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//===-- RegisterCoalescer.h - Register Coalescing Interface -----*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file contains the abstract interface for register coalescers,
// allowing them to interact with and query register allocators.
namespace llvm {
class MachineInstr;
class TargetRegisterInfo;
class TargetRegisterClass;
class TargetInstrInfo;
/// CoalescerPair - 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 TargetInstrInfo &TII;
const TargetRegisterInfo &TRI;
/// DstReg - The register that will be left after coalescing. It can be a
/// virtual or physical register.
unsigned DstReg;
/// SrcReg - the virtual register that will be coalesced into dstReg.
unsigned SrcReg;
/// subReg_ - The subregister index of srcReg in DstReg. It is possible the
/// coalesce SrcReg into a subreg of the larger DstReg when DstReg is a
/// virtual register.
unsigned SubIdx;
/// Partial - True when the original copy was a partial subregister copy.
bool Partial;
/// CrossClass - True when both regs are virtual, and newRC is constrained.
bool CrossClass;
/// Flipped - True when DstReg and SrcReg are reversed from the original
/// copy instruction.
bool Flipped;
/// NewRC - The register class of the coalesced register, or NULL if DstReg
/// is a physreg.
const TargetRegisterClass *NewRC;
CoalescerPair(const TargetInstrInfo &tii, const TargetRegisterInfo &tri)
: TII(tii), TRI(tri), DstReg(0), SrcReg(0), SubIdx(0),
Partial(false), CrossClass(false), Flipped(false), NewRC(0) {}
/// setRegisters - set registers to match the copy instruction MI. Return
/// false if MI is not a coalescable copy instruction.
bool setRegisters(const MachineInstr*);
/// flip - Swap SrcReg and DstReg. Return false if swapping is impossible
/// because DstReg is a physical register, or SubIdx is set.
bool flip();
/// isCoalescable - Return true if MI is a copy instruction that will become
/// an identity copy after coalescing.
bool isCoalescable(const MachineInstr*) const;
/// isPhys - Return true if DstReg is a physical register.
bool isPhys() const { return !NewRC; }
/// isPartial - Return true if the original copy instruction did not copy
/// the full register, but was a subreg operation.
bool isPartial() const { return Partial; }
/// isCrossClass - Return true if DstReg is virtual and NewRC is a smaller
/// register class than DstReg's.
bool isCrossClass() const { return CrossClass; }
/// isFlipped - Return true when getSrcReg is the register being defined by
/// the original copy instruction.
bool isFlipped() const { return Flipped; }
/// getDstReg - Return the register (virtual or physical) that will remain
/// after coalescing.
unsigned getDstReg() const { return DstReg; }
/// getSrcReg - Return the virtual register that will be coalesced away.
unsigned getSrcReg() const { return SrcReg; }
/// getSubIdx - Return the subregister index in DstReg that SrcReg will be
/// coalesced into, or 0.
unsigned getSubIdx() const { return SubIdx; }
/// getNewRC - Return the register class of the coalesced register.
const TargetRegisterClass *getNewRC() const { return NewRC; }
} // End llvm namespace