// 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 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");
}
}
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();
}