LLVM  9.0.0svn
LoopRerollPass.cpp
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1 //===- LoopReroll.cpp - Loop rerolling 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 implements a simple loop reroller.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/ADT/APInt.h"
14 #include "llvm/ADT/BitVector.h"
15 #include "llvm/ADT/DenseMap.h"
16 #include "llvm/ADT/DenseSet.h"
17 #include "llvm/ADT/MapVector.h"
18 #include "llvm/ADT/STLExtras.h"
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include "llvm/ADT/SmallVector.h"
21 #include "llvm/ADT/Statistic.h"
24 #include "llvm/Analysis/LoopInfo.h"
25 #include "llvm/Analysis/LoopPass.h"
32 #include "llvm/IR/BasicBlock.h"
33 #include "llvm/IR/Constants.h"
34 #include "llvm/IR/DataLayout.h"
35 #include "llvm/IR/DerivedTypes.h"
36 #include "llvm/IR/Dominators.h"
37 #include "llvm/IR/IRBuilder.h"
38 #include "llvm/IR/InstrTypes.h"
39 #include "llvm/IR/Instruction.h"
40 #include "llvm/IR/Instructions.h"
41 #include "llvm/IR/IntrinsicInst.h"
42 #include "llvm/IR/Intrinsics.h"
43 #include "llvm/IR/Module.h"
44 #include "llvm/IR/Type.h"
45 #include "llvm/IR/Use.h"
46 #include "llvm/IR/User.h"
47 #include "llvm/IR/Value.h"
48 #include "llvm/Pass.h"
49 #include "llvm/Support/Casting.h"
51 #include "llvm/Support/Debug.h"
53 #include "llvm/Transforms/Scalar.h"
54 #include "llvm/Transforms/Utils.h"
57 #include <cassert>
58 #include <cstddef>
59 #include <cstdint>
60 #include <cstdlib>
61 #include <iterator>
62 #include <map>
63 #include <utility>
64 
65 using namespace llvm;
66 
67 #define DEBUG_TYPE "loop-reroll"
68 
69 STATISTIC(NumRerolledLoops, "Number of rerolled loops");
70 
71 static cl::opt<unsigned>
72 NumToleratedFailedMatches("reroll-num-tolerated-failed-matches", cl::init(400),
73  cl::Hidden,
74  cl::desc("The maximum number of failures to tolerate"
75  " during fuzzy matching. (default: 400)"));
76 
77 // This loop re-rolling transformation aims to transform loops like this:
78 //
79 // int foo(int a);
80 // void bar(int *x) {
81 // for (int i = 0; i < 500; i += 3) {
82 // foo(i);
83 // foo(i+1);
84 // foo(i+2);
85 // }
86 // }
87 //
88 // into a loop like this:
89 //
90 // void bar(int *x) {
91 // for (int i = 0; i < 500; ++i)
92 // foo(i);
93 // }
94 //
95 // It does this by looking for loops that, besides the latch code, are composed
96 // of isomorphic DAGs of instructions, with each DAG rooted at some increment
97 // to the induction variable, and where each DAG is isomorphic to the DAG
98 // rooted at the induction variable (excepting the sub-DAGs which root the
99 // other induction-variable increments). In other words, we're looking for loop
100 // bodies of the form:
101 //
102 // %iv = phi [ (preheader, ...), (body, %iv.next) ]
103 // f(%iv)
104 // %iv.1 = add %iv, 1 <-- a root increment
105 // f(%iv.1)
106 // %iv.2 = add %iv, 2 <-- a root increment
107 // f(%iv.2)
108 // %iv.scale_m_1 = add %iv, scale-1 <-- a root increment
109 // f(%iv.scale_m_1)
110 // ...
111 // %iv.next = add %iv, scale
112 // %cmp = icmp(%iv, ...)
113 // br %cmp, header, exit
114 //
115 // where each f(i) is a set of instructions that, collectively, are a function
116 // only of i (and other loop-invariant values).
117 //
118 // As a special case, we can also reroll loops like this:
119 //
120 // int foo(int);
121 // void bar(int *x) {
122 // for (int i = 0; i < 500; ++i) {
123 // x[3*i] = foo(0);
124 // x[3*i+1] = foo(0);
125 // x[3*i+2] = foo(0);
126 // }
127 // }
128 //
129 // into this:
130 //
131 // void bar(int *x) {
132 // for (int i = 0; i < 1500; ++i)
133 // x[i] = foo(0);
134 // }
135 //
136 // in which case, we're looking for inputs like this:
137 //
138 // %iv = phi [ (preheader, ...), (body, %iv.next) ]
139 // %scaled.iv = mul %iv, scale
140 // f(%scaled.iv)
141 // %scaled.iv.1 = add %scaled.iv, 1
142 // f(%scaled.iv.1)
143 // %scaled.iv.2 = add %scaled.iv, 2
144 // f(%scaled.iv.2)
145 // %scaled.iv.scale_m_1 = add %scaled.iv, scale-1
146 // f(%scaled.iv.scale_m_1)
147 // ...
148 // %iv.next = add %iv, 1
149 // %cmp = icmp(%iv, ...)
150 // br %cmp, header, exit
151 
152 namespace {
153 
155  /// The maximum number of iterations that we'll try and reroll.
156  IL_MaxRerollIterations = 32,
157  /// The bitvector index used by loop induction variables and other
158  /// instructions that belong to all iterations.
159  IL_All,
160  IL_End
161  };
162 
163  class LoopReroll : public LoopPass {
164  public:
165  static char ID; // Pass ID, replacement for typeid
166 
167  LoopReroll() : LoopPass(ID) {
169  }
170 
171  bool runOnLoop(Loop *L, LPPassManager &LPM) override;
172 
173  void getAnalysisUsage(AnalysisUsage &AU) const override {
176  }
177 
178  protected:
179  AliasAnalysis *AA;
180  LoopInfo *LI;
181  ScalarEvolution *SE;
182  TargetLibraryInfo *TLI;
183  DominatorTree *DT;
184  bool PreserveLCSSA;
185 
186  using SmallInstructionVector = SmallVector<Instruction *, 16>;
187  using SmallInstructionSet = SmallPtrSet<Instruction *, 16>;
188 
189  // Map between induction variable and its increment
191 
192  // For loop with multiple induction variable, remember the one used only to
193  // control the loop.
194  Instruction *LoopControlIV;
195 
196  // A chain of isomorphic instructions, identified by a single-use PHI
197  // representing a reduction. Only the last value may be used outside the
198  // loop.
199  struct SimpleLoopReduction {
200  SimpleLoopReduction(Instruction *P, Loop *L) : Instructions(1, P) {
201  assert(isa<PHINode>(P) && "First reduction instruction must be a PHI");
202  add(L);
203  }
204 
205  bool valid() const {
206  return Valid;
207  }
208 
209  Instruction *getPHI() const {
210  assert(Valid && "Using invalid reduction");
211  return Instructions.front();
212  }
213 
214  Instruction *getReducedValue() const {
215  assert(Valid && "Using invalid reduction");
216  return Instructions.back();
217  }
218 
219  Instruction *get(size_t i) const {
220  assert(Valid && "Using invalid reduction");
221  return Instructions[i+1];
222  }
223 
224  Instruction *operator [] (size_t i) const { return get(i); }
225 
226  // The size, ignoring the initial PHI.
227  size_t size() const {
228  assert(Valid && "Using invalid reduction");
229  return Instructions.size()-1;
230  }
231 
232  using iterator = SmallInstructionVector::iterator;
233  using const_iterator = SmallInstructionVector::const_iterator;
234 
235  iterator begin() {
236  assert(Valid && "Using invalid reduction");
237  return std::next(Instructions.begin());
238  }
239 
240  const_iterator begin() const {
241  assert(Valid && "Using invalid reduction");
242  return std::next(Instructions.begin());
243  }
244 
245  iterator end() { return Instructions.end(); }
246  const_iterator end() const { return Instructions.end(); }
247 
248  protected:
249  bool Valid = false;
250  SmallInstructionVector Instructions;
251 
252  void add(Loop *L);
253  };
254 
255  // The set of all reductions, and state tracking of possible reductions
256  // during loop instruction processing.
257  struct ReductionTracker {
258  using SmallReductionVector = SmallVector<SimpleLoopReduction, 16>;
259 
260  // Add a new possible reduction.
261  void addSLR(SimpleLoopReduction &SLR) { PossibleReds.push_back(SLR); }
262 
263  // Setup to track possible reductions corresponding to the provided
264  // rerolling scale. Only reductions with a number of non-PHI instructions
265  // that is divisible by the scale are considered. Three instructions sets
266  // are filled in:
267  // - A set of all possible instructions in eligible reductions.
268  // - A set of all PHIs in eligible reductions
269  // - A set of all reduced values (last instructions) in eligible
270  // reductions.
271  void restrictToScale(uint64_t Scale,
272  SmallInstructionSet &PossibleRedSet,
273  SmallInstructionSet &PossibleRedPHISet,
274  SmallInstructionSet &PossibleRedLastSet) {
275  PossibleRedIdx.clear();
276  PossibleRedIter.clear();
277  Reds.clear();
278 
279  for (unsigned i = 0, e = PossibleReds.size(); i != e; ++i)
280  if (PossibleReds[i].size() % Scale == 0) {
281  PossibleRedLastSet.insert(PossibleReds[i].getReducedValue());
282  PossibleRedPHISet.insert(PossibleReds[i].getPHI());
283 
284  PossibleRedSet.insert(PossibleReds[i].getPHI());
285  PossibleRedIdx[PossibleReds[i].getPHI()] = i;
286  for (Instruction *J : PossibleReds[i]) {
287  PossibleRedSet.insert(J);
288  PossibleRedIdx[J] = i;
289  }
290  }
291  }
292 
293  // The functions below are used while processing the loop instructions.
