1 //===-------- InlineSpiller.cpp - Insert spills and restores inline -------===//
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 // The inline spiller modifies the machine function directly instead of
11 // inserting spills and restores in VirtRegMap.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "regalloc"
17 #include "LiveRangeEdit.h"
18 #include "VirtRegMap.h"
19 #include "llvm/Analysis/AliasAnalysis.h"
20 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
21 #include "llvm/CodeGen/LiveStackAnalysis.h"
22 #include "llvm/CodeGen/MachineDominators.h"
23 #include "llvm/CodeGen/MachineFrameInfo.h"
24 #include "llvm/CodeGen/MachineFunction.h"
25 #include "llvm/CodeGen/MachineLoopInfo.h"
26 #include "llvm/CodeGen/MachineRegisterInfo.h"
27 #include "llvm/Target/TargetMachine.h"
28 #include "llvm/Target/TargetInstrInfo.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/raw_ostream.h"
35 class InlineSpiller : public Spiller {
36 MachineFunctionPass &Pass;
41 MachineDominatorTree &MDT;
42 MachineLoopInfo &Loops;
44 MachineFrameInfo &MFI;
45 MachineRegisterInfo &MRI;
46 const TargetInstrInfo &TII;
47 const TargetRegisterInfo &TRI;
49 // Variables that are valid during spill(), but used by multiple methods.
51 const TargetRegisterClass *RC;
55 // All registers to spill to StackSlot, including the main register.
56 SmallVector<unsigned, 8> RegsToSpill;
58 // All COPY instructions to/from snippets.
59 // They are ignored since both operands refer to the same stack slot.
60 SmallPtrSet<MachineInstr*, 8> SnippetCopies;
62 // Values that failed to remat at some point.
63 SmallPtrSet<VNInfo*, 8> UsedValues;
65 // Information about a value that was defined by a copy from a sibling
68 // True when all reaching defs were reloads: No spill is necessary.
69 bool AllDefsAreReloads;
71 // The preferred register to spill.
74 // The value of SpillReg that should be spilled.
77 // A defining instruction that is not a sibling copy or a reload, or NULL.
78 // This can be used as a template for rematerialization.
81 SibValueInfo(unsigned Reg, VNInfo *VNI)
82 : AllDefsAreReloads(false), SpillReg(Reg), SpillVNI(VNI), DefMI(0) {}
85 // Values in RegsToSpill defined by sibling copies.
86 typedef DenseMap<VNInfo*, SibValueInfo> SibValueMap;
87 SibValueMap SibValues;
89 // Dead defs generated during spilling.
90 SmallVector<MachineInstr*, 8> DeadDefs;
95 InlineSpiller(MachineFunctionPass &pass,
100 LIS(pass.getAnalysis<LiveIntervals>()),
101 LSS(pass.getAnalysis<LiveStacks>()),
102 AA(&pass.getAnalysis<AliasAnalysis>()),
103 MDT(pass.getAnalysis<MachineDominatorTree>()),
104 Loops(pass.getAnalysis<MachineLoopInfo>()),
106 MFI(*mf.getFrameInfo()),
107 MRI(mf.getRegInfo()),
108 TII(*mf.getTarget().getInstrInfo()),
109 TRI(*mf.getTarget().getRegisterInfo()) {}
111 void spill(LiveRangeEdit &);
114 bool isSnippet(const LiveInterval &SnipLI);
115 void collectRegsToSpill();
117 bool isRegToSpill(unsigned Reg) {
118 return std::find(RegsToSpill.begin(),
119 RegsToSpill.end(), Reg) != RegsToSpill.end();
122 bool isSibling(unsigned Reg);
123 void traceSiblingValue(unsigned, VNInfo*, VNInfo*);
124 void analyzeSiblingValues();
126 bool hoistSpill(LiveInterval &SpillLI, MachineInstr *CopyMI);
127 void eliminateRedundantSpills(LiveInterval &LI, VNInfo *VNI);
129 bool reMaterializeFor(MachineBasicBlock::iterator MI);
130 void reMaterializeAll();
132 bool coalesceStackAccess(MachineInstr *MI, unsigned Reg);
133 bool foldMemoryOperand(MachineBasicBlock::iterator MI,
134 const SmallVectorImpl<unsigned> &Ops,
135 MachineInstr *LoadMI = 0);
136 void insertReload(LiveInterval &NewLI, MachineBasicBlock::iterator MI);
137 void insertSpill(LiveInterval &NewLI, const LiveInterval &OldLI,
138 MachineBasicBlock::iterator MI);
140 void spillAroundUses(unsigned Reg);
145 Spiller *createInlineSpiller(MachineFunctionPass &pass,
148 return new InlineSpiller(pass, mf, vrm);
152 //===----------------------------------------------------------------------===//
154 //===----------------------------------------------------------------------===//
156 // When spilling a virtual register, we also spill any snippets it is connected
157 // to. The snippets are small live ranges that only have a single real use,
158 // leftovers from live range splitting. Spilling them enables memory operand
159 // folding or tightens the live range around the single use.
