// Add newly allocated physical registers to the MBB live in sets.
void RegAllocBase::addMBBLiveIns(MachineFunction *MF) {
NamedRegionTimer T("MBB Live Ins", TimerGroupName, TimePassesIsEnabled);
SlotIndexes *Indexes = LIS->getSlotIndexes();
if (MF->size() <= 1)
return;
LiveIntervalUnion::SegmentIter SI;
for (unsigned PhysReg = 0; PhysReg < PhysReg2LiveUnion.numRegs(); ++PhysReg) {
LiveIntervalUnion &LiveUnion = PhysReg2LiveUnion[PhysReg];
if (LiveUnion.empty())
continue;
MachineFunction::iterator MBB = llvm::next(MF->begin());
MachineFunction::iterator MFE = MF->end();
SlotIndex Start, Stop;
tie(Start, Stop) = Indexes->getMBBRange(MBB);
SI.setMap(LiveUnion.getMap());
SI.find(Start);
while (SI.valid()) {
if (SI.start() <= Start) {
if (!MBB->isLiveIn(PhysReg))
MBB->addLiveIn(PhysReg);
} else if (SI.start() > Stop)
MBB = Indexes->getMBBFromIndex(SI.start().getPrevIndex());
if (++MBB == MFE)
break;
tie(Start, Stop) = Indexes->getMBBRange(MBB);
SI.advanceTo(Start);
}
}
}
static void extendSegmentsToUses(LiveRange &LR, const SlotIndexes &Indexes,
ShrinkToUsesWorkList &WorkList,
const LiveRange &OldRange) {
// Keep track of the PHIs that are in use.
SmallPtrSet<VNInfo*, 8> UsedPHIs;
// Blocks that have already been added to WorkList as live-out.
SmallPtrSet<MachineBasicBlock*, 16> LiveOut;
// Extend intervals to reach all uses in WorkList.
while (!WorkList.empty()) {
SlotIndex Idx = WorkList.back().first;
VNInfo *VNI = WorkList.back().second;
WorkList.pop_back();
const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(Idx.getPrevSlot());
SlotIndex BlockStart = Indexes.getMBBStartIdx(MBB);
// Extend the live range for VNI to be live at Idx.
if (VNInfo *ExtVNI = LR.extendInBlock(BlockStart, Idx)) {
assert(ExtVNI == VNI && "Unexpected existing value number");
(void)ExtVNI;
// Is this a PHIDef we haven't seen before?
if (!VNI->isPHIDef() || VNI->def != BlockStart ||
!UsedPHIs.insert(VNI).second)
continue;
// The PHI is live, make sure the predecessors are live-out.
for (auto &Pred : MBB->predecessors()) {
if (!LiveOut.insert(Pred).second)
continue;
SlotIndex Stop = Indexes.getMBBEndIdx(Pred);
// A predecessor is not required to have a live-out value for a PHI.
if (VNInfo *PVNI = OldRange.getVNInfoBefore(Stop))
WorkList.push_back(std::make_pair(Stop, PVNI));
}
continue;
}
// VNI is live-in to MBB.
DEBUG(dbgs() << " live-in at " << BlockStart << '\n');
LR.addSegment(LiveRange::Segment(BlockStart, Idx, VNI));
// Make sure VNI is live-out from the predecessors.
for (auto &Pred : MBB->predecessors()) {
if (!LiveOut.insert(Pred).second)
continue;
SlotIndex Stop = Indexes.getMBBEndIdx(Pred);
assert(OldRange.getVNInfoBefore(Stop) == VNI &&
"Wrong value out of predecessor");
WorkList.push_back(std::make_pair(Stop, VNI));
}
}
}
static void createDeadDef(SlotIndexes &Indexes, VNInfo::Allocator &Alloc,
LiveRange &LR, const MachineOperand &MO) {
const MachineInstr &MI = *MO.getParent();
SlotIndex DefIdx =
Indexes.getInstructionIndex(MI).getRegSlot(MO.isEarlyClobber());
// Create the def in LR. This may find an existing def.
