1//==-- llvm/Support/CheckedArithmetic.h - Safe arithmetical operations *- C++ // 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// This file contains generic functions for operating on integers which 10// give the indication on whether the operation has overflown. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_SUPPORT_CHECKEDARITHMETIC_H 15#define LLVM_SUPPORT_CHECKEDARITHMETIC_H 16 17#include "llvm/ADT/APInt.h" 18#include "llvm/ADT/Optional.h" 19 20#include <type_traits> 21 22namespace { 23 24/// Utility function to apply a given method of \c APInt \p F to \p LHS and 25/// \p RHS. 26/// \return Empty optional if the operation overflows, or result otherwise. 27template <typename T, typename F> 28typename std::enable_if<std::is_integral<T>::value && sizeof(T) * 8 <= 64, 29 llvm::Optional<T>>::type 30checkedOp(T LHS, T RHS, F Op, bool Signed = true) { 31 llvm::APInt ALHS(/*BitSize=*/sizeof(T) * 8, LHS, Signed); 32 llvm::APInt ARHS(/*BitSize=*/sizeof(T) * 8, RHS, Signed); 33 bool Overflow; 34 llvm::APInt Out = (ALHS.*Op)(ARHS, Overflow); 35 if (Overflow) 36 return llvm::None; 37 return Signed ? Out.getSExtValue() : Out.getZExtValue(); 38} 39} 40 41namespace llvm { 42 43/// Add two signed integers \p LHS and \p RHS. 44/// \return Optional of sum if no signed overflow occurred, 45/// \c None otherwise. 46template <typename T> 47typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type 48checkedAdd(T LHS, T RHS) { 49 return checkedOp(LHS, RHS, &llvm::APInt::sadd_ov); 50} 51 52/// Subtract two signed integers \p LHS and \p RHS. 53/// \return Optional of sum if no signed overflow occurred, 54/// \c None otherwise. 55template <typename T> 56typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type 57checkedSub(T LHS, T RHS) { 58 return checkedOp(LHS, RHS, &llvm::APInt::ssub_ov); 59} 60 61/// Multiply two signed integers \p LHS and \p RHS. 62/// \return Optional of product if no signed overflow occurred, 63/// \c None otherwise. 64template <typename T> 65typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type 66checkedMul(T LHS, T RHS) { 67 return checkedOp(LHS, RHS, &llvm::APInt::smul_ov); 68} 69 70/// Multiply A and B, and add C to the resulting product. 71/// \return Optional of result if no signed overflow occurred, 72/// \c None otherwise. 73template <typename T> 74typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type 75checkedMulAdd(T A, T B, T C) { 76 if (auto Product = checkedMul(A, B)) 77 return checkedAdd(*Product, C); 78 return llvm::None; 79} 80 81/// Add two unsigned integers \p LHS and \p RHS. 82/// \return Optional of sum if no unsigned overflow occurred, 83/// \c None otherwise. 84template <typename T> 85typename std::enable_if<std::is_unsigned<T>::value, llvm::Optional<T>>::type 86checkedAddUnsigned(T LHS, T RHS) { 87 return checkedOp(LHS, RHS, &llvm::APInt::uadd_ov, /*Signed=*/false); 88} 89 90/// Multiply two unsigned integers \p LHS and \p RHS. 91/// \return Optional of product if no unsigned overflow occurred, 92/// \c None otherwise. 93template <typename T> 94typename std::enable_if<std::is_unsigned<T>::value, llvm::Optional<T>>::type 95checkedMulUnsigned(T LHS, T RHS) { 96 return checkedOp(LHS, RHS, &llvm::APInt::umul_ov, /*Signed=*/false); 97} 98 99/// Multiply unsigned integers A and B, and add C to the resulting product. 100/// \return Optional of result if no unsigned overflow occurred, 101/// \c None otherwise. 102template <typename T> 103typename std::enable_if<std::is_unsigned<T>::value, llvm::Optional<T>>::type 104checkedMulAddUnsigned(T A, T B, T C) { 105 if (auto Product = checkedMulUnsigned(A, B)) 106 return checkedAddUnsigned(*Product, C); 107 return llvm::None; 108} 109 110} // End llvm namespace 111 112#endif 113