294 
295  // Are the two instructions both from reductions, and furthermore, from
296  // the same reduction?
297  bool isPairInSame(Instruction *J1, Instruction *J2) {
298  DenseMap<Instruction *, int>::iterator J1I = PossibleRedIdx.find(J1);
299  if (J1I != PossibleRedIdx.end()) {
300  DenseMap<Instruction *, int>::iterator J2I = PossibleRedIdx.find(J2);
301  if (J2I != PossibleRedIdx.end() && J1I->second == J2I->second)
302  return true;
303  }
304 
305  return false;
306  }
307 
308  // The two provided instructions, the first from the base iteration, and
309  // the second from iteration i, form a matched pair. If these are part of
310  // a reduction, record that fact.
311  void recordPair(Instruction *J1, Instruction *J2, unsigned i) {
312  if (PossibleRedIdx.count(J1)) {
313  assert(PossibleRedIdx.count(J2) &&
314  "Recording reduction vs. non-reduction instruction?");
315 
316  PossibleRedIter[J1] = 0;
317  PossibleRedIter[J2] = i;
318 
319  int Idx = PossibleRedIdx[J1];
320  assert(Idx == PossibleRedIdx[J2] &&
321  "Recording pair from different reductions?");
322  Reds.insert(Idx);
323  }
324  }
325 
326  // The functions below can be called after we've finished processing all
327  // instructions in the loop, and we know which reductions were selected.
328 
329  bool validateSelected();
330  void replaceSelected();
331 
332  protected:
333  // The vector of all possible reductions (for any scale).
334  SmallReductionVector PossibleReds;
335 
336  DenseMap<Instruction *, int> PossibleRedIdx;
337  DenseMap<Instruction *, int> PossibleRedIter;
338  DenseSet<int> Reds;
339  };
340 
341  // A DAGRootSet models an induction variable being used in a rerollable
342  // loop. For example,
343  //
344  // x[i*3+0] = y1
345  // x[i*3+1] = y2
346  // x[i*3+2] = y3
347  //
348  // Base instruction -> i*3
349  // +---+----+
350  // / | \
351  // ST[y1] +1 +2 <-- Roots
352  // | |
353  // ST[y2] ST[y3]
354  //
355  // There may be multiple DAGRoots, for example:
356  //
357  // x[i*2+0] = ... (1)
358  // x[i*2+1] = ... (1)
359  // x[i*2+4] = ... (2)
360  // x[i*2+5] = ... (2)
361  // x[(i+1234)*2+5678] = ... (3)
362  // x[(i+1234)*2+5679] = ... (3)
363  //
364  // The loop will be rerolled by adding a new loop induction variable,
365  // one for the Base instruction in each DAGRootSet.
366  //
367  struct DAGRootSet {
368  Instruction *BaseInst;
369  SmallInstructionVector Roots;
370 
371  // The instructions between IV and BaseInst (but not including BaseInst).
372  SmallInstructionSet SubsumedInsts;
373  };
374 
375  // The set of all DAG roots, and state tracking of all roots
376  // for a particular induction variable.
377  struct DAGRootTracker {
378  DAGRootTracker(LoopReroll *Parent, Loop *L, Instruction *IV,
381  bool PreserveLCSSA,
383  Instruction *LoopCtrlIV)
384  : Parent(Parent), L(L), SE(SE), AA(AA), TLI(TLI), DT(DT), LI(LI),
385  PreserveLCSSA(PreserveLCSSA), IV(IV), IVToIncMap(IncrMap),
386  LoopControlIV(LoopCtrlIV) {}
387 
388  /// Stage 1: Find all the DAG roots for the induction variable.
389  bool findRoots();
390 
391  /// Stage 2: Validate if the found roots are valid.
392  bool validate(ReductionTracker &Reductions);
393 
394  /// Stage 3: Assuming validate() returned true, perform the
395  /// replacement.
396  /// @param BackedgeTakenCount The backedge-taken count of L.
397  void replace(const SCEV *BackedgeTakenCount);
398 
399  protected:
401 
402  void findRootsRecursive(Instruction *IVU,
403  SmallInstructionSet SubsumedInsts);
404  bool findRootsBase(Instruction *IVU, SmallInstructionSet SubsumedInsts);
405  bool collectPossibleRoots(Instruction *Base,
406  std::map<int64_t,Instruction*> &Roots);
407  bool validateRootSet(DAGRootSet &DRS);
408 
409  bool collectUsedInstructions(SmallInstructionSet &PossibleRedSet);
410  void collectInLoopUserSet(const SmallInstructionVector &Roots,
411  const SmallInstructionSet &Exclude,
412  const SmallInstructionSet &Final,
414  void collectInLoopUserSet(Instruction *Root,
415  const SmallInstructionSet &Exclude,
416  const SmallInstructionSet &Final,
417  DenseSet<Instruction *> &Users);
418 
419  UsesTy::iterator nextInstr(int Val, UsesTy &In,
420  const SmallInstructionSet &Exclude,
421  UsesTy::iterator *StartI=nullptr);
422  bool isBaseInst(Instruction *I);
423  bool isRootInst(Instruction *I);
424  bool instrDependsOn(Instruction *I,
425  UsesTy::iterator Start,
426  UsesTy::iterator End);
427  void replaceIV(DAGRootSet &DRS, const SCEV *Start, const SCEV *IncrExpr);
428 
429  LoopReroll *Parent;
430 
431  // Members of Parent, replicated here for brevity.
432  Loop *L;
433  ScalarEvolution *SE;
434  AliasAnalysis *AA;
435  TargetLibraryInfo *TLI;
436  DominatorTree *DT;
437  LoopInfo *LI;
438  bool PreserveLCSSA;
439 
440  // The loop induction variable.
441  Instruction *IV;
442 
443  // Loop step amount.
444  int64_t Inc;
445 
446  // Loop reroll count; if Inc == 1, this records the scaling applied
447  // to the indvar: a[i*2+0] = ...; a[i*2+1] = ... ;
448  // If Inc is not 1, Scale = Inc.
449  uint64_t Scale;
450 
451  // The roots themselves.
453 
454  // All increment instructions for IV.
455  SmallInstructionVector LoopIncs;
456 
457  // Map of all instructions in the loop (in order) to the iterations
458  // they are used in (or specially, IL_All for instructions
459  // used in the loop increment mechanism).
460  UsesTy Uses;
461 
462  // Map between induction variable and its increment
464 
465  Instruction *LoopControlIV;
466  };
467 
468  // Check if it is a compare-like instruction whose user is a branch
469  bool isCompareUsedByBranch(Instruction *I) {
470  auto *TI = I->getParent()->getTerminator();
471  if (!isa<BranchInst>(TI) || !isa<CmpInst>(I))
472  return false;
473  return I->hasOneUse() && TI->getOperand(0) == I;
474  };
475 
476  bool isLoopControlIV(Loop *L, Instruction *IV);
477  void collectPossibleIVs(Loop *L, SmallInstructionVector &PossibleIVs);
478  void collectPossibleReductions(Loop *L,
479  ReductionTracker &Reductions);
480  bool reroll(Instruction *IV, Loop *L, BasicBlock *Header,
481  const SCEV *BackedgeTakenCount, ReductionTracker &Reductions);
482  };
483 
484 } // end anonymous namespace
485 
486 char LoopReroll::ID = 0;
487 
488 INITIALIZE_PASS_BEGIN(LoopReroll, "loop-reroll", "Reroll loops", false, false)
491 INITIALIZE_PASS_END(LoopReroll, "loop-reroll", "Reroll loops", false, false)
492 
494  return new LoopReroll;
495 }
496 
497 // Returns true if the provided instruction is used outside the given loop.
498 // This operates like Instruction::isUsedOutsideOfBlock, but considers PHIs in
499 // non-loop blocks to be outside the loop.
501  for (User *U : I->users()) {
502  if (!L->contains(cast<Instruction>(U)))
503  return true;
504  }
505  return false;
506 }
507 
508 // Check if an IV is only used to control the loop. There are two cases:
509 // 1. It only has one use which is loop increment, and the increment is only
510 // used by comparison and the PHI (could has sext with nsw in between), and the
511 // comparison is only used by branch.
512 // 2. It is used by loop increment and the comparison, the loop increment is
513 // only used by the PHI, and the comparison is used only by the branch.
514 bool LoopReroll::isLoopControlIV(Loop *L, Instruction *IV) {
515  unsigned IVUses = IV->getNumUses();
516  if (IVUses != 2 && IVUses != 1)
517  return false;
518 
519  for (auto *User : IV->users()) {
520  int32_t IncOrCmpUses = User->getNumUses();
521  bool IsCompInst = isCompareUsedByBranch(cast<Instruction>(User));
522 
523  // User can only have one or two uses.
524  if (IncOrCmpUses != 2 && IncOrCmpUses != 1)
525  return false;
526 
527  // Case 1
528  if (IVUses == 1) {
529  // The only user must be the loop increment.