161 // This minimizes register pressure and maximizes the store-to-load distance for
162 // spill slots which can be important in tight loops.
164 /// isFullCopyOf - If MI is a COPY to or from Reg, return the other register,
165 /// otherwise return 0.
166 static unsigned isFullCopyOf(const MachineInstr *MI, unsigned Reg) {
169 if (MI->getOperand(0).getSubReg() != 0)
171 if (MI->getOperand(1).getSubReg() != 0)
173 if (MI->getOperand(0).getReg() == Reg)
174 return MI->getOperand(1).getReg();
175 if (MI->getOperand(1).getReg() == Reg)
176 return MI->getOperand(0).getReg();
180 /// isSnippet - Identify if a live interval is a snippet that should be spilled.
181 /// It is assumed that SnipLI is a virtual register with the same original as
183 bool InlineSpiller::isSnippet(const LiveInterval &SnipLI) {
184 unsigned Reg = Edit->getReg();
186 // A snippet is a tiny live range with only a single instruction using it
187 // besides copies to/from Reg or spills/fills. We accept:
189 // %snip = COPY %Reg / FILL fi#
191 // %Reg = COPY %snip / SPILL %snip, fi#
193 if (SnipLI.getNumValNums() > 2 || !LIS.intervalIsInOneMBB(SnipLI))
196 MachineInstr *UseMI = 0;
198 // Check that all uses satisfy our criteria.
199 for (MachineRegisterInfo::reg_nodbg_iterator
200 RI = MRI.reg_nodbg_begin(SnipLI.reg);
201 MachineInstr *MI = RI.skipInstruction();) {
203 // Allow copies to/from Reg.
204 if (isFullCopyOf(MI, Reg))
207 // Allow stack slot loads.
209 if (SnipLI.reg == TII.isLoadFromStackSlot(MI, FI) && FI == StackSlot)
212 // Allow stack slot stores.
213 if (SnipLI.reg == TII.isStoreToStackSlot(MI, FI) && FI == StackSlot)
216 // Allow a single additional instruction.
217 if (UseMI && MI != UseMI)
224 /// collectRegsToSpill - Collect live range snippets that only have a single
226 void InlineSpiller::collectRegsToSpill() {
227 unsigned Reg = Edit->getReg();
229 // Main register always spills.
230 RegsToSpill.assign(1, Reg);
231 SnippetCopies.clear();
233 // Snippets all have the same original, so there can't be any for an original
238 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(Reg);
239 MachineInstr *MI = RI.skipInstruction();) {
240 unsigned SnipReg = isFullCopyOf(MI, Reg);
241 if (!isSibling(SnipReg))
243 LiveInterval &SnipLI = LIS.getInterval(SnipReg);
244 if (!isSnippet(SnipLI))
246 SnippetCopies.insert(MI);
247 if (!isRegToSpill(SnipReg))
248 RegsToSpill.push_back(SnipReg);
250 DEBUG(dbgs() << "\talso spill snippet " << SnipLI << '\n');
255 //===----------------------------------------------------------------------===//
257 //===----------------------------------------------------------------------===//
259 // After live range splitting, some values to be spilled may be defined by
260 // copies from sibling registers. We trace the sibling copies back to the
261 // original value if it still exists. We need it for rematerialization.
263 // Even when the value can't be rematerialized, we still want to determine if
264 // the value has already been spilled, or we may want to hoist the spill from a
267 bool InlineSpiller::isSibling(unsigned Reg) {
268 return TargetRegisterInfo::isVirtualRegister(Reg) &&
269 VRM.getOriginal(Reg) == Original;
272 /// traceSiblingValue - Trace a value that is about to be spilled back to the
273 /// real defining instructions by looking through sibling copies. Always stay
274 /// within the range of OrigVNI so the registers are known to carry the same
277 /// Determine if the value is defined by all reloads, so spilling isn't
278 /// necessary - the value is already in the stack slot.
