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//==- TargetRegisterInfo.cpp - Target Register Information Implementation --==//
// 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 the TargetRegisterInfo interface.
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/CodeGen/VirtRegMap.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MachineValueType.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Printable.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <utility>
#define DEBUG_TYPE "target-reg-info"
using namespace llvm;
TargetRegisterInfo::TargetRegisterInfo(const TargetRegisterInfoDesc *ID,
regclass_iterator RCB, regclass_iterator RCE,
const char *const *SRINames,
const LaneBitmask *SRILaneMasks,
LaneBitmask SRICoveringLanes,
const RegClassInfo *const RCIs,
unsigned Mode)
: InfoDesc(ID), SubRegIndexNames(SRINames),
RegClassBegin(RCB), RegClassEnd(RCE),
RCInfos(RCIs), HwMode(Mode) {
TargetRegisterInfo::~TargetRegisterInfo() = default;
void TargetRegisterInfo::markSuperRegs(BitVector &RegisterSet, unsigned Reg)
const {
for (MCSuperRegIterator AI(Reg, this, true); AI.isValid(); ++AI)
bool TargetRegisterInfo::checkAllSuperRegsMarked(const BitVector &RegisterSet,
ArrayRef<MCPhysReg> Exceptions) const {
// Check that all super registers of reserved regs are reserved as well.
BitVector Checked(getNumRegs());
for (unsigned Reg : RegisterSet.set_bits()) {
if (Checked[Reg])
for (MCSuperRegIterator SR(Reg, this); SR.isValid(); ++SR) {
if (!RegisterSet[*SR] && !is_contained(Exceptions, Reg)) {
dbgs() << "Error: Super register " << printReg(*SR, this)
<< " of reserved register " << printReg(Reg, this)
<< " is not reserved.\n";
return false;
// We transitively check superregs. So we can remember this for later
// to avoid compiletime explosion in deep register hierarchies.
return true;
namespace llvm {
Printable printReg(Register Reg, const TargetRegisterInfo *TRI,
unsigned SubIdx, const MachineRegisterInfo *MRI) {
return Printable([Reg, TRI, SubIdx, MRI](raw_ostream &OS) {
if (!Reg)
OS << "$noreg";
else if (Register::isStackSlot(Reg))
OS << "SS#" << Register::stackSlot2Index(Reg);
else if (Register::isVirtualRegister(Reg)) {
StringRef Name = MRI ? MRI->getVRegName(Reg) : "";
if (Name != "") {
OS << '%' << Name;
} else {
OS << '%' << Register::virtReg2Index(Reg);
} else if (!TRI)
OS << '$' << "physreg" << Reg;
else if (Reg < TRI->getNumRegs()) {
OS << '$';
printLowerCase(TRI->getName(Reg), OS);
} else
llvm_unreachable("Register kind is unsupported.");
if (SubIdx) {
if (TRI)
OS << ':' << TRI->getSubRegIndexName(SubIdx);
OS << ":sub(" << SubIdx << ')';
Printable printRegUnit(unsigned Unit, const TargetRegisterInfo *TRI) {
return Printable([Unit, TRI](raw_ostream &OS) {
// Generic printout when TRI is missing.
if (!TRI) {
OS << "Unit~" << Unit;
// Check for invalid register units.
if (Unit >= TRI->getNumRegUnits()) {
OS << "BadUnit~" << Unit;
// Normal units have at least one root.
MCRegUnitRootIterator Roots(Unit, TRI);
assert(Roots.isValid() && "Unit has no roots.");
OS << TRI->getName(*Roots);
for (++Roots; Roots.isValid(); ++Roots)
OS << '~' << TRI->getName(*Roots);
Printable printVRegOrUnit(unsigned Unit, const TargetRegisterInfo *TRI) {
return Printable([Unit, TRI](raw_ostream &OS) {
if (Register::isVirtualRegister(Unit)) {
OS << '%' << Register::virtReg2Index(Unit);
} else {
OS << printRegUnit(Unit, TRI);
Printable printRegClassOrBank(unsigned Reg, const MachineRegisterInfo &RegInfo,
const TargetRegisterInfo *TRI) {
return Printable([Reg, &RegInfo, TRI](raw_ostream &OS) {
if (RegInfo.getRegClassOrNull(Reg))
OS << StringRef(TRI->getRegClassName(RegInfo.getRegClass(Reg))).lower();
else if (RegInfo.getRegBankOrNull(Reg))
OS << StringRef(RegInfo.getRegBankOrNull(Reg)->getName()).lower();
else {
OS << "_";
assert((RegInfo.def_empty(Reg) || RegInfo.getType(Reg).isValid()) &&
"Generic registers must have a valid type");
} // end namespace llvm
/// getAllocatableClass - Return the maximal subclass of the given register
/// class that is alloctable, or NULL.
