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"
55 #include "llvm/Analysis/LoopInfo.h"
60 #include "llvm/IR/CFG.h"
61 #include "llvm/IR/Constants.h"
62 #include "llvm/IR/DataLayout.h"
63 #include "llvm/IR/Dominators.h"
64 #include "llvm/IR/Function.h"
65 #include "llvm/IR/Instructions.h"
66 #include "llvm/IR/IntrinsicInst.h"
67 #include "llvm/IR/LLVMContext.h"
68 #include "llvm/IR/Module.h"
69 #include "llvm/IR/Type.h"
70 #include "llvm/Support/Debug.h"
72 #include "llvm/Transforms/Utils.h"
76 using namespace llvm;
77 
78 #define DEBUG_TYPE "loop-simplify"
79 
80 STATISTIC(NumNested , "Number of nested loops split out");
81 
82 // If the block isn't already, move the new block to right after some 'outside
83 // block' block. This prevents the preheader from being placed inside the loop
84 // body, e.g. when the loop hasn't been rotated.
87  Loop *L) {
88  // Check to see if NewBB is already well placed.
89  Function::iterator BBI = --NewBB->getIterator();
90  for (unsigned i = 0, e = SplitPreds.size(); i != e; ++i) {
91  if (&*BBI == SplitPreds[i])
92  return;
93  }
94 
95  // If it isn't already after an outside block, move it after one. This is
96  // always good as it makes the uncond branch from the outside block into a
97  // fall-through.
98 
99  // Figure out *which* outside block to put this after. Prefer an outside
100  // block that neighbors a BB actually in the loop.
101  BasicBlock *FoundBB = nullptr;
102  for (unsigned i = 0, e = SplitPreds.size(); i != e; ++i) {
103  Function::iterator BBI = SplitPreds[i]->getIterator();
104  if (++BBI != NewBB->getParent()->end() && L->contains(&*BBI)) {
105  FoundBB = SplitPreds[i];
106  break;
107  }
108  }
109 
110  // If our heuristic for a *good* bb to place this after doesn't find
111  // anything, just pick something. It's likely better than leaving it within
112  // the loop.
113  if (!FoundBB)
114  FoundBB = SplitPreds[0];
115  NewBB->moveAfter(FoundBB);
116 }
117 
118 /// InsertPreheaderForLoop - Once we discover that a loop doesn't have a
119 /// preheader, this method is called to insert one. This method has two phases:
120 /// preheader insertion and analysis updating.
121 ///
123  LoopInfo *LI, MemorySSAUpdater *MSSAU,
124  bool PreserveLCSSA) {
125  BasicBlock *Header = L->getHeader();
126 
127  // Compute the set of predecessors of the loop that are not in the loop.
128  SmallVector<BasicBlock*, 8> OutsideBlocks;
129  for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
130  PI != PE; ++PI) {
131  BasicBlock *P = *PI;
132  if (!L->contains(P)) { // Coming in from outside the loop?
133  // If the loop is branched to from an indirect terminator, we won't
134  // be able to fully transform the loop, because it prohibits
135  // edge splitting.
137  return nullptr;
138 
139  // Keep track of it.
140  OutsideBlocks.push_back(P);
141  }
142  }
143 
144  // Split out the loop pre-header.
145  BasicBlock *PreheaderBB;
146  PreheaderBB = SplitBlockPredecessors(Header, OutsideBlocks, ".preheader", DT,
147  LI, MSSAU, PreserveLCSSA);
148  if (!PreheaderBB)
149  return nullptr;
150 
151  LLVM_DEBUG(dbgs() << "LoopSimplify: Creating pre-header "
152  << PreheaderBB->getName() << "\n");
153 
154  // Make sure that NewBB is put someplace intelligent, which doesn't mess up
155  // code layout too horribly.
156  placeSplitBlockCarefully(PreheaderBB, OutsideBlocks, L);
157 
158  return PreheaderBB;
159 }
160 
161 /// Add the specified block, and all of its predecessors, to the specified set,
162 /// if it's not already in there. Stop predecessor traversal when we reach
163 /// StopBlock.
164 static void addBlockAndPredsToSet(BasicBlock *InputBB, BasicBlock *StopBlock,
165  std::set<BasicBlock*> &Blocks) {
167  Worklist.push_back(InputBB);
168  do {
169  BasicBlock *BB = Worklist.pop_back_val();
170  if (Blocks.insert(BB).second && BB != StopBlock)
171  // If BB is not already processed and it is not a stop block then
172  // insert its predecessor in the work list
173  for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
174  BasicBlock *WBB = *I;
175  Worklist.push_back(WBB);
176  }
177  } while (!Worklist.empty());
178 }
179 
180 /// The first part of loop-nestification is to find a PHI node that tells
181 /// us how to partition the loops.
183  AssumptionCache *AC) {
184  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
185  for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ) {
186  PHINode *PN = cast<PHINode>(I);
187  ++I;
188  if (Value *V = SimplifyInstruction(PN, {DL, nullptr, DT, AC})) {
189  // This is a degenerate PHI already, don't modify it!
