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 "spiller"
18 #include "VirtRegMap.h"
19 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
20 #include "llvm/CodeGen/MachineFrameInfo.h"
21 #include "llvm/CodeGen/MachineFunction.h"
22 #include "llvm/CodeGen/MachineLoopInfo.h"
23 #include "llvm/CodeGen/MachineRegisterInfo.h"
24 #include "llvm/Target/TargetMachine.h"
25 #include "llvm/Target/TargetInstrInfo.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/raw_ostream.h"
32 class InlineSpiller : public Spiller {
33 MachineFunctionPass &pass_;
36 MachineLoopInfo &loops_;
38 MachineFrameInfo &mfi_;
39 MachineRegisterInfo &mri_;
40 const TargetInstrInfo &tii_;
41 const TargetRegisterInfo &tri_;
42 const BitVector reserved_;
44 SplitAnalysis splitAnalysis_;
46 // Variables that are valid during spill(), but used by multiple methods.
48 SmallVectorImpl<LiveInterval*> *newIntervals_;
49 const TargetRegisterClass *rc_;
51 const SmallVectorImpl<LiveInterval*> *spillIs_;
53 // Values of the current interval that can potentially remat.
54 SmallPtrSet<VNInfo*, 8> reMattable_;
56 // Values in reMattable_ that failed to remat at some point.
57 SmallPtrSet<VNInfo*, 8> usedValues_;
62 InlineSpiller(MachineFunctionPass &pass,
67 lis_(pass.getAnalysis<LiveIntervals>()),
68 loops_(pass.getAnalysis<MachineLoopInfo>()),
70 mfi_(*mf.getFrameInfo()),
71 mri_(mf.getRegInfo()),
72 tii_(*mf.getTarget().getInstrInfo()),
73 tri_(*mf.getTarget().getRegisterInfo()),
74 reserved_(tri_.getReservedRegs(mf_)),
75 splitAnalysis_(mf, lis_, loops_) {}
77 void spill(LiveInterval *li,
78 SmallVectorImpl<LiveInterval*> &newIntervals,
79 SmallVectorImpl<LiveInterval*> &spillIs);
84 bool allUsesAvailableAt(const MachineInstr *OrigMI, SlotIndex OrigIdx,
86 bool reMaterializeFor(MachineBasicBlock::iterator MI);
87 void reMaterializeAll();
89 bool coalesceStackAccess(MachineInstr *MI);
90 bool foldMemoryOperand(MachineBasicBlock::iterator MI,
91 const SmallVectorImpl<unsigned> &Ops);
92 void insertReload(LiveInterval &NewLI, MachineBasicBlock::iterator MI);
93 void insertSpill(LiveInterval &NewLI, MachineBasicBlock::iterator MI);
98 Spiller *createInlineSpiller(MachineFunctionPass &pass,
101 return new InlineSpiller(pass, mf, vrm);
105 /// split - try splitting the current interval into pieces that may allocate
106 /// separately. Return true if successful.
107 bool InlineSpiller::split() {
108 splitAnalysis_.analyze(li_);
110 if (const MachineLoop *loop = splitAnalysis_.getBestSplitLoop()) {
111 // We can split, but li_ may be left intact with fewer uses.
112 if (SplitEditor(splitAnalysis_, lis_, vrm_, *newIntervals_)
113 .splitAroundLoop(loop))
117 // Try splitting into single block intervals.
118 SplitAnalysis::BlockPtrSet blocks;
119 if (splitAnalysis_.getMultiUseBlocks(blocks)) {
120 if (SplitEditor(splitAnalysis_, lis_, vrm_, *newIntervals_)
121 .splitSingleBlocks(blocks))
125 // Try splitting inside a basic block.
126 if (const MachineBasicBlock *MBB = splitAnalysis_.getBlockForInsideSplit()) {
127 if (SplitEditor(splitAnalysis_, lis_, vrm_, *newIntervals_)
128 .splitInsideBlock(MBB))
132 // We may have been able to split out some uses, but the original interval is
133 // intact, and it should still be spilled.
137 /// allUsesAvailableAt - Return true if all registers used by OrigMI at
138 /// OrigIdx are also available with the same value at UseIdx.
139 bool InlineSpiller::allUsesAvailableAt(const MachineInstr *OrigMI,
142 OrigIdx = OrigIdx.getUseIndex();
143 UseIdx = UseIdx.getUseIndex();
144 for (unsigned i = 0, e = OrigMI->getNumOperands(); i != e; ++i) {
145 const MachineOperand &MO = OrigMI->getOperand(i);
146 if (!MO.isReg() || !MO.getReg() || MO.getReg() == li_->reg)
148 // Reserved registers are OK.
