LLVM  9.0.0svn
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"
26 #include "llvm/IR/CFG.h"
27 #include "llvm/IR/Dominators.h"
28 #include "llvm/IR/Instructions.h"
29 #include "llvm/IR/Type.h"
31 #include "llvm/Transforms/Utils.h"
35 using namespace llvm;
36 
37 #define DEBUG_TYPE "break-crit-edges"
38 
39 STATISTIC(NumBroken, "Number of blocks inserted");
40 
41 namespace {
42  struct BreakCriticalEdges : public FunctionPass {
43  static char ID; // Pass identification, replacement for typeid
44  BreakCriticalEdges() : FunctionPass(ID) {
46  }
47 
48  bool runOnFunction(Function &F) override {
49  auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
50  auto *DT = DTWP ? &DTWP->getDomTree() : nullptr;
51  auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
52  auto *LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
53  unsigned N =
55  NumBroken += N;
56  return N > 0;
57  }
58 
59  void getAnalysisUsage(AnalysisUsage &AU) const override {
62 
63  // No loop canonicalization guarantees are broken by this pass.
65  }
66  };
67 }
68 
69 char BreakCriticalEdges::ID = 0;
70 INITIALIZE_PASS(BreakCriticalEdges, "break-crit-edges",
71  "Break critical edges in CFG", false, false)
72 
73 // Publicly exposed interface to pass...
74 char &llvm::BreakCriticalEdgesID = BreakCriticalEdges::ID;
76  return new BreakCriticalEdges();
77 }
78 
81  auto *DT = AM.getCachedResult<DominatorTreeAnalysis>(F);
82  auto *LI = AM.getCachedResult<LoopAnalysis>(F);
84  NumBroken += N;
85  if (N == 0)
86  return PreservedAnalyses::all();
89  PA.preserve<LoopAnalysis>();
90  return PA;
91 }
92 
93 //===----------------------------------------------------------------------===//
94 // Implementation of the external critical edge manipulation functions
95 //===----------------------------------------------------------------------===//
96 
97 /// When a loop exit edge is split, LCSSA form may require new PHIs in the new
98 /// exit block. This function inserts the new PHIs, as needed. Preds is a list
99 /// of preds inside the loop, SplitBB is the new loop exit block, and DestBB is
100 /// the old loop exit, now the successor of SplitBB.
102  BasicBlock *SplitBB,
103  BasicBlock *DestBB) {
104  // SplitBB shouldn't have anything non-trivial in it yet.
105  assert((SplitBB->getFirstNonPHI() == SplitBB->getTerminator() ||
106  SplitBB->isLandingPad()) && "SplitBB has non-PHI nodes!");
107 
108  // For each PHI in the destination block.
109  for (PHINode &PN : DestBB->phis()) {
110  unsigned Idx = PN.getBasicBlockIndex(SplitBB);
111  Value *V = PN.getIncomingValue(Idx);
112 
113  // If the input is a PHI which already satisfies LCSSA, don't create
114  // a new one.
115  if (const PHINode *VP = dyn_cast<PHINode>(V))
116  if (VP->getParent() == SplitBB)
117  continue;
118 
119  // Otherwise a new PHI is needed. Create one and populate it.
120  PHINode *NewPN = PHINode::Create(
121  PN.getType(), Preds.size(), "split",
122  SplitBB->isLandingPad() ? &SplitBB->front() : SplitBB->getTerminator());
123  for (unsigned i = 0, e = Preds.size(); i != e; ++i)
124  NewPN->addIncoming(V, Preds[i]);
125 
126  // Update the original PHI.
127  PN.setIncomingValue(Idx, NewPN);
128  }
129 }
130 
131 BasicBlock *
132 llvm::SplitCriticalEdge(Instruction *TI, unsigned SuccNum,
133  const CriticalEdgeSplittingOptions &Options) {
134  if (!isCriticalEdge(TI, SuccNum, Options.MergeIdenticalEdges))
135  return nullptr;
136 
137  assert(!isa<IndirectBrInst>(TI) &&
138  "Cannot split critical edge from IndirectBrInst");
139 
140  BasicBlock *TIBB = TI->getParent();
141  BasicBlock *DestBB = TI->getSuccessor(SuccNum);
142 
143  // Splitting the critical edge to a pad block is non-trivial. Don't do
144  // it in this generic function.
145  if (DestBB->isEHPad()) return nullptr;
146 
147  // Don't split the non-fallthrough edge from a callbr.
148  if (isa<CallBrInst>(TI) && SuccNum > 0)
149  return nullptr;
150 
151  // Create a new basic block, linking it into the CFG.