190  PN->replaceAllUsesWith(V);
191  PN->eraseFromParent();
192  continue;
193  }
194 
195  // Scan this PHI node looking for a use of the PHI node by itself.
196  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
197  if (PN->getIncomingValue(i) == PN &&
198  L->contains(PN->getIncomingBlock(i)))
199  // We found something tasty to remove.
200  return PN;
201  }
202  return nullptr;
203 }
204 
205 /// If this loop has multiple backedges, try to pull one of them out into
206 /// a nested loop.
207 ///
208 /// This is important for code that looks like
209 /// this:
210 ///
211 /// Loop:
212 /// ...
213 /// br cond, Loop, Next
214 /// ...
215 /// br cond2, Loop, Out
216 ///
217 /// To identify this common case, we look at the PHI nodes in the header of the
218 /// loop. PHI nodes with unchanging values on one backedge correspond to values
219 /// that change in the "outer" loop, but not in the "inner" loop.
220 ///
221 /// If we are able to separate out a loop, return the new outer loop that was
222 /// created.
223 ///
224 static Loop *separateNestedLoop(Loop *L, BasicBlock *Preheader,
225  DominatorTree *DT, LoopInfo *LI,
226  ScalarEvolution *SE, bool PreserveLCSSA,
227  AssumptionCache *AC, MemorySSAUpdater *MSSAU) {
228  // Don't try to separate loops without a preheader.
229  if (!Preheader)
230  return nullptr;
231 
232  // The header is not a landing pad; preheader insertion should ensure this.
233  BasicBlock *Header = L->getHeader();
234  assert(!Header->isEHPad() && "Can't insert backedge to EH pad");
235 
236  PHINode *PN = findPHIToPartitionLoops(L, DT, AC);
237  if (!PN) return nullptr; // No known way to partition.
238 
239  // Pull out all predecessors that have varying values in the loop. This
240  // handles the case when a PHI node has multiple instances of itself as
241  // arguments.
242  SmallVector<BasicBlock*, 8> OuterLoopPreds;
243  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
244  if (PN->getIncomingValue(i) != PN ||
245  !L->contains(PN->getIncomingBlock(i))) {
246  // We can't split indirect control flow edges.
247  if (PN->getIncomingBlock(i)->getTerminator()->isIndirectTerminator())
248  return nullptr;
249  OuterLoopPreds.push_back(PN->getIncomingBlock(i));
250  }
251  }
252  LLVM_DEBUG(dbgs() << "LoopSimplify: Splitting out a new outer loop\n");
253 
254  // If ScalarEvolution is around and knows anything about values in
255  // this loop, tell it to forget them, because we're about to
256  // substantially change it.
257  if (SE)
258  SE->forgetLoop(L);
259 
260  BasicBlock *NewBB = SplitBlockPredecessors(Header, OuterLoopPreds, ".outer",
261  DT, LI, MSSAU, PreserveLCSSA);
262 
263  // Make sure that NewBB is put someplace intelligent, which doesn't mess up
264  // code layout too horribly.
265  placeSplitBlockCarefully(NewBB, OuterLoopPreds, L);
266 
267  // Create the new outer loop.
268  Loop *NewOuter = LI->AllocateLoop();
269 
270  // Change the parent loop to use the outer loop as its child now.
271  if (Loop *Parent = L->getParentLoop())
272  Parent->replaceChildLoopWith(L, NewOuter);
273  else
274  LI->changeTopLevelLoop(L, NewOuter);
275 
276  // L is now a subloop of our outer loop.
277  NewOuter->addChildLoop(L);
278 
279  for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
280  I != E; ++I)
281  NewOuter->addBlockEntry(*I);
282 
283  // Now reset the header in L, which had been moved by
284  // SplitBlockPredecessors for the outer loop.
285  L->moveToHeader(Header);
286 
287  // Determine which blocks should stay in L and which should be moved out to
288  // the Outer loop now.
289  std::set<BasicBlock*> BlocksInL;
290  for (pred_iterator PI=pred_begin(Header), E = pred_end(Header); PI!=E; ++PI) {
291  BasicBlock *P = *PI;
292  if (DT->dominates(Header, P))
293  addBlockAndPredsToSet(P, Header, BlocksInL);
294  }
295 
296  // Scan all of the loop children of L, moving them to OuterLoop if they are
297  // not part of the inner loop.
298  const std::vector<Loop*> &SubLoops = L->getSubLoops();
299  for (size_t I = 0; I != SubLoops.size(); )
300  if (BlocksInL.count(SubLoops[I]->getHeader()))
301  ++I; // Loop remains in L
302  else
303  NewOuter->addChildLoop(L->removeChildLoop(SubLoops.begin() + I));
304 
305  SmallVector<BasicBlock *, 8> OuterLoopBlocks;
306  OuterLoopBlocks.push_back(NewBB);
307  // Now that we know which blocks are in L and which need to be moved to
308  // OuterLoop, move any blocks that need it.
