LLVM  8.0.0svn
LoopUnrollRuntime.cpp
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1 //===-- UnrollLoopRuntime.cpp - Runtime Loop unrolling utilities ----------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements some loop unrolling utilities for loops with run-time
11 // trip counts. See LoopUnroll.cpp for unrolling loops with compile-time
12 // trip counts.
13 //
14 // The functions in this file are used to generate extra code when the
15 // run-time trip count modulo the unroll factor is not 0. When this is the
16 // case, we need to generate code to execute these 'left over' iterations.
17 //
18 // The current strategy generates an if-then-else sequence prior to the
19 // unrolled loop to execute the 'left over' iterations before or after the
20 // unrolled loop.
21 //
22 //===----------------------------------------------------------------------===//
23 
24 #include "llvm/ADT/SmallPtrSet.h"
25 #include "llvm/ADT/Statistic.h"
30 #include "llvm/IR/BasicBlock.h"
31 #include "llvm/IR/Dominators.h"
32 #include "llvm/IR/Metadata.h"
33 #include "llvm/IR/Module.h"
34 #include "llvm/Support/Debug.h"
36 #include "llvm/Transforms/Utils.h"
41 #include <algorithm>
42 
43 using namespace llvm;
44 
45 #define DEBUG_TYPE "loop-unroll"
46 
47 STATISTIC(NumRuntimeUnrolled,
48  "Number of loops unrolled with run-time trip counts");
50  "unroll-runtime-multi-exit", cl::init(false), cl::Hidden,
51  cl::desc("Allow runtime unrolling for loops with multiple exits, when "
52  "epilog is generated"));
53 
54 /// Connect the unrolling prolog code to the original loop.
55 /// The unrolling prolog code contains code to execute the
56 /// 'extra' iterations if the run-time trip count modulo the
57 /// unroll count is non-zero.
58 ///
59 /// This function performs the following:
60 /// - Create PHI nodes at prolog end block to combine values
61 /// that exit the prolog code and jump around the prolog.
62 /// - Add a PHI operand to a PHI node at the loop exit block
63 /// for values that exit the prolog and go around the loop.
64 /// - Branch around the original loop if the trip count is less
65 /// than the unroll factor.
66 ///
67 static void ConnectProlog(Loop *L, Value *BECount, unsigned Count,
68  BasicBlock *PrologExit,
69  BasicBlock *OriginalLoopLatchExit,
70  BasicBlock *PreHeader, BasicBlock *NewPreHeader,
72  LoopInfo *LI, bool PreserveLCSSA) {
73  BasicBlock *Latch = L->getLoopLatch();
74  assert(Latch && "Loop must have a latch");
75  BasicBlock *PrologLatch = cast<BasicBlock>(VMap[Latch]);
76 
77  // Create a PHI node for each outgoing value from the original loop
78  // (which means it is an outgoing value from the prolog code too).
79  // The new PHI node is inserted in the prolog end basic block.
80  // The new PHI node value is added as an operand of a PHI node in either
81  // the loop header or the loop exit block.
82  for (BasicBlock *Succ : successors(Latch)) {
83  for (PHINode &PN : Succ->phis()) {
84  // Add a new PHI node to the prolog end block and add the
85  // appropriate incoming values.
86  PHINode *NewPN = PHINode::Create(PN.getType(), 2, PN.getName() + ".unr",
87  PrologExit->getFirstNonPHI());
88  // Adding a value to the new PHI node from the original loop preheader.
89  // This is the value that skips all the prolog code.
90  if (L->contains(&PN)) {
91  NewPN->addIncoming(PN.getIncomingValueForBlock(NewPreHeader),
92  PreHeader);
93  } else {
94  NewPN->addIncoming(UndefValue::get(PN.getType()), PreHeader);
95  }
96 
97  Value *V = PN.getIncomingValueForBlock(Latch);
98  if (Instruction *I = dyn_cast<Instruction>(V)) {
99  if (L->contains(I)) {
100  V = VMap.lookup(I);
101  }
102  }
103  // Adding a value to the new PHI node from the last prolog block
104  // that was created.
105  NewPN->addIncoming(V, PrologLatch);
106 
107  // Update the existing PHI node operand with the value from the
108  // new PHI node. How this is done depends on if the existing
109  // PHI node is in the original loop block, or the exit block.
110  if (L->contains(&PN)) {
111  PN.setIncomingValue(PN.getBasicBlockIndex(NewPreHeader), NewPN);
112  } else {
113  PN.addIncoming(NewPN, PrologExit);
114  }
115  }
116  }
117 
118  // Make sure that created prolog loop is in simplified form
119  SmallVector<BasicBlock *, 4> PrologExitPreds;
120  Loop *PrologLoop = LI->getLoopFor(PrologLatch);
121  if (PrologLoop) {
122  for (BasicBlock *PredBB : predecessors(PrologExit))
123  if (PrologLoop->contains(PredBB))
124  PrologExitPreds.push_back(PredBB);
125 
126  SplitBlockPredecessors(PrologExit, PrologExitPreds, ".unr-lcssa", DT, LI,
127  nullptr, PreserveLCSSA);
128  }
129 
130  // Create a branch around the original loop, which is taken if there are no
131  // iterations remaining to be executed after running the prologue.
132  Instruction *InsertPt = PrologExit->getTerminator();
133  IRBuilder<> B(InsertPt);
134 
135  assert(Count != 0 && "nonsensical Count!");
136 
137  // If BECount <u (Count - 1) then (BECount + 1) % Count == (BECount + 1)
138  // This means %xtraiter is (BECount + 1) and all of the iterations of this
139  // loop were executed by the prologue. Note that if BECount <u (Count - 1)
140  // then (BECount + 1) cannot unsigned-overflow.
141  Value *BrLoopExit =
142  B.CreateICmpULT(BECount, ConstantInt::get(BECount->getType(), Count - 1));
143  // Split the exit to maintain loop canonicalization guarantees
144  SmallVector<BasicBlock *, 4> Preds(predecessors(OriginalLoopLatchExit));
145  SplitBlockPredecessors(OriginalLoopLatchExit, Preds, ".unr-lcssa", DT, LI,
146  nullptr, PreserveLCSSA);
147  // Add the branch to the exit block (around the unrolled loop)
148  B.CreateCondBr(BrLoopExit, OriginalLoopLatchExit, NewPreHeader);
149  InsertPt->eraseFromParent();
150  if (DT)
151  DT->changeImmediateDominator(OriginalLoopLatchExit, PrologExit);
152 }
153 
154 /// Connect the unrolling epilog code to the original loop.
155 /// The unrolling epilog code contains code to execute the
156 /// 'extra' iterations if the run-time trip count modulo the
157 /// unroll count is non-zero.
158 ///
159 /// This function performs the following:
160 /// - Update PHI nodes at the unrolling loop exit and epilog loop exit
161 /// - Create PHI nodes at the unrolling loop exit to combine
162 /// values that exit the unrolling loop code and jump around it.