530  // The loop increment must have two uses.
531  if (IsCompInst || IncOrCmpUses != 2)
532  return false;
533  }
534 
535  // Case 2
536  if (IVUses == 2 && IncOrCmpUses != 1)
537  return false;
538 
539  // The users of the IV must be a binary operation or a comparison
540  if (auto *BO = dyn_cast<BinaryOperator>(User)) {
541  if (BO->getOpcode() == Instruction::Add) {
542  // Loop Increment
543  // User of Loop Increment should be either PHI or CMP
544  for (auto *UU : User->users()) {
545  if (PHINode *PN = dyn_cast<PHINode>(UU)) {
546  if (PN != IV)
547  return false;
548  }
549  // Must be a CMP or an ext (of a value with nsw) then CMP
550  else {
551  Instruction *UUser = dyn_cast<Instruction>(UU);
552  // Skip SExt if we are extending an nsw value
553  // TODO: Allow ZExt too
554  if (BO->hasNoSignedWrap() && UUser && UUser->hasOneUse() &&
555  isa<SExtInst>(UUser))
556  UUser = dyn_cast<Instruction>(*(UUser->user_begin()));
557  if (!isCompareUsedByBranch(UUser))
558  return false;
559  }
560  }
561  } else
562  return false;
563  // Compare : can only have one use, and must be branch
564  } else if (!IsCompInst)
565  return false;
566  }
567  return true;
568 }
569 
570 // Collect the list of loop induction variables with respect to which it might
571 // be possible to reroll the loop.
572 void LoopReroll::collectPossibleIVs(Loop *L,
573  SmallInstructionVector &PossibleIVs) {
574  BasicBlock *Header = L->getHeader();
575  for (BasicBlock::iterator I = Header->begin(),
576  IE = Header->getFirstInsertionPt(); I != IE; ++I) {
577  if (!isa<PHINode>(I))
578  continue;
579  if (!I->getType()->isIntegerTy() && !I->getType()->isPointerTy())
580  continue;
581 
582  if (const SCEVAddRecExpr *PHISCEV =
583  dyn_cast<SCEVAddRecExpr>(SE->getSCEV(&*I))) {
584  if (PHISCEV->getLoop() != L)
585  continue;
586  if (!PHISCEV->isAffine())
587  continue;
588  auto IncSCEV = dyn_cast<SCEVConstant>(PHISCEV->getStepRecurrence(*SE));
589  if (IncSCEV) {
590  IVToIncMap[&*I] = IncSCEV->getValue()->getSExtValue();
591  LLVM_DEBUG(dbgs() << "LRR: Possible IV: " << *I << " = " << *PHISCEV
592  << "\n");
593 
594  if (isLoopControlIV(L, &*I)) {
595  assert(!LoopControlIV && "Found two loop control only IV");
596  LoopControlIV = &(*I);
597  LLVM_DEBUG(dbgs() << "LRR: Possible loop control only IV: " << *I
598  << " = " << *PHISCEV << "\n");
599  } else
600  PossibleIVs.push_back(&*I);
601  }
602  }
603  }
604 }
605 
606 // Add the remainder of the reduction-variable chain to the instruction vector
607 // (the initial PHINode has already been added). If successful, the object is
608 // marked as valid.
610  assert(!Valid && "Cannot add to an already-valid chain");
611 
612  // The reduction variable must be a chain of single-use instructions
613  // (including the PHI), except for the last value (which is used by the PHI
614  // and also outside the loop).
615  Instruction *C = Instructions.front();
616  if (C->user_empty())
617  return;
618 
619  do {
620  C = cast<Instruction>(*C->user_begin());
621  if (C->hasOneUse()) {
622  if (!C->isBinaryOp())
623  return;
624 
625  if (!(isa<PHINode>(Instructions.back()) ||
626  C->isSameOperationAs(Instructions.back())))
627  return;
628 
629  Instructions.push_back(C);
630  }
631  } while (C->hasOneUse());
632 
633  if (Instructions.size() < 2 ||
634  !C->isSameOperationAs(Instructions.back()) ||
635  C->use_empty())
636  return;
637 
638  // C is now the (potential) last instruction in the reduction chain.
639  for (User *U : C->users()) {
640  // The only in-loop user can be the initial PHI.
641  if (L->contains(cast<Instruction>(U)))
642  if (cast<Instruction>(U) != Instructions.front())
643  return;
644  }
645 
646  Instructions.push_back(C);
647  Valid = true;
648 }
649 
650 // Collect the vector of possible reduction variables.
651 void LoopReroll::collectPossibleReductions(Loop *L,
652  ReductionTracker &Reductions) {
653  BasicBlock *Header = L->getHeader();
654  for (BasicBlock::iterator I = Header->begin(),
655  IE = Header->getFirstInsertionPt(); I != IE; ++I) {
656  if (!isa<PHINode>(I))
657  continue;
658  if (!I->getType()->isSingleValueType())
659  continue;
660 
661  SimpleLoopReduction SLR(&*I, L);
662  if (!SLR.valid())
663  continue;
664 
665  LLVM_DEBUG(dbgs() << "LRR: Possible reduction: " << *I << " (with "
666  << SLR.size() << " chained instructions)\n");
667  Reductions.addSLR(SLR);
668  }
669 }
670 
671 // Collect the set of all users of the provided root instruction. This set of
672 // users contains not only the direct users of the root instruction, but also
673 // all users of those users, and so on. There are two exceptions:
674 //
675 // 1. Instructions in the set of excluded instructions are never added to the
676 // use set (even if they are users). This is used, for example, to exclude
677 // including root increments in the use set of the primary IV.
678 //
679 // 2. Instructions in the set of final instructions are added to the use set
680 // if they are users, but their users are not added. This is used, for
681 // example, to prevent a reduction update from forcing all later reduction
682 // updates into the use set.
683 void LoopReroll::DAGRootTracker::collectInLoopUserSet(
684  Instruction *Root, const SmallInstructionSet &Exclude,
685  const SmallInstructionSet &Final,
687  SmallInstructionVector Queue(1, Root);
688  while (!Queue.empty()) {
689  Instruction *I = Queue.pop_back_val();
690  if (!Users.insert(I).second)
691  continue;
692 
693  if (!Final.count(I))
694  for (Use &U : I->uses()) {
695  Instruction *User = cast<Instruction>(U.getUser());
696  if (PHINode *PN = dyn_cast<PHINode>(User)) {
697  // Ignore "wrap-around" uses to PHIs of this loop's header.
698  if (PN->getIncomingBlock(U) == L->getHeader())
699  continue;
700  }
701 
702  if (L->contains(User) && !Exclude.count(User)) {
703  Queue.push_back(User);
704  }
705  }
706 
707  // We also want to collect single-user "feeder" values.
708  for (User::op_iterator OI = I->op_begin(),
709  OIE = I->op_end(); OI != OIE; ++OI) {
710  if (Instruction *Op = dyn_cast<Instruction>(*OI))
711  if (Op->hasOneUse() && L->contains(Op) && !Exclude.count(Op) &&
712  !Final.count(Op))
713  Queue.push_back(Op);
714  }
715  }
716 }
717 
718 // Collect all of the users of all of the provided root instructions (combined
719 // into a single set).
720 void LoopReroll::DAGRootTracker::collectInLoopUserSet(
721  const SmallInstructionVector &Roots,
722  const SmallInstructionSet &Exclude,
723  const SmallInstructionSet &Final,
724  DenseSet<Instruction *> &Users) {
725  for (Instruction *Root : Roots)
726  collectInLoopUserSet(Root, Exclude, Final, Users);
727 }
728 
730  if (LoadInst *LI = dyn_cast<LoadInst>(I))
731  return LI->isUnordered();
732  if (StoreInst *SI = dyn_cast<StoreInst>(I))
733  return SI->isUnordered();
734  if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I))
735  return !MI->isVolatile();
736  return false;
737 }
738 
739 /// Return true if IVU is a "simple" arithmetic operation.
740 /// This is used for narrowing the search space for DAGRoots; only arithmetic
741 /// and GEPs can be part of a DAGRoot.
742 static bool isSimpleArithmeticOp(User *IVU) {
743  if (Instruction *I = dyn_cast<Instruction>(IVU)) {
744  switch (I->getOpcode()) {
745  default: return false;
746  case Instruction::Add:
747  case Instruction::Sub:
748  case Instruction::Mul:
749  case Instruction::Shl:
750  case Instruction::AShr:
751  case Instruction::LShr:
752  case Instruction::GetElementPtr:
753  case Instruction::Trunc:
754  case Instruction::ZExt:
755  case Instruction::SExt:
756  return true;
757  }
758  }
759  return false;
760 }
761 
762 static bool isLoopIncrement(User *U, Instruction *IV) {
764 
765  if ((BO && BO->getOpcode() != Instruction::Add) ||
766  (!BO && !isa<GetElementPtrInst>(U)))
767  return false;
768 
769  for (auto *UU : U->users()) {
770  PHINode *PN = dyn_cast<PHINode>(UU);
771  if (PN && PN == IV)
772  return true;
773  }
774  return false;
775 }
776 
777 bool LoopReroll::DAGRootTracker::
778 collectPossibleRoots(Instruction *Base, std::map<int64_t,Instruction*> &Roots) {
779  SmallInstructionVector BaseUsers;
780 
781  for (auto *I : Base->users()) {
782  ConstantInt *CI = nullptr;
783 
784  if (isLoopIncrement(I, IV)) {
785  LoopIncs.push_back(cast<Instruction>(I));
786  continue;
787  }
788 
789  // The root nodes must be either GEPs, ORs or ADDs.
