Quotes should be printed before private prefix; some code clean up.
[llvm/msp430.git] / lib / CodeGen / StackSlotColoring.cpp
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1 //===-- StackSlotColoring.cpp - Stack slot coloring pass. -----------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the stack slot coloring pass.
12 //===----------------------------------------------------------------------===//
14 #define DEBUG_TYPE "stackcoloring"
15 #include "VirtRegMap.h"
16 #include "llvm/CodeGen/Passes.h"
17 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
18 #include "llvm/CodeGen/LiveStackAnalysis.h"
19 #include "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineLoopInfo.h"
21 #include "llvm/CodeGen/MachineRegisterInfo.h"
22 #include "llvm/CodeGen/PseudoSourceValue.h"
23 #include "llvm/Support/CommandLine.h"
24 #include "llvm/Support/Compiler.h"
25 #include "llvm/Support/Debug.h"
26 #include "llvm/Target/TargetInstrInfo.h"
27 #include "llvm/Target/TargetMachine.h"
28 #include "llvm/ADT/BitVector.h"
29 #include "llvm/ADT/SmallVector.h"
30 #include "llvm/ADT/Statistic.h"
31 #include <vector>
32 using namespace llvm;
34 static cl::opt<bool>
35 DisableSharing("no-stack-slot-sharing",
36 cl::init(false), cl::Hidden,
37 cl::desc("Suppress slot sharing during stack coloring"));
39 static cl::opt<bool>
40 ColorWithRegsOpt("color-ss-with-regs",
41 cl::init(false), cl::Hidden,
42 cl::desc("Color stack slots with free registers"));
45 static cl::opt<int> DCELimit("ssc-dce-limit", cl::init(-1), cl::Hidden);
47 STATISTIC(NumEliminated, "Number of stack slots eliminated due to coloring");
48 STATISTIC(NumRegRepl, "Number of stack slot refs replaced with reg refs");
49 STATISTIC(NumLoadElim, "Number of loads eliminated");
50 STATISTIC(NumStoreElim, "Number of stores eliminated");
51 STATISTIC(NumDead, "Number of trivially dead stack accesses eliminated");
53 namespace {
54 class VISIBILITY_HIDDEN StackSlotColoring : public MachineFunctionPass {
55 bool ColorWithRegs;
56 LiveStacks* LS;
57 VirtRegMap* VRM;
58 MachineFrameInfo *MFI;
59 MachineRegisterInfo *MRI;
60 const TargetInstrInfo *TII;
61 const TargetRegisterInfo *TRI;
62 const MachineLoopInfo *loopInfo;
64 // SSIntervals - Spill slot intervals.
65 std::vector<LiveInterval*> SSIntervals;
67 // SSRefs - Keep a list of frame index references for each spill slot.
68 SmallVector<SmallVector<MachineInstr*, 8>, 16> SSRefs;
70 // OrigAlignments - Alignments of stack objects before coloring.
71 SmallVector<unsigned, 16> OrigAlignments;
73 // OrigSizes - Sizess of stack objects before coloring.
74 SmallVector<unsigned, 16> OrigSizes;
76 // AllColors - If index is set, it's a spill slot, i.e. color.
77 // FIXME: This assumes PEI locate spill slot with smaller indices
78 // closest to stack pointer / frame pointer. Therefore, smaller
79 // index == better color.
80 BitVector AllColors;
82 // NextColor - Next "color" that's not yet used.
83 int NextColor;
85 // UsedColors - "Colors" that have been assigned.
86 BitVector UsedColors;
88 // Assignments - Color to intervals mapping.