309  for (unsigned i = 0; i != L->getBlocks().size(); ++i) {
310  BasicBlock *BB = L->getBlocks()[i];
311  if (!BlocksInL.count(BB)) {
312  // Move this block to the parent, updating the exit blocks sets
313  L->removeBlockFromLoop(BB);
314  if ((*LI)[BB] == L) {
315  LI->changeLoopFor(BB, NewOuter);
316  OuterLoopBlocks.push_back(BB);
317  }
318  --i;
319  }
320  }
321 
322  // Split edges to exit blocks from the inner loop, if they emerged in the
323  // process of separating the outer one.
324  formDedicatedExitBlocks(L, DT, LI, MSSAU, PreserveLCSSA);
325 
326  if (PreserveLCSSA) {
327  // Fix LCSSA form for L. Some values, which previously were only used inside
328  // L, can now be used in NewOuter loop. We need to insert phi-nodes for them
329  // in corresponding exit blocks.
330  // We don't need to form LCSSA recursively, because there cannot be uses
331  // inside a newly created loop of defs from inner loops as those would
332  // already be a use of an LCSSA phi node.
333  formLCSSA(*L, *DT, LI, SE);
334 
335  assert(NewOuter->isRecursivelyLCSSAForm(*DT, *LI) &&
336  "LCSSA is broken after separating nested loops!");
337  }
338 
339  return NewOuter;
340 }
341 
342 /// This method is called when the specified loop has more than one
343 /// backedge in it.
344 ///
345 /// If this occurs, revector all of these backedges to target a new basic block
346 /// and have that block branch to the loop header. This ensures that loops
347 /// have exactly one backedge.
349  DominatorTree *DT, LoopInfo *LI,
350  MemorySSAUpdater *MSSAU) {
351  assert(L->getNumBackEdges() > 1 && "Must have > 1 backedge!");
352 
353  // Get information about the loop
354  BasicBlock *Header = L->getHeader();
355  Function *F = Header->getParent();
356 
357  // Unique backedge insertion currently depends on having a preheader.
358  if (!Preheader)
359  return nullptr;
360 
361  // The header is not an EH pad; preheader insertion should ensure this.
362  assert(!Header->isEHPad() && "Can't insert backedge to EH pad");
363 
364  // Figure out which basic blocks contain back-edges to the loop header.
365  std::vector<BasicBlock*> BackedgeBlocks;
366  for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I){
367  BasicBlock *P = *I;
368 
369  // Indirect edges cannot be split, so we must fail if we find one.
371  return nullptr;
372 
373  if (P != Preheader) BackedgeBlocks.push_back(P);
374  }
375 
376  // Create and insert the new backedge block...
377  BasicBlock *BEBlock = BasicBlock::Create(Header->getContext(),
378  Header->getName() + ".backedge", F);
379  BranchInst *BETerminator = BranchInst::Create(Header, BEBlock);
380  BETerminator->setDebugLoc(Header->getFirstNonPHI()->getDebugLoc());
381 
382  LLVM_DEBUG(dbgs() << "LoopSimplify: Inserting unique backedge block "
383  << BEBlock->getName() << "\n");
384 
385  // Move the new backedge block to right after the last backedge block.
386  Function::iterator InsertPos = ++BackedgeBlocks.back()->getIterator();
387  F->getBasicBlockList().splice(InsertPos, F->getBasicBlockList(), BEBlock);
388 
389  // Now that the block has been inserted into the function, create PHI nodes in
390  // the backedge block which correspond to any PHI nodes in the header block.
391  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
392  PHINode *PN = cast<PHINode>(I);
393  PHINode *NewPN = PHINode::Create(PN->getType(), BackedgeBlocks.size(),
394  PN->getName()+".be", BETerminator);
395 
396  // Loop over the PHI node, moving all entries except the one for the
397  // preheader over to the new PHI node.
398  unsigned PreheaderIdx = ~0U;
399  bool HasUniqueIncomingValue = true;
400  Value *UniqueValue = nullptr;
401  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
402  BasicBlock *IBB = PN->getIncomingBlock(i);
403  Value *IV = PN->getIncomingValue(i);
404  if (IBB == Preheader) {
405  PreheaderIdx = i;
406  } else {
407  NewPN->addIncoming(IV, IBB);
408  if (HasUniqueIncomingValue) {
409  if (!UniqueValue)
410  UniqueValue = IV;
411  else if (UniqueValue != IV)
412  HasUniqueIncomingValue = false;
413  }
414  }
415  }
416 
417  // Delete all of the incoming values from the old PN except the preheader's
418  assert(PreheaderIdx != ~0U && "PHI has no preheader entry??");
419  if (PreheaderIdx != 0) {
420  PN->setIncomingValue(0, PN->getIncomingValue(PreheaderIdx));
421  PN->setIncomingBlock(0, PN->getIncomingBlock(PreheaderIdx));
422  }
423  // Nuke all entries except the zero'th.
424  for (unsigned i = 0, e = PN->getNumIncomingValues()-1; i != e; ++i)
425  PN->removeIncomingValue(e-i, false);
426 
427  // Finally, add the newly constructed PHI node as the entry for the BEBlock.
