1//===- StackSlotColoring.cpp - Stack slot coloring pass. ------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the stack slot coloring pass.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/CodeGen/StackSlotColoring.h"
14#include "llvm/ADT/BitVector.h"
15#include "llvm/ADT/SmallVector.h"
16#include "llvm/ADT/Statistic.h"
17#include "llvm/CodeGen/LiveDebugVariables.h"
18#include "llvm/CodeGen/LiveInterval.h"
19#include "llvm/CodeGen/LiveIntervalUnion.h"
20#include "llvm/CodeGen/LiveIntervals.h"
21#include "llvm/CodeGen/LiveStacks.h"
22#include "llvm/CodeGen/MachineBasicBlock.h"
23#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
24#include "llvm/CodeGen/MachineDominators.h"
25#include "llvm/CodeGen/MachineFrameInfo.h"
26#include "llvm/CodeGen/MachineFunction.h"
27#include "llvm/CodeGen/MachineFunctionPass.h"
28#include "llvm/CodeGen/MachineInstr.h"
29#include "llvm/CodeGen/MachineMemOperand.h"
30#include "llvm/CodeGen/MachineOperand.h"
31#include "llvm/CodeGen/Passes.h"
32#include "llvm/CodeGen/PseudoSourceValue.h"
33#include "llvm/CodeGen/PseudoSourceValueManager.h"
34#include "llvm/CodeGen/SlotIndexes.h"
35#include "llvm/CodeGen/TargetInstrInfo.h"
36#include "llvm/CodeGen/TargetSubtargetInfo.h"
37#include "llvm/InitializePasses.h"
38#include "llvm/Pass.h"
39#include "llvm/Support/Casting.h"
40#include "llvm/Support/CommandLine.h"
41#include "llvm/Support/Debug.h"
42#include "llvm/Support/raw_ostream.h"
43#include <cassert>
44#include <cstdint>
45#include <iterator>
46#include <vector>
47
48using namespace llvm;
49
50#define DEBUG_TYPE "stack-slot-coloring"
51
52static cl::opt<bool>
53DisableSharing("no-stack-slot-sharing",
54 cl::init(Val: false), cl::Hidden,
55 cl::desc("Suppress slot sharing during stack coloring"));
56
57static cl::opt<int> DCELimit("ssc-dce-limit", cl::init(Val: -1), cl::Hidden);
58
59STATISTIC(NumEliminated, "Number of stack slots eliminated due to coloring");
60STATISTIC(NumDead, "Number of trivially dead stack accesses eliminated");
61
62namespace {
63
64class StackSlotColoring {
65 MachineFrameInfo *MFI = nullptr;
66 const TargetInstrInfo *TII = nullptr;
67 LiveStacks *LS = nullptr;
68 const MachineBlockFrequencyInfo *MBFI = nullptr;
69 SlotIndexes *Indexes = nullptr;
70
71 // SSIntervals - Spill slot intervals.
72 std::vector<LiveInterval *> SSIntervals;
73
74 // SSRefs - Keep a list of MachineMemOperands for each spill slot.
75 // MachineMemOperands can be shared between instructions, so we need
76 // to be careful that renames like [FI0, FI1] -> [FI1, FI2] do not
77 // become FI0 -> FI1 -> FI2.
78 SmallVector<SmallVector<MachineMemOperand *, 8>, 16> SSRefs;
79
80 // OrigAlignments - Alignments of stack objects before coloring.
81 SmallVector<Align, 16> OrigAlignments;
82
83 // OrigSizes - Sizes of stack objects before coloring.
84 SmallVector<unsigned, 16> OrigSizes;
85
86 // AllColors - If index is set, it's a spill slot, i.e. color.
87 // FIXME: This assumes PEI locate spill slot with smaller indices
88 // closest to stack pointer / frame pointer. Therefore, smaller
89 // index == better color. This is per stack ID.
90 SmallVector<BitVector, 2> AllColors;
91
92 // NextColor - Next "color" that's not yet used. This is per stack ID.
93 SmallVector<int, 2> NextColors = {-1};
94
95 // UsedColors - "Colors" that have been assigned. This is per stack ID
96 SmallVector<BitVector, 2> UsedColors;
97
98 // Join all intervals sharing one color into a single LiveIntervalUnion to
99 // speedup range overlap test.