89 SmallVector<SmallVector<LiveInterval*,4>, 16> Assignments;
91 public:
92 static char ID; // Pass identification
93 StackSlotColoring() :
94 MachineFunctionPass(&ID), ColorWithRegs(false), NextColor(-1) {}
95 StackSlotColoring(bool RegColor) :
96 MachineFunctionPass(&ID), ColorWithRegs(RegColor), NextColor(-1) {}
98 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
99 AU.addRequired<LiveStacks>();
100 AU.addRequired<VirtRegMap>();
101 AU.addPreserved<VirtRegMap>();
102 AU.addRequired<MachineLoopInfo>();
103 AU.addPreserved<MachineLoopInfo>();
104 AU.addPreservedID(MachineDominatorsID);
105 MachineFunctionPass::getAnalysisUsage(AU);
108 virtual bool runOnMachineFunction(MachineFunction &MF);
109 virtual const char* getPassName() const {
110 return "Stack Slot Coloring";
113 private:
114 void InitializeSlots();
115 void ScanForSpillSlotRefs(MachineFunction &MF);
116 bool OverlapWithAssignments(LiveInterval *li, int Color) const;
117 int ColorSlot(LiveInterval *li);
118 bool ColorSlots(MachineFunction &MF);
119 bool ColorSlotsWithFreeRegs(SmallVector<int, 16> &SlotMapping,
120 SmallVector<SmallVector<int, 4>, 16> &RevMap,
121 BitVector &SlotIsReg);
122 void RewriteInstruction(MachineInstr *MI, int OldFI, int NewFI,
123 MachineFunction &MF);
124 bool PropagateBackward(MachineBasicBlock::iterator MII,
125 MachineBasicBlock *MBB,
126 unsigned OldReg, unsigned NewReg);
127 bool PropagateForward(MachineBasicBlock::iterator MII,
128 MachineBasicBlock *MBB,
129 unsigned OldReg, unsigned NewReg);
130 void UnfoldAndRewriteInstruction(MachineInstr *MI, int OldFI,
131 unsigned Reg, const TargetRegisterClass *RC,
132 MachineFunction &MF);
133 bool AllMemRefsCanBeUnfolded(int SS);
134 bool RemoveDeadStores(MachineBasicBlock* MBB);
136 } // end anonymous namespace
138 char StackSlotColoring::ID = 0;
140 static RegisterPass<StackSlotColoring>
141 X("stack-slot-coloring", "Stack Slot Coloring");
143 FunctionPass *llvm::createStackSlotColoringPass(bool RegColor) {
144 return new StackSlotColoring(RegColor);
147 namespace {
148 // IntervalSorter - Comparison predicate that sort live intervals by
149 // their weight.
150 struct IntervalSorter {
151 bool operator()(LiveInterval* LHS, LiveInterval* RHS) const {
152 return LHS->weight > RHS->weight;
157 /// ScanForSpillSlotRefs - Scan all the machine instructions for spill slot
158 /// references and update spill slot weights.
159 void StackSlotColoring::ScanForSpillSlotRefs(MachineFunction &MF) {
160 SSRefs.resize(MFI->getObjectIndexEnd());
162 // FIXME: Need the equivalent of MachineRegisterInfo for frameindex operands.
163 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
164 MBBI != E; ++MBBI) {
165 MachineBasicBlock *MBB = &*MBBI;
166 unsigned loopDepth = loopInfo->getLoopDepth(MBB);
167 for (MachineBasicBlock::iterator MII = MBB->begin(), EE = MBB->end();
168 MII != EE; ++MII) {
169 MachineInstr *MI = &*MII;
170 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
171 MachineOperand &MO = MI->getOperand(i);
172 if (!MO.isFI())
173 continue;
174 int FI = MO.getIndex();
175 if (FI < 0)
176 continue;
177 if (!LS->hasInterval(FI))
178 continue;
179 LiveInterval &li = LS->getInterval(FI);
180 li.weight += LiveIntervals::getSpillWeight(false, true, loopDepth);
181 SSRefs[FI].push_back(MI);
187 /// InitializeSlots - Process all spill stack slot liveintervals and add them
188 /// to a sorted (by weight) list.