428  PN->addIncoming(NewPN, BEBlock);
429 
430  // As an optimization, if all incoming values in the new PhiNode (which is a
431  // subset of the incoming values of the old PHI node) have the same value,
432  // eliminate the PHI Node.
433  if (HasUniqueIncomingValue) {
434  NewPN->replaceAllUsesWith(UniqueValue);
435  BEBlock->getInstList().erase(NewPN);
436  }
437  }
438 
439  // Now that all of the PHI nodes have been inserted and adjusted, modify the
440  // backedge blocks to jump to the BEBlock instead of the header.
441  // If one of the backedges has llvm.loop metadata attached, we remove
442  // it from the backedge and add it to BEBlock.
443  unsigned LoopMDKind = BEBlock->getContext().getMDKindID("llvm.loop");
444  MDNode *LoopMD = nullptr;
445  for (unsigned i = 0, e = BackedgeBlocks.size(); i != e; ++i) {
446  Instruction *TI = BackedgeBlocks[i]->getTerminator();
447  if (!LoopMD)
448  LoopMD = TI->getMetadata(LoopMDKind);
449  TI->setMetadata(LoopMDKind, nullptr);
450  TI->replaceSuccessorWith(Header, BEBlock);
451  }
452  BEBlock->getTerminator()->setMetadata(LoopMDKind, LoopMD);
453 
454  //===--- Update all analyses which we must preserve now -----------------===//
455 
456  // Update Loop Information - we know that this block is now in the current
457  // loop and all parent loops.
458  L->addBasicBlockToLoop(BEBlock, *LI);
459 
460  // Update dominator information
461  DT->splitBlock(BEBlock);
462 
463  if (MSSAU)
464  MSSAU->updatePhisWhenInsertingUniqueBackedgeBlock(Header, Preheader,
465  BEBlock);
466 
467  return BEBlock;
468 }
469 
470 /// Simplify one loop and queue further loops for simplification.
471 static bool simplifyOneLoop(Loop *L, SmallVectorImpl<Loop *> &Worklist,
472  DominatorTree *DT, LoopInfo *LI,
474  MemorySSAUpdater *MSSAU, bool PreserveLCSSA) {
475  bool Changed = false;
476  if (MSSAU && VerifyMemorySSA)
477  MSSAU->getMemorySSA()->verifyMemorySSA();
478 
479 ReprocessLoop:
480 
481  // Check to see that no blocks (other than the header) in this loop have
482  // predecessors that are not in the loop. This is not valid for natural
483  // loops, but can occur if the blocks are unreachable. Since they are
484  // unreachable we can just shamelessly delete those CFG edges!
485  for (Loop::block_iterator BB = L->block_begin(), E = L->block_end();
486  BB != E; ++BB) {
487  if (*BB == L->getHeader()) continue;
488 
490  for (pred_iterator PI = pred_begin(*BB),
491  PE = pred_end(*BB); PI != PE; ++PI) {
492  BasicBlock *P = *PI;
493  if (!L->contains(P))
494  BadPreds.insert(P);
495  }
496 
497  // Delete each unique out-of-loop (and thus dead) predecessor.
498  for (BasicBlock *P : BadPreds) {
499 
500  LLVM_DEBUG(dbgs() << "LoopSimplify: Deleting edge from dead predecessor "
501  << P->getName() << "\n");
502 
503  // Zap the dead pred's terminator and replace it with unreachable.
504  Instruction *TI = P->getTerminator();
505  changeToUnreachable(TI, /*UseLLVMTrap=*/false, PreserveLCSSA,
506  /*DTU=*/nullptr, MSSAU);
507  Changed = true;
508  }
509  }
510 
511  if (MSSAU && VerifyMemorySSA)
512  MSSAU->getMemorySSA()->verifyMemorySSA();
513 
514  // If there are exiting blocks with branches on undef, resolve the undef in
515  // the direction which will exit the loop. This will help simplify loop
516  // trip count computations.
517  SmallVector<BasicBlock*, 8> ExitingBlocks;
518  L->getExitingBlocks(ExitingBlocks);
519  for (BasicBlock *ExitingBlock : ExitingBlocks)
520  if (BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator()))
521  if (BI->isConditional()) {
522  if (UndefValue *Cond = dyn_cast<UndefValue>(BI->getCondition())) {
523 
524  LLVM_DEBUG(dbgs()
525  << "LoopSimplify: Resolving \"br i1 undef\" to exit in "
526  << ExitingBlock->getName() << "\n");
527 
528  BI->setCondition(ConstantInt::get(Cond->getType(),
529  !L->contains(BI->getSuccessor(0))));
530 
531  Changed = true;
532  }
533  }
534 
535  // Does the loop already have a preheader? If so, don't insert one.
536  BasicBlock *Preheader = L->getLoopPreheader();
537  if (!Preheader) {
538  Preheader = InsertPreheaderForLoop(L, DT, LI, MSSAU, PreserveLCSSA);
539  if (Preheader)
540  Changed = true;
541  }
542 
543  // Next, check to make sure that all exit nodes of the loop only have
544  // predecessors that are inside of the loop. This check guarantees that the
545  // loop preheader/header will dominate the exit blocks. If the exit block has
546  // predecessors from outside of the loop, split the edge now.