100 class ColorAssignmentInfo {
101 // Single liverange (used to avoid creation of LiveIntervalUnion).
102 LiveInterval *SingleLI = nullptr;
103 // LiveIntervalUnion to perform overlap test.
104 LiveIntervalUnion *LIU = nullptr;
105 // LiveIntervalUnion has a parameter in its constructor so doing this
106 // dirty magic.
107 uint8_t LIUPad[sizeof(LiveIntervalUnion)];
108
109 public:
110 ~ColorAssignmentInfo() {
111 if (LIU)
112 LIU->~LiveIntervalUnion(); // Dirty magic again.
113 }
114
115 // Return true if LiveInterval overlaps with any
116 // intervals that have already been assigned to this color.
117 bool overlaps(LiveInterval *LI) const {
118 if (LIU)
119 return LiveIntervalUnion::Query(*LI, *LIU).checkInterference();
120 return SingleLI ? SingleLI->overlaps(other: *LI) : false;
121 }
122
123 // Add new LiveInterval to this color.
124 void add(LiveInterval *LI, LiveIntervalUnion::Allocator &Alloc) {
125 assert(!overlaps(LI));
126 if (LIU) {
127 LIU->unify(VirtReg: *LI, Range: *LI);
128 } else if (SingleLI) {
129 LIU = new (LIUPad) LiveIntervalUnion(Alloc);
130 LIU->unify(VirtReg: *SingleLI, Range: *SingleLI);
131 LIU->unify(VirtReg: *LI, Range: *LI);
132 SingleLI = nullptr;
133 } else
134 SingleLI = LI;
135 }
136 };
137
138 LiveIntervalUnion::Allocator LIUAlloc;
139
140 // Assignments - Color to intervals mapping.
141 SmallVector<ColorAssignmentInfo, 16> Assignments;
142
143public:
144 StackSlotColoring(MachineFunction &MF, LiveStacks *LS,
145 MachineBlockFrequencyInfo *MBFI, SlotIndexes *Indexes)
146 : MFI(&MF.getFrameInfo()), TII(MF.getSubtarget().getInstrInfo()), LS(LS),
147 MBFI(MBFI), Indexes(Indexes) {}
148 bool run(MachineFunction &MF);
149
150private:
151 void InitializeSlots();
152 void ScanForSpillSlotRefs(MachineFunction &MF);
153 int ColorSlot(LiveInterval *li);
154 bool ColorSlots(MachineFunction &MF);
155 void RewriteInstruction(MachineInstr &MI, SmallVectorImpl<int> &SlotMapping,
156 MachineFunction &MF);
157 bool RemoveDeadStores(MachineBasicBlock *MBB);
158};
159
160class StackSlotColoringLegacy : public MachineFunctionPass {
161public:
162 static char ID; // Pass identification
163
164 StackSlotColoringLegacy() : MachineFunctionPass(ID) {}
165
166 void getAnalysisUsage(AnalysisUsage &AU) const override {
167 AU.setPreservesCFG();
168 AU.addRequired<SlotIndexesWrapperPass>();
169 AU.addPreserved<SlotIndexesWrapperPass>();
170 AU.addRequired<LiveStacksWrapperLegacy>();
171 AU.addRequired<MachineBlockFrequencyInfoWrapperPass>();
172 AU.addPreserved<MachineBlockFrequencyInfoWrapperPass>();
173 AU.addPreservedID(ID&: MachineDominatorsID);
174
175 // In some Target's pipeline, register allocation (RA) might be
176 // split into multiple phases based on register class. So, this pass
177 // may be invoked multiple times requiring it to save these analyses to be
178 // used by RA later.
179 AU.addPreserved<LiveIntervalsWrapperPass>();
180 AU.addPreserved<LiveDebugVariablesWrapperLegacy>();
181
182 MachineFunctionPass::getAnalysisUsage(AU);
183 }
184
185 bool runOnMachineFunction(MachineFunction &MF) override;
186};
187
188} // end anonymous namespace
189
190char StackSlotColoringLegacy::ID = 0;
191
192char &llvm::StackSlotColoringID = StackSlotColoringLegacy::ID;
193
194INITIALIZE_PASS_BEGIN(StackSlotColoringLegacy, DEBUG_TYPE,
195 "Stack Slot Coloring", false, false)
196INITIALIZE_PASS_DEPENDENCY(SlotIndexesWrapperPass)
197INITIALIZE_PASS_DEPENDENCY(LiveStacksWrapperLegacy)
198INITIALIZE_PASS_DEPENDENCY(MachineLoopInfoWrapperPass)
199INITIALIZE_PASS_END(StackSlotColoringLegacy, DEBUG_TYPE, "Stack Slot Coloring",
200 false, false)
201
202namespace {
203
204// IntervalSorter - Comparison predicate that sort live intervals by
205// their weight.
