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llvm-6502/lib/CodeGen/Spiller.cpp

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Reorganization: Move the Spiller out of VirtRegMap.cpp into its own files. No (intended) functionality change. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66720 91177308-0d34-0410-b5e6-96231b3b80d8
2009-03-11 22:31:21 +00:00
//===-- llvm/CodeGen/Spiller.cpp - Spiller -------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "spiller"
#include "Spiller.h"
Reorganize some #include's. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66780 91177308-0d34-0410-b5e6-96231b3b80d8
2009-03-12 06:58:19 +00:00
#include "llvm/Support/Compiler.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
Reorganization: Move the Spiller out of VirtRegMap.cpp into its own files. No (intended) functionality change. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66720 91177308-0d34-0410-b5e6-96231b3b80d8
2009-03-11 22:31:21 +00:00
#include <algorithm>
using namespace llvm;
STATISTIC(NumDSE , "Number of dead stores elided");
STATISTIC(NumDSS , "Number of dead spill slots removed");
STATISTIC(NumCommutes, "Number of instructions commuted");
STATISTIC(NumDRM , "Number of re-materializable defs elided");
STATISTIC(NumStores , "Number of stores added");
STATISTIC(NumPSpills , "Number of physical register spills");
STATISTIC(NumOmitted , "Number of reloads omited");
STATISTIC(NumCopified, "Number of available reloads turned into copies");
STATISTIC(NumReMats , "Number of re-materialization");
STATISTIC(NumLoads , "Number of loads added");
STATISTIC(NumReused , "Number of values reused");
STATISTIC(NumDCE , "Number of copies elided");
namespace {
enum SpillerName { simple, local };
}
static cl::opt<SpillerName>
SpillerOpt("spiller",
cl::desc("Spiller to use: (default: local)"),
cl::Prefix,
cl::values(clEnumVal(simple, "simple spiller"),
clEnumVal(local, "local spiller"),
clEnumValEnd),
cl::init(local));
// ****************************** //
// Simple Spiller Implementation //
// ****************************** //
Spiller::~Spiller() {}
bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
DOUT << "********** REWRITE MACHINE CODE **********\n";
DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
const TargetMachine &TM = MF.getTarget();
const TargetInstrInfo &TII = *TM.getInstrInfo();
const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
// LoadedRegs - Keep track of which vregs are loaded, so that we only load
// each vreg once (in the case where a spilled vreg is used by multiple
// operands). This is always smaller than the number of operands to the
// current machine instr, so it should be small.
std::vector<unsigned> LoadedRegs;
for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
MBBI != E; ++MBBI) {
DOUT << MBBI->getBasicBlock()->getName() << ":\n";
MachineBasicBlock &MBB = *MBBI;
for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
MII != E; ++MII) {
MachineInstr &MI = *MII;
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (MO.isReg() && MO.getReg()) {
if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
unsigned VirtReg = MO.getReg();
unsigned SubIdx = MO.getSubReg();
unsigned PhysReg = VRM.getPhys(VirtReg);
unsigned RReg = SubIdx ? TRI.getSubReg(PhysReg, SubIdx) : PhysReg;
if (!VRM.isAssignedReg(VirtReg)) {
int StackSlot = VRM.getStackSlot(VirtReg);
const TargetRegisterClass* RC =
MF.getRegInfo().getRegClass(VirtReg);
if (MO.isUse() &&
std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
== LoadedRegs.end()) {
TII.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
MachineInstr *LoadMI = prior(MII);
VRM.addSpillSlotUse(StackSlot, LoadMI);
LoadedRegs.push_back(VirtReg);
++NumLoads;
DOUT << '\t' << *LoadMI;
}
if (MO.isDef()) {
TII.storeRegToStackSlot(MBB, next(MII), PhysReg, true,
StackSlot, RC);
MachineInstr *StoreMI = next(MII);
VRM.addSpillSlotUse(StackSlot, StoreMI);
++NumStores;
}
}
MF.getRegInfo().setPhysRegUsed(RReg);
MI.getOperand(i).setReg(RReg);
} else {
MF.getRegInfo().setPhysRegUsed(MO.getReg());
}
}
}
DOUT << '\t' << MI;
LoadedRegs.clear();
}
}
return true;
}
// ****************** //
// Utility Functions //
// ****************** //
/// InvalidateKill - A MI that defines the specified register is being deleted,
/// invalidate the register kill information.
static void InvalidateKill(unsigned Reg, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps) {
if (RegKills[Reg]) {
KillOps[Reg]->setIsKill(false);
KillOps[Reg] = NULL;
RegKills.reset(Reg);
}
}
/// findSinglePredSuccessor - Return via reference a vector of machine basic
/// blocks each of which is a successor of the specified BB and has no other
/// predecessor.
static void findSinglePredSuccessor(MachineBasicBlock *MBB,
SmallVectorImpl<MachineBasicBlock *> &Succs) {
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI) {
MachineBasicBlock *SuccMBB = *SI;
if (SuccMBB->pred_size() == 1)
Succs.push_back(SuccMBB);
}
}
/// InvalidateKills - MI is going to be deleted. If any of its operands are
/// marked kill, then invalidate the information.
static void InvalidateKills(MachineInstr &MI, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
SmallVector<unsigned, 2> *KillRegs = NULL) {
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg() || !MO.isUse() || !MO.isKill())
continue;
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg))
continue;
if (KillRegs)
KillRegs->push_back(Reg);
assert(Reg < KillOps.size());
if (KillOps[Reg] == &MO) {
RegKills.reset(Reg);
KillOps[Reg] = NULL;
}
}
}
/// InvalidateRegDef - If the def operand of the specified def MI is now dead
/// (since it's spill instruction is removed), mark it isDead. Also checks if
/// the def MI has other definition operands that are not dead. Returns it by
/// reference.
static bool InvalidateRegDef(MachineBasicBlock::iterator I,
MachineInstr &NewDef, unsigned Reg,
bool &HasLiveDef) {
// Due to remat, it's possible this reg isn't being reused. That is,
// the def of this reg (by prev MI) is now dead.
MachineInstr *DefMI = I;
MachineOperand *DefOp = NULL;
for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = DefMI->getOperand(i);
if (MO.isReg() && MO.isDef()) {
if (MO.getReg() == Reg)
DefOp = &MO;
else if (!MO.isDead())
HasLiveDef = true;
}
}
if (!DefOp)
return false;
bool FoundUse = false, Done = false;
MachineBasicBlock::iterator E = &NewDef;
++I; ++E;
for (; !Done && I != E; ++I) {
MachineInstr *NMI = I;
for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) {
MachineOperand &MO = NMI->getOperand(j);
if (!MO.isReg() || MO.getReg() != Reg)
continue;
if (MO.isUse())
FoundUse = true;
Done = true; // Stop after scanning all the operands of this MI.
}
}
if (!FoundUse) {
// Def is dead!
DefOp->setIsDead();
return true;
}
return false;
}
/// UpdateKills - Track and update kill info. If a MI reads a register that is
/// marked kill, then it must be due to register reuse. Transfer the kill info
/// over.
static void UpdateKills(MachineInstr &MI, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
const TargetRegisterInfo* TRI) {
const TargetInstrDesc &TID = MI.getDesc();
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg() || !MO.isUse())
continue;
unsigned Reg = MO.getReg();
if (Reg == 0)
continue;
if (RegKills[Reg] && KillOps[Reg]->getParent() != &MI) {
// That can't be right. Register is killed but not re-defined and it's
// being reused. Let's fix that.
