LLVM  8.0.0svn
LoopSimplify.cpp
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1 //===- LoopSimplify.cpp - Loop Canonicalization Pass ----------------------===//
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 pass performs several transformations to transform natural loops into a
11 // simpler form, which makes subsequent analyses and transformations simpler and
12 // more effective.
13 //
14 // Loop pre-header insertion guarantees that there is a single, non-critical
15 // entry edge from outside of the loop to the loop header. This simplifies a
16 // number of analyses and transformations, such as LICM.
17 //
18 // Loop exit-block insertion guarantees that all exit blocks from the loop
19 // (blocks which are outside of the loop that have predecessors inside of the
20 // loop) only have predecessors from inside of the loop (and are thus dominated
21 // by the loop header). This simplifies transformations such as store-sinking
22 // that are built into LICM.
23 //
24 // This pass also guarantees that loops will have exactly one backedge.
25 //
26 // Indirectbr instructions introduce several complications. If the loop
27 // contains or is entered by an indirectbr instruction, it may not be possible
28 // to transform the loop and make these guarantees. Client code should check
29 // that these conditions are true before relying on them.
30 //
31 // Note that the simplifycfg pass will clean up blocks which are split out but
32 // end up being unnecessary, so usage of this pass should not pessimize
33 // generated code.
34 //
35 // This pass obviously modifies the CFG, but updates loop information and
36 // dominator information.
37 //
38 //===----------------------------------------------------------------------===//
39 
42 #include "llvm/ADT/SetOperations.h"
43 #include "llvm/ADT/SetVector.h"
44 #include "llvm/ADT/SmallVector.h"
45 #include "llvm/ADT/Statistic.h"
52 #include "llvm/Analysis/LoopInfo.h"
56 #include "llvm/IR/CFG.h"
57 #include "llvm/IR/Constants.h"
58 #include "llvm/IR/DataLayout.h"
59 #include "llvm/IR/Dominators.h"
60 #include "llvm/IR/Function.h"
61 #include "llvm/IR/Instructions.h"
62 #include "llvm/IR/IntrinsicInst.h"
63 #include "llvm/IR/LLVMContext.h"
64 #include "llvm/IR/Module.h"
65 #include "llvm/IR/Type.h"
66 #include "llvm/Support/Debug.h"
68 #include "llvm/Transforms/Utils.h"
71 using namespace llvm;
72 
73 #define DEBUG_TYPE "loop-simplify"
74 
75 STATISTIC(NumNested , "Number of nested loops split out");
76 
77 // If the block isn't already, move the new block to right after some 'outside
78 // block' block. This prevents the preheader from being placed inside the loop
79 // body, e.g. when the loop hasn't been rotated.
82  Loop *L) {
83  // Check to see if NewBB is already well placed.
84  Function::iterator BBI = --NewBB->getIterator();
85  for (unsigned i = 0, e = SplitPreds.size(); i != e; ++i) {
86  if (&*BBI == SplitPreds[i])
87  return;
88  }
89 
90  // If it isn't already after an outside block, move it after one. This is
91  // always good as it makes the uncond branch from the outside block into a
92  // fall-through.
93 
94  // Figure out *which* outside block to put this after. Prefer an outside
95  // block that neighbors a BB actually in the loop.
96  BasicBlock *FoundBB = nullptr;
97  for (unsigned i = 0, e = SplitPreds.size(); i != e; ++i) {
98  Function::iterator BBI = SplitPreds[i]->getIterator();
99  if (++BBI != NewBB->getParent()->end() && L->contains(&*BBI)) {
100  FoundBB = SplitPreds[i];
101  break;
102  }
103  }
104 
105  // If our heuristic for a *good* bb to place this after doesn't find
106  // anything, just pick something. It's likely better than leaving it within
107  // the loop.
108  if (!FoundBB)
109  FoundBB = SplitPreds[0];
110  NewBB->moveAfter(FoundBB);
111 }
112 
113 /// InsertPreheaderForLoop - Once we discover that a loop doesn't have a
114 /// preheader, this method is called to insert one. This method has two phases:
115 /// preheader insertion and analysis updating.
116 ///
118  LoopInfo *LI, bool PreserveLCSSA) {
119  BasicBlock *Header = L->getHeader();
120 
121  // Compute the set of predecessors of the loop that are not in the loop.
122  SmallVector<BasicBlock*, 8> OutsideBlocks;
123  for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
124  PI != PE; ++PI) {
125  BasicBlock *P = *PI;
126  if (!L->contains(P)) { // Coming in from outside the loop?
127  // If the loop is branched to from an indirect branch, we won't
128  // be able to fully transform the loop, because it prohibits
129  // edge splitting.
130  if (isa<IndirectBrInst>(P->getTerminator())) return nullptr;
131 
132  // Keep track of it.
133  OutsideBlocks.push_back(P);
134  }
135  }
136 
137  // Split out the loop pre-header.
138  BasicBlock *PreheaderBB;
139  PreheaderBB = SplitBlockPredecessors(Header, OutsideBlocks, ".preheader", DT,
140  LI, nullptr, PreserveLCSSA);
141  if (!PreheaderBB)
142  return nullptr;
143 
144  LLVM_DEBUG(dbgs() << "LoopSimplify: Creating pre-header "
145  << PreheaderBB->getName() << "\n");
146 
147  // Make sure that NewBB is put someplace intelligent, which doesn't mess up
148  // code layout too horribly.
149  placeSplitBlockCarefully(PreheaderBB, OutsideBlocks, L);
150 
151  return PreheaderBB;
152 }
153 
154 /// Add the specified block, and all of its predecessors, to the specified set,
155 /// if it's not already in there. Stop predecessor traversal when we reach
156 /// StopBlock.