790  if (auto *BO = dyn_cast<BinaryOperator>(I)) {
791  if (BO->getOpcode() == Instruction::Add ||
792  BO->getOpcode() == Instruction::Or)
793  CI = dyn_cast<ConstantInt>(BO->getOperand(1));
794  } else if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
795  Value *LastOperand = GEP->getOperand(GEP->getNumOperands()-1);
796  CI = dyn_cast<ConstantInt>(LastOperand);
797  }
798 
799  if (!CI) {
800  if (Instruction *II = dyn_cast<Instruction>(I)) {
801  BaseUsers.push_back(II);
802  continue;
803  } else {
804  LLVM_DEBUG(dbgs() << "LRR: Aborting due to non-instruction: " << *I
805  << "\n");
806  return false;
807  }
808  }
809 
810  int64_t V = std::abs(CI->getValue().getSExtValue());
811  if (Roots.find(V) != Roots.end())
812  // No duplicates, please.
813  return false;
814 
815  Roots[V] = cast<Instruction>(I);
816  }
817 
818  // Make sure we have at least two roots.
819  if (Roots.empty() || (Roots.size() == 1 && BaseUsers.empty()))
820  return false;
821 
822  // If we found non-loop-inc, non-root users of Base, assume they are
823  // for the zeroth root index. This is because "add %a, 0" gets optimized
824  // away.
825  if (BaseUsers.size()) {
826  if (Roots.find(0) != Roots.end()) {
827  LLVM_DEBUG(dbgs() << "LRR: Multiple roots found for base - aborting!\n");
828  return false;
829  }
830  Roots[0] = Base;
831  }
832 
833  // Calculate the number of users of the base, or lowest indexed, iteration.
834  unsigned NumBaseUses = BaseUsers.size();
835  if (NumBaseUses == 0)
836  NumBaseUses = Roots.begin()->second->getNumUses();
837 
838  // Check that every node has the same number of users.
839  for (auto &KV : Roots) {
840  if (KV.first == 0)
841  continue;
842  if (!KV.second->hasNUses(NumBaseUses)) {
843  LLVM_DEBUG(dbgs() << "LRR: Aborting - Root and Base #users not the same: "
844  << "#Base=" << NumBaseUses
845  << ", #Root=" << KV.second->getNumUses() << "\n");
846  return false;
847  }
848  }
849 
850  return true;
851 }
852 
853 void LoopReroll::DAGRootTracker::
854 findRootsRecursive(Instruction *I, SmallInstructionSet SubsumedInsts) {
855  // Does the user look like it could be part of a root set?
856  // All its users must be simple arithmetic ops.
857  if (I->hasNUsesOrMore(IL_MaxRerollIterations + 1))
858  return;
859 
860  if (I != IV && findRootsBase(I, SubsumedInsts))
861  return;
862 
863  SubsumedInsts.insert(I);
864 
865  for (User *V : I->users()) {
866  Instruction *I = cast<Instruction>(V);
867  if (is_contained(LoopIncs, I))
868  continue;
869 
870  if (!isSimpleArithmeticOp(I))
871  continue;
872 
873  // The recursive call makes a copy of SubsumedInsts.
874  findRootsRecursive(I, SubsumedInsts);
875  }
876 }
877 
878 bool LoopReroll::DAGRootTracker::validateRootSet(DAGRootSet &DRS) {
879  if (DRS.Roots.empty())
880  return false;
881 
882  // Consider a DAGRootSet with N-1 roots (so N different values including
883  // BaseInst).
884  // Define d = Roots[0] - BaseInst, which should be the same as
885  // Roots[I] - Roots[I-1] for all I in [1..N).
886  // Define D = BaseInst@J - BaseInst@J-1, where "@J" means the value at the
887  // loop iteration J.
888  //
889  // Now, For the loop iterations to be consecutive:
890  // D = d * N
891  const auto *ADR = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(DRS.BaseInst));
892  if (!ADR)
893  return false;
894 
895  // Check that the first root is evenly spaced.
896  unsigned N = DRS.Roots.size() + 1;
897  const SCEV *StepSCEV = SE->getMinusSCEV(SE->getSCEV(DRS.Roots[0]), ADR);
898  const SCEV *ScaleSCEV = SE->getConstant(StepSCEV->getType(), N);
899  if (ADR->getStepRecurrence(*SE) != SE->getMulExpr(StepSCEV, ScaleSCEV))
900  return false;
901 
902  // Check that the remainling roots are evenly spaced.
903  for (unsigned i = 1; i < N - 1; ++i) {
904  const SCEV *NewStepSCEV = SE->getMinusSCEV(SE->getSCEV(DRS.Roots[i]),
905  SE->getSCEV(DRS.Roots[i-1]));
906  if (NewStepSCEV != StepSCEV)
907  return false;
908  }
909 
910  return true;
911 }
912 
913 bool LoopReroll::DAGRootTracker::
914 findRootsBase(Instruction *IVU, SmallInstructionSet SubsumedInsts) {
915  // The base of a RootSet must be an AddRec, so it can be erased.
916  const auto *IVU_ADR = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(IVU));
917  if (!IVU_ADR || IVU_ADR->getLoop() != L)
918  return false;
919 
920  std::map<int64_t, Instruction*> V;
921  if (!collectPossibleRoots(IVU, V))
922  return false;
923 
924  // If we didn't get a root for index zero, then IVU must be
925  // subsumed.
926  if (V.find(0) == V.end())
927  SubsumedInsts.insert(IVU);
928 
929  // Partition the vector into monotonically increasing indexes.
930  DAGRootSet DRS;
931  DRS.BaseInst = nullptr;
932 
933  SmallVector<DAGRootSet, 16> PotentialRootSets;
934 
935  for (auto &KV : V) {
936  if (!DRS.BaseInst) {
937  DRS.BaseInst = KV.second;
938  DRS.SubsumedInsts = SubsumedInsts;
939  } else if (DRS.Roots.empty()) {
940  DRS.Roots.push_back(KV.second);
941  } else if (V.find(KV.first - 1) != V.end()) {
942  DRS.Roots.push_back(KV.second);
943  } else {
944  // Linear sequence terminated.
945  if (!validateRootSet(DRS))
946  return false;
947 
948  // Construct a new DAGRootSet with the next sequence.
949  PotentialRootSets.push_back(DRS);
950  DRS.BaseInst = KV.second;
951  DRS.Roots.clear();
952  }
953  }
954 
955  if (!validateRootSet(DRS))
956  return false;
957 
958  PotentialRootSets.push_back(DRS);
959 
960  RootSets.append(PotentialRootSets.begin(), PotentialRootSets.end());
961 
962  return true;
963 }
964 
965 bool LoopReroll::DAGRootTracker::findRoots() {
966  Inc = IVToIncMap[IV];
967 
968  assert(RootSets.empty() && "Unclean state!");
969  if (std::abs(Inc) == 1) {
970  for (auto *IVU : IV->users()) {
971  if (isLoopIncrement(IVU, IV))
972  LoopIncs.push_back(cast<Instruction>(IVU));
973  }
974  findRootsRecursive(IV, SmallInstructionSet());
975  LoopIncs.push_back(IV);
976  } else {
977  if (!findRootsBase(IV, SmallInstructionSet()))
978  return false;
979  }
980 
981  // Ensure all sets have the same size.
982  if (RootSets.empty()) {
983  LLVM_DEBUG(dbgs() << "LRR: Aborting because no root sets found!\n");
984  return false;
985  }
986  for (auto &V : RootSets) {
987  if (V.Roots.empty() || V.Roots.size() != RootSets[0].Roots.size()) {
988  LLVM_DEBUG(
989  dbgs()
990  << "LRR: Aborting because not all root sets have the same size\n");
991  return false;
992  }
993  }
994 
995  Scale = RootSets[0].Roots.size() + 1;
996 
997  if (Scale > IL_MaxRerollIterations) {
998  LLVM_DEBUG(dbgs() << "LRR: Aborting - too many iterations found. "
999  << "#Found=" << Scale
1000  << ", #Max=" << IL_MaxRerollIterations << "\n");
1001  return false;
1002  }
1003 
1004  LLVM_DEBUG(dbgs() << "LRR: Successfully found roots: Scale=" << Scale
1005  << "\n");
1006 
1007  return true;
1008 }
1009 
1010 bool LoopReroll::DAGRootTracker::collectUsedInstructions(SmallInstructionSet &PossibleRedSet) {
1011  // Populate the MapVector with all instructions in the block, in order first,
1012  // so we can iterate over the contents later in perfect order.
1013  for (auto &I : *L->getHeader()) {
1014  Uses[&I].resize(IL_End);
1015  }
1016 
1017  SmallInstructionSet Exclude;
1018  for (auto &DRS : RootSets) {
1019  Exclude.insert(DRS.Roots.begin(), DRS.Roots.end());
1020  Exclude.insert(DRS.SubsumedInsts.begin(), DRS.SubsumedInsts.end());
1021  Exclude.insert(DRS.BaseInst);
1022  }
1023  Exclude.insert(LoopIncs.begin(), LoopIncs.end());
1024 
1025  for (auto &DRS : RootSets) {
1026  DenseSet<Instruction*> VBase;
1027  collectInLoopUserSet(DRS.BaseInst, Exclude, PossibleRedSet, VBase);
1028  for (auto *I : VBase) {
1029  Uses[I].set(0);
1030  }
1031 
1032  unsigned Idx = 1;
1033  for (auto *Root : DRS.Roots) {
1035  collectInLoopUserSet(Root, Exclude, PossibleRedSet, V);
1036 
1037  // While we're here, check the use sets are the same size.
