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//===--- X86DomainReassignment.cpp - Selectively switch register classes---===//
// 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 pass attempts to find instruction chains (closures) in one domain,
// and convert them to equivalent instructions in a different domain,
// if profitable.
#include "X86.h"
#include "X86InstrInfo.h"
#include "X86Subtarget.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Printable.h"
#include <bitset>
using namespace llvm;
#define DEBUG_TYPE "x86-domain-reassignment"
STATISTIC(NumClosuresConverted, "Number of closures converted by the pass");
static cl::opt<bool> DisableX86DomainReassignment(
"disable-x86-domain-reassignment", cl::Hidden,
cl::desc("X86: Disable Virtual Register Reassignment."), cl::init(false));
namespace {
enum RegDomain { NoDomain = -1, GPRDomain, MaskDomain, OtherDomain, NumDomains };
static bool isGPR(const TargetRegisterClass *RC) {
return X86::GR64RegClass.hasSubClassEq(RC) ||
X86::GR32RegClass.hasSubClassEq(RC) ||
X86::GR16RegClass.hasSubClassEq(RC) ||
static bool isMask(const TargetRegisterClass *RC,
const TargetRegisterInfo *TRI) {
return X86::VK16RegClass.hasSubClassEq(RC);
static RegDomain getDomain(const TargetRegisterClass *RC,
const TargetRegisterInfo *TRI) {
if (isGPR(RC))
return GPRDomain;
if (isMask(RC, TRI))
return MaskDomain;
return OtherDomain;
/// Return a register class equivalent to \p SrcRC, in \p Domain.
static const TargetRegisterClass *getDstRC(const TargetRegisterClass *SrcRC,
RegDomain Domain) {
assert(Domain == MaskDomain && "add domain");
if (X86::GR8RegClass.hasSubClassEq(SrcRC))
return &X86::VK8RegClass;
if (X86::GR16RegClass.hasSubClassEq(SrcRC))
return &X86::VK16RegClass;
if (X86::GR32RegClass.hasSubClassEq(SrcRC))
return &X86::VK32RegClass;
if (X86::GR64RegClass.hasSubClassEq(SrcRC))
return &X86::VK64RegClass;
llvm_unreachable("add register class");
return nullptr;
/// Abstract Instruction Converter class.
class InstrConverterBase {
unsigned SrcOpcode;
InstrConverterBase(unsigned SrcOpcode) : SrcOpcode(SrcOpcode) {}
virtual ~InstrConverterBase() {}
/// \returns true if \p MI is legal to convert.
virtual bool isLegal(const MachineInstr *MI,
const TargetInstrInfo *TII) const {
assert(MI->getOpcode() == SrcOpcode &&
"Wrong instruction passed to converter");
return true;
/// Applies conversion to \p MI.
/// \returns true if \p MI is no longer need, and can be deleted.
virtual bool convertInstr(MachineInstr *MI, const TargetInstrInfo *TII,
MachineRegisterInfo *MRI) const = 0;
/// \returns the cost increment incurred by converting \p MI.
virtual double getExtraCost(const MachineInstr *MI,
MachineRegisterInfo *MRI) const = 0;
/// An Instruction Converter which ignores the given instruction.
/// For example, PHI instructions can be safely ignored since only the registers
/// need to change.
class InstrIgnore : public InstrConverterBase {
InstrIgnore(unsigned SrcOpcode) : InstrConverterBase(SrcOpcode) {}
bool convertInstr(MachineInstr *MI, const TargetInstrInfo *TII,
MachineRegisterInfo *MRI) const override {
assert(isLegal(MI, TII) && "Cannot convert instruction");
return false;
double getExtraCost(const MachineInstr *MI,
MachineRegisterInfo *MRI) const override {
return 0;
/// An Instruction Converter which replaces an instruction with another.
class InstrReplacer : public InstrConverterBase {
/// Opcode of the destination instruction.
unsigned DstOpcode;
InstrReplacer(unsigned SrcOpcode, unsigned DstOpcode)
: InstrConverterBase(SrcOpcode), DstOpcode(DstOpcode) {}
bool isLegal(const MachineInstr *MI,
const TargetInstrInfo *TII) const override {
if (!InstrConverterBase::isLegal(MI, TII))
return false;
// It's illegal to replace an instruction that implicitly defines a register
// with an instruction that doesn't, unless that register dead.