157 static void addBlockAndPredsToSet(BasicBlock *InputBB, BasicBlock *StopBlock,
158  std::set<BasicBlock*> &Blocks) {
160  Worklist.push_back(InputBB);
161  do {
162  BasicBlock *BB = Worklist.pop_back_val();
163  if (Blocks.insert(BB).second && BB != StopBlock)
164  // If BB is not already processed and it is not a stop block then
165  // insert its predecessor in the work list
166  for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
167  BasicBlock *WBB = *I;
168  Worklist.push_back(WBB);
169  }
170  } while (!Worklist.empty());
171 }
172 
173 /// The first part of loop-nestification is to find a PHI node that tells
174 /// us how to partition the loops.
176  AssumptionCache *AC) {
177  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
178  for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ) {
179  PHINode *PN = cast<PHINode>(I);
180  ++I;
181  if (Value *V = SimplifyInstruction(PN, {DL, nullptr, DT, AC})) {
182  // This is a degenerate PHI already, don't modify it!
183  PN->replaceAllUsesWith(V);
184  PN->eraseFromParent();
185  continue;
186  }
187 
188  // Scan this PHI node looking for a use of the PHI node by itself.
189  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
190  if (PN->getIncomingValue(i) == PN &&
191  L->contains(PN->getIncomingBlock(i)))
192  // We found something tasty to remove.
193  return PN;
194  }
195  return nullptr;
196 }
197 
198 /// If this loop has multiple backedges, try to pull one of them out into
199 /// a nested loop.
200 ///
201 /// This is important for code that looks like
202 /// this:
203 ///
204 /// Loop:
205 /// ...
206 /// br cond, Loop, Next
207 /// ...
208 /// br cond2, Loop, Out
209 ///
210 /// To identify this common case, we look at the PHI nodes in the header of the
211 /// loop. PHI nodes with unchanging values on one backedge correspond to values
212 /// that change in the "outer" loop, but not in the "inner" loop.
213 ///
214 /// If we are able to separate out a loop, return the new outer loop that was
215 /// created.
216 ///
217 static Loop *separateNestedLoop(Loop *L, BasicBlock *Preheader,
218  DominatorTree *DT, LoopInfo *LI,
219  ScalarEvolution *SE, bool PreserveLCSSA,
220  AssumptionCache *AC) {
221  // Don't try to separate loops without a preheader.
222  if (!Preheader)
223  return nullptr;
224 
225  // The header is not a landing pad; preheader insertion should ensure this.
226  BasicBlock *Header = L->getHeader();
227  assert(!Header->isEHPad() && "Can't insert backedge to EH pad");
228 
229  PHINode *PN = findPHIToPartitionLoops(L, DT, AC);
230  if (!PN) return nullptr; // No known way to partition.
231 
232  // Pull out all predecessors that have varying values in the loop. This
233  // handles the case when a PHI node has multiple instances of itself as
234  // arguments.
235  SmallVector<BasicBlock*, 8> OuterLoopPreds;
236  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
237  if (PN->getIncomingValue(i) != PN ||
238  !L->contains(PN->getIncomingBlock(i))) {
239  // We can't split indirectbr edges.
240  if (isa<IndirectBrInst>(PN->getIncomingBlock(i)->getTerminator()))
241  return nullptr;
242  OuterLoopPreds.push_back(PN->getIncomingBlock(i));
243  }
244  }
245  LLVM_DEBUG(dbgs() << "LoopSimplify: Splitting out a new outer loop\n");
246 
247  // If ScalarEvolution is around and knows anything about values in
248  // this loop, tell it to forget them, because we're about to
249  // substantially change it.
250  if (SE)
251  SE->forgetLoop(L);
252 
253  BasicBlock *NewBB = SplitBlockPredecessors(Header, OuterLoopPreds, ".outer",
254  DT, LI, nullptr, PreserveLCSSA);
255 
256  // Make sure that NewBB is put someplace intelligent, which doesn't mess up
257  // code layout too horribly.
258  placeSplitBlockCarefully(NewBB, OuterLoopPreds, L);
259 
260  // Create the new outer loop.
261  Loop *NewOuter = LI->AllocateLoop();
262 
263  // Change the parent loop to use the outer loop as its child now.
264  if (Loop *Parent = L->getParentLoop())
265  Parent->replaceChildLoopWith(L, NewOuter);
266  else
267  LI->changeTopLevelLoop(L, NewOuter);
268 
269  // L is now a subloop of our outer loop.
270  NewOuter->addChildLoop(L);
271 
272  for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
273  I != E; ++I)
274  NewOuter->addBlockEntry(*I);
275 
276  // Now reset the header in L, which had been moved by
277  // SplitBlockPredecessors for the outer loop.
278  L->moveToHeader(Header);
279 
280  // Determine which blocks should stay in L and which should be moved out to
281  // the Outer loop now.
282  std::set<BasicBlock*> BlocksInL;
283  for (pred_iterator PI=pred_begin(Header), E = pred_end(Header); PI!=E; ++PI) {
284  BasicBlock *P = *PI;
285  if (DT->dominates(Header, P))
286  addBlockAndPredsToSet(P, Header, BlocksInL);
287  }
288 
289  // Scan all of the loop children of L, moving them to OuterLoop if they are
290  // not part of the inner loop.
291  const std::vector<Loop*> &SubLoops = L->getSubLoops();
292  for (size_t I = 0; I != SubLoops.size(); )
293  if (BlocksInL.count(SubLoops[I]->getHeader()))
294  ++I; // Loop remains in L
295  else
296  NewOuter->addChildLoop(L->removeChildLoop(SubLoops.begin() + I));
297 
298  SmallVector<BasicBlock *, 8> OuterLoopBlocks;
299  OuterLoopBlocks.push_back(NewBB);
300  // Now that we know which blocks are in L and which need to be moved to
301  // OuterLoop, move any blocks that need it.