163 /// - Update PHI operands in the epilog loop by the new PHI nodes
164 /// - Branch around the epilog loop if extra iters (ModVal) is zero.
165 ///
166 static void ConnectEpilog(Loop *L, Value *ModVal, BasicBlock *NewExit,
167  BasicBlock *Exit, BasicBlock *PreHeader,
168  BasicBlock *EpilogPreHeader, BasicBlock *NewPreHeader,
169  ValueToValueMapTy &VMap, DominatorTree *DT,
170  LoopInfo *LI, bool PreserveLCSSA) {
171  BasicBlock *Latch = L->getLoopLatch();
172  assert(Latch && "Loop must have a latch");
173  BasicBlock *EpilogLatch = cast<BasicBlock>(VMap[Latch]);
174 
175  // Loop structure should be the following:
176  //
177  // PreHeader
178  // NewPreHeader
179  // Header
180  // ...
181  // Latch
182  // NewExit (PN)
183  // EpilogPreHeader
184  // EpilogHeader
185  // ...
186  // EpilogLatch
187  // Exit (EpilogPN)
188 
189  // Update PHI nodes at NewExit and Exit.
190  for (PHINode &PN : NewExit->phis()) {
191  // PN should be used in another PHI located in Exit block as
192  // Exit was split by SplitBlockPredecessors into Exit and NewExit
193  // Basicaly it should look like:
194  // NewExit:
195  // PN = PHI [I, Latch]
196  // ...
197  // Exit:
198  // EpilogPN = PHI [PN, EpilogPreHeader]
199  //
200  // There is EpilogPreHeader incoming block instead of NewExit as
201  // NewExit was spilt 1 more time to get EpilogPreHeader.
202  assert(PN.hasOneUse() && "The phi should have 1 use");
203  PHINode *EpilogPN = cast<PHINode>(PN.use_begin()->getUser());
204  assert(EpilogPN->getParent() == Exit && "EpilogPN should be in Exit block");
205 
206  // Add incoming PreHeader from branch around the Loop
207  PN.addIncoming(UndefValue::get(PN.getType()), PreHeader);
208 
209  Value *V = PN.getIncomingValueForBlock(Latch);
211  if (I && L->contains(I))
212  // If value comes from an instruction in the loop add VMap value.
213  V = VMap.lookup(I);
214  // For the instruction out of the loop, constant or undefined value
215  // insert value itself.
216  EpilogPN->addIncoming(V, EpilogLatch);
217 
218  assert(EpilogPN->getBasicBlockIndex(EpilogPreHeader) >= 0 &&
219  "EpilogPN should have EpilogPreHeader incoming block");
220  // Change EpilogPreHeader incoming block to NewExit.
221  EpilogPN->setIncomingBlock(EpilogPN->getBasicBlockIndex(EpilogPreHeader),
222  NewExit);
223  // Now PHIs should look like:
224  // NewExit:
225  // PN = PHI [I, Latch], [undef, PreHeader]
226  // ...
227  // Exit:
228  // EpilogPN = PHI [PN, NewExit], [VMap[I], EpilogLatch]
229  }
230 
231  // Create PHI nodes at NewExit (from the unrolling loop Latch and PreHeader).
232  // Update corresponding PHI nodes in epilog loop.
233  for (BasicBlock *Succ : successors(Latch)) {
234  // Skip this as we already updated phis in exit blocks.
235  if (!L->contains(Succ))
236  continue;
237  for (PHINode &PN : Succ->phis()) {
238  // Add new PHI nodes to the loop exit block and update epilog
239  // PHIs with the new PHI values.
240  PHINode *NewPN = PHINode::Create(PN.getType(), 2, PN.getName() + ".unr",
241  NewExit->getFirstNonPHI());
242  // Adding a value to the new PHI node from the unrolling loop preheader.
243  NewPN->addIncoming(PN.getIncomingValueForBlock(NewPreHeader), PreHeader);
244  // Adding a value to the new PHI node from the unrolling loop latch.
245  NewPN->addIncoming(PN.getIncomingValueForBlock(Latch), Latch);
246 
247  // Update the existing PHI node operand with the value from the new PHI
248  // node. Corresponding instruction in epilog loop should be PHI.
249  PHINode *VPN = cast<PHINode>(VMap[&PN]);
250  VPN->setIncomingValue(VPN->getBasicBlockIndex(EpilogPreHeader), NewPN);
251  }
252  }
253 
254  Instruction *InsertPt = NewExit->getTerminator();
255  IRBuilder<> B(InsertPt);
256  Value *BrLoopExit = B.CreateIsNotNull(ModVal, "lcmp.mod");
257  assert(Exit && "Loop must have a single exit block only");
258  // Split the epilogue exit to maintain loop canonicalization guarantees
260  SplitBlockPredecessors(Exit, Preds, ".epilog-lcssa", DT, LI, nullptr,
261  PreserveLCSSA);
262  // Add the branch to the exit block (around the unrolling loop)
263  B.CreateCondBr(BrLoopExit, EpilogPreHeader, Exit);
264  InsertPt->eraseFromParent();
265  if (DT)
266  DT->changeImmediateDominator(Exit, NewExit);
267 
268  // Split the main loop exit to maintain canonicalization guarantees.
269  SmallVector<BasicBlock*, 4> NewExitPreds{Latch};
270  SplitBlockPredecessors(NewExit, NewExitPreds, ".loopexit", DT, LI, nullptr,
271  PreserveLCSSA);
272 }
273 
274 /// Create a clone of the blocks in a loop and connect them together.
275 /// If CreateRemainderLoop is false, loop structure will not be cloned,
276 /// otherwise a new loop will be created including all cloned blocks, and the
277 /// iterator of it switches to count NewIter down to 0.
278 /// The cloned blocks should be inserted between InsertTop and InsertBot.
279 /// If loop structure is cloned InsertTop should be new preheader, InsertBot
280 /// new loop exit.
281 /// Return the new cloned loop that is created when CreateRemainderLoop is true.
282 static Loop *
283 CloneLoopBlocks(Loop *L, Value *NewIter, const bool CreateRemainderLoop,
284  const bool UseEpilogRemainder, const bool UnrollRemainder,
285  BasicBlock *InsertTop,
286  BasicBlock *InsertBot, BasicBlock *Preheader,
287  std::vector<BasicBlock *> &NewBlocks, LoopBlocksDFS &LoopBlocks,
288  ValueToValueMapTy &VMap, DominatorTree *DT, LoopInfo *LI) {
289  StringRef suffix = UseEpilogRemainder ? "epil" : "prol";
290  BasicBlock *Header = L->getHeader();
291  BasicBlock *Latch = L->getLoopLatch();
292  Function *F = Header->getParent();
293  LoopBlocksDFS::RPOIterator BlockBegin = LoopBlocks.beginRPO();
294  LoopBlocksDFS::RPOIterator BlockEnd = LoopBlocks.endRPO();
295  Loop *ParentLoop = L->getParentLoop();
296  NewLoopsMap NewLoops;
297  NewLoops[ParentLoop] = ParentLoop;
298  if (!CreateRemainderLoop)
299  NewLoops[L] = ParentLoop;
300 
301  // For each block in the original loop, create a new copy,
302  // and update the value map with the newly created values.
