1 //===-- MachineSSAUpdater.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 MachineSSAUpdater class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CODEGEN_MACHINESSAUPDATER_H
15 #define LLVM_CODEGEN_MACHINESSAUPDATER_H
18 class MachineBasicBlock;
20 template<typename T> class SmallVectorImpl;
22 /// SSAUpdater - This class updates SSA form for a set of values defined in
23 /// multiple blocks. This is used when code duplication or another unstructured
24 /// transformation wants to rewrite a set of uses of one value with uses of a
26 class MachineSSAUpdater {
27 /// AvailableVals - This keeps track of which value to use on a per-block
28 /// basis. When we insert PHI nodes, we keep track of them here.
29 //typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
32 /// IncomingPredInfo - We use this as scratch space when doing our recursive
33 /// walk. This should only be used in GetValueInBlockInternal, normally it
35 //std::vector<std::pair<MachineBasicBlock*, unsigned > > IncomingPredInfo;
38 /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI
39 /// nodes that it creates to the vector.
40 SmallVectorImpl<MachineInstr*> *InsertedPHIs;
42 /// MachineSSAUpdater constructor. If InsertedPHIs is specified, it will be
43 /// filled in with all PHI Nodes created by rewriting.
44 explicit MachineSSAUpdater(SmallVectorImpl<MachineInstr*> *InsertedPHIs = 0);
47 /// Initialize - Reset this object to get ready for a new set of SSA
51 /// AddAvailableValue - Indicate that a rewritten value is available at the
52 /// end of the specified block with the specified value.
53 void AddAvailableValue(MachineBasicBlock *BB, unsigned V);
55 /// HasValueForBlock - Return true if the MachineSSAUpdater already has a
56 /// value for the specified block.
57 bool HasValueForBlock(MachineBasicBlock *BB) const;
59 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
60 /// live at the end of the specified block.
61 unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB);
63 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
64 /// is live in the middle of the specified block.
66 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
67 /// important case: if there is a definition of the rewritten value after the
68 /// 'use' in BB. Consider code like this:
74 /// br Cond, SomeBB, OutBB
76 /// In this case, there are two values (X1 and X2) added to the AvailableVals
77 /// set by the client of the rewriter, and those values are both live out of
78 /// their respective blocks. However, the use of X happens in the *middle* of
79 /// a block. Because of this, we need to insert a new PHI node in SomeBB to
80 /// merge the appropriate values, and this value isn't live out of the block.
82 unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB);
84 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
85 /// which use their value in the corresponding predecessor. Note that this
86 /// will not work if the use is supposed to be rewritten to a value defined in
87 /// the same block as the use, but above it. Any 'AddAvailableValue's added
88 /// for the use's block will be considered to be below it.
89 void RewriteUse(unsigned &U);
92 unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
93 void operator=(const MachineSSAUpdater&); // DO NOT IMPLEMENT
94 MachineSSAUpdater(const MachineSSAUpdater&); // DO NOT IMPLEMENT
97 } // End llvm namespace