LLVM  7.0.0svn
LoopStrengthReduce.cpp
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1 //===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
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 transformation analyzes and transforms the induction variables (and
11 // computations derived from them) into forms suitable for efficient execution
12 // on the target.
13 //
14 // This pass performs a strength reduction on array references inside loops that
15 // have as one or more of their components the loop induction variable, it
16 // rewrites expressions to take advantage of scaled-index addressing modes
17 // available on the target, and it performs a variety of other optimizations
18 // related to loop induction variables.
19 //
20 // Terminology note: this code has a lot of handling for "post-increment" or
21 // "post-inc" users. This is not talking about post-increment addressing modes;
22 // it is instead talking about code like this:
23 //
24 // %i = phi [ 0, %entry ], [ %i.next, %latch ]
25 // ...
26 // %i.next = add %i, 1
27 // %c = icmp eq %i.next, %n
28 //
29 // The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
30 // it's useful to think about these as the same register, with some uses using
31 // the value of the register before the add and some using it after. In this
32 // example, the icmp is a post-increment user, since it uses %i.next, which is
33 // the value of the induction variable after the increment. The other common
34 // case of post-increment users is users outside the loop.
35 //
36 // TODO: More sophistication in the way Formulae are generated and filtered.
37 //
38 // TODO: Handle multiple loops at a time.
39 //
40 // TODO: Should the addressing mode BaseGV be changed to a ConstantExpr instead
41 // of a GlobalValue?
42 //
43 // TODO: When truncation is free, truncate ICmp users' operands to make it a
44 // smaller encoding (on x86 at least).
45 //
46 // TODO: When a negated register is used by an add (such as in a list of
47 // multiple base registers, or as the increment expression in an addrec),
48 // we may not actually need both reg and (-1 * reg) in registers; the
49 // negation can be implemented by using a sub instead of an add. The
50 // lack of support for taking this into consideration when making
51 // register pressure decisions is partly worked around by the "Special"
52 // use kind.
53 //
54 //===----------------------------------------------------------------------===//
55 
57 #include "llvm/ADT/APInt.h"
58 #include "llvm/ADT/DenseMap.h"
59 #include "llvm/ADT/DenseSet.h"
60 #include "llvm/ADT/Hashing.h"
62 #include "llvm/ADT/STLExtras.h"
63 #include "llvm/ADT/SetVector.h"
65 #include "llvm/ADT/SmallPtrSet.h"
66 #include "llvm/ADT/SmallSet.h"
67 #include "llvm/ADT/SmallVector.h"
69 #include "llvm/Analysis/IVUsers.h"
71 #include "llvm/Analysis/LoopInfo.h"
72 #include "llvm/Analysis/LoopPass.h"
78 #include "llvm/IR/BasicBlock.h"
79 #include "llvm/IR/Constant.h"
80 #include "llvm/IR/Constants.h"
81 #include "llvm/IR/DerivedTypes.h"
82 #include "llvm/IR/Dominators.h"
83 #include "llvm/IR/GlobalValue.h"
84 #include "llvm/IR/IRBuilder.h"
85 #include "llvm/IR/InstrTypes.h"
86 #include "llvm/IR/Instruction.h"
87 #include "llvm/IR/Instructions.h"
88 #include "llvm/IR/IntrinsicInst.h"
89 #include "llvm/IR/Intrinsics.h"
90 #include "llvm/IR/Module.h"
91 #include "llvm/IR/OperandTraits.h"
92 #include "llvm/IR/Operator.h"
93 #include "llvm/IR/PassManager.h"
94 #include "llvm/IR/Type.h"
95 #include "llvm/IR/Use.h"
96 #include "llvm/IR/User.h"
97 #include "llvm/IR/Value.h"
98 #include "llvm/IR/ValueHandle.h"
99 #include "llvm/Pass.h"
100 #include "llvm/Support/Casting.h"
102 #include "llvm/Support/Compiler.h"
103 #include "llvm/Support/Debug.h"
105 #include "llvm/Support/MathExtras.h"
107 #include "llvm/Transforms/Scalar.h"
110 #include <algorithm>
111 #include <cassert>
112 #include <cstddef>
113 #include <cstdint>
114 #include <cstdlib>
115 #include <iterator>
116 #include <limits>
117 #include <map>
118 #include <utility>
119 
120 using namespace llvm;
121 
122 #define DEBUG_TYPE "loop-reduce"
123 
124 /// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for
125 /// bail out. This threshold is far beyond the number of users that LSR can
126 /// conceivably solve, so it should not affect generated code, but catches the
127 /// worst cases before LSR burns too much compile time and stack space.
128 static const unsigned MaxIVUsers = 200;
129 
130 // Temporary flag to cleanup congruent phis after LSR phi expansion.
131 // It's currently disabled until we can determine whether it's truly useful or
132 // not. The flag should be removed after the v3.0 release.
133 // This is now needed for ivchains.
135  "enable-lsr-phielim", cl::Hidden, cl::init(true),
136  cl::desc("Enable LSR phi elimination"));
137 
138 // The flag adds instruction count to solutions cost comparision.
139 static cl::opt<bool> InsnsCost(
140  "lsr-insns-cost", cl::Hidden, cl::init(true),
141  cl::desc("Add instruction count to a LSR cost model"));
142 
143 // Flag to choose how to narrow complex lsr solution
145  "lsr-exp-narrow", cl::Hidden, cl::init(false),
146  cl::desc("Narrow LSR complex solution using"
147  " expectation of registers number"));
148 
149 // Flag to narrow search space by filtering non-optimal formulae with
150 // the same ScaledReg and Scale.
152  "lsr-filter-same-scaled-reg", cl::Hidden, cl::init(true),
153  cl::desc("Narrow LSR search space by filtering non-optimal formulae"
154  " with the same ScaledReg and Scale"));
155 
156 #ifndef NDEBUG
157 // Stress test IV chain generation.
159  "stress-ivchain", cl::Hidden, cl::init(false),
160  cl::desc("Stress test LSR IV chains"));
161 #else
162 static bool StressIVChain = false;
163 #endif
164 
165 namespace {
166 
167 struct MemAccessTy {
168  /// Used in situations where the accessed memory type is unknown.
169  static const unsigned UnknownAddressSpace =
171 
172  Type *MemTy = nullptr;
173  unsigned AddrSpace = UnknownAddressSpace;
174 
175  MemAccessTy() = default;
176  MemAccessTy(Type *Ty, unsigned AS) : MemTy(Ty), AddrSpace(AS) {}
177 
178  bool operator==(MemAccessTy Other) const {
179  return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace;
180  }
181 
182  bool operator!=(MemAccessTy Other) const { return !(*this == Other); }
183 
184  static MemAccessTy getUnknown(LLVMContext &Ctx,
185  unsigned AS = UnknownAddressSpace) {
186  return MemAccessTy(Type::getVoidTy(Ctx), AS);
187  }
188 };
189 
190 /// This class holds data which is used to order reuse candidates.
191 class RegSortData {
192 public:
193  /// This represents the set of LSRUse indices which reference
194  /// a particular register.
195  SmallBitVector UsedByIndices;
196 
197  void print(raw_ostream &OS) const;
198  void dump() const;
199 };
200 
201 } // end anonymous namespace
202 
203 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
204 void RegSortData::print(raw_ostream &OS) const {
205  OS << "[NumUses=" << UsedByIndices.count() << ']';
206 }
207 
208 LLVM_DUMP_METHOD void RegSortData::dump() const {
209  print(errs()); errs() << '\n';
210 }
211 #endif
212 
213 namespace {
214 
215 /// Map register candidates to information about how they are used.
216 class RegUseTracker {
217  using RegUsesTy = DenseMap<const SCEV *, RegSortData>;
218 
219  RegUsesTy RegUsesMap;
221 
222 public:
223  void countRegister(const SCEV *Reg, size_t LUIdx);
224  void dropRegister(const SCEV *Reg, size_t LUIdx);
225  void swapAndDropUse(size_t LUIdx, size_t LastLUIdx);
226 
227  bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
228 
229  const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
230 
231  void clear();
232 
234  using const_iterator = SmallVectorImpl<const SCEV *>::const_iterator;
235 
236  iterator begin() { return RegSequence.begin(); }
237  iterator end() { return RegSequence.end(); }
238  const_iterator begin() const { return RegSequence.begin(); }
239  const_iterator end() const { return RegSequence.end(); }
240 };
241 
242 } // end anonymous namespace
243 
244 void
245 RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) {
246  std::pair<RegUsesTy::iterator, bool> Pair =
247  RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
248  RegSortData &RSD = Pair.first->second;
249  if (Pair.second)
250  RegSequence.push_back(Reg);
251  RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
252  RSD.UsedByIndices.set(LUIdx);
253 }
254 
255 void
256 RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) {
257  RegUsesTy::iterator It = RegUsesMap.find(Reg);
258  assert(It != RegUsesMap.end());
259  RegSortData &RSD = It->second;
260  assert(RSD.UsedByIndices.size() > LUIdx);
261  RSD.UsedByIndices.reset(LUIdx);
262 }
263 
264 void
265 RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
266  assert(LUIdx <= LastLUIdx);
267 
268  // Update RegUses. The data structure is not optimized for this purpose;
269  // we must iterate through it and update each of the bit vectors.
270  for (auto &Pair : RegUsesMap) {
271  SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
272  if (LUIdx < UsedByIndices.size())
273  UsedByIndices[LUIdx] =
274  LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false;
275  UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
276  }
277 }
278 
279 bool
280 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
281  RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
282  if (I == RegUsesMap.end())
283  return false;
284  const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
285  int i = UsedByIndices.find_first();
286  if (i == -1) return false;
287  if ((size_t)i != LUIdx) return true;
288  return UsedByIndices.find_next(i) != -1;
289 }
290 
291 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
292  RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
293  assert(I != RegUsesMap.end() && "Unknown register!");
294  return I->second.UsedByIndices;
295 }
296 
297 void RegUseTracker::clear() {
298  RegUsesMap.clear();
299  RegSequence.clear();
300 }
301 
302 namespace {
303 
304 /// This class holds information that describes a formula for computing
305 /// satisfying a use. It may include broken-out immediates and scaled registers.
306 struct Formula {
307  /// Global base address used for complex addressing.
308  GlobalValue *BaseGV = nullptr;
309 
310  /// Base offset for complex addressing.
311  int64_t BaseOffset = 0;
312 
313  /// Whether any complex addressing has a base register.
314  bool HasBaseReg = false;
315 
316  /// The scale of any complex addressing.
317  int64_t Scale = 0;
318 
319  /// The list of "base" registers for this use. When this is non-empty. The
320  /// canonical representation of a formula is
321  /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
322  /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
323  /// 3. The reg containing recurrent expr related with currect loop in the
324  /// formula should be put in the ScaledReg.
325  /// #1 enforces that the scaled register is always used when at least two
326  /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
327  /// #2 enforces that 1 * reg is reg.
328  /// #3 ensures invariant regs with respect to current loop can be combined
329  /// together in LSR codegen.
330  /// This invariant can be temporarly broken while building a formula.
331  /// However, every formula inserted into the LSRInstance must be in canonical
332  /// form.
334 
335  /// The 'scaled' register for this use. This should be non-null when Scale is
336  /// not zero.
337  const SCEV *ScaledReg = nullptr;
338 
339  /// An additional constant offset which added near the use. This requires a
340  /// temporary register, but the offset itself can live in an add immediate
341  /// field rather than a register.
342  int64_t UnfoldedOffset = 0;
343 
344  Formula() = default;
345 
346  void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
347 
348  bool isCanonical(const Loop &L) const;
349 
350  void canonicalize(const Loop &L);
351 
352  bool unscale();
353 
354  bool hasZeroEnd() const;
355 
356  size_t getNumRegs() const;
357  Type *getType() const;
358 
359  void deleteBaseReg(const SCEV *&S);
360 
361  bool referencesReg(const SCEV *S) const;
362  bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
363  const RegUseTracker &RegUses) const;
364 
365  void print(raw_ostream &OS) const;
366  void dump() const;
367 };
368 
369 } // end anonymous namespace
370 
371 /// Recursion helper for initialMatch.
372 static void DoInitialMatch(const SCEV *S, Loop *L,
375  ScalarEvolution &SE) {
376  // Collect expressions which properly dominate the loop header.
377  if (SE.properlyDominates(S, L->getHeader())) {
378  Good.push_back(S);
379  return;
380  }
381 
382  // Look at add operands.
383  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
384  for (const SCEV *S : Add->operands())
385  DoInitialMatch(S, L, Good, Bad, SE);
386  return;
387  }
388 
389  // Look at addrec operands.
390  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
391  if (!AR->getStart()->isZero() && AR->isAffine()) {
392  DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
393  DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
394  AR->getStepRecurrence(SE),
395  // FIXME: AR->getNoWrapFlags()
396  AR->getLoop(), SCEV::FlagAnyWrap),
397  L, Good, Bad, SE);
398  return;
399  }
400 
401  // Handle a multiplication by -1 (negation) if it didn't fold.
402  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
403  if (Mul->getOperand(0)->isAllOnesValue()) {
404  SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
405  const SCEV *NewMul = SE.getMulExpr(Ops);
406 
409  DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
410  const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
411  SE.getEffectiveSCEVType(NewMul->getType())));
412  for (const SCEV *S : MyGood)
413  Good.push_back(SE.getMulExpr(NegOne, S));
414  for (const SCEV *S : MyBad)
415  Bad.push_back(SE.getMulExpr(NegOne, S));
416  return;
417  }
418 
419  // Ok, we can't do anything interesting. Just stuff the whole thing into a
420  // register and hope for the best.
421  Bad.push_back(S);
422 }
423 
424 /// Incorporate loop-variant parts of S into this Formula, attempting to keep
425 /// all loop-invariant and loop-computable values in a single base register.
426 void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
429  DoInitialMatch(S, L, Good, Bad, SE);
430  if (!Good.empty()) {
431  const SCEV *Sum = SE.getAddExpr(Good);
432  if (!Sum->isZero())
433  BaseRegs.push_back(Sum);
434  HasBaseReg = true;
435  }
436  if (!Bad.empty()) {
437  const SCEV *Sum = SE.getAddExpr(Bad);
438  if (!Sum->isZero())
439  BaseRegs.push_back(Sum);
440  HasBaseReg = true;
441  }
442  canonicalize(*L);
443 }
444 
445 /// \brief Check whether or not this formula statisfies the canonical
446 /// representation.
447 /// \see Formula::BaseRegs.
448 bool Formula::isCanonical(const Loop &L) const {
449  if (!ScaledReg)
450  return BaseRegs.size() <= 1;
451 
452  if (Scale != 1)
453  return true;
454 
455  if (Scale == 1 && BaseRegs.empty())
456  return false;
457 
458  const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
459  if (SAR && SAR->getLoop() == &L)
460  return true;
461 
462  // If ScaledReg is not a recurrent expr, or it is but its loop is not current
463  // loop, meanwhile BaseRegs contains a recurrent expr reg related with current
464  // loop, we want to swap the reg in BaseRegs with ScaledReg.
465  auto I =
466  find_if(make_range(BaseRegs.begin(), BaseRegs.end()), [&](const SCEV *S) {
467  return isa<const SCEVAddRecExpr>(S) &&
468  (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
469  });
470  return I == BaseRegs.end();
471 }
472 
473 /// \brief Helper method to morph a formula into its canonical representation.
474 /// \see Formula::BaseRegs.
475 /// Every formula having more than one base register, must use the ScaledReg
476 /// field. Otherwise, we would have to do special cases everywhere in LSR
477 /// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
478 /// On the other hand, 1*reg should be canonicalized into reg.
479 void Formula::canonicalize(const Loop &L) {
480  if (isCanonical(L))
481  return;
482  // So far we did not need this case. This is easy to implement but it is
483  // useless to maintain dead code. Beside it could hurt compile time.
484  assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.");
485 
486  // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
487  if (!ScaledReg) {
488  ScaledReg = BaseRegs.back();
489  BaseRegs.pop_back();
490  Scale = 1;
491  }
492 
493  // If ScaledReg is an invariant with respect to L, find the reg from
494  // BaseRegs containing the recurrent expr related with Loop L. Swap the
495  // reg with ScaledReg.
496  const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
497  if (!SAR || SAR->getLoop() != &L) {
498  auto I = find_if(make_range(BaseRegs.begin(), BaseRegs.end()),
499  [&](const SCEV *S) {
500  return isa<const SCEVAddRecExpr>(S) &&
501  (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
502  });
503  if (I != BaseRegs.end())
504  std::swap(ScaledReg, *I);
505  }
506 }
507 
508 /// \brief Get rid of the scale in the formula.
509 /// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
510 /// \return true if it was possible to get rid of the scale, false otherwise.
511 /// \note After this operation the formula may not be in the canonical form.
512 bool Formula::unscale() {
513  if (Scale != 1)
514  return false;
515  Scale = 0;
516  BaseRegs.push_back(ScaledReg);
517  ScaledReg = nullptr;
518  return true;
519 }
520 
521 bool Formula::hasZeroEnd() const {
522  if (UnfoldedOffset || BaseOffset)
523  return false;
524  if (BaseRegs.size() != 1 || ScaledReg)
525  return false;
526  return true;
527 }
528 
529 /// Return the total number of register operands used by this formula. This does
530 /// not include register uses implied by non-constant addrec strides.
531 size_t Formula::getNumRegs() const {
532  return !!ScaledReg + BaseRegs.size();
533 }
534 
535 /// Return the type of this formula, if it has one, or null otherwise. This type
536 /// is meaningless except for the bit size.
537 Type *Formula::getType() const {
538  return !BaseRegs.empty() ? BaseRegs.front()->getType() :
539  ScaledReg ? ScaledReg->getType() :
540  BaseGV ? BaseGV->getType() :
541  nullptr;
542 }
543 
544 /// Delete the given base reg from the BaseRegs list.
545 void Formula::deleteBaseReg(const SCEV *&S) {
546  if (&S != &BaseRegs.back())
547  std::swap(S, BaseRegs.back());
548  BaseRegs.pop_back();
549 }
550 
551 /// Test if this formula references the given register.
552 bool Formula::referencesReg(const SCEV *S) const {
553  return S == ScaledReg || is_contained(BaseRegs, S);
554 }
555 
556 /// Test whether this formula uses registers which are used by uses other than
557 /// the use with the given index.
558 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
559  const RegUseTracker &RegUses) const {
560  if (ScaledReg)
561  if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
562  return true;
563  for (const SCEV *BaseReg : BaseRegs)
564  if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
565  return true;
566  return false;
567 }
568 
569 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
570 void Formula::print(raw_ostream &OS) const {
571  bool First = true;
572  if (BaseGV) {
573  if (!First) OS << " + "; else First = false;
574  BaseGV->printAsOperand(OS, /*PrintType=*/false);
575  }
576  if (BaseOffset != 0) {
577  if (!First) OS << " + "; else First = false;
578  OS << BaseOffset;
579  }
580  for (const SCEV *BaseReg : BaseRegs) {
581  if (!First) OS << " + "; else First = false;
582  OS << "reg(" << *BaseReg << ')';
583  }
584  if (HasBaseReg && BaseRegs.empty()) {
585  if (!First) OS << " + "; else First = false;
586  OS << "**error: HasBaseReg**";
587  } else if (!HasBaseReg && !BaseRegs.empty()) {
588  if (!First) OS << " + "; else First = false;
589  OS << "**error: !HasBaseReg**";
590  }
591  if (Scale != 0) {
592  if (!First) OS << " + "; else First = false;
593  OS << Scale << "*reg(";
594  if (ScaledReg)
595  OS << *ScaledReg;
596  else
597  OS << "<unknown>";
598  OS << ')';
599  }
600  if (UnfoldedOffset != 0) {
601  if (!First) OS << " + ";
602  OS << "imm(" << UnfoldedOffset << ')';
603  }
604 }
605 
606 LLVM_DUMP_METHOD void Formula::dump() const {
607  print(errs()); errs() << '\n';
608 }
609 #endif
610 
611 /// Return true if the given addrec can be sign-extended without changing its
612 /// value.
613 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
614  Type *WideTy =
616  return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
617 }
618 
619 /// Return true if the given add can be sign-extended without changing its
620 /// value.
621 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
622  Type *WideTy =
624  return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
625 }
626 
627 /// Return true if the given mul can be sign-extended without changing its
628 /// value.
629 static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
630  Type *WideTy =
632  SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
633  return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
634 }
635 
636 /// Return an expression for LHS /s RHS, if it can be determined and if the
637 /// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
638 /// is true, expressions like (X * Y) /s Y are simplified to Y, ignoring that
639 /// the multiplication may overflow, which is useful when the result will be
640 /// used in a context where the most significant bits are ignored.
641 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
642  ScalarEvolution &SE,
643  bool IgnoreSignificantBits = false) {
644  // Handle the trivial case, which works for any SCEV type.
645  if (LHS == RHS)
646  return SE.getConstant(LHS->getType(), 1);
647 
648  // Handle a few RHS special cases.
649  const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
650  if (RC) {
651  const APInt &RA = RC->getAPInt();
652  // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
653  // some folding.
654  if (RA.isAllOnesValue())
655  return SE.getMulExpr(LHS, RC);
656  // Handle x /s 1 as x.
657  if (RA == 1)
658  return LHS;
659  }
660 
661  // Check for a division of a constant by a constant.
662  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
663  if (!RC)
664  return nullptr;
665  const APInt &LA = C->getAPInt();
666  const APInt &RA = RC->getAPInt();
667  if (LA.srem(RA) != 0)
668  return nullptr;
669  return SE.getConstant(LA.sdiv(RA));
670  }
671 
672  // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
673  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
674  if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
675  const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
676  IgnoreSignificantBits);
677  if (!Step) return nullptr;
678  const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
679  IgnoreSignificantBits);
680  if (!Start) return nullptr;
681  // FlagNW is independent of the start value, step direction, and is
682  // preserved with smaller magnitude steps.
683  // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
684  return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
685  }
686  return nullptr;
687  }
688 
689  // Distribute the sdiv over add operands, if the add doesn't overflow.
690  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
691  if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
693  for (const SCEV *S : Add->operands()) {
694  const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
695  if (!Op) return nullptr;
696  Ops.push_back(Op);
697  }
698  return SE.getAddExpr(Ops);
699  }
700  return nullptr;
701  }
702 
703  // Check for a multiply operand that we can pull RHS out of.
704  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
705  if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
707  bool Found = false;
708  for (const SCEV *S : Mul->operands()) {
709  if (!Found)
710  if (const SCEV *Q = getExactSDiv(S, RHS, SE,
711  IgnoreSignificantBits)) {
712  S = Q;
713  Found = true;
714  }
715  Ops.push_back(S);
716  }
717  return Found ? SE.getMulExpr(Ops) : nullptr;
718  }
719  return nullptr;
720  }
721 
722  // Otherwise we don't know.
723  return nullptr;
724 }
725 
726 /// If S involves the addition of a constant integer value, return that integer
727 /// value, and mutate S to point to a new SCEV with that value excluded.
728 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
729  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
730  if (C->getAPInt().getMinSignedBits() <= 64) {
731  S = SE.getConstant(C->getType(), 0);
732  return C->getValue()->getSExtValue();
733  }
734  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
735  SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
736  int64_t Result = ExtractImmediate(NewOps.front(), SE);
737  if (Result != 0)
738  S = SE.getAddExpr(NewOps);
739  return Result;
740  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
741  SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
742  int64_t Result = ExtractImmediate(NewOps.front(), SE);
743  if (Result != 0)
744  S = SE.getAddRecExpr(NewOps, AR->getLoop(),
745  // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
747  return Result;
748  }
749  return 0;
750 }
751 
752 /// If S involves the addition of a GlobalValue address, return that symbol, and
753 /// mutate S to point to a new SCEV with that value excluded.
755  if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
756  if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
757  S = SE.getConstant(GV->getType(), 0);
758  return GV;
759  }
760  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
761  SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
762  GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
763  if (Result)
764  S = SE.getAddExpr(NewOps);
765  return Result;
766  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
767  SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
768  GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
769  if (Result)
770  S = SE.getAddRecExpr(NewOps, AR->getLoop(),
771  // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
773  return Result;
774  }
775  return nullptr;
776 }
777 
778 /// Returns true if the specified instruction is using the specified value as an
779 /// address.
