1 //===- llvm/Support/ScaledNumber.h - Support for scaled numbers -*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains functions (and a class) useful for working with scaled
11 // numbers -- in particular, pairs of integers where one represents digits and
12 // another represents a scale. The functions are helpers and live in the
13 // namespace ScaledNumbers. The class ScaledNumber is useful for modelling
14 // certain cost metrics that need simple, integer-like semantics that are easy
17 // These might remind you of soft-floats. If you want one of those, you're in
18 // the wrong place. Look at include/llvm/ADT/APFloat.h instead.
20 //===----------------------------------------------------------------------===//
22 #ifndef LLVM_SUPPORT_SCALEDNUMBER_H
23 #define LLVM_SUPPORT_SCALEDNUMBER_H
30 namespace ScaledNumbers {
32 /// \brief Get the width of a number.
33 template <class DigitsT> inline int getWidth() { return sizeof(DigitsT) * 8; }
35 /// \brief Conditionally round up a scaled number.
37 /// Given \c Digits and \c Scale, round up iff \c ShouldRound is \c true.
38 /// Always returns \c Scale unless there's an overflow, in which case it
39 /// returns \c 1+Scale.
41 /// \pre adding 1 to \c Scale will not overflow INT16_MAX.
42 template <class DigitsT>
43 inline std::pair<DigitsT, int16_t> getRounded(DigitsT Digits, int16_t Scale,
45 static_assert(!std::numeric_limits<DigitsT>::is_signed, "expected unsigned");
50 return std::make_pair(DigitsT(1) << (getWidth<DigitsT>() - 1), Scale + 1);
51 return std::make_pair(Digits, Scale);