LR.createDeadDef(DefIdx, Alloc);
}
static void determineMissingVNIs(const SlotIndexes &Indexes, LiveInterval &LI) {
SmallPtrSet<const MachineBasicBlock*, 5> Visited;
LiveRange::iterator OutIt;
VNInfo *PrevValNo = nullptr;
for (LiveRange::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
LiveRange::Segment &S = *I;
// Determine final VNI if necessary.
if (S.valno == nullptr) {
// This can only happen at the begin of a basic block.
assert(S.start.isBlock() && "valno should only be missing at block begin");
Visited.clear();
const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(S.start);
for (const MachineBasicBlock *Pred : MBB->predecessors()) {
VNInfo *VNI = searchForVNI(Indexes, LI, Pred, Visited);
if (VNI != nullptr) {
S.valno = VNI;
break;
}
}
assert(S.valno != nullptr && "could not determine valno");
}
// Merge with previous segment if it has the same VNI.
if (PrevValNo == S.valno && OutIt->end == S.start) {
OutIt->end = S.end;
} else {
// Didn't merge. Move OutIt to next segment.
if (PrevValNo == nullptr)
OutIt = LI.begin();
else
++OutIt;
if (OutIt != I)
*OutIt = *I;
PrevValNo = S.valno;
}
}
// If we merged some segments chop off the end.
++OutIt;
LI.segments.erase(OutIt, LI.end());
}
bool LiveRangeCalc::isJointlyDominated(const MachineBasicBlock *MBB,
ArrayRef<SlotIndex> Defs,
const SlotIndexes &Indexes) {
const MachineFunction &MF = *MBB->getParent();
BitVector DefBlocks(MF.getNumBlockIDs());
for (SlotIndex I : Defs)
DefBlocks.set(Indexes.getMBBFromIndex(I)->getNumber());
SetVector<unsigned> PredQueue;
PredQueue.insert(MBB->getNumber());
for (unsigned i = 0; i != PredQueue.size(); ++i) {
unsigned BN = PredQueue[i];
if (DefBlocks[BN])
return true;
const MachineBasicBlock *B = MF.getBlockNumbered(BN);
for (const MachineBasicBlock *P : B->predecessors())
PredQueue.insert(P->getNumber());
}
return false;
}
static void determineMissingVNIs(const SlotIndexes &Indexes, LiveInterval &LI) {
SmallPtrSet<const MachineBasicBlock*, 5> Visited;
for (LiveRange::Segment &S : LI.segments) {
if (S.valno != nullptr)
continue;
// This can only happen at the begin of a basic block.
assert(S.start.isBlock() && "valno should only be missing at block begin");
Visited.clear();
const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(S.start);
for (const MachineBasicBlock *Pred : MBB->predecessors()) {
VNInfo *VNI = searchForVNI(Indexes, LI, Pred, Visited);
if (VNI != nullptr) {
S.valno = VNI;
break;
}
}
assert(S.valno != nullptr && "could not determine valno");
}
}
bool LiveInterval::overlaps(const LiveInterval &Other,
const CoalescerPair &CP,
const SlotIndexes &Indexes) const {
assert(!empty() && "empty interval");
if (Other.empty())
return false;
// Use binary searches to find initial positions.
const_iterator I = find(Other.beginIndex());
const_iterator IE = end();
if (I == IE)
return false;
const_iterator J = Other.find(I->start);
const_iterator JE = Other.end();
if (J == JE)
return false;
for (;;) {
// J has just been advanced to satisfy:
assert(J->end >= I->start);
// Check for an overlap.
if (J->start < I->end) {
// I and J are overlapping. Find the later start.