149 if (MO.isUndef() || !lis_.hasInterval(MO.getReg()))
151 // We don't want to move any defs.
154 // We cannot depend on virtual registers in spillIs_. They will be spilled.
155 for (unsigned si = 0, se = spillIs_->size(); si != se; ++si)
156 if ((*spillIs_)[si]->reg == MO.getReg())
159 LiveInterval &LI = lis_.getInterval(MO.getReg());
160 const VNInfo *OVNI = LI.getVNInfoAt(OrigIdx);
163 if (OVNI != LI.getVNInfoAt(UseIdx))
169 /// reMaterializeFor - Attempt to rematerialize li_->reg before MI instead of
171 bool InlineSpiller::reMaterializeFor(MachineBasicBlock::iterator MI) {
172 SlotIndex UseIdx = lis_.getInstructionIndex(MI).getUseIndex();
173 VNInfo *OrigVNI = li_->getVNInfoAt(UseIdx);
175 DEBUG(dbgs() << "\tadding <undef> flags: ");
176 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
177 MachineOperand &MO = MI->getOperand(i);
178 if (MO.isReg() && MO.isUse() && MO.getReg() == li_->reg)
181 DEBUG(dbgs() << UseIdx << '\t' << *MI);
184 if (!reMattable_.count(OrigVNI)) {
185 DEBUG(dbgs() << "\tusing non-remat valno " << OrigVNI->id << ": "
186 << UseIdx << '\t' << *MI);
189 MachineInstr *OrigMI = lis_.getInstructionFromIndex(OrigVNI->def);
190 if (!allUsesAvailableAt(OrigMI, OrigVNI->def, UseIdx)) {
191 usedValues_.insert(OrigVNI);
192 DEBUG(dbgs() << "\tcannot remat for " << UseIdx << '\t' << *MI);
196 // If the instruction also writes li_->reg, it had better not require the same
197 // register for uses and defs.
199 SmallVector<unsigned, 8> Ops;
200 tie(Reads, Writes) = MI->readsWritesVirtualRegister(li_->reg, &Ops);
202 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
203 MachineOperand &MO = MI->getOperand(Ops[i]);
204 if (MO.isUse() ? MI->isRegTiedToDefOperand(Ops[i]) : MO.getSubReg()) {
205 usedValues_.insert(OrigVNI);
206 DEBUG(dbgs() << "\tcannot remat tied reg: " << UseIdx << '\t' << *MI);
212 // Alocate a new register for the remat.
213 unsigned NewVReg = mri_.createVirtualRegister(rc_);
215 LiveInterval &NewLI = lis_.getOrCreateInterval(NewVReg);
216 NewLI.markNotSpillable();
217 newIntervals_->push_back(&NewLI);
219 // Finally we can rematerialize OrigMI before MI.
220 MachineBasicBlock &MBB = *MI->getParent();
221 tii_.reMaterialize(MBB, MI, NewLI.reg, 0, OrigMI, tri_);
222 MachineBasicBlock::iterator RematMI = MI;
223 SlotIndex DefIdx = lis_.InsertMachineInstrInMaps(--RematMI).getDefIndex();
224 DEBUG(dbgs() << "\tremat: " << DefIdx << '\t' << *RematMI);
227 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
228 MachineOperand &MO = MI->getOperand(Ops[i]);
229 if (MO.isReg() && MO.isUse() && MO.getReg() == li_->reg) {
234 DEBUG(dbgs() << "\t " << UseIdx << '\t' << *MI);
236 VNInfo *DefVNI = NewLI.getNextValue(DefIdx, 0, true,
237 lis_.getVNInfoAllocator());
238 NewLI.addRange(LiveRange(DefIdx, UseIdx.getDefIndex(), DefVNI));
239 DEBUG(dbgs() << "\tinterval: " << NewLI << '\n');
243 /// reMaterializeAll - Try to rematerialize as many uses of li_ as possible,
244 /// and trim the live ranges after.
245 void InlineSpiller::reMaterializeAll() {
246 // Do a quick scan of the interval values to find if any are remattable.
