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StructurizeCFG.cpp
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1 //===- StructurizeCFG.cpp -------------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "llvm/ADT/DenseMap.h"
11 #include "llvm/ADT/MapVector.h"
13 #include "llvm/ADT/STLExtras.h"
14 #include "llvm/ADT/SmallPtrSet.h"
15 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/Analysis/LoopInfo.h"
22 #include "llvm/IR/Argument.h"
23 #include "llvm/IR/BasicBlock.h"
24 #include "llvm/IR/CFG.h"
25 #include "llvm/IR/Constant.h"
26 #include "llvm/IR/Constants.h"
27 #include "llvm/IR/Dominators.h"
28 #include "llvm/IR/Function.h"
29 #include "llvm/IR/InstrTypes.h"
30 #include "llvm/IR/Instruction.h"
31 #include "llvm/IR/Instructions.h"
32 #include "llvm/IR/Metadata.h"
33 #include "llvm/IR/PatternMatch.h"
34 #include "llvm/IR/Type.h"
35 #include "llvm/IR/Use.h"
36 #include "llvm/IR/User.h"
37 #include "llvm/IR/Value.h"
38 #include "llvm/Pass.h"
39 #include "llvm/Support/Casting.h"
40 #include "llvm/Support/Debug.h"
43 #include "llvm/Transforms/Scalar.h"
44 #include "llvm/Transforms/Utils.h"
46 #include <algorithm>
47 #include <cassert>
48 #include <utility>
49 
50 using namespace llvm;
51 using namespace llvm::PatternMatch;
52 
53 #define DEBUG_TYPE "structurizecfg"
54 
55 // The name for newly created blocks.
56 static const char *const FlowBlockName = "Flow";
57 
58 namespace {
59 
60 static cl::opt<bool> ForceSkipUniformRegions(
61  "structurizecfg-skip-uniform-regions",
62  cl::Hidden,
63  cl::desc("Force whether the StructurizeCFG pass skips uniform regions"),
64  cl::init(false));
65 
66 // Definition of the complex types used in this pass.
67 
68 using BBValuePair = std::pair<BasicBlock *, Value *>;
69 
70 using RNVector = SmallVector<RegionNode *, 8>;
71 using BBVector = SmallVector<BasicBlock *, 8>;
72 using BranchVector = SmallVector<BranchInst *, 8>;
73 using BBValueVector = SmallVector<BBValuePair, 2>;
74 
75 using BBSet = SmallPtrSet<BasicBlock *, 8>;
76 
78 using BB2BBVecMap = MapVector<BasicBlock *, BBVector>;
79 
80 using BBPhiMap = DenseMap<BasicBlock *, PhiMap>;
81 using BBPredicates = DenseMap<BasicBlock *, Value *>;
84 
85 /// Finds the nearest common dominator of a set of BasicBlocks.
86 ///
87 /// For every BB you add to the set, you can specify whether we "remember" the
88 /// block. When you get the common dominator, you can also ask whether it's one
89 /// of the blocks we remembered.
90 class NearestCommonDominator {
91  DominatorTree *DT;
92  BasicBlock *Result = nullptr;
93  bool ResultIsRemembered = false;
94 
95  /// Add BB to the resulting dominator.
96  void addBlock(BasicBlock *BB, bool Remember) {
97  if (!Result) {
98  Result = BB;
99  ResultIsRemembered = Remember;
100  return;
101  }
102 
103  BasicBlock *NewResult = DT->findNearestCommonDominator(Result, BB);
104  if (NewResult != Result)
105  ResultIsRemembered = false;
106  if (NewResult == BB)
107  ResultIsRemembered |= Remember;
108  Result = NewResult;
109  }
110 
111 public:
112  explicit NearestCommonDominator(DominatorTree *DomTree) : DT(DomTree) {}
113 
114  void addBlock(BasicBlock *BB) {
115  addBlock(BB, /* Remember = */ false);
116  }
117 
118  void addAndRememberBlock(BasicBlock *BB) {
119  addBlock(BB, /* Remember = */ true);
120  }
121 
122  /// Get the nearest common dominator of all the BBs added via addBlock() and
123  /// addAndRememberBlock().
124  BasicBlock *result() { return Result; }
125 
126  /// Is the BB returned by getResult() one of the blocks we added to the set
127  /// with addAndRememberBlock()?
128  bool resultIsRememberedBlock() { return ResultIsRemembered; }
129 };
130 
131 /// Transforms the control flow graph on one single entry/exit region
132 /// at a time.
133 ///
134 /// After the transform all "If"/"Then"/"Else" style control flow looks like
135 /// this:
136 ///
137 /// \verbatim
138 /// 1
139 /// ||
140 /// | |
141 /// 2 |
142 /// | /
143 /// |/
144 /// 3
145 /// || Where:
146 /// | | 1 = "If" block, calculates the condition
147 /// 4 | 2 = "Then" subregion, runs if the condition is true
148 /// | / 3 = "Flow" blocks, newly inserted flow blocks, rejoins the flow
149 /// |/ 4 = "Else" optional subregion, runs if the condition is false
150 /// 5 5 = "End" block, also rejoins the control flow
151 /// \endverbatim
152 ///
153 /// Control flow is expressed as a branch where the true exit goes into the
154 /// "Then"/"Else" region, while the false exit skips the region
155 /// The condition for the optional "Else" region is expressed as a PHI node.
156 /// The incoming values of the PHI node are true for the "If" edge and false
157 /// for the "Then" edge.
158 ///
159 /// Additionally to that even complicated loops look like this:
160 ///
161 /// \verbatim
162 /// 1
163 /// ||
164 /// | |
165 /// 2 ^ Where:
166 /// | / 1 = "Entry" block
167 /// |/ 2 = "Loop" optional subregion, with all exits at "Flow" block
168 /// 3 3 = "Flow" block, with back edge to entry block
169 /// |
170 /// \endverbatim
171 ///
172 /// The back edge of the "Flow" block is always on the false side of the branch
173 /// while the true side continues the general flow. So the loop condition
174 /// consist of a network of PHI nodes where the true incoming values expresses
175 /// breaks and the false values expresses continue states.
