LLVM  9.0.0svn
LoopSimplify.cpp
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1 //===- LoopSimplify.cpp - Loop Canonicalization 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 // This pass performs several transformations to transform natural loops into a
10 // simpler form, which makes subsequent analyses and transformations simpler and
11 // more effective.
12 //
13 // Loop pre-header insertion guarantees that there is a single, non-critical
14 // entry edge from outside of the loop to the loop header. This simplifies a
15 // number of analyses and transformations, such as LICM.
16 //
17 // Loop exit-block insertion guarantees that all exit blocks from the loop
18 // (blocks which are outside of the loop that have predecessors inside of the
19 // loop) only have predecessors from inside of the loop (and are thus dominated
20 // by the loop header). This simplifies transformations such as store-sinking
21 // that are built into LICM.
22 //
23 // This pass also guarantees that loops will have exactly one backedge.
24 //
25 // Indirectbr instructions introduce several complications. If the loop
26 // contains or is entered by an indirectbr instruction, it may not be possible
27 // to transform the loop and make these guarantees. Client code should check
28 // that these conditions are true before relying on them.
29 //
30 // Similar complications arise from callbr instructions, particularly in
31 // asm-goto where blockaddress expressions are used.
32 //
33 // Note that the simplifycfg pass will clean up blocks which are split out but
34 // end up being unnecessary, so usage of this pass should not pessimize
35 // generated code.
36 //
37 // This pass obviously modifies the CFG, but updates loop information and
38 // dominator information.
39 //
40 //===----------------------------------------------------------------------===//
41 
44 #include "llvm/ADT/SetOperations.h"
45 #include "llvm/ADT/SetVector.h"
46 #include "llvm/ADT/SmallVector.h"
47 #include "llvm/ADT/Statistic.h"
54 #include "llvm/Analysis/LoopInfo.h"
58 #include "llvm/IR/CFG.h"
59 #include "llvm/IR/Constants.h"
60 #include "llvm/IR/DataLayout.h"
61 #include "llvm/IR/Dominators.h"
62 #include "llvm/IR/Function.h"
63 #include "llvm/IR/Instructions.h"
64 #include "llvm/IR/IntrinsicInst.h"
65 #include "llvm/IR/LLVMContext.h"
66 #include "llvm/IR/Module.h"
67 #include "llvm/IR/Type.h"
68 #include "llvm/Support/Debug.h"
70 #include "llvm/Transforms/Utils.h"
73 using namespace llvm;
74 
75 #define DEBUG_TYPE "loop-simplify"
76 
77 STATISTIC(NumNested , "Number of nested loops split out");
78 
79 // If the block isn't already, move the new block to right after some 'outside
80 // block' block. This prevents the preheader from being placed inside the loop
81 // body, e.g. when the loop hasn't been rotated.
84  Loop *L) {
85  // Check to see if NewBB is already well placed.
86  Function::iterator BBI = --NewBB->getIterator();
87  for (unsigned i = 0, e = SplitPreds.size(); i != e; ++i) {
88  if (&*BBI == SplitPreds[i])
89  return;
90  }
91 
92  // If it isn't already after an outside block, move it after one. This is
93  // always good as it makes the uncond branch from the outside block into a
94  // fall-through.
95 
96  // Figure out *which* outside block to put this after. Prefer an outside
97  // block that neighbors a BB actually in the loop.
98  BasicBlock *FoundBB = nullptr;
99  for (unsigned i = 0, e = SplitPreds.size(); i != e; ++i) {
100  Function::iterator BBI = SplitPreds[i]->getIterator();
101  if (++BBI != NewBB->getParent()->end() && L->contains(&*BBI)) {
102  FoundBB = SplitPreds[i];
103  break;
104  }
105  }
106 
107  // If our heuristic for a *good* bb to place this after doesn't find
108  // anything, just pick something. It's likely better than leaving it within
109  // the loop.
110  if (!FoundBB)
111  FoundBB = SplitPreds[0];
112  NewBB->moveAfter(FoundBB);
113 }
114 
115 /// InsertPreheaderForLoop - Once we discover that a loop doesn't have a
116 /// preheader, this method is called to insert one. This method has two phases:
117 /// preheader insertion and analysis updating.
118 ///
120  LoopInfo *LI, bool PreserveLCSSA) {
121  BasicBlock *Header = L->getHeader();
122 
123  // Compute the set of predecessors of the loop that are not in the loop.
124  SmallVector<BasicBlock*, 8> OutsideBlocks;
125  for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
126  PI != PE; ++PI) {
127  BasicBlock *P = *PI;
128  if (!L->contains(P)) { // Coming in from outside the loop?
129  // If the loop is branched to from an indirect terminator, we won't
130  // be able to fully transform the loop, because it prohibits
131  // edge splitting.
133  return nullptr;
134 
135  // Keep track of it.
136  OutsideBlocks.push_back(P);
137  }
138  }
139 
140  // Split out the loop pre-header.