206struct IntervalSorter {
207 bool operator()(LiveInterval* LHS, LiveInterval* RHS) const {
208 return LHS->weight() > RHS->weight();
209 }
210};
211
212} // end anonymous namespace
213
214/// ScanForSpillSlotRefs - Scan all the machine instructions for spill slot
215/// references and update spill slot weights.
216void StackSlotColoring::ScanForSpillSlotRefs(MachineFunction &MF) {
217 SSRefs.resize(N: MFI->getObjectIndexEnd());
218
219 // FIXME: Need the equivalent of MachineRegisterInfo for frameindex operands.
220 for (MachineBasicBlock &MBB : MF) {
221 for (MachineInstr &MI : MBB) {
222 for (const MachineOperand &MO : MI.operands()) {
223 if (!MO.isFI())
224 continue;
225 int FI = MO.getIndex();
226 if (FI < 0)
227 continue;
228 if (!LS->hasInterval(Slot: FI))
229 continue;
230 LiveInterval &li = LS->getInterval(Slot: FI);
231 if (!MI.isDebugInstr())
232 li.incrementWeight(
233 Inc: LiveIntervals::getSpillWeight(isDef: false, isUse: true, MBFI, MI));
234 }
235 for (MachineMemOperand *MMO : MI.memoperands()) {
236 if (const FixedStackPseudoSourceValue *FSV =
237 dyn_cast_or_null<FixedStackPseudoSourceValue>(
238 Val: MMO->getPseudoValue())) {
239 int FI = FSV->getFrameIndex();
240 if (FI >= 0)
241 SSRefs[FI].push_back(Elt: MMO);
242 }
243 }
244 }
245 }
246}
247
248/// InitializeSlots - Process all spill stack slot liveintervals and add them
249/// to a sorted (by weight) list.
250void StackSlotColoring::InitializeSlots() {
251 int LastFI = MFI->getObjectIndexEnd();
252
253 // There is always at least one stack ID.
254 AllColors.resize(N: 1);
255 UsedColors.resize(N: 1);
256
257 OrigAlignments.resize(N: LastFI);
258 OrigSizes.resize(N: LastFI);
259 AllColors[0].resize(N: LastFI);
260 UsedColors[0].resize(N: LastFI);
261 Assignments.resize(N: LastFI);
262
263 using Pair = std::iterator_traits<LiveStacks::iterator>::value_type;
264
265 SmallVector<Pair *, 16> Intervals;
266
267 Intervals.reserve(N: LS->getNumIntervals());
268 for (auto &I : *LS)
269 Intervals.push_back(Elt: &I);
270 llvm::sort(C&: Intervals,
271 Comp: [](Pair *LHS, Pair *RHS) { return LHS->first < RHS->first; });
272
273 // Gather all spill slots into a list.
274 LLVM_DEBUG(dbgs() << "Spill slot intervals:\n");
275 for (auto *I : Intervals) {
276 LiveInterval &li = I->second;
277 LLVM_DEBUG(li.dump());
278 int FI = li.reg().stackSlotIndex();
279 if (MFI->isDeadObjectIndex(ObjectIdx: FI))
280 continue;
281
282 SSIntervals.push_back(x: &li);
283 OrigAlignments[FI] = MFI->getObjectAlign(ObjectIdx: FI);
284 OrigSizes[FI] = MFI->getObjectSize(ObjectIdx: FI);
285
286 auto StackID = MFI->getStackID(ObjectIdx: FI);
287 if (StackID != 0) {
288 if (StackID >= AllColors.size()) {
289 AllColors.resize(N: StackID + 1);
290 UsedColors.resize(N: StackID + 1);
291 }
292 AllColors[StackID].resize(N: LastFI);
293 UsedColors[StackID].resize(N: LastFI);
294 }
295
296 AllColors[StackID].set(FI);
297 }
298 LLVM_DEBUG(dbgs() << '\n');
299
300 // Sort them by weight.
