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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"
68 #include "llvm/Analysis/IVUsers.h"
69 #include "llvm/Analysis/LoopInfo.h"
70 #include "llvm/Analysis/LoopPass.h"
76 #include "llvm/IR/BasicBlock.h"
77 #include "llvm/IR/Constant.h"
78 #include "llvm/IR/Constants.h"
79 #include "llvm/IR/DerivedTypes.h"
80 #include "llvm/IR/Dominators.h"
81 #include "llvm/IR/GlobalValue.h"
82 #include "llvm/IR/IRBuilder.h"
83 #include "llvm/IR/Instruction.h"
84 #include "llvm/IR/Instructions.h"
85 #include "llvm/IR/IntrinsicInst.h"
86 #include "llvm/IR/Module.h"
87 #include "llvm/IR/OperandTraits.h"
88 #include "llvm/IR/Operator.h"
89 #include "llvm/IR/Type.h"
90 #include "llvm/IR/Value.h"
91 #include "llvm/IR/ValueHandle.h"
92 #include "llvm/Pass.h"
93 #include "llvm/Support/Casting.h"
95 #include "llvm/Support/Compiler.h"
96 #include "llvm/Support/Debug.h"
100 #include "llvm/Transforms/Scalar.h"
104 #include <algorithm>
105 #include <cassert>
106 #include <cstddef>
107 #include <cstdint>
108 #include <cstdlib>
109 #include <iterator>
110 #include <map>
111 #include <tuple>
112 #include <utility>
113 
114 using namespace llvm;
115 
116 #define DEBUG_TYPE "loop-reduce"
117 
118 /// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for
119 /// bail out. This threshold is far beyond the number of users that LSR can
120 /// conceivably solve, so it should not affect generated code, but catches the
121 /// worst cases before LSR burns too much compile time and stack space.
122 static const unsigned MaxIVUsers = 200;
123 
124 // Temporary flag to cleanup congruent phis after LSR phi expansion.
125 // It's currently disabled until we can determine whether it's truly useful or
126 // not. The flag should be removed after the v3.0 release.
127 // This is now needed for ivchains.
129  "enable-lsr-phielim", cl::Hidden, cl::init(true),
130  cl::desc("Enable LSR phi elimination"));
131 
132 // The flag adds instruction count to solutions cost comparision.
133 static cl::opt<bool> InsnsCost(
134  "lsr-insns-cost", cl::Hidden, cl::init(false),
135  cl::desc("Add instruction count to a LSR cost model"));
136 
137 // Flag to choose how to narrow complex lsr solution
139  "lsr-exp-narrow", cl::Hidden, cl::init(false),
140  cl::desc("Narrow LSR complex solution using"
141  " expectation of registers number"));
142 
143 // Flag to narrow search space by filtering non-optimal formulae with
144 // the same ScaledReg and Scale.
146  "lsr-filter-same-scaled-reg", cl::Hidden, cl::init(true),
147  cl::desc("Narrow LSR search space by filtering non-optimal formulae"
148  " with the same ScaledReg and Scale"));
149 
150 #ifndef NDEBUG
151 // Stress test IV chain generation.
153  "stress-ivchain", cl::Hidden, cl::init(false),
154  cl::desc("Stress test LSR IV chains"));
155 #else
156 static bool StressIVChain = false;
157 #endif
158 
159 namespace {
160 
161 struct MemAccessTy {
162  /// Used in situations where the accessed memory type is unknown.
163  static const unsigned UnknownAddressSpace = ~0u;
164 
165  Type *MemTy;
166  unsigned AddrSpace;
167 
168  MemAccessTy() : MemTy(nullptr), AddrSpace(UnknownAddressSpace) {}
169 
170  MemAccessTy(Type *Ty, unsigned AS) :
171  MemTy(Ty), AddrSpace(AS) {}
172 
173  bool operator==(MemAccessTy Other) const {
174  return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace;
175  }
176 
177  bool operator!=(MemAccessTy Other) const { return !(*this == Other); }
178 
179  static MemAccessTy getUnknown(LLVMContext &Ctx,
180  unsigned AS = UnknownAddressSpace) {
181  return MemAccessTy(Type::getVoidTy(Ctx), AS);
182  }
183 };
184 
185 /// This class holds data which is used to order reuse candidates.
186 class RegSortData {
187 public:
188  /// This represents the set of LSRUse indices which reference
189  /// a particular register.
190  SmallBitVector UsedByIndices;
191 
192  void print(raw_ostream &OS) const;
193  void dump() const;
194 };
195 
196 } // end anonymous namespace
197 
198 void RegSortData::print(raw_ostream &OS) const {
199  OS << "[NumUses=" << UsedByIndices.count() << ']';
200 }
201 
202 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
203 LLVM_DUMP_METHOD void RegSortData::dump() const {
204  print(errs()); errs() << '\n';
205 }
206 #endif
207 
208 namespace {
209 
210 /// Map register candidates to information about how they are used.
211 class RegUseTracker {
212  typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
213 
214  RegUsesTy RegUsesMap;
216 
217 public:
218  void countRegister(const SCEV *Reg, size_t LUIdx);
219  void dropRegister(const SCEV *Reg, size_t LUIdx);
220  void swapAndDropUse(size_t LUIdx, size_t LastLUIdx);
221 
222  bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
223 
224  const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
225 
226  void clear();
227 
229  typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
230  iterator begin() { return RegSequence.begin(); }
231  iterator end() { return RegSequence.end(); }
232  const_iterator begin() const { return RegSequence.begin(); }
233  const_iterator end() const { return RegSequence.end(); }
234 };
235 
236 } // end anonymous namespace
237 
238 void
239 RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) {
240  std::pair<RegUsesTy::iterator, bool> Pair =
241  RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
242  RegSortData &RSD = Pair.first->second;
243  if (Pair.second)
244  RegSequence.push_back(Reg);
245  RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
246  RSD.UsedByIndices.set(LUIdx);
247 }
248 
249 void
250 RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) {
251  RegUsesTy::iterator It = RegUsesMap.find(Reg);
252  assert(It != RegUsesMap.end());
253  RegSortData &RSD = It->second;
254  assert(RSD.UsedByIndices.size() > LUIdx);
255  RSD.UsedByIndices.reset(LUIdx);
256 }
257 
258 void
259 RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
260  assert(LUIdx <= LastLUIdx);
261 
262  // Update RegUses. The data structure is not optimized for this purpose;
263  // we must iterate through it and update each of the bit vectors.
264  for (auto &Pair : RegUsesMap) {
265  SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
266  if (LUIdx < UsedByIndices.size())
267  UsedByIndices[LUIdx] =
268  LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false;
269  UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
270  }
271 }
272 
273 bool
274 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
275  RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
276  if (I == RegUsesMap.end())
277  return false;
278  const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
279  int i = UsedByIndices.find_first();
280  if (i == -1) return false;
281  if ((size_t)i != LUIdx) return true;
282  return UsedByIndices.find_next(i) != -1;
283 }
284 
285 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
286  RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
287  assert(I != RegUsesMap.end() && "Unknown register!");
288  return I->second.UsedByIndices;
289 }
290 
291 void RegUseTracker::clear() {
292  RegUsesMap.clear();
293  RegSequence.clear();
294 }
295 
296 namespace {
297 
298 /// This class holds information that describes a formula for computing
299 /// satisfying a use. It may include broken-out immediates and scaled registers.
300 struct Formula {
301  /// Global base address used for complex addressing.
302  GlobalValue *BaseGV;
303 
304  /// Base offset for complex addressing.
305  int64_t BaseOffset;
306 
307  /// Whether any complex addressing has a base register.
308  bool HasBaseReg;
309 
310  /// The scale of any complex addressing.
311  int64_t Scale;
312 
313  /// The list of "base" registers for this use. When this is non-empty. The
314  /// canonical representation of a formula is
315  /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
316  /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
317  /// 3. The reg containing recurrent expr related with currect loop in the
318  /// formula should be put in the ScaledReg.
319  /// #1 enforces that the scaled register is always used when at least two
320  /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
321  /// #2 enforces that 1 * reg is reg.
322  /// #3 ensures invariant regs with respect to current loop can be combined
323  /// together in LSR codegen.
324  /// This invariant can be temporarly broken while building a formula.
325  /// However, every formula inserted into the LSRInstance must be in canonical
326  /// form.
328 
329  /// The 'scaled' register for this use. This should be non-null when Scale is
330  /// not zero.
331  const SCEV *ScaledReg;
332 
333  /// An additional constant offset which added near the use. This requires a
334  /// temporary register, but the offset itself can live in an add immediate
335  /// field rather than a register.
336  int64_t UnfoldedOffset;
337 
338  Formula()
339  : BaseGV(nullptr), BaseOffset(0), HasBaseReg(false), Scale(0),
340  ScaledReg(nullptr), UnfoldedOffset(0) {}
341 
342  void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
343 
344  bool isCanonical(const Loop &L) const;
345 
346  void canonicalize(const Loop &L);
347 
348  bool unscale();
349 
350  bool hasZeroEnd() const;
351 
352  size_t getNumRegs() const;
353  Type *getType() const;
354 
355  void deleteBaseReg(const SCEV *&S);
356 
357  bool referencesReg(const SCEV *S) const;
358  bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
359  const RegUseTracker &RegUses) const;
360 
361  void print(raw_ostream &OS) const;
362  void dump() const;
363 };
364 
365 } // end anonymous namespace
366 
367 /// Recursion helper for initialMatch.
368 static void DoInitialMatch(const SCEV *S, Loop *L,
371  ScalarEvolution &SE) {
372  // Collect expressions which properly dominate the loop header.
373  if (SE.properlyDominates(S, L->getHeader())) {
374  Good.push_back(S);
375  return;
376  }
377 
378  // Look at add operands.
379  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
380  for (const SCEV *S : Add->operands())
381  DoInitialMatch(S, L, Good, Bad, SE);
382  return;
383  }
384 
385  // Look at addrec operands.
386  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
387  if (!AR->getStart()->isZero() && AR->isAffine()) {
388  DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
389  DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
390  AR->getStepRecurrence(SE),
391  // FIXME: AR->getNoWrapFlags()
392  AR->getLoop(), SCEV::FlagAnyWrap),
393  L, Good, Bad, SE);
394  return;
395  }
396 
397  // Handle a multiplication by -1 (negation) if it didn't fold.
398  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
399  if (Mul->getOperand(0)->isAllOnesValue()) {
400  SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
401  const SCEV *NewMul = SE.getMulExpr(Ops);
402 
405  DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
406  const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
407  SE.getEffectiveSCEVType(NewMul->getType())));
408  for (const SCEV *S : MyGood)
409  Good.push_back(SE.getMulExpr(NegOne, S));
410  for (const SCEV *S : MyBad)
411  Bad.push_back(SE.getMulExpr(NegOne, S));
412  return;
413  }
414 
415  // Ok, we can't do anything interesting. Just stuff the whole thing into a
416  // register and hope for the best.
417  Bad.push_back(S);
418 }
419 
420 /// Incorporate loop-variant parts of S into this Formula, attempting to keep
421 /// all loop-invariant and loop-computable values in a single base register.
422 void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
425  DoInitialMatch(S, L, Good, Bad, SE);
426  if (!Good.empty()) {
427  const SCEV *Sum = SE.getAddExpr(Good);
428  if (!Sum->isZero())
429  BaseRegs.push_back(Sum);
430  HasBaseReg = true;
431  }
432  if (!Bad.empty()) {
433  const SCEV *Sum = SE.getAddExpr(Bad);
434  if (!Sum->isZero())
435  BaseRegs.push_back(Sum);
436  HasBaseReg = true;
437  }
438  canonicalize(*L);
439 }
440 
441 /// \brief Check whether or not this formula statisfies the canonical
442 /// representation.
443 /// \see Formula::BaseRegs.
444 bool Formula::isCanonical(const Loop &L) const {
445  if (!ScaledReg)
446  return BaseRegs.size() <= 1;
447 
448  if (Scale != 1)
449  return true;
450 
451  if (Scale == 1 && BaseRegs.empty())
452  return false;
453 
454  const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
455  if (SAR && SAR->getLoop() == &L)
456  return true;
457 
458  // If ScaledReg is not a recurrent expr, or it is but its loop is not current
459  // loop, meanwhile BaseRegs contains a recurrent expr reg related with current
460  // loop, we want to swap the reg in BaseRegs with ScaledReg.
461  auto I =
462  find_if(make_range(BaseRegs.begin(), BaseRegs.end()), [&](const SCEV *S) {
463  return isa<const SCEVAddRecExpr>(S) &&
464  (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
465  });
466  return I == BaseRegs.end();
467 }
468 
469 /// \brief Helper method to morph a formula into its canonical representation.
470 /// \see Formula::BaseRegs.
471 /// Every formula having more than one base register, must use the ScaledReg
472 /// field. Otherwise, we would have to do special cases everywhere in LSR
473 /// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
474 /// On the other hand, 1*reg should be canonicalized into reg.
475 void Formula::canonicalize(const Loop &L) {
476  if (isCanonical(L))
477  return;
478  // So far we did not need this case. This is easy to implement but it is
479  // useless to maintain dead code. Beside it could hurt compile time.
480  assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.");
481 
482  // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
483  if (!ScaledReg) {
484  ScaledReg = BaseRegs.back();
485  BaseRegs.pop_back();
486  Scale = 1;
487  }
488 
489  // If ScaledReg is an invariant with respect to L, find the reg from
490  // BaseRegs containing the recurrent expr related with Loop L. Swap the
491  // reg with ScaledReg.
492  const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
493  if (!SAR || SAR->getLoop() != &L) {
494  auto I = find_if(make_range(BaseRegs.begin(), BaseRegs.end()),
495  [&](const SCEV *S) {
496  return isa<const SCEVAddRecExpr>(S) &&
497  (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
498  });
499  if (I != BaseRegs.end())
500  std::swap(ScaledReg, *I);
501  }
502 }
503 
504 /// \brief Get rid of the scale in the formula.
505 /// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
506 /// \return true if it was possible to get rid of the scale, false otherwise.
507 /// \note After this operation the formula may not be in the canonical form.
508 bool Formula::unscale() {
509  if (Scale != 1)
510  return false;
511  Scale = 0;
512  BaseRegs.push_back(ScaledReg);
513  ScaledReg = nullptr;
514  return true;
515 }
516 
517 bool Formula::hasZeroEnd() const {
518  if (UnfoldedOffset || BaseOffset)
519  return false;
520  if (BaseRegs.size() != 1 || ScaledReg)
521  return false;
522  return true;
523 }
524 
525 /// Return the total number of register operands used by this formula. This does
526 /// not include register uses implied by non-constant addrec strides.
527 size_t Formula::getNumRegs() const {
528  return !!ScaledReg + BaseRegs.size();
529 }
530 
531 /// Return the type of this formula, if it has one, or null otherwise. This type
532 /// is meaningless except for the bit size.
533 Type *Formula::getType() const {
534  return !BaseRegs.empty() ? BaseRegs.front()->getType() :
535  ScaledReg ? ScaledReg->getType() :
536  BaseGV ? BaseGV->getType() :
537  nullptr;
538 }
539 
540 /// Delete the given base reg from the BaseRegs list.
541 void Formula::deleteBaseReg(const SCEV *&S) {
542  if (&S != &BaseRegs.back())
543  std::swap(S, BaseRegs.back());
544  BaseRegs.pop_back();
545 }
546 
547 /// Test if this formula references the given register.
548 bool Formula::referencesReg(const SCEV *S) const {
549  return S == ScaledReg || is_contained(BaseRegs, S);
550 }
551 
552 /// Test whether this formula uses registers which are used by uses other than
553 /// the use with the given index.
554 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
555  const RegUseTracker &RegUses) const {
556  if (ScaledReg)
557  if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
558  return true;
559  for (const SCEV *BaseReg : BaseRegs)
560  if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
561  return true;
562  return false;
563 }
564 
565 void Formula::print(raw_ostream &OS) const {
566  bool First = true;
567  if (BaseGV) {
568  if (!First) OS << " + "; else First = false;
569  BaseGV->printAsOperand(OS, /*PrintType=*/false);
570  }
571  if (BaseOffset != 0) {
572  if (!First) OS << " + "; else First = false;
573  OS << BaseOffset;
574  }
575  for (const SCEV *BaseReg : BaseRegs) {
576  if (!First) OS << " + "; else First = false;
577  OS << "reg(" << *BaseReg << ')';
578  }
579  if (HasBaseReg && BaseRegs.empty()) {
580  if (!First) OS << " + "; else First = false;
581  OS << "**error: HasBaseReg**";
582  } else if (!HasBaseReg && !BaseRegs.empty()) {
583  if (!First) OS << " + "; else First = false;
584  OS << "**error: !HasBaseReg**";
585  }
586  if (Scale != 0) {
587  if (!First) OS << " + "; else First = false;
588  OS << Scale << "*reg(";
589  if (ScaledReg)
590  OS << *ScaledReg;
591  else
592  OS << "<unknown>";
593  OS << ')';
594  }
595  if (UnfoldedOffset != 0) {
596  if (!First) OS << " + ";
597  OS << "imm(" << UnfoldedOffset << ')';
598  }
599 }
600 
601 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
602 LLVM_DUMP_METHOD void Formula::dump() const {
603  print(errs()); errs() << '\n';
604 }
605 #endif
606 
607 /// Return true if the given addrec can be sign-extended without changing its
608 /// value.
609 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
610  Type *WideTy =
612  return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
613 }
614 
615 /// Return true if the given add can be sign-extended without changing its
616 /// value.
617 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
618  Type *WideTy =
620  return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
621 }
622 
623 /// Return true if the given mul can be sign-extended without changing its
624 /// value.
625 static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
626  Type *WideTy =
628  SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
629  return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
630 }
631 
632 /// Return an expression for LHS /s RHS, if it can be determined and if the
633 /// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
634 /// is true, expressions like (X * Y) /s Y are simplified to Y, ignoring that
635 /// the multiplication may overflow, which is useful when the result will be
636 /// used in a context where the most significant bits are ignored.
637 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
638  ScalarEvolution &SE,
639  bool IgnoreSignificantBits = false) {
640  // Handle the trivial case, which works for any SCEV type.
641  if (LHS == RHS)
642  return SE.getConstant(LHS->getType(), 1);
643 
644  // Handle a few RHS special cases.
645  const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
646  if (RC) {
647  const APInt &RA = RC->getAPInt();
648  // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
649  // some folding.
650  if (RA.isAllOnesValue())
651  return SE.getMulExpr(LHS, RC);
652  // Handle x /s 1 as x.
653  if (RA == 1)
654  return LHS;
655  }
656 
657  // Check for a division of a constant by a constant.
658  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
659  if (!RC)
660  return nullptr;
661  const APInt &LA = C->getAPInt();
662  const APInt &RA = RC->getAPInt();
663  if (LA.srem(RA) != 0)
664  return nullptr;
665  return SE.getConstant(LA.sdiv(RA));
666  }
667 
668  // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
669  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
670  if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
671  const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
672  IgnoreSignificantBits);
673  if (!Step) return nullptr;
674  const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
675  IgnoreSignificantBits);
676  if (!Start) return nullptr;
677  // FlagNW is independent of the start value, step direction, and is
678  // preserved with smaller magnitude steps.
679  // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
680  return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
681  }
682  return nullptr;
683  }
684 
685  // Distribute the sdiv over add operands, if the add doesn't overflow.
686  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
687  if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
689  for (const SCEV *S : Add->operands()) {
690  const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
691  if (!Op) return nullptr;
692  Ops.push_back(Op);
693  }
694  return SE.getAddExpr(Ops);
695  }
696  return nullptr;
697  }
698 
699  // Check for a multiply operand that we can pull RHS out of.
