1 //===-- MachineSSAUpdater.h - Unstructured SSA Update Tool ------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file declares the MachineSSAUpdater class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_CODEGEN_MACHINESSAUPDATER_H 15 #define LLVM_CODEGEN_MACHINESSAUPDATER_H 16 17 namespace llvm { 18 class MachineBasicBlock; 19 class MachineFunction; 20 class MachineInstr; 21 class MachineOperand; 22 class MachineRegisterInfo; 23 class TargetInstrInfo; 24 class TargetRegisterClass; 25 template<typename T> class SmallVectorImpl; 26 template<typename T> class SSAUpdaterTraits; 27 class BumpPtrAllocator; 28 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>; 35 36 private: 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; 40 void *AV; 41 42 /// VR - Current virtual register whose uses are being updated. 43 unsigned VR; 44 45 /// VRC - Register class of the current virtual register. 46 const TargetRegisterClass *VRC; 47 48 /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI 49 /// nodes that it creates to the vector. 50 SmallVectorImpl<MachineInstr*> *InsertedPHIs; 51 52 const TargetInstrInfo *TII; 53 MachineRegisterInfo *MRI; 54 public: 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); 59 ~MachineSSAUpdater(); 60 61 /// Initialize - Reset this object to get ready for a new set of SSA 62 /// updates. 63 void Initialize(unsigned V); 64 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); 68 69 /// HasValueForBlock - Return true if the MachineSSAUpdater already has a 70 /// value for the specified block. 71 bool HasValueForBlock(MachineBasicBlock *BB) const; 72 73 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is 74 /// live at the end of the specified block. 75 unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB); 76 77 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that 78 /// is live in the middle of the specified block. 79 /// 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: 83 /// 84 /// X1 = ... 85 /// SomeBB: 86 /// use(X) 87 /// X2 = ... 88 /// br Cond, SomeBB, OutBB 89 /// 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. 95 /// 96 unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB); 97 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); 104 105 private: 106 void ReplaceRegWith(unsigned OldReg, unsigned NewReg); 107 unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB); 108 109 void operator=(const MachineSSAUpdater&); // DO NOT IMPLEMENT 110 MachineSSAUpdater(const MachineSSAUpdater&); // DO NOT IMPLEMENT 111 }; 112 113 } // End llvm namespace 114 115 #endif 116
