LLVM  6.0.0svn
BasicBlockUtils.cpp
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1 //===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This family of functions perform manipulations on basic blocks, and
11 // instructions contained within basic blocks.
12 //
13 //===----------------------------------------------------------------------===//
14 
17 #include "llvm/Analysis/CFG.h"
18 #include "llvm/Analysis/LoopInfo.h"
20 #include "llvm/IR/Constant.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/Dominators.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/Instructions.h"
25 #include "llvm/IR/IntrinsicInst.h"
26 #include "llvm/IR/Type.h"
27 #include "llvm/IR/ValueHandle.h"
29 #include "llvm/Transforms/Scalar.h"
31 #include <algorithm>
32 using namespace llvm;
33 
35  assert((pred_begin(BB) == pred_end(BB) ||
36  // Can delete self loop.
37  BB->getSinglePredecessor() == BB) && "Block is not dead!");
38  TerminatorInst *BBTerm = BB->getTerminator();
39 
40  // Loop through all of our successors and make sure they know that one
41  // of their predecessors is going away.
42  for (BasicBlock *Succ : BBTerm->successors())
43  Succ->removePredecessor(BB);
44 
45  // Zap all the instructions in the block.
46  while (!BB->empty()) {
47  Instruction &I = BB->back();
48  // If this instruction is used, replace uses with an arbitrary value.
49  // Because control flow can't get here, we don't care what we replace the
50  // value with. Note that since this block is unreachable, and all values
51  // contained within it must dominate their uses, that all uses will
52  // eventually be removed (they are themselves dead).
53  if (!I.use_empty())
55  BB->getInstList().pop_back();
56  }
57 
58  // Zap the block!
59  BB->eraseFromParent();
60 }
61 
63  MemoryDependenceResults *MemDep) {
64  if (!isa<PHINode>(BB->begin())) return;
65 
66  while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
67  if (PN->getIncomingValue(0) != PN)
68  PN->replaceAllUsesWith(PN->getIncomingValue(0));
69  else
70  PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
71 
72  if (MemDep)
73  MemDep->removeInstruction(PN); // Memdep updates AA itself.
74 
75  PN->eraseFromParent();
76  }
77 }
78 
80  // Recursively deleting a PHI may cause multiple PHIs to be deleted
81  // or RAUW'd undef, so use an array of WeakTrackingVH for the PHIs to delete.
83  for (BasicBlock::iterator I = BB->begin();
84  PHINode *PN = dyn_cast<PHINode>(I); ++I)
85  PHIs.push_back(PN);
86 
87  bool Changed = false;
88  for (unsigned i = 0, e = PHIs.size(); i != e; ++i)
89  if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*()))
90  Changed |= RecursivelyDeleteDeadPHINode(PN, TLI);
91 
92  return Changed;
93 }
94 
96  LoopInfo *LI,
97  MemoryDependenceResults *MemDep) {
98  // Don't merge away blocks who have their address taken.
99  if (BB->hasAddressTaken()) return false;
100 
101  // Can't merge if there are multiple predecessors, or no predecessors.
102  BasicBlock *PredBB = BB->getUniquePredecessor();
103  if (!PredBB) return false;
104 
105  // Don't break self-loops.
106  if (PredBB == BB) return false;
107  // Don't break unwinding instructions.
108  if (PredBB->getTerminator()->isExceptional())
109  return false;
110 
111  succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB));
112  BasicBlock *OnlySucc = BB;
113  for (; SI != SE; ++SI)
114  if (*SI != OnlySucc) {
115  OnlySucc = nullptr; // There are multiple distinct successors!
116  break;
117  }
118 
119  // Can't merge if there are multiple successors.
120  if (!OnlySucc) return false;
121 
122  // Can't merge if there is PHI loop.
123  for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
124  if (PHINode *PN = dyn_cast<PHINode>(BI)) {
125  for (Value *IncValue : PN->incoming_values())
126  if (IncValue == PN)
127  return false;
128  } else
129  break;
130  }
131 
132  // Begin by getting rid of unneeded PHIs.
133  if (isa<PHINode>(BB->front()))
134  FoldSingleEntryPHINodes(BB, MemDep);
135 
136  // Delete the unconditional branch from the predecessor...
137  PredBB->getInstList().pop_back();
138 
139  // Make all PHI nodes that referred to BB now refer to Pred as their
140  // source...
141  BB->replaceAllUsesWith(PredBB);
142 
143  // Move all definitions in the successor to the predecessor...
144  PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
145 
146  // Inherit predecessors name if it exists.
147  if (!PredBB->hasName())
148  PredBB->takeName(BB);
149 
150  // Finally, erase the old block and update dominator info.
151  if (DT)
152  if (DomTreeNode *DTN = DT->getNode(BB)) {
153  DomTreeNode *PredDTN = DT->getNode(PredBB);
154  SmallVector<DomTreeNode *, 8> Children(DTN->begin(), DTN->end());
155  for (DomTreeNode *DI : Children)
156  DT->changeImmediateDominator(DI, PredDTN);
157 
158  DT->eraseNode(BB);
159  }
160 
161  if (LI)
162  LI->removeBlock(BB);
163 
164  if (MemDep)
166 
167  BB->eraseFromParent();
168  return true;
169 }
170 
172  BasicBlock::iterator &BI, Value *V) {
173  Instruction &I = *BI;
174  // Replaces all of the uses of the instruction with uses of the value
175  I.replaceAllUsesWith(V);
176 
177  // Make sure to propagate a name if there is one already.