301 llvm::stable_sort(Range&: SSIntervals, C: IntervalSorter());
302
303 NextColors.resize(N: AllColors.size());
304
305 // Get first "color".
306 for (unsigned I = 0, E = AllColors.size(); I != E; ++I)
307 NextColors[I] = AllColors[I].find_first();
308}
309
310/// ColorSlot - Assign a "color" (stack slot) to the specified stack slot.
311int StackSlotColoring::ColorSlot(LiveInterval *li) {
312 int Color = -1;
313 bool Share = false;
314 int FI = li->reg().stackSlotIndex();
315 uint8_t StackID = MFI->getStackID(ObjectIdx: FI);
316
317 if (!DisableSharing) {
318
319 // Check if it's possible to reuse any of the used colors.
320 Color = UsedColors[StackID].find_first();
321 while (Color != -1) {
322 if (!Assignments[Color].overlaps(LI: li)) {
323 Share = true;
324 ++NumEliminated;
325 break;
326 }
327 Color = UsedColors[StackID].find_next(Prev: Color);
328 }
329 }
330
331 if (Color != -1 && MFI->getStackID(ObjectIdx: Color) != MFI->getStackID(ObjectIdx: FI)) {
332 LLVM_DEBUG(dbgs() << "cannot share FIs with different stack IDs\n");
333 Share = false;
334 }
335
336 // Assign it to the first available color (assumed to be the best) if it's
337 // not possible to share a used color with other objects.
338 if (!Share) {
339 assert(NextColors[StackID] != -1 && "No more spill slots?");
340 Color = NextColors[StackID];
341 UsedColors[StackID].set(Color);
342 NextColors[StackID] = AllColors[StackID].find_next(Prev: NextColors[StackID]);
343 }
344
345 assert(MFI->getStackID(Color) == MFI->getStackID(FI));
346
347 // Record the assignment.
348 Assignments[Color].add(LI: li, Alloc&: LIUAlloc);
349 LLVM_DEBUG(dbgs() << "Assigning fi#" << FI << " to fi#" << Color << "\n");
350
351 // Change size and alignment of the allocated slot. If there are multiple
352 // objects sharing the same slot, then make sure the size and alignment
353 // are large enough for all.
354 Align Alignment = OrigAlignments[FI];
355 if (!Share || Alignment > MFI->getObjectAlign(ObjectIdx: Color))
356 MFI->setObjectAlignment(ObjectIdx: Color, Alignment);
357 int64_t Size = OrigSizes[FI];
358 if (!Share || Size > MFI->getObjectSize(ObjectIdx: Color))
359 MFI->setObjectSize(ObjectIdx: Color, Size);
360 return Color;
361}
362
363/// Colorslots - Color all spill stack slots and rewrite all frameindex machine
364/// operands in the function.
365bool StackSlotColoring::ColorSlots(MachineFunction &MF) {
366 unsigned NumObjs = MFI->getObjectIndexEnd();
367 SmallVector<int, 16> SlotMapping(NumObjs, -1);
368 SmallVector<float, 16> SlotWeights(NumObjs, 0.0);
369 SmallVector<SmallVector<int, 4>, 16> RevMap(NumObjs);
370 BitVector UsedColors(NumObjs);
371
372 LLVM_DEBUG(dbgs() << "Color spill slot intervals:\n");
373 bool Changed = false;
374 for (LiveInterval *li : SSIntervals) {
375 int SS = li->reg().stackSlotIndex();
376 int NewSS = ColorSlot(li);
377 assert(NewSS >= 0 && "Stack coloring failed?");
378 SlotMapping[SS] = NewSS;
379 RevMap[NewSS].push_back(Elt: SS);
380 SlotWeights[NewSS] += li->weight();
381 UsedColors.set(NewSS);
382 Changed |= (SS != NewSS);
383 }
384
385 LLVM_DEBUG(dbgs() << "\nSpill slots after coloring:\n");
386 for (LiveInterval *li : SSIntervals) {
387 int SS = li->reg().stackSlotIndex();
388 li->setWeight(SlotWeights[SS]);
389 }
390 // Sort them by new weight.