for (auto &MO : MI->implicit_operands())
if (MO.isReg() && MO.isDef() && !MO.isDead() &&
return false;
return true;
bool convertInstr(MachineInstr *MI, const TargetInstrInfo *TII,
MachineRegisterInfo *MRI) const override {
assert(isLegal(MI, TII) && "Cannot convert instruction");
MachineInstrBuilder Bld =
BuildMI(*MI->getParent(), MI, MI->getDebugLoc(), TII->get(DstOpcode));
// Transfer explicit operands from original instruction. Implicit operands
// are handled by BuildMI.
for (auto &Op : MI->explicit_operands())
return true;
double getExtraCost(const MachineInstr *MI,
MachineRegisterInfo *MRI) const override {
// Assuming instructions have the same cost.
return 0;
/// An Instruction Converter which replaces an instruction with another, and
/// adds a COPY from the new instruction's destination to the old one's.
class InstrReplacerDstCOPY : public InstrConverterBase {
unsigned DstOpcode;
InstrReplacerDstCOPY(unsigned SrcOpcode, unsigned DstOpcode)
: InstrConverterBase(SrcOpcode), DstOpcode(DstOpcode) {}
bool convertInstr(MachineInstr *MI, const TargetInstrInfo *TII,
MachineRegisterInfo *MRI) const override {
assert(isLegal(MI, TII) && "Cannot convert instruction");
MachineBasicBlock *MBB = MI->getParent();
auto &DL = MI->getDebugLoc();
Register Reg = MRI->createVirtualRegister(
TII->getRegClass(TII->get(DstOpcode), 0, MRI->getTargetRegisterInfo(),
MachineInstrBuilder Bld = BuildMI(*MBB, MI, DL, TII->get(DstOpcode), Reg);
for (unsigned Idx = 1, End = MI->getNumOperands(); Idx < End; ++Idx)
BuildMI(*MBB, MI, DL, TII->get(TargetOpcode::COPY))
return true;
double getExtraCost(const MachineInstr *MI,
MachineRegisterInfo *MRI) const override {
// Assuming instructions have the same cost, and that COPY is in the same
// domain so it will be eliminated.
return 0;
/// An Instruction Converter for replacing COPY instructions.
class InstrCOPYReplacer : public InstrReplacer {
RegDomain DstDomain;
InstrCOPYReplacer(unsigned SrcOpcode, RegDomain DstDomain, unsigned DstOpcode)
: InstrReplacer(SrcOpcode, DstOpcode), DstDomain(DstDomain) {}
bool isLegal(const MachineInstr *MI,
const TargetInstrInfo *TII) const override {
if (!InstrConverterBase::isLegal(MI, TII))
return false;
// Don't allow copies to/flow GR8/GR16 physical registers.
// FIXME: Is there some better way to support this?
Register DstReg = MI->getOperand(0).getReg();
if (Register::isPhysicalRegister(DstReg) &&
(X86::GR8RegClass.contains(DstReg) ||
return false;
Register SrcReg = MI->getOperand(1).getReg();
if (Register::isPhysicalRegister(SrcReg) &&
(X86::GR8RegClass.contains(SrcReg) ||
return false;
return true;
double getExtraCost(const MachineInstr *MI,
MachineRegisterInfo *MRI) const override {
assert(MI->getOpcode() == TargetOpcode::COPY && "Expected a COPY");
for (auto &MO : MI->operands()) {
// Physical registers will not be converted. Assume that converting the
// COPY to the destination domain will eventually result in a actual
// instruction.
if (Register::isPhysicalRegister(MO.getReg()))
return 1;
RegDomain OpDomain = getDomain(MRI->getRegClass(MO.getReg()),
// Converting a cross domain COPY to a same domain COPY should eliminate
// an insturction
if (OpDomain == DstDomain)
return -1;
return 0;
/// An Instruction Converter which replaces an instruction with a COPY.
class InstrReplaceWithCopy : public InstrConverterBase {
// Source instruction operand Index, to be used as the COPY source.
unsigned SrcOpIdx;
InstrReplaceWithCopy(unsigned SrcOpcode, unsigned SrcOpIdx)
: InstrConverterBase(SrcOpcode), SrcOpIdx(SrcOpIdx) {}
bool convertInstr(MachineInstr *MI, const TargetInstrInfo *TII,
MachineRegisterInfo *MRI) const override {
assert(isLegal(MI, TII) && "Cannot convert instruction");
BuildMI(*MI->getParent(), MI, MI->getDebugLoc(),
.add({MI->getOperand(0), MI->getOperand(SrcOpIdx)});
return true;
double getExtraCost(const MachineInstr *MI,
MachineRegisterInfo *MRI) const override {
return 0;
// Key type to be used by the Instruction Converters map.
