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//===- llvm/CodeGen/VirtRegMap.h - Virtual Register Map ---------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file implements a virtual register map. This maps virtual registers to
// physical registers and virtual registers to stack slots. It is created and
// updated by a register allocator and then used by a machine code rewriter that
// adds spill code and rewrites virtual into physical register references.
#include "llvm/ADT/IndexedMap.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Pass.h"
#include <cassert>
namespace llvm {
class MachineFunction;
class MachineRegisterInfo;
class raw_ostream;
class TargetInstrInfo;
class VirtRegMap : public MachineFunctionPass {
enum {
NO_STACK_SLOT = (1L << 30)-1,
MAX_STACK_SLOT = (1L << 18)-1
MachineRegisterInfo *MRI;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
MachineFunction *MF;
/// Virt2PhysMap - This is a virtual to physical register
/// mapping. Each virtual register is required to have an entry in
/// it; even spilled virtual registers (the register mapped to a
/// spilled register is the temporary used to load it from the
/// stack).
IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2PhysMap;
/// Virt2StackSlotMap - This is virtual register to stack slot
/// mapping. Each spilled virtual register has an entry in it
/// which corresponds to the stack slot this register is spilled
/// at.
IndexedMap<int, VirtReg2IndexFunctor> Virt2StackSlotMap;
/// Virt2SplitMap - This is virtual register to splitted virtual register
/// mapping.
IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2SplitMap;
/// createSpillSlot - Allocate a spill slot for RC from MFI.
unsigned createSpillSlot(const TargetRegisterClass *RC);
static char ID;
VirtRegMap() : MachineFunctionPass(ID), Virt2PhysMap(NO_PHYS_REG),
Virt2StackSlotMap(NO_STACK_SLOT), Virt2SplitMap(0) {}
VirtRegMap(const VirtRegMap &) = delete;
VirtRegMap &operator=(const VirtRegMap &) = delete;
bool runOnMachineFunction(MachineFunction &MF) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
MachineFunction &getMachineFunction() const {
assert(MF && "getMachineFunction called before runOnMachineFunction");
return *MF;
MachineRegisterInfo &getRegInfo() const { return *MRI; }
const TargetRegisterInfo &getTargetRegInfo() const { return *TRI; }
void grow();
/// returns true if the specified virtual register is
/// mapped to a physical register
bool hasPhys(unsigned virtReg) const {
return getPhys(virtReg) != NO_PHYS_REG;
/// returns the physical register mapped to the specified
/// virtual register
unsigned getPhys(unsigned virtReg) const {
return Virt2PhysMap[virtReg];
/// creates a mapping for the specified virtual register to
/// the specified physical register
void assignVirt2Phys(unsigned virtReg, MCPhysReg physReg);
/// clears the specified virtual register's, physical
/// register mapping
void clearVirt(unsigned virtReg) {
assert(Virt2PhysMap[virtReg] != NO_PHYS_REG &&
"attempt to clear a not assigned virtual register");
Virt2PhysMap[virtReg] = NO_PHYS_REG;
/// clears all virtual to physical register mappings
void clearAllVirt() {
/// returns true if VirtReg is assigned to its preferred physreg.
bool hasPreferredPhys(unsigned VirtReg);
/// returns true if VirtReg has a known preferred register.
/// This returns false if VirtReg has a preference that is a virtual
/// register that hasn't been assigned yet.
bool hasKnownPreference(unsigned VirtReg);
/// records virtReg is a split live interval from SReg.
void setIsSplitFromReg(unsigned virtReg, unsigned SReg) {
Virt2SplitMap[virtReg] = SReg;
/// returns the live interval virtReg is split from.
unsigned getPreSplitReg(unsigned virtReg) const {
return Virt2SplitMap[virtReg];
/// getOriginal - Return the original virtual register that VirtReg descends
/// from through splitting.
/// A register that was not created by splitting is its own original.
/// This operation is idempotent.
unsigned getOriginal(unsigned VirtReg) const {
unsigned Orig = getPreSplitReg(VirtReg);
return Orig ? Orig : VirtReg;
/// returns true if the specified virtual register is not
/// mapped to a stack slot or rematerialized.
bool isAssignedReg(unsigned virtReg) const {
if (getStackSlot(virtReg) == NO_STACK_SLOT)
return true;
// Split register can be assigned a physical register as well as a
// stack slot or remat id.
return (Virt2SplitMap[virtReg] && Virt2PhysMap[virtReg] != NO_PHYS_REG);
/// returns the stack slot mapped to the specified virtual
/// register
int getStackSlot(unsigned virtReg) const {
return Virt2StackSlotMap[virtReg];
/// create a mapping for the specifed virtual register to
/// the next available stack slot
int assignVirt2StackSlot(unsigned virtReg);
/// create a mapping for the specified virtual register to
/// the specified stack slot
void assignVirt2StackSlot(unsigned virtReg, int SS);
void print(raw_ostream &OS, const Module* M = nullptr) const override;
void dump() const;
inline raw_ostream &operator<<(raw_ostream &OS, const VirtRegMap &VRM) {
return OS;
} // end llvm namespace