1 //===-- SSAUpdater.h - Unstructured SSA Update Tool -------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file declares the SSAUpdater class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_TRANSFORMS_UTILS_SSAUPDATER_H
15 #define LLVM_TRANSFORMS_UTILS_SSAUPDATER_H
22 template<typename T> class SmallVectorImpl;
23 template<typename T> class SSAUpdaterTraits;
26 class BumpPtrAllocator;
28 /// SSAUpdater - This class updates SSA form for a set of values defined in
29 /// multiple blocks. This is used when code duplication or another unstructured
30 /// transformation wants to rewrite a set of uses of one value with uses of a
33 friend class SSAUpdaterTraits<SSAUpdater>;
36 /// AvailableVals - This keeps track of which value to use on a per-block
37 /// basis. When we insert PHI nodes, we keep track of them here.
38 //typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
41 /// ProtoType holds the type of the values being rewritten.
42 const Type *ProtoType;
44 // PHI nodes are given a name based on ProtoName.
45 std::string ProtoName;
47 /// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
48 /// it creates to the vector.
49 SmallVectorImpl<PHINode*> *InsertedPHIs;
52 /// SSAUpdater constructor. If InsertedPHIs is specified, it will be filled
53 /// in with all PHI Nodes created by rewriting.
54 explicit SSAUpdater(SmallVectorImpl<PHINode*> *InsertedPHIs = 0);
57 /// Initialize - Reset this object to get ready for a new set of SSA
58 /// updates with type 'Ty'. PHI nodes get a name based on 'Name'.
59 void Initialize(const Type *Ty, StringRef Name);
61 /// AddAvailableValue - Indicate that a rewritten value is available at the
62 /// end of the specified block with the specified value.
63 void AddAvailableValue(BasicBlock *BB, Value *V);
65 /// HasValueForBlock - Return true if the SSAUpdater already has a value for
66 /// the specified block.
67 bool HasValueForBlock(BasicBlock *BB) const;
69 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
70 /// live at the end of the specified block.
71 Value *GetValueAtEndOfBlock(BasicBlock *BB);
73 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
74 /// is live in the middle of the specified block.
76 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
77 /// important case: if there is a definition of the rewritten value after the
78 /// 'use' in BB. Consider code like this:
84 /// br Cond, SomeBB, OutBB
86 /// In this case, there are two values (X1 and X2) added to the AvailableVals
87 /// set by the client of the rewriter, and those values are both live out of
88 /// their respective blocks. However, the use of X happens in the *middle* of
89 /// a block. Because of this, we need to insert a new PHI node in SomeBB to
90 /// merge the appropriate values, and this value isn't live out of the block.
92 Value *GetValueInMiddleOfBlock(BasicBlock *BB);
94 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
95 /// which use their value in the corresponding predecessor. Note that this
96 /// will not work if the use is supposed to be rewritten to a value defined in
97 /// the same block as the use, but above it. Any 'AddAvailableValue's added
98 /// for the use's block will be considered to be below it.
99 void RewriteUse(Use &U);
101 /// RewriteUseAfterInsertions - Rewrite a use, just like RewriteUse. However,
102 /// this version of the method can rewrite uses in the same block as a
103 /// definition, because it assumes that all uses of a value are below any
105 void RewriteUseAfterInsertions(Use &U);
108 Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
110 void operator=(const SSAUpdater&); // DO NOT IMPLEMENT
111 SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT
114 /// LoadAndStorePromoter - This little helper class provides a convenient way to
115 /// promote a collection of loads and stores into SSA Form using the SSAUpdater.
116 /// This handles complexities that SSAUpdater doesn't, such as multiple loads
117 /// and stores in one block.
119 /// Clients of this class are expected to subclass this and implement the
122 class LoadAndStorePromoter {
128 LoadAndStorePromoter(const SmallVectorImpl<Instruction*> &Insts,
129 SSAUpdater &S, DbgDeclareInst *DDI, DIBuilder *DIB,
130 StringRef Name = StringRef());
131 virtual ~LoadAndStorePromoter() {}
133 /// run - This does the promotion. Insts is a list of loads and stores to
134 /// promote, and Name is the basename for the PHIs to insert. After this is
135 /// complete, the loads and stores are removed from the code.
136 void run(const SmallVectorImpl<Instruction*> &Insts) const;
139 /// Return true if the specified instruction is in the Inst list (which was
140 /// passed into the run method). Clients should implement this with a more
141 /// efficient version if possible.
142 virtual bool isInstInList(Instruction *I,
143 const SmallVectorImpl<Instruction*> &Insts) const {
144 for (unsigned i = 0, e = Insts.size(); i != e; ++i)
150 /// doExtraRewritesBeforeFinalDeletion - This hook is invoked after all the
151 /// stores are found and inserted as available values, but
152 virtual void doExtraRewritesBeforeFinalDeletion() const {
155 /// replaceLoadWithValue - Clients can choose to implement this to get
156 /// notified right before a load is RAUW'd another value.
157 virtual void replaceLoadWithValue(LoadInst *LI, Value *V) const {
160 /// This is called before each instruction is deleted.
161 virtual void instructionDeleted(Instruction *I) const {
166 } // End llvm namespace