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llvm-mirror/lib/CodeGen/VirtRegMap.cpp
Jakob Stoklund Olesen ed06c64ecb Also add <imp-use,kill> flags for redefined super-registers. 
For example:

  %vreg10:dsub_0<def,undef> = COPY %vreg1
  %vreg10:dsub_1<def> = COPY %vreg2

is rewritten as:

  %D2<def> = COPY %D0, %Q1<imp-def>
  %D3<def> = COPY %D1, %Q1<imp-use,kill>, %Q1<imp-def>

The first COPY doesn't care about the previous value of %Q1, so it
doesn't read that register.

The second COPY is a partial redefinition of %Q1, so it implicitly kills
and redefines that register.

This makes it possible to recognize instructions that can harmlessly
clobber the full super-register.  The write and don't read the
super-register.

llvm-svn: 141139
2011-10-05 00:01:48 +00:00

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//===-- llvm/CodeGen/VirtRegMap.cpp - Virtual Register Map ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the VirtRegMap class.
//
// It also contains implementations of the Spiller interface, which, given a
// virtual register map and a machine function, eliminates all virtual
// references by replacing them with physical register references - adding spill
// code as necessary.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "virtregmap"
#include "VirtRegMap.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SlotIndexes.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include <algorithm>
using namespace llvm;
STATISTIC(NumSpillSlots, "Number of spill slots allocated");
STATISTIC(NumIdCopies, "Number of identity moves eliminated after rewriting");
//===----------------------------------------------------------------------===//
// VirtRegMap implementation
//===----------------------------------------------------------------------===//
char VirtRegMap::ID = 0;
INITIALIZE_PASS(VirtRegMap, "virtregmap", "Virtual Register Map", false, false)
bool VirtRegMap::runOnMachineFunction(MachineFunction &mf) {
MRI = &mf.getRegInfo();
TII = mf.getTarget().getInstrInfo();
TRI = mf.getTarget().getRegisterInfo();
MF = &mf;
ReMatId = MAX_STACK_SLOT+1;
LowSpillSlot = HighSpillSlot = NO_STACK_SLOT;
Virt2PhysMap.clear();
Virt2StackSlotMap.clear();
Virt2ReMatIdMap.clear();
Virt2SplitMap.clear();
Virt2SplitKillMap.clear();
ReMatMap.clear();
ImplicitDefed.clear();
SpillSlotToUsesMap.clear();
MI2VirtMap.clear();
SpillPt2VirtMap.clear();
RestorePt2VirtMap.clear();
EmergencySpillMap.clear();
EmergencySpillSlots.clear();
SpillSlotToUsesMap.resize(8);
ImplicitDefed.resize(MF->getRegInfo().getNumVirtRegs());
allocatableRCRegs.clear();
for (TargetRegisterInfo::regclass_iterator I = TRI->regclass_begin(),
E = TRI->regclass_end(); I != E; ++I)
allocatableRCRegs.insert(std::make_pair(*I,
TRI->getAllocatableSet(mf, *I)));
grow();
return false;
}
void VirtRegMap::grow() {
unsigned NumRegs = MF->getRegInfo().getNumVirtRegs();
Virt2PhysMap.resize(NumRegs);
Virt2StackSlotMap.resize(NumRegs);
Virt2ReMatIdMap.resize(NumRegs);
Virt2SplitMap.resize(NumRegs);
Virt2SplitKillMap.resize(NumRegs);
ReMatMap.resize(NumRegs);
ImplicitDefed.resize(NumRegs);
}
unsigned VirtRegMap::createSpillSlot(const TargetRegisterClass *RC) {
int SS = MF->getFrameInfo()->CreateSpillStackObject(RC->getSize(),
RC->getAlignment());
if (LowSpillSlot == NO_STACK_SLOT)
LowSpillSlot = SS;
if (HighSpillSlot == NO_STACK_SLOT || SS > HighSpillSlot)
HighSpillSlot = SS;
assert(SS >= LowSpillSlot && "Unexpected low spill slot");
unsigned Idx = SS-LowSpillSlot;
while (Idx >= SpillSlotToUsesMap.size())
SpillSlotToUsesMap.resize(SpillSlotToUsesMap.size()*2);
++NumSpillSlots;
return SS;
}
unsigned VirtRegMap::getRegAllocPref(unsigned virtReg) {
std::pair<unsigned, unsigned> Hint = MRI->getRegAllocationHint(virtReg);
unsigned physReg = Hint.second;
if (TargetRegisterInfo::isVirtualRegister(physReg) && hasPhys(physReg))
physReg = getPhys(physReg);
if (Hint.first == 0)
return (TargetRegisterInfo::isPhysicalRegister(physReg))
