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
173 // In some Target's pipeline, register allocation (RA) might be
174 // split into multiple phases based on register class. So, this pass
175 // may be invoked multiple times requiring it to save these analyses to be
176 // used by RA later.
177 AU.addPreserved<LiveIntervalsWrapperPass>();
178 AU.addPreserved<LiveDebugVariablesWrapperLegacy>();
179
180 MachineFunctionPass::getAnalysisUsage(AU);
181 }
182
183 bool runOnMachineFunction(MachineFunction &MF) override;
184};
185
186} // end anonymous namespace
187
188char StackSlotColoringLegacy::ID = 0;
189
190char &llvm::StackSlotColoringID = StackSlotColoringLegacy::ID;
191
192INITIALIZE_PASS_BEGIN(StackSlotColoringLegacy, DEBUG_TYPE,
193 "Stack Slot Coloring", false, false)
194INITIALIZE_PASS_DEPENDENCY(SlotIndexesWrapperPass)
195INITIALIZE_PASS_DEPENDENCY(LiveStacksWrapperLegacy)
196INITIALIZE_PASS_DEPENDENCY(MachineLoopInfoWrapperPass)
197INITIALIZE_PASS_END(StackSlotColoringLegacy, DEBUG_TYPE, "Stack Slot Coloring",
198 false, false)
199
200namespace {
201
202// IntervalSorter - Comparison predicate that sort live intervals by
203// their weight.
204struct IntervalSorter {
205 bool operator()(LiveInterval* LHS, LiveInterval* RHS) const {
206 return LHS->weight() > RHS->weight();
207 }
208};
209
210} // end anonymous namespace
211
212/// ScanForSpillSlotRefs - Scan all the machine instructions for spill slot
213/// references and update spill slot weights.
214void StackSlotColoring::ScanForSpillSlotRefs(MachineFunction &MF) {
215 SSRefs.resize(N: MFI->getObjectIndexEnd());
216
217 // FIXME: Need the equivalent of MachineRegisterInfo for frameindex operands.
218 for (MachineBasicBlock &MBB : MF) {
219 for (MachineInstr &MI : MBB) {
220 for (const MachineOperand &MO : MI.operands()) {
221 if (!MO.isFI())
222 continue;
223 int FI = MO.getIndex();
224 if (FI < 0)
225 continue;
226 if (!LS->hasInterval(Slot: FI))
227 continue;
228 LiveInterval &li = LS->getInterval(Slot: FI);
229 if (!MI.isDebugInstr())
230 li.incrementWeight(
231 Inc: LiveIntervals::getSpillWeight(isDef: false, isUse: true, MBFI, MI));
232 }
233 for (MachineMemOperand *MMO : MI.memoperands()) {
234 if (const FixedStackPseudoSourceValue *FSV =
235 dyn_cast_or_null<FixedStackPseudoSourceValue>(
236 Val: MMO->getPseudoValue())) {
237 int FI = FSV->getFrameIndex();
238 if (FI >= 0)
239 SSRefs[FI].push_back(Elt: MMO);
240 }
241 }
242 }
243 }
244}
245
246/// InitializeSlots - Process all spill stack slot liveintervals and add them
247/// to a sorted (by weight) list.
248void StackSlotColoring::InitializeSlots() {
249 int LastFI = MFI->getObjectIndexEnd();
250
251 // There is always at least one stack ID.
252 AllColors.resize(N: 1);
253 UsedColors.resize(N: 1);
254
255 OrigAlignments.resize(N: LastFI);
256 OrigSizes.resize(N: LastFI);
257 AllColors[0].resize(N: LastFI);
258 UsedColors[0].resize(N: LastFI);
259 Assignments.resize(N: LastFI);
260
261 using Pair = std::iterator_traits<LiveStacks::iterator>::value_type;
262
263 SmallVector<Pair *, 16> Intervals;
264
265 Intervals.reserve(N: LS->getNumIntervals());
266 for (auto &I : *LS)
267 Intervals.push_back(Elt: &I);
268 llvm::sort(C&: Intervals,
269 Comp: [](Pair *LHS, Pair *RHS) { return LHS->first < RHS->first; });
270
271 // Gather all spill slots into a list.