153  TIBB->getName() + "." + DestBB->getName() + "_crit_edge");
154  // Create our unconditional branch.
155  BranchInst *NewBI = BranchInst::Create(DestBB, NewBB);
156  NewBI->setDebugLoc(TI->getDebugLoc());
157 
158  // Branch to the new block, breaking the edge.
159  TI->setSuccessor(SuccNum, NewBB);
160 
161  // Insert the block into the function... right after the block TI lives in.
162  Function &F = *TIBB->getParent();
163  Function::iterator FBBI = TIBB->getIterator();
164  F.getBasicBlockList().insert(++FBBI, NewBB);
165 
166  // If there are any PHI nodes in DestBB, we need to update them so that they
167  // merge incoming values from NewBB instead of from TIBB.
168  {
169  unsigned BBIdx = 0;
170  for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) {
171  // We no longer enter through TIBB, now we come in through NewBB.
172  // Revector exactly one entry in the PHI node that used to come from
173  // TIBB to come from NewBB.
174  PHINode *PN = cast<PHINode>(I);
175 
176  // Reuse the previous value of BBIdx if it lines up. In cases where we
177  // have multiple phi nodes with *lots* of predecessors, this is a speed
178  // win because we don't have to scan the PHI looking for TIBB. This
179  // happens because the BB list of PHI nodes are usually in the same
180  // order.
181  if (PN->getIncomingBlock(BBIdx) != TIBB)
182  BBIdx = PN->getBasicBlockIndex(TIBB);
183  PN->setIncomingBlock(BBIdx, NewBB);
184  }
185  }
186 
187  // If there are any other edges from TIBB to DestBB, update those to go
188  // through the split block, making those edges non-critical as well (and
189  // reducing the number of phi entries in the DestBB if relevant).
190  if (Options.MergeIdenticalEdges) {
191  for (unsigned i = SuccNum+1, e = TI->getNumSuccessors(); i != e; ++i) {
192  if (TI->getSuccessor(i) != DestBB) continue;
193 
194  // Remove an entry for TIBB from DestBB phi nodes.
195  DestBB->removePredecessor(TIBB, Options.KeepOneInputPHIs);
196 
197  // We found another edge to DestBB, go to NewBB instead.
198  TI->setSuccessor(i, NewBB);
199  }
200  }
201 
202  // If we have nothing to update, just return.
203  auto *DT = Options.DT;
204  auto *LI = Options.LI;
205  auto *MSSAU = Options.MSSAU;
206  if (MSSAU)
208  DestBB, NewBB, {TIBB}, Options.MergeIdenticalEdges);
209 
210  if (!DT && !LI)
211  return NewBB;
212 
213  if (DT) {
214  // Update the DominatorTree.
215  // ---> NewBB -----\
216  // / V
217  // TIBB -------\\------> DestBB
218  //
219  // First, inform the DT about the new path from TIBB to DestBB via NewBB,
220  // then delete the old edge from TIBB to DestBB. By doing this in that order
221  // DestBB stays reachable in the DT the whole time and its subtree doesn't
222  // get disconnected.
224  Updates.push_back({DominatorTree::Insert, TIBB, NewBB});
225  Updates.push_back({DominatorTree::Insert, NewBB, DestBB});
226  if (llvm::find(successors(TIBB), DestBB) == succ_end(TIBB))
227  Updates.push_back({DominatorTree::Delete, TIBB, DestBB});
228 
229  DT->applyUpdates(Updates);
230  }
231 
232  // Update LoopInfo if it is around.
233  if (LI) {
234  if (Loop *TIL = LI->getLoopFor(TIBB)) {
235  // If one or the other blocks were not in a loop, the new block is not
236  // either, and thus LI doesn't need to be updated.
237  if (Loop *DestLoop = LI->getLoopFor(DestBB)) {
238  if (TIL == DestLoop) {
239  // Both in the same loop, the NewBB joins loop.
240  DestLoop->addBasicBlockToLoop(NewBB, *LI);
241  } else if (TIL->contains(DestLoop)) {
242  // Edge from an outer loop to an inner loop. Add to the outer loop.
243  TIL->addBasicBlockToLoop(NewBB, *LI);
244  } else if (DestLoop->contains(TIL)) {
245  // Edge from an inner loop to an outer loop. Add to the outer loop.
246  DestLoop->addBasicBlockToLoop(NewBB, *LI);
247  } else {
248  // Edge from two loops with no containment relation. Because these
249  // are natural loops, we know that the destination block must be the
250  // header of its loop (adding a branch into a loop elsewhere would
251  // create an irreducible loop).