302  for (unsigned i = 0; i != L->getBlocks().size(); ++i) {
303  BasicBlock *BB = L->getBlocks()[i];
304  if (!BlocksInL.count(BB)) {
305  // Move this block to the parent, updating the exit blocks sets
306  L->removeBlockFromLoop(BB);
307  if ((*LI)[BB] == L) {
308  LI->changeLoopFor(BB, NewOuter);
309  OuterLoopBlocks.push_back(BB);
310  }
311  --i;
312  }
313  }
314 
315  // Split edges to exit blocks from the inner loop, if they emerged in the
316  // process of separating the outer one.
317  formDedicatedExitBlocks(L, DT, LI, PreserveLCSSA);
318 
319  if (PreserveLCSSA) {
320  // Fix LCSSA form for L. Some values, which previously were only used inside
321  // L, can now be used in NewOuter loop. We need to insert phi-nodes for them
322  // in corresponding exit blocks.
323  // We don't need to form LCSSA recursively, because there cannot be uses
324  // inside a newly created loop of defs from inner loops as those would
325  // already be a use of an LCSSA phi node.
326  formLCSSA(*L, *DT, LI, SE);
327 
328  assert(NewOuter->isRecursivelyLCSSAForm(*DT, *LI) &&
329  "LCSSA is broken after separating nested loops!");
330  }
331 
332  return NewOuter;
333 }
334 
335 /// This method is called when the specified loop has more than one
336 /// backedge in it.
337 ///
338 /// If this occurs, revector all of these backedges to target a new basic block
339 /// and have that block branch to the loop header. This ensures that loops
340 /// have exactly one backedge.
342  DominatorTree *DT, LoopInfo *LI) {
343  assert(L->getNumBackEdges() > 1 && "Must have > 1 backedge!");
344 
345  // Get information about the loop
346  BasicBlock *Header = L->getHeader();
347  Function *F = Header->getParent();
348 
349  // Unique backedge insertion currently depends on having a preheader.
350  if (!Preheader)
351  return nullptr;
352 
353  // The header is not an EH pad; preheader insertion should ensure this.
354  assert(!Header->isEHPad() && "Can't insert backedge to EH pad");
355 
356  // Figure out which basic blocks contain back-edges to the loop header.
357  std::vector<BasicBlock*> BackedgeBlocks;
358  for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I){
359  BasicBlock *P = *I;
360 
361  // Indirectbr edges cannot be split, so we must fail if we find one.
362  if (isa<IndirectBrInst>(P->getTerminator()))
363  return nullptr;
364 
365  if (P != Preheader) BackedgeBlocks.push_back(P);
366  }
367 
368  // Create and insert the new backedge block...
369  BasicBlock *BEBlock = BasicBlock::Create(Header->getContext(),
370  Header->getName() + ".backedge", F);
371  BranchInst *BETerminator = BranchInst::Create(Header, BEBlock);
372  BETerminator->setDebugLoc(Header->getFirstNonPHI()->getDebugLoc());
373 
374  LLVM_DEBUG(dbgs() << "LoopSimplify: Inserting unique backedge block "
375  << BEBlock->getName() << "\n");
376 
377  // Move the new backedge block to right after the last backedge block.
378  Function::iterator InsertPos = ++BackedgeBlocks.back()->getIterator();
379  F->getBasicBlockList().splice(InsertPos, F->getBasicBlockList(), BEBlock);
380 
381  // Now that the block has been inserted into the function, create PHI nodes in
382  // the backedge block which correspond to any PHI nodes in the header block.
383  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
384  PHINode *PN = cast<PHINode>(I);
385  PHINode *NewPN = PHINode::Create(PN->getType(), BackedgeBlocks.size(),
386  PN->getName()+".be", BETerminator);
387 
388  // Loop over the PHI node, moving all entries except the one for the
389  // preheader over to the new PHI node.
390  unsigned PreheaderIdx = ~0U;
391  bool HasUniqueIncomingValue = true;
392  Value *UniqueValue = nullptr;
393  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
394  BasicBlock *IBB = PN->getIncomingBlock(i);
395  Value *IV = PN->getIncomingValue(i);
396  if (IBB == Preheader) {
397  PreheaderIdx = i;
398  } else {
399  NewPN->addIncoming(IV, IBB);
400  if (HasUniqueIncomingValue) {
401  if (!UniqueValue)
402  UniqueValue = IV;
403  else if (UniqueValue != IV)
404  HasUniqueIncomingValue = false;
405  }
406  }
407  }
408 
409  // Delete all of the incoming values from the old PN except the preheader's
410  assert(PreheaderIdx != ~0U && "PHI has no preheader entry??");
411  if (PreheaderIdx != 0) {
412  PN->setIncomingValue(0, PN->getIncomingValue(PreheaderIdx));
413  PN->setIncomingBlock(0, PN->getIncomingBlock(PreheaderIdx));
414  }
415  // Nuke all entries except the zero'th.
416  for (unsigned i = 0, e = PN->getNumIncomingValues()-1; i != e; ++i)
417  PN->removeIncomingValue(e-i, false);
418 
419  // Finally, add the newly constructed PHI node as the entry for the BEBlock.
420  PN->addIncoming(NewPN, BEBlock);
421 
422  // As an optimization, if all incoming values in the new PhiNode (which is a
423  // subset of the incoming values of the old PHI node) have the same value,
424  // eliminate the PHI Node.
425  if (HasUniqueIncomingValue) {
426  NewPN->replaceAllUsesWith(UniqueValue);
427  BEBlock->getInstList().erase(NewPN);
428  }
429  }
430 
431  // Now that all of the PHI nodes have been inserted and adjusted, modify the
432  // backedge blocks to jump to the BEBlock instead of the header.
433  // If one of the backedges has llvm.loop metadata attached, we remove
434  // it from the backedge and add it to BEBlock.