303  for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
304  BasicBlock *NewBB = CloneBasicBlock(*BB, VMap, "." + suffix, F);
305  NewBlocks.push_back(NewBB);
306 
307  // If we're unrolling the outermost loop, there's no remainder loop,
308  // and this block isn't in a nested loop, then the new block is not
309  // in any loop. Otherwise, add it to loopinfo.
310  if (CreateRemainderLoop || LI->getLoopFor(*BB) != L || ParentLoop)
311  addClonedBlockToLoopInfo(*BB, NewBB, LI, NewLoops);
312 
313  VMap[*BB] = NewBB;
314  if (Header == *BB) {
315  // For the first block, add a CFG connection to this newly
316  // created block.
317  InsertTop->getTerminator()->setSuccessor(0, NewBB);
318  }
319 
320  if (DT) {
321  if (Header == *BB) {
322  // The header is dominated by the preheader.
323  DT->addNewBlock(NewBB, InsertTop);
324  } else {
325  // Copy information from original loop to unrolled loop.
326  BasicBlock *IDomBB = DT->getNode(*BB)->getIDom()->getBlock();
327  DT->addNewBlock(NewBB, cast<BasicBlock>(VMap[IDomBB]));
328  }
329  }
330 
331  if (Latch == *BB) {
332  // For the last block, if CreateRemainderLoop is false, create a direct
333  // jump to InsertBot. If not, create a loop back to cloned head.
334  VMap.erase((*BB)->getTerminator());
335  BasicBlock *FirstLoopBB = cast<BasicBlock>(VMap[Header]);
336  BranchInst *LatchBR = cast<BranchInst>(NewBB->getTerminator());
337  IRBuilder<> Builder(LatchBR);
338  if (!CreateRemainderLoop) {
339  Builder.CreateBr(InsertBot);
340  } else {
341  PHINode *NewIdx = PHINode::Create(NewIter->getType(), 2,
342  suffix + ".iter",
343  FirstLoopBB->getFirstNonPHI());
344  Value *IdxSub =
345  Builder.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
346  NewIdx->getName() + ".sub");
347  Value *IdxCmp =
348  Builder.CreateIsNotNull(IdxSub, NewIdx->getName() + ".cmp");
349  Builder.CreateCondBr(IdxCmp, FirstLoopBB, InsertBot);
350  NewIdx->addIncoming(NewIter, InsertTop);
351  NewIdx->addIncoming(IdxSub, NewBB);
352  }
353  LatchBR->eraseFromParent();
354  }
355  }
356 
357  // Change the incoming values to the ones defined in the preheader or
358  // cloned loop.
359  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
360  PHINode *NewPHI = cast<PHINode>(VMap[&*I]);
361  if (!CreateRemainderLoop) {
362  if (UseEpilogRemainder) {
363  unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
364  NewPHI->setIncomingBlock(idx, InsertTop);
365  NewPHI->removeIncomingValue(Latch, false);
366  } else {
367  VMap[&*I] = NewPHI->getIncomingValueForBlock(Preheader);
368  cast<BasicBlock>(VMap[Header])->getInstList().erase(NewPHI);
369  }
370  } else {
371  unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
372  NewPHI->setIncomingBlock(idx, InsertTop);
373  BasicBlock *NewLatch = cast<BasicBlock>(VMap[Latch]);
374  idx = NewPHI->getBasicBlockIndex(Latch);
375  Value *InVal = NewPHI->getIncomingValue(idx);
376  NewPHI->setIncomingBlock(idx, NewLatch);
377  if (Value *V = VMap.lookup(InVal))
378  NewPHI->setIncomingValue(idx, V);
379  }
380  }
381  if (CreateRemainderLoop) {
382  Loop *NewLoop = NewLoops[L];
383  assert(NewLoop && "L should have been cloned");
384 
385  // Only add loop metadata if the loop is not going to be completely
386  // unrolled.
387  if (UnrollRemainder)
388  return NewLoop;
389 
390  // Add unroll disable metadata to disable future unrolling for this loop.
391  NewLoop->setLoopAlreadyUnrolled();
392  return NewLoop;
393  }
394  else
395  return nullptr;
396 }
397 
398 /// Returns true if we can safely unroll a multi-exit/exiting loop. OtherExits
399 /// is populated with all the loop exit blocks other than the LatchExit block.
400 static bool
402  BasicBlock *LatchExit, bool PreserveLCSSA,
403  bool UseEpilogRemainder) {
404 
405  // We currently have some correctness constrains in unrolling a multi-exit
406  // loop. Check for these below.
407 
408  // We rely on LCSSA form being preserved when the exit blocks are transformed.
409  if (!PreserveLCSSA)
410  return false;
412  L->getUniqueExitBlocks(Exits);
413  for (auto *BB : Exits)
414  if (BB != LatchExit)
415  OtherExits.push_back(BB);
416 
417  // TODO: Support multiple exiting blocks jumping to the `LatchExit` when
418  // UnrollRuntimeMultiExit is true. This will need updating the logic in
419  // connectEpilog/connectProlog.
420  if (!LatchExit->getSinglePredecessor()) {
421  LLVM_DEBUG(
422  dbgs() << "Bailout for multi-exit handling when latch exit has >1 "
423  "predecessor.\n");
424  return false;
425  }
426  // FIXME: We bail out of multi-exit unrolling when epilog loop is generated
427  // and L is an inner loop. This is because in presence of multiple exits, the
428  // outer loop is incorrect: we do not add the EpilogPreheader and exit to the
429  // outer loop. This is automatically handled in the prolog case, so we do not
430  // have that bug in prolog generation.
431  if (UseEpilogRemainder && L->getParentLoop())
432  return false;
433 
434  // All constraints have been satisfied.
435  return true;
436 }
437 
438 /// Returns true if we can profitably unroll the multi-exit loop L. Currently,
439 /// we return true only if UnrollRuntimeMultiExit is set to true.
441  Loop *L, SmallVectorImpl<BasicBlock *> &OtherExits, BasicBlock *LatchExit,
442  bool PreserveLCSSA, bool UseEpilogRemainder) {
443 
444 #if !defined(NDEBUG)
445  SmallVector<BasicBlock *, 8> OtherExitsDummyCheck;
446  assert(canSafelyUnrollMultiExitLoop(L, OtherExitsDummyCheck, LatchExit,
447  PreserveLCSSA, UseEpilogRemainder) &&
448  "Should be safe to unroll before checking profitability!");
449 #endif
450 
451  // Priority goes to UnrollRuntimeMultiExit if it's supplied.