700  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
701  if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
703  bool Found = false;
704  for (const SCEV *S : Mul->operands()) {
705  if (!Found)
706  if (const SCEV *Q = getExactSDiv(S, RHS, SE,
707  IgnoreSignificantBits)) {
708  S = Q;
709  Found = true;
710  }
711  Ops.push_back(S);
712  }
713  return Found ? SE.getMulExpr(Ops) : nullptr;
714  }
715  return nullptr;
716  }
717 
718  // Otherwise we don't know.
719  return nullptr;
720 }
721 
722 /// If S involves the addition of a constant integer value, return that integer
723 /// value, and mutate S to point to a new SCEV with that value excluded.
724 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
725  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
726  if (C->getAPInt().getMinSignedBits() <= 64) {
727  S = SE.getConstant(C->getType(), 0);
728  return C->getValue()->getSExtValue();
729  }
730  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
731  SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
732  int64_t Result = ExtractImmediate(NewOps.front(), SE);
733  if (Result != 0)
734  S = SE.getAddExpr(NewOps);
735  return Result;
736  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
737  SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
738  int64_t Result = ExtractImmediate(NewOps.front(), SE);
739  if (Result != 0)
740  S = SE.getAddRecExpr(NewOps, AR->getLoop(),
741  // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
743  return Result;
744  }
745  return 0;
746 }
747 
748 /// If S involves the addition of a GlobalValue address, return that symbol, and
749 /// mutate S to point to a new SCEV with that value excluded.
751  if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
752  if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
753  S = SE.getConstant(GV->getType(), 0);
754  return GV;
755  }
756  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
757  SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
758  GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
759  if (Result)
760  S = SE.getAddExpr(NewOps);
761  return Result;
762  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
763  SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
764  GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
765  if (Result)
766  S = SE.getAddRecExpr(NewOps, AR->getLoop(),
767  // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
769  return Result;
770  }
771  return nullptr;
772 }
773 
774 /// Returns true if the specified instruction is using the specified value as an
775 /// address.
776 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
777  bool isAddress = isa<LoadInst>(Inst);
778  if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
779  if (SI->getPointerOperand() == OperandVal)
780  isAddress = true;
781  } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
782  // Addressing modes can also be folded into prefetches and a variety
783  // of intrinsics.
784  switch (II->getIntrinsicID()) {
785  default: break;
786  case Intrinsic::prefetch:
787  if (II->getArgOperand(0) == OperandVal)
788  isAddress = true;
789  break;
790  }
791  } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
792  if (RMW->getPointerOperand() == OperandVal)
793  isAddress = true;
794  } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
795  if (CmpX->getPointerOperand() == OperandVal)
796  isAddress = true;
797  }
798  return isAddress;
799 }
800 
801 /// Return the type of the memory being accessed.
802 static MemAccessTy getAccessType(const Instruction *Inst) {
803  MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
804  if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
805  AccessTy.MemTy = SI->getOperand(0)->getType();
806  AccessTy.AddrSpace = SI->getPointerAddressSpace();
807  } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
808  AccessTy.AddrSpace = LI->getPointerAddressSpace();
809  } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
810  AccessTy.AddrSpace = RMW->getPointerAddressSpace();
811  } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
812  AccessTy.AddrSpace = CmpX->getPointerAddressSpace();
813  }
814 
815  // All pointers have the same requirements, so canonicalize them to an
816  // arbitrary pointer type to minimize variation.
817  if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
818  AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
819  PTy->getAddressSpace());
820 
821  return AccessTy;
822 }
823 
824 /// Return true if this AddRec is already a phi in its loop.
825 static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
826  for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
827  PHINode *PN = dyn_cast<PHINode>(I); ++I) {
828  if (SE.isSCEVable(PN->getType()) &&
829  (SE.getEffectiveSCEVType(PN->getType()) ==
830  SE.getEffectiveSCEVType(AR->getType())) &&
831  SE.getSCEV(PN) == AR)
832  return true;
833  }
834  return false;
835 }
836 
837 /// Check if expanding this expression is likely to incur significant cost. This
838 /// is tricky because SCEV doesn't track which expressions are actually computed
839 /// by the current IR.
840 ///
841 /// We currently allow expansion of IV increments that involve adds,
842 /// multiplication by constants, and AddRecs from existing phis.
843 ///
844 /// TODO: Allow UDivExpr if we can find an existing IV increment that is an
845 /// obvious multiple of the UDivExpr.
846 static bool isHighCostExpansion(const SCEV *S,
847  SmallPtrSetImpl<const SCEV*> &Processed,
848  ScalarEvolution &SE) {
849  // Zero/One operand expressions
850  switch (S->getSCEVType()) {
851  case scUnknown:
852  case scConstant:
853  return false;
854  case scTruncate:
855  return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
856  Processed, SE);
857  case scZeroExtend:
858  return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
859  Processed, SE);
860  case scSignExtend:
861  return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
862  Processed, SE);
863  }
864 
865  if (!Processed.insert(S).second)
866  return false;
867 
868  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
869  for (const SCEV *S : Add->operands()) {
870  if (isHighCostExpansion(S, Processed, SE))
871  return true;
872  }
873  return false;
874  }
875 
876  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
877  if (Mul->getNumOperands() == 2) {
878  // Multiplication by a constant is ok
879  if (isa<SCEVConstant>(Mul->getOperand(0)))
880  return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
881 
882  // If we have the value of one operand, check if an existing
883  // multiplication already generates this expression.
884  if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
885  Value *UVal = U->getValue();
886  for (User *UR : UVal->users()) {
887  // If U is a constant, it may be used by a ConstantExpr.
888  Instruction *UI = dyn_cast<Instruction>(UR);
889  if (UI && UI->getOpcode() == Instruction::Mul &&
890  SE.isSCEVable(UI->getType())) {
891  return SE.getSCEV(UI) == Mul;
892  }
893  }
894  }
895  }
896  }
897 
898  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
899  if (isExistingPhi(AR, SE))
900  return false;
901  }
902 
903  // Fow now, consider any other type of expression (div/mul/min/max) high cost.
904  return true;
905 }
906 
907 /// If any of the instructions is the specified set are trivially dead, delete
908 /// them and see if this makes any of their operands subsequently dead.
909 static bool
911  bool Changed = false;
912 
913  while (!DeadInsts.empty()) {
914  Value *V = DeadInsts.pop_back_val();
915  Instruction *I = dyn_cast_or_null<Instruction>(V);
916 
917  if (!I || !isInstructionTriviallyDead(I))
918  continue;
919 
920  for (Use &O : I->operands())
921  if (Instruction *U = dyn_cast<Instruction>(O)) {
922  O = nullptr;
923  if (U->use_empty())
924  DeadInsts.emplace_back(U);
925  }
926 
927  I->eraseFromParent();
928  Changed = true;
929  }
930 
931  return Changed;
932 }
933 
934 namespace {
935 
936 class LSRUse;
937 
938 } // end anonymous namespace
939 
940 /// \brief Check if the addressing mode defined by \p F is completely
941 /// folded in \p LU at isel time.
942 /// This includes address-mode folding and special icmp tricks.
943 /// This function returns true if \p LU can accommodate what \p F
944 /// defines and up to 1 base + 1 scaled + offset.
945 /// In other words, if \p F has several base registers, this function may
946 /// still return true. Therefore, users still need to account for
947 /// additional base registers and/or unfolded offsets to derive an
948 /// accurate cost model.
949 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
950  const LSRUse &LU, const Formula &F);
951 // Get the cost of the scaling factor used in F for LU.
952 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
953  const LSRUse &LU, const Formula &F,
954  const Loop &L);
955 
956 namespace {
957 
958 /// This class is used to measure and compare candidate formulae.
959 class Cost {
961 
962 public:
963  Cost() {
964  C.Insns = 0;
965  C.NumRegs = 0;
966  C.AddRecCost = 0;
967  C.NumIVMuls = 0;
968  C.NumBaseAdds = 0;
969  C.ImmCost = 0;
970  C.SetupCost = 0;
971  C.ScaleCost = 0;
972  }
973 
974  bool isLess(Cost &Other, const TargetTransformInfo &TTI);
975 
976  void Lose();
977 
978 #ifndef NDEBUG
979  // Once any of the metrics loses, they must all remain losers.
980  bool isValid() {
981  return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds
982  | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u)
983  || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds
984  & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u);
985  }
986 #endif
987 
988  bool isLoser() {
989  assert(isValid() && "invalid cost");
990  return C.NumRegs == ~0u;
991  }
992 
993  void RateFormula(const TargetTransformInfo &TTI,
994  const Formula &F,
996  const DenseSet<const SCEV *> &VisitedRegs,
997  const Loop *L,
999  const LSRUse &LU,
1000  SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
1001 
1002  void print(raw_ostream &OS) const;
1003  void dump() const;
1004 
1005 private:
1006  void RateRegister(const SCEV *Reg,
1008  const Loop *L,
1009  ScalarEvolution &SE, DominatorTree &DT);
1010  void RatePrimaryRegister(const SCEV *Reg,
1012  const Loop *L,
1013  ScalarEvolution &SE, DominatorTree &DT,
1014  SmallPtrSetImpl<const SCEV *> *LoserRegs);
1015 };
1016 
1017 /// An operand value in an instruction which is to be replaced with some
1018 /// equivalent, possibly strength-reduced, replacement.
1019 struct LSRFixup {
1020  /// The instruction which will be updated.
1021  Instruction *UserInst;
1022 
1023  /// The operand of the instruction which will be replaced. The operand may be
1024  /// used more than once; every instance will be replaced.
1025  Value *OperandValToReplace;
1026 
1027  /// If this user is to use the post-incremented value of an induction
1028  /// variable, this variable is non-null and holds the loop associated with the
1029  /// induction variable.
1030  PostIncLoopSet PostIncLoops;
1031 
1032  /// A constant offset to be added to the LSRUse expression. This allows
1033  /// multiple fixups to share the same LSRUse with different offsets, for
1034  /// example in an unrolled loop.
1035  int64_t Offset;
1036 
1037  bool isUseFullyOutsideLoop(const Loop *L) const;
1038 
1039  LSRFixup();
1040 
1041  void print(raw_ostream &OS) const;
1042  void dump() const;
1043 };
1044 
1045 /// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
1046 /// SmallVectors of const SCEV*.
1047 struct UniquifierDenseMapInfo {
1048  static SmallVector<const SCEV *, 4> getEmptyKey() {
1050  V.push_back(reinterpret_cast<const SCEV *>(-1));
1051  return V;
1052  }
1053 
1054  static SmallVector<const SCEV *, 4> getTombstoneKey() {
1056  V.push_back(reinterpret_cast<const SCEV *>(-2));
1057  return V;
1058  }
1059 
1060  static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1061  return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1062  }
1063 
1064  static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1065  const SmallVector<const SCEV *, 4> &RHS) {
1066  return LHS == RHS;
1067  }
1068 };
1069 
1070 /// This class holds the state that LSR keeps for each use in IVUsers, as well
1071 /// as uses invented by LSR itself. It includes information about what kinds of
1072 /// things can be folded into the user, information about the user itself, and
1073 /// information about how the use may be satisfied. TODO: Represent multiple
1074 /// users of the same expression in common?
1075 class LSRUse {
1076  DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1077 
1078 public:
1079  /// An enum for a kind of use, indicating what types of scaled and immediate
1080  /// operands it might support.
1081  enum KindType {
1082  Basic, ///< A normal use, with no folding.
1083  Special, ///< A special case of basic, allowing -1 scales.
1084  Address, ///< An address use; folding according to TargetLowering
1085  ICmpZero ///< An equality icmp with both operands folded into one.
1086  // TODO: Add a generic icmp too?
1087  };
1088 
1089  typedef PointerIntPair<const SCEV *, 2, KindType> SCEVUseKindPair;
1090 
1091  KindType Kind;
1092  MemAccessTy AccessTy;
1093 
1094  /// The list of operands which are to be replaced.
1096 
1097  /// Keep track of the min and max offsets of the fixups.
1098  int64_t MinOffset;
1099  int64_t MaxOffset;
1100 
1101  /// This records whether all of the fixups using this LSRUse are outside of
1102  /// the loop, in which case some special-case heuristics may be used.
1103  bool AllFixupsOutsideLoop;
1104 
1105  /// RigidFormula is set to true to guarantee that this use will be associated
1106  /// with a single formula--the one that initially matched. Some SCEV
1107  /// expressions cannot be expanded. This allows LSR to consider the registers
1108  /// used by those expressions without the need to expand them later after
1109  /// changing the formula.
1110  bool RigidFormula;
1111 
1112  /// This records the widest use type for any fixup using this
1113  /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1114  /// fixup widths to be equivalent, because the narrower one may be relying on
1115  /// the implicit truncation to truncate away bogus bits.
1116  Type *WidestFixupType;
1117 
1118  /// A list of ways to build a value that can satisfy this user. After the
1119  /// list is populated, one of these is selected heuristically and used to
1120  /// formulate a replacement for OperandValToReplace in UserInst.
1121  SmallVector<Formula, 12> Formulae;
1122 
1123  /// The set of register candidates used by all formulae in this LSRUse.
1125 
1126  LSRUse(KindType K, MemAccessTy AT)
1127  : Kind(K), AccessTy(AT), MinOffset(INT64_MAX), MaxOffset(INT64_MIN),
1128  AllFixupsOutsideLoop(true), RigidFormula(false),
1129  WidestFixupType(nullptr) {}
1130 
1131  LSRFixup &getNewFixup() {
1132  Fixups.push_back(LSRFixup());
1133  return Fixups.back();
1134  }
1135 
1136  void pushFixup(LSRFixup &f) {
1137  Fixups.push_back(f);
1138  if (f.Offset > MaxOffset)
1139  MaxOffset = f.Offset;
1140  if (f.Offset < MinOffset)
1141  MinOffset = f.Offset;
1142  }
1143 
1144  bool HasFormulaWithSameRegs(const Formula &F) const;
1145  float getNotSelectedProbability(const SCEV *Reg) const;
1146  bool InsertFormula(const Formula &F, const Loop &L);
1147  void DeleteFormula(Formula &F);
1148  void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1149 
1150  void print(raw_ostream &OS) const;
1151  void dump() const;
1152 };
1153 
1154 } // end anonymous namespace
1155 
1156 /// Tally up interesting quantities from the given register.
1157 void Cost::RateRegister(const SCEV *Reg,
1159  const Loop *L,
1160  ScalarEvolution &SE, DominatorTree &DT) {
1161  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1162  // If this is an addrec for another loop, it should be an invariant
1163  // with respect to L since L is the innermost loop (at least
1164  // for now LSR only handles innermost loops).
1165  if (AR->getLoop() != L) {
1166  // If the AddRec exists, consider it's register free and leave it alone.
1167  if (isExistingPhi(AR, SE))
1168  return;
1169 
1170  // It is bad to allow LSR for current loop to add induction variables
1171  // for its sibling loops.
1172  if (!AR->getLoop()->contains(L)) {
1173  Lose();
1174  return;
1175  }
1176 
1177  // Otherwise, it will be an invariant with respect to Loop L.
1178  ++C.NumRegs;
1179  return;
1180  }
1181  C.AddRecCost += 1; /// TODO: This should be a function of the stride.
1182 
1183  // Add the step value register, if it needs one.
1184  // TODO: The non-affine case isn't precisely modeled here.
1185  if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1186  if (!Regs.count(AR->getOperand(1))) {
1187  RateRegister(AR->getOperand(1), Regs, L, SE, DT);
1188  if (isLoser())
1189  return;
1190  }
1191  }
1192  }
1193  ++C.NumRegs;
1194 
1195  // Rough heuristic; favor registers which don't require extra setup
1196  // instructions in the preheader.
1197  if (!isa<SCEVUnknown>(Reg) &&
1198  !isa<SCEVConstant>(Reg) &&
1199  !(isa<SCEVAddRecExpr>(Reg) &&
1200  (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
1201  isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
1202  ++C.SetupCost;
1203 
1204  C.NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1205  SE.hasComputableLoopEvolution(Reg, L);
1206 }
1207 
1208 /// Record this register in the set. If we haven't seen it before, rate
1209 /// it. Optional LoserRegs provides a way to declare any formula that refers to
1210 /// one of those regs an instant loser.
1211 void Cost::RatePrimaryRegister(const SCEV *Reg,
1213  const Loop *L,
1214  ScalarEvolution &SE, DominatorTree &DT,
1215  SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1216  if (LoserRegs && LoserRegs->count(Reg)) {
1217  Lose();
1218  return;
1219  }
1220  if (Regs.insert(Reg).second) {
1221  RateRegister(Reg, Regs, L, SE, DT);
1222  if (LoserRegs && isLoser())
1223  LoserRegs->insert(Reg);
1224  }
1225 }
1226 
1227 void Cost::RateFormula(const TargetTransformInfo &TTI,
1228  const Formula &F,
1230  const DenseSet<const SCEV *> &VisitedRegs,
1231  const Loop *L,
1232  ScalarEvolution &SE, DominatorTree &DT,
1233  const LSRUse &LU,
1234  SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1235  assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula");
1236  // Tally up the registers.
1237  unsigned PrevAddRecCost = C.AddRecCost;
1238  unsigned PrevNumRegs = C.NumRegs;
1239  unsigned PrevNumBaseAdds = C.NumBaseAdds;
1240  if (const SCEV *ScaledReg = F.ScaledReg) {
1241  if (VisitedRegs.count(ScaledReg)) {
1242  Lose();
1243  return;
1244  }
1245  RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs);
1246  if (isLoser())
1247  return;
1248  }
1249  for (const SCEV *BaseReg : F.BaseRegs) {
1250  if (VisitedRegs.count(BaseReg)) {
1251  Lose();
1252  return;
1253  }
1254  RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs);
1255  if (isLoser())
1256  return;
1257  }
1258 
1259  // Determine how many (unfolded) adds we'll need inside the loop.
1260  size_t NumBaseParts = F.getNumRegs();
1261  if (NumBaseParts > 1)
1262  // Do not count the base and a possible second register if the target
1263  // allows to fold 2 registers.
1264  C.NumBaseAdds +=
1265  NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(TTI, LU, F)));
1266  C.NumBaseAdds += (F.UnfoldedOffset != 0);
1267 
1268  // Accumulate non-free scaling amounts.
1269  C.ScaleCost += getScalingFactorCost(TTI, LU, F, *L);
1270 
1271  // Tally up the non-zero immediates.
1272  for (const LSRFixup &Fixup : LU.Fixups) {
1273  int64_t O = Fixup.Offset;
1274  int64_t Offset = (uint64_t)O + F.BaseOffset;
1275  if (F.BaseGV)
1276  C.ImmCost += 64; // Handle symbolic values conservatively.
1277  // TODO: This should probably be the pointer size.
1278  else if (Offset != 0)
1279  C.ImmCost += APInt(64, Offset, true).getMinSignedBits();
1280 
1281  // Check with target if this offset with this instruction is
1282  // specifically not supported.
1283  if ((isa<LoadInst>(Fixup.UserInst) || isa<StoreInst>(Fixup.UserInst)) &&
1284  !TTI.isFoldableMemAccessOffset(Fixup.UserInst, Offset))
1285  C.NumBaseAdds++;
1286  }
1287 
1288  // If we don't count instruction cost exit here.
1289  if (!InsnsCost) {
1290  assert(isValid() && "invalid cost");
1291  return;
1292  }
1293 
1294  // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as
1295  // additional instruction (at least fill).