780 static bool isAddressUse(const TargetTransformInfo &TTI,
781  Instruction *Inst, Value *OperandVal) {
782  bool isAddress = isa<LoadInst>(Inst);
783  if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
784  if (SI->getPointerOperand() == OperandVal)
785  isAddress = true;
786  } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
787  // Addressing modes can also be folded into prefetches and a variety
788  // of intrinsics.
789  switch (II->getIntrinsicID()) {
790  case Intrinsic::memset:
791  case Intrinsic::prefetch:
792  if (II->getArgOperand(0) == OperandVal)
793  isAddress = true;
794  break;
795  case Intrinsic::memmove:
796  case Intrinsic::memcpy:
797  if (II->getArgOperand(0) == OperandVal ||
798  II->getArgOperand(1) == OperandVal)
799  isAddress = true;
800  break;
801  default: {
802  MemIntrinsicInfo IntrInfo;
803  if (TTI.getTgtMemIntrinsic(II, IntrInfo)) {
804  if (IntrInfo.PtrVal == OperandVal)
805  isAddress = true;
806  }
807  }
808  }
809  } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
810  if (RMW->getPointerOperand() == OperandVal)
811  isAddress = true;
812  } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
813  if (CmpX->getPointerOperand() == OperandVal)
814  isAddress = true;
815  }
816  return isAddress;
817 }
818 
819 /// Return the type of the memory being accessed.
820 static MemAccessTy getAccessType(const TargetTransformInfo &TTI,
821  Instruction *Inst) {
822  MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
823  if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
824  AccessTy.MemTy = SI->getOperand(0)->getType();
825  AccessTy.AddrSpace = SI->getPointerAddressSpace();
826  } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
827  AccessTy.AddrSpace = LI->getPointerAddressSpace();
828  } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
829  AccessTy.AddrSpace = RMW->getPointerAddressSpace();
830  } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
831  AccessTy.AddrSpace = CmpX->getPointerAddressSpace();
832  } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
833  switch (II->getIntrinsicID()) {
834  case Intrinsic::prefetch:
835  AccessTy.AddrSpace = II->getArgOperand(0)->getType()->getPointerAddressSpace();
836  break;
837  default: {
838  MemIntrinsicInfo IntrInfo;
839  if (TTI.getTgtMemIntrinsic(II, IntrInfo) && IntrInfo.PtrVal) {
840  AccessTy.AddrSpace
841  = IntrInfo.PtrVal->getType()->getPointerAddressSpace();
842  }
843 
844  break;
845  }
846  }
847  }
848 
849  // All pointers have the same requirements, so canonicalize them to an
850  // arbitrary pointer type to minimize variation.
851  if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
852  AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
853  PTy->getAddressSpace());
854 
855  return AccessTy;
856 }
857 
858 /// Return true if this AddRec is already a phi in its loop.
859 static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
860  for (PHINode &PN : AR->getLoop()->getHeader()->phis()) {
861  if (SE.isSCEVable(PN.getType()) &&
862  (SE.getEffectiveSCEVType(PN.getType()) ==
863  SE.getEffectiveSCEVType(AR->getType())) &&
864  SE.getSCEV(&PN) == AR)
865  return true;
866  }
867  return false;
868 }
869 
870 /// Check if expanding this expression is likely to incur significant cost. This
871 /// is tricky because SCEV doesn't track which expressions are actually computed
872 /// by the current IR.
873 ///
874 /// We currently allow expansion of IV increments that involve adds,
875 /// multiplication by constants, and AddRecs from existing phis.
876 ///
877 /// TODO: Allow UDivExpr if we can find an existing IV increment that is an
878 /// obvious multiple of the UDivExpr.
879 static bool isHighCostExpansion(const SCEV *S,
880  SmallPtrSetImpl<const SCEV*> &Processed,
881  ScalarEvolution &SE) {
882  // Zero/One operand expressions
883  switch (S->getSCEVType()) {
884  case scUnknown:
885  case scConstant:
886  return false;
887  case scTruncate:
888  return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
889  Processed, SE);
890  case scZeroExtend:
891  return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
892  Processed, SE);
893  case scSignExtend:
894  return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
895  Processed, SE);
896  }
897 
898  if (!Processed.insert(S).second)
899  return false;
900 
901  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
902  for (const SCEV *S : Add->operands()) {
903  if (isHighCostExpansion(S, Processed, SE))
904  return true;
905  }
906  return false;
907  }
908 
909  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
910  if (Mul->getNumOperands() == 2) {
911  // Multiplication by a constant is ok
912  if (isa<SCEVConstant>(Mul->getOperand(0)))
913  return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
914 
915  // If we have the value of one operand, check if an existing
916  // multiplication already generates this expression.
917  if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
918  Value *UVal = U->getValue();
919  for (User *UR : UVal->users()) {
920  // If U is a constant, it may be used by a ConstantExpr.
921  Instruction *UI = dyn_cast<Instruction>(UR);
922  if (UI && UI->getOpcode() == Instruction::Mul &&
923  SE.isSCEVable(UI->getType())) {
924  return SE.getSCEV(UI) == Mul;
925  }
926  }
927  }
928  }
929  }
930 
931  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
932  if (isExistingPhi(AR, SE))
933  return false;
934  }
935 
936  // Fow now, consider any other type of expression (div/mul/min/max) high cost.
937  return true;
938 }
939 
940 /// If any of the instructions is the specified set are trivially dead, delete
941 /// them and see if this makes any of their operands subsequently dead.
942 static bool
944  bool Changed = false;
945 
946  while (!DeadInsts.empty()) {
947  Value *V = DeadInsts.pop_back_val();
948  Instruction *I = dyn_cast_or_null<Instruction>(V);
949 
950  if (!I || !isInstructionTriviallyDead(I))
951  continue;
952 
953  for (Use &O : I->operands())
954  if (Instruction *U = dyn_cast<Instruction>(O)) {
955  O = nullptr;
956  if (U->use_empty())
957  DeadInsts.emplace_back(U);
958  }
959 
960  I->eraseFromParent();
961  Changed = true;
962  }
963 
964  return Changed;
965 }
966 
967 namespace {
968 
969 class LSRUse;
970 
971 } // end anonymous namespace
972 
973 /// \brief Check if the addressing mode defined by \p F is completely
974 /// folded in \p LU at isel time.
975 /// This includes address-mode folding and special icmp tricks.
976 /// This function returns true if \p LU can accommodate what \p F
977 /// defines and up to 1 base + 1 scaled + offset.
978 /// In other words, if \p F has several base registers, this function may
979 /// still return true. Therefore, users still need to account for
980 /// additional base registers and/or unfolded offsets to derive an
981 /// accurate cost model.
982 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
983  const LSRUse &LU, const Formula &F);
984 
985 // Get the cost of the scaling factor used in F for LU.
986 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
987  const LSRUse &LU, const Formula &F,
988  const Loop &L);
989 
990 namespace {
991 
992 /// This class is used to measure and compare candidate formulae.
993 class Cost {
995 
996 public:
997  Cost() {
998  C.Insns = 0;
999  C.NumRegs = 0;
1000  C.AddRecCost = 0;
1001  C.NumIVMuls = 0;
1002  C.NumBaseAdds = 0;
1003  C.ImmCost = 0;
1004  C.SetupCost = 0;
1005  C.ScaleCost = 0;
1006  }
1007 
1008  bool isLess(Cost &Other, const TargetTransformInfo &TTI);
1009 
1010  void Lose();
1011 
1012 #ifndef NDEBUG
1013  // Once any of the metrics loses, they must all remain losers.
1014  bool isValid() {
1015  return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds
1016  | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u)
1017  || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds
1018  & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u);
1019  }
1020 #endif
1021 
1022  bool isLoser() {
1023  assert(isValid() && "invalid cost");
1024  return C.NumRegs == ~0u;
1025  }
1026 
1027  void RateFormula(const TargetTransformInfo &TTI,
1028  const Formula &F,
1030  const DenseSet<const SCEV *> &VisitedRegs,
1031  const Loop *L,
1032  ScalarEvolution &SE, DominatorTree &DT,
1033  const LSRUse &LU,
1034  SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
1035 
1036  void print(raw_ostream &OS) const;
1037  void dump() const;
1038 
1039 private:
1040  void RateRegister(const SCEV *Reg,
1042  const Loop *L,
1043  ScalarEvolution &SE, DominatorTree &DT);
1044  void RatePrimaryRegister(const SCEV *Reg,
1046  const Loop *L,
1047  ScalarEvolution &SE, DominatorTree &DT,
1048  SmallPtrSetImpl<const SCEV *> *LoserRegs);
1049 };
1050 
1051 /// An operand value in an instruction which is to be replaced with some
1052 /// equivalent, possibly strength-reduced, replacement.
1053 struct LSRFixup {
1054  /// The instruction which will be updated.
1055  Instruction *UserInst = nullptr;
1056 
1057  /// The operand of the instruction which will be replaced. The operand may be
1058  /// used more than once; every instance will be replaced.
1059  Value *OperandValToReplace = nullptr;
1060 
1061  /// If this user is to use the post-incremented value of an induction
1062  /// variable, this set is non-empty and holds the loops associated with the
1063  /// induction variable.
1064  PostIncLoopSet PostIncLoops;
1065 
1066  /// A constant offset to be added to the LSRUse expression. This allows
1067  /// multiple fixups to share the same LSRUse with different offsets, for
1068  /// example in an unrolled loop.
1069  int64_t Offset = 0;
1070 
1071  LSRFixup() = default;
1072 
1073  bool isUseFullyOutsideLoop(const Loop *L) const;
1074 
1075  void print(raw_ostream &OS) const;
1076  void dump() const;
1077 };
1078 
1079 /// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
1080 /// SmallVectors of const SCEV*.
1081 struct UniquifierDenseMapInfo {
1082  static SmallVector<const SCEV *, 4> getEmptyKey() {
1084  V.push_back(reinterpret_cast<const SCEV *>(-1));
1085  return V;
1086  }
1087 
1088  static SmallVector<const SCEV *, 4> getTombstoneKey() {
1090  V.push_back(reinterpret_cast<const SCEV *>(-2));
1091  return V;
1092  }
1093 
1094  static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1095  return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1096  }
1097 
1098  static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1099  const SmallVector<const SCEV *, 4> &RHS) {
1100  return LHS == RHS;
1101  }
1102 };
1103 
1104 /// This class holds the state that LSR keeps for each use in IVUsers, as well
1105 /// as uses invented by LSR itself. It includes information about what kinds of
1106 /// things can be folded into the user, information about the user itself, and
1107 /// information about how the use may be satisfied. TODO: Represent multiple
1108 /// users of the same expression in common?
1109 class LSRUse {
1110  DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1111 
1112 public:
1113  /// An enum for a kind of use, indicating what types of scaled and immediate
1114  /// operands it might support.
1115  enum KindType {
1116  Basic, ///< A normal use, with no folding.
1117  Special, ///< A special case of basic, allowing -1 scales.
1118  Address, ///< An address use; folding according to TargetLowering
1119  ICmpZero ///< An equality icmp with both operands folded into one.
1120  // TODO: Add a generic icmp too?
1121  };
1122 
1123  using SCEVUseKindPair = PointerIntPair<const SCEV *, 2, KindType>;
1124 
1125  KindType Kind;
1126  MemAccessTy AccessTy;
1127 
1128  /// The list of operands which are to be replaced.
1130 
1131  /// Keep track of the min and max offsets of the fixups.
1132  int64_t MinOffset = std::numeric_limits<int64_t>::max();
1133  int64_t MaxOffset = std::numeric_limits<int64_t>::min();
1134 
1135  /// This records whether all of the fixups using this LSRUse are outside of
1136  /// the loop, in which case some special-case heuristics may be used.
1137  bool AllFixupsOutsideLoop = true;
1138 
1139  /// RigidFormula is set to true to guarantee that this use will be associated
1140  /// with a single formula--the one that initially matched. Some SCEV
1141  /// expressions cannot be expanded. This allows LSR to consider the registers
1142  /// used by those expressions without the need to expand them later after
1143  /// changing the formula.
1144  bool RigidFormula = false;
1145 
1146  /// This records the widest use type for any fixup using this
1147  /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1148  /// fixup widths to be equivalent, because the narrower one may be relying on
1149  /// the implicit truncation to truncate away bogus bits.
1150  Type *WidestFixupType = nullptr;
1151 
1152  /// A list of ways to build a value that can satisfy this user. After the
1153  /// list is populated, one of these is selected heuristically and used to
1154  /// formulate a replacement for OperandValToReplace in UserInst.
1155  SmallVector<Formula, 12> Formulae;
1156 
1157  /// The set of register candidates used by all formulae in this LSRUse.
1159 
1160  LSRUse(KindType K, MemAccessTy AT) : Kind(K), AccessTy(AT) {}
1161 
1162  LSRFixup &getNewFixup() {
1163  Fixups.push_back(LSRFixup());
1164  return Fixups.back();
1165  }
1166 
1167  void pushFixup(LSRFixup &f) {
1168  Fixups.push_back(f);
1169  if (f.Offset > MaxOffset)
1170  MaxOffset = f.Offset;
1171  if (f.Offset < MinOffset)
1172  MinOffset = f.Offset;
1173  }
1174 
1175  bool HasFormulaWithSameRegs(const Formula &F) const;
1176  float getNotSelectedProbability(const SCEV *Reg) const;
1177  bool InsertFormula(const Formula &F, const Loop &L);
1178  void DeleteFormula(Formula &F);
1179  void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1180 
1181  void print(raw_ostream &OS) const;
1182  void dump() const;
1183 };
1184 
1185 } // end anonymous namespace
1186 
1187 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1188  LSRUse::KindType Kind, MemAccessTy AccessTy,
1189  GlobalValue *BaseGV, int64_t BaseOffset,
1190  bool HasBaseReg, int64_t Scale,
1191  Instruction *Fixup = nullptr);
1192 
1193 /// Tally up interesting quantities from the given register.
1194 void Cost::RateRegister(const SCEV *Reg,
1196  const Loop *L,
1197  ScalarEvolution &SE, DominatorTree &DT) {
1198  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1199  // If this is an addrec for another loop, it should be an invariant
1200  // with respect to L since L is the innermost loop (at least
1201  // for now LSR only handles innermost loops).
1202  if (AR->getLoop() != L) {
1203  // If the AddRec exists, consider it's register free and leave it alone.
1204  if (isExistingPhi(AR, SE))
1205  return;
1206 
1207  // It is bad to allow LSR for current loop to add induction variables
1208  // for its sibling loops.
1209  if (!AR->getLoop()->contains(L)) {
1210  Lose();
1211  return;
1212  }
1213 
1214  // Otherwise, it will be an invariant with respect to Loop L.
1215  ++C.NumRegs;
1216  return;
1217  }
1218  C.AddRecCost += 1; /// TODO: This should be a function of the stride.
1219 
1220  // Add the step value register, if it needs one.
1221  // TODO: The non-affine case isn't precisely modeled here.
1222  if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1223  if (!Regs.count(AR->getOperand(1))) {
1224  RateRegister(AR->getOperand(1), Regs, L, SE, DT);
1225  if (isLoser())
1226  return;
1227  }
1228  }
1229  }
1230  ++C.NumRegs;
1231 
1232  // Rough heuristic; favor registers which don't require extra setup
1233  // instructions in the preheader.
1234  if (!isa<SCEVUnknown>(Reg) &&
1235  !isa<SCEVConstant>(Reg) &&
1236  !(isa<SCEVAddRecExpr>(Reg) &&
1237  (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
1238  isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
1239  ++C.SetupCost;
1240 
1241  C.NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1242  SE.hasComputableLoopEvolution(Reg, L);
1243 }
1244 
1245 /// Record this register in the set. If we haven't seen it before, rate
1246 /// it. Optional LoserRegs provides a way to declare any formula that refers to
1247 /// one of those regs an instant loser.
1248 void Cost::RatePrimaryRegister(const SCEV *Reg,
1250  const Loop *L,
1251  ScalarEvolution &SE, DominatorTree &DT,
1252  SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1253  if (LoserRegs && LoserRegs->count(Reg)) {
1254  Lose();
1255  return;
1256  }
1257  if (Regs.insert(Reg).second) {
1258  RateRegister(Reg, Regs, L, SE, DT);
1259  if (LoserRegs && isLoser())
1260  LoserRegs->insert(Reg);
1261  }
1262 }
1263 
1264 void Cost::RateFormula(const TargetTransformInfo &TTI,
1265  const Formula &F,
1267  const DenseSet<const SCEV *> &VisitedRegs,
1268  const Loop *L,
1269  ScalarEvolution &SE, DominatorTree &DT,
1270  const LSRUse &LU,
1271  SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1272  assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula");
1273  // Tally up the registers.
1274  unsigned PrevAddRecCost = C.AddRecCost;
1275  unsigned PrevNumRegs = C.NumRegs;
1276  unsigned PrevNumBaseAdds = C.NumBaseAdds;
1277  if (const SCEV *ScaledReg = F.ScaledReg) {
1278  if (VisitedRegs.count(ScaledReg)) {
1279  Lose();
1280  return;
1281  }
1282  RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs);
1283  if (isLoser())
1284  return;
1285  }
1286  for (const SCEV *BaseReg : F.BaseRegs) {
1287  if (VisitedRegs.count(BaseReg)) {
1288  Lose();
1289  return;
1290  }
1291  RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs);
1292  if (isLoser())
1293  return;
1294  }
1295 
1296  // Determine how many (unfolded) adds we'll need inside the loop.
1297  size_t NumBaseParts = F.getNumRegs();
1298  if (NumBaseParts > 1)
1299  // Do not count the base and a possible second register if the target
1300  // allows to fold 2 registers.
1301  C.NumBaseAdds +=
1302  NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(TTI, LU, F)));
1303  C.NumBaseAdds += (F.UnfoldedOffset != 0);
1304 
1305  // Accumulate non-free scaling amounts.
1306  C.ScaleCost += getScalingFactorCost(TTI, LU, F, *L);
1307 
1308  // Tally up the non-zero immediates.
1309  for (const LSRFixup &Fixup : LU.Fixups) {
1310  int64_t O = Fixup.Offset;
1311  int64_t Offset = (uint64_t)O + F.BaseOffset;
1312  if (F.BaseGV)
1313  C.ImmCost += 64; // Handle symbolic values conservatively.
1314  // TODO: This should probably be the pointer size.
1315  else if (Offset != 0)
1316  C.ImmCost += APInt(64, Offset, true).getMinSignedBits();
1317 
1318  // Check with target if this offset with this instruction is
1319  // specifically not supported.
1320  if (LU.Kind == LSRUse::Address && Offset != 0 &&
1321  !isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1322  Offset, F.HasBaseReg, F.Scale, Fixup.UserInst))
1323  C.NumBaseAdds++;
1324  }
1325 
1326  // If we don't count instruction cost exit here.
1327  if (!InsnsCost) {
1328  assert(isValid() && "invalid cost");
1329  return;
1330  }
1331 
1332  // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as
1333  // additional instruction (at least fill).
1334  unsigned TTIRegNum = TTI.getNumberOfRegisters(false) - 1;
1335  if (C.NumRegs > TTIRegNum) {
1336  // Cost already exceeded TTIRegNum, then only newly added register can add
1337  // new instructions.
1338  if (PrevNumRegs > TTIRegNum)
1339  C.Insns += (C.NumRegs - PrevNumRegs);
1340  else
1341  C.Insns += (C.NumRegs - TTIRegNum);
1342  }
1343 
1344  // If ICmpZero formula ends with not 0, it could not be replaced by
1345  // just add or sub. We'll need to compare final result of AddRec.
1346  // That means we'll need an additional instruction.
1347  // For -10 + {0, +, 1}:
1348  // i = i + 1;
1349  // cmp i, 10
1350  //
1351  // For {-10, +, 1}:
1352  // i = i + 1;
1353  if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd())
1354  C.Insns++;
1355  // Each new AddRec adds 1 instruction to calculation.
1356  C.Insns += (C.AddRecCost - PrevAddRecCost);
1357 
1358  // BaseAdds adds instructions for unfolded registers.
1359  if (LU.Kind != LSRUse::ICmpZero)
1360  C.Insns += C.NumBaseAdds - PrevNumBaseAdds;
1361  assert(isValid() && "invalid cost");
1362 }
1363 
1364 /// Set this cost to a losing value.
1365 void Cost::Lose() {
1368  C.AddRecCost = std::numeric_limits<unsigned>::max();
1369  C.NumIVMuls = std::numeric_limits<unsigned>::max();
1370  C.NumBaseAdds = std::numeric_limits<unsigned>::max();
1372  C.SetupCost = std::numeric_limits<unsigned>::max();
1373  C.ScaleCost = std::numeric_limits<unsigned>::max();
1374 }
1375 
1376 /// Choose the lower cost.
1377 bool Cost::isLess(Cost &Other, const TargetTransformInfo &TTI) {
1378  if (InsnsCost.getNumOccurrences() > 0 && InsnsCost &&
1379  C.Insns != Other.C.Insns)
1380  return C.Insns < Other.C.Insns;
1381  return TTI.isLSRCostLess(C, Other.C);
1382 }
1383 
1384 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1385 void Cost::print(raw_ostream &OS) const {
1386  if (InsnsCost)
1387  OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s ");
1388  OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s");
1389  if (C.AddRecCost != 0)
1390  OS << ", with addrec cost " << C.AddRecCost;
1391  if (C.NumIVMuls != 0)
1392  OS << ", plus " << C.NumIVMuls << " IV mul"
1393  << (C.NumIVMuls == 1 ? "" : "s");
1394  if (C.NumBaseAdds != 0)
1395  OS << ", plus " << C.NumBaseAdds << " base add"
1396  << (C.NumBaseAdds == 1 ? "" : "s");
1397  if (C.ScaleCost != 0)
1398  OS << ", plus " << C.ScaleCost << " scale cost";
1399  if (C.ImmCost != 0)
1400  OS << ", plus " << C.ImmCost << " imm cost";
1401  if (C.SetupCost != 0)
1402  OS << ", plus " << C.SetupCost << " setup cost";
1403 }
1404 
1405 LLVM_DUMP_METHOD void Cost::dump() const {
1406  print(errs()); errs() << '\n';
1407 }
1408 #endif
1409 
1410 /// Test whether this fixup always uses its value outside of the given loop.
1411 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1412  // PHI nodes use their value in their incoming blocks.
1413  if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1414  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1415  if (PN->getIncomingValue(i) == OperandValToReplace &&
1416  L->contains(PN->getIncomingBlock(i)))
1417  return false;
1418  return true;
1419  }
1420 
1421  return !L->contains(UserInst);
1422 }
1423 
1424 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1425 void LSRFixup::print(raw_ostream &OS) const {
1426  OS << "UserInst=";
1427  // Store is common and interesting enough to be worth special-casing.
1428  if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1429  OS << "store ";
1430  Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1431  } else if (UserInst->getType()->isVoidTy())
1432  OS << UserInst->getOpcodeName();
1433  else
1434  UserInst->printAsOperand(OS, /*PrintType=*/false);
1435 
1436  OS << ", OperandValToReplace=";
1437  OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1438 
1439  for (const Loop *PIL : PostIncLoops) {
1440  OS << ", PostIncLoop=";
1441  PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1442  }
1443 
1444  if (Offset != 0)
1445  OS << ", Offset=" << Offset;
1446 }
1447 
1448 LLVM_DUMP_METHOD void LSRFixup::dump() const {
1449  print(errs()); errs() << '\n';
1450 }
1451 #endif
1452 
1453 /// Test whether this use as a formula which has the same registers as the given
1454 /// formula.
1455 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1456  SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1457  if (F.ScaledReg) Key.push_back(F.ScaledReg);
1458  // Unstable sort by host order ok, because this is only used for uniquifying.
1459  std::sort(Key.begin(), Key.end());
1460  return Uniquifier.count(Key);
1461 }
1462 
1463 /// The function returns a probability of selecting formula without Reg.