272 LLVM_DEBUG(dbgs() << "Spill slot intervals:\n");
273 for (auto *I : Intervals) {
274 LiveInterval &li = I->second;
275 LLVM_DEBUG(li.dump());
276 int FI = li.reg().stackSlotIndex();
277 if (MFI->isDeadObjectIndex(ObjectIdx: FI))
278 continue;
279
280 SSIntervals.push_back(x: &li);
281 OrigAlignments[FI] = MFI->getObjectAlign(ObjectIdx: FI);
282 OrigSizes[FI] = MFI->getObjectSize(ObjectIdx: FI);
283
284 auto StackID = MFI->getStackID(ObjectIdx: FI);
285 if (StackID != 0) {
286 if (StackID >= AllColors.size()) {
287 AllColors.resize(N: StackID + 1);
288 UsedColors.resize(N: StackID + 1);
289 }
290 AllColors[StackID].resize(N: LastFI);
291 UsedColors[StackID].resize(N: LastFI);
292 }
293
294 AllColors[StackID].set(FI);
295 }
296 LLVM_DEBUG(dbgs() << '\n');
297
298 // Sort them by weight.
299 llvm::stable_sort(Range&: SSIntervals, C: IntervalSorter());
300
301 NextColors.resize(N: AllColors.size());
302
303 // Get first "color".
304 for (unsigned I = 0, E = AllColors.size(); I != E; ++I)
305 NextColors[I] = AllColors[I].find_first();
306}
307
308/// ColorSlot - Assign a "color" (stack slot) to the specified stack slot.
309int StackSlotColoring::ColorSlot(LiveInterval *li) {
310 int Color = -1;
311 bool Share = false;
312 int FI = li->reg().stackSlotIndex();
313 uint8_t StackID = MFI->getStackID(ObjectIdx: FI);
314
315 if (!DisableSharing) {
316
317 // Check if it's possible to reuse any of the used colors.
318 Color = UsedColors[StackID].find_first();
319 while (Color != -1) {
320 if (!Assignments[Color].overlaps(LI: li)) {
321 Share = true;
322 ++NumEliminated;
323 break;
324 }
325 Color = UsedColors[StackID].find_next(Prev: Color);
326 }
327 }
328
329 if (Color != -1 && MFI->getStackID(ObjectIdx: Color) != MFI->getStackID(ObjectIdx: FI)) {
330 LLVM_DEBUG(dbgs() << "cannot share FIs with different stack IDs\n");
331 Share = false;
332 }
333
334 // Assign it to the first available color (assumed to be the best) if it's
335 // not possible to share a used color with other objects.
336 if (!Share) {
337 assert(NextColors[StackID] != -1 && "No more spill slots?");
338 Color = NextColors[StackID];
339 UsedColors[StackID].set(Color);
340 NextColors[StackID] = AllColors[StackID].find_next(Prev: NextColors[StackID]);
341 }
342
343 assert(MFI->getStackID(Color) == MFI->getStackID(FI));
344
345 // Record the assignment.
346 Assignments[Color].add(LI: li, Alloc&: LIUAlloc);
347 LLVM_DEBUG(dbgs() << "Assigning fi#" << FI << " to fi#" << Color << "\n");
348
349 // Change size and alignment of the allocated slot. If there are multiple
350 // objects sharing the same slot, then make sure the size and alignment
351 // are large enough for all.
352 Align Alignment = OrigAlignments[FI];
353 if (!Share || Alignment > MFI->getObjectAlign(ObjectIdx: Color))
354 MFI->setObjectAlignment(ObjectIdx: Color, Alignment);
355 int64_t Size = OrigSizes[FI];
356 if (!Share || Size > MFI->getObjectSize(ObjectIdx: Color))
357 MFI->setObjectSize(ObjectIdx: Color, Size);
358 return Color;
359}
360
361/// Colorslots - Color all spill stack slots and rewrite all frameindex machine
362/// operands in the function.
363bool StackSlotColoring::ColorSlots(MachineFunction &MF) {
364 unsigned NumObjs = MFI->getObjectIndexEnd();
365 SmallVector<int, 16> SlotMapping(NumObjs, -1);
366 SmallVector<float, 16> SlotWeights(NumObjs, 0.0);
367 SmallVector<SmallVector<int, 4>, 16> RevMap(NumObjs);
368 BitVector UsedColors(NumObjs);
369
370 LLVM_DEBUG(dbgs() << "Color spill slot intervals:\n");
371 bool Changed = false;
372 for (LiveInterval *li : SSIntervals) {
373 int SS = li->reg().stackSlotIndex();
374 int NewSS = ColorSlot(li);
375 assert(NewSS >= 0 && "Stack coloring failed?");
376 SlotMapping[SS] = NewSS;
377 RevMap[NewSS].push_back(Elt: SS);
378 SlotWeights[NewSS] += li->weight();
379 UsedColors.set(NewSS);
380 Changed |= (SS != NewSS);
381 }
382
383 LLVM_DEBUG(dbgs() << "\nSpill slots after coloring:\n");
384 for (LiveInterval *li : SSIntervals) {
385 int SS = li->reg().stackSlotIndex();
386 li->setWeight(SlotWeights[SS]);
387 }
388 // Sort them by new weight.
