1 //===-- SSAUpdater.h - Unstructured SSA Update Tool -------------*- 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 declares the SSAUpdater class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_TRANSFORMS_UTILS_SSAUPDATER_H 15 #define LLVM_TRANSFORMS_UTILS_SSAUPDATER_H 16 17 #include "llvm/ADT/StringRef.h" 18 19 namespace llvm { 20 class BasicBlock; 21 class Instruction; 22 class LoadInst; 23 template<typename T> class SmallVectorImpl; 24 template<typename T> class SSAUpdaterTraits; 25 class PHINode; 26 class Type; 27 class Use; 28 class Value; 29 30 /// SSAUpdater - This class updates SSA form for a set of values defined in 31 /// multiple blocks. This is used when code duplication or another unstructured 32 /// transformation wants to rewrite a set of uses of one value with uses of a 33 /// set of values. 34 class SSAUpdater { 35 friend class SSAUpdaterTraits<SSAUpdater>; 36 37 private: 38 /// AvailableVals - This keeps track of which value to use on a per-block 39 /// basis. When we insert PHI nodes, we keep track of them here. 40 //typedef DenseMap<BasicBlock*, Value*> AvailableValsTy; 41 void *AV; 42 43 /// ProtoType holds the type of the values being rewritten. 44 Type *ProtoType; 45 46 // PHI nodes are given a name based on ProtoName. 47 std::string ProtoName; 48 49 /// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that 50 /// it creates to the vector. 51 SmallVectorImpl<PHINode*> *InsertedPHIs; 52 53 public: 54 /// SSAUpdater constructor. If InsertedPHIs is specified, it will be filled 55 /// in with all PHI Nodes created by rewriting. 56 explicit SSAUpdater(SmallVectorImpl<PHINode*> *InsertedPHIs = 0); 57 ~SSAUpdater(); 58 59 /// Initialize - Reset this object to get ready for a new set of SSA 60 /// updates with type 'Ty'. PHI nodes get a name based on 'Name'. 61 void Initialize(Type *Ty, StringRef Name); 62 63 /// AddAvailableValue - Indicate that a rewritten value is available at the 64 /// end of the specified block with the specified value. 65 void AddAvailableValue(BasicBlock *BB, Value *V); 66 67 /// HasValueForBlock - Return true if the SSAUpdater already has a value for 68 /// the specified block. 69 bool HasValueForBlock(BasicBlock *BB) const; 70 71 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is 72 /// live at the end of the specified block. 73 Value *GetValueAtEndOfBlock(BasicBlock *BB); 74 75 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that 76 /// is live in the middle of the specified block. 77 /// 78 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one 79 /// important case: if there is a definition of the rewritten value after the 80 /// 'use' in BB. Consider code like this: 81 /// 82 /// X1 = ... 83 /// SomeBB: 84 /// use(X) 85 /// X2 = ... 86 /// br Cond, SomeBB, OutBB 87 /// 88 /// In this case, there are two values (X1 and X2) added to the AvailableVals 89 /// set by the client of the rewriter, and those values are both live out of 90 /// their respective blocks. However, the use of X happens in the *middle* of 91 /// a block. Because of this, we need to insert a new PHI node in SomeBB to 92 /// merge the appropriate values, and this value isn't live out of the block. 93 /// 94 Value *GetValueInMiddleOfBlock(BasicBlock *BB); 95 96 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes, 97 /// which use their value in the corresponding predecessor. Note that this 98 /// will not work if the use is supposed to be rewritten to a value defined in 99 /// the same block as the use, but above it. Any 'AddAvailableValue's added 100 /// for the use's block will be considered to be below it. 101 void RewriteUse(Use &U); 102 103 /// RewriteUseAfterInsertions - Rewrite a use, just like RewriteUse. However, 104 /// this version of the method can rewrite uses in the same block as a 105 /// definition, because it assumes that all uses of a value are below any 106 /// inserted values. 107 void RewriteUseAfterInsertions(Use &U); 108 109 private: 110 Value *GetValueAtEndOfBlockInternal(BasicBlock *BB); 111 112 void operator=(const SSAUpdater&); // DO NOT IMPLEMENT 113 SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT 114 }; 115 116 /// LoadAndStorePromoter - This little helper class provides a convenient way to 117 /// promote a collection of loads and stores into SSA Form using the SSAUpdater. 118 /// This handles complexities that SSAUpdater doesn't, such as multiple loads 119 /// and stores in one block. 120 /// 121 /// Clients of this class are expected to subclass this and implement the 122 /// virtual methods. 123 /// 124 class LoadAndStorePromoter { 125 protected: 126 SSAUpdater &SSA; 127 public: 128 LoadAndStorePromoter(const SmallVectorImpl<Instruction*> &Insts, 129 SSAUpdater &S, StringRef Name = StringRef()); 130 virtual ~LoadAndStorePromoter() {} 131 132 /// run - This does the promotion. Insts is a list of loads and stores to 133 /// promote, and Name is the basename for the PHIs to insert. After this is 134 /// complete, the loads and stores are removed from the code. 135 void run(const SmallVectorImpl<Instruction*> &Insts) const; 136 137 138 /// Return true if the specified instruction is in the Inst list (which was 139 /// passed into the run method). Clients should implement this with a more 140 /// efficient version if possible. 141 virtual bool isInstInList(Instruction *I, 142 const SmallVectorImpl<Instruction*> &Insts) const; 143 144 /// doExtraRewritesBeforeFinalDeletion - This hook is invoked after all the 145 /// stores are found and inserted as available values, but 146 virtual void doExtraRewritesBeforeFinalDeletion() const { 147 } 148 149 /// replaceLoadWithValue - Clients can choose to implement this to get 150 /// notified right before a load is RAUW'd another value. 151 virtual void replaceLoadWithValue(LoadInst *LI, Value *V) const { 152 } 153 154 /// This is called before each instruction is deleted. 155 virtual void instructionDeleted(Instruction *I) const { 156 } 157 158 /// updateDebugInfo - This is called to update debug info associated with the 159 /// instruction. 160 virtual void updateDebugInfo(Instruction *I) const { 161 } 162 }; 163 164 } // End llvm namespace 165 166 #endif 167