452  if (UnrollRuntimeMultiExit.getNumOccurrences())
453  return UnrollRuntimeMultiExit;
454 
455  // The main pain point with multi-exit loop unrolling is that once unrolled,
456  // we will not be able to merge all blocks into a straight line code.
457  // There are branches within the unrolled loop that go to the OtherExits.
458  // The second point is the increase in code size, but this is true
459  // irrespective of multiple exits.
460 
461  // Note: Both the heuristics below are coarse grained. We are essentially
462  // enabling unrolling of loops that have a single side exit other than the
463  // normal LatchExit (i.e. exiting into a deoptimize block).
464  // The heuristics considered are:
465  // 1. low number of branches in the unrolled version.
466  // 2. high predictability of these extra branches.
467  // We avoid unrolling loops that have more than two exiting blocks. This
468  // limits the total number of branches in the unrolled loop to be atmost
469  // the unroll factor (since one of the exiting blocks is the latch block).
470  SmallVector<BasicBlock*, 4> ExitingBlocks;
471  L->getExitingBlocks(ExitingBlocks);
472  if (ExitingBlocks.size() > 2)
473  return false;
474 
475  // The second heuristic is that L has one exit other than the latchexit and
476  // that exit is a deoptimize block. We know that deoptimize blocks are rarely
477  // taken, which also implies the branch leading to the deoptimize block is
478  // highly predictable.
479  return (OtherExits.size() == 1 &&
480  OtherExits[0]->getTerminatingDeoptimizeCall());
481  // TODO: These can be fine-tuned further to consider code size or deopt states
482  // that are captured by the deoptimize exit block.
483  // Also, we can extend this to support more cases, if we actually
484  // know of kinds of multiexit loops that would benefit from unrolling.
485 }
486 
487 /// Insert code in the prolog/epilog code when unrolling a loop with a
488 /// run-time trip-count.
489 ///
490 /// This method assumes that the loop unroll factor is total number
491 /// of loop bodies in the loop after unrolling. (Some folks refer
492 /// to the unroll factor as the number of *extra* copies added).
493 /// We assume also that the loop unroll factor is a power-of-two. So, after
494 /// unrolling the loop, the number of loop bodies executed is 2,
495 /// 4, 8, etc. Note - LLVM converts the if-then-sequence to a switch
496 /// instruction in SimplifyCFG.cpp. Then, the backend decides how code for
497 /// the switch instruction is generated.
498 ///
499 /// ***Prolog case***
500 /// extraiters = tripcount % loopfactor
501 /// if (extraiters == 0) jump Loop:
502 /// else jump Prol:
503 /// Prol: LoopBody;
504 /// extraiters -= 1 // Omitted if unroll factor is 2.
505 /// if (extraiters != 0) jump Prol: // Omitted if unroll factor is 2.
506 /// if (tripcount < loopfactor) jump End:
507 /// Loop:
508 /// ...
509 /// End:
510 ///
511 /// ***Epilog case***
512 /// extraiters = tripcount % loopfactor
513 /// if (tripcount < loopfactor) jump LoopExit:
514 /// unroll_iters = tripcount - extraiters
515 /// Loop: LoopBody; (executes unroll_iter times);
516 /// unroll_iter -= 1
517 /// if (unroll_iter != 0) jump Loop:
518 /// LoopExit:
519 /// if (extraiters == 0) jump EpilExit:
520 /// Epil: LoopBody; (executes extraiters times)
521 /// extraiters -= 1 // Omitted if unroll factor is 2.
522 /// if (extraiters != 0) jump Epil: // Omitted if unroll factor is 2.
523 /// EpilExit:
524 
525 bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
526  bool AllowExpensiveTripCount,
527  bool UseEpilogRemainder,
528  bool UnrollRemainder,
529  LoopInfo *LI, ScalarEvolution *SE,
531  bool PreserveLCSSA) {
532  LLVM_DEBUG(dbgs() << "Trying runtime unrolling on Loop: \n");
533  LLVM_DEBUG(L->dump());
534  LLVM_DEBUG(UseEpilogRemainder ? dbgs() << "Using epilog remainder.\n"
535  : dbgs() << "Using prolog remainder.\n");
536 
537  // Make sure the loop is in canonical form.
538  if (!L->isLoopSimplifyForm()) {
539  LLVM_DEBUG(dbgs() << "Not in simplify form!\n");
540  return false;
541  }
542 
543  // Guaranteed by LoopSimplifyForm.
544  BasicBlock *Latch = L->getLoopLatch();
545  BasicBlock *Header = L->getHeader();
546 
547  BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
548  unsigned ExitIndex = LatchBR->getSuccessor(0) == Header ? 1 : 0;
549  BasicBlock *LatchExit = LatchBR->getSuccessor(ExitIndex);
550  // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the
551  // targets of the Latch be an exit block out of the loop. This needs
552  // to be guaranteed by the callers of UnrollRuntimeLoopRemainder.
553  assert(!L->contains(LatchExit) &&
554  "one of the loop latch successors should be the exit block!");
555  // These are exit blocks other than the target of the latch exiting block.
556  SmallVector<BasicBlock *, 4> OtherExits;
557  bool isMultiExitUnrollingEnabled =
558  canSafelyUnrollMultiExitLoop(L, OtherExits, LatchExit, PreserveLCSSA,
559  UseEpilogRemainder) &&
560  canProfitablyUnrollMultiExitLoop(L, OtherExits, LatchExit, PreserveLCSSA,
561  UseEpilogRemainder);
562  // Support only single exit and exiting block unless multi-exit loop unrolling is enabled.
563  if (!isMultiExitUnrollingEnabled &&
564  (!L->getExitingBlock() || OtherExits.size())) {
565  LLVM_DEBUG(
566  dbgs()
567  << "Multiple exit/exiting blocks in loop and multi-exit unrolling not "
568  "enabled!\n");
569  return false;
570  }
571  // Use Scalar Evolution to compute the trip count. This allows more loops to
572  // be unrolled than relying on induction var simplification.
573  if (!SE)
574  return false;
575 
576  // Only unroll loops with a computable trip count, and the trip count needs
577  // to be an int value (allowing a pointer type is a TODO item).
578  // We calculate the backedge count by using getExitCount on the Latch block,
579  // which is proven to be the only exiting block in this loop. This is same as
580  // calculating getBackedgeTakenCount on the loop (which computes SCEV for all
581  // exiting blocks).
582  const SCEV *BECountSC = SE->getExitCount(L, Latch);
583  if (isa<SCEVCouldNotCompute>(BECountSC) ||
584  !BECountSC->getType()->isIntegerTy()) {
585  LLVM_DEBUG(dbgs() << "Could not compute exit block SCEV\n");
586  return false;
587  }
588 
589  unsigned BEWidth = cast<IntegerType>(BECountSC->getType())->getBitWidth();
590 
591  // Add 1 since the backedge count doesn't include the first loop iteration.