SlotIndex Def = std::max(I->start, J->start);
// Allow the overlap if Def is a coalescable copy.
if (Def.isBlock() ||
!CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
return true;
}
// Advance the iterator that ends first to check for more overlaps.
if (J->end > I->end) {
std::swap(I, J);
std::swap(IE, JE);
}
// Advance J until J->end >= I->start.
do
if (++J == JE)
return false;
while (J->end < I->start);
}
}
void LiveInterval::computeSubRangeUndefs(SmallVectorImpl<SlotIndex> &Undefs,
LaneBitmask LaneMask,
const MachineRegisterInfo &MRI,
const SlotIndexes &Indexes) const {
assert(TargetRegisterInfo::isVirtualRegister(reg));
LaneBitmask VRegMask = MRI.getMaxLaneMaskForVReg(reg);
assert((VRegMask & LaneMask).any());
const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
for (const MachineOperand &MO : MRI.def_operands(reg)) {
if (!MO.isUndef())
continue;
unsigned SubReg = MO.getSubReg();
assert(SubReg != 0 && "Undef should only be set on subreg defs");
LaneBitmask DefMask = TRI.getSubRegIndexLaneMask(SubReg);
LaneBitmask UndefMask = VRegMask & ~DefMask;
if ((UndefMask & LaneMask).any()) {
const MachineInstr &MI = *MO.getParent();
bool EarlyClobber = MO.isEarlyClobber();
SlotIndex Pos = Indexes.getInstructionIndex(MI).getRegSlot(EarlyClobber);
Undefs.push_back(Pos);
}
}
}
MachineBasicBlock *
MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
// Splitting the critical edge to a landing pad block is non-trivial. Don't do
// it in this generic function.
if (Succ->isLandingPad())
return nullptr;
MachineFunction *MF = getParent();
DebugLoc dl; // FIXME: this is nowhere
// Performance might be harmed on HW that implements branching using exec mask
// where both sides of the branches are always executed.
if (MF->getTarget().requiresStructuredCFG())
return nullptr;
// We may need to update this's terminator, but we can't do that if
// AnalyzeBranch fails. If this uses a jump table, we won't touch it.
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 4> Cond;
if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
return nullptr;
// Avoid bugpoint weirdness: A block may end with a conditional branch but
// jumps to the same MBB is either case. We have duplicate CFG edges in that
// case that we can't handle. Since this never happens in properly optimized
// code, just skip those edges.
if (TBB && TBB == FBB) {
DEBUG(dbgs() << "Won't split critical edge after degenerate BB#"
<< getNumber() << '\n');
return nullptr;
}
MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
MF->insert(std::next(MachineFunction::iterator(this)), NMBB);
DEBUG(dbgs() << "Splitting critical edge:"
" BB#" << getNumber()
<< " -- BB#" << NMBB->getNumber()
<< " -- BB#" << Succ->getNumber() << '\n');
LiveIntervals *LIS = P->getAnalysisIfAvailable<LiveIntervals>();
SlotIndexes *Indexes = P->getAnalysisIfAvailable<SlotIndexes>();
if (LIS)
LIS->insertMBBInMaps(NMBB);
else if (Indexes)
Indexes->insertMBBInMaps(NMBB);
// On some targets like Mips, branches may kill virtual registers. Make sure
// that LiveVariables is properly updated after updateTerminator replaces the
// terminators.
LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>();
// Collect a list of virtual registers killed by the terminators.
SmallVector<unsigned, 4> KilledRegs;
if (LV)
for (instr_iterator I = getFirstInstrTerminator(), E = instr_end();
I != E; ++I) {
MachineInstr *MI = I;
for (MachineInstr::mop_iterator OI = MI->operands_begin(),
OE = MI->operands_end(); OI != OE; ++OI) {
if (!OI->isReg() || OI->getReg() == 0 ||
!OI->isUse() || !OI->isKill() || OI->isUndef())
continue;
unsigned Reg = OI->getReg();
if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
LV->getVarInfo(Reg).removeKill(MI)) {
KilledRegs.push_back(Reg);
DEBUG(dbgs() << "Removing terminator kill: " << *MI);
OI->setIsKill(false);
}
}
}
SmallVector<unsigned, 4> UsedRegs;
if (LIS) {
for (instr_iterator I = getFirstInstrTerminator(), E = instr_end();
I != E; ++I) {
MachineInstr *MI = I;
for (MachineInstr::mop_iterator OI = MI->operands_begin(),
OE = MI->operands_end(); OI != OE; ++OI) {
if (!OI->isReg() || OI->getReg() == 0)
continue;
unsigned Reg = OI->getReg();
if (std::find(UsedRegs.begin(), UsedRegs.end(), Reg) == UsedRegs.end())
UsedRegs.push_back(Reg);
}
}
}
ReplaceUsesOfBlockWith(Succ, NMBB);
// If updateTerminator() removes instructions, we need to remove them from
// SlotIndexes.
