/// shrinkToUses - After removing some uses of a register, shrink its live
/// range to just the remaining uses. This method does not compute reaching
/// defs for new uses, and it doesn't remove dead defs.
bool LiveIntervals::shrinkToUses(LiveInterval *li,
SmallVectorImpl<MachineInstr*> *dead) {
DEBUG(dbgs() << "Shrink: " << *li << '\n');
assert(TargetRegisterInfo::isVirtualRegister(li->reg)
&& "Can only shrink virtual registers");
// Find all the values used, including PHI kills.
SmallVector<std::pair<SlotIndex, VNInfo*>, 16> WorkList;
// Blocks that have already been added to WorkList as live-out.
SmallPtrSet<MachineBasicBlock*, 16> LiveOut;
// Visit all instructions reading li->reg.
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(li->reg);
MachineInstr *UseMI = I.skipInstruction();) {
if (UseMI->isDebugValue() || !UseMI->readsVirtualRegister(li->reg))
continue;
SlotIndex Idx = getInstructionIndex(UseMI).getRegSlot();
LiveRangeQuery LRQ(*li, Idx);
VNInfo *VNI = LRQ.valueIn();
if (!VNI) {
// This shouldn't happen: readsVirtualRegister returns true, but there is
// no live value. It is likely caused by a target getting <undef> flags
// wrong.
DEBUG(dbgs() << Idx << '\t' << *UseMI
<< "Warning: Instr claims to read non-existent value in "
<< *li << '\n');
continue;
}
// Special case: An early-clobber tied operand reads and writes the
// register one slot early.
if (VNInfo *DefVNI = LRQ.valueDefined())
Idx = DefVNI->def;
WorkList.push_back(std::make_pair(Idx, VNI));
}
// Create a new live interval with only minimal live segments per def.
LiveInterval NewLI(li->reg, 0);
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
NewLI.addRange(LiveRange(VNI->def, VNI->def.getDeadSlot(), VNI));
}
// Keep track of the PHIs that are in use.
SmallPtrSet<VNInfo*, 8> UsedPHIs;
// 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 = getMBBFromIndex(Idx.getPrevSlot());
SlotIndex BlockStart = getMBBStartIdx(MBB);
// Extend the live range for VNI to be live at Idx.
if (VNInfo *ExtVNI = NewLI.extendInBlock(BlockStart, Idx)) {
(void)ExtVNI;
assert(ExtVNI == VNI && "Unexpected existing value number");
// Is this a PHIDef we haven't seen before?
if (!VNI->isPHIDef() || VNI->def != BlockStart || !UsedPHIs.insert(VNI))
continue;
// The PHI is live, make sure the predecessors are live-out.
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
if (!LiveOut.insert(*PI))
continue;
SlotIndex Stop = getMBBEndIdx(*PI);
// A predecessor is not required to have a live-out value for a PHI.
if (VNInfo *PVNI = li->getVNInfoBefore(Stop))
WorkList.push_back(std::make_pair(Stop, PVNI));
}
continue;
}
// VNI is live-in to MBB.
DEBUG(dbgs() << " live-in at " << BlockStart << '\n');
NewLI.addRange(LiveRange(BlockStart, Idx, VNI));
// Make sure VNI is live-out from the predecessors.
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
if (!LiveOut.insert(*PI))
continue;
SlotIndex Stop = getMBBEndIdx(*PI);
assert(li->getVNInfoBefore(Stop) == VNI &&
"Wrong value out of predecessor");
WorkList.push_back(std::make_pair(Stop, VNI));
}
}
// Handle dead values.
bool CanSeparate = false;
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
LiveInterval::iterator LII = NewLI.FindLiveRangeContaining(VNI->def);
assert(LII != NewLI.end() && "Missing live range for PHI");
if (LII->end != VNI->def.getDeadSlot())
continue;
if (VNI->isPHIDef()) {
// This is a dead PHI. Remove it.
VNI->markUnused();
NewLI.removeRange(*LII);
DEBUG(dbgs() << "Dead PHI at " << VNI->def << " may separate interval\n");
CanSeparate = true;
} else {
// This is a dead def. Make sure the instruction knows.