1296  unsigned TTIRegNum = TTI.getNumberOfRegisters(false) - 1;
1297  if (C.NumRegs > TTIRegNum) {
1298  // Cost already exceeded TTIRegNum, then only newly added register can add
1299  // new instructions.
1300  if (PrevNumRegs > TTIRegNum)
1301  C.Insns += (C.NumRegs - PrevNumRegs);
1302  else
1303  C.Insns += (C.NumRegs - TTIRegNum);
1304  }
1305 
1306  // If ICmpZero formula ends with not 0, it could not be replaced by
1307  // just add or sub. We'll need to compare final result of AddRec.
1308  // That means we'll need an additional instruction.
1309  // For -10 + {0, +, 1}:
1310  // i = i + 1;
1311  // cmp i, 10
1312  //
1313  // For {-10, +, 1}:
1314  // i = i + 1;
1315  if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd())
1316  C.Insns++;
1317  // Each new AddRec adds 1 instruction to calculation.
1318  C.Insns += (C.AddRecCost - PrevAddRecCost);
1319 
1320  // BaseAdds adds instructions for unfolded registers.
1321  if (LU.Kind != LSRUse::ICmpZero)
1322  C.Insns += C.NumBaseAdds - PrevNumBaseAdds;
1323  assert(isValid() && "invalid cost");
1324 }
1325 
1326 /// Set this cost to a losing value.
1327 void Cost::Lose() {
1328  C.Insns = ~0u;
1329  C.NumRegs = ~0u;
1330  C.AddRecCost = ~0u;
1331  C.NumIVMuls = ~0u;
1332  C.NumBaseAdds = ~0u;
1333  C.ImmCost = ~0u;
1334  C.SetupCost = ~0u;
1335  C.ScaleCost = ~0u;
1336 }
1337 
1338 /// Choose the lower cost.
1339 bool Cost::isLess(Cost &Other, const TargetTransformInfo &TTI) {
1340  if (InsnsCost.getNumOccurrences() > 0 && InsnsCost &&
1341  C.Insns != Other.C.Insns)
1342  return C.Insns < Other.C.Insns;
1343  return TTI.isLSRCostLess(C, Other.C);
1344 }
1345 
1346 void Cost::print(raw_ostream &OS) const {
1347  if (InsnsCost)
1348  OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s ");
1349  OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s");
1350  if (C.AddRecCost != 0)
1351  OS << ", with addrec cost " << C.AddRecCost;
1352  if (C.NumIVMuls != 0)
1353  OS << ", plus " << C.NumIVMuls << " IV mul"
1354  << (C.NumIVMuls == 1 ? "" : "s");
1355  if (C.NumBaseAdds != 0)
1356  OS << ", plus " << C.NumBaseAdds << " base add"
1357  << (C.NumBaseAdds == 1 ? "" : "s");
1358  if (C.ScaleCost != 0)
1359  OS << ", plus " << C.ScaleCost << " scale cost";
1360  if (C.ImmCost != 0)
1361  OS << ", plus " << C.ImmCost << " imm cost";
1362  if (C.SetupCost != 0)
1363  OS << ", plus " << C.SetupCost << " setup cost";
1364 }
1365 
1366 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1367 LLVM_DUMP_METHOD void Cost::dump() const {
1368  print(errs()); errs() << '\n';
1369 }
1370 #endif
1371 
1372 LSRFixup::LSRFixup()
1373  : UserInst(nullptr), OperandValToReplace(nullptr),
1374  Offset(0) {}
1375 
1376 /// Test whether this fixup always uses its value outside of the given loop.
1377 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1378  // PHI nodes use their value in their incoming blocks.
1379  if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1380  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1381  if (PN->getIncomingValue(i) == OperandValToReplace &&
1382  L->contains(PN->getIncomingBlock(i)))
1383  return false;
1384  return true;
1385  }
1386 
1387  return !L->contains(UserInst);
1388 }
1389 
1390 void LSRFixup::print(raw_ostream &OS) const {
1391  OS << "UserInst=";
1392  // Store is common and interesting enough to be worth special-casing.
1393  if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1394  OS << "store ";
1395  Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1396  } else if (UserInst->getType()->isVoidTy())
1397  OS << UserInst->getOpcodeName();
1398  else
1399  UserInst->printAsOperand(OS, /*PrintType=*/false);
1400 
1401  OS << ", OperandValToReplace=";
1402  OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1403 
1404  for (const Loop *PIL : PostIncLoops) {
1405  OS << ", PostIncLoop=";
1406  PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1407  }
1408 
1409  if (Offset != 0)
1410  OS << ", Offset=" << Offset;
1411 }
1412 
1413 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1414 LLVM_DUMP_METHOD void LSRFixup::dump() const {
1415  print(errs()); errs() << '\n';
1416 }
1417 #endif
1418 
1419 /// Test whether this use as a formula which has the same registers as the given
1420 /// formula.
1421 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1422  SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1423  if (F.ScaledReg) Key.push_back(F.ScaledReg);
1424  // Unstable sort by host order ok, because this is only used for uniquifying.
1425  std::sort(Key.begin(), Key.end());
1426  return Uniquifier.count(Key);
1427 }
1428 
1429 /// The function returns a probability of selecting formula without Reg.
1430 float LSRUse::getNotSelectedProbability(const SCEV *Reg) const {
1431  unsigned FNum = 0;
1432  for (const Formula &F : Formulae)
1433  if (F.referencesReg(Reg))
1434  FNum++;
1435  return ((float)(Formulae.size() - FNum)) / Formulae.size();
1436 }
1437 
1438 /// If the given formula has not yet been inserted, add it to the list, and
1439 /// return true. Return false otherwise. The formula must be in canonical form.
1440 bool LSRUse::InsertFormula(const Formula &F, const Loop &L) {
1441  assert(F.isCanonical(L) && "Invalid canonical representation");
1442 
1443  if (!Formulae.empty() && RigidFormula)
1444  return false;
1445 
1446  SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1447  if (F.ScaledReg) Key.push_back(F.ScaledReg);
1448  // Unstable sort by host order ok, because this is only used for uniquifying.
1449  std::sort(Key.begin(), Key.end());
1450 
1451  if (!Uniquifier.insert(Key).second)
1452  return false;
1453 
1454  // Using a register to hold the value of 0 is not profitable.
1455  assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1456  "Zero allocated in a scaled register!");
1457 #ifndef NDEBUG
1458  for (const SCEV *BaseReg : F.BaseRegs)
1459  assert(!BaseReg->isZero() && "Zero allocated in a base register!");
1460 #endif
1461 
1462  // Add the formula to the list.
1463  Formulae.push_back(F);
1464 
1465  // Record registers now being used by this use.
1466  Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1467  if (F.ScaledReg)
1468  Regs.insert(F.ScaledReg);
1469 
1470  return true;
1471 }
1472 
1473 /// Remove the given formula from this use's list.
1474 void LSRUse::DeleteFormula(Formula &F) {
1475  if (&F != &Formulae.back())
1476  std::swap(F, Formulae.back());
1477  Formulae.pop_back();
1478 }
1479 
1480 /// Recompute the Regs field, and update RegUses.
1481 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1482  // Now that we've filtered out some formulae, recompute the Regs set.
1483  SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1484  Regs.clear();
1485  for (const Formula &F : Formulae) {
1486  if (F.ScaledReg) Regs.insert(F.ScaledReg);
1487  Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1488  }
1489 
1490  // Update the RegTracker.
1491  for (const SCEV *S : OldRegs)
1492  if (!Regs.count(S))
1493  RegUses.dropRegister(S, LUIdx);
1494 }
1495 
1496 void LSRUse::print(raw_ostream &OS) const {
1497  OS << "LSR Use: Kind=";
1498  switch (Kind) {
1499  case Basic: OS << "Basic"; break;
1500  case Special: OS << "Special"; break;
1501  case ICmpZero: OS << "ICmpZero"; break;
1502  case Address:
1503  OS << "Address of ";
1504  if (AccessTy.MemTy->isPointerTy())
1505  OS << "pointer"; // the full pointer type could be really verbose
1506  else {
1507  OS << *AccessTy.MemTy;
1508  }
1509 
1510  OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1511  }
1512 
1513  OS << ", Offsets={";
1514  bool NeedComma = false;
1515  for (const LSRFixup &Fixup : Fixups) {
1516  if (NeedComma) OS << ',';
1517  OS << Fixup.Offset;
1518  NeedComma = true;
1519  }
1520  OS << '}';
1521 
1522  if (AllFixupsOutsideLoop)
1523  OS << ", all-fixups-outside-loop";
1524 
1525  if (WidestFixupType)
1526  OS << ", widest fixup type: " << *WidestFixupType;
1527 }
1528 
1529 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1530 LLVM_DUMP_METHOD void LSRUse::dump() const {
1531  print(errs()); errs() << '\n';
1532 }
1533 #endif
1534 
1536  LSRUse::KindType Kind, MemAccessTy AccessTy,
1537  GlobalValue *BaseGV, int64_t BaseOffset,
1538  bool HasBaseReg, int64_t Scale) {
1539  switch (Kind) {
1540  case LSRUse::Address:
1541  return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1542  HasBaseReg, Scale, AccessTy.AddrSpace);
1543 
1544  case LSRUse::ICmpZero:
1545  // There's not even a target hook for querying whether it would be legal to
1546  // fold a GV into an ICmp.
1547  if (BaseGV)
1548  return false;
1549 
1550  // ICmp only has two operands; don't allow more than two non-trivial parts.
1551  if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1552  return false;
1553 
1554  // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1555  // putting the scaled register in the other operand of the icmp.
1556  if (Scale != 0 && Scale != -1)
1557  return false;
1558 
1559  // If we have low-level target information, ask the target if it can fold an
1560  // integer immediate on an icmp.
1561  if (BaseOffset != 0) {
1562  // We have one of:
1563  // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1564  // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1565  // Offs is the ICmp immediate.
1566  if (Scale == 0)
1567  // The cast does the right thing with INT64_MIN.
1568  BaseOffset = -(uint64_t)BaseOffset;
1569  return TTI.isLegalICmpImmediate(BaseOffset);
1570  }
1571 
1572  // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1573  return true;
1574 
1575  case LSRUse::Basic:
1576  // Only handle single-register values.
1577  return !BaseGV && Scale == 0 && BaseOffset == 0;
1578 
1579  case LSRUse::Special:
1580  // Special case Basic to handle -1 scales.
1581  return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1582  }
1583 
1584  llvm_unreachable("Invalid LSRUse Kind!");
1585 }
1586 
1588  int64_t MinOffset, int64_t MaxOffset,
1589  LSRUse::KindType Kind, MemAccessTy AccessTy,
1590  GlobalValue *BaseGV, int64_t BaseOffset,
1591  bool HasBaseReg, int64_t Scale) {
1592  // Check for overflow.
1593  if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1594  (MinOffset > 0))
1595  return false;
1596  MinOffset = (uint64_t)BaseOffset + MinOffset;
1597  if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1598  (MaxOffset > 0))
1599  return false;
1600  MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1601 
1602  return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1603  HasBaseReg, Scale) &&
1604  isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1605  HasBaseReg, Scale);
1606 }
1607 
1609  int64_t MinOffset, int64_t MaxOffset,
1610  LSRUse::KindType Kind, MemAccessTy AccessTy,
1611  const Formula &F, const Loop &L) {
1612  // For the purpose of isAMCompletelyFolded either having a canonical formula
1613  // or a scale not equal to zero is correct.
1614  // Problems may arise from non canonical formulae having a scale == 0.
1615  // Strictly speaking it would best to just rely on canonical formulae.
1616  // However, when we generate the scaled formulae, we first check that the
1617  // scaling factor is profitable before computing the actual ScaledReg for
1618  // compile time sake.
1619  assert((F.isCanonical(L) || F.Scale != 0));
1620  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1621  F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1622 }
1623 
1624 /// Test whether we know how to expand the current formula.
1625 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1626  int64_t MaxOffset, LSRUse::KindType Kind,
1627  MemAccessTy AccessTy, GlobalValue *BaseGV,
1628  int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1629  // We know how to expand completely foldable formulae.
1630  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1631  BaseOffset, HasBaseReg, Scale) ||
1632  // Or formulae that use a base register produced by a sum of base
1633  // registers.
1634  (Scale == 1 &&
1635  isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1636  BaseGV, BaseOffset, true, 0));
1637 }
1638 
1639 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1640  int64_t MaxOffset, LSRUse::KindType Kind,
1641  MemAccessTy AccessTy, const Formula &F) {
1642  return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1643  F.BaseOffset, F.HasBaseReg, F.Scale);
1644 }
1645 
1647  const LSRUse &LU, const Formula &F) {
1648  return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1649  LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1650  F.Scale);
1651 }
1652 
1653 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1654  const LSRUse &LU, const Formula &F,
1655  const Loop &L) {
1656  if (!F.Scale)
1657  return 0;
1658 
1659  // If the use is not completely folded in that instruction, we will have to
1660  // pay an extra cost only for scale != 1.
1661  if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1662  LU.AccessTy, F, L))
1663  return F.Scale != 1;
1664 
1665  switch (LU.Kind) {
1666  case LSRUse::Address: {
1667  // Check the scaling factor cost with both the min and max offsets.
1668  int ScaleCostMinOffset = TTI.getScalingFactorCost(
1669  LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1670  F.Scale, LU.AccessTy.AddrSpace);
1671  int ScaleCostMaxOffset = TTI.getScalingFactorCost(
1672  LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1673  F.Scale, LU.AccessTy.AddrSpace);
1674 
1675  assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&
1676  "Legal addressing mode has an illegal cost!");
1677  return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1678  }
1679  case LSRUse::ICmpZero:
1680  case LSRUse::Basic:
1681  case LSRUse::Special:
1682  // The use is completely folded, i.e., everything is folded into the
1683  // instruction.
1684  return 0;
1685  }
1686 
1687  llvm_unreachable("Invalid LSRUse Kind!");
1688 }
1689 
1690 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1691  LSRUse::KindType Kind, MemAccessTy AccessTy,
1692  GlobalValue *BaseGV, int64_t BaseOffset,
1693  bool HasBaseReg) {
1694  // Fast-path: zero is always foldable.
1695  if (BaseOffset == 0 && !BaseGV) return true;
1696 
1697  // Conservatively, create an address with an immediate and a
1698  // base and a scale.
1699  int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1700 
1701  // Canonicalize a scale of 1 to a base register if the formula doesn't
1702  // already have a base register.
1703  if (!HasBaseReg && Scale == 1) {
1704  Scale = 0;
1705  HasBaseReg = true;
1706  }
1707 
1708  return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1709  HasBaseReg, Scale);
1710 }
1711 
1712 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1713  ScalarEvolution &SE, int64_t MinOffset,
1714  int64_t MaxOffset, LSRUse::KindType Kind,
1715  MemAccessTy AccessTy, const SCEV *S,
1716  bool HasBaseReg) {
1717  // Fast-path: zero is always foldable.
1718  if (S->isZero()) return true;
1719 
1720  // Conservatively, create an address with an immediate and a
1721  // base and a scale.
1722  int64_t BaseOffset = ExtractImmediate(S, SE);
1723  GlobalValue *BaseGV = ExtractSymbol(S, SE);
1724 
1725  // If there's anything else involved, it's not foldable.
1726  if (!S->isZero()) return false;
1727 
1728  // Fast-path: zero is always foldable.
1729  if (BaseOffset == 0 && !BaseGV) return true;
1730 
1731  // Conservatively, create an address with an immediate and a
1732  // base and a scale.
1733  int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1734 
1735  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1736  BaseOffset, HasBaseReg, Scale);
1737 }
1738 
1739 namespace {
1740 
1741 /// An individual increment in a Chain of IV increments. Relate an IV user to
1742 /// an expression that computes the IV it uses from the IV used by the previous
1743 /// link in the Chain.
1744 ///
1745 /// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1746 /// original IVOperand. The head of the chain's IVOperand is only valid during
1747 /// chain collection, before LSR replaces IV users. During chain generation,
1748 /// IncExpr can be used to find the new IVOperand that computes the same
1749 /// expression.
1750 struct IVInc {
1751  Instruction *UserInst;
1752  Value* IVOperand;
1753  const SCEV *IncExpr;
1754 
1755  IVInc(Instruction *U, Value *O, const SCEV *E):
1756  UserInst(U), IVOperand(O), IncExpr(E) {}
1757 };
1758 
1759 // The list of IV increments in program order. We typically add the head of a
1760 // chain without finding subsequent links.
1761 struct IVChain {
1762  SmallVector<IVInc,1> Incs;
1763  const SCEV *ExprBase;
1764 
1765  IVChain() : ExprBase(nullptr) {}
1766 
1767  IVChain(const IVInc &Head, const SCEV *Base)
1768  : Incs(1, Head), ExprBase(Base) {}
1769 
1770  typedef SmallVectorImpl<IVInc>::const_iterator const_iterator;
1771 
1772  // Return the first increment in the chain.
1773  const_iterator begin() const {
1774  assert(!Incs.empty());
1775  return std::next(Incs.begin());
1776  }
1777  const_iterator end() const {
1778  return Incs.end();
1779  }
1780 
1781  // Returns true if this chain contains any increments.
1782  bool hasIncs() const { return Incs.size() >= 2; }
1783 
1784  // Add an IVInc to the end of this chain.
1785  void add(const IVInc &X) { Incs.push_back(X); }
1786 
1787  // Returns the last UserInst in the chain.
1788  Instruction *tailUserInst() const { return Incs.back().UserInst; }
1789 
1790  // Returns true if IncExpr can be profitably added to this chain.
1791  bool isProfitableIncrement(const SCEV *OperExpr,
1792  const SCEV *IncExpr,
1793  ScalarEvolution&);
1794 };
1795 
1796 /// Helper for CollectChains to track multiple IV increment uses. Distinguish
1797 /// between FarUsers that definitely cross IV increments and NearUsers that may
1798 /// be used between IV increments.
1799 struct ChainUsers {
1801  SmallPtrSet<Instruction*, 4> NearUsers;
1802 };
1803 
1804 /// This class holds state for the main loop strength reduction logic.
1805 class LSRInstance {
1806  IVUsers &IU;
1807  ScalarEvolution &SE;
1808  DominatorTree &DT;
1809  LoopInfo &LI;
1810  const TargetTransformInfo &TTI;
1811  Loop *const L;
1812  bool Changed;
1813 
1814  /// This is the insert position that the current loop's induction variable
1815  /// increment should be placed. In simple loops, this is the latch block's
1816  /// terminator. But in more complicated cases, this is a position which will
1817  /// dominate all the in-loop post-increment users.
1818  Instruction *IVIncInsertPos;
1819 
1820  /// Interesting factors between use strides.
1821  ///
1822  /// We explicitly use a SetVector which contains a SmallSet, instead of the
1823  /// default, a SmallDenseSet, because we need to use the full range of
1824  /// int64_ts, and there's currently no good way of doing that with
1825  /// SmallDenseSet.
1827 
1828  /// Interesting use types, to facilitate truncation reuse.
1830 
1831  /// The list of interesting uses.
1833 
1834  /// Track which uses use which register candidates.
1835  RegUseTracker RegUses;
1836 
1837  // Limit the number of chains to avoid quadratic behavior. We don't expect to
1838  // have more than a few IV increment chains in a loop. Missing a Chain falls
1839  // back to normal LSR behavior for those uses.
1840  static const unsigned MaxChains = 8;
1841 
1842  /// IV users can form a chain of IV increments.
1844 
1845  /// IV users that belong to profitable IVChains.