SmallVector<MachineInstr*, 4> Terminators;
if (Indexes) {
for (instr_iterator I = getFirstInstrTerminator(), E = instr_end();
I != E; ++I)
Terminators.push_back(I);
}
updateTerminator();
if (Indexes) {
SmallVector<MachineInstr*, 4> NewTerminators;
for (instr_iterator I = getFirstInstrTerminator(), E = instr_end();
I != E; ++I)
NewTerminators.push_back(I);
for (SmallVectorImpl<MachineInstr*>::iterator I = Terminators.begin(),
E = Terminators.end(); I != E; ++I) {
if (std::find(NewTerminators.begin(), NewTerminators.end(), *I) ==
NewTerminators.end())
Indexes->removeMachineInstrFromMaps(*I);
}
}
// Insert unconditional "jump Succ" instruction in NMBB if necessary.
NMBB->addSuccessor(Succ);
if (!NMBB->isLayoutSuccessor(Succ)) {
Cond.clear();
MF->getSubtarget().getInstrInfo()->InsertBranch(*NMBB, Succ, nullptr, Cond,
dl);
if (Indexes) {
for (instr_iterator I = NMBB->instr_begin(), E = NMBB->instr_end();
I != E; ++I) {
// Some instructions may have been moved to NMBB by updateTerminator(),
// so we first remove any instruction that already has an index.
if (Indexes->hasIndex(I))
Indexes->removeMachineInstrFromMaps(I);
Indexes->insertMachineInstrInMaps(I);
}
}
}
// Fix PHI nodes in Succ so they refer to NMBB instead of this
for (MachineBasicBlock::instr_iterator
i = Succ->instr_begin(),e = Succ->instr_end();
i != e && i->isPHI(); ++i)
for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
if (i->getOperand(ni+1).getMBB() == this)
i->getOperand(ni+1).setMBB(NMBB);
// Inherit live-ins from the successor
for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(),
E = Succ->livein_end(); I != E; ++I)
NMBB->addLiveIn(*I);
// Update LiveVariables.
const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
if (LV) {
// Restore kills of virtual registers that were killed by the terminators.
while (!KilledRegs.empty()) {
unsigned Reg = KilledRegs.pop_back_val();
for (instr_iterator I = instr_end(), E = instr_begin(); I != E;) {
if (!(--I)->addRegisterKilled(Reg, TRI, /* addIfNotFound= */ false))
continue;
if (TargetRegisterInfo::isVirtualRegister(Reg))
LV->getVarInfo(Reg).Kills.push_back(I);
DEBUG(dbgs() << "Restored terminator kill: " << *I);
break;
}
}
// Update relevant live-through information.
LV->addNewBlock(NMBB, this, Succ);
}
if (LIS) {
// After splitting the edge and updating SlotIndexes, live intervals may be
// in one of two situations, depending on whether this block was the last in
// the function. If the original block was the last in the function, all live
// intervals will end prior to the beginning of the new split block. If the
// original block was not at the end of the function, all live intervals will
// extend to the end of the new split block.
bool isLastMBB =
std::next(MachineFunction::iterator(NMBB)) == getParent()->end();
SlotIndex StartIndex = Indexes->getMBBEndIdx(this);
SlotIndex PrevIndex = StartIndex.getPrevSlot();
SlotIndex EndIndex = Indexes->getMBBEndIdx(NMBB);
// Find the registers used from NMBB in PHIs in Succ.
