text: //===-- llvm/Target/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.
  //
  //===----------------------------------------------------------------------===//
  //
  // This 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_TARGET_SUBTARGETFEATURE_H
  #define LLVM_TARGET_SUBTARGETFEATURE_H
  
  #include <string>
  #include <vector>
  #include <iosfwd>
  #include <cstring>
  #include "llvm/Support/DataTypes.h"
  
  namespace llvm {
  
  //===----------------------------------------------------------------------===//
  ///
  /// SubtargetFeatureKV - 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
    uint32_t Value;                       // K-V integer value
    uint32_t Implies;                     // K-V bit mask
    
    // Compare routine for std binary search
    bool operator<(const SubtargetFeatureKV &S) const {
      return strcmp(Key, S.Key) < 0;
    }
  };
    
  //===----------------------------------------------------------------------===//
  ///
  /// SubtargetInfoKV - Used to provide key value pairs for CPU and arbitrary
  /// pointers.
  //
  struct SubtargetInfoKV {
    const char *Key;                      // K-V key string
    void *Value;                          // K-V pointer value
    
    // Compare routine for std binary search
    bool operator<(const SubtargetInfoKV &S) const {
      return strcmp(Key, S.Key) < 0;
    }
  };
    
  //===----------------------------------------------------------------------===//
  ///
  /// SubtargetFeatures - Manages the enabling and disabling of subtarget 
  /// specific features.  Features are encoded as a string of the form
  ///   "cpu,+attr1,+attr2,-attr3,...,+attrN"
  /// A comma separates each feature from the next (all lowercase.)
  /// The first feature is always the CPU subtype (eg. pentiumm).  If the CPU
  /// value is "generic" then the CPU subtype should be generic for the target.
  /// 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(const std::string &Initial = std::string());
  
    /// Features string accessors.
    std::string getString() const;
    void setString(const std::string &Initial);
  
    /// Set the CPU string.  Replaces previous setting.  Setting to "" clears CPU.
    void setCPU(const std::string &String);
    
    /// Setting CPU string only if no string is set.
    void setCPUIfNone(const std::string &String);
    
    /// Adding Features.
    void AddFeature(const std::string &String, bool IsEnabled = true);
             
    /// Get feature bits.
    uint32_t getBits(const SubtargetFeatureKV *CPUTable,
                           size_t CPUTableSize,
                     const SubtargetFeatureKV *FeatureTable,
                           size_t FeatureTableSize);
                           
    /// Get info pointer
    void *getInfo(const SubtargetInfoKV *Table, size_t TableSize);
    
    /// Print feature string.
    void print(std::ostream &OS) const;
    void print(std::ostream *OS) const { if (OS) print(*OS); }
    
    // Dump feature info.
    void dump() const;
  };
  
  } // End namespace llvm
  
  #endif
  