1 //===- MipsDelaySlotFiller.cpp - Mips Delay Slot Filler -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Simple pass to fill delay slots with useful instructions.
12 //===----------------------------------------------------------------------===//
14 #include "MCTargetDesc/MipsMCNaCl.h"
16 #include "MipsInstrInfo.h"
17 #include "MipsRegisterInfo.h"
18 #include "MipsSubtarget.h"
19 #include "llvm/ADT/BitVector.h"
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/PointerUnion.h"
22 #include "llvm/ADT/SmallPtrSet.h"
23 #include "llvm/ADT/SmallVector.h"
24 #include "llvm/ADT/Statistic.h"
25 #include "llvm/ADT/StringRef.h"
26 #include "llvm/Analysis/AliasAnalysis.h"
27 #include "llvm/Analysis/ValueTracking.h"
28 #include "llvm/CodeGen/MachineBasicBlock.h"
29 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
30 #include "llvm/CodeGen/MachineFunction.h"
31 #include "llvm/CodeGen/MachineFunctionPass.h"
32 #include "llvm/CodeGen/MachineInstr.h"
33 #include "llvm/CodeGen/MachineInstrBuilder.h"
34 #include "llvm/CodeGen/MachineOperand.h"
35 #include "llvm/CodeGen/MachineRegisterInfo.h"
36 #include "llvm/CodeGen/PseudoSourceValue.h"
37 #include "llvm/CodeGen/TargetRegisterInfo.h"
38 #include "llvm/CodeGen/TargetSubtargetInfo.h"
39 #include "llvm/MC/MCInstrDesc.h"
40 #include "llvm/MC/MCRegisterInfo.h"
41 #include "llvm/Support/Casting.h"
42 #include "llvm/Support/CodeGen.h"
43 #include "llvm/Support/CommandLine.h"
44 #include "llvm/Support/ErrorHandling.h"
45 #include "llvm/Target/TargetMachine.h"
54 #define DEBUG_TYPE "delay-slot-filler"
56 STATISTIC(FilledSlots, "Number of delay slots filled");
57 STATISTIC(UsefulSlots, "Number of delay slots filled with instructions that"
60 static cl::opt<bool> DisableDelaySlotFiller(
61 "disable-mips-delay-filler",
63 cl::desc("Fill all delay slots with NOPs."),
66 static cl::opt<bool> DisableForwardSearch(
67 "disable-mips-df-forward-search",
69 cl::desc("Disallow MIPS delay filler to search forward."),
72 static cl::opt<bool> DisableSuccBBSearch(
73 "disable-mips-df-succbb-search",
75 cl::desc("Disallow MIPS delay filler to search successor basic blocks."),
78 static cl::opt<bool> DisableBackwardSearch(
79 "disable-mips-df-backward-search",
81 cl::desc("Disallow MIPS delay filler to search backward."),
84 enum CompactBranchPolicy {
85 CB_Never, ///< The policy 'never' may in some circumstances or for some
86 ///< ISAs not be absolutely adhered to.
87 CB_Optimal, ///< Optimal is the default and will produce compact branches
88 ///< when delay slots cannot be filled.
89 CB_Always ///< 'always' may in some circumstances may not be
90 ///< absolutely adhered to there may not be a corresponding
91 ///< compact form of a branch.
94 static cl::opt<CompactBranchPolicy> MipsCompactBranchPolicy(
95 "mips-compact-branches",cl::Optional,
97 cl::desc("MIPS Specific: Compact branch policy."),
99 clEnumValN(CB_Never, "never", "Do not use compact branches if possible."),
100 clEnumValN(CB_Optimal, "optimal", "Use compact branches where appropiate (default)."),
101 clEnumValN(CB_Always, "always", "Always use compact branches if possible.")
107 using Iter = MachineBasicBlock::iterator;
108 using ReverseIter = MachineBasicBlock::reverse_iterator;
109 using BB2BrMap = SmallDenseMap<MachineBasicBlock *, MachineInstr *, 2>;
113 RegDefsUses(const TargetRegisterInfo &TRI);
115 void init(const MachineInstr &MI);
117 /// This function sets all caller-saved registers in Defs.