280 /// Find a defining instruction that may be a candidate for rematerialization.
282 void InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI,
284 DEBUG(dbgs() << "Tracing value " << PrintReg(UseReg) << ':'
285 << UseVNI->id << '@' << UseVNI->def << '\n');
286 SmallPtrSet<VNInfo*, 8> Visited;
287 SmallVector<std::pair<unsigned, VNInfo*>, 8> WorkList;
288 WorkList.push_back(std::make_pair(UseReg, UseVNI));
290 // Best spill candidate seen so far. This must dominate UseVNI.
291 SibValueInfo SVI(UseReg, UseVNI);
292 MachineBasicBlock *UseMBB = LIS.getMBBFromIndex(UseVNI->def);
293 unsigned SpillDepth = Loops.getLoopDepth(UseMBB);
294 bool SeenOrigPHI = false; // Original PHI met.
299 tie(Reg, VNI) = WorkList.pop_back_val();
300 if (!Visited.insert(VNI))
303 // Is this value a better spill candidate?
304 if (!isRegToSpill(Reg)) {
305 MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
306 if (MBB != UseMBB && MDT.dominates(MBB, UseMBB)) {
307 // This is a valid spill location dominating UseVNI.
308 // Prefer to spill at a smaller loop depth.
309 unsigned Depth = Loops.getLoopDepth(MBB);
310 if (Depth < SpillDepth) {
311 DEBUG(dbgs() << " spill depth " << Depth << ": " << PrintReg(Reg)
312 << ':' << VNI->id << '@' << VNI->def << '\n');
320 // Trace through PHI-defs created by live range splitting.
321 if (VNI->isPHIDef()) {
322 if (VNI->def == OrigVNI->def) {
323 DEBUG(dbgs() << " orig phi value " << PrintReg(Reg) << ':'
324 << VNI->id << '@' << VNI->def << '\n');
328 // Get values live-out of predecessors.
329 LiveInterval &LI = LIS.getInterval(Reg);
330 MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
331 for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
332 PE = MBB->pred_end(); PI != PE; ++PI) {
333 VNInfo *PVNI = LI.getVNInfoAt(LIS.getMBBEndIdx(*PI).getPrevSlot());
335 WorkList.push_back(std::make_pair(Reg, PVNI));
340 MachineInstr *MI = LIS.getInstructionFromIndex(VNI->def);
341 assert(MI && "Missing def");
343 // Trace through sibling copies.
344 if (unsigned SrcReg = isFullCopyOf(MI, Reg)) {
345 if (isSibling(SrcReg)) {
346 LiveInterval &SrcLI = LIS.getInterval(SrcReg);
347 VNInfo *SrcVNI = SrcLI.getVNInfoAt(VNI->def.getUseIndex());
348 assert(SrcVNI && "Copy from non-existing value");
349 DEBUG(dbgs() << " copy of " << PrintReg(SrcReg) << ':'
350 << SrcVNI->id << '@' << SrcVNI->def << '\n');
351 WorkList.push_back(std::make_pair(SrcReg, SrcVNI));
356 // Track reachable reloads.
358 if (Reg == TII.isLoadFromStackSlot(MI, FI) && FI == StackSlot) {
359 DEBUG(dbgs() << " reload " << PrintReg(Reg) << ':'
360 << VNI->id << "@" << VNI->def << '\n');
361 SVI.AllDefsAreReloads = true;
365 // We have an 'original' def. Don't record trivial cases.
367 DEBUG(dbgs() << "Not a sibling copy.\n");
371 // Potential remat candidate.
372 DEBUG(dbgs() << " def " << PrintReg(Reg) << ':'
373 << VNI->id << '@' << VNI->def << '\t' << *MI);
375 } while (!WorkList.empty());
377 if (SeenOrigPHI || SVI.DefMI)
378 SVI.AllDefsAreReloads = false;
381 if (SVI.AllDefsAreReloads)
382 dbgs() << "All defs are reloads.\n";
384 dbgs() << "Prefer to spill " << PrintReg(SVI.SpillReg) << ':'
385 << SVI.SpillVNI->id << '@' << SVI.SpillVNI->def << '\n';
387 SibValues.insert(std::make_pair(UseVNI, SVI));
390 /// analyzeSiblingValues - Trace values defined by sibling copies back to
391 /// something that isn't a sibling copy.