1847 
1848  void OptimizeShadowIV();
1849  bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1850  ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1851  void OptimizeLoopTermCond();
1852 
1853  void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1854  SmallVectorImpl<ChainUsers> &ChainUsersVec);
1855  void FinalizeChain(IVChain &Chain);
1856  void CollectChains();
1857  void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1858  SmallVectorImpl<WeakTrackingVH> &DeadInsts);
1859 
1860  void CollectInterestingTypesAndFactors();
1861  void CollectFixupsAndInitialFormulae();
1862 
1863  // Support for sharing of LSRUses between LSRFixups.
1865  UseMapTy UseMap;
1866 
1867  bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1868  LSRUse::KindType Kind, MemAccessTy AccessTy);
1869 
1870  std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
1871  MemAccessTy AccessTy);
1872 
1873  void DeleteUse(LSRUse &LU, size_t LUIdx);
1874 
1875  LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1876 
1877  void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1878  void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1879  void CountRegisters(const Formula &F, size_t LUIdx);
1880  bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1881 
1882  void CollectLoopInvariantFixupsAndFormulae();
1883 
1884  void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1885  unsigned Depth = 0);
1886 
1887  void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1888  const Formula &Base, unsigned Depth,
1889  size_t Idx, bool IsScaledReg = false);
1890  void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1891  void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1892  const Formula &Base, size_t Idx,
1893  bool IsScaledReg = false);
1894  void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1895  void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1896  const Formula &Base,
1897  const SmallVectorImpl<int64_t> &Worklist,
1898  size_t Idx, bool IsScaledReg = false);
1899  void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1900  void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1901  void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1902  void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1903  void GenerateCrossUseConstantOffsets();
1904  void GenerateAllReuseFormulae();
1905 
1906  void FilterOutUndesirableDedicatedRegisters();
1907 
1908  size_t EstimateSearchSpaceComplexity() const;
1909  void NarrowSearchSpaceByDetectingSupersets();
1910  void NarrowSearchSpaceByCollapsingUnrolledCode();
1911  void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1912  void NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
1913  void NarrowSearchSpaceByDeletingCostlyFormulas();
1914  void NarrowSearchSpaceByPickingWinnerRegs();
1915  void NarrowSearchSpaceUsingHeuristics();
1916 
1917  void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1918  Cost &SolutionCost,
1920  const Cost &CurCost,
1921  const SmallPtrSet<const SCEV *, 16> &CurRegs,
1922  DenseSet<const SCEV *> &VisitedRegs) const;
1923  void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1924 
1926  HoistInsertPosition(BasicBlock::iterator IP,
1927  const SmallVectorImpl<Instruction *> &Inputs) const;
1929  AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1930  const LSRFixup &LF,
1931  const LSRUse &LU,
1932  SCEVExpander &Rewriter) const;
1933 
1934  Value *Expand(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
1935  BasicBlock::iterator IP, SCEVExpander &Rewriter,
1936  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
1937  void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
1938  const Formula &F, SCEVExpander &Rewriter,
1939  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
1940  void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
1941  SCEVExpander &Rewriter,
1942  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
1943  void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
1944 
1945 public:
1946  LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
1947  LoopInfo &LI, const TargetTransformInfo &TTI);
1948 
1949  bool getChanged() const { return Changed; }
1950 
1951  void print_factors_and_types(raw_ostream &OS) const;
1952  void print_fixups(raw_ostream &OS) const;
1953  void print_uses(raw_ostream &OS) const;
1954  void print(raw_ostream &OS) const;
1955  void dump() const;
1956 };
1957 
1958 } // end anonymous namespace
1959 
1960 /// If IV is used in a int-to-float cast inside the loop then try to eliminate
1961 /// the cast operation.
1962 void LSRInstance::OptimizeShadowIV() {
1963  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1964  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1965  return;
1966 
1967  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1968  UI != E; /* empty */) {
1969  IVUsers::const_iterator CandidateUI = UI;
1970  ++UI;
1971  Instruction *ShadowUse = CandidateUI->getUser();
1972  Type *DestTy = nullptr;
1973  bool IsSigned = false;
1974 
1975  /* If shadow use is a int->float cast then insert a second IV
1976  to eliminate this cast.
1977 
1978  for (unsigned i = 0; i < n; ++i)
1979  foo((double)i);
1980 
1981  is transformed into
1982 
1983  double d = 0.0;
1984  for (unsigned i = 0; i < n; ++i, ++d)
1985  foo(d);
1986  */
1987  if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
1988  IsSigned = false;
1989  DestTy = UCast->getDestTy();
1990  }
1991  else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
1992  IsSigned = true;
1993  DestTy = SCast->getDestTy();
1994  }
1995  if (!DestTy) continue;
1996 
1997  // If target does not support DestTy natively then do not apply
1998  // this transformation.
1999  if (!TTI.isTypeLegal(DestTy)) continue;
2000 
2001  PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2002  if (!PH) continue;
2003  if (PH->getNumIncomingValues() != 2) continue;
2004 
2005  Type *SrcTy = PH->getType();
2006  int Mantissa = DestTy->getFPMantissaWidth();
2007  if (Mantissa == -1) continue;
2008  if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
2009  continue;
2010 
2011  unsigned Entry, Latch;
2012  if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2013  Entry = 0;
2014  Latch = 1;
2015  } else {
2016  Entry = 1;
2017  Latch = 0;
2018  }
2019 
2021  if (!Init) continue;
2022  Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
2023  (double)Init->getSExtValue() :
2024  (double)Init->getZExtValue());
2025 
2026  BinaryOperator *Incr =
2028  if (!Incr) continue;
2029  if (Incr->getOpcode() != Instruction::Add
2030  && Incr->getOpcode() != Instruction::Sub)
2031  continue;
2032 
2033  /* Initialize new IV, double d = 0.0 in above example. */
2034  ConstantInt *C = nullptr;
2035  if (Incr->getOperand(0) == PH)
2036  C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2037  else if (Incr->getOperand(1) == PH)
2038  C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2039  else
2040  continue;
2041 
2042  if (!C) continue;
2043 
2044  // Ignore negative constants, as the code below doesn't handle them
2045  // correctly. TODO: Remove this restriction.
2046  if (!C->getValue().isStrictlyPositive()) continue;
2047 
2048  /* Add new PHINode. */
2049  PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
2050 
2051  /* create new increment. '++d' in above example. */
2052  Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2053  BinaryOperator *NewIncr =
2054  BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
2055  Instruction::FAdd : Instruction::FSub,
2056  NewPH, CFP, "IV.S.next.", Incr);
2057 
2058  NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2059  NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2060 
2061  /* Remove cast operation */
2062  ShadowUse->replaceAllUsesWith(NewPH);
2063  ShadowUse->eraseFromParent();
2064  Changed = true;
2065  break;
2066  }
2067 }
2068 
2069 /// If Cond has an operand that is an expression of an IV, set the IV user and
2070 /// stride information and return true, otherwise return false.
2071 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
2072  for (IVStrideUse &U : IU)
2073  if (U.getUser() == Cond) {
2074  // NOTE: we could handle setcc instructions with multiple uses here, but
2075  // InstCombine does it as well for simple uses, it's not clear that it
2076  // occurs enough in real life to handle.
2077  CondUse = &U;
2078  return true;
2079  }
2080  return false;
2081 }
2082 
2083 /// Rewrite the loop's terminating condition if it uses a max computation.
2084 ///
2085 /// This is a narrow solution to a specific, but acute, problem. For loops
2086 /// like this:
2087 ///
2088 /// i = 0;
2089 /// do {
2090 /// p[i] = 0.0;
2091 /// } while (++i < n);
2092 ///
2093 /// the trip count isn't just 'n', because 'n' might not be positive. And
2094 /// unfortunately this can come up even for loops where the user didn't use
2095 /// a C do-while loop. For example, seemingly well-behaved top-test loops
2096 /// will commonly be lowered like this:
2097 //
2098 /// if (n > 0) {
2099 /// i = 0;
2100 /// do {
2101 /// p[i] = 0.0;
2102 /// } while (++i < n);
2103 /// }
2104 ///
2105 /// and then it's possible for subsequent optimization to obscure the if
2106 /// test in such a way that indvars can't find it.
2107 ///
2108 /// When indvars can't find the if test in loops like this, it creates a
2109 /// max expression, which allows it to give the loop a canonical
2110 /// induction variable:
2111 ///
2112 /// i = 0;
2113 /// max = n < 1 ? 1 : n;
2114 /// do {
2115 /// p[i] = 0.0;
2116 /// } while (++i != max);
2117 ///
2118 /// Canonical induction variables are necessary because the loop passes
2119 /// are designed around them. The most obvious example of this is the
2120 /// LoopInfo analysis, which doesn't remember trip count values. It
2121 /// expects to be able to rediscover the trip count each time it is
2122 /// needed, and it does this using a simple analysis that only succeeds if
2123 /// the loop has a canonical induction variable.
2124 ///
2125 /// However, when it comes time to generate code, the maximum operation
2126 /// can be quite costly, especially if it's inside of an outer loop.
2127 ///
2128 /// This function solves this problem by detecting this type of loop and
2129 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2130 /// the instructions for the maximum computation.
2131 ///
2132 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
2133  // Check that the loop matches the pattern we're looking for.
2134  if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2135  Cond->getPredicate() != CmpInst::ICMP_NE)
2136  return Cond;
2137 
2138  SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2139  if (!Sel || !Sel->hasOneUse()) return Cond;
2140 
2141  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2142  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2143  return Cond;
2144  const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2145 
2146  // Add one to the backedge-taken count to get the trip count.
2147  const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2148  if (IterationCount != SE.getSCEV(Sel)) return Cond;
2149 
2150  // Check for a max calculation that matches the pattern. There's no check
2151  // for ICMP_ULE here because the comparison would be with zero, which
2152  // isn't interesting.
2154  const SCEVNAryExpr *Max = nullptr;
2155  if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2156  Pred = ICmpInst::ICMP_SLE;
2157  Max = S;
2158  } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2159  Pred = ICmpInst::ICMP_SLT;
2160  Max = S;
2161  } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2162  Pred = ICmpInst::ICMP_ULT;
2163  Max = U;
2164  } else {
2165  // No match; bail.
2166  return Cond;
2167  }
2168 
2169  // To handle a max with more than two operands, this optimization would
2170  // require additional checking and setup.
2171  if (Max->getNumOperands() != 2)
2172  return Cond;
2173 
2174  const SCEV *MaxLHS = Max->getOperand(0);
2175  const SCEV *MaxRHS = Max->getOperand(1);
2176 
2177  // ScalarEvolution canonicalizes constants to the left. For < and >, look
2178  // for a comparison with 1. For <= and >=, a comparison with zero.
2179  if (!MaxLHS ||
2180  (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2181  return Cond;
2182 
2183  // Check the relevant induction variable for conformance to
2184  // the pattern.
2185  const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2186  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2187  if (!AR || !AR->isAffine() ||
2188  AR->getStart() != One ||
2189  AR->getStepRecurrence(SE) != One)
2190  return Cond;
2191 
2192  assert(AR->getLoop() == L &&
2193  "Loop condition operand is an addrec in a different loop!");
2194 
2195  // Check the right operand of the select, and remember it, as it will
2196  // be used in the new comparison instruction.
2197  Value *NewRHS = nullptr;
2198  if (ICmpInst::isTrueWhenEqual(Pred)) {
2199  // Look for n+1, and grab n.
2200  if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2201  if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2202  if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2203  NewRHS = BO->getOperand(0);
2204  if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2205  if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2206  if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2207  NewRHS = BO->getOperand(0);
2208  if (!NewRHS)
2209  return Cond;
2210  } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2211  NewRHS = Sel->getOperand(1);
2212  else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2213  NewRHS = Sel->getOperand(2);
2214  else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2215  NewRHS = SU->getValue();
2216  else
2217  // Max doesn't match expected pattern.
2218  return Cond;
2219 
2220  // Determine the new comparison opcode. It may be signed or unsigned,
2221  // and the original comparison may be either equality or inequality.
2222  if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2223  Pred = CmpInst::getInversePredicate(Pred);
2224 
2225  // Ok, everything looks ok to change the condition into an SLT or SGE and
2226  // delete the max calculation.
2227  ICmpInst *NewCond =
2228  new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2229 
2230  // Delete the max calculation instructions.
2231  Cond->replaceAllUsesWith(NewCond);
2232  CondUse->setUser(NewCond);
2233  Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2234  Cond->eraseFromParent();
2235  Sel->eraseFromParent();
2236  if (Cmp->use_empty())
2237  Cmp->eraseFromParent();
2238  return NewCond;
2239 }
2240 
2241 /// Change loop terminating condition to use the postinc iv when possible.
2242 void
2243 LSRInstance::OptimizeLoopTermCond() {
2245 
2246  // We need a different set of heuristics for rotated and non-rotated loops.
2247  // If a loop is rotated then the latch is also the backedge, so inserting
2248  // post-inc expressions just before the latch is ideal. To reduce live ranges
2249  // it also makes sense to rewrite terminating conditions to use post-inc
2250  // expressions.
2251  //
2252  // If the loop is not rotated then the latch is not a backedge; the latch
2253  // check is done in the loop head. Adding post-inc expressions before the
2254  // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2255  // in the loop body. In this case we do *not* want to use post-inc expressions
2256  // in the latch check, and we want to insert post-inc expressions before
2257  // the backedge.
2258  BasicBlock *LatchBlock = L->getLoopLatch();
2259  SmallVector<BasicBlock*, 8> ExitingBlocks;
2260  L->getExitingBlocks(ExitingBlocks);
2261  if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2262  return LatchBlock != BB;
2263  })) {
2264  // The backedge doesn't exit the loop; treat this as a head-tested loop.
2265  IVIncInsertPos = LatchBlock->getTerminator();
2266  return;
2267  }
2268 
2269  // Otherwise treat this as a rotated loop.
2270  for (BasicBlock *ExitingBlock : ExitingBlocks) {
2271 
2272  // Get the terminating condition for the loop if possible. If we
2273  // can, we want to change it to use a post-incremented version of its
2274  // induction variable, to allow coalescing the live ranges for the IV into
2275  // one register value.
2276 
2277  BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2278  if (!TermBr)
2279  continue;
2280  // FIXME: Overly conservative, termination condition could be an 'or' etc..
2281  if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2282  continue;
2283 
2284  // Search IVUsesByStride to find Cond's IVUse if there is one.
2285  IVStrideUse *CondUse = nullptr;
2286  ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2287  if (!FindIVUserForCond(Cond, CondUse))
2288  continue;
2289 
2290  // If the trip count is computed in terms of a max (due to ScalarEvolution
2291  // being unable to find a sufficient guard, for example), change the loop
2292  // comparison to use SLT or ULT instead of NE.
2293  // One consequence of doing this now is that it disrupts the count-down
2294  // optimization. That's not always a bad thing though, because in such
2295  // cases it may still be worthwhile to avoid a max.
2296  Cond = OptimizeMax(Cond, CondUse);
2297 
2298  // If this exiting block dominates the latch block, it may also use
2299  // the post-inc value if it won't be shared with other uses.
2300  // Check for dominance.
2301  if (!DT.dominates(ExitingBlock, LatchBlock))
2302  continue;
2303 
2304  // Conservatively avoid trying to use the post-inc value in non-latch
2305  // exits if there may be pre-inc users in intervening blocks.
2306  if (LatchBlock != ExitingBlock)
2307  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2308  // Test if the use is reachable from the exiting block. This dominator
2309  // query is a conservative approximation of reachability.
2310  if (&*UI != CondUse &&
2311  !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2312  // Conservatively assume there may be reuse if the quotient of their
2313  // strides could be a legal scale.
2314  const SCEV *A = IU.getStride(*CondUse, L);
2315  const SCEV *B = IU.getStride(*UI, L);
2316  if (!A || !B) continue;
2317  if (SE.getTypeSizeInBits(A->getType()) !=
2318  SE.getTypeSizeInBits(B->getType())) {
2319  if (SE.getTypeSizeInBits(A->getType()) >
2320  SE.getTypeSizeInBits(B->getType()))
2321  B = SE.getSignExtendExpr(B, A->getType());
2322  else
2323  A = SE.getSignExtendExpr(A, B->getType());
2324  }
2325  if (const SCEVConstant *D =
2326  dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2327  const ConstantInt *C = D->getValue();
2328  // Stride of one or negative one can have reuse with non-addresses.
2329  if (C->isOne() || C->isMinusOne())
2330  goto decline_post_inc;
2331  // Avoid weird situations.
2332  if (C->getValue().getMinSignedBits() >= 64 ||
2333  C->getValue().isMinSignedValue())
2334  goto decline_post_inc;
2335  // Check for possible scaled-address reuse.
2336  MemAccessTy AccessTy = getAccessType(UI->getUser());
2337  int64_t Scale = C->getSExtValue();
2338  if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2339  /*BaseOffset=*/0,
2340  /*HasBaseReg=*/false, Scale,
2341  AccessTy.AddrSpace))
2342  goto decline_post_inc;
2343  Scale = -Scale;
2344  if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2345  /*BaseOffset=*/0,
2346  /*HasBaseReg=*/false, Scale,
2347  AccessTy.AddrSpace))
2348  goto decline_post_inc;
2349  }
2350  }
2351 
2352  DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
2353  << *Cond << '\n');
2354 
2355  // It's possible for the setcc instruction to be anywhere in the loop, and
2356  // possible for it to have multiple users. If it is not immediately before
2357  // the exiting block branch, move it.
2358  if (&*++BasicBlock::iterator(Cond) != TermBr) {
2359  if (Cond->hasOneUse()) {
2360  Cond->moveBefore(TermBr);
2361  } else {
2362  // Clone the terminating condition and insert into the loopend.
2363  ICmpInst *OldCond = Cond;
2364  Cond = cast<ICmpInst>(Cond->clone());
2365  Cond->setName(L->getHeader()->getName() + ".termcond");
2366  ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2367 
2368  // Clone the IVUse, as the old use still exists!
2369  CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2370  TermBr->replaceUsesOfWith(OldCond, Cond);
2371  }
2372  }
2373 
2374  // If we get to here, we know that we can transform the setcc instruction to
2375  // use the post-incremented version of the IV, allowing us to coalesce the
2376  // live ranges for the IV correctly.
2377  CondUse->transformToPostInc(L);
2378  Changed = true;
2379 
2380  PostIncs.insert(Cond);
2381  decline_post_inc:;
2382  }
2383 
2384  // Determine an insertion point for the loop induction variable increment. It
2385  // must dominate all the post-inc comparisons we just set up, and it must
2386  // dominate the loop latch edge.
2387  IVIncInsertPos = L->getLoopLatch()->getTerminator();
2388  for (Instruction *Inst : PostIncs) {
2389  BasicBlock *BB =
2390  DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2391  Inst->getParent());
2392  if (BB == Inst->getParent())
2393  IVIncInsertPos = Inst;
2394  else if (BB != IVIncInsertPos->getParent())
2395  IVIncInsertPos = BB->getTerminator();
2396  }
2397 }
2398 
2399 /// Determine if the given use can accommodate a fixup at the given offset and
2400 /// other details. If so, update the use and return true.
2401 bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2402  bool HasBaseReg, LSRUse::KindType Kind,
2403  MemAccessTy AccessTy) {
2404  int64_t NewMinOffset = LU.MinOffset;
2405  int64_t NewMaxOffset = LU.MaxOffset;
2406  MemAccessTy NewAccessTy = AccessTy;
2407 
2408  // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2409  // something conservative, however this can pessimize in the case that one of
2410  // the uses will have all its uses outside the loop, for example.
2411  if (LU.Kind != Kind)
2412  return false;
2413 
2414  // Check for a mismatched access type, and fall back conservatively as needed.