118 void setCallerSaved(const MachineInstr &MI);
120 /// This function sets all unallocatable registers in Defs.
121 void setUnallocatableRegs(const MachineFunction &MF);
123 /// Set bits in Uses corresponding to MBB's live-out registers except for
124 /// the registers that are live-in to SuccBB.
125 void addLiveOut(const MachineBasicBlock &MBB,
126 const MachineBasicBlock &SuccBB);
128 bool update(const MachineInstr &MI, unsigned Begin, unsigned End);
131 bool checkRegDefsUses(BitVector &NewDefs, BitVector &NewUses, unsigned Reg,
134 /// Returns true if Reg or its alias is in RegSet.
135 bool isRegInSet(const BitVector &RegSet, unsigned Reg) const;
137 const TargetRegisterInfo &TRI;
138 BitVector Defs, Uses;
141 /// Base class for inspecting loads and stores.
142 class InspectMemInstr {
144 InspectMemInstr(bool ForbidMemInstr_) : ForbidMemInstr(ForbidMemInstr_) {}
145 virtual ~InspectMemInstr() = default;
147 /// Return true if MI cannot be moved to delay slot.
148 bool hasHazard(const MachineInstr &MI);
151 /// Flags indicating whether loads or stores have been seen.
152 bool OrigSeenLoad = false;
153 bool OrigSeenStore = false;
154 bool SeenLoad = false;
155 bool SeenStore = false;
157 /// Memory instructions are not allowed to move to delay slot if this flag
162 virtual bool hasHazard_(const MachineInstr &MI) = 0;
165 /// This subclass rejects any memory instructions.
166 class NoMemInstr : public InspectMemInstr {
168 NoMemInstr() : InspectMemInstr(true) {}
171 bool hasHazard_(const MachineInstr &MI) override { return true; }
174 /// This subclass accepts loads from stacks and constant loads.
175 class LoadFromStackOrConst : public InspectMemInstr {
177 LoadFromStackOrConst() : InspectMemInstr(false) {}
180 bool hasHazard_(const MachineInstr &MI) override;
183 /// This subclass uses memory dependence information to determine whether a
184 /// memory instruction can be moved to a delay slot.
185 class MemDefsUses : public InspectMemInstr {
187 MemDefsUses(const DataLayout &DL, const MachineFrameInfo *MFI);
190 using ValueType = PointerUnion<const Value *, const PseudoSourceValue *>;
192 bool hasHazard_(const MachineInstr &MI) override;
194 /// Update Defs and Uses. Return true if there exist dependences that
195 /// disqualify the delay slot candidate between V and values in Uses and
197 bool updateDefsUses(ValueType V, bool MayStore);
199 /// Get the list of underlying objects of MI's memory operand.
200 bool getUnderlyingObjects(const MachineInstr &MI,
201 SmallVectorImpl<ValueType> &Objects) const;
203 const MachineFrameInfo *MFI;
204 SmallPtrSet<ValueType, 4> Uses, Defs;
205 const DataLayout &DL;
207 /// Flags indicating whether loads or stores with no underlying objects have
209 bool SeenNoObjLoad = false;
210 bool SeenNoObjStore = false;
213 class Filler : public MachineFunctionPass {
215 Filler() : MachineFunctionPass(ID) {}
217 StringRef getPassName() const override { return "Mips Delay Slot Filler"; }
219 bool runOnMachineFunction(MachineFunction &F) override {
221 bool Changed = false;
222 for (MachineFunction::iterator FI = F.begin(), FE = F.end();
224 Changed |= runOnMachineBasicBlock(*FI);
226 // This pass invalidates liveness information when it reorders
227 // instructions to fill delay slot. Without this, -verify-machineinstrs
230 F.getRegInfo().invalidateLiveness();
235 MachineFunctionProperties getRequiredProperties() const override {
236 return MachineFunctionProperties().set(
237 MachineFunctionProperties::Property::NoVRegs);
240 void getAnalysisUsage(AnalysisUsage &AU) const override {
241 AU.addRequired<MachineBranchProbabilityInfo>();
242 MachineFunctionPass::getAnalysisUsage(AU);
246 bool runOnMachineBasicBlock(MachineBasicBlock &MBB);
248 Iter replaceWithCompactBranch(MachineBasicBlock &MBB, Iter Branch,
251 /// This function checks if it is valid to move Candidate to the delay slot
252 /// and returns true if it isn't. It also updates memory and register
253 /// dependence information.
