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include/llvm/Support/CheckedArithmetic.h
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| 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 | | ||||
| 20 | #include <functional> | ||||
vsk: This include can go away now. | |||||
| 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, and write the output into \p Res. | ||||
| 27 | /// \return Whether the operation overflows. | ||||
| 28 | template <typename T, typename F> | ||||
| 29 | typename std::enable_if<std::is_integral<T>::value && sizeof(T) * 8 <= 64, | ||||
| 30 | bool>::type | ||||
| 31 | checkedOp(T LHS, T RHS, F Op, T *Res = nullptr, bool Signed = true) { | ||||
| 32 | llvm::APInt ALHS(/*BitSize=*/sizeof(T) * 8, LHS, Signed); | ||||
Done ReplyCan you move this out of the llvm namespace, into an anonymous namespace? vsk: Can you move this out of the llvm namespace, into an anonymous namespace? | |||||
| 33 | llvm::APInt ARHS(/*BitSize=*/sizeof(T) * 8, RHS, Signed); | ||||
| 34 | bool Overflow; | ||||
Not Done ReplyI'd rather just have the type of the function be some free template parameter, then, so it's clear the object isn't copied. vsk: I'd rather just have the type of the function be some free template parameter, then, so it's… | |||||
Done ReplyCould you elaborate? george.karpenkov: Could you elaborate? | |||||
Not Done ReplyI'm suggesting adding 'typename F' to the template parameter list and using F as the type of Op. It's shorter, and since there's no std::function, it signals to the reader that there are no unnecessary copies happening. Taken together this makes the code easier to read. vsk: I'm suggesting adding 'typename F' to the template parameter list and using F as the type of Op. | |||||
| 35 | llvm::APInt Out = (ALHS.*Op)(ARHS, Overflow); | ||||
| 36 | if (!Overflow && Res) | ||||
| 37 | *Res = Out.getSExtValue(); | ||||
| 38 | return Overflow; | ||||
| 39 | } | ||||
| 40 | } | ||||
| 41 | | ||||
| 42 | namespace llvm { | ||||
| 43 | | ||||
| 44 | /// Add two signed integers \p LHS and \p RHS, write into \p Res if non-null | ||||
| 45 | /// and the operation does not oveflow. | ||||
| 46 | /// Does not guarantee saturating arithmetic. | ||||
| 47 | /// \return Whether the result overflows. | ||||
| 48 | template <typename T> | ||||
| 49 | typename std::enable_if<std::is_signed<T>::value, bool>::type | ||||
| 50 | checkedAdd(T LHS, T RHS, T *Res = nullptr) { | ||||
| 51 | return checkedOp(LHS, RHS, &llvm::APInt::sadd_ov, Res); | ||||
| 52 | } | ||||
| 53 | | ||||
| 54 | /// Multiply two signed integers \p LHS and \p RHS, write into \p Res if | ||||
| 55 | /// non-null and the operation does not oveflow. | ||||
| 56 | /// Does not guarantee saturating arithmetic. | ||||
| 57 | /// \return Whether the result overflows. | ||||
| 58 | template <typename T> | ||||
| 59 | typename std::enable_if<std::is_signed<T>::value, bool>::type | ||||
| 60 | checkedMul(T LHS, T RHS, T *Res = nullptr) { | ||||
| 61 | return checkedOp(LHS, RHS, &llvm::APInt::smul_ov, Res); | ||||
| 62 | } | ||||
| 63 | | ||||
| 64 | /// Add two unsigned integers \p LHS and \p RHS, write into \p Res if non-null | ||||
| 65 | /// and the operation does not oveflow. | ||||
| 66 | /// Does not guarantee saturating arithmetic. | ||||
| 67 | /// \return Whether the result overflows. | ||||
| 68 | template <typename T> | ||||
| 69 | typename std::enable_if<std::is_unsigned<T>::value, bool>::type | ||||
| 70 | checkedAddUnsigned(T LHS, T RHS, T *Res = nullptr) { | ||||
| 71 | return checkedOp(LHS, RHS, &llvm::APInt::uadd_ov, Res, /*Signed=*/false); | ||||
| 72 | } | ||||
| 73 | | ||||
| 74 | /// Multiply two unsigned integers \p LHS and \p RHS, write into \p Res if | ||||
| 75 | /// non-null and the operation does not oveflow. | ||||
| 76 | /// Does not guarantee saturating arithmetic. | ||||
| 77 | /// \return Whether the result overflows. | ||||
| 78 | template <typename T> | ||||
| 79 | typename std::enable_if<std::is_unsigned<T>::value, bool>::type | ||||
| 80 | checkedMulUnsigned(T LHS, T RHS, T *Res = nullptr) { | ||||
| 81 | return checkedOp(LHS, RHS, &llvm::APInt::umul_ov, Res, /*Signed=*/false); | ||||
| 82 | } | ||||
| 83 | | ||||
| 84 | } // End llvm namespace | ||||
| 85 | | ||||
| 86 | #endif | ||||
This include can go away now.