LLVM  12.0.0git
BreakCriticalEdges.cpp
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1 //===- BreakCriticalEdges.cpp - Critical Edge Elimination Pass ------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // BreakCriticalEdges pass - Break all of the critical edges in the CFG by
10 // inserting a dummy basic block. This pass may be "required" by passes that
11 // cannot deal with critical edges. For this usage, the structure type is
12 // forward declared. This pass obviously invalidates the CFG, but can update
13 // dominator trees.
14 //
15 //===----------------------------------------------------------------------===//
16 
18 #include "llvm/ADT/SetVector.h"
19 #include "llvm/ADT/SmallVector.h"
20 #include "llvm/ADT/Statistic.h"
23 #include "llvm/Analysis/CFG.h"
24 #include "llvm/Analysis/LoopInfo.h"
27 #include "llvm/IR/CFG.h"
28 #include "llvm/IR/Dominators.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/Type.h"
31 #include "llvm/InitializePasses.h"
33 #include "llvm/Transforms/Utils.h"
37 using namespace llvm;
38 
39 #define DEBUG_TYPE "break-crit-edges"
40 
41 STATISTIC(NumBroken, "Number of blocks inserted");
42 
43 namespace {
44  struct BreakCriticalEdges : public FunctionPass {
45  static char ID; // Pass identification, replacement for typeid
46  BreakCriticalEdges() : FunctionPass(ID) {
48  }
49 
50  bool runOnFunction(Function &F) override {
51  auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
52  auto *DT = DTWP ? &DTWP->getDomTree() : nullptr;
53 
54  auto *PDTWP = getAnalysisIfAvailable<PostDominatorTreeWrapperPass>();
55  auto *PDT = PDTWP ? &PDTWP->getPostDomTree() : nullptr;
56 
57  auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
58  auto *LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
59  unsigned N =
61  NumBroken += N;
62  return N > 0;
63  }
64 
65  void getAnalysisUsage(AnalysisUsage &AU) const override {
68 
69  // No loop canonicalization guarantees are broken by this pass.
71  }
72  };
73 }
74 
75 char BreakCriticalEdges::ID = 0;
76 INITIALIZE_PASS(BreakCriticalEdges, "break-crit-edges",
77  "Break critical edges in CFG", false, false)
78 
79 // Publicly exposed interface to pass...
80 char &llvm::BreakCriticalEdgesID = BreakCriticalEdges::ID;
82  return new BreakCriticalEdges();
83 }
84 
87  auto *DT = AM.getCachedResult<DominatorTreeAnalysis>(F);
88  auto *LI = AM.getCachedResult<LoopAnalysis>(F);
90  NumBroken += N;
91  if (N == 0)
92  return PreservedAnalyses::all();
95  PA.preserve<LoopAnalysis>();
96  return PA;
97 }
98 
99 //===----------------------------------------------------------------------===//
100 // Implementation of the external critical edge manipulation functions
101 //===----------------------------------------------------------------------===//
102 
103 /// When a loop exit edge is split, LCSSA form may require new PHIs in the new
104 /// exit block. This function inserts the new PHIs, as needed. Preds is a list
105 /// of preds inside the loop, SplitBB is the new loop exit block, and DestBB is
106 /// the old loop exit, now the successor of SplitBB.
108  BasicBlock *SplitBB,
109  BasicBlock *DestBB) {
110  // SplitBB shouldn't have anything non-trivial in it yet.
111  assert((SplitBB->getFirstNonPHI() == SplitBB->getTerminator() ||
112  SplitBB->isLandingPad()) && "SplitBB has non-PHI nodes!");
113 
114  // For each PHI in the destination block.
115  for (PHINode &PN : DestBB->phis()) {
116  unsigned Idx = PN.getBasicBlockIndex(SplitBB);
117  Value *V = PN.getIncomingValue(Idx);
118 
119  // If the input is a PHI which already satisfies LCSSA, don't create
120  // a new one.
121  if (const PHINode *VP = dyn_cast<PHINode>(V))
122  if (VP->getParent() == SplitBB)
123  continue;
124 
125  // Otherwise a new PHI is needed. Create one and populate it.