254 bool delayHasHazard(const MachineInstr &Candidate, RegDefsUses &RegDU,
255 InspectMemInstr &IM) const;
257 /// This function searches range [Begin, End) for an instruction that can be
258 /// moved to the delay slot. Returns true on success.
259 template<typename IterTy>
260 bool searchRange(MachineBasicBlock &MBB, IterTy Begin, IterTy End,
261 RegDefsUses &RegDU, InspectMemInstr &IM, Iter Slot,
262 IterTy &Filler) const;
264 /// This function searches in the backward direction for an instruction that
265 /// can be moved to the delay slot. Returns true on success.
266 bool searchBackward(MachineBasicBlock &MBB, MachineInstr &Slot) const;
268 /// This function searches MBB in the forward direction for an instruction
269 /// that can be moved to the delay slot. Returns true on success.
270 bool searchForward(MachineBasicBlock &MBB, Iter Slot) const;
272 /// This function searches one of MBB's successor blocks for an instruction
273 /// that can be moved to the delay slot and inserts clones of the
274 /// instruction into the successor's predecessor blocks.
275 bool searchSuccBBs(MachineBasicBlock &MBB, Iter Slot) const;
277 /// Pick a successor block of MBB. Return NULL if MBB doesn't have a
278 /// successor block that is not a landing pad.
279 MachineBasicBlock *selectSuccBB(MachineBasicBlock &B) const;
281 /// This function analyzes MBB and returns an instruction with an unoccupied
282 /// slot that branches to Dst.
283 std::pair<MipsInstrInfo::BranchType, MachineInstr *>
284 getBranch(MachineBasicBlock &MBB, const MachineBasicBlock &Dst) const;
286 /// Examine Pred and see if it is possible to insert an instruction into
287 /// one of its branches delay slot or its end.
288 bool examinePred(MachineBasicBlock &Pred, const MachineBasicBlock &Succ,
289 RegDefsUses &RegDU, bool &HasMultipleSuccs,
290 BB2BrMap &BrMap) const;
292 bool terminateSearch(const MachineInstr &Candidate) const;
294 const TargetMachine *TM = nullptr;
299 } // end anonymous namespace
303 static bool hasUnoccupiedSlot(const MachineInstr *MI) {
304 return MI->hasDelaySlot() && !MI->isBundledWithSucc();
307 /// This function inserts clones of Filler into predecessor blocks.
308 static void insertDelayFiller(Iter Filler, const BB2BrMap &BrMap) {
309 MachineFunction *MF = Filler->getParent()->getParent();
311 for (BB2BrMap::const_iterator I = BrMap.begin(); I != BrMap.end(); ++I) {
313 MIBundleBuilder(I->second).append(MF->CloneMachineInstr(&*Filler));
316 I->first->insert(I->first->end(), MF->CloneMachineInstr(&*Filler));
321 /// This function adds registers Filler defines to MBB's live-in register list.
322 static void addLiveInRegs(Iter Filler, MachineBasicBlock &MBB) {
323 for (unsigned I = 0, E = Filler->getNumOperands(); I != E; ++I) {
324 const MachineOperand &MO = Filler->getOperand(I);
327 if (!MO.isReg() || !MO.isDef() || !(R = MO.getReg()))
331 const MachineFunction &MF = *MBB.getParent();
332 assert(MF.getSubtarget().getRegisterInfo()->getAllocatableSet(MF).test(R) &&
333 "Shouldn't move an instruction with unallocatable registers across "
334 "basic block boundaries.");
337 if (!MBB.isLiveIn(R))
342 RegDefsUses::RegDefsUses(const TargetRegisterInfo &TRI)
343 : TRI(TRI), Defs(TRI.getNumRegs(), false), Uses(TRI.getNumRegs(), false) {}
345 void RegDefsUses::init(const MachineInstr &MI) {
346 // Add all register operands which are explicit and non-variadic.
