1//===-- ControlHeightReduction.cpp - Control Height Reduction -------------===//
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 pass merges conditional blocks of code and reduces the number of
10// conditional branches in the hot paths based on profiles.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Transforms/Instrumentation/ControlHeightReduction.h"
15#include "llvm/ADT/DenseMap.h"
16#include "llvm/ADT/DenseSet.h"
17#include "llvm/ADT/SmallVector.h"
18#include "llvm/ADT/StringSet.h"
19#include "llvm/Analysis/BlockFrequencyInfo.h"
20#include "llvm/Analysis/GlobalsModRef.h"
21#include "llvm/Analysis/OptimizationRemarkEmitter.h"
22#include "llvm/Analysis/ProfileSummaryInfo.h"
23#include "llvm/Analysis/RegionInfo.h"
24#include "llvm/Analysis/RegionIterator.h"
25#include "llvm/Analysis/ValueTracking.h"
26#include "llvm/IR/CFG.h"
27#include "llvm/IR/Dominators.h"
28#include "llvm/IR/IRBuilder.h"
29#include "llvm/IR/IntrinsicInst.h"
30#include "llvm/IR/MDBuilder.h"
31#include "llvm/IR/Module.h"
32#include "llvm/IR/PassManager.h"
33#include "llvm/IR/ProfDataUtils.h"
34#include "llvm/Support/BranchProbability.h"
35#include "llvm/Support/CommandLine.h"
36#include "llvm/Support/MemoryBuffer.h"
37#include "llvm/Transforms/Utils.h"
38#include "llvm/Transforms/Utils/BasicBlockUtils.h"
39#include "llvm/Transforms/Utils/Cloning.h"
40#include "llvm/Transforms/Utils/ValueMapper.h"
41
42#include <optional>
43#include <set>
44#include <sstream>
45
46using namespace llvm;
47
48#define DEBUG_TYPE "chr"
49
50#define CHR_DEBUG(X) LLVM_DEBUG(X)
51
52static cl::opt<bool> DisableCHR("disable-chr", cl::init(Val: false), cl::Hidden,
53 cl::desc("Disable CHR for all functions"));
54
55static cl::opt<bool> ForceCHR("force-chr", cl::init(Val: false), cl::Hidden,
56 cl::desc("Apply CHR for all functions"));
57
58static cl::opt<double> CHRBiasThreshold(
59 "chr-bias-threshold", cl::init(Val: 0.99), cl::Hidden,
60 cl::desc("CHR considers a branch bias greater than this ratio as biased"));
61
62static cl::opt<unsigned> CHRMergeThreshold(
63 "chr-merge-threshold", cl::init(Val: 2), cl::Hidden,
64 cl::desc("CHR merges a group of N branches/selects where N >= this value"));
65
66static cl::opt<std::string> CHRModuleList(
67 "chr-module-list", cl::init(Val: ""), cl::Hidden,
68 cl::desc("Specify file to retrieve the list of modules to apply CHR to"));
69
70static cl::opt<std::string> CHRFunctionList(
71 "chr-function-list", cl::init(Val: ""), cl::Hidden,
72 cl::desc("Specify file to retrieve the list of functions to apply CHR to"));
73
74static cl::opt<unsigned> CHRDupThreshsold(
75 "chr-dup-threshold", cl::init(Val: 3), cl::Hidden,
76 cl::desc("Max number of duplications by CHR for a region"));
77
78static StringSet<> CHRModules;
79static StringSet<> CHRFunctions;
80
81static void parseCHRFilterFiles() {
82 if (!CHRModuleList.empty()) {
83 auto FileOrErr = MemoryBuffer::getFile(Filename: CHRModuleList);
84 if (!FileOrErr) {
85 errs() << "Error: Couldn't read the chr-module-list file " << CHRModuleList << "\n";
86 std::exit(status: 1);
87 }
88 StringRef Buf = FileOrErr->get()->getBuffer();
89 SmallVector<StringRef, 0> Lines;
90 Buf.split(A&: Lines, Separator: '\n');
91 for (StringRef Line : Lines) {
92 Line = Line.trim();
93 if (!Line.empty())
94 CHRModules.insert(key: Line);
95 }
96 }
97 if (!CHRFunctionList.empty()) {
98 auto FileOrErr = MemoryBuffer::getFile(Filename: CHRFunctionList);
99 if (!FileOrErr) {
100 errs() << "Error: Couldn't read the chr-function-list file " << CHRFunctionList << "\n";
101 std::exit(status: 1);
102 }
103 StringRef Buf = FileOrErr->get()->getBuffer();
104 SmallVector<StringRef, 0> Lines;
105 Buf.split(A&: Lines, Separator: '\n');
106 for (StringRef Line : Lines) {
107 Line = Line.trim();
108 if (!Line.empty())
109 CHRFunctions.insert(key: Line);
110 }
111 }
112}
113
114namespace {
115
116struct CHRStats {
117 CHRStats() = default;
118 void print(raw_ostream &OS) const {
119 OS << "CHRStats: NumBranches " << NumBranches
120 << " NumBranchesDelta " << NumBranchesDelta
121 << " WeightedNumBranchesDelta " << WeightedNumBranchesDelta;
122 }
123 // The original number of conditional branches / selects
124 uint64_t NumBranches = 0;
125 // The decrease of the number of conditional branches / selects in the hot
126 // paths due to CHR.
127 uint64_t NumBranchesDelta = 0;
128 // NumBranchesDelta weighted by the profile count at the scope entry.
129 uint64_t WeightedNumBranchesDelta = 0;
130};
131
132// RegInfo - some properties of a Region.
133struct RegInfo {
134 RegInfo() = default;
135 RegInfo(Region *RegionIn) : R(RegionIn) {}
136 Region *R = nullptr;
137 bool HasBranch = false;
138 SmallVector<SelectInst *, 8> Selects;
139};
140
141typedef DenseMap<Region *, DenseSet<Instruction *>> HoistStopMapTy;
142
143// CHRScope - a sequence of regions to CHR together. It corresponds to a
144// sequence of conditional blocks. It can have subscopes which correspond to
145// nested conditional blocks. Nested CHRScopes form a tree.
146class CHRScope {
147 public:
148 CHRScope(RegInfo RI) : BranchInsertPoint(nullptr) {
149 assert(RI.R && "Null RegionIn");
150 RegInfos.push_back(Elt: RI);
151 }
152
153 Region *getParentRegion() {
154 assert(RegInfos.size() > 0 && "Empty CHRScope");
155 Region *Parent = RegInfos[0].R->getParent();
156 assert(Parent && "Unexpected to call this on the top-level region");
157 return Parent;
158 }
159
160 BasicBlock *getEntryBlock() {
161 assert(RegInfos.size() > 0 && "Empty CHRScope");
162 return RegInfos.front().R->getEntry();
163 }
164
165 BasicBlock *getExitBlock() {
166 assert(RegInfos.size() > 0 && "Empty CHRScope");
167 return RegInfos.back().R->getExit();
168 }
169
170 bool appendable(CHRScope *Next) {
171 // The next scope is appendable only if this scope is directly connected to
172 // it (which implies it post-dominates this scope) and this scope dominates
173 // it (no edge to the next scope outside this scope).
174 BasicBlock *NextEntry = Next->getEntryBlock();
175 if (getExitBlock() != NextEntry)
176 // Not directly connected.
177 return false;
178 Region *LastRegion = RegInfos.back().R;
179 for (BasicBlock *Pred : predecessors(BB: NextEntry))
180 if (!LastRegion->contains(BB: Pred))
181 // There's an edge going into the entry of the next scope from outside
182 // of this scope.
183 return false;
184 return true;
185 }
186
187 void append(CHRScope *Next) {
188 assert(RegInfos.size() > 0 && "Empty CHRScope");
189 assert(Next->RegInfos.size() > 0 && "Empty CHRScope");
190 assert(getParentRegion() == Next->getParentRegion() &&
191 "Must be siblings");
192 assert(getExitBlock() == Next->getEntryBlock() &&
193 "Must be adjacent");
194 RegInfos.append(in_start: Next->RegInfos.begin(), in_end: Next->RegInfos.end());
195 Subs.append(in_start: Next->Subs.begin(), in_end: Next->Subs.end());
196 }
197
198 void addSub(CHRScope *SubIn) {
199#ifndef NDEBUG
200 bool IsChild = false;
201 for (RegInfo &RI : RegInfos)
202 if (RI.R == SubIn->getParentRegion()) {
203 IsChild = true;
204 break;
205 }
206 assert(IsChild && "Must be a child");
207#endif
208 Subs.push_back(Elt: SubIn);
209 }
210
211 // Split this scope at the boundary region into two, which will belong to the
212 // tail and returns the tail.
213 CHRScope *split(Region *Boundary) {
214 assert(Boundary && "Boundary null");
215 assert(RegInfos.begin()->R != Boundary &&
216 "Can't be split at beginning");
217 auto BoundaryIt = llvm::find_if(
218 Range&: RegInfos, P: [&Boundary](const RegInfo &RI) { return Boundary == RI.R; });
219 if (BoundaryIt == RegInfos.end())
220 return nullptr;
221 ArrayRef<RegInfo> TailRegInfos(BoundaryIt, RegInfos.end());
222 DenseSet<Region *> TailRegionSet;
223 for (const RegInfo &RI : TailRegInfos)
224 TailRegionSet.insert(V: RI.R);
225
226 auto TailIt =
227 std::stable_partition(first: Subs.begin(), last: Subs.end(), pred: [&](CHRScope *Sub) {
228 assert(Sub && "null Sub");
229 Region *Parent = Sub->getParentRegion();
230 if (TailRegionSet.count(V: Parent))
231 return false;
232
233 assert(llvm::any_of(
234 RegInfos,
235 [&Parent](const RegInfo &RI) { return Parent == RI.R; }) &&
236 "Must be in head");
237 return true;
238 });
239 ArrayRef<CHRScope *> TailSubs(TailIt, Subs.end());
240
241 assert(HoistStopMap.empty() && "MapHoistStops must be empty");
242 auto *Scope = new CHRScope(TailRegInfos, TailSubs);
243 RegInfos.erase(CS: BoundaryIt, CE: RegInfos.end());
244 Subs.erase(CS: TailIt, CE: Subs.end());
245 return Scope;
246 }
247
248 bool contains(Instruction *I) const {
249 BasicBlock *Parent = I->getParent();
250 for (const RegInfo &RI : RegInfos)
251 if (RI.R->contains(BB: Parent))
252 return true;
253 return false;
254 }
255
256 void print(raw_ostream &OS) const;
257
258 SmallVector<RegInfo, 8> RegInfos; // Regions that belong to this scope
259 SmallVector<CHRScope *, 8> Subs; // Subscopes.
260
261 // The instruction at which to insert the CHR conditional branch (and hoist
262 // the dependent condition values).
263 Instruction *BranchInsertPoint;
264
265 // True-biased and false-biased regions (conditional blocks),
266 // respectively. Used only for the outermost scope and includes regions in
267 // subscopes. The rest are unbiased.
268 DenseSet<Region *> TrueBiasedRegions;
269 DenseSet<Region *> FalseBiasedRegions;
270 // Among the biased regions, the regions that get CHRed.
271 SmallVector<RegInfo, 8> CHRRegions;
272
273 // True-biased and false-biased selects, respectively. Used only for the
274 // outermost scope and includes ones in subscopes.
275 DenseSet<SelectInst *> TrueBiasedSelects;
276 DenseSet<SelectInst *> FalseBiasedSelects;
277
278 // Map from one of the above regions to the instructions to stop
279 // hoisting instructions at through use-def chains.
280 HoistStopMapTy HoistStopMap;
281
282 private:
283 CHRScope(ArrayRef<RegInfo> RegInfosIn, ArrayRef<CHRScope *> SubsIn)
284 : RegInfos(RegInfosIn.begin(), RegInfosIn.end()),
285 Subs(SubsIn.begin(), SubsIn.end()), BranchInsertPoint(nullptr) {}
286};
287
288class CHR {
289 public:
290 CHR(Function &Fin, BlockFrequencyInfo &BFIin, DominatorTree &DTin,
291 ProfileSummaryInfo &PSIin, RegionInfo &RIin,
292 OptimizationRemarkEmitter &OREin)
293 : F(Fin), BFI(BFIin), DT(DTin), PSI(PSIin), RI(RIin), ORE(OREin) {}
294
295 ~CHR() {
296 for (CHRScope *Scope : Scopes) {
297 delete Scope;
298 }
299 }
300
301 bool run();
302
303 private:
304 // See the comments in CHR::run() for the high level flow of the algorithm and
305 // what the following functions do.