1464 float LSRUse::getNotSelectedProbability(const SCEV *Reg) const {
1465  unsigned FNum = 0;
1466  for (const Formula &F : Formulae)
1467  if (F.referencesReg(Reg))
1468  FNum++;
1469  return ((float)(Formulae.size() - FNum)) / Formulae.size();
1470 }
1471 
1472 /// If the given formula has not yet been inserted, add it to the list, and
1473 /// return true. Return false otherwise. The formula must be in canonical form.
1474 bool LSRUse::InsertFormula(const Formula &F, const Loop &L) {
1475  assert(F.isCanonical(L) && "Invalid canonical representation");
1476 
1477  if (!Formulae.empty() && RigidFormula)
1478  return false;
1479 
1480  SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1481  if (F.ScaledReg) Key.push_back(F.ScaledReg);
1482  // Unstable sort by host order ok, because this is only used for uniquifying.
1483  std::sort(Key.begin(), Key.end());
1484 
1485  if (!Uniquifier.insert(Key).second)
1486  return false;
1487 
1488  // Using a register to hold the value of 0 is not profitable.
1489  assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1490  "Zero allocated in a scaled register!");
1491 #ifndef NDEBUG
1492  for (const SCEV *BaseReg : F.BaseRegs)
1493  assert(!BaseReg->isZero() && "Zero allocated in a base register!");
1494 #endif
1495 
1496  // Add the formula to the list.
1497  Formulae.push_back(F);
1498 
1499  // Record registers now being used by this use.
1500  Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1501  if (F.ScaledReg)
1502  Regs.insert(F.ScaledReg);
1503 
1504  return true;
1505 }
1506 
1507 /// Remove the given formula from this use's list.
1508 void LSRUse::DeleteFormula(Formula &F) {
1509  if (&F != &Formulae.back())
1510  std::swap(F, Formulae.back());
1511  Formulae.pop_back();
1512 }
1513 
1514 /// Recompute the Regs field, and update RegUses.
1515 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1516  // Now that we've filtered out some formulae, recompute the Regs set.
1517  SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1518  Regs.clear();
1519  for (const Formula &F : Formulae) {
1520  if (F.ScaledReg) Regs.insert(F.ScaledReg);
1521  Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1522  }
1523 
1524  // Update the RegTracker.
1525  for (const SCEV *S : OldRegs)
1526  if (!Regs.count(S))
1527  RegUses.dropRegister(S, LUIdx);
1528 }
1529 
1530 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1531 void LSRUse::print(raw_ostream &OS) const {
1532  OS << "LSR Use: Kind=";
1533  switch (Kind) {
1534  case Basic: OS << "Basic"; break;
1535  case Special: OS << "Special"; break;
1536  case ICmpZero: OS << "ICmpZero"; break;
1537  case Address:
1538  OS << "Address of ";
1539  if (AccessTy.MemTy->isPointerTy())
1540  OS << "pointer"; // the full pointer type could be really verbose
1541  else {
1542  OS << *AccessTy.MemTy;
1543  }
1544 
1545  OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1546  }
1547 
1548  OS << ", Offsets={";
1549  bool NeedComma = false;
1550  for (const LSRFixup &Fixup : Fixups) {
1551  if (NeedComma) OS << ',';
1552  OS << Fixup.Offset;
1553  NeedComma = true;
1554  }
1555  OS << '}';
1556 
1557  if (AllFixupsOutsideLoop)
1558  OS << ", all-fixups-outside-loop";
1559 
1560  if (WidestFixupType)
1561  OS << ", widest fixup type: " << *WidestFixupType;
1562 }
1563 
1564 LLVM_DUMP_METHOD void LSRUse::dump() const {
1565  print(errs()); errs() << '\n';
1566 }
1567 #endif
1568 
1570  LSRUse::KindType Kind, MemAccessTy AccessTy,
1571  GlobalValue *BaseGV, int64_t BaseOffset,
1572  bool HasBaseReg, int64_t Scale,
1573  Instruction *Fixup/*= nullptr*/) {
1574  switch (Kind) {
1575  case LSRUse::Address:
1576  return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1577  HasBaseReg, Scale, AccessTy.AddrSpace, Fixup);
1578 
1579  case LSRUse::ICmpZero:
1580  // There's not even a target hook for querying whether it would be legal to
1581  // fold a GV into an ICmp.
1582  if (BaseGV)
1583  return false;
1584 
1585  // ICmp only has two operands; don't allow more than two non-trivial parts.
1586  if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1587  return false;
1588 
1589  // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1590  // putting the scaled register in the other operand of the icmp.
1591  if (Scale != 0 && Scale != -1)
1592  return false;
1593 
1594  // If we have low-level target information, ask the target if it can fold an
1595  // integer immediate on an icmp.
1596  if (BaseOffset != 0) {
1597  // We have one of:
1598  // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1599  // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1600  // Offs is the ICmp immediate.
1601  if (Scale == 0)
1602  // The cast does the right thing with
1603  // std::numeric_limits<int64_t>::min().
1604  BaseOffset = -(uint64_t)BaseOffset;
1605  return TTI.isLegalICmpImmediate(BaseOffset);
1606  }
1607 
1608  // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1609  return true;
1610 
1611  case LSRUse::Basic:
1612  // Only handle single-register values.
1613  return !BaseGV && Scale == 0 && BaseOffset == 0;
1614 
1615  case LSRUse::Special:
1616  // Special case Basic to handle -1 scales.
1617  return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1618  }
1619 
1620  llvm_unreachable("Invalid LSRUse Kind!");
1621 }
1622 
1624  int64_t MinOffset, int64_t MaxOffset,
1625  LSRUse::KindType Kind, MemAccessTy AccessTy,
1626  GlobalValue *BaseGV, int64_t BaseOffset,
1627  bool HasBaseReg, int64_t Scale) {
1628  // Check for overflow.
1629  if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1630  (MinOffset > 0))
1631  return false;
1632  MinOffset = (uint64_t)BaseOffset + MinOffset;
1633  if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1634  (MaxOffset > 0))
1635  return false;
1636  MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1637 
1638  return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1639  HasBaseReg, Scale) &&
1640  isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1641  HasBaseReg, Scale);
1642 }
1643 
1645  int64_t MinOffset, int64_t MaxOffset,
1646  LSRUse::KindType Kind, MemAccessTy AccessTy,
1647  const Formula &F, const Loop &L) {
1648  // For the purpose of isAMCompletelyFolded either having a canonical formula
1649  // or a scale not equal to zero is correct.
1650  // Problems may arise from non canonical formulae having a scale == 0.
1651  // Strictly speaking it would best to just rely on canonical formulae.
1652  // However, when we generate the scaled formulae, we first check that the
1653  // scaling factor is profitable before computing the actual ScaledReg for
1654  // compile time sake.
1655  assert((F.isCanonical(L) || F.Scale != 0));
1656  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1657  F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1658 }
1659 
1660 /// Test whether we know how to expand the current formula.
1661 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1662  int64_t MaxOffset, LSRUse::KindType Kind,
1663  MemAccessTy AccessTy, GlobalValue *BaseGV,
1664  int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1665  // We know how to expand completely foldable formulae.
1666  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1667  BaseOffset, HasBaseReg, Scale) ||
1668  // Or formulae that use a base register produced by a sum of base
1669  // registers.
1670  (Scale == 1 &&
1671  isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1672  BaseGV, BaseOffset, true, 0));
1673 }
1674 
1675 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1676  int64_t MaxOffset, LSRUse::KindType Kind,
1677  MemAccessTy AccessTy, const Formula &F) {
1678  return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1679  F.BaseOffset, F.HasBaseReg, F.Scale);
1680 }
1681 
1683  const LSRUse &LU, const Formula &F) {
1684  // Target may want to look at the user instructions.
1685  if (LU.Kind == LSRUse::Address && TTI.LSRWithInstrQueries()) {
1686  for (const LSRFixup &Fixup : LU.Fixups)
1687  if (!isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1688  (F.BaseOffset + Fixup.Offset), F.HasBaseReg,
1689  F.Scale, Fixup.UserInst))
1690  return false;
1691  return true;
1692  }
1693 
1694  return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1695  LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1696  F.Scale);
1697 }
1698 
1699 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1700  const LSRUse &LU, const Formula &F,
1701  const Loop &L) {
1702  if (!F.Scale)
1703  return 0;
1704 
1705  // If the use is not completely folded in that instruction, we will have to
1706  // pay an extra cost only for scale != 1.
1707  if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1708  LU.AccessTy, F, L))
1709  return F.Scale != 1;
1710 
1711  switch (LU.Kind) {
1712  case LSRUse::Address: {
1713  // Check the scaling factor cost with both the min and max offsets.
1714  int ScaleCostMinOffset = TTI.getScalingFactorCost(
1715  LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1716  F.Scale, LU.AccessTy.AddrSpace);
1717  int ScaleCostMaxOffset = TTI.getScalingFactorCost(
1718  LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1719  F.Scale, LU.AccessTy.AddrSpace);
1720 
1721  assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&
1722  "Legal addressing mode has an illegal cost!");
1723  return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1724  }
1725  case LSRUse::ICmpZero:
1726  case LSRUse::Basic:
1727  case LSRUse::Special:
1728  // The use is completely folded, i.e., everything is folded into the
1729  // instruction.
1730  return 0;
1731  }
1732 
1733  llvm_unreachable("Invalid LSRUse Kind!");
1734 }
1735 
1736 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1737  LSRUse::KindType Kind, MemAccessTy AccessTy,
1738  GlobalValue *BaseGV, int64_t BaseOffset,
1739  bool HasBaseReg) {
1740  // Fast-path: zero is always foldable.
1741  if (BaseOffset == 0 && !BaseGV) return true;
1742 
1743  // Conservatively, create an address with an immediate and a
1744  // base and a scale.
1745  int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1746 
1747  // Canonicalize a scale of 1 to a base register if the formula doesn't
1748  // already have a base register.
1749  if (!HasBaseReg && Scale == 1) {
1750  Scale = 0;
1751  HasBaseReg = true;
1752  }
1753 
1754  return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1755  HasBaseReg, Scale);
1756 }
1757 
1758 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1759  ScalarEvolution &SE, int64_t MinOffset,
1760  int64_t MaxOffset, LSRUse::KindType Kind,
1761  MemAccessTy AccessTy, const SCEV *S,
1762  bool HasBaseReg) {
1763  // Fast-path: zero is always foldable.
1764  if (S->isZero()) return true;
1765 
1766  // Conservatively, create an address with an immediate and a
1767  // base and a scale.
1768  int64_t BaseOffset = ExtractImmediate(S, SE);
1769  GlobalValue *BaseGV = ExtractSymbol(S, SE);
1770 
1771  // If there's anything else involved, it's not foldable.
1772  if (!S->isZero()) return false;
1773 
1774  // Fast-path: zero is always foldable.
1775  if (BaseOffset == 0 && !BaseGV) return true;
1776 
1777  // Conservatively, create an address with an immediate and a
1778  // base and a scale.
1779  int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1780 
1781  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1782  BaseOffset, HasBaseReg, Scale);
1783 }
1784 
1785 namespace {
1786 
1787 /// An individual increment in a Chain of IV increments. Relate an IV user to
1788 /// an expression that computes the IV it uses from the IV used by the previous
1789 /// link in the Chain.
1790 ///
1791 /// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1792 /// original IVOperand. The head of the chain's IVOperand is only valid during
1793 /// chain collection, before LSR replaces IV users. During chain generation,
1794 /// IncExpr can be used to find the new IVOperand that computes the same
1795 /// expression.
1796 struct IVInc {
1797  Instruction *UserInst;
1798  Value* IVOperand;
1799  const SCEV *IncExpr;
1800 
1801  IVInc(Instruction *U, Value *O, const SCEV *E)
1802  : UserInst(U), IVOperand(O), IncExpr(E) {}
1803 };
1804 
1805 // The list of IV increments in program order. We typically add the head of a
1806 // chain without finding subsequent links.
1807 struct IVChain {
1808  SmallVector<IVInc, 1> Incs;
1809  const SCEV *ExprBase = nullptr;
1810 
1811  IVChain() = default;
1812  IVChain(const IVInc &Head, const SCEV *Base)
1813  : Incs(1, Head), ExprBase(Base) {}
1814 
1815  using const_iterator = SmallVectorImpl<IVInc>::const_iterator;
1816 
1817  // Return the first increment in the chain.
1818  const_iterator begin() const {
1819  assert(!Incs.empty());
1820  return std::next(Incs.begin());
1821  }
1822  const_iterator end() const {
1823  return Incs.end();
1824  }
1825 
1826  // Returns true if this chain contains any increments.
1827  bool hasIncs() const { return Incs.size() >= 2; }
1828 
1829  // Add an IVInc to the end of this chain.
1830  void add(const IVInc &X) { Incs.push_back(X); }
1831 
1832  // Returns the last UserInst in the chain.
1833  Instruction *tailUserInst() const { return Incs.back().UserInst; }
1834 
1835  // Returns true if IncExpr can be profitably added to this chain.
1836  bool isProfitableIncrement(const SCEV *OperExpr,
1837  const SCEV *IncExpr,
1838  ScalarEvolution&);
1839 };
1840 
1841 /// Helper for CollectChains to track multiple IV increment uses. Distinguish
1842 /// between FarUsers that definitely cross IV increments and NearUsers that may
1843 /// be used between IV increments.
1844 struct ChainUsers {
1846  SmallPtrSet<Instruction*, 4> NearUsers;
1847 };
1848 
1849 /// This class holds state for the main loop strength reduction logic.
1850 class LSRInstance {
1851  IVUsers &IU;
1852  ScalarEvolution &SE;
1853  DominatorTree &DT;
1854  LoopInfo &LI;
1855  const TargetTransformInfo &TTI;
1856  Loop *const L;
1857  bool Changed = false;
1858 
1859  /// This is the insert position that the current loop's induction variable
1860  /// increment should be placed. In simple loops, this is the latch block's
1861  /// terminator. But in more complicated cases, this is a position which will
1862  /// dominate all the in-loop post-increment users.
1863  Instruction *IVIncInsertPos = nullptr;
1864 
1865  /// Interesting factors between use strides.
1866  ///
1867  /// We explicitly use a SetVector which contains a SmallSet, instead of the
1868  /// default, a SmallDenseSet, because we need to use the full range of
1869  /// int64_ts, and there's currently no good way of doing that with
1870  /// SmallDenseSet.
1872 
1873  /// Interesting use types, to facilitate truncation reuse.
1875 
1876  /// The list of interesting uses.
1878 
1879  /// Track which uses use which register candidates.
1880  RegUseTracker RegUses;
1881 
1882  // Limit the number of chains to avoid quadratic behavior. We don't expect to
1883  // have more than a few IV increment chains in a loop. Missing a Chain falls
1884  // back to normal LSR behavior for those uses.
1885  static const unsigned MaxChains = 8;
1886 
1887  /// IV users can form a chain of IV increments.
1889 
1890  /// IV users that belong to profitable IVChains.
1892 
1893  void OptimizeShadowIV();
1894  bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1895  ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1896  void OptimizeLoopTermCond();
1897 
1898  void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1899  SmallVectorImpl<ChainUsers> &ChainUsersVec);
1900  void FinalizeChain(IVChain &Chain);
1901  void CollectChains();
1902  void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1903  SmallVectorImpl<WeakTrackingVH> &DeadInsts);
1904 
1905  void CollectInterestingTypesAndFactors();
1906  void CollectFixupsAndInitialFormulae();
1907 
1908  // Support for sharing of LSRUses between LSRFixups.
1910  UseMapTy UseMap;
1911 
1912  bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1913  LSRUse::KindType Kind, MemAccessTy AccessTy);
1914 
1915  std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
1916  MemAccessTy AccessTy);
1917 
1918  void DeleteUse(LSRUse &LU, size_t LUIdx);
1919 
1920  LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1921 
1922  void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1923  void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1924  void CountRegisters(const Formula &F, size_t LUIdx);
1925  bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1926 
1927  void CollectLoopInvariantFixupsAndFormulae();
1928 
1929  void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1930  unsigned Depth = 0);
1931 
1932  void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1933  const Formula &Base, unsigned Depth,
1934  size_t Idx, bool IsScaledReg = false);
1935  void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1936  void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1937  const Formula &Base, size_t Idx,
1938  bool IsScaledReg = false);
1939  void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1940  void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1941  const Formula &Base,
1942  const SmallVectorImpl<int64_t> &Worklist,
1943  size_t Idx, bool IsScaledReg = false);
1944  void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1945  void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1946  void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1947  void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1948  void GenerateCrossUseConstantOffsets();
1949  void GenerateAllReuseFormulae();
1950 
1951  void FilterOutUndesirableDedicatedRegisters();
1952 
1953  size_t EstimateSearchSpaceComplexity() const;
1954  void NarrowSearchSpaceByDetectingSupersets();
1955  void NarrowSearchSpaceByCollapsingUnrolledCode();
1956  void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1957  void NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
1958  void NarrowSearchSpaceByDeletingCostlyFormulas();
1959  void NarrowSearchSpaceByPickingWinnerRegs();
1960  void NarrowSearchSpaceUsingHeuristics();
1961 
1962  void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1963  Cost &SolutionCost,
1965  const Cost &CurCost,
1966  const SmallPtrSet<const SCEV *, 16> &CurRegs,
1967  DenseSet<const SCEV *> &VisitedRegs) const;
1968  void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1969 
1971  HoistInsertPosition(BasicBlock::iterator IP,
1972  const SmallVectorImpl<Instruction *> &Inputs) const;
1974  AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1975  const LSRFixup &LF,
1976  const LSRUse &LU,
1977  SCEVExpander &Rewriter) const;
1978 
1979  Value *Expand(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
1980  BasicBlock::iterator IP, SCEVExpander &Rewriter,
1981  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
1982  void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
1983  const Formula &F, SCEVExpander &Rewriter,
1984  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
1985  void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
1986  SCEVExpander &Rewriter,
1987  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
1988  void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
1989 
1990 public:
1991  LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
1992  LoopInfo &LI, const TargetTransformInfo &TTI);
1993 
1994  bool getChanged() const { return Changed; }
1995 
1996  void print_factors_and_types(raw_ostream &OS) const;
1997  void print_fixups(raw_ostream &OS) const;
1998  void print_uses(raw_ostream &OS) const;
1999  void print(raw_ostream &OS) const;
2000  void dump() const;
2001 };
2002 
2003 } // end anonymous namespace
2004 
2005 /// If IV is used in a int-to-float cast inside the loop then try to eliminate
2006 /// the cast operation.
2007 void LSRInstance::OptimizeShadowIV() {
2008  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2009  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2010  return;
2011 
2012  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
2013  UI != E; /* empty */) {
2014  IVUsers::const_iterator CandidateUI = UI;
2015  ++UI;
2016  Instruction *ShadowUse = CandidateUI->getUser();
2017  Type *DestTy = nullptr;
2018  bool IsSigned = false;
2019 
2020  /* If shadow use is a int->float cast then insert a second IV
2021  to eliminate this cast.
2022 
2023  for (unsigned i = 0; i < n; ++i)
2024  foo((double)i);
2025 
2026  is transformed into
2027 
2028  double d = 0.0;
2029  for (unsigned i = 0; i < n; ++i, ++d)
2030  foo(d);
2031  */
2032  if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
2033  IsSigned = false;
2034  DestTy = UCast->getDestTy();
2035  }
2036  else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
2037  IsSigned = true;
2038  DestTy = SCast->getDestTy();
2039  }
2040  if (!DestTy) continue;
2041 
2042  // If target does not support DestTy natively then do not apply
2043  // this transformation.
2044  if (!TTI.isTypeLegal(DestTy)) continue;
2045 
2046  PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2047  if (!PH) continue;
2048  if (PH->getNumIncomingValues() != 2) continue;
2049 
2050  // If the calculation in integers overflows, the result in FP type will
2051  // differ. So we only can do this transformation if we are guaranteed to not
2052  // deal with overflowing values
2053  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PH));
2054  if (!AR) continue;
2055  if (IsSigned && !AR->hasNoSignedWrap()) continue;
2056  if (!IsSigned && !AR->hasNoUnsignedWrap()) continue;
2057 
2058  Type *SrcTy = PH->getType();
2059  int Mantissa = DestTy->getFPMantissaWidth();
2060  if (Mantissa == -1) continue;
2061  if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
2062  continue;
2063 
2064  unsigned Entry, Latch;
2065  if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2066  Entry = 0;
2067  Latch = 1;
2068  } else {
2069  Entry = 1;
2070  Latch = 0;
2071  }
2072 
2074  if (!Init) continue;
2075  Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
2076  (double)Init->getSExtValue() :
2077  (double)Init->getZExtValue());
2078 
2079  BinaryOperator *Incr =
2081  if (!Incr) continue;
2082  if (Incr->getOpcode() != Instruction::Add
2083  && Incr->getOpcode() != Instruction::Sub)
2084  continue;
2085 
2086  /* Initialize new IV, double d = 0.0 in above example. */
2087  ConstantInt *C = nullptr;
2088  if (Incr->getOperand(0) == PH)
2089  C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2090  else if (Incr->getOperand(1) == PH)
2091  C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2092  else
2093  continue;
2094 
2095  if (!C) continue;
2096 
2097  // Ignore negative constants, as the code below doesn't handle them
2098  // correctly. TODO: Remove this restriction.
2099  if (!C->getValue().isStrictlyPositive()) continue;
2100 
2101  /* Add new PHINode. */
2102  PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
2103 
2104  /* create new increment. '++d' in above example. */
2105  Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2106  BinaryOperator *NewIncr =
2107  BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
2108  Instruction::FAdd : Instruction::FSub,
2109  NewPH, CFP, "IV.S.next.", Incr);
2110 
2111  NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2112  NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2113 
2114  /* Remove cast operation */
2115  ShadowUse->replaceAllUsesWith(NewPH);
2116  ShadowUse->eraseFromParent();
2117  Changed = true;
2118  break;
2119  }
2120 }
2121 
2122 /// If Cond has an operand that is an expression of an IV, set the IV user and
2123 /// stride information and return true, otherwise return false.
2124 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
2125  for (IVStrideUse &U : IU)
2126  if (U.getUser() == Cond) {
2127  // NOTE: we could handle setcc instructions with multiple uses here, but
2128  // InstCombine does it as well for simple uses, it's not clear that it
2129  // occurs enough in real life to handle.
2130  CondUse = &U;
2131  return true;
2132  }
2133  return false;
2134 }
2135 
2136 /// Rewrite the loop's terminating condition if it uses a max computation.
2137 ///
2138 /// This is a narrow solution to a specific, but acute, problem. For loops
2139 /// like this:
2140 ///
2141 /// i = 0;
2142 /// do {
2143 /// p[i] = 0.0;
2144 /// } while (++i < n);
2145 ///
2146 /// the trip count isn't just 'n', because 'n' might not be positive. And
2147 /// unfortunately this can come up even for loops where the user didn't use
2148 /// a C do-while loop. For example, seemingly well-behaved top-test loops
2149 /// will commonly be lowered like this:
2150 ///
2151 /// if (n > 0) {
2152 /// i = 0;
2153 /// do {
2154 /// p[i] = 0.0;
2155 /// } while (++i < n);
2156 /// }
2157 ///
2158 /// and then it's possible for subsequent optimization to obscure the if
2159 /// test in such a way that indvars can't find it.
2160 ///
2161 /// When indvars can't find the if test in loops like this, it creates a
2162 /// max expression, which allows it to give the loop a canonical
2163 /// induction variable:
2164 ///
2165 /// i = 0;
2166 /// max = n < 1 ? 1 : n;
2167 /// do {
2168 /// p[i] = 0.0;
2169 /// } while (++i != max);
2170 ///
2171 /// Canonical induction variables are necessary because the loop passes
2172 /// are designed around them. The most obvious example of this is the
2173 /// LoopInfo analysis, which doesn't remember trip count values. It
2174 /// expects to be able to rediscover the trip count each time it is
2175 /// needed, and it does this using a simple analysis that only succeeds if
2176 /// the loop has a canonical induction variable.
2177 ///
2178 /// However, when it comes time to generate code, the maximum operation
2179 /// can be quite costly, especially if it's inside of an outer loop.
2180 ///
2181 /// This function solves this problem by detecting this type of loop and
2182 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2183 /// the instructions for the maximum computation.
2184 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
2185  // Check that the loop matches the pattern we're looking for.