176 class StructurizeCFG : public RegionPass {
177  bool SkipUniformRegions;
178 
179  Type *Boolean;
180  ConstantInt *BoolTrue;
181  ConstantInt *BoolFalse;
182  UndefValue *BoolUndef;
183 
184  Function *Func;
185  Region *ParentRegion;
186 
188  DominatorTree *DT;
189  LoopInfo *LI;
190 
192  BBSet Visited;
193 
194  BBPhiMap DeletedPhis;
195  BB2BBVecMap AddedPhis;
196 
197  PredMap Predicates;
198  BranchVector Conditions;
199 
200  BB2BBMap Loops;
201  PredMap LoopPreds;
202  BranchVector LoopConds;
203 
204  RegionNode *PrevNode;
205 
206  void orderNodes();
207 
208  Loop *getAdjustedLoop(RegionNode *RN);
209  unsigned getAdjustedLoopDepth(RegionNode *RN);
210 
211  void analyzeLoops(RegionNode *N);
212 
213  Value *invert(Value *Condition);
214 
215  Value *buildCondition(BranchInst *Term, unsigned Idx, bool Invert);
216 
217  void gatherPredicates(RegionNode *N);
218 
219  void collectInfos();
220 
221  void insertConditions(bool Loops);
222 
223  void delPhiValues(BasicBlock *From, BasicBlock *To);
224 
225  void addPhiValues(BasicBlock *From, BasicBlock *To);
226 
227  void setPhiValues();
228 
229  void killTerminator(BasicBlock *BB);
230 
231  void changeExit(RegionNode *Node, BasicBlock *NewExit,
232  bool IncludeDominator);
233 
234  BasicBlock *getNextFlow(BasicBlock *Dominator);
235 
236  BasicBlock *needPrefix(bool NeedEmpty);
237 
238  BasicBlock *needPostfix(BasicBlock *Flow, bool ExitUseAllowed);
239 
240  void setPrevNode(BasicBlock *BB);
241 
242  bool dominatesPredicates(BasicBlock *BB, RegionNode *Node);
243 
244  bool isPredictableTrue(RegionNode *Node);
245 
246  void wireFlow(bool ExitUseAllowed, BasicBlock *LoopEnd);
247 
248  void handleLoops(bool ExitUseAllowed, BasicBlock *LoopEnd);
249 
250  void createFlow();
251 
252  void rebuildSSA();
253 
254 public:
255  static char ID;
256 
257  explicit StructurizeCFG(bool SkipUniformRegions_ = false)
258  : RegionPass(ID),
259  SkipUniformRegions(SkipUniformRegions_) {
260  if (ForceSkipUniformRegions.getNumOccurrences())
261  SkipUniformRegions = ForceSkipUniformRegions.getValue();
263  }
264 
265  bool doInitialization(Region *R, RGPassManager &RGM) override;
266 
267  bool runOnRegion(Region *R, RGPassManager &RGM) override;
268 
269  StringRef getPassName() const override { return "Structurize control flow"; }
270 
271  void getAnalysisUsage(AnalysisUsage &AU) const override {
272  if (SkipUniformRegions)
277 
280  }
281 };
282 
283 } // end anonymous namespace
284 
285 char StructurizeCFG::ID = 0;
286 
287 INITIALIZE_PASS_BEGIN(StructurizeCFG, "structurizecfg", "Structurize the CFG",
288  false, false)
290 INITIALIZE_PASS_DEPENDENCY(LowerSwitch)
293 INITIALIZE_PASS_END(StructurizeCFG, "structurizecfg", "Structurize the CFG",
294  false, false)
295 
296 /// Initialize the types and constants used in the pass
297 bool StructurizeCFG::doInitialization(Region *R, RGPassManager &RGM) {
298  LLVMContext &Context = R->getEntry()->getContext();
299 
300  Boolean = Type::getInt1Ty(Context);
301  BoolTrue = ConstantInt::getTrue(Context);
302  BoolFalse = ConstantInt::getFalse(Context);
303  BoolUndef = UndefValue::get(Boolean);
304 
305  return false;
306 }
307 
308 /// Use the exit block to determine the loop if RN is a SubRegion.
309 Loop *StructurizeCFG::getAdjustedLoop(RegionNode *RN) {
310  if (RN->isSubRegion()) {
311  Region *SubRegion = RN->getNodeAs<Region>();
312  return LI->getLoopFor(SubRegion->getExit());
313  }
314 
315  return LI->getLoopFor(RN->getEntry());
316 }
317 
318 /// Use the exit block to determine the loop depth if RN is a SubRegion.
319 unsigned StructurizeCFG::getAdjustedLoopDepth(RegionNode *RN) {
320  if (RN->isSubRegion()) {
321  Region *SubR = RN->getNodeAs<Region>();
322  return LI->getLoopDepth(SubR->getExit());
323  }
324 
325  return LI->getLoopDepth(RN->getEntry());
326 }
327 
328 /// Build up the general order of nodes
329 void StructurizeCFG::orderNodes() {
330  ReversePostOrderTraversal<Region*> RPOT(ParentRegion);
332 
333  // The reverse post-order traversal of the list gives us an ordering close
334  // to what we want. The only problem with it is that sometimes backedges
335  // for outer loops will be visited before backedges for inner loops.
336  for (RegionNode *RN : RPOT) {
337  Loop *Loop = getAdjustedLoop(RN);
338  ++LoopBlocks[Loop];
339  }
340 
341  unsigned CurrentLoopDepth = 0;
342  Loop *CurrentLoop = nullptr;
343  for (auto I = RPOT.begin(), E = RPOT.end(); I != E; ++I) {
344  RegionNode *RN = cast<RegionNode>(*I);
345  unsigned LoopDepth = getAdjustedLoopDepth(RN);
346 
347  if (is_contained(Order, *I))
348  continue;
349 
350  if (LoopDepth < CurrentLoopDepth) {
351  // Make sure we have visited all blocks in this loop before moving back to
352  // the outer loop.