const TargetRegisterClass *
TargetRegisterInfo::getAllocatableClass(const TargetRegisterClass *RC) const {
if (!RC || RC->isAllocatable())
return RC;
for (BitMaskClassIterator It(RC->getSubClassMask(), *this); It.isValid();
++It) {
const TargetRegisterClass *SubRC = getRegClass(It.getID());
if (SubRC->isAllocatable())
return SubRC;
return nullptr;
/// getMinimalPhysRegClass - Returns the Register Class of a physical
/// register of the given type, picking the most sub register class of
/// the right type that contains this physreg.
const TargetRegisterClass *
TargetRegisterInfo::getMinimalPhysRegClass(unsigned reg, MVT VT) const {
assert(Register::isPhysicalRegister(reg) &&
"reg must be a physical register");
// Pick the most sub register class of the right type that contains
// this physreg.
const TargetRegisterClass* BestRC = nullptr;
for (const TargetRegisterClass* RC : regclasses()) {
if ((VT == MVT::Other || isTypeLegalForClass(*RC, VT)) &&
RC->contains(reg) && (!BestRC || BestRC->hasSubClass(RC)))
BestRC = RC;
assert(BestRC && "Couldn't find the register class");
return BestRC;
/// getAllocatableSetForRC - Toggle the bits that represent allocatable
/// registers for the specific register class.
static void getAllocatableSetForRC(const MachineFunction &MF,
const TargetRegisterClass *RC, BitVector &R){
assert(RC->isAllocatable() && "invalid for nonallocatable sets");
ArrayRef<MCPhysReg> Order = RC->getRawAllocationOrder(MF);
for (unsigned i = 0; i != Order.size(); ++i)
BitVector TargetRegisterInfo::getAllocatableSet(const MachineFunction &MF,
const TargetRegisterClass *RC) const {
BitVector Allocatable(getNumRegs());
if (RC) {
// A register class with no allocatable subclass returns an empty set.
const TargetRegisterClass *SubClass = getAllocatableClass(RC);
if (SubClass)
getAllocatableSetForRC(MF, SubClass, Allocatable);
} else {
for (const TargetRegisterClass *C : regclasses())
if (C->isAllocatable())
getAllocatableSetForRC(MF, C, Allocatable);
// Mask out the reserved registers
BitVector Reserved = getReservedRegs(MF);
Allocatable &= Reserved.flip();
return Allocatable;
static inline
const TargetRegisterClass *firstCommonClass(const uint32_t *A,
const uint32_t *B,
const TargetRegisterInfo *TRI) {
for (unsigned I = 0, E = TRI->getNumRegClasses(); I < E; I += 32)
if (unsigned Common = *A++ & *B++)
return TRI->getRegClass(I + countTrailingZeros(Common));
return nullptr;
const TargetRegisterClass *
TargetRegisterInfo::getCommonSubClass(const TargetRegisterClass *A,
const TargetRegisterClass *B) const {
// First take care of the trivial cases.
if (A == B)
return A;
if (!A || !B)
return nullptr;
// Register classes are ordered topologically, so the largest common
// sub-class it the common sub-class with the smallest ID.
return firstCommonClass(A->getSubClassMask(), B->getSubClassMask(), this);
const TargetRegisterClass *
TargetRegisterInfo::getMatchingSuperRegClass(const TargetRegisterClass *A,
const TargetRegisterClass *B,
unsigned Idx) const {
assert(A && B && "Missing register class");
assert(Idx && "Bad sub-register index");
// Find Idx in the list of super-register indices.
for (SuperRegClassIterator RCI(B, this); RCI.isValid(); ++RCI)
if (RCI.getSubReg() == Idx)
// The bit mask contains all register classes that are projected into B
// by Idx. Find a class that is also a sub-class of A.
return firstCommonClass(RCI.getMask(), A->getSubClassMask(), this);
return nullptr;
const TargetRegisterClass *TargetRegisterInfo::
getCommonSuperRegClass(const TargetRegisterClass *RCA, unsigned SubA,
const TargetRegisterClass *RCB, unsigned SubB,
unsigned &PreA, unsigned &PreB) const {
assert(RCA && SubA && RCB && SubB && "Invalid arguments");
// Search all pairs of sub-register indices that project into RCA and RCB
// respectively. This is quadratic, but usually the sets are very small. On
// most targets like X86, there will only be a single sub-register index
// (e.g., sub_16bit projecting into GR16).