189 void StackSlotColoring::InitializeSlots() {
190 int LastFI = MFI->getObjectIndexEnd();
191 OrigAlignments.resize(LastFI);
192 OrigSizes.resize(LastFI);
193 AllColors.resize(LastFI);
194 UsedColors.resize(LastFI);
195 Assignments.resize(LastFI);
197 // Gather all spill slots into a list.
198 DOUT << "Spill slot intervals:\n";
199 for (LiveStacks::iterator i = LS->begin(), e = LS->end(); i != e; ++i) {
200 LiveInterval &li = i->second;
201 DEBUG(li.dump());
202 int FI = li.getStackSlotIndex();
203 if (MFI->isDeadObjectIndex(FI))
204 continue;
205 SSIntervals.push_back(&li);
206 OrigAlignments[FI] = MFI->getObjectAlignment(FI);
207 OrigSizes[FI] = MFI->getObjectSize(FI);
208 AllColors.set(FI);
210 DOUT << '\n';
212 // Sort them by weight.
213 std::stable_sort(SSIntervals.begin(), SSIntervals.end(), IntervalSorter());
215 // Get first "color".
216 NextColor = AllColors.find_first();
219 /// OverlapWithAssignments - Return true if LiveInterval overlaps with any
220 /// LiveIntervals that have already been assigned to the specified color.
221 bool
222 StackSlotColoring::OverlapWithAssignments(LiveInterval *li, int Color) const {
223 const SmallVector<LiveInterval*,4> &OtherLIs = Assignments[Color];
224 for (unsigned i = 0, e = OtherLIs.size(); i != e; ++i) {
225 LiveInterval *OtherLI = OtherLIs[i];
226 if (OtherLI->overlaps(*li))
227 return true;
229 return false;
232 /// ColorSlotsWithFreeRegs - If there are any free registers available, try
233 /// replacing spill slots references with registers instead.
234 bool
235 StackSlotColoring::ColorSlotsWithFreeRegs(SmallVector<int, 16> &SlotMapping,
236 SmallVector<SmallVector<int, 4>, 16> &RevMap,
237 BitVector &SlotIsReg) {
238 if (!(ColorWithRegs || ColorWithRegsOpt) || !VRM->HasUnusedRegisters())
239 return false;
241 bool Changed = false;
242 DOUT << "Assigning unused registers to spill slots:\n";
243 for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i) {
244 LiveInterval *li = SSIntervals[i];
245 int SS = li->getStackSlotIndex();
246 if (!UsedColors[SS] || li->weight < 20)
247 // If the weight is < 20, i.e. two references in a loop with depth 1,
248 // don't bother with it.
249 continue;
251 // These slots allow to share the same registers.
252 bool AllColored = true;
253 SmallVector<unsigned, 4> ColoredRegs;
254 for (unsigned j = 0, ee = RevMap[SS].size(); j != ee; ++j) {
255 int RSS = RevMap[SS][j];
256 const TargetRegisterClass *RC = LS->getIntervalRegClass(RSS);
257 // If it's not colored to another stack slot, try coloring it
258 // to a "free" register.
259 if (!RC) {
260 AllColored = false;
261 continue;
263 unsigned Reg = VRM->getFirstUnusedRegister(RC);
264 if (!Reg) {
265 AllColored = false;
266 continue;
268 if (!AllMemRefsCanBeUnfolded(RSS)) {
269 AllColored = false;
270 continue;
271 } else {
272 DOUT << "Assigning fi#" << RSS << " to " << TRI->getName(Reg) << '\n';
273 ColoredRegs.push_back(Reg);
274 SlotMapping[RSS] = Reg;
275 SlotIsReg.set(RSS);
276 Changed = true;
280 // Register and its sub-registers are no longer free.
281 while (!ColoredRegs.empty()) {
282 unsigned Reg = ColoredRegs.back();
283 ColoredRegs.pop_back();
284 VRM->setRegisterUsed(Reg);
285 // If reg is a callee-saved register, it will have to be spilled in
286 // the prologue.