435  unsigned LoopMDKind = BEBlock->getContext().getMDKindID("llvm.loop");
436  MDNode *LoopMD = nullptr;
437  for (unsigned i = 0, e = BackedgeBlocks.size(); i != e; ++i) {
438  TerminatorInst *TI = BackedgeBlocks[i]->getTerminator();
439  if (!LoopMD)
440  LoopMD = TI->getMetadata(LoopMDKind);
441  TI->setMetadata(LoopMDKind, nullptr);
442  for (unsigned Op = 0, e = TI->getNumSuccessors(); Op != e; ++Op)
443  if (TI->getSuccessor(Op) == Header)
444  TI->setSuccessor(Op, BEBlock);
445  }
446  BEBlock->getTerminator()->setMetadata(LoopMDKind, LoopMD);
447 
448  //===--- Update all analyses which we must preserve now -----------------===//
449 
450  // Update Loop Information - we know that this block is now in the current
451  // loop and all parent loops.
452  L->addBasicBlockToLoop(BEBlock, *LI);
453 
454  // Update dominator information
455  DT->splitBlock(BEBlock);
456 
457  return BEBlock;
458 }
459 
460 /// Simplify one loop and queue further loops for simplification.
461 static bool simplifyOneLoop(Loop *L, SmallVectorImpl<Loop *> &Worklist,
462  DominatorTree *DT, LoopInfo *LI,
464  bool PreserveLCSSA) {
465  bool Changed = false;
466 ReprocessLoop:
467 
468  // Check to see that no blocks (other than the header) in this loop have
469  // predecessors that are not in the loop. This is not valid for natural
470  // loops, but can occur if the blocks are unreachable. Since they are
471  // unreachable we can just shamelessly delete those CFG edges!
472  for (Loop::block_iterator BB = L->block_begin(), E = L->block_end();
473  BB != E; ++BB) {
474  if (*BB == L->getHeader()) continue;
475 
477  for (pred_iterator PI = pred_begin(*BB),
478  PE = pred_end(*BB); PI != PE; ++PI) {
479  BasicBlock *P = *PI;
480  if (!L->contains(P))
481  BadPreds.insert(P);
482  }
483 
484  // Delete each unique out-of-loop (and thus dead) predecessor.
485  for (BasicBlock *P : BadPreds) {
486 
487  LLVM_DEBUG(dbgs() << "LoopSimplify: Deleting edge from dead predecessor "
488  << P->getName() << "\n");
489 
490  // Zap the dead pred's terminator and replace it with unreachable.
491  TerminatorInst *TI = P->getTerminator();
492  changeToUnreachable(TI, /*UseLLVMTrap=*/false, PreserveLCSSA);
493  Changed = true;
494  }
495  }
496 
497  // If there are exiting blocks with branches on undef, resolve the undef in
498  // the direction which will exit the loop. This will help simplify loop
499  // trip count computations.
500  SmallVector<BasicBlock*, 8> ExitingBlocks;
501  L->getExitingBlocks(ExitingBlocks);
502  for (BasicBlock *ExitingBlock : ExitingBlocks)
503  if (BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator()))
504  if (BI->isConditional()) {
505  if (UndefValue *Cond = dyn_cast<UndefValue>(BI->getCondition())) {
506 
507  LLVM_DEBUG(dbgs()
508  << "LoopSimplify: Resolving \"br i1 undef\" to exit in "
509  << ExitingBlock->getName() << "\n");
510 
511  BI->setCondition(ConstantInt::get(Cond->getType(),
512  !L->contains(BI->getSuccessor(0))));
513 
514  Changed = true;
515  }
516  }
517 
518  // Does the loop already have a preheader? If so, don't insert one.
519  BasicBlock *Preheader = L->getLoopPreheader();
520  if (!Preheader) {
521  Preheader = InsertPreheaderForLoop(L, DT, LI, PreserveLCSSA);
522  if (Preheader)
523  Changed = true;
524  }
525 
526  // Next, check to make sure that all exit nodes of the loop only have
527  // predecessors that are inside of the loop. This check guarantees that the
528  // loop preheader/header will dominate the exit blocks. If the exit block has
529  // predecessors from outside of the loop, split the edge now.
530  if (formDedicatedExitBlocks(L, DT, LI, PreserveLCSSA))
531  Changed = true;
532 
533  // If the header has more than two predecessors at this point (from the
534  // preheader and from multiple backedges), we must adjust the loop.
535  BasicBlock *LoopLatch = L->getLoopLatch();
536  if (!LoopLatch) {
537  // If this is really a nested loop, rip it out into a child loop. Don't do
538  // this for loops with a giant number of backedges, just factor them into a
539  // common backedge instead.
540  if (L->getNumBackEdges() < 8) {
541  if (Loop *OuterL =
542  separateNestedLoop(L, Preheader, DT, LI, SE, PreserveLCSSA, AC)) {
543  ++NumNested;
544  // Enqueue the outer loop as it should be processed next in our
545  // depth-first nest walk.
546  Worklist.push_back(OuterL);
547 
548  // This is a big restructuring change, reprocess the whole loop.
549  Changed = true;
550  // GCC doesn't tail recursion eliminate this.
551  // FIXME: It isn't clear we can't rely on LLVM to TRE this.
552  goto ReprocessLoop;
553  }
554  }
555 
556  // If we either couldn't, or didn't want to, identify nesting of the loops,
557  // insert a new block that all backedges target, then make it jump to the
558  // loop header.
559  LoopLatch = insertUniqueBackedgeBlock(L, Preheader, DT, LI);
560  if (LoopLatch)
561  Changed = true;
562  }
563 
564  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
565 
566  // Scan over the PHI nodes in the loop header. Since they now have only two
567  // incoming values (the loop is canonicalized), we may have simplified the PHI
568  // down to 'X = phi [X, Y]', which should be replaced with 'Y'.