353 
354  auto LoopI = I;
355  while (unsigned &BlockCount = LoopBlocks[CurrentLoop]) {
356  LoopI++;
357  if (getAdjustedLoop(cast<RegionNode>(*LoopI)) == CurrentLoop) {
358  --BlockCount;
359  Order.push_back(*LoopI);
360  }
361  }
362  }
363 
364  CurrentLoop = getAdjustedLoop(RN);
365  if (CurrentLoop)
366  LoopBlocks[CurrentLoop]--;
367 
368  CurrentLoopDepth = LoopDepth;
369  Order.push_back(*I);
370  }
371 
372  // This pass originally used a post-order traversal and then operated on
373  // the list in reverse. Now that we are using a reverse post-order traversal
374  // rather than re-working the whole pass to operate on the list in order,
375  // we just reverse the list and continue to operate on it in reverse.
376  std::reverse(Order.begin(), Order.end());
377 }
378 
379 /// Determine the end of the loops
380 void StructurizeCFG::analyzeLoops(RegionNode *N) {
381  if (N->isSubRegion()) {
382  // Test for exit as back edge
383  BasicBlock *Exit = N->getNodeAs<Region>()->getExit();
384  if (Visited.count(Exit))
385  Loops[Exit] = N->getEntry();
386 
387  } else {
388  // Test for successors as back edge
389  BasicBlock *BB = N->getNodeAs<BasicBlock>();
390  BranchInst *Term = cast<BranchInst>(BB->getTerminator());
391 
392  for (BasicBlock *Succ : Term->successors())
393  if (Visited.count(Succ))
394  Loops[Succ] = BB;
395  }
396 }
397 
398 /// Invert the given condition
399 Value *StructurizeCFG::invert(Value *Condition) {
400  // First: Check if it's a constant
401  if (Constant *C = dyn_cast<Constant>(Condition))
402  return ConstantExpr::getNot(C);
403 
404  // Second: If the condition is already inverted, return the original value
405  Value *NotCondition;
406  if (match(Condition, m_Not(m_Value(NotCondition))))
407  return NotCondition;
408 
409  if (Instruction *Inst = dyn_cast<Instruction>(Condition)) {
410  // Third: Check all the users for an invert
411  BasicBlock *Parent = Inst->getParent();
412  for (User *U : Condition->users())
413  if (Instruction *I = dyn_cast<Instruction>(U))
414  if (I->getParent() == Parent && match(I, m_Not(m_Specific(Condition))))
415  return I;
416 
417  // Last option: Create a new instruction
418  return BinaryOperator::CreateNot(Condition, "", Parent->getTerminator());
419  }
420 
421  if (Argument *Arg = dyn_cast<Argument>(Condition)) {
422  BasicBlock &EntryBlock = Arg->getParent()->getEntryBlock();
423  return BinaryOperator::CreateNot(Condition,
424  Arg->getName() + ".inv",
425  EntryBlock.getTerminator());
426  }
427 
428  llvm_unreachable("Unhandled condition to invert");
429 }
430 
431 /// Build the condition for one edge
432 Value *StructurizeCFG::buildCondition(BranchInst *Term, unsigned Idx,
433  bool Invert) {
434  Value *Cond = Invert ? BoolFalse : BoolTrue;
435  if (Term->isConditional()) {
436  Cond = Term->getCondition();
437 
438  if (Idx != (unsigned)Invert)
439  Cond = invert(Cond);
440  }
441  return Cond;
442 }
443 
444 /// Analyze the predecessors of each block and build up predicates
445 void StructurizeCFG::gatherPredicates(RegionNode *N) {
446  RegionInfo *RI = ParentRegion->getRegionInfo();
447  BasicBlock *BB = N->getEntry();
448  BBPredicates &Pred = Predicates[BB];
449  BBPredicates &LPred = LoopPreds[BB];
450 
451  for (BasicBlock *P : predecessors(BB)) {
452  // Ignore it if it's a branch from outside into our region entry
453  if (!ParentRegion->contains(P))
454  continue;
455 
456  Region *R = RI->getRegionFor(P);
457  if (R == ParentRegion) {
458  // It's a top level block in our region
459  BranchInst *Term = cast<BranchInst>(P->getTerminator());
460  for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
461  BasicBlock *Succ = Term->getSuccessor(i);
462  if (Succ != BB)
463  continue;
464 
465  if (Visited.count(P)) {
466  // Normal forward edge
467  if (Term->isConditional()) {
468  // Try to treat it like an ELSE block
469  BasicBlock *Other = Term->getSuccessor(!i);
470  if (Visited.count(Other) && !Loops.count(Other) &&
471  !Pred.count(Other) && !Pred.count(P)) {
472 
473  Pred[Other] = BoolFalse;
474  Pred[P] = BoolTrue;
475  continue;
476  }
477  }
478  Pred[P] = buildCondition(Term, i, false);
479  } else {
480  // Back edge
481  LPred[P] = buildCondition(Term, i, true);
482  }
483  }
484  } else {
485  // It's an exit from a sub region
486  while (R->getParent() != ParentRegion)
487  R = R->getParent();
488 
489  // Edge from inside a subregion to its entry, ignore it
490  if (*R == *N)
491  continue;
492 
493  BasicBlock *Entry = R->getEntry();
494  if (Visited.count(Entry))
495  Pred[Entry] = BoolTrue;
496  else
497  LPred[Entry] = BoolFalse;
498  }
499  }
500 }
501 
502 /// Collect various loop and predicate infos
503 void StructurizeCFG::collectInfos() {
504  // Reset predicate
505  Predicates.clear();