392 void InlineSpiller::analyzeSiblingValues() {
395 // No siblings at all?
396 if (Edit->getReg() == Original)
399 LiveInterval &OrigLI = LIS.getInterval(Original);
400 for (unsigned i = 0, e = RegsToSpill.size(); i != e; ++i) {
401 unsigned Reg = RegsToSpill[i];
402 LiveInterval &LI = LIS.getInterval(Reg);
403 for (LiveInterval::const_vni_iterator VI = LI.vni_begin(),
404 VE = LI.vni_end(); VI != VE; ++VI) {
406 if (VNI->isUnused() || !(VNI->isPHIDef() || VNI->getCopy()))
408 VNInfo *OrigVNI = OrigLI.getVNInfoAt(VNI->def);
409 if (OrigVNI->def != VNI->def)
410 traceSiblingValue(Reg, VNI, OrigVNI);
415 /// hoistSpill - Given a sibling copy that defines a value to be spilled, insert
416 /// a spill at a better location.
417 bool InlineSpiller::hoistSpill(LiveInterval &SpillLI, MachineInstr *CopyMI) {
418 SlotIndex Idx = LIS.getInstructionIndex(CopyMI);
419 VNInfo *VNI = SpillLI.getVNInfoAt(Idx.getDefIndex());
420 assert(VNI && VNI->def == Idx.getDefIndex() && "Not defined by copy");
421 SibValueMap::const_iterator I = SibValues.find(VNI);
422 if (I == SibValues.end())
425 const SibValueInfo &SVI = I->second;
427 // Let the normal folding code deal with the boring case.
428 if (!SVI.AllDefsAreReloads && SVI.SpillVNI == VNI)
431 // Conservatively extend the stack slot range to the range of the original
432 // value. We may be able to do better with stack slot coloring by being more
434 LiveInterval &StackInt = LSS.getInterval(StackSlot);
435 LiveInterval &OrigLI = LIS.getInterval(Original);
436 VNInfo *OrigVNI = OrigLI.getVNInfoAt(Idx);
437 StackInt.MergeValueInAsValue(OrigLI, OrigVNI, StackInt.getValNumInfo(0));
438 DEBUG(dbgs() << "\tmerged orig valno " << OrigVNI->id << ": "
439 << StackInt << '\n');
441 // Already spilled everywhere.
442 if (SVI.AllDefsAreReloads)
445 // We are going to spill SVI.SpillVNI immediately after its def, so clear out
446 // any later spills of the same value.
447 eliminateRedundantSpills(LIS.getInterval(SVI.SpillReg), SVI.SpillVNI);
449 MachineBasicBlock *MBB = LIS.getMBBFromIndex(SVI.SpillVNI->def);
450 MachineBasicBlock::iterator MII;
451 if (SVI.SpillVNI->isPHIDef())
452 MII = MBB->SkipPHIsAndLabels(MBB->begin());
454 MII = LIS.getInstructionFromIndex(SVI.SpillVNI->def);
457 // Insert spill without kill flag immediately after def.
458 TII.storeRegToStackSlot(*MBB, MII, SVI.SpillReg, false, StackSlot, RC, &TRI);
459 --MII; // Point to store instruction.
460 LIS.InsertMachineInstrInMaps(MII);
461 VRM.addSpillSlotUse(StackSlot, MII);
462 DEBUG(dbgs() << "\thoisted: " << SVI.SpillVNI->def << '\t' << *MII);
466 /// eliminateRedundantSpills - SLI:VNI is known to be on the stack. Remove any
467 /// redundant spills of this value in SLI.reg and sibling copies.
468 void InlineSpiller::eliminateRedundantSpills(LiveInterval &SLI, VNInfo *VNI) {
469 SmallVector<std::pair<LiveInterval*, VNInfo*>, 8> WorkList;
470 WorkList.push_back(std::make_pair(&SLI, VNI));
471 LiveInterval &StackInt = LSS.getInterval(StackSlot);
475 tie(LI, VNI) = WorkList.pop_back_val();
476 unsigned Reg = LI->reg;
477 DEBUG(dbgs() << "Checking redundant spills for " << PrintReg(Reg) << ':'
478 << VNI->id << '@' << VNI->def << '\n');
480 // Regs to spill are taken care of.
481 if (isRegToSpill(Reg))
484 // Add all of VNI's live range to StackInt.