1038  if (V.size() != VBase.size()) {
1039  LLVM_DEBUG(dbgs() << "LRR: Aborting - use sets are different sizes\n");
1040  return false;
1041  }
1042 
1043  for (auto *I : V) {
1044  Uses[I].set(Idx);
1045  }
1046  ++Idx;
1047  }
1048 
1049  // Make sure our subsumed instructions are remembered too.
1050  for (auto *I : DRS.SubsumedInsts) {
1051  Uses[I].set(IL_All);
1052  }
1053  }
1054 
1055  // Make sure the loop increments are also accounted for.
1056 
1057  Exclude.clear();
1058  for (auto &DRS : RootSets) {
1059  Exclude.insert(DRS.Roots.begin(), DRS.Roots.end());
1060  Exclude.insert(DRS.SubsumedInsts.begin(), DRS.SubsumedInsts.end());
1061  Exclude.insert(DRS.BaseInst);
1062  }
1063 
1065  collectInLoopUserSet(LoopIncs, Exclude, PossibleRedSet, V);
1066  for (auto *I : V) {
1067  Uses[I].set(IL_All);
1068  }
1069 
1070  return true;
1071 }
1072 
1073 /// Get the next instruction in "In" that is a member of set Val.
1074 /// Start searching from StartI, and do not return anything in Exclude.
1075 /// If StartI is not given, start from In.begin().
1077 LoopReroll::DAGRootTracker::nextInstr(int Val, UsesTy &In,
1078  const SmallInstructionSet &Exclude,
1079  UsesTy::iterator *StartI) {
1080  UsesTy::iterator I = StartI ? *StartI : In.begin();
1081  while (I != In.end() && (I->second.test(Val) == 0 ||
1082  Exclude.count(I->first) != 0))
1083  ++I;
1084  return I;
1085 }
1086 
1087 bool LoopReroll::DAGRootTracker::isBaseInst(Instruction *I) {
1088  for (auto &DRS : RootSets) {
1089  if (DRS.BaseInst == I)
1090  return true;
1091  }
1092  return false;
1093 }
1094 
1095 bool LoopReroll::DAGRootTracker::isRootInst(Instruction *I) {
1096  for (auto &DRS : RootSets) {
1097  if (is_contained(DRS.Roots, I))
1098  return true;
1099  }
1100  return false;
1101 }
1102 
1103 /// Return true if instruction I depends on any instruction between
1104 /// Start and End.
1105 bool LoopReroll::DAGRootTracker::instrDependsOn(Instruction *I,
1106  UsesTy::iterator Start,
1107  UsesTy::iterator End) {
1108  for (auto *U : I->users()) {
1109  for (auto It = Start; It != End; ++It)
1110  if (U == It->first)
1111  return true;
1112  }
1113  return false;
1114 }
1115 
1116 static bool isIgnorableInst(const Instruction *I) {
1117  if (isa<DbgInfoIntrinsic>(I))
1118  return true;
1119  const IntrinsicInst* II = dyn_cast<IntrinsicInst>(I);
1120  if (!II)
1121  return false;
1122  switch (II->getIntrinsicID()) {
1123  default:
1124  return false;
1125  case Intrinsic::annotation:
1126  case Intrinsic::ptr_annotation:
1127  case Intrinsic::var_annotation:
1128  // TODO: the following intrinsics may also be whitelisted:
1129  // lifetime_start, lifetime_end, invariant_start, invariant_end
1130  return true;
1131  }
1132  return false;
1133 }
1134 
1135 bool LoopReroll::DAGRootTracker::validate(ReductionTracker &Reductions) {
1136  // We now need to check for equivalence of the use graph of each root with
1137  // that of the primary induction variable (excluding the roots). Our goal
1138  // here is not to solve the full graph isomorphism problem, but rather to
1139  // catch common cases without a lot of work. As a result, we will assume
1140  // that the relative order of the instructions in each unrolled iteration
1141  // is the same (although we will not make an assumption about how the
1142  // different iterations are intermixed). Note that while the order must be
1143  // the same, the instructions may not be in the same basic block.
1144 
1145  // An array of just the possible reductions for this scale factor. When we
1146  // collect the set of all users of some root instructions, these reduction
1147  // instructions are treated as 'final' (their uses are not considered).
1148  // This is important because we don't want the root use set to search down
1149  // the reduction chain.
1150  SmallInstructionSet PossibleRedSet;
1151  SmallInstructionSet PossibleRedLastSet;
1152  SmallInstructionSet PossibleRedPHISet;
1153  Reductions.restrictToScale(Scale, PossibleRedSet,
1154  PossibleRedPHISet, PossibleRedLastSet);
1155 
1156  // Populate "Uses" with where each instruction is used.
1157  if (!collectUsedInstructions(PossibleRedSet))
1158  return false;
1159 
1160  // Make sure we mark the reduction PHIs as used in all iterations.
1161  for (auto *I : PossibleRedPHISet) {
1162  Uses[I].set(IL_All);
1163  }
1164 
1165  // Make sure we mark loop-control-only PHIs as used in all iterations. See
1166  // comment above LoopReroll::isLoopControlIV for more information.
1167  BasicBlock *Header = L->getHeader();
1168  if (LoopControlIV && LoopControlIV != IV) {
1169  for (auto *U : LoopControlIV->users()) {
1170  Instruction *IVUser = dyn_cast<Instruction>(U);
1171  // IVUser could be loop increment or compare
1172  Uses[IVUser].set(IL_All);
1173  for (auto *UU : IVUser->users()) {
1174  Instruction *UUser = dyn_cast<Instruction>(UU);
1175  // UUser could be compare, PHI or branch
1176  Uses[UUser].set(IL_All);
1177  // Skip SExt
1178  if (isa<SExtInst>(UUser)) {
1179  UUser = dyn_cast<Instruction>(*(UUser->user_begin()));
1180  Uses[UUser].set(IL_All);
1181  }
1182  // Is UUser a compare instruction?
1183  if (UU->hasOneUse()) {
1184  Instruction *BI = dyn_cast<BranchInst>(*UUser->user_begin());
1185  if (BI == cast<BranchInst>(Header->getTerminator()))
1186  Uses[BI].set(IL_All);
1187  }
1188  }
1189  }
1190  }
1191 
1192  // Make sure all instructions in the loop are in one and only one
1193  // set.
1194  for (auto &KV : Uses) {
1195  if (KV.second.count() != 1 && !isIgnorableInst(KV.first)) {
1196  LLVM_DEBUG(
1197  dbgs() << "LRR: Aborting - instruction is not used in 1 iteration: "
1198  << *KV.first << " (#uses=" << KV.second.count() << ")\n");
1199  return false;
1200  }
1201  }
1202 
1203  LLVM_DEBUG(for (auto &KV
1204  : Uses) {
1205  dbgs() << "LRR: " << KV.second.find_first() << "\t" << *KV.first << "\n";
1206  });
1207 
1208  for (unsigned Iter = 1; Iter < Scale; ++Iter) {
1209  // In addition to regular aliasing information, we need to look for
1210  // instructions from later (future) iterations that have side effects
1211  // preventing us from reordering them past other instructions with side
1212  // effects.
1213  bool FutureSideEffects = false;
1214  AliasSetTracker AST(*AA);
1215  // The map between instructions in f(%iv.(i+1)) and f(%iv).
1217 
1218  // Compare iteration Iter to the base.
1219  SmallInstructionSet Visited;
1220  auto BaseIt = nextInstr(0, Uses, Visited);
1221  auto RootIt = nextInstr(Iter, Uses, Visited);
1222  auto LastRootIt = Uses.begin();
1223 
1224  while (BaseIt != Uses.end() && RootIt != Uses.end()) {
1225  Instruction *BaseInst = BaseIt->first;
1226  Instruction *RootInst = RootIt->first;
1227 
1228  // Skip over the IV or root instructions; only match their users.
1229  bool Continue = false;
1230  if (isBaseInst(BaseInst)) {
1231  Visited.insert(BaseInst);
1232  BaseIt = nextInstr(0, Uses, Visited);
1233  Continue = true;
1234  }
1235  if (isRootInst(RootInst)) {
1236  LastRootIt = RootIt;
1237  Visited.insert(RootInst);
1238  RootIt = nextInstr(Iter, Uses, Visited);
1239  Continue = true;
1240  }
1241  if (Continue) continue;
1242 
1243  if (!BaseInst->isSameOperationAs(RootInst)) {
1244  // Last chance saloon. We don't try and solve the full isomorphism
1245  // problem, but try and at least catch the case where two instructions
1246  // *of different types* are round the wrong way. We won't be able to
1247  // efficiently tell, given two ADD instructions, which way around we
1248  // should match them, but given an ADD and a SUB, we can at least infer
1249  // which one is which.
1250  //
1251  // This should allow us to deal with a greater subset of the isomorphism
1252  // problem. It does however change a linear algorithm into a quadratic
1253  // one, so limit the number of probes we do.