506 
507  // and loop infos
508  Loops.clear();
509  LoopPreds.clear();
510 
511  // Reset the visited nodes
512  Visited.clear();
513 
514  for (RegionNode *RN : reverse(Order)) {
515  LLVM_DEBUG(dbgs() << "Visiting: "
516  << (RN->isSubRegion() ? "SubRegion with entry: " : "")
517  << RN->getEntry()->getName() << " Loop Depth: "
518  << LI->getLoopDepth(RN->getEntry()) << "\n");
519 
520  // Analyze all the conditions leading to a node
521  gatherPredicates(RN);
522 
523  // Remember that we've seen this node
524  Visited.insert(RN->getEntry());
525 
526  // Find the last back edges
527  analyzeLoops(RN);
528  }
529 }
530 
531 /// Insert the missing branch conditions
532 void StructurizeCFG::insertConditions(bool Loops) {
533  BranchVector &Conds = Loops ? LoopConds : Conditions;
534  Value *Default = Loops ? BoolTrue : BoolFalse;
535  SSAUpdater PhiInserter;
536 
537  for (BranchInst *Term : Conds) {
538  assert(Term->isConditional());
539 
540  BasicBlock *Parent = Term->getParent();
541  BasicBlock *SuccTrue = Term->getSuccessor(0);
542  BasicBlock *SuccFalse = Term->getSuccessor(1);
543 
544  PhiInserter.Initialize(Boolean, "");
545  PhiInserter.AddAvailableValue(&Func->getEntryBlock(), Default);
546  PhiInserter.AddAvailableValue(Loops ? SuccFalse : Parent, Default);
547 
548  BBPredicates &Preds = Loops ? LoopPreds[SuccFalse] : Predicates[SuccTrue];
549 
550  NearestCommonDominator Dominator(DT);
551  Dominator.addBlock(Parent);
552 
553  Value *ParentValue = nullptr;
554  for (std::pair<BasicBlock *, Value *> BBAndPred : Preds) {
555  BasicBlock *BB = BBAndPred.first;
556  Value *Pred = BBAndPred.second;
557 
558  if (BB == Parent) {
559  ParentValue = Pred;
560  break;
561  }
562  PhiInserter.AddAvailableValue(BB, Pred);
563  Dominator.addAndRememberBlock(BB);
564  }
565 
566  if (ParentValue) {
567  Term->setCondition(ParentValue);
568  } else {
569  if (!Dominator.resultIsRememberedBlock())
570  PhiInserter.AddAvailableValue(Dominator.result(), Default);
571 
572  Term->setCondition(PhiInserter.GetValueInMiddleOfBlock(Parent));
573  }
574  }
575 }
576 
577 /// Remove all PHI values coming from "From" into "To" and remember
578 /// them in DeletedPhis
579 void StructurizeCFG::delPhiValues(BasicBlock *From, BasicBlock *To) {
580  PhiMap &Map = DeletedPhis[To];
581  for (PHINode &Phi : To->phis()) {
582  while (Phi.getBasicBlockIndex(From) != -1) {
583  Value *Deleted = Phi.removeIncomingValue(From, false);
584  Map[&Phi].push_back(std::make_pair(From, Deleted));
585  }
586  }
587 }
588 
589 /// Add a dummy PHI value as soon as we knew the new predecessor
590 void StructurizeCFG::addPhiValues(BasicBlock *From, BasicBlock *To) {
591  for (PHINode &Phi : To->phis()) {
592  Value *Undef = UndefValue::get(Phi.getType());
593  Phi.addIncoming(Undef, From);
594  }
595  AddedPhis[To].push_back(From);
596 }
597 
598 /// Add the real PHI value as soon as everything is set up
599 void StructurizeCFG::setPhiValues() {
600  SmallVector<PHINode *, 8> InsertedPhis;
601  SSAUpdater Updater(&InsertedPhis);
602  for (const auto &AddedPhi : AddedPhis) {
603  BasicBlock *To = AddedPhi.first;
604  const BBVector &From = AddedPhi.second;
605 
606  if (!DeletedPhis.count(To))
607  continue;
608 
609  PhiMap &Map = DeletedPhis[To];
610  for (const auto &PI : Map) {
611  PHINode *Phi = PI.first;
612  Value *Undef = UndefValue::get(Phi->getType());
613  Updater.Initialize(Phi->getType(), "");
614  Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
615  Updater.AddAvailableValue(To, Undef);
616 
617  NearestCommonDominator Dominator(DT);
618  Dominator.addBlock(To);
619  for (const auto &VI : PI.second) {
620  Updater.AddAvailableValue(VI.first, VI.second);
621  Dominator.addAndRememberBlock(VI.first);
622  }
623 
624  if (!Dominator.resultIsRememberedBlock())
625  Updater.AddAvailableValue(Dominator.result(), Undef);
626 
627  for (BasicBlock *FI : From) {
628  int Idx = Phi->getBasicBlockIndex(FI);
629  assert(Idx != -1);
630  Phi->setIncomingValue(Idx, Updater.GetValueAtEndOfBlock(FI));
631  }
632  }
633 
634  DeletedPhis.erase(To);
635  }
636  assert(DeletedPhis.empty());
637 
638  // Simplify any phis inserted by the SSAUpdater if possible
639  bool Changed;
640  do {
641  Changed = false;
642 
643  SimplifyQuery Q(Func->getParent()->getDataLayout());
644  Q.DT = DT;
645  for (size_t i = 0; i < InsertedPhis.size(); ++i) {
646  PHINode *Phi = InsertedPhis[i];
647  if (Value *V = SimplifyInstruction(Phi, Q)) {
648  Phi->replaceAllUsesWith(V);
649  Phi->eraseFromParent();
650  InsertedPhis[i] = InsertedPhis.back();
651  InsertedPhis.pop_back();
652  i--;
653  Changed = true;
654  }
655  }
656  } while (Changed);
657 }
658 
659 /// Remove phi values from all successors and then remove the terminator.