178  if (I.hasName() && !V->hasName())
179  V->takeName(&I);
180 
181  // Delete the unnecessary instruction now...
182  BI = BIL.erase(BI);
183 }
184 
187  assert(I->getParent() == nullptr &&
188  "ReplaceInstWithInst: Instruction already inserted into basic block!");
189 
190  // Copy debug location to newly added instruction, if it wasn't already set
191  // by the caller.
192  if (!I->getDebugLoc())
193  I->setDebugLoc(BI->getDebugLoc());
194 
195  // Insert the new instruction into the basic block...
196  BasicBlock::iterator New = BIL.insert(BI, I);
197 
198  // Replace all uses of the old instruction, and delete it.
199  ReplaceInstWithValue(BIL, BI, I);
200 
201  // Move BI back to point to the newly inserted instruction
202  BI = New;
203 }
204 
206  BasicBlock::iterator BI(From);
207  ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
208 }
209 
211  LoopInfo *LI) {
212  unsigned SuccNum = GetSuccessorNumber(BB, Succ);
213 
214  // If this is a critical edge, let SplitCriticalEdge do it.
215  TerminatorInst *LatchTerm = BB->getTerminator();
216  if (SplitCriticalEdge(LatchTerm, SuccNum, CriticalEdgeSplittingOptions(DT, LI)
217  .setPreserveLCSSA()))
218  return LatchTerm->getSuccessor(SuccNum);
219 
220  // If the edge isn't critical, then BB has a single successor or Succ has a
221  // single pred. Split the block.
222  if (BasicBlock *SP = Succ->getSinglePredecessor()) {
223  // If the successor only has a single pred, split the top of the successor
224  // block.
225  assert(SP == BB && "CFG broken");
226  SP = nullptr;
227  return SplitBlock(Succ, &Succ->front(), DT, LI);
228  }
229 
230  // Otherwise, if BB has a single successor, split it at the bottom of the
231  // block.
232  assert(BB->getTerminator()->getNumSuccessors() == 1 &&
233  "Should have a single succ!");
234  return SplitBlock(BB, BB->getTerminator(), DT, LI);
235 }
236 
237 unsigned
239  const CriticalEdgeSplittingOptions &Options) {
240  unsigned NumBroken = 0;
241  for (BasicBlock &BB : F) {
242  TerminatorInst *TI = BB.getTerminator();
243  if (TI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(TI))
244  for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
245  if (SplitCriticalEdge(TI, i, Options))
246  ++NumBroken;
247  }
248  return NumBroken;
249 }
250 
252  DominatorTree *DT, LoopInfo *LI) {
253  BasicBlock::iterator SplitIt = SplitPt->getIterator();
254  while (isa<PHINode>(SplitIt) || SplitIt->isEHPad())
255  ++SplitIt;
256  BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
257 
258  // The new block lives in whichever loop the old one did. This preserves
259  // LCSSA as well, because we force the split point to be after any PHI nodes.
260  if (LI)
261  if (Loop *L = LI->getLoopFor(Old))
262  L->addBasicBlockToLoop(New, *LI);
263 
264  if (DT)
265  // Old dominates New. New node dominates all other nodes dominated by Old.
266  if (DomTreeNode *OldNode = DT->getNode(Old)) {
267  std::vector<DomTreeNode *> Children(OldNode->begin(), OldNode->end());
268 
269  DomTreeNode *NewNode = DT->addNewBlock(New, Old);
270  for (DomTreeNode *I : Children)
271  DT->changeImmediateDominator(I, NewNode);
272  }
273 
274  return New;
275 }
276 
277 /// Update DominatorTree, LoopInfo, and LCCSA analysis information.
280  DominatorTree *DT, LoopInfo *LI,
281  bool PreserveLCSSA, bool &HasLoopExit) {
282  // Update dominator tree if available.
283  if (DT)
284  DT->splitBlock(NewBB);
285 
286  // The rest of the logic is only relevant for updating the loop structures.
287  if (!LI)
288  return;
289 
290  Loop *L = LI->getLoopFor(OldBB);
291 
292  // If we need to preserve loop analyses, collect some information about how
293  // this split will affect loops.
294  bool IsLoopEntry = !!L;
295  bool SplitMakesNewLoopHeader = false;
296  for (BasicBlock *Pred : Preds) {
297  // If we need to preserve LCSSA, determine if any of the preds is a loop
298  // exit.
299  if (PreserveLCSSA)
300  if (Loop *PL = LI->getLoopFor(Pred))
301  if (!PL->contains(OldBB))
302  HasLoopExit = true;
303 
304  // If we need to preserve LoopInfo, note whether any of the preds crosses
305  // an interesting loop boundary.
