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      1 //===- llvm/MC/SubtargetFeature.h - CPU characteristics ---------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 /// \file Defines and manages user or tool specified CPU characteristics.
     11 /// The intent is to be able to package specific features that should or should
     12 /// not be used on a specific target processor.  A tool, such as llc, could, as
     13 /// as example, gather chip info from the command line, a long with features
     14 /// that should be used on that chip.
     15 //
     16 //===----------------------------------------------------------------------===//
     17 
     18 #ifndef LLVM_MC_SUBTARGETFEATURE_H
     19 #define LLVM_MC_SUBTARGETFEATURE_H
     20 
     21 #include "llvm/ADT/StringRef.h"
     22 #include <bitset>
     23 #include <initializer_list>
     24 #include <string>
     25 #include <vector>
     26 
     27 namespace llvm {
     28 
     29 template <typename T> class ArrayRef;
     30 class raw_ostream;
     31 class Triple;
     32 
     33 const unsigned MAX_SUBTARGET_FEATURES = 192;
     34 /// Container class for subtarget features.
     35 /// This is convenient because std::bitset does not have a constructor
     36 /// with an initializer list of set bits.
     37 class FeatureBitset : public std::bitset<MAX_SUBTARGET_FEATURES> {
     38 public:
     39   // Cannot inherit constructors because it's not supported by VC++..
     40   FeatureBitset() = default;
     41 
     42   FeatureBitset(const bitset<MAX_SUBTARGET_FEATURES>& B) : bitset(B) {}
     43 
     44   FeatureBitset(std::initializer_list<unsigned> Init) {
     45     for (auto I : Init)
     46       set(I);
     47   }
     48 };
     49 
     50 //===----------------------------------------------------------------------===//
     51 
     52 /// Used to provide key value pairs for feature and CPU bit flags.
     53 struct SubtargetFeatureKV {
     54   const char *Key;                      ///< K-V key string
     55   const char *Desc;                     ///< Help descriptor
     56   FeatureBitset Value;                  ///< K-V integer value
     57   FeatureBitset Implies;                ///< K-V bit mask
     58 
     59   /// Compare routine for std::lower_bound
     60   bool operator<(StringRef S) const {
     61     return StringRef(Key) < S;
     62   }
     63 
     64   /// Compare routine for std::is_sorted.
     65   bool operator<(const SubtargetFeatureKV &Other) const {
     66     return StringRef(Key) < StringRef(Other.Key);
     67   }
     68 };
     69 
     70 //===----------------------------------------------------------------------===//
     71 
     72 /// Used to provide key value pairs for CPU and arbitrary pointers.
     73 struct SubtargetInfoKV {
     74   const char *Key;                      ///< K-V key string
     75   const void *Value;                    ///< K-V pointer value
     76 
     77   /// Compare routine for std::lower_bound
     78   bool operator<(StringRef S) const {
     79     return StringRef(Key) < S;
     80   }
     81 };
     82 
     83 //===----------------------------------------------------------------------===//
     84 
     85 /// Manages the enabling and disabling of subtarget specific features.
     86 ///
     87 /// Features are encoded as a string of the form
     88 ///   "+attr1,+attr2,-attr3,...,+attrN"
     89 /// A comma separates each feature from the next (all lowercase.)
     90 /// Each of the remaining features is prefixed with + or - indicating whether
     91 /// that feature should be enabled or disabled contrary to the cpu
     92 /// specification.
     93 class SubtargetFeatures {
     94   std::vector<std::string> Features;    ///< Subtarget features as a vector
     95 
     96 public:
     97   explicit SubtargetFeatures(StringRef Initial = "");
     98 
     99   /// Returns features as a string.
    100   std::string getString() const;
    101 
    102   /// Adds Features.
    103   void AddFeature(StringRef String, bool Enable = true);
    104 
    105   /// Toggles a feature and update the feature bits.
    106   static void ToggleFeature(FeatureBitset &Bits, StringRef String,
    107                             ArrayRef<SubtargetFeatureKV> FeatureTable);
    108 
    109   /// Applies the feature flag and update the feature bits.
    110   static void ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
    111                                ArrayRef<SubtargetFeatureKV> FeatureTable);
    112 
    113   /// Returns feature bits of a CPU.
    114   FeatureBitset getFeatureBits(StringRef CPU,
    115                                ArrayRef<SubtargetFeatureKV> CPUTable,
    116                                ArrayRef<SubtargetFeatureKV> FeatureTable);
    117 
    118   /// Returns the vector of individual subtarget features.
    119   const std::vector<std::string> &getFeatures() const { return Features; }
    120 
    121   /// Prints feature string.
    122   void print(raw_ostream &OS) const;
    123 
    124   // Dumps feature info.
    125   void dump() const;
    126 
    127   /// Adds the default features for the specified target triple.
    128   void getDefaultSubtargetFeatures(const Triple& Triple);
    129 };
    130 
    131 } // end namespace llvm
    132 
    133 #endif // LLVM_MC_SUBTARGETFEATURE_H
    134