252  assert(DestLoop->getHeader() == DestBB &&
253  "Should not create irreducible loops!");
254  if (Loop *P = DestLoop->getParentLoop())
255  P->addBasicBlockToLoop(NewBB, *LI);
256  }
257  }
258 
259  // If TIBB is in a loop and DestBB is outside of that loop, we may need
260  // to update LoopSimplify form and LCSSA form.
261  if (!TIL->contains(DestBB)) {
262  assert(!TIL->contains(NewBB) &&
263  "Split point for loop exit is contained in loop!");
264 
265  // Update LCSSA form in the newly created exit block.
266  if (Options.PreserveLCSSA) {
267  createPHIsForSplitLoopExit(TIBB, NewBB, DestBB);
268  }
269 
270  // The only that we can break LoopSimplify form by splitting a critical
271  // edge is if after the split there exists some edge from TIL to DestBB
272  // *and* the only edge into DestBB from outside of TIL is that of
273  // NewBB. If the first isn't true, then LoopSimplify still holds, NewBB
274  // is the new exit block and it has no non-loop predecessors. If the
275  // second isn't true, then DestBB was not in LoopSimplify form prior to
276  // the split as it had a non-loop predecessor. In both of these cases,
277  // the predecessor must be directly in TIL, not in a subloop, or again
278  // LoopSimplify doesn't hold.
280  for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB); I != E;
281  ++I) {
282  BasicBlock *P = *I;
283  if (P == NewBB)
284  continue; // The new block is known.
285  if (LI->getLoopFor(P) != TIL) {
286  // No need to re-simplify, it wasn't to start with.
287  LoopPreds.clear();
288  break;
289  }
290  LoopPreds.push_back(P);
291  }
292  if (!LoopPreds.empty()) {
293  assert(!DestBB->isEHPad() && "We don't split edges to EH pads!");
294  BasicBlock *NewExitBB = SplitBlockPredecessors(
295  DestBB, LoopPreds, "split", DT, LI, MSSAU, Options.PreserveLCSSA);
296  if (Options.PreserveLCSSA)
297  createPHIsForSplitLoopExit(LoopPreds, NewExitBB, DestBB);
298  }
299  }
300  }
301  }
302 
303  return NewBB;
304 }
305 
306 // Return the unique indirectbr predecessor of a block. This may return null
307 // even if such a predecessor exists, if it's not useful for splitting.
308 // If a predecessor is found, OtherPreds will contain all other (non-indirectbr)
309 // predecessors of BB.
310 static BasicBlock *
312  // If the block doesn't have any PHIs, we don't care about it, since there's
313  // no point in splitting it.
314  PHINode *PN = dyn_cast<PHINode>(BB->begin());
315  if (!PN)
316  return nullptr;
317 
318  // Verify we have exactly one IBR predecessor.
319  // Conservatively bail out if one of the other predecessors is not a "regular"
320  // terminator (that is, not a switch or a br).
321  BasicBlock *IBB = nullptr;
322  for (unsigned Pred = 0, E = PN->getNumIncomingValues(); Pred != E; ++Pred) {
323  BasicBlock *PredBB = PN->getIncomingBlock(Pred);
324  Instruction *PredTerm = PredBB->getTerminator();
325  switch (PredTerm->getOpcode()) {
326  case Instruction::IndirectBr:
327  if (IBB)
328  return nullptr;
329  IBB = PredBB;
330  break;
331  case Instruction::Br:
332  case Instruction::Switch:
333  OtherPreds.push_back(PredBB);
334  continue;
335  default:
336  return nullptr;
337  }
338  }
339 
340  return IBB;
341 }
342 
346  // Check whether the function has any indirectbrs, and collect which blocks
347  // they may jump to. Since most functions don't have indirect branches,
348  // this lowers the common case's overhead to O(Blocks) instead of O(Edges).
350  for (auto &BB : F) {
351  auto *IBI = dyn_cast<IndirectBrInst>(BB.getTerminator());
352  if (!IBI)
353  continue;
354 
355  for (unsigned Succ = 0, E = IBI->getNumSuccessors(); Succ != E; ++Succ)
356  Targets.insert(IBI->getSuccessor(Succ));
357  }
358 
359  if (Targets.empty())
360  return false;
361 
362  bool ShouldUpdateAnalysis = BPI && BFI;
363  bool Changed = false;
364  for (BasicBlock *Target : Targets) {
366  BasicBlock *IBRPred = findIBRPredecessor(Target, OtherPreds);
367  // If we did not found an indirectbr, or the indirectbr is the only
368  // incoming edge, this isn't the kind of edge we're looking for.