287 MRI->setPhysRegUsed(Reg);
288 for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) {
289 VRM->setRegisterUsed(*AS);
290 MRI->setPhysRegUsed(*AS);
293 // This spill slot is dead after the rewrites
294 if (AllColored) {
295 MFI->RemoveStackObject(SS);
296 ++NumEliminated;
299 DOUT << '\n';
301 return Changed;
304 /// ColorSlot - Assign a "color" (stack slot) to the specified stack slot.
306 int StackSlotColoring::ColorSlot(LiveInterval *li) {
307 int Color = -1;
308 bool Share = false;
309 if (!DisableSharing) {
310 // Check if it's possible to reuse any of the used colors.
311 Color = UsedColors.find_first();
312 while (Color != -1) {
313 if (!OverlapWithAssignments(li, Color)) {
314 Share = true;
315 ++NumEliminated;
316 break;
318 Color = UsedColors.find_next(Color);
322 // Assign it to the first available color (assumed to be the best) if it's
323 // not possible to share a used color with other objects.
324 if (!Share) {
325 assert(NextColor != -1 && "No more spill slots?");
326 Color = NextColor;
327 UsedColors.set(Color);
328 NextColor = AllColors.find_next(NextColor);
331 // Record the assignment.
332 Assignments[Color].push_back(li);
333 int FI = li->getStackSlotIndex();
334 DOUT << "Assigning fi#" << FI << " to fi#" << Color << "\n";
336 // Change size and alignment of the allocated slot. If there are multiple
337 // objects sharing the same slot, then make sure the size and alignment
338 // are large enough for all.
339 unsigned Align = OrigAlignments[FI];
340 if (!Share || Align > MFI->getObjectAlignment(Color))
341 MFI->setObjectAlignment(Color, Align);
342 int64_t Size = OrigSizes[FI];
343 if (!Share || Size > MFI->getObjectSize(Color))
344 MFI->setObjectSize(Color, Size);
345 return Color;
348 /// Colorslots - Color all spill stack slots and rewrite all frameindex machine
349 /// operands in the function.
350 bool StackSlotColoring::ColorSlots(MachineFunction &MF) {
351 unsigned NumObjs = MFI->getObjectIndexEnd();
352 SmallVector<int, 16> SlotMapping(NumObjs, -1);
353 SmallVector<float, 16> SlotWeights(NumObjs, 0.0);
354 SmallVector<SmallVector<int, 4>, 16> RevMap(NumObjs);
355 BitVector SlotIsReg(NumObjs);
356 BitVector UsedColors(NumObjs);
358 DOUT << "Color spill slot intervals:\n";
359 bool Changed = false;
360 for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i) {
361 LiveInterval *li = SSIntervals[i];
362 int SS = li->getStackSlotIndex();
363 int NewSS = ColorSlot(li);
364 assert(NewSS >= 0 && "Stack coloring failed?");
365 SlotMapping[SS] = NewSS;
366 RevMap[NewSS].push_back(SS);
367 SlotWeights[NewSS] += li->weight;
368 UsedColors.set(NewSS);
369 Changed |= (SS != NewSS);
372 DOUT << "\nSpill slots after coloring:\n";
373 for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i) {
374 LiveInterval *li = SSIntervals[i];
375 int SS = li->getStackSlotIndex();
376 li->weight = SlotWeights[SS];
378 // Sort them by new weight.
379 std::stable_sort(SSIntervals.begin(), SSIntervals.end(), IntervalSorter());
381 #ifndef NDEBUG
382 for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i)
383 DEBUG(SSIntervals[i]->dump());
384 DOUT << '\n';
385 #endif
387 // Can we "color" a stack slot with a unused register?
388 Changed |= ColorSlotsWithFreeRegs(SlotMapping, RevMap, SlotIsReg);
390 if (!Changed)
391 return false;
393 // Rewrite all MO_FrameIndex operands.
