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2ce70890ce
Start extracting helper functions out of -block-freq's `UnsignedFloat` into `Support/ScaledNumber.h` with the eventual goal of moving and renaming the class to `ScaledNumber`. The bike shed about names is still being painted, but I'm going with this for now. llvm-svn: 211333
58 lines
2.0 KiB
C++
58 lines
2.0 KiB
C++
//===- llvm/Support/ScaledNumber.h - Support for scaled numbers -*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains functions (and a class) useful for working with scaled
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// numbers -- in particular, pairs of integers where one represents digits and
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// another represents a scale. The functions are helpers and live in the
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// namespace ScaledNumbers. The class ScaledNumber is useful for modelling
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// certain cost metrics that need simple, integer-like semantics that are easy
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// to reason about.
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//
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// These might remind you of soft-floats. If you want one of those, you're in
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// the wrong place. Look at include/llvm/ADT/APFloat.h instead.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_SCALEDNUMBER_H
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#define LLVM_SUPPORT_SCALEDNUMBER_H
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#include <cstdint>
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#include <limits>
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#include <utility>
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namespace llvm {
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namespace ScaledNumbers {
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/// \brief Get the width of a number.
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template <class DigitsT> inline int getWidth() { return sizeof(DigitsT) * 8; }
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/// \brief Conditionally round up a scaled number.
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///
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/// Given \c Digits and \c Scale, round up iff \c ShouldRound is \c true.
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/// Always returns \c Scale unless there's an overflow, in which case it
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/// returns \c 1+Scale.
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///
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/// \pre adding 1 to \c Scale will not overflow INT16_MAX.
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template <class DigitsT>
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inline std::pair<DigitsT, int16_t> getRounded(DigitsT Digits, int16_t Scale,
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bool ShouldRound) {
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static_assert(!std::numeric_limits<DigitsT>::is_signed, "expected unsigned");
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if (ShouldRound)
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if (!++Digits)
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// Overflow.
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return std::make_pair(DigitsT(1) << (getWidth<DigitsT>() - 1), Scale + 1);
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return std::make_pair(Digits, Scale);
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}
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}
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}
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#endif
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