126  PHINode *NewPN = PHINode::Create(
127  PN.getType(), Preds.size(), "split",
128  SplitBB->isLandingPad() ? &SplitBB->front() : SplitBB->getTerminator());
129  for (unsigned i = 0, e = Preds.size(); i != e; ++i)
130  NewPN->addIncoming(V, Preds[i]);
131 
132  // Update the original PHI.
133  PN.setIncomingValue(Idx, NewPN);
134  }
135 }
136 
138  const CriticalEdgeSplittingOptions &Options,
139  const Twine &BBName) {
140  if (!isCriticalEdge(TI, SuccNum, Options.MergeIdenticalEdges))
141  return nullptr;
142 
143  assert(!isa<IndirectBrInst>(TI) &&
144  "Cannot split critical edge from IndirectBrInst");
145 
146  BasicBlock *TIBB = TI->getParent();
147  BasicBlock *DestBB = TI->getSuccessor(SuccNum);
148 
149  // Splitting the critical edge to a pad block is non-trivial. Don't do
150  // it in this generic function.
151  if (DestBB->isEHPad()) return nullptr;
152 
153  if (Options.IgnoreUnreachableDests &&
154  isa<UnreachableInst>(DestBB->getFirstNonPHIOrDbgOrLifetime()))
155  return nullptr;
156 
157  auto *LI = Options.LI;
159  // Check if extra modifications will be required to preserve loop-simplify
160  // form after splitting. If it would require splitting blocks with IndirectBr
161  // or CallBr terminators, bail out if preserving loop-simplify form is
162  // requested.
163  if (LI) {
164  if (Loop *TIL = LI->getLoopFor(TIBB)) {
165 
166  // The only way that we can break LoopSimplify form by splitting a
167  // critical edge is if after the split there exists some edge from TIL to
168  // DestBB *and* the only edge into DestBB from outside of TIL is that of
169  // NewBB. If the first isn't true, then LoopSimplify still holds, NewBB
170  // is the new exit block and it has no non-loop predecessors. If the
171  // second isn't true, then DestBB was not in LoopSimplify form prior to
172  // the split as it had a non-loop predecessor. In both of these cases,
173  // the predecessor must be directly in TIL, not in a subloop, or again
174  // LoopSimplify doesn't hold.
175  for (BasicBlock *P : predecessors(DestBB)) {
176  if (P == TIBB)
177  continue; // The new block is known.
178  if (LI->getLoopFor(P) != TIL) {
179  // No need to re-simplify, it wasn't to start with.
180  LoopPreds.clear();
181  break;
182  }
183  LoopPreds.push_back(P);
184  }
185  // Loop-simplify form can be preserved, if we can split all in-loop
186  // predecessors.
187  if (any_of(LoopPreds, [](BasicBlock *Pred) {
188  const Instruction *T = Pred->getTerminator();
189  if (const auto *CBR = dyn_cast<CallBrInst>(T))
190  return CBR->getDefaultDest() != Pred;
191  return isa<IndirectBrInst>(T);
192  })) {
193  if (Options.PreserveLoopSimplify)
194  return nullptr;
195  LoopPreds.clear();
196  }
197  }
198  }
199 
200  // Create a new basic block, linking it into the CFG.
201  BasicBlock *NewBB = nullptr;
202  if (BBName.str() != "")
203  NewBB = BasicBlock::Create(TI->getContext(), BBName);
204  else
205  NewBB = BasicBlock::Create(TI->getContext(), TIBB->getName() + "." +
206  DestBB->getName() +
207  "_crit_edge");
208  // Create our unconditional branch.
209  BranchInst *NewBI = BranchInst::Create(DestBB, NewBB);
210  NewBI->setDebugLoc(TI->getDebugLoc());
211 
212  // Insert the block into the function... right after the block TI lives in.
213  Function &F = *TIBB->getParent();
214  Function::iterator FBBI = TIBB->getIterator();
215  F.getBasicBlockList().insert(++FBBI, NewBB);
216 
217  // Branch to the new block, breaking the edge.