394 for (unsigned SS = 0, SE = SSRefs.size(); SS != SE; ++SS) {
395 bool isReg = SlotIsReg[SS];
396 int NewFI = SlotMapping[SS];
397 if (NewFI == -1 || (NewFI == (int)SS && !isReg))
398 continue;
400 SmallVector<MachineInstr*, 8> &RefMIs = SSRefs[SS];
401 for (unsigned i = 0, e = RefMIs.size(); i != e; ++i)
402 if (!isReg)
403 RewriteInstruction(RefMIs[i], SS, NewFI, MF);
404 else {
405 // Rewrite to use a register instead.
406 const TargetRegisterClass *RC = LS->getIntervalRegClass(SS);
407 UnfoldAndRewriteInstruction(RefMIs[i], SS, NewFI, RC, MF);
411 // Delete unused stack slots.
412 while (NextColor != -1) {
413 DOUT << "Removing unused stack object fi#" << NextColor << "\n";
414 MFI->RemoveStackObject(NextColor);
415 NextColor = AllColors.find_next(NextColor);
418 return true;
421 /// AllMemRefsCanBeUnfolded - Return true if all references of the specified
422 /// spill slot index can be unfolded.
423 bool StackSlotColoring::AllMemRefsCanBeUnfolded(int SS) {
424 SmallVector<MachineInstr*, 8> &RefMIs = SSRefs[SS];
425 for (unsigned i = 0, e = RefMIs.size(); i != e; ++i) {
426 MachineInstr *MI = RefMIs[i];
427 if (TII->isLoadFromStackSlot(MI, SS) ||
428 TII->isStoreToStackSlot(MI, SS))
429 // Restore and spill will become copies.
430 return true;
431 if (!TII->getOpcodeAfterMemoryUnfold(MI->getOpcode(), false, false))
432 return false;
433 for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) {
434 MachineOperand &MO = MI->getOperand(j);
435 if (MO.isFI() && MO.getIndex() != SS)
436 // If it uses another frameindex, we can, currently* unfold it.
437 return false;
440 return true;
443 /// RewriteInstruction - Rewrite specified instruction by replacing references
444 /// to old frame index with new one.
445 void StackSlotColoring::RewriteInstruction(MachineInstr *MI, int OldFI,
446 int NewFI, MachineFunction &MF) {
447 for (unsigned i = 0, ee = MI->getNumOperands(); i != ee; ++i) {
448 MachineOperand &MO = MI->getOperand(i);
449 if (!MO.isFI())
450 continue;
451 int FI = MO.getIndex();
452 if (FI != OldFI)
453 continue;
454 MO.setIndex(NewFI);
457 // Update the MachineMemOperand for the new memory location.
458 // FIXME: We need a better method of managing these too.
459 SmallVector<MachineMemOperand, 2> MMOs(MI->memoperands_begin(),
460 MI->memoperands_end());
461 MI->clearMemOperands(MF);
462 const Value *OldSV = PseudoSourceValue::getFixedStack(OldFI);
463 for (unsigned i = 0, ee = MMOs.size(); i != ee; ++i) {
464 if (MMOs[i].getValue() != OldSV)
465 MI->addMemOperand(MF, MMOs[i]);
466 else {
467 MachineMemOperand MMO(PseudoSourceValue::getFixedStack(NewFI),
468 MMOs[i].getFlags(), MMOs[i].getOffset(),
469 MMOs[i].getSize(), MMOs[i].getAlignment());
470 MI->addMemOperand(MF, MMO);
475 /// PropagateBackward - Traverse backward and look for the definition of
476 /// OldReg. If it can successfully update all of the references with NewReg,
477 /// do so and return true.
478 bool StackSlotColoring::PropagateBackward(MachineBasicBlock::iterator MII,
479 MachineBasicBlock *MBB,
480 unsigned OldReg, unsigned NewReg) {
481 if (MII == MBB->begin())
482 return false;
484 SmallVector<MachineOperand*, 4> Refs;
485 while (--MII != MBB->begin()) {
486 bool FoundDef = false; // Not counting 2address def.