? physReg : 0;
return TRI->ResolveRegAllocHint(Hint.first, physReg, *MF);
}
int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
assert(TargetRegisterInfo::isVirtualRegister(virtReg));
assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
"attempt to assign stack slot to already spilled register");
const TargetRegisterClass* RC = MF->getRegInfo().getRegClass(virtReg);
return Virt2StackSlotMap[virtReg] = createSpillSlot(RC);
}
void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int SS) {
assert(TargetRegisterInfo::isVirtualRegister(virtReg));
assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
"attempt to assign stack slot to already spilled register");
assert((SS >= 0 ||
(SS >= MF->getFrameInfo()->getObjectIndexBegin())) &&
"illegal fixed frame index");
Virt2StackSlotMap[virtReg] = SS;
}
int VirtRegMap::assignVirtReMatId(unsigned virtReg) {
assert(TargetRegisterInfo::isVirtualRegister(virtReg));
assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
"attempt to assign re-mat id to already spilled register");
Virt2ReMatIdMap[virtReg] = ReMatId;
return ReMatId++;
}
void VirtRegMap::assignVirtReMatId(unsigned virtReg, int id) {
assert(TargetRegisterInfo::isVirtualRegister(virtReg));
assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
"attempt to assign re-mat id to already spilled register");
Virt2ReMatIdMap[virtReg] = id;
}
int VirtRegMap::getEmergencySpillSlot(const TargetRegisterClass *RC) {
std::map<const TargetRegisterClass*, int>::iterator I =
EmergencySpillSlots.find(RC);
if (I != EmergencySpillSlots.end())
return I->second;
return EmergencySpillSlots[RC] = createSpillSlot(RC);
}
void VirtRegMap::addSpillSlotUse(int FI, MachineInstr *MI) {
if (!MF->getFrameInfo()->isFixedObjectIndex(FI)) {
// If FI < LowSpillSlot, this stack reference was produced by
// instruction selection and is not a spill
if (FI >= LowSpillSlot) {
assert(FI >= 0 && "Spill slot index should not be negative!");
assert((unsigned)FI-LowSpillSlot < SpillSlotToUsesMap.size()
&& "Invalid spill slot");
SpillSlotToUsesMap[FI-LowSpillSlot].insert(MI);
}
}
}
void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
MachineInstr *NewMI, ModRef MRInfo) {
// Move previous memory references folded to new instruction.
MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
MI2VirtMap.erase(I++);
}
// add new memory reference
MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
}
void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *MI, ModRef MRInfo) {
MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(MI);
MI2VirtMap.insert(IP, std::make_pair(MI, std::make_pair(VirtReg, MRInfo)));
}
void VirtRegMap::RemoveMachineInstrFromMaps(MachineInstr *MI) {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isFI())
continue;
int FI = MO.getIndex();
if (MF->getFrameInfo()->isFixedObjectIndex(FI))
continue;
// This stack reference was produced by instruction selection and
// is not a spill
if (FI < LowSpillSlot)
continue;
assert((unsigned)FI-LowSpillSlot < SpillSlotToUsesMap.size()
&& "Invalid spill slot");
SpillSlotToUsesMap[FI-LowSpillSlot].erase(MI);
}
MI2VirtMap.erase(MI);
SpillPt2VirtMap.erase(MI);
RestorePt2VirtMap.erase(MI);
EmergencySpillMap.erase(MI);
}
/// FindUnusedRegisters - Gather a list of allocatable registers that
/// have not been allocated to any virtual register.
bool VirtRegMap::FindUnusedRegisters(LiveIntervals* LIs) {
unsigned NumRegs = TRI->getNumRegs();
UnusedRegs.reset();
UnusedRegs.resize(NumRegs);
BitVector Used(NumRegs);
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (Virt2PhysMap[Reg] != (unsigned)VirtRegMap::NO_PHYS_REG)
Used.set(Virt2PhysMap[Reg]);
}
BitVector Allocatable = TRI->getAllocatableSet(*MF);
bool AnyUnused = false;
for (unsigned Reg = 1; Reg < NumRegs; ++Reg) {
if (Allocatable[Reg] && !Used[Reg] && !LIs->hasInterval(Reg)) {
bool ReallyUnused = true;
for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) {
if (Used[*AS] || LIs->hasInterval(*AS)) {
