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;
24 class BumpPtrAllocator;
26 /// SSAUpdater - This class updates SSA form for a set of values defined in
27 /// multiple blocks. This is used when code duplication or another unstructured
28 /// transformation wants to rewrite a set of uses of one value with uses of a
31 friend class SSAUpdaterTraits<SSAUpdater>;
34 /// AvailableVals - This keeps track of which value to use on a per-block
35 /// basis. When we insert PHI nodes, we keep track of them here.
36 //typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
39 /// ProtoType holds the type of the values being rewritten.
40 const Type *ProtoType;
42 // PHI nodes are given a name based on ProtoName.
43 std::string ProtoName;
45 /// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
46 /// it creates to the vector.
47 SmallVectorImpl<PHINode*> *InsertedPHIs;
50 /// SSAUpdater constructor. If InsertedPHIs is specified, it will be filled
51 /// in with all PHI Nodes created by rewriting.
52 explicit SSAUpdater(SmallVectorImpl<PHINode*> *InsertedPHIs = 0);
55 /// Initialize - Reset this object to get ready for a new set of SSA
56 /// updates with type 'Ty'. PHI nodes get a name based on 'Name'.
57 void Initialize(const Type *Ty, StringRef Name);
59 /// AddAvailableValue - Indicate that a rewritten value is available at the
60 /// end of the specified block with the specified value.
61 void AddAvailableValue(BasicBlock *BB, Value *V);
63 /// HasValueForBlock - Return true if the SSAUpdater already has a value for
64 /// the specified block.
65 bool HasValueForBlock(BasicBlock *BB) const;
67 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
68 /// live at the end of the specified block.
69 Value *GetValueAtEndOfBlock(BasicBlock *BB);
71 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
72 /// is live in the middle of the specified block.
74 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
75 /// important case: if there is a definition of the rewritten value after the
76 /// 'use' in BB. Consider code like this:
82 /// br Cond, SomeBB, OutBB
84 /// In this case, there are two values (X1 and X2) added to the AvailableVals
85 /// set by the client of the rewriter, and those values are both live out of
86 /// their respective blocks. However, the use of X happens in the *middle* of
87 /// a block. Because of this, we need to insert a new PHI node in SomeBB to
88 /// merge the appropriate values, and this value isn't live out of the block.
90 Value *GetValueInMiddleOfBlock(BasicBlock *BB);
92 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
93 /// which use their value in the corresponding predecessor. Note that this
94 /// will not work if the use is supposed to be rewritten to a value defined in
95 /// the same block as the use, but above it. Any 'AddAvailableValue's added
96 /// for the use's block will be considered to be below it.
97 void RewriteUse(Use &U);
99 /// RewriteUseAfterInsertions - Rewrite a use, just like RewriteUse. However,
100 /// this version of the method can rewrite uses in the same block as a
101 /// definition, because it assumes that all uses of a value are below any
103 void RewriteUseAfterInsertions(Use &U);
106 Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
108 void operator=(const SSAUpdater&); // DO NOT IMPLEMENT
109 SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT
112 } // End llvm namespace