592  const SCEV *TripCountSC =
593  SE->getAddExpr(BECountSC, SE->getConstant(BECountSC->getType(), 1));
594  if (isa<SCEVCouldNotCompute>(TripCountSC)) {
595  LLVM_DEBUG(dbgs() << "Could not compute trip count SCEV.\n");
596  return false;
597  }
598 
599  BasicBlock *PreHeader = L->getLoopPreheader();
600  BranchInst *PreHeaderBR = cast<BranchInst>(PreHeader->getTerminator());
601  const DataLayout &DL = Header->getModule()->getDataLayout();
602  SCEVExpander Expander(*SE, DL, "loop-unroll");
603  if (!AllowExpensiveTripCount &&
604  Expander.isHighCostExpansion(TripCountSC, L, PreHeaderBR)) {
605  LLVM_DEBUG(dbgs() << "High cost for expanding trip count scev!\n");
606  return false;
607  }
608 
609  // This constraint lets us deal with an overflowing trip count easily; see the
610  // comment on ModVal below.
611  if (Log2_32(Count) > BEWidth) {
612  LLVM_DEBUG(
613  dbgs()
614  << "Count failed constraint on overflow trip count calculation.\n");
615  return false;
616  }
617 
618  // Loop structure is the following:
619  //
620  // PreHeader
621  // Header
622  // ...
623  // Latch
624  // LatchExit
625 
626  BasicBlock *NewPreHeader;
627  BasicBlock *NewExit = nullptr;
628  BasicBlock *PrologExit = nullptr;
629  BasicBlock *EpilogPreHeader = nullptr;
630  BasicBlock *PrologPreHeader = nullptr;
631 
632  if (UseEpilogRemainder) {
633  // If epilog remainder
634  // Split PreHeader to insert a branch around loop for unrolling.
635  NewPreHeader = SplitBlock(PreHeader, PreHeader->getTerminator(), DT, LI);
636  NewPreHeader->setName(PreHeader->getName() + ".new");
637  // Split LatchExit to create phi nodes from branch above.
638  SmallVector<BasicBlock*, 4> Preds(predecessors(LatchExit));
639  NewExit = SplitBlockPredecessors(LatchExit, Preds, ".unr-lcssa", DT, LI,
640  nullptr, PreserveLCSSA);
641  // NewExit gets its DebugLoc from LatchExit, which is not part of the
642  // original Loop.
643  // Fix this by setting Loop's DebugLoc to NewExit.
644  auto *NewExitTerminator = NewExit->getTerminator();
645  NewExitTerminator->setDebugLoc(Header->getTerminator()->getDebugLoc());
646  // Split NewExit to insert epilog remainder loop.
647  EpilogPreHeader = SplitBlock(NewExit, NewExitTerminator, DT, LI);
648  EpilogPreHeader->setName(Header->getName() + ".epil.preheader");
649  } else {
650  // If prolog remainder
651  // Split the original preheader twice to insert prolog remainder loop
652  PrologPreHeader = SplitEdge(PreHeader, Header, DT, LI);
653  PrologPreHeader->setName(Header->getName() + ".prol.preheader");
654  PrologExit = SplitBlock(PrologPreHeader, PrologPreHeader->getTerminator(),
655  DT, LI);
656  PrologExit->setName(Header->getName() + ".prol.loopexit");
657  // Split PrologExit to get NewPreHeader.
658  NewPreHeader = SplitBlock(PrologExit, PrologExit->getTerminator(), DT, LI);
659  NewPreHeader->setName(PreHeader->getName() + ".new");
660  }
661  // Loop structure should be the following:
662  // Epilog Prolog
663  //
664  // PreHeader PreHeader
665  // *NewPreHeader *PrologPreHeader
666  // Header *PrologExit
667  // ... *NewPreHeader
668  // Latch Header
669  // *NewExit ...
670  // *EpilogPreHeader Latch
671  // LatchExit LatchExit
672 
673  // Calculate conditions for branch around loop for unrolling
674  // in epilog case and around prolog remainder loop in prolog case.
675  // Compute the number of extra iterations required, which is:
676  // extra iterations = run-time trip count % loop unroll factor
677  PreHeaderBR = cast<BranchInst>(PreHeader->getTerminator());
678  Value *TripCount = Expander.expandCodeFor(TripCountSC, TripCountSC->getType(),
679  PreHeaderBR);
680  Value *BECount = Expander.expandCodeFor(BECountSC, BECountSC->getType(),
681  PreHeaderBR);
682  IRBuilder<> B(PreHeaderBR);
683  Value *ModVal;
684  // Calculate ModVal = (BECount + 1) % Count.
685  // Note that TripCount is BECount + 1.
686  if (isPowerOf2_32(Count)) {
687  // When Count is power of 2 we don't BECount for epilog case, however we'll
688  // need it for a branch around unrolling loop for prolog case.
689  ModVal = B.CreateAnd(TripCount, Count - 1, "xtraiter");
690  // 1. There are no iterations to be run in the prolog/epilog loop.
691  // OR
692  // 2. The addition computing TripCount overflowed.
693  //
694  // If (2) is true, we know that TripCount really is (1 << BEWidth) and so
695  // the number of iterations that remain to be run in the original loop is a
696  // multiple Count == (1 << Log2(Count)) because Log2(Count) <= BEWidth (we
697  // explicitly check this above).
698  } else {
699  // As (BECount + 1) can potentially unsigned overflow we count
700  // (BECount % Count) + 1 which is overflow safe as BECount % Count < Count.
701  Value *ModValTmp = B.CreateURem(BECount,
702  ConstantInt::get(BECount->getType(),
703  Count));
704  Value *ModValAdd = B.CreateAdd(ModValTmp,
705  ConstantInt::get(ModValTmp->getType(), 1));
706  // At that point (BECount % Count) + 1 could be equal to Count.
707  // To handle this case we need to take mod by Count one more time.
708  ModVal = B.CreateURem(ModValAdd,
709  ConstantInt::get(BECount->getType(), Count),
710  "xtraiter");
711  }
712  Value *BranchVal =
713  UseEpilogRemainder ? B.CreateICmpULT(BECount,
714  ConstantInt::get(BECount->getType(),
715  Count - 1)) :
716  B.CreateIsNotNull(ModVal, "lcmp.mod");
717  BasicBlock *RemainderLoop = UseEpilogRemainder ? NewExit : PrologPreHeader;
718  BasicBlock *UnrollingLoop = UseEpilogRemainder ? NewPreHeader : PrologExit;
719  // Branch to either remainder (extra iterations) loop or unrolling loop.
720  B.CreateCondBr(BranchVal, RemainderLoop, UnrollingLoop);
721  PreHeaderBR->eraseFromParent();
722  if (DT) {
723  if (UseEpilogRemainder)
724  DT->changeImmediateDominator(NewExit, PreHeader);
725  else
726  DT->changeImmediateDominator(PrologExit, PreHeader);
727  }
728  Function *F = Header->getParent();
729  // Get an ordered list of blocks in the loop to help with the ordering of the
730  // cloned blocks in the prolog/epilog code
731  LoopBlocksDFS LoopBlocks(L);
732  LoopBlocks.perform(LI);
733 
734  //
735  // For each extra loop iteration, create a copy of the loop's basic blocks
736  // and generate a condition that branches to the copy depending on the
737  // number of 'left over' iterations.