660 void StructurizeCFG::killTerminator(BasicBlock *BB) {
661  Instruction *Term = BB->getTerminator();
662  if (!Term)
663  return;
664 
665  for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
666  SI != SE; ++SI)
667  delPhiValues(BB, *SI);
668 
669  if (DA)
670  DA->removeValue(Term);
671  Term->eraseFromParent();
672 }
673 
674 /// Let node exit(s) point to NewExit
675 void StructurizeCFG::changeExit(RegionNode *Node, BasicBlock *NewExit,
676  bool IncludeDominator) {
677  if (Node->isSubRegion()) {
678  Region *SubRegion = Node->getNodeAs<Region>();
679  BasicBlock *OldExit = SubRegion->getExit();
680  BasicBlock *Dominator = nullptr;
681 
682  // Find all the edges from the sub region to the exit
683  for (auto BBI = pred_begin(OldExit), E = pred_end(OldExit); BBI != E;) {
684  // Incrememt BBI before mucking with BB's terminator.
685  BasicBlock *BB = *BBI++;
686 
687  if (!SubRegion->contains(BB))
688  continue;
689 
690  // Modify the edges to point to the new exit
691  delPhiValues(BB, OldExit);
692  BB->getTerminator()->replaceUsesOfWith(OldExit, NewExit);
693  addPhiValues(BB, NewExit);
694 
695  // Find the new dominator (if requested)
696  if (IncludeDominator) {
697  if (!Dominator)
698  Dominator = BB;
699  else
700  Dominator = DT->findNearestCommonDominator(Dominator, BB);
701  }
702  }
703 
704  // Change the dominator (if requested)
705  if (Dominator)
706  DT->changeImmediateDominator(NewExit, Dominator);
707 
708  // Update the region info
709  SubRegion->replaceExit(NewExit);
710  } else {
711  BasicBlock *BB = Node->getNodeAs<BasicBlock>();
712  killTerminator(BB);
713  BranchInst::Create(NewExit, BB);
714  addPhiValues(BB, NewExit);
715  if (IncludeDominator)
716  DT->changeImmediateDominator(NewExit, BB);
717  }
718 }
719 
720 /// Create a new flow node and update dominator tree and region info
721 BasicBlock *StructurizeCFG::getNextFlow(BasicBlock *Dominator) {
722  LLVMContext &Context = Func->getContext();
723  BasicBlock *Insert = Order.empty() ? ParentRegion->getExit() :
724  Order.back()->getEntry();
725  BasicBlock *Flow = BasicBlock::Create(Context, FlowBlockName,
726  Func, Insert);
727  DT->addNewBlock(Flow, Dominator);
728  ParentRegion->getRegionInfo()->setRegionFor(Flow, ParentRegion);
729  return Flow;
730 }
731 
732 /// Create a new or reuse the previous node as flow node
733 BasicBlock *StructurizeCFG::needPrefix(bool NeedEmpty) {
734  BasicBlock *Entry = PrevNode->getEntry();
735 
736  if (!PrevNode->isSubRegion()) {
737  killTerminator(Entry);
738  if (!NeedEmpty || Entry->getFirstInsertionPt() == Entry->end())
739  return Entry;
740  }
741 
742  // create a new flow node
743  BasicBlock *Flow = getNextFlow(Entry);
744 
745  // and wire it up
746  changeExit(PrevNode, Flow, true);
747  PrevNode = ParentRegion->getBBNode(Flow);
748  return Flow;
749 }
750 
751 /// Returns the region exit if possible, otherwise just a new flow node
752 BasicBlock *StructurizeCFG::needPostfix(BasicBlock *Flow,
753  bool ExitUseAllowed) {
754  if (!Order.empty() || !ExitUseAllowed)
755  return getNextFlow(Flow);
756 
757  BasicBlock *Exit = ParentRegion->getExit();
758  DT->changeImmediateDominator(Exit, Flow);
759  addPhiValues(Flow, Exit);
760  return Exit;
761 }
762 
763 /// Set the previous node
764 void StructurizeCFG::setPrevNode(BasicBlock *BB) {
765  PrevNode = ParentRegion->contains(BB) ? ParentRegion->getBBNode(BB)
766  : nullptr;
767 }
768 
769 /// Does BB dominate all the predicates of Node?
770 bool StructurizeCFG::dominatesPredicates(BasicBlock *BB, RegionNode *Node) {
771  BBPredicates &Preds = Predicates[Node->getEntry()];
772  return llvm::all_of(Preds, [&](std::pair<BasicBlock *, Value *> Pred) {
773  return DT->dominates(BB, Pred.first);
774  });
775 }
776 
777 /// Can we predict that this node will always be called?