141  BasicBlock *PreheaderBB;
142  PreheaderBB = SplitBlockPredecessors(Header, OutsideBlocks, ".preheader", DT,
143  LI, nullptr, PreserveLCSSA);
144  if (!PreheaderBB)
145  return nullptr;
146 
147  LLVM_DEBUG(dbgs() << "LoopSimplify: Creating pre-header "
148  << PreheaderBB->getName() << "\n");
149 
150  // Make sure that NewBB is put someplace intelligent, which doesn't mess up
151  // code layout too horribly.
152  placeSplitBlockCarefully(PreheaderBB, OutsideBlocks, L);
153 
154  return PreheaderBB;
155 }
156 
157 /// Add the specified block, and all of its predecessors, to the specified set,
158 /// if it's not already in there. Stop predecessor traversal when we reach
159 /// StopBlock.
160 static void addBlockAndPredsToSet(BasicBlock *InputBB, BasicBlock *StopBlock,
161  std::set<BasicBlock*> &Blocks) {
163  Worklist.push_back(InputBB);
164  do {
165  BasicBlock *BB = Worklist.pop_back_val();
166  if (Blocks.insert(BB).second && BB != StopBlock)
167  // If BB is not already processed and it is not a stop block then
168  // insert its predecessor in the work list
169  for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
170  BasicBlock *WBB = *I;
171  Worklist.push_back(WBB);
172  }
173  } while (!Worklist.empty());
174 }
175 
176 /// The first part of loop-nestification is to find a PHI node that tells
177 /// us how to partition the loops.
179  AssumptionCache *AC) {
180  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
181  for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ) {
182  PHINode *PN = cast<PHINode>(I);
183  ++I;
184  if (Value *V = SimplifyInstruction(PN, {DL, nullptr, DT, AC})) {
185  // This is a degenerate PHI already, don't modify it!
186  PN->replaceAllUsesWith(V);
187  PN->eraseFromParent();
188  continue;
189  }
190 
191  // Scan this PHI node looking for a use of the PHI node by itself.
192  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
193  if (PN->getIncomingValue(i) == PN &&
194  L->contains(PN->getIncomingBlock(i)))
195  // We found something tasty to remove.
196  return PN;
197  }
198  return nullptr;
199 }
200 
201 /// If this loop has multiple backedges, try to pull one of them out into
202 /// a nested loop.
203 ///
204 /// This is important for code that looks like
205 /// this:
206 ///
207 /// Loop:
208 /// ...
209 /// br cond, Loop, Next
210 /// ...
211 /// br cond2, Loop, Out
212 ///
213 /// To identify this common case, we look at the PHI nodes in the header of the
214 /// loop. PHI nodes with unchanging values on one backedge correspond to values
215 /// that change in the "outer" loop, but not in the "inner" loop.
216 ///
217 /// If we are able to separate out a loop, return the new outer loop that was
218 /// created.
219 ///
220 static Loop *separateNestedLoop(Loop *L, BasicBlock *Preheader,
221  DominatorTree *DT, LoopInfo *LI,
222  ScalarEvolution *SE, bool PreserveLCSSA,
223  AssumptionCache *AC) {
224  // Don't try to separate loops without a preheader.
225  if (!Preheader)
226  return nullptr;
227 
228  // The header is not a landing pad; preheader insertion should ensure this.
229  BasicBlock *Header = L->getHeader();
230  assert(!Header->isEHPad() && "Can't insert backedge to EH pad");
231 
232  PHINode *PN = findPHIToPartitionLoops(L, DT, AC);
233  if (!PN) return nullptr; // No known way to partition.
234 
235  // Pull out all predecessors that have varying values in the loop. This
236  // handles the case when a PHI node has multiple instances of itself as
237  // arguments.
238  SmallVector<BasicBlock*, 8> OuterLoopPreds;
239  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
240  if (PN->getIncomingValue(i) != PN ||
241  !L->contains(PN->getIncomingBlock(i))) {
242  // We can't split indirect control flow edges.
243  if (PN->getIncomingBlock(i)->getTerminator()->isIndirectTerminator())
244  return nullptr;
245  OuterLoopPreds.push_back(PN->getIncomingBlock(i));
246  }
247  }
248  LLVM_DEBUG(dbgs() << "LoopSimplify: Splitting out a new outer loop\n");
249 
250  // If ScalarEvolution is around and knows anything about values in
251  // this loop, tell it to forget them, because we're about to
252  // substantially change it.
253  if (SE)
254  SE->forgetLoop(L);
255 
256  BasicBlock *NewBB = SplitBlockPredecessors(Header, OuterLoopPreds, ".outer",
257  DT, LI, nullptr, PreserveLCSSA);
258 
259  // Make sure that NewBB is put someplace intelligent, which doesn't mess up
260  // code layout too horribly.
261  placeSplitBlockCarefully(NewBB, OuterLoopPreds, L);
262 
263  // Create the new outer loop.
264  Loop *NewOuter = LI->AllocateLoop();
265 
266  // Change the parent loop to use the outer loop as its child now.