306  if (!L)
307  continue;
308  if (L->contains(Pred))
309  IsLoopEntry = false;
310  else
311  SplitMakesNewLoopHeader = true;
312  }
313 
314  // Unless we have a loop for OldBB, nothing else to do here.
315  if (!L)
316  return;
317 
318  if (IsLoopEntry) {
319  // Add the new block to the nearest enclosing loop (and not an adjacent
320  // loop). To find this, examine each of the predecessors and determine which
321  // loops enclose them, and select the most-nested loop which contains the
322  // loop containing the block being split.
323  Loop *InnermostPredLoop = nullptr;
324  for (BasicBlock *Pred : Preds) {
325  if (Loop *PredLoop = LI->getLoopFor(Pred)) {
326  // Seek a loop which actually contains the block being split (to avoid
327  // adjacent loops).
328  while (PredLoop && !PredLoop->contains(OldBB))
329  PredLoop = PredLoop->getParentLoop();
330 
331  // Select the most-nested of these loops which contains the block.
332  if (PredLoop && PredLoop->contains(OldBB) &&
333  (!InnermostPredLoop ||
334  InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
335  InnermostPredLoop = PredLoop;
336  }
337  }
338 
339  if (InnermostPredLoop)
340  InnermostPredLoop->addBasicBlockToLoop(NewBB, *LI);
341  } else {
342  L->addBasicBlockToLoop(NewBB, *LI);
343  if (SplitMakesNewLoopHeader)
344  L->moveToHeader(NewBB);
345  }
346 }
347 
348 /// Update the PHI nodes in OrigBB to include the values coming from NewBB.
349 /// This also updates AliasAnalysis, if available.
350 static void UpdatePHINodes(BasicBlock *OrigBB, BasicBlock *NewBB,
352  bool HasLoopExit) {
353  // Otherwise, create a new PHI node in NewBB for each PHI node in OrigBB.
354  SmallPtrSet<BasicBlock *, 16> PredSet(Preds.begin(), Preds.end());
355  for (BasicBlock::iterator I = OrigBB->begin(); isa<PHINode>(I); ) {
356  PHINode *PN = cast<PHINode>(I++);
357 
358  // Check to see if all of the values coming in are the same. If so, we
359  // don't need to create a new PHI node, unless it's needed for LCSSA.
360  Value *InVal = nullptr;
361  if (!HasLoopExit) {
362  InVal = PN->getIncomingValueForBlock(Preds[0]);
363  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
364  if (!PredSet.count(PN->getIncomingBlock(i)))
365  continue;
366  if (!InVal)
367  InVal = PN->getIncomingValue(i);
368  else if (InVal != PN->getIncomingValue(i)) {
369  InVal = nullptr;
370  break;
371  }
372  }
373  }
374 
375  if (InVal) {
376  // If all incoming values for the new PHI would be the same, just don't
377  // make a new PHI. Instead, just remove the incoming values from the old
378  // PHI.
379 
380  // NOTE! This loop walks backwards for a reason! First off, this minimizes
381  // the cost of removal if we end up removing a large number of values, and
382  // second off, this ensures that the indices for the incoming values
383  // aren't invalidated when we remove one.
384  for (int64_t i = PN->getNumIncomingValues() - 1; i >= 0; --i)
385  if (PredSet.count(PN->getIncomingBlock(i)))
386  PN->removeIncomingValue(i, false);
387 
388  // Add an incoming value to the PHI node in the loop for the preheader
389  // edge.
390  PN->addIncoming(InVal, NewBB);
391  continue;
392  }
393 
394  // If the values coming into the block are not the same, we need a new
395  // PHI.
396  // Create the new PHI node, insert it into NewBB at the end of the block
397  PHINode *NewPHI =
398  PHINode::Create(PN->getType(), Preds.size(), PN->getName() + ".ph", BI);
399 
400  // NOTE! This loop walks backwards for a reason! First off, this minimizes
401  // the cost of removal if we end up removing a large number of values, and
402  // second off, this ensures that the indices for the incoming values aren't
403  // invalidated when we remove one.
404  for (int64_t i = PN->getNumIncomingValues() - 1; i >= 0; --i) {
405  BasicBlock *IncomingBB = PN->getIncomingBlock(i);
406  if (PredSet.count(IncomingBB)) {
407  Value *V = PN->removeIncomingValue(i, false);
408  NewPHI->addIncoming(V, IncomingBB);
409  }
410  }
411 
412  PN->addIncoming(NewPHI, NewBB);
413  }
414 }
415 
418  const char *Suffix, DominatorTree *DT,
419  LoopInfo *LI, bool PreserveLCSSA) {
420  // Do not attempt to split that which cannot be split.
421  if (!BB->canSplitPredecessors())
422  return nullptr;
423 
424  // For the landingpads we need to act a bit differently.
425  // Delegate this work to the SplitLandingPadPredecessors.
426  if (BB->isLandingPad()) {
428  std::string NewName = std::string(Suffix) + ".split-lp";
429 
430  SplitLandingPadPredecessors(BB, Preds, Suffix, NewName.c_str(), NewBBs, DT,
431  LI, PreserveLCSSA);
432  return NewBBs[0];
433  }
434 
435  // Create new basic block, insert right before the original block.
