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//===- RegisterCoalescer.h - Register Coalescing Interface ------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains the abstract interface for register coalescers,
// allowing them to interact with and query register allocators.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_CODEGEN_REGISTERCOALESCER_H
#define LLVM_LIB_CODEGEN_REGISTERCOALESCER_H
#include "llvm/CodeGen/Register.h"
namespace llvm {
class MachineInstr;
class TargetRegisterClass;
class TargetRegisterInfo;
/// A helper class for register coalescers. When deciding if
/// two registers can be coalesced, CoalescerPair can determine if a copy
/// instruction would become an identity copy after coalescing.
class CoalescerPair {
const TargetRegisterInfo &TRI;
/// The register that will be left after coalescing. It can be a
/// virtual or physical register.
Register DstReg;
/// The virtual register that will be coalesced into dstReg.
Register SrcReg;
/// The sub-register index of the old DstReg in the new coalesced register.
unsigned DstIdx = 0;
/// The sub-register index of the old SrcReg in the new coalesced register.
unsigned SrcIdx = 0;
/// True when the original copy was a partial subregister copy.
bool Partial = false;
/// True when both regs are virtual and newRC is constrained.
bool CrossClass = false;
/// True when DstReg and SrcReg are reversed from the original
/// copy instruction.
bool Flipped = false;
/// The register class of the coalesced register, or NULL if DstReg
/// is a physreg. This register class may be a super-register of both
/// SrcReg and DstReg.
const TargetRegisterClass *NewRC = nullptr;
public:
CoalescerPair(const TargetRegisterInfo &tri) : TRI(tri) {}
/// Create a CoalescerPair representing a virtreg-to-physreg copy.
/// No need to call setRegisters().
CoalescerPair(Register VirtReg, MCRegister PhysReg,
const TargetRegisterInfo &tri)
: TRI(tri), DstReg(PhysReg), SrcReg(VirtReg) {}
/// Set registers to match the copy instruction MI. Return
/// false if MI is not a coalescable copy instruction.
bool setRegisters(const MachineInstr*);
/// Swap SrcReg and DstReg. Return false if swapping is impossible
/// because DstReg is a physical register, or SubIdx is set.
bool flip();
/// Return true if MI is a copy instruction that will become
/// an identity copy after coalescing.
bool isCoalescable(const MachineInstr*) const;
/// Return true if DstReg is a physical register.
bool isPhys() const { return !NewRC; }
/// Return true if the original copy instruction did not copy
/// the full register, but was a subreg operation.
bool isPartial() const { return Partial; }
/// Return true if DstReg is virtual and NewRC is a smaller
/// register class than DstReg's.
bool isCrossClass() const { return CrossClass; }
/// Return true when getSrcReg is the register being defined by
/// the original copy instruction.
bool isFlipped() const { return Flipped; }
/// Return the register (virtual or physical) that will remain
/// after coalescing.
Register getDstReg() const { return DstReg; }
/// Return the virtual register that will be coalesced away.
Register getSrcReg() const { return SrcReg; }
/// Return the subregister index that DstReg will be coalesced into, or 0.
unsigned getDstIdx() const { return DstIdx; }
/// Return the subregister index that SrcReg will be coalesced into, or 0.
unsigned getSrcIdx() const { return SrcIdx; }
/// Return the register class of the coalesced register.
const TargetRegisterClass *getNewRC() const { return NewRC; }
};
} // end namespace llvm
#endif // LLVM_LIB_CODEGEN_REGISTERCOALESCER_H
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