2186  if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2187  Cond->getPredicate() != CmpInst::ICMP_NE)
2188  return Cond;
2189 
2190  SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2191  if (!Sel || !Sel->hasOneUse()) return Cond;
2192 
2193  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2194  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2195  return Cond;
2196  const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2197 
2198  // Add one to the backedge-taken count to get the trip count.
2199  const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2200  if (IterationCount != SE.getSCEV(Sel)) return Cond;
2201 
2202  // Check for a max calculation that matches the pattern. There's no check
2203  // for ICMP_ULE here because the comparison would be with zero, which
2204  // isn't interesting.
2206  const SCEVNAryExpr *Max = nullptr;
2207  if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2208  Pred = ICmpInst::ICMP_SLE;
2209  Max = S;
2210  } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2211  Pred = ICmpInst::ICMP_SLT;
2212  Max = S;
2213  } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2214  Pred = ICmpInst::ICMP_ULT;
2215  Max = U;
2216  } else {
2217  // No match; bail.
2218  return Cond;
2219  }
2220 
2221  // To handle a max with more than two operands, this optimization would
2222  // require additional checking and setup.
2223  if (Max->getNumOperands() != 2)
2224  return Cond;
2225 
2226  const SCEV *MaxLHS = Max->getOperand(0);
2227  const SCEV *MaxRHS = Max->getOperand(1);
2228 
2229  // ScalarEvolution canonicalizes constants to the left. For < and >, look
2230  // for a comparison with 1. For <= and >=, a comparison with zero.
2231  if (!MaxLHS ||
2232  (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2233  return Cond;
2234 
2235  // Check the relevant induction variable for conformance to
2236  // the pattern.
2237  const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2238  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2239  if (!AR || !AR->isAffine() ||
2240  AR->getStart() != One ||
2241  AR->getStepRecurrence(SE) != One)
2242  return Cond;
2243 
2244  assert(AR->getLoop() == L &&
2245  "Loop condition operand is an addrec in a different loop!");
2246 
2247  // Check the right operand of the select, and remember it, as it will
2248  // be used in the new comparison instruction.
2249  Value *NewRHS = nullptr;
2250  if (ICmpInst::isTrueWhenEqual(Pred)) {
2251  // Look for n+1, and grab n.
2252  if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2253  if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2254  if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2255  NewRHS = BO->getOperand(0);
2256  if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2257  if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2258  if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2259  NewRHS = BO->getOperand(0);
2260  if (!NewRHS)
2261  return Cond;
2262  } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2263  NewRHS = Sel->getOperand(1);
2264  else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2265  NewRHS = Sel->getOperand(2);
2266  else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2267  NewRHS = SU->getValue();
2268  else
2269  // Max doesn't match expected pattern.
2270  return Cond;
2271 
2272  // Determine the new comparison opcode. It may be signed or unsigned,
2273  // and the original comparison may be either equality or inequality.
2274  if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2275  Pred = CmpInst::getInversePredicate(Pred);
2276 
2277  // Ok, everything looks ok to change the condition into an SLT or SGE and
2278  // delete the max calculation.
2279  ICmpInst *NewCond =
2280  new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2281 
2282  // Delete the max calculation instructions.
2283  Cond->replaceAllUsesWith(NewCond);
2284  CondUse->setUser(NewCond);
2285  Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2286  Cond->eraseFromParent();
2287  Sel->eraseFromParent();
2288  if (Cmp->use_empty())
2289  Cmp->eraseFromParent();
2290  return NewCond;
2291 }
2292 
2293 /// Change loop terminating condition to use the postinc iv when possible.
2294 void
2295 LSRInstance::OptimizeLoopTermCond() {
2297 
2298  // We need a different set of heuristics for rotated and non-rotated loops.
2299  // If a loop is rotated then the latch is also the backedge, so inserting
2300  // post-inc expressions just before the latch is ideal. To reduce live ranges
2301  // it also makes sense to rewrite terminating conditions to use post-inc
2302  // expressions.
2303  //
2304  // If the loop is not rotated then the latch is not a backedge; the latch
2305  // check is done in the loop head. Adding post-inc expressions before the
2306  // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2307  // in the loop body. In this case we do *not* want to use post-inc expressions
2308  // in the latch check, and we want to insert post-inc expressions before
2309  // the backedge.
2310  BasicBlock *LatchBlock = L->getLoopLatch();
2311  SmallVector<BasicBlock*, 8> ExitingBlocks;
2312  L->getExitingBlocks(ExitingBlocks);
2313  if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2314  return LatchBlock != BB;
2315  })) {
2316  // The backedge doesn't exit the loop; treat this as a head-tested loop.
2317  IVIncInsertPos = LatchBlock->getTerminator();
2318  return;
2319  }
2320 
2321  // Otherwise treat this as a rotated loop.
2322  for (BasicBlock *ExitingBlock : ExitingBlocks) {
2323  // Get the terminating condition for the loop if possible. If we
2324  // can, we want to change it to use a post-incremented version of its
2325  // induction variable, to allow coalescing the live ranges for the IV into
2326  // one register value.
2327 
2328  BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2329  if (!TermBr)
2330  continue;
2331  // FIXME: Overly conservative, termination condition could be an 'or' etc..
2332  if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2333  continue;
2334 
2335  // Search IVUsesByStride to find Cond's IVUse if there is one.
2336  IVStrideUse *CondUse = nullptr;
2337  ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2338  if (!FindIVUserForCond(Cond, CondUse))
2339  continue;
2340 
2341  // If the trip count is computed in terms of a max (due to ScalarEvolution
2342  // being unable to find a sufficient guard, for example), change the loop
2343  // comparison to use SLT or ULT instead of NE.
2344  // One consequence of doing this now is that it disrupts the count-down
2345  // optimization. That's not always a bad thing though, because in such
2346  // cases it may still be worthwhile to avoid a max.
2347  Cond = OptimizeMax(Cond, CondUse);
2348 
2349  // If this exiting block dominates the latch block, it may also use
2350  // the post-inc value if it won't be shared with other uses.
2351  // Check for dominance.
2352  if (!DT.dominates(ExitingBlock, LatchBlock))
2353  continue;
2354 
2355  // Conservatively avoid trying to use the post-inc value in non-latch
2356  // exits if there may be pre-inc users in intervening blocks.
2357  if (LatchBlock != ExitingBlock)
2358  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2359  // Test if the use is reachable from the exiting block. This dominator
2360  // query is a conservative approximation of reachability.
2361  if (&*UI != CondUse &&
2362  !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2363  // Conservatively assume there may be reuse if the quotient of their
2364  // strides could be a legal scale.
2365  const SCEV *A = IU.getStride(*CondUse, L);
2366  const SCEV *B = IU.getStride(*UI, L);
2367  if (!A || !B) continue;
2368  if (SE.getTypeSizeInBits(A->getType()) !=
2369  SE.getTypeSizeInBits(B->getType())) {
2370  if (SE.getTypeSizeInBits(A->getType()) >
2371  SE.getTypeSizeInBits(B->getType()))
2372  B = SE.getSignExtendExpr(B, A->getType());
2373  else
2374  A = SE.getSignExtendExpr(A, B->getType());
2375  }
2376  if (const SCEVConstant *D =
2377  dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2378  const ConstantInt *C = D->getValue();
2379  // Stride of one or negative one can have reuse with non-addresses.
2380  if (C->isOne() || C->isMinusOne())
2381  goto decline_post_inc;
2382  // Avoid weird situations.
2383  if (C->getValue().getMinSignedBits() >= 64 ||
2384  C->getValue().isMinSignedValue())
2385  goto decline_post_inc;
2386  // Check for possible scaled-address reuse.
2387  MemAccessTy AccessTy = getAccessType(TTI, UI->getUser());
2388  int64_t Scale = C->getSExtValue();
2389  if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2390  /*BaseOffset=*/0,
2391  /*HasBaseReg=*/false, Scale,
2392  AccessTy.AddrSpace))
2393  goto decline_post_inc;
2394  Scale = -Scale;
2395  if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2396  /*BaseOffset=*/0,
2397  /*HasBaseReg=*/false, Scale,
2398  AccessTy.AddrSpace))
2399  goto decline_post_inc;
2400  }
2401  }
2402 
2403  DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
2404  << *Cond << '\n');
2405 
2406  // It's possible for the setcc instruction to be anywhere in the loop, and
2407  // possible for it to have multiple users. If it is not immediately before
2408  // the exiting block branch, move it.
2409  if (&*++BasicBlock::iterator(Cond) != TermBr) {
2410  if (Cond->hasOneUse()) {
2411  Cond->moveBefore(TermBr);
2412  } else {
2413  // Clone the terminating condition and insert into the loopend.
2414  ICmpInst *OldCond = Cond;
2415  Cond = cast<ICmpInst>(Cond->clone());
2416  Cond->setName(L->getHeader()->getName() + ".termcond");
2417  ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2418 
2419  // Clone the IVUse, as the old use still exists!
2420  CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2421  TermBr->replaceUsesOfWith(OldCond, Cond);
2422  }
2423  }
2424 
2425  // If we get to here, we know that we can transform the setcc instruction to
2426  // use the post-incremented version of the IV, allowing us to coalesce the
2427  // live ranges for the IV correctly.
2428  CondUse->transformToPostInc(L);
2429  Changed = true;
2430 
2431  PostIncs.insert(Cond);
2432  decline_post_inc:;
2433  }
2434 
2435  // Determine an insertion point for the loop induction variable increment. It
2436  // must dominate all the post-inc comparisons we just set up, and it must
2437  // dominate the loop latch edge.
2438  IVIncInsertPos = L->getLoopLatch()->getTerminator();
2439  for (Instruction *Inst : PostIncs) {
2440  BasicBlock *BB =
2441  DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2442  Inst->getParent());
2443  if (BB == Inst->getParent())
2444  IVIncInsertPos = Inst;
2445  else if (BB != IVIncInsertPos->getParent())
2446  IVIncInsertPos = BB->getTerminator();
2447  }
2448 }
2449 
2450 /// Determine if the given use can accommodate a fixup at the given offset and
2451 /// other details. If so, update the use and return true.
2452 bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2453  bool HasBaseReg, LSRUse::KindType Kind,
2454  MemAccessTy AccessTy) {
2455  int64_t NewMinOffset = LU.MinOffset;
2456  int64_t NewMaxOffset = LU.MaxOffset;
2457  MemAccessTy NewAccessTy = AccessTy;
2458 
2459  // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2460  // something conservative, however this can pessimize in the case that one of
2461  // the uses will have all its uses outside the loop, for example.
2462  if (LU.Kind != Kind)
2463  return false;
2464 
2465  // Check for a mismatched access type, and fall back conservatively as needed.
2466  // TODO: Be less conservative when the type is similar and can use the same
2467  // addressing modes.
2468  if (Kind == LSRUse::Address) {
2469  if (AccessTy.MemTy != LU.AccessTy.MemTy) {
2470  NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(),
2471  AccessTy.AddrSpace);
2472  }
2473  }
2474 
2475  // Conservatively assume HasBaseReg is true for now.
2476  if (NewOffset < LU.MinOffset) {
2477  if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2478  LU.MaxOffset - NewOffset, HasBaseReg))
2479  return false;
2480  NewMinOffset = NewOffset;
2481  } else if (NewOffset > LU.MaxOffset) {
2482  if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2483  NewOffset - LU.MinOffset, HasBaseReg))
2484  return false;
2485  NewMaxOffset = NewOffset;
2486  }
2487 
2488  // Update the use.
2489  LU.MinOffset = NewMinOffset;
2490  LU.MaxOffset = NewMaxOffset;
2491  LU.AccessTy = NewAccessTy;
2492  return true;
2493 }
2494 
2495 /// Return an LSRUse index and an offset value for a fixup which needs the given
2496 /// expression, with the given kind and optional access type. Either reuse an
2497 /// existing use or create a new one, as needed.
2498 std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2499  LSRUse::KindType Kind,
2500  MemAccessTy AccessTy) {
2501  const SCEV *Copy = Expr;
2502  int64_t Offset = ExtractImmediate(Expr, SE);
2503 
2504  // Basic uses can't accept any offset, for example.
2505  if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2506  Offset, /*HasBaseReg=*/ true)) {
2507  Expr = Copy;
2508  Offset = 0;
2509  }
2510 
2511  std::pair<UseMapTy::iterator, bool> P =
2512  UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2513  if (!P.second) {
2514  // A use already existed with this base.
2515  size_t LUIdx = P.first->second;
2516  LSRUse &LU = Uses[LUIdx];
2517  if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2518  // Reuse this use.
2519  return std::make_pair(LUIdx, Offset);
2520  }
2521 
2522  // Create a new use.
2523  size_t LUIdx = Uses.size();
2524  P.first->second = LUIdx;
2525  Uses.push_back(LSRUse(Kind, AccessTy));
2526  LSRUse &LU = Uses[LUIdx];
2527 
2528  LU.MinOffset = Offset;
2529  LU.MaxOffset = Offset;
2530  return std::make_pair(LUIdx, Offset);
2531 }
2532 
2533 /// Delete the given use from the Uses list.
2534 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2535  if (&LU != &Uses.back())
2536  std::swap(LU, Uses.back());
2537  Uses.pop_back();
2538 
2539  // Update RegUses.
2540  RegUses.swapAndDropUse(LUIdx, Uses.size());
2541 }
2542 
2543 /// Look for a use distinct from OrigLU which is has a formula that has the same
2544 /// registers as the given formula.
2545 LSRUse *
2546 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2547  const LSRUse &OrigLU) {
2548  // Search all uses for the formula. This could be more clever.
2549  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2550  LSRUse &LU = Uses[LUIdx];
2551  // Check whether this use is close enough to OrigLU, to see whether it's
2552  // worthwhile looking through its formulae.
2553  // Ignore ICmpZero uses because they may contain formulae generated by
2554  // GenerateICmpZeroScales, in which case adding fixup offsets may
2555  // be invalid.
2556  if (&LU != &OrigLU &&
2557  LU.Kind != LSRUse::ICmpZero &&
2558  LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2559  LU.WidestFixupType == OrigLU.WidestFixupType &&
2560  LU.HasFormulaWithSameRegs(OrigF)) {
2561  // Scan through this use's formulae.
2562  for (const Formula &F : LU.Formulae) {
2563  // Check to see if this formula has the same registers and symbols
2564  // as OrigF.
2565  if (F.BaseRegs == OrigF.BaseRegs &&
2566  F.ScaledReg == OrigF.ScaledReg &&
2567  F.BaseGV == OrigF.BaseGV &&
2568  F.Scale == OrigF.Scale &&
2569  F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2570  if (F.BaseOffset == 0)
2571  return &LU;
2572  // This is the formula where all the registers and symbols matched;
2573  // there aren't going to be any others. Since we declined it, we
2574  // can skip the rest of the formulae and proceed to the next LSRUse.
2575  break;
2576  }
2577  }
2578  }
2579  }
2580 
2581  // Nothing looked good.
2582  return nullptr;
2583 }
2584 
2585 void LSRInstance::CollectInterestingTypesAndFactors() {
2587 
2588  // Collect interesting types and strides.
2590  for (const IVStrideUse &U : IU) {
2591  const SCEV *Expr = IU.getExpr(U);
2592 
2593  // Collect interesting types.
2594  Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2595 
2596  // Add strides for mentioned loops.
2597  Worklist.push_back(Expr);
2598  do {
2599  const SCEV *S = Worklist.pop_back_val();
2600  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2601  if (AR->getLoop() == L)
2602  Strides.insert(AR->getStepRecurrence(SE));
2603  Worklist.push_back(AR->getStart());
2604  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2605  Worklist.append(Add->op_begin(), Add->op_end());
2606  }
2607  } while (!Worklist.empty());
2608  }
2609 
2610  // Compute interesting factors from the set of interesting strides.
2612  I = Strides.begin(), E = Strides.end(); I != E; ++I)
2614  std::next(I); NewStrideIter != E; ++NewStrideIter) {
2615  const SCEV *OldStride = *I;
2616  const SCEV *NewStride = *NewStrideIter;
2617 
2618  if (SE.getTypeSizeInBits(OldStride->getType()) !=
2619  SE.getTypeSizeInBits(NewStride->getType())) {
2620  if (SE.getTypeSizeInBits(OldStride->getType()) >
2621  SE.getTypeSizeInBits(NewStride->getType()))
2622  NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2623  else
2624  OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2625  }
2626  if (const SCEVConstant *Factor =
2627  dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2628  SE, true))) {
2629  if (Factor->getAPInt().getMinSignedBits() <= 64)
2630  Factors.insert(Factor->getAPInt().getSExtValue());
2631  } else if (const SCEVConstant *Factor =
2632  dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2633  NewStride,
2634  SE, true))) {
2635  if (Factor->getAPInt().getMinSignedBits() <= 64)
2636  Factors.insert(Factor->getAPInt().getSExtValue());
2637  }
2638  }
2639 
2640  // If all uses use the same type, don't bother looking for truncation-based
2641  // reuse.
2642  if (Types.size() == 1)
2643  Types.clear();
2644 
2645  DEBUG(print_factors_and_types(dbgs()));
2646 }
2647 
2648 /// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2649 /// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2650 /// IVStrideUses, we could partially skip this.
2651 static User::op_iterator
2653  Loop *L, ScalarEvolution &SE) {
2654  for(; OI != OE; ++OI) {
2655  if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2656  if (!SE.isSCEVable(Oper->getType()))
2657  continue;
2658 
2659  if (const SCEVAddRecExpr *AR =
2660  dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2661  if (AR->getLoop() == L)
2662  break;
2663  }
2664  }
2665  }
2666  return OI;
2667 }
2668 
2669 /// IVChain logic must consistenctly peek base TruncInst operands, so wrap it in
2670 /// a convenient helper.
2671 static Value *getWideOperand(Value *Oper) {
2672  if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2673  return Trunc->getOperand(0);
2674  return Oper;
2675 }
2676 
2677 /// Return true if we allow an IV chain to include both types.
2678 static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2679  Type *LType = LVal->getType();
2680  Type *RType = RVal->getType();
2681  return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy() &&
2682  // Different address spaces means (possibly)
2683  // different types of the pointer implementation,
2684  // e.g. i16 vs i32 so disallow that.
2685  (LType->getPointerAddressSpace() ==
2686  RType->getPointerAddressSpace()));
2687 }
2688 
2689 /// Return an approximation of this SCEV expression's "base", or NULL for any
2690 /// constant. Returning the expression itself is conservative. Returning a
2691 /// deeper subexpression is more precise and valid as long as it isn't less
2692 /// complex than another subexpression. For expressions involving multiple
2693 /// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2694 /// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2695 /// IVInc==b-a.
2696 ///
2697 /// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2698 /// SCEVUnknown, we simply return the rightmost SCEV operand.
2699 static const SCEV *getExprBase(const SCEV *S) {
2700  switch (S->getSCEVType()) {
2701  default: // uncluding scUnknown.
2702  return S;
2703  case scConstant:
2704  return nullptr;
2705  case scTruncate:
2706  return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2707  case scZeroExtend:
2708  return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2709  case scSignExtend:
2710  return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2711  case scAddExpr: {
2712  // Skip over scaled operands (scMulExpr) to follow add operands as long as
2713  // there's nothing more complex.
2714  // FIXME: not sure if we want to recognize negation.
2715  const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2716  for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2717  E(Add->op_begin()); I != E; ++I) {
2718  const SCEV *SubExpr = *I;
2719  if (SubExpr->getSCEVType() == scAddExpr)
2720  return getExprBase(SubExpr);
2721 
2722  if (SubExpr->getSCEVType() != scMulExpr)
2723  return SubExpr;
2724  }
2725  return S; // all operands are scaled, be conservative.
2726  }
2727  case scAddRecExpr:
2728  return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2729  }
2730 }
2731 
2732 /// Return true if the chain increment is profitable to expand into a loop
2733 /// invariant value, which may require its own register. A profitable chain
2734 /// increment will be an offset relative to the same base. We allow such offsets
2735 /// to potentially be used as chain increment as long as it's not obviously
2736 /// expensive to expand using real instructions.
2737 bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2738  const SCEV *IncExpr,
2739  ScalarEvolution &SE) {
2740  // Aggressively form chains when -stress-ivchain.
2741  if (StressIVChain)
2742  return true;
2743 
2744  // Do not replace a constant offset from IV head with a nonconstant IV
2745  // increment.
2746  if (!isa<SCEVConstant>(IncExpr)) {
2747  const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2748  if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2749  return false;
2750  }
2751 
2752  SmallPtrSet<const SCEV*, 8> Processed;
2753  return !isHighCostExpansion(IncExpr, Processed, SE);
2754 }
2755 
2756 /// Return true if the number of registers needed for the chain is estimated to
2757 /// be less than the number required for the individual IV users. First prohibit
2758 /// any IV users that keep the IV live across increments (the Users set should
2759 /// be empty). Next count the number and type of increments in the chain.
2760 ///
2761 /// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2762 /// effectively use postinc addressing modes. Only consider it profitable it the
2763 /// increments can be computed in fewer registers when chained.
2764 ///
2765 /// TODO: Consider IVInc free if it's already used in another chains.
2766 static bool
2768  ScalarEvolution &SE, const TargetTransformInfo &TTI) {
2769  if (StressIVChain)
2770  return true;
2771 
2772  if (!Chain.hasIncs())
2773  return false;
2774 
2775  if (!Users.empty()) {
2776  DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";
2777  for (Instruction *Inst : Users) {
2778  dbgs() << " " << *Inst << "\n";
2779  });
2780  return false;
2781  }
2782  assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2783 
2784  // The chain itself may require a register, so intialize cost to 1.
2785  int cost = 1;
2786 
2787  // A complete chain likely eliminates the need for keeping the original IV in
2788  // a register. LSR does not currently know how to form a complete chain unless
2789  // the header phi already exists.
2790  if (isa<PHINode>(Chain.tailUserInst())
2791  && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2792  --cost;
2793  }
2794  const SCEV *LastIncExpr = nullptr;
2795  unsigned NumConstIncrements = 0;
2796  unsigned NumVarIncrements = 0;
2797  unsigned NumReusedIncrements = 0;
2798  for (const IVInc &Inc : Chain) {
2799  if (Inc.IncExpr->isZero())
2800  continue;
2801 
2802  // Incrementing by zero or some constant is neutral. We assume constants can
2803  // be folded into an addressing mode or an add's immediate operand.
2804  if (isa<SCEVConstant>(Inc.IncExpr)) {
2805  ++NumConstIncrements;
2806  continue;
2807  }
2808 
2809  if (Inc.IncExpr == LastIncExpr)
2810  ++NumReusedIncrements;
2811  else
2812  ++NumVarIncrements;
2813 
2814  LastIncExpr = Inc.IncExpr;
2815  }
2816  // An IV chain with a single increment is handled by LSR's postinc
2817  // uses. However, a chain with multiple increments requires keeping the IV's
2818  // value live longer than it needs to be if chained.
2819  if (NumConstIncrements > 1)
2820  --cost;
2821 
2822  // Materializing increment expressions in the preheader that didn't exist in
2823  // the original code may cost a register. For example, sign-extended array
2824  // indices can produce ridiculous increments like this:
2825  // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2826  cost += NumVarIncrements;
2827 
2828  // Reusing variable increments likely saves a register to hold the multiple of
2829  // the stride.
2830  cost -= NumReusedIncrements;
2831 
2832  DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost
2833  << "\n");
2834 
2835  return cost < 0;
2836 }
2837 
2838 /// Add this IV user to an existing chain or make it the head of a new chain.
2839 void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2840  SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2841  // When IVs are used as types of varying widths, they are generally converted
2842  // to a wider type with some uses remaining narrow under a (free) trunc.
2843  Value *const NextIV = getWideOperand(IVOper);
2844  const SCEV *const OperExpr = SE.getSCEV(NextIV);
2845  const SCEV *const OperExprBase = getExprBase(OperExpr);
2846 
2847  // Visit all existing chains. Check if its IVOper can be computed as a
2848  // profitable loop invariant increment from the last link in the Chain.
