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
23 class SmallVectorImpl;
25 /// SSAUpdater - This class updates SSA form for a set of values defined in
26 /// multiple blocks. This is used when code duplication or another unstructured
27 /// transformation wants to rewrite a set of uses of one value with uses of a
30 /// AvailableVals - This keeps track of which value to use on a per-block
31 /// basis. When we insert PHI nodes, we keep track of them here. We use
32 /// TrackingVH's for the value of the map because we RAUW PHI nodes when we
33 /// eliminate them, and want the TrackingVH's to track this.
34 //typedef DenseMap<BasicBlock*, TrackingVH<Value> > AvailableValsTy;
37 /// PrototypeValue is an arbitrary representative value, which we derive names
38 /// and a type for PHI nodes.
39 Value *PrototypeValue;
41 /// IncomingPredInfo - We use this as scratch space when doing our recursive
42 /// walk. This should only be used in GetValueInBlockInternal, normally it
44 //std::vector<std::pair<BasicBlock*, TrackingVH<Value> > > IncomingPredInfo;
47 /// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
48 /// it creates to the vector.
49 SmallVectorImpl<PHINode*> *InsertedPHIs;
51 /// SSAUpdater constructor. If InsertedPHIs is specified, it will be filled
52 /// in with all PHI Nodes created by rewriting.
53 explicit SSAUpdater(SmallVectorImpl<PHINode*> *InsertedPHIs = 0);
56 /// Initialize - Reset this object to get ready for a new set of SSA
57 /// updates. ProtoValue is the value used to name PHI nodes.
58 void Initialize(Value *ProtoValue);
60 /// AddAvailableValue - Indicate that a rewritten value is available at the
61 /// end of the specified block with the specified value.
62 void AddAvailableValue(BasicBlock *BB, Value *V);
64 /// HasValueForBlock - Return true if the SSAUpdater already has a value for
65 /// the specified block.
66 bool HasValueForBlock(BasicBlock *BB) const;
68 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
69 /// live at the end of the specified block.
70 Value *GetValueAtEndOfBlock(BasicBlock *BB);
72 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
73 /// is live in the middle of the specified block.
75 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
76 /// important case: if there is a definition of the rewritten value after the
77 /// 'use' in BB. Consider code like this:
83 /// br Cond, SomeBB, OutBB
85 /// In this case, there are two values (X1 and X2) added to the AvailableVals
86 /// set by the client of the rewriter, and those values are both live out of
87 /// their respective blocks. However, the use of X happens in the *middle* of
88 /// a block. Because of this, we need to insert a new PHI node in SomeBB to
89 /// merge the appropriate values, and this value isn't live out of the block.
91 Value *GetValueInMiddleOfBlock(BasicBlock *BB);
93 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
94 /// which use their value in the corresponding predecessor. Note that this
95 /// will not work if the use is supposed to be rewritten to a value defined in
96 /// the same block as the use, but above it. Any 'AddAvailableValue's added
97 /// for the use's block will be considered to be below it.
98 void RewriteUse(Use &U);
101 Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
102 void operator=(const SSAUpdater&); // DO NOT IMPLEMENT
103 SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT
106 } // End llvm namespace