778 bool StructurizeCFG::isPredictableTrue(RegionNode *Node) {
779  BBPredicates &Preds = Predicates[Node->getEntry()];
780  bool Dominated = false;
781 
782  // Regionentry is always true
783  if (!PrevNode)
784  return true;
785 
786  for (std::pair<BasicBlock*, Value*> Pred : Preds) {
787  BasicBlock *BB = Pred.first;
788  Value *V = Pred.second;
789 
790  if (V != BoolTrue)
791  return false;
792 
793  if (!Dominated && DT->dominates(BB, PrevNode->getEntry()))
794  Dominated = true;
795  }
796 
797  // TODO: The dominator check is too strict
798  return Dominated;
799 }
800 
801 /// Take one node from the order vector and wire it up
802 void StructurizeCFG::wireFlow(bool ExitUseAllowed,
803  BasicBlock *LoopEnd) {
804  RegionNode *Node = Order.pop_back_val();
805  Visited.insert(Node->getEntry());
806 
807  if (isPredictableTrue(Node)) {
808  // Just a linear flow
809  if (PrevNode) {
810  changeExit(PrevNode, Node->getEntry(), true);
811  }
812  PrevNode = Node;
813  } else {
814  // Insert extra prefix node (or reuse last one)
815  BasicBlock *Flow = needPrefix(false);
816 
817  // Insert extra postfix node (or use exit instead)
818  BasicBlock *Entry = Node->getEntry();
819  BasicBlock *Next = needPostfix(Flow, ExitUseAllowed);
820 
821  // let it point to entry and next block
822  Conditions.push_back(BranchInst::Create(Entry, Next, BoolUndef, Flow));
823  addPhiValues(Flow, Entry);
824  DT->changeImmediateDominator(Entry, Flow);
825 
826  PrevNode = Node;
827  while (!Order.empty() && !Visited.count(LoopEnd) &&
828  dominatesPredicates(Entry, Order.back())) {
829  handleLoops(false, LoopEnd);
830  }
831 
832  changeExit(PrevNode, Next, false);
833  setPrevNode(Next);
834  }
835 }
836 
837 void StructurizeCFG::handleLoops(bool ExitUseAllowed,
838  BasicBlock *LoopEnd) {
839  RegionNode *Node = Order.back();
840  BasicBlock *LoopStart = Node->getEntry();
841 
842  if (!Loops.count(LoopStart)) {
843  wireFlow(ExitUseAllowed, LoopEnd);
844  return;
845  }
846 
847  if (!isPredictableTrue(Node))
848  LoopStart = needPrefix(true);
849 
850  LoopEnd = Loops[Node->getEntry()];
851  wireFlow(false, LoopEnd);
852  while (!Visited.count(LoopEnd)) {
853  handleLoops(false, LoopEnd);
854  }
855 
856  // If the start of the loop is the entry block, we can't branch to it so
857  // insert a new dummy entry block.
858  Function *LoopFunc = LoopStart->getParent();
859  if (LoopStart == &LoopFunc->getEntryBlock()) {
860  LoopStart->setName("entry.orig");
861 
862  BasicBlock *NewEntry =
863  BasicBlock::Create(LoopStart->getContext(),
864  "entry",
865  LoopFunc,
866  LoopStart);
867  BranchInst::Create(LoopStart, NewEntry);
868  DT->setNewRoot(NewEntry);
869  }
870 
871  // Create an extra loop end node
872  LoopEnd = needPrefix(false);
873  BasicBlock *Next = needPostfix(LoopEnd, ExitUseAllowed);
874  LoopConds.push_back(BranchInst::Create(Next, LoopStart,
875  BoolUndef, LoopEnd));
876  addPhiValues(LoopEnd, LoopStart);
877  setPrevNode(Next);
878 }
879 
880 /// After this function control flow looks like it should be, but
881 /// branches and PHI nodes only have undefined conditions.
882 void StructurizeCFG::createFlow() {
883  BasicBlock *Exit = ParentRegion->getExit();
884  bool EntryDominatesExit = DT->dominates(ParentRegion->getEntry(), Exit);
885 
886  DeletedPhis.clear();
887  AddedPhis.clear();
888  Conditions.clear();
889  LoopConds.clear();
890 
891  PrevNode = nullptr;
892  Visited.clear();
893 
894  while (!Order.empty()) {
895  handleLoops(EntryDominatesExit, nullptr);
896  }
897 
898  if (PrevNode)
899  changeExit(PrevNode, Exit, EntryDominatesExit);
900  else
901  assert(EntryDominatesExit);
902 }
903 
904 /// Handle a rare case where the disintegrated nodes instructions
905 /// no longer dominate all their uses. Not sure if this is really necessary
906 void StructurizeCFG::rebuildSSA() {
907  SSAUpdater Updater;
908  for (BasicBlock *BB : ParentRegion->blocks())
909  for (Instruction &I : *BB) {
910  bool Initialized = false;
911  // We may modify the use list as we iterate over it, so be careful to
912  // compute the next element in the use list at the top of the loop.
913  for (auto UI = I.use_begin(), E = I.use_end(); UI != E;) {
914  Use &U = *UI++;
915  Instruction *User = cast<Instruction>(U.getUser());
916  if (User->getParent() == BB) {
917  continue;
918  } else if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
919  if (UserPN->getIncomingBlock(U) == BB)
920  continue;
921  }
922 
923  if (DT->dominates(&I, User))
924  continue;
925 
926  if (!Initialized) {
927  Value *Undef = UndefValue::get(I.getType());
928  Updater.Initialize(I.getType(), "");
929  Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
930  Updater.AddAvailableValue(BB, &I);
931  Initialized = true;
932  }
933  Updater.RewriteUseAfterInsertions(U);
934  }
935  }
936 }
937 
938 static bool hasOnlyUniformBranches(Region *R, unsigned UniformMDKindID,
939  const LegacyDivergenceAnalysis &DA) {
940  for (auto E : R->elements()) {
941  if (!E->isSubRegion()) {
942  auto Br = dyn_cast<BranchInst>(E->getEntry()->getTerminator());
943  if (!Br || !Br->isConditional())
944  continue;
945 
946  if (!DA.isUniform(Br))
947  return false;
948  LLVM_DEBUG(dbgs() << "BB: " << Br->getParent()->getName()
949  << " has uniform terminator\n");
950  } else {
951  // Explicitly refuse to treat regions as uniform if they have non-uniform
952  // subregions. We cannot rely on DivergenceAnalysis for branches in
953  // subregions because those branches may have been removed and re-created,
954  // so we look for our metadata instead.
955  //
956  // Warning: It would be nice to treat regions as uniform based only on
957  // their direct child basic blocks' terminators, regardless of whether
958  // subregions are uniform or not. However, this requires a very careful
959  // look at SIAnnotateControlFlow to make sure nothing breaks there.