391 llvm::stable_sort(Range&: SSIntervals, C: IntervalSorter());
392
393#ifndef NDEBUG
394 for (LiveInterval *li : SSIntervals)
395 LLVM_DEBUG(li->dump());
396 LLVM_DEBUG(dbgs() << '\n');
397#endif
398
399 if (!Changed)
400 return false;
401
402 // Rewrite all MachineMemOperands.
403 for (unsigned SS = 0, SE = SSRefs.size(); SS != SE; ++SS) {
404 int NewFI = SlotMapping[SS];
405 if (NewFI == -1 || (NewFI == (int)SS))
406 continue;
407
408 const PseudoSourceValue *NewSV = MF.getPSVManager().getFixedStack(FI: NewFI);
409 SmallVectorImpl<MachineMemOperand *> &RefMMOs = SSRefs[SS];
410 for (MachineMemOperand *MMO : RefMMOs)
411 MMO->setValue(NewSV);
412 }
413
414 // Rewrite all MO_FrameIndex operands. Look for dead stores.
415 for (MachineBasicBlock &MBB : MF) {
416 for (MachineInstr &MI : MBB)
417 RewriteInstruction(MI, SlotMapping, MF);
418 RemoveDeadStores(MBB: &MBB);
419 }
420
421 // Delete unused stack slots.
422 for (int StackID = 0, E = AllColors.size(); StackID != E; ++StackID) {
423 int NextColor = NextColors[StackID];
424 while (NextColor != -1) {
425 LLVM_DEBUG(dbgs() << "Removing unused stack object fi#" << NextColor << "\n");
426 MFI->RemoveStackObject(ObjectIdx: NextColor);
427 NextColor = AllColors[StackID].find_next(Prev: NextColor);
428 }
429 }
430
431 return true;
432}
433
434/// RewriteInstruction - Rewrite specified instruction by replacing references
435/// to old frame index with new one.
436void StackSlotColoring::RewriteInstruction(MachineInstr &MI,
437 SmallVectorImpl<int> &SlotMapping,
438 MachineFunction &MF) {
439 // Update the operands.
440 for (MachineOperand &MO : MI.operands()) {
441 if (!MO.isFI())
442 continue;
443 int OldFI = MO.getIndex();
444 if (OldFI < 0)
445 continue;
446 int NewFI = SlotMapping[OldFI];
447 if (NewFI == -1 || NewFI == OldFI)
448 continue;
449
450 assert(MFI->getStackID(OldFI) == MFI->getStackID(NewFI));
451 MO.setIndex(NewFI);
452 }
453
454 // The MachineMemOperands have already been updated.
455}
456
457/// RemoveDeadStores - Scan through a basic block and look for loads followed
458/// by stores. If they're both using the same stack slot, then the store is
459/// definitely dead. This could obviously be much more aggressive (consider
460/// pairs with instructions between them), but such extensions might have a
461/// considerable compile time impact.
462bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
463 // FIXME: This could be much more aggressive, but we need to investigate
464 // the compile time impact of doing so.
465 bool changed = false;
466
467 SmallVector<MachineInstr*, 4> toErase;
468
469 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
470 I != E; ++I) {
471 if (DCELimit != -1 && (int)NumDead >= DCELimit)
472 break;
473 int FirstSS, SecondSS;
474 if (TII->isStackSlotCopy(MI: *I, DestFrameIndex&: FirstSS, SrcFrameIndex&: SecondSS) && FirstSS == SecondSS &&
475 FirstSS != -1) {
476 ++NumDead;
477 changed = true;
478 toErase.push_back(Elt: &*I);
479 continue;
480 }
481
482 MachineBasicBlock::iterator NextMI = std::next(x: I);
483 MachineBasicBlock::iterator ProbableLoadMI = I;
484
485 Register LoadReg;
486 Register StoreReg;
487 TypeSize LoadSize = TypeSize::getZero();
488 TypeSize StoreSize = TypeSize::getZero();
489 if (!(LoadReg = TII->isLoadFromStackSlot(MI: *I, FrameIndex&: FirstSS, MemBytes&: LoadSize)))
490 continue;
491 // Skip the ...pseudo debugging... instructions between a load and store.
