+ // Only consider reloads for now and remats which do not have register
+ // operands. FIXME: Consider unfold load folding instructions.
+ if (Def && !RuledOut) {
+ int FI = INT_MIN;
+ if ((!HasNonInvariantUse && IsLICMCandidate(*MI)) ||
+ (TII->isLoadFromStackSlot(MI, FI) && MFI->isSpillSlotObjectIndex(FI)))
+ Candidates.push_back(CandidateInfo(MI, Def, FI));
+ }
+}
+
+/// HoistRegionPostRA - Walk the specified region of the CFG and hoist loop
+/// invariants out to the preheader.
+void MachineLICM::HoistRegionPostRA() {
+ MachineBasicBlock *Preheader = getCurPreheader();
+ if (!Preheader)
+ return;
+
+ unsigned NumRegs = TRI->getNumRegs();
+ BitVector PhysRegDefs(NumRegs); // Regs defined once in the loop.
+ BitVector PhysRegClobbers(NumRegs); // Regs defined more than once.
+
+ SmallVector<CandidateInfo, 32> Candidates;
+ SmallSet<int, 32> StoredFIs;
+
+ // Walk the entire region, count number of defs for each register, and
+ // collect potential LICM candidates.
+ const std::vector<MachineBasicBlock*> Blocks = CurLoop->getBlocks();
+ for (unsigned i = 0, e = Blocks.size(); i != e; ++i) {
+ MachineBasicBlock *BB = Blocks[i];
+
+ // If the header of the loop containing this basic block is a landing pad,
+ // then don't try to hoist instructions out of this loop.
+ const MachineLoop *ML = MLI->getLoopFor(BB);
+ if (ML && ML->getHeader()->isLandingPad()) continue;
+
+ // Conservatively treat live-in's as an external def.
+ // FIXME: That means a reload that're reused in successor block(s) will not
+ // be LICM'ed.
+ for (MachineBasicBlock::livein_iterator I = BB->livein_begin(),
+ E = BB->livein_end(); I != E; ++I) {
+ unsigned Reg = *I;
+ for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+ PhysRegDefs.set(*AI);
+ }
+
+ SpeculationState = SpeculateUnknown;
+ for (MachineBasicBlock::iterator
+ MII = BB->begin(), E = BB->end(); MII != E; ++MII) {
+ MachineInstr *MI = &*MII;
+ ProcessMI(MI, PhysRegDefs, PhysRegClobbers, StoredFIs, Candidates);
+ }
+ }
+
+ // Gather the registers read / clobbered by the terminator.
+ BitVector TermRegs(NumRegs);
+ MachineBasicBlock::iterator TI = Preheader->getFirstTerminator();
+ if (TI != Preheader->end()) {
+ for (unsigned i = 0, e = TI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = TI->getOperand(i);
+ if (!MO.isReg())
+ continue;
+ unsigned Reg = MO.getReg();
+ if (!Reg)
+ continue;
+ for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+ TermRegs.set(*AI);
+ }
+ }
+
+ // Now evaluate whether the potential candidates qualify.
+ // 1. Check if the candidate defined register is defined by another
+ // instruction in the loop.
+ // 2. If the candidate is a load from stack slot (always true for now),
+ // check if the slot is stored anywhere in the loop.
+ // 3. Make sure candidate def should not clobber
+ // registers read by the terminator. Similarly its def should not be
+ // clobbered by the terminator.
+ for (unsigned i = 0, e = Candidates.size(); i != e; ++i) {
+ if (Candidates[i].FI != INT_MIN &&
+ StoredFIs.count(Candidates[i].FI))
+ continue;
+
+ unsigned Def = Candidates[i].Def;
+ if (!PhysRegClobbers.test(Def) && !TermRegs.test(Def)) {
+ bool Safe = true;
+ MachineInstr *MI = Candidates[i].MI;
+ for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) {
+ const MachineOperand &MO = MI->getOperand(j);
+ if (!MO.isReg() || MO.isDef() || !MO.getReg())
+ continue;
+ unsigned Reg = MO.getReg();
+ if (PhysRegDefs.test(Reg) ||
+ PhysRegClobbers.test(Reg)) {
+ // If it's using a non-loop-invariant register, then it's obviously
+ // not safe to hoist.