547  if (formDedicatedExitBlocks(L, DT, LI, MSSAU, PreserveLCSSA))
548  Changed = true;
549 
550  if (MSSAU && VerifyMemorySSA)
551  MSSAU->getMemorySSA()->verifyMemorySSA();
552 
553  // If the header has more than two predecessors at this point (from the
554  // preheader and from multiple backedges), we must adjust the loop.
555  BasicBlock *LoopLatch = L->getLoopLatch();
556  if (!LoopLatch) {
557  // If this is really a nested loop, rip it out into a child loop. Don't do
558  // this for loops with a giant number of backedges, just factor them into a
559  // common backedge instead.
560  if (L->getNumBackEdges() < 8) {
561  if (Loop *OuterL = separateNestedLoop(L, Preheader, DT, LI, SE,
562  PreserveLCSSA, AC, MSSAU)) {
563  ++NumNested;
564  // Enqueue the outer loop as it should be processed next in our
565  // depth-first nest walk.
566  Worklist.push_back(OuterL);
567 
568  // This is a big restructuring change, reprocess the whole loop.
569  Changed = true;
570  // GCC doesn't tail recursion eliminate this.
571  // FIXME: It isn't clear we can't rely on LLVM to TRE this.
572  goto ReprocessLoop;
573  }
574  }
575 
576  // If we either couldn't, or didn't want to, identify nesting of the loops,
577  // insert a new block that all backedges target, then make it jump to the
578  // loop header.
579  LoopLatch = insertUniqueBackedgeBlock(L, Preheader, DT, LI, MSSAU);
580  if (LoopLatch)
581  Changed = true;
582  }
583 
584  if (MSSAU && VerifyMemorySSA)
585  MSSAU->getMemorySSA()->verifyMemorySSA();
586 
587  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
588 
589  // Scan over the PHI nodes in the loop header. Since they now have only two
590  // incoming values (the loop is canonicalized), we may have simplified the PHI
591  // down to 'X = phi [X, Y]', which should be replaced with 'Y'.
592  PHINode *PN;
593  for (BasicBlock::iterator I = L->getHeader()->begin();
594  (PN = dyn_cast<PHINode>(I++)); )
595  if (Value *V = SimplifyInstruction(PN, {DL, nullptr, DT, AC})) {
596  if (SE) SE->forgetValue(PN);
597  if (!PreserveLCSSA || LI->replacementPreservesLCSSAForm(PN, V)) {
598  PN->replaceAllUsesWith(V);
599  PN->eraseFromParent();
600  }
601  }
602 
603  // If this loop has multiple exits and the exits all go to the same
604  // block, attempt to merge the exits. This helps several passes, such
605  // as LoopRotation, which do not support loops with multiple exits.
606  // SimplifyCFG also does this (and this code uses the same utility
607  // function), however this code is loop-aware, where SimplifyCFG is
608  // not. That gives it the advantage of being able to hoist
609  // loop-invariant instructions out of the way to open up more
610  // opportunities, and the disadvantage of having the responsibility
611  // to preserve dominator information.
612  auto HasUniqueExitBlock = [&]() {
613  BasicBlock *UniqueExit = nullptr;
614  for (auto *ExitingBB : ExitingBlocks)
615  for (auto *SuccBB : successors(ExitingBB)) {
616  if (L->contains(SuccBB))
617  continue;
618 
619  if (!UniqueExit)
620  UniqueExit = SuccBB;
621  else if (UniqueExit != SuccBB)
622  return false;
623  }
624 
625  return true;
626  };
627  if (HasUniqueExitBlock()) {
628  for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
629  BasicBlock *ExitingBlock = ExitingBlocks[i];
630  if (!ExitingBlock->getSinglePredecessor()) continue;
631  BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
632  if (!BI || !BI->isConditional()) continue;
633  CmpInst *CI = dyn_cast<CmpInst>(BI->getCondition());
634  if (!CI || CI->getParent() != ExitingBlock) continue;
635 
636  // Attempt to hoist out all instructions except for the
637  // comparison and the branch.
638  bool AllInvariant = true;
639  bool AnyInvariant = false;
640  for (auto I = ExitingBlock->instructionsWithoutDebug().begin(); &*I != BI; ) {
641  Instruction *Inst = &*I++;
642  if (Inst == CI)
643  continue;
644  if (!L->makeLoopInvariant(
645  Inst, AnyInvariant,
646  Preheader ? Preheader->getTerminator() : nullptr, MSSAU)) {
647  AllInvariant = false;
648  break;
649  }
650  }
651  if (AnyInvariant) {
652  Changed = true;
653  // The loop disposition of all SCEV expressions that depend on any
654  // hoisted values have also changed.
655  if (SE)
656  SE->forgetLoopDispositions(L);
657  }
658  if (!AllInvariant) continue;
659 
660  // The block has now been cleared of all instructions except for
661  // a comparison and a conditional branch. SimplifyCFG may be able
662  // to fold it now.
