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//==-- llvm/Support/CheckedArithmetic.h - Safe arithmetical operations *- C++ //
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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 "llvm/ADT/Optional.h"
#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>
typename std::enable_if<std::is_integral<T>::value && sizeof(T) * 8 <= 64,
llvm::Optional<T>>::type
checkedOp(T LHS, T RHS, F Op, bool Signed = true) {
llvm::APInt ALHS(/*BitSize=*/sizeof(T) * 8, LHS, Signed);
llvm::APInt ARHS(/*BitSize=*/sizeof(T) * 8, RHS, Signed);
bool Overflow;
llvm::APInt Out = (ALHS.*Op)(ARHS, Overflow);
if (Overflow)
return llvm::None;
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 None otherwise.
template <typename T>
typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type
checkedAdd(T LHS, T RHS) {
return checkedOp(LHS, RHS, &llvm::APInt::sadd_ov);
}
/// Multiply two signed integers \p LHS and \p RHS.
/// \return Optional of product if no signed overflow occurred,
/// \c None otherwise.
template <typename T>
typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type
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 None otherwise.
template <typename T>
typename std::enable_if<std::is_signed<T>::value, llvm::Optional<T>>::type
checkedMulAdd(T A, T B, T C) {
if (auto Product = checkedMul(A, B))
return checkedAdd(*Product, C);
return llvm::None;
}
/// Add two unsigned integers \p LHS and \p RHS.
/// \return Optional of sum if no unsigned overflow occurred,
/// \c None otherwise.
template <typename T>
typename std::enable_if<std::is_unsigned<T>::value, llvm::Optional<T>>::type
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 None otherwise.
template <typename T>
typename std::enable_if<std::is_unsigned<T>::value, llvm::Optional<T>>::type
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 None otherwise.
template <typename T>
typename std::enable_if<std::is_unsigned<T>::value, llvm::Optional<T>>::type
checkedMulAddUnsigned(T A, T B, T C) {
if (auto Product = checkedMulUnsigned(A, B))
return checkedAddUnsigned(*Product, C);
return llvm::None;
}
} // End llvm namespace
#endif
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