1254  auto TryIt = RootIt;
1255  unsigned N = NumToleratedFailedMatches;
1256  while (TryIt != Uses.end() &&
1257  !BaseInst->isSameOperationAs(TryIt->first) &&
1258  N--) {
1259  ++TryIt;
1260  TryIt = nextInstr(Iter, Uses, Visited, &TryIt);
1261  }
1262 
1263  if (TryIt == Uses.end() || TryIt == RootIt ||
1264  instrDependsOn(TryIt->first, RootIt, TryIt)) {
1265  LLVM_DEBUG(dbgs() << "LRR: iteration root match failed at "
1266  << *BaseInst << " vs. " << *RootInst << "\n");
1267  return false;
1268  }
1269 
1270  RootIt = TryIt;
1271  RootInst = TryIt->first;
1272  }
1273 
1274  // All instructions between the last root and this root
1275  // may belong to some other iteration. If they belong to a
1276  // future iteration, then they're dangerous to alias with.
1277  //
1278  // Note that because we allow a limited amount of flexibility in the order
1279  // that we visit nodes, LastRootIt might be *before* RootIt, in which
1280  // case we've already checked this set of instructions so we shouldn't
1281  // do anything.
1282  for (; LastRootIt < RootIt; ++LastRootIt) {
1283  Instruction *I = LastRootIt->first;
1284  if (LastRootIt->second.find_first() < (int)Iter)
1285  continue;
1286  if (I->mayWriteToMemory())
1287  AST.add(I);
1288  // Note: This is specifically guarded by a check on isa<PHINode>,
1289  // which while a valid (somewhat arbitrary) micro-optimization, is
1290  // needed because otherwise isSafeToSpeculativelyExecute returns
1291  // false on PHI nodes.
1292  if (!isa<PHINode>(I) && !isUnorderedLoadStore(I) &&
1294  // Intervening instructions cause side effects.
1295  FutureSideEffects = true;
1296  }
1297 
1298  // Make sure that this instruction, which is in the use set of this
1299  // root instruction, does not also belong to the base set or the set of
1300  // some other root instruction.
1301  if (RootIt->second.count() > 1) {
1302  LLVM_DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst
1303  << " vs. " << *RootInst << " (prev. case overlap)\n");
1304  return false;
1305  }
1306 
1307  // Make sure that we don't alias with any instruction in the alias set
1308  // tracker. If we do, then we depend on a future iteration, and we
1309  // can't reroll.
1310  if (RootInst->mayReadFromMemory())
1311  for (auto &K : AST) {
1312  if (K.aliasesUnknownInst(RootInst, *AA)) {
1313  LLVM_DEBUG(dbgs() << "LRR: iteration root match failed at "
1314  << *BaseInst << " vs. " << *RootInst
1315  << " (depends on future store)\n");
1316  return false;
1317  }
1318  }
1319 
1320  // If we've past an instruction from a future iteration that may have
1321  // side effects, and this instruction might also, then we can't reorder
1322  // them, and this matching fails. As an exception, we allow the alias
1323  // set tracker to handle regular (unordered) load/store dependencies.
1324  if (FutureSideEffects && ((!isUnorderedLoadStore(BaseInst) &&
1325  !isSafeToSpeculativelyExecute(BaseInst)) ||
1326  (!isUnorderedLoadStore(RootInst) &&
1327  !isSafeToSpeculativelyExecute(RootInst)))) {
1328  LLVM_DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst
1329  << " vs. " << *RootInst
1330  << " (side effects prevent reordering)\n");
1331  return false;
1332  }
1333 
1334  // For instructions that are part of a reduction, if the operation is
1335  // associative, then don't bother matching the operands (because we
1336  // already know that the instructions are isomorphic, and the order
1337  // within the iteration does not matter). For non-associative reductions,
1338  // we do need to match the operands, because we need to reject
1339  // out-of-order instructions within an iteration!
1340  // For example (assume floating-point addition), we need to reject this:
1341  // x += a[i]; x += b[i];
1342  // x += a[i+1]; x += b[i+1];
1343  // x += b[i+2]; x += a[i+2];
1344  bool InReduction = Reductions.isPairInSame(BaseInst, RootInst);
1345 
1346  if (!(InReduction && BaseInst->isAssociative())) {
1347  bool Swapped = false, SomeOpMatched = false;
1348  for (unsigned j = 0; j < BaseInst->getNumOperands(); ++j) {
1349  Value *Op2 = RootInst->getOperand(j);
1350 
1351  // If this is part of a reduction (and the operation is not
1352  // associatve), then we match all operands, but not those that are
1353  // part of the reduction.
1354  if (InReduction)
1355  if (Instruction *Op2I = dyn_cast<Instruction>(Op2))
1356  if (Reductions.isPairInSame(RootInst, Op2I))
1357  continue;
1358 
1359  DenseMap<Value *, Value *>::iterator BMI = BaseMap.find(Op2);
1360  if (BMI != BaseMap.end()) {
1361  Op2 = BMI->second;
1362  } else {
1363  for (auto &DRS : RootSets) {
1364  if (DRS.Roots[Iter-1] == (Instruction*) Op2) {
1365  Op2 = DRS.BaseInst;
1366  break;
1367  }
1368  }
1369  }
1370 
1371  if (BaseInst->getOperand(Swapped ? unsigned(!j) : j) != Op2) {
1372  // If we've not already decided to swap the matched operands, and
1373  // we've not already matched our first operand (note that we could
1374  // have skipped matching the first operand because it is part of a
1375  // reduction above), and the instruction is commutative, then try
1376  // the swapped match.
1377  if (!Swapped && BaseInst->isCommutative() && !SomeOpMatched &&
1378  BaseInst->getOperand(!j) == Op2) {
1379  Swapped = true;
1380  } else {
1381  LLVM_DEBUG(dbgs()
1382  << "LRR: iteration root match failed at " << *BaseInst
1383  << " vs. " << *RootInst << " (operand " << j << ")\n");
1384  return false;
1385  }
1386  }
1387 
1388  SomeOpMatched = true;
1389  }
1390  }
1391 
1392  if ((!PossibleRedLastSet.count(BaseInst) &&
1393  hasUsesOutsideLoop(BaseInst, L)) ||
1394  (!PossibleRedLastSet.count(RootInst) &&
1395  hasUsesOutsideLoop(RootInst, L))) {
1396  LLVM_DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst
1397  << " vs. " << *RootInst << " (uses outside loop)\n");
1398  return false;
1399  }
1400 
1401  Reductions.recordPair(BaseInst, RootInst, Iter);
1402  BaseMap.insert(std::make_pair(RootInst, BaseInst));
1403 
1404  LastRootIt = RootIt;
1405  Visited.insert(BaseInst);
1406  Visited.insert(RootInst);
1407  BaseIt = nextInstr(0, Uses, Visited);
1408  RootIt = nextInstr(Iter, Uses, Visited);
1409  }
1410  assert(BaseIt == Uses.end() && RootIt == Uses.end() &&
1411  "Mismatched set sizes!");
1412  }
1413 
1414  LLVM_DEBUG(dbgs() << "LRR: Matched all iteration increments for " << *IV
1415  << "\n");
1416 
1417  return true;
1418 }
1419 
1420 void LoopReroll::DAGRootTracker::replace(const SCEV *BackedgeTakenCount) {
1421  BasicBlock *Header = L->getHeader();
1422 
1423  // Compute the start and increment for each BaseInst before we start erasing
1424  // instructions.
1425  SmallVector<const SCEV *, 8> StartExprs;
1426  SmallVector<const SCEV *, 8> IncrExprs;
1427  for (auto &DRS : RootSets) {
1428  const SCEVAddRecExpr *IVSCEV =
1429  cast<SCEVAddRecExpr>(SE->getSCEV(DRS.BaseInst));
1430  StartExprs.push_back(IVSCEV->getStart());
1431  IncrExprs.push_back(SE->getMinusSCEV(SE->getSCEV(DRS.Roots[0]), IVSCEV));
1432  }
1433 
1434  // Remove instructions associated with non-base iterations.
1435  for (BasicBlock::reverse_iterator J = Header->rbegin(), JE = Header->rend();
1436  J != JE;) {
1437  unsigned I = Uses[&*J].find_first();
1438  if (I > 0 && I < IL_All) {
1439  LLVM_DEBUG(dbgs() << "LRR: removing: " << *J << "\n");
1440  J++->eraseFromParent();
1441  continue;
1442  }
1443 
1444  ++J;
1445  }
1446 
1447  // Rewrite each BaseInst using SCEV.
1448  for (size_t i = 0, e = RootSets.size(); i != e; ++i)
1449  // Insert the new induction variable.
1450  replaceIV(RootSets[i], StartExprs[i], IncrExprs[i]);
1451 
1452  { // Limit the lifetime of SCEVExpander.
1453  BranchInst *BI = cast<BranchInst>(Header->getTerminator());
1454  const DataLayout &DL = Header->getModule()->getDataLayout();
1455  SCEVExpander Expander(*SE, DL, "reroll");
1456  auto Zero = SE->getZero(BackedgeTakenCount->getType());
1457  auto One = SE->getOne(BackedgeTakenCount->getType());
1458  auto NewIVSCEV = SE->getAddRecExpr(Zero, One, L, SCEV::FlagAnyWrap);
1459  Value *NewIV =
1460  Expander.expandCodeFor(NewIVSCEV, BackedgeTakenCount->getType(),
1461  Header->getFirstNonPHIOrDbg());
1462  // FIXME: This arithmetic can overflow.