218  TI->setSuccessor(SuccNum, NewBB);
219 
220  // If there are any PHI nodes in DestBB, we need to update them so that they
221  // merge incoming values from NewBB instead of from TIBB.
222  {
223  unsigned BBIdx = 0;
224  for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) {
225  // We no longer enter through TIBB, now we come in through NewBB.
226  // Revector exactly one entry in the PHI node that used to come from
227  // TIBB to come from NewBB.
228  PHINode *PN = cast<PHINode>(I);
229 
230  // Reuse the previous value of BBIdx if it lines up. In cases where we
231  // have multiple phi nodes with *lots* of predecessors, this is a speed
232  // win because we don't have to scan the PHI looking for TIBB. This
233  // happens because the BB list of PHI nodes are usually in the same
234  // order.
235  if (PN->getIncomingBlock(BBIdx) != TIBB)
236  BBIdx = PN->getBasicBlockIndex(TIBB);
237  PN->setIncomingBlock(BBIdx, NewBB);
238  }
239  }
240 
241  // If there are any other edges from TIBB to DestBB, update those to go
242  // through the split block, making those edges non-critical as well (and
243  // reducing the number of phi entries in the DestBB if relevant).
244  if (Options.MergeIdenticalEdges) {
245  for (unsigned i = SuccNum+1, e = TI->getNumSuccessors(); i != e; ++i) {
246  if (TI->getSuccessor(i) != DestBB) continue;
247 
248  // Remove an entry for TIBB from DestBB phi nodes.
249  DestBB->removePredecessor(TIBB, Options.KeepOneInputPHIs);
250 
251  // We found another edge to DestBB, go to NewBB instead.
252  TI->setSuccessor(i, NewBB);
253  }
254  }
255 
256  // If we have nothing to update, just return.
257  auto *DT = Options.DT;
258  auto *PDT = Options.PDT;
259  auto *MSSAU = Options.MSSAU;
260  if (MSSAU)
262  DestBB, NewBB, {TIBB}, Options.MergeIdenticalEdges);
263 
264  if (!DT && !PDT && !LI)
265  return NewBB;
266 
267  if (DT || PDT) {
268  // Update the DominatorTree.
269  // ---> NewBB -----\
270  // / V
271  // TIBB -------\\------> DestBB
272  //
273  // First, inform the DT about the new path from TIBB to DestBB via NewBB,
274  // then delete the old edge from TIBB to DestBB. By doing this in that order
275  // DestBB stays reachable in the DT the whole time and its subtree doesn't
276  // get disconnected.
278  Updates.push_back({DominatorTree::Insert, TIBB, NewBB});
279  Updates.push_back({DominatorTree::Insert, NewBB, DestBB});
280  if (!llvm::is_contained(successors(TIBB), DestBB))
281  Updates.push_back({DominatorTree::Delete, TIBB, DestBB});
282 
283  if (DT)
284  DT->applyUpdates(Updates);
285  if (PDT)
286  PDT->applyUpdates(Updates);
287  }
288 
289  // Update LoopInfo if it is around.
290  if (LI) {
291  if (Loop *TIL = LI->getLoopFor(TIBB)) {
292  // If one or the other blocks were not in a loop, the new block is not
293  // either, and thus LI doesn't need to be updated.
294  if (Loop *DestLoop = LI->getLoopFor(DestBB)) {
295  if (TIL == DestLoop) {
296  // Both in the same loop, the NewBB joins loop.
297  DestLoop->addBasicBlockToLoop(NewBB, *LI);
298  } else if (TIL->contains(DestLoop)) {
299  // Edge from an outer loop to an inner loop. Add to the outer loop.
300  TIL->addBasicBlockToLoop(NewBB, *LI);
301  } else if (DestLoop->contains(TIL)) {
302  // Edge from an inner loop to an outer loop. Add to the outer loop.
303  DestLoop->addBasicBlockToLoop(NewBB, *LI);
304  } else {
305  // Edge from two loops with no containment relation. Because these
306  // are natural loops, we know that the destination block must be the
307  // header of its loop (adding a branch into a loop elsewhere would
308  // create an irreducible loop).