306
307 void findScopes(SmallVectorImpl<CHRScope *> &Output) {
308 Region *R = RI.getTopLevelRegion();
309 if (CHRScope *Scope = findScopes(R, NextRegion: nullptr, ParentRegion: nullptr, Scopes&: Output)) {
310 Output.push_back(Elt: Scope);
311 }
312 }
313 CHRScope *findScopes(Region *R, Region *NextRegion, Region *ParentRegion,
314 SmallVectorImpl<CHRScope *> &Scopes);
315 CHRScope *findScope(Region *R);
316 void checkScopeHoistable(CHRScope *Scope);
317
318 void splitScopes(SmallVectorImpl<CHRScope *> &Input,
319 SmallVectorImpl<CHRScope *> &Output);
320 SmallVector<CHRScope *, 8> splitScope(CHRScope *Scope,
321 CHRScope *Outer,
322 DenseSet<Value *> *OuterConditionValues,
323 Instruction *OuterInsertPoint,
324 SmallVectorImpl<CHRScope *> &Output,
325 DenseSet<Instruction *> &Unhoistables);
326
327 void classifyBiasedScopes(SmallVectorImpl<CHRScope *> &Scopes);
328 void classifyBiasedScopes(CHRScope *Scope, CHRScope *OutermostScope);
329
330 void filterScopes(SmallVectorImpl<CHRScope *> &Input,
331 SmallVectorImpl<CHRScope *> &Output);
332
333 void setCHRRegions(SmallVectorImpl<CHRScope *> &Input,
334 SmallVectorImpl<CHRScope *> &Output);
335 void setCHRRegions(CHRScope *Scope, CHRScope *OutermostScope);
336
337 void sortScopes(SmallVectorImpl<CHRScope *> &Input,
338 SmallVectorImpl<CHRScope *> &Output);
339
340 void transformScopes(SmallVectorImpl<CHRScope *> &CHRScopes);
341 void transformScopes(CHRScope *Scope, DenseSet<PHINode *> &TrivialPHIs);
342 void cloneScopeBlocks(CHRScope *Scope,
343 BasicBlock *PreEntryBlock,
344 BasicBlock *ExitBlock,
345 Region *LastRegion,
346 ValueToValueMapTy &VMap);
347 BranchInst *createMergedBranch(BasicBlock *PreEntryBlock,
348 BasicBlock *EntryBlock,
349 BasicBlock *NewEntryBlock,
350 ValueToValueMapTy &VMap);
351 void fixupBranchesAndSelects(CHRScope *Scope, BasicBlock *PreEntryBlock,
352 BranchInst *MergedBR, uint64_t ProfileCount);
353 void fixupBranch(Region *R, CHRScope *Scope, IRBuilder<> &IRB,
354 Value *&MergedCondition, BranchProbability &CHRBranchBias);
355 void fixupSelect(SelectInst *SI, CHRScope *Scope, IRBuilder<> &IRB,
356 Value *&MergedCondition, BranchProbability &CHRBranchBias);
357 void addToMergedCondition(bool IsTrueBiased, Value *Cond,
358 Instruction *BranchOrSelect, CHRScope *Scope,
359 IRBuilder<> &IRB, Value *&MergedCondition);
360 unsigned getRegionDuplicationCount(const Region *R) {
361 unsigned Count = 0;
362 // Find out how many times region R is cloned. Note that if the parent
363 // of R is cloned, R is also cloned, but R's clone count is not updated
364 // from the clone of the parent. We need to accumlate all the counts
365 // from the ancestors to get the clone count.
366 while (R) {
367 Count += DuplicationCount[R];
368 R = R->getParent();
369 }
370 return Count;
371 }
372
373 Function &F;
374 BlockFrequencyInfo &BFI;
375 DominatorTree &DT;
376 ProfileSummaryInfo &PSI;
377 RegionInfo &RI;
378 OptimizationRemarkEmitter &ORE;
379 CHRStats Stats;
380
381 // All the true-biased regions in the function
382 DenseSet<Region *> TrueBiasedRegionsGlobal;
383 // All the false-biased regions in the function
384 DenseSet<Region *> FalseBiasedRegionsGlobal;
385 // All the true-biased selects in the function
386 DenseSet<SelectInst *> TrueBiasedSelectsGlobal;
387 // All the false-biased selects in the function
388 DenseSet<SelectInst *> FalseBiasedSelectsGlobal;
389 // A map from biased regions to their branch bias
390 DenseMap<Region *, BranchProbability> BranchBiasMap;
391 // A map from biased selects to their branch bias
392 DenseMap<SelectInst *, BranchProbability> SelectBiasMap;
393 // All the scopes.
394 DenseSet<CHRScope *> Scopes;
395 // This maps records how many times this region is cloned.
396 DenseMap<const Region *, unsigned> DuplicationCount;
397};
398
399} // end anonymous namespace
400
401static inline
402raw_ostream LLVM_ATTRIBUTE_UNUSED &operator<<(raw_ostream &OS,
403 const CHRStats &Stats) {
404 Stats.print(OS);
405 return OS;
406}
407
408static inline
409raw_ostream &operator<<(raw_ostream &OS, const CHRScope &Scope) {
410 Scope.print(OS);
411 return OS;
412}
413
414static bool shouldApply(Function &F, ProfileSummaryInfo &PSI) {
415 if (DisableCHR)
416 return false;
417
418 if (ForceCHR)
419 return true;
420
421 if (!CHRModuleList.empty() || !CHRFunctionList.empty()) {
422 if (CHRModules.count(Key: F.getParent()->getName()))
423 return true;
424 return CHRFunctions.count(Key: F.getName());
425 }
426
427 return PSI.isFunctionEntryHot(F: &F);
428}
429
430static void LLVM_ATTRIBUTE_UNUSED dumpIR(Function &F, const char *Label,
431 CHRStats *Stats) {
432 StringRef FuncName = F.getName();
433 StringRef ModuleName = F.getParent()->getName();
434 (void)(FuncName); // Unused in release build.
435 (void)(ModuleName); // Unused in release build.
436 CHR_DEBUG(dbgs() << "CHR IR dump " << Label << " " << ModuleName << " "
437 << FuncName);
438 if (Stats)
439 CHR_DEBUG(dbgs() << " " << *Stats);
440 CHR_DEBUG(dbgs() << "\n");
441 CHR_DEBUG(F.dump());
442}
443
444void CHRScope::print(raw_ostream &OS) const {
445 assert(RegInfos.size() > 0 && "Empty CHRScope");
446 OS << "CHRScope[";
447 OS << RegInfos.size() << ", Regions[";
448 for (const RegInfo &RI : RegInfos) {
449 OS << RI.R->getNameStr();
450 if (RI.HasBranch)
451 OS << " B";
452 if (RI.Selects.size() > 0)
453 OS << " S" << RI.Selects.size();
454 OS << ", ";
455 }
456 if (RegInfos[0].R->getParent()) {
457 OS << "], Parent " << RegInfos[0].R->getParent()->getNameStr();
458 } else {
459 // top level region
460 OS << "]";
461 }
462 OS << ", Subs[";
463 for (CHRScope *Sub : Subs) {
464 OS << *Sub << ", ";
465 }
466 OS << "]]";
467}
468
469// Return true if the given instruction type can be hoisted by CHR.
470static bool isHoistableInstructionType(Instruction *I) {
471 return isa<BinaryOperator>(Val: I) || isa<CastInst>(Val: I) || isa<SelectInst>(Val: I) ||
472 isa<GetElementPtrInst>(Val: I) || isa<CmpInst>(Val: I) ||
473 isa<InsertElementInst>(Val: I) || isa<ExtractElementInst>(Val: I) ||
474 isa<ShuffleVectorInst>(Val: I) || isa<ExtractValueInst>(Val: I) ||
475 isa<InsertValueInst>(Val: I);
476}
477
478// Return true if the given instruction can be hoisted by CHR.
479static bool isHoistable(Instruction *I, DominatorTree &DT) {
480 if (!isHoistableInstructionType(I))
481 return false;
482 return isSafeToSpeculativelyExecute(I, CtxI: nullptr, AC: nullptr, DT: &DT);
483}
484
485// Recursively traverse the use-def chains of the given value and return a set
486// of the unhoistable base values defined within the scope (excluding the
487// first-region entry block) or the (hoistable or unhoistable) base values that
488// are defined outside (including the first-region entry block) of the
489// scope. The returned set doesn't include constants.
490static const std::set<Value *> &
491getBaseValues(Value *V, DominatorTree &DT,
492 DenseMap<Value *, std::set<Value *>> &Visited) {
493 auto It = Visited.find(Val: V);
494 if (It != Visited.end()) {
495 return It->second;
496 }
497 std::set<Value *> Result;
498 if (auto *I = dyn_cast<Instruction>(Val: V)) {
499 // We don't stop at a block that's not in the Scope because we would miss
500 // some instructions that are based on the same base values if we stop
501 // there.
502 if (!isHoistable(I, DT)) {
503 Result.insert(x: I);
504 return Visited.insert(KV: std::make_pair(x&: V, y: std::move(Result))).first->second;
505 }
506 // I is hoistable above the Scope.
507 for (Value *Op : I->operands()) {
508 const std::set<Value *> &OpResult = getBaseValues(V: Op, DT, Visited);
509 Result.insert(first: OpResult.begin(), last: OpResult.end());
510 }
511 return Visited.insert(KV: std::make_pair(x&: V, y: std::move(Result))).first->second;
512 }
513 if (isa<Argument>(Val: V)) {
514 Result.insert(x: V);
515 }
516 // We don't include others like constants because those won't lead to any
517 // chance of folding of conditions (eg two bit checks merged into one check)
518 // after CHR.
519 return Visited.insert(KV: std::make_pair(x&: V, y: std::move(Result))).first->second;
520}
521
522// Return true if V is already hoisted or can be hoisted (along with its
523// operands) above the insert point. When it returns true and HoistStops is
524// non-null, the instructions to stop hoisting at through the use-def chains are
525// inserted into HoistStops.
526static bool
527checkHoistValue(Value *V, Instruction *InsertPoint, DominatorTree &DT,
528 DenseSet<Instruction *> &Unhoistables,
529 DenseSet<Instruction *> *HoistStops,
530 DenseMap<Instruction *, bool> &Visited) {
531 assert(InsertPoint && "Null InsertPoint");
532 if (auto *I = dyn_cast<Instruction>(Val: V)) {
533 auto It = Visited.find(Val: I);
534 if (It != Visited.end()) {
535 return It->second;
536 }
537 assert(DT.getNode(I->getParent()) && "DT must contain I's parent block");
538 assert(DT.getNode(InsertPoint->getParent()) && "DT must contain Destination");
539 if (Unhoistables.count(V: I)) {
540 // Don't hoist if they are not to be hoisted.
541 Visited[I] = false;
542 return false;
543 }
544 if (DT.dominates(Def: I, User: InsertPoint)) {
545 // We are already above the insert point. Stop here.
546 if (HoistStops)
547 HoistStops->insert(V: I);
548 Visited[I] = true;
549 return true;
550 }
551 // We aren't not above the insert point, check if we can hoist it above the
552 // insert point.
553 if (isHoistable(I, DT)) {
554 // Check operands first.
555 DenseSet<Instruction *> OpsHoistStops;
556 bool AllOpsHoisted = true;
557 for (Value *Op : I->operands()) {
558 if (!checkHoistValue(V: Op, InsertPoint, DT, Unhoistables, HoistStops: &OpsHoistStops,
559 Visited)) {
560 AllOpsHoisted = false;
561 break;
562 }
563 }
564 if (AllOpsHoisted) {
565 CHR_DEBUG(dbgs() << "checkHoistValue " << *I << "\n");
566 if (HoistStops)
567 HoistStops->insert(I: OpsHoistStops.begin(), E: OpsHoistStops.end());
568 Visited[I] = true;
569 return true;
570 }
571 }
572 Visited[I] = false;
573 return false;
574 }
575 // Non-instructions are considered hoistable.
576 return true;
577}
578
579// Constructs the true and false branch probabilities if the the instruction has
580// valid branch weights. Returns true when this was successful, false otherwise.
581static bool extractBranchProbabilities(Instruction *I,
582 BranchProbability &TrueProb,
583 BranchProbability &FalseProb) {
584 uint64_t TrueWeight;
585 uint64_t FalseWeight;
586 if (!extractBranchWeights(I: *I, TrueVal&: TrueWeight, FalseVal&: FalseWeight))
587 return false;
588 uint64_t SumWeight = TrueWeight + FalseWeight;
589
590 assert(SumWeight >= TrueWeight && SumWeight >= FalseWeight &&
591 "Overflow calculating branch probabilities.");
592
593 // Guard against 0-to-0 branch weights to avoid a division-by-zero crash.