249 for (LiveInterval::const_vni_iterator I = li_->vni_begin(),
250 E = li_->vni_end(); I != E; ++I) {
252 if (VNI->isUnused() || !VNI->isDefAccurate())
254 MachineInstr *DefMI = lis_.getInstructionFromIndex(VNI->def);
255 if (!DefMI || !tii_.isTriviallyReMaterializable(DefMI))
257 reMattable_.insert(VNI);
260 // Often, no defs are remattable.
261 if (reMattable_.empty())
264 // Try to remat before all uses of li_->reg.
265 bool anyRemat = false;
266 for (MachineRegisterInfo::use_nodbg_iterator
267 RI = mri_.use_nodbg_begin(li_->reg);
268 MachineInstr *MI = RI.skipInstruction();)
269 anyRemat |= reMaterializeFor(MI);
274 // Remove any values that were completely rematted.
275 bool anyRemoved = false;
276 for (SmallPtrSet<VNInfo*, 8>::iterator I = reMattable_.begin(),
277 E = reMattable_.end(); I != E; ++I) {
279 if (VNI->hasPHIKill() || usedValues_.count(VNI))
281 MachineInstr *DefMI = lis_.getInstructionFromIndex(VNI->def);
282 DEBUG(dbgs() << "\tremoving dead def: " << VNI->def << '\t' << *DefMI);
283 lis_.RemoveMachineInstrFromMaps(DefMI);
284 vrm_.RemoveMachineInstrFromMaps(DefMI);
285 DefMI->eraseFromParent();
286 VNI->setIsDefAccurate(false);
293 // Removing values may cause debug uses where li_ is not live.
294 for (MachineRegisterInfo::use_iterator RI = mri_.use_begin(li_->reg);
295 MachineInstr *MI = RI.skipInstruction();) {
296 if (!MI->isDebugValue())
298 // Try to preserve the debug value if li_ is live immediately after it.
299 MachineBasicBlock::iterator NextMI = MI;
301 if (NextMI != MI->getParent()->end() && !lis_.isNotInMIMap(NextMI)) {
302 VNInfo *VNI = li_->getVNInfoAt(lis_.getInstructionIndex(NextMI));
303 if (VNI && (VNI->hasPHIKill() || usedValues_.count(VNI)))
306 DEBUG(dbgs() << "Removing debug info due to remat:" << "\t" << *MI);
307 MI->eraseFromParent();
311 /// If MI is a load or store of stackSlot_, it can be removed.
312 bool InlineSpiller::coalesceStackAccess(MachineInstr *MI) {
315 if (!(reg = tii_.isLoadFromStackSlot(MI, FI)) &&
316 !(reg = tii_.isStoreToStackSlot(MI, FI)))
319 // We have a stack access. Is it the right register and slot?
320 if (reg != li_->reg || FI != stackSlot_)
323 DEBUG(dbgs() << "Coalescing stack access: " << *MI);
324 lis_.RemoveMachineInstrFromMaps(MI);
325 MI->eraseFromParent();
329 /// foldMemoryOperand - Try folding stack slot references in Ops into MI.
330 /// Return true on success, and MI will be erased.
331 bool InlineSpiller::foldMemoryOperand(MachineBasicBlock::iterator MI,
332 const SmallVectorImpl<unsigned> &Ops) {
333 // TargetInstrInfo::foldMemoryOperand only expects explicit, non-tied
335 SmallVector<unsigned, 8> FoldOps;
336 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
337 unsigned Idx = Ops[i];
338 MachineOperand &MO = MI->getOperand(Idx);
341 // FIXME: Teach targets to deal with subregs.
344 // Tied use operands should not be passed to foldMemoryOperand.
345 if (!MI->isRegTiedToDefOperand(Idx))
346 FoldOps.push_back(Idx);
349 MachineInstr *FoldMI = tii_.foldMemoryOperand(MI, FoldOps, stackSlot_);
352 lis_.ReplaceMachineInstrInMaps(MI, FoldMI);
353 vrm_.addSpillSlotUse(stackSlot_, FoldMI);
354 MI->eraseFromParent();
355 DEBUG(dbgs() << "\tfolded: " << *FoldMI);
359 /// insertReload - Insert a reload of NewLI.reg before MI.
360 void InlineSpiller::insertReload(LiveInterval &NewLI,
361 MachineBasicBlock::iterator MI) {
362 MachineBasicBlock &MBB = *MI->getParent();
363 SlotIndex Idx = lis_.getInstructionIndex(MI).getDefIndex();
364 tii_.loadRegFromStackSlot(MBB, MI, NewLI.reg, stackSlot_, rc_, &tri_);
365 --MI; // Point to load instruction.