738  //
739  std::vector<BasicBlock *> NewBlocks;
740  ValueToValueMapTy VMap;
741 
742  // For unroll factor 2 remainder loop will have 1 iterations.
743  // Do not create 1 iteration loop.
744  bool CreateRemainderLoop = (Count != 2);
745 
746  // Clone all the basic blocks in the loop. If Count is 2, we don't clone
747  // the loop, otherwise we create a cloned loop to execute the extra
748  // iterations. This function adds the appropriate CFG connections.
749  BasicBlock *InsertBot = UseEpilogRemainder ? LatchExit : PrologExit;
750  BasicBlock *InsertTop = UseEpilogRemainder ? EpilogPreHeader : PrologPreHeader;
751  Loop *remainderLoop = CloneLoopBlocks(
752  L, ModVal, CreateRemainderLoop, UseEpilogRemainder, UnrollRemainder,
753  InsertTop, InsertBot,
754  NewPreHeader, NewBlocks, LoopBlocks, VMap, DT, LI);
755 
756  // Insert the cloned blocks into the function.
757  F->getBasicBlockList().splice(InsertBot->getIterator(),
758  F->getBasicBlockList(),
759  NewBlocks[0]->getIterator(),
760  F->end());
761 
762  // Now the loop blocks are cloned and the other exiting blocks from the
763  // remainder are connected to the original Loop's exit blocks. The remaining
764  // work is to update the phi nodes in the original loop, and take in the
765  // values from the cloned region. Also update the dominator info for
766  // OtherExits and their immediate successors, since we have new edges into
767  // OtherExits.
768  SmallPtrSet<BasicBlock*, 8> ImmediateSuccessorsOfExitBlocks;
769  for (auto *BB : OtherExits) {
770  for (auto &II : *BB) {
771 
772  // Given we preserve LCSSA form, we know that the values used outside the
773  // loop will be used through these phi nodes at the exit blocks that are
774  // transformed below.
775  if (!isa<PHINode>(II))
776  break;
777  PHINode *Phi = cast<PHINode>(&II);
778  unsigned oldNumOperands = Phi->getNumIncomingValues();
779  // Add the incoming values from the remainder code to the end of the phi
780  // node.
781  for (unsigned i =0; i < oldNumOperands; i++){
782  Value *newVal = VMap.lookup(Phi->getIncomingValue(i));
783  // newVal can be a constant or derived from values outside the loop, and
784  // hence need not have a VMap value. Also, since lookup already generated
785  // a default "null" VMap entry for this value, we need to populate that
786  // VMap entry correctly, with the mapped entry being itself.
787  if (!newVal) {
788  newVal = Phi->getIncomingValue(i);
789  VMap[Phi->getIncomingValue(i)] = Phi->getIncomingValue(i);
790  }
791  Phi->addIncoming(newVal,
792  cast<BasicBlock>(VMap[Phi->getIncomingBlock(i)]));
793  }
794  }
795 #if defined(EXPENSIVE_CHECKS) && !defined(NDEBUG)
796  for (BasicBlock *SuccBB : successors(BB)) {
797  assert(!(any_of(OtherExits,
798  [SuccBB](BasicBlock *EB) { return EB == SuccBB; }) ||
799  SuccBB == LatchExit) &&
800  "Breaks the definition of dedicated exits!");
801  }
802 #endif
803  // Update the dominator info because the immediate dominator is no longer the
804  // header of the original Loop. BB has edges both from L and remainder code.
805  // Since the preheader determines which loop is run (L or directly jump to
806  // the remainder code), we set the immediate dominator as the preheader.
807  if (DT) {
808  DT->changeImmediateDominator(BB, PreHeader);
809  // Also update the IDom for immediate successors of BB. If the current
810  // IDom is the header, update the IDom to be the preheader because that is
811  // the nearest common dominator of all predecessors of SuccBB. We need to
812  // check for IDom being the header because successors of exit blocks can
813  // have edges from outside the loop, and we should not incorrectly update
814  // the IDom in that case.
815  for (BasicBlock *SuccBB: successors(BB))
816  if (ImmediateSuccessorsOfExitBlocks.insert(SuccBB).second) {
817  if (DT->getNode(SuccBB)->getIDom()->getBlock() == Header) {
818  assert(!SuccBB->getSinglePredecessor() &&
819  "BB should be the IDom then!");
820  DT->changeImmediateDominator(SuccBB, PreHeader);
821  }
822  }
823  }
824  }
825 
826  // Loop structure should be the following:
827  // Epilog Prolog
828  //
829  // PreHeader PreHeader
830  // NewPreHeader PrologPreHeader
831  // Header PrologHeader
832  // ... ...
833  // Latch PrologLatch
834  // NewExit PrologExit
835  // EpilogPreHeader NewPreHeader
836  // EpilogHeader Header
837  // ... ...
838  // EpilogLatch Latch
839  // LatchExit LatchExit
840 
841  // Rewrite the cloned instruction operands to use the values created when the
842  // clone is created.
843  for (BasicBlock *BB : NewBlocks) {
844  for (Instruction &I : *BB) {
845  RemapInstruction(&I, VMap,
847  }
848  }
849 
850  if (UseEpilogRemainder) {
851  // Connect the epilog code to the original loop and update the
852  // PHI functions.
853  ConnectEpilog(L, ModVal, NewExit, LatchExit, PreHeader,
854  EpilogPreHeader, NewPreHeader, VMap, DT, LI,
855  PreserveLCSSA);
856 
857  // Update counter in loop for unrolling.
858  // I should be multiply of Count.
859  IRBuilder<> B2(NewPreHeader->getTerminator());
860  Value *TestVal = B2.CreateSub(TripCount, ModVal, "unroll_iter");
861  BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
862  B2.SetInsertPoint(LatchBR);
863  PHINode *NewIdx = PHINode::Create(TestVal->getType(), 2, "niter",
864  Header->getFirstNonPHI());
865  Value *IdxSub =
866  B2.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
867  NewIdx->getName() + ".nsub");
868  Value *IdxCmp;
869  if (LatchBR->getSuccessor(0) == Header)
870  IdxCmp = B2.CreateIsNotNull(IdxSub, NewIdx->getName() + ".ncmp");
871  else
872  IdxCmp = B2.CreateIsNull(IdxSub, NewIdx->getName() + ".ncmp");
873  NewIdx->addIncoming(TestVal, NewPreHeader);
874  NewIdx->addIncoming(IdxSub, Latch);
875  LatchBR->setCondition(IdxCmp);
876  } else {
877  // Connect the prolog code to the original loop and update the
878  // PHI functions.
