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"
18 #include "llvm/Support/Compiler.h"
24 template<typename T> class SmallVectorImpl;
25 template<typename T> class SSAUpdaterTraits;
31 /// SSAUpdater - This class updates SSA form for a set of values defined in
32 /// multiple blocks. This is used when code duplication or another unstructured
33 /// transformation wants to rewrite a set of uses of one value with uses of a
36 friend class SSAUpdaterTraits<SSAUpdater>;
39 /// AvailableVals - This keeps track of which value to use on a per-block
40 /// basis. When we insert PHI nodes, we keep track of them here.
41 //typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
44 /// ProtoType holds the type of the values being rewritten.
47 // PHI nodes are given a name based on ProtoName.
48 std::string ProtoName;
50 /// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
51 /// it creates to the vector.
52 SmallVectorImpl<PHINode*> *InsertedPHIs;
55 /// SSAUpdater constructor. If InsertedPHIs is specified, it will be filled
56 /// in with all PHI Nodes created by rewriting.
57 explicit SSAUpdater(SmallVectorImpl<PHINode*> *InsertedPHIs = 0);
60 /// Initialize - Reset this object to get ready for a new set of SSA
61 /// updates with type 'Ty'. PHI nodes get a name based on 'Name'.
62 void Initialize(Type *Ty, StringRef Name);
64 /// AddAvailableValue - Indicate that a rewritten value is available at the
65 /// end of the specified block with the specified value.
66 void AddAvailableValue(BasicBlock *BB, Value *V);
68 /// HasValueForBlock - Return true if the SSAUpdater already has a value for
69 /// the specified block.
70 bool HasValueForBlock(BasicBlock *BB) const;
72 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
73 /// live at the end of the specified block.
74 Value *GetValueAtEndOfBlock(BasicBlock *BB);
76 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
77 /// is live in the middle of the specified block.
79 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
80 /// important case: if there is a definition of the rewritten value after the
81 /// 'use' in BB. Consider code like this:
87 /// br Cond, SomeBB, OutBB
89 /// In this case, there are two values (X1 and X2) added to the AvailableVals
90 /// set by the client of the rewriter, and those values are both live out of
91 /// their respective blocks. However, the use of X happens in the *middle* of
92 /// a block. Because of this, we need to insert a new PHI node in SomeBB to
93 /// merge the appropriate values, and this value isn't live out of the block.
95 Value *GetValueInMiddleOfBlock(BasicBlock *BB);
97 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
98 /// which use their value in the corresponding predecessor. Note that this
99 /// will not work if the use is supposed to be rewritten to a value defined in
100 /// the same block as the use, but above it. Any 'AddAvailableValue's added
101 /// for the use's block will be considered to be below it.
102 void RewriteUse(Use &U);
104 /// RewriteUseAfterInsertions - Rewrite a use, just like RewriteUse. However,
105 /// this version of the method can rewrite uses in the same block as a
106 /// definition, because it assumes that all uses of a value are below any
108 void RewriteUseAfterInsertions(Use &U);
111 Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
113 void operator=(const SSAUpdater&) LLVM_DELETED_FUNCTION;
114 SSAUpdater(const SSAUpdater&) LLVM_DELETED_FUNCTION;
117 /// LoadAndStorePromoter - This little helper class provides a convenient way to
118 /// promote a collection of loads and stores into SSA Form using the SSAUpdater.
119 /// This handles complexities that SSAUpdater doesn't, such as multiple loads
120 /// and stores in one block.
122 /// Clients of this class are expected to subclass this and implement the
125 class LoadAndStorePromoter {
129 LoadAndStorePromoter(const SmallVectorImpl<Instruction*> &Insts,
130 SSAUpdater &S, 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;
145 /// doExtraRewritesBeforeFinalDeletion - This hook is invoked after all the
146 /// stores are found and inserted as available values, but
147 virtual void doExtraRewritesBeforeFinalDeletion() const {
150 /// replaceLoadWithValue - Clients can choose to implement this to get
151 /// notified right before a load is RAUW'd another value.
152 virtual void replaceLoadWithValue(LoadInst *LI, Value *V) const {
155 /// This is called before each instruction is deleted.
156 virtual void instructionDeleted(Instruction *I) const {
159 /// updateDebugInfo - This is called to update debug info associated with the
161 virtual void updateDebugInfo(Instruction *I) const {
165 } // End llvm namespace