// The worst case is a register class like DPR on ARM.
// We have indices dsub_0..dsub_7 projecting into that class.
// It is very common that one register class is a sub-register of the other.
// Arrange for RCA to be the larger register so the answer will be found in
// the first iteration. This makes the search linear for the most common
// case.
const TargetRegisterClass *BestRC = nullptr;
unsigned *BestPreA = &PreA;
unsigned *BestPreB = &PreB;
if (getRegSizeInBits(*RCA) < getRegSizeInBits(*RCB)) {
std::swap(RCA, RCB);
std::swap(SubA, SubB);
std::swap(BestPreA, BestPreB);
// Also terminate the search one we have found a register class as small as
// RCA.
unsigned MinSize = getRegSizeInBits(*RCA);
for (SuperRegClassIterator IA(RCA, this, true); IA.isValid(); ++IA) {
unsigned FinalA = composeSubRegIndices(IA.getSubReg(), SubA);
for (SuperRegClassIterator IB(RCB, this, true); IB.isValid(); ++IB) {
// Check if a common super-register class exists for this index pair.
const TargetRegisterClass *RC =
firstCommonClass(IA.getMask(), IB.getMask(), this);
if (!RC || getRegSizeInBits(*RC) < MinSize)
// The indexes must compose identically: PreA+SubA == PreB+SubB.
unsigned FinalB = composeSubRegIndices(IB.getSubReg(), SubB);
if (FinalA != FinalB)
// Is RC a better candidate than BestRC?
if (BestRC && getRegSizeInBits(*RC) >= getRegSizeInBits(*BestRC))
// Yes, RC is the smallest super-register seen so far.
BestRC = RC;
*BestPreA = IA.getSubReg();
*BestPreB = IB.getSubReg();
// Bail early if we reached MinSize. We won't find a better candidate.
if (getRegSizeInBits(*BestRC) == MinSize)
return BestRC;
return BestRC;
/// Check if the registers defined by the pair (RegisterClass, SubReg)
/// share the same register file.
static bool shareSameRegisterFile(const TargetRegisterInfo &TRI,
const TargetRegisterClass *DefRC,
unsigned DefSubReg,
const TargetRegisterClass *SrcRC,
unsigned SrcSubReg) {
// Same register class.
if (DefRC == SrcRC)
return true;
// Both operands are sub registers. Check if they share a register class.
unsigned SrcIdx, DefIdx;
if (SrcSubReg && DefSubReg) {
return TRI.getCommonSuperRegClass(SrcRC, SrcSubReg, DefRC, DefSubReg,
SrcIdx, DefIdx) != nullptr;
// At most one of the register is a sub register, make it Src to avoid
// duplicating the test.
if (!SrcSubReg) {
std::swap(DefSubReg, SrcSubReg);
std::swap(DefRC, SrcRC);
// One of the register is a sub register, check if we can get a superclass.
if (SrcSubReg)
return TRI.getMatchingSuperRegClass(SrcRC, DefRC, SrcSubReg) != nullptr;
// Plain copy.
return TRI.getCommonSubClass(DefRC, SrcRC) != nullptr;
bool TargetRegisterInfo::shouldRewriteCopySrc(const TargetRegisterClass *DefRC,
unsigned DefSubReg,
const TargetRegisterClass *SrcRC,
unsigned SrcSubReg) const {
// If this source does not incur a cross register bank copy, use it.
return shareSameRegisterFile(*this, DefRC, DefSubReg, SrcRC, SrcSubReg);
// Compute target-independent register allocator hints to help eliminate copies.