569  PHINode *PN;
570  for (BasicBlock::iterator I = L->getHeader()->begin();
571  (PN = dyn_cast<PHINode>(I++)); )
572  if (Value *V = SimplifyInstruction(PN, {DL, nullptr, DT, AC})) {
573  if (SE) SE->forgetValue(PN);
574  if (!PreserveLCSSA || LI->replacementPreservesLCSSAForm(PN, V)) {
575  PN->replaceAllUsesWith(V);
576  PN->eraseFromParent();
577  }
578  }
579 
580  // If this loop has multiple exits and the exits all go to the same
581  // block, attempt to merge the exits. This helps several passes, such
582  // as LoopRotation, which do not support loops with multiple exits.
583  // SimplifyCFG also does this (and this code uses the same utility
584  // function), however this code is loop-aware, where SimplifyCFG is
585  // not. That gives it the advantage of being able to hoist
586  // loop-invariant instructions out of the way to open up more
587  // opportunities, and the disadvantage of having the responsibility
588  // to preserve dominator information.
589  auto HasUniqueExitBlock = [&]() {
590  BasicBlock *UniqueExit = nullptr;
591  for (auto *ExitingBB : ExitingBlocks)
592  for (auto *SuccBB : successors(ExitingBB)) {
593  if (L->contains(SuccBB))
594  continue;
595 
596  if (!UniqueExit)
597  UniqueExit = SuccBB;
598  else if (UniqueExit != SuccBB)
599  return false;
600  }
601 
602  return true;
603  };
604  if (HasUniqueExitBlock()) {
605  for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
606  BasicBlock *ExitingBlock = ExitingBlocks[i];
607  if (!ExitingBlock->getSinglePredecessor()) continue;
608  BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
609  if (!BI || !BI->isConditional()) continue;
610  CmpInst *CI = dyn_cast<CmpInst>(BI->getCondition());
611  if (!CI || CI->getParent() != ExitingBlock) continue;
612 
613  // Attempt to hoist out all instructions except for the
614  // comparison and the branch.
615  bool AllInvariant = true;
616  bool AnyInvariant = false;
617  for (auto I = ExitingBlock->instructionsWithoutDebug().begin(); &*I != BI; ) {
618  Instruction *Inst = &*I++;
619  if (Inst == CI)
620  continue;
621  if (!L->makeLoopInvariant(Inst, AnyInvariant,
622  Preheader ? Preheader->getTerminator()
623  : nullptr)) {
624  AllInvariant = false;
625  break;
626  }
627  }
628  if (AnyInvariant) {
629  Changed = true;
630  // The loop disposition of all SCEV expressions that depend on any
631  // hoisted values have also changed.
632  if (SE)
633  SE->forgetLoopDispositions(L);
634  }
635  if (!AllInvariant) continue;
636 
637  // The block has now been cleared of all instructions except for
638  // a comparison and a conditional branch. SimplifyCFG may be able
639  // to fold it now.
640  if (!FoldBranchToCommonDest(BI))
641  continue;
642 
643  // Success. The block is now dead, so remove it from the loop,
644  // update the dominator tree and delete it.
645  LLVM_DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block "
646  << ExitingBlock->getName() << "\n");
647 
648  assert(pred_begin(ExitingBlock) == pred_end(ExitingBlock));
649  Changed = true;
650  LI->removeBlock(ExitingBlock);
651 
652  DomTreeNode *Node = DT->getNode(ExitingBlock);
653  const std::vector<DomTreeNodeBase<BasicBlock> *> &Children =
654  Node->getChildren();
655  while (!Children.empty()) {
656  DomTreeNode *Child = Children.front();
657  DT->changeImmediateDominator(Child, Node->getIDom());
658  }
659  DT->eraseNode(ExitingBlock);
660 
662  ExitingBlock, /* DontDeleteUselessPHIs */ PreserveLCSSA);
664  ExitingBlock, /* DontDeleteUselessPHIs */ PreserveLCSSA);
665  ExitingBlock->eraseFromParent();
666  }
667  }
668 
669  // Changing exit conditions for blocks may affect exit counts of this loop and
670  // any of its paretns, so we must invalidate the entire subtree if we've made
671  // any changes.
672  if (Changed && SE)
673  SE->forgetTopmostLoop(L);
674 
675  return Changed;
676 }
677 
680  bool PreserveLCSSA) {
681  bool Changed = false;
682 
683 #ifndef NDEBUG
684  // If we're asked to preserve LCSSA, the loop nest needs to start in LCSSA
685  // form.
686  if (PreserveLCSSA) {
687  assert(DT && "DT not available.");
688  assert(LI && "LI not available.");
689  assert(L->isRecursivelyLCSSAForm(*DT, *LI) &&
690  "Requested to preserve LCSSA, but it's already broken.");
691  }
692 #endif
693 
694  // Worklist maintains our depth-first queue of loops in this nest to process.
695  SmallVector<Loop *, 4> Worklist;
696  Worklist.push_back(L);
697 
698  // Walk the worklist from front to back, pushing newly found sub loops onto
699  // the back. This will let us process loops from back to front in depth-first
700  // order. We can use this simple process because loops form a tree.
701  for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) {
702  Loop *L2 = Worklist[Idx];
703  Worklist.append(L2->begin(), L2->end());
704  }
705 
706  while (!Worklist.empty())
707  Changed |= simplifyOneLoop(Worklist.pop_back_val(), Worklist, DT, LI, SE,
708  AC, PreserveLCSSA);
709 
710  return Changed;
711 }
712 
713 namespace {
714  struct LoopSimplify : public FunctionPass {
715  static char ID; // Pass identification, replacement for typeid
716  LoopSimplify() : FunctionPass(ID) {
718  }
719 
720  bool runOnFunction(Function &F) override;
721 
722  void getAnalysisUsage(AnalysisUsage &AU) const override {
724 
725  // We need loop information to identify the loops...