309  assert(DestLoop->getHeader() == DestBB &&
310  "Should not create irreducible loops!");
311  if (Loop *P = DestLoop->getParentLoop())
312  P->addBasicBlockToLoop(NewBB, *LI);
313  }
314  }
315 
316  // If TIBB is in a loop and DestBB is outside of that loop, we may need
317  // to update LoopSimplify form and LCSSA form.
318  if (!TIL->contains(DestBB)) {
319  assert(!TIL->contains(NewBB) &&
320  "Split point for loop exit is contained in loop!");
321 
322  // Update LCSSA form in the newly created exit block.
323  if (Options.PreserveLCSSA) {
324  createPHIsForSplitLoopExit(TIBB, NewBB, DestBB);
325  }
326 
327  if (!LoopPreds.empty()) {
328  assert(!DestBB->isEHPad() && "We don't split edges to EH pads!");
329  BasicBlock *NewExitBB = SplitBlockPredecessors(
330  DestBB, LoopPreds, "split", DT, LI, MSSAU, Options.PreserveLCSSA);
331  if (Options.PreserveLCSSA)
332  createPHIsForSplitLoopExit(LoopPreds, NewExitBB, DestBB);
333  }
334  }
335  }
336  }
337 
338  return NewBB;
339 }
340 
341 // Return the unique indirectbr predecessor of a block. This may return null
342 // even if such a predecessor exists, if it's not useful for splitting.
343 // If a predecessor is found, OtherPreds will contain all other (non-indirectbr)
344 // predecessors of BB.
345 static BasicBlock *
347  // If the block doesn't have any PHIs, we don't care about it, since there's
348  // no point in splitting it.
349  PHINode *PN = dyn_cast<PHINode>(BB->begin());
350  if (!PN)
351  return nullptr;
352 
353  // Verify we have exactly one IBR predecessor.
354  // Conservatively bail out if one of the other predecessors is not a "regular"
355  // terminator (that is, not a switch or a br).
356  BasicBlock *IBB = nullptr;
357  for (unsigned Pred = 0, E = PN->getNumIncomingValues(); Pred != E; ++Pred) {
358  BasicBlock *PredBB = PN->getIncomingBlock(Pred);
359  Instruction *PredTerm = PredBB->getTerminator();
360  switch (PredTerm->getOpcode()) {
361  case Instruction::IndirectBr:
362  if (IBB)
363  return nullptr;
364  IBB = PredBB;
365  break;
366  case Instruction::Br:
367  case Instruction::Switch:
368  OtherPreds.push_back(PredBB);
369  continue;
370  default:
371  return nullptr;
372  }
373  }
374 
375  return IBB;
376 }
377 
381  // Check whether the function has any indirectbrs, and collect which blocks
382  // they may jump to. Since most functions don't have indirect branches,
383  // this lowers the common case's overhead to O(Blocks) instead of O(Edges).
385  for (auto &BB : F) {
386  auto *IBI = dyn_cast<IndirectBrInst>(BB.getTerminator());
387  if (!IBI)
388  continue;
389 
390  for (unsigned Succ = 0, E = IBI->getNumSuccessors(); Succ != E; ++Succ)
391  Targets.insert(IBI->getSuccessor(Succ));
392  }
393 
394  if (Targets.empty())
395  return false;
396 
397  bool ShouldUpdateAnalysis = BPI && BFI;
398  bool Changed = false;
399  for (BasicBlock *Target : Targets) {
401  BasicBlock *IBRPred = findIBRPredecessor(Target, OtherPreds);
402  // If we did not found an indirectbr, or the indirectbr is the only
403  // incoming edge, this isn't the kind of edge we're looking for.
404  if (!IBRPred || OtherPreds.empty())
405  continue;
406 
407  // Don't even think about ehpads/landingpads.
408  Instruction *FirstNonPHI = Target->getFirstNonPHI();
409  if (FirstNonPHI->isEHPad() || Target->isLandingPad())
410  continue;
411 
412  // Remember edge probabilities if needed.
