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