728 
731 
739  AU.addPreservedID(BreakCriticalEdgesID); // No critical edges added.
740  }
741 
742  /// verifyAnalysis() - Verify LoopSimplifyForm's guarantees.
743  void verifyAnalysis() const override;
744  };
745 }
746 
747 char LoopSimplify::ID = 0;
748 INITIALIZE_PASS_BEGIN(LoopSimplify, "loop-simplify",
749  "Canonicalize natural loops", false, false)
753 INITIALIZE_PASS_END(LoopSimplify, "loop-simplify",
754  "Canonicalize natural loops", false, false)
755 
756 // Publicly exposed interface to pass...
757 char &llvm::LoopSimplifyID = LoopSimplify::ID;
758 Pass *llvm::createLoopSimplifyPass() { return new LoopSimplify(); }
759 
760 /// runOnFunction - Run down all loops in the CFG (recursively, but we could do
761 /// it in any convenient order) inserting preheaders...
762 ///
764  bool Changed = false;
765  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
766  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
767  auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
768  ScalarEvolution *SE = SEWP ? &SEWP->getSE() : nullptr;
769  AssumptionCache *AC =
770  &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
771 
772  bool PreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
773 
774  // Simplify each loop nest in the function.
775  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
776  Changed |= simplifyLoop(*I, DT, LI, SE, AC, PreserveLCSSA);
777 
778 #ifndef NDEBUG
779  if (PreserveLCSSA) {
780  bool InLCSSA = all_of(
781  *LI, [&](Loop *L) { return L->isRecursivelyLCSSAForm(*DT, *LI); });
782  assert(InLCSSA && "LCSSA is broken after loop-simplify.");
783  }
784 #endif
785  return Changed;
786 }
787 
790  bool Changed = false;
791  LoopInfo *LI = &AM.getResult<LoopAnalysis>(F);
795 
796  // Note that we don't preserve LCSSA in the new PM, if you need it run LCSSA
797  // after simplifying the loops.
798  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
799  Changed |= simplifyLoop(*I, DT, LI, SE, AC, /*PreserveLCSSA*/ false);
800 
801  if (!Changed)
802  return PreservedAnalyses::all();
803 
806  PA.preserve<LoopAnalysis>();
807  PA.preserve<BasicAA>();
808  PA.preserve<GlobalsAA>();
809  PA.preserve<SCEVAA>();
812  return PA;
813 }
814 
815 // FIXME: Restore this code when we re-enable verification in verifyAnalysis
816 // below.
817 #if 0
818 static void verifyLoop(Loop *L) {
819  // Verify subloops.
820  for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
821  verifyLoop(*I);
822 
823  // It used to be possible to just assert L->isLoopSimplifyForm(), however
824  // with the introduction of indirectbr, there are now cases where it's
825  // not possible to transform a loop as necessary. We can at least check
826  // that there is an indirectbr near any time there's trouble.
827 
828  // Indirectbr can interfere with preheader and unique backedge insertion.
829  if (!L->getLoopPreheader() || !L->getLoopLatch()) {
830  bool HasIndBrPred = false;
831  for (pred_iterator PI = pred_begin(L->getHeader()),
832  PE = pred_end(L->getHeader()); PI != PE; ++PI)
833  if (isa<IndirectBrInst>((*PI)->getTerminator())) {
834  HasIndBrPred = true;
835  break;
836  }
837  assert(HasIndBrPred &&
838  "LoopSimplify has no excuse for missing loop header info!");
839  (void)HasIndBrPred;
840  }
841 
842  // Indirectbr can interfere with exit block canonicalization.
843  if (!L->hasDedicatedExits()) {
844  bool HasIndBrExiting = false;
845  SmallVector<BasicBlock*, 8> ExitingBlocks;
846  L->getExitingBlocks(ExitingBlocks);
847  for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
848  if (isa<IndirectBrInst>((ExitingBlocks[i])->getTerminator())) {
849  HasIndBrExiting = true;
850  break;
851  }
852  }
853 
854  assert(HasIndBrExiting &&
855  "LoopSimplify has no excuse for missing exit block info!");
856  (void)HasIndBrExiting;
857  }
858 }
859 #endif
860 
861 void LoopSimplify::verifyAnalysis() const {
862  // FIXME: This routine is being called mid-way through the loop pass manager
863  // as loop passes destroy this analysis. That's actually fine, but we have no
864  // way of expressing that here. Once all of the passes that destroy this are
865  // hoisted out of the loop pass manager we can add back verification here.
866 #if 0
867  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
868  verifyLoop(*I);
869 #endif
870 }
Legacy wrapper pass to provide the GlobalsAAResult object.
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:81
static void addBlockAndPredsToSet(BasicBlock *InputBB, BasicBlock *StopBlock, std::set< BasicBlock *> &Blocks)
Add the specified block, and all of its predecessors, to the specified set, if it&#39;s not already in th...
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:68
loop Canonicalize natural loops
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:111
Pass * createLoopSimplifyPass()
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:675
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
void removePredecessor(BasicBlock *Pred, bool DontDeleteUselessPHIs=false)
Notify the BasicBlock that the predecessor Pred is no longer able to reach it.
Definition: BasicBlock.cpp:295
void addIncoming(Value *V, BasicBlock *BB)
Add an incoming value to the end of the PHI list.
BlockT * getLoopLatch() const
If there is a single latch block for this loop, return it.
Definition: LoopInfoImpl.h:225
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
void splitBlock(NodeT *NewBB)
splitBlock - BB is split and now it has one successor.
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:770
iterator erase(iterator where)
Definition: ilist.h:267
AnalysisPass to compute dependence information in a function.