2849  unsigned ChainIdx = 0, NChains = IVChainVec.size();
2850  const SCEV *LastIncExpr = nullptr;
2851  for (; ChainIdx < NChains; ++ChainIdx) {
2852  IVChain &Chain = IVChainVec[ChainIdx];
2853 
2854  // Prune the solution space aggressively by checking that both IV operands
2855  // are expressions that operate on the same unscaled SCEVUnknown. This
2856  // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2857  // first avoids creating extra SCEV expressions.
2858  if (!StressIVChain && Chain.ExprBase != OperExprBase)
2859  continue;
2860 
2861  Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2862  if (!isCompatibleIVType(PrevIV, NextIV))
2863  continue;
2864 
2865  // A phi node terminates a chain.
2866  if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2867  continue;
2868 
2869  // The increment must be loop-invariant so it can be kept in a register.
2870  const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2871  const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2872  if (!SE.isLoopInvariant(IncExpr, L))
2873  continue;
2874 
2875  if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2876  LastIncExpr = IncExpr;
2877  break;
2878  }
2879  }
2880  // If we haven't found a chain, create a new one, unless we hit the max. Don't
2881  // bother for phi nodes, because they must be last in the chain.
2882  if (ChainIdx == NChains) {
2883  if (isa<PHINode>(UserInst))
2884  return;
2885  if (NChains >= MaxChains && !StressIVChain) {
2886  DEBUG(dbgs() << "IV Chain Limit\n");
2887  return;
2888  }
2889  LastIncExpr = OperExpr;
2890  // IVUsers may have skipped over sign/zero extensions. We don't currently
2891  // attempt to form chains involving extensions unless they can be hoisted
2892  // into this loop's AddRec.
2893  if (!isa<SCEVAddRecExpr>(LastIncExpr))
2894  return;
2895  ++NChains;
2896  IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2897  OperExprBase));
2898  ChainUsersVec.resize(NChains);
2899  DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst
2900  << ") IV=" << *LastIncExpr << "\n");
2901  } else {
2902  DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst
2903  << ") IV+" << *LastIncExpr << "\n");
2904  // Add this IV user to the end of the chain.
2905  IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2906  }
2907  IVChain &Chain = IVChainVec[ChainIdx];
2908 
2909  SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2910  // This chain's NearUsers become FarUsers.
2911  if (!LastIncExpr->isZero()) {
2912  ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2913  NearUsers.end());
2914  NearUsers.clear();
2915  }
2916 
2917  // All other uses of IVOperand become near uses of the chain.
2918  // We currently ignore intermediate values within SCEV expressions, assuming
2919  // they will eventually be used be the current chain, or can be computed
2920  // from one of the chain increments. To be more precise we could
2921  // transitively follow its user and only add leaf IV users to the set.
2922  for (User *U : IVOper->users()) {
2923  Instruction *OtherUse = dyn_cast<Instruction>(U);
2924  if (!OtherUse)
2925  continue;
2926  // Uses in the chain will no longer be uses if the chain is formed.
2927  // Include the head of the chain in this iteration (not Chain.begin()).
2928  IVChain::const_iterator IncIter = Chain.Incs.begin();
2929  IVChain::const_iterator IncEnd = Chain.Incs.end();
2930  for( ; IncIter != IncEnd; ++IncIter) {
2931  if (IncIter->UserInst == OtherUse)
2932  break;
2933  }
2934  if (IncIter != IncEnd)
2935  continue;
2936 
2937  if (SE.isSCEVable(OtherUse->getType())
2938  && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2939  && IU.isIVUserOrOperand(OtherUse)) {
2940  continue;
2941  }
2942  NearUsers.insert(OtherUse);
2943  }
2944 
2945  // Since this user is part of the chain, it's no longer considered a use
2946  // of the chain.
2947  ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2948 }
2949 
2950 /// Populate the vector of Chains.
2951 ///
2952 /// This decreases ILP at the architecture level. Targets with ample registers,
2953 /// multiple memory ports, and no register renaming probably don't want
2954 /// this. However, such targets should probably disable LSR altogether.
2955 ///
2956 /// The job of LSR is to make a reasonable choice of induction variables across
2957 /// the loop. Subsequent passes can easily "unchain" computation exposing more
2958 /// ILP *within the loop* if the target wants it.
2959 ///
2960 /// Finding the best IV chain is potentially a scheduling problem. Since LSR
2961 /// will not reorder memory operations, it will recognize this as a chain, but
2962 /// will generate redundant IV increments. Ideally this would be corrected later
2963 /// by a smart scheduler:
2964 /// = A[i]
2965 /// = A[i+x]
2966 /// A[i] =
2967 /// A[i+x] =
2968 ///
2969 /// TODO: Walk the entire domtree within this loop, not just the path to the
2970 /// loop latch. This will discover chains on side paths, but requires
2971 /// maintaining multiple copies of the Chains state.
2972 void LSRInstance::CollectChains() {
2973  DEBUG(dbgs() << "Collecting IV Chains.\n");
2974  SmallVector<ChainUsers, 8> ChainUsersVec;
2975 
2976  SmallVector<BasicBlock *,8> LatchPath;
2977  BasicBlock *LoopHeader = L->getHeader();
2978  for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
2979  Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
2980  LatchPath.push_back(Rung->getBlock());
2981  }
2982  LatchPath.push_back(LoopHeader);
2983 
2984  // Walk the instruction stream from the loop header to the loop latch.
2985  for (BasicBlock *BB : reverse(LatchPath)) {
2986  for (Instruction &I : *BB) {
2987  // Skip instructions that weren't seen by IVUsers analysis.
2988  if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
2989  continue;
2990 
2991  // Ignore users that are part of a SCEV expression. This way we only
2992  // consider leaf IV Users. This effectively rediscovers a portion of
2993  // IVUsers analysis but in program order this time.
2994  if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
2995  continue;
2996 
2997  // Remove this instruction from any NearUsers set it may be in.
2998  for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
2999  ChainIdx < NChains; ++ChainIdx) {
3000  ChainUsersVec[ChainIdx].NearUsers.erase(&I);
3001  }
3002  // Search for operands that can be chained.
3003  SmallPtrSet<Instruction*, 4> UniqueOperands;
3004  User::op_iterator IVOpEnd = I.op_end();
3005  User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
3006  while (IVOpIter != IVOpEnd) {
3007  Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
3008  if (UniqueOperands.insert(IVOpInst).second)
3009  ChainInstruction(&I, IVOpInst, ChainUsersVec);
3010  IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3011  }
3012  } // Continue walking down the instructions.
3013  } // Continue walking down the domtree.
3014  // Visit phi backedges to determine if the chain can generate the IV postinc.
3015  for (PHINode &PN : L->getHeader()->phis()) {
3016  if (!SE.isSCEVable(PN.getType()))
3017  continue;
3018 
3019  Instruction *IncV =
3020  dyn_cast<Instruction>(PN.getIncomingValueForBlock(L->getLoopLatch()));
3021  if (IncV)
3022  ChainInstruction(&PN, IncV, ChainUsersVec);
3023  }
3024  // Remove any unprofitable chains.
3025  unsigned ChainIdx = 0;
3026  for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
3027  UsersIdx < NChains; ++UsersIdx) {
3028  if (!isProfitableChain(IVChainVec[UsersIdx],
3029  ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
3030  continue;
3031  // Preserve the chain at UsesIdx.
3032  if (ChainIdx != UsersIdx)
3033  IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
3034  FinalizeChain(IVChainVec[ChainIdx]);
3035  ++ChainIdx;
3036  }
3037  IVChainVec.resize(ChainIdx);
3038 }
3039 
3040 void LSRInstance::FinalizeChain(IVChain &Chain) {
3041  assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
3042  DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n");
3043 
3044  for (const IVInc &Inc : Chain) {
3045  DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n");
3046  auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
3047  assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand");
3048  IVIncSet.insert(UseI);
3049  }
3050 }
3051 
3052 /// Return true if the IVInc can be folded into an addressing mode.
3053 static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
3054  Value *Operand, const TargetTransformInfo &TTI) {
3055  const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
3056  if (!IncConst || !isAddressUse(TTI, UserInst, Operand))
3057  return false;
3058 
3059  if (IncConst->getAPInt().getMinSignedBits() > 64)
3060  return false;
3061 
3062  MemAccessTy AccessTy = getAccessType(TTI, UserInst);
3063  int64_t IncOffset = IncConst->getValue()->getSExtValue();
3064  if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
3065  IncOffset, /*HaseBaseReg=*/false))
3066  return false;
3067 
3068  return true;
3069 }
3070 
3071 /// Generate an add or subtract for each IVInc in a chain to materialize the IV
3072 /// user's operand from the previous IV user's operand.
3073 void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
3074  SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
3075  // Find the new IVOperand for the head of the chain. It may have been replaced
3076  // by LSR.
3077  const IVInc &Head = Chain.Incs[0];
3078  User::op_iterator IVOpEnd = Head.UserInst->op_end();
3079  // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
3080  User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
3081  IVOpEnd, L, SE);
3082  Value *IVSrc = nullptr;
3083  while (IVOpIter != IVOpEnd) {
3084  IVSrc = getWideOperand(*IVOpIter);
3085 
3086  // If this operand computes the expression that the chain needs, we may use
3087  // it. (Check this after setting IVSrc which is used below.)
3088  //
3089  // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
3090  // narrow for the chain, so we can no longer use it. We do allow using a
3091  // wider phi, assuming the LSR checked for free truncation. In that case we
3092  // should already have a truncate on this operand such that
3093  // getSCEV(IVSrc) == IncExpr.
3094  if (SE.getSCEV(*IVOpIter) == Head.IncExpr
3095  || SE.getSCEV(IVSrc) == Head.IncExpr) {
3096  break;
3097  }
3098  IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3099  }
3100  if (IVOpIter == IVOpEnd) {
3101  // Gracefully give up on this chain.
3102  DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
3103  return;
3104  }
3105 
3106  DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
3107  Type *IVTy = IVSrc->getType();
3108  Type *IntTy = SE.getEffectiveSCEVType(IVTy);
3109  const SCEV *LeftOverExpr = nullptr;
3110  for (const IVInc &Inc : Chain) {
3111  Instruction *InsertPt = Inc.UserInst;
3112  if (isa<PHINode>(InsertPt))
3113  InsertPt = L->getLoopLatch()->getTerminator();
3114 
3115  // IVOper will replace the current IV User's operand. IVSrc is the IV
3116  // value currently held in a register.
3117  Value *IVOper = IVSrc;
3118  if (!Inc.IncExpr->isZero()) {
3119  // IncExpr was the result of subtraction of two narrow values, so must
3120  // be signed.
3121  const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
3122  LeftOverExpr = LeftOverExpr ?
3123  SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
3124  }
3125  if (LeftOverExpr && !LeftOverExpr->isZero()) {
3126  // Expand the IV increment.
3127  Rewriter.clearPostInc();
3128  Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
3129  const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
3130  SE.getUnknown(IncV));
3131  IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
3132 
3133  // If an IV increment can't be folded, use it as the next IV value.
3134  if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
3135  assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
3136  IVSrc = IVOper;
3137  LeftOverExpr = nullptr;
3138  }
3139  }
3140  Type *OperTy = Inc.IVOperand->getType();
3141  if (IVTy != OperTy) {
3142  assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
3143  "cannot extend a chained IV");
3144  IRBuilder<> Builder(InsertPt);
3145  IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
3146  }
3147  Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
3148  DeadInsts.emplace_back(Inc.IVOperand);
3149  }
3150  // If LSR created a new, wider phi, we may also replace its postinc. We only
3151  // do this if we also found a wide value for the head of the chain.
3152  if (isa<PHINode>(Chain.tailUserInst())) {
3153  for (PHINode &Phi : L->getHeader()->phis()) {
3154  if (!isCompatibleIVType(&Phi, IVSrc))
3155  continue;
3156  Instruction *PostIncV = dyn_cast<Instruction>(
3157  Phi.getIncomingValueForBlock(L->getLoopLatch()));
3158  if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
3159  continue;
3160  Value *IVOper = IVSrc;
3161  Type *PostIncTy = PostIncV->getType();
3162  if (IVTy != PostIncTy) {
3163  assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
3164  IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
3165  Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
3166  IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
3167  }
3168  Phi.replaceUsesOfWith(PostIncV, IVOper);
3169  DeadInsts.emplace_back(PostIncV);
3170  }
3171  }
3172 }
3173 
3174 void LSRInstance::CollectFixupsAndInitialFormulae() {
3175  for (const IVStrideUse &U : IU) {
3176  Instruction *UserInst = U.getUser();
3177  // Skip IV users that are part of profitable IV Chains.
3178  User::op_iterator UseI =
3179  find(UserInst->operands(), U.getOperandValToReplace());
3180  assert(UseI != UserInst->op_end() && "cannot find IV operand");
3181  if (IVIncSet.count(UseI)) {
3182  DEBUG(dbgs() << "Use is in profitable chain: " << **UseI << '\n');
3183  continue;
3184  }
3185 
3186  LSRUse::KindType Kind = LSRUse::Basic;
3187  MemAccessTy AccessTy;
3188  if (isAddressUse(TTI, UserInst, U.getOperandValToReplace())) {
3189  Kind = LSRUse::Address;
3190  AccessTy = getAccessType(TTI, UserInst);
3191  }
3192 
3193  const SCEV *S = IU.getExpr(U);
3194  PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3195 
3196  // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3197  // (N - i == 0), and this allows (N - i) to be the expression that we work
3198  // with rather than just N or i, so we can consider the register
3199  // requirements for both N and i at the same time. Limiting this code to
3200  // equality icmps is not a problem because all interesting loops use
3201  // equality icmps, thanks to IndVarSimplify.
3202  if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst))
3203  if (CI->isEquality()) {
3204  // Swap the operands if needed to put the OperandValToReplace on the
3205  // left, for consistency.
3206  Value *NV = CI->getOperand(1);
3207  if (NV == U.getOperandValToReplace()) {
3208  CI->setOperand(1, CI->getOperand(0));
3209  CI->setOperand(0, NV);
3210  NV = CI->getOperand(1);
3211  Changed = true;
3212  }
3213 
3214  // x == y --> x - y == 0
3215  const SCEV *N = SE.getSCEV(NV);
3216  if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3217  // S is normalized, so normalize N before folding it into S
3218  // to keep the result normalized.
3219  N = normalizeForPostIncUse(N, TmpPostIncLoops, SE);
3220  Kind = LSRUse::ICmpZero;
3221  S = SE.getMinusSCEV(N, S);
3222  }
3223 
3224  // -1 and the negations of all interesting strides (except the negation
3225  // of -1) are now also interesting.
3226  for (size_t i = 0, e = Factors.size(); i != e; ++i)
3227  if (Factors[i] != -1)
3228  Factors.insert(-(uint64_t)Factors[i]);
3229  Factors.insert(-1);
3230  }
3231 
3232  // Get or create an LSRUse.
3233  std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3234  size_t LUIdx = P.first;
3235  int64_t Offset = P.second;
3236  LSRUse &LU = Uses[LUIdx];
3237 
3238  // Record the fixup.
3239  LSRFixup &LF = LU.getNewFixup();
3240  LF.UserInst = UserInst;
3241  LF.OperandValToReplace = U.getOperandValToReplace();
3242  LF.PostIncLoops = TmpPostIncLoops;
3243  LF.Offset = Offset;
3244  LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3245 
3246  if (!LU.WidestFixupType ||
3247  SE.getTypeSizeInBits(LU.WidestFixupType) <
3248  SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3249  LU.WidestFixupType = LF.OperandValToReplace->getType();
3250 
3251  // If this is the first use of this LSRUse, give it a formula.
3252  if (LU.Formulae.empty()) {
3253  InsertInitialFormula(S, LU, LUIdx);
3254  CountRegisters(LU.Formulae.back(), LUIdx);
3255  }
3256  }
3257 
3258  DEBUG(print_fixups(dbgs()));
3259 }
3260 
3261 /// Insert a formula for the given expression into the given use, separating out
3262 /// loop-variant portions from loop-invariant and loop-computable portions.
3263 void
3264 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3265  // Mark uses whose expressions cannot be expanded.
3266  if (!isSafeToExpand(S, SE))
3267  LU.RigidFormula = true;
3268 
3269  Formula F;
3270  F.initialMatch(S, L, SE);
3271  bool Inserted = InsertFormula(LU, LUIdx, F);
3272  assert(Inserted && "Initial formula already exists!"); (void)Inserted;
3273 }
3274 
3275 /// Insert a simple single-register formula for the given expression into the
3276 /// given use.
3277 void
3278 LSRInstance::InsertSupplementalFormula(const SCEV *S,
3279  LSRUse &LU, size_t LUIdx) {
3280  Formula F;
3281  F.BaseRegs.push_back(S);
3282  F.HasBaseReg = true;
3283  bool Inserted = InsertFormula(LU, LUIdx, F);
3284  assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
3285 }
3286 
3287 /// Note which registers are used by the given formula, updating RegUses.
3288 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3289  if (F.ScaledReg)
3290  RegUses.countRegister(F.ScaledReg, LUIdx);
3291  for (const SCEV *BaseReg : F.BaseRegs)
3292  RegUses.countRegister(BaseReg, LUIdx);
3293 }
3294 
3295 /// If the given formula has not yet been inserted, add it to the list, and
3296 /// return true. Return false otherwise.
3297 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3298  // Do not insert formula that we will not be able to expand.
3299  assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&
3300  "Formula is illegal");
3301 
3302  if (!LU.InsertFormula(F, *L))
3303  return false;
3304 
3305  CountRegisters(F, LUIdx);
3306  return true;
3307 }
3308 
3309 /// Check for other uses of loop-invariant values which we're tracking. These
3310 /// other uses will pin these values in registers, making them less profitable
3311 /// for elimination.
3312 /// TODO: This currently misses non-constant addrec step registers.
3313 /// TODO: Should this give more weight to users inside the loop?
3314 void
3315 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3316  SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3318 
3319  while (!Worklist.empty()) {
3320  const SCEV *S = Worklist.pop_back_val();
3321 
3322  // Don't process the same SCEV twice
3323  if (!Visited.insert(S).second)
3324  continue;
3325 
3326  if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3327  Worklist.append(N->op_begin(), N->op_end());
3328  else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3329  Worklist.push_back(C->getOperand());
3330  else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3331  Worklist.push_back(D->getLHS());
3332  Worklist.push_back(D->getRHS());
3333  } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3334  const Value *V = US->getValue();
3335  if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3336  // Look for instructions defined outside the loop.
3337  if (L->contains(Inst)) continue;
3338  } else if (isa<UndefValue>(V))
3339  // Undef doesn't have a live range, so it doesn't matter.
3340  continue;
3341  for (const Use &U : V->uses()) {
3342  const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3343  // Ignore non-instructions.
3344  if (!UserInst)
3345  continue;
3346  // Ignore instructions in other functions (as can happen with
3347  // Constants).
3348  if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3349  continue;
3350  // Ignore instructions not dominated by the loop.
3351  const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3352  UserInst->getParent() :
3353  cast<PHINode>(UserInst)->getIncomingBlock(
3354  PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3355  if (!DT.dominates(L->getHeader(), UseBB))
3356  continue;
3357  // Don't bother if the instruction is in a BB which ends in an EHPad.
3358  if (UseBB->getTerminator()->isEHPad())
3359  continue;
3360  // Don't bother rewriting PHIs in catchswitch blocks.
3361  if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator()))
3362  continue;
3363  // Ignore uses which are part of other SCEV expressions, to avoid
3364  // analyzing them multiple times.
3365  if (SE.isSCEVable(UserInst->getType())) {
3366  const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3367  // If the user is a no-op, look through to its uses.
3368  if (!isa<SCEVUnknown>(UserS))
3369  continue;
3370  if (UserS == US) {
3371  Worklist.push_back(
3372  SE.getUnknown(const_cast<Instruction *>(UserInst)));
3373  continue;
3374  }
3375  }
3376  // Ignore icmp instructions which are already being analyzed.
3377  if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3378  unsigned OtherIdx = !U.getOperandNo();
3379  Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3380  if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3381  continue;
3382  }
3383 
3384  std::pair<size_t, int64_t> P = getUse(
3385  S, LSRUse::Basic, MemAccessTy());
3386  size_t LUIdx = P.first;
3387  int64_t Offset = P.second;
3388  LSRUse &LU = Uses[LUIdx];
3389  LSRFixup &LF = LU.getNewFixup();
3390  LF.UserInst = const_cast<Instruction *>(UserInst);
3391  LF.OperandValToReplace = U;
3392  LF.Offset = Offset;
3393  LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3394  if (!LU.WidestFixupType ||
3395  SE.getTypeSizeInBits(LU.WidestFixupType) <
3396  SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3397  LU.WidestFixupType = LF.OperandValToReplace->getType();
3398  InsertSupplementalFormula(US, LU, LUIdx);
3399  CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3400  break;
3401  }
3402  }
3403  }
3404 }
3405 
3406 /// Split S into subexpressions which can be pulled out into separate
3407 /// registers. If C is non-null, multiply each subexpression by C.
3408 ///
3409 /// Return remainder expression after factoring the subexpressions captured by
3410 /// Ops. If Ops is complete, return NULL.
3411 static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3413  const Loop *L,
3414  ScalarEvolution &SE,
3415  unsigned Depth = 0) {
3416  // Arbitrarily cap recursion to protect compile time.
3417  if (Depth >= 3)
3418  return S;
3419 
3420  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3421  // Break out add operands.
3422  for (const SCEV *S : Add->operands()) {
3423  const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3424  if (Remainder)
3425  Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3426  }
3427  return nullptr;
3428  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3429  // Split a non-zero base out of an addrec.
3430  if (AR->getStart()->isZero() || !AR->isAffine())
3431  return S;
3432 
3433  const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3434  C, Ops, L, SE, Depth+1);
3435  // Split the non-zero AddRec unless it is part of a nested recurrence that
3436  // does not pertain to this loop.
3437  if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3438  Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3439  Remainder = nullptr;
3440  }
3441  if (Remainder != AR->getStart()) {
3442  if (!Remainder)
3443  Remainder = SE.getConstant(AR->getType(), 0);
3444  return SE.getAddRecExpr(Remainder,
3445  AR->getStepRecurrence(SE),
3446  AR->getLoop(),
3447  //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3449  }
3450  } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3451  // Break (C * (a + b + c)) into C*a + C*b + C*c.
3452  if (Mul->getNumOperands() != 2)
3453  return S;
3454  if (const SCEVConstant *Op0 =
3455  dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3456  C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3457  const SCEV *Remainder =
3458  CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3459  if (Remainder)
3460  Ops.push_back(SE.getMulExpr(C, Remainder));
3461  return nullptr;
3462  }
3463  }
3464  return S;
3465 }
3466 
3467 /// \brief Helper function for LSRInstance::GenerateReassociations.
3468 void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3469  const Formula &Base,
3470  unsigned Depth, size_t Idx,
3471  bool IsScaledReg) {
3472  const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3474  const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3475  if (Remainder)
3476  AddOps.push_back(Remainder);
3477 
3478  if (AddOps.size() == 1)
3479  return;
3480 
3482  JE = AddOps.end();
3483  J != JE; ++J) {
3484  // Loop-variant "unknown" values are uninteresting; we won't be able to
3485  // do anything meaningful with them.
3486  if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3487  continue;
3488 
3489  // Don't pull a constant into a register if the constant could be folded
3490  // into an immediate field.
3491  if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3492  LU.AccessTy, *J, Base.getNumRegs() > 1))
3493  continue;
3494 
3495  // Collect all operands except *J.
3496  SmallVector<const SCEV *, 8> InnerAddOps(
3497  ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3498  InnerAddOps.append(std::next(J),
3499  ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3500 
3501  // Don't leave just a constant behind in a register if the constant could
3502  // be folded into an immediate field.
3503  if (InnerAddOps.size() == 1 &&
3504  isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3505  LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3506  continue;
3507 
3508  const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3509  if (InnerSum->isZero())
3510  continue;
3511  Formula F = Base;
3512 
3513  // Add the remaining pieces of the add back into the new formula.
3514  const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3515  if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3516  TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3517  InnerSumSC->getValue()->getZExtValue())) {
3518  F.UnfoldedOffset =
3519  (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3520  if (IsScaledReg)
3521  F.ScaledReg = nullptr;
3522  else
3523  F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3524  } else if (IsScaledReg)
3525  F.ScaledReg = InnerSum;
3526  else
3527  F.BaseRegs[Idx] = InnerSum;
3528 
3529  // Add J as its own register, or an unfolded immediate.