// A converter is identified by <destination domain, source opcode>
typedef std::pair<int, unsigned> InstrConverterBaseKeyTy;
typedef DenseMap<InstrConverterBaseKeyTy, InstrConverterBase *>
/// A closure is a set of virtual register representing all of the edges in
/// the closure, as well as all of the instructions connected by those edges.
/// A closure may encompass virtual registers in the same register bank that
/// have different widths. For example, it may contain 32-bit GPRs as well as
/// 64-bit GPRs.
/// A closure that computes an address (i.e. defines a virtual register that is
/// used in a memory operand) excludes the instructions that contain memory
/// operands using the address. Such an instruction will be included in a
/// different closure that manipulates the loaded or stored value.
class Closure {
/// Virtual registers in the closure.
DenseSet<unsigned> Edges;
/// Instructions in the closure.
SmallVector<MachineInstr *, 8> Instrs;
/// Domains which this closure can legally be reassigned to.
std::bitset<NumDomains> LegalDstDomains;
/// An ID to uniquely identify this closure, even when it gets
/// moved around
unsigned ID;
Closure(unsigned ID, std::initializer_list<RegDomain> LegalDstDomainList) : ID(ID) {
for (RegDomain D : LegalDstDomainList)
/// Mark this closure as illegal for reassignment to all domains.
void setAllIllegal() { LegalDstDomains.reset(); }
/// \returns true if this closure has domains which are legal to reassign to.
bool hasLegalDstDomain() const { return LegalDstDomains.any(); }
/// \returns true if is legal to reassign this closure to domain \p RD.
bool isLegal(RegDomain RD) const { return LegalDstDomains[RD]; }
/// Mark this closure as illegal for reassignment to domain \p RD.
void setIllegal(RegDomain RD) { LegalDstDomains[RD] = false; }
bool empty() const { return Edges.empty(); }
bool insertEdge(unsigned Reg) {
return Edges.insert(Reg).second;
using const_edge_iterator = DenseSet<unsigned>::const_iterator;
iterator_range<const_edge_iterator> edges() const {
return iterator_range<const_edge_iterator>(Edges.begin(), Edges.end());
void addInstruction(MachineInstr *I) {
ArrayRef<MachineInstr *> instructions() const {
return Instrs;
LLVM_DUMP_METHOD void dump(const MachineRegisterInfo *MRI) const {
dbgs() << "Registers: ";
bool First = true;
for (unsigned Reg : Edges) {
if (!First)
dbgs() << ", ";
First = false;
dbgs() << printReg(Reg, MRI->getTargetRegisterInfo(), 0, MRI);
dbgs() << "\n" << "Instructions:";
for (MachineInstr *MI : Instrs) {
dbgs() << "\n ";
dbgs() << "\n";
unsigned getID() const {
return ID;
class X86DomainReassignment : public MachineFunctionPass {
const X86Subtarget *STI;
MachineRegisterInfo *MRI;
const X86InstrInfo *TII;
/// All edges that are included in some closure
DenseSet<unsigned> EnclosedEdges;
/// All instructions that are included in some closure.
DenseMap<MachineInstr *, unsigned> EnclosedInstrs;
static char ID;
X86DomainReassignment() : MachineFunctionPass(ID) { }
bool runOnMachineFunction(MachineFunction &MF) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
StringRef getPassName() const override {
return "X86 Domain Reassignment Pass";
/// A map of available Instruction Converters.