413  SmallVector<BranchProbability, 4> EdgeProbabilities;
414  if (ShouldUpdateAnalysis) {
415  EdgeProbabilities.reserve(Target->getTerminator()->getNumSuccessors());
416  for (unsigned I = 0, E = Target->getTerminator()->getNumSuccessors();
417  I < E; ++I)
418  EdgeProbabilities.emplace_back(BPI->getEdgeProbability(Target, I));
419  BPI->eraseBlock(Target);
420  }
421 
422  BasicBlock *BodyBlock = Target->splitBasicBlock(FirstNonPHI, ".split");
423  if (ShouldUpdateAnalysis) {
424  // Copy the BFI/BPI from Target to BodyBlock.
425  BPI->setEdgeProbability(BodyBlock, EdgeProbabilities);
426  BFI->setBlockFreq(BodyBlock, BFI->getBlockFreq(Target).getFrequency());
427  }
428  // It's possible Target was its own successor through an indirectbr.
429  // In this case, the indirectbr now comes from BodyBlock.
430  if (IBRPred == Target)
431  IBRPred = BodyBlock;
432 
433  // At this point Target only has PHIs, and BodyBlock has the rest of the
434  // block's body. Create a copy of Target that will be used by the "direct"
435  // preds.
436  ValueToValueMapTy VMap;
437  BasicBlock *DirectSucc = CloneBasicBlock(Target, VMap, ".clone", &F);
438 
439  BlockFrequency BlockFreqForDirectSucc;
440  for (BasicBlock *Pred : OtherPreds) {
441  // If the target is a loop to itself, then the terminator of the split
442  // block (BodyBlock) needs to be updated.
443  BasicBlock *Src = Pred != Target ? Pred : BodyBlock;
444  Src->getTerminator()->replaceUsesOfWith(Target, DirectSucc);
445  if (ShouldUpdateAnalysis)
446  BlockFreqForDirectSucc += BFI->getBlockFreq(Src) *
447  BPI->getEdgeProbability(Src, DirectSucc);
448  }
449  if (ShouldUpdateAnalysis) {
450  BFI->setBlockFreq(DirectSucc, BlockFreqForDirectSucc.getFrequency());
451  BlockFrequency NewBlockFreqForTarget =
452  BFI->getBlockFreq(Target) - BlockFreqForDirectSucc;
453  BFI->setBlockFreq(Target, NewBlockFreqForTarget.getFrequency());
454  }
455 
456  // Ok, now fix up the PHIs. We know the two blocks only have PHIs, and that
457  // they are clones, so the number of PHIs are the same.
458  // (a) Remove the edge coming from IBRPred from the "Direct" PHI
459  // (b) Leave that as the only edge in the "Indirect" PHI.
460  // (c) Merge the two in the body block.
461  BasicBlock::iterator Indirect = Target->begin(),
462  End = Target->getFirstNonPHI()->getIterator();
463  BasicBlock::iterator Direct = DirectSucc->begin();
464  BasicBlock::iterator MergeInsert = BodyBlock->getFirstInsertionPt();
465 
466  assert(&*End == Target->getTerminator() &&
467  "Block was expected to only contain PHIs");
468 
469  while (Indirect != End) {
470  PHINode *DirPHI = cast<PHINode>(Direct);
471  PHINode *IndPHI = cast<PHINode>(Indirect);
472 
473  // Now, clean up - the direct block shouldn't get the indirect value,
474  // and vice versa.
475  DirPHI->removeIncomingValue(IBRPred);
476  Direct++;
477 
478  // Advance the pointer here, to avoid invalidation issues when the old
479  // PHI is erased.
480  Indirect++;
481 
482  PHINode *NewIndPHI = PHINode::Create(IndPHI->getType(), 1, "ind", IndPHI);
483  NewIndPHI->addIncoming(IndPHI->getIncomingValueForBlock(IBRPred),
484  IBRPred);
485 
486  // Create a PHI in the body block, to merge the direct and indirect
487  // predecessors.