594 if (SumWeight == 0)
595 return false;
596
597 TrueProb = BranchProbability::getBranchProbability(Numerator: TrueWeight, Denominator: SumWeight);
598 FalseProb = BranchProbability::getBranchProbability(Numerator: FalseWeight, Denominator: SumWeight);
599 return true;
600}
601
602static BranchProbability getCHRBiasThreshold() {
603 return BranchProbability::getBranchProbability(
604 Numerator: static_cast<uint64_t>(CHRBiasThreshold * 1000000), Denominator: 1000000);
605}
606
607// A helper for CheckBiasedBranch and CheckBiasedSelect. If TrueProb >=
608// CHRBiasThreshold, put Key into TrueSet and return true. If FalseProb >=
609// CHRBiasThreshold, put Key into FalseSet and return true. Otherwise, return
610// false.
611template <typename K, typename S, typename M>
612static bool checkBias(K *Key, BranchProbability TrueProb,
613 BranchProbability FalseProb, S &TrueSet, S &FalseSet,
614 M &BiasMap) {
615 BranchProbability Threshold = getCHRBiasThreshold();
616 if (TrueProb >= Threshold) {
617 TrueSet.insert(Key);
618 BiasMap[Key] = TrueProb;
619 return true;
620 } else if (FalseProb >= Threshold) {
621 FalseSet.insert(Key);
622 BiasMap[Key] = FalseProb;
623 return true;
624 }
625 return false;
626}
627
628// Returns true and insert a region into the right biased set and the map if the
629// branch of the region is biased.
630static bool checkBiasedBranch(BranchInst *BI, Region *R,
631 DenseSet<Region *> &TrueBiasedRegionsGlobal,
632 DenseSet<Region *> &FalseBiasedRegionsGlobal,
633 DenseMap<Region *, BranchProbability> &BranchBiasMap) {
634 if (!BI->isConditional())
635 return false;
636 BranchProbability ThenProb, ElseProb;
637 if (!extractBranchProbabilities(I: BI, TrueProb&: ThenProb, FalseProb&: ElseProb))
638 return false;
639 BasicBlock *IfThen = BI->getSuccessor(i: 0);
640 BasicBlock *IfElse = BI->getSuccessor(i: 1);
641 assert((IfThen == R->getExit() || IfElse == R->getExit()) &&
642 IfThen != IfElse &&
643 "Invariant from findScopes");
644 if (IfThen == R->getExit()) {
645 // Swap them so that IfThen/ThenProb means going into the conditional code
646 // and IfElse/ElseProb means skipping it.
647 std::swap(a&: IfThen, b&: IfElse);
648 std::swap(a&: ThenProb, b&: ElseProb);
649 }
650 CHR_DEBUG(dbgs() << "BI " << *BI << " ");
651 CHR_DEBUG(dbgs() << "ThenProb " << ThenProb << " ");
652 CHR_DEBUG(dbgs() << "ElseProb " << ElseProb << "\n");
653 return checkBias(Key: R, TrueProb: ThenProb, FalseProb: ElseProb,
654 TrueSet&: TrueBiasedRegionsGlobal, FalseSet&: FalseBiasedRegionsGlobal,
655 BiasMap&: BranchBiasMap);
656}
657
658// Returns true and insert a select into the right biased set and the map if the
659// select is biased.
660static bool checkBiasedSelect(
661 SelectInst *SI, Region *R,
662 DenseSet<SelectInst *> &TrueBiasedSelectsGlobal,
663 DenseSet<SelectInst *> &FalseBiasedSelectsGlobal,
664 DenseMap<SelectInst *, BranchProbability> &SelectBiasMap) {
665 BranchProbability TrueProb, FalseProb;
666 if (!extractBranchProbabilities(I: SI, TrueProb, FalseProb))
667 return false;
668 CHR_DEBUG(dbgs() << "SI " << *SI << " ");
669 CHR_DEBUG(dbgs() << "TrueProb " << TrueProb << " ");
670 CHR_DEBUG(dbgs() << "FalseProb " << FalseProb << "\n");
671 return checkBias(Key: SI, TrueProb, FalseProb,
672 TrueSet&: TrueBiasedSelectsGlobal, FalseSet&: FalseBiasedSelectsGlobal,
673 BiasMap&: SelectBiasMap);
674}
675
676// Returns the instruction at which to hoist the dependent condition values and
677// insert the CHR branch for a region. This is the terminator branch in the
678// entry block or the first select in the entry block, if any.
679static Instruction* getBranchInsertPoint(RegInfo &RI) {
680 Region *R = RI.R;
681 BasicBlock *EntryBB = R->getEntry();
682 // The hoist point is by default the terminator of the entry block, which is
683 // the same as the branch instruction if RI.HasBranch is true.
684 Instruction *HoistPoint = EntryBB->getTerminator();
685 for (SelectInst *SI : RI.Selects) {
686 if (SI->getParent() == EntryBB) {
687 // Pick the first select in Selects in the entry block. Note Selects is
688 // sorted in the instruction order within a block (asserted below).
689 HoistPoint = SI;
690 break;
691 }
692 }
693 assert(HoistPoint && "Null HoistPoint");
694#ifndef NDEBUG
695 // Check that HoistPoint is the first one in Selects in the entry block,
696 // if any.
697 DenseSet<Instruction *> EntryBlockSelectSet;
698 for (SelectInst *SI : RI.Selects) {
699 if (SI->getParent() == EntryBB) {
700 EntryBlockSelectSet.insert(SI);
701 }
702 }
703 for (Instruction &I : *EntryBB) {
704 if (EntryBlockSelectSet.contains(&I)) {
705 assert(&I == HoistPoint &&
706 "HoistPoint must be the first one in Selects");
707 break;
708 }
709 }
710#endif
711 return HoistPoint;
712}
713
714// Find a CHR scope in the given region.
715CHRScope * CHR::findScope(Region *R) {
716 CHRScope *Result = nullptr;
717 BasicBlock *Entry = R->getEntry();
718 BasicBlock *Exit = R->getExit(); // null if top level.
719 assert(Entry && "Entry must not be null");
720 assert((Exit == nullptr) == (R->isTopLevelRegion()) &&
721 "Only top level region has a null exit");
722 if (Entry)
723 CHR_DEBUG(dbgs() << "Entry " << Entry->getName() << "\n");
724 else
725 CHR_DEBUG(dbgs() << "Entry null\n");
726 if (Exit)
727 CHR_DEBUG(dbgs() << "Exit " << Exit->getName() << "\n");
728 else
729 CHR_DEBUG(dbgs() << "Exit null\n");
730 // Exclude cases where Entry is part of a subregion (hence it doesn't belong
731 // to this region).
732 bool EntryInSubregion = RI.getRegionFor(BB: Entry) != R;
733 if (EntryInSubregion)
734 return nullptr;
735 // Exclude loops
736 for (BasicBlock *Pred : predecessors(BB: Entry))
737 if (R->contains(BB: Pred))
738 return nullptr;
739 // If any of the basic blocks have address taken, we must skip this region
740 // because we cannot clone basic blocks that have address taken.
741 for (BasicBlock *BB : R->blocks()) {
742 if (BB->hasAddressTaken())
743 return nullptr;
744 // If we encounter llvm.coro.id, skip this region because if the basic block
745 // is cloned, we end up inserting a token type PHI node to the block with
746 // llvm.coro.begin.
747 // FIXME: This could lead to less optimal codegen, because the region is
748 // excluded, it can prevent CHR from merging adjacent regions into bigger
749 // scope and hoisting more branches.
750 for (Instruction &I : *BB)
751 if (auto *II = dyn_cast<IntrinsicInst>(Val: &I))
752 if (II->getIntrinsicID() == Intrinsic::coro_id)
753 return nullptr;
754 }
755
756 if (Exit) {
757 // Try to find an if-then block (check if R is an if-then).
758 // if (cond) {
759 // ...
760 // }
761 auto *BI = dyn_cast<BranchInst>(Val: Entry->getTerminator());
762 if (BI)
763 CHR_DEBUG(dbgs() << "BI.isConditional " << BI->isConditional() << "\n");
764 else
765 CHR_DEBUG(dbgs() << "BI null\n");
766 if (BI && BI->isConditional()) {
767 BasicBlock *S0 = BI->getSuccessor(i: 0);
768 BasicBlock *S1 = BI->getSuccessor(i: 1);
769 CHR_DEBUG(dbgs() << "S0 " << S0->getName() << "\n");
770 CHR_DEBUG(dbgs() << "S1 " << S1->getName() << "\n");
771 if (S0 != S1 && (S0 == Exit || S1 == Exit)) {
772 RegInfo RI(R);
773 RI.HasBranch = checkBiasedBranch(
774 BI, R, TrueBiasedRegionsGlobal, FalseBiasedRegionsGlobal,
775 BranchBiasMap);
776 Result = new CHRScope(RI);
777 Scopes.insert(V: Result);
778 CHR_DEBUG(dbgs() << "Found a region with a branch\n");
779 ++Stats.NumBranches;
780 if (!RI.HasBranch) {
781 ORE.emit(RemarkBuilder: [&]() {
782 return OptimizationRemarkMissed(DEBUG_TYPE, "BranchNotBiased", BI)
783 << "Branch not biased";
784 });
785 }
786 }
787 }
788 }
789 {
790 // Try to look for selects in the direct child blocks (as opposed to in
791 // subregions) of R.
792 // ...
793 // if (..) { // Some subregion
794 // ...
795 // }
796 // if (..) { // Some subregion
797 // ...
798 // }
799 // ...
800 // a = cond ? b : c;
801 // ...
802 SmallVector<SelectInst *, 8> Selects;
803 for (RegionNode *E : R->elements()) {
804 if (E->isSubRegion())
805 continue;
806 // This returns the basic block of E if E is a direct child of R (not a
807 // subregion.)
808 BasicBlock *BB = E->getEntry();
809 // Need to push in the order to make it easier to find the first Select
810 // later.
811 for (Instruction &I : *BB) {
812 if (auto *SI = dyn_cast<SelectInst>(Val: &I)) {
813 Selects.push_back(Elt: SI);
814 ++Stats.NumBranches;
815 }
816 }
817 }
818 if (Selects.size() > 0) {
819 auto AddSelects = [&](RegInfo &RI) {
820 for (auto *SI : Selects)
821 if (checkBiasedSelect(SI, R: RI.R,
822 TrueBiasedSelectsGlobal,
823 FalseBiasedSelectsGlobal,
824 SelectBiasMap))
825 RI.Selects.push_back(Elt: SI);
826 else
827 ORE.emit(RemarkBuilder: [&]() {
828 return OptimizationRemarkMissed(DEBUG_TYPE, "SelectNotBiased", SI)
829 << "Select not biased";
830 });
831 };
832 if (!Result) {
833 CHR_DEBUG(dbgs() << "Found a select-only region\n");
834 RegInfo RI(R);
835 AddSelects(RI);
836 Result = new CHRScope(RI);
837 Scopes.insert(V: Result);
838 } else {
839 CHR_DEBUG(dbgs() << "Found select(s) in a region with a branch\n");
840 AddSelects(Result->RegInfos[0]);
841 }
842 }
843 }
844
845 if (Result) {
846 checkScopeHoistable(Scope: Result);
847 }
848 return Result;
849}
850
851// Check that any of the branch and the selects in the region could be
852// hoisted above the the CHR branch insert point (the most dominating of
853// them, either the branch (at the end of the first block) or the first
854// select in the first block). If the branch can't be hoisted, drop the
855// selects in the first blocks.
856//
857// For example, for the following scope/region with selects, we want to insert
858// the merged branch right before the first select in the first/entry block by
859// hoisting c1, c2, c3, and c4.
860//
861// // Branch insert point here.
862// a = c1 ? b : c; // Select 1
863// d = c2 ? e : f; // Select 2
864// if (c3) { // Branch
865// ...
866// c4 = foo() // A call.
867// g = c4 ? h : i; // Select 3
868// }
869//
870// But suppose we can't hoist c4 because it's dependent on the preceding
871// call. Then, we drop Select 3. Furthermore, if we can't hoist c2, we also drop
872// Select 2. If we can't hoist c3, we drop Selects 1 & 2.
873void CHR::checkScopeHoistable(CHRScope *Scope) {
874 RegInfo &RI = Scope->RegInfos[0];
875 Region *R = RI.R;
876 BasicBlock *EntryBB = R->getEntry();
877 auto *Branch = RI.HasBranch ?