960  for (auto BB : E->getNodeAs<Region>()->blocks()) {
961  auto Br = dyn_cast<BranchInst>(BB->getTerminator());
962  if (!Br || !Br->isConditional())
963  continue;
964 
965  if (!Br->getMetadata(UniformMDKindID))
966  return false;
967  }
968  }
969  }
970  return true;
971 }
972 
973 /// Run the transformation for each region found
974 bool StructurizeCFG::runOnRegion(Region *R, RGPassManager &RGM) {
975  if (R->isTopLevelRegion())
976  return false;
977 
978  DA = nullptr;
979 
980  if (SkipUniformRegions) {
981  // TODO: We could probably be smarter here with how we handle sub-regions.
982  // We currently rely on the fact that metadata is set by earlier invocations
983  // of the pass on sub-regions, and that this metadata doesn't get lost --
984  // but we shouldn't rely on metadata for correctness!
985  unsigned UniformMDKindID =
986  R->getEntry()->getContext().getMDKindID("structurizecfg.uniform");
987  DA = &getAnalysis<LegacyDivergenceAnalysis>();
988 
989  if (hasOnlyUniformBranches(R, UniformMDKindID, *DA)) {
990  LLVM_DEBUG(dbgs() << "Skipping region with uniform control flow: " << *R
991  << '\n');
992 
993  // Mark all direct child block terminators as having been treated as
994  // uniform. To account for a possible future in which non-uniform
995  // sub-regions are treated more cleverly, indirect children are not
996  // marked as uniform.
997  MDNode *MD = MDNode::get(R->getEntry()->getParent()->getContext(), {});
998  for (RegionNode *E : R->elements()) {
999  if (E->isSubRegion())
1000  continue;
1001 
1002  if (Instruction *Term = E->getEntry()->getTerminator())
1003  Term->setMetadata(UniformMDKindID, MD);
1004  }
1005 
1006  return false;
1007  }
1008  }
1009 
1010  Func = R->getEntry()->getParent();
1011  ParentRegion = R;
1012 
1013  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1014  LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
1015 
1016  orderNodes();
1017  collectInfos();
1018  createFlow();
1019  insertConditions(false);
1020  insertConditions(true);
1021  setPhiValues();
1022  rebuildSSA();
1023 
1024  // Cleanup
1025  Order.clear();
1026  Visited.clear();
1027  DeletedPhis.clear();
1028  AddedPhis.clear();
1029  Predicates.clear();
1030  Conditions.clear();
1031  Loops.clear();
1032  LoopPreds.clear();
1033  LoopConds.clear();
1034 
1035  return true;
1036 }
1037 
1038 Pass *llvm::createStructurizeCFGPass(bool SkipUniformRegions) {
1039  return new StructurizeCFG(SkipUniformRegions);
1040 }
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:81
uint64_t CallInst * C
T * getNodeAs() const
Get the content of this RegionNode.
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:68
static ConstantInt * getFalse(LLVMContext &Context)
Definition: Constants.cpp:584
class_match< Value > m_Value()
Match an arbitrary value and ignore it.
Definition: PatternMatch.h:72
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
static IntegerType * getInt1Ty(LLVMContext &C)
Definition: Type.cpp:173
Helper class for SSA formation on a set of values defined in multiple blocks.
Definition: SSAUpdater.h:39
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
This class represents an incoming formal argument to a Function.
Definition: Argument.h:30
LLVMContext & Context
static BinaryOperator * CreateNot(Value *Op, const Twine &Name="", Instruction *InsertBefore=nullptr)
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
void Initialize(Type *Ty, StringRef Name)
Reset this object to get ready for a new set of SSA updates with type &#39;Ty&#39;.
Definition: SSAUpdater.cpp:54
structurizecfg
void AddAvailableValue(BasicBlock *BB, Value *V)
Indicate that a rewritten value is available in the specified block with the specified value...
Definition: SSAUpdater.cpp:72
This file contains the declarations for metadata subclasses.
NodeT * findNearestCommonDominator(NodeT *A, NodeT *B) const
findNearestCommonDominator - Find nearest common dominator basic block for basic block A and B...
This class implements a map that also provides access to all stored values in a deterministic order...
Definition: MapVector.h:38
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1042
BasicBlock * getSuccessor(unsigned i) const
Metadata node.
Definition: Metadata.h:864
static const char *const FlowBlockName
Value * getCondition() const
const Instruction * getTerminator() const LLVM_READONLY
Returns the terminator instruction if the block is well formed or null if the block is not well forme...
Definition: BasicBlock.cpp:138
This defines the Use class.
BlockT * getExit() const
Get the exit BasicBlock of the Region.
Definition: RegionInfo.h:361
bool isSubRegion() const
Is this RegionNode a subregion?
Definition: RegionInfo.h:190
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:33
The pass manager to schedule RegionPasses.
Definition: RegionPass.h:89
bool match(Val *V, const Pattern &P)
Definition: PatternMatch.h:49
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
Hexagon Hardware Loops
int getBasicBlockIndex(const BasicBlock *BB) const
Return the first index of the specified basic block in the value list for this PHI.
&#39;undef&#39; values are things that do not have specified contents.
Definition: Constants.h:1275
unsigned getNumSuccessors() const
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
void setName(const Twine &Name)
Change the name of the value.
Definition: Value.cpp:295
ELFYAML::ELF_STO Other
Definition: ELFYAML.cpp:773
Interval::succ_iterator succ_begin(Interval *I)
succ_begin/succ_end - define methods so that Intervals may be used just like BasicBlocks can with the...
Definition: Interval.h:103
auto reverse(ContainerTy &&C, typename std::enable_if< has_rbegin< ContainerTy >::value >::type *=nullptr) -> decltype(make_range(C.rbegin(), C.rend()))
Definition: STLExtras.h:251
User * getUser() const LLVM_READONLY
Returns the User that contains this Use.
Definition: Use.cpp:41
block_range blocks()
Returns a range view of the basic blocks in the region.