492 while ((NextMI != E) && NextMI->isDebugInstr()) {
493 ++NextMI;
494 ++I;
495 }
496 if (NextMI == E) continue;
497 if (!(StoreReg = TII->isStoreToStackSlot(MI: *NextMI, FrameIndex&: SecondSS, MemBytes&: StoreSize)))
498 continue;
499 if (FirstSS != SecondSS || LoadReg != StoreReg || FirstSS == -1 ||
500 LoadSize != StoreSize || !MFI->isSpillSlotObjectIndex(ObjectIdx: FirstSS))
501 continue;
502
503 ++NumDead;
504 changed = true;
505
506 if (NextMI->findRegisterUseOperandIdx(Reg: LoadReg, /*TRI=*/nullptr, isKill: true) !=
507 -1) {
508 ++NumDead;
509 toErase.push_back(Elt: &*ProbableLoadMI);
510 }
511
512 toErase.push_back(Elt: &*NextMI);
513 ++I;
514 }
515
516 for (MachineInstr *MI : toErase) {
517 if (Indexes)
518 Indexes->removeMachineInstrFromMaps(MI&: *MI);
519 MI->eraseFromParent();
520 }
521
522 return changed;
523}
524
525bool StackSlotColoring::run(MachineFunction &MF) {
526 LLVM_DEBUG({
527 dbgs() << "********** Stack Slot Coloring **********\n"
528 << "********** Function: " << MF.getName() << '\n';
529 });
530
531 bool Changed = false;
532
533 unsigned NumSlots = LS->getNumIntervals();
534 if (NumSlots == 0)
535 // Nothing to do!
536 return false;
537
538 // If there are calls to setjmp or sigsetjmp, don't perform stack slot
539 // coloring. The stack could be modified before the longjmp is executed,
540 // resulting in the wrong value being used afterwards.
541 if (MF.exposesReturnsTwice())
542 return false;
543
544 // Gather spill slot references
545 ScanForSpillSlotRefs(MF);
546 InitializeSlots();
547 Changed = ColorSlots(MF);
548
549 for (int &Next : NextColors)
550 Next = -1;
551
552 SSIntervals.clear();
553 for (auto &RefMMOs : SSRefs)
554 RefMMOs.clear();
555 SSRefs.clear();
556 OrigAlignments.clear();
557 OrigSizes.clear();
558 AllColors.clear();
559 UsedColors.clear();
560 Assignments.clear();
561
562 return Changed;
563}
564
565bool StackSlotColoringLegacy::runOnMachineFunction(MachineFunction &MF) {
566 if (skipFunction(F: MF.getFunction()))
567 return false;
568
569 LiveStacks *LS = &getAnalysis<LiveStacksWrapperLegacy>().getLS();
570 MachineBlockFrequencyInfo *MBFI =
571 &getAnalysis<MachineBlockFrequencyInfoWrapperPass>().getMBFI();
572 SlotIndexes *Indexes = &getAnalysis<SlotIndexesWrapperPass>().getSI();
573 StackSlotColoring Impl(MF, LS, MBFI, Indexes);
574 return Impl.run(MF);
575}
576
577PreservedAnalyses
578StackSlotColoringPass::run(MachineFunction &MF,
579 MachineFunctionAnalysisManager &MFAM) {
580 LiveStacks *LS = &MFAM.getResult<LiveStacksAnalysis>(IR&: MF);
581 MachineBlockFrequencyInfo *MBFI =
582 &MFAM.getResult<MachineBlockFrequencyAnalysis>(IR&: MF);
583 SlotIndexes *Indexes = &MFAM.getResult<SlotIndexesAnalysis>(IR&: MF);
584 StackSlotColoring Impl(MF, LS, MBFI, Indexes);
585 bool Changed = Impl.run(MF);
586 if (!Changed)
587 return PreservedAnalyses::all();
588
589 auto PA = getMachineFunctionPassPreservedAnalyses();
590 PA.preserveSet<CFGAnalyses>();
591 PA.preserve<SlotIndexesAnalysis>();
592 PA.preserve<MachineBlockFrequencyAnalysis>();
593 PA.preserve<MachineDominatorTreeAnalysis>();
594 PA.preserve<LiveIntervalsAnalysis>();
595 PA.preserve<LiveDebugVariablesAnalysis>();
596 return PA;
597}
598