KillOps[Reg]->setIsKill(false);
KillOps[Reg] = NULL;
RegKills.reset(Reg);
if (i < TID.getNumOperands() &&
TID.getOperandConstraint(i, TOI::TIED_TO) == -1)
// Unless it's a two-address operand, this is the new kill.
MO.setIsKill();
}
if (MO.isKill()) {
RegKills.set(Reg);
KillOps[Reg] = &MO;
}
}
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg() || !MO.isDef())
continue;
unsigned Reg = MO.getReg();
RegKills.reset(Reg);
KillOps[Reg] = NULL;
// It also defines (or partially define) aliases.
for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) {
RegKills.reset(*AS);
KillOps[*AS] = NULL;
}
}
}
/// ReMaterialize - Re-materialize definition for Reg targetting DestReg.
///
static void ReMaterialize(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
unsigned DestReg, unsigned Reg,
const TargetInstrInfo *TII,
const TargetRegisterInfo *TRI,
VirtRegMap &VRM) {
TII->reMaterialize(MBB, MII, DestReg, VRM.getReMaterializedMI(Reg));
MachineInstr *NewMI = prior(MII);
for (unsigned i = 0, e = NewMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = NewMI->getOperand(i);
if (!MO.isReg() || MO.getReg() == 0)
continue;
unsigned VirtReg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(VirtReg))
continue;
assert(MO.isUse());
unsigned SubIdx = MO.getSubReg();
unsigned Phys = VRM.getPhys(VirtReg);
assert(Phys);
unsigned RReg = SubIdx ? TRI->getSubReg(Phys, SubIdx) : Phys;
MO.setReg(RReg);
}
++NumReMats;
}
/// findSuperReg - Find the SubReg's super-register of given register class
/// where its SubIdx sub-register is SubReg.
static unsigned findSuperReg(const TargetRegisterClass *RC, unsigned SubReg,
unsigned SubIdx, const TargetRegisterInfo *TRI) {
for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
I != E; ++I) {
unsigned Reg = *I;
if (TRI->getSubReg(Reg, SubIdx) == SubReg)
return Reg;
}
return 0;
}
// ******************************** //
// Available Spills Implementation //
// ******************************** //
/// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
/// stackslot register. The register is still available but is no longer
/// allowed to be modifed.
void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
std::multimap<unsigned, int>::iterator I =
PhysRegsAvailable.lower_bound(PhysReg);
while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
int SlotOrReMat = I->second;
I++;
assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
"Bidirectional map mismatch!");
SpillSlotsOrReMatsAvailable[SlotOrReMat] &= ~1;
DOUT << "PhysReg " << TRI->getName(PhysReg)
<< " copied, it is available for use but can no longer be modified\n";
}
}
/// disallowClobberPhysReg - Unset the CanClobber bit of the specified
/// stackslot register and its aliases. The register and its aliases may
/// still available but is no longer allowed to be modifed.
void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
for (const unsigned *AS = TRI->getAliasSet(PhysReg); *AS; ++AS)
disallowClobberPhysRegOnly(*AS);
disallowClobberPhysRegOnly(PhysReg);
}
/// ClobberPhysRegOnly - This is called when the specified physreg changes
/// value. We use this to invalidate any info about stuff we thing lives in it.
void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
std::multimap<unsigned, int>::iterator I =
PhysRegsAvailable.lower_bound(PhysReg);
while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
int SlotOrReMat = I->second;
PhysRegsAvailable.erase(I++);
assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
"Bidirectional map mismatch!");
SpillSlotsOrReMatsAvailable.erase(SlotOrReMat);
DOUT << "PhysReg " << TRI->getName(PhysReg)
<< " clobbered, invalidating ";
if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
DOUT << "RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1 << "\n";
else
DOUT << "SS#" << SlotOrReMat << "\n";
}
}
/// ClobberPhysReg - This is called when the specified physreg changes
/// value. We use this to invalidate any info about stuff we thing lives in
/// it and any of its aliases.
void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
for (const unsigned *AS = TRI->getAliasSet(PhysReg); *AS; ++AS)
ClobberPhysRegOnly(*AS);
ClobberPhysRegOnly(PhysReg);
}
/// AddAvailableRegsToLiveIn - Availability information is being kept coming
/// into the specified MBB. Add available physical registers as potential
/// live-in's. If they are reused in the MBB, they will be added to the
/// live-in set to make register scavenger and post-allocation scheduler.
void AvailableSpills::AddAvailableRegsToLiveIn(MachineBasicBlock &MBB,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps) {
std::set<unsigned> NotAvailable;
for (std::multimap<unsigned, int>::iterator
I = PhysRegsAvailable.begin(), E = PhysRegsAvailable.end();
I != E; ++I) {
unsigned Reg = I->first;
const TargetRegisterClass* RC = TRI->getPhysicalRegisterRegClass(Reg);
// FIXME: A temporary workaround. We can't reuse available value if it's
// not safe to move the def of the virtual register's class. e.g.
// X86::RFP* register classes. Do not add it as a live-in.
if (!TII->isSafeToMoveRegClassDefs(RC))
// This is no longer available.
NotAvailable.insert(Reg);
else {
MBB.addLiveIn(Reg);
InvalidateKill(Reg, RegKills, KillOps);
}
// Skip over the same register.
std::multimap<unsigned, int>::iterator NI = next(I);
while (NI != E && NI->first == Reg) {
++I;
++NI;
}
}
for (std::set<unsigned>::iterator I = NotAvailable.begin(),
E = NotAvailable.end(); I != E; ++I) {
ClobberPhysReg(*I);
for (const unsigned *SubRegs = TRI->getSubRegisters(*I);
*SubRegs; ++SubRegs)
ClobberPhysReg(*SubRegs);
}
}
/// ModifyStackSlotOrReMat - This method is called when the value in a stack
/// slot changes. This removes information about which register the previous
/// value for this slot lives in (as the previous value is dead now).
void AvailableSpills::ModifyStackSlotOrReMat(int SlotOrReMat) {
std::map<int, unsigned>::iterator It =
SpillSlotsOrReMatsAvailable.find(SlotOrReMat);
if (It == SpillSlotsOrReMatsAvailable.end()) return;
unsigned Reg = It->second >> 1;
SpillSlotsOrReMatsAvailable.erase(It);
// This register may hold the value of multiple stack slots, only remove this
// stack slot from the set of values the register contains.
std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
for (; ; ++I) {
assert(I != PhysRegsAvailable.end() && I->first == Reg &&
"Map inverse broken!");
if (I->second == SlotOrReMat) break;
}
PhysRegsAvailable.erase(I);
}
// ************************** //
// Reuse Info Implementation //
// ************************** //
/// GetRegForReload - We are about to emit a reload into PhysReg. If there
/// is some other operand that is using the specified register, either pick
/// a new register to use, or evict the previous reload and use this reg.
unsigned ReuseInfo::GetRegForReload(unsigned PhysReg, MachineInstr *MI,
AvailableSpills &Spills,
std::vector<MachineInstr*> &MaybeDeadStores,
SmallSet<unsigned, 8> &Rejected,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
const TargetInstrInfo* TII = MI->getParent()->getParent()->getTarget()
.getInstrInfo();
if (Reuses.empty()) return PhysReg; // This is most often empty.
for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
ReusedOp &Op = Reuses[ro];
// If we find some other reuse that was supposed to use this register
// exactly for its reload, we can change this reload to use ITS reload
// register. That is, unless its reload register has already been
// considered and subsequently rejected because it has also been reused
// by another operand.
if (Op.PhysRegReused == PhysReg &&
Rejected.count(Op.AssignedPhysReg) == 0) {
// Yup, use the reload register that we didn't use before.
unsigned NewReg = Op.AssignedPhysReg;
Rejected.insert(PhysReg);
return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected,
RegKills, KillOps, VRM);
} else {
// Otherwise, we might also have a problem if a previously reused
// value aliases the new register. If so, codegen the previous reload
// and use this one.
unsigned PRRU = Op.PhysRegReused;
const TargetRegisterInfo *TRI = Spills.getRegInfo();
if (TRI->areAliases(PRRU, PhysReg)) {
// Okay, we found out that an alias of a reused register
// was used. This isn't good because it means we have
// to undo a previous reuse.