663  if (!FoldBranchToCommonDest(BI, MSSAU))
664  continue;
665 
666  // Success. The block is now dead, so remove it from the loop,
667  // update the dominator tree and delete it.
668  LLVM_DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block "
669  << ExitingBlock->getName() << "\n");
670 
671  assert(pred_begin(ExitingBlock) == pred_end(ExitingBlock));
672  Changed = true;
673  LI->removeBlock(ExitingBlock);
674 
675  DomTreeNode *Node = DT->getNode(ExitingBlock);
676  const std::vector<DomTreeNodeBase<BasicBlock> *> &Children =
677  Node->getChildren();
678  while (!Children.empty()) {
679  DomTreeNode *Child = Children.front();
680  DT->changeImmediateDominator(Child, Node->getIDom());
681  }
682  DT->eraseNode(ExitingBlock);
683  if (MSSAU) {
684  SmallPtrSet<BasicBlock *, 1> ExitBlockSet{ExitingBlock};
685  MSSAU->removeBlocks(ExitBlockSet);
686  }
687 
689  ExitingBlock, /* KeepOneInputPHIs */ PreserveLCSSA);
691  ExitingBlock, /* KeepOneInputPHIs */ PreserveLCSSA);
692  ExitingBlock->eraseFromParent();
693  }
694  }
695 
696  // Changing exit conditions for blocks may affect exit counts of this loop and
697  // any of its paretns, so we must invalidate the entire subtree if we've made
698  // any changes.
699  if (Changed && SE)
700  SE->forgetTopmostLoop(L);
701 
702  if (MSSAU && VerifyMemorySSA)
703  MSSAU->getMemorySSA()->verifyMemorySSA();
704 
705  return Changed;
706 }
707 
710  MemorySSAUpdater *MSSAU, bool PreserveLCSSA) {
711  bool Changed = false;
712 
713 #ifndef NDEBUG
714  // If we're asked to preserve LCSSA, the loop nest needs to start in LCSSA
715  // form.
716  if (PreserveLCSSA) {
717  assert(DT && "DT not available.");
718  assert(LI && "LI not available.");
719  assert(L->isRecursivelyLCSSAForm(*DT, *LI) &&
720  "Requested to preserve LCSSA, but it's already broken.");
721  }
722 #endif
723 
724  // Worklist maintains our depth-first queue of loops in this nest to process.
725  SmallVector<Loop *, 4> Worklist;
726  Worklist.push_back(L);
727 
728  // Walk the worklist from front to back, pushing newly found sub loops onto
729  // the back. This will let us process loops from back to front in depth-first
730  // order. We can use this simple process because loops form a tree.
731  for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) {
732  Loop *L2 = Worklist[Idx];
733  Worklist.append(L2->begin(), L2->end());
734  }
735 
736  while (!Worklist.empty())
737  Changed |= simplifyOneLoop(Worklist.pop_back_val(), Worklist, DT, LI, SE,
738  AC, MSSAU, PreserveLCSSA);
739 
740  return Changed;
741 }
742 
743 namespace {
744  struct LoopSimplify : public FunctionPass {
745  static char ID; // Pass identification, replacement for typeid
746  LoopSimplify() : FunctionPass(ID) {
748  }
749 
750  bool runOnFunction(Function &F) override;
751 
752  void getAnalysisUsage(AnalysisUsage &AU) const override {
754 
755  // We need loop information to identify the loops...
758 
761 
769  AU.addPreservedID(BreakCriticalEdgesID); // No critical edges added.
773  }
774 
775  /// verifyAnalysis() - Verify LoopSimplifyForm's guarantees.
776  void verifyAnalysis() const override;
777  };
778 }
779 
780 char LoopSimplify::ID = 0;
781 INITIALIZE_PASS_BEGIN(LoopSimplify, "loop-simplify",
782  "Canonicalize natural loops", false, false)
786 INITIALIZE_PASS_END(LoopSimplify, "loop-simplify",
787  "Canonicalize natural loops", false, false)
788 
789 // Publicly exposed interface to pass...
790 char &llvm::LoopSimplifyID = LoopSimplify::ID;
791 Pass *llvm::createLoopSimplifyPass() { return new LoopSimplify(); }
792 
793 /// runOnFunction - Run down all loops in the CFG (recursively, but we could do
794 /// it in any convenient order) inserting preheaders...
795 ///
797  bool Changed = false;
798  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
799  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
800  auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
801  ScalarEvolution *SE = SEWP ? &SEWP->getSE() : nullptr;
802  AssumptionCache *AC =
803  &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
804  MemorySSA *MSSA = nullptr;
805  std::unique_ptr<MemorySSAUpdater> MSSAU;
807  auto *MSSAAnalysis = getAnalysisIfAvailable<MemorySSAWrapperPass>();
808  if (MSSAAnalysis) {
809  MSSA = &MSSAAnalysis->getMSSA();
810  MSSAU = make_unique<MemorySSAUpdater>(MSSA);
811  }
812  }
813 
814  bool PreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
815 
816  // Simplify each loop nest in the function.