2415  // TODO: Be less conservative when the type is similar and can use the same
2416  // addressing modes.
2417  if (Kind == LSRUse::Address) {
2418  if (AccessTy.MemTy != LU.AccessTy.MemTy) {
2419  NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(),
2420  AccessTy.AddrSpace);
2421  }
2422  }
2423 
2424  // Conservatively assume HasBaseReg is true for now.
2425  if (NewOffset < LU.MinOffset) {
2426  if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2427  LU.MaxOffset - NewOffset, HasBaseReg))
2428  return false;
2429  NewMinOffset = NewOffset;
2430  } else if (NewOffset > LU.MaxOffset) {
2431  if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2432  NewOffset - LU.MinOffset, HasBaseReg))
2433  return false;
2434  NewMaxOffset = NewOffset;
2435  }
2436 
2437  // Update the use.
2438  LU.MinOffset = NewMinOffset;
2439  LU.MaxOffset = NewMaxOffset;
2440  LU.AccessTy = NewAccessTy;
2441  return true;
2442 }
2443 
2444 /// Return an LSRUse index and an offset value for a fixup which needs the given
2445 /// expression, with the given kind and optional access type. Either reuse an
2446 /// existing use or create a new one, as needed.
2447 std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2448  LSRUse::KindType Kind,
2449  MemAccessTy AccessTy) {
2450  const SCEV *Copy = Expr;
2451  int64_t Offset = ExtractImmediate(Expr, SE);
2452 
2453  // Basic uses can't accept any offset, for example.
2454  if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2455  Offset, /*HasBaseReg=*/ true)) {
2456  Expr = Copy;
2457  Offset = 0;
2458  }
2459 
2460  std::pair<UseMapTy::iterator, bool> P =
2461  UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2462  if (!P.second) {
2463  // A use already existed with this base.
2464  size_t LUIdx = P.first->second;
2465  LSRUse &LU = Uses[LUIdx];
2466  if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2467  // Reuse this use.
2468  return std::make_pair(LUIdx, Offset);
2469  }
2470 
2471  // Create a new use.
2472  size_t LUIdx = Uses.size();
2473  P.first->second = LUIdx;
2474  Uses.push_back(LSRUse(Kind, AccessTy));
2475  LSRUse &LU = Uses[LUIdx];
2476 
2477  LU.MinOffset = Offset;
2478  LU.MaxOffset = Offset;
2479  return std::make_pair(LUIdx, Offset);
2480 }
2481 
2482 /// Delete the given use from the Uses list.
2483 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2484  if (&LU != &Uses.back())
2485  std::swap(LU, Uses.back());
2486  Uses.pop_back();
2487 
2488  // Update RegUses.
2489  RegUses.swapAndDropUse(LUIdx, Uses.size());
2490 }
2491 
2492 /// Look for a use distinct from OrigLU which is has a formula that has the same
2493 /// registers as the given formula.
2494 LSRUse *
2495 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2496  const LSRUse &OrigLU) {
2497  // Search all uses for the formula. This could be more clever.
2498  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2499  LSRUse &LU = Uses[LUIdx];
2500  // Check whether this use is close enough to OrigLU, to see whether it's
2501  // worthwhile looking through its formulae.
2502  // Ignore ICmpZero uses because they may contain formulae generated by
2503  // GenerateICmpZeroScales, in which case adding fixup offsets may
2504  // be invalid.
2505  if (&LU != &OrigLU &&
2506  LU.Kind != LSRUse::ICmpZero &&
2507  LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2508  LU.WidestFixupType == OrigLU.WidestFixupType &&
2509  LU.HasFormulaWithSameRegs(OrigF)) {
2510  // Scan through this use's formulae.
2511  for (const Formula &F : LU.Formulae) {
2512  // Check to see if this formula has the same registers and symbols
2513  // as OrigF.
2514  if (F.BaseRegs == OrigF.BaseRegs &&
2515  F.ScaledReg == OrigF.ScaledReg &&
2516  F.BaseGV == OrigF.BaseGV &&
2517  F.Scale == OrigF.Scale &&
2518  F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2519  if (F.BaseOffset == 0)
2520  return &LU;
2521  // This is the formula where all the registers and symbols matched;
2522  // there aren't going to be any others. Since we declined it, we
2523  // can skip the rest of the formulae and proceed to the next LSRUse.
2524  break;
2525  }
2526  }
2527  }
2528  }
2529 
2530  // Nothing looked good.
2531  return nullptr;
2532 }
2533 
2534 void LSRInstance::CollectInterestingTypesAndFactors() {
2536 
2537  // Collect interesting types and strides.
2539  for (const IVStrideUse &U : IU) {
2540  const SCEV *Expr = IU.getExpr(U);
2541 
2542  // Collect interesting types.
2543  Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2544 
2545  // Add strides for mentioned loops.
2546  Worklist.push_back(Expr);
2547  do {
2548  const SCEV *S = Worklist.pop_back_val();
2549  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2550  if (AR->getLoop() == L)
2551  Strides.insert(AR->getStepRecurrence(SE));
2552  Worklist.push_back(AR->getStart());
2553  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2554  Worklist.append(Add->op_begin(), Add->op_end());
2555  }
2556  } while (!Worklist.empty());
2557  }
2558 
2559  // Compute interesting factors from the set of interesting strides.
2561  I = Strides.begin(), E = Strides.end(); I != E; ++I)
2563  std::next(I); NewStrideIter != E; ++NewStrideIter) {
2564  const SCEV *OldStride = *I;
2565  const SCEV *NewStride = *NewStrideIter;
2566 
2567  if (SE.getTypeSizeInBits(OldStride->getType()) !=
2568  SE.getTypeSizeInBits(NewStride->getType())) {
2569  if (SE.getTypeSizeInBits(OldStride->getType()) >
2570  SE.getTypeSizeInBits(NewStride->getType()))
2571  NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2572  else
2573  OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2574  }
2575  if (const SCEVConstant *Factor =
2576  dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2577  SE, true))) {
2578  if (Factor->getAPInt().getMinSignedBits() <= 64)
2579  Factors.insert(Factor->getAPInt().getSExtValue());
2580  } else if (const SCEVConstant *Factor =
2581  dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2582  NewStride,
2583  SE, true))) {
2584  if (Factor->getAPInt().getMinSignedBits() <= 64)
2585  Factors.insert(Factor->getAPInt().getSExtValue());
2586  }
2587  }
2588 
2589  // If all uses use the same type, don't bother looking for truncation-based
2590  // reuse.
2591  if (Types.size() == 1)
2592  Types.clear();
2593 
2594  DEBUG(print_factors_and_types(dbgs()));
2595 }
2596 
2597 /// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2598 /// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2599 /// IVStrideUses, we could partially skip this.
2600 static User::op_iterator
2602  Loop *L, ScalarEvolution &SE) {
2603  for(; OI != OE; ++OI) {
2604  if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2605  if (!SE.isSCEVable(Oper->getType()))
2606  continue;
2607 
2608  if (const SCEVAddRecExpr *AR =
2609  dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2610  if (AR->getLoop() == L)
2611  break;
2612  }
2613  }
2614  }
2615  return OI;
2616 }
2617 
2618 /// IVChain logic must consistenctly peek base TruncInst operands, so wrap it in
2619 /// a convenient helper.
2620 static Value *getWideOperand(Value *Oper) {
2621  if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2622  return Trunc->getOperand(0);
2623  return Oper;
2624 }
2625 
2626 /// Return true if we allow an IV chain to include both types.
2627 static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2628  Type *LType = LVal->getType();
2629  Type *RType = RVal->getType();
2630  return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy() &&
2631  // Different address spaces means (possibly)
2632  // different types of the pointer implementation,
2633  // e.g. i16 vs i32 so disallow that.
2634  (LType->getPointerAddressSpace() ==
2635  RType->getPointerAddressSpace()));
2636 }
2637 
2638 /// Return an approximation of this SCEV expression's "base", or NULL for any
2639 /// constant. Returning the expression itself is conservative. Returning a
2640 /// deeper subexpression is more precise and valid as long as it isn't less
2641 /// complex than another subexpression. For expressions involving multiple
2642 /// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2643 /// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2644 /// IVInc==b-a.
2645 ///
2646 /// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2647 /// SCEVUnknown, we simply return the rightmost SCEV operand.
2648 static const SCEV *getExprBase(const SCEV *S) {
2649  switch (S->getSCEVType()) {
2650  default: // uncluding scUnknown.
2651  return S;
2652  case scConstant:
2653  return nullptr;
2654  case scTruncate:
2655  return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2656  case scZeroExtend:
2657  return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2658  case scSignExtend:
2659  return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2660  case scAddExpr: {
2661  // Skip over scaled operands (scMulExpr) to follow add operands as long as
2662  // there's nothing more complex.
2663  // FIXME: not sure if we want to recognize negation.
2664  const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2665  for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2666  E(Add->op_begin()); I != E; ++I) {
2667  const SCEV *SubExpr = *I;
2668  if (SubExpr->getSCEVType() == scAddExpr)
2669  return getExprBase(SubExpr);
2670 
2671  if (SubExpr->getSCEVType() != scMulExpr)
2672  return SubExpr;
2673  }
2674  return S; // all operands are scaled, be conservative.
2675  }
2676  case scAddRecExpr:
2677  return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2678  }
2679 }
2680 
2681 /// Return true if the chain increment is profitable to expand into a loop
2682 /// invariant value, which may require its own register. A profitable chain
2683 /// increment will be an offset relative to the same base. We allow such offsets
2684 /// to potentially be used as chain increment as long as it's not obviously
2685 /// expensive to expand using real instructions.
2686 bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2687  const SCEV *IncExpr,
2688  ScalarEvolution &SE) {
2689  // Aggressively form chains when -stress-ivchain.
2690  if (StressIVChain)
2691  return true;
2692 
2693  // Do not replace a constant offset from IV head with a nonconstant IV
2694  // increment.
2695  if (!isa<SCEVConstant>(IncExpr)) {
2696  const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2697  if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2698  return false;
2699  }
2700 
2701  SmallPtrSet<const SCEV*, 8> Processed;
2702  return !isHighCostExpansion(IncExpr, Processed, SE);
2703 }
2704 
2705 /// Return true if the number of registers needed for the chain is estimated to
2706 /// be less than the number required for the individual IV users. First prohibit
2707 /// any IV users that keep the IV live across increments (the Users set should
2708 /// be empty). Next count the number and type of increments in the chain.
2709 ///
2710 /// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2711 /// effectively use postinc addressing modes. Only consider it profitable it the
2712 /// increments can be computed in fewer registers when chained.
2713 ///
2714 /// TODO: Consider IVInc free if it's already used in another chains.
2715 static bool
2717  ScalarEvolution &SE, const TargetTransformInfo &TTI) {
2718  if (StressIVChain)
2719  return true;
2720 
2721  if (!Chain.hasIncs())
2722  return false;
2723 
2724  if (!Users.empty()) {
2725  DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";
2726  for (Instruction *Inst : Users) {
2727  dbgs() << " " << *Inst << "\n";
2728  });
2729  return false;
2730  }
2731  assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2732 
2733  // The chain itself may require a register, so intialize cost to 1.
2734  int cost = 1;
2735 
2736  // A complete chain likely eliminates the need for keeping the original IV in
2737  // a register. LSR does not currently know how to form a complete chain unless
2738  // the header phi already exists.
2739  if (isa<PHINode>(Chain.tailUserInst())
2740  && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2741  --cost;
2742  }
2743  const SCEV *LastIncExpr = nullptr;
2744  unsigned NumConstIncrements = 0;
2745  unsigned NumVarIncrements = 0;
2746  unsigned NumReusedIncrements = 0;
2747  for (const IVInc &Inc : Chain) {
2748  if (Inc.IncExpr->isZero())
2749  continue;
2750 
2751  // Incrementing by zero or some constant is neutral. We assume constants can
2752  // be folded into an addressing mode or an add's immediate operand.
2753  if (isa<SCEVConstant>(Inc.IncExpr)) {
2754  ++NumConstIncrements;
2755  continue;
2756  }
2757 
2758  if (Inc.IncExpr == LastIncExpr)
2759  ++NumReusedIncrements;
2760  else
2761  ++NumVarIncrements;
2762 
2763  LastIncExpr = Inc.IncExpr;
2764  }
2765  // An IV chain with a single increment is handled by LSR's postinc
2766  // uses. However, a chain with multiple increments requires keeping the IV's
2767  // value live longer than it needs to be if chained.
2768  if (NumConstIncrements > 1)
2769  --cost;
2770 
2771  // Materializing increment expressions in the preheader that didn't exist in
2772  // the original code may cost a register. For example, sign-extended array
2773  // indices can produce ridiculous increments like this:
2774  // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2775  cost += NumVarIncrements;
2776 
2777  // Reusing variable increments likely saves a register to hold the multiple of
2778  // the stride.
2779  cost -= NumReusedIncrements;
2780 
2781  DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost
2782  << "\n");
2783 
2784  return cost < 0;
2785 }
2786 
2787 /// Add this IV user to an existing chain or make it the head of a new chain.
2788 void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2789  SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2790  // When IVs are used as types of varying widths, they are generally converted
2791  // to a wider type with some uses remaining narrow under a (free) trunc.
2792  Value *const NextIV = getWideOperand(IVOper);
2793  const SCEV *const OperExpr = SE.getSCEV(NextIV);
2794  const SCEV *const OperExprBase = getExprBase(OperExpr);
2795 
2796  // Visit all existing chains. Check if its IVOper can be computed as a
2797  // profitable loop invariant increment from the last link in the Chain.
2798  unsigned ChainIdx = 0, NChains = IVChainVec.size();
2799  const SCEV *LastIncExpr = nullptr;
2800  for (; ChainIdx < NChains; ++ChainIdx) {
2801  IVChain &Chain = IVChainVec[ChainIdx];
2802 
2803  // Prune the solution space aggressively by checking that both IV operands
2804  // are expressions that operate on the same unscaled SCEVUnknown. This
2805  // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2806  // first avoids creating extra SCEV expressions.
2807  if (!StressIVChain && Chain.ExprBase != OperExprBase)
2808  continue;
2809 
2810  Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2811  if (!isCompatibleIVType(PrevIV, NextIV))
2812  continue;
2813 
2814  // A phi node terminates a chain.
2815  if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2816  continue;
2817 
2818  // The increment must be loop-invariant so it can be kept in a register.
2819  const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2820  const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2821  if (!SE.isLoopInvariant(IncExpr, L))
2822  continue;
2823 
2824  if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2825  LastIncExpr = IncExpr;
2826  break;
2827  }
2828  }
2829  // If we haven't found a chain, create a new one, unless we hit the max. Don't
2830  // bother for phi nodes, because they must be last in the chain.
2831  if (ChainIdx == NChains) {
2832  if (isa<PHINode>(UserInst))
2833  return;
2834  if (NChains >= MaxChains && !StressIVChain) {
2835  DEBUG(dbgs() << "IV Chain Limit\n");
2836  return;
2837  }
2838  LastIncExpr = OperExpr;
2839  // IVUsers may have skipped over sign/zero extensions. We don't currently
2840  // attempt to form chains involving extensions unless they can be hoisted
2841  // into this loop's AddRec.
2842  if (!isa<SCEVAddRecExpr>(LastIncExpr))
2843  return;
2844  ++NChains;
2845  IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2846  OperExprBase));
2847  ChainUsersVec.resize(NChains);
2848  DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst
2849  << ") IV=" << *LastIncExpr << "\n");
2850  } else {
2851  DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst
2852  << ") IV+" << *LastIncExpr << "\n");
2853  // Add this IV user to the end of the chain.
2854  IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2855  }
2856  IVChain &Chain = IVChainVec[ChainIdx];
2857 
2858  SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2859  // This chain's NearUsers become FarUsers.
2860  if (!LastIncExpr->isZero()) {
2861  ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2862  NearUsers.end());
2863  NearUsers.clear();
2864  }
2865 
2866  // All other uses of IVOperand become near uses of the chain.
2867  // We currently ignore intermediate values within SCEV expressions, assuming
2868  // they will eventually be used be the current chain, or can be computed
2869  // from one of the chain increments. To be more precise we could
2870  // transitively follow its user and only add leaf IV users to the set.
2871  for (User *U : IVOper->users()) {
2872  Instruction *OtherUse = dyn_cast<Instruction>(U);
2873  if (!OtherUse)
2874  continue;
2875  // Uses in the chain will no longer be uses if the chain is formed.
2876  // Include the head of the chain in this iteration (not Chain.begin()).
2877  IVChain::const_iterator IncIter = Chain.Incs.begin();
2878  IVChain::const_iterator IncEnd = Chain.Incs.end();
2879  for( ; IncIter != IncEnd; ++IncIter) {
2880  if (IncIter->UserInst == OtherUse)
2881  break;
2882  }
2883  if (IncIter != IncEnd)
2884  continue;
2885 
2886  if (SE.isSCEVable(OtherUse->getType())
2887  && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2888  && IU.isIVUserOrOperand(OtherUse)) {
2889  continue;
2890  }
2891  NearUsers.insert(OtherUse);
2892  }
2893 
2894  // Since this user is part of the chain, it's no longer considered a use
2895  // of the chain.
2896  ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2897 }
2898 
2899 /// Populate the vector of Chains.
2900 ///
2901 /// This decreases ILP at the architecture level. Targets with ample registers,
2902 /// multiple memory ports, and no register renaming probably don't want
2903 /// this. However, such targets should probably disable LSR altogether.
2904 ///
2905 /// The job of LSR is to make a reasonable choice of induction variables across
2906 /// the loop. Subsequent passes can easily "unchain" computation exposing more
2907 /// ILP *within the loop* if the target wants it.
2908 ///
2909 /// Finding the best IV chain is potentially a scheduling problem. Since LSR
2910 /// will not reorder memory operations, it will recognize this as a chain, but
2911 /// will generate redundant IV increments. Ideally this would be corrected later
2912 /// by a smart scheduler:
2913 /// = A[i]
2914 /// = A[i+x]
2915 /// A[i] =
2916 /// A[i+x] =
2917 ///
2918 /// TODO: Walk the entire domtree within this loop, not just the path to the
2919 /// loop latch. This will discover chains on side paths, but requires
2920 /// maintaining multiple copies of the Chains state.
2921 void LSRInstance::CollectChains() {
2922  DEBUG(dbgs() << "Collecting IV Chains.\n");
2923  SmallVector<ChainUsers, 8> ChainUsersVec;
2924 
2925  SmallVector<BasicBlock *,8> LatchPath;
2926  BasicBlock *LoopHeader = L->getHeader();
2927  for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
2928  Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
2929  LatchPath.push_back(Rung->getBlock());
2930  }
2931  LatchPath.push_back(LoopHeader);
2932 
2933  // Walk the instruction stream from the loop header to the loop latch.
2934  for (BasicBlock *BB : reverse(LatchPath)) {
2935  for (Instruction &I : *BB) {
2936  // Skip instructions that weren't seen by IVUsers analysis.
2937  if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
2938  continue;
2939 
2940  // Ignore users that are part of a SCEV expression. This way we only
2941  // consider leaf IV Users. This effectively rediscovers a portion of
2942  // IVUsers analysis but in program order this time.
2943  if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
2944  continue;
2945 
2946  // Remove this instruction from any NearUsers set it may be in.
2947  for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
2948  ChainIdx < NChains; ++ChainIdx) {
2949  ChainUsersVec[ChainIdx].NearUsers.erase(&I);
2950  }
2951  // Search for operands that can be chained.