878 cast<BranchInst>(Val: EntryBB->getTerminator()) : nullptr;
879 SmallVector<SelectInst *, 8> &Selects = RI.Selects;
880 if (RI.HasBranch || !Selects.empty()) {
881 Instruction *InsertPoint = getBranchInsertPoint(RI);
882 CHR_DEBUG(dbgs() << "InsertPoint " << *InsertPoint << "\n");
883 // Avoid a data dependence from a select or a branch to a(nother)
884 // select. Note no instruction can't data-depend on a branch (a branch
885 // instruction doesn't produce a value).
886 DenseSet<Instruction *> Unhoistables;
887 // Initialize Unhoistables with the selects.
888 for (SelectInst *SI : Selects) {
889 Unhoistables.insert(V: SI);
890 }
891 // Remove Selects that can't be hoisted.
892 for (auto it = Selects.begin(); it != Selects.end(); ) {
893 SelectInst *SI = *it;
894 if (SI == InsertPoint) {
895 ++it;
896 continue;
897 }
898 DenseMap<Instruction *, bool> Visited;
899 bool IsHoistable = checkHoistValue(V: SI->getCondition(), InsertPoint,
900 DT, Unhoistables, HoistStops: nullptr, Visited);
901 if (!IsHoistable) {
902 CHR_DEBUG(dbgs() << "Dropping select " << *SI << "\n");
903 ORE.emit(RemarkBuilder: [&]() {
904 return OptimizationRemarkMissed(DEBUG_TYPE,
905 "DropUnhoistableSelect", SI)
906 << "Dropped unhoistable select";
907 });
908 it = Selects.erase(CI: it);
909 // Since we are dropping the select here, we also drop it from
910 // Unhoistables.
911 Unhoistables.erase(V: SI);
912 } else
913 ++it;
914 }
915 // Update InsertPoint after potentially removing selects.
916 InsertPoint = getBranchInsertPoint(RI);
917 CHR_DEBUG(dbgs() << "InsertPoint " << *InsertPoint << "\n");
918 if (RI.HasBranch && InsertPoint != Branch) {
919 DenseMap<Instruction *, bool> Visited;
920 bool IsHoistable = checkHoistValue(V: Branch->getCondition(), InsertPoint,
921 DT, Unhoistables, HoistStops: nullptr, Visited);
922 if (!IsHoistable) {
923 // If the branch isn't hoistable, drop the selects in the entry
924 // block, preferring the branch, which makes the branch the hoist
925 // point.
926 assert(InsertPoint != Branch && "Branch must not be the hoist point");
927 CHR_DEBUG(dbgs() << "Dropping selects in entry block \n");
928 CHR_DEBUG(
929 for (SelectInst *SI : Selects) {
930 dbgs() << "SI " << *SI << "\n";
931 });
932 for (SelectInst *SI : Selects) {
933 ORE.emit(RemarkBuilder: [&]() {
934 return OptimizationRemarkMissed(DEBUG_TYPE,
935 "DropSelectUnhoistableBranch", SI)
936 << "Dropped select due to unhoistable branch";
937 });
938 }
939 llvm::erase_if(C&: Selects, P: [EntryBB](SelectInst *SI) {
940 return SI->getParent() == EntryBB;
941 });
942 Unhoistables.clear();
943 InsertPoint = Branch;
944 }
945 }
946 CHR_DEBUG(dbgs() << "InsertPoint " << *InsertPoint << "\n");
947#ifndef NDEBUG
948 if (RI.HasBranch) {
949 assert(!DT.dominates(Branch, InsertPoint) &&
950 "Branch can't be already above the hoist point");
951 DenseMap<Instruction *, bool> Visited;
952 assert(checkHoistValue(Branch->getCondition(), InsertPoint,
953 DT, Unhoistables, nullptr, Visited) &&
954 "checkHoistValue for branch");
955 }
956 for (auto *SI : Selects) {
957 assert(!DT.dominates(SI, InsertPoint) &&
958 "SI can't be already above the hoist point");
959 DenseMap<Instruction *, bool> Visited;
960 assert(checkHoistValue(SI->getCondition(), InsertPoint, DT,
961 Unhoistables, nullptr, Visited) &&
962 "checkHoistValue for selects");
963 }
964 CHR_DEBUG(dbgs() << "Result\n");
965 if (RI.HasBranch) {
966 CHR_DEBUG(dbgs() << "BI " << *Branch << "\n");
967 }
968 for (auto *SI : Selects) {
969 CHR_DEBUG(dbgs() << "SI " << *SI << "\n");
970 }
971#endif
972 }
973}
974
975// Traverse the region tree, find all nested scopes and merge them if possible.
976CHRScope * CHR::findScopes(Region *R, Region *NextRegion, Region *ParentRegion,
977 SmallVectorImpl<CHRScope *> &Scopes) {
978 CHR_DEBUG(dbgs() << "findScopes " << R->getNameStr() << "\n");
979 CHRScope *Result = findScope(R);
980 // Visit subscopes.
981 CHRScope *ConsecutiveSubscope = nullptr;
982 SmallVector<CHRScope *, 8> Subscopes;
983 for (auto It = R->begin(); It != R->end(); ++It) {
984 const std::unique_ptr<Region> &SubR = *It;
985 auto NextIt = std::next(x: It);
986 Region *NextSubR = NextIt != R->end() ? NextIt->get() : nullptr;
987 CHR_DEBUG(dbgs() << "Looking at subregion " << SubR.get()->getNameStr()
988 << "\n");
989 CHRScope *SubCHRScope = findScopes(R: SubR.get(), NextRegion: NextSubR, ParentRegion: R, Scopes);
990 if (SubCHRScope) {
991 CHR_DEBUG(dbgs() << "Subregion Scope " << *SubCHRScope << "\n");
992 } else {
993 CHR_DEBUG(dbgs() << "Subregion Scope null\n");
994 }
995 if (SubCHRScope) {
996 if (!ConsecutiveSubscope)
997 ConsecutiveSubscope = SubCHRScope;
998 else if (!ConsecutiveSubscope->appendable(Next: SubCHRScope)) {
999 Subscopes.push_back(Elt: ConsecutiveSubscope);
1000 ConsecutiveSubscope = SubCHRScope;
1001 } else
1002 ConsecutiveSubscope->append(Next: SubCHRScope);
1003 } else {
1004 if (ConsecutiveSubscope) {
1005 Subscopes.push_back(Elt: ConsecutiveSubscope);
1006 }
1007 ConsecutiveSubscope = nullptr;
1008 }
1009 }
1010 if (ConsecutiveSubscope) {
1011 Subscopes.push_back(Elt: ConsecutiveSubscope);
1012 }
1013 for (CHRScope *Sub : Subscopes) {
1014 if (Result) {
1015 // Combine it with the parent.
1016 Result->addSub(SubIn: Sub);
1017 } else {
1018 // Push Subscopes as they won't be combined with the parent.
1019 Scopes.push_back(Elt: Sub);
1020 }
1021 }
1022 return Result;
1023}
1024
1025static DenseSet<Value *> getCHRConditionValuesForRegion(RegInfo &RI) {
1026 DenseSet<Value *> ConditionValues;
1027 if (RI.HasBranch) {
1028 auto *BI = cast<BranchInst>(Val: RI.R->getEntry()->getTerminator());
1029 ConditionValues.insert(V: BI->getCondition());
1030 }
1031 for (SelectInst *SI : RI.Selects) {
1032 ConditionValues.insert(V: SI->getCondition());
1033 }
1034 return ConditionValues;
1035}
1036
1037
1038// Determine whether to split a scope depending on the sets of the branch
1039// condition values of the previous region and the current region. We split
1040// (return true) it if 1) the condition values of the inner/lower scope can't be
1041// hoisted up to the outer/upper scope, or 2) the two sets of the condition
1042// values have an empty intersection (because the combined branch conditions
1043// won't probably lead to a simpler combined condition).
1044static bool shouldSplit(Instruction *InsertPoint,
1045 DenseSet<Value *> &PrevConditionValues,
1046 DenseSet<Value *> &ConditionValues,
1047 DominatorTree &DT,
1048 DenseSet<Instruction *> &Unhoistables) {
1049 assert(InsertPoint && "Null InsertPoint");
1050 CHR_DEBUG(
1051 dbgs() << "shouldSplit " << *InsertPoint << " PrevConditionValues ";
1052 for (Value *V : PrevConditionValues) {
1053 dbgs() << *V << ", ";
1054 }
1055 dbgs() << " ConditionValues ";
1056 for (Value *V : ConditionValues) {
1057 dbgs() << *V << ", ";
1058 }
1059 dbgs() << "\n");
1060 // If any of Bases isn't hoistable to the hoist point, split.
1061 for (Value *V : ConditionValues) {
1062 DenseMap<Instruction *, bool> Visited;
1063 if (!checkHoistValue(V, InsertPoint, DT, Unhoistables, HoistStops: nullptr, Visited)) {
1064 CHR_DEBUG(dbgs() << "Split. checkHoistValue false " << *V << "\n");
1065 return true; // Not hoistable, split.
1066 }
1067 }
1068 // If PrevConditionValues or ConditionValues is empty, don't split to avoid
1069 // unnecessary splits at scopes with no branch/selects. If
1070 // PrevConditionValues and ConditionValues don't intersect at all, split.
1071 if (!PrevConditionValues.empty() && !ConditionValues.empty()) {
1072 // Use std::set as DenseSet doesn't work with set_intersection.
1073 std::set<Value *> PrevBases, Bases;
1074 DenseMap<Value *, std::set<Value *>> Visited;
1075 for (Value *V : PrevConditionValues) {
1076 const std::set<Value *> &BaseValues = getBaseValues(V, DT, Visited);
1077 PrevBases.insert(first: BaseValues.begin(), last: BaseValues.end());
1078 }
1079 for (Value *V : ConditionValues) {
1080 const std::set<Value *> &BaseValues = getBaseValues(V, DT, Visited);
1081 Bases.insert(first: BaseValues.begin(), last: BaseValues.end());
1082 }
1083 CHR_DEBUG(
1084 dbgs() << "PrevBases ";
1085 for (Value *V : PrevBases) {
1086 dbgs() << *V << ", ";
1087 }
1088 dbgs() << " Bases ";
1089 for (Value *V : Bases) {
1090 dbgs() << *V << ", ";
1091 }
1092 dbgs() << "\n");
1093 std::vector<Value *> Intersection;
1094 std::set_intersection(first1: PrevBases.begin(), last1: PrevBases.end(), first2: Bases.begin(),
1095 last2: Bases.end(), result: std::back_inserter(x&: Intersection));
1096 if (Intersection.empty()) {
1097 // Empty intersection, split.
1098 CHR_DEBUG(dbgs() << "Split. Intersection empty\n");
1099 return true;
1100 }
1101 }
1102 CHR_DEBUG(dbgs() << "No split\n");
1103 return false; // Don't split.
1104}
1105
1106static void getSelectsInScope(CHRScope *Scope,
1107 DenseSet<Instruction *> &Output) {
1108 for (RegInfo &RI : Scope->RegInfos)
1109 for (SelectInst *SI : RI.Selects)
1110 Output.insert(V: SI);
1111 for (CHRScope *Sub : Scope->Subs)
1112 getSelectsInScope(Scope: Sub, Output);
1113}
1114
1115void CHR::splitScopes(SmallVectorImpl<CHRScope *> &Input,
1116 SmallVectorImpl<CHRScope *> &Output) {
1117 for (CHRScope *Scope : Input) {
1118 assert(!Scope->BranchInsertPoint &&
1119 "BranchInsertPoint must not be set");
1120 DenseSet<Instruction *> Unhoistables;
1121 getSelectsInScope(Scope, Output&: Unhoistables);
1122 splitScope(Scope, Outer: nullptr, OuterConditionValues: nullptr, OuterInsertPoint: nullptr, Output, Unhoistables);
1123 }
1124#ifndef NDEBUG
1125 for (CHRScope *Scope : Output) {
1126 assert(Scope->BranchInsertPoint && "BranchInsertPoint must be set");
1127 }
1128#endif
1129}
1130
1131SmallVector<CHRScope *, 8> CHR::splitScope(
1132 CHRScope *Scope,
1133 CHRScope *Outer,
1134 DenseSet<Value *> *OuterConditionValues,
1135 Instruction *OuterInsertPoint,
1136 SmallVectorImpl<CHRScope *> &Output,
1137 DenseSet<Instruction *> &Unhoistables) {
1138 if (Outer) {
1139 assert(OuterConditionValues && "Null OuterConditionValues");
1140 assert(OuterInsertPoint && "Null OuterInsertPoint");
1141 }
1142 bool PrevSplitFromOuter = true;
1143 DenseSet<Value *> PrevConditionValues;
1144 Instruction *PrevInsertPoint = nullptr;
1145 SmallVector<CHRScope *, 8> Splits;
1146 SmallVector<bool, 8> SplitsSplitFromOuter;
1147 SmallVector<DenseSet<Value *>, 8> SplitsConditionValues;
1148 SmallVector<Instruction *, 8> SplitsInsertPoints;
1149 SmallVector<RegInfo, 8> RegInfos(Scope->RegInfos); // Copy
1150 for (RegInfo &RI : RegInfos) {
1151 Instruction *InsertPoint = getBranchInsertPoint(RI);
1152 DenseSet<Value *> ConditionValues = getCHRConditionValuesForRegion(RI);
1153 CHR_DEBUG(
1154 dbgs() << "ConditionValues ";
1155 for (Value *V : ConditionValues) {
1156 dbgs() << *V << ", ";
1157 }
1158 dbgs() << "\n");
1159 if (RI.R == RegInfos[0].R) {
1160 // First iteration. Check to see if we should split from the outer.
