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Diffstat (limited to 'include/llvm/Support/ScaledNumber.h')
-rw-r--r-- | include/llvm/Support/ScaledNumber.h | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/include/llvm/Support/ScaledNumber.h b/include/llvm/Support/ScaledNumber.h new file mode 100644 index 0000000000..afdc7dc188 --- /dev/null +++ b/include/llvm/Support/ScaledNumber.h @@ -0,0 +1,57 @@ +//===- llvm/Support/ScaledNumber.h - Support for scaled numbers -*- 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 functions (and a class) useful for working with scaled +// numbers -- in particular, pairs of integers where one represents digits and +// another represents a scale. The functions are helpers and live in the +// namespace ScaledNumbers. The class ScaledNumber is useful for modelling +// certain cost metrics that need simple, integer-like semantics that are easy +// to reason about. +// +// These might remind you of soft-floats. If you want one of those, you're in +// the wrong place. Look at include/llvm/ADT/APFloat.h instead. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_SUPPORT_SCALEDNUMBER_H +#define LLVM_SUPPORT_SCALEDNUMBER_H + +#include <cstdint> +#include <limits> +#include <utility> + +namespace llvm { +namespace ScaledNumbers { + +/// \brief Get the width of a number. +template <class DigitsT> inline int getWidth() { return sizeof(DigitsT) * 8; } + +/// \brief Conditionally round up a scaled number. +/// +/// Given \c Digits and \c Scale, round up iff \c ShouldRound is \c true. +/// Always returns \c Scale unless there's an overflow, in which case it +/// returns \c 1+Scale. +/// +/// \pre adding 1 to \c Scale will not overflow INT16_MAX. +template <class DigitsT> +inline std::pair<DigitsT, int16_t> getRounded(DigitsT Digits, int16_t Scale, + bool ShouldRound) { + static_assert(!std::numeric_limits<DigitsT>::is_signed, "expected unsigned"); + + if (ShouldRound) + if (!++Digits) + // Overflow. + return std::make_pair(DigitsT(1) << (getWidth<DigitsT>() - 1), Scale + 1); + return std::make_pair(Digits, Scale); +} +} +} + +#endif + |