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