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 class BumpPtrAllocator; 30 31 /// MachineSSAUpdater - This class updates SSA form for a set of virtual 32 /// registers defined in multiple blocks. This is used when code duplication 33 /// or another unstructured transformation wants to rewrite a set of uses of one 34 /// vreg with uses of a set of vregs. 35 class MachineSSAUpdater { 36 friend class SSAUpdaterTraits<MachineSSAUpdater>; 37 38 private: 39 /// AvailableVals - This keeps track of which value to use on a per-block 40 /// basis. When we insert PHI nodes, we keep track of them here. 41 //typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy; 42 void *AV; 43 44 /// VR - Current virtual register whose uses are being updated. 45 unsigned VR; 46 47 /// VRC - Register class of the current virtual register. 48 const TargetRegisterClass *VRC; 49 50 /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI 51 /// nodes that it creates to the vector. 52 SmallVectorImpl<MachineInstr*> *InsertedPHIs; 53 54 const TargetInstrInfo *TII; 55 MachineRegisterInfo *MRI; 56 public: 57 /// MachineSSAUpdater constructor. If InsertedPHIs is specified, it will be 58 /// filled in with all PHI Nodes created by rewriting. 59 explicit MachineSSAUpdater(MachineFunction &MF, 60 SmallVectorImpl<MachineInstr*> *InsertedPHIs = 0); 61 ~MachineSSAUpdater(); 62 63 /// Initialize - Reset this object to get ready for a new set of SSA 64 /// updates. 65 void Initialize(unsigned V); 66 67 /// AddAvailableValue - Indicate that a rewritten value is available at the 68 /// end of the specified block with the specified value. 69 void AddAvailableValue(MachineBasicBlock *BB, unsigned V); 70 71 /// HasValueForBlock - Return true if the MachineSSAUpdater already has a 72 /// value for the specified block. 73 bool HasValueForBlock(MachineBasicBlock *BB) const; 74 75 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is 76 /// live at the end of the specified block. 77 unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB); 78 79 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that 80 /// is live in the middle of the specified block. 81 /// 82 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one 83 /// important case: if there is a definition of the rewritten value after the 84 /// 'use' in BB. Consider code like this: 85 /// 86 /// X1 = ... 87 /// SomeBB: 88 /// use(X) 89 /// X2 = ... 90 /// br Cond, SomeBB, OutBB 91 /// 92 /// In this case, there are two values (X1 and X2) added to the AvailableVals 93 /// set by the client of the rewriter, and those values are both live out of 94 /// their respective blocks. However, the use of X happens in the *middle* of 95 /// a block. Because of this, we need to insert a new PHI node in SomeBB to 96 /// merge the appropriate values, and this value isn't live out of the block. 97 /// 98 unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB); 99 100 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes, 101 /// which use their value in the corresponding predecessor. Note that this 102 /// will not work if the use is supposed to be rewritten to a value defined in 103 /// the same block as the use, but above it. Any 'AddAvailableValue's added 104 /// for the use's block will be considered to be below it. 105 void RewriteUse(MachineOperand &U); 106 107 private: 108 void ReplaceRegWith(unsigned OldReg, unsigned NewReg); 109 unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB); 110 111 void operator=(const MachineSSAUpdater&) LLVM_DELETED_FUNCTION; 112 MachineSSAUpdater(const MachineSSAUpdater&) LLVM_DELETED_FUNCTION; 113 }; 114 115 } // End llvm namespace 116 117 #endif 118