MachineBasicBlock *MBB = MI->getParent();
const TargetRegisterClass *AliasRC =
MBB->getParent()->getRegInfo().getRegClass(Op.VirtReg);
// Copy Op out of the vector and remove it, we're going to insert an
// explicit load for it.
ReusedOp NewOp = Op;
Reuses.erase(Reuses.begin()+ro);
// Ok, we're going to try to reload the assigned physreg into the
// slot that we were supposed to in the first place. However, that
// register could hold a reuse. Check to see if it conflicts or
// would prefer us to use a different register.
unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
MI, Spills, MaybeDeadStores,
Rejected, RegKills, KillOps, VRM);
MachineBasicBlock::iterator MII = MI;
if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) {
ReMaterialize(*MBB, MII, NewPhysReg, NewOp.VirtReg, TII, TRI,VRM);
} else {
TII->loadRegFromStackSlot(*MBB, MII, NewPhysReg,
NewOp.StackSlotOrReMat, AliasRC);
MachineInstr *LoadMI = prior(MII);
VRM.addSpillSlotUse(NewOp.StackSlotOrReMat, LoadMI);
// Any stores to this stack slot are not dead anymore.
MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL;
++NumLoads;
}
Spills.ClobberPhysReg(NewPhysReg);
Spills.ClobberPhysReg(NewOp.PhysRegReused);
unsigned SubIdx = MI->getOperand(NewOp.Operand).getSubReg();
unsigned RReg = SubIdx ? TRI->getSubReg(NewPhysReg, SubIdx) : NewPhysReg;
MI->getOperand(NewOp.Operand).setReg(RReg);
Spills.addAvailable(NewOp.StackSlotOrReMat, NewPhysReg);
--MII;
UpdateKills(*MII, RegKills, KillOps, TRI);
DOUT << '\t' << *MII;
DOUT << "Reuse undone!\n";
--NumReused;
// Finally, PhysReg is now available, go ahead and use it.
return PhysReg;
}
}
}
return PhysReg;
}
// ***************************** //
// Local Spiller Implementation //
// ***************************** //
bool LocalSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
RegInfo = &MF.getRegInfo();
TRI = MF.getTarget().getRegisterInfo();
TII = MF.getTarget().getInstrInfo();
DOUT << "\n**** Local spiller rewriting function '"
<< MF.getFunction()->getName() << "':\n";
DOUT << "**** Machine Instrs (NOTE! Does not include spills and reloads!)"
" ****\n";
DEBUG(MF.dump());
// Spills - Keep track of which spilled values are available in physregs
// so that we can choose to reuse the physregs instead of emitting
// reloads. This is usually refreshed per basic block.
AvailableSpills Spills(TRI, TII);
// Keep track of kill information.
BitVector RegKills(TRI->getNumRegs());
std::vector<MachineOperand*> KillOps;
KillOps.resize(TRI->getNumRegs(), NULL);
// SingleEntrySuccs - Successor blocks which have a single predecessor.
SmallVector<MachineBasicBlock*, 4> SinglePredSuccs;
SmallPtrSet<MachineBasicBlock*,16> EarlyVisited;
// Traverse the basic blocks depth first.
MachineBasicBlock *Entry = MF.begin();
SmallPtrSet<MachineBasicBlock*,16> Visited;
for (df_ext_iterator<MachineBasicBlock*,
SmallPtrSet<MachineBasicBlock*,16> >
DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited);
DFI != E; ++DFI) {
MachineBasicBlock *MBB = *DFI;
if (!EarlyVisited.count(MBB))
RewriteMBB(*MBB, VRM, Spills, RegKills, KillOps);
// If this MBB is the only predecessor of a successor. Keep the
// availability information and visit it next.
do {
// Keep visiting single predecessor successor as long as possible.
SinglePredSuccs.clear();
findSinglePredSuccessor(MBB, SinglePredSuccs);
if (SinglePredSuccs.empty())
MBB = 0;
else {
// FIXME: More than one successors, each of which has MBB has
// the only predecessor.
MBB = SinglePredSuccs[0];
if (!Visited.count(MBB) && EarlyVisited.insert(MBB)) {
Spills.AddAvailableRegsToLiveIn(*MBB, RegKills, KillOps);
RewriteMBB(*MBB, VRM, Spills, RegKills, KillOps);
}
}
} while (MBB);
// Clear the availability info.
Spills.clear();
}
DOUT << "**** Post Machine Instrs ****\n";
DEBUG(MF.dump());
// Mark unused spill slots.
MachineFrameInfo *MFI = MF.getFrameInfo();
int SS = VRM.getLowSpillSlot();
if (SS != VirtRegMap::NO_STACK_SLOT)
for (int e = VRM.getHighSpillSlot(); SS <= e; ++SS)
if (!VRM.isSpillSlotUsed(SS)) {
MFI->RemoveStackObject(SS);
++NumDSS;
}
return true;
}
/// PrepForUnfoldOpti - Turn a store folding instruction into a load folding
/// instruction. e.g.
/// xorl %edi, %eax
/// movl %eax, -32(%ebp)
/// movl -36(%ebp), %eax
/// orl %eax, -32(%ebp)
/// ==>
/// xorl %edi, %eax
/// orl -36(%ebp), %eax
/// mov %eax, -32(%ebp)
/// This enables unfolding optimization for a subsequent instruction which will
/// also eliminate the newly introduced store instruction.
bool LocalSpiller::PrepForUnfoldOpti(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
std::vector<MachineInstr*> &MaybeDeadStores,
AvailableSpills &Spills,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
MachineFunction &MF = *MBB.getParent();
MachineInstr &MI = *MII;
unsigned UnfoldedOpc = 0;
unsigned UnfoldPR = 0;
unsigned UnfoldVR = 0;
int FoldedSS = VirtRegMap::NO_STACK_SLOT;
VirtRegMap::MI2VirtMapTy::const_iterator I, End;
for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ) {
// Only transform a MI that folds a single register.
if (UnfoldedOpc)
return false;
UnfoldVR = I->second.first;
VirtRegMap::ModRef MR = I->second.second;
// MI2VirtMap be can updated which invalidate the iterator.
// Increment the iterator first.
++I;
if (VRM.isAssignedReg(UnfoldVR))
continue;
// If this reference is not a use, any previous store is now dead.
// Otherwise, the store to this stack slot is not dead anymore.
