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;
19 class MachineFunction;
22 class MachineRegisterInfo;
23 class TargetInstrInfo;
24 class TargetRegisterClass;
25 template<typename T> class SmallVectorImpl;
26 template<typename T> class SSAUpdaterTraits;
27 class BumpPtrAllocator;
29 /// MachineSSAUpdater - This class updates SSA form for a set of virtual
30 /// registers defined in multiple blocks. This is used when code duplication
31 /// or another unstructured transformation wants to rewrite a set of uses of one
32 /// vreg with uses of a set of vregs.
33 class MachineSSAUpdater {
34 friend class SSAUpdaterTraits<MachineSSAUpdater>;
37 /// AvailableVals - This keeps track of which value to use on a per-block
38 /// basis. When we insert PHI nodes, we keep track of them here.
39 //typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
42 /// VR - Current virtual register whose uses are being updated.
45 /// VRC - Register class of the current virtual register.
46 const TargetRegisterClass *VRC;
48 /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI
49 /// nodes that it creates to the vector.
50 SmallVectorImpl<MachineInstr*> *InsertedPHIs;
52 const TargetInstrInfo *TII;
53 MachineRegisterInfo *MRI;
55 /// MachineSSAUpdater constructor. If InsertedPHIs is specified, it will be
56 /// filled in with all PHI Nodes created by rewriting.
57 explicit MachineSSAUpdater(MachineFunction &MF,
58 SmallVectorImpl<MachineInstr*> *InsertedPHIs = 0);
61 /// Initialize - Reset this object to get ready for a new set of SSA
63 void Initialize(unsigned V);
65 /// AddAvailableValue - Indicate that a rewritten value is available at the
66 /// end of the specified block with the specified value.
67 void AddAvailableValue(MachineBasicBlock *BB, unsigned V);
69 /// HasValueForBlock - Return true if the MachineSSAUpdater already has a
70 /// value for the specified block.
71 bool HasValueForBlock(MachineBasicBlock *BB) const;
73 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
74 /// live at the end of the specified block.
75 unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB);
77 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
78 /// is live in the middle of the specified block.
80 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
81 /// important case: if there is a definition of the rewritten value after the
82 /// 'use' in BB. Consider code like this:
88 /// br Cond, SomeBB, OutBB
90 /// In this case, there are two values (X1 and X2) added to the AvailableVals
91 /// set by the client of the rewriter, and those values are both live out of
92 /// their respective blocks. However, the use of X happens in the *middle* of
93 /// a block. Because of this, we need to insert a new PHI node in SomeBB to
94 /// merge the appropriate values, and this value isn't live out of the block.
96 unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB);
98 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
99 /// which use their value in the corresponding predecessor. Note that this
100 /// will not work if the use is supposed to be rewritten to a value defined in
101 /// the same block as the use, but above it. Any 'AddAvailableValue's added
102 /// for the use's block will be considered to be below it.
103 void RewriteUse(MachineOperand &U);
106 void ReplaceRegWith(unsigned OldReg, unsigned NewReg);
107 unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
109 void operator=(const MachineSSAUpdater&); // DO NOT IMPLEMENT
110 MachineSSAUpdater(const MachineSSAUpdater&); // DO NOT IMPLEMENT
113 } // End llvm namespace