267  if (Loop *Parent = L->getParentLoop())
268  Parent->replaceChildLoopWith(L, NewOuter);
269  else
270  LI->changeTopLevelLoop(L, NewOuter);
271 
272  // L is now a subloop of our outer loop.
273  NewOuter->addChildLoop(L);
274 
275  for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
276  I != E; ++I)
277  NewOuter->addBlockEntry(*I);
278 
279  // Now reset the header in L, which had been moved by
280  // SplitBlockPredecessors for the outer loop.
281  L->moveToHeader(Header);
282 
283  // Determine which blocks should stay in L and which should be moved out to
284  // the Outer loop now.
285  std::set<BasicBlock*> BlocksInL;
286  for (pred_iterator PI=pred_begin(Header), E = pred_end(Header); PI!=E; ++PI) {
287  BasicBlock *P = *PI;
288  if (DT->dominates(Header, P))
289  addBlockAndPredsToSet(P, Header, BlocksInL);
290  }
291 
292  // Scan all of the loop children of L, moving them to OuterLoop if they are
293  // not part of the inner loop.
294  const std::vector<Loop*> &SubLoops = L->getSubLoops();
295  for (size_t I = 0; I != SubLoops.size(); )
296  if (BlocksInL.count(SubLoops[I]->getHeader()))
297  ++I; // Loop remains in L
298  else
299  NewOuter->addChildLoop(L->removeChildLoop(SubLoops.begin() + I));
300 
301  SmallVector<BasicBlock *, 8> OuterLoopBlocks;
302  OuterLoopBlocks.push_back(NewBB);
303  // Now that we know which blocks are in L and which need to be moved to
304  // OuterLoop, move any blocks that need it.
305  for (unsigned i = 0; i != L->getBlocks().size(); ++i) {
306  BasicBlock *BB = L->getBlocks()[i];
307  if (!BlocksInL.count(BB)) {
308  // Move this block to the parent, updating the exit blocks sets
309  L->removeBlockFromLoop(BB);
310  if ((*LI)[BB] == L) {
311  LI->changeLoopFor(BB, NewOuter);
312  OuterLoopBlocks.push_back(BB);
313  }
314  --i;
315  }
316  }
317 
318  // Split edges to exit blocks from the inner loop, if they emerged in the
319  // process of separating the outer one.
320  formDedicatedExitBlocks(L, DT, LI, PreserveLCSSA);
321 
322  if (PreserveLCSSA) {
323  // Fix LCSSA form for L. Some values, which previously were only used inside
324  // L, can now be used in NewOuter loop. We need to insert phi-nodes for them
325  // in corresponding exit blocks.
326  // We don't need to form LCSSA recursively, because there cannot be uses
327  // inside a newly created loop of defs from inner loops as those would
328  // already be a use of an LCSSA phi node.
329  formLCSSA(*L, *DT, LI, SE);
330 
331  assert(NewOuter->isRecursivelyLCSSAForm(*DT, *LI) &&
332  "LCSSA is broken after separating nested loops!");
333  }
334 
335  return NewOuter;
336 }
337 
338 /// This method is called when the specified loop has more than one
339 /// backedge in it.
340 ///
341 /// If this occurs, revector all of these backedges to target a new basic block
342 /// and have that block branch to the loop header. This ensures that loops
343 /// have exactly one backedge.
345  DominatorTree *DT, LoopInfo *LI) {
346  assert(L->getNumBackEdges() > 1 && "Must have > 1 backedge!");
347 
348  // Get information about the loop
349  BasicBlock *Header = L->getHeader();
350  Function *F = Header->getParent();
351 
352  // Unique backedge insertion currently depends on having a preheader.
353  if (!Preheader)
354  return nullptr;
355 
356  // The header is not an EH pad; preheader insertion should ensure this.
357  assert(!Header->isEHPad() && "Can't insert backedge to EH pad");
358 
359  // Figure out which basic blocks contain back-edges to the loop header.
360  std::vector<BasicBlock*> BackedgeBlocks;
361  for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I){
362  BasicBlock *P = *I;
363 
364  // Indirect edges cannot be split, so we must fail if we find one.
366  return nullptr;
367 
368  if (P != Preheader) BackedgeBlocks.push_back(P);
369  }
370 
371  // Create and insert the new backedge block...
372  BasicBlock *BEBlock = BasicBlock::Create(Header->getContext(),
373  Header->getName() + ".backedge", F);
374  BranchInst *BETerminator = BranchInst::Create(Header, BEBlock);
375  BETerminator->setDebugLoc(Header->getFirstNonPHI()->getDebugLoc());
376 
377  LLVM_DEBUG(dbgs() << "LoopSimplify: Inserting unique backedge block "
378  << BEBlock->getName() << "\n");
379 
380  // Move the new backedge block to right after the last backedge block.
381  Function::iterator InsertPos = ++BackedgeBlocks.back()->getIterator();
382  F->getBasicBlockList().splice(InsertPos, F->getBasicBlockList(), BEBlock);
383 
384  // Now that the block has been inserted into the function, create PHI nodes in
385  // the backedge block which correspond to any PHI nodes in the header block.