InstrConverterBaseMap Converters;
/// Initialize Converters map.
void initConverters();
/// Starting from \Reg, expand the closure as much as possible.
void buildClosure(Closure &, unsigned Reg);
/// Enqueue \p Reg to be considered for addition to the closure.
void visitRegister(Closure &, unsigned Reg, RegDomain &Domain,
SmallVectorImpl<unsigned> &Worklist);
/// Reassign the closure to \p Domain.
void reassign(const Closure &C, RegDomain Domain) const;
/// Add \p MI to the closure.
void encloseInstr(Closure &C, MachineInstr *MI);
/// /returns true if it is profitable to reassign the closure to \p Domain.
bool isReassignmentProfitable(const Closure &C, RegDomain Domain) const;
/// Calculate the total cost of reassigning the closure to \p Domain.
double calculateCost(const Closure &C, RegDomain Domain) const;
char X86DomainReassignment::ID = 0;
} // End anonymous namespace.
void X86DomainReassignment::visitRegister(Closure &C, unsigned Reg,
RegDomain &Domain,
SmallVectorImpl<unsigned> &Worklist) {
if (EnclosedEdges.count(Reg))
if (!Register::isVirtualRegister(Reg))
if (!MRI->hasOneDef(Reg))
RegDomain RD = getDomain(MRI->getRegClass(Reg), MRI->getTargetRegisterInfo());
// First edge in closure sets the domain.
if (Domain == NoDomain)
Domain = RD;
if (Domain != RD)
void X86DomainReassignment::encloseInstr(Closure &C, MachineInstr *MI) {
auto I = EnclosedInstrs.find(MI);
if (I != EnclosedInstrs.end()) {
if (I->second != C.getID())
// Instruction already belongs to another closure, avoid conflicts between
// closure and mark this closure as illegal.
EnclosedInstrs[MI] = C.getID();
// Mark closure as illegal for reassignment to domains, if there is no
// converter for the instruction or if the converter cannot convert the
// instruction.
for (int i = 0; i != NumDomains; ++i) {
if (C.isLegal((RegDomain)i)) {
InstrConverterBase *IC = Converters.lookup({i, MI->getOpcode()});
if (!IC || !IC->isLegal(MI, TII))
double X86DomainReassignment::calculateCost(const Closure &C,
RegDomain DstDomain) const {
assert(C.isLegal(DstDomain) && "Cannot calculate cost for illegal closure");
double Cost = 0.0;
for (auto *MI : C.instructions())
Cost +=
Converters.lookup({DstDomain, MI->getOpcode()})->getExtraCost(MI, MRI);
return Cost;
bool X86DomainReassignment::isReassignmentProfitable(const Closure &C,
RegDomain Domain) const {
return calculateCost(C, Domain) < 0.0;
void X86DomainReassignment::reassign(const Closure &C, RegDomain Domain) const {
assert(C.isLegal(Domain) && "Cannot convert illegal closure");
// Iterate all instructions in the closure, convert each one using the
// appropriate converter.
SmallVector<MachineInstr *, 8> ToErase;
for (auto *MI : C.instructions())
if (Converters.lookup({Domain, MI->getOpcode()})
->convertInstr(MI, TII, MRI))
// Iterate all registers in the closure, replace them with registers in the
// destination domain.
for (unsigned Reg : C.edges()) {
MRI->setRegClass(Reg, getDstRC(MRI->getRegClass(Reg), Domain));
for (auto &MO : MRI->use_operands(Reg)) {
if (MO.isReg())
// Remove all subregister references as they are not valid in the
// destination domain.
for (auto MI : ToErase)
/// \returns true when \p Reg is used as part of an address calculation in \p
/// MI.
static bool usedAsAddr(const MachineInstr &MI, unsigned Reg,
const TargetInstrInfo *TII) {
if (!MI.mayLoadOrStore())
return false;
const MCInstrDesc &Desc = TII->get(MI.getOpcode());
int MemOpStart = X86II::getMemoryOperandNo(Desc.TSFlags);
if (MemOpStart == -1)
return false;
MemOpStart += X86II::getOperandBias(Desc);
for (unsigned MemOpIdx = MemOpStart,
MemOpEnd = MemOpStart + X86::AddrNumOperands;
MemOpIdx < MemOpEnd; ++MemOpIdx) {
auto &Op = MI.getOperand(MemOpIdx);
if (Op.isReg() && Op.getReg() == Reg)
return true;
return false;
void X86DomainReassignment::buildClosure(Closure &C, unsigned Reg) {
SmallVector<unsigned, 4> Worklist;
RegDomain Domain = NoDomain;
visitRegister(C, Reg, Domain, Worklist);
while (!Worklist.empty()) {
unsigned CurReg = Worklist.pop_back_val();
// Register already in this closure.
if (!C.insertEdge(CurReg))
MachineInstr *DefMI = MRI->getVRegDef(CurReg);
encloseInstr(C, DefMI);
// Add register used by the defining MI to the worklist.
