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      1 //===- CFG.h - Process LLVM structures as graphs ----------------*- 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 specializations of GraphTraits that allow Function and
     11 // BasicBlock graphs to be treated as proper graphs for generic algorithms.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #ifndef LLVM_IR_CFG_H
     16 #define LLVM_IR_CFG_H
     17 
     18 #include "llvm/ADT/GraphTraits.h"
     19 #include "llvm/ADT/iterator.h"
     20 #include "llvm/ADT/iterator_range.h"
     21 #include "llvm/IR/BasicBlock.h"
     22 #include "llvm/IR/Function.h"
     23 #include "llvm/IR/InstrTypes.h"
     24 #include "llvm/IR/Value.h"
     25 #include "llvm/Support/Casting.h"
     26 #include "llvm/Support/type_traits.h"
     27 #include <cassert>
     28 #include <cstddef>
     29 #include <iterator>
     30 
     31 namespace llvm {
     32 
     33 //===----------------------------------------------------------------------===//
     34 // BasicBlock pred_iterator definition
     35 //===----------------------------------------------------------------------===//
     36 
     37 template <class Ptr, class USE_iterator> // Predecessor Iterator
     38 class PredIterator : public std::iterator<std::forward_iterator_tag,
     39                                           Ptr, ptrdiff_t, Ptr*, Ptr*> {
     40   typedef std::iterator<std::forward_iterator_tag, Ptr, ptrdiff_t, Ptr*,
     41                                                                     Ptr*> super;
     42   typedef PredIterator<Ptr, USE_iterator> Self;
     43   USE_iterator It;
     44 
     45   inline void advancePastNonTerminators() {
     46     // Loop to ignore non-terminator uses (for example BlockAddresses).
     47     while (!It.atEnd() && !isa<TerminatorInst>(*It))
     48       ++It;
     49   }
     50 
     51 public:
     52   typedef typename super::pointer pointer;
     53   typedef typename super::reference reference;
     54 
     55   PredIterator() = default;
     56   explicit inline PredIterator(Ptr *bb) : It(bb->user_begin()) {
     57     advancePastNonTerminators();
     58   }
     59   inline PredIterator(Ptr *bb, bool) : It(bb->user_end()) {}
     60 
     61   inline bool operator==(const Self& x) const { return It == x.It; }
     62   inline bool operator!=(const Self& x) const { return !operator==(x); }
     63 
     64   inline reference operator*() const {
     65     assert(!It.atEnd() && "pred_iterator out of range!");
     66     return cast<TerminatorInst>(*It)->getParent();
     67   }
     68   inline pointer *operator->() const { return &operator*(); }
     69 
     70   inline Self& operator++() {   // Preincrement
     71     assert(!It.atEnd() && "pred_iterator out of range!");
     72     ++It; advancePastNonTerminators();
     73     return *this;
     74   }
     75 
     76   inline Self operator++(int) { // Postincrement
     77     Self tmp = *this; ++*this; return tmp;
     78   }
     79 
     80   /// getOperandNo - Return the operand number in the predecessor's
     81   /// terminator of the successor.
     82   unsigned getOperandNo() const {
     83     return It.getOperandNo();
     84   }
     85 
     86   /// getUse - Return the operand Use in the predecessor's terminator
     87   /// of the successor.
     88   Use &getUse() const {
     89     return It.getUse();
     90   }
     91 };
     92 
     93 typedef PredIterator<BasicBlock, Value::user_iterator> pred_iterator;
     94 typedef PredIterator<const BasicBlock,
     95                      Value::const_user_iterator> const_pred_iterator;
     96 typedef iterator_range<pred_iterator> pred_range;
     97 typedef iterator_range<const_pred_iterator> pred_const_range;
     98 
     99 inline pred_iterator pred_begin(BasicBlock *BB) { return pred_iterator(BB); }
    100 inline const_pred_iterator pred_begin(const BasicBlock *BB) {
    101   return const_pred_iterator(BB);
    102 }
    103 inline pred_iterator pred_end(BasicBlock *BB) { return pred_iterator(BB, true);}
    104 inline const_pred_iterator pred_end(const BasicBlock *BB) {
    105   return const_pred_iterator(BB, true);
    106 }
    107 inline bool pred_empty(const BasicBlock *BB) {
    108   return pred_begin(BB) == pred_end(BB);
    109 }
    110 inline pred_range predecessors(BasicBlock *BB) {
    111   return pred_range(pred_begin(BB), pred_end(BB));
    112 }
    113 inline pred_const_range predecessors(const BasicBlock *BB) {
    114   return pred_const_range(pred_begin(BB), pred_end(BB));
    115 }
    116 
    117 //===----------------------------------------------------------------------===//
    118 // BasicBlock succ_iterator helpers
    119 //===----------------------------------------------------------------------===//
    120 
    121 typedef TerminatorInst::SuccIterator<TerminatorInst *, BasicBlock>
    122     succ_iterator;
    123 typedef TerminatorInst::SuccIterator<const TerminatorInst *, const BasicBlock>
    124     succ_const_iterator;
    125 typedef iterator_range<succ_iterator> succ_range;
    126 typedef iterator_range<succ_const_iterator> succ_const_range;
    127 
    128 inline succ_iterator succ_begin(BasicBlock *BB) {
    129   return succ_iterator(BB->getTerminator());
    130 }
    131 inline succ_const_iterator succ_begin(const BasicBlock *BB) {
    132   return succ_const_iterator(BB->getTerminator());
    133 }
    134 inline succ_iterator succ_end(BasicBlock *BB) {
    135   return succ_iterator(BB->getTerminator(), true);
    136 }
    137 inline succ_const_iterator succ_end(const BasicBlock *BB) {
    138   return succ_const_iterator(BB->getTerminator(), true);
    139 }
    140 inline bool succ_empty(const BasicBlock *BB) {
    141   return succ_begin(BB) == succ_end(BB);
    142 }
    143 inline succ_range successors(BasicBlock *BB) {
    144   return succ_range(succ_begin(BB), succ_end(BB));
    145 }
    146 inline succ_const_range successors(const BasicBlock *BB) {
    147   return succ_const_range(succ_begin(BB), succ_end(BB));
    148 }
    149 
    150 template <typename T, typename U>
    151 struct isPodLike<TerminatorInst::SuccIterator<T, U>> {
    152   static const bool value = isPodLike<T>::value;
    153 };
    154 
    155 //===--------------------------------------------------------------------===//
    156 // GraphTraits specializations for basic block graphs (CFGs)
    157 //===--------------------------------------------------------------------===//
    158 
    159 // Provide specializations of GraphTraits to be able to treat a function as a
    160 // graph of basic blocks...