488  PHINode *MergePHI =
489  PHINode::Create(IndPHI->getType(), 2, "merge", &*MergeInsert);
490  MergePHI->addIncoming(NewIndPHI, Target);
491  MergePHI->addIncoming(DirPHI, DirectSucc);
492 
493  IndPHI->replaceAllUsesWith(MergePHI);
494  IndPHI->eraseFromParent();
495  }
496 
497  Changed = true;
498  }
499 
500  return Changed;
501 }
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks 'this' from the containing basic block and deletes it.
Definition: Instruction.cpp:77
reference emplace_back(ArgTypes &&... Args)
Definition: SmallVector.h:856
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
void addIncoming(Value *V, BasicBlock *BB)
Add an incoming value to the end of the PHI list.
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
const Instruction * getFirstNonPHIOrDbgOrLifetime(bool SkipPseudoOp=false) const
Returns a pointer to the first instruction in this block that is not a PHINode, a debug intrinsic,...
Definition: BasicBlock.cpp:233
This class represents lattice values for constants.
Definition: AllocatorList.h:23
BasicBlock * getSuccessor(unsigned Idx) const
Return the specified successor. This instruction must be a terminator.
void removePredecessor(BasicBlock *Pred, bool KeepOneInputPHIs=false)
Update PHI nodes in this BasicBlock before removal of predecessor Pred.
Definition: BasicBlock.cpp:321
uint64_t getFrequency() const
Returns the frequency as a fixpoint number scaled by the entry frequency.
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:868
STATISTIC(NumFunctions, "Total number of functions")
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:249
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.
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:148
void setSuccessor(unsigned Idx, BasicBlock *BB)
Update the specified successor to point at the provided block.
void initializeBreakCriticalEdgesPass(PassRegistry &)
void reserve(size_type N)
Definition: SmallVector.h:584
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:296
Value * removeIncomingValue(unsigned Idx, bool DeletePHIIfEmpty=true)
Remove an incoming value.
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Option class for critical edge splitting.
int getBasicBlockIndex(const BasicBlock *BB) const
Return the first index of the specified basic block in the value list for this PHI.
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:80
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:43
Analysis pass that exposes the LoopInfo for a function.
Definition: LoopInfo.h:1224
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:246
bool insert(const value_type &X)
Insert a new element into the SetVector.
Definition: SetVector.h:141
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: APInt.h:32
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:160
AnalysisUsage & addPreservedID(const void *ID)
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:523
void wireOldPredecessorsToNewImmediatePredecessor(BasicBlock *Old, BasicBlock *New, ArrayRef< BasicBlock * > Preds, bool IdenticalEdgesWereMerged=true)
A new empty BasicBlock (New) now branches directly to Old.
unsigned getNumSuccessors() const
Return the number of successors that this instruction has.
void replaceUsesOfWith(Value *From, Value *To)
Replace uses of one Value with another.
Definition: User.cpp:21
BlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation to estimate IR basic block frequen...
static bool runOnFunction(Function &F, bool PostInlining)
#define P(N)
const Instruction * getFirstNonPHI() const
Returns a pointer to the first instruction in this block that is not a PHINode instruction.
Definition: BasicBlock.cpp:212
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:155
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:249
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
Conditional or Unconditional Branch instruction.
char & BreakCriticalEdgesID
size_t size() const
size - Get the array size.
Definition: ArrayRef.h:156
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
Value * getIncomingValueForBlock(const BasicBlock *BB) const
const Instruction & front() const
Definition: BasicBlock.h:308
FunctionPass * createBreakCriticalEdgesPass()
BasicBlock * SplitCriticalEdge(Instruction *TI, unsigned SuccNum, const CriticalEdgeSplittingOptions &Options=CriticalEdgeSplittingOptions(), const Twine &BBName="")
If this edge is a critical edge, insert a new node to split the critical edge.
void eraseBlock(const BasicBlock *BB)
Forget analysis results for the given basic block.
Represent the analysis usage information of a pass.
bool any_of(R &&range, UnaryPredicate P)
Provide wrappers to std::any_of which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1505
constexpr double e
Definition: MathExtras.h:58
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:298
static BasicBlock * Create(LLVMContext &Context, const Twine &Name="", Function *Parent=nullptr, BasicBlock *InsertBefore=nullptr)
Creates a new BasicBlock.