SmallSet<unsigned, 8> PHISrcRegs;
for (MachineBasicBlock::instr_iterator
I = Succ->instr_begin(), E = Succ->instr_end();
I != E && I->isPHI(); ++I) {
for (unsigned ni = 1, ne = I->getNumOperands(); ni != ne; ni += 2) {
if (I->getOperand(ni+1).getMBB() == NMBB) {
MachineOperand &MO = I->getOperand(ni);
unsigned Reg = MO.getReg();
PHISrcRegs.insert(Reg);
if (MO.isUndef())
continue;
LiveInterval &LI = LIS->getInterval(Reg);
VNInfo *VNI = LI.getVNInfoAt(PrevIndex);
assert(VNI && "PHI sources should be live out of their predecessors.");
LI.addSegment(LiveInterval::Segment(StartIndex, EndIndex, VNI));
}
}
}
MachineRegisterInfo *MRI = &getParent()->getRegInfo();
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (PHISrcRegs.count(Reg) || !LIS->hasInterval(Reg))
continue;
LiveInterval &LI = LIS->getInterval(Reg);
if (!LI.liveAt(PrevIndex))
continue;
bool isLiveOut = LI.liveAt(LIS->getMBBStartIdx(Succ));
if (isLiveOut && isLastMBB) {
VNInfo *VNI = LI.getVNInfoAt(PrevIndex);
assert(VNI && "LiveInterval should have VNInfo where it is live.");
LI.addSegment(LiveInterval::Segment(StartIndex, EndIndex, VNI));
} else if (!isLiveOut && !isLastMBB) {
LI.removeSegment(StartIndex, EndIndex);
}
}
// Update all intervals for registers whose uses may have been modified by
// updateTerminator().
LIS->repairIntervalsInRange(this, getFirstTerminator(), end(), UsedRegs);
}
if (MachineDominatorTree *MDT =
P->getAnalysisIfAvailable<MachineDominatorTree>())
MDT->recordSplitCriticalEdge(this, Succ, NMBB);
if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>())
if (MachineLoop *TIL = MLI->getLoopFor(this)) {
// If one or the other blocks were not in a loop, the new block is not
// either, and thus LI doesn't need to be updated.
if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) {
if (TIL == DestLoop) {
// Both in the same loop, the NMBB joins loop.
DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
} else if (TIL->contains(DestLoop)) {
// Edge from an outer loop to an inner loop. Add to the outer loop.
TIL->addBasicBlockToLoop(NMBB, MLI->getBase());
} else if (DestLoop->contains(TIL)) {
// Edge from an inner loop to an outer loop. Add to the outer loop.
DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
} else {
// Edge from two loops with no containment relation. Because these
// are natural loops, we know that the destination block must be the
// header of its loop (adding a branch into a loop elsewhere would
// create an irreducible loop).
assert(DestLoop->getHeader() == Succ &&
"Should not create irreducible loops!");
if (MachineLoop *P = DestLoop->getParentLoop())
P->addBasicBlockToLoop(NMBB, MLI->getBase());
}
}
}
return NMBB;
}
void LiveInterval::constructMainRangeFromSubranges(
const SlotIndexes &Indexes, VNInfo::Allocator &VNIAllocator) {
// The basic observations on which this algorithm is based:
// - Each Def/ValNo in a subrange must have a corresponding def on the main
// range, but not further defs/valnos are necessary.
// - If any of the subranges is live at a point the main liverange has to be
// live too, conversily if no subrange is live the main range mustn't be
// live either.
// We do this by scannig through all the subranges simultaneously creating new
// segments in the main range as segments start/ends come up in the subranges.
assert(hasSubRanges() && "expected subranges to be present");
assert(segments.empty() && valnos.empty() && "expected empty main range");
// Collect subrange, iterator pairs for the walk and determine first and last
// SlotIndex involved.
SmallVector<std::pair<const SubRange*, const_iterator>, 4> SRs;
SlotIndex First;
SlotIndex Last;
for (const SubRange &SR : subranges()) {
if (SR.empty())
continue;
SRs.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;
}
// Walk over all subranges simultaneously.