389 llvm::stable_sort(Range&: SSIntervals, C: IntervalSorter());
390
391#ifndef NDEBUG
392 for (LiveInterval *li : SSIntervals)
393 LLVM_DEBUG(li->dump());
394 LLVM_DEBUG(dbgs() << '\n');
395#endif
396
397 if (!Changed)
398 return false;
399
400 // Rewrite all MachineMemOperands.
401 for (unsigned SS = 0, SE = SSRefs.size(); SS != SE; ++SS) {
402 int NewFI = SlotMapping[SS];
403 if (NewFI == -1 || (NewFI == (int)SS))
404 continue;
405
406 const PseudoSourceValue *NewSV = MF.getPSVManager().getFixedStack(FI: NewFI);
407 SmallVectorImpl<MachineMemOperand *> &RefMMOs = SSRefs[SS];
408 for (MachineMemOperand *MMO : RefMMOs)
409 MMO->setValue(NewSV);
410 }
411
412 // Rewrite all MO_FrameIndex operands. Look for dead stores.
413 for (MachineBasicBlock &MBB : MF) {
414 for (MachineInstr &MI : MBB)
415 RewriteInstruction(MI, SlotMapping, MF);
416 RemoveDeadStores(MBB: &MBB);
417 }
418
419 // Delete unused stack slots.
420 for (int StackID = 0, E = AllColors.size(); StackID != E; ++StackID) {
421 int NextColor = NextColors[StackID];
422 while (NextColor != -1) {
423 LLVM_DEBUG(dbgs() << "Removing unused stack object fi#" << NextColor << "\n");
424 MFI->RemoveStackObject(ObjectIdx: NextColor);
425 NextColor = AllColors[StackID].find_next(Prev: NextColor);
426 }
427 }
428
429 return true;
430}
431
432/// RewriteInstruction - Rewrite specified instruction by replacing references
433/// to old frame index with new one.
434void StackSlotColoring::RewriteInstruction(MachineInstr &MI,
435 SmallVectorImpl<int> &SlotMapping,
436 MachineFunction &MF) {
437 // Update the operands.
438 for (MachineOperand &MO : MI.operands()) {
439 if (!MO.isFI())
440 continue;
441 int OldFI = MO.getIndex();
442 if (OldFI < 0)
443 continue;
444 int NewFI = SlotMapping[OldFI];
445 if (NewFI == -1 || NewFI == OldFI)
446 continue;
447
448 assert(MFI->getStackID(OldFI) == MFI->getStackID(NewFI));
449 MO.setIndex(NewFI);
450 }
451
452 // The MachineMemOperands have already been updated.
453}
454
455/// RemoveDeadStores - Scan through a basic block and look for loads followed
456/// by stores. If they're both using the same stack slot, then the store is
457/// definitely dead. This could obviously be much more aggressive (consider
458/// pairs with instructions between them), but such extensions might have a
459/// considerable compile time impact.
460bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
461 // FIXME: This could be much more aggressive, but we need to investigate
462 // the compile time impact of doing so.
463 bool changed = false;
464
465 SmallVector<MachineInstr*, 4> toErase;
466
467 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
468 I != E; ++I) {
469 if (DCELimit != -1 && (int)NumDead >= DCELimit)
470 break;
471 int FirstSS, SecondSS;
472 if (TII->isStackSlotCopy(MI: *I, DestFrameIndex&: FirstSS, SrcFrameIndex&: SecondSS) && FirstSS == SecondSS &&
473 FirstSS != -1) {
474 ++NumDead;
475 changed = true;
476 toErase.push_back(Elt: &*I);
477 continue;
478 }
479
480 MachineBasicBlock::iterator NextMI = std::next(x: I);
481 MachineBasicBlock::iterator ProbableLoadMI = I;
482
483 Register LoadReg;
484 Register StoreReg;
485 TypeSize LoadSize = TypeSize::getZero();
486 TypeSize StoreSize = TypeSize::getZero();
487 if (!(LoadReg = TII->isLoadFromStackSlot(MI: *I, FrameIndex&: FirstSS, MemBytes&: LoadSize)))
488 continue;
489 // Skip the ...pseudo debugging... instructions between a load and store.