485 StackInt.MergeValueInAsValue(*LI, VNI, StackInt.getValNumInfo(0));
486 DEBUG(dbgs() << "Merged to stack int: " << StackInt << '\n');
488 // Find all spills and copies of VNI.
489 for (MachineRegisterInfo::use_nodbg_iterator UI = MRI.use_nodbg_begin(Reg);
490 MachineInstr *MI = UI.skipInstruction();) {
491 if (!MI->isCopy() && !MI->getDesc().mayStore())
493 SlotIndex Idx = LIS.getInstructionIndex(MI);
494 if (LI->getVNInfoAt(Idx) != VNI)
497 // Follow sibling copies down the dominator tree.
498 if (unsigned DstReg = isFullCopyOf(MI, Reg)) {
499 if (isSibling(DstReg)) {
500 LiveInterval &DstLI = LIS.getInterval(DstReg);
501 VNInfo *DstVNI = DstLI.getVNInfoAt(Idx.getDefIndex());
502 assert(DstVNI && "Missing defined value");
503 assert(DstVNI->def == Idx.getDefIndex() && "Wrong copy def slot");
504 WorkList.push_back(std::make_pair(&DstLI, DstVNI));
511 if (Reg == TII.isStoreToStackSlot(MI, FI) && FI == StackSlot) {
512 DEBUG(dbgs() << "Redundant spill " << Idx << '\t' << *MI);
513 // eliminateDeadDefs won't normally remove stores, so switch opcode.
514 MI->setDesc(TII.get(TargetOpcode::KILL));
515 DeadDefs.push_back(MI);
518 } while (!WorkList.empty());
521 /// reMaterializeFor - Attempt to rematerialize before MI instead of reloading.
522 bool InlineSpiller::reMaterializeFor(MachineBasicBlock::iterator MI) {
523 SlotIndex UseIdx = LIS.getInstructionIndex(MI).getUseIndex();
524 VNInfo *OrigVNI = Edit->getParent().getVNInfoAt(UseIdx);
527 DEBUG(dbgs() << "\tadding <undef> flags: ");
528 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
529 MachineOperand &MO = MI->getOperand(i);
530 if (MO.isReg() && MO.isUse() && MO.getReg() == Edit->getReg())
533 DEBUG(dbgs() << UseIdx << '\t' << *MI);
537 // FIXME: Properly remat for snippets as well.
538 if (SnippetCopies.count(MI)) {
539 UsedValues.insert(OrigVNI);
543 LiveRangeEdit::Remat RM(OrigVNI);
544 if (!Edit->canRematerializeAt(RM, UseIdx, false, LIS)) {
545 UsedValues.insert(OrigVNI);
546 DEBUG(dbgs() << "\tcannot remat for " << UseIdx << '\t' << *MI);
550 // If the instruction also writes Edit->getReg(), it had better not require
551 // the same register for uses and defs.
553 SmallVector<unsigned, 8> Ops;
554 tie(Reads, Writes) = MI->readsWritesVirtualRegister(Edit->getReg(), &Ops);
556 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
557 MachineOperand &MO = MI->getOperand(Ops[i]);
558 if (MO.isUse() ? MI->isRegTiedToDefOperand(Ops[i]) : MO.getSubReg()) {
559 UsedValues.insert(OrigVNI);
560 DEBUG(dbgs() << "\tcannot remat tied reg: " << UseIdx << '\t' << *MI);
566 // Before rematerializing into a register for a single instruction, try to
567 // fold a load into the instruction. That avoids allocating a new register.
568 if (RM.OrigMI->getDesc().canFoldAsLoad() &&
569 foldMemoryOperand(MI, Ops, RM.OrigMI)) {
570 Edit->markRematerialized(RM.ParentVNI);
574 // Alocate a new register for the remat.
575 LiveInterval &NewLI = Edit->create(LIS, VRM);
576 NewLI.markNotSpillable();
578 // Rematting for a copy: Set allocation hint to be the destination register.
580 MRI.setRegAllocationHint(NewLI.reg, 0, MI->getOperand(0).getReg());
582 // Finally we can rematerialize OrigMI before MI.