1463  auto TripCount = SE->getAddExpr(BackedgeTakenCount, One);
1464  auto ScaledTripCount = SE->getMulExpr(
1465  TripCount, SE->getConstant(BackedgeTakenCount->getType(), Scale));
1466  auto ScaledBECount = SE->getMinusSCEV(ScaledTripCount, One);
1467  Value *TakenCount =
1468  Expander.expandCodeFor(ScaledBECount, BackedgeTakenCount->getType(),
1469  Header->getFirstNonPHIOrDbg());
1470  Value *Cond =
1471  new ICmpInst(BI, CmpInst::ICMP_EQ, NewIV, TakenCount, "exitcond");
1472  BI->setCondition(Cond);
1473 
1474  if (BI->getSuccessor(1) != Header)
1475  BI->swapSuccessors();
1476  }
1477 
1478  SimplifyInstructionsInBlock(Header, TLI);
1479  DeleteDeadPHIs(Header, TLI);
1480 }
1481 
1482 void LoopReroll::DAGRootTracker::replaceIV(DAGRootSet &DRS,
1483  const SCEV *Start,
1484  const SCEV *IncrExpr) {
1485  BasicBlock *Header = L->getHeader();
1486  Instruction *Inst = DRS.BaseInst;
1487 
1488  const SCEV *NewIVSCEV =
1489  SE->getAddRecExpr(Start, IncrExpr, L, SCEV::FlagAnyWrap);
1490 
1491  { // Limit the lifetime of SCEVExpander.
1492  const DataLayout &DL = Header->getModule()->getDataLayout();
1493  SCEVExpander Expander(*SE, DL, "reroll");
1494  Value *NewIV = Expander.expandCodeFor(NewIVSCEV, Inst->getType(),
1495  Header->getFirstNonPHIOrDbg());
1496 
1497  for (auto &KV : Uses)
1498  if (KV.second.find_first() == 0)
1499  KV.first->replaceUsesOfWith(Inst, NewIV);
1500  }
1501 }
1502 
1503 // Validate the selected reductions. All iterations must have an isomorphic
1504 // part of the reduction chain and, for non-associative reductions, the chain
1505 // entries must appear in order.
1506 bool LoopReroll::ReductionTracker::validateSelected() {
1507  // For a non-associative reduction, the chain entries must appear in order.
1508  for (int i : Reds) {
1509  int PrevIter = 0, BaseCount = 0, Count = 0;
1510  for (Instruction *J : PossibleReds[i]) {
1511  // Note that all instructions in the chain must have been found because
1512  // all instructions in the function must have been assigned to some
1513  // iteration.
1514  int Iter = PossibleRedIter[J];
1515  if (Iter != PrevIter && Iter != PrevIter + 1 &&
1516  !PossibleReds[i].getReducedValue()->isAssociative()) {
1517  LLVM_DEBUG(dbgs() << "LRR: Out-of-order non-associative reduction: "
1518  << J << "\n");
1519  return false;
1520  }
1521 
1522  if (Iter != PrevIter) {
1523  if (Count != BaseCount) {
1524  LLVM_DEBUG(dbgs()
1525  << "LRR: Iteration " << PrevIter << " reduction use count "
1526  << Count << " is not equal to the base use count "
1527  << BaseCount << "\n");
1528  return false;
1529  }
1530 
1531  Count = 0;
1532  }
1533 
1534  ++Count;
1535  if (Iter == 0)
1536  ++BaseCount;
1537 
1538  PrevIter = Iter;
1539  }
1540  }
1541 
1542  return true;
1543 }
1544 
1545 // For all selected reductions, remove all parts except those in the first
1546 // iteration (and the PHI). Replace outside uses of the reduced value with uses
1547 // of the first-iteration reduced value (in other words, reroll the selected
1548 // reductions).
1549 void LoopReroll::ReductionTracker::replaceSelected() {
1550  // Fixup reductions to refer to the last instruction associated with the
1551  // first iteration (not the last).
1552  for (int i : Reds) {
1553  int j = 0;
1554  for (int e = PossibleReds[i].size(); j != e; ++j)
1555  if (PossibleRedIter[PossibleReds[i][j]] != 0) {
1556  --j;
1557  break;
1558  }
1559 
1560  // Replace users with the new end-of-chain value.
1561  SmallInstructionVector Users;
1562  for (User *U : PossibleReds[i].getReducedValue()->users()) {
1563  Users.push_back(cast<Instruction>(U));
1564  }
1565 
1566  for (Instruction *User : Users)
1567  User->replaceUsesOfWith(PossibleReds[i].getReducedValue(),
1568  PossibleReds[i][j]);
1569  }
1570 }
1571 
1572 // Reroll the provided loop with respect to the provided induction variable.
1573 // Generally, we're looking for a loop like this:
1574 //
1575 // %iv = phi [ (preheader, ...), (body, %iv.next) ]
1576 // f(%iv)
1577 // %iv.1 = add %iv, 1 <-- a root increment
1578 // f(%iv.1)
1579 // %iv.2 = add %iv, 2 <-- a root increment
1580 // f(%iv.2)
1581 // %iv.scale_m_1 = add %iv, scale-1 <-- a root increment
1582 // f(%iv.scale_m_1)
1583 // ...
1584 // %iv.next = add %iv, scale
1585 // %cmp = icmp(%iv, ...)
1586 // br %cmp, header, exit
1587 //
1588 // Notably, we do not require that f(%iv), f(%iv.1), etc. be isolated groups of
1589 // instructions. In other words, the instructions in f(%iv), f(%iv.1), etc. can
1590 // be intermixed with eachother. The restriction imposed by this algorithm is
1591 // that the relative order of the isomorphic instructions in f(%iv), f(%iv.1),
1592 // etc. be the same.
1593 //
1594 // First, we collect the use set of %iv, excluding the other increment roots.
1595 // This gives us f(%iv). Then we iterate over the loop instructions (scale-1)
1596 // times, having collected the use set of f(%iv.(i+1)), during which we:
1597 // - Ensure that the next unmatched instruction in f(%iv) is isomorphic to
1598 // the next unmatched instruction in f(%iv.(i+1)).
1599 // - Ensure that both matched instructions don't have any external users
1600 // (with the exception of last-in-chain reduction instructions).
1601 // - Track the (aliasing) write set, and other side effects, of all
1602 // instructions that belong to future iterations that come before the matched
1603 // instructions. If the matched instructions read from that write set, then
1604 // f(%iv) or f(%iv.(i+1)) has some dependency on instructions in
1605 // f(%iv.(j+1)) for some j > i, and we cannot reroll the loop. Similarly,
1606 // if any of these future instructions had side effects (could not be
1607 // speculatively executed), and so do the matched instructions, when we
1608 // cannot reorder those side-effect-producing instructions, and rerolling
1609 // fails.
1610 //
1611 // Finally, we make sure that all loop instructions are either loop increment
1612 // roots, belong to simple latch code, parts of validated reductions, part of
1613 // f(%iv) or part of some f(%iv.i). If all of that is true (and all reductions
1614 // have been validated), then we reroll the loop.
1615 bool LoopReroll::reroll(Instruction *IV, Loop *L, BasicBlock *Header,
1616  const SCEV *BackedgeTakenCount,
1617  ReductionTracker &Reductions) {
1618  DAGRootTracker DAGRoots(this, L, IV, SE, AA, TLI, DT, LI, PreserveLCSSA,
1619  IVToIncMap, LoopControlIV);
1620 
1621  if (!DAGRoots.findRoots())
1622  return false;
1623  LLVM_DEBUG(dbgs() << "LRR: Found all root induction increments for: " << *IV
1624  << "\n");
1625 
1626  if (!DAGRoots.validate(Reductions))
1627  return false;
1628  if (!Reductions.validateSelected())
1629  return false;
1630  // At this point, we've validated the rerolling, and we're committed to
1631  // making changes!
1632 
1633  Reductions.replaceSelected();
1634  DAGRoots.replace(BackedgeTakenCount);
1635 
1636  ++NumRerolledLoops;
1637  return true;
1638 }
1639 
1640 bool LoopReroll::runOnLoop(Loop *L, LPPassManager &LPM) {
1641  if (skipLoop(L))
1642  return false;
1643 
1644  AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
1645  LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
1646  SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
1647  TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
1648  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1649  PreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
1650 
1651  BasicBlock *Header = L->getHeader();
1652  LLVM_DEBUG(dbgs() << "LRR: F[" << Header->getParent()->getName() << "] Loop %"
1653  << Header->getName() << " (" << L->getNumBlocks()
1654  << " block(s))\n");
1655 
1656  // For now, we'll handle only single BB loops.
1657  if (L->getNumBlocks() > 1)
1658  return false;
1659 
1660  if (!SE->hasLoopInvariantBackedgeTakenCount(L))
1661  return false;
1662 
1663  const SCEV *BackedgeTakenCount = SE->getBackedgeTakenCount(L);
1664  LLVM_DEBUG(dbgs() << "\n Before Reroll:\n" << *(L->getHeader()) << "\n");
1665  LLVM_DEBUG(dbgs() << "LRR: backedge-taken count = " << *BackedgeTakenCount
1666  << "\n");
1667 
1668  // First, we need to find the induction variable with respect to which we can
1669  // reroll (there may be several possible options).
