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
17 #include "llvm/ADT/StringRef.h"
23 template<typename T> class SmallVectorImpl;
24 template<typename T> class SSAUpdaterTraits;
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
35 friend class SSAUpdaterTraits<SSAUpdater>;
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;
43 /// ProtoType holds the type of the values being rewritten.
46 // PHI nodes are given a name based on ProtoName.
47 std::string ProtoName;
49 /// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
50 /// it creates to the vector.
51 SmallVectorImpl<PHINode*> *InsertedPHIs;
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);
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);
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);
67 /// HasValueForBlock - Return true if the SSAUpdater already has a value for
68 /// the specified block.
69 bool HasValueForBlock(BasicBlock *BB) const;
71 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
72 /// live at the end of the specified block.
73 Value *GetValueAtEndOfBlock(BasicBlock *BB);
75 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
76 /// is live in the middle of the specified block.
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:
86 /// br Cond, SomeBB, OutBB
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.
94 Value *GetValueInMiddleOfBlock(BasicBlock *BB);
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);
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
107 void RewriteUseAfterInsertions(Use &U);
110 Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
112 void operator=(const SSAUpdater&) LLVM_DELETED_FUNCTION;
113 SSAUpdater(const SSAUpdater&) LLVM_DELETED_FUNCTION;
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.
121 /// Clients of this class are expected to subclass this and implement the
124 class LoadAndStorePromoter {
128 LoadAndStorePromoter(const SmallVectorImpl<Instruction*> &Insts,
129 SSAUpdater &S, StringRef Name = StringRef());
130 virtual ~LoadAndStorePromoter() {}
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;
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;
144 /// doExtraRewritesBeforeFinalDeletion - This hook is invoked after all the
145 /// stores are found and inserted as available values, but
146 virtual void doExtraRewritesBeforeFinalDeletion() const {
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 {
154 /// This is called before each instruction is deleted.
155 virtual void instructionDeleted(Instruction *I) const {
158 /// updateDebugInfo - This is called to update debug info associated with the
160 virtual void updateDebugInfo(Instruction *I) const {
164 } // End llvm namespace