1161 if (Outer) {
1162 CHR_DEBUG(dbgs() << "Outer " << *Outer << "\n");
1163 CHR_DEBUG(dbgs() << "Should split from outer at "
1164 << RI.R->getNameStr() << "\n");
1165 if (shouldSplit(InsertPoint: OuterInsertPoint, PrevConditionValues&: *OuterConditionValues,
1166 ConditionValues, DT, Unhoistables)) {
1167 PrevConditionValues = ConditionValues;
1168 PrevInsertPoint = InsertPoint;
1169 ORE.emit(RemarkBuilder: [&]() {
1170 return OptimizationRemarkMissed(DEBUG_TYPE,
1171 "SplitScopeFromOuter",
1172 RI.R->getEntry()->getTerminator())
1173 << "Split scope from outer due to unhoistable branch/select "
1174 << "and/or lack of common condition values";
1175 });
1176 } else {
1177 // Not splitting from the outer. Use the outer bases and insert
1178 // point. Union the bases.
1179 PrevSplitFromOuter = false;
1180 PrevConditionValues = *OuterConditionValues;
1181 PrevConditionValues.insert(I: ConditionValues.begin(),
1182 E: ConditionValues.end());
1183 PrevInsertPoint = OuterInsertPoint;
1184 }
1185 } else {
1186 CHR_DEBUG(dbgs() << "Outer null\n");
1187 PrevConditionValues = ConditionValues;
1188 PrevInsertPoint = InsertPoint;
1189 }
1190 } else {
1191 CHR_DEBUG(dbgs() << "Should split from prev at "
1192 << RI.R->getNameStr() << "\n");
1193 if (shouldSplit(InsertPoint: PrevInsertPoint, PrevConditionValues, ConditionValues,
1194 DT, Unhoistables)) {
1195 CHRScope *Tail = Scope->split(Boundary: RI.R);
1196 Scopes.insert(V: Tail);
1197 Splits.push_back(Elt: Scope);
1198 SplitsSplitFromOuter.push_back(Elt: PrevSplitFromOuter);
1199 SplitsConditionValues.push_back(Elt: PrevConditionValues);
1200 SplitsInsertPoints.push_back(Elt: PrevInsertPoint);
1201 Scope = Tail;
1202 PrevConditionValues = ConditionValues;
1203 PrevInsertPoint = InsertPoint;
1204 PrevSplitFromOuter = true;
1205 ORE.emit(RemarkBuilder: [&]() {
1206 return OptimizationRemarkMissed(DEBUG_TYPE,
1207 "SplitScopeFromPrev",
1208 RI.R->getEntry()->getTerminator())
1209 << "Split scope from previous due to unhoistable branch/select "
1210 << "and/or lack of common condition values";
1211 });
1212 } else {
1213 // Not splitting. Union the bases. Keep the hoist point.
1214 PrevConditionValues.insert(I: ConditionValues.begin(), E: ConditionValues.end());
1215 }
1216 }
1217 }
1218 Splits.push_back(Elt: Scope);
1219 SplitsSplitFromOuter.push_back(Elt: PrevSplitFromOuter);
1220 SplitsConditionValues.push_back(Elt: PrevConditionValues);
1221 assert(PrevInsertPoint && "Null PrevInsertPoint");
1222 SplitsInsertPoints.push_back(Elt: PrevInsertPoint);
1223 assert(Splits.size() == SplitsConditionValues.size() &&
1224 Splits.size() == SplitsSplitFromOuter.size() &&
1225 Splits.size() == SplitsInsertPoints.size() && "Mismatching sizes");
1226 for (size_t I = 0; I < Splits.size(); ++I) {
1227 CHRScope *Split = Splits[I];
1228 DenseSet<Value *> &SplitConditionValues = SplitsConditionValues[I];
1229 Instruction *SplitInsertPoint = SplitsInsertPoints[I];
1230 SmallVector<CHRScope *, 8> NewSubs;
1231 DenseSet<Instruction *> SplitUnhoistables;
1232 getSelectsInScope(Scope: Split, Output&: SplitUnhoistables);
1233 for (CHRScope *Sub : Split->Subs) {
1234 SmallVector<CHRScope *, 8> SubSplits = splitScope(
1235 Scope: Sub, Outer: Split, OuterConditionValues: &SplitConditionValues, OuterInsertPoint: SplitInsertPoint, Output,
1236 Unhoistables&: SplitUnhoistables);
1237 llvm::append_range(C&: NewSubs, R&: SubSplits);
1238 }
1239 Split->Subs = NewSubs;
1240 }
1241 SmallVector<CHRScope *, 8> Result;
1242 for (size_t I = 0; I < Splits.size(); ++I) {
1243 CHRScope *Split = Splits[I];
1244 if (SplitsSplitFromOuter[I]) {
1245 // Split from the outer.
1246 Output.push_back(Elt: Split);
1247 Split->BranchInsertPoint = SplitsInsertPoints[I];
1248 CHR_DEBUG(dbgs() << "BranchInsertPoint " << *SplitsInsertPoints[I]
1249 << "\n");
1250 } else {
1251 // Connected to the outer.
1252 Result.push_back(Elt: Split);
1253 }
1254 }
1255 if (!Outer)
1256 assert(Result.empty() &&
1257 "If no outer (top-level), must return no nested ones");
1258 return Result;
1259}
1260
1261void CHR::classifyBiasedScopes(SmallVectorImpl<CHRScope *> &Scopes) {
1262 for (CHRScope *Scope : Scopes) {
1263 assert(Scope->TrueBiasedRegions.empty() && Scope->FalseBiasedRegions.empty() && "Empty");
1264 classifyBiasedScopes(Scope, OutermostScope: Scope);
1265 CHR_DEBUG(
1266 dbgs() << "classifyBiasedScopes " << *Scope << "\n";
1267 dbgs() << "TrueBiasedRegions ";
1268 for (Region *R : Scope->TrueBiasedRegions) {
1269 dbgs() << R->getNameStr() << ", ";
1270 }
1271 dbgs() << "\n";
1272 dbgs() << "FalseBiasedRegions ";
1273 for (Region *R : Scope->FalseBiasedRegions) {
1274 dbgs() << R->getNameStr() << ", ";
1275 }
1276 dbgs() << "\n";
1277 dbgs() << "TrueBiasedSelects ";
1278 for (SelectInst *SI : Scope->TrueBiasedSelects) {
1279 dbgs() << *SI << ", ";
1280 }
1281 dbgs() << "\n";
1282 dbgs() << "FalseBiasedSelects ";
1283 for (SelectInst *SI : Scope->FalseBiasedSelects) {
1284 dbgs() << *SI << ", ";
1285 }
1286 dbgs() << "\n";);
1287 }
1288}
1289
1290void CHR::classifyBiasedScopes(CHRScope *Scope, CHRScope *OutermostScope) {
1291 for (RegInfo &RI : Scope->RegInfos) {
1292 if (RI.HasBranch) {
1293 Region *R = RI.R;
1294 if (TrueBiasedRegionsGlobal.contains(V: R))
1295 OutermostScope->TrueBiasedRegions.insert(V: R);
1296 else if (FalseBiasedRegionsGlobal.contains(V: R))
1297 OutermostScope->FalseBiasedRegions.insert(V: R);
1298 else
1299 llvm_unreachable("Must be biased");
1300 }
1301 for (SelectInst *SI : RI.Selects) {
1302 if (TrueBiasedSelectsGlobal.contains(V: SI))
1303 OutermostScope->TrueBiasedSelects.insert(V: SI);
1304 else if (FalseBiasedSelectsGlobal.contains(V: SI))
1305 OutermostScope->FalseBiasedSelects.insert(V: SI);
1306 else
1307 llvm_unreachable("Must be biased");
1308 }
1309 }
1310 for (CHRScope *Sub : Scope->Subs) {
1311 classifyBiasedScopes(Scope: Sub, OutermostScope);
1312 }
1313}
1314
1315static bool hasAtLeastTwoBiasedBranches(CHRScope *Scope) {
1316 unsigned NumBiased = Scope->TrueBiasedRegions.size() +
1317 Scope->FalseBiasedRegions.size() +
1318 Scope->TrueBiasedSelects.size() +
1319 Scope->FalseBiasedSelects.size();
1320 return NumBiased >= CHRMergeThreshold;
1321}
1322
1323void CHR::filterScopes(SmallVectorImpl<CHRScope *> &Input,
1324 SmallVectorImpl<CHRScope *> &Output) {
1325 for (CHRScope *Scope : Input) {
1326 // Filter out the ones with only one region and no subs.
1327 if (!hasAtLeastTwoBiasedBranches(Scope)) {
1328 CHR_DEBUG(dbgs() << "Filtered out by biased branches truthy-regions "
1329 << Scope->TrueBiasedRegions.size()
1330 << " falsy-regions " << Scope->FalseBiasedRegions.size()
1331 << " true-selects " << Scope->TrueBiasedSelects.size()
1332 << " false-selects " << Scope->FalseBiasedSelects.size() << "\n");
1333 ORE.emit(RemarkBuilder: [&]() {
1334 return OptimizationRemarkMissed(
1335 DEBUG_TYPE,
1336 "DropScopeWithOneBranchOrSelect",
1337 Scope->RegInfos[0].R->getEntry()->getTerminator())
1338 << "Drop scope with < "
1339 << ore::NV("CHRMergeThreshold", CHRMergeThreshold)
1340 << " biased branch(es) or select(s)";
1341 });
1342 continue;
1343 }
1344 Output.push_back(Elt: Scope);
1345 }
1346}
1347
1348void CHR::setCHRRegions(SmallVectorImpl<CHRScope *> &Input,
1349 SmallVectorImpl<CHRScope *> &Output) {
1350 for (CHRScope *Scope : Input) {
1351 assert(Scope->HoistStopMap.empty() && Scope->CHRRegions.empty() &&
1352 "Empty");
1353 setCHRRegions(Scope, OutermostScope: Scope);
1354 Output.push_back(Elt: Scope);
1355 CHR_DEBUG(
1356 dbgs() << "setCHRRegions HoistStopMap " << *Scope << "\n";
1357 for (auto pair : Scope->HoistStopMap) {
1358 Region *R = pair.first;
1359 dbgs() << "Region " << R->getNameStr() << "\n";
1360 for (Instruction *I : pair.second) {
1361 dbgs() << "HoistStop " << *I << "\n";
1362 }
1363 }
1364 dbgs() << "CHRRegions" << "\n";
1365 for (RegInfo &RI : Scope->CHRRegions) {
1366 dbgs() << RI.R->getNameStr() << "\n";
1367 });
1368 }
1369}
1370
1371void CHR::setCHRRegions(CHRScope *Scope, CHRScope *OutermostScope) {
1372 DenseSet<Instruction *> Unhoistables;
1373 // Put the biased selects in Unhoistables because they should stay where they
1374 // are and constant-folded after CHR (in case one biased select or a branch
1375 // can depend on another biased select.)
1376 for (RegInfo &RI : Scope->RegInfos) {
1377 for (SelectInst *SI : RI.Selects) {
1378 Unhoistables.insert(V: SI);
1379 }
1380 }
1381 Instruction *InsertPoint = OutermostScope->BranchInsertPoint;
1382 for (RegInfo &RI : Scope->RegInfos) {
1383 Region *R = RI.R;
1384 DenseSet<Instruction *> HoistStops;
1385 bool IsHoisted = false;
1386 if (RI.HasBranch) {
1387 assert((OutermostScope->TrueBiasedRegions.contains(R) ||
1388 OutermostScope->FalseBiasedRegions.contains(R)) &&
1389 "Must be truthy or falsy");
1390 auto *BI = cast<BranchInst>(Val: R->getEntry()->getTerminator());
1391 // Note checkHoistValue fills in HoistStops.