386  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
387  PHINode *PN = cast<PHINode>(I);
388  PHINode *NewPN = PHINode::Create(PN->getType(), BackedgeBlocks.size(),
389  PN->getName()+".be", BETerminator);
390 
391  // Loop over the PHI node, moving all entries except the one for the
392  // preheader over to the new PHI node.
393  unsigned PreheaderIdx = ~0U;
394  bool HasUniqueIncomingValue = true;
395  Value *UniqueValue = nullptr;
396  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
397  BasicBlock *IBB = PN->getIncomingBlock(i);
398  Value *IV = PN->getIncomingValue(i);
399  if (IBB == Preheader) {
400  PreheaderIdx = i;
401  } else {
402  NewPN->addIncoming(IV, IBB);
403  if (HasUniqueIncomingValue) {
404  if (!UniqueValue)
405  UniqueValue = IV;
406  else if (UniqueValue != IV)
407  HasUniqueIncomingValue = false;
408  }
409  }
410  }
411 
412  // Delete all of the incoming values from the old PN except the preheader's
413  assert(PreheaderIdx != ~0U && "PHI has no preheader entry??");
414  if (PreheaderIdx != 0) {
415  PN->setIncomingValue(0, PN->getIncomingValue(PreheaderIdx));
416  PN->setIncomingBlock(0, PN->getIncomingBlock(PreheaderIdx));
417  }
418  // Nuke all entries except the zero'th.
419  for (unsigned i = 0, e = PN->getNumIncomingValues()-1; i != e; ++i)
420  PN->removeIncomingValue(e-i, false);
421 
422  // Finally, add the newly constructed PHI node as the entry for the BEBlock.
423  PN->addIncoming(NewPN, BEBlock);
424 
425  // As an optimization, if all incoming values in the new PhiNode (which is a
426  // subset of the incoming values of the old PHI node) have the same value,
427  // eliminate the PHI Node.
428  if (HasUniqueIncomingValue) {
429  NewPN->replaceAllUsesWith(UniqueValue);
430  BEBlock->getInstList().erase(NewPN);
431  }
432  }
433 
434  // Now that all of the PHI nodes have been inserted and adjusted, modify the
435  // backedge blocks to jump to the BEBlock instead of the header.
436  // If one of the backedges has llvm.loop metadata attached, we remove
437  // it from the backedge and add it to BEBlock.
438  unsigned LoopMDKind = BEBlock->getContext().getMDKindID("llvm.loop");
439  MDNode *LoopMD = nullptr;
440  for (unsigned i = 0, e = BackedgeBlocks.size(); i != e; ++i) {
441  Instruction *TI = BackedgeBlocks[i]->getTerminator();
442  if (!LoopMD)
443  LoopMD = TI->getMetadata(LoopMDKind);
444  TI->setMetadata(LoopMDKind, nullptr);
445  for (unsigned Op = 0, e = TI->getNumSuccessors(); Op != e; ++Op)
446  if (TI->getSuccessor(Op) == Header)
447  TI->setSuccessor(Op, BEBlock);
448  }
449  BEBlock->getTerminator()->setMetadata(LoopMDKind, LoopMD);
450 
451  //===--- Update all analyses which we must preserve now -----------------===//
452 
453  // Update Loop Information - we know that this block is now in the current
454  // loop and all parent loops.
455  L->addBasicBlockToLoop(BEBlock, *LI);
456 
457  // Update dominator information
458  DT->splitBlock(BEBlock);
459 
460  return BEBlock;
461 }
462 
463 /// Simplify one loop and queue further loops for simplification.
464 static bool simplifyOneLoop(Loop *L, SmallVectorImpl<Loop *> &Worklist,
465  DominatorTree *DT, LoopInfo *LI,
467  bool PreserveLCSSA) {
468  bool Changed = false;
469 ReprocessLoop:
470 
471  // Check to see that no blocks (other than the header) in this loop have
472  // predecessors that are not in the loop. This is not valid for natural
473  // loops, but can occur if the blocks are unreachable. Since they are
474  // unreachable we can just shamelessly delete those CFG edges!
475  for (Loop::block_iterator BB = L->block_begin(), E = L->block_end();
476  BB != E; ++BB) {
477  if (*BB == L->getHeader()) continue;
478 
480  for (pred_iterator PI = pred_begin(*BB),
481  PE = pred_end(*BB); PI != PE; ++PI) {
482  BasicBlock *P = *PI;
483  if (!L->contains(P))
484  BadPreds.insert(P);
485  }
486 
487  // Delete each unique out-of-loop (and thus dead) predecessor.
488  for (BasicBlock *P : BadPreds) {
489 
490  LLVM_DEBUG(dbgs() << "LoopSimplify: Deleting edge from dead predecessor "
491  << P->getName() << "\n");
492 
493  // Zap the dead pred's terminator and replace it with unreachable.