FoldedSS = VRM.getStackSlot(UnfoldVR);
MachineInstr* DeadStore = MaybeDeadStores[FoldedSS];
if (DeadStore && (MR & VirtRegMap::isModRef)) {
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(FoldedSS);
if (!PhysReg || !DeadStore->readsRegister(PhysReg))
continue;
UnfoldPR = PhysReg;
UnfoldedOpc = TII->getOpcodeAfterMemoryUnfold(MI.getOpcode(),
false, true);
}
}
if (!UnfoldedOpc)
return false;
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg() || MO.getReg() == 0 || !MO.isUse())
continue;
unsigned VirtReg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(VirtReg) || MO.getSubReg())
continue;
if (VRM.isAssignedReg(VirtReg)) {
unsigned PhysReg = VRM.getPhys(VirtReg);
if (PhysReg && TRI->regsOverlap(PhysReg, UnfoldPR))
return false;
} else if (VRM.isReMaterialized(VirtReg))
continue;
int SS = VRM.getStackSlot(VirtReg);
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
if (PhysReg) {
if (TRI->regsOverlap(PhysReg, UnfoldPR))
return false;
continue;
}
if (VRM.hasPhys(VirtReg)) {
PhysReg = VRM.getPhys(VirtReg);
if (!TRI->regsOverlap(PhysReg, UnfoldPR))
continue;
}
// Ok, we'll need to reload the value into a register which makes
// it impossible to perform the store unfolding optimization later.
// Let's see if it is possible to fold the load if the store is
// unfolded. This allows us to perform the store unfolding
// optimization.
SmallVector<MachineInstr*, 4> NewMIs;
if (TII->unfoldMemoryOperand(MF, &MI, UnfoldVR, false, false, NewMIs)) {
assert(NewMIs.size() == 1);
MachineInstr *NewMI = NewMIs.back();
NewMIs.clear();
int Idx = NewMI->findRegisterUseOperandIdx(VirtReg, false);
assert(Idx != -1);
SmallVector<unsigned, 1> Ops;
Ops.push_back(Idx);
MachineInstr *FoldedMI = TII->foldMemoryOperand(MF, NewMI, Ops, SS);
if (FoldedMI) {
VRM.addSpillSlotUse(SS, FoldedMI);
if (!VRM.hasPhys(UnfoldVR))
VRM.assignVirt2Phys(UnfoldVR, UnfoldPR);
VRM.virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef);
MII = MBB.insert(MII, FoldedMI);
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
MF.DeleteMachineInstr(NewMI);
return true;
}
MF.DeleteMachineInstr(NewMI);
}
}
return false;
}
/// CommuteToFoldReload -
/// Look for
/// r1 = load fi#1
/// r1 = op r1, r2<kill>
/// store r1, fi#1
///
/// If op is commutable and r2 is killed, then we can xform these to
/// r2 = op r2, fi#1
/// store r2, fi#1
bool LocalSpiller::CommuteToFoldReload(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
unsigned VirtReg, unsigned SrcReg, int SS,
AvailableSpills &Spills,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
const TargetRegisterInfo *TRI,
VirtRegMap &VRM) {
if (MII == MBB.begin() || !MII->killsRegister(SrcReg))
return false;
MachineFunction &MF = *MBB.getParent();
MachineInstr &MI = *MII;
MachineBasicBlock::iterator DefMII = prior(MII);
MachineInstr *DefMI = DefMII;
const TargetInstrDesc &TID = DefMI->getDesc();
unsigned NewDstIdx;
if (DefMII != MBB.begin() &&
TID.isCommutable() &&
TII->CommuteChangesDestination(DefMI, NewDstIdx)) {
MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
unsigned NewReg = NewDstMO.getReg();
if (!NewDstMO.isKill() || TRI->regsOverlap(NewReg, SrcReg))
return false;
MachineInstr *ReloadMI = prior(DefMII);
int FrameIdx;
unsigned DestReg = TII->isLoadFromStackSlot(ReloadMI, FrameIdx);
if (DestReg != SrcReg || FrameIdx != SS)
return false;
int UseIdx = DefMI->findRegisterUseOperandIdx(DestReg, false);
if (UseIdx == -1)
return false;
int DefIdx = TID.getOperandConstraint(UseIdx, TOI::TIED_TO);
if (DefIdx == -1)
return false;
assert(DefMI->getOperand(DefIdx).isReg() &&
DefMI->getOperand(DefIdx).getReg() == SrcReg);
// Now commute def instruction.
MachineInstr *CommutedMI = TII->commuteInstruction(DefMI, true);
if (!CommutedMI)
return false;
SmallVector<unsigned, 1> Ops;
Ops.push_back(NewDstIdx);
MachineInstr *FoldedMI = TII->foldMemoryOperand(MF, CommutedMI, Ops, SS);
// Not needed since foldMemoryOperand returns new MI.
MF.DeleteMachineInstr(CommutedMI);
if (!FoldedMI)
return false;
VRM.addSpillSlotUse(SS, FoldedMI);
VRM.virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef);
// Insert new def MI and spill MI.
const TargetRegisterClass* RC = MF.getRegInfo().getRegClass(VirtReg);
TII->storeRegToStackSlot(MBB, &MI, NewReg, true, SS, RC);
MII = prior(MII);
MachineInstr *StoreMI = MII;
VRM.addSpillSlotUse(SS, StoreMI);
VRM.virtFolded(VirtReg, StoreMI, VirtRegMap::isMod);
MII = MBB.insert(MII, FoldedMI); // Update MII to backtrack.
// Delete all 3 old instructions.
InvalidateKills(*ReloadMI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(ReloadMI);
MBB.erase(ReloadMI);
InvalidateKills(*DefMI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(DefMI);
MBB.erase(DefMI);
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
// If NewReg was previously holding value of some SS, it's now clobbered.
// This has to be done now because it's a physical register. When this
// instruction is re-visited, it's ignored.
Spills.ClobberPhysReg(NewReg);
++NumCommutes;
return true;
}
return false;
}
/// SpillRegToStackSlot - Spill a register to a specified stack slot. Check if
/// the last store to the same slot is now dead. If so, remove the last store.
void LocalSpiller::SpillRegToStackSlot(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
int Idx, unsigned PhysReg, int StackSlot,
const TargetRegisterClass *RC,
bool isAvailable, MachineInstr *&LastStore,
AvailableSpills &Spills,
SmallSet<MachineInstr*, 4> &ReMatDefs,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
TII->storeRegToStackSlot(MBB, next(MII), PhysReg, true, StackSlot, RC);
MachineInstr *StoreMI = next(MII);
VRM.addSpillSlotUse(StackSlot, StoreMI);
DOUT << "Store:\t" << *StoreMI;
// If there is a dead store to this stack slot, nuke it now.
if (LastStore) {
DOUT << "Removed dead store:\t" << *LastStore;
++NumDSE;
SmallVector<unsigned, 2> KillRegs;
InvalidateKills(*LastStore, RegKills, KillOps, &KillRegs);
MachineBasicBlock::iterator PrevMII = LastStore;
bool CheckDef = PrevMII != MBB.begin();
if (CheckDef)
--PrevMII;
VRM.RemoveMachineInstrFromMaps(LastStore);
MBB.erase(LastStore);
if (CheckDef) {
// Look at defs of killed registers on the store. Mark the defs
// as dead since the store has been deleted and they aren't
// being reused.
for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
bool HasOtherDef = false;
if (InvalidateRegDef(PrevMII, *MII, KillRegs[j], HasOtherDef)) {
MachineInstr *DeadDef = PrevMII;
if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
// FIXME: This assumes a remat def does not have side
// effects.