490 while ((NextMI != E) && NextMI->isDebugInstr()) {
491 ++NextMI;
492 ++I;
493 }
494 if (NextMI == E) continue;
495 if (!(StoreReg = TII->isStoreToStackSlot(MI: *NextMI, FrameIndex&: SecondSS, MemBytes&: StoreSize)))
496 continue;
497 // Skip if the stack size is unknown.
498 if (!LoadSize || !StoreSize)
499 continue;
500 if (FirstSS != SecondSS || LoadReg != StoreReg || FirstSS == -1 ||
501 LoadSize != StoreSize || !MFI->isSpillSlotObjectIndex(ObjectIdx: FirstSS))
502 continue;
503
504 ++NumDead;
505 changed = true;
506
507 if (NextMI->findRegisterUseOperandIdx(Reg: LoadReg, /*TRI=*/nullptr, isKill: true) !=
508 -1) {
509 ++NumDead;
510 toErase.push_back(Elt: &*ProbableLoadMI);
511 }
512
513 toErase.push_back(Elt: &*NextMI);
514 ++I;
515 }
516
517 for (MachineInstr *MI : toErase) {
518 if (Indexes)
519 Indexes->removeMachineInstrFromMaps(MI&: *MI);
520 MI->eraseFromParent();
521 }
522
523 return changed;
524}
525
526bool StackSlotColoring::run(MachineFunction &MF) {
527 LLVM_DEBUG({
528 dbgs() << "********** Stack Slot Coloring **********\n"
529 << "********** Function: " << MF.getName() << '\n';
530 });
531
532 bool Changed = false;
533
534 unsigned NumSlots = LS->getNumIntervals();
535 if (NumSlots == 0)
536 // Nothing to do!
537 return false;
538
539 // If there are calls to setjmp or sigsetjmp, don't perform stack slot
540 // coloring. The stack could be modified before the longjmp is executed,
541 // resulting in the wrong value being used afterwards.
542 if (MF.exposesReturnsTwice())
543 return false;
544
545 // Gather spill slot references
546 ScanForSpillSlotRefs(MF);
547 InitializeSlots();
548 Changed = ColorSlots(MF);
549
550 for (int &Next : NextColors)
551 Next = -1;
552
553 SSIntervals.clear();
554 for (auto &RefMMOs : SSRefs)
555 RefMMOs.clear();
556 SSRefs.clear();
557 OrigAlignments.clear();
558 OrigSizes.clear();
559 AllColors.clear();
560 UsedColors.clear();
561 Assignments.clear();
562
563 return Changed;
564}
565
566bool StackSlotColoringLegacy::runOnMachineFunction(MachineFunction &MF) {
567 if (skipFunction(F: MF.getFunction()))
568 return false;
569
570 LiveStacks *LS = &getAnalysis<LiveStacksWrapperLegacy>().getLS();
571 MachineBlockFrequencyInfo *MBFI =
572 &getAnalysis<MachineBlockFrequencyInfoWrapperPass>().getMBFI();
573 SlotIndexes *Indexes = &getAnalysis<SlotIndexesWrapperPass>().getSI();
574 StackSlotColoring Impl(MF, LS, MBFI, Indexes);
575 return Impl.run(MF);
576}
577
578PreservedAnalyses
579StackSlotColoringPass::run(MachineFunction &MF,
580 MachineFunctionAnalysisManager &MFAM) {
581 LiveStacks *LS = &MFAM.getResult<LiveStacksAnalysis>(IR&: MF);
582 MachineBlockFrequencyInfo *MBFI =
583 &MFAM.getResult<MachineBlockFrequencyAnalysis>(IR&: MF);
584 SlotIndexes *Indexes = &MFAM.getResult<SlotIndexesAnalysis>(IR&: MF);
585 StackSlotColoring Impl(MF, LS, MBFI, Indexes);
586 bool Changed = Impl.run(MF);
587 if (!Changed)
588 return PreservedAnalyses::all();
589
590 auto PA = getMachineFunctionPassPreservedAnalyses();
591 PA.preserveSet<CFGAnalyses>();
592 PA.preserve<SlotIndexesAnalysis>();
593 PA.preserve<LiveIntervalsAnalysis>();
594 PA.preserve<LiveDebugVariablesAnalysis>();
595 return PA;
596}
597