879  ConnectProlog(L, BECount, Count, PrologExit, LatchExit, PreHeader,
880  NewPreHeader, VMap, DT, LI, PreserveLCSSA);
881  }
882 
883  // If this loop is nested, then the loop unroller changes the code in the any
884  // of its parent loops, so the Scalar Evolution pass needs to be run again.
885  SE->forgetTopmostLoop(L);
886 
887  // Canonicalize to LoopSimplifyForm both original and remainder loops. We
888  // cannot rely on the LoopUnrollPass to do this because it only does
889  // canonicalization for parent/subloops and not the sibling loops.
890  if (OtherExits.size() > 0) {
891  // Generate dedicated exit blocks for the original loop, to preserve
892  // LoopSimplifyForm.
893  formDedicatedExitBlocks(L, DT, LI, PreserveLCSSA);
894  // Generate dedicated exit blocks for the remainder loop if one exists, to
895  // preserve LoopSimplifyForm.
896  if (remainderLoop)
897  formDedicatedExitBlocks(remainderLoop, DT, LI, PreserveLCSSA);
898  }
899 
900  if (remainderLoop && UnrollRemainder) {
901  LLVM_DEBUG(dbgs() << "Unrolling remainder loop\n");
902  UnrollLoop(remainderLoop, /*Count*/ Count - 1, /*TripCount*/ Count - 1,
903  /*Force*/ false, /*AllowRuntime*/ false,
904  /*AllowExpensiveTripCount*/ false, /*PreserveCondBr*/ true,
905  /*PreserveOnlyFirst*/ false, /*TripMultiple*/ 1,
906  /*PeelCount*/ 0, /*UnrollRemainder*/ false, LI, SE, DT, AC,
907  /*ORE*/ nullptr, PreserveLCSSA);
908  }
909 
910  NumRuntimeUnrolled++;
911  return true;
912 }
static unsigned getBitWidth(Type *Ty, const DataLayout &DL)
Returns the bitwidth of the given scalar or pointer type.
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:68
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:111
BranchInst * CreateCondBr(Value *Cond, BasicBlock *True, BasicBlock *False, MDNode *BranchWeights=nullptr, MDNode *Unpredictable=nullptr)
Create a conditional &#39;br Cond, TrueDest, FalseDest&#39; instruction.
Definition: IRBuilder.h:842
static bool canSafelyUnrollMultiExitLoop(Loop *L, SmallVectorImpl< BasicBlock *> &OtherExits, BasicBlock *LatchExit, bool PreserveLCSSA, bool UseEpilogRemainder)
Returns true if we can safely unroll a multi-exit/exiting loop.
void addIncoming(Value *V, BasicBlock *BB)
Add an incoming value to the end of the PHI list.
BlockT * getLoopLatch() const
If there is a single latch block for this loop, return it.
Definition: LoopInfoImpl.h:225
Value * CreateIsNotNull(Value *Arg, const Twine &Name="")
Return an i1 value testing if Arg is not null.
Definition: IRBuilder.h:1996
const SCEV * getConstant(ConstantInt *V)
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
Value * CreateICmpULT(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1752
iterator end()
Definition: Function.h:658
The main scalar evolution driver.
This file contains the declarations for metadata subclasses.
BlockT * getLoopPreheader() const
If there is a preheader for this loop, return it.
Definition: LoopInfoImpl.h:174
bool isHighCostExpansion(const SCEV *Expr, Loop *L, const Instruction *At=nullptr)
Return true for expressions that may incur non-trivial cost to evaluate at runtime.
A cache of @llvm.assume calls within a function.
BasicBlock * getSuccessor(unsigned i) const
STATISTIC(NumFunctions, "Total number of functions")
F(f)
void setSuccessor(unsigned Idx, BasicBlock *BB)
Update the specified successor to point at the provided block.
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:264
BasicBlock * SplitEdge(BasicBlock *From, BasicBlock *To, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr, MemorySSAUpdater *MSSAU=nullptr)
Split the edge connecting specified block.
const Module * getModule() const
Return the module owning the function this basic block belongs to, or nullptr if the function does no...
Definition: BasicBlock.cpp:134
Value * removeIncomingValue(unsigned Idx, bool DeletePHIIfEmpty=true)
Remove an incoming value.
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:364
int getBasicBlockIndex(const BasicBlock *BB) const
Return the first index of the specified basic block in the value list for this PHI.
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
Definition: LoopInfo.h:684
static Loop * CloneLoopBlocks(Loop *L, Value *NewIter, const bool CreateRemainderLoop, const bool UseEpilogRemainder, const bool UnrollRemainder, BasicBlock *InsertTop, BasicBlock *InsertBot, BasicBlock *Preheader, std::vector< BasicBlock *> &NewBlocks, LoopBlocksDFS &LoopBlocks, ValueToValueMapTy &VMap, DominatorTree *DT, LoopInfo *LI)
Create a clone of the blocks in a loop and connect them together.
bool isIntegerTy() const
True if this is an instance of IntegerType.
Definition: Type.h:197
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:731
Value * CreateAdd(Value *LHS, Value *RHS, const Twine &Name="", bool HasNUW=false, bool HasNSW=false)
Definition: IRBuilder.h:962
void setName(const Twine &Name)
Change the name of the value.
Definition: Value.cpp:295
RPOIterator endRPO() const
Definition: LoopIterator.h:141
BlockT * getHeader() const
Definition: LoopInfo.h:100
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
ValueT lookup(const KeyT &Val) const
lookup - Return the entry for the specified key, or a default constructed value if no such entry exis...
Definition: ValueMap.h:171
void perform(LoopInfo *LI)
Traverse the loop blocks and store the DFS result.
Definition: LoopInfo.cpp:752
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:145
If this flag is set, the remapper knows that only local values within a function (such as an instruct...
Definition: ValueMapper.h:73
static void ConnectProlog(Loop *L, Value *BECount, unsigned Count, BasicBlock *PrologExit, BasicBlock *OriginalLoopLatchExit, BasicBlock *PreHeader, BasicBlock *NewPreHeader, ValueToValueMapTy &VMap, DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA)
Connect the unrolling prolog code to the original loop.
NodeT * getBlock() const
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...
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:410
static cl::opt< bool > UnrollRuntimeMultiExit("unroll-runtime-multi-exit", cl::init(false), cl::Hidden, cl::desc("Allow runtime unrolling for loops with multiple exits, when " "epilog is generated"))
const Instruction * getFirstNonPHI() const
Returns a pointer to the first instruction in this block that is not a PHINode instruction.
Definition: BasicBlock.cpp:189
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:304
void dump() const
Definition: LoopInfo.cpp:370
const BasicBlock * getSinglePredecessor() const
Return the predecessor of this block if it has a single predecessor block.
Definition: BasicBlock.cpp:235
constexpr bool isPowerOf2_32(uint32_t Value)
Return true if the argument is a power of two > 0.
Definition: MathExtras.h:429
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
Conditional or Unconditional Branch instruction.