1392 DenseMap<Instruction *, bool> Visited;
1393 bool IsHoistable = checkHoistValue(V: BI->getCondition(), InsertPoint, DT,
1394 Unhoistables, HoistStops: &HoistStops, Visited);
1395 assert(IsHoistable && "Must be hoistable");
1396 (void)(IsHoistable); // Unused in release build
1397 IsHoisted = true;
1398 }
1399 for (SelectInst *SI : RI.Selects) {
1400 assert((OutermostScope->TrueBiasedSelects.contains(SI) ||
1401 OutermostScope->FalseBiasedSelects.contains(SI)) &&
1402 "Must be true or false biased");
1403 // Note checkHoistValue fills in HoistStops.
1404 DenseMap<Instruction *, bool> Visited;
1405 bool IsHoistable = checkHoistValue(V: SI->getCondition(), InsertPoint, DT,
1406 Unhoistables, HoistStops: &HoistStops, Visited);
1407 assert(IsHoistable && "Must be hoistable");
1408 (void)(IsHoistable); // Unused in release build
1409 IsHoisted = true;
1410 }
1411 if (IsHoisted) {
1412 OutermostScope->CHRRegions.push_back(Elt: RI);
1413 OutermostScope->HoistStopMap[R] = HoistStops;
1414 }
1415 }
1416 for (CHRScope *Sub : Scope->Subs)
1417 setCHRRegions(Scope: Sub, OutermostScope);
1418}
1419
1420static bool CHRScopeSorter(CHRScope *Scope1, CHRScope *Scope2) {
1421 return Scope1->RegInfos[0].R->getDepth() < Scope2->RegInfos[0].R->getDepth();
1422}
1423
1424void CHR::sortScopes(SmallVectorImpl<CHRScope *> &Input,
1425 SmallVectorImpl<CHRScope *> &Output) {
1426 Output.resize(N: Input.size());
1427 llvm::copy(Range&: Input, Out: Output.begin());
1428 llvm::stable_sort(Range&: Output, C: CHRScopeSorter);
1429}
1430
1431// Return true if V is already hoisted or was hoisted (along with its operands)
1432// to the insert point.
1433static void hoistValue(Value *V, Instruction *HoistPoint, Region *R,
1434 HoistStopMapTy &HoistStopMap,
1435 DenseSet<Instruction *> &HoistedSet,
1436 DenseSet<PHINode *> &TrivialPHIs,
1437 DominatorTree &DT) {
1438 auto IT = HoistStopMap.find(Val: R);
1439 assert(IT != HoistStopMap.end() && "Region must be in hoist stop map");
1440 DenseSet<Instruction *> &HoistStops = IT->second;
1441 if (auto *I = dyn_cast<Instruction>(Val: V)) {
1442 if (I == HoistPoint)
1443 return;
1444 if (HoistStops.count(V: I))
1445 return;
1446 if (auto *PN = dyn_cast<PHINode>(Val: I))
1447 if (TrivialPHIs.count(V: PN))
1448 // The trivial phi inserted by the previous CHR scope could replace a
1449 // non-phi in HoistStops. Note that since this phi is at the exit of a
1450 // previous CHR scope, which dominates this scope, it's safe to stop
1451 // hoisting there.
1452 return;
1453 if (HoistedSet.count(V: I))
1454 // Already hoisted, return.
1455 return;
1456 assert(isHoistableInstructionType(I) && "Unhoistable instruction type");
1457 assert(DT.getNode(I->getParent()) && "DT must contain I's block");
1458 assert(DT.getNode(HoistPoint->getParent()) &&
1459 "DT must contain HoistPoint block");
1460 if (DT.dominates(Def: I, User: HoistPoint))
1461 // We are already above the hoist point. Stop here. This may be necessary
1462 // when multiple scopes would independently hoist the same
1463 // instruction. Since an outer (dominating) scope would hoist it to its
1464 // entry before an inner (dominated) scope would to its entry, the inner
1465 // scope may see the instruction already hoisted, in which case it
1466 // potentially wrong for the inner scope to hoist it and could cause bad
1467 // IR (non-dominating def), but safe to skip hoisting it instead because
1468 // it's already in a block that dominates the inner scope.
1469 return;
1470 for (Value *Op : I->operands()) {
1471 hoistValue(V: Op, HoistPoint, R, HoistStopMap, HoistedSet, TrivialPHIs, DT);
1472 }
1473 I->moveBefore(MovePos: HoistPoint);
1474 HoistedSet.insert(V: I);
1475 CHR_DEBUG(dbgs() << "hoistValue " << *I << "\n");
1476 }
1477}
1478
1479// Hoist the dependent condition values of the branches and the selects in the
1480// scope to the insert point.
1481static void hoistScopeConditions(CHRScope *Scope, Instruction *HoistPoint,
1482 DenseSet<PHINode *> &TrivialPHIs,
1483 DominatorTree &DT) {
1484 DenseSet<Instruction *> HoistedSet;
1485 for (const RegInfo &RI : Scope->CHRRegions) {
1486 Region *R = RI.R;
1487 bool IsTrueBiased = Scope->TrueBiasedRegions.count(V: R);
1488 bool IsFalseBiased = Scope->FalseBiasedRegions.count(V: R);
1489 if (RI.HasBranch && (IsTrueBiased || IsFalseBiased)) {
1490 auto *BI = cast<BranchInst>(Val: R->getEntry()->getTerminator());
1491 hoistValue(V: BI->getCondition(), HoistPoint, R, HoistStopMap&: Scope->HoistStopMap,
1492 HoistedSet, TrivialPHIs, DT);
1493 }
1494 for (SelectInst *SI : RI.Selects) {
1495 bool IsTrueBiased = Scope->TrueBiasedSelects.count(V: SI);
1496 bool IsFalseBiased = Scope->FalseBiasedSelects.count(V: SI);
1497 if (!(IsTrueBiased || IsFalseBiased))
1498 continue;
1499 hoistValue(V: SI->getCondition(), HoistPoint, R, HoistStopMap&: Scope->HoistStopMap,
1500 HoistedSet, TrivialPHIs, DT);
1501 }
1502 }
1503}
1504
1505// Negate the predicate if an ICmp if it's used only by branches or selects by
1506// swapping the operands of the branches or the selects. Returns true if success.
1507static bool negateICmpIfUsedByBranchOrSelectOnly(ICmpInst *ICmp,
1508 Instruction *ExcludedUser,
1509 CHRScope *Scope) {
1510 for (User *U : ICmp->users()) {
1511 if (U == ExcludedUser)
1512 continue;
1513 if (isa<BranchInst>(Val: U) && cast<BranchInst>(Val: U)->isConditional())
1514 continue;
1515 if (isa<SelectInst>(Val: U) && cast<SelectInst>(Val: U)->getCondition() == ICmp)
1516 continue;
1517 return false;
1518 }
1519 for (User *U : ICmp->users()) {
1520 if (U == ExcludedUser)
1521 continue;
1522 if (auto *BI = dyn_cast<BranchInst>(Val: U)) {
1523 assert(BI->isConditional() && "Must be conditional");
1524 BI->swapSuccessors();
1525 // Don't need to swap this in terms of
1526 // TrueBiasedRegions/FalseBiasedRegions because true-based/false-based
1527 // mean whehter the branch is likely go into the if-then rather than
1528 // successor0/successor1 and because we can tell which edge is the then or
1529 // the else one by comparing the destination to the region exit block.
1530 continue;
1531 }
1532 if (auto *SI = dyn_cast<SelectInst>(Val: U)) {
1533 // Swap operands
1534 SI->swapValues();
1535 SI->swapProfMetadata();
1536 if (Scope->TrueBiasedSelects.count(V: SI)) {
1537 assert(!Scope->FalseBiasedSelects.contains(SI) &&
1538 "Must not be already in");
1539 Scope->FalseBiasedSelects.insert(V: SI);
1540 } else if (Scope->FalseBiasedSelects.count(V: SI)) {
1541 assert(!Scope->TrueBiasedSelects.contains(SI) &&
1542 "Must not be already in");
1543 Scope->TrueBiasedSelects.insert(V: SI);
1544 }
1545 continue;
1546 }
1547 llvm_unreachable("Must be a branch or a select");
1548 }
1549 ICmp->setPredicate(CmpInst::getInversePredicate(pred: ICmp->getPredicate()));
1550 return true;
1551}
1552
1553// A helper for transformScopes. Insert a trivial phi at the scope exit block
1554// for a value that's defined in the scope but used outside it (meaning it's
1555// alive at the exit block).
1556static void insertTrivialPHIs(CHRScope *Scope,
1557 BasicBlock *EntryBlock, BasicBlock *ExitBlock,
1558 DenseSet<PHINode *> &TrivialPHIs) {
1559 SmallSetVector<BasicBlock *, 8> BlocksInScope;
1560 for (RegInfo &RI : Scope->RegInfos) {
1561 for (BasicBlock *BB : RI.R->blocks()) { // This includes the blocks in the
1562 // sub-Scopes.
1563 BlocksInScope.insert(X: BB);
1564 }
1565 }
1566 CHR_DEBUG({
1567 dbgs() << "Inserting redundant phis\n";
1568 for (BasicBlock *BB : BlocksInScope)
1569 dbgs() << "BlockInScope " << BB->getName() << "\n";
1570 });
1571 for (BasicBlock *BB : BlocksInScope) {
1572 for (Instruction &I : *BB) {
1573 SmallVector<Instruction *, 8> Users;
1574 for (User *U : I.users()) {
1575 if (auto *UI = dyn_cast<Instruction>(Val: U)) {
1576 if (!BlocksInScope.contains(key: UI->getParent()) &&
1577 // Unless there's already a phi for I at the exit block.
1578 !(isa<PHINode>(Val: UI) && UI->getParent() == ExitBlock)) {
1579 CHR_DEBUG(dbgs() << "V " << I << "\n");
1580 CHR_DEBUG(dbgs() << "Used outside scope by user " << *UI << "\n");
1581 Users.push_back(Elt: UI);
1582 } else if (UI->getParent() == EntryBlock && isa<PHINode>(Val: UI)) {
1583 // There's a loop backedge from a block that's dominated by this
1584 // scope to the entry block.
1585 CHR_DEBUG(dbgs() << "V " << I << "\n");
1586 CHR_DEBUG(dbgs()
1587 << "Used at entry block (for a back edge) by a phi user "
1588 << *UI << "\n");
1589 Users.push_back(Elt: UI);
1590 }
1591 }
1592 }
1593 if (Users.size() > 0) {
1594 // Insert a trivial phi for I (phi [&I, P0], [&I, P1], ...) at
1595 // ExitBlock. Replace I with the new phi in UI unless UI is another
1596 // phi at ExitBlock.
1597 PHINode *PN = PHINode::Create(Ty: I.getType(), NumReservedValues: pred_size(BB: ExitBlock), NameStr: "");
1598 PN->insertBefore(InsertPos: ExitBlock->begin());
1599 for (BasicBlock *Pred : predecessors(BB: ExitBlock)) {
1600 PN->addIncoming(V: &I, BB: Pred);
1601 }
1602 TrivialPHIs.insert(V: PN);
1603 CHR_DEBUG(dbgs() << "Insert phi " << *PN << "\n");
1604 for (Instruction *UI : Users) {
1605 for (unsigned J = 0, NumOps = UI->getNumOperands(); J < NumOps; ++J) {
1606 if (UI->getOperand(i: J) == &I) {
1607 UI->setOperand(i: J, Val: PN);
1608 }
1609 }
1610 CHR_DEBUG(dbgs() << "Updated user " << *UI << "\n");
1611 }
1612 }
1613 }
1614 }
1615}
1616
1617// Assert that all the CHR regions of the scope have a biased branch or select.
1618static void LLVM_ATTRIBUTE_UNUSED
1619assertCHRRegionsHaveBiasedBranchOrSelect(CHRScope *Scope) {
1620#ifndef NDEBUG
1621 auto HasBiasedBranchOrSelect = [](RegInfo &RI, CHRScope *Scope) {
1622 if (Scope->TrueBiasedRegions.count(RI.R) ||
1623 Scope->FalseBiasedRegions.count(RI.R))
1624 return true;
1625 for (SelectInst *SI : RI.Selects)
1626 if (Scope->TrueBiasedSelects.count(SI) ||
1627 Scope->FalseBiasedSelects.count(SI))
1628 return true;
1629 return false;
1630 };
1631 for (RegInfo &RI : Scope->CHRRegions) {
1632 assert(HasBiasedBranchOrSelect(RI, Scope) &&
1633 "Must have biased branch or select");
1634 }
1635#endif
1636}
1637
1638// Assert that all the condition values of the biased branches and selects have
1639// been hoisted to the pre-entry block or outside of the scope.