487 bool FoundUse = false;
488 bool FoundKill = false;
489 const TargetInstrDesc &TID = MII->getDesc();
490 for (unsigned i = 0, e = MII->getNumOperands(); i != e; ++i) {
491 MachineOperand &MO = MII->getOperand(i);
492 if (!MO.isReg())
493 continue;
494 unsigned Reg = MO.getReg();
495 if (Reg == 0)
496 continue;
497 if (Reg == OldReg) {
498 const TargetRegisterClass *RC = getInstrOperandRegClass(TRI, TID, i);
499 if (RC && !RC->contains(NewReg))
500 return false;
502 if (MO.isUse()) {
503 FoundUse = true;
504 if (MO.isKill())
505 FoundKill = true;
506 Refs.push_back(&MO);
507 } else {
508 Refs.push_back(&MO);
509 if (!MII->isRegTiedToUseOperand(i))
510 FoundDef = true;
512 } else if (TRI->regsOverlap(Reg, NewReg)) {
513 return false;
514 } else if (TRI->regsOverlap(Reg, OldReg)) {
515 if (!MO.isUse() || !MO.isKill())
516 return false;
519 if (FoundDef) {
520 for (unsigned i = 0, e = Refs.size(); i != e; ++i)
521 Refs[i]->setReg(NewReg);
522 return true;
525 return false;
528 /// PropagateForward - Traverse forward and look for the kill of OldReg. If
529 /// it can successfully update all of the uses with NewReg, do so and
530 /// return true.
531 bool StackSlotColoring::PropagateForward(MachineBasicBlock::iterator MII,
532 MachineBasicBlock *MBB,
533 unsigned OldReg, unsigned NewReg) {
534 if (MII == MBB->end())
535 return false;
537 SmallVector<MachineOperand*, 4> Uses;
538 while (++MII != MBB->end()) {
539 bool FoundUse = false;
540 bool FoundKill = false;
541 const TargetInstrDesc &TID = MII->getDesc();
542 for (unsigned i = 0, e = MII->getNumOperands(); i != e; ++i) {
543 MachineOperand &MO = MII->getOperand(i);
544 if (!MO.isReg())
545 continue;
546 unsigned Reg = MO.getReg();
547 if (Reg == 0)
548 continue;
549 if (Reg == OldReg) {
550 if (MO.isDef())
551 return false;
553 const TargetRegisterClass *RC = getInstrOperandRegClass(TRI, TID, i);
554 if (RC && !RC->contains(NewReg))
555 return false;
556 FoundUse = true;
557 if (MO.isKill())
558 FoundKill = true;
559 Uses.push_back(&MO);
560 } else if (TRI->regsOverlap(Reg, NewReg) ||
561 TRI->regsOverlap(Reg, OldReg))
562 return false;
564 if (FoundKill) {
565 for (unsigned i = 0, e = Uses.size(); i != e; ++i)
566 Uses[i]->setReg(NewReg);
567 return true;
570 return false;
573 /// UnfoldAndRewriteInstruction - Rewrite specified instruction by unfolding
574 /// folded memory references and replacing those references with register
575 /// references instead.