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
This is the interface for a simple mod/ref and alias analysis over globals.
ArrayRef< BasicBlock *>::const_iterator block_iterator
Definition: LoopInfo.h:153
BasicBlock * getSuccessor(unsigned Idx) const
Return the specified successor. This instruction must be a terminator.
iterator end()
Definition: Function.h:658
static void placeSplitBlockCarefully(BasicBlock *NewBB, SmallVectorImpl< BasicBlock *> &SplitPreds, Loop *L)
bool hasDedicatedExits() const
Return true if no exit block for the loop has a predecessor that is outside the loop.
Definition: LoopInfoImpl.h:86
bool isRecursivelyLCSSAForm(DominatorTree &DT, const LoopInfo &LI) const
Return true if this Loop and all inner subloops are in LCSSA form.
Definition: LoopInfo.cpp:183
Legacy pass manager pass to access dependence information.
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:379
LoopT * removeChildLoop(iterator I)
This removes the specified child from being a subloop of this loop.
Definition: LoopInfo.h:340
The main scalar evolution driver.
BlockT * getLoopPreheader() const
If there is a preheader for this loop, return it.
Definition: LoopInfoImpl.h:174
An immutable pass that tracks lazily created AssumptionCache objects.
BasicBlock * InsertPreheaderForLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA)
InsertPreheaderForLoop - Once we discover that a loop doesn&#39;t have a preheader, this method is called...
A cache of @llvm.assume calls within a function.
bool makeLoopInvariant(Value *V, bool &Changed, Instruction *InsertPt=nullptr) const
If the given value is an instruction inside of the loop and it can be hoisted, do so to make it trivi...
Definition: LoopInfo.cpp:67
void replaceChildLoopWith(LoopT *OldChild, LoopT *NewChild)
This is used when splitting loops up.
Definition: LoopInfoImpl.h:281
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1042
BasicBlock * getSuccessor(unsigned i) const
STATISTIC(NumFunctions, "Total number of functions")
Metadata node.
Definition: Metadata.h:864
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:231
F(f)
static Loop * separateNestedLoop(Loop *L, BasicBlock *Preheader, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, bool PreserveLCSSA, AssumptionCache *AC)
If this loop has multiple backedges, try to pull one of them out into a nested loop.
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Value * getCondition() const
void setSuccessor(unsigned Idx, BasicBlock *BB)
Update the specified successor to point at the provided block.
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:33
void eraseNode(NodeT *BB)
eraseNode - Removes a node from the dominator tree.
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:264
unsigned getMDKindID(StringRef Name) const
getMDKindID - Return a unique non-zero ID for the specified metadata kind.
static PHINode * findPHIToPartitionLoops(Loop *L, DominatorTree *DT, AssumptionCache *AC)
The first part of loop-nestification is to find a PHI node that tells us how to partition the loops...
AnalysisUsage & addRequired()
const Module * getModule() const
Return the module owning the function this basic block belongs to, or nullptr if the function does no...
Definition: BasicBlock.cpp:134
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
unsigned getNumBackEdges() const
Calculate the number of back edges to the loop header.
Definition: LoopInfo.h:227
Value * removeIncomingValue(unsigned Idx, bool DeletePHIIfEmpty=true)
Remove an incoming value.
This is the interface for a SCEV-based alias analysis.
unsigned changeToUnreachable(Instruction *I, bool UseLLVMTrap, bool PreserveLCSSA=false, DomTreeUpdater *DTU=nullptr)
Insert an unreachable instruction before the specified instruction, making it and the rest of the cod...
Definition: Local.cpp:1914
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:364
bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, bool PreserveLCSSA)
Simplify each loop in a loop nest recursively.
&#39;undef&#39; values are things that do not have specified contents.
Definition: Constants.h:1275
void addBlockEntry(BlockT *BB)
This adds a basic block directly to the basic block list.
Definition: LoopInfo.h:359
std::vector< Loop *>::const_iterator iterator
iterator/begin/end - The interface to the top-level loops in the current function.
Definition: LoopInfo.h:656
Analysis pass that exposes the LoopInfo for a function.
Definition: LoopInfo.h:939
BlockT * getHeader() const
Definition: LoopInfo.h:100
std::vector< Loop *>::const_iterator iterator
Definition: LoopInfo.h:139
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:251
MDNode * getMetadata(unsigned KindID) const
Get the metadata of given kind attached to this Instruction.
Definition: Instruction.h:217
const std::vector< DomTreeNodeBase * > & getChildren() const
AnalysisUsage & addPreservedID(const void *ID)
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:439
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:145
unsigned getNumSuccessors() const
Return the number of successors that this instruction has.
void forgetLoopDispositions(const Loop *L)
Called when the client has changed the disposition of values in this loop.
static BasicBlock * insertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader, DominatorTree *DT, LoopInfo *LI)
This method is called when the specified loop has more than one backedge in it.
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...
bool FoldBranchToCommonDest(BranchInst *BI, unsigned BonusInstThreshold=1)
If this basic block is ONLY a setcc and a branch, and if a predecessor branches to us and one of our ...
Subclasses of this class are all able to terminate a basic block.
Definition: InstrTypes.h:55
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:154
const BasicBlock * getSinglePredecessor() const
Return the predecessor of this block if it has a single predecessor block.
Definition: BasicBlock.cpp:235
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
Conditional or Unconditional Branch instruction.
char & BreakCriticalEdgesID
iterator_range< filter_iterator< BasicBlock::const_iterator, std::function< bool(const Instruction &)> > > instructionsWithoutDebug() const
Return a const iterator range over the instructions in the block, skipping any debug instructions...
Definition: BasicBlock.cpp:95
void changeImmediateDominator(DomTreeNodeBase< NodeT > *N, DomTreeNodeBase< NodeT > *NewIDom)
changeImmediateDominator - This method is used to update the dominator tree information when a node&#39;s...