3530  const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3531  if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3532  TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3533  SC->getValue()->getZExtValue()))
3534  F.UnfoldedOffset =
3535  (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3536  else
3537  F.BaseRegs.push_back(*J);
3538  // We may have changed the number of register in base regs, adjust the
3539  // formula accordingly.
3540  F.canonicalize(*L);
3541 
3542  if (InsertFormula(LU, LUIdx, F))
3543  // If that formula hadn't been seen before, recurse to find more like
3544  // it.
3545  GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth + 1);
3546  }
3547 }
3548 
3549 /// Split out subexpressions from adds and the bases of addrecs.
3550 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3551  Formula Base, unsigned Depth) {
3552  assert(Base.isCanonical(*L) && "Input must be in the canonical form");
3553  // Arbitrarily cap recursion to protect compile time.
3554  if (Depth >= 3)
3555  return;
3556 
3557  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3558  GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3559 
3560  if (Base.Scale == 1)
3561  GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3562  /* Idx */ -1, /* IsScaledReg */ true);
3563 }
3564 
3565 /// Generate a formula consisting of all of the loop-dominating registers added
3566 /// into a single register.
3567 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3568  Formula Base) {
3569  // This method is only interesting on a plurality of registers.
3570  if (Base.BaseRegs.size() + (Base.Scale == 1) <= 1)
3571  return;
3572 
3573  // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3574  // processing the formula.
3575  Base.unscale();
3576  Formula F = Base;
3577  F.BaseRegs.clear();
3579  for (const SCEV *BaseReg : Base.BaseRegs) {
3580  if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3581  !SE.hasComputableLoopEvolution(BaseReg, L))
3582  Ops.push_back(BaseReg);
3583  else
3584  F.BaseRegs.push_back(BaseReg);
3585  }
3586  if (Ops.size() > 1) {
3587  const SCEV *Sum = SE.getAddExpr(Ops);
3588  // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3589  // opportunity to fold something. For now, just ignore such cases
3590  // rather than proceed with zero in a register.
3591  if (!Sum->isZero()) {
3592  F.BaseRegs.push_back(Sum);
3593  F.canonicalize(*L);
3594  (void)InsertFormula(LU, LUIdx, F);
3595  }
3596  }
3597 }
3598 
3599 /// \brief Helper function for LSRInstance::GenerateSymbolicOffsets.
3600 void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3601  const Formula &Base, size_t Idx,
3602  bool IsScaledReg) {
3603  const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3604  GlobalValue *GV = ExtractSymbol(G, SE);
3605  if (G->isZero() || !GV)
3606  return;
3607  Formula F = Base;
3608  F.BaseGV = GV;
3609  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3610  return;
3611  if (IsScaledReg)
3612  F.ScaledReg = G;
3613  else
3614  F.BaseRegs[Idx] = G;
3615  (void)InsertFormula(LU, LUIdx, F);
3616 }
3617 
3618 /// Generate reuse formulae using symbolic offsets.
3619 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3620  Formula Base) {
3621  // We can't add a symbolic offset if the address already contains one.
3622  if (Base.BaseGV) return;
3623 
3624  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3625  GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3626  if (Base.Scale == 1)
3627  GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3628  /* IsScaledReg */ true);
3629 }
3630 
3631 /// \brief Helper function for LSRInstance::GenerateConstantOffsets.
3632 void LSRInstance::GenerateConstantOffsetsImpl(
3633  LSRUse &LU, unsigned LUIdx, const Formula &Base,
3634  const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3635  const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3636  for (int64_t Offset : Worklist) {
3637  Formula F = Base;
3638  F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3639  if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind,
3640  LU.AccessTy, F)) {
3641  // Add the offset to the base register.
3642  const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3643  // If it cancelled out, drop the base register, otherwise update it.
3644  if (NewG->isZero()) {
3645  if (IsScaledReg) {
3646  F.Scale = 0;
3647  F.ScaledReg = nullptr;
3648  } else
3649  F.deleteBaseReg(F.BaseRegs[Idx]);
3650  F.canonicalize(*L);
3651  } else if (IsScaledReg)
3652  F.ScaledReg = NewG;
3653  else
3654  F.BaseRegs[Idx] = NewG;
3655 
3656  (void)InsertFormula(LU, LUIdx, F);
3657  }
3658  }
3659 
3660  int64_t Imm = ExtractImmediate(G, SE);
3661  if (G->isZero() || Imm == 0)
3662  return;
3663  Formula F = Base;
3664  F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3665  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3666  return;
3667  if (IsScaledReg)
3668  F.ScaledReg = G;
3669  else
3670  F.BaseRegs[Idx] = G;
3671  (void)InsertFormula(LU, LUIdx, F);
3672 }
3673 
3674 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3675 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3676  Formula Base) {
3677  // TODO: For now, just add the min and max offset, because it usually isn't
3678  // worthwhile looking at everything inbetween.
3679  SmallVector<int64_t, 2> Worklist;
3680  Worklist.push_back(LU.MinOffset);
3681  if (LU.MaxOffset != LU.MinOffset)
3682  Worklist.push_back(LU.MaxOffset);
3683 
3684  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3685  GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3686  if (Base.Scale == 1)
3687  GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3688  /* IsScaledReg */ true);
3689 }
3690 
3691 /// For ICmpZero, check to see if we can scale up the comparison. For example, x
3692 /// == y -> x*c == y*c.
3693 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3694  Formula Base) {
3695  if (LU.Kind != LSRUse::ICmpZero) return;
3696 
3697  // Determine the integer type for the base formula.
3698  Type *IntTy = Base.getType();
3699  if (!IntTy) return;
3700  if (SE.getTypeSizeInBits(IntTy) > 64) return;
3701 
3702  // Don't do this if there is more than one offset.
3703  if (LU.MinOffset != LU.MaxOffset) return;
3704 
3705  // Check if transformation is valid. It is illegal to multiply pointer.
3706  if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
3707  return;
3708  for (const SCEV *BaseReg : Base.BaseRegs)
3709  if (BaseReg->getType()->isPointerTy())
3710  return;
3711  assert(!Base.BaseGV && "ICmpZero use is not legal!");
3712 
3713  // Check each interesting stride.
3714  for (int64_t Factor : Factors) {
3715  // Check that the multiplication doesn't overflow.
3716  if (Base.BaseOffset == std::numeric_limits<int64_t>::min() && Factor == -1)
3717  continue;
3718  int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3719  if (NewBaseOffset / Factor != Base.BaseOffset)
3720  continue;
3721  // If the offset will be truncated at this use, check that it is in bounds.
3722  if (!IntTy->isPointerTy() &&
3723  !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3724  continue;
3725 
3726  // Check that multiplying with the use offset doesn't overflow.
3727  int64_t Offset = LU.MinOffset;
3728  if (Offset == std::numeric_limits<int64_t>::min() && Factor == -1)
3729  continue;
3730  Offset = (uint64_t)Offset * Factor;
3731  if (Offset / Factor != LU.MinOffset)
3732  continue;
3733  // If the offset will be truncated at this use, check that it is in bounds.
3734  if (!IntTy->isPointerTy() &&
3735  !ConstantInt::isValueValidForType(IntTy, Offset))
3736  continue;
3737 
3738  Formula F = Base;
3739  F.BaseOffset = NewBaseOffset;
3740 
3741  // Check that this scale is legal.
3742  if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3743  continue;
3744 
3745  // Compensate for the use having MinOffset built into it.
3746  F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3747 
3748  const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3749 
3750  // Check that multiplying with each base register doesn't overflow.
3751  for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3752  F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3753  if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3754  goto next;
3755  }
3756 
3757  // Check that multiplying with the scaled register doesn't overflow.
3758  if (F.ScaledReg) {
3759  F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3760  if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3761  continue;
3762  }
3763 
3764  // Check that multiplying with the unfolded offset doesn't overflow.
3765  if (F.UnfoldedOffset != 0) {
3766  if (F.UnfoldedOffset == std::numeric_limits<int64_t>::min() &&
3767  Factor == -1)
3768  continue;
3769  F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3770  if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3771  continue;
3772  // If the offset will be truncated, check that it is in bounds.
3773  if (!IntTy->isPointerTy() &&
3774  !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3775  continue;
3776  }
3777 
3778  // If we make it here and it's legal, add it.
3779  (void)InsertFormula(LU, LUIdx, F);
3780  next:;
3781  }
3782 }
3783 
3784 /// Generate stride factor reuse formulae by making use of scaled-offset address
3785 /// modes, for example.
3786 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3787  // Determine the integer type for the base formula.
3788  Type *IntTy = Base.getType();
3789  if (!IntTy) return;
3790 
3791  // If this Formula already has a scaled register, we can't add another one.
3792  // Try to unscale the formula to generate a better scale.
3793  if (Base.Scale != 0 && !Base.unscale())
3794  return;
3795 
3796  assert(Base.Scale == 0 && "unscale did not did its job!");
3797 
3798  // Check each interesting stride.
3799  for (int64_t Factor : Factors) {
3800  Base.Scale = Factor;
3801  Base.HasBaseReg = Base.BaseRegs.size() > 1;
3802  // Check whether this scale is going to be legal.
3803  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3804  Base)) {
3805  // As a special-case, handle special out-of-loop Basic users specially.
3806  // TODO: Reconsider this special case.
3807  if (LU.Kind == LSRUse::Basic &&
3808  isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3809  LU.AccessTy, Base) &&
3810  LU.AllFixupsOutsideLoop)
3811  LU.Kind = LSRUse::Special;
3812  else
3813  continue;
3814  }
3815  // For an ICmpZero, negating a solitary base register won't lead to
3816  // new solutions.
3817  if (LU.Kind == LSRUse::ICmpZero &&
3818  !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3819  continue;
3820  // For each addrec base reg, if its loop is current loop, apply the scale.
3821  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3822  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]);
3823  if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) {
3824  const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3825  if (FactorS->isZero())
3826  continue;
3827  // Divide out the factor, ignoring high bits, since we'll be
3828  // scaling the value back up in the end.
3829  if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3830  // TODO: This could be optimized to avoid all the copying.
3831  Formula F = Base;
3832  F.ScaledReg = Quotient;
3833  F.deleteBaseReg(F.BaseRegs[i]);
3834  // The canonical representation of 1*reg is reg, which is already in
3835  // Base. In that case, do not try to insert the formula, it will be
3836  // rejected anyway.
3837  if (F.Scale == 1 && (F.BaseRegs.empty() ||
3838  (AR->getLoop() != L && LU.AllFixupsOutsideLoop)))
3839  continue;
3840  // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate
3841  // non canonical Formula with ScaledReg's loop not being L.
3842  if (F.Scale == 1 && LU.AllFixupsOutsideLoop)
3843  F.canonicalize(*L);
3844  (void)InsertFormula(LU, LUIdx, F);
3845  }
3846  }
3847  }
3848  }
3849 }
3850 
3851 /// Generate reuse formulae from different IV types.
3852 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3853  // Don't bother truncating symbolic values.
3854  if (Base.BaseGV) return;
3855 
3856  // Determine the integer type for the base formula.
3857  Type *DstTy = Base.getType();
3858  if (!DstTy) return;
3859  DstTy = SE.getEffectiveSCEVType(DstTy);
3860 
3861  for (Type *SrcTy : Types) {
3862  if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
3863  Formula F = Base;
3864 
3865  if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
3866  for (const SCEV *&BaseReg : F.BaseRegs)
3867  BaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
3868 
3869  // TODO: This assumes we've done basic processing on all uses and
3870  // have an idea what the register usage is.
3871  if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3872  continue;
3873 
3874  F.canonicalize(*L);
3875  (void)InsertFormula(LU, LUIdx, F);
3876  }
3877  }
3878 }
3879 
3880 namespace {
3881 
3882 /// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
3883 /// modifications so that the search phase doesn't have to worry about the data
3884 /// structures moving underneath it.
3885 struct WorkItem {
3886  size_t LUIdx;
3887  int64_t Imm;
3888  const SCEV *OrigReg;
3889 
3890  WorkItem(size_t LI, int64_t I, const SCEV *R)
3891  : LUIdx(LI), Imm(I), OrigReg(R) {}
3892 
3893  void print(raw_ostream &OS) const;
3894  void dump() const;
3895 };
3896 
3897 } // end anonymous namespace
3898 
3899 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
3900 void WorkItem::print(raw_ostream &OS) const {
3901  OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3902  << " , add offset " << Imm;
3903 }
3904 
3905 LLVM_DUMP_METHOD void WorkItem::dump() const {
3906  print(errs()); errs() << '\n';
3907 }
3908 #endif
3909 
3910 /// Look for registers which are a constant distance apart and try to form reuse
3911 /// opportunities between them.
3912 void LSRInstance::GenerateCrossUseConstantOffsets() {
3913  // Group the registers by their value without any added constant offset.
3914  using ImmMapTy = std::map<int64_t, const SCEV *>;
3915 
3917  DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3919  for (const SCEV *Use : RegUses) {
3920  const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
3921  int64_t Imm = ExtractImmediate(Reg, SE);
3922  auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
3923  if (Pair.second)
3924  Sequence.push_back(Reg);
3925  Pair.first->second.insert(std::make_pair(Imm, Use));
3926  UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
3927  }
3928 
3929  // Now examine each set of registers with the same base value. Build up
3930  // a list of work to do and do the work in a separate step so that we're
3931  // not adding formulae and register counts while we're searching.
3932  SmallVector<WorkItem, 32> WorkItems;
3933  SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3934  for (const SCEV *Reg : Sequence) {
3935  const ImmMapTy &Imms = Map.find(Reg)->second;
3936 
3937  // It's not worthwhile looking for reuse if there's only one offset.
3938  if (Imms.size() == 1)
3939  continue;
3940 
3941  DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
3942  for (const auto &Entry : Imms)
3943  dbgs() << ' ' << Entry.first;
3944  dbgs() << '\n');
3945 
3946  // Examine each offset.
3947  for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3948  J != JE; ++J) {
3949  const SCEV *OrigReg = J->second;
3950 
3951  int64_t JImm = J->first;
3952  const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
3953 
3954  if (!isa<SCEVConstant>(OrigReg) &&
3955  UsedByIndicesMap[Reg].count() == 1) {
3956  DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
3957  continue;
3958  }
3959 
3960  // Conservatively examine offsets between this orig reg a few selected
3961  // other orig regs.
3962  ImmMapTy::const_iterator OtherImms[] = {
3963  Imms.begin(), std::prev(Imms.end()),
3964  Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) /
3965  2)
3966  };
3967  for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
3968  ImmMapTy::const_iterator M = OtherImms[i];
3969  if (M == J || M == JE) continue;
3970 
3971  // Compute the difference between the two.
3972  int64_t Imm = (uint64_t)JImm - M->first;
3973  for (unsigned LUIdx : UsedByIndices.set_bits())
3974  // Make a memo of this use, offset, and register tuple.
3975  if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
3976  WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
3977  }
3978  }
3979  }
3980 
3981  Map.clear();
3982  Sequence.clear();
3983  UsedByIndicesMap.clear();
3984  UniqueItems.clear();
3985 
3986  // Now iterate through the worklist and add new formulae.
3987  for (const WorkItem &WI : WorkItems) {
3988  size_t LUIdx = WI.LUIdx;
3989  LSRUse &LU = Uses[LUIdx];
3990  int64_t Imm = WI.Imm;
3991  const SCEV *OrigReg = WI.OrigReg;
3992 
3993  Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
3994  const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
3995  unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
3996 
3997  // TODO: Use a more targeted data structure.
3998  for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
3999  Formula F = LU.Formulae[L];
4000  // FIXME: The code for the scaled and unscaled registers looks
4001  // very similar but slightly different. Investigate if they
4002  // could be merged. That way, we would not have to unscale the
4003  // Formula.
4004  F.unscale();
4005  // Use the immediate in the scaled register.
4006  if (F.ScaledReg == OrigReg) {
4007  int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
4008  // Don't create 50 + reg(-50).
4009  if (F.referencesReg(SE.getSCEV(
4010  ConstantInt::get(IntTy, -(uint64_t)Offset))))
4011  continue;
4012  Formula NewF = F;
4013  NewF.BaseOffset = Offset;
4014  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4015  NewF))
4016  continue;
4017  NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
4018 
4019  // If the new scale is a constant in a register, and adding the constant
4020  // value to the immediate would produce a value closer to zero than the
4021  // immediate itself, then the formula isn't worthwhile.
4022  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
4023  if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
4024  (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
4025  .ule(std::abs(NewF.BaseOffset)))
4026  continue;
4027 
4028  // OK, looks good.
4029  NewF.canonicalize(*this->L);
4030  (void)InsertFormula(LU, LUIdx, NewF);
4031  } else {
4032  // Use the immediate in a base register.
4033  for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
4034  const SCEV *BaseReg = F.BaseRegs[N];
4035  if (BaseReg != OrigReg)
4036  continue;
4037  Formula NewF = F;
4038  NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
4039  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
4040  LU.Kind, LU.AccessTy, NewF)) {
4041  if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
4042  continue;
4043  NewF = F;
4044  NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
4045  }
4046  NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
4047 
4048  // If the new formula has a constant in a register, and adding the
4049  // constant value to the immediate would produce a value closer to
4050  // zero than the immediate itself, then the formula isn't worthwhile.
4051  for (const SCEV *NewReg : NewF.BaseRegs)
4052  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
4053  if ((C->getAPInt() + NewF.BaseOffset)
4054  .abs()
4055  .slt(std::abs(NewF.BaseOffset)) &&
4056  (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
4057  countTrailingZeros<uint64_t>(NewF.BaseOffset))
4058  goto skip_formula;
4059 
4060  // Ok, looks good.
4061  NewF.canonicalize(*this->L);
4062  (void)InsertFormula(LU, LUIdx, NewF);
4063  break;
4064  skip_formula:;
4065  }
4066  }
4067  }
4068  }
4069 }
4070 
4071 /// Generate formulae for each use.
4072 void
4073 LSRInstance::GenerateAllReuseFormulae() {
4074  // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
4075  // queries are more precise.
4076  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4077  LSRUse &LU = Uses[LUIdx];
4078  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4079  GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
4080  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4081  GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
4082  }
4083  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4084  LSRUse &LU = Uses[LUIdx];
4085  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4086  GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
4087  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4088  GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
4089  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4090  GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
4091  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4092  GenerateScales(LU, LUIdx, LU.Formulae[i]);
4093  }
4094  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4095  LSRUse &LU = Uses[LUIdx];
4096  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4097  GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
4098  }
4099 
4100  GenerateCrossUseConstantOffsets();
4101 
4102  DEBUG(dbgs() << "\n"
4103  "After generating reuse formulae:\n";
4104  print_uses(dbgs()));
4105 }
4106 
4107 /// If there are multiple formulae with the same set of registers used
4108 /// by other uses, pick the best one and delete the others.
4109 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
4110  DenseSet<const SCEV *> VisitedRegs;
4113 #ifndef NDEBUG
4114  bool ChangedFormulae = false;
4115 #endif
4116 
4117  // Collect the best formula for each unique set of shared registers. This
4118  // is reset for each use.
4119  using BestFormulaeTy =
4120  DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>;
4121 
4122  BestFormulaeTy BestFormulae;
4123 
4124  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4125  LSRUse &LU = Uses[LUIdx];
4126  DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
4127 
4128  bool Any = false;
4129  for (size_t FIdx = 0, NumForms = LU.Formulae.size();
4130  FIdx != NumForms; ++FIdx) {
4131  Formula &F = LU.Formulae[FIdx];
4132 
4133  // Some formulas are instant losers. For example, they may depend on
4134  // nonexistent AddRecs from other loops. These need to be filtered
4135  // immediately, otherwise heuristics could choose them over others leading
4136  // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
4137  // avoids the need to recompute this information across formulae using the
4138  // same bad AddRec. Passing LoserRegs is also essential unless we remove
4139  // the corresponding bad register from the Regs set.
4140  Cost CostF;
4141  Regs.clear();
4142  CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, SE, DT, LU, &LoserRegs);
4143  if (CostF.isLoser()) {
4144  // During initial formula generation, undesirable formulae are generated
4145  // by uses within other loops that have some non-trivial address mode or
4146  // use the postinc form of the IV. LSR needs to provide these formulae
4147  // as the basis of rediscovering the desired formula that uses an AddRec
4148  // corresponding to the existing phi. Once all formulae have been
4149  // generated, these initial losers may be pruned.
4150  DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());
4151  dbgs() << "\n");
4152  }
4153  else {
4155  for (const SCEV *Reg : F.BaseRegs) {
4156  if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
4157  Key.push_back(Reg);
4158  }
4159  if (F.ScaledReg &&
4160  RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
4161  Key.push_back(F.ScaledReg);
4162  // Unstable sort by host order ok, because this is only used for
4163  // uniquifying.
4164  std::sort(Key.begin(), Key.end());
4165 
4166  std::pair<BestFormulaeTy::const_iterator, bool> P =
4167  BestFormulae.insert(std::make_pair(Key, FIdx));
4168  if (P.second)
4169  continue;
4170 
4171  Formula &Best = LU.Formulae[P.first->second];
4172 
4173  Cost CostBest;
4174  Regs.clear();
4175  CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, SE, DT, LU);
4176  if (CostF.isLess(CostBest, TTI))
4177  std::swap(F, Best);
4178  DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
4179  dbgs() << "\n"
4180  " in favor of formula "; Best.print(dbgs());
4181  dbgs() << '\n');
4182  }
4183 #ifndef NDEBUG
4184  ChangedFormulae = true;
4185 #endif
4186  LU.DeleteFormula(F);
4187  --FIdx;
4188  --NumForms;
4189  Any = true;
4190  }
4191 
4192  // Now that we've filtered out some formulae, recompute the Regs set.
4193  if (Any)
4194  LU.RecomputeRegs(LUIdx, RegUses);
4195 
4196  // Reset this to prepare for the next use.
4197  BestFormulae.clear();
4198  }
4199 
4200  DEBUG(if (ChangedFormulae) {
4201  dbgs() << "\n"
4202  "After filtering out undesirable candidates:\n";
4203  print_uses(dbgs());
4204  });
4205 }
4206 
4207 // This is a rough guess that seems to work fairly well.
4209 
4210 /// Estimate the worst-case number of solutions the solver might have to
4211 /// consider. It almost never considers this many solutions because it prune the
4212 /// search space, but the pruning isn't always sufficient.
4213 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4214  size_t Power = 1;
4215  for (const LSRUse &LU : Uses) {
4216  size_t FSize = LU.Formulae.size();
4217  if (FSize >= ComplexityLimit) {
4218  Power = ComplexityLimit;
4219  break;
4220  }
4221  Power *= FSize;
4222  if (Power >= ComplexityLimit)
4223  break;
4224  }
4225  return Power;
4226 }
4227 
4228 /// When one formula uses a superset of the registers of another formula, it
4229 /// won't help reduce register pressure (though it may not necessarily hurt
4230 /// register pressure); remove it to simplify the system.
4231 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4232  if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4233  DEBUG(dbgs() << "The search space is too complex.\n");
4234 
4235  DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
4236  "which use a superset of registers used by other "
4237  "formulae.\n");
4238 
4239  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4240  LSRUse &LU = Uses[LUIdx];
4241  bool Any = false;
4242  for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4243  Formula &F = LU.Formulae[i];
4244  // Look for a formula with a constant or GV in a register. If the use
4245  // also has a formula with that same value in an immediate field,
4246  // delete the one that uses a register.
4248  I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4249  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4250  Formula NewF = F;
4251  NewF.BaseOffset += C->getValue()->getSExtValue();
4252  NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4253  (I - F.BaseRegs.begin()));
4254  if (LU.HasFormulaWithSameRegs(NewF)) {
4255  DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4256  LU.DeleteFormula(F);
4257  --i;
4258  --e;
4259  Any = true;
4260  break;
4261  }
4262  } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4263  if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4264  if (!F.BaseGV) {
4265  Formula NewF = F;
4266  NewF.BaseGV = GV;
4267  NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4268  (I - F.BaseRegs.begin()));
4269  if (LU.HasFormulaWithSameRegs(NewF)) {
4270  DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4271  dbgs() << '\n');
4272  LU.DeleteFormula(F);
4273  --i;
4274  --e;
4275  Any = true;
4276  break;
4277  }
4278  }
4279  }
4280  }
4281  }
4282  if (Any)
4283  LU.RecomputeRegs(LUIdx, RegUses);
4284  }
4285 
4286  DEBUG(dbgs() << "After pre-selection:\n";
4287  print_uses(dbgs()));
4288  }
4289 }
4290 
4291 /// When there are many registers for expressions like A, A+1, A+2, etc.,
4292 /// allocate a single register for them.