Definition: BasicBlock.h:100
self_iterator getIterator()
Definition: ilist_node.h:81
bool isCriticalEdge(const Instruction *TI, unsigned SuccNum, bool AllowIdenticalEdges=false)
Return true if the specified edge is a critical edge.
Definition: CFG.cpp:95
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:161
BranchProbability getEdgeProbability(const BasicBlock *Src, unsigned IndexInSuccessors) const
Get an edge's probability, relative to other out-edges of the Src.
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:37
char & LoopSimplifyID
bool isLandingPad() const
Return true if this basic block is a landing pad.
Definition: BasicBlock.cpp:467
A SetVector that performs no allocations if smaller than a certain size.
Definition: SetVector.h:307
Iterator for intrusive lists based on ilist_node.
void setIncomingBlock(unsigned i, BasicBlock *BB)
bool PreserveLoopSimplify
SplitCriticalEdge is guaranteed to preserve loop-simplify form if LI is provided.
BasicBlock * SplitBlockPredecessors(BasicBlock *BB, ArrayRef< BasicBlock * > Preds, const char *Suffix, DominatorTree *DT, LoopInfo *LI=nullptr, MemorySSAUpdater *MSSAU=nullptr, bool PreserveLCSSA=false)
This method introduces at least one new basic block into the function and moves some of the predecess...
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1116
static BranchInst * Create(BasicBlock *IfTrue, Instruction *InsertBefore=nullptr)
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...
pred_range predecessors(BasicBlock *BB)
Definition: CFG.h:125
void setEdgeProbability(const BasicBlock *Src, const SmallVectorImpl< BranchProbability > &Probs)
Set the raw probabilities for all edges from the given block.
unsigned getNumIncomingValues() const
Return the number of incoming edges.
Target - Wrapper for Target specific information.
BasicBlock * CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap, const Twine &NameSuffix="", Function *F=nullptr, ClonedCodeInfo *CodeInfo=nullptr, DebugInfoFinder *DIFinder=nullptr)
Return a copy of the specified basic block, but without embedding the block into a particular functio...
This file provides various utilities for inspecting and working with the control flow graph in LLVM I...
Analysis providing branch probability information.
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:365
bool SplitIndirectBrCriticalEdges(Function &F, BranchProbabilityInfo *BPI=nullptr, BlockFrequencyInfo *BFI=nullptr)
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:529
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:295
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:107
#define I(x, y, z)
Definition: MD5.cpp:59
#define N
bool empty() const
Determine if the SetVector is empty or not.
Definition: SetVector.h:72
PassT::Result * getCachedResult(IRUnitT &IR) const
Get the cached result of an analysis pass for a given IR unit.
Definition: PassManager.h:804
void preserve()
Mark an analysis as preserved.
Definition: PassManager.h:176
iterator_range< const_phi_iterator > phis() const
Returns a range that iterates over the phis in the basic block.
Definition: BasicBlock.h:354
std::string str() const
Return the twine contents as a std::string.
Definition: Twine.cpp:17
static BasicBlock * findIBRPredecessor(BasicBlock *BB, SmallVectorImpl< BasicBlock * > &OtherPreds)
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
bool isEHPad() const
Return true if this basic block is an exception handling block.
Definition: BasicBlock.h:465
LLVM Value Representation.
Definition: Value.h:75
succ_range successors(Instruction *I)
Definition: CFG.h:260
bool isEHPad() const
Return true if the instruction is a variety of EH-block.
Definition: Instruction.h:637
The legacy pass manager's analysis pass to compute loop information.
Definition: LoopInfo.h:1249
A container for analyses that lazily runs them and caches their results.
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:278
static void createPHIsForSplitLoopExit(ArrayRef< BasicBlock * > Preds, BasicBlock *SplitBB, BasicBlock *DestBB)
When a loop exit edge is split, LCSSA form may require new PHIs in the new exit block.
const BasicBlock * getParent() const
Definition: Instruction.h:94
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:1563