MachineInstr *MI = getInstructionFromIndex(VNI->def);
assert(MI && "No instruction defining live value");
MI->addRegisterDead(li->reg, TRI);
if (dead && MI->allDefsAreDead()) {
DEBUG(dbgs() << "All defs dead: " << VNI->def << '\t' << *MI);
dead->push_back(MI);
}
}
}
// Move the trimmed ranges back.
li->ranges.swap(NewLI.ranges);
DEBUG(dbgs() << "Shrunk: " << *li << '\n');
return CanSeparate;
}
/// Update the live interval information to reflect the removal of the given
/// instruction from the program. As with "addInstrToLiveness", this function
/// is called while the program code is being changed.
void HexagonExpandCondsets::removeInstrFromLiveness(MachineInstr *MI) {
SlotIndex MX = LIS->getInstructionIndex(*MI).getRegSlot();
DEBUG(dbgs() << "removing instr\n " << MX << " " << *MI);
// For each def in MI:
// If MI starts a live segment, merge this segment with the previous segment.
//
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isDef())
continue;
unsigned DefR = Op.getReg();
LiveInterval &LID = LIS->getInterval(DefR);
LiveInterval::iterator LT = LID.FindSegmentContaining(MX);
assert(LT != LID.end() && "Expecting live segments");
DEBUG(dbgs() << "removing def at " << MX << " of " << PrintReg(DefR, TRI)
<< " with interval\n " << LID << "\n");
if (LT->start != MX)
continue;
VNInfo *MVN = LT->valno;
if (LT != LID.begin()) {
// If the current live segment is not the first, the task is easy. If
// the previous segment continues into the current block, extend it to
// the end of the current one, and merge the value numbers.
// Otherwise, remove the current segment, and make the end of it "undef".
LiveInterval::iterator P = std::prev(LT);
SlotIndex PE = P->end.isBlock() ? P->end.getPrevIndex() : P->end;
MachineBasicBlock *MB = MI->getParent();
MachineBasicBlock *PB = LIS->getMBBFromIndex(PE);
if (PB != MB && !LIS->isLiveInToMBB(LID, MB)) {
makeDefined(DefR, LT->end, false);
LID.removeSegment(*LT);
} else {
// Make the segments adjacent, so that merge-vn can also merge the
// segments.
P->end = LT->start;
makeUndead(DefR, P->valno->def);
LID.MergeValueNumberInto(MVN, P->valno);
}
} else {
LiveInterval::iterator N = std::next(LT);
LiveInterval::iterator RmB = LT, RmE = N;
while (N != LID.end()) {
// Iterate until the first register-based definition is found
// (i.e. skip all block-boundary entries).
LiveInterval::iterator Next = std::next(N);
if (N->start.isRegister()) {
makeDefined(DefR, N->start, false);
break;
}
if (N->end.isRegister()) {
makeDefined(DefR, N->end, false);
RmE = Next;
break;
}
RmE = Next;
N = Next;
}
// Erase the segments in one shot to avoid invalidating iterators.
LID.segments.erase(RmB, RmE);
}
bool VNUsed = false;
for (LiveInterval::iterator I = LID.begin(), E = LID.end(); I != E; ++I) {
if (I->valno != MVN)
continue;
VNUsed = true;
break;
}
if (!VNUsed)
MVN->markUnused();
DEBUG(dbgs() << "new interval: ");
if (!LID.empty()) {
DEBUG(dbgs() << LID << "\n");
LID.verify();
} else {
DEBUG(dbgs() << "<empty>\n");
LIS->removeInterval(DefR);
}
}
// For uses there is nothing to do. The intervals will be updated via
// shrinkToUses.
SmallVector<unsigned,4> Uses;
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isUse())
continue;
unsigned R = Op.getReg();
if (!TargetRegisterInfo::isVirtualRegister(R))
continue;
Uses.push_back(R);
}
LIS->RemoveMachineInstrFromMaps(*MI);
MI->eraseFromParent();
for (unsigned i = 0, n = Uses.size(); i < n; ++i) {
LiveInterval &LI = LIS->getInterval(Uses[i]);
shrinkToUses(Uses[i], LI);
}
}
