-void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
- MachineBasicBlock::iterator mi,
- SlotIndex MIIdx,
- MachineOperand& MO,
- unsigned MOIdx,
- LiveInterval &interval) {
- DEBUG(dbgs() << "\t\tregister: " << PrintReg(interval.reg, TRI));
-
- // Virtual registers may be defined multiple times (due to phi
- // elimination and 2-addr elimination). Much of what we do only has to be
- // done once for the vreg. We use an empty interval to detect the first
- // time we see a vreg.
- LiveVariables::VarInfo& vi = LV->getVarInfo(interval.reg);
- if (interval.empty()) {
- // Get the Idx of the defining instructions.
- SlotIndex defIndex = MIIdx.getRegSlot(MO.isEarlyClobber());
-
- // Make sure the first definition is not a partial redefinition.
- assert(!MO.readsReg() && "First def cannot also read virtual register "
- "missing <undef> flag?");
-
- VNInfo *ValNo = interval.getNextValue(defIndex, VNInfoAllocator);
- assert(ValNo->id == 0 && "First value in interval is not 0?");
-
- // Loop over all of the blocks that the vreg is defined in. There are
- // two cases we have to handle here. The most common case is a vreg
- // whose lifetime is contained within a basic block. In this case there
- // will be a single kill, in MBB, which comes after the definition.
- if (vi.Kills.size() == 1 && vi.Kills[0]->getParent() == mbb) {
- // FIXME: what about dead vars?
- SlotIndex killIdx;
- if (vi.Kills[0] != mi)
- killIdx = getInstructionIndex(vi.Kills[0]).getRegSlot();
- else
- killIdx = defIndex.getDeadSlot();
-
- // If the kill happens after the definition, we have an intra-block
- // live range.
- if (killIdx > defIndex) {
- assert(vi.AliveBlocks.empty() &&
- "Shouldn't be alive across any blocks!");
- LiveRange LR(defIndex, killIdx, ValNo);
- interval.addRange(LR);
- DEBUG(dbgs() << " +" << LR << "\n");
- return;
- }
- }
-
- // The other case we handle is when a virtual register lives to the end
- // of the defining block, potentially live across some blocks, then is
- // live into some number of blocks, but gets killed. Start by adding a
- // range that goes from this definition to the end of the defining block.
- LiveRange NewLR(defIndex, getMBBEndIdx(mbb), ValNo);
- DEBUG(dbgs() << " +" << NewLR);
- interval.addRange(NewLR);
-
- bool PHIJoin = LV->isPHIJoin(interval.reg);
-
- if (PHIJoin) {
- // A phi join register is killed at the end of the MBB and revived as a
- // new valno in the killing blocks.
- assert(vi.AliveBlocks.empty() && "Phi join can't pass through blocks");
- DEBUG(dbgs() << " phi-join");
- ValNo->setHasPHIKill(true);
- } else {
- // Iterate over all of the blocks that the variable is completely
- // live in, adding [insrtIndex(begin), instrIndex(end)+4) to the
- // live interval.
- for (SparseBitVector<>::iterator I = vi.AliveBlocks.begin(),
- E = vi.AliveBlocks.end(); I != E; ++I) {
- MachineBasicBlock *aliveBlock = MF->getBlockNumbered(*I);
- LiveRange LR(getMBBStartIdx(aliveBlock), getMBBEndIdx(aliveBlock),
- ValNo);
- interval.addRange(LR);
- DEBUG(dbgs() << " +" << LR);
- }
- }
-
- // Finally, this virtual register is live from the start of any killing
- // block to the 'use' slot of the killing instruction.
