SlotIndexes *Indexes;
LiveIntervals *LIS;
VirtRegMap *VRM;
- SparseSet<unsigned> PhysRegs;
void rewrite();
void addMBBLiveIns();
+ bool readsUndefSubreg(const MachineOperand &MO) const;
+ void addLiveInsForSubRanges(const LiveInterval &LI, unsigned PhysReg) const;
+
public:
static char ID;
VirtRegRewriter() : MachineFunctionPass(ID) {}
return true;
}
+void VirtRegRewriter::addLiveInsForSubRanges(const LiveInterval &LI,
+ unsigned PhysReg) const {
+ assert(!LI.empty());
+ assert(LI.hasSubRanges());
+
+ typedef std::pair<const LiveInterval::SubRange *,
+ LiveInterval::const_iterator> SubRangeIteratorPair;
+ SmallVector<SubRangeIteratorPair, 4> SubRanges;
+ SlotIndex First;
+ SlotIndex Last;
+ for (const LiveInterval::SubRange &SR : LI.subranges()) {
+ SubRanges.push_back(std::make_pair(&SR, SR.begin()));
+ if (!First.isValid() || SR.segments.front().start < First)
+ First = SR.segments.front().start;
+ if (!Last.isValid() || SR.segments.back().end > Last)
+ Last = SR.segments.back().end;
+ }
+
+ // Check all mbb start positions between First and Last while
+ // simulatenously advancing an iterator for each subrange.
+ for (SlotIndexes::MBBIndexIterator MBBI = Indexes->findMBBIndex(First);
+ MBBI != Indexes->MBBIndexEnd() && MBBI->first <= Last; ++MBBI) {
+ SlotIndex MBBBegin = MBBI->first;
+ // Advance all subrange iterators so that their end position is just
+ // behind MBBBegin (or the iterator is at the end).
+ LaneBitmask LaneMask = 0;
+ for (auto &RangeIterPair : SubRanges) {
+ const LiveInterval::SubRange *SR = RangeIterPair.first;
+ LiveInterval::const_iterator &SRI = RangeIterPair.second;
+ while (SRI != SR->end() && SRI->end <= MBBBegin)
+ ++SRI;
+ if (SRI == SR->end())
+ continue;
+ if (SRI->start <= MBBBegin)
+ LaneMask |= SR->LaneMask;
+ }
+ if (LaneMask == 0)
+ continue;
+ MachineBasicBlock *MBB = MBBI->second;
+ MBB->addLiveIn(PhysReg, LaneMask);
+ }
+}
+
// Compute MBB live-in lists from virtual register live ranges and their
// assignments.
void VirtRegRewriter::addMBBLiveIns() {
- SmallVector<MachineBasicBlock*, 16> LiveIn;
for (unsigned Idx = 0, IdxE = MRI->getNumVirtRegs(); Idx != IdxE; ++Idx) {
unsigned VirtReg = TargetRegisterInfo::index2VirtReg(Idx);
if (MRI->reg_nodbg_empty(VirtReg))
assert(PhysReg != VirtRegMap::NO_PHYS_REG && "Unmapped virtual register.");
if (LI.hasSubRanges()) {
- for (LiveInterval::SubRange &S : LI.subranges()) {
- for (const auto &Seg : S.segments) {
- if (!Indexes->findLiveInMBBs(Seg.start, Seg.end, LiveIn))
- continue;
- for (MCSubRegIndexIterator SR(PhysReg, TRI); SR.isValid(); ++SR) {
- unsigned SubReg = SR.getSubReg();
- unsigned SubRegIndex = SR.getSubRegIndex();
- unsigned SubRegLaneMask = TRI->getSubRegIndexLaneMask(SubRegIndex);
- if ((SubRegLaneMask & S.LaneMask) == 0)
- continue;
- for (unsigned i = 0, e = LiveIn.size(); i != e; ++i) {
- LiveIn[i]->addLiveIn(SubReg);
- }
- }
- LiveIn.clear();
- }
- }
+ addLiveInsForSubRanges(LI, PhysReg);
} else {
- // Scan the segments of LI.
