1    :  // Copyright 2015 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  //
  15    :  // Declares the assembler's label.
  16    :  
  17    :  #ifndef SYZYGY_ASSM_LABEL_BASE_H_
  18    :  #define SYZYGY_ASSM_LABEL_BASE_H_
  19    :  
  20    :  #include <vector>
  21    :  
  22    :  #include "base/basictypes.h"
  23    :  #include "base/macros.h"
  24    :  
  25    :  namespace assm {
  26    :  
  27    :  // Fwd.
  28    :  template <class ReferenceType>
  29    :  class AssemblerBase;
  30    :  
  31    :  // A label comes into existence unbound, and must be bound to the current
  32    :  // location at some point. Typical usage might go:
  33    :  //
  34    :  // Label success(&assm);
  35    :  // assm.cmp(...)
  36    :  // assm.j(kNotZero, &success);
  37    :  // ...
  38    :  // success.Bind();  // Binds the label to the assembler's current location.
  39    :  // ...
  40    :  template <class ReferenceType>
  41    :  class LabelBase {
  42    :   public:
  43    :    typedef AssemblerBase<ReferenceType> Assembler;
  44    :  
  45    :    explicit LabelBase(Assembler* assm);
  46    :    ~LabelBase();
  47    :  
  48    :    // Binds the label to the current assembly address.
  49    :    // @returns true on success.
  50    :    // @note binding can fail if the assembler's serializer doesn't support it,
  51    :    //     or if any use of the label is out of range for a PC-relative reference
  52    :    //     to the current address.
  53    :    bool Bind();
  54    :  
  55    :   private:
  56    :    friend class Assembler;
  57    :  
  58    :    struct LabelUsage {
  59    :      // The location of the use.
  60    :      uint32 location;
  61    :      // The size of the
  62    :      RegisterSize size;
  63    :    };
  64    :  
  65  E :    bool bound() const { return bound_; }
  66  E :    uint32 location() const { return location_; }
  67    :  
  68    :    // Interface for assembler to declare usage of unbound labels.
  69    :    void Use(uint32 location, RegisterSize size);
  70    :  
  71    :    // Revisits label usages and writes them with the correct value.
  72    :    bool Finalize();
  73    :  
  74    :    // The assembler this label belongs to.
  75    :    Assembler* assm_;
  76    :  
  77    :    // True iff the label is bound.
  78    :    bool bound_;
  79    :  
  80    :    // The location this label is bound to. Valid iff bound_ is true;
  81    :    uint32 location_;
  82    :  
  83    :    // Keeps track of where the unbound label has been used.
  84    :    std::vector<LabelUsage> uses_;
  85    :  
  86    :    DISALLOW_COPY_AND_ASSIGN(LabelBase);
  87    :  };
  88    :  
  89    :  template <class ReferenceType>
  90    :  LabelBase<ReferenceType>::LabelBase(Assembler* assm) :
  91  E :      assm_(assm), bound_(false), location_(0) {
  92  E :    DCHECK(assm != NULL);
  93  E :  }
  94    :  
  95    :  template <class ReferenceType>
  96  E :  LabelBase<ReferenceType>::~LabelBase() {
  97  E :    DCHECK_EQ(0U, uses_.size());
  98  E :  }
  99    :  
 100    :  template <class ReferenceType>
 101  E :  bool LabelBase<ReferenceType>::Bind() {
 102  E :    bound_ = true;
 103  E :    location_ = assm_->location();
 104    :  
 105  E :    return Finalize();
 106  E :  }
 107    :  
 108    :  template <class ReferenceType>
 109  E :  void LabelBase<ReferenceType>::Use(uint32 location, RegisterSize size) {
 110  E :    DCHECK(!bound_);
 111  E :    LabelUsage usage = { location, size };
 112  E :    uses_.push_back(usage);
 113  E :  }
 114    :  
 115    :  template <class ReferenceType>
 116  E :  bool LabelBase<ReferenceType>::Finalize() {
 117  E :    bool success = true;
 118  E :    for (auto usage: uses_) {
 119  E :      success = assm_->FinalizeLabel(usage.location, location_, usage.size);
 120  E :      if (!success)
 121  E :        break;
 122    :    }
 123  E :    uses_.clear();
 124    :  
 125  E :    return success;
 126  E :  }
 127    :  
 128    :  }  // namespace assm
 129    :  
 130    :  #endif  // SYZYGY_ASSM_LABEL_BASE_H_