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/*========================== begin_copyright_notice ============================
Copyright (C) 2020-2021 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ===========================*/
#ifndef IGCLLVM_SUPPORT_MATHEXTRAS_H
#define IGCLLVM_SUPPORT_MATHEXTRAS_H
#include "llvm/Config/llvm-config.h"
#include "llvm/Support/MathExtras.h"
namespace IGCLLVM
{
#if LLVM_VERSION_MAJOR < 10
// NOTE: Implementation of SubOverflow and MulOverflow is taken from llvm 10
// from llvm/Support/MathExtras.h.
/// Subtract two signed integers, computing the two's complement truncated
/// result, returning true if an overflow ocurred.
template <typename T>
typename std::enable_if<std::is_signed<T>::value, T>::type
SubOverflow(T X, T Y, T &Result) {
// Perform the unsigned addition.
using U = typename std::make_unsigned<T>::type;
const U UX = static_cast<U>(X);
const U UY = static_cast<U>(Y);
const U UResult = UX - UY;
// Convert to signed.
Result = static_cast<T>(UResult);
// Subtracting a positive number from a negative results in a negative number.
if (X <= 0 && Y > 0)
return Result >= 0;
// Subtracting a negative number from a positive results in a positive number.
if (X >= 0 && Y < 0)
return Result <= 0;
return false;
}
/// Multiply two signed integers, computing the two's complement truncated
/// result, returning true if an overflow ocurred.
template <typename T>
typename std::enable_if<std::is_signed<T>::value, T>::type
MulOverflow(T X, T Y, T &Result) {
// Perform the unsigned multiplication on absolute values.
using U = typename std::make_unsigned<T>::type;
const U UX = X < 0 ? (0 - static_cast<U>(X)) : static_cast<U>(X);
const U UY = Y < 0 ? (0 - static_cast<U>(Y)) : static_cast<U>(Y);
const U UResult = UX * UY;
// Convert to signed.
const bool IsNegative = (X < 0) ^ (Y < 0);
Result = IsNegative ? (0 - UResult) : UResult;
// If any of the args was 0, result is 0 and no overflow occurs.
if (UX == 0 || UY == 0)
return false;
// UX and UY are in [1, 2^n], where n is the number of digits.
// Check how the max allowed absolute value (2^n for negative, 2^(n-1) for
// positive) divided by an argument compares to the other.
if (IsNegative)
return UX > (static_cast<U>(std::numeric_limits<T>::max()) + U(1)) / UY;
else
return UX > (static_cast<U>(std::numeric_limits<T>::max())) / UY;
}
#else
using llvm::SubOverflow;
using llvm::MulOverflow;
#endif
}
#endif
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