817  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
818  Changed |= simplifyLoop(*I, DT, LI, SE, AC, MSSAU.get(), PreserveLCSSA);
819 
820 #ifndef NDEBUG
821  if (PreserveLCSSA) {
822  bool InLCSSA = all_of(
823  *LI, [&](Loop *L) { return L->isRecursivelyLCSSAForm(*DT, *LI); });
824  assert(InLCSSA && "LCSSA is broken after loop-simplify.");
825  }
826 #endif
827  return Changed;
828 }
829 
832  bool Changed = false;
833  LoopInfo *LI = &AM.getResult<LoopAnalysis>(F);
837 
838  // Note that we don't preserve LCSSA in the new PM, if you need it run LCSSA
839  // after simplifying the loops. MemorySSA is not preserved either.
840  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
841  Changed |=
842  simplifyLoop(*I, DT, LI, SE, AC, nullptr, /*PreserveLCSSA*/ false);
843 
844  if (!Changed)
845  return PreservedAnalyses::all();
846 
849  PA.preserve<LoopAnalysis>();
850  PA.preserve<BasicAA>();
851  PA.preserve<GlobalsAA>();
852  PA.preserve<SCEVAA>();
855  // BPI maps conditional terminators to probabilities, LoopSimplify can insert
856  // blocks, but it does so only by splitting existing blocks and edges. This
857  // results in the interesting property that all new terminators inserted are
858  // unconditional branches which do not appear in BPI. All deletions are
859  // handled via ValueHandle callbacks w/in BPI.
861  return PA;
862 }
863 
864 // FIXME: Restore this code when we re-enable verification in verifyAnalysis
865 // below.
866 #if 0
867 static void verifyLoop(Loop *L) {
868  // Verify subloops.
869  for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
870  verifyLoop(*I);
871 
872  // It used to be possible to just assert L->isLoopSimplifyForm(), however
873  // with the introduction of indirectbr, there are now cases where it's
874  // not possible to transform a loop as necessary. We can at least check
875  // that there is an indirectbr near any time there's trouble.
876 
877  // Indirectbr can interfere with preheader and unique backedge insertion.
878  if (!L->getLoopPreheader() || !L->getLoopLatch()) {
879  bool HasIndBrPred = false;
880  for (pred_iterator PI = pred_begin(L->getHeader()),
881  PE = pred_end(L->getHeader()); PI != PE; ++PI)
882  if (isa<IndirectBrInst>((*PI)->getTerminator())) {
883  HasIndBrPred = true;
884  break;
885  }
886  assert(HasIndBrPred &&
887  "LoopSimplify has no excuse for missing loop header info!");
888  (void)HasIndBrPred;
889  }
890 
891  // Indirectbr can interfere with exit block canonicalization.
892  if (!L->hasDedicatedExits()) {
893  bool HasIndBrExiting = false;
894  SmallVector<BasicBlock*, 8> ExitingBlocks;
895  L->getExitingBlocks(ExitingBlocks);
896  for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
897  if (isa<IndirectBrInst>((ExitingBlocks[i])->getTerminator())) {
898  HasIndBrExiting = true;
899  break;
900  }
901  }
902 
903  assert(HasIndBrExiting &&
904  "LoopSimplify has no excuse for missing exit block info!");
905  (void)HasIndBrExiting;
906  }
907 }
908 #endif
909 
910 void LoopSimplify::verifyAnalysis() const {
911  // FIXME: This routine is being called mid-way through the loop pass manager
912  // as loop passes destroy this analysis. That's actually fine, but we have no
913  // way of expressing that here. Once all of the passes that destroy this are
914  // hoisted out of the loop pass manager we can add back verification here.
915 #if 0
916  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
917  verifyLoop(*I);
918 #endif
919 }
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:722
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, MemorySSAUpdater *MSSAU, bool PreserveLCSSA)
Simplify each loop in a loop nest recursively.
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.
bool VerifyMemorySSA
Enables verification of MemorySSA.
Definition: MemorySSA.cpp:82
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:776
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:155
iterator end()
Definition: Function.h:674
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:416
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:415
LoopT * removeChildLoop(iterator I)
This removes the specified child from being a subloop of this loop.
Definition: LoopInfo.h:376
The main scalar evolution driver.
void removeBlocks(const SmallPtrSetImpl< BasicBlock *> &DeadBlocks)
Remove all MemoryAcceses in a set of BasicBlocks about to be deleted.
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.
A cache of @llvm.assume calls within a function.
void replaceSuccessorWith(BasicBlock *OldBB, BasicBlock *NewBB)
Replace specified successor OldBB to point at the provided block.
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:1192
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)
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Value * getCondition() const
static Loop * separateNestedLoop(Loop *L, BasicBlock *Preheader, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, bool PreserveLCSSA, AssumptionCache *AC, MemorySSAUpdater *MSSAU)
If this loop has multiple backedges, try to pull one of them out into a nested loop.
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
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
Legacy analysis pass which computes MemorySSA.