Definition: RegionInfo.h:625
virtual void getAnalysisUsage(AnalysisUsage &) const
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
Definition: Pass.cpp:92
BlockT * getEntry() const
Get the entry BasicBlock of this RegionNode.
Definition: RegionInfo.h:176
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
static bool hasOnlyUniformBranches(Region *R, unsigned UniformMDKindID, const LegacyDivergenceAnalysis &DA)
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:439
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:145
Interval::succ_iterator succ_end(Interval *I)
Definition: Interval.h:106
void replaceUsesOfWith(Value *From, Value *To)
Replace uses of one Value with another.
Definition: User.cpp:21
const BasicBlock & getEntryBlock() const
Definition: Function.h:640
static MDTuple * get(LLVMContext &Context, ArrayRef< Metadata *> MDs)
Definition: Metadata.h:1166
#define P(N)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:410
Value * GetValueInMiddleOfBlock(BasicBlock *BB)
Construct SSA form, materializing a value that is live in the middle of the specified block...
Definition: SSAUpdater.cpp:100
const_iterator getFirstInsertionPt() const
Returns an iterator to the first instruction in this block that is suitable for inserting a non-PHI i...
Definition: BasicBlock.cpp:219
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:69
void RewriteUseAfterInsertions(Use &U)
Rewrite a use like RewriteUse but handling in-block definitions.
Definition: SSAUpdater.cpp:207
Conditional or Unconditional Branch instruction.
A pass that runs on each Region in a function.
Definition: RegionPass.h:34
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:42
This file contains the declarations for the subclasses of Constant, which represent the different fla...
void replaceExit(BlockT *BB)
Replace the exit basic block of the region with the new basic block.
Interval::pred_iterator pred_begin(Interval *I)
pred_begin/pred_end - define methods so that Intervals may be used just like BasicBlocks can with the...
Definition: Interval.h:113
int getNumOccurrences() const
Definition: CommandLine.h:371
specificval_ty m_Specific(const Value *V)
Match if we have a specific specified value.
Definition: PatternMatch.h:499
unsigned char Boolean
Definition: ConvertUTF.h:113
Represent the analysis usage information of a pass.
Annotate SI Control Flow
const Instruction & back() const
Definition: BasicBlock.h:277
Interval::pred_iterator pred_end(Interval *I)
Definition: Interval.h:116
static BasicBlock * Create(LLVMContext &Context, const Twine &Name="", Function *Parent=nullptr, BasicBlock *InsertBefore=nullptr)
Creates a new BasicBlock.
Definition: BasicBlock.h:100
static Constant * getNot(Constant *C)
Definition: Constants.cpp:2180
bool isTopLevelRegion() const
Check if a Region is the TopLevel region.
Definition: RegionInfo.h:387
INITIALIZE_PASS_BEGIN(StructurizeCFG, "structurizecfg", "Structurize the CFG", false, false) INITIALIZE_PASS_END(StructurizeCFG
char & LowerSwitchID
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1392
void initializeStructurizeCFGPass(PassRegistry &)
size_t size() const
Definition: SmallVector.h:53
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
void setMetadata(unsigned KindID, MDNode *Node)
Set the metadata of the specified kind to the specified node.
Definition: Metadata.cpp:1226
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
This is the shared class of boolean and integer constants.
Definition: Constants.h:84
BlockVerifier::State From
BlockT * getEntry() const
Get the entry BasicBlock of the Region.
Definition: RegionInfo.h:324
iterator end()
Definition: BasicBlock.h:265
AnalysisUsage & addRequiredID(const void *ID)
Definition: Pass.cpp:299
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
static BranchInst * Create(BasicBlock *IfTrue, Instruction *InsertBefore=nullptr)
bool isConditional() const
pred_range predecessors(BasicBlock *BB)
Definition: CFG.h:123
static ConstantInt * getTrue(LLVMContext &Context)
Definition: Constants.cpp:577
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
iterator_range< user_iterator > users()
Definition: Value.h:400
amdgpu Simplify well known AMD library false Value Value * Arg
This file provides various utilities for inspecting and working with the control flow graph in LLVM I...
bool contains(const BlockT *BB) const
Check if the region contains a BasicBlock.
Structurize the CFG
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:459
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:224
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:107
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
iterator_range< const_phi_iterator > phis() const
Returns a range that iterates over the phis in the basic block.
Definition: BasicBlock.h:319
void setCondition(Value *V)
RegionT * getParent() const
Get the parent of the Region.
Definition: RegionInfo.h:366
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM Value Representation.
Definition: Value.h:73
bool isUniform(const Value *V) const
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:964
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
const DominatorTree * DT
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:260
Value * GetValueAtEndOfBlock(BasicBlock *BB)
Construct SSA form, materializing a value that is live at the end of the specified block...
Definition: SSAUpdater.cpp:95
void setIncomingValue(unsigned i, Value *V)
#define LLVM_DEBUG(X)
Definition: Debug.h:123
Pass * createStructurizeCFGPass(bool SkipUniformRegions=false)
When SkipUniformRegions is true the structizer will not structurize regions that only contain uniform...
iterator_range< element_iterator > elements()
Definition: RegionInfo.h:654
Value * SimplifyInstruction(Instruction *I, const SimplifyQuery &Q, OptimizationRemarkEmitter *ORE=nullptr)
See if we can compute a simplified version of this instruction.
RegionT * getRegionFor(BlockT *BB) const
Get the smallest region that contains a BasicBlock.
BinaryOp_match< ValTy, cst_pred_ty< is_all_ones >, Instruction::Xor, true > m_Not(const ValTy &V)
Matches a &#39;Not&#39; as &#39;xor V, -1&#39; or &#39;xor -1, V&#39;.
const BasicBlock * getParent() const
Definition: Instruction.h:67
bool is_contained(R &&Range, const E &Element)
Wrapper function around std::find to detect if an element exists in a container.
Definition: STLExtras.h:1101