1640static void LLVM_ATTRIBUTE_UNUSED assertBranchOrSelectConditionHoisted(
1641 CHRScope *Scope, BasicBlock *PreEntryBlock) {
1642 CHR_DEBUG(dbgs() << "Biased regions condition values \n");
1643 for (RegInfo &RI : Scope->CHRRegions) {
1644 Region *R = RI.R;
1645 bool IsTrueBiased = Scope->TrueBiasedRegions.count(V: R);
1646 bool IsFalseBiased = Scope->FalseBiasedRegions.count(V: R);
1647 if (RI.HasBranch && (IsTrueBiased || IsFalseBiased)) {
1648 auto *BI = cast<BranchInst>(Val: R->getEntry()->getTerminator());
1649 Value *V = BI->getCondition();
1650 CHR_DEBUG(dbgs() << *V << "\n");
1651 if (auto *I = dyn_cast<Instruction>(Val: V)) {
1652 (void)(I); // Unused in release build.
1653 assert((I->getParent() == PreEntryBlock ||
1654 !Scope->contains(I)) &&
1655 "Must have been hoisted to PreEntryBlock or outside the scope");
1656 }
1657 }
1658 for (SelectInst *SI : RI.Selects) {
1659 bool IsTrueBiased = Scope->TrueBiasedSelects.count(V: SI);
1660 bool IsFalseBiased = Scope->FalseBiasedSelects.count(V: SI);
1661 if (!(IsTrueBiased || IsFalseBiased))
1662 continue;
1663 Value *V = SI->getCondition();
1664 CHR_DEBUG(dbgs() << *V << "\n");
1665 if (auto *I = dyn_cast<Instruction>(Val: V)) {
1666 (void)(I); // Unused in release build.
1667 assert((I->getParent() == PreEntryBlock ||
1668 !Scope->contains(I)) &&
1669 "Must have been hoisted to PreEntryBlock or outside the scope");
1670 }
1671 }
1672 }
1673}
1674
1675void CHR::transformScopes(CHRScope *Scope, DenseSet<PHINode *> &TrivialPHIs) {
1676 CHR_DEBUG(dbgs() << "transformScopes " << *Scope << "\n");
1677
1678 assert(Scope->RegInfos.size() >= 1 && "Should have at least one Region");
1679
1680 for (RegInfo &RI : Scope->RegInfos) {
1681 const Region *R = RI.R;
1682 unsigned Duplication = getRegionDuplicationCount(R);
1683 CHR_DEBUG(dbgs() << "Dup count for R=" << R << " is " << Duplication
1684 << "\n");
1685 if (Duplication >= CHRDupThreshsold) {
1686 CHR_DEBUG(dbgs() << "Reached the dup threshold of " << Duplication
1687 << " for this region");
1688 ORE.emit(RemarkBuilder: [&]() {
1689 return OptimizationRemarkMissed(DEBUG_TYPE, "DupThresholdReached",
1690 R->getEntry()->getTerminator())
1691 << "Reached the duplication threshold for the region";
1692 });
1693 return;
1694 }
1695 }
1696 for (RegInfo &RI : Scope->RegInfos) {
1697 DuplicationCount[RI.R]++;
1698 }
1699
1700 Region *FirstRegion = Scope->RegInfos[0].R;
1701 BasicBlock *EntryBlock = FirstRegion->getEntry();
1702 Region *LastRegion = Scope->RegInfos[Scope->RegInfos.size() - 1].R;
1703 BasicBlock *ExitBlock = LastRegion->getExit();
1704 std::optional<uint64_t> ProfileCount = BFI.getBlockProfileCount(BB: EntryBlock);
1705
1706 if (ExitBlock) {
1707 // Insert a trivial phi at the exit block (where the CHR hot path and the
1708 // cold path merges) for a value that's defined in the scope but used
1709 // outside it (meaning it's alive at the exit block). We will add the
1710 // incoming values for the CHR cold paths to it below. Without this, we'd
1711 // miss updating phi's for such values unless there happens to already be a
1712 // phi for that value there.
1713 insertTrivialPHIs(Scope, EntryBlock, ExitBlock, TrivialPHIs);
1714 }
1715
1716 // Split the entry block of the first region. The new block becomes the new
1717 // entry block of the first region. The old entry block becomes the block to
1718 // insert the CHR branch into. Note DT gets updated. Since DT gets updated
1719 // through the split, we update the entry of the first region after the split,
1720 // and Region only points to the entry and the exit blocks, rather than
1721 // keeping everything in a list or set, the blocks membership and the
1722 // entry/exit blocks of the region are still valid after the split.
1723 CHR_DEBUG(dbgs() << "Splitting entry block " << EntryBlock->getName()
1724 << " at " << *Scope->BranchInsertPoint << "\n");
1725 BasicBlock *NewEntryBlock =
1726 SplitBlock(Old: EntryBlock, SplitPt: Scope->BranchInsertPoint, DT: &DT);
1727 assert(NewEntryBlock->getSinglePredecessor() == EntryBlock &&
1728 "NewEntryBlock's only pred must be EntryBlock");
1729 FirstRegion->replaceEntryRecursive(NewEntry: NewEntryBlock);
1730 BasicBlock *PreEntryBlock = EntryBlock;
1731
1732 ValueToValueMapTy VMap;
1733 // Clone the blocks in the scope (excluding the PreEntryBlock) to split into a
1734 // hot path (originals) and a cold path (clones) and update the PHIs at the
1735 // exit block.
1736 cloneScopeBlocks(Scope, PreEntryBlock, ExitBlock, LastRegion, VMap);
1737
1738 // Replace the old (placeholder) branch with the new (merged) conditional
1739 // branch.
1740 BranchInst *MergedBr = createMergedBranch(PreEntryBlock, EntryBlock,
1741 NewEntryBlock, VMap);
1742
1743#ifndef NDEBUG
1744 assertCHRRegionsHaveBiasedBranchOrSelect(Scope);
1745#endif
1746
1747 // Hoist the conditional values of the branches/selects.
1748 hoistScopeConditions(Scope, HoistPoint: PreEntryBlock->getTerminator(), TrivialPHIs, DT);
1749
1750#ifndef NDEBUG
1751 assertBranchOrSelectConditionHoisted(Scope, PreEntryBlock);
1752#endif
1753
1754 // Create the combined branch condition and constant-fold the branches/selects
1755 // in the hot path.
1756 fixupBranchesAndSelects(Scope, PreEntryBlock, MergedBR: MergedBr,
1757 ProfileCount: ProfileCount.value_or(u: 0));
1758}
1759
1760// A helper for transformScopes. Clone the blocks in the scope (excluding the
1761// PreEntryBlock) to split into a hot path and a cold path and update the PHIs
1762// at the exit block.
1763void CHR::cloneScopeBlocks(CHRScope *Scope,
1764 BasicBlock *PreEntryBlock,
1765 BasicBlock *ExitBlock,
1766 Region *LastRegion,
1767 ValueToValueMapTy &VMap) {
1768 // Clone all the blocks. The original blocks will be the hot-path
1769 // CHR-optimized code and the cloned blocks will be the original unoptimized
1770 // code. This is so that the block pointers from the
1771 // CHRScope/Region/RegionInfo can stay valid in pointing to the hot-path code
1772 // which CHR should apply to.
1773 SmallVector<BasicBlock*, 8> NewBlocks;
1774 for (RegInfo &RI : Scope->RegInfos)
1775 for (BasicBlock *BB : RI.R->blocks()) { // This includes the blocks in the
1776 // sub-Scopes.
1777 assert(BB != PreEntryBlock && "Don't copy the preetntry block");
1778 BasicBlock *NewBB = CloneBasicBlock(BB, VMap, NameSuffix: ".nonchr", F: &F);
1779 NewBlocks.push_back(Elt: NewBB);
1780 VMap[BB] = NewBB;
1781
1782 // Unreachable predecessors will not be cloned and will not have an edge
1783 // to the cloned block. As such, also remove them from any phi nodes.
1784 for (PHINode &PN : make_early_inc_range(Range: NewBB->phis()))
1785 PN.removeIncomingValueIf(Predicate: [&](unsigned Idx) {
1786 return !DT.isReachableFromEntry(A: PN.getIncomingBlock(i: Idx));
1787 });
1788 }
1789
1790 // Place the cloned blocks right after the original blocks (right before the
1791 // exit block of.)
1792 if (ExitBlock)
1793 F.splice(ToIt: ExitBlock->getIterator(), FromF: &F, FromBeginIt: NewBlocks[0]->getIterator(),
1794 FromEndIt: F.end());
1795
1796 // Update the cloned blocks/instructions to refer to themselves.
1797 for (BasicBlock *NewBB : NewBlocks)
1798 for (Instruction &I : *NewBB)
1799 RemapInstruction(I: &I, VM&: VMap,
1800 Flags: RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
1801
1802 // Add the cloned blocks to the PHIs of the exit blocks. ExitBlock is null for
1803 // the top-level region but we don't need to add PHIs. The trivial PHIs
1804 // inserted above will be updated here.
1805 if (ExitBlock)
1806 for (PHINode &PN : ExitBlock->phis())
1807 for (unsigned I = 0, NumOps = PN.getNumIncomingValues(); I < NumOps;
1808 ++I) {
1809 BasicBlock *Pred = PN.getIncomingBlock(i: I);
1810 if (LastRegion->contains(BB: Pred)) {
1811 Value *V = PN.getIncomingValue(i: I);
1812 auto It = VMap.find(Val: V);
1813 if (It != VMap.end()) V = It->second;
1814 assert(VMap.find(Pred) != VMap.end() && "Pred must have been cloned");
1815 PN.addIncoming(V, BB: cast<BasicBlock>(Val&: VMap[Pred]));
1816 }
1817 }
1818}
1819
1820// A helper for transformScope. Replace the old (placeholder) branch with the
1821// new (merged) conditional branch.
1822BranchInst *CHR::createMergedBranch(BasicBlock *PreEntryBlock,
1823 BasicBlock *EntryBlock,
1824 BasicBlock *NewEntryBlock,
1825 ValueToValueMapTy &VMap) {
1826 BranchInst *OldBR = cast<BranchInst>(Val: PreEntryBlock->getTerminator());
1827 assert(OldBR->isUnconditional() && OldBR->getSuccessor(0) == NewEntryBlock &&
1828 "SplitBlock did not work correctly!");
1829 assert(NewEntryBlock->getSinglePredecessor() == EntryBlock &&
1830 "NewEntryBlock's only pred must be EntryBlock");
1831 assert(VMap.find(NewEntryBlock) != VMap.end() &&
1832 "NewEntryBlock must have been copied");
1833 OldBR->dropAllReferences();
1834 OldBR->eraseFromParent();
1835 // The true predicate is a placeholder. It will be replaced later in
1836 // fixupBranchesAndSelects().
1837 BranchInst *NewBR = BranchInst::Create(IfTrue: NewEntryBlock,
1838 IfFalse: cast<BasicBlock>(Val&: VMap[NewEntryBlock]),
1839 Cond: ConstantInt::getTrue(Context&: F.getContext()));
1840 NewBR->insertInto(ParentBB: PreEntryBlock, It: PreEntryBlock->end());
1841 assert(NewEntryBlock->getSinglePredecessor() == EntryBlock &&
1842 "NewEntryBlock's only pred must be EntryBlock");
1843 return NewBR;
1844}
1845
1846// A helper for transformScopes. Create the combined branch condition and
1847// constant-fold the branches/selects in the hot path.