437  BB->getContext(), BB->getName() + Suffix, BB->getParent(), BB);
438 
439  // The new block unconditionally branches to the old block.
440  BranchInst *BI = BranchInst::Create(BB, NewBB);
441  BI->setDebugLoc(BB->getFirstNonPHIOrDbg()->getDebugLoc());
442 
443  // Move the edges from Preds to point to NewBB instead of BB.
444  for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
445  // This is slightly more strict than necessary; the minimum requirement
446  // is that there be no more than one indirectbr branching to BB. And
447  // all BlockAddress uses would need to be updated.
448  assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
449  "Cannot split an edge from an IndirectBrInst");
450  Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
451  }
452 
453  // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
454  // node becomes an incoming value for BB's phi node. However, if the Preds
455  // list is empty, we need to insert dummy entries into the PHI nodes in BB to
456  // account for the newly created predecessor.
457  if (Preds.size() == 0) {
458  // Insert dummy values as the incoming value.
459  for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
460  cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
461  return NewBB;
462  }
463 
464  // Update DominatorTree, LoopInfo, and LCCSA analysis information.
465  bool HasLoopExit = false;
466  UpdateAnalysisInformation(BB, NewBB, Preds, DT, LI, PreserveLCSSA,
467  HasLoopExit);
468 
469  // Update the PHI nodes in BB with the values coming from NewBB.
470  UpdatePHINodes(BB, NewBB, Preds, BI, HasLoopExit);
471  return NewBB;
472 }
473 
476  const char *Suffix1, const char *Suffix2,
478  DominatorTree *DT, LoopInfo *LI,
479  bool PreserveLCSSA) {
480  assert(OrigBB->isLandingPad() && "Trying to split a non-landing pad!");
481 
482  // Create a new basic block for OrigBB's predecessors listed in Preds. Insert
483  // it right before the original block.
484  BasicBlock *NewBB1 = BasicBlock::Create(OrigBB->getContext(),
485  OrigBB->getName() + Suffix1,
486  OrigBB->getParent(), OrigBB);
487  NewBBs.push_back(NewBB1);
488 
489  // The new block unconditionally branches to the old block.
490  BranchInst *BI1 = BranchInst::Create(OrigBB, NewBB1);
491  BI1->setDebugLoc(OrigBB->getFirstNonPHI()->getDebugLoc());
492 
493  // Move the edges from Preds to point to NewBB1 instead of OrigBB.
494  for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
495  // This is slightly more strict than necessary; the minimum requirement
496  // is that there be no more than one indirectbr branching to BB. And
497  // all BlockAddress uses would need to be updated.
498  assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
499  "Cannot split an edge from an IndirectBrInst");
500  Preds[i]->getTerminator()->replaceUsesOfWith(OrigBB, NewBB1);
501  }
502 
503  bool HasLoopExit = false;
504  UpdateAnalysisInformation(OrigBB, NewBB1, Preds, DT, LI, PreserveLCSSA,
505  HasLoopExit);
506 
507  // Update the PHI nodes in OrigBB with the values coming from NewBB1.
508  UpdatePHINodes(OrigBB, NewBB1, Preds, BI1, HasLoopExit);
509 
510  // Move the remaining edges from OrigBB to point to NewBB2.
511  SmallVector<BasicBlock*, 8> NewBB2Preds;
512  for (pred_iterator i = pred_begin(OrigBB), e = pred_end(OrigBB);
513  i != e; ) {
514  BasicBlock *Pred = *i++;
515  if (Pred == NewBB1) continue;
516  assert(!isa<IndirectBrInst>(Pred->getTerminator()) &&
517  "Cannot split an edge from an IndirectBrInst");
518  NewBB2Preds.push_back(Pred);
519  e = pred_end(OrigBB);
520  }
521 
522  BasicBlock *NewBB2 = nullptr;
523  if (!NewBB2Preds.empty()) {
524  // Create another basic block for the rest of OrigBB's predecessors.
525  NewBB2 = BasicBlock::Create(OrigBB->getContext(),
526  OrigBB->getName() + Suffix2,
527  OrigBB->getParent(), OrigBB);
528  NewBBs.push_back(NewBB2);
529 
530  // The new block unconditionally branches to the old block.
531  BranchInst *BI2 = BranchInst::Create(OrigBB, NewBB2);
532  BI2->setDebugLoc(OrigBB->getFirstNonPHI()->getDebugLoc());
533 
534  // Move the remaining edges from OrigBB to point to NewBB2.
535  for (BasicBlock *NewBB2Pred : NewBB2Preds)
536  NewBB2Pred->getTerminator()->replaceUsesOfWith(OrigBB, NewBB2);
537 
538  // Update DominatorTree, LoopInfo, and LCCSA analysis information.
539  HasLoopExit = false;
540  UpdateAnalysisInformation(OrigBB, NewBB2, NewBB2Preds, DT, LI,
541  PreserveLCSSA, HasLoopExit);
542 
543  // Update the PHI nodes in OrigBB with the values coming from NewBB2.
