SubtargetFeature.h

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//===- llvm/MC/SubtargetFeature.h - CPU characteristics ---------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
/// \file Defines and manages user or tool specified CPU characteristics.
/// The intent is to be able to package specific features that should or should
/// not be used on a specific target processor.  A tool, such as llc, could, as
/// as example, gather chip info from the command line, a long with features
/// that should be used on that chip.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_MC_SUBTARGETFEATURE_H
#define LLVM_MC_SUBTARGETFEATURE_H

#include "llvm/ADT/StringRef.h"
#include <bitset>
#include <initializer_list>
#include <string>
#include <vector>

namespace llvm {

template <typename T> class ArrayRef;
class raw_ostream;
class Triple;

const unsigned MAX_SUBTARGET_FEATURES = 192;
/// Container class for subtarget features.
/// This is convenient because std::bitset does not have a constructor
/// with an initializer list of set bits.
class FeatureBitset : public std::bitset<MAX_SUBTARGET_FEATURES> {
public:
  // Cannot inherit constructors because it's not supported by VC++..
  FeatureBitset() = default;

  FeatureBitset(const bitset<MAX_SUBTARGET_FEATURES>& B) : bitset(B) {}

  FeatureBitset(std::initializer_list<unsigned> Init) {
    for (auto I : Init)
      set(I);
  }
};

//===----------------------------------------------------------------------===//

/// Used to provide key value pairs for feature and CPU bit flags.
struct SubtargetFeatureKV {
  const char *Key;                      ///< K-V key string
  const char *Desc;                     ///< Help descriptor
  FeatureBitset Value;                  ///< K-V integer value
  FeatureBitset Implies;                ///< K-V bit mask

  /// Compare routine for std::lower_bound
  bool operator<(StringRef S) const {
    return StringRef(Key) < S;
  }

  /// Compare routine for std::is_sorted.
  bool operator<(const SubtargetFeatureKV &Other) const {
    return StringRef(Key) < StringRef(Other.Key);
  }
};

//===----------------------------------------------------------------------===//

/// Used to provide key value pairs for CPU and arbitrary pointers.
struct SubtargetInfoKV {
  const char *Key;                      ///< K-V key string
  const void *Value;                    ///< K-V pointer value

  /// Compare routine for std::lower_bound
  bool operator<(StringRef S) const {
    return StringRef(Key) < S;
  }
};

//===----------------------------------------------------------------------===//

/// Manages the enabling and disabling of subtarget specific features.
///
/// Features are encoded as a string of the form
///   "+attr1,+attr2,-attr3,...,+attrN"
/// A comma separates each feature from the next (all lowercase.)
/// Each of the remaining features is prefixed with + or - indicating whether
/// that feature should be enabled or disabled contrary to the cpu
/// specification.
class SubtargetFeatures {
  std::vector<std::string> Features;    ///< Subtarget features as a vector

public:
  explicit SubtargetFeatures(StringRef Initial = "");

  /// Returns features as a string.
  std::string getString() const;

  /// Adds Features.
  void AddFeature(StringRef String, bool Enable = true);

  /// Toggles a feature and update the feature bits.
  static void ToggleFeature(FeatureBitset &Bits, StringRef String,
                            ArrayRef<SubtargetFeatureKV> FeatureTable);

  /// Applies the feature flag and update the feature bits.
  static void ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
                               ArrayRef<SubtargetFeatureKV> FeatureTable);

  /// Returns feature bits of a CPU.
  FeatureBitset getFeatureBits(StringRef CPU,
                               ArrayRef<SubtargetFeatureKV> CPUTable,
                               ArrayRef<SubtargetFeatureKV> FeatureTable);

  /// Returns the vector of individual subtarget features.
  const std::vector<std::string> &getFeatures() const { return Features; }

  /// Prints feature string.
  void print(raw_ostream &OS) const;

  // Dumps feature info.
  void dump() const;

  /// Adds the default features for the specified target triple.
  void getDefaultSubtargetFeatures(const Triple& Triple);
};

} // end namespace llvm

#endif // LLVM_MC_SUBTARGETFEATURE_H