DomTreeNodeBase * getIDom() const
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This file contains the declarations for the subclasses of Constant, which represent the different fla...
iterator end() const
Definition: LoopInfo.h:660
static bool simplifyOneLoop(Loop *L, SmallVectorImpl< Loop *> &Worklist, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, bool PreserveLCSSA)
Simplify one loop and queue further loops for simplification.
char & LCSSAID
Definition: LCSSA.cpp:424
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:371
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
Represent the analysis usage information of a pass.
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:329
Analysis pass providing a never-invalidated alias analysis result.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
Interval::pred_iterator pred_end(Interval *I)
Definition: Interval.h:116
Analysis pass providing a never-invalidated alias analysis result.
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
void forgetValue(Value *V)
This method should be called by the client when it has changed a value in a way that may effect its v...
void getExitingBlocks(SmallVectorImpl< BlockT *> &ExitingBlocks) const
Return all blocks inside the loop that have successors outside of the loop.
Definition: LoopInfoImpl.h:35
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:160
size_t size() const
Definition: SmallVector.h:53
Value * getIncomingValue(unsigned i) const
Return incoming value number x.
DomTreeNodeBase< NodeT > * getNode(const NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
void setMetadata(unsigned KindID, MDNode *Node)
Set the metadata of the specified kind to the specified node.
Definition: Metadata.cpp:1226
char & LoopSimplifyID
bool formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution *SE)
Put loop into LCSSA form.
Definition: LCSSA.cpp:289
A function analysis which provides an AssumptionCache.
const InstListType & getInstList() const
Return the underlying instruction list container.
Definition: BasicBlock.h:329
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:110
Iterator for intrusive lists based on ilist_node.
void moveAfter(BasicBlock *MovePos)
Unlink this basic block from its current function and insert it right after MovePos in the function M...
Definition: BasicBlock.cpp:128
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
Legacy wrapper pass to provide the SCEVAAResult object.
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:847
bool dominates(const Instruction *Def, const Use &U) const
Return true if Def dominates a use in User.
Definition: Dominators.cpp:249
Module.h This file contains the declarations for the Module class.
iterator begin() const
Definition: LoopInfo.h:142
LoopT * AllocateLoop(ArgsTy &&... Args)
Definition: LoopInfo.h:648
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:381
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:621
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.
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
iterator begin() const
Definition: LoopInfo.h:659
Analysis pass that exposes the ScalarEvolution for a function.
LoopT * getParentLoop() const
Definition: LoopInfo.h:101
const std::vector< LoopT * > & getSubLoops() const
Return the loops contained entirely within this loop.
Definition: LoopInfo.h:131
Analysis pass providing a never-invalidated alias analysis result.
This file provides various utilities for inspecting and working with the control flow graph in LLVM I...
void forgetLoop(const Loop *L)
This method should be called by the client when it has changed a loop in a way that may effect Scalar...
void addChildLoop(LoopT *NewChild)
Add the specified loop to be a child of this loop.
Definition: LoopInfo.h:331
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:56
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:459
ArrayRef< BlockT * > getBlocks() const
Get a list of the basic blocks which make up this loop.
Definition: LoopInfo.h:149
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:224
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:115
#define I(x, y, z)
Definition: MD5.cpp:58
PassT::Result * getCachedResult(IRUnitT &IR) const
Get the cached result of an analysis pass for a given IR unit.
Definition: PassManager.h:789
void changeTopLevelLoop(LoopT *OldLoop, LoopT *NewLoop)
Replace the specified loop in the top-level loops list with the indicated loop.
Definition: LoopInfo.h:726
iterator end() const
Definition: LoopInfo.h:143
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
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h:633
block_iterator block_end() const
Definition: LoopInfo.h:155
void changeLoopFor(BlockT *BB, LoopT *L)
Change the top-level loop that contains BB to the specified loop.
Definition: LoopInfo.h:716
void preserve()
Mark an analysis as preserved.
Definition: PassManager.h:175
void removeBlockFromLoop(BlockT *BB)
This removes the specified basic block from the current loop, updating the Blocks as appropriate...
Definition: LoopInfo.h:396
void initializeLoopSimplifyPass(PassRegistry &)
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
bool isEHPad() const
Return true if this basic block is an exception handling block.
Definition: BasicBlock.h:394
LLVM Value Representation.
Definition: Value.h:73
succ_range successors(Instruction *I)
Definition: CFG.h:262
bool formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA)
Ensure that all exit blocks of the loop are dedicated exits.
Definition: LoopUtils.cpp:45
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:964
INITIALIZE_PASS_BEGIN(LoopSimplify, "loop-simplify", "Canonicalize natural loops", false, false) INITIALIZE_PASS_END(LoopSimplify
This is the interface for LLVM&#39;s primary stateless and local alias analysis.
A container for analyses that lazily runs them and caches their results.
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:260
bool replacementPreservesLCSSAForm(Instruction *From, Value *To)
Returns true if replacing From with To everywhere is guaranteed to preserve LCSSA form...
Definition: LoopInfo.h:826
A wrapper pass to provide the legacy pass manager access to a suitably prepared AAResults object...
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:138
void setIncomingValue(unsigned i, Value *V)
loop simplify
#define LLVM_DEBUG(X)
Definition: Debug.h:123
block_iterator block_begin() const
Definition: LoopInfo.h:154
Value * SimplifyInstruction(Instruction *I, const SimplifyQuery &Q, OptimizationRemarkEmitter *ORE=nullptr)
See if we can compute a simplified version of this instruction.
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:743
const BasicBlock * getParent() const
Definition: Instruction.h:67
Legacy wrapper pass to provide the BasicAAResult object.
void forgetTopmostLoop(const Loop *L)