366 SlotIndex LoadIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
367 vrm_.addSpillSlotUse(stackSlot_, MI);
368 DEBUG(dbgs() << "\treload: " << LoadIdx << '\t' << *MI);
369 VNInfo *LoadVNI = NewLI.getNextValue(LoadIdx, 0, true,
370 lis_.getVNInfoAllocator());
371 NewLI.addRange(LiveRange(LoadIdx, Idx, LoadVNI));
374 /// insertSpill - Insert a spill of NewLI.reg after MI.
375 void InlineSpiller::insertSpill(LiveInterval &NewLI,
376 MachineBasicBlock::iterator MI) {
377 MachineBasicBlock &MBB = *MI->getParent();
378 SlotIndex Idx = lis_.getInstructionIndex(MI).getDefIndex();
379 tii_.storeRegToStackSlot(MBB, ++MI, NewLI.reg, true, stackSlot_, rc_, &tri_);
380 --MI; // Point to store instruction.
381 SlotIndex StoreIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
382 vrm_.addSpillSlotUse(stackSlot_, MI);
383 DEBUG(dbgs() << "\tspilled: " << StoreIdx << '\t' << *MI);
384 VNInfo *StoreVNI = NewLI.getNextValue(Idx, 0, true,
385 lis_.getVNInfoAllocator());
386 NewLI.addRange(LiveRange(Idx, StoreIdx, StoreVNI));
389 void InlineSpiller::spill(LiveInterval *li,
390 SmallVectorImpl<LiveInterval*> &newIntervals,
391 SmallVectorImpl<LiveInterval*> &spillIs) {
392 DEBUG(dbgs() << "Inline spilling " << *li << "\n");
393 assert(li->isSpillable() && "Attempting to spill already spilled value.");
394 assert(!li->isStackSlot() && "Trying to spill a stack slot.");
397 newIntervals_ = &newIntervals;
398 rc_ = mri_.getRegClass(li->reg);
406 // Remat may handle everything.
410 stackSlot_ = vrm_.getStackSlot(li->reg);
411 if (stackSlot_ == VirtRegMap::NO_STACK_SLOT)
412 stackSlot_ = vrm_.assignVirt2StackSlot(li->reg);
414 // Iterate over instructions using register.
415 for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(li->reg);
416 MachineInstr *MI = RI.skipInstruction();) {
418 // Debug values are not allowed to affect codegen.
419 if (MI->isDebugValue()) {
420 // Modify DBG_VALUE now that the value is in a spill slot.
421 uint64_t Offset = MI->getOperand(1).getImm();
422 const MDNode *MDPtr = MI->getOperand(2).getMetadata();
423 DebugLoc DL = MI->getDebugLoc();
424 if (MachineInstr *NewDV = tii_.emitFrameIndexDebugValue(mf_, stackSlot_,
425 Offset, MDPtr, DL)) {
426 DEBUG(dbgs() << "Modifying debug info due to spill:" << "\t" << *MI);
427 MachineBasicBlock *MBB = MI->getParent();
428 MBB->insert(MBB->erase(MI), NewDV);
430 DEBUG(dbgs() << "Removing debug info due to spill:" << "\t" << *MI);
431 MI->eraseFromParent();
436 // Stack slot accesses may coalesce away.
437 if (coalesceStackAccess(MI))
440 // Analyze instruction.
442 SmallVector<unsigned, 8> Ops;
443 tie(Reads, Writes) = MI->readsWritesVirtualRegister(li->reg, &Ops);
445 // Attempt to fold memory ops.
446 if (foldMemoryOperand(MI, Ops))
449 // Allocate interval around instruction.
450 // FIXME: Infer regclass from instruction alone.
451 unsigned NewVReg = mri_.createVirtualRegister(rc_);
453 LiveInterval &NewLI = lis_.getOrCreateInterval(NewVReg);
454 NewLI.markNotSpillable();
457 insertReload(NewLI, MI);
459 // Rewrite instruction operands.
460 bool hasLiveDef = false;
461 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
462 MachineOperand &MO = MI->getOperand(Ops[i]);
465 if (!MI->isRegTiedToDefOperand(Ops[i]))
473 // FIXME: Use a second vreg if instruction has no tied ops.
474 if (Writes && hasLiveDef)
475 insertSpill(NewLI, MI);
477 DEBUG(dbgs() << "\tinterval: " << NewLI << '\n');
478 newIntervals.push_back(&NewLI);