- for (const auto &Seg : LI.segments) {
- if (!Indexes->findLiveInMBBs(Seg.start, Seg.end, LiveIn))
- continue;
- for (unsigned i = 0, e = LiveIn.size(); i != e; ++i)
- LiveIn[i]->addLiveIn(PhysReg);
- LiveIn.clear();
+ // Go over MBB begin positions and see if we have segments covering them.
+ // The following works because segments and the MBBIndex list are both
+ // sorted by slot indexes.
+ SlotIndexes::MBBIndexIterator I = Indexes->MBBIndexBegin();
+ for (const auto &Seg : LI) {
+ I = Indexes->advanceMBBIndex(I, Seg.start);
+ for (; I != Indexes->MBBIndexEnd() && I->first < Seg.end; ++I) {
+ MachineBasicBlock *MBB = I->second;
+ MBB->addLiveIn(PhysReg);
+ }
}
}
}
MBB.sortUniqueLiveIns();
}
+/// Returns true if the given machine operand \p MO only reads undefined lanes.
+/// The function only works for use operands with a subregister set.
+bool VirtRegRewriter::readsUndefSubreg(const MachineOperand &MO) const {
+ // Shortcut if the operand is already marked undef.
+ if (MO.isUndef())
+ return true;
+
+ unsigned Reg = MO.getReg();
+ const LiveInterval &LI = LIS->getInterval(Reg);
+ const MachineInstr &MI = *MO.getParent();
+ SlotIndex BaseIndex = LIS->getInstructionIndex(&MI);
+ // This code is only meant to handle reading undefined subregisters which
+ // we couldn't properly detect before.
+ assert(LI.liveAt(BaseIndex) &&
+ "Reads of completely dead register should be marked undef already");
+ unsigned SubRegIdx = MO.getSubReg();
+ LaneBitmask UseMask = TRI->getSubRegIndexLaneMask(SubRegIdx);
+ // See if any of the relevant subregister liveranges is defined at this point.
+ for (const LiveInterval::SubRange &SR : LI.subranges()) {
+ if ((SR.LaneMask & UseMask) != 0 && SR.liveAt(BaseIndex))
+ return false;
+ }
+ return true;
+}
+
void VirtRegRewriter::rewrite() {
bool NoSubRegLiveness = !MRI->subRegLivenessEnabled();
SmallVector<unsigned, 8> SuperDeads;
SmallVector<unsigned, 8> SuperDefs;
SmallVector<unsigned, 8> SuperKills;
- SmallPtrSet<const MachineInstr *, 4> NoReturnInsts;
-
- // Here we have a SparseSet to hold which PhysRegs are actually encountered
- // in the MF we are about to iterate over so that later when we call
- // setPhysRegUsed, we are only doing it for physRegs that were actually found
- // in the program and not for all of the possible physRegs for the given
- // target architecture. If the target has a lot of physRegs, then for a small
- // program there will be a significant compile time reduction here.
- PhysRegs.clear();
- PhysRegs.setUniverse(TRI->getNumRegs());
-
- // The function with uwtable should guarantee that the stack unwinder
- // can unwind the stack to the previous frame. Thus, we can't apply the
- // noreturn optimization if the caller function has uwtable attribute.
- bool HasUWTable = MF->getFunction()->hasFnAttribute(Attribute::UWTable);
for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
MBBI != MBBE; ++MBBI) {
DEBUG(MBBI->print(dbgs(), Indexes));
- bool IsExitBB = MBBI->succ_empty();
for (MachineBasicBlock::instr_iterator
MII = MBBI->instr_begin(), MIE = MBBI->instr_end(); MII != MIE;) {
- MachineInstr *MI = MII;
+ MachineInstr *MI = &*MII;
++MII;
- // Check if this instruction is a call to a noreturn function. If this
- // is a call to noreturn function and we don't need the stack unwinding
- // functionality (i.e. this function does not have uwtable attribute and
- // the callee function has the nounwind attribute), then we can ignore
- // the definitions set by this instruction.