583 SlotIndex DefIdx = Edit->rematerializeAt(*MI->getParent(), MI, NewLI.reg, RM,
585 DEBUG(dbgs() << "\tremat: " << DefIdx << '\t'
586 << *LIS.getInstructionFromIndex(DefIdx));
589 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
590 MachineOperand &MO = MI->getOperand(Ops[i]);
591 if (MO.isReg() && MO.isUse() && MO.getReg() == Edit->getReg()) {
592 MO.setReg(NewLI.reg);
596 DEBUG(dbgs() << "\t " << UseIdx << '\t' << *MI);
598 VNInfo *DefVNI = NewLI.getNextValue(DefIdx, 0, LIS.getVNInfoAllocator());
599 NewLI.addRange(LiveRange(DefIdx, UseIdx.getDefIndex(), DefVNI));
600 DEBUG(dbgs() << "\tinterval: " << NewLI << '\n');
604 /// reMaterializeAll - Try to rematerialize as many uses as possible,
605 /// and trim the live ranges after.
606 void InlineSpiller::reMaterializeAll() {
607 // Do a quick scan of the interval values to find if any are remattable.
608 if (!Edit->anyRematerializable(LIS, TII, AA))
613 // Try to remat before all uses of Edit->getReg().
614 bool anyRemat = false;
615 for (MachineRegisterInfo::use_nodbg_iterator
616 RI = MRI.use_nodbg_begin(Edit->getReg());
617 MachineInstr *MI = RI.skipInstruction();)
618 anyRemat |= reMaterializeFor(MI);
623 // Remove any values that were completely rematted.
624 bool anyRemoved = false;
625 for (LiveInterval::vni_iterator I = Edit->getParent().vni_begin(),
626 E = Edit->getParent().vni_end(); I != E; ++I) {
628 if (VNI->hasPHIKill() || !Edit->didRematerialize(VNI) ||
629 UsedValues.count(VNI))
631 MachineInstr *DefMI = LIS.getInstructionFromIndex(VNI->def);
632 DEBUG(dbgs() << "\tremoving dead def: " << VNI->def << '\t' << *DefMI);
633 LIS.RemoveMachineInstrFromMaps(DefMI);
634 VRM.RemoveMachineInstrFromMaps(DefMI);
635 DefMI->eraseFromParent();
636 VNI->def = SlotIndex();
643 // Removing values may cause debug uses where parent is not live.
644 for (MachineRegisterInfo::use_iterator RI = MRI.use_begin(Edit->getReg());
645 MachineInstr *MI = RI.skipInstruction();) {
646 if (!MI->isDebugValue())
648 // Try to preserve the debug value if parent is live immediately after it.
649 MachineBasicBlock::iterator NextMI = MI;
651 if (NextMI != MI->getParent()->end() && !LIS.isNotInMIMap(NextMI)) {
652 SlotIndex Idx = LIS.getInstructionIndex(NextMI);
653 VNInfo *VNI = Edit->getParent().getVNInfoAt(Idx);
654 if (VNI && (VNI->hasPHIKill() || UsedValues.count(VNI)))
657 DEBUG(dbgs() << "Removing debug info due to remat:" << "\t" << *MI);
658 MI->eraseFromParent();
662 /// If MI is a load or store of StackSlot, it can be removed.
663 bool InlineSpiller::coalesceStackAccess(MachineInstr *MI, unsigned Reg) {
666 if (!(InstrReg = TII.isLoadFromStackSlot(MI, FI)) &&
667 !(InstrReg = TII.isStoreToStackSlot(MI, FI)))
670 // We have a stack access. Is it the right register and slot?
671 if (InstrReg != Reg || FI != StackSlot)
674 DEBUG(dbgs() << "Coalescing stack access: " << *MI);
675 LIS.RemoveMachineInstrFromMaps(MI);
676 MI->eraseFromParent();
680 /// foldMemoryOperand - Try folding stack slot references in Ops into MI.
681 /// @param MI Instruction using or defining the current register.
682 /// @param Ops Operand indices from readsWritesVirtualRegister().
683 /// @param LoadMI Load instruction to use instead of stack slot when non-null.
684 /// @return True on success, and MI will be erased.
685 bool InlineSpiller::foldMemoryOperand(MachineBasicBlock::iterator MI,
686 const SmallVectorImpl<unsigned> &Ops,
687 MachineInstr *LoadMI) {
688 // TargetInstrInfo::foldMemoryOperand only expects explicit, non-tied
690 SmallVector<unsigned, 8> FoldOps;
691 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
692 unsigned Idx = Ops[i];
693 MachineOperand &MO = MI->getOperand(Idx);
696 // FIXME: Teach targets to deal with subregs.
699 // We cannot fold a load instruction into a def.
