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/Register.h" 18 19 namespace llvm { 20 21 class MachineInstr; 22 class TargetRegisterClass; 23 class TargetRegisterInfo; 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 Register DstReg; 34 35 /// The virtual register that will be coalesced into dstReg. 36 Register SrcReg; 37 38 /// The sub-register index of the old DstReg in the new coalesced register. 39 unsigned DstIdx = 0; 40 41 /// The sub-register index of the old SrcReg in the new coalesced register. 42 unsigned SrcIdx = 0; 43 44 /// True when the original copy was a partial subregister copy. 45 bool Partial = false; 46 47 /// True when both regs are virtual and newRC is constrained. 48 bool CrossClass = false; 49 50 /// True when DstReg and SrcReg are reversed from the original 51 /// copy instruction. 52 bool Flipped = false; 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 = nullptr; 58 59 public: 60 CoalescerPair(const TargetRegisterInfo &tri) : TRI(tri) {} 61 62 /// Create a CoalescerPair representing a virtreg-to-physreg copy. 63 /// No need to call setRegisters(). 64 CoalescerPair(Register VirtReg, MCRegister PhysReg, 65 const TargetRegisterInfo &tri) 66 : TRI(tri), DstReg(PhysReg), SrcReg(VirtReg) {} 67 68 /// Set registers to match the copy instruction MI. Return 69 /// false if MI is not a coalescable copy instruction. 70 bool setRegisters(const MachineInstr *); 71 72 /// Swap SrcReg and DstReg. Return false if swapping is impossible 73 /// because DstReg is a physical register, or SubIdx is set. 74 bool flip(); 75 76 /// Return true if MI is a copy instruction that will become 77 /// an identity copy after coalescing. 78 bool isCoalescable(const MachineInstr *) const; 79 80 /// Return true if DstReg is a physical register. 81 bool isPhys() const { return !NewRC; } 82 83 /// Return true if the original copy instruction did not copy 84 /// the full register, but was a subreg operation. 85 bool isPartial() const { return Partial; } 86 87 /// Return true if DstReg is virtual and NewRC is a smaller 88 /// register class than DstReg's. 89 bool isCrossClass() const { return CrossClass; } 90 91 /// Return true when getSrcReg is the register being defined by 92 /// the original copy instruction. 93 bool isFlipped() const { return Flipped; } 94 95 /// Return the register (virtual or physical) that will remain 96 /// after coalescing. 97 Register getDstReg() const { return DstReg; } 98 99 /// Return the virtual register that will be coalesced away. 100 Register getSrcReg() const { return SrcReg; } 101 102 /// Return the subregister index that DstReg will be coalesced into, or 0. 103 unsigned getDstIdx() const { return DstIdx; } 104 105 /// Return the subregister index that SrcReg will be coalesced into, or 0. 106 unsigned getSrcIdx() const { return SrcIdx; } 107 108 /// Return the register class of the coalesced register. 109 const TargetRegisterClass *getNewRC() const { return NewRC; } 110 }; 111 112 } // end namespace llvm 113 114 #endif // LLVM_LIB_CODEGEN_REGISTERCOALESCER_H 115