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
Value * getIncomingValueForBlock(const BasicBlock *BB) const
void setLoopAlreadyUnrolled()
Add llvm.loop.unroll.disable to this loop&#39;s loop id metadata.
Definition: LoopInfo.cpp:260
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:371
const SCEV * getAddExpr(SmallVectorImpl< const SCEV *> &Ops, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap, unsigned Depth=0)
Get a canonical add expression, or something simpler if possible.
size_t size() const
Definition: BasicBlock.h:274
static bool canProfitablyUnrollMultiExitLoop(Loop *L, SmallVectorImpl< BasicBlock *> &OtherExits, BasicBlock *LatchExit, bool PreserveLCSSA, bool UseEpilogRemainder)
Returns true if we can profitably unroll the multi-exit loop L.
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:329
bool any_of(R &&Range, UnaryPredicate P)
Provide wrappers to std::any_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1049
Value * expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I)
Insert code to directly compute the specified SCEV expression into the program.
std::vector< BasicBlock * >::const_reverse_iterator RPOIterator
Definition: LoopIterator.h:102
self_iterator getIterator()
Definition: ilist_node.h:82
void getExitingBlocks(SmallVectorImpl< BlockT *> &ExitingBlocks) const
Return all blocks inside the loop that have successors outside of the loop.
Definition: LoopInfoImpl.h:35
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1392
bool UnrollRuntimeLoopRemainder(Loop *L, unsigned Count, bool AllowExpensiveTripCount, bool UseEpilogRemainder, bool UnrollRemainder, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC, bool PreserveLCSSA)
Insert code in the prolog/epilog code when unrolling a loop with a run-time trip-count.
size_t size() const
Definition: SmallVector.h:53
Value * getIncomingValue(unsigned i) const
Return incoming value number x.
DomTreeNodeBase< NodeT > * getNode(const NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
static void ConnectEpilog(Loop *L, Value *ModVal, BasicBlock *NewExit, BasicBlock *Exit, BasicBlock *PreHeader, BasicBlock *EpilogPreHeader, BasicBlock *NewPreHeader, ValueToValueMapTy &VMap, DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA)
Connect the unrolling epilog code to the original loop.
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:110
Iterator for intrusive lists based on ilist_node.
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
Type * getType() const
Return the LLVM type of this SCEV expression.
void setIncomingBlock(unsigned i, BasicBlock *BB)
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
Module.h This file contains the declarations for the Module class.
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 PHINode * Create(Type *Ty, unsigned NumReservedValues, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Constructors - NumReservedValues is a hint for the number of incoming edges that this phi node will h...
pred_range predecessors(BasicBlock *BB)
Definition: CFG.h:123
unsigned getNumIncomingValues() const
Return the number of incoming edges.
Value * CreateURem(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1041
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
unsigned Log2_32(uint32_t Value)
Return the floor log base 2 of the specified value, -1 if the value is zero.
Definition: MathExtras.h:539
const Loop * addClonedBlockToLoopInfo(BasicBlock *OriginalBB, BasicBlock *ClonedBB, LoopInfo *LI, NewLoopsMap &NewLoops)
Adds ClonedBB to LoopInfo, creates a new loop for ClonedBB if necessary and adds a mapping from the o...
Definition: LoopUnroll.cpp:190
Store the result of a depth first search within basic blocks contained by a single loop...
Definition: LoopIterator.h:98
BasicBlock * CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap, const Twine &NameSuffix="", Function *F=nullptr, ClonedCodeInfo *CodeInfo=nullptr, DebugInfoFinder *DIFinder=nullptr)
CloneBasicBlock - Return a copy of the specified basic block, but without embedding the block into a ...
void RemapInstruction(Instruction *I, ValueToValueMapTy &VM, RemapFlags Flags=RF_None, ValueMapTypeRemapper *TypeMapper=nullptr, ValueMaterializer *Materializer=nullptr)
Convert the instruction operands from referencing the current values into those specified by VM...
Definition: ValueMapper.h:251
This class uses information about analyze scalars to rewrite expressions in canonical form...
If this flag is set, the remapper ignores missing function-local entries (Argument, Instruction, BasicBlock) that are not in the value map.
Definition: ValueMapper.h:91
LoopT * getParentLoop() const
Definition: LoopInfo.h:101
bool isLoopSimplifyForm() const
Return true if the Loop is in the form that the LoopSimplify form transforms loops to...
Definition: LoopInfo.cpp:192
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:307
This class represents an analyzed expression in the program.
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:459
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:224
BasicBlock * getIncomingBlock(unsigned i) const
Return incoming basic block number i.
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:108
#define I(x, y, z)
Definition: MD5.cpp:58
DomTreeNodeBase< NodeT > * addNewBlock(NodeT *BB, NodeT *DomBB)
Add a new node to the dominator tree information.
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h:633
iterator_range< const_phi_iterator > phis() const
Returns a range that iterates over the phis in the basic block.
Definition: BasicBlock.h:320
Value * CreateAnd(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1112
void setCondition(Value *V)
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM Value Representation.
Definition: Value.h:73
succ_range successors(Instruction *I)
Definition: CFG.h:262
RPOIterator beginRPO() const
Reverse iterate over the cached postorder blocks.
Definition: LoopIterator.h:137
BasicBlock * SplitBlock(BasicBlock *Old, Instruction *SplitPt, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr, MemorySSAUpdater *MSSAU=nullptr)
Split the specified block at the specified instruction - everything before SplitPt stays in Old and e...
bool formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA)
Ensure that all exit blocks of the loop are dedicated exits.
Definition: LoopUtils.cpp:45
void getUniqueExitBlocks(SmallVectorImpl< BlockT *> &ExitBlocks) const
Return all unique successor blocks of this loop.
Definition: LoopInfoImpl.h:100
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
const SCEV * getExitCount(const Loop *L, BasicBlock *ExitingBlock)
Get the expression for the number of loop iterations for which this loop is guaranteed not to exit vi...
const TerminatorInst * getTerminator() const LLVM_READONLY
Returns the terminator instruction if the block is well formed or null if the block is not well forme...
Definition: BasicBlock.cpp:138
void setIncomingValue(unsigned i, Value *V)
#define LLVM_DEBUG(X)
Definition: Debug.h:123
LoopUnrollResult UnrollLoop(Loop *L, unsigned Count, unsigned TripCount, bool Force, bool AllowRuntime, bool AllowExpensiveTripCount, bool PreserveCondBr, bool PreserveOnlyFirst, unsigned TripMultiple, unsigned PeelCount, bool UnrollRemainder, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC, OptimizationRemarkEmitter *ORE, bool PreserveLCSSA)
Unroll the given loop by Count.
Definition: LoopUnroll.cpp:332
BlockT * getExitingBlock() const
If getExitingBlocks would return exactly one block, return that block.
Definition: LoopInfoImpl.h:50
bool erase(const KeyT &Val)
Definition: ValueMap.h:197
void forgetTopmostLoop(const Loop *L)