4293 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4294  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4295  return;
4296 
4297  DEBUG(dbgs() << "The search space is too complex.\n"
4298  "Narrowing the search space by assuming that uses separated "
4299  "by a constant offset will use the same registers.\n");
4300 
4301  // This is especially useful for unrolled loops.
4302 
4303  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4304  LSRUse &LU = Uses[LUIdx];
4305  for (const Formula &F : LU.Formulae) {
4306  if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4307  continue;
4308 
4309  LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4310  if (!LUThatHas)
4311  continue;
4312 
4313  if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4314  LU.Kind, LU.AccessTy))
4315  continue;
4316 
4317  DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n');
4318 
4319  LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4320 
4321  // Transfer the fixups of LU to LUThatHas.
4322  for (LSRFixup &Fixup : LU.Fixups) {
4323  Fixup.Offset += F.BaseOffset;
4324  LUThatHas->pushFixup(Fixup);
4325  DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n');
4326  }
4327 
4328  // Delete formulae from the new use which are no longer legal.
4329  bool Any = false;
4330  for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4331  Formula &F = LUThatHas->Formulae[i];
4332  if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4333  LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4334  DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4335  dbgs() << '\n');
4336  LUThatHas->DeleteFormula(F);
4337  --i;
4338  --e;
4339  Any = true;
4340  }
4341  }
4342 
4343  if (Any)
4344  LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4345 
4346  // Delete the old use.
4347  DeleteUse(LU, LUIdx);
4348  --LUIdx;
4349  --NumUses;
4350  break;
4351  }
4352  }
4353 
4354  DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4355 }
4356 
4357 /// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4358 /// we've done more filtering, as it may be able to find more formulae to
4359 /// eliminate.
4360 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4361  if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4362  DEBUG(dbgs() << "The search space is too complex.\n");
4363 
4364  DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
4365  "undesirable dedicated registers.\n");
4366 
4367  FilterOutUndesirableDedicatedRegisters();
4368 
4369  DEBUG(dbgs() << "After pre-selection:\n";
4370  print_uses(dbgs()));
4371  }
4372 }
4373 
4374 /// If a LSRUse has multiple formulae with the same ScaledReg and Scale.
4375 /// Pick the best one and delete the others.
4376 /// This narrowing heuristic is to keep as many formulae with different
4377 /// Scale and ScaledReg pair as possible while narrowing the search space.
4378 /// The benefit is that it is more likely to find out a better solution
4379 /// from a formulae set with more Scale and ScaledReg variations than
4380 /// a formulae set with the same Scale and ScaledReg. The picking winner
4381 /// reg heurstic will often keep the formulae with the same Scale and
4382 /// ScaledReg and filter others, and we want to avoid that if possible.
4383 void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() {
4384  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4385  return;
4386 
4387  DEBUG(dbgs() << "The search space is too complex.\n"
4388  "Narrowing the search space by choosing the best Formula "
4389  "from the Formulae with the same Scale and ScaledReg.\n");
4390 
4391  // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse.
4392  using BestFormulaeTy = DenseMap<std::pair<const SCEV *, int64_t>, size_t>;
4393 
4394  BestFormulaeTy BestFormulae;
4395 #ifndef NDEBUG
4396  bool ChangedFormulae = false;
4397 #endif
4398  DenseSet<const SCEV *> VisitedRegs;
4400 
4401  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4402  LSRUse &LU = Uses[LUIdx];
4403  DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
4404 
4405  // Return true if Formula FA is better than Formula FB.
4406  auto IsBetterThan = [&](Formula &FA, Formula &FB) {
4407  // First we will try to choose the Formula with fewer new registers.
4408  // For a register used by current Formula, the more the register is
4409  // shared among LSRUses, the less we increase the register number
4410  // counter of the formula.
4411  size_t FARegNum = 0;
4412  for (const SCEV *Reg : FA.BaseRegs) {
4413  const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4414  FARegNum += (NumUses - UsedByIndices.count() + 1);
4415  }
4416  size_t FBRegNum = 0;
4417  for (const SCEV *Reg : FB.BaseRegs) {
4418  const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4419  FBRegNum += (NumUses - UsedByIndices.count() + 1);
4420  }
4421  if (FARegNum != FBRegNum)
4422  return FARegNum < FBRegNum;
4423 
4424  // If the new register numbers are the same, choose the Formula with
4425  // less Cost.
4426  Cost CostFA, CostFB;
4427  Regs.clear();
4428  CostFA.RateFormula(TTI, FA, Regs, VisitedRegs, L, SE, DT, LU);
4429  Regs.clear();
4430  CostFB.RateFormula(TTI, FB, Regs, VisitedRegs, L, SE, DT, LU);
4431  return CostFA.isLess(CostFB, TTI);
4432  };
4433 
4434  bool Any = false;
4435  for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4436  ++FIdx) {
4437  Formula &F = LU.Formulae[FIdx];
4438  if (!F.ScaledReg)
4439  continue;
4440  auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx});
4441  if (P.second)
4442  continue;
4443 
4444  Formula &Best = LU.Formulae[P.first->second];
4445  if (IsBetterThan(F, Best))
4446  std::swap(F, Best);
4447  DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
4448  dbgs() << "\n"
4449  " in favor of formula ";
4450  Best.print(dbgs()); dbgs() << '\n');
4451 #ifndef NDEBUG
4452  ChangedFormulae = true;
4453 #endif
4454  LU.DeleteFormula(F);
4455  --FIdx;
4456  --NumForms;
4457  Any = true;
4458  }
4459  if (Any)
4460  LU.RecomputeRegs(LUIdx, RegUses);
4461 
4462  // Reset this to prepare for the next use.
4463  BestFormulae.clear();
4464  }
4465 
4466  DEBUG(if (ChangedFormulae) {
4467  dbgs() << "\n"
4468  "After filtering out undesirable candidates:\n";
4469  print_uses(dbgs());
4470  });
4471 }
4472 
4473 /// The function delete formulas with high registers number expectation.
4474 /// Assuming we don't know the value of each formula (already delete
4475 /// all inefficient), generate probability of not selecting for each
4476 /// register.
4477 /// For example,
4478 /// Use1:
4479 /// reg(a) + reg({0,+,1})
4480 /// reg(a) + reg({-1,+,1}) + 1
4481 /// reg({a,+,1})
4482 /// Use2:
4483 /// reg(b) + reg({0,+,1})
4484 /// reg(b) + reg({-1,+,1}) + 1
4485 /// reg({b,+,1})
4486 /// Use3:
4487 /// reg(c) + reg(b) + reg({0,+,1})
4488 /// reg(c) + reg({b,+,1})
4489 ///
4490 /// Probability of not selecting
4491 /// Use1 Use2 Use3
4492 /// reg(a) (1/3) * 1 * 1
4493 /// reg(b) 1 * (1/3) * (1/2)
4494 /// reg({0,+,1}) (2/3) * (2/3) * (1/2)
4495 /// reg({-1,+,1}) (2/3) * (2/3) * 1
4496 /// reg({a,+,1}) (2/3) * 1 * 1
4497 /// reg({b,+,1}) 1 * (2/3) * (2/3)
4498 /// reg(c) 1 * 1 * 0
4499 ///
4500 /// Now count registers number mathematical expectation for each formula:
4501 /// Note that for each use we exclude probability if not selecting for the use.
4502 /// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding
4503 /// probabilty 1/3 of not selecting for Use1).
4504 /// Use1:
4505 /// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted
4506 /// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted
4507 /// reg({a,+,1}) 1
4508 /// Use2:
4509 /// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted
4510 /// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted
4511 /// reg({b,+,1}) 2/3
4512 /// Use3:
4513 /// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted
4514 /// reg(c) + reg({b,+,1}) 1 + 2/3
4515 void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() {
4516  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4517  return;
4518  // Ok, we have too many of formulae on our hands to conveniently handle.
4519  // Use a rough heuristic to thin out the list.
4520 
4521  // Set of Regs wich will be 100% used in final solution.
4522  // Used in each formula of a solution (in example above this is reg(c)).
4523  // We can skip them in calculations.
4525  DEBUG(dbgs() << "The search space is too complex.\n");
4526 
4527  // Map each register to probability of not selecting
4529  for (const SCEV *Reg : RegUses) {
4530  if (UniqRegs.count(Reg))
4531  continue;
4532  float PNotSel = 1;
4533  for (const LSRUse &LU : Uses) {
4534  if (!LU.Regs.count(Reg))
4535  continue;
4536  float P = LU.getNotSelectedProbability(Reg);
4537  if (P != 0.0)
4538  PNotSel *= P;
4539  else
4540  UniqRegs.insert(Reg);
4541  }
4542  RegNumMap.insert(std::make_pair(Reg, PNotSel));
4543  }
4544 
4545  DEBUG(dbgs() << "Narrowing the search space by deleting costly formulas\n");
4546 
4547  // Delete formulas where registers number expectation is high.
4548  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4549  LSRUse &LU = Uses[LUIdx];
4550  // If nothing to delete - continue.
4551  if (LU.Formulae.size() < 2)
4552  continue;
4553  // This is temporary solution to test performance. Float should be
4554  // replaced with round independent type (based on integers) to avoid
4555  // different results for different target builds.
4556  float FMinRegNum = LU.Formulae[0].getNumRegs();
4557  float FMinARegNum = LU.Formulae[0].getNumRegs();
4558  size_t MinIdx = 0;
4559  for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4560  Formula &F = LU.Formulae[i];
4561  float FRegNum = 0;
4562  float FARegNum = 0;
4563  for (const SCEV *BaseReg : F.BaseRegs) {
4564  if (UniqRegs.count(BaseReg))
4565  continue;
4566  FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4567  if (isa<SCEVAddRecExpr>(BaseReg))
4568  FARegNum +=
4569  RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4570  }
4571  if (const SCEV *ScaledReg = F.ScaledReg) {
4572  if (!UniqRegs.count(ScaledReg)) {
4573  FRegNum +=
4574  RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4575  if (isa<SCEVAddRecExpr>(ScaledReg))
4576  FARegNum +=
4577  RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4578  }
4579  }
4580  if (FMinRegNum > FRegNum ||
4581  (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) {
4582  FMinRegNum = FRegNum;
4583  FMinARegNum = FARegNum;
4584  MinIdx = i;
4585  }
4586  }
4587  DEBUG(dbgs() << " The formula "; LU.Formulae[MinIdx].print(dbgs());
4588  dbgs() << " with min reg num " << FMinRegNum << '\n');
4589  if (MinIdx != 0)
4590  std::swap(LU.Formulae[MinIdx], LU.Formulae[0]);
4591  while (LU.Formulae.size() != 1) {
4592  DEBUG(dbgs() << " Deleting "; LU.Formulae.back().print(dbgs());
4593  dbgs() << '\n');
4594  LU.Formulae.pop_back();
4595  }
4596  LU.RecomputeRegs(LUIdx, RegUses);
4597  assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula");
4598  Formula &F = LU.Formulae[0];
4599  DEBUG(dbgs() << " Leaving only "; F.print(dbgs()); dbgs() << '\n');
4600  // When we choose the formula, the regs become unique.
4601  UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
4602  if (F.ScaledReg)
4603  UniqRegs.insert(F.ScaledReg);
4604  }
4605  DEBUG(dbgs() << "After pre-selection:\n";
4606  print_uses(dbgs()));
4607 }
4608 
4609 /// Pick a register which seems likely to be profitable, and then in any use
4610 /// which has any reference to that register, delete all formulae which do not
4611 /// reference that register.
4612 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4613  // With all other options exhausted, loop until the system is simple
4614  // enough to handle.
4616  while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4617  // Ok, we have too many of formulae on our hands to conveniently handle.
4618  // Use a rough heuristic to thin out the list.
4619  DEBUG(dbgs() << "The search space is too complex.\n");
4620 
4621  // Pick the register which is used by the most LSRUses, which is likely
4622  // to be a good reuse register candidate.
4623  const SCEV *Best = nullptr;
4624  unsigned BestNum = 0;
4625  for (const SCEV *Reg : RegUses) {
4626  if (Taken.count(Reg))
4627  continue;
4628  if (!Best) {
4629  Best = Reg;
4630  BestNum = RegUses.getUsedByIndices(Reg).count();
4631  } else {
4632  unsigned Count = RegUses.getUsedByIndices(Reg).count();
4633  if (Count > BestNum) {
4634  Best = Reg;
4635  BestNum = Count;
4636  }
4637  }
4638  }
4639 
4640  DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
4641  << " will yield profitable reuse.\n");
4642  Taken.insert(Best);
4643 
4644  // In any use with formulae which references this register, delete formulae
4645  // which don't reference it.
4646  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4647  LSRUse &LU = Uses[LUIdx];
4648  if (!LU.Regs.count(Best)) continue;
4649 
4650  bool Any = false;
4651  for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4652  Formula &F = LU.Formulae[i];
4653  if (!F.referencesReg(Best)) {
4654  DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4655  LU.DeleteFormula(F);
4656  --e;
4657  --i;
4658  Any = true;
4659  assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
4660  continue;
4661  }
4662  }
4663 
4664  if (Any)
4665  LU.RecomputeRegs(LUIdx, RegUses);
4666  }
4667 
4668  DEBUG(dbgs() << "After pre-selection:\n";
4669  print_uses(dbgs()));
4670  }
4671 }
4672 
4673 /// If there are an extraordinary number of formulae to choose from, use some
4674 /// rough heuristics to prune down the number of formulae. This keeps the main
4675 /// solver from taking an extraordinary amount of time in some worst-case
4676 /// scenarios.
4677 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4678  NarrowSearchSpaceByDetectingSupersets();
4679  NarrowSearchSpaceByCollapsingUnrolledCode();
4680  NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4681  if (FilterSameScaledReg)
4682  NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
4683  if (LSRExpNarrow)
4684  NarrowSearchSpaceByDeletingCostlyFormulas();
4685  else
4686  NarrowSearchSpaceByPickingWinnerRegs();
4687 }
4688 
4689 /// This is the recursive solver.
4690 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4691  Cost &SolutionCost,
4693  const Cost &CurCost,
4694  const SmallPtrSet<const SCEV *, 16> &CurRegs,
4695  DenseSet<const SCEV *> &VisitedRegs) const {
4696  // Some ideas:
4697  // - prune more:
4698  // - use more aggressive filtering
4699  // - sort the formula so that the most profitable solutions are found first
4700  // - sort the uses too
4701  // - search faster:
4702  // - don't compute a cost, and then compare. compare while computing a cost
4703  // and bail early.
4704  // - track register sets with SmallBitVector
4705 
4706  const LSRUse &LU = Uses[Workspace.size()];
4707 
4708  // If this use references any register that's already a part of the
4709  // in-progress solution, consider it a requirement that a formula must
4710  // reference that register in order to be considered. This prunes out
4711  // unprofitable searching.
4713  for (const SCEV *S : CurRegs)
4714  if (LU.Regs.count(S))
4715  ReqRegs.insert(S);
4716 
4718  Cost NewCost;
4719  for (const Formula &F : LU.Formulae) {
4720  // Ignore formulae which may not be ideal in terms of register reuse of
4721  // ReqRegs. The formula should use all required registers before
4722  // introducing new ones.
4723  int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4724  for (const SCEV *Reg : ReqRegs) {
4725  if ((F.ScaledReg && F.ScaledReg == Reg) ||
4726  is_contained(F.BaseRegs, Reg)) {
4727  --NumReqRegsToFind;
4728  if (NumReqRegsToFind == 0)
4729  break;
4730  }
4731  }
4732  if (NumReqRegsToFind != 0) {
4733  // If none of the formulae satisfied the required registers, then we could
4734  // clear ReqRegs and try again. Currently, we simply give up in this case.
4735  continue;
4736  }
4737 
4738  // Evaluate the cost of the current formula. If it's already worse than
4739  // the current best, prune the search at that point.
4740  NewCost = CurCost;
4741  NewRegs = CurRegs;
4742  NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, SE, DT, LU);
4743  if (NewCost.isLess(SolutionCost, TTI)) {
4744  Workspace.push_back(&F);
4745  if (Workspace.size() != Uses.size()) {
4746  SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4747  NewRegs, VisitedRegs);
4748  if (F.getNumRegs() == 1 && Workspace.size() == 1)
4749  VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4750  } else {
4751  DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
4752  dbgs() << ".\n Regs:";
4753  for (const SCEV *S : NewRegs)
4754  dbgs() << ' ' << *S;
4755  dbgs() << '\n');
4756 
4757  SolutionCost = NewCost;
4758  Solution = Workspace;
4759  }
4760  Workspace.pop_back();
4761  }
4762  }
4763 }
4764 
4765 /// Choose one formula from each use. Return the results in the given Solution
4766 /// vector.
4767 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4769  Cost SolutionCost;
4770  SolutionCost.Lose();
4771  Cost CurCost;
4773  DenseSet<const SCEV *> VisitedRegs;
4774  Workspace.reserve(Uses.size());
4775 
4776  // SolveRecurse does all the work.
4777  SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4778  CurRegs, VisitedRegs);
4779  if (Solution.empty()) {
4780  DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
4781  return;
4782  }
4783 
4784  // Ok, we've now made all our decisions.
4785  DEBUG(dbgs() << "\n"
4786  "The chosen solution requires "; SolutionCost.print(dbgs());
4787  dbgs() << ":\n";
4788  for (size_t i = 0, e = Uses.size(); i != e; ++i) {
4789  dbgs() << " ";
4790  Uses[i].print(dbgs());
4791  dbgs() << "\n"
4792  " ";
4793  Solution[i]->print(dbgs());
4794  dbgs() << '\n';
4795  });
4796 
4797  assert(Solution.size() == Uses.size() && "Malformed solution!");
4798 }
4799 
4800 /// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
4801 /// we can go while still being dominated by the input positions. This helps
4802 /// canonicalize the insert position, which encourages sharing.
4804 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4805  const SmallVectorImpl<Instruction *> &Inputs)
4806  const {
4807  Instruction *Tentative = &*IP;
4808  while (true) {
4809  bool AllDominate = true;
4810  Instruction *BetterPos = nullptr;
4811  // Don't bother attempting to insert before a catchswitch, their basic block
4812  // cannot have other non-PHI instructions.
4813  if (isa<CatchSwitchInst>(Tentative))
4814  return IP;
4815 
4816  for (Instruction *Inst : Inputs) {
4817  if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4818  AllDominate = false;
4819  break;
4820  }
4821  // Attempt to find an insert position in the middle of the block,
4822  // instead of at the end, so that it can be used for other expansions.
4823  if (Tentative->getParent() == Inst->getParent() &&
4824  (!BetterPos || !DT.dominates(Inst, BetterPos)))
4825  BetterPos = &*std::next(BasicBlock::iterator(Inst));
4826  }
4827  if (!AllDominate)
4828  break;
4829  if (BetterPos)
4830  IP = BetterPos->getIterator();
4831  else
4832  IP = Tentative->getIterator();
4833 
4834  const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4835  unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4836 
4837  BasicBlock *IDom;
4838  for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4839  if (!Rung) return IP;
4840  Rung = Rung->getIDom();
4841  if (!Rung) return IP;
4842  IDom = Rung->getBlock();
4843 
4844  // Don't climb into a loop though.
4845  const Loop *IDomLoop = LI.getLoopFor(IDom);
4846  unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4847  if (IDomDepth <= IPLoopDepth &&
4848  (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4849  break;
4850  }
4851 
4852  Tentative = IDom->getTerminator();
4853  }
4854 
4855  return IP;
4856 }
4857 
4858 /// Determine an input position which will be dominated by the operands and
4859 /// which will dominate the result.
4861 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4862  const LSRFixup &LF,
4863  const LSRUse &LU,
4864  SCEVExpander &Rewriter) const {
4865  // Collect some instructions which must be dominated by the
4866  // expanding replacement. These must be dominated by any operands that
4867  // will be required in the expansion.
4869  if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4870  Inputs.push_back(I);
4871  if (LU.Kind == LSRUse::ICmpZero)
4872  if (Instruction *I =
4873  dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4874  Inputs.push_back(I);
4875  if (LF.PostIncLoops.count(L)) {
4876  if (LF.isUseFullyOutsideLoop(L))
4877  Inputs.push_back(L->getLoopLatch()->getTerminator());
4878  else
4879  Inputs.push_back(IVIncInsertPos);
4880  }
4881  // The expansion must also be dominated by the increment positions of any
4882  // loops it for which it is using post-inc mode.
4883  for (const Loop *PIL : LF.PostIncLoops) {
4884  if (PIL == L) continue;
4885 
4886  // Be dominated by the loop exit.
4887  SmallVector<BasicBlock *, 4> ExitingBlocks;
4888  PIL->getExitingBlocks(ExitingBlocks);
4889  if (!ExitingBlocks.empty()) {
4890  BasicBlock *BB = ExitingBlocks[0];
4891  for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4892  BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4893  Inputs.push_back(BB->getTerminator());
4894  }
4895  }
4896 
4897  assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad()
4898  && !isa<DbgInfoIntrinsic>(LowestIP) &&
4899  "Insertion point must be a normal instruction");
4900 
4901  // Then, climb up the immediate dominator tree as far as we can go while
4902  // still being dominated by the input positions.
4903  BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4904 
4905  // Don't insert instructions before PHI nodes.
4906  while (isa<PHINode>(IP)) ++IP;
4907 
4908  // Ignore landingpad instructions.
4909  while (IP->isEHPad()) ++IP;
4910 
4911  // Ignore debug intrinsics.
4912  while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4913 
4914  // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4915  // IP consistent across expansions and allows the previously inserted
4916  // instructions to be reused by subsequent expansion.
4917  while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
4918  ++IP;
4919 
4920  return IP;
4921 }
4922 
4923 /// Emit instructions for the leading candidate expression for this LSRUse (this
4924 /// is called "expanding").
4925 Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF,
4926  const Formula &F, BasicBlock::iterator IP,
4927  SCEVExpander &Rewriter,
4928  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
4929  if (LU.RigidFormula)
4930  return LF.OperandValToReplace;
4931 
4932  // Determine an input position which will be dominated by the operands and
4933  // which will dominate the result.
4934  IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4935  Rewriter.setInsertPoint(&*IP);
4936 
4937  // Inform the Rewriter if we have a post-increment use, so that it can
4938  // perform an advantageous expansion.
4939  Rewriter.setPostInc(LF.PostIncLoops);
4940 
4941  // This is the type that the user actually needs.
4942  Type *OpTy = LF.OperandValToReplace->getType();
4943  // This will be the type that we'll initially expand to.
4944  Type *Ty = F.getType();
4945  if (!Ty)
4946  // No type known; just expand directly to the ultimate type.
4947  Ty = OpTy;
4948  else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
4949  // Expand directly to the ultimate type if it's the right size.
4950  Ty = OpTy;
4951  // This is the type to do integer arithmetic in.
4952  Type *IntTy = SE.getEffectiveSCEVType(Ty);
4953 
4954  // Build up a list of operands to add together to form the full base.
4956 
4957  // Expand the BaseRegs portion.
4958  for (const SCEV *Reg : F.BaseRegs) {
4959  assert(!Reg->isZero() && "Zero allocated in a base register!");
4960 
4961  // If we're expanding for a post-inc user, make the post-inc adjustment.
4962  Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE);
4963  Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
4964  }
4965 
4966  // Expand the ScaledReg portion.
4967  Value *ICmpScaledV = nullptr;
4968  if (F.Scale != 0) {
4969  const SCEV *ScaledS = F.ScaledReg;
4970 
4971  // If we're expanding for a post-inc user, make the post-inc adjustment.