1670  SmallInstructionVector PossibleIVs;
1671  IVToIncMap.clear();
1672  LoopControlIV = nullptr;
1673  collectPossibleIVs(L, PossibleIVs);
1674 
1675  if (PossibleIVs.empty()) {
1676  LLVM_DEBUG(dbgs() << "LRR: No possible IVs found\n");
1677  return false;
1678  }
1679 
1680  ReductionTracker Reductions;
1681  collectPossibleReductions(L, Reductions);
1682  bool Changed = false;
1683 
1684  // For each possible IV, collect the associated possible set of 'root' nodes
1685  // (i+1, i+2, etc.).
1686  for (Instruction *PossibleIV : PossibleIVs)
1687  if (reroll(PossibleIV, L, Header, BackedgeTakenCount, Reductions)) {
1688  Changed = true;
1689  break;
1690  }
1691  LLVM_DEBUG(dbgs() << "\n After Reroll:\n" << *(L->getHeader()) << "\n");
1692 
1693  // Trip count of L has changed so SE must be re-evaluated.
1694  if (Changed)
1695  SE->forgetLoop(L);
1696 
1697  return Changed;
1698 }
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:80
uint64_t CallInst * C
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:110
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:233
Pass * createLoopRerollPass()
iterator_range< use_iterator > uses()
Definition: Value.h:354
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
const_iterator begin(StringRef path, Style style=Style::native)
Get begin iterator over path.
Definition: Path.cpp:224
bool isSameOperationAs(const Instruction *I, unsigned flags=0) const
This function determines if the specified instruction executes the same operation as the current one...
This class represents lattice values for constants.
Definition: AllocatorList.h:23
BinaryOps getOpcode() const
Definition: InstrTypes.h:402
void swapSuccessors()
Swap the successors of this branch instruction.
bool user_empty() const
Definition: Value.h:363
Implements a dense probed hash-table based set.
Definition: DenseSet.h:249
void push_back(const T &Elt)
Definition: SmallVector.h:211
static cl::opt< unsigned > NumToleratedFailedMatches("reroll-num-tolerated-failed-matches", cl::init(400), cl::Hidden, cl::desc("The maximum number of failures to tolerate" " during fuzzy matching. (default: 400)"))
void add(Value *Ptr, LocationSize Size, const AAMDNodes &AAInfo)
These methods are used to add different types of instructions to the alias sets.
The main scalar evolution driver.
void replace(Container &Cont, typename Container::iterator ContIt, typename Container::iterator ContEnd, RandomAccessIterator ValIt, RandomAccessIterator ValEnd)
Given a sequence container Cont, replace the range [ContIt, ContEnd) with the range [ValIt...
Definition: STLExtras.h:1398
bool mayWriteToMemory() const
Return true if this instruction may modify memory.
This class implements a map that also provides access to all stored values in a deterministic order...
Definition: MapVector.h:37
BasicBlock * getSuccessor(unsigned i) const
STATISTIC(NumFunctions, "Total number of functions")
bool SimplifyInstructionsInBlock(BasicBlock *BB, const TargetLibraryInfo *TLI=nullptr)
Scan the specified basic block and try to simplify any instructions in it and recursively delete dead...
Definition: Local.cpp:596
void initializeLoopRerollPass(PassRegistry &)
reverse_iterator rend()
Definition: BasicBlock.h:275
An instruction for reading from memory.
Definition: Instructions.h:167
reverse_iterator rbegin()
Definition: BasicBlock.h:273
Hexagon Common GEP
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
iv Induction Variable Users
Definition: IVUsers.cpp:51
This defines the Use class.
op_iterator op_begin()
Definition: User.h:229
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:268
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:221
static bool isIgnorableInst(const Instruction *I)
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
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:369
static bool isUnorderedLoadStore(Instruction *I)
A Use represents the edge between a Value definition and its users.
Definition: Use.h:55
static bool hasUsesOutsideLoop(Instruction *I, Loop *L)
This file implements a class to represent arbitrary precision integral constant values and operations...
BlockT * getHeader() const
Definition: LoopInfo.h:102
ConstantInt * getValue() const
int64_t getSExtValue() const
Get sign extended value.
Definition: APInt.h:1574
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:244
This node represents a polynomial recurrence on the trip count of the specified loop.
bool DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI=nullptr)
Examine each PHI in the given block and delete it if it is dead.
const APInt & getValue() const
Return the constant as an APInt value reference.
Definition: Constants.h:137
An instruction for storing to memory.
Definition: Instructions.h:320
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:144
Value * getOperand(unsigned i) const
Definition: User.h:169
void replaceUsesOfWith(Value *From, Value *To)
Replace uses of one Value with another.
Definition: User.cpp:20
iterator find(const_arg_type_t< KeyT > Val)
Definition: DenseMap.h:176
#define P(N)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:432
friend const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:233
bool hasNUsesOrMore(unsigned N) const
Return true if this value has N users or more.
Definition: Value.cpp:135
const_iterator getFirstInsertionPt() const
Returns an iterator to the first instruction in this block that is suitable for inserting a non-PHI i...
Definition: BasicBlock.cpp:216
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
Conditional or Unconditional Branch instruction.
This file contains the declarations for the subclasses of Constant, which represent the different fla...
char & LCSSAID
Definition: LCSSA.cpp:467
bool isAssociative() const LLVM_READONLY
Return true if the instruction is associative:
Represent the analysis usage information of a pass.
op_iterator op_end()
Definition: User.h:231
This instruction compares its operands according to the predicate given to the constructor.
bool isBinaryOp() const
Definition: Instruction.h:130
Value * expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I)
Insert code to directly compute the specified SCEV expression into the program.
static void replace(Module &M, GlobalVariable *Old, GlobalVariable *New)
static bool isLoopIncrement(User *U, Instruction *IV)
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
Intrinsic::ID getIntrinsicID() const
Return the intrinsic ID of this intrinsic.
Definition: IntrinsicInst.h:50
IterationLimits
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:112
This is the common base class for memset/memcpy/memmove.
Iterator for intrusive lists based on ilist_node.
unsigned getNumOperands() const
Definition: User.h:191
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:417
This is the shared class of boolean and integer constants.
Definition: Constants.h:83
auto size(R &&Range, typename std::enable_if< std::is_same< typename std::iterator_traits< decltype(Range.begin())>::iterator_category, std::random_access_iterator_tag >::value, void >::type *=nullptr) -> decltype(std::distance(Range.begin(), Range.end()))
Get the size of a range.
Definition: STLExtras.h:1173
Type * getType() const
Return the LLVM type of this SCEV expression.
static uint64_t add(uint64_t LeftOp, uint64_t RightOp)
Definition: FileCheck.cpp:169
Module.h This file contains the declarations for the Module class.
Provides information about what library functions are available for the current target.
#define INITIALIZE_PASS_BEGIN(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:47
typename VectorType::iterator iterator
Definition: MapVector.h:49
bool isCommutative() const
Return true if the instruction is commutative:
Definition: Instruction.h:488
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
iterator_range< user_iterator > users()
Definition: Value.h:399
This class uses information about analyze scalars to rewrite expressions in canonical form...
static bool isSimpleArithmeticOp(User *IVU)
Return true if IVU is a "simple" arithmetic operation.
unsigned getNumBlocks() const
Get the number of blocks in this loop in constant time.
Definition: LoopInfo.h:165
unsigned getNumUses() const
This method computes the number of uses of this Value.
Definition: Value.cpp:160
iv users
Definition: IVUsers.cpp:51
This class represents an analyzed expression in the program.
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:501
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:214
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:106
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
APFloat abs(APFloat X)
Returns the absolute value of the argument.
Definition: APFloat.h:1223
bool mayReadFromMemory() const
Return true if this instruction may read memory.
void getLoopAnalysisUsage(AnalysisUsage &AU)
Helper to consistently add the set of standard passes to a loop pass&#39;s AnalysisUsage.
Definition: LoopUtils.cpp:136
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
void setCondition(Value *V)
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
user_iterator user_begin()
Definition: Value.h:375
bool isSafeToSpeculativelyExecute(const Value *V, const Instruction *CtxI=nullptr, const DominatorTree *DT=nullptr)
Return true if the instruction does not have any effects besides calculating the result and does not ...
LLVM Value Representation.
Definition: Value.h:72
IRTranslator LLVM IR MI
bool hasOneUse() const
Return true if there is exactly one user of this value.
Definition: Value.h:412
const Instruction * getFirstNonPHIOrDbg() const
Returns a pointer to the first instruction in this block that is not a PHINode or a debug intrinsic...
Definition: BasicBlock.cpp:196
int64_t getSExtValue() const
Return the constant as a 64-bit integer value after it has been sign extended as appropriate for the ...
Definition: Constants.h:156
static bool isAssociative(const COFFSection &Section)
#define LLVM_DEBUG(X)
Definition: Debug.h:122
bool use_empty() const
Definition: Value.h:322
void validate(const Triple &TT, const FeatureBitset &FeatureBits)
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:43
const BasicBlock * getParent() const
Definition: Instruction.h:66
This class represents a constant integer value.
bool is_contained(R &&Range, const E &Element)
Wrapper function around std::find to detect if an element exists in a container.
Definition: STLExtras.h:1251