544  UpdatePHINodes(OrigBB, NewBB2, NewBB2Preds, BI2, HasLoopExit);
545  }
546 
547  LandingPadInst *LPad = OrigBB->getLandingPadInst();
548  Instruction *Clone1 = LPad->clone();
549  Clone1->setName(Twine("lpad") + Suffix1);
550  NewBB1->getInstList().insert(NewBB1->getFirstInsertionPt(), Clone1);
551 
552  if (NewBB2) {
553  Instruction *Clone2 = LPad->clone();
554  Clone2->setName(Twine("lpad") + Suffix2);
555  NewBB2->getInstList().insert(NewBB2->getFirstInsertionPt(), Clone2);
556 
557  // Create a PHI node for the two cloned landingpad instructions only
558  // if the original landingpad instruction has some uses.
559  if (!LPad->use_empty()) {
560  assert(!LPad->getType()->isTokenTy() &&
561  "Split cannot be applied if LPad is token type. Otherwise an "
562  "invalid PHINode of token type would be created.");
563  PHINode *PN = PHINode::Create(LPad->getType(), 2, "lpad.phi", LPad);
564  PN->addIncoming(Clone1, NewBB1);
565  PN->addIncoming(Clone2, NewBB2);
566  LPad->replaceAllUsesWith(PN);
567  }
568  LPad->eraseFromParent();
569  } else {
570  // There is no second clone. Just replace the landing pad with the first
571  // clone.
572  LPad->replaceAllUsesWith(Clone1);
573  LPad->eraseFromParent();
574  }
575 }
576 
578  BasicBlock *Pred) {
579  Instruction *UncondBranch = Pred->getTerminator();
580  // Clone the return and add it to the end of the predecessor.
581  Instruction *NewRet = RI->clone();
582  Pred->getInstList().push_back(NewRet);
583 
584  // If the return instruction returns a value, and if the value was a
585  // PHI node in "BB", propagate the right value into the return.
586  for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
587  i != e; ++i) {
588  Value *V = *i;
589  Instruction *NewBC = nullptr;
590  if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) {
591  // Return value might be bitcasted. Clone and insert it before the
592  // return instruction.
593  V = BCI->getOperand(0);
594  NewBC = BCI->clone();
595  Pred->getInstList().insert(NewRet->getIterator(), NewBC);
596  *i = NewBC;
597  }
598  if (PHINode *PN = dyn_cast<PHINode>(V)) {
599  if (PN->getParent() == BB) {
600  if (NewBC)
601  NewBC->setOperand(0, PN->getIncomingValueForBlock(Pred));
602  else
603  *i = PN->getIncomingValueForBlock(Pred);
604  }
605  }
606  }
607 
608  // Update any PHI nodes in the returning block to realize that we no
609  // longer branch to them.
610  BB->removePredecessor(Pred);
611  UncondBranch->eraseFromParent();
612  return cast<ReturnInst>(NewRet);
613 }
614 
617  bool Unreachable, MDNode *BranchWeights,
618  DominatorTree *DT, LoopInfo *LI) {
619  BasicBlock *Head = SplitBefore->getParent();
620  BasicBlock *Tail = Head->splitBasicBlock(SplitBefore->getIterator());
621  TerminatorInst *HeadOldTerm = Head->getTerminator();
622  LLVMContext &C = Head->getContext();
623  BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
624  TerminatorInst *CheckTerm;
625  if (Unreachable)
626  CheckTerm = new UnreachableInst(C, ThenBlock);
627  else
628  CheckTerm = BranchInst::Create(Tail, ThenBlock);
629  CheckTerm->setDebugLoc(SplitBefore->getDebugLoc());
630  BranchInst *HeadNewTerm =
631  BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/Tail, Cond);
632  HeadNewTerm->setMetadata(LLVMContext::MD_prof, BranchWeights);
633  ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);
634 
635  if (DT) {
636  if (DomTreeNode *OldNode = DT->getNode(Head)) {
637  std::vector<DomTreeNode *> Children(OldNode->begin(), OldNode->end());
638 
639  DomTreeNode *NewNode = DT->addNewBlock(Tail, Head);
640  for (DomTreeNode *Child : Children)
641  DT->changeImmediateDominator(Child, NewNode);
642 
643  // Head dominates ThenBlock.