1848void CHR::fixupBranchesAndSelects(CHRScope *Scope,
1849 BasicBlock *PreEntryBlock,
1850 BranchInst *MergedBR,
1851 uint64_t ProfileCount) {
1852 Value *MergedCondition = ConstantInt::getTrue(Context&: F.getContext());
1853 BranchProbability CHRBranchBias(1, 1);
1854 uint64_t NumCHRedBranches = 0;
1855 IRBuilder<> IRB(PreEntryBlock->getTerminator());
1856 for (RegInfo &RI : Scope->CHRRegions) {
1857 Region *R = RI.R;
1858 if (RI.HasBranch) {
1859 fixupBranch(R, Scope, IRB, MergedCondition, CHRBranchBias);
1860 ++NumCHRedBranches;
1861 }
1862 for (SelectInst *SI : RI.Selects) {
1863 fixupSelect(SI, Scope, IRB, MergedCondition, CHRBranchBias);
1864 ++NumCHRedBranches;
1865 }
1866 }
1867 Stats.NumBranchesDelta += NumCHRedBranches - 1;
1868 Stats.WeightedNumBranchesDelta += (NumCHRedBranches - 1) * ProfileCount;
1869 ORE.emit(RemarkBuilder: [&]() {
1870 return OptimizationRemark(DEBUG_TYPE,
1871 "CHR",
1872 // Refer to the hot (original) path
1873 MergedBR->getSuccessor(i: 0)->getTerminator())
1874 << "Merged " << ore::NV("NumCHRedBranches", NumCHRedBranches)
1875 << " branches or selects";
1876 });
1877 MergedBR->setCondition(MergedCondition);
1878 uint32_t Weights[] = {
1879 static_cast<uint32_t>(CHRBranchBias.scale(Num: 1000)),
1880 static_cast<uint32_t>(CHRBranchBias.getCompl().scale(Num: 1000)),
1881 };
1882 setBranchWeights(I&: *MergedBR, Weights, /*IsExpected=*/false);
1883 CHR_DEBUG(dbgs() << "CHR branch bias " << Weights[0] << ":" << Weights[1]
1884 << "\n");
1885}
1886
1887// A helper for fixupBranchesAndSelects. Add to the combined branch condition
1888// and constant-fold a branch in the hot path.
1889void CHR::fixupBranch(Region *R, CHRScope *Scope,
1890 IRBuilder<> &IRB,
1891 Value *&MergedCondition,
1892 BranchProbability &CHRBranchBias) {
1893 bool IsTrueBiased = Scope->TrueBiasedRegions.count(V: R);
1894 assert((IsTrueBiased || Scope->FalseBiasedRegions.count(R)) &&
1895 "Must be truthy or falsy");
1896 auto *BI = cast<BranchInst>(Val: R->getEntry()->getTerminator());
1897 assert(BranchBiasMap.contains(R) && "Must be in the bias map");
1898 BranchProbability Bias = BranchBiasMap[R];
1899 assert(Bias >= getCHRBiasThreshold() && "Must be highly biased");
1900 // Take the min.
1901 if (CHRBranchBias > Bias)
1902 CHRBranchBias = Bias;
1903 BasicBlock *IfThen = BI->getSuccessor(i: 1);
1904 BasicBlock *IfElse = BI->getSuccessor(i: 0);
1905 BasicBlock *RegionExitBlock = R->getExit();
1906 assert(RegionExitBlock && "Null ExitBlock");
1907 assert((IfThen == RegionExitBlock || IfElse == RegionExitBlock) &&
1908 IfThen != IfElse && "Invariant from findScopes");
1909 if (IfThen == RegionExitBlock) {
1910 // Swap them so that IfThen means going into it and IfElse means skipping
1911 // it.
1912 std::swap(a&: IfThen, b&: IfElse);
1913 }
1914 CHR_DEBUG(dbgs() << "IfThen " << IfThen->getName()
1915 << " IfElse " << IfElse->getName() << "\n");
1916 Value *Cond = BI->getCondition();
1917 BasicBlock *HotTarget = IsTrueBiased ? IfThen : IfElse;
1918 bool ConditionTrue = HotTarget == BI->getSuccessor(i: 0);
1919 addToMergedCondition(IsTrueBiased: ConditionTrue, Cond, BranchOrSelect: BI, Scope, IRB,
1920 MergedCondition);
1921 // Constant-fold the branch at ClonedEntryBlock.
1922 assert(ConditionTrue == (HotTarget == BI->getSuccessor(0)) &&
1923 "The successor shouldn't change");
1924 Value *NewCondition = ConditionTrue ?
1925 ConstantInt::getTrue(Context&: F.getContext()) :
1926 ConstantInt::getFalse(Context&: F.getContext());
1927 BI->setCondition(NewCondition);
1928}
1929
1930// A helper for fixupBranchesAndSelects. Add to the combined branch condition
1931// and constant-fold a select in the hot path.
1932void CHR::fixupSelect(SelectInst *SI, CHRScope *Scope,
1933 IRBuilder<> &IRB,
1934 Value *&MergedCondition,
1935 BranchProbability &CHRBranchBias) {
1936 bool IsTrueBiased = Scope->TrueBiasedSelects.count(V: SI);
1937 assert((IsTrueBiased ||
1938 Scope->FalseBiasedSelects.count(SI)) && "Must be biased");
1939 assert(SelectBiasMap.contains(SI) && "Must be in the bias map");
1940 BranchProbability Bias = SelectBiasMap[SI];
1941 assert(Bias >= getCHRBiasThreshold() && "Must be highly biased");
1942 // Take the min.
1943 if (CHRBranchBias > Bias)
1944 CHRBranchBias = Bias;
1945 Value *Cond = SI->getCondition();
1946 addToMergedCondition(IsTrueBiased, Cond, BranchOrSelect: SI, Scope, IRB,
1947 MergedCondition);
1948 Value *NewCondition = IsTrueBiased ?
1949 ConstantInt::getTrue(Context&: F.getContext()) :
1950 ConstantInt::getFalse(Context&: F.getContext());
1951 SI->setCondition(NewCondition);
1952}
1953
1954// A helper for fixupBranch/fixupSelect. Add a branch condition to the merged
1955// condition.
1956void CHR::addToMergedCondition(bool IsTrueBiased, Value *Cond,
1957 Instruction *BranchOrSelect, CHRScope *Scope,
1958 IRBuilder<> &IRB, Value *&MergedCondition) {
1959 if (!IsTrueBiased) {
1960 // If Cond is an icmp and all users of V except for BranchOrSelect is a
1961 // branch, negate the icmp predicate and swap the branch targets and avoid
1962 // inserting an Xor to negate Cond.
1963 auto *ICmp = dyn_cast<ICmpInst>(Val: Cond);
1964 if (!ICmp ||
1965 !negateICmpIfUsedByBranchOrSelectOnly(ICmp, ExcludedUser: BranchOrSelect, Scope))
1966 Cond = IRB.CreateXor(LHS: ConstantInt::getTrue(Context&: F.getContext()), RHS: Cond);
1967 }
1968
1969 // Freeze potentially poisonous conditions.
1970 if (!isGuaranteedNotToBeUndefOrPoison(V: Cond))
1971 Cond = IRB.CreateFreeze(V: Cond);
1972
1973 // Use logical and to avoid propagating poison from later conditions.
1974 MergedCondition = IRB.CreateLogicalAnd(Cond1: MergedCondition, Cond2: Cond);
1975}
1976
1977void CHR::transformScopes(SmallVectorImpl<CHRScope *> &CHRScopes) {
1978 unsigned I = 0;
1979 DenseSet<PHINode *> TrivialPHIs;
1980 for (CHRScope *Scope : CHRScopes) {
1981 transformScopes(Scope, TrivialPHIs);
1982 CHR_DEBUG(
1983 std::ostringstream oss;
1984 oss << " after transformScopes " << I++;
1985 dumpIR(F, oss.str().c_str(), nullptr));
1986 (void)I;
1987 }
1988}
1989
1990static void LLVM_ATTRIBUTE_UNUSED
1991dumpScopes(SmallVectorImpl<CHRScope *> &Scopes, const char *Label) {
1992 dbgs() << Label << " " << Scopes.size() << "\n";
1993 for (CHRScope *Scope : Scopes) {
1994 dbgs() << *Scope << "\n";
1995 }
1996}
1997
1998bool CHR::run() {
1999 if (!shouldApply(F, PSI))
2000 return false;
2001
2002 CHR_DEBUG(dumpIR(F, "before", nullptr));
2003
2004 bool Changed = false;
2005 {
2006 CHR_DEBUG(
2007 dbgs() << "RegionInfo:\n";
2008 RI.print(dbgs()));
2009
2010 // Recursively traverse the region tree and find regions that have biased
2011 // branches and/or selects and create scopes.
2012 SmallVector<CHRScope *, 8> AllScopes;
2013 findScopes(Output&: AllScopes);
2014 CHR_DEBUG(dumpScopes(AllScopes, "All scopes"));
2015
2016 // Split the scopes if 1) the conditional values of the biased
2017 // branches/selects of the inner/lower scope can't be hoisted up to the
2018 // outermost/uppermost scope entry, or 2) the condition values of the biased
2019 // branches/selects in a scope (including subscopes) don't share at least
2020 // one common value.
2021 SmallVector<CHRScope *, 8> SplitScopes;
2022 splitScopes(Input&: AllScopes, Output&: SplitScopes);
2023 CHR_DEBUG(dumpScopes(SplitScopes, "Split scopes"));
2024
2025 // After splitting, set the biased regions and selects of a scope (a tree
2026 // root) that include those of the subscopes.
2027 classifyBiasedScopes(Scopes&: SplitScopes);
2028 CHR_DEBUG(dbgs() << "Set per-scope bias " << SplitScopes.size() << "\n");
2029
2030 // Filter out the scopes that has only one biased region or select (CHR
2031 // isn't useful in such a case).
2032 SmallVector<CHRScope *, 8> FilteredScopes;
2033 filterScopes(Input&: SplitScopes, Output&: FilteredScopes);
2034 CHR_DEBUG(dumpScopes(FilteredScopes, "Filtered scopes"));
2035
2036 // Set the regions to be CHR'ed and their hoist stops for each scope.
2037 SmallVector<CHRScope *, 8> SetScopes;
2038 setCHRRegions(Input&: FilteredScopes, Output&: SetScopes);
2039 CHR_DEBUG(dumpScopes(SetScopes, "Set CHR regions"));
2040
2041 // Sort CHRScopes by the depth so that outer CHRScopes comes before inner
2042 // ones. We need to apply CHR from outer to inner so that we apply CHR only
2043 // to the hot path, rather than both hot and cold paths.
2044 SmallVector<CHRScope *, 8> SortedScopes;
2045 sortScopes(Input&: SetScopes, Output&: SortedScopes);
2046 CHR_DEBUG(dumpScopes(SortedScopes, "Sorted scopes"));
2047
2048 CHR_DEBUG(
2049 dbgs() << "RegionInfo:\n";
2050 RI.print(dbgs()));
2051
2052 // Apply the CHR transformation.
2053 if (!SortedScopes.empty()) {
2054 transformScopes(CHRScopes&: SortedScopes);
2055 Changed = true;
2056 }
2057 }
2058
2059 if (Changed) {
2060 CHR_DEBUG(dumpIR(F, "after", &Stats));
2061 ORE.emit(RemarkBuilder: [&]() {
2062 return OptimizationRemark(DEBUG_TYPE, "Stats", &F)
2063 << ore::NV("Function", &F) << " "
2064 << "Reduced the number of branches in hot paths by "
2065 << ore::NV("NumBranchesDelta", Stats.NumBranchesDelta)
2066 << " (static) and "
2067 << ore::NV("WeightedNumBranchesDelta", Stats.WeightedNumBranchesDelta)
2068 << " (weighted by PGO count)";
2069 });
2070 }
2071
2072 return Changed;
2073}
2074
2075namespace llvm {
2076
2077ControlHeightReductionPass::ControlHeightReductionPass() {
2078 parseCHRFilterFiles();
2079}
2080
2081PreservedAnalyses ControlHeightReductionPass::run(
2082 Function &F,
2083 FunctionAnalysisManager &FAM) {
2084 auto &MAMProxy = FAM.getResult<ModuleAnalysisManagerFunctionProxy>(IR&: F);
2085 auto PPSI = MAMProxy.getCachedResult<ProfileSummaryAnalysis>(IR&: *F.getParent());
2086 // If there is no profile summary, we should not do CHR.
2087 if (!PPSI || !PPSI->hasProfileSummary())
2088 return PreservedAnalyses::all();
2089 auto &PSI = *PPSI;
2090 auto &BFI = FAM.getResult<BlockFrequencyAnalysis>(IR&: F);
2091 auto &DT = FAM.getResult<DominatorTreeAnalysis>(IR&: F);
2092 auto &RI = FAM.getResult<RegionInfoAnalysis>(IR&: F);
2093 auto &ORE = FAM.getResult<OptimizationRemarkEmitterAnalysis>(IR&: F);
2094 bool Changed = CHR(F, BFI, DT, PSI, RI, ORE).run();
2095 if (!Changed)
2096 return PreservedAnalyses::all();
2097 return PreservedAnalyses::none();
2098}
2099
2100} // namespace llvm
2101