <= 64, std::optional<T>> |
| checkedOp(T LHS, T RHS, F Op, bool Signed = true) { |
| llvm::APInt ALHS(sizeof(T) * 8, LHS, Signed); |
| llvm::APInt ARHS(sizeof(T) * 8, RHS, Signed); |
| bool Overflow; |
| llvm::APInt Out = (ALHS.*Op)(ARHS, Overflow); |
| if (Overflow) |
| return std::nullopt; |
| 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 std::nullopt otherwise. |
| template <typename T> |
| std::enable_if_t<std::is_signed_v<T>, std::optional<T>> checkedAdd(T LHS, |
| T RHS) { |
| return checkedOp(LHS, RHS, &llvm::APInt::sadd_ov); |
| } |
| |
| /// Subtract two signed integers \p LHS and \p RHS. |
| /// \return Optional of sum if no signed overflow occurred, |
| /// \c std::nullopt otherwise. |
| template <typename T> |
| std::enable_if_t<std::is_signed_v<T>, std::optional<T>> checkedSub(T LHS, |
| T RHS) { |
| return checkedOp(LHS, RHS, &llvm::APInt::ssub_ov); |
| } |
| |
| /// Multiply two signed integers \p LHS and \p RHS. |
| /// \return Optional of product if no signed overflow occurred, |
| /// \c std::nullopt otherwise. |
| template <typename T> |
| std::enable_if_t<std::is_signed_v<T>, std::optional<T>> 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 std::nullopt otherwise. |
| template <typename T> |
| std::enable_if_t<std::is_signed_v<T>, std::optional<T>> checkedMulAdd(T A, T B, |
| T C) { |
| if (auto Product = checkedMul(A, B)) |
| return checkedAdd(*Product, C); |
| return std::nullopt; |
| } |
| |
| /// Add two unsigned integers \p LHS and \p RHS. |
| /// \return Optional of sum if no unsigned overflow occurred, |
| /// \c std::nullopt otherwise. |
| template <typename T> |
| std::enable_if_t<std::is_unsigned_v<T>, std::optional<T>> |
| 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 std::nullopt otherwise. |
| template <typename T> |
| std::enable_if_t<std::is_unsigned_v<T>, std::optional<T>> |
| 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 std::nullopt otherwise. |
| template <typename T> |
| std::enable_if_t<std::is_unsigned_v<T>, std::optional<T>> |
| checkedMulAddUnsigned(T A, T B, T C) { |
| if (auto Product = checkedMulUnsigned(A, B)) |
| return checkedAddUnsigned(*Product, C); |
| return std::nullopt; |
| } |
| |
| } // End llvm namespace |
| |
| #endif |