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 22 namespace { 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. 27 template <typename T, typename F> 28 std::enable_if_t<std::is_integral<T>::value && sizeof(T) * 8 <= 64, 29 llvm::Optional<T>> 30 checkedOp(T LHS, T RHS, F Op, bool Signed = true) { 31 llvm::APInt ALHS(sizeof(T) * 8, LHS, Signed); 32 llvm::APInt ARHS(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 41 namespace 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. 46 template <typename T> 47 std::enable_if_t<std::is_signed<T>::value, llvm::Optional<T>> 48 checkedAdd(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. 55 template <typename T> 56 std::enable_if_t<std::is_signed<T>::value, llvm::Optional<T>> 57 checkedSub(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. 64 template <typename T> 65 std::enable_if_t<std::is_signed<T>::value, llvm::Optional<T>> 66 checkedMul(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. 73 template <typename T> 74 std::enable_if_t<std::is_signed<T>::value, llvm::Optional<T>> 75 checkedMulAdd(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. 84 template <typename T> 85 std::enable_if_t<std::is_unsigned<T>::value, llvm::Optional<T>> 86 checkedAddUnsigned(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. 93 template <typename T> 94 std::enable_if_t<std::is_unsigned<T>::value, llvm::Optional<T>> 95 checkedMulUnsigned(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. 102 template <typename T> 103 std::enable_if_t<std::is_unsigned<T>::value, llvm::Optional<T>> 104 checkedMulAddUnsigned(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