347 update(MI, 0, MI.getDesc().getNumOperands());
349 // If MI is a call, add RA to Defs to prevent users of RA from going into
354 // Add all implicit register operands of branch instructions except
357 update(MI, MI.getDesc().getNumOperands(), MI.getNumOperands());
358 Defs.reset(Mips::AT);
362 void RegDefsUses::setCallerSaved(const MachineInstr &MI) {
365 // Add RA/RA_64 to Defs to prevent users of RA/RA_64 from going into
366 // the delay slot. The reason is that RA/RA_64 must not be changed
367 // in the delay slot so that the callee can return to the caller.
368 if (MI.definesRegister(Mips::RA) || MI.definesRegister(Mips::RA_64)) {
370 Defs.set(Mips::RA_64);
373 // If MI is a call, add all caller-saved registers to Defs.
374 BitVector CallerSavedRegs(TRI.getNumRegs(), true);
376 CallerSavedRegs.reset(Mips::ZERO);
377 CallerSavedRegs.reset(Mips::ZERO_64);
379 for (const MCPhysReg *R = TRI.getCalleeSavedRegs(MI.getParent()->getParent());
381 for (MCRegAliasIterator AI(*R, &TRI, true); AI.isValid(); ++AI)
382 CallerSavedRegs.reset(*AI);
384 Defs |= CallerSavedRegs;
387 void RegDefsUses::setUnallocatableRegs(const MachineFunction &MF) {
388 BitVector AllocSet = TRI.getAllocatableSet(MF);
390 for (unsigned R : AllocSet.set_bits())
391 for (MCRegAliasIterator AI(R, &TRI, false); AI.isValid(); ++AI)
394 AllocSet.set(Mips::ZERO);
395 AllocSet.set(Mips::ZERO_64);
397 Defs |= AllocSet.flip();
400 void RegDefsUses::addLiveOut(const MachineBasicBlock &MBB,
401 const MachineBasicBlock &SuccBB) {
402 for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
403 SE = MBB.succ_end(); SI != SE; ++SI)
405 for (const auto &LI : (*SI)->liveins())
406 Uses.set(LI.PhysReg);
409 bool RegDefsUses::update(const MachineInstr &MI, unsigned Begin, unsigned End) {
410 BitVector NewDefs(TRI.getNumRegs()), NewUses(TRI.getNumRegs());
411 bool HasHazard = false;
413 for (unsigned I = Begin; I != End; ++I) {
414 const MachineOperand &MO = MI.getOperand(I);
416 if (MO.isReg() && MO.getReg())
417 HasHazard |= checkRegDefsUses(NewDefs, NewUses, MO.getReg(), MO.isDef());
426 bool RegDefsUses::checkRegDefsUses(BitVector &NewDefs, BitVector &NewUses,
427 unsigned Reg, bool IsDef) const {
430 // check whether Reg has already been defined or used.
431 return (isRegInSet(Defs, Reg) || isRegInSet(Uses, Reg));
435 // check whether Reg has already been defined.
436 return isRegInSet(Defs, Reg);
439 bool RegDefsUses::isRegInSet(const BitVector &RegSet, unsigned Reg) const {
440 // Check Reg and all aliased Registers.
441 for (MCRegAliasIterator AI(Reg, &TRI, true); AI.isValid(); ++AI)
442 if (RegSet.test(*AI))
447 bool InspectMemInstr::hasHazard(const MachineInstr &MI) {
448 if (!MI.mayStore() && !MI.mayLoad())
454 OrigSeenLoad = SeenLoad;
455 OrigSeenStore = SeenStore;
456 SeenLoad |= MI.mayLoad();
457 SeenStore |= MI.mayStore();
459 // If MI is an ordered or volatile memory reference, disallow moving
460 // subsequent loads and stores to delay slot.