700 if (LoadMI && MO.isDef())
702 // Tied use operands should not be passed to foldMemoryOperand.
703 if (!MI->isRegTiedToDefOperand(Idx))
704 FoldOps.push_back(Idx);
707 MachineInstr *FoldMI =
708 LoadMI ? TII.foldMemoryOperand(MI, FoldOps, LoadMI)
709 : TII.foldMemoryOperand(MI, FoldOps, StackSlot);
712 LIS.ReplaceMachineInstrInMaps(MI, FoldMI);
714 VRM.addSpillSlotUse(StackSlot, FoldMI);
715 MI->eraseFromParent();
716 DEBUG(dbgs() << "\tfolded: " << *FoldMI);
720 /// insertReload - Insert a reload of NewLI.reg before MI.
721 void InlineSpiller::insertReload(LiveInterval &NewLI,
722 MachineBasicBlock::iterator MI) {
723 MachineBasicBlock &MBB = *MI->getParent();
724 SlotIndex Idx = LIS.getInstructionIndex(MI).getDefIndex();
725 TII.loadRegFromStackSlot(MBB, MI, NewLI.reg, StackSlot, RC, &TRI);
726 --MI; // Point to load instruction.
727 SlotIndex LoadIdx = LIS.InsertMachineInstrInMaps(MI).getDefIndex();
728 VRM.addSpillSlotUse(StackSlot, MI);
729 DEBUG(dbgs() << "\treload: " << LoadIdx << '\t' << *MI);
730 VNInfo *LoadVNI = NewLI.getNextValue(LoadIdx, 0,
731 LIS.getVNInfoAllocator());
732 NewLI.addRange(LiveRange(LoadIdx, Idx, LoadVNI));
735 /// insertSpill - Insert a spill of NewLI.reg after MI.
736 void InlineSpiller::insertSpill(LiveInterval &NewLI, const LiveInterval &OldLI,
737 MachineBasicBlock::iterator MI) {
738 MachineBasicBlock &MBB = *MI->getParent();
740 // Get the defined value. It could be an early clobber so keep the def index.
741 SlotIndex Idx = LIS.getInstructionIndex(MI).getDefIndex();
742 VNInfo *VNI = OldLI.getVNInfoAt(Idx);
743 assert(VNI && VNI->def.getDefIndex() == Idx && "Inconsistent VNInfo");
746 TII.storeRegToStackSlot(MBB, ++MI, NewLI.reg, true, StackSlot, RC, &TRI);
747 --MI; // Point to store instruction.
748 SlotIndex StoreIdx = LIS.InsertMachineInstrInMaps(MI).getDefIndex();
749 VRM.addSpillSlotUse(StackSlot, MI);
750 DEBUG(dbgs() << "\tspilled: " << StoreIdx << '\t' << *MI);
751 VNInfo *StoreVNI = NewLI.getNextValue(Idx, 0, LIS.getVNInfoAllocator());
752 NewLI.addRange(LiveRange(Idx, StoreIdx, StoreVNI));
755 /// spillAroundUses - insert spill code around each use of Reg.
756 void InlineSpiller::spillAroundUses(unsigned Reg) {
757 LiveInterval &OldLI = LIS.getInterval(Reg);
759 // Iterate over instructions using Reg.
760 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(Reg);
761 MachineInstr *MI = RI.skipInstruction();) {
763 // Debug values are not allowed to affect codegen.
764 if (MI->isDebugValue()) {
765 // Modify DBG_VALUE now that the value is in a spill slot.
766 uint64_t Offset = MI->getOperand(1).getImm();
767 const MDNode *MDPtr = MI->getOperand(2).getMetadata();
768 DebugLoc DL = MI->getDebugLoc();
769 if (MachineInstr *NewDV = TII.emitFrameIndexDebugValue(MF, StackSlot,
770 Offset, MDPtr, DL)) {
771 DEBUG(dbgs() << "Modifying debug info due to spill:" << "\t" << *MI);
772 MachineBasicBlock *MBB = MI->getParent();
773 MBB->insert(MBB->erase(MI), NewDV);
775 DEBUG(dbgs() << "Removing debug info due to spill:" << "\t" << *MI);
776 MI->eraseFromParent();
781 // Ignore copies to/from snippets. We'll delete them.
782 if (SnippetCopies.count(MI))
785 // Stack slot accesses may coalesce away.
786 if (coalesceStackAccess(MI, Reg))
789 // Analyze instruction.