494  Instruction *TI = P->getTerminator();
495  changeToUnreachable(TI, /*UseLLVMTrap=*/false, PreserveLCSSA);
496  Changed = true;
497  }
498  }
499 
500  // If there are exiting blocks with branches on undef, resolve the undef in
501  // the direction which will exit the loop. This will help simplify loop
502  // trip count computations.
503  SmallVector<BasicBlock*, 8> ExitingBlocks;
504  L->getExitingBlocks(ExitingBlocks);
505  for (BasicBlock *ExitingBlock : ExitingBlocks)
506  if (BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator()))
507  if (BI->isConditional()) {
508  if (UndefValue *Cond = dyn_cast<UndefValue>(BI->getCondition())) {
509 
510  LLVM_DEBUG(dbgs()
511  << "LoopSimplify: Resolving \"br i1 undef\" to exit in "
512  << ExitingBlock->getName() << "\n");
513 
514  BI->setCondition(ConstantInt::get(Cond->getType(),
515  !L->contains(BI->getSuccessor(0))));
516 
517  Changed = true;
518  }
519  }
520 
521  // Does the loop already have a preheader? If so, don't insert one.
522  BasicBlock *Preheader = L->getLoopPreheader();
523  if (!Preheader) {
524  Preheader = InsertPreheaderForLoop(L, DT, LI, PreserveLCSSA);
525  if (Preheader)
526  Changed = true;
527  }
528 
529  // Next, check to make sure that all exit nodes of the loop only have
530  // predecessors that are inside of the loop. This check guarantees that the
531  // loop preheader/header will dominate the exit blocks. If the exit block has
532  // predecessors from outside of the loop, split the edge now.
533  if (formDedicatedExitBlocks(L, DT, LI, PreserveLCSSA))
534  Changed = true;
535 
536  // If the header has more than two predecessors at this point (from the
537  // preheader and from multiple backedges), we must adjust the loop.
538  BasicBlock *LoopLatch = L->getLoopLatch();
539  if (!LoopLatch) {
540  // If this is really a nested loop, rip it out into a child loop. Don't do
541  // this for loops with a giant number of backedges, just factor them into a
542  // common backedge instead.
543  if (L->getNumBackEdges() < 8) {
544  if (Loop *OuterL =
545  separateNestedLoop(L, Preheader, DT, LI, SE, PreserveLCSSA, AC)) {
546  ++NumNested;
547  // Enqueue the outer loop as it should be processed next in our
548  // depth-first nest walk.
549  Worklist.push_back(OuterL);
550 
551  // This is a big restructuring change, reprocess the whole loop.
552  Changed = true;
553  // GCC doesn't tail recursion eliminate this.
554  // FIXME: It isn't clear we can't rely on LLVM to TRE this.
555  goto ReprocessLoop;
556  }
557  }
558 
559  // If we either couldn't, or didn't want to, identify nesting of the loops,
560  // insert a new block that all backedges target, then make it jump to the
561  // loop header.
562  LoopLatch = insertUniqueBackedgeBlock(L, Preheader, DT, LI);
563  if (LoopLatch)
564  Changed = true;
565  }
566 
567  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
568 
569  // Scan over the PHI nodes in the loop header. Since they now have only two
570  // incoming values (the loop is canonicalized), we may have simplified the PHI
571  // down to 'X = phi [X, Y]', which should be replaced with 'Y'.
572  PHINode *PN;
573  for (BasicBlock::iterator I = L->getHeader()->begin();
574  (PN = dyn_cast<PHINode>(I++)); )
575  if (Value *V = SimplifyInstruction(PN, {DL, nullptr, DT, AC})) {
576  if (SE) SE->forgetValue(PN);
577  if (!PreserveLCSSA || LI->replacementPreservesLCSSAForm(PN, V)) {
578  PN->replaceAllUsesWith(V);
579  PN->eraseFromParent();
580  }
581  }
582 
583  // If this loop has multiple exits and the exits all go to the same
584  // block, attempt to merge the exits. This helps several passes, such
585  // as LoopRotation, which do not support loops with multiple exits.
586  // SimplifyCFG also does this (and this code uses the same utility
587  // function), however this code is loop-aware, where SimplifyCFG is
588  // not. That gives it the advantage of being able to hoist
589  // loop-invariant instructions out of the way to open up more
590  // opportunities, and the disadvantage of having the responsibility
591  // to preserve dominator information.
592  auto HasUniqueExitBlock = [&]() {
593  BasicBlock *UniqueExit = nullptr;
594  for (auto *ExitingBB : ExitingBlocks)
595  for (auto *SuccBB : successors(ExitingBB)) {
596  if (L->contains(SuccBB))
597  continue;
598 
599  if (!UniqueExit)
600  UniqueExit = SuccBB;
601  else if (UniqueExit != SuccBB)
602  return false;
603  }
604 
605  return true;
606  };
607  if (HasUniqueExitBlock()) {
608  for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
609  BasicBlock *ExitingBlock = ExitingBlocks[i];
610  if (!ExitingBlock->getSinglePredecessor()) continue;
611  BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
612  if (!BI || !BI->isConditional()) continue;
613  CmpInst *CI = dyn_cast<CmpInst>(BI->getCondition());
614  if (!CI || CI->getParent() != ExitingBlock) continue;
615 
616  // Attempt to hoist out all instructions except for the
617  // comparison and the branch.