461 if (MI.hasOrderedMemoryRef() && (OrigSeenLoad || OrigSeenStore)) {
462 ForbidMemInstr = true;
466 return hasHazard_(MI);
469 bool LoadFromStackOrConst::hasHazard_(const MachineInstr &MI) {
473 if (!MI.hasOneMemOperand() || !(*MI.memoperands_begin())->getPseudoValue())
476 if (const PseudoSourceValue *PSV =
477 (*MI.memoperands_begin())->getPseudoValue()) {
478 if (isa<FixedStackPseudoSourceValue>(PSV))
480 return !PSV->isConstant(nullptr) && !PSV->isStack();
486 MemDefsUses::MemDefsUses(const DataLayout &DL, const MachineFrameInfo *MFI_)
487 : InspectMemInstr(false), MFI(MFI_), DL(DL) {}
489 bool MemDefsUses::hasHazard_(const MachineInstr &MI) {
490 bool HasHazard = false;
491 SmallVector<ValueType, 4> Objs;
493 // Check underlying object list.
494 if (getUnderlyingObjects(MI, Objs)) {
495 for (SmallVectorImpl<ValueType>::const_iterator I = Objs.begin();
496 I != Objs.end(); ++I)
497 HasHazard |= updateDefsUses(*I, MI.mayStore());
502 // No underlying objects found.
503 HasHazard = MI.mayStore() && (OrigSeenLoad || OrigSeenStore);
504 HasHazard |= MI.mayLoad() || OrigSeenStore;
506 SeenNoObjLoad |= MI.mayLoad();
507 SeenNoObjStore |= MI.mayStore();
512 bool MemDefsUses::updateDefsUses(ValueType V, bool MayStore) {
514 return !Defs.insert(V).second || Uses.count(V) || SeenNoObjStore ||
518 return Defs.count(V) || SeenNoObjStore;
522 getUnderlyingObjects(const MachineInstr &MI,
523 SmallVectorImpl<ValueType> &Objects) const {
524 if (!MI.hasOneMemOperand() ||
525 (!(*MI.memoperands_begin())->getValue() &&
526 !(*MI.memoperands_begin())->getPseudoValue()))
529 if (const PseudoSourceValue *PSV =
530 (*MI.memoperands_begin())->getPseudoValue()) {
531 if (!PSV->isAliased(MFI))
533 Objects.push_back(PSV);
537 const Value *V = (*MI.memoperands_begin())->getValue();
539 SmallVector<Value *, 4> Objs;
540 GetUnderlyingObjects(const_cast<Value *>(V), Objs, DL);
542 for (SmallVectorImpl<Value *>::iterator I = Objs.begin(), E = Objs.end();
544 if (!isIdentifiedObject(V))
547 Objects.push_back(*I);
553 // Replace Branch with the compact branch instruction.
554 Iter Filler::replaceWithCompactBranch(MachineBasicBlock &MBB, Iter Branch,
555 const DebugLoc &DL) {
556 const MipsSubtarget &STI = MBB.getParent()->getSubtarget<MipsSubtarget>();
557 const MipsInstrInfo *TII = STI.getInstrInfo();
559 unsigned NewOpcode = TII->getEquivalentCompactForm(Branch);
560 Branch = TII->genInstrWithNewOpc(NewOpcode, Branch);
562 std::next(Branch)->eraseFromParent();
566 // For given opcode returns opcode of corresponding instruction with short
568 // For the pseudo TAILCALL*_MM instructions return the short delay slot
569 // form. Unfortunately, TAILCALL<->b16 is denied as b16 has a limited range
570 // that is too short to make use of for tail calls.
571 static int getEquivalentCallShort(int Opcode) {
574 return Mips::BGEZALS_MM;
576 return Mips::BLTZALS_MM;
578 return Mips::JALS_MM;
580 return Mips::JALRS_MM;
581 case Mips::JALR16_MM:
582 return Mips::JALRS16_MM;
583 case Mips::TAILCALL_MM:
584 llvm_unreachable("Attempting to shorten the TAILCALL_MM pseudo!");
585 case Mips::TAILCALLREG:
586 return Mips::JR16_MM;
588 llvm_unreachable("Unexpected call instruction for microMIPS.");
592 /// runOnMachineBasicBlock - Fill in delay slots for the given basic block.