2952  SmallPtrSet<Instruction*, 4> UniqueOperands;
2953  User::op_iterator IVOpEnd = I.op_end();
2954  User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
2955  while (IVOpIter != IVOpEnd) {
2956  Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
2957  if (UniqueOperands.insert(IVOpInst).second)
2958  ChainInstruction(&I, IVOpInst, ChainUsersVec);
2959  IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
2960  }
2961  } // Continue walking down the instructions.
2962  } // Continue walking down the domtree.
2963  // Visit phi backedges to determine if the chain can generate the IV postinc.
2964  for (BasicBlock::iterator I = L->getHeader()->begin();
2965  PHINode *PN = dyn_cast<PHINode>(I); ++I) {
2966  if (!SE.isSCEVable(PN->getType()))
2967  continue;
2968 
2969  Instruction *IncV =
2971  if (IncV)
2972  ChainInstruction(PN, IncV, ChainUsersVec);
2973  }
2974  // Remove any unprofitable chains.
2975  unsigned ChainIdx = 0;
2976  for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
2977  UsersIdx < NChains; ++UsersIdx) {
2978  if (!isProfitableChain(IVChainVec[UsersIdx],
2979  ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
2980  continue;
2981  // Preserve the chain at UsesIdx.
2982  if (ChainIdx != UsersIdx)
2983  IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
2984  FinalizeChain(IVChainVec[ChainIdx]);
2985  ++ChainIdx;
2986  }
2987  IVChainVec.resize(ChainIdx);
2988 }
2989 
2990 void LSRInstance::FinalizeChain(IVChain &Chain) {
2991  assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2992  DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n");
2993 
2994  for (const IVInc &Inc : Chain) {
2995  DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n");
2996  auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
2997  assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand");
2998  IVIncSet.insert(UseI);
2999  }
3000 }
3001 
3002 /// Return true if the IVInc can be folded into an addressing mode.
3003 static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
3004  Value *Operand, const TargetTransformInfo &TTI) {
3005  const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
3006  if (!IncConst || !isAddressUse(UserInst, Operand))
3007  return false;
3008 
3009  if (IncConst->getAPInt().getMinSignedBits() > 64)
3010  return false;
3011 
3012  MemAccessTy AccessTy = getAccessType(UserInst);
3013  int64_t IncOffset = IncConst->getValue()->getSExtValue();
3014  if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
3015  IncOffset, /*HaseBaseReg=*/false))
3016  return false;
3017 
3018  return true;
3019 }
3020 
3021 /// Generate an add or subtract for each IVInc in a chain to materialize the IV
3022 /// user's operand from the previous IV user's operand.
3023 void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
3024  SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
3025  // Find the new IVOperand for the head of the chain. It may have been replaced
3026  // by LSR.
3027  const IVInc &Head = Chain.Incs[0];
3028  User::op_iterator IVOpEnd = Head.UserInst->op_end();
3029  // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
3030  User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
3031  IVOpEnd, L, SE);
3032  Value *IVSrc = nullptr;
3033  while (IVOpIter != IVOpEnd) {
3034  IVSrc = getWideOperand(*IVOpIter);
3035 
3036  // If this operand computes the expression that the chain needs, we may use
3037  // it. (Check this after setting IVSrc which is used below.)
3038  //
3039  // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
3040  // narrow for the chain, so we can no longer use it. We do allow using a
3041  // wider phi, assuming the LSR checked for free truncation. In that case we
3042  // should already have a truncate on this operand such that
3043  // getSCEV(IVSrc) == IncExpr.
3044  if (SE.getSCEV(*IVOpIter) == Head.IncExpr
3045  || SE.getSCEV(IVSrc) == Head.IncExpr) {
3046  break;
3047  }
3048  IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3049  }
3050  if (IVOpIter == IVOpEnd) {
3051  // Gracefully give up on this chain.
3052  DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
3053  return;
3054  }
3055 
3056  DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
3057  Type *IVTy = IVSrc->getType();
3058  Type *IntTy = SE.getEffectiveSCEVType(IVTy);
3059  const SCEV *LeftOverExpr = nullptr;
3060  for (const IVInc &Inc : Chain) {
3061  Instruction *InsertPt = Inc.UserInst;
3062  if (isa<PHINode>(InsertPt))
3063  InsertPt = L->getLoopLatch()->getTerminator();
3064 
3065  // IVOper will replace the current IV User's operand. IVSrc is the IV
3066  // value currently held in a register.
3067  Value *IVOper = IVSrc;
3068  if (!Inc.IncExpr->isZero()) {
3069  // IncExpr was the result of subtraction of two narrow values, so must
3070  // be signed.
3071  const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
3072  LeftOverExpr = LeftOverExpr ?
3073  SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
3074  }
3075  if (LeftOverExpr && !LeftOverExpr->isZero()) {
3076  // Expand the IV increment.
3077  Rewriter.clearPostInc();
3078  Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
3079  const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
3080  SE.getUnknown(IncV));
3081  IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
3082 
3083  // If an IV increment can't be folded, use it as the next IV value.
3084  if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
3085  assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
3086  IVSrc = IVOper;
3087  LeftOverExpr = nullptr;
3088  }
3089  }
3090  Type *OperTy = Inc.IVOperand->getType();
3091  if (IVTy != OperTy) {
3092  assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
3093  "cannot extend a chained IV");
3094  IRBuilder<> Builder(InsertPt);
3095  IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
3096  }
3097  Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
3098  DeadInsts.emplace_back(Inc.IVOperand);
3099  }
3100  // If LSR created a new, wider phi, we may also replace its postinc. We only
3101  // do this if we also found a wide value for the head of the chain.
3102  if (isa<PHINode>(Chain.tailUserInst())) {
3103  for (BasicBlock::iterator I = L->getHeader()->begin();
3104  PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
3105  if (!isCompatibleIVType(Phi, IVSrc))
3106  continue;
3107  Instruction *PostIncV = dyn_cast<Instruction>(
3108  Phi->getIncomingValueForBlock(L->getLoopLatch()));
3109  if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
3110  continue;
3111  Value *IVOper = IVSrc;
3112  Type *PostIncTy = PostIncV->getType();
3113  if (IVTy != PostIncTy) {
3114  assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
3115  IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
3116  Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
3117  IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
3118  }
3119  Phi->replaceUsesOfWith(PostIncV, IVOper);
3120  DeadInsts.emplace_back(PostIncV);
3121  }
3122  }
3123 }
3124 
3125 void LSRInstance::CollectFixupsAndInitialFormulae() {
3126  for (const IVStrideUse &U : IU) {
3127  Instruction *UserInst = U.getUser();
3128  // Skip IV users that are part of profitable IV Chains.
3129  User::op_iterator UseI =
3130  find(UserInst->operands(), U.getOperandValToReplace());
3131  assert(UseI != UserInst->op_end() && "cannot find IV operand");
3132  if (IVIncSet.count(UseI)) {
3133  DEBUG(dbgs() << "Use is in profitable chain: " << **UseI << '\n');
3134  continue;
3135  }
3136 
3137  LSRUse::KindType Kind = LSRUse::Basic;
3138  MemAccessTy AccessTy;
3139  if (isAddressUse(UserInst, U.getOperandValToReplace())) {
3140  Kind = LSRUse::Address;
3141  AccessTy = getAccessType(UserInst);
3142  }
3143 
3144  const SCEV *S = IU.getExpr(U);
3145  PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3146 
3147  // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3148  // (N - i == 0), and this allows (N - i) to be the expression that we work
3149  // with rather than just N or i, so we can consider the register
3150  // requirements for both N and i at the same time. Limiting this code to
3151  // equality icmps is not a problem because all interesting loops use
3152  // equality icmps, thanks to IndVarSimplify.
3153  if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst))
3154  if (CI->isEquality()) {
3155  // Swap the operands if needed to put the OperandValToReplace on the
3156  // left, for consistency.
3157  Value *NV = CI->getOperand(1);
3158  if (NV == U.getOperandValToReplace()) {
3159  CI->setOperand(1, CI->getOperand(0));
3160  CI->setOperand(0, NV);
3161  NV = CI->getOperand(1);
3162  Changed = true;
3163  }
3164 
3165  // x == y --> x - y == 0
3166  const SCEV *N = SE.getSCEV(NV);
3167  if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3168  // S is normalized, so normalize N before folding it into S
3169  // to keep the result normalized.
3170  N = normalizeForPostIncUse(N, TmpPostIncLoops, SE);
3171  Kind = LSRUse::ICmpZero;
3172  S = SE.getMinusSCEV(N, S);
3173  }
3174 
3175  // -1 and the negations of all interesting strides (except the negation
3176  // of -1) are now also interesting.
3177  for (size_t i = 0, e = Factors.size(); i != e; ++i)
3178  if (Factors[i] != -1)
3179  Factors.insert(-(uint64_t)Factors[i]);
3180  Factors.insert(-1);
3181  }
3182 
3183  // Get or create an LSRUse.
3184  std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3185  size_t LUIdx = P.first;
3186  int64_t Offset = P.second;
3187  LSRUse &LU = Uses[LUIdx];
3188 
3189  // Record the fixup.
3190  LSRFixup &LF = LU.getNewFixup();
3191  LF.UserInst = UserInst;
3192  LF.OperandValToReplace = U.getOperandValToReplace();
3193  LF.PostIncLoops = TmpPostIncLoops;
3194  LF.Offset = Offset;
3195  LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3196 
3197  if (!LU.WidestFixupType ||
3198  SE.getTypeSizeInBits(LU.WidestFixupType) <
3199  SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3200  LU.WidestFixupType = LF.OperandValToReplace->getType();
3201 
3202  // If this is the first use of this LSRUse, give it a formula.
3203  if (LU.Formulae.empty()) {
3204  InsertInitialFormula(S, LU, LUIdx);
3205  CountRegisters(LU.Formulae.back(), LUIdx);
3206  }
3207  }
3208 
3209  DEBUG(print_fixups(dbgs()));
3210 }
3211 
3212 /// Insert a formula for the given expression into the given use, separating out
3213 /// loop-variant portions from loop-invariant and loop-computable portions.
3214 void
3215 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3216  // Mark uses whose expressions cannot be expanded.
3217  if (!isSafeToExpand(S, SE))
3218  LU.RigidFormula = true;
3219 
3220  Formula F;
3221  F.initialMatch(S, L, SE);
3222  bool Inserted = InsertFormula(LU, LUIdx, F);
3223  assert(Inserted && "Initial formula already exists!"); (void)Inserted;
3224 }
3225 
3226 /// Insert a simple single-register formula for the given expression into the
3227 /// given use.
3228 void
3229 LSRInstance::InsertSupplementalFormula(const SCEV *S,
3230  LSRUse &LU, size_t LUIdx) {
3231  Formula F;
3232  F.BaseRegs.push_back(S);
3233  F.HasBaseReg = true;
3234  bool Inserted = InsertFormula(LU, LUIdx, F);
3235  assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
3236 }
3237 
3238 /// Note which registers are used by the given formula, updating RegUses.
3239 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3240  if (F.ScaledReg)
3241  RegUses.countRegister(F.ScaledReg, LUIdx);
3242  for (const SCEV *BaseReg : F.BaseRegs)
3243  RegUses.countRegister(BaseReg, LUIdx);
3244 }
3245 
3246 /// If the given formula has not yet been inserted, add it to the list, and
3247 /// return true. Return false otherwise.
3248 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3249  // Do not insert formula that we will not be able to expand.
3250  assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&
3251  "Formula is illegal");
3252 
3253  if (!LU.InsertFormula(F, *L))
3254  return false;
3255 
3256  CountRegisters(F, LUIdx);
3257  return true;
3258 }
3259 
3260 /// Check for other uses of loop-invariant values which we're tracking. These
3261 /// other uses will pin these values in registers, making them less profitable
3262 /// for elimination.
3263 /// TODO: This currently misses non-constant addrec step registers.
3264 /// TODO: Should this give more weight to users inside the loop?
3265 void
3266 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3267  SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3269 
3270  while (!Worklist.empty()) {
3271  const SCEV *S = Worklist.pop_back_val();
3272 
3273  // Don't process the same SCEV twice
3274  if (!Visited.insert(S).second)
3275  continue;
3276 
3277  if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3278  Worklist.append(N->op_begin(), N->op_end());
3279  else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3280  Worklist.push_back(C->getOperand());
3281  else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3282  Worklist.push_back(D->getLHS());
3283  Worklist.push_back(D->getRHS());
3284  } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3285  const Value *V = US->getValue();
3286  if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3287  // Look for instructions defined outside the loop.
3288  if (L->contains(Inst)) continue;
3289  } else if (isa<UndefValue>(V))
3290  // Undef doesn't have a live range, so it doesn't matter.
3291  continue;
3292  for (const Use &U : V->uses()) {
3293  const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3294  // Ignore non-instructions.
3295  if (!UserInst)
3296  continue;
3297  // Ignore instructions in other functions (as can happen with
3298  // Constants).
3299  if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3300  continue;
3301  // Ignore instructions not dominated by the loop.
3302  const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3303  UserInst->getParent() :
3304  cast<PHINode>(UserInst)->getIncomingBlock(
3305  PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3306  if (!DT.dominates(L->getHeader(), UseBB))
3307  continue;
3308  // Don't bother if the instruction is in a BB which ends in an EHPad.
3309  if (UseBB->getTerminator()->isEHPad())
3310  continue;
3311  // Don't bother rewriting PHIs in catchswitch blocks.
3312  if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator()))
3313  continue;
3314  // Ignore uses which are part of other SCEV expressions, to avoid
3315  // analyzing them multiple times.
3316  if (SE.isSCEVable(UserInst->getType())) {
3317  const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3318  // If the user is a no-op, look through to its uses.
3319  if (!isa<SCEVUnknown>(UserS))
3320  continue;
3321  if (UserS == US) {
3322  Worklist.push_back(
3323  SE.getUnknown(const_cast<Instruction *>(UserInst)));
3324  continue;
3325  }
3326  }
3327  // Ignore icmp instructions which are already being analyzed.
3328  if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3329  unsigned OtherIdx = !U.getOperandNo();
3330  Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3331  if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3332  continue;
3333  }
3334 
3335  std::pair<size_t, int64_t> P = getUse(
3336  S, LSRUse::Basic, MemAccessTy());
3337  size_t LUIdx = P.first;
3338  int64_t Offset = P.second;
3339  LSRUse &LU = Uses[LUIdx];
3340  LSRFixup &LF = LU.getNewFixup();
3341  LF.UserInst = const_cast<Instruction *>(UserInst);
3342  LF.OperandValToReplace = U;
3343  LF.Offset = Offset;
3344  LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3345  if (!LU.WidestFixupType ||
3346  SE.getTypeSizeInBits(LU.WidestFixupType) <
3347  SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3348  LU.WidestFixupType = LF.OperandValToReplace->getType();
3349  InsertSupplementalFormula(US, LU, LUIdx);
3350  CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3351  break;
3352  }
3353  }
3354  }
3355 }
3356 
3357 /// Split S into subexpressions which can be pulled out into separate
3358 /// registers. If C is non-null, multiply each subexpression by C.
3359 ///
3360 /// Return remainder expression after factoring the subexpressions captured by
3361 /// Ops. If Ops is complete, return NULL.
3362 static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3364  const Loop *L,
3365  ScalarEvolution &SE,
3366  unsigned Depth = 0) {
3367  // Arbitrarily cap recursion to protect compile time.
3368  if (Depth >= 3)
3369  return S;
3370 
3371  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3372  // Break out add operands.
3373  for (const SCEV *S : Add->operands()) {
3374  const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3375  if (Remainder)
3376  Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3377  }
3378  return nullptr;
3379  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3380  // Split a non-zero base out of an addrec.
3381  if (AR->getStart()->isZero() || !AR->isAffine())
3382  return S;
3383 
3384  const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3385  C, Ops, L, SE, Depth+1);
3386  // Split the non-zero AddRec unless it is part of a nested recurrence that
3387  // does not pertain to this loop.
3388  if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3389  Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3390  Remainder = nullptr;
3391  }
3392  if (Remainder != AR->getStart()) {
3393  if (!Remainder)
3394  Remainder = SE.getConstant(AR->getType(), 0);
3395  return SE.getAddRecExpr(Remainder,
3396  AR->getStepRecurrence(SE),
3397  AR->getLoop(),
3398  //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3400  }
3401  } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3402  // Break (C * (a + b + c)) into C*a + C*b + C*c.
3403  if (Mul->getNumOperands() != 2)
3404  return S;
3405  if (const SCEVConstant *Op0 =
3406  dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3407  C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3408  const SCEV *Remainder =
3409  CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3410  if (Remainder)
3411  Ops.push_back(SE.getMulExpr(C, Remainder));
3412  return nullptr;
3413  }
3414  }
3415  return S;
3416 }
3417 
3418 /// \brief Helper function for LSRInstance::GenerateReassociations.
3419 void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3420  const Formula &Base,
3421  unsigned Depth, size_t Idx,
3422  bool IsScaledReg) {
3423  const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3425  const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3426  if (Remainder)
3427  AddOps.push_back(Remainder);
3428 
3429  if (AddOps.size() == 1)
3430  return;
3431 
3433  JE = AddOps.end();
3434  J != JE; ++J) {
3435 
3436  // Loop-variant "unknown" values are uninteresting; we won't be able to
3437  // do anything meaningful with them.
3438  if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3439  continue;
3440 
3441  // Don't pull a constant into a register if the constant could be folded
3442  // into an immediate field.
3443  if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3444  LU.AccessTy, *J, Base.getNumRegs() > 1))
3445  continue;
3446 
3447  // Collect all operands except *J.
3448  SmallVector<const SCEV *, 8> InnerAddOps(
3449  ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3450  InnerAddOps.append(std::next(J),
3451  ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3452 
3453  // Don't leave just a constant behind in a register if the constant could
3454  // be folded into an immediate field.
3455  if (InnerAddOps.size() == 1 &&
3456  isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3457  LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3458  continue;
3459 
3460  const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3461  if (InnerSum->isZero())
3462  continue;
3463  Formula F = Base;
3464 
3465  // Add the remaining pieces of the add back into the new formula.
3466  const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3467  if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3468  TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3469  InnerSumSC->getValue()->getZExtValue())) {
3470  F.UnfoldedOffset =
3471  (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3472  if (IsScaledReg)
3473  F.ScaledReg = nullptr;
3474  else
3475  F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3476  } else if (IsScaledReg)
3477  F.ScaledReg = InnerSum;
3478  else
3479  F.BaseRegs[Idx] = InnerSum;
3480 
3481  // Add J as its own register, or an unfolded immediate.
3482  const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3483  if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3484  TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3485  SC->getValue()->getZExtValue()))
3486  F.UnfoldedOffset =
3487  (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3488  else
3489  F.BaseRegs.push_back(*J);
3490  // We may have changed the number of register in base regs, adjust the
3491  // formula accordingly.
3492  F.canonicalize(*L);
3493 
3494  if (InsertFormula(LU, LUIdx, F))
3495  // If that formula hadn't been seen before, recurse to find more like
3496  // it.
3497  GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth + 1);
3498  }
3499 }
3500 
3501 /// Split out subexpressions from adds and the bases of addrecs.
3502 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3503  Formula Base, unsigned Depth) {
3504  assert(Base.isCanonical(*L) && "Input must be in the canonical form");
3505  // Arbitrarily cap recursion to protect compile time.
3506  if (Depth >= 3)
3507  return;
3508 
3509  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3510  GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3511 
3512  if (Base.Scale == 1)
3513  GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3514  /* Idx */ -1, /* IsScaledReg */ true);
3515 }
3516 
3517 /// Generate a formula consisting of all of the loop-dominating registers added
3518 /// into a single register.