791 SmallVector<unsigned, 8> Ops;
792 tie(Reads, Writes) = MI->readsWritesVirtualRegister(Reg, &Ops);
794 // Check for a sibling copy.
795 unsigned SibReg = isFullCopyOf(MI, Reg);
796 if (!isSibling(SibReg))
799 // Hoist the spill of a sib-reg copy.
800 if (SibReg && Writes && !Reads && hoistSpill(OldLI, MI)) {
801 // This COPY is now dead, the value is already in the stack slot.
802 MI->getOperand(0).setIsDead();
803 DeadDefs.push_back(MI);
807 // Attempt to fold memory ops.
808 if (foldMemoryOperand(MI, Ops))
811 // Allocate interval around instruction.
812 // FIXME: Infer regclass from instruction alone.
813 LiveInterval &NewLI = Edit->create(LIS, VRM);
814 NewLI.markNotSpillable();
817 insertReload(NewLI, MI);
819 // Rewrite instruction operands.
820 bool hasLiveDef = false;
821 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
822 MachineOperand &MO = MI->getOperand(Ops[i]);
823 MO.setReg(NewLI.reg);
825 if (!MI->isRegTiedToDefOperand(Ops[i]))
833 // FIXME: Use a second vreg if instruction has no tied ops.
834 if (Writes && hasLiveDef)
835 insertSpill(NewLI, OldLI, MI);
837 DEBUG(dbgs() << "\tinterval: " << NewLI << '\n');
841 void InlineSpiller::spill(LiveRangeEdit &edit) {
843 assert(!TargetRegisterInfo::isStackSlot(edit.getReg())
844 && "Trying to spill a stack slot.");
845 // Share a stack slot among all descendants of Original.
846 Original = VRM.getOriginal(edit.getReg());
847 StackSlot = VRM.getStackSlot(Original);
849 DEBUG(dbgs() << "Inline spilling "
850 << MRI.getRegClass(edit.getReg())->getName()
851 << ':' << edit.getParent() << "\nFrom original "
852 << LIS.getInterval(Original) << '\n');
853 assert(edit.getParent().isSpillable() &&
854 "Attempting to spill already spilled value.");
855 assert(DeadDefs.empty() && "Previous spill didn't remove dead defs");
857 collectRegsToSpill();
858 analyzeSiblingValues();
861 // Remat may handle everything.
862 if (Edit->getParent().empty())
865 RC = MRI.getRegClass(edit.getReg());
867 if (StackSlot == VirtRegMap::NO_STACK_SLOT)
868 StackSlot = VRM.assignVirt2StackSlot(Original);
870 if (Original != edit.getReg())
871 VRM.assignVirt2StackSlot(edit.getReg(), StackSlot);
873 // Update LiveStacks now that we are committed to spilling.
874 LiveInterval &stacklvr = LSS.getOrCreateInterval(StackSlot, RC);
875 if (!stacklvr.hasAtLeastOneValue())
876 stacklvr.getNextValue(SlotIndex(), 0, LSS.getVNInfoAllocator());
877 for (unsigned i = 0, e = RegsToSpill.size(); i != e; ++i)
878 stacklvr.MergeRangesInAsValue(LIS.getInterval(RegsToSpill[i]),
879 stacklvr.getValNumInfo(0));
880 DEBUG(dbgs() << "Merged spilled regs: " << stacklvr << '\n');
882 // Spill around uses of all RegsToSpill.
883 for (unsigned i = 0, e = RegsToSpill.size(); i != e; ++i)
884 spillAroundUses(RegsToSpill[i]);
886 // Hoisted spills may cause dead code.
887 if (!DeadDefs.empty()) {
888 DEBUG(dbgs() << "Eliminating " << DeadDefs.size() << " dead defs\n");
889 Edit->eliminateDeadDefs(DeadDefs, LIS, VRM, TII);
892 // Finally delete the SnippetCopies.
893 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(edit.getReg());
894 MachineInstr *MI = RI.skipInstruction();) {
895 assert(SnippetCopies.count(MI) && "Remaining use wasn't a snippet copy");
896 // FIXME: Do this with a LiveRangeEdit callback.
897 VRM.RemoveMachineInstrFromMaps(MI);
898 LIS.RemoveMachineInstrFromMaps(MI);
899 MI->eraseFromParent();
902 for (unsigned i = 0, e = RegsToSpill.size(); i != e; ++i)
903 edit.eraseVirtReg(RegsToSpill[i], LIS);