+ Safe = false;
+ break;
+ }
+ }
+ if (Safe)
+ HoistPostRA(MI, Candidates[i].Def);
+ }
+ }
+}
+
+/// AddToLiveIns - Add register 'Reg' to the livein sets of BBs in the current
+/// loop, and make sure it is not killed by any instructions in the loop.
+void MachineLICM::AddToLiveIns(unsigned Reg) {
+ const std::vector<MachineBasicBlock*> Blocks = CurLoop->getBlocks();
+ for (unsigned i = 0, e = Blocks.size(); i != e; ++i) {
+ MachineBasicBlock *BB = Blocks[i];
+ if (!BB->isLiveIn(Reg))
+ BB->addLiveIn(Reg);
+ for (MachineBasicBlock::iterator
+ MII = BB->begin(), E = BB->end(); MII != E; ++MII) {
+ MachineInstr *MI = &*MII;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.getReg() || MO.isDef()) continue;
+ if (MO.getReg() == Reg || TRI->isSuperRegister(Reg, MO.getReg()))
+ MO.setIsKill(false);
+ }
+ }
+ }
+}
+
+/// HoistPostRA - When an instruction is found to only use loop invariant
+/// operands that is safe to hoist, this instruction is called to do the
+/// dirty work.
+void MachineLICM::HoistPostRA(MachineInstr *MI, unsigned Def) {
+ MachineBasicBlock *Preheader = getCurPreheader();
+
+ // Now move the instructions to the predecessor, inserting it before any
+ // terminator instructions.
+ DEBUG(dbgs() << "Hoisting to BB#" << Preheader->getNumber() << " from BB#"
+ << MI->getParent()->getNumber() << ": " << *MI);
+
+ // Splice the instruction to the preheader.
+ MachineBasicBlock *MBB = MI->getParent();
+ Preheader->splice(Preheader->getFirstTerminator(), MBB, MI);
+
+ // Add register to livein list to all the BBs in the current loop since a
+ // loop invariant must be kept live throughout the whole loop. This is
+ // important to ensure later passes do not scavenge the def register.
+ AddToLiveIns(Def);
+
+ ++NumPostRAHoisted;
+ Changed = true;
+}
+
+// IsGuaranteedToExecute - Check if this mbb is guaranteed to execute.
+// If not then a load from this mbb may not be safe to hoist.
+bool MachineLICM::IsGuaranteedToExecute(MachineBasicBlock *BB) {
+ if (SpeculationState != SpeculateUnknown)
+ return SpeculationState == SpeculateFalse;
+
+ if (BB != CurLoop->getHeader()) {
+ // Check loop exiting blocks.
+ SmallVector<MachineBasicBlock*, 8> CurrentLoopExitingBlocks;
+ CurLoop->getExitingBlocks(CurrentLoopExitingBlocks);
+ for (unsigned i = 0, e = CurrentLoopExitingBlocks.size(); i != e; ++i)
+ if (!DT->dominates(BB, CurrentLoopExitingBlocks[i])) {
+ SpeculationState = SpeculateTrue;
+ return false;
+ }
+ }
+
+ SpeculationState = SpeculateFalse;
+ return true;
+}
+
+void MachineLICM::EnterScope(MachineBasicBlock *MBB) {
+ DEBUG(dbgs() << "Entering: " << MBB->getName() << '\n');
+
+ // Remember livein register pressure.
+ BackTrace.push_back(RegPressure);
+}
+
+void MachineLICM::ExitScope(MachineBasicBlock *MBB) {
+ DEBUG(dbgs() << "Exiting: " << MBB->getName() << '\n');
+ BackTrace.pop_back();