- if (!HasUWTable && IsExitBB && MI->isCall()) {
- for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
- MOE = MI->operands_end(); MOI != MOE; ++MOI) {
- MachineOperand &MO = *MOI;
- if (!MO.isGlobal())
- continue;
- const Function *Func = dyn_cast<Function>(MO.getGlobal());
- if (!Func || !Func->hasFnAttribute(Attribute::NoReturn) ||
- // We need to keep correct unwind information
- // even if the function will not return, since the
- // runtime may need it.
- !Func->hasFnAttribute(Attribute::NoUnwind))
- continue;
- NoReturnInsts.insert(MI);
- break;
- }
- }
-
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
MachineOperand &MO = *MOI;
if (MO.isRegMask())
MRI->addPhysRegsUsedFromRegMask(MO.getRegMask());
- // If we encounter a VirtReg or PhysReg then get at the PhysReg and add
- // it to the physreg bitset. Later we use only the PhysRegs that were
- // actually encountered in the MF to populate the MRI's used physregs.
- if (MO.isReg() && MO.getReg())
- PhysRegs.insert(
- TargetRegisterInfo::isVirtualRegister(MO.getReg()) ?
- VRM->getPhys(MO.getReg()) :
- MO.getReg());
-
if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue;
unsigned VirtReg = MO.getReg();
assert(!MRI->isReserved(PhysReg) && "Reserved register assignment");
// 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 (NoSubRegLiveness && 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 (NoSubRegLiveness) {
+ unsigned SubReg = MO.getSubReg();
+ if (SubReg != 0) {
+ if (NoSubRegLiveness) {
+ // 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()) {
+ // Also add implicit defs for the super-register.
if (MO.isDead())
SuperDeads.push_back(PhysReg);
else
SuperDefs.push_back(PhysReg);
}
+ } else {
+ if (MO.isUse()) {
+ if (readsUndefSubreg(MO))
+ // We need to add an <undef> flag if the subregister is
+ // completely undefined (and we are not adding super-register
+ // defs).
+ MO.setIsUndef(true);
+ } else if (!MO.isDead()) {
+ assert(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.
+ if (MO.isDef())
+ MO.setIsUndef(false);
+
// PhysReg operands cannot have subregister indexes.
- PhysReg = TRI->getSubReg(PhysReg, MO.getSubReg());
+ PhysReg = TRI->getSubReg(PhysReg, SubReg);
assert(PhysReg && "Invalid SubReg for physical register");
MO.setSubReg(0);
}
}
}
}
-
- // Tell MRI about physical registers in use.
- if (NoReturnInsts.empty()) {
- for (SparseSet<unsigned>::iterator
- RegI = PhysRegs.begin(), E = PhysRegs.end(); RegI != E; ++RegI)
- if (!MRI->reg_nodbg_empty(*RegI))
- MRI->setPhysRegUsed(*RegI);
- } else {
- for (SparseSet<unsigned>::iterator
- I = PhysRegs.begin(), E = PhysRegs.end(); I != E; ++I) {
- unsigned Reg = *I;
- if (MRI->reg_nodbg_empty(Reg))
- continue;
- // Check if this register has a use that will impact the rest of the
- // code. Uses in debug and noreturn instructions do not impact the
- // generated code.
- for (MachineInstr &It : MRI->reg_nodbg_instructions(Reg)) {
- if (!NoReturnInsts.count(&It)) {
- MRI->setPhysRegUsed(Reg);
- break;
- }
- }
- }
- }
}
projects / oota-llvm.git / blobdiff