644  DT->addNewBlock(ThenBlock, Head);
645  }
646  }
647 
648  if (LI) {
649  if (Loop *L = LI->getLoopFor(Head)) {
650  L->addBasicBlockToLoop(ThenBlock, *LI);
651  L->addBasicBlockToLoop(Tail, *LI);
652  }
653  }
654 
655  return CheckTerm;
656 }
657 
659  TerminatorInst **ThenTerm,
660  TerminatorInst **ElseTerm,
661  MDNode *BranchWeights) {
662  BasicBlock *Head = SplitBefore->getParent();
663  BasicBlock *Tail = Head->splitBasicBlock(SplitBefore->getIterator());
664  TerminatorInst *HeadOldTerm = Head->getTerminator();
665  LLVMContext &C = Head->getContext();
666  BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
667  BasicBlock *ElseBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
668  *ThenTerm = BranchInst::Create(Tail, ThenBlock);
669  (*ThenTerm)->setDebugLoc(SplitBefore->getDebugLoc());
670  *ElseTerm = BranchInst::Create(Tail, ElseBlock);
671  (*ElseTerm)->setDebugLoc(SplitBefore->getDebugLoc());
672  BranchInst *HeadNewTerm =
673  BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/ElseBlock, Cond);
674  HeadNewTerm->setMetadata(LLVMContext::MD_prof, BranchWeights);
675  ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);
676 }
677 
678 
680  BasicBlock *&IfFalse) {
681  PHINode *SomePHI = dyn_cast<PHINode>(BB->begin());
682  BasicBlock *Pred1 = nullptr;
683  BasicBlock *Pred2 = nullptr;
684 
685  if (SomePHI) {
686  if (SomePHI->getNumIncomingValues() != 2)
687  return nullptr;
688  Pred1 = SomePHI->getIncomingBlock(0);
689  Pred2 = SomePHI->getIncomingBlock(1);
690  } else {
691  pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
692  if (PI == PE) // No predecessor
693  return nullptr;
694  Pred1 = *PI++;
695  if (PI == PE) // Only one predecessor
696  return nullptr;
697  Pred2 = *PI++;
698  if (PI != PE) // More than two predecessors
699  return nullptr;
700  }
701 
702  // We can only handle branches. Other control flow will be lowered to
703  // branches if possible anyway.
704  BranchInst *Pred1Br = dyn_cast<BranchInst>(Pred1->getTerminator());
705  BranchInst *Pred2Br = dyn_cast<BranchInst>(Pred2->getTerminator());
706  if (!Pred1Br || !Pred2Br)
707  return nullptr;
708 
709  // Eliminate code duplication by ensuring that Pred1Br is conditional if
710  // either are.
711  if (Pred2Br->isConditional()) {
712  // If both branches are conditional, we don't have an "if statement". In
713  // reality, we could transform this case, but since the condition will be
714  // required anyway, we stand no chance of eliminating it, so the xform is
715  // probably not profitable.
716  if (Pred1Br->isConditional())
717  return nullptr;
718 
719  std::swap(Pred1, Pred2);
720  std::swap(Pred1Br, Pred2Br);
721  }
722 
723  if (Pred1Br->isConditional()) {
724  // The only thing we have to watch out for here is to make sure that Pred2
725  // doesn't have incoming edges from other blocks. If it does, the condition
726  // doesn't dominate BB.
727  if (!Pred2->getSinglePredecessor())
728  return nullptr;
729 
730  // If we found a conditional branch predecessor, make sure that it branches
731  // to BB and Pred2Br. If it doesn't, this isn't an "if statement".
732  if (Pred1Br->getSuccessor(0) == BB &&
733  Pred1Br->getSuccessor(1) == Pred2) {
734  IfTrue = Pred1;
735  IfFalse = Pred2;
736  } else if (Pred1Br->getSuccessor(0) == Pred2 &&
737  Pred1Br->getSuccessor(1) == BB) {
738  IfTrue = Pred2;
739  IfFalse = Pred1;
740  } else {
741  // We know that one arm of the conditional goes to BB, so the other must
742  // go somewhere unrelated, and this must not be an "if statement".
743  return nullptr;
744  }
745 
746  return Pred1Br->getCondition();
747  }
748 
749  // Ok, if we got here, both predecessors end with an unconditional branch to
750  // BB. Don't panic! If both blocks only have a single (identical)
751  // predecessor, and THAT is a conditional branch, then we're all ok!
752  BasicBlock *CommonPred = Pred1->getSinglePredecessor();
753  if (CommonPred == nullptr || CommonPred != Pred2->getSinglePredecessor())
754  return nullptr;
755 
756  // Otherwise, if this is a conditional branch, then we can use it!
757  BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator());
758  if (!BI) return nullptr;
759 
760  assert(BI->isConditional() && "Two successors but not conditional?");
761  if (BI->getSuccessor(0) == Pred1) {
762  IfTrue = Pred1;
763  IfFalse = Pred2;
764  } else {
765  IfTrue = Pred2;
766  IfFalse = Pred1;
767  }
768  return BI->getCondition();
769 }
uint64_t CallInst * C
DomTreeNodeBase< NodeT > * getNode(NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
Return a value (possibly void), from a function.
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:69
bool canSplitPredecessors() const
Definition: BasicBlock.cpp:346
void invalidateCachedPredecessors()
Clears the PredIteratorCache info.
void ReplaceInstWithInst(BasicBlock::InstListType &BIL, BasicBlock::iterator &BI, Instruction *I)
Replace the instruction specified by BI with the instruction specified by I.
void removePredecessor(BasicBlock *Pred, bool DontDeleteUselessPHIs=false)
Notify the BasicBlock that the predecessor Pred is no longer able to reach it.