4972  PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4973  ScaledS = denormalizeForPostIncUse(ScaledS, Loops, SE);
4974 
4975  if (LU.Kind == LSRUse::ICmpZero) {
4976  // Expand ScaleReg as if it was part of the base regs.
4977  if (F.Scale == 1)
4978  Ops.push_back(
4979  SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
4980  else {
4981  // An interesting way of "folding" with an icmp is to use a negated
4982  // scale, which we'll implement by inserting it into the other operand
4983  // of the icmp.
4984  assert(F.Scale == -1 &&
4985  "The only scale supported by ICmpZero uses is -1!");
4986  ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
4987  }
4988  } else {
4989  // Otherwise just expand the scaled register and an explicit scale,
4990  // which is expected to be matched as part of the address.
4991 
4992  // Flush the operand list to suppress SCEVExpander hoisting address modes.
4993  // Unless the addressing mode will not be folded.
4994  if (!Ops.empty() && LU.Kind == LSRUse::Address &&
4995  isAMCompletelyFolded(TTI, LU, F)) {
4996  Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
4997  Ops.clear();
4998  Ops.push_back(SE.getUnknown(FullV));
4999  }
5000  ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
5001  if (F.Scale != 1)
5002  ScaledS =
5003  SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
5004  Ops.push_back(ScaledS);
5005  }
5006  }
5007 
5008  // Expand the GV portion.
5009  if (F.BaseGV) {
5010  // Flush the operand list to suppress SCEVExpander hoisting.
5011  if (!Ops.empty()) {
5012  Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5013  Ops.clear();
5014  Ops.push_back(SE.getUnknown(FullV));
5015  }
5016  Ops.push_back(SE.getUnknown(F.BaseGV));
5017  }
5018 
5019  // Flush the operand list to suppress SCEVExpander hoisting of both folded and
5020  // unfolded offsets. LSR assumes they both live next to their uses.
5021  if (!Ops.empty()) {
5022  Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5023  Ops.clear();
5024  Ops.push_back(SE.getUnknown(FullV));
5025  }
5026 
5027  // Expand the immediate portion.
5028  int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
5029  if (Offset != 0) {
5030  if (LU.Kind == LSRUse::ICmpZero) {
5031  // The other interesting way of "folding" with an ICmpZero is to use a
5032  // negated immediate.
5033  if (!ICmpScaledV)
5034  ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
5035  else {
5036  Ops.push_back(SE.getUnknown(ICmpScaledV));
5037  ICmpScaledV = ConstantInt::get(IntTy, Offset);
5038  }
5039  } else {
5040  // Just add the immediate values. These again are expected to be matched
5041  // as part of the address.
5042  Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
5043  }
5044  }
5045 
5046  // Expand the unfolded offset portion.
5047  int64_t UnfoldedOffset = F.UnfoldedOffset;
5048  if (UnfoldedOffset != 0) {
5049  // Just add the immediate values.
5051  UnfoldedOffset)));
5052  }
5053 
5054  // Emit instructions summing all the operands.
5055  const SCEV *FullS = Ops.empty() ?
5056  SE.getConstant(IntTy, 0) :
5057  SE.getAddExpr(Ops);
5058  Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
5059 
5060  // We're done expanding now, so reset the rewriter.
5061  Rewriter.clearPostInc();
5062 
5063  // An ICmpZero Formula represents an ICmp which we're handling as a
5064  // comparison against zero. Now that we've expanded an expression for that
5065  // form, update the ICmp's other operand.
5066  if (LU.Kind == LSRUse::ICmpZero) {
5067  ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
5068  DeadInsts.emplace_back(CI->getOperand(1));
5069  assert(!F.BaseGV && "ICmp does not support folding a global value and "
5070  "a scale at the same time!");
5071  if (F.Scale == -1) {
5072  if (ICmpScaledV->getType() != OpTy) {
5073  Instruction *Cast =
5074  CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
5075  OpTy, false),
5076  ICmpScaledV, OpTy, "tmp", CI);
5077  ICmpScaledV = Cast;
5078  }
5079  CI->setOperand(1, ICmpScaledV);
5080  } else {
5081  // A scale of 1 means that the scale has been expanded as part of the
5082  // base regs.
5083  assert((F.Scale == 0 || F.Scale == 1) &&
5084  "ICmp does not support folding a global value and "
5085  "a scale at the same time!");
5087  -(uint64_t)Offset);
5088  if (C->getType() != OpTy)
5090  OpTy, false),
5091  C, OpTy);
5092 
5093  CI->setOperand(1, C);
5094  }
5095  }
5096 
5097  return FullV;
5098 }
5099 
5100 /// Helper for Rewrite. PHI nodes are special because the use of their operands
5101 /// effectively happens in their predecessor blocks, so the expression may need
5102 /// to be expanded in multiple places.
5103 void LSRInstance::RewriteForPHI(
5104  PHINode *PN, const LSRUse &LU, const LSRFixup &LF, const Formula &F,
5105  SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5107  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
5108  if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
5109  BasicBlock *BB = PN->getIncomingBlock(i);
5110 
5111  // If this is a critical edge, split the edge so that we do not insert
5112  // the code on all predecessor/successor paths. We do this unless this
5113  // is the canonical backedge for this loop, which complicates post-inc
5114  // users.
5115  if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
5116  !isa<IndirectBrInst>(BB->getTerminator()) &&
5117  !isa<CatchSwitchInst>(BB->getTerminator())) {
5118  BasicBlock *Parent = PN->getParent();
5119  Loop *PNLoop = LI.getLoopFor(Parent);
5120  if (!PNLoop || Parent != PNLoop->getHeader()) {
5121  // Split the critical edge.
5122  BasicBlock *NewBB = nullptr;
5123  if (!Parent->isLandingPad()) {
5124  NewBB = SplitCriticalEdge(BB, Parent,
5126  .setMergeIdenticalEdges()
5127  .setDontDeleteUselessPHIs());
5128  } else {
5130  SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
5131  NewBB = NewBBs[0];
5132  }
5133  // If NewBB==NULL, then SplitCriticalEdge refused to split because all
5134  // phi predecessors are identical. The simple thing to do is skip
5135  // splitting in this case rather than complicate the API.
5136  if (NewBB) {
5137  // If PN is outside of the loop and BB is in the loop, we want to
5138  // move the block to be immediately before the PHI block, not
5139  // immediately after BB.
5140  if (L->contains(BB) && !L->contains(PN))
5141  NewBB->moveBefore(PN->getParent());
5142 
5143  // Splitting the edge can reduce the number of PHI entries we have.
5144  e = PN->getNumIncomingValues();
5145  BB = NewBB;
5146  i = PN->getBasicBlockIndex(BB);
5147  }
5148  }
5149  }
5150 
5151  std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
5152  Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
5153  if (!Pair.second)
5154  PN->setIncomingValue(i, Pair.first->second);
5155  else {
5156  Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
5157  Rewriter, DeadInsts);
5158 
5159  // If this is reuse-by-noop-cast, insert the noop cast.
5160  Type *OpTy = LF.OperandValToReplace->getType();
5161  if (FullV->getType() != OpTy)
5162  FullV =
5164  OpTy, false),
5165  FullV, LF.OperandValToReplace->getType(),
5166  "tmp", BB->getTerminator());
5167 
5168  PN->setIncomingValue(i, FullV);
5169  Pair.first->second = FullV;
5170  }
5171  }
5172 }
5173 
5174 /// Emit instructions for the leading candidate expression for this LSRUse (this
5175 /// is called "expanding"), and update the UserInst to reference the newly
5176 /// expanded value.
5177 void LSRInstance::Rewrite(const LSRUse &LU, const LSRFixup &LF,
5178  const Formula &F, SCEVExpander &Rewriter,
5179  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5180  // First, find an insertion point that dominates UserInst. For PHI nodes,
5181  // find the nearest block which dominates all the relevant uses.
5182  if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
5183  RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
5184  } else {
5185  Value *FullV =
5186  Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
5187 
5188  // If this is reuse-by-noop-cast, insert the noop cast.
5189  Type *OpTy = LF.OperandValToReplace->getType();
5190  if (FullV->getType() != OpTy) {
5191  Instruction *Cast =
5192  CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
5193  FullV, OpTy, "tmp", LF.UserInst);
5194  FullV = Cast;
5195  }
5196 
5197  // Update the user. ICmpZero is handled specially here (for now) because
5198  // Expand may have updated one of the operands of the icmp already, and
5199  // its new value may happen to be equal to LF.OperandValToReplace, in
5200  // which case doing replaceUsesOfWith leads to replacing both operands
5201  // with the same value. TODO: Reorganize this.
5202  if (LU.Kind == LSRUse::ICmpZero)
5203  LF.UserInst->setOperand(0, FullV);
5204  else
5205  LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
5206  }
5207 
5208  DeadInsts.emplace_back(LF.OperandValToReplace);
5209 }
5210 
5211 /// Rewrite all the fixup locations with new values, following the chosen
5212 /// solution.
5213 void LSRInstance::ImplementSolution(
5214  const SmallVectorImpl<const Formula *> &Solution) {
5215  // Keep track of instructions we may have made dead, so that
5216  // we can remove them after we are done working.
5218 
5220  "lsr");
5221 #ifndef NDEBUG
5222  Rewriter.setDebugType(DEBUG_TYPE);
5223 #endif
5224  Rewriter.disableCanonicalMode();
5225  Rewriter.enableLSRMode();
5226  Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
5227 
5228  // Mark phi nodes that terminate chains so the expander tries to reuse them.
5229  for (const IVChain &Chain : IVChainVec) {
5230  if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
5231  Rewriter.setChainedPhi(PN);
5232  }
5233 
5234  // Expand the new value definitions and update the users.
5235  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5236  for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
5237  Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
5238  Changed = true;
5239  }
5240 
5241  for (const IVChain &Chain : IVChainVec) {
5242  GenerateIVChain(Chain, Rewriter, DeadInsts);
5243  Changed = true;
5244  }
5245  // Clean up after ourselves. This must be done before deleting any
5246  // instructions.
5247  Rewriter.clear();
5248 
5249  Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
5250 }
5251 
5252 LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5253  DominatorTree &DT, LoopInfo &LI,
5254  const TargetTransformInfo &TTI)
5255  : IU(IU), SE(SE), DT(DT), LI(LI), TTI(TTI), L(L) {
5256  // If LoopSimplify form is not available, stay out of trouble.
5257  if (!L->isLoopSimplifyForm())
5258  return;
5259 
5260  // If there's no interesting work to be done, bail early.
5261  if (IU.empty()) return;
5262 
5263  // If there's too much analysis to be done, bail early. We won't be able to
5264  // model the problem anyway.
5265  unsigned NumUsers = 0;
5266  for (const IVStrideUse &U : IU) {
5267  if (++NumUsers > MaxIVUsers) {
5268  (void)U;
5269  DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << U << "\n");
5270  return;
5271  }
5272  // Bail out if we have a PHI on an EHPad that gets a value from a
5273  // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is
5274  // no good place to stick any instructions.
5275  if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
5276  auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
5277  if (isa<FuncletPadInst>(FirstNonPHI) ||
5278  isa<CatchSwitchInst>(FirstNonPHI))
5279  for (BasicBlock *PredBB : PN->blocks())
5280  if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
5281  return;
5282  }
5283  }
5284 
5285 #ifndef NDEBUG
5286  // All dominating loops must have preheaders, or SCEVExpander may not be able
5287  // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
5288  //
5289  // IVUsers analysis should only create users that are dominated by simple loop
5290  // headers. Since this loop should dominate all of its users, its user list
5291  // should be empty if this loop itself is not within a simple loop nest.
5292  for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
5293  Rung; Rung = Rung->getIDom()) {
5294  BasicBlock *BB = Rung->getBlock();
5295  const Loop *DomLoop = LI.getLoopFor(BB);
5296  if (DomLoop && DomLoop->getHeader() == BB) {
5297  assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
5298  }
5299  }
5300 #endif // DEBUG
5301 
5302  DEBUG(dbgs() << "\nLSR on loop ";
5303  L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false);
5304  dbgs() << ":\n");
5305 
5306  // First, perform some low-level loop optimizations.
5307  OptimizeShadowIV();
5308  OptimizeLoopTermCond();
5309 
5310  // If loop preparation eliminates all interesting IV users, bail.
5311  if (IU.empty()) return;
5312 
5313  // Skip nested loops until we can model them better with formulae.
5314  if (!L->empty()) {
5315  DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
5316  return;
5317  }
5318 
5319  // Start collecting data and preparing for the solver.
5320  CollectChains();
5321  CollectInterestingTypesAndFactors();
5322  CollectFixupsAndInitialFormulae();
5323  CollectLoopInvariantFixupsAndFormulae();
5324 
5325  assert(!Uses.empty() && "IVUsers reported at least one use");
5326  DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
5327  print_uses(dbgs()));
5328 
5329  // Now use the reuse data to generate a bunch of interesting ways
5330  // to formulate the values needed for the uses.
5331  GenerateAllReuseFormulae();
5332 
5333  FilterOutUndesirableDedicatedRegisters();
5334  NarrowSearchSpaceUsingHeuristics();
5335 
5337  Solve(Solution);
5338 
5339  // Release memory that is no longer needed.
5340  Factors.clear();
5341  Types.clear();
5342  RegUses.clear();
5343 
5344  if (Solution.empty())
5345  return;
5346 
5347 #ifndef NDEBUG
5348  // Formulae should be legal.
5349  for (const LSRUse &LU : Uses) {
5350  for (const Formula &F : LU.Formulae)
5351  assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
5352  F) && "Illegal formula generated!");
5353  };
5354 #endif
5355 
5356  // Now that we've decided what we want, make it so.
5357  ImplementSolution(Solution);
5358 }
5359 
5360 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5361 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
5362  if (Factors.empty() && Types.empty()) return;
5363 
5364  OS << "LSR has identified the following interesting factors and types: ";
5365  bool First = true;
5366 
5367  for (int64_t Factor : Factors) {
5368  if (!First) OS << ", ";
5369  First = false;
5370  OS << '*' << Factor;
5371  }
5372 
5373  for (Type *Ty : Types) {
5374  if (!First) OS << ", ";
5375  First = false;
5376  OS << '(' << *Ty << ')';
5377  }
5378  OS << '\n';
5379 }
5380 
5381 void LSRInstance::print_fixups(raw_ostream &OS) const {
5382  OS << "LSR is examining the following fixup sites:\n";
5383  for (const LSRUse &LU : Uses)
5384  for (const LSRFixup &LF : LU.Fixups) {
5385  dbgs() << " ";
5386  LF.print(OS);
5387  OS << '\n';
5388  }
5389 }
5390 
5391 void LSRInstance::print_uses(raw_ostream &OS) const {
5392  OS << "LSR is examining the following uses:\n";
5393  for (const LSRUse &LU : Uses) {
5394  dbgs() << " ";
5395  LU.print(OS);
5396  OS << '\n';
5397  for (const Formula &F : LU.Formulae) {
5398  OS << " ";
5399  F.print(OS);
5400  OS << '\n';
5401  }
5402  }
5403 }
5404 
5405 void LSRInstance::print(raw_ostream &OS) const {
5406  print_factors_and_types(OS);
5407  print_fixups(OS);
5408  print_uses(OS);
5409 }
5410 
5411 LLVM_DUMP_METHOD void LSRInstance::dump() const {
5412  print(errs()); errs() << '\n';
5413 }
5414 #endif
5415 
5416 namespace {
5417 
5418 class LoopStrengthReduce : public LoopPass {
5419 public:
5420  static char ID; // Pass ID, replacement for typeid
5421 
5422  LoopStrengthReduce();
5423 
5424 private:
5425  bool runOnLoop(Loop *L, LPPassManager &LPM) override;
5426  void getAnalysisUsage(AnalysisUsage &AU) const override;
5427 };
5428 
5429 } // end anonymous namespace
5430 
5431 LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
5432  initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
5433 }
5434 
5435 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
5436  // We split critical edges, so we change the CFG. However, we do update
5437  // many analyses if they are around.
5439 
5447  // Requiring LoopSimplify a second time here prevents IVUsers from running
5448  // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5453 }
5454 
5456  DominatorTree &DT, LoopInfo &LI,
5457  const TargetTransformInfo &TTI) {
5458  bool Changed = false;
5459 
5460  // Run the main LSR transformation.
5461  Changed |= LSRInstance(L, IU, SE, DT, LI, TTI).getChanged();
5462 
5463  // Remove any extra phis created by processing inner loops.
5464  Changed |= DeleteDeadPHIs(L->getHeader());
5465  if (EnablePhiElim && L->isLoopSimplifyForm()) {
5467  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
5468  SCEVExpander Rewriter(SE, DL, "lsr");
5469 #ifndef NDEBUG
5470  Rewriter.setDebugType(DEBUG_TYPE);
5471 #endif
5472  unsigned numFolded = Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, &TTI);
5473  if (numFolded) {
5474  Changed = true;
5476  DeleteDeadPHIs(L->getHeader());
5477  }
5478  }
5479  return Changed;
5480 }
5481 
5482 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5483  if (skipLoop(L))
5484  return false;
5485 
5486  auto &IU = getAnalysis<IVUsersWrapperPass>().getIU();
5487  auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
5488  auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
5489  auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
5490  const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
5491  *L->getHeader()->getParent());
5492  return ReduceLoopStrength(L, IU, SE, DT, LI, TTI);
5493 }
5494 
5495 PreservedAnalyses LoopStrengthReducePass::run(Loop &L, LoopAnalysisManager &AM,
5497  LPMUpdater &) {
5498  if (!ReduceLoopStrength(&L, AM.getResult<IVUsersAnalysis>(L, AR), AR.SE,
5499  AR.DT, AR.LI, AR.TTI))
5500  return PreservedAnalyses::all();
5501 
5503 }
5504 
5505 char LoopStrengthReduce::ID = 0;
5506 
5507 INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
5508  "Loop Strength Reduction", false, false)
5514 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
5515 INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
5516  "Loop Strength Reduction", false, false)
5517 
5518 Pass *llvm::createLoopStrengthReducePass() { return new LoopStrengthReduce(); }
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:81
static bool isValueValidForType(Type *Ty, uint64_t V)
This static method returns true if the type Ty is big enough to represent the value V...
Definition: Constants.cpp:1171
uint64_t CallInst * C
DomTreeNodeBase< NodeT > * getNode(NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:67
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:109
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:245
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
iterator_range< use_iterator > uses()
Definition: Value.h:360
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
raw_ostream & errs()
This returns a reference to a raw_ostream for standard error.
BlockT * getLoopLatch() const
If there is a single latch block for this loop, return it.
Definition: LoopInfoImpl.h:157
GCNRegPressure max(const GCNRegPressure &P1, const GCNRegPressure &P2)
PreservedAnalyses getLoopPassPreservedAnalyses()
Returns the minimum set of Analyses that all loop passes must preserve.
const_iterator begin(StringRef path, Style style=Style::native)
Get begin iterator over path.
Definition: Path.cpp:236
DiagnosticInfoOptimizationBase::Argument NV
typename SuperClass::const_iterator const_iterator
Definition: SmallVector.h:329
static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE)
Return true if this AddRec is already a phi in its loop.
Pass * createLoopStrengthReducePass()
This is a &#39;bitvector&#39; (really, a variable-sized bit array), optimized for the case when the array is ...
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:687
const SCEV * getConstant(ConstantInt *V)
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
bool isLegalAddImmediate(int64_t Imm) const
Return true if the specified immediate is legal add immediate, that is the target has add instruction...
#define LLVM_DUMP_METHOD
Mark debug helper function definitions like dump() that should not be stripped from debug builds...
Definition: Compiler.h:449
size_type size() const
Determine the number of elements in the SetVector.
Definition: SetVector.h:78
Type * getEffectiveSCEVType(Type *Ty) const
Return a type with the same bitwidth as the given type and which represents how SCEV will treat the g...
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:136
APInt sdiv(const APInt &RHS) const
Signed division function for APInt.
Definition: APInt.cpp:1600
an instruction that atomically checks whether a specified value is in a memory location, and, if it is, stores a new value there.
Definition: Instructions.h:514
const SCEV * normalizeForPostIncUse(const SCEV *S, const PostIncLoopSet &Loops, ScalarEvolution &SE)
Normalize S to be post-increment for all loops present in Loops.
static const size_t ComplexityLimit
Implements a dense probed hash-table based set.
Definition: DenseSet.h:221
unsigned getLoopDepth() const
Return the nesting level of this loop.
Definition: LoopInfo.h:92
This provides a very simple, boring adaptor for a begin and end iterator into a range type...
The main scalar evolution driver.
bool isZero() const
Return true if the expression is a constant zero.
unsigned getNumberOfRegisters(bool Vector) const
BlockT * getLoopPreheader() const
If there is a preheader for this loop, return it.
Definition: LoopInfoImpl.h:106
static PointerType * get(Type *ElementType, unsigned AddressSpace)
This constructs a pointer to an object of the specified type in a numbered address space...
Definition: Type.cpp:617
unsigned less than
Definition: InstrTypes.h:878
static const unsigned MaxIVUsers
MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for bail out...
bool properlyDominates(const SCEV *S, const BasicBlock *BB)
Return true if elements that makes up the given SCEV properly dominate the specified basic block...
void initializeLoopStrengthReducePass(PassRegistry &)
uint64_t getTypeSizeInBits(Type *Ty) const
Return the size in bits of the specified type, for which isSCEVable must return true.
void setDebugType(const char *s)
NodeT * findNearestCommonDominator(NodeT *A, NodeT *B) const
findNearestCommonDominator - Find nearest common dominator basic block for basic block A and B...
bool isLoopInvariant(const SCEV *S, const Loop *L)
Return true if the value of the given SCEV is unchanging in the specified loop.
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:814
void resize(unsigned N, bool t=false)
Grow or shrink the bitvector.
static void dump(StringRef Title, SpillInfo const &Spills)
Definition: CoroFrame.cpp:283
static bool isCanonical(const MDString *S)
bool properlyDominates(const DomTreeNodeBase< NodeT > *A, const DomTreeNodeBase< NodeT > *B) const
properlyDominates - Returns true iff A dominates B and A != B.
The adaptor from a function pass to a loop pass computes these analyses and makes them available to t...
F(f)
unsigned getPointerAddressSpace() const
Get the address space of this pointer or pointer vector type.
Definition: DerivedTypes.h:503
An instruction for reading from memory.
Definition: Instructions.h:164
an instruction that atomically reads a memory location, combines it with another value, and then stores the result back.
Definition: Instructions.h:677
Value * getCondition() const
iv Induction Variable Users
Definition: IVUsers.cpp:51
This defines the Use class.
void reserve(size_type N)
Definition: SmallVector.h:378
loop data prefetch
iterator end()
Get an iterator to the end of the SetVector.
Definition: SetVector.h:93
INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce", "Loop Strength Reduction", false, false) INITIALIZE_PASS_END(LoopStrengthReduce
This is the base class for unary cast operator classes.
A templated base class for SmallPtrSet which provides the typesafe interface that is common across al...
Definition: SmallPtrSet.h:344
SI optimize exec mask operations pre RA
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:191
#define DEBUG_TYPE
AnalysisUsage & addRequired()
const Module * getModule() const
Return the module owning the function this basic block belongs to, or nullptr it the function does no...
Definition: BasicBlock.cpp:116
bool isLegalICmpImmediate(int64_t Imm) const
Return true if the specified immediate is legal icmp immediate, that is the target has icmp instructi...
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
Hexagon Hardware Loops
This class represents the LLVM &#39;select&#39; instruction.
Predicate getInversePredicate() const
For example, EQ -> NE, UGT -> ULE, SLT -> SGE, OEQ -> UNE, UGT -> OLE, OLT -> UGE, etc.
Definition: InstrTypes.h:951
static cl::opt< bool > InsnsCost("lsr-insns-cost", cl::Hidden, cl::init(true), cl::desc("Add instruction count to a LSR cost model"))
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:361
Option class for critical edge splitting.
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:678
bool isLegalAddressingMode(Type *Ty, GlobalValue *BaseGV, int64_t BaseOffset, bool HasBaseReg, int64_t Scale, unsigned AddrSpace=0, Instruction *I=nullptr) const
Return true if the addressing mode represented by AM is legal for this target, for a load/store of th...
void clearPostInc()
Disable all post-inc expansion.