Definition: MemorySSA.h:963
unsigned getNumBackEdges() const
Calculate the number of back edges to the loop header.
Definition: LoopInfo.h:229
Value * removeIncomingValue(unsigned Idx, bool DeletePHIIfEmpty=true)
Remove an incoming value.
This is the interface for a SCEV-based alias analysis.
MemorySSA * getMemorySSA() const
Get handle on MemorySSA.
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:369
&#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:395
Encapsulates MemorySSA, including all data associated with memory accesses.
Definition: MemorySSA.h:703
std::vector< Loop *>::const_iterator iterator
iterator/begin/end - The interface to the top-level loops in the current function.
Definition: LoopInfo.h:864
Analysis pass that exposes the LoopInfo for a function.
Definition: LoopInfo.h:1147
BlockT * getHeader() const
Definition: LoopInfo.h:102
Analysis pass which computes BranchProbabilityInfo.
std::vector< Loop *>::const_iterator iterator
Definition: LoopInfo.h:141
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
Legacy analysis pass which computes BranchProbabilityInfo.
bool formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI, MemorySSAUpdater *MSSAU, bool PreserveLCSSA)
Ensure that all exit blocks of the loop are dedicated exits.
Definition: LoopUtils.cpp:49
void forgetLoopDispositions(const Loop *L)
Called when the client has changed the disposition of values in this loop.
bool FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU=nullptr, 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 ...
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...
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
void updatePhisWhenInsertingUniqueBackedgeBlock(BasicBlock *LoopHeader, BasicBlock *LoopPreheader, BasicBlock *BackedgeBlock)
Update MemorySSA when inserting a unique backedge block for a loop.
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")
static bool simplifyOneLoop(Loop *L, SmallVectorImpl< Loop *> &Worklist, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, MemorySSAUpdater *MSSAU, bool PreserveLCSSA)
Simplify one loop and queue further loops for simplification.
This file contains the declarations for the subclasses of Constant, which represent the different fla...
iterator end() const
Definition: LoopInfo.h:868
char & LCSSAID
Definition: LCSSA.cpp:467
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:1222
char & LoopSimplifyID
bool formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution *SE)
Put loop into LCSSA form.
Definition: LCSSA.cpp:320
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:112
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)
void verifyMemorySSA() const
Verify that MemorySSA is self consistent (IE definitions dominate all uses, uses appear in the right ...
Definition: MemorySSA.cpp:1848
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:837
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:144
LoopT * AllocateLoop(ArgsTy &&... Args)
Definition: LoopInfo.h:856
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:374
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:631
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:867
Analysis pass that exposes the ScalarEvolution for a function.
LoopT * getParentLoop() const
Definition: LoopInfo.h:103
const std::vector< LoopT * > & getSubLoops() const
Return the loops contained entirely within this loop.
Definition: LoopInfo.h:133
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:367
cl::opt< bool > EnableMSSALoopDependency
Enables memory ssa as a dependency for loop passes.
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:55
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:501
ArrayRef< BlockT * > getBlocks() const
Get a list of the basic blocks which make up this loop.
Definition: LoopInfo.h:151
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:795
void changeTopLevelLoop(LoopT *OldLoop, LoopT *NewLoop)
Replace the specified loop in the top-level loops list with the indicated loop.
Definition: LoopInfo.h:934
iterator end() const
Definition: LoopInfo.h:145
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:332
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h:649
block_iterator block_end() const
Definition: LoopInfo.h:157
void changeLoopFor(BlockT *BB, LoopT *L)
Change the top-level loop that contains BB to the specified loop.
Definition: LoopInfo.h:924
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:432
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:406
LLVM Value Representation.
Definition: Value.h:72
succ_range successors(Instruction *I)
Definition: CFG.h:259
static BasicBlock * insertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader, DominatorTree *DT, LoopInfo *LI, MemorySSAUpdater *MSSAU)
This method is called when the specified loop has more than one backedge in it.
BasicBlock * InsertPreheaderForLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, MemorySSAUpdater *MSSAU, bool PreserveLCSSA)
InsertPreheaderForLoop - Once we discover that a loop doesn&#39;t have a preheader, this method is called...
This file exposes an interface to building/using memory SSA to walk memory instructions using a use/d...
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:1172
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:1034
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:156
Value * SimplifyInstruction(Instruction *I, const SimplifyQuery &Q, OptimizationRemarkEmitter *ORE=nullptr)
See if we can compute a simplified version of this instruction.
unsigned changeToUnreachable(Instruction *I, bool UseLLVMTrap, bool PreserveLCSSA=false, DomTreeUpdater *DTU=nullptr, MemorySSAUpdater *MSSAU=nullptr)
Insert an unreachable instruction before the specified instruction, making it and the rest of the cod...
Definition: Local.cpp:1917
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:951
const BasicBlock * getParent() const
Definition: Instruction.h:66
Legacy wrapper pass to provide the BasicAAResult object.
void forgetTopmostLoop(const Loop *L)
bool makeLoopInvariant(Value *V, bool &Changed, Instruction *InsertPt=nullptr, MemorySSAUpdater *MSSAU=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:71