593 /// We assume there is only one delay slot per delayed instruction.
594 bool Filler::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
595 bool Changed = false;
596 const MipsSubtarget &STI = MBB.getParent()->getSubtarget<MipsSubtarget>();
597 bool InMicroMipsMode = STI.inMicroMipsMode();
598 const MipsInstrInfo *TII = STI.getInstrInfo();
600 for (Iter I = MBB.begin(); I != MBB.end(); ++I) {
601 if (!hasUnoccupiedSlot(&*I))
604 // Delay slot filling is disabled at -O0, or in microMIPS32R6.
605 if (!DisableDelaySlotFiller && (TM->getOptLevel() != CodeGenOpt::None) &&
606 !(InMicroMipsMode && STI.hasMips32r6())) {
610 if (MipsCompactBranchPolicy.getValue() != CB_Always ||
611 !TII->getEquivalentCompactForm(I)) {
612 if (searchBackward(MBB, *I)) {
614 } else if (I->isTerminator()) {
615 if (searchSuccBBs(MBB, I)) {
618 } else if (searchForward(MBB, I)) {
624 // Get instruction with delay slot.
625 MachineBasicBlock::instr_iterator DSI = I.getInstrIterator();
627 if (InMicroMipsMode && TII->getInstSizeInBytes(*std::next(DSI)) == 2 &&
629 // If instruction in delay slot is 16b change opcode to
630 // corresponding instruction with short delay slot.
632 // TODO: Implement an instruction mapping table of 16bit opcodes to
633 // 32bit opcodes so that an instruction can be expanded. This would
634 // save 16 bits as a TAILCALL_MM pseudo requires a fullsized nop.
635 // TODO: Permit b16 when branching backwards to the the same function
636 // if it is in range.
637 DSI->setDesc(TII->get(getEquivalentCallShort(DSI->getOpcode())));
645 // For microMIPS if instruction is BEQ or BNE with one ZERO register, then
646 // instead of adding NOP replace this instruction with the corresponding
647 // compact branch instruction, i.e. BEQZC or BNEZC. Additionally
648 // PseudoReturn and PseudoIndirectBranch are expanded to JR_MM, so they can
649 // be replaced with JRC16_MM.
651 // For MIPSR6 attempt to produce the corresponding compact (no delay slot)
652 // form of the CTI. For indirect jumps this will not require inserting a
653 // NOP and for branches will hopefully avoid requiring a NOP.
654 if ((InMicroMipsMode ||
655 (STI.hasMips32r6() && MipsCompactBranchPolicy != CB_Never)) &&
656 TII->getEquivalentCompactForm(I)) {
657 I = replaceWithCompactBranch(MBB, I, I->getDebugLoc());
662 // Bundle the NOP to the instruction with the delay slot.
663 BuildMI(MBB, std::next(I), I->getDebugLoc(), TII->get(Mips::NOP));
664 MIBundleBuilder(MBB, I, std::next(I, 2));
672 template<typename IterTy>
673 bool Filler::searchRange(MachineBasicBlock &MBB, IterTy Begin, IterTy End,
674 RegDefsUses &RegDU, InspectMemInstr& IM, Iter Slot,
675 IterTy &Filler) const {
676 for (IterTy I = Begin; I != End;) {
681 if (CurrI->isDebugValue())
684 if (terminateSearch(*CurrI))
687 assert((!CurrI->isCall() && !CurrI->isReturn() && !CurrI->isBranch()) &&
688 "Cannot put calls, returns or branches in delay slot.");
690 if (CurrI->isKill()) {
691 CurrI->eraseFromParent();
695 if (delayHasHazard(*CurrI, RegDU, IM))
698 const MipsSubtarget &STI = MBB.getParent()->getSubtarget<MipsSubtarget>();
699 if (STI.isTargetNaCl()) {
700 // In NaCl, instructions that must be masked are forbidden in delay slots.