    161 
    162 template <> struct GraphTraits<BasicBlock*> {
    163   typedef BasicBlock *NodeRef;
    164   typedef succ_iterator ChildIteratorType;
    165 
    166   static NodeRef getEntryNode(BasicBlock *BB) { return BB; }
    167   static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); }
    168   static ChildIteratorType child_end(NodeRef N) { return succ_end(N); }
    169 };
    170 
    171 template <> struct GraphTraits<const BasicBlock*> {
    172   typedef const BasicBlock *NodeRef;
    173   typedef succ_const_iterator ChildIteratorType;
    174 
    175   static NodeRef getEntryNode(const BasicBlock *BB) { return BB; }
    176 
    177   static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); }
    178   static ChildIteratorType child_end(NodeRef N) { return succ_end(N); }
    179 };
    180 
    181 // Provide specializations of GraphTraits to be able to treat a function as a
    182 // graph of basic blocks... and to walk it in inverse order.  Inverse order for
    183 // a function is considered to be when traversing the predecessor edges of a BB
    184 // instead of the successor edges.
    185 //
    186 template <> struct GraphTraits<Inverse<BasicBlock*>> {
    187   typedef BasicBlock *NodeRef;
    188   typedef pred_iterator ChildIteratorType;
    189   static NodeRef getEntryNode(Inverse<BasicBlock *> G) { return G.Graph; }
    190   static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); }
    191   static ChildIteratorType child_end(NodeRef N) { return pred_end(N); }
    192 };
    193 
    194 template <> struct GraphTraits<Inverse<const BasicBlock*>> {
    195   typedef const BasicBlock *NodeRef;
    196   typedef const_pred_iterator ChildIteratorType;
    197   static NodeRef getEntryNode(Inverse<const BasicBlock *> G) { return G.Graph; }
    198   static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); }
    199   static ChildIteratorType child_end(NodeRef N) { return pred_end(N); }
    200 };
    201 
    202 //===--------------------------------------------------------------------===//
    203 // GraphTraits specializations for function basic block graphs (CFGs)
    204 //===--------------------------------------------------------------------===//
    205 
    206 // Provide specializations of GraphTraits to be able to treat a function as a
    207 // graph of basic blocks... these are the same as the basic block iterators,
    208 // except that the root node is implicitly the first node of the function.
    209 //
    210 template <> struct GraphTraits<Function*> : public GraphTraits<BasicBlock*> {
    211   static NodeRef getEntryNode(Function *F) { return &F->getEntryBlock(); }
    212 
    213   // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
    214   typedef pointer_iterator<Function::iterator> nodes_iterator;
    215 
    216   static nodes_iterator nodes_begin(Function *F) {
    217     return nodes_iterator(F->begin());
    218   }
    219 
    220   static nodes_iterator nodes_end(Function *F) {
    221     return nodes_iterator(F->end());
    222   }
    223 
    224   static size_t size(Function *F) { return F->size(); }
    225 };
    226 template <> struct GraphTraits<const Function*> :
    227   public GraphTraits<const BasicBlock*> {
    228   static NodeRef getEntryNode(const Function *F) { return &F->getEntryBlock(); }
    229 
    230   // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
    231   typedef pointer_iterator<Function::const_iterator> nodes_iterator;
    232 
    233   static nodes_iterator nodes_begin(const Function *F) {
    234     return nodes_iterator(F->begin());
    235   }
    236 
    237   static nodes_iterator nodes_end(const Function *F) {
    238     return nodes_iterator(F->end());
    239   }
    240 
    241   static size_t size(const Function *F) { return F->size(); }
    242 };
    243 
    244 // Provide specializations of GraphTraits to be able to treat a function as a
    245 // graph of basic blocks... and to walk it in inverse order.  Inverse order for
    246 // a function is considered to be when traversing the predecessor edges of a BB
    247 // instead of the successor edges.
    248 //
    249 template <> struct GraphTraits<Inverse<Function*>> :
    250   public GraphTraits<Inverse<BasicBlock*>> {
    251   static NodeRef getEntryNode(Inverse<Function *> G) {
    252     return &G.Graph->getEntryBlock();
    253   }
    254 };
    255 template <> struct GraphTraits<Inverse<const Function*>> :
    256   public GraphTraits<Inverse<const BasicBlock*>> {
    257   static NodeRef getEntryNode(Inverse<const Function *> G) {
    258     return &G.Graph->getEntryBlock();
    259   }
    260 };
    261 
    262 } // end namespace llvm
    263 
    264 #endif // LLVM_IR_CFG_H
    265