1 //===-- RegisterCoalescer.h - Register Coalescing Interface -----*- 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 contains the abstract interface for register coalescers, 11 // allowing them to interact with and query register allocators. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_LIB_CODEGEN_REGISTERCOALESCER_H 16 #define LLVM_LIB_CODEGEN_REGISTERCOALESCER_H 17 18 namespace llvm { 19 20 class MachineInstr; 21 class TargetRegisterInfo; 22 class TargetRegisterClass; 23 class TargetInstrInfo; 24 25 /// A helper class for register coalescers. When deciding if 26 /// two registers can be coalesced, CoalescerPair can determine if a copy 27 /// instruction would become an identity copy after coalescing. 28 class CoalescerPair { 29 const TargetRegisterInfo &TRI; 30 31 /// The register that will be left after coalescing. It can be a 32 /// virtual or physical register. 33 unsigned DstReg; 34 35 /// The virtual register that will be coalesced into dstReg. 36 unsigned SrcReg; 37 38 /// The sub-register index of the old DstReg in the new coalesced register. 39 unsigned DstIdx; 40 41 /// The sub-register index of the old SrcReg in the new coalesced register. 42 unsigned SrcIdx; 43 44 /// True when the original copy was a partial subregister copy. 45 bool Partial; 46 47 /// True when both regs are virtual and newRC is constrained. 48 bool CrossClass; 49 50 /// True when DstReg and SrcReg are reversed from the original 51 /// copy instruction. 52 bool Flipped; 53 54 /// The register class of the coalesced register, or NULL if DstReg 55 /// is a physreg. This register class may be a super-register of both 56 /// SrcReg and DstReg. 57 const TargetRegisterClass *NewRC; 58 59 public: 60 CoalescerPair(const TargetRegisterInfo &tri) 61 : TRI(tri), DstReg(0), SrcReg(0), DstIdx(0), SrcIdx(0), 62 Partial(false), CrossClass(false), Flipped(false), NewRC(nullptr) {} 63 64 /// Create a CoalescerPair representing a virtreg-to-physreg copy. 65 /// No need to call setRegisters(). 66 CoalescerPair(unsigned VirtReg, unsigned PhysReg, 67 const TargetRegisterInfo &tri) 68 : TRI(tri), DstReg(PhysReg), SrcReg(VirtReg), DstIdx(0), SrcIdx(0), 69 Partial(false), CrossClass(false), Flipped(false), NewRC(nullptr) {} 70 71 /// Set registers to match the copy instruction MI. Return 72 /// false if MI is not a coalescable copy instruction. 73 bool setRegisters(const MachineInstr*); 74 75 /// Swap SrcReg and DstReg. Return false if swapping is impossible 76 /// because DstReg is a physical register, or SubIdx is set. 77 bool flip(); 78 79 /// Return true if MI is a copy instruction that will become 80 /// an identity copy after coalescing. 81 bool isCoalescable(const MachineInstr*) const; 82 83 /// Return true if DstReg is a physical register. 84 bool isPhys() const { return !NewRC; } 85 86 /// Return true if the original copy instruction did not copy 87 /// the full register, but was a subreg operation. 88 bool isPartial() const { return Partial; } 89 90 /// Return true if DstReg is virtual and NewRC is a smaller 91 /// register class than DstReg's. 92 bool isCrossClass() const { return CrossClass; } 93 94 /// Return true when getSrcReg is the register being defined by 95 /// the original copy instruction. 96 bool isFlipped() const { return Flipped; } 97 98 /// Return the register (virtual or physical) that will remain 99 /// after coalescing. 100 unsigned getDstReg() const { return DstReg; } 101 102 /// Return the virtual register that will be coalesced away. 103 unsigned getSrcReg() const { return SrcReg; } 104 105 /// Return the subregister index that DstReg will be coalesced into, or 0. 106 unsigned getDstIdx() const { return DstIdx; } 107 108 /// Return the subregister index that SrcReg will be coalesced into, or 0. 109 unsigned getSrcIdx() const { return SrcIdx; } 110 111 /// Return the register class of the coalesced register. 112 const TargetRegisterClass *getNewRC() const { return NewRC; } 113 }; 114 } // End llvm namespace 115 116 #endif 117