Definition: BasicBlock.cpp:276
Provides a lazy, caching interface for making common memory aliasing information queries, backed by LLVM&#39;s alias analysis passes.
void addIncoming(Value *V, BasicBlock *BB)
Add an incoming value to the end of the PHI list.
void SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore, TerminatorInst **ThenTerm, TerminatorInst **ElseTerm, MDNode *BranchWeights=nullptr)
SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen, but also creates the ElseBlock...
void splitBlock(NodeT *NewBB)
splitBlock - BB is split and now it has one successor.
iterator erase(iterator where)
Definition: ilist.h:280
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
BasicBlock * SplitBlock(BasicBlock *Old, Instruction *SplitPt, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr)
Split the specified block at the specified instruction - everything before SplitPt stays in Old and e...
iterator begin() const
Definition: ArrayRef.h:137
BasicBlock * getSuccessor(unsigned idx) const
Return the specified successor.
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:136
unsigned getLoopDepth() const
Return the nesting level of this loop.
Definition: LoopInfo.h:99
void DeleteDeadBlock(BasicBlock *BB)
Delete the specified block, which must have no predecessors.
std::pair< std::string, std::string > SplitBefore(std::string X, std::string S)
Definition: FuzzerUtil.h:68
void moveToHeader(BlockT *BB)
This method is used to move BB (which must be part of this loop) to be the loop header of the loop (t...
Definition: LoopInfo.h:336
BasicBlock * getSuccessor(unsigned i) const
Metadata node.
Definition: Metadata.h:862
F(f)
unsigned SplitAllCriticalEdges(Function &F, const CriticalEdgeSplittingOptions &Options=CriticalEdgeSplittingOptions())
Loop over all of the edges in the CFG, breaking critical edges as they are found. ...
Value * getCondition() const
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:33
op_iterator op_begin()
Definition: User.h:214
void eraseNode(NodeT *BB)
eraseNode - Removes a node from the dominator tree.
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:252
Value * removeIncomingValue(unsigned Idx, bool DeletePHIIfEmpty=true)
Remove an incoming value.
Option class for critical edge splitting.
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
Definition: LoopInfo.h:631
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:284
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
bool empty() const
Definition: BasicBlock.h:263
Instruction * clone() const
Create a copy of &#39;this&#39; instruction that is identical in all ways except the following: ...
static void UpdatePHINodes(BasicBlock *OrigBB, BasicBlock *NewBB, ArrayRef< BasicBlock *> Preds, BranchInst *BI, bool HasLoopExit)
Update the PHI nodes in OrigBB to include the values coming from NewBB.
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase< BlockT, LoopT > &LI)
This method is used by other analyses to update loop information.
Definition: LoopInfoImpl.h:183
const BasicBlock * getUniquePredecessor() const
Return the predecessor of this block if it has a unique predecessor block.
Definition: BasicBlock.cpp:230
bool DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI=nullptr)
Examine each PHI in the given block and delete it if it is dead.
This class represents a no-op cast from one type to another.
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory)...
Definition: APInt.h:33
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:428
void SplitLandingPadPredecessors(BasicBlock *OrigBB, ArrayRef< BasicBlock *> Preds, const char *Suffix, const char *Suffix2, SmallVectorImpl< BasicBlock *> &NewBBs, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr, bool PreserveLCSSA=false)
This method transforms the landing pad, OrigBB, by introducing two new basic blocks into the function...
void ReplaceInstWithValue(BasicBlock::InstListType &BIL, BasicBlock::iterator &BI, Value *V)
Replace all uses of an instruction (specified by BI) with a value, then remove and delete the origina...
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:290
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:140
Interval::succ_iterator succ_end(Interval *I)
Definition: Interval.h:106
static void UpdateAnalysisInformation(BasicBlock *OldBB, BasicBlock *NewBB, ArrayRef< BasicBlock *> Preds, DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA, bool &HasLoopExit)
Update DominatorTree, LoopInfo, and LCCSA analysis information.
BasicBlock * SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, const CriticalEdgeSplittingOptions &Options=CriticalEdgeSplittingOptions())
If this edge is a critical edge, insert a new node to split the critical edge.
succ_range successors()
Definition: InstrTypes.h:267
The landingpad instruction holds all of the information necessary to generate correct exception handl...
const Instruction * getFirstNonPHI() const
Returns a pointer to the first instruction in this block that is not a PHINode instruction.
Definition: BasicBlock.cpp:171
Subclasses of this class are all able to terminate a basic block.
Definition: InstrTypes.h:54
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:200
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:281
const BasicBlock * getSinglePredecessor() const
Return the predecessor of this block if it has a single predecessor block.
Definition: BasicBlock.cpp:217
bool hasName() const
Definition: Value.h:251
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:69
Conditional or Unconditional Branch instruction.
void changeImmediateDominator(DomTreeNodeBase< NodeT > *N, DomTreeNodeBase< NodeT > *NewIDom)
changeImmediateDominator - This method is used to update the dominator tree information when a node&#39;s...
size_t size() const
size - Get the array size.
Definition: ArrayRef.h:149
This function has undefined behavior.