// Do not add registers which are used in address calculation, they will be
// added to a different closure.
int OpEnd = DefMI->getNumOperands();
const MCInstrDesc &Desc = DefMI->getDesc();
int MemOp = X86II::getMemoryOperandNo(Desc.TSFlags);
if (MemOp != -1)
MemOp += X86II::getOperandBias(Desc);
for (int OpIdx = 0; OpIdx < OpEnd; ++OpIdx) {
if (OpIdx == MemOp) {
// skip address calculation.
OpIdx += (X86::AddrNumOperands - 1);
auto &Op = DefMI->getOperand(OpIdx);
if (!Op.isReg() || !Op.isUse())
visitRegister(C, Op.getReg(), Domain, Worklist);
// Expand closure through register uses.
for (auto &UseMI : MRI->use_nodbg_instructions(CurReg)) {
// We would like to avoid converting closures which calculare addresses,
// as this should remain in GPRs.
if (usedAsAddr(UseMI, CurReg, TII)) {
encloseInstr(C, &UseMI);
for (auto &DefOp : UseMI.defs()) {
if (!DefOp.isReg())
Register DefReg = DefOp.getReg();
if (!Register::isVirtualRegister(DefReg)) {
visitRegister(C, DefReg, Domain, Worklist);
void X86DomainReassignment::initConverters() {
Converters[{MaskDomain, TargetOpcode::PHI}] =
new InstrIgnore(TargetOpcode::PHI);
Converters[{MaskDomain, TargetOpcode::IMPLICIT_DEF}] =
new InstrIgnore(TargetOpcode::IMPLICIT_DEF);
Converters[{MaskDomain, TargetOpcode::INSERT_SUBREG}] =
new InstrReplaceWithCopy(TargetOpcode::INSERT_SUBREG, 2);
Converters[{MaskDomain, TargetOpcode::COPY}] =
new InstrCOPYReplacer(TargetOpcode::COPY, MaskDomain, TargetOpcode::COPY);
auto createReplacerDstCOPY = [&](unsigned From, unsigned To) {
Converters[{MaskDomain, From}] = new InstrReplacerDstCOPY(From, To);
createReplacerDstCOPY(X86::MOVZX32rm16, X86::KMOVWkm);
createReplacerDstCOPY(X86::MOVZX64rm16, X86::KMOVWkm);
createReplacerDstCOPY(X86::MOVZX32rr16, X86::KMOVWkk);
createReplacerDstCOPY(X86::MOVZX64rr16, X86::KMOVWkk);
if (STI->hasDQI()) {
createReplacerDstCOPY(X86::MOVZX16rm8, X86::KMOVBkm);
createReplacerDstCOPY(X86::MOVZX32rm8, X86::KMOVBkm);
createReplacerDstCOPY(X86::MOVZX64rm8, X86::KMOVBkm);
createReplacerDstCOPY(X86::MOVZX16rr8, X86::KMOVBkk);
createReplacerDstCOPY(X86::MOVZX32rr8, X86::KMOVBkk);
createReplacerDstCOPY(X86::MOVZX64rr8, X86::KMOVBkk);
auto createReplacer = [&](unsigned From, unsigned To) {
Converters[{MaskDomain, From}] = new InstrReplacer(From, To);
createReplacer(X86::MOV16rm, X86::KMOVWkm);
createReplacer(X86::MOV16mr, X86::KMOVWmk);
createReplacer(X86::MOV16rr, X86::KMOVWkk);
createReplacer(X86::SHR16ri, X86::KSHIFTRWri);
createReplacer(X86::SHL16ri, X86::KSHIFTLWri);
createReplacer(X86::NOT16r, X86::KNOTWrr);
createReplacer(X86::OR16rr, X86::KORWrr);
createReplacer(X86::AND16rr, X86::KANDWrr);
createReplacer(X86::XOR16rr, X86::KXORWrr);
if (STI->hasBWI()) {
createReplacer(X86::MOV32rm, X86::KMOVDkm);
createReplacer(X86::MOV64rm, X86::KMOVQkm);
createReplacer(X86::MOV32mr, X86::KMOVDmk);
createReplacer(X86::MOV64mr, X86::KMOVQmk);
createReplacer(X86::MOV32rr, X86::KMOVDkk);
createReplacer(X86::MOV64rr, X86::KMOVQkk);
createReplacer(X86::SHR32ri, X86::KSHIFTRDri);
createReplacer(X86::SHR64ri, X86::KSHIFTRQri);
createReplacer(X86::SHL32ri, X86::KSHIFTLDri);
createReplacer(X86::SHL64ri, X86::KSHIFTLQri);
createReplacer(X86::ADD32rr, X86::KADDDrr);
createReplacer(X86::ADD64rr, X86::KADDQrr);
createReplacer(X86::NOT32r, X86::KNOTDrr);
createReplacer(X86::NOT64r, X86::KNOTQrr);
createReplacer(X86::OR32rr, X86::KORDrr);
createReplacer(X86::OR64rr, X86::KORQrr);
createReplacer(X86::AND32rr, X86::KANDDrr);
createReplacer(X86::AND64rr, X86::KANDQrr);
createReplacer(X86::ANDN32rr, X86::KANDNDrr);
createReplacer(X86::ANDN64rr, X86::KANDNQrr);
createReplacer(X86::XOR32rr, X86::KXORDrr);
createReplacer(X86::XOR64rr, X86::KXORQrr);
// TODO: KTEST is not a replacement for TEST due to flag differences. Need
// to prove only Z flag is used.