618  bool AllInvariant = true;
619  bool AnyInvariant = false;
620  for (auto I = ExitingBlock->instructionsWithoutDebug().begin(); &*I != BI; ) {
621  Instruction *Inst = &*I++;
622  if (Inst == CI)
623  continue;
624  if (!L->makeLoopInvariant(Inst, AnyInvariant,
625  Preheader ? Preheader->getTerminator()
626  : nullptr)) {
627  AllInvariant = false;
628  break;
629  }
630  }
631  if (AnyInvariant) {
632  Changed = true;
633  // The loop disposition of all SCEV expressions that depend on any
634  // hoisted values have also changed.
635  if (SE)
636  SE->forgetLoopDispositions(L);
637  }
638  if (!AllInvariant) continue;
639 
640  // The block has now been cleared of all instructions except for
641  // a comparison and a conditional branch. SimplifyCFG may be able
642  // to fold it now.
643  if (!FoldBranchToCommonDest(BI))
644  continue;
645 
646  // Success. The block is now dead, so remove it from the loop,
647  // update the dominator tree and delete it.
648  LLVM_DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block "
649  << ExitingBlock->getName() << "\n");
650 
651  assert(pred_begin(ExitingBlock) == pred_end(ExitingBlock));
652  Changed = true;
653  LI->removeBlock(ExitingBlock);
654 
655  DomTreeNode *Node = DT->getNode(ExitingBlock);
656  const std::vector<DomTreeNodeBase<BasicBlock> *> &Children =
657  Node->getChildren();
658  while (!Children.empty()) {
659  DomTreeNode *Child = Children.front();
660  DT->changeImmediateDominator(Child, Node->getIDom());
661  }
662  DT->eraseNode(ExitingBlock);
663 
665  ExitingBlock, /* KeepOneInputPHIs */ PreserveLCSSA);
667  ExitingBlock, /* KeepOneInputPHIs */ PreserveLCSSA);
668  ExitingBlock->eraseFromParent();
669  }
670  }
671 
672  // Changing exit conditions for blocks may affect exit counts of this loop and
673  // any of its paretns, so we must invalidate the entire subtree if we've made
674  // any changes.
675  if (Changed && SE)
676  SE->forgetTopmostLoop(L);
677 
678  return Changed;
679 }
680 
683  bool PreserveLCSSA) {
684  bool Changed = false;
685 
686 #ifndef NDEBUG
687  // If we're asked to preserve LCSSA, the loop nest needs to start in LCSSA
688  // form.
689  if (PreserveLCSSA) {
690  assert(DT && "DT not available.");
691  assert(LI && "LI not available.");
692  assert(L->isRecursivelyLCSSAForm(*DT, *LI) &&
693  "Requested to preserve LCSSA, but it's already broken.");
694  }
695 #endif
696 
697  // Worklist maintains our depth-first queue of loops in this nest to process.
698  SmallVector<Loop *, 4> Worklist;
699  Worklist.push_back(L);
700 
701  // Walk the worklist from front to back, pushing newly found sub loops onto
702  // the back. This will let us process loops from back to front in depth-first
703  // order. We can use this simple process because loops form a tree.
704  for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) {
705  Loop *L2 = Worklist[Idx];
706  Worklist.append(L2->begin(), L2->end());
707  }
708 
709  while (!Worklist.empty())
710  Changed |= simplifyOneLoop(Worklist.pop_back_val(), Worklist, DT, LI, SE,
711  AC, PreserveLCSSA);
712 
713  return Changed;
714 }
715 
716 namespace {
717  struct LoopSimplify : public FunctionPass {
718  static char ID; // Pass identification, replacement for typeid
719  LoopSimplify() : FunctionPass(ID) {
721  }
722 
723  bool runOnFunction(Function &F) override;
724 
725  void getAnalysisUsage(AnalysisUsage &AU) const override {
727 
728  // We need loop information to identify the loops...
731 
734 
742  AU.addPreservedID(BreakCriticalEdgesID); // No critical edges added.
743  }
744 
745  /// verifyAnalysis() - Verify LoopSimplifyForm's guarantees.
746  void verifyAnalysis() const override;
747  };
748 }
749 
750 char LoopSimplify::ID = 0;
751 INITIALIZE_PASS_BEGIN(LoopSimplify, "loop-simplify",
752  "Canonicalize natural loops", false, false)
756 INITIALIZE_PASS_END(LoopSimplify, "loop-simplify",
757  "Canonicalize natural loops", false, false)
758 
759 // Publicly exposed interface to pass...