ReallyUnused = false;
break;
}
}
if (ReallyUnused) {
AnyUnused = true;
UnusedRegs.set(Reg);
}
}
}
return AnyUnused;
}
void VirtRegMap::rewrite(SlotIndexes *Indexes) {
DEBUG(dbgs() << "********** REWRITE VIRTUAL REGISTERS **********\n"
<< "********** Function: "
<< MF->getFunction()->getName() << '\n');
DEBUG(dump());
SmallVector<unsigned, 8> SuperDeads;
SmallVector<unsigned, 8> SuperDefs;
SmallVector<unsigned, 8> SuperKills;
for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
MBBI != MBBE; ++MBBI) {
DEBUG(MBBI->print(dbgs(), Indexes));
for (MachineBasicBlock::iterator MII = MBBI->begin(), MIE = MBBI->end();
MII != MIE;) {
MachineInstr *MI = MII;
++MII;
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
MachineOperand &MO = *MOI;
if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue;
unsigned VirtReg = MO.getReg();
unsigned PhysReg = getPhys(VirtReg);
assert(PhysReg != NO_PHYS_REG && "Instruction uses unmapped VirtReg");
// Preserve semantics of sub-register operands.
if (MO.getSubReg()) {
// A virtual register kill refers to the whole register, so we may
// have to add <imp-use,kill> operands for the super-register. A
// partial redef always kills and redefines the super-register.
if (MO.readsReg() && (MO.isDef() || MO.isKill()))
SuperKills.push_back(PhysReg);
if (MO.isDef()) {
// The <def,undef> flag only makes sense for sub-register defs, and
// we are substituting a full physreg. An <imp-use,kill> operand
// from the SuperKills list will represent the partial read of the
// super-register.
MO.setIsUndef(false);
// Also add implicit defs for the super-register.
if (MO.isDead())
SuperDeads.push_back(PhysReg);
else
SuperDefs.push_back(PhysReg);
}
// PhysReg operands cannot have subregister indexes.
PhysReg = TRI->getSubReg(PhysReg, MO.getSubReg());
assert(PhysReg && "Invalid SubReg for physical register");
MO.setSubReg(0);
}
// Rewrite. Note we could have used MachineOperand::substPhysReg(), but
// we need the inlining here.
MO.setReg(PhysReg);
}
// Add any missing super-register kills after rewriting the whole
// instruction.
while (!SuperKills.empty())
MI->addRegisterKilled(SuperKills.pop_back_val(), TRI, true);
while (!SuperDeads.empty())
MI->addRegisterDead(SuperDeads.pop_back_val(), TRI, true);
while (!SuperDefs.empty())
MI->addRegisterDefined(SuperDefs.pop_back_val(), TRI);
DEBUG(dbgs() << "> " << *MI);
// Finally, remove any identity copies.
if (MI->isIdentityCopy()) {
++NumIdCopies;
if (MI->getNumOperands() == 2) {
DEBUG(dbgs() << "Deleting identity copy.\n");
RemoveMachineInstrFromMaps(MI);
if (Indexes)
Indexes->removeMachineInstrFromMaps(MI);
// It's safe to erase MI because MII has already been incremented.
MI->eraseFromParent();
} else {
// Transform identity copy to a KILL to deal with subregisters.
MI->setDesc(TII->get(TargetOpcode::KILL));
DEBUG(dbgs() << "Identity copy: " << *MI);
}
}
}
}
// Tell MRI about physical registers in use.
for (unsigned Reg = 1, RegE = TRI->getNumRegs(); Reg != RegE; ++Reg)
if (!MRI->reg_nodbg_empty(Reg))
MRI->setPhysRegUsed(Reg);
}
void VirtRegMap::print(raw_ostream &OS, const Module* M) const {
const TargetRegisterInfo* TRI = MF->getTarget().getRegisterInfo();
const MachineRegisterInfo &MRI = MF->getRegInfo();
OS << "********** REGISTER MAP **********\n";
for (unsigned i = 0, e = MRI.getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (Virt2PhysMap[Reg] != (unsigned)VirtRegMap::NO_PHYS_REG) {
OS << '[' << PrintReg(Reg, TRI) << " -> "
<< PrintReg(Virt2PhysMap[Reg], TRI) << "] "
<< MRI.getRegClass(Reg)->getName() << "\n";
}
}
for (unsigned i = 0, e = MRI.getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (Virt2StackSlotMap[Reg] != VirtRegMap::NO_STACK_SLOT) {
OS << '[' << PrintReg(Reg, TRI) << " -> fi#" << Virt2StackSlotMap[Reg]
<< "] " << MRI.getRegClass(Reg)->getName() << "\n";
}
}
OS << '\n';
}
void VirtRegMap::dump() const {
print(dbgs());
}
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