Value * getIncomingValueForBlock(const BasicBlock *BB) const
const Instruction & front() const
Definition: BasicBlock.h:264
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
op_iterator op_end()
Definition: User.h:216
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:342
const Instruction & back() const
Definition: BasicBlock.h:266
Interval::pred_iterator pred_end(Interval *I)
Definition: Interval.h:116
BasicBlock * SplitBlockPredecessors(BasicBlock *BB, ArrayRef< BasicBlock *> Preds, const char *Suffix, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr, bool PreserveLCSSA=false)
This method introduces at least one new basic block into the function and moves some of the predecess...
static BasicBlock * Create(LLVMContext &Context, const Twine &Name="", Function *Parent=nullptr, BasicBlock *InsertBefore=nullptr)
Creates a new BasicBlock.
Definition: BasicBlock.h:101
self_iterator getIterator()
Definition: ilist_node.h:82
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1320
Value * getIncomingValue(unsigned i) const
Return incoming value number x.
void setMetadata(unsigned KindID, MDNode *Node)
Set the metadata of the specified kind to the specified node.
Definition: Metadata.cpp:1214
bool isLandingPad() const
Return true if this basic block is a landing pad.
Definition: BasicBlock.cpp:442
bool hasAddressTaken() const
Returns true if there are any uses of this basic block other than direct branches, switches, etc.
Definition: BasicBlock.h:376
const InstListType & getInstList() const
Return the underlying instruction list container.
Definition: BasicBlock.h:317
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:117
Iterator for intrusive lists based on ilist_node.
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:410
iterator end()
Definition: BasicBlock.h:254
bool isExceptional() const
Definition: InstrTypes.h:84
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:864
Provides information about what library functions are available for the current target.
iterator end() const
Definition: ArrayRef.h:138
bool RecursivelyDeleteDeadPHINode(PHINode *PN, const TargetLibraryInfo *TLI=nullptr)
If the specified value is an effectively dead PHI node, due to being a def-use chain of single-use no...
Definition: Local.cpp:427
Value * GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, BasicBlock *&IfFalse)
Check whether BB is the merge point of a if-region.
TerminatorInst * SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore, bool Unreachable, MDNode *BranchWeights=nullptr, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr)
Split the containing block at the specified instruction - everything before SplitBefore stays in the ...
static BranchInst * Create(BasicBlock *IfTrue, Instruction *InsertBefore=nullptr)
bool isConditional() const
static PHINode * Create(Type *Ty, unsigned NumReservedValues, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Constructors - NumReservedValues is a hint for the number of incoming edges that this phi node will h...
unsigned getNumIncomingValues() const
Return the number of incoming edges.
void setOperand(unsigned i, Value *Val)
Definition: User.h:159
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:923
void push_back(pointer val)
Definition: ilist.h:326
void FoldSingleEntryPHINodes(BasicBlock *BB, MemoryDependenceResults *MemDep=nullptr)
We know that BB has one predecessor.
LoopT * getParentLoop() const
Definition: LoopInfo.h:108
unsigned GetSuccessorNumber(const BasicBlock *BB, const BasicBlock *Succ)
Search for the specified successor of basic block BB and return its position in the terminator instru...
Definition: CFG.cpp:72
iterator insert(iterator where, pointer New)
Definition: ilist.h:241
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:284
bool MergeBlockIntoPredecessor(BasicBlock *BB, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr, MemoryDependenceResults *MemDep=nullptr)
Attempts to merge a block into its predecessor, if possible.
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:404
bool isTokenTy() const
Return true if this is &#39;token&#39;.
Definition: Type.h:194
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:218
BasicBlock * getIncomingBlock(unsigned i) const
Return incoming basic block number i.
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:108
SymbolTableList< BasicBlock >::iterator eraseFromParent()
Unlink &#39;this&#39; from the containing function and delete it.
Definition: BasicBlock.cpp:97
#define I(x, y, z)
Definition: MD5.cpp:58
DomTreeNodeBase< NodeT > * addNewBlock(NodeT *BB, NodeT *DomBB)
Add a new node to the dominator tree information.
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
ReturnInst * FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB, BasicBlock *Pred)
This method duplicates the specified return instruction into a predecessor which ends in an unconditi...
BasicBlock * splitBasicBlock(iterator I, const Twine &BBName="")
Split the basic block into two basic blocks at the specified instruction.
Definition: BasicBlock.cpp:382
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
unsigned getNumSuccessors() const
Return the number of successors that this terminator has.
LLVM Value Representation.
Definition: Value.h:73
void removeInstruction(Instruction *InstToRemove)
Removes an instruction from the dependence analysis, updating the dependence of instructions that pre...
BasicBlock * SplitEdge(BasicBlock *From, BasicBlock *To, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr)
Split the edge connecting specified block.
const LandingPadInst * getLandingPadInst() const
Return the landingpad instruction associated with the landing pad.
Definition: BasicBlock.cpp:447
const Instruction * getFirstNonPHIOrDbg() const
Returns a pointer to the first instruction in this block that is not a PHINode or a debug intrinsic...
Definition: BasicBlock.cpp:178
const TerminatorInst * 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:120
void pop_back()
Definition: ilist.h:331
bool use_empty() const
Definition: Value.h:322
void removeBlock(BlockT *BB)
This method completely removes BB from all data structures, including all of the Loop objects it is n...
Definition: LoopInfo.h:690
const BasicBlock * getParent() const
Definition: Instruction.h:66