- for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) {
- MachineInstr *Kill = vi.Kills[i];
- SlotIndex Start = getMBBStartIdx(Kill->getParent());
- SlotIndex killIdx = getInstructionIndex(Kill).getRegSlot();
-
- // Create interval with one of a NEW value number. Note that this value
- // number isn't actually defined by an instruction, weird huh? :)
- if (PHIJoin) {
- assert(getInstructionFromIndex(Start) == 0 &&
- "PHI def index points at actual instruction.");
- ValNo = interval.getNextValue(Start, VNInfoAllocator);
- ValNo->setIsPHIDef(true);
- }
- LiveRange LR(Start, killIdx, ValNo);
- interval.addRange(LR);
- DEBUG(dbgs() << " +" << LR);
- }
-
- } else {
- if (MultipleDefsBySameMI(*mi, MOIdx))
- // Multiple defs of the same virtual register by the same instruction.
- // e.g. %reg1031:5<def>, %reg1031:6<def> = VLD1q16 %reg1024<kill>, ...
- // This is likely due to elimination of REG_SEQUENCE instructions. Return
- // here since there is nothing to do.
- return;
-
- // If this is the second time we see a virtual register definition, it
- // must be due to phi elimination or two addr elimination. If this is
- // the result of two address elimination, then the vreg is one of the
- // def-and-use register operand.
-
- // It may also be partial redef like this:
- // 80 %reg1041:6<def> = VSHRNv4i16 %reg1034<kill>, 12, pred:14, pred:%reg0
- // 120 %reg1041:5<def> = VSHRNv4i16 %reg1039<kill>, 12, pred:14, pred:%reg0
- bool PartReDef = isPartialRedef(MIIdx, MO, interval);
- if (PartReDef || mi->isRegTiedToUseOperand(MOIdx)) {
- // If this is a two-address definition, then we have already processed
- // the live range. The only problem is that we didn't realize there
- // are actually two values in the live interval. Because of this we
- // need to take the LiveRegion that defines this register and split it
- // into two values.
- SlotIndex RedefIndex = MIIdx.getRegSlot(MO.isEarlyClobber());
-
- const LiveRange *OldLR =
- interval.getLiveRangeContaining(RedefIndex.getRegSlot(true));
- VNInfo *OldValNo = OldLR->valno;
- SlotIndex DefIndex = OldValNo->def.getRegSlot();
-
- // Delete the previous value, which should be short and continuous,
- // because the 2-addr copy must be in the same MBB as the redef.
- interval.removeRange(DefIndex, RedefIndex);
-
- // The new value number (#1) is defined by the instruction we claimed
- // defined value #0.
- VNInfo *ValNo = interval.createValueCopy(OldValNo, VNInfoAllocator);
-
- // Value#0 is now defined by the 2-addr instruction.
- OldValNo->def = RedefIndex;
-
- // Add the new live interval which replaces the range for the input copy.
- LiveRange LR(DefIndex, RedefIndex, ValNo);
- DEBUG(dbgs() << " replace range with " << LR);
- interval.addRange(LR);
-
- // If this redefinition is dead, we need to add a dummy unit live
- // range covering the def slot.
- if (MO.isDead())
- interval.addRange(LiveRange(RedefIndex, RedefIndex.getDeadSlot(),
- OldValNo));
-
- DEBUG(dbgs() << " RESULT: " << interval);
- } else if (LV->isPHIJoin(interval.reg)) {
- // In the case of PHI elimination, each variable definition is only
- // live until the end of the block. We've already taken care of the
- // rest of the live range.
-
- SlotIndex defIndex = MIIdx.getRegSlot();
- if (MO.isEarlyClobber())
- defIndex = MIIdx.getRegSlot(true);
-
- VNInfo *ValNo = interval.getNextValue(defIndex, VNInfoAllocator);
-
- SlotIndex killIndex = getMBBEndIdx(mbb);
- LiveRange LR(defIndex, killIndex, ValNo);
- interval.addRange(LR);
- ValNo->setHasPHIKill(true);
- DEBUG(dbgs() << " phi-join +" << LR);
- } else {
- llvm_unreachable("Multiply defined register");
- }