701 // We only check for loads, stores and SP changes. Calls, returns and
702 // branches are not checked because non-NaCl targets never put them in
705 if ((isBasePlusOffsetMemoryAccess(CurrI->getOpcode(), &AddrIdx) &&
706 baseRegNeedsLoadStoreMask(CurrI->getOperand(AddrIdx).getReg())) ||
707 CurrI->modifiesRegister(Mips::SP, STI.getRegisterInfo()))
711 bool InMicroMipsMode = STI.inMicroMipsMode();
712 const MipsInstrInfo *TII = STI.getInstrInfo();
713 unsigned Opcode = (*Slot).getOpcode();
714 // This is complicated by the tail call optimization. For non-PIC code
715 // there is only a 32bit sized unconditional branch which can be assumed
716 // to be able to reach the target. b16 only has a range of +/- 1 KB.
717 // It's entirely possible that the target function is reachable with b16
718 // but we don't have enough information to make that decision.
719 if (InMicroMipsMode && TII->getInstSizeInBytes(*CurrI) == 2 &&
720 (Opcode == Mips::JR || Opcode == Mips::PseudoIndirectBranch ||
721 Opcode == Mips::PseudoReturn || Opcode == Mips::TAILCALL))
731 bool Filler::searchBackward(MachineBasicBlock &MBB, MachineInstr &Slot) const {
732 if (DisableBackwardSearch)
735 auto *Fn = MBB.getParent();
736 RegDefsUses RegDU(*Fn->getSubtarget().getRegisterInfo());
737 MemDefsUses MemDU(Fn->getDataLayout(), &Fn->getFrameInfo());
742 MachineBasicBlock::iterator SlotI = Slot;
743 if (!searchRange(MBB, ++SlotI.getReverse(), MBB.rend(), RegDU, MemDU, Slot,
747 MBB.splice(std::next(SlotI), &MBB, Filler.getReverse());
748 MIBundleBuilder(MBB, SlotI, std::next(SlotI, 2));
753 bool Filler::searchForward(MachineBasicBlock &MBB, Iter Slot) const {
754 // Can handle only calls.
755 if (DisableForwardSearch || !Slot->isCall())
758 RegDefsUses RegDU(*MBB.getParent()->getSubtarget().getRegisterInfo());
762 RegDU.setCallerSaved(*Slot);
764 if (!searchRange(MBB, std::next(Slot), MBB.end(), RegDU, NM, Slot, Filler))
767 MBB.splice(std::next(Slot), &MBB, Filler);
768 MIBundleBuilder(MBB, Slot, std::next(Slot, 2));
773 bool Filler::searchSuccBBs(MachineBasicBlock &MBB, Iter Slot) const {
774 if (DisableSuccBBSearch)
777 MachineBasicBlock *SuccBB = selectSuccBB(MBB);
782 RegDefsUses RegDU(*MBB.getParent()->getSubtarget().getRegisterInfo());
783 bool HasMultipleSuccs = false;
785 std::unique_ptr<InspectMemInstr> IM;
787 auto *Fn = MBB.getParent();
789 // Iterate over SuccBB's predecessor list.
790 for (MachineBasicBlock::pred_iterator PI = SuccBB->pred_begin(),
791 PE = SuccBB->pred_end(); PI != PE; ++PI)
792 if (!examinePred(**PI, *SuccBB, RegDU, HasMultipleSuccs, BrMap))
795 // Do not allow moving instructions which have unallocatable register operands
796 // across basic block boundaries.
797 RegDU.setUnallocatableRegs(*Fn);
799 // Only allow moving loads from stack or constants if any of the SuccBB's
800 // predecessors have multiple successors.
801 if (HasMultipleSuccs) {
802 IM.reset(new LoadFromStackOrConst());
804 const MachineFrameInfo &MFI = Fn->getFrameInfo();
805 IM.reset(new MemDefsUses(Fn->getDataLayout(), &MFI));
808 if (!searchRange(MBB, SuccBB->begin(), SuccBB->end(), RegDU, *IM, Slot,
812 insertDelayFiller(Filler, BrMap);
813 addLiveInRegs(Filler, *SuccBB);
814 Filler->eraseFromParent();
819 MachineBasicBlock *Filler::selectSuccBB(MachineBasicBlock &B) const {
823 // Select the successor with the larget edge weight.