760 char &llvm::LoopSimplifyID = LoopSimplify::ID;
761 Pass *llvm::createLoopSimplifyPass() { return new LoopSimplify(); }
762 
763 /// runOnFunction - Run down all loops in the CFG (recursively, but we could do
764 /// it in any convenient order) inserting preheaders...
765 ///
767  bool Changed = false;
768  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
769  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
770  auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
771  ScalarEvolution *SE = SEWP ? &SEWP->getSE() : nullptr;
772  AssumptionCache *AC =
773  &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
774 
775  bool PreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
776 
777  // Simplify each loop nest in the function.
778  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
779  Changed |= simplifyLoop(*I, DT, LI, SE, AC, PreserveLCSSA);
780 
781 #ifndef NDEBUG
782  if (PreserveLCSSA) {
783  bool InLCSSA = all_of(
784  *LI, [&](Loop *L) { return L->isRecursivelyLCSSAForm(*DT, *LI); });
785  assert(InLCSSA && "LCSSA is broken after loop-simplify.");
786  }
787 #endif
788  return Changed;
789 }
790 
793  bool Changed = false;
794  LoopInfo *LI = &AM.getResult<LoopAnalysis>(F);
798 
799  // Note that we don't preserve LCSSA in the new PM, if you need it run LCSSA
800  // after simplifying the loops.
801  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
802  Changed |= simplifyLoop(*I, DT, LI, SE, AC, /*PreserveLCSSA*/ false);
803 
804  if (!Changed)
805  return PreservedAnalyses::all();
806 
809  PA.preserve<LoopAnalysis>();
810  PA.preserve<BasicAA>();
811  PA.preserve<GlobalsAA>();
812  PA.preserve<SCEVAA>();
815  return PA;
816 }
817 
818 // FIXME: Restore this code when we re-enable verification in verifyAnalysis
819 // below.
820 #if 0
821 static void verifyLoop(Loop *L) {
822  // Verify subloops.
823  for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
824  verifyLoop(*I);
825 
826  // It used to be possible to just assert L->isLoopSimplifyForm(), however
827  // with the introduction of indirectbr, there are now cases where it's
828  // not possible to transform a loop as necessary. We can at least check
829  // that there is an indirectbr near any time there's trouble.
830 
831  // Indirectbr can interfere with preheader and unique backedge insertion.
832  if (!L->getLoopPreheader() || !L->getLoopLatch()) {
833  bool HasIndBrPred = false;
834  for (pred_iterator PI = pred_begin(L->getHeader()),
835  PE = pred_end(L->getHeader()); PI != PE; ++PI)
836  if (isa<IndirectBrInst>((*PI)->getTerminator())) {
837  HasIndBrPred = true;
838  break;
839  }
840  assert(HasIndBrPred &&
841  "LoopSimplify has no excuse for missing loop header info!");
842  (void)HasIndBrPred;
843  }
844 
845  // Indirectbr can interfere with exit block canonicalization.
846  if (!L->hasDedicatedExits()) {
847  bool HasIndBrExiting = false;
848  SmallVector<BasicBlock*, 8> ExitingBlocks;
849  L->getExitingBlocks(ExitingBlocks);
850  for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
851  if (isa<IndirectBrInst>((ExitingBlocks[i])->getTerminator())) {
852  HasIndBrExiting = true;
853  break;
854  }
855  }
856 
857  assert(HasIndBrExiting &&
858  "LoopSimplify has no excuse for missing exit block info!");
859  (void)HasIndBrExiting;
860  }
861 }
862 #endif
863 
864 void LoopSimplify::verifyAnalysis() const {
865  // FIXME: This routine is being called mid-way through the loop pass manager
866  // as loop passes destroy this analysis. That's actually fine, but we have no
867  // way of expressing that here. Once all of the passes that destroy this are
868  // hoisted out of the loop pass manager we can add back verification here.
869 #if 0
870  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
871  verifyLoop(*I);
872 #endif
873 }
Legacy wrapper pass to provide the GlobalsAAResult object.
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:80
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:67
loop Canonicalize natural loops
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:110
Pass * createLoopSimplifyPass()
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:636
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.
BlockT * getLoopLatch() const
If there is a single latch block for this loop, return it.
Definition: LoopInfoImpl.h:224
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:769
iterator erase(iterator where)
Definition: ilist.h:265
AnalysisPass to compute dependence information in a function.
This class represents lattice values for constants.
Definition: AllocatorList.h:23
This is the interface for a simple mod/ref and alias analysis over globals.
ArrayRef< BasicBlock *>::const_iterator block_iterator
Definition: LoopInfo.h:152
BasicBlock * getSuccessor(unsigned Idx) const
Return the specified successor. This instruction must be a terminator.
iterator end()
Definition: Function.h:657
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:85
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 removePredecessor(BasicBlock *Pred, bool KeepOneInputPHIs=false)
Notify the BasicBlock that the predecessor Pred is no longer able to reach it.
Definition: BasicBlock.cpp:301
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:378
LoopT * removeChildLoop(iterator I)
This removes the specified child from being a subloop of this loop.