3519 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3520  Formula Base) {
3521  // This method is only interesting on a plurality of registers.
3522  if (Base.BaseRegs.size() + (Base.Scale == 1) <= 1)
3523  return;
3524 
3525  // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3526  // processing the formula.
3527  Base.unscale();
3528  Formula F = Base;
3529  F.BaseRegs.clear();
3531  for (const SCEV *BaseReg : Base.BaseRegs) {
3532  if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3533  !SE.hasComputableLoopEvolution(BaseReg, L))
3534  Ops.push_back(BaseReg);
3535  else
3536  F.BaseRegs.push_back(BaseReg);
3537  }
3538  if (Ops.size() > 1) {
3539  const SCEV *Sum = SE.getAddExpr(Ops);
3540  // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3541  // opportunity to fold something. For now, just ignore such cases
3542  // rather than proceed with zero in a register.
3543  if (!Sum->isZero()) {
3544  F.BaseRegs.push_back(Sum);
3545  F.canonicalize(*L);
3546  (void)InsertFormula(LU, LUIdx, F);
3547  }
3548  }
3549 }
3550 
3551 /// \brief Helper function for LSRInstance::GenerateSymbolicOffsets.
3552 void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3553  const Formula &Base, size_t Idx,
3554  bool IsScaledReg) {
3555  const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3556  GlobalValue *GV = ExtractSymbol(G, SE);
3557  if (G->isZero() || !GV)
3558  return;
3559  Formula F = Base;
3560  F.BaseGV = GV;
3561  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3562  return;
3563  if (IsScaledReg)
3564  F.ScaledReg = G;
3565  else
3566  F.BaseRegs[Idx] = G;
3567  (void)InsertFormula(LU, LUIdx, F);
3568 }
3569 
3570 /// Generate reuse formulae using symbolic offsets.
3571 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3572  Formula Base) {
3573  // We can't add a symbolic offset if the address already contains one.
3574  if (Base.BaseGV) return;
3575 
3576  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3577  GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3578  if (Base.Scale == 1)
3579  GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3580  /* IsScaledReg */ true);
3581 }
3582 
3583 /// \brief Helper function for LSRInstance::GenerateConstantOffsets.
3584 void LSRInstance::GenerateConstantOffsetsImpl(
3585  LSRUse &LU, unsigned LUIdx, const Formula &Base,
3586  const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3587  const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3588  for (int64_t Offset : Worklist) {
3589  Formula F = Base;
3590  F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3591  if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind,
3592  LU.AccessTy, F)) {
3593  // Add the offset to the base register.
3594  const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3595  // If it cancelled out, drop the base register, otherwise update it.
3596  if (NewG->isZero()) {
3597  if (IsScaledReg) {
3598  F.Scale = 0;
3599  F.ScaledReg = nullptr;
3600  } else
3601  F.deleteBaseReg(F.BaseRegs[Idx]);
3602  F.canonicalize(*L);
3603  } else if (IsScaledReg)
3604  F.ScaledReg = NewG;
3605  else
3606  F.BaseRegs[Idx] = NewG;
3607 
3608  (void)InsertFormula(LU, LUIdx, F);
3609  }
3610  }
3611 
3612  int64_t Imm = ExtractImmediate(G, SE);
3613  if (G->isZero() || Imm == 0)
3614  return;
3615  Formula F = Base;
3616  F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3617  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3618  return;
3619  if (IsScaledReg)
3620  F.ScaledReg = G;
3621  else
3622  F.BaseRegs[Idx] = G;
3623  (void)InsertFormula(LU, LUIdx, F);
3624 }
3625 
3626 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3627 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3628  Formula Base) {
3629  // TODO: For now, just add the min and max offset, because it usually isn't
3630  // worthwhile looking at everything inbetween.
3631  SmallVector<int64_t, 2> Worklist;
3632  Worklist.push_back(LU.MinOffset);
3633  if (LU.MaxOffset != LU.MinOffset)
3634  Worklist.push_back(LU.MaxOffset);
3635 
3636  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3637  GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3638  if (Base.Scale == 1)
3639  GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3640  /* IsScaledReg */ true);
3641 }
3642 
3643 /// For ICmpZero, check to see if we can scale up the comparison. For example, x
3644 /// == y -> x*c == y*c.
3645 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3646  Formula Base) {
3647  if (LU.Kind != LSRUse::ICmpZero) return;
3648 
3649  // Determine the integer type for the base formula.
3650  Type *IntTy = Base.getType();
3651  if (!IntTy) return;
3652  if (SE.getTypeSizeInBits(IntTy) > 64) return;
3653 
3654  // Don't do this if there is more than one offset.
3655  if (LU.MinOffset != LU.MaxOffset) return;
3656 
3657  assert(!Base.BaseGV && "ICmpZero use is not legal!");
3658 
3659  // Check each interesting stride.
3660  for (int64_t Factor : Factors) {
3661  // Check that the multiplication doesn't overflow.
3662  if (Base.BaseOffset == INT64_MIN && Factor == -1)
3663  continue;
3664  int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3665  if (NewBaseOffset / Factor != Base.BaseOffset)
3666  continue;
3667  // If the offset will be truncated at this use, check that it is in bounds.
3668  if (!IntTy->isPointerTy() &&
3669  !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3670  continue;
3671 
3672  // Check that multiplying with the use offset doesn't overflow.
3673  int64_t Offset = LU.MinOffset;
3674  if (Offset == INT64_MIN && Factor == -1)
3675  continue;
3676  Offset = (uint64_t)Offset * Factor;
3677  if (Offset / Factor != LU.MinOffset)
3678  continue;
3679  // If the offset will be truncated at this use, check that it is in bounds.
3680  if (!IntTy->isPointerTy() &&
3681  !ConstantInt::isValueValidForType(IntTy, Offset))
3682  continue;
3683 
3684  Formula F = Base;
3685  F.BaseOffset = NewBaseOffset;
3686 
3687  // Check that this scale is legal.
3688  if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3689  continue;
3690 
3691  // Compensate for the use having MinOffset built into it.
3692  F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3693 
3694  const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3695 
3696  // Check that multiplying with each base register doesn't overflow.
3697  for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3698  F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3699  if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3700  goto next;
3701  }
3702 
3703  // Check that multiplying with the scaled register doesn't overflow.
3704  if (F.ScaledReg) {
3705  F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3706  if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3707  continue;
3708  }
3709 
3710  // Check that multiplying with the unfolded offset doesn't overflow.
3711  if (F.UnfoldedOffset != 0) {
3712  if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
3713  continue;
3714  F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3715  if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3716  continue;
3717  // If the offset will be truncated, check that it is in bounds.
3718  if (!IntTy->isPointerTy() &&
3719  !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3720  continue;
3721  }
3722 
3723  // If we make it here and it's legal, add it.
3724  (void)InsertFormula(LU, LUIdx, F);
3725  next:;
3726  }
3727 }
3728 
3729 /// Generate stride factor reuse formulae by making use of scaled-offset address
3730 /// modes, for example.
3731 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3732  // Determine the integer type for the base formula.
3733  Type *IntTy = Base.getType();
3734  if (!IntTy) return;
3735 
3736  // If this Formula already has a scaled register, we can't add another one.
3737  // Try to unscale the formula to generate a better scale.
3738  if (Base.Scale != 0 && !Base.unscale())
3739  return;
3740 
3741  assert(Base.Scale == 0 && "unscale did not did its job!");
3742 
3743  // Check each interesting stride.
3744  for (int64_t Factor : Factors) {
3745  Base.Scale = Factor;
3746  Base.HasBaseReg = Base.BaseRegs.size() > 1;
3747  // Check whether this scale is going to be legal.
3748  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3749  Base)) {
3750  // As a special-case, handle special out-of-loop Basic users specially.
3751  // TODO: Reconsider this special case.
3752  if (LU.Kind == LSRUse::Basic &&
3753  isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3754  LU.AccessTy, Base) &&
3755  LU.AllFixupsOutsideLoop)
3756  LU.Kind = LSRUse::Special;
3757  else
3758  continue;
3759  }
3760  // For an ICmpZero, negating a solitary base register won't lead to
3761  // new solutions.
3762  if (LU.Kind == LSRUse::ICmpZero &&
3763  !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3764  continue;
3765  // For each addrec base reg, if its loop is current loop, apply the scale.
3766  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3767  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]);
3768  if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) {
3769  const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3770  if (FactorS->isZero())
3771  continue;
3772  // Divide out the factor, ignoring high bits, since we'll be
3773  // scaling the value back up in the end.
3774  if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3775  // TODO: This could be optimized to avoid all the copying.
3776  Formula F = Base;
3777  F.ScaledReg = Quotient;
3778  F.deleteBaseReg(F.BaseRegs[i]);
3779  // The canonical representation of 1*reg is reg, which is already in
3780  // Base. In that case, do not try to insert the formula, it will be
3781  // rejected anyway.
3782  if (F.Scale == 1 && (F.BaseRegs.empty() ||
3783  (AR->getLoop() != L && LU.AllFixupsOutsideLoop)))
3784  continue;
3785  // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate
3786  // non canonical Formula with ScaledReg's loop not being L.
3787  if (F.Scale == 1 && LU.AllFixupsOutsideLoop)
3788  F.canonicalize(*L);
3789  (void)InsertFormula(LU, LUIdx, F);
3790  }
3791  }
3792  }
3793  }
3794 }
3795 
3796 /// Generate reuse formulae from different IV types.
3797 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3798  // Don't bother truncating symbolic values.
3799  if (Base.BaseGV) return;
3800 
3801  // Determine the integer type for the base formula.
3802  Type *DstTy = Base.getType();
3803  if (!DstTy) return;
3804  DstTy = SE.getEffectiveSCEVType(DstTy);
3805 
3806  for (Type *SrcTy : Types) {
3807  if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
3808  Formula F = Base;
3809 
3810  if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
3811  for (const SCEV *&BaseReg : F.BaseRegs)
3812  BaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
3813 
3814  // TODO: This assumes we've done basic processing on all uses and
3815  // have an idea what the register usage is.
3816  if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3817  continue;
3818 
3819  F.canonicalize(*L);
3820  (void)InsertFormula(LU, LUIdx, F);
3821  }
3822  }
3823 }
3824 
3825 namespace {
3826 
3827 /// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
3828 /// modifications so that the search phase doesn't have to worry about the data
3829 /// structures moving underneath it.
3830 struct WorkItem {
3831  size_t LUIdx;
3832  int64_t Imm;
3833  const SCEV *OrigReg;
3834 
3835  WorkItem(size_t LI, int64_t I, const SCEV *R)
3836  : LUIdx(LI), Imm(I), OrigReg(R) {}
3837 
3838  void print(raw_ostream &OS) const;
3839  void dump() const;
3840 };
3841 
3842 } // end anonymous namespace
3843 
3844 void WorkItem::print(raw_ostream &OS) const {
3845  OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3846  << " , add offset " << Imm;
3847 }
3848 
3849 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
3850 LLVM_DUMP_METHOD void WorkItem::dump() const {
3851  print(errs()); errs() << '\n';
3852 }
3853 #endif
3854 
3855 /// Look for registers which are a constant distance apart and try to form reuse
3856 /// opportunities between them.
3857 void LSRInstance::GenerateCrossUseConstantOffsets() {
3858  // Group the registers by their value without any added constant offset.
3859  typedef std::map<int64_t, const SCEV *> ImmMapTy;
3861  DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3863  for (const SCEV *Use : RegUses) {
3864  const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
3865  int64_t Imm = ExtractImmediate(Reg, SE);
3866  auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
3867  if (Pair.second)
3868  Sequence.push_back(Reg);
3869  Pair.first->second.insert(std::make_pair(Imm, Use));
3870  UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
3871  }
3872 
3873  // Now examine each set of registers with the same base value. Build up
3874  // a list of work to do and do the work in a separate step so that we're
3875  // not adding formulae and register counts while we're searching.
3876  SmallVector<WorkItem, 32> WorkItems;
3877  SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3878  for (const SCEV *Reg : Sequence) {
3879  const ImmMapTy &Imms = Map.find(Reg)->second;
3880 
3881  // It's not worthwhile looking for reuse if there's only one offset.
3882  if (Imms.size() == 1)
3883  continue;
3884 
3885  DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
3886  for (const auto &Entry : Imms)
3887  dbgs() << ' ' << Entry.first;
3888  dbgs() << '\n');
3889 
3890  // Examine each offset.
3891  for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3892  J != JE; ++J) {
3893  const SCEV *OrigReg = J->second;
3894 
3895  int64_t JImm = J->first;
3896  const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
3897 
3898  if (!isa<SCEVConstant>(OrigReg) &&
3899  UsedByIndicesMap[Reg].count() == 1) {
3900  DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
3901  continue;
3902  }
3903 
3904  // Conservatively examine offsets between this orig reg a few selected
3905  // other orig regs.
3906  ImmMapTy::const_iterator OtherImms[] = {
3907  Imms.begin(), std::prev(Imms.end()),
3908  Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) /
3909  2)
3910  };
3911  for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
3912  ImmMapTy::const_iterator M = OtherImms[i];
3913  if (M == J || M == JE) continue;
3914 
3915  // Compute the difference between the two.
3916  int64_t Imm = (uint64_t)JImm - M->first;
3917  for (unsigned LUIdx : UsedByIndices.set_bits())
3918  // Make a memo of this use, offset, and register tuple.
3919  if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
3920  WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
3921  }
3922  }
3923  }
3924 
3925  Map.clear();
3926  Sequence.clear();
3927  UsedByIndicesMap.clear();
3928  UniqueItems.clear();
3929 
3930  // Now iterate through the worklist and add new formulae.
3931  for (const WorkItem &WI : WorkItems) {
3932  size_t LUIdx = WI.LUIdx;
3933  LSRUse &LU = Uses[LUIdx];
3934  int64_t Imm = WI.Imm;
3935  const SCEV *OrigReg = WI.OrigReg;
3936 
3937  Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
3938  const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
3939  unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
3940 
3941  // TODO: Use a more targeted data structure.
3942  for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
3943  Formula F = LU.Formulae[L];
3944  // FIXME: The code for the scaled and unscaled registers looks
3945  // very similar but slightly different. Investigate if they
3946  // could be merged. That way, we would not have to unscale the
3947  // Formula.
3948  F.unscale();
3949  // Use the immediate in the scaled register.
3950  if (F.ScaledReg == OrigReg) {
3951  int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
3952  // Don't create 50 + reg(-50).
3953  if (F.referencesReg(SE.getSCEV(
3954  ConstantInt::get(IntTy, -(uint64_t)Offset))))
3955  continue;
3956  Formula NewF = F;
3957  NewF.BaseOffset = Offset;
3958  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3959  NewF))
3960  continue;
3961  NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
3962 
3963  // If the new scale is a constant in a register, and adding the constant
3964  // value to the immediate would produce a value closer to zero than the
3965  // immediate itself, then the formula isn't worthwhile.
3966  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
3967  if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
3968  (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
3969  .ule(std::abs(NewF.BaseOffset)))
3970  continue;
3971 
3972  // OK, looks good.
3973  NewF.canonicalize(*this->L);
3974  (void)InsertFormula(LU, LUIdx, NewF);
3975  } else {
3976  // Use the immediate in a base register.
3977  for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
3978  const SCEV *BaseReg = F.BaseRegs[N];
3979  if (BaseReg != OrigReg)
3980  continue;
3981  Formula NewF = F;
3982  NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
3983  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
3984  LU.Kind, LU.AccessTy, NewF)) {
3985  if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
3986  continue;
3987  NewF = F;
3988  NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
3989  }
3990  NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
3991 
3992  // If the new formula has a constant in a register, and adding the
3993  // constant value to the immediate would produce a value closer to
3994  // zero than the immediate itself, then the formula isn't worthwhile.
3995  for (const SCEV *NewReg : NewF.BaseRegs)
3996  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
3997  if ((C->getAPInt() + NewF.BaseOffset)
3998  .abs()
3999  .slt(std::abs(NewF.BaseOffset)) &&
4000  (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
4001  countTrailingZeros<uint64_t>(NewF.BaseOffset))
4002  goto skip_formula;
4003 
4004  // Ok, looks good.
4005  NewF.canonicalize(*this->L);
4006  (void)InsertFormula(LU, LUIdx, NewF);
4007  break;
4008  skip_formula:;
4009  }
4010  }
4011  }
4012  }
4013 }
4014 
4015 /// Generate formulae for each use.
4016 void
4017 LSRInstance::GenerateAllReuseFormulae() {
4018  // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
4019  // queries are more precise.
4020  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4021  LSRUse &LU = Uses[LUIdx];
4022  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4023  GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
4024  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4025  GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
4026  }
4027  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4028  LSRUse &LU = Uses[LUIdx];
4029  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4030  GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
4031  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4032  GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
4033  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4034  GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
4035  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4036  GenerateScales(LU, LUIdx, LU.Formulae[i]);
4037  }
4038  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4039  LSRUse &LU = Uses[LUIdx];
4040  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4041  GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
4042  }
4043 
4044  GenerateCrossUseConstantOffsets();
4045 
4046  DEBUG(dbgs() << "\n"
4047  "After generating reuse formulae:\n";
4048  print_uses(dbgs()));
4049 }
4050 
4051 /// If there are multiple formulae with the same set of registers used
4052 /// by other uses, pick the best one and delete the others.
4053 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
4054  DenseSet<const SCEV *> VisitedRegs;
4057 #ifndef NDEBUG
4058  bool ChangedFormulae = false;
4059 #endif
4060 
4061  // Collect the best formula for each unique set of shared registers. This
4062  // is reset for each use.
4063  typedef DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>
4064  BestFormulaeTy;
4065  BestFormulaeTy BestFormulae;
4066 
4067  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4068  LSRUse &LU = Uses[LUIdx];
4069  DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
4070 
4071  bool Any = false;
4072  for (size_t FIdx = 0, NumForms = LU.Formulae.size();
4073  FIdx != NumForms; ++FIdx) {
4074  Formula &F = LU.Formulae[FIdx];
4075 
4076  // Some formulas are instant losers. For example, they may depend on
4077  // nonexistent AddRecs from other loops. These need to be filtered
4078  // immediately, otherwise heuristics could choose them over others leading
4079  // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
4080  // avoids the need to recompute this information across formulae using the
4081  // same bad AddRec. Passing LoserRegs is also essential unless we remove
4082  // the corresponding bad register from the Regs set.
4083  Cost CostF;
4084  Regs.clear();
4085  CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, SE, DT, LU, &LoserRegs);
4086  if (CostF.isLoser()) {
4087  // During initial formula generation, undesirable formulae are generated
4088  // by uses within other loops that have some non-trivial address mode or
4089  // use the postinc form of the IV. LSR needs to provide these formulae
4090  // as the basis of rediscovering the desired formula that uses an AddRec
4091  // corresponding to the existing phi. Once all formulae have been
4092  // generated, these initial losers may be pruned.
4093  DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());
4094  dbgs() << "\n");
4095  }
4096  else {
4098  for (const SCEV *Reg : F.BaseRegs) {
4099  if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
4100  Key.push_back(Reg);
4101  }
4102  if (F.ScaledReg &&
4103  RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
4104  Key.push_back(F.ScaledReg);
4105  // Unstable sort by host order ok, because this is only used for
4106  // uniquifying.