369  if (!IBRPred || OtherPreds.empty())
370  continue;
371 
372  // Don't even think about ehpads/landingpads.
373  Instruction *FirstNonPHI = Target->getFirstNonPHI();
374  if (FirstNonPHI->isEHPad() || Target->isLandingPad())
375  continue;
376 
377  BasicBlock *BodyBlock = Target->splitBasicBlock(FirstNonPHI, ".split");
378  if (ShouldUpdateAnalysis) {
379  // Copy the BFI/BPI from Target to BodyBlock.
380  for (unsigned I = 0, E = BodyBlock->getTerminator()->getNumSuccessors();
381  I < E; ++I)
382  BPI->setEdgeProbability(BodyBlock, I,
383  BPI->getEdgeProbability(Target, I));
384  BFI->setBlockFreq(BodyBlock, BFI->getBlockFreq(Target).getFrequency());
385  }
386  // It's possible Target was its own successor through an indirectbr.
387  // In this case, the indirectbr now comes from BodyBlock.
388  if (IBRPred == Target)
389  IBRPred = BodyBlock;
390 
391  // At this point Target only has PHIs, and BodyBlock has the rest of the
392  // block's body. Create a copy of Target that will be used by the "direct"
393  // preds.
394  ValueToValueMapTy VMap;
395  BasicBlock *DirectSucc = CloneBasicBlock(Target, VMap, ".clone", &F);
396 
397  BlockFrequency BlockFreqForDirectSucc;
398  for (BasicBlock *Pred : OtherPreds) {
399  // If the target is a loop to itself, then the terminator of the split
400  // block (BodyBlock) needs to be updated.
401  BasicBlock *Src = Pred != Target ? Pred : BodyBlock;
402  Src->getTerminator()->replaceUsesOfWith(Target, DirectSucc);
403  if (ShouldUpdateAnalysis)
404  BlockFreqForDirectSucc += BFI->getBlockFreq(Src) *
405  BPI->getEdgeProbability(Src, DirectSucc);
406  }
407  if (ShouldUpdateAnalysis) {
408  BFI->setBlockFreq(DirectSucc, BlockFreqForDirectSucc.getFrequency());
409  BlockFrequency NewBlockFreqForTarget =
410  BFI->getBlockFreq(Target) - BlockFreqForDirectSucc;
411  BFI->setBlockFreq(Target, NewBlockFreqForTarget.getFrequency());
412  BPI->eraseBlock(Target);
413  }
414 
415  // Ok, now fix up the PHIs. We know the two blocks only have PHIs, and that
416  // they are clones, so the number of PHIs are the same.
417  // (a) Remove the edge coming from IBRPred from the "Direct" PHI
418  // (b) Leave that as the only edge in the "Indirect" PHI.
419  // (c) Merge the two in the body block.
420  BasicBlock::iterator Indirect = Target->begin(),
421  End = Target->getFirstNonPHI()->getIterator();
422  BasicBlock::iterator Direct = DirectSucc->begin();
423  BasicBlock::iterator MergeInsert = BodyBlock->getFirstInsertionPt();
424 
425  assert(&*End == Target->getTerminator() &&
426  "Block was expected to only contain PHIs");
427 
428  while (Indirect != End) {
429  PHINode *DirPHI = cast<PHINode>(Direct);
430  PHINode *IndPHI = cast<PHINode>(Indirect);
431 
432  // Now, clean up - the direct block shouldn't get the indirect value,
433  // and vice versa.
434  DirPHI->removeIncomingValue(IBRPred);
435  Direct++;
436 
437  // Advance the pointer here, to avoid invalidation issues when the old
438  // PHI is erased.
439  Indirect++;
440 
441  PHINode *NewIndPHI = PHINode::Create(IndPHI->getType(), 1, "ind", IndPHI);
442  NewIndPHI->addIncoming(IndPHI->getIncomingValueForBlock(IBRPred),
443  IBRPred);
444 
445  // Create a PHI in the body block, to merge the direct and indirect
446  // predecessors.
447  PHINode *MergePHI =
448  PHINode::Create(IndPHI->getType(), 2, "merge", &*MergeInsert);
449  MergePHI->addIncoming(NewIndPHI, Target);
450  MergePHI->addIncoming(DirPHI, DirectSucc);
451 
452  IndPHI->replaceAllUsesWith(MergePHI);
453  IndPHI->eraseFromParent();
454  }
455 
456  Changed = true;
457  }
458 
459  return Changed;
460 }
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...
