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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 // This 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/ArrayRef.h"
     22 #include "llvm/ADT/Triple.h"
     23 #include "llvm/Support/DataTypes.h"
     24 #include <bitset>
     25 
     26 namespace llvm {
     27   class raw_ostream;
     28   class StringRef;
     29 
     30 // A container class for subtarget features.
     31 // This is convenient because std::bitset does not have a constructor
     32 // with an initializer list of set bits.
     33 const unsigned MAX_SUBTARGET_FEATURES = 128;
     34 class FeatureBitset : public std::bitset<MAX_SUBTARGET_FEATURES> {
     35 public:
     36   // Cannot inherit constructors because it's not supported by VC++..
     37   FeatureBitset() : bitset() {}
     38 
     39   FeatureBitset(const bitset<MAX_SUBTARGET_FEATURES>& B) : bitset(B) {}
     40 
     41   FeatureBitset(std::initializer_list<unsigned> Init) : bitset() {
     42     for (auto I = Init.begin() , E = Init.end(); I != E; ++I)
     43       set(*I);
     44   }
     45 };
     46 
     47 //===----------------------------------------------------------------------===//
     48 ///
     49 /// SubtargetFeatureKV - Used to provide key value pairs for feature and
     50 /// CPU bit flags.
     51 //
     52 struct SubtargetFeatureKV {
     53   const char *Key;                      // K-V key string
     54   const char *Desc;                     // Help descriptor
     55   FeatureBitset Value;                  // K-V integer value
     56   FeatureBitset Implies;                // K-V bit mask
     57 
     58   // Compare routine for std::lower_bound
     59   bool operator<(StringRef S) const {
     60     return StringRef(Key) < S;
     61   }
     62 };
     63 
     64 //===----------------------------------------------------------------------===//
     65 ///
     66 /// SubtargetInfoKV - Used to provide key value pairs for CPU and arbitrary
     67 /// pointers.
     68 //
     69 struct SubtargetInfoKV {
     70   const char *Key;                      // K-V key string
     71   const void *Value;                    // K-V pointer value
     72 
     73   // Compare routine for std::lower_bound
     74   bool operator<(StringRef S) const {
     75     return StringRef(Key) < S;
     76   }
     77 };
     78 
     79 //===----------------------------------------------------------------------===//
     80 ///
     81 /// SubtargetFeatures - Manages the enabling and disabling of subtarget
     82 /// specific features.  Features are encoded as a string of the form
     83 ///   "+attr1,+attr2,-attr3,...,+attrN"
     84 /// A comma separates each feature from the next (all lowercase.)
     85 /// Each of the remaining features is prefixed with + or - indicating whether
     86 /// that feature should be enabled or disabled contrary to the cpu
     87 /// specification.
     88 ///
     89 
     90 class SubtargetFeatures {
     91   std::vector<std::string> Features;    // Subtarget features as a vector
     92 public:
     93   explicit SubtargetFeatures(StringRef Initial = "");
     94 
     95   /// Features string accessors.
     96   std::string getString() const;
     97 
     98   /// Adding Features.
     99   void AddFeature(StringRef String, bool Enable = true);
    100 
    101   /// ToggleFeature - Toggle a feature and returns the newly updated feature
    102   /// bits.
    103   FeatureBitset ToggleFeature(FeatureBitset Bits, StringRef String,
    104                          ArrayRef<SubtargetFeatureKV> FeatureTable);
    105 
    106   /// Apply the feature flag and return the newly updated feature bits.
    107   FeatureBitset ApplyFeatureFlag(FeatureBitset Bits, StringRef Feature,
    108                                  ArrayRef<SubtargetFeatureKV> FeatureTable);
    109 
    110   /// Get feature bits of a CPU.
    111   FeatureBitset getFeatureBits(StringRef CPU,
    112                           ArrayRef<SubtargetFeatureKV> CPUTable,
    113                           ArrayRef<SubtargetFeatureKV> FeatureTable);
    114 
    115   /// Print feature string.
    116   void print(raw_ostream &OS) const;
    117 
    118   // Dump feature info.
    119   void dump() const;
    120 
    121   /// Adds the default features for the specified target triple.
    122   void getDefaultSubtargetFeatures(const Triple& Triple);
    123 };
    124 
    125 } // End namespace llvm
    126 
    127 #endif
    128