4107  std::sort(Key.begin(), Key.end());
4108 
4109  std::pair<BestFormulaeTy::const_iterator, bool> P =
4110  BestFormulae.insert(std::make_pair(Key, FIdx));
4111  if (P.second)
4112  continue;
4113 
4114  Formula &Best = LU.Formulae[P.first->second];
4115 
4116  Cost CostBest;
4117  Regs.clear();
4118  CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, SE, DT, LU);
4119  if (CostF.isLess(CostBest, TTI))
4120  std::swap(F, Best);
4121  DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
4122  dbgs() << "\n"
4123  " in favor of formula "; Best.print(dbgs());
4124  dbgs() << '\n');
4125  }
4126 #ifndef NDEBUG
4127  ChangedFormulae = true;
4128 #endif
4129  LU.DeleteFormula(F);
4130  --FIdx;
4131  --NumForms;
4132  Any = true;
4133  }
4134 
4135  // Now that we've filtered out some formulae, recompute the Regs set.
4136  if (Any)
4137  LU.RecomputeRegs(LUIdx, RegUses);
4138 
4139  // Reset this to prepare for the next use.
4140  BestFormulae.clear();
4141  }
4142 
4143  DEBUG(if (ChangedFormulae) {
4144  dbgs() << "\n"
4145  "After filtering out undesirable candidates:\n";
4146  print_uses(dbgs());
4147  });
4148 }
4149 
4150 // This is a rough guess that seems to work fairly well.
4151 static const size_t ComplexityLimit = UINT16_MAX;
4152 
4153 /// Estimate the worst-case number of solutions the solver might have to
4154 /// consider. It almost never considers this many solutions because it prune the
4155 /// search space, but the pruning isn't always sufficient.
4156 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4157  size_t Power = 1;
4158  for (const LSRUse &LU : Uses) {
4159  size_t FSize = LU.Formulae.size();
4160  if (FSize >= ComplexityLimit) {
4161  Power = ComplexityLimit;
4162  break;
4163  }
4164  Power *= FSize;
4165  if (Power >= ComplexityLimit)
4166  break;
4167  }
4168  return Power;
4169 }
4170 
4171 /// When one formula uses a superset of the registers of another formula, it
4172 /// won't help reduce register pressure (though it may not necessarily hurt
4173 /// register pressure); remove it to simplify the system.
4174 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4175  if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4176  DEBUG(dbgs() << "The search space is too complex.\n");
4177 
4178  DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
4179  "which use a superset of registers used by other "
4180  "formulae.\n");
4181 
4182  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4183  LSRUse &LU = Uses[LUIdx];
4184  bool Any = false;
4185  for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4186  Formula &F = LU.Formulae[i];
4187  // Look for a formula with a constant or GV in a register. If the use
4188  // also has a formula with that same value in an immediate field,
4189  // delete the one that uses a register.
4191  I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4192  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4193  Formula NewF = F;
4194  NewF.BaseOffset += C->getValue()->getSExtValue();
4195  NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4196  (I - F.BaseRegs.begin()));
4197  if (LU.HasFormulaWithSameRegs(NewF)) {
4198  DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4199  LU.DeleteFormula(F);
4200  --i;
4201  --e;
4202  Any = true;
4203  break;
4204  }
4205  } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4206  if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4207  if (!F.BaseGV) {
4208  Formula NewF = F;
4209  NewF.BaseGV = GV;
4210  NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4211  (I - F.BaseRegs.begin()));
4212  if (LU.HasFormulaWithSameRegs(NewF)) {
4213  DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4214  dbgs() << '\n');
4215  LU.DeleteFormula(F);
4216  --i;
4217  --e;
4218  Any = true;
4219  break;
4220  }
4221  }
4222  }
4223  }
4224  }
4225  if (Any)
4226  LU.RecomputeRegs(LUIdx, RegUses);
4227  }
4228 
4229  DEBUG(dbgs() << "After pre-selection:\n";
4230  print_uses(dbgs()));
4231  }
4232 }
4233 
4234 /// When there are many registers for expressions like A, A+1, A+2, etc.,
4235 /// allocate a single register for them.
4236 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4237  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4238  return;
4239 
4240  DEBUG(dbgs() << "The search space is too complex.\n"
4241  "Narrowing the search space by assuming that uses separated "
4242  "by a constant offset will use the same registers.\n");
4243 
4244  // This is especially useful for unrolled loops.
4245 
4246  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4247  LSRUse &LU = Uses[LUIdx];
4248  for (const Formula &F : LU.Formulae) {
4249  if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4250  continue;
4251 
4252  LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4253  if (!LUThatHas)
4254  continue;
4255 
4256  if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4257  LU.Kind, LU.AccessTy))
4258  continue;
4259 
4260  DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n');
4261 
4262  LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4263 
4264  // Transfer the fixups of LU to LUThatHas.
4265  for (LSRFixup &Fixup : LU.Fixups) {
4266  Fixup.Offset += F.BaseOffset;
4267  LUThatHas->pushFixup(Fixup);
4268  DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n');
4269  }
4270 
4271  // Delete formulae from the new use which are no longer legal.
4272  bool Any = false;
4273  for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4274  Formula &F = LUThatHas->Formulae[i];
4275  if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4276  LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4277  DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4278  dbgs() << '\n');
4279  LUThatHas->DeleteFormula(F);
4280  --i;
4281  --e;
4282  Any = true;
4283  }
4284  }
4285 
4286  if (Any)
4287  LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4288 
4289  // Delete the old use.
4290  DeleteUse(LU, LUIdx);
4291  --LUIdx;
4292  --NumUses;
4293  break;
4294  }
4295  }
4296 
4297  DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4298 }
4299 
4300 /// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4301 /// we've done more filtering, as it may be able to find more formulae to
4302 /// eliminate.
4303 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4304  if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4305  DEBUG(dbgs() << "The search space is too complex.\n");
4306 
4307  DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
4308  "undesirable dedicated registers.\n");
4309 
4310  FilterOutUndesirableDedicatedRegisters();
4311 
4312  DEBUG(dbgs() << "After pre-selection:\n";
4313  print_uses(dbgs()));
4314  }
4315 }
4316 
4317 /// If a LSRUse has multiple formulae with the same ScaledReg and Scale.
4318 /// Pick the best one and delete the others.
4319 /// This narrowing heuristic is to keep as many formulae with different
4320 /// Scale and ScaledReg pair as possible while narrowing the search space.
4321 /// The benefit is that it is more likely to find out a better solution
4322 /// from a formulae set with more Scale and ScaledReg variations than
4323 /// a formulae set with the same Scale and ScaledReg. The picking winner
4324 /// reg heurstic will often keep the formulae with the same Scale and
4325 /// ScaledReg and filter others, and we want to avoid that if possible.
4326 void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() {
4327  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4328  return;
4329 
4330  DEBUG(dbgs() << "The search space is too complex.\n"
4331  "Narrowing the search space by choosing the best Formula "
4332  "from the Formulae with the same Scale and ScaledReg.\n");
4333 
4334  // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse.
4335  typedef DenseMap<std::pair<const SCEV *, int64_t>, size_t> BestFormulaeTy;
4336  BestFormulaeTy BestFormulae;
4337 #ifndef NDEBUG
4338  bool ChangedFormulae = false;
4339 #endif
4340  DenseSet<const SCEV *> VisitedRegs;
4342 
4343  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4344  LSRUse &LU = Uses[LUIdx];
4345  DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
4346 
4347  // Return true if Formula FA is better than Formula FB.
4348  auto IsBetterThan = [&](Formula &FA, Formula &FB) {
4349  // First we will try to choose the Formula with fewer new registers.
4350  // For a register used by current Formula, the more the register is
4351  // shared among LSRUses, the less we increase the register number
4352  // counter of the formula.
4353  size_t FARegNum = 0;
4354  for (const SCEV *Reg : FA.BaseRegs) {
4355  const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4356  FARegNum += (NumUses - UsedByIndices.count() + 1);
4357  }
4358  size_t FBRegNum = 0;
4359  for (const SCEV *Reg : FB.BaseRegs) {
4360  const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4361  FBRegNum += (NumUses - UsedByIndices.count() + 1);
4362  }
4363  if (FARegNum != FBRegNum)
4364  return FARegNum < FBRegNum;
4365 
4366  // If the new register numbers are the same, choose the Formula with
4367  // less Cost.
4368  Cost CostFA, CostFB;
4369  Regs.clear();
4370  CostFA.RateFormula(TTI, FA, Regs, VisitedRegs, L, SE, DT, LU);
4371  Regs.clear();
4372  CostFB.RateFormula(TTI, FB, Regs, VisitedRegs, L, SE, DT, LU);
4373  return CostFA.isLess(CostFB, TTI);
4374  };
4375 
4376  bool Any = false;
4377  for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4378  ++FIdx) {
4379  Formula &F = LU.Formulae[FIdx];
4380  if (!F.ScaledReg)
4381  continue;
4382  auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx});
4383  if (P.second)
4384  continue;
4385 
4386  Formula &Best = LU.Formulae[P.first->second];
4387  if (IsBetterThan(F, Best))
4388  std::swap(F, Best);
4389  DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
4390  dbgs() << "\n"
4391  " in favor of formula ";
4392  Best.print(dbgs()); dbgs() << '\n');
4393 #ifndef NDEBUG
4394  ChangedFormulae = true;
4395 #endif
4396  LU.DeleteFormula(F);
4397  --FIdx;
4398  --NumForms;
4399  Any = true;
4400  }
4401  if (Any)
4402  LU.RecomputeRegs(LUIdx, RegUses);
4403 
4404  // Reset this to prepare for the next use.
4405  BestFormulae.clear();
4406  }
4407 
4408  DEBUG(if (ChangedFormulae) {
4409  dbgs() << "\n"
4410  "After filtering out undesirable candidates:\n";
4411  print_uses(dbgs());
4412  });
4413 }
4414 
4415 /// The function delete formulas with high registers number expectation.
4416 /// Assuming we don't know the value of each formula (already delete
4417 /// all inefficient), generate probability of not selecting for each
4418 /// register.
4419 /// For example,
4420 /// Use1:
4421 /// reg(a) + reg({0,+,1})
4422 /// reg(a) + reg({-1,+,1}) + 1
4423 /// reg({a,+,1})
4424 /// Use2:
4425 /// reg(b) + reg({0,+,1})
4426 /// reg(b) + reg({-1,+,1}) + 1
4427 /// reg({b,+,1})
4428 /// Use3:
4429 /// reg(c) + reg(b) + reg({0,+,1})
4430 /// reg(c) + reg({b,+,1})
4431 ///
4432 /// Probability of not selecting
4433 /// Use1 Use2 Use3
4434 /// reg(a) (1/3) * 1 * 1
4435 /// reg(b) 1 * (1/3) * (1/2)
4436 /// reg({0,+,1}) (2/3) * (2/3) * (1/2)
4437 /// reg({-1,+,1}) (2/3) * (2/3) * 1
4438 /// reg({a,+,1}) (2/3) * 1 * 1
4439 /// reg({b,+,1}) 1 * (2/3) * (2/3)
4440 /// reg(c) 1 * 1 * 0
4441 ///
4442 /// Now count registers number mathematical expectation for each formula:
4443 /// Note that for each use we exclude probability if not selecting for the use.
4444 /// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding
4445 /// probabilty 1/3 of not selecting for Use1).
4446 /// Use1:
4447 /// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted
4448 /// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted
4449 /// reg({a,+,1}) 1
4450 /// Use2:
4451 /// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted
4452 /// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted
4453 /// reg({b,+,1}) 2/3
4454 /// Use3:
4455 /// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted
4456 /// reg(c) + reg({b,+,1}) 1 + 2/3
4457 
4458 void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() {
4459  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4460  return;
4461  // Ok, we have too many of formulae on our hands to conveniently handle.
4462  // Use a rough heuristic to thin out the list.
4463 
4464  // Set of Regs wich will be 100% used in final solution.
4465  // Used in each formula of a solution (in example above this is reg(c)).
4466  // We can skip them in calculations.
4468  DEBUG(dbgs() << "The search space is too complex.\n");
4469 
4470  // Map each register to probability of not selecting
4472  for (const SCEV *Reg : RegUses) {
4473  if (UniqRegs.count(Reg))
4474  continue;
4475  float PNotSel = 1;
4476  for (const LSRUse &LU : Uses) {
4477  if (!LU.Regs.count(Reg))
4478  continue;
4479  float P = LU.getNotSelectedProbability(Reg);
4480  if (P != 0.0)
4481  PNotSel *= P;
4482  else
4483  UniqRegs.insert(Reg);
4484  }
4485  RegNumMap.insert(std::make_pair(Reg, PNotSel));
4486  }
4487 
4488  DEBUG(dbgs() << "Narrowing the search space by deleting costly formulas\n");
4489 
4490  // Delete formulas where registers number expectation is high.
4491  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4492  LSRUse &LU = Uses[LUIdx];
4493  // If nothing to delete - continue.
4494  if (LU.Formulae.size() < 2)
4495  continue;
4496  // This is temporary solution to test performance. Float should be
4497  // replaced with round independent type (based on integers) to avoid
4498  // different results for different target builds.
4499  float FMinRegNum = LU.Formulae[0].getNumRegs();
4500  float FMinARegNum = LU.Formulae[0].getNumRegs();
4501  size_t MinIdx = 0;
4502  for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4503  Formula &F = LU.Formulae[i];
4504  float FRegNum = 0;
4505  float FARegNum = 0;
4506  for (const SCEV *BaseReg : F.BaseRegs) {
4507  if (UniqRegs.count(BaseReg))
4508  continue;
4509  FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4510  if (isa<SCEVAddRecExpr>(BaseReg))
4511  FARegNum +=
4512  RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4513  }
4514  if (const SCEV *ScaledReg = F.ScaledReg) {
4515  if (!UniqRegs.count(ScaledReg)) {
4516  FRegNum +=
4517  RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4518  if (isa<SCEVAddRecExpr>(ScaledReg))
4519  FARegNum +=
4520  RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4521  }
4522  }
4523  if (FMinRegNum > FRegNum ||
4524  (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) {
4525  FMinRegNum = FRegNum;
4526  FMinARegNum = FARegNum;
4527  MinIdx = i;
4528  }
4529  }
4530  DEBUG(dbgs() << " The formula "; LU.Formulae[MinIdx].print(dbgs());
4531  dbgs() << " with min reg num " << FMinRegNum << '\n');
4532  if (MinIdx != 0)
4533  std::swap(LU.Formulae[MinIdx], LU.Formulae[0]);
4534  while (LU.Formulae.size() != 1) {
4535  DEBUG(dbgs() << " Deleting "; LU.Formulae.back().print(dbgs());
4536  dbgs() << '\n');
4537  LU.Formulae.pop_back();
4538  }
4539  LU.RecomputeRegs(LUIdx, RegUses);
4540  assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula");
4541  Formula &F = LU.Formulae[0];
4542  DEBUG(dbgs() << " Leaving only "; F.print(dbgs()); dbgs() << '\n');
4543  // When we choose the formula, the regs become unique.
4544  UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
4545  if (F.ScaledReg)
4546  UniqRegs.insert(F.ScaledReg);
4547  }
4548  DEBUG(dbgs() << "After pre-selection:\n";
4549  print_uses(dbgs()));
4550 }
4551 
4552 
4553 /// Pick a register which seems likely to be profitable, and then in any use
4554 /// which has any reference to that register, delete all formulae which do not
4555 /// reference that register.
4556 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4557  // With all other options exhausted, loop until the system is simple
4558  // enough to handle.
4560  while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4561  // Ok, we have too many of formulae on our hands to conveniently handle.
4562  // Use a rough heuristic to thin out the list.
4563  DEBUG(dbgs() << "The search space is too complex.\n");
4564 
4565  // Pick the register which is used by the most LSRUses, which is likely
4566  // to be a good reuse register candidate.
4567  const SCEV *Best = nullptr;
4568  unsigned BestNum = 0;
4569  for (const SCEV *Reg : RegUses) {
4570  if (Taken.count(Reg))
4571  continue;
4572  if (!Best) {
4573  Best = Reg;
4574  BestNum = RegUses.getUsedByIndices(Reg).count();
4575  } else {
4576  unsigned Count = RegUses.getUsedByIndices(Reg).count();
4577  if (Count > BestNum) {
4578  Best = Reg;
4579  BestNum = Count;
4580  }
4581  }
4582  }
4583 
4584  DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
4585  << " will yield profitable reuse.\n");
4586  Taken.insert(Best);
4587 
4588  // In any use with formulae which references this register, delete formulae
4589  // which don't reference it.
4590  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4591  LSRUse &LU = Uses[LUIdx];
4592  if (!LU.Regs.count(Best)) continue;
4593 
4594  bool Any = false;
4595  for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4596  Formula &F = LU.Formulae[i];
4597  if (!F.referencesReg(Best)) {
4598  DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4599  LU.DeleteFormula(F);
4600  --e;
4601  --i;
4602  Any = true;
4603  assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
4604  continue;
4605  }
4606  }
4607 
4608  if (Any)
4609  LU.RecomputeRegs(LUIdx, RegUses);
4610  }
4611 
4612  DEBUG(dbgs() << "After pre-selection:\n";
4613  print_uses(dbgs()));
4614  }
4615 }
4616 
4617 /// If there are an extraordinary number of formulae to choose from, use some
4618 /// rough heuristics to prune down the number of formulae. This keeps the main
4619 /// solver from taking an extraordinary amount of time in some worst-case
4620 /// scenarios.
4621 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4622  NarrowSearchSpaceByDetectingSupersets();
4623  NarrowSearchSpaceByCollapsingUnrolledCode();
4624  NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4625  if (FilterSameScaledReg)
4626  NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
4627  if (LSRExpNarrow)
4628  NarrowSearchSpaceByDeletingCostlyFormulas();
4629  else
4630  NarrowSearchSpaceByPickingWinnerRegs();
4631 }
4632 
4633 /// This is the recursive solver.
4634 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4635  Cost &SolutionCost,
4637  const Cost &CurCost,
4638  const SmallPtrSet<const SCEV *, 16> &CurRegs,
4639  DenseSet<const SCEV *> &VisitedRegs) const {
4640  // Some ideas:
4641  // - prune more:
4642  // - use more aggressive filtering
4643  // - sort the formula so that the most profitable solutions are found first
4644  // - sort the uses too
4645  // - search faster:
4646  // - don't compute a cost, and then compare. compare while computing a cost
4647  // and bail early.
4648  // - track register sets with SmallBitVector
4649 
4650  const LSRUse &LU = Uses[Workspace.size()];
4651 
4652  // If this use references any register that's already a part of the
4653  // in-progress solution, consider it a requirement that a formula must
4654  // reference that register in order to be considered. This prunes out
4655  // unprofitable searching.
4657  for (const SCEV *S : CurRegs)
4658  if (LU.Regs.count(S))
4659  ReqRegs.insert(S);
4660 
4662  Cost NewCost;
4663  for (const Formula &F : LU.Formulae) {
4664  // Ignore formulae which may not be ideal in terms of register reuse of
4665  // ReqRegs. The formula should use all required registers before
4666  // introducing new ones.
4667  int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4668  for (const SCEV *Reg : ReqRegs) {
4669  if ((F.ScaledReg && F.ScaledReg == Reg) ||
4670  is_contained(F.BaseRegs, Reg)) {
4671  --NumReqRegsToFind;
4672  if (NumReqRegsToFind == 0)
4673  break;
4674  }
4675  }
4676  if (NumReqRegsToFind != 0) {
4677  // If none of the formulae satisfied the required registers, then we could
4678  // clear ReqRegs and try again. Currently, we simply give up in this case.
4679  continue;
4680  }
4681 
4682  // Evaluate the cost of the current formula. If it's already worse than
4683  // the current best, prune the search at that point.
4684  NewCost = CurCost;
4685  NewRegs = CurRegs;
4686  NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, SE, DT, LU);
4