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 #include "llvm/Support/Compiler.h" 18 19 namespace llvm { 20 class MachineBasicBlock; 21 class MachineFunction; 22 class MachineInstr; 23 class MachineOperand; 24 class MachineRegisterInfo; 25 class TargetInstrInfo; 26 class TargetRegisterClass; 27 template<typename T> class SmallVectorImpl; 28 template<typename T> class SSAUpdaterTraits; 29 30 /// MachineSSAUpdater - This class updates SSA form for a set of virtual 31 /// registers defined in multiple blocks. This is used when code duplication 32 /// or another unstructured transformation wants to rewrite a set of uses of one 33 /// vreg with uses of a set of vregs. 34 class MachineSSAUpdater { 35 friend class SSAUpdaterTraits<MachineSSAUpdater>; 36 37 private: 38 /// AvailableVals - This keeps track of which value to use on a per-block 39 /// basis. When we insert PHI nodes, we keep track of them here. 40 //typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy; 41 void *AV; 42 43 /// VR - Current virtual register whose uses are being updated. 44 unsigned VR; 45 46 /// VRC - Register class of the current virtual register. 47 const TargetRegisterClass *VRC; 48 49 /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI 50 /// nodes that it creates to the vector. 51 SmallVectorImpl<MachineInstr*> *InsertedPHIs; 52 53 const TargetInstrInfo *TII; 54 MachineRegisterInfo *MRI; 55 public: 56 /// MachineSSAUpdater constructor. If InsertedPHIs is specified, it will be 57 /// filled in with all PHI Nodes created by rewriting. 58 explicit MachineSSAUpdater(MachineFunction &MF, 59 SmallVectorImpl<MachineInstr*> *InsertedPHIs = nullptr); 60 ~MachineSSAUpdater(); 61 62 /// Initialize - Reset this object to get ready for a new set of SSA 63 /// updates. 64 void Initialize(unsigned V); 65 66 /// AddAvailableValue - Indicate that a rewritten value is available at the 67 /// end of the specified block with the specified value. 68 void AddAvailableValue(MachineBasicBlock *BB, unsigned V); 69 70 /// HasValueForBlock - Return true if the MachineSSAUpdater already has a 71 /// value for the specified block. 72 bool HasValueForBlock(MachineBasicBlock *BB) const; 73 74 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is 75 /// live at the end of the specified block. 76 unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB); 77 78 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that 79 /// is live in the middle of the specified block. 80 /// 81 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one 82 /// important case: if there is a definition of the rewritten value after the 83 /// 'use' in BB. Consider code like this: 84 /// 85 /// X1 = ... 86 /// SomeBB: 87 /// use(X) 88 /// X2 = ... 89 /// br Cond, SomeBB, OutBB 90 /// 91 /// In this case, there are two values (X1 and X2) added to the AvailableVals 92 /// set by the client of the rewriter, and those values are both live out of 93 /// their respective blocks. However, the use of X happens in the *middle* of 94 /// a block. Because of this, we need to insert a new PHI node in SomeBB to 95 /// merge the appropriate values, and this value isn't live out of the block. 96 /// 97 unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB); 98 99 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes, 100 /// which use their value in the corresponding predecessor. Note that this 101 /// will not work if the use is supposed to be rewritten to a value defined in 102 /// the same block as the use, but above it. Any 'AddAvailableValue's added 103 /// for the use's block will be considered to be below it. 104 void RewriteUse(MachineOperand &U); 105 106 private: 107 unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB); 108 109 void operator=(const MachineSSAUpdater&) = delete; 110 MachineSSAUpdater(const MachineSSAUpdater&) = delete; 111 }; 112 113 } // End llvm namespace 114 115 #endif 116