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)
Notify the BasicBlock that the predecessor Pred is no longer able to reach it.
Definition: BasicBlock.cpp:301
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:705
STATISTIC(NumFunctions, "Total number of functions")
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:230
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:137
void setSuccessor(unsigned Idx, BasicBlock *BB)
Update the specified successor to point at the provided block.
void initializeBreakCriticalEdgesPass(PassRegistry &)
static BasicBlock * findIBRPredecessor(BasicBlock *BB, SmallVectorImpl< BasicBlock *> &OtherPreds)
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:268
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.
Analysis pass that exposes the LoopInfo for a function.
Definition: LoopInfo.h:944
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:125
BasicBlock * SplitCriticalEdge(Instruction *TI, unsigned SuccNum, const CriticalEdgeSplittingOptions &Options=CriticalEdgeSplittingOptions())
If this edge is a critical edge, insert a new node to split the critical edge.
AnalysisUsage & addPreservedID(const void *ID)
unsigned getNumSuccessors() const
Return the number of successors that this instruction has.
Interval::succ_iterator succ_end(Interval *I)
Definition: Interval.h:105
void replaceUsesOfWith(Value *From, Value *To)
Replace uses of one Value with another.
Definition: User.cpp:20
BlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation to estimate IR basic block frequen...
static bool runOnFunction(Function &F, bool PostInlining)
#define P(N)
BasicBlock * SplitBlockPredecessors(BasicBlock *BB, ArrayRef< BasicBlock *> Preds, const char *Suffix, DominatorTree *DT=nullptr, 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...
const Instruction * getFirstNonPHI() const
Returns a pointer to the first instruction in this block that is not a PHINode instruction.
Definition: BasicBlock.cpp:189
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
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:216
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
Conditional or Unconditional Branch instruction.
char & BreakCriticalEdgesID
size_t size() const
size - Get the array size.
Definition: ArrayRef.h:148
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
const Instruction & front() const
Definition: BasicBlock.h:280
Indirect Branch Instruction.
FunctionPass * createBreakCriticalEdgesPass()
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:112
void eraseBlock(const BasicBlock *BB)
Forget analysis results for the given basic block.
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
Interval::pred_iterator pred_end(Interval *I)
Definition: Interval.h:115
static BasicBlock * Create(LLVMContext &Context, const Twine &Name="", Function *Parent=nullptr, BasicBlock *InsertBefore=nullptr)
Creates a new BasicBlock.
Definition: BasicBlock.h:99
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:87
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
auto find(R &&Range, const T &Val) -> decltype(adl_begin(Range))
Provide wrappers to std::find which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1206
BranchProbability getEdgeProbability(const BasicBlock *Src, unsigned IndexInSuccessors) const
Get an edge&#39;s probability, relative to other out-edges of the Src.
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:33
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:297
Iterator for intrusive lists based on ilist_node.
void setIncomingBlock(unsigned i, BasicBlock *BB)
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:839
void wireOldPredecessorsToNewImmediatePredecessor(BasicBlock *Old, BasicBlock *New, ArrayRef< BasicBlock *> Preds, bool IdenticalEdgesWereMerged=true)
A new empty BasicBlock (New) now branches directly to Old.
void setEdgeProbability(const BasicBlock *Src, unsigned IndexInSuccessors, BranchProbability Prob)
Set the raw edge probability for the given edge.
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...
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.
iterator insert(iterator where, pointer New)
Definition: ilist.h:226
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:324
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.
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:55
bool SplitIndirectBrCriticalEdges(Function &F, BranchProbabilityInfo *BPI=nullptr, BlockFrequencyInfo *BFI=nullptr)
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:464
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:214
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:106
#define I(x, y, z)
Definition: MD5.cpp:58
#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:788
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:322
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h:632
void preserve()
Mark an analysis as preserved.
Definition: PassManager.h:174
iterator_range< const_phi_iterator > phis() const
Returns a range that iterates over the phis in the basic block.
Definition: BasicBlock.h:324
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
bool isEHPad() const
Return true if this basic block is an exception handling block.
Definition: BasicBlock.h:398
LLVM Value Representation.
Definition: Value.h:72
succ_range successors(Instruction *I)
Definition: CFG.h:259
bool isEHPad() const
Return true if the instruction is a variety of EH-block.
Definition: Instruction.h:586
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:969
A container for analyses that lazily runs them and caches their results.
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:259
const BasicBlock * getParent() const
Definition: Instruction.h:66