TargetRegisterInfo::getRegAllocationHints(unsigned VirtReg,
ArrayRef<MCPhysReg> Order,
SmallVectorImpl<MCPhysReg> &Hints,
const MachineFunction &MF,
const VirtRegMap *VRM,
const LiveRegMatrix *Matrix) const {
const MachineRegisterInfo &MRI = MF.getRegInfo();
const std::pair<unsigned, SmallVector<unsigned, 4>> &Hints_MRI =
SmallSet<unsigned, 32> HintedRegs;
// First hint may be a target hint.
bool Skip = (Hints_MRI.first != 0);
for (auto Reg : Hints_MRI.second) {
if (Skip) {
Skip = false;
// Target-independent hints are either a physical or a virtual register.
unsigned Phys = Reg;
if (VRM && Register::isVirtualRegister(Phys))
Phys = VRM->getPhys(Phys);
// Don't add the same reg twice (Hints_MRI may contain multiple virtual
// registers allocated to the same physreg).
if (!HintedRegs.insert(Phys).second)
// Check that Phys is a valid hint in VirtReg's register class.
if (!Register::isPhysicalRegister(Phys))
if (MRI.isReserved(Phys))
// Check that Phys is in the allocation order. We shouldn't heed hints
// from VirtReg's register class if they aren't in the allocation order. The
// target probably has a reason for removing the register.
if (!is_contained(Order, Phys))
// All clear, tell the register allocator to prefer this register.
return false;
bool TargetRegisterInfo::isCalleeSavedPhysReg(
unsigned PhysReg, const MachineFunction &MF) const {
if (PhysReg == 0)
return false;
const uint32_t *callerPreservedRegs =
getCallPreservedMask(MF, MF.getFunction().getCallingConv());
if (callerPreservedRegs) {
assert(Register::isPhysicalRegister(PhysReg) &&
"Expected physical register");
return (callerPreservedRegs[PhysReg / 32] >> PhysReg % 32) & 1;
return false;
bool TargetRegisterInfo::canRealignStack(const MachineFunction &MF) const {
return !MF.getFunction().hasFnAttribute("no-realign-stack");
bool TargetRegisterInfo::needsStackRealignment(
const MachineFunction &MF) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
const Function &F = MF.getFunction();
unsigned StackAlign = TFI->getStackAlignment();
bool requiresRealignment = ((MFI.getMaxAlignment() > StackAlign) ||
if (F.hasFnAttribute("stackrealign") || requiresRealignment) {
if (canRealignStack(MF))
return true;
LLVM_DEBUG(dbgs() << "Can't realign function's stack: " << F.getName()
<< "\n");
return false;
bool TargetRegisterInfo::regmaskSubsetEqual(const uint32_t *mask0,
const uint32_t *mask1) const {
unsigned N = (getNumRegs()+31) / 32;
for (unsigned I = 0; I < N; ++I)
if ((mask0[I] & mask1[I]) != mask0[I])
return false;
return true;
unsigned TargetRegisterInfo::getRegSizeInBits(unsigned Reg,
const MachineRegisterInfo &MRI) const {
const TargetRegisterClass *RC{};
if (Register::isPhysicalRegister(Reg)) {
// The size is not directly available for physical registers.
// Instead, we need to access a register class that contains Reg and
// get the size of that register class.
RC = getMinimalPhysRegClass(Reg);
} else {
LLT Ty = MRI.getType(Reg);
unsigned RegSize = Ty.isValid() ? Ty.getSizeInBits() : 0;
// If Reg is not a generic register, query the register class to
// get its size.
if (RegSize)
return RegSize;
// Since Reg is not a generic register, it must have a register class.
RC = MRI.getRegClass(Reg);
assert(RC && "Unable to deduce the register class");
return getRegSizeInBits(*RC);
TargetRegisterInfo::lookThruCopyLike(unsigned SrcReg,
const MachineRegisterInfo *MRI) const {
while (true) {
const MachineInstr *MI = MRI->getVRegDef(SrcReg);
if (!MI->isCopyLike())
return SrcReg;
unsigned CopySrcReg;
if (MI->isCopy())
CopySrcReg = MI->getOperand(1).getReg();
else {
assert(MI->isSubregToReg() && "Bad opcode for lookThruCopyLike");
CopySrcReg = MI->getOperand(2).getReg();
if (!Register::isVirtualRegister(CopySrcReg))
return CopySrcReg;
SrcReg = CopySrcReg;
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void TargetRegisterInfo::dumpReg(unsigned Reg, unsigned SubRegIndex,
const TargetRegisterInfo *TRI) {
dbgs() << printReg(Reg, TRI, SubRegIndex) << "\n";