1 //===- RegisterCoalescer.h - Register Coalescing Interface ------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file contains the abstract interface for register coalescers, 10 // allowing them to interact with and query register allocators. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_LIB_CODEGEN_REGISTERCOALESCER_H 15 #define LLVM_LIB_CODEGEN_REGISTERCOALESCER_H 16 17 #include "llvm/CodeGen/MachinePassManager.h" 18 #include "llvm/CodeGen/Register.h" 19 20 namespace llvm { 21 22 class MachineInstr; 23 class TargetRegisterClass; 24 class TargetRegisterInfo; 25 26 /// A helper class for register coalescers. When deciding if 27 /// two registers can be coalesced, CoalescerPair can determine if a copy 28 /// instruction would become an identity copy after coalescing. 29 class CoalescerPair { 30 const TargetRegisterInfo &TRI; 31 32 /// The register that will be left after coalescing. It can be a 33 /// virtual or physical register. 34 Register DstReg; 35 36 /// The virtual register that will be coalesced into dstReg. 37 Register SrcReg; 38 39 /// The sub-register index of the old DstReg in the new coalesced register. 40 unsigned DstIdx = 0; 41 42 /// The sub-register index of the old SrcReg in the new coalesced register. 43 unsigned SrcIdx = 0; 44 45 /// True when the original copy was a partial subregister copy. 46 bool Partial = false; 47 48 /// True when both regs are virtual and newRC is constrained. 49 bool CrossClass = false; 50 51 /// True when DstReg and SrcReg are reversed from the original 52 /// copy instruction. 53 bool Flipped = false; 54 55 /// The register class of the coalesced register, or NULL if DstReg 56 /// is a physreg. This register class may be a super-register of both 57 /// SrcReg and DstReg. 58 const TargetRegisterClass *NewRC = nullptr; 59 60 public: CoalescerPair(const TargetRegisterInfo & tri)61 CoalescerPair(const TargetRegisterInfo &tri) : TRI(tri) {} 62 63 /// Create a CoalescerPair representing a virtreg-to-physreg copy. 64 /// No need to call setRegisters(). CoalescerPair(Register VirtReg,MCRegister PhysReg,const TargetRegisterInfo & tri)65 CoalescerPair(Register VirtReg, MCRegister PhysReg, 66 const TargetRegisterInfo &tri) 67 : TRI(tri), DstReg(PhysReg), SrcReg(VirtReg) {} 68 69 /// Set registers to match the copy instruction MI. Return 70 /// false if MI is not a coalescable copy instruction. 71 bool setRegisters(const MachineInstr *); 72 73 /// Swap SrcReg and DstReg. Return false if swapping is impossible 74 /// because DstReg is a physical register, or SubIdx is set. 75 bool flip(); 76 77 /// Return true if MI is a copy instruction that will become 78 /// an identity copy after coalescing. 79 bool isCoalescable(const MachineInstr *) const; 80 81 /// Return true if DstReg is a physical register. isPhys()82 bool isPhys() const { return !NewRC; } 83 84 /// Return true if the original copy instruction did not copy 85 /// the full register, but was a subreg operation. isPartial()86 bool isPartial() const { return Partial; } 87 88 /// Return true if DstReg is virtual and NewRC is a smaller 89 /// register class than DstReg's. isCrossClass()90 bool isCrossClass() const { return CrossClass; } 91 92 /// Return true when getSrcReg is the register being defined by 93 /// the original copy instruction. isFlipped()94 bool isFlipped() const { return Flipped; } 95 96 /// Return the register (virtual or physical) that will remain 97 /// after coalescing. getDstReg()98 Register getDstReg() const { return DstReg; } 99 100 /// Return the virtual register that will be coalesced away. getSrcReg()101 Register getSrcReg() const { return SrcReg; } 102 103 /// Return the subregister index that DstReg will be coalesced into, or 0. getDstIdx()104 unsigned getDstIdx() const { return DstIdx; } 105 106 /// Return the subregister index that SrcReg will be coalesced into, or 0. getSrcIdx()107 unsigned getSrcIdx() const { return SrcIdx; } 108 109 /// Return the register class of the coalesced register. getNewRC()110 const TargetRegisterClass *getNewRC() const { return NewRC; } 111 }; 112 113 } // end namespace llvm 114 115 #endif // LLVM_LIB_CODEGEN_REGISTERCOALESCER_H 116