Definition: LoopInfo.h:339
The main scalar evolution driver.
BlockT * getLoopPreheader() const
If there is a preheader for this loop, return it.
Definition: LoopInfoImpl.h:173
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:280
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:1185
BasicBlock * getSuccessor(unsigned i) const
STATISTIC(NumFunctions, "Total number of functions")
Metadata node.
Definition: Metadata.h:863
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:230
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
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.
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:32
void eraseNode(NodeT *BB)
eraseNode - Removes a node from the dominator tree.
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:268
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:133
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:50
unsigned getNumBackEdges() const
Calculate the number of back edges to the loop header.
Definition: LoopInfo.h:226
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:1907
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:369
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:1285
void addBlockEntry(BlockT *BB)
This adds a basic block directly to the basic block list.
Definition: LoopInfo.h:358
std::vector< Loop *>::const_iterator iterator
iterator/begin/end - The interface to the top-level loops in the current function.
Definition: LoopInfo.h:661
Analysis pass that exposes the LoopInfo for a function.
Definition: LoopInfo.h:944
BlockT * getHeader() const
Definition: LoopInfo.h:99
std::vector< Loop *>::const_iterator iterator
Definition: LoopInfo.h:138
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:244
void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase< BlockT, LoopT > &LI)
This method is used by other analyses to update loop information.
Definition: LoopInfoImpl.h:250
MDNode * getMetadata(unsigned KindID) const
Get the metadata of given kind attached to this Instruction.
Definition: Instruction.h:234
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:429
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:144
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 ...
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
const BasicBlock * getSinglePredecessor() const
Return the predecessor of this block if it has a single predecessor block.
Definition: BasicBlock.cpp:233
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
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:94
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:665
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:463
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:370
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
Represent the analysis usage information of a pass.
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:327
Analysis pass providing a never-invalidated alias analysis result.
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
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:99
self_iterator getIterator()
Definition: ilist_node.h:81
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:34
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
size_t size() const
Definition: SmallVector.h:52
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:1225
char & LoopSimplifyID
bool formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution *SE)
Put loop into LCSSA form.
Definition: LCSSA.cpp:318
A function analysis which provides an AssumptionCache.
const InstListType & getInstList() const
Return the underlying instruction list container.
Definition: BasicBlock.h:333
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:109
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:127
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:417
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:839
bool dominates(const Instruction *Def, const Use &U) const
Return true if Def dominates a use in User.
Definition: Dominators.cpp:248
Module.h This file contains the declarations for the Module class.
iterator begin() const
Definition: LoopInfo.h:141
LoopT * AllocateLoop(ArgsTy &&... Args)
Definition: LoopInfo.h:653
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:373
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:132
iterator begin() const
Definition: LoopInfo.h:664
Analysis pass that exposes the ScalarEvolution for a function.
LoopT * getParentLoop() const
Definition: LoopInfo.h:100
const std::vector< LoopT * > & getSubLoops() const
Return the loops contained entirely within this loop.
Definition: LoopInfo.h:130
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:330
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:55
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:464
ArrayRef< BlockT * > getBlocks() const
Get a list of the basic blocks which make up this loop.
Definition: LoopInfo.h:148
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
SymbolTableList< BasicBlock >::iterator eraseFromParent()
Unlink &#39;this&#39; from the containing function and delete it.
Definition: BasicBlock.cpp:114
#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:788
void changeTopLevelLoop(LoopT *OldLoop, LoopT *NewLoop)
Replace the specified loop in the top-level loops list with the indicated loop.
Definition: LoopInfo.h:731
iterator end() const
Definition: LoopInfo.h:142
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
block_iterator block_end() const
Definition: LoopInfo.h:154
void changeLoopFor(BlockT *BB, LoopT *L)
Change the top-level loop that contains BB to the specified loop.
Definition: LoopInfo.h:721
void preserve()
Mark an analysis as preserved.
Definition: PassManager.h:174
void removeBlockFromLoop(BlockT *BB)
This removes the specified basic block from the current loop, updating the Blocks as appropriate...
Definition: LoopInfo.h:395
void initializeLoopSimplifyPass(PassRegistry &)
bool isIndirectTerminator() const
Definition: Instruction.h:138
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 formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA)
Ensure that all exit blocks of the loop are dedicated exits.
Definition: LoopUtils.cpp:48
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:969
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:259
bool replacementPreservesLCSSAForm(Instruction *From, Value *To)
Returns true if replacing From with To everywhere is guaranteed to preserve LCSSA form...
Definition: LoopInfo.h:831
A wrapper pass to provide the legacy pass manager access to a suitably prepared AAResults object...
void setIncomingValue(unsigned i, Value *V)
loop simplify
#define LLVM_DEBUG(X)
Definition: Debug.h:122
block_iterator block_begin() const
Definition: LoopInfo.h:153
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:748
const BasicBlock * getParent() const
Definition: Instruction.h:66
Legacy wrapper pass to provide the BasicAAResult object.
void forgetTopmostLoop(const Loop *L)