//createReplacer(X86::TEST32rr, X86::KTESTDrr);
//createReplacer(X86::TEST64rr, X86::KTESTQrr);
if (STI->hasDQI()) {
createReplacer(X86::ADD8rr, X86::KADDBrr);
createReplacer(X86::ADD16rr, X86::KADDWrr);
createReplacer(X86::AND8rr, X86::KANDBrr);
createReplacer(X86::MOV8rm, X86::KMOVBkm);
createReplacer(X86::MOV8mr, X86::KMOVBmk);
createReplacer(X86::MOV8rr, X86::KMOVBkk);
createReplacer(X86::NOT8r, X86::KNOTBrr);
createReplacer(X86::OR8rr, X86::KORBrr);
createReplacer(X86::SHR8ri, X86::KSHIFTRBri);
createReplacer(X86::SHL8ri, X86::KSHIFTLBri);
// TODO: KTEST is not a replacement for TEST due to flag differences. Need
// to prove only Z flag is used.
//createReplacer(X86::TEST8rr, X86::KTESTBrr);
//createReplacer(X86::TEST16rr, X86::KTESTWrr);
createReplacer(X86::XOR8rr, X86::KXORBrr);
bool X86DomainReassignment::runOnMachineFunction(MachineFunction &MF) {
if (skipFunction(MF.getFunction()))
return false;
if (DisableX86DomainReassignment)
return false;
dbgs() << "***** Machine Function before Domain Reassignment *****\n");
STI = &MF.getSubtarget<X86Subtarget>();
// GPR->K is the only transformation currently supported, bail out early if no
// AVX512.
// TODO: We're also bailing of AVX512BW isn't supported since we use VK32 and
// VK64 for GR32/GR64, but those aren't legal classes on KNL. If the register
// coalescer doesn't clean it up and we generate a spill we will crash.
if (!STI->hasAVX512() || !STI->hasBWI())
return false;
MRI = &MF.getRegInfo();
assert(MRI->isSSA() && "Expected MIR to be in SSA form");
TII = STI->getInstrInfo();
bool Changed = false;
std::vector<Closure> Closures;
// Go over all virtual registers and calculate a closure.
unsigned ClosureID = 0;
for (unsigned Idx = 0; Idx < MRI->getNumVirtRegs(); ++Idx) {
unsigned Reg = Register::index2VirtReg(Idx);
// GPR only current source domain supported.
if (!isGPR(MRI->getRegClass(Reg)))
// Register already in closure.
if (EnclosedEdges.count(Reg))
// Calculate closure starting with Reg.
Closure C(ClosureID++, {MaskDomain});
buildClosure(C, Reg);
// Collect all closures that can potentially be converted.
if (!C.empty() && C.isLegal(MaskDomain))
for (Closure &C : Closures) {
if (isReassignmentProfitable(C, MaskDomain)) {
reassign(C, MaskDomain);
Changed = true;
dbgs() << "***** Machine Function after Domain Reassignment *****\n");
return Changed;
INITIALIZE_PASS(X86DomainReassignment, "x86-domain-reassignment",
"X86 Domain Reassignment Pass", false, false)
/// Returns an instance of the Domain Reassignment pass.
FunctionPass *llvm::createX86DomainReassignmentPass() {
return new X86DomainReassignment();