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;
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
33 typedef SmallVectorImpl<BBInfo*> BlockListTy;
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 /// PrototypeValue is an arbitrary representative value, which we derive names
42 /// and a type for PHI nodes.
43 Value *PrototypeValue;
45 /// BBMap - The GetValueAtEndOfBlock method maintains this mapping from
46 /// basic blocks to BBInfo structures.
47 /// typedef DenseMap<BasicBlock*, BBInfo*> BBMapTy;
50 /// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
51 /// it creates to the vector.
52 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. ProtoValue is the value used to name PHI nodes.
61 void Initialize(Value *ProtoValue);
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);
104 Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
105 void BuildBlockList(BasicBlock *BB, BlockListTy *BlockList,
106 BumpPtrAllocator *Allocator);
107 void FindDominators(BlockListTy *BlockList);
108 void FindPHIPlacement(BlockListTy *BlockList);
109 void FindAvailableVals(BlockListTy *BlockList);
110 void FindExistingPHI(BasicBlock *BB, BlockListTy *BlockList);
111 bool CheckIfPHIMatches(PHINode *PHI);
112 void RecordMatchingPHI(PHINode *PHI);
114 void operator=(const SSAUpdater&); // DO NOT IMPLEMENT
115 SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT
118 } // End llvm namespace