Segment CurrentSegment;
bool ConstructingSegment = false;
bool NeedVNIFixup = false;
unsigned ActiveMask = 0;
SlotIndex Pos = First;
while (true) {
SlotIndex NextPos = Last;
enum {
NOTHING,
BEGIN_SEGMENT,
END_SEGMENT,
} Event = NOTHING;
// Which subregister lanes are affected by the current event.
unsigned EventMask = 0;
// Whether a BEGIN_SEGMENT is also a valno definition point.
bool IsDef = false;
// Find the next begin or end of a subrange segment. Combine masks if we
// have multiple begins/ends at the same position. Ends take precedence over
// Begins.
for (auto &SRP : SRs) {
const SubRange &SR = *SRP.first;
const_iterator &I = SRP.second;
// Advance iterator of subrange to a segment involving Pos; the earlier
// segments are already merged at this point.
while (I != SR.end() &&
(I->end < Pos ||
(I->end == Pos && (ActiveMask & SR.LaneMask) == 0)))
++I;
if (I == SR.end())
continue;
if ((ActiveMask & SR.LaneMask) == 0 &&
Pos <= I->start && I->start <= NextPos) {
// Merge multiple begins at the same position.
if (I->start == NextPos && Event == BEGIN_SEGMENT) {
EventMask |= SR.LaneMask;
IsDef |= I->valno->def == I->start;
} else if (I->start < NextPos || Event != END_SEGMENT) {
Event = BEGIN_SEGMENT;
NextPos = I->start;
EventMask = SR.LaneMask;
IsDef = I->valno->def == I->start;
}
}
if ((ActiveMask & SR.LaneMask) != 0 &&
Pos <= I->end && I->end <= NextPos) {
// Merge multiple ends at the same position.
if (I->end == NextPos && Event == END_SEGMENT)
EventMask |= SR.LaneMask;
else {
Event = END_SEGMENT;
NextPos = I->end;
EventMask = SR.LaneMask;
}
}
}
// Advance scan position.
Pos = NextPos;
if (Event == BEGIN_SEGMENT) {
if (ConstructingSegment && IsDef) {
// Finish previous segment because we have to start a new one.
CurrentSegment.end = Pos;
append(CurrentSegment);
ConstructingSegment = false;
}
// Start a new segment if necessary.
if (!ConstructingSegment) {
// Determine value number for the segment.
VNInfo *VNI;
if (IsDef) {
VNI = getNextValue(Pos, VNIAllocator);
} else {
// We have to reuse an existing value number, if we are lucky
// then we already passed one of the predecessor blocks and determined
// its value number (with blocks in reverse postorder this would be
// always true but we have no such guarantee).
assert(Pos.isBlock());
const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(Pos);
// See if any of the predecessor blocks has a lower number and a VNI
for (const MachineBasicBlock *Pred : MBB->predecessors()) {
SlotIndex PredEnd = Indexes.getMBBEndIdx(Pred);
VNI = getVNInfoBefore(PredEnd);
if (VNI != nullptr)
break;
}
// Def will come later: We have to do an extra fixup pass.
if (VNI == nullptr)
NeedVNIFixup = true;
}
// In rare cases we can produce adjacent segments with the same value
// number (if they come from different subranges, but happen to have
// the same defining instruction). VNIFixup will fix those cases.
if (!empty() && segments.back().end == Pos &&
segments.back().valno == VNI)
NeedVNIFixup = true;
CurrentSegment.start = Pos;
CurrentSegment.valno = VNI;
ConstructingSegment = true;
}
ActiveMask |= EventMask;
} else if (Event == END_SEGMENT) {
assert(ConstructingSegment);
// Finish segment if no lane is active anymore.
ActiveMask &= ~EventMask;
if (ActiveMask == 0) {
CurrentSegment.end = Pos;
append(CurrentSegment);
ConstructingSegment = false;
}
} else {
// We reached the end of the last subranges and can stop.
assert(Event == NOTHING);
break;
}
}
// We might not be able to assign new valnos for all segments if the basic
// block containing the definition comes after a segment using the valno.
// Do a fixup pass for this uncommon case.
if (NeedVNIFixup)
determineMissingVNIs(Indexes, *this);
assert(ActiveMask == 0 && !ConstructingSegment && "all segments ended");
verify();
}