824 auto &Prob = getAnalysis<MachineBranchProbabilityInfo>();
825 MachineBasicBlock *S = *std::max_element(
826 B.succ_begin(), B.succ_end(),
827 [&](const MachineBasicBlock *Dst0, const MachineBasicBlock *Dst1) {
828 return Prob.getEdgeProbability(&B, Dst0) <
829 Prob.getEdgeProbability(&B, Dst1);
831 return S->isEHPad() ? nullptr : S;
834 std::pair<MipsInstrInfo::BranchType, MachineInstr *>
835 Filler::getBranch(MachineBasicBlock &MBB, const MachineBasicBlock &Dst) const {
836 const MipsInstrInfo *TII =
837 MBB.getParent()->getSubtarget<MipsSubtarget>().getInstrInfo();
838 MachineBasicBlock *TrueBB = nullptr, *FalseBB = nullptr;
839 SmallVector<MachineInstr*, 2> BranchInstrs;
840 SmallVector<MachineOperand, 2> Cond;
842 MipsInstrInfo::BranchType R =
843 TII->analyzeBranch(MBB, TrueBB, FalseBB, Cond, false, BranchInstrs);
845 if ((R == MipsInstrInfo::BT_None) || (R == MipsInstrInfo::BT_NoBranch))
846 return std::make_pair(R, nullptr);
848 if (R != MipsInstrInfo::BT_CondUncond) {
849 if (!hasUnoccupiedSlot(BranchInstrs[0]))
850 return std::make_pair(MipsInstrInfo::BT_None, nullptr);
852 assert(((R != MipsInstrInfo::BT_Uncond) || (TrueBB == &Dst)));
854 return std::make_pair(R, BranchInstrs[0]);
857 assert((TrueBB == &Dst) || (FalseBB == &Dst));
859 // Examine the conditional branch. See if its slot is occupied.
860 if (hasUnoccupiedSlot(BranchInstrs[0]))
861 return std::make_pair(MipsInstrInfo::BT_Cond, BranchInstrs[0]);
863 // If that fails, try the unconditional branch.
864 if (hasUnoccupiedSlot(BranchInstrs[1]) && (FalseBB == &Dst))
865 return std::make_pair(MipsInstrInfo::BT_Uncond, BranchInstrs[1]);
867 return std::make_pair(MipsInstrInfo::BT_None, nullptr);
870 bool Filler::examinePred(MachineBasicBlock &Pred, const MachineBasicBlock &Succ,
871 RegDefsUses &RegDU, bool &HasMultipleSuccs,
872 BB2BrMap &BrMap) const {
873 std::pair<MipsInstrInfo::BranchType, MachineInstr *> P =
874 getBranch(Pred, Succ);
876 // Return if either getBranch wasn't able to analyze the branches or there
877 // were no branches with unoccupied slots.
878 if (P.first == MipsInstrInfo::BT_None)
881 if ((P.first != MipsInstrInfo::BT_Uncond) &&
882 (P.first != MipsInstrInfo::BT_NoBranch)) {
883 HasMultipleSuccs = true;
884 RegDU.addLiveOut(Pred, Succ);
887 BrMap[&Pred] = P.second;
891 bool Filler::delayHasHazard(const MachineInstr &Candidate, RegDefsUses &RegDU,
892 InspectMemInstr &IM) const {
893 assert(!Candidate.isKill() &&
894 "KILL instructions should have been eliminated at this point.");
896 bool HasHazard = Candidate.isImplicitDef();
898 HasHazard |= IM.hasHazard(Candidate);
899 HasHazard |= RegDU.update(Candidate, 0, Candidate.getNumOperands());
904 bool Filler::terminateSearch(const MachineInstr &Candidate) const {
905 return (Candidate.isTerminator() || Candidate.isCall() ||
906 Candidate.isPosition() || Candidate.isInlineAsm() ||
907 Candidate.hasUnmodeledSideEffects());
910 /// createMipsDelaySlotFillerPass - Returns a pass that fills in delay
911 /// slots in Mips MachineFunctions
912 FunctionPass *llvm::createMipsDelaySlotFillerPass() { return new Filler(); }