576 void StackSlotColoring::UnfoldAndRewriteInstruction(MachineInstr *MI, int OldFI,
577 unsigned Reg,
578 const TargetRegisterClass *RC,
579 MachineFunction &MF) {
580 MachineBasicBlock *MBB = MI->getParent();
581 if (unsigned DstReg = TII->isLoadFromStackSlot(MI, OldFI)) {
582 if (PropagateForward(MI, MBB, DstReg, Reg)) {
583 DOUT << "Eliminated load: ";
584 DEBUG(MI->dump());
585 ++NumLoadElim;
586 } else {
587 TII->copyRegToReg(*MBB, MI, DstReg, Reg, RC, RC);
588 ++NumRegRepl;
590 } else if (unsigned SrcReg = TII->isStoreToStackSlot(MI, OldFI)) {
591 if (MI->killsRegister(SrcReg) && PropagateBackward(MI, MBB, SrcReg, Reg)) {
592 DOUT << "Eliminated store: ";
593 DEBUG(MI->dump());
594 ++NumStoreElim;
595 } else {
596 TII->copyRegToReg(*MBB, MI, Reg, SrcReg, RC, RC);
597 ++NumRegRepl;
599 } else {
600 SmallVector<MachineInstr*, 4> NewMIs;
601 bool Success = TII->unfoldMemoryOperand(MF, MI, Reg, false, false, NewMIs);
602 assert(Success && "Failed to unfold!");
603 MBB->insert(MI, NewMIs[0]);
604 ++NumRegRepl;
606 MBB->erase(MI);
609 /// RemoveDeadStores - Scan through a basic block and look for loads followed
610 /// by stores. If they're both using the same stack slot, then the store is
611 /// definitely dead. This could obviously be much more aggressive (consider
612 /// pairs with instructions between them), but such extensions might have a
613 /// considerable compile time impact.
614 bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
615 // FIXME: This could be much more aggressive, but we need to investigate
616 // the compile time impact of doing so.
617 bool changed = false;
619 SmallVector<MachineInstr*, 4> toErase;
621 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
622 I != E; ++I) {
623 if (DCELimit != -1 && (int)NumDead >= DCELimit)
624 break;
626 MachineBasicBlock::iterator NextMI = next(I);
627 if (NextMI == MBB->end()) continue;
629 int FirstSS, SecondSS;
630 unsigned LoadReg = 0;
631 unsigned StoreReg = 0;
632 if (!(LoadReg = TII->isLoadFromStackSlot(I, FirstSS))) continue;
633 if (!(StoreReg = TII->isStoreToStackSlot(NextMI, SecondSS))) continue;
634 if (FirstSS != SecondSS || LoadReg != StoreReg || FirstSS == -1) continue;
636 ++NumDead;
637 changed = true;
639 if (NextMI->findRegisterUseOperandIdx(LoadReg, true, 0) != -1) {
640 ++NumDead;
641 toErase.push_back(I);
644 toErase.push_back(NextMI);
645 ++I;
648 for (SmallVector<MachineInstr*, 4>::iterator I = toErase.begin(),
649 E = toErase.end(); I != E; ++I)
650 (*I)->eraseFromParent();
652 return changed;
656 bool StackSlotColoring::runOnMachineFunction(MachineFunction &MF) {
657 DOUT << "********** Stack Slot Coloring **********\n";
659 MFI = MF.getFrameInfo();
660 MRI = &MF.getRegInfo();
661 TII = MF.getTarget().getInstrInfo();
662 TRI = MF.getTarget().getRegisterInfo();
663 LS = &getAnalysis<LiveStacks>();
664 VRM = &getAnalysis<VirtRegMap>();
665 loopInfo = &getAnalysis<MachineLoopInfo>();
667 bool Changed = false;
669 unsigned NumSlots = LS->getNumIntervals();
670 if (NumSlots < 2) {
671 if (NumSlots == 0 || !VRM->HasUnusedRegisters())
672 // Nothing to do!
673 return false;
676 // Gather spill slot references
677 ScanForSpillSlotRefs(MF);
678 InitializeSlots();
679 Changed = ColorSlots(MF);
681 NextColor = -1;
682 SSIntervals.clear();
683 for (unsigned i = 0, e = SSRefs.size(); i != e; ++i)
684 SSRefs[i].clear();
685 SSRefs.clear();
686 OrigAlignments.clear();
687 OrigSizes.clear();
688 AllColors.clear();
689 UsedColors.clear();
690 for (unsigned i = 0, e = Assignments.size(); i != e; ++i)
691 Assignments[i].clear();
692 Assignments.clear();
694 if (Changed) {
695 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
696 Changed |= RemoveDeadStores(I);
699 return Changed;