VRM.RemoveMachineInstrFromMaps(DeadDef);
MBB.erase(DeadDef);
++NumDRM;
}
}
}
}
}
LastStore = next(MII);
// If the stack slot value was previously available in some other
// register, change it now. Otherwise, make the register available,
// in PhysReg.
Spills.ModifyStackSlotOrReMat(StackSlot);
Spills.ClobberPhysReg(PhysReg);
Spills.addAvailable(StackSlot, PhysReg, isAvailable);
++NumStores;
}
/// TransferDeadness - A identity copy definition is dead and it's being
/// removed. Find the last def or use and mark it as dead / kill.
void LocalSpiller::TransferDeadness(MachineBasicBlock *MBB, unsigned CurDist,
unsigned Reg, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps) {
int LastUDDist = -1;
MachineInstr *LastUDMI = NULL;
for (MachineRegisterInfo::reg_iterator RI = RegInfo->reg_begin(Reg),
RE = RegInfo->reg_end(); RI != RE; ++RI) {
MachineInstr *UDMI = &*RI;
if (UDMI->getParent() != MBB)
continue;
DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UDMI);
if (DI == DistanceMap.end() || DI->second > CurDist)
continue;
if ((int)DI->second < LastUDDist)
continue;
LastUDDist = DI->second;
LastUDMI = UDMI;
}
if (LastUDMI) {
const TargetInstrDesc &TID = LastUDMI->getDesc();
MachineOperand *LastUD = NULL;
for (unsigned i = 0, e = LastUDMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = LastUDMI->getOperand(i);
if (!MO.isReg() || MO.getReg() != Reg)
continue;
if (!LastUD || (LastUD->isUse() && MO.isDef()))
LastUD = &MO;
if (TID.getOperandConstraint(i, TOI::TIED_TO) != -1)
return;
}
if (LastUD->isDef())
LastUD->setIsDead();
else {
LastUD->setIsKill();
RegKills.set(Reg);
KillOps[Reg] = LastUD;
}
}
}
/// rewriteMBB - Keep track of which spills are available even after the
/// register allocator is done with them. If possible, avid reloading vregs.
void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM,
AvailableSpills &Spills, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps) {
DOUT << "\n**** Local spiller rewriting MBB '"
<< MBB.getBasicBlock()->getName() << ":\n";
MachineFunction &MF = *MBB.getParent();
// MaybeDeadStores - When we need to write a value back into a stack slot,
// keep track of the inserted store. If the stack slot value is never read
// (because the value was used from some available register, for example), and
// subsequently stored to, the original store is dead. This map keeps track
// of inserted stores that are not used. If we see a subsequent store to the
// same stack slot, the original store is deleted.
std::vector<MachineInstr*> MaybeDeadStores;
MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL);
// ReMatDefs - These are rematerializable def MIs which are not deleted.
SmallSet<MachineInstr*, 4> ReMatDefs;
// Clear kill info.
SmallSet<unsigned, 2> KilledMIRegs;
RegKills.reset();
KillOps.clear();
KillOps.resize(TRI->getNumRegs(), NULL);
unsigned Dist = 0;
DistanceMap.clear();
for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
MII != E; ) {
MachineBasicBlock::iterator NextMII = MII; ++NextMII;
VirtRegMap::MI2VirtMapTy::const_iterator I, End;
bool Erased = false;
bool BackTracked = false;
if (PrepForUnfoldOpti(MBB, MII,
MaybeDeadStores, Spills, RegKills, KillOps, VRM))
NextMII = next(MII);
MachineInstr &MI = *MII;
const TargetInstrDesc &TID = MI.getDesc();
if (VRM.hasEmergencySpills(&MI)) {
// Spill physical register(s) in the rare case the allocator has run out
// of registers to allocate.
SmallSet<int, 4> UsedSS;
std::vector<unsigned> &EmSpills = VRM.getEmergencySpills(&MI);
for (unsigned i = 0, e = EmSpills.size(); i != e; ++i) {
unsigned PhysReg = EmSpills[i];
const TargetRegisterClass *RC =
TRI->getPhysicalRegisterRegClass(PhysReg);
assert(RC && "Unable to determine register class!");
int SS = VRM.getEmergencySpillSlot(RC);
if (UsedSS.count(SS))
assert(0 && "Need to spill more than one physical registers!");
UsedSS.insert(SS);
TII->storeRegToStackSlot(MBB, MII, PhysReg, true, SS, RC);
MachineInstr *StoreMI = prior(MII);
VRM.addSpillSlotUse(SS, StoreMI);
TII->loadRegFromStackSlot(MBB, next(MII), PhysReg, SS, RC);
MachineInstr *LoadMI = next(MII);
VRM.addSpillSlotUse(SS, LoadMI);
++NumPSpills;
}
NextMII = next(MII);
}
// Insert restores here if asked to.
if (VRM.isRestorePt(&MI)) {
std::vector<unsigned> &RestoreRegs = VRM.getRestorePtRestores(&MI);
for (unsigned i = 0, e = RestoreRegs.size(); i != e; ++i) {
unsigned VirtReg = RestoreRegs[e-i-1]; // Reverse order.
if (!VRM.getPreSplitReg(VirtReg))
continue; // Split interval spilled again.
unsigned Phys = VRM.getPhys(VirtReg);
RegInfo->setPhysRegUsed(Phys);
// Check if the value being restored if available. If so, it must be
// from a predecessor BB that fallthrough into this BB. We do not
// expect:
// BB1:
// r1 = load fi#1
// ...
// = r1<kill>
// ... # r1 not clobbered
// ...
// = load fi#1
bool DoReMat = VRM.isReMaterialized(VirtReg);
int SSorRMId = DoReMat
? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
if (InReg == Phys) {
// If the value is already available in the expected register, save
// a reload / remat.
if (SSorRMId)
DOUT << "Reusing RM#" << SSorRMId-VirtRegMap::MAX_STACK_SLOT-1;
else
DOUT << "Reusing SS#" << SSorRMId;
DOUT << " from physreg "
<< TRI->getName(InReg) << " for vreg"
<< VirtReg <<" instead of reloading into physreg "
<< TRI->getName(Phys) << "\n";
++NumOmitted;
continue;
} else if (InReg && InReg != Phys) {
if (SSorRMId)
DOUT << "Reusing RM#" << SSorRMId-VirtRegMap::MAX_STACK_SLOT-1;
else
DOUT << "Reusing SS#" << SSorRMId;
DOUT << " from physreg "
<< TRI->getName(InReg) << " for vreg"
<< VirtReg <<" by copying it into physreg "
<< TRI->getName(Phys) << "\n";
// If the reloaded / remat value is available in another register,
// copy it to the desired register.
TII->copyRegToReg(MBB, &MI, Phys, InReg, RC, RC);
// This invalidates Phys.
Spills.ClobberPhysReg(Phys);
// Remember it's available.
Spills.addAvailable(SSorRMId, Phys);
// Mark is killed.
MachineInstr *CopyMI = prior(MII);
MachineOperand *KillOpnd = CopyMI->findRegisterUseOperand(InReg);
KillOpnd->setIsKill();
UpdateKills(*CopyMI, RegKills, KillOps, TRI);
DOUT << '\t' << *CopyMI;
++NumCopified;
continue;
}
if (VRM.isReMaterialized(VirtReg)) {
ReMaterialize(MBB, MII, Phys, VirtReg, TII, TRI, VRM);
} else {
const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
TII->loadRegFromStackSlot(MBB, &MI, Phys, SSorRMId, RC);
MachineInstr *LoadMI = prior(MII);
VRM.addSpillSlotUse(SSorRMId, LoadMI);
++NumLoads;
}
// This invalidates Phys.
Spills.ClobberPhysReg(Phys);
// Remember it's available.
Spills.addAvailable(SSorRMId, Phys);
UpdateKills(*prior(MII), RegKills, KillOps, TRI);
DOUT << '\t' << *prior(MII);
}
}
// Insert spills here if asked to.
if (VRM.isSpillPt(&MI)) {
std::vector<std::pair<unsigned,bool> > &SpillRegs =
VRM.getSpillPtSpills(&MI);
for (unsigned i = 0, e = SpillRegs.size(); i != e; ++i) {
unsigned VirtReg = SpillRegs[i].first;
bool isKill = SpillRegs[i].second;
if (!VRM.getPreSplitReg(VirtReg))
continue; // Split interval spilled again.
const TargetRegisterClass *RC = RegInfo->getRegClass(VirtReg);
unsigned Phys = VRM.getPhys(VirtReg);
int StackSlot = VRM.getStackSlot(VirtReg);
TII->storeRegToStackSlot(MBB, next(MII), Phys, isKill, StackSlot, RC);
MachineInstr *StoreMI = next(MII);
VRM.addSpillSlotUse(StackSlot, StoreMI);
DOUT << "Store:\t" << *StoreMI;
VRM.virtFolded(VirtReg, StoreMI, VirtRegMap::isMod);
}
NextMII = next(MII);
}
/// ReusedOperands - Keep track of operand reuse in case we need to undo
/// reuse.
ReuseInfo ReusedOperands(MI, TRI);
SmallVector<unsigned, 4> VirtUseOps;
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg() || MO.getReg() == 0)
continue; // Ignore non-register operands.
unsigned VirtReg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(VirtReg)) {
// Ignore physregs for spilling, but remember that it is used by this
// function.
RegInfo->setPhysRegUsed(VirtReg);
continue;
}
// We want to process implicit virtual register uses first.
if (MO.isImplicit())
// If the virtual register is implicitly defined, emit a implicit_def
// before so scavenger knows it's "defined".
VirtUseOps.insert(VirtUseOps.begin(), i);
else
VirtUseOps.push_back(i);
}
// Process all of the spilled uses and all non spilled reg references.
SmallVector<int, 2> PotentialDeadStoreSlots;
KilledMIRegs.clear();
for (unsigned j = 0, e = VirtUseOps.size(); j != e; ++j) {
unsigned i = VirtUseOps[j];
MachineOperand &MO = MI.getOperand(i);
unsigned VirtReg = MO.getReg();
assert(TargetRegisterInfo::isVirtualRegister(VirtReg) &&
"Not a virtual register?");
unsigned SubIdx = MO.getSubReg();
if (VRM.isAssignedReg(VirtReg)) {
// This virtual register was assigned a physreg!
unsigned Phys = VRM.getPhys(VirtReg);
RegInfo->setPhysRegUsed(Phys);
if (MO.isDef())
ReusedOperands.markClobbered(Phys);
unsigned RReg = SubIdx ? TRI->getSubReg(Phys, SubIdx) : Phys;
MI.getOperand(i).setReg(RReg);
if (VRM.isImplicitlyDefined(VirtReg))
BuildMI(MBB, &MI, MI.getDebugLoc(),
TII->get(TargetInstrInfo::IMPLICIT_DEF), RReg);
continue;
}
// This virtual register is now known to be a spilled value.
if (!MO.isUse())
continue; // Handle defs in the loop below (handle use&def here though)
bool DoReMat = VRM.isReMaterialized(VirtReg);
int SSorRMId = DoReMat
? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
int ReuseSlot = SSorRMId;
// Check to see if this stack slot is available.
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
// If this is a sub-register use, make sure the reuse register is in the
// right register class. For example, for x86 not all of the 32-bit
// registers have accessible sub-registers.
// Similarly so for EXTRACT_SUBREG. Consider this:
// EDI = op
// MOV32_mr fi#1, EDI
// ...
// = EXTRACT_SUBREG fi#1
// fi#1 is available in EDI, but it cannot be reused because it's not in
// the right register file.
if (PhysReg &&
(SubIdx || MI.getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)) {
const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
if (!RC->contains(PhysReg))
PhysReg = 0;
}
if (PhysReg) {
// This spilled operand might be part of a two-address operand. If this
// is the case, then changing it will necessarily require changing the
// def part of the instruction as well. However, in some cases, we
// aren't allowed to modify the reused register. If none of these cases
// apply, reuse it.
bool CanReuse = true;
int ti = TID.getOperandConstraint(i, TOI::TIED_TO);
if (ti != -1) {
// Okay, we have a two address operand. We can reuse this physreg as
// long as we are allowed to clobber the value and there isn't an
// earlier def that has already clobbered the physreg.
CanReuse = Spills.canClobberPhysReg(ReuseSlot) &&
!ReusedOperands.isClobbered(PhysReg);
}
if (CanReuse) {
// If this stack slot value is already available, reuse it!
if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
else
DOUT << "Reusing SS#" << ReuseSlot;
DOUT << " from physreg "
<< TRI->getName(PhysReg) << " for vreg"
<< VirtReg <<" instead of reloading into physreg "
<< TRI->getName(VRM.getPhys(VirtReg)) << "\n";
unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
MI.getOperand(i).setReg(RReg);
// The only technical detail we have is that we don't know that
// PhysReg won't be clobbered by a reloaded stack slot that occurs
// later in the instruction. In particular, consider 'op V1, V2'.
// If V1 is available in physreg R0, we would choose to reuse it
// here, instead of reloading it into the register the allocator
// indicated (say R1). However, V2 might have to be reloaded
// later, and it might indicate that it needs to live in R0. When
// this occurs, we need to have information available that
// indicates it is safe to use R1 for the reload instead of R0.
//
// To further complicate matters, we might conflict with an alias,
// or R0 and R1 might not be compatible with each other. In this
// case, we actually insert a reload for V1 in R1, ensuring that
// we can get at R0 or its alias.
ReusedOperands.addReuse(i, ReuseSlot, PhysReg,
VRM.getPhys(VirtReg), VirtReg);
if (ti != -1)
// Only mark it clobbered if this is a use&def operand.
ReusedOperands.markClobbered(PhysReg);
++NumReused;
if (MI.getOperand(i).isKill() &&
ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) {
// The store of this spilled value is potentially dead, but we
// won't know for certain until we've confirmed that the re-use
// above is valid, which means waiting until the other operands
// are processed. For now we just track the spill slot, we'll
// remove it after the other operands are processed if valid.
PotentialDeadStoreSlots.push_back(ReuseSlot);
}
// Mark is isKill if it's there no other uses of the same virtual
// register and it's not a two-address operand. IsKill will be
// unset if reg is reused.
if (ti == -1 && KilledMIRegs.count(VirtReg) == 0) {
MI.getOperand(i).setIsKill();
KilledMIRegs.insert(VirtReg);
}
continue;
} // CanReuse
// Otherwise we have a situation where we have a two-address instruction
// whose mod/ref operand needs to be reloaded. This reload is already
// available in some register "PhysReg", but if we used PhysReg as the
// operand to our 2-addr instruction, the instruction would modify
// PhysReg. This isn't cool if something later uses PhysReg and expects
// to get its initial value.
//
// To avoid this problem, and to avoid doing a load right after a store,
// we emit a copy from PhysReg into the designated register for this
// operand.
unsigned DesignatedReg = VRM.getPhys(VirtReg);
assert(DesignatedReg && "Must map virtreg to physreg!");
// Note that, if we reused a register for a previous operand, the
// register we want to reload into might not actually be
// available. If this occurs, use the register indicated by the
// reuser.
if (ReusedOperands.hasReuses())
DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
Spills, MaybeDeadStores, RegKills, KillOps, VRM);
// If the mapped designated register is actually the physreg we have
// incoming, we don't need to inserted a dead copy.
if (DesignatedReg == PhysReg) {
// If this stack slot value is already available, reuse it!
if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
else
DOUT << "Reusing SS#" << ReuseSlot;
DOUT << " from physreg " << TRI->getName(PhysReg)
<< " for vreg" << VirtReg
<< " instead of reloading into same physreg.\n";
unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
MI.getOperand(i).setReg(RReg);
ReusedOperands.markClobbered(RReg);
++NumReused;
continue;
}
const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
RegInfo->setPhysRegUsed(DesignatedReg);
ReusedOperands.markClobbered(DesignatedReg);
TII->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC, RC);
MachineInstr *CopyMI = prior(MII);
UpdateKills(*CopyMI, RegKills, KillOps, TRI);
// This invalidates DesignatedReg.
Spills.ClobberPhysReg(DesignatedReg);
Spills.addAvailable(ReuseSlot, DesignatedReg);
unsigned RReg =
SubIdx ? TRI->getSubReg(DesignatedReg, SubIdx) : DesignatedReg;
MI.getOperand(i).setReg(RReg);
DOUT << '\t' << *prior(MII);
++NumReused;
continue;
} // if (PhysReg)
// Otherwise, reload it and remember that we have it.
PhysReg = VRM.getPhys(VirtReg);
assert(PhysReg && "Must map virtreg to physreg!");
// Note that, if we reused a register for a previous operand, the
// register we want to reload into might not actually be
// available. If this occurs, use the register indicated by the
// reuser.
if (ReusedOperands.hasReuses())
PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
Spills, MaybeDeadStores, RegKills, KillOps, VRM);
RegInfo->setPhysRegUsed(PhysReg);
ReusedOperands.markClobbered(PhysReg);
if (DoReMat) {
ReMaterialize(MBB, MII, PhysReg, VirtReg, TII, TRI, VRM);
} else {
const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
TII->loadRegFromStackSlot(MBB, &MI, PhysReg, SSorRMId, RC);
MachineInstr *LoadMI = prior(MII);
VRM.addSpillSlotUse(SSorRMId, LoadMI);
++NumLoads;
}
// This invalidates PhysReg.
Spills.ClobberPhysReg(PhysReg);
// Any stores to this stack slot are not dead anymore.
if (!DoReMat)
MaybeDeadStores[SSorRMId] = NULL;
Spills.addAvailable(SSorRMId, PhysReg);
// Assumes this is the last use. IsKill will be unset if reg is reused
// unless it's a two-address operand.
if (TID.getOperandConstraint(i, TOI::TIED_TO) == -1 &&
KilledMIRegs.count(VirtReg) == 0) {
MI.getOperand(i).setIsKill();
KilledMIRegs.insert(VirtReg);
}
unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
MI.getOperand(i).setReg(RReg);
UpdateKills(*prior(MII), RegKills, KillOps, TRI);
DOUT << '\t' << *prior(MII);
}
// Ok - now we can remove stores that have been confirmed dead.
for (unsigned j = 0, e = PotentialDeadStoreSlots.size(); j != e; ++j) {
// This was the last use and the spilled value is still available
// for reuse. That means the spill was unnecessary!
int PDSSlot = PotentialDeadStoreSlots[j];
MachineInstr* DeadStore = MaybeDeadStores[PDSSlot];
if (DeadStore) {
DOUT << "Removed dead store:\t" << *DeadStore;
InvalidateKills(*DeadStore, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(DeadStore);
MBB.erase(DeadStore);
MaybeDeadStores[PDSSlot] = NULL;
++NumDSE;
}
}
DOUT << '\t' << MI;
// If we have folded references to memory operands, make sure we clear all
// physical registers that may contain the value of the spilled virtual
// register
SmallSet<int, 2> FoldedSS;
for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ) {
unsigned VirtReg = I->second.first;
VirtRegMap::ModRef MR = I->second.second;
DOUT << "Folded vreg: " << VirtReg << " MR: " << MR;
// MI2VirtMap be can updated which invalidate the iterator.
// Increment the iterator first.
++I;
int SS = VRM.getStackSlot(VirtReg);
if (SS == VirtRegMap::NO_STACK_SLOT)
continue;
FoldedSS.insert(SS);
DOUT << " - StackSlot: " << SS << "\n";
// If this folded instruction is just a use, check to see if it's a
// straight load from the virt reg slot.
if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
int FrameIdx;
unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx);
if (DestReg && FrameIdx == SS) {
// If this spill slot is available, turn it into a copy (or nothing)
// instead of leaving it as a load!
if (unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SS)) {
DOUT << "Promoted Load To Copy: " << MI;
if (DestReg != InReg) {
const TargetRegisterClass *RC = RegInfo->getRegClass(VirtReg);
TII->copyRegToReg(MBB, &MI, DestReg, InReg, RC, RC);
MachineOperand *DefMO = MI.findRegisterDefOperand(DestReg);
unsigned SubIdx = DefMO->getSubReg();
// Revisit the copy so we make sure to notice the effects of the
// operation on the destreg (either needing to RA it if it's
// virtual or needing to clobber any values if it's physical).
NextMII = &MI;
--NextMII; // backtrack to the copy.
// Propagate the sub-register index over.
if (SubIdx) {
DefMO = NextMII->findRegisterDefOperand(DestReg);
DefMO->setSubReg(SubIdx);
}
// Mark is killed.
MachineOperand *KillOpnd = NextMII->findRegisterUseOperand(InReg);
KillOpnd->setIsKill();
BackTracked = true;
} else {
DOUT << "Removing now-noop copy: " << MI;
// Unset last kill since it's being reused.
InvalidateKill(InReg, RegKills, KillOps);
}
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
goto ProcessNextInst;
}
} else {
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
SmallVector<MachineInstr*, 4> NewMIs;
if (PhysReg &&
TII->unfoldMemoryOperand(MF, &MI, PhysReg, false, false, NewMIs)) {
MBB.insert(MII, NewMIs[0]);
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
--NextMII; // backtrack to the unfolded instruction.
BackTracked = true;
goto ProcessNextInst;
}
}
}
// If this reference is not a use, any previous store is now dead.
// Otherwise, the store to this stack slot is not dead anymore.
MachineInstr* DeadStore = MaybeDeadStores[SS];
if (DeadStore) {
bool isDead = !(MR & VirtRegMap::isRef);
MachineInstr *NewStore = NULL;
if (MR & VirtRegMap::isModRef) {
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
SmallVector<MachineInstr*, 4> NewMIs;
// We can reuse this physreg as long as we are allowed to clobber
// the value and there isn't an earlier def that has already clobbered
// the physreg.
if (PhysReg &&
!TII->isStoreToStackSlot(&MI, SS)) { // Not profitable!
MachineOperand *KillOpnd =
DeadStore->findRegisterUseOperand(PhysReg, true);
// Note, if the store is storing a sub-register, it's possible the
// super-register is needed below.
if (KillOpnd && !KillOpnd->getSubReg() &&
TII->unfoldMemoryOperand(MF, &MI, PhysReg, false, true,NewMIs)){
MBB.insert(MII, NewMIs[0]);
NewStore = NewMIs[1];
MBB.insert(MII, NewStore);
VRM.addSpillSlotUse(SS, NewStore);
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
--NextMII;
--NextMII; // backtrack to the unfolded instruction.
BackTracked = true;
isDead = true;
}
}
}
if (isDead) { // Previous store is dead.
// If we get here, the store is dead, nuke it now.
DOUT << "Removed dead store:\t" << *DeadStore;
InvalidateKills(*DeadStore, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(DeadStore);
MBB.erase(DeadStore);
if (!NewStore)
++NumDSE;
}
MaybeDeadStores[SS] = NULL;
if (NewStore) {
// Treat this store as a spill merged into a copy. That makes the
// stack slot value available.
VRM.virtFolded(VirtReg, NewStore, VirtRegMap::isMod);
goto ProcessNextInst;
}
}
// If the spill slot value is available, and this is a new definition of
// the value, the value is not available anymore.
if (MR & VirtRegMap::isMod) {
// Notice that the value in this stack slot has been modified.
Spills.ModifyStackSlotOrReMat(SS);
// If this is *just* a mod of the value, check to see if this is just a
// store to the spill slot (i.e. the spill got merged into the copy). If
// so, realize that the vreg is available now, and add the store to the
// MaybeDeadStore info.
int StackSlot;
if (!(MR & VirtRegMap::isRef)) {
if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
assert(TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
"Src hasn't been allocated yet?");
if (CommuteToFoldReload(MBB, MII, VirtReg, SrcReg, StackSlot,
Spills, RegKills, KillOps, TRI, VRM)) {
NextMII = next(MII);
BackTracked = true;
goto ProcessNextInst;
}
// Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
// this as a potentially dead store in case there is a subsequent
// store into the stack slot without a read from it.
MaybeDeadStores[StackSlot] = &MI;
// If the stack slot value was previously available in some other
// register, change it now. Otherwise, make the register
// available in PhysReg.
Spills.addAvailable(StackSlot, SrcReg, false/*!clobber*/);
}
}
}
}
// Process all of the spilled defs.
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!(MO.isReg() && MO.getReg() && MO.isDef()))
continue;
unsigned VirtReg = MO.getReg();
if (!TargetRegisterInfo::isVirtualRegister(VirtReg)) {
// Check to see if this is a noop copy. If so, eliminate the
// instruction before considering the dest reg to be changed.
unsigned Src, Dst, SrcSR, DstSR;
if (TII->isMoveInstr(MI, Src, Dst, SrcSR, DstSR) && Src == Dst) {
++NumDCE;
DOUT << "Removing now-noop copy: " << MI;
SmallVector<unsigned, 2> KillRegs;
InvalidateKills(MI, RegKills, KillOps, &KillRegs);
if (MO.isDead() && !KillRegs.empty()) {
// Source register or an implicit super/sub-register use is killed.
assert(KillRegs[0] == Dst ||
TRI->isSubRegister(KillRegs[0], Dst) ||
TRI->isSuperRegister(KillRegs[0], Dst));
// Last def is now dead.
TransferDeadness(&MBB, Dist, Src, RegKills, KillOps);
}
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
Spills.disallowClobberPhysReg(VirtReg);
goto ProcessNextInst;
}
// If it's not a no-op copy, it clobbers the value in the destreg.
Spills.ClobberPhysReg(VirtReg);
ReusedOperands.markClobbered(VirtReg);
// Check to see if this instruction is a load from a stack slot into
// a register. If so, this provides the stack slot value in the reg.
int FrameIdx;
if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
assert(DestReg == VirtReg && "Unknown load situation!");
// If it is a folded reference, then it's not safe to clobber.
bool Folded = FoldedSS.count(FrameIdx);
// Otherwise, if it wasn't available, remember that it is now!
Spills.addAvailable(FrameIdx, DestReg, !Folded);
goto ProcessNextInst;
}
continue;
}
unsigned SubIdx = MO.getSubReg();
bool DoReMat = VRM.isReMaterialized(VirtReg);
if (DoReMat)
ReMatDefs.insert(&MI);
// The only vregs left are stack slot definitions.
int StackSlot = VRM.getStackSlot(VirtReg);
const TargetRegisterClass *RC = RegInfo->getRegClass(VirtReg);
// If this def is part of a two-address operand, make sure to execute
// the store from the correct physical register.
unsigned PhysReg;
int TiedOp = MI.getDesc().findTiedToSrcOperand(i);
if (TiedOp != -1) {
PhysReg = MI.getOperand(TiedOp).getReg();
if (SubIdx) {
unsigned SuperReg = findSuperReg(RC, PhysReg, SubIdx, TRI);
assert(SuperReg && TRI->getSubReg(SuperReg, SubIdx) == PhysReg &&
"Can't find corresponding super-register!");
PhysReg = SuperReg;
}
} else {
PhysReg = VRM.getPhys(VirtReg);
if (ReusedOperands.isClobbered(PhysReg)) {
// Another def has taken the assigned physreg. It must have been a
// use&def which got it due to reuse. Undo the reuse!
PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
Spills, MaybeDeadStores, RegKills, KillOps, VRM);
}
}
assert(PhysReg && "VR not assigned a physical register?");
RegInfo->setPhysRegUsed(PhysReg);
unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
ReusedOperands.markClobbered(RReg);
MI.getOperand(i).setReg(RReg);
if (!MO.isDead()) {
MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
SpillRegToStackSlot(MBB, MII, -1, PhysReg, StackSlot, RC, true,
LastStore, Spills, ReMatDefs, RegKills, KillOps, VRM);
NextMII = next(MII);
// Check to see if this is a noop copy. If so, eliminate the
// instruction before considering the dest reg to be changed.
{
unsigned Src, Dst, SrcSR, DstSR;
if (TII->isMoveInstr(MI, Src, Dst, SrcSR, DstSR) && Src == Dst) {
++NumDCE;
DOUT << "Removing now-noop copy: " << MI;
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
UpdateKills(*LastStore, RegKills, KillOps, TRI);
goto ProcessNextInst;
}
}
}
}
ProcessNextInst:
DistanceMap.insert(std::make_pair(&MI, Dist++));
if (!Erased && !BackTracked) {
for (MachineBasicBlock::iterator II = &MI; II != NextMII; ++II)
UpdateKills(*II, RegKills, KillOps, TRI);
}
MII = NextMII;
}
}
llvm::Spiller* llvm::createSpiller() {
switch (SpillerOpt) {
default: assert(0 && "Unreachable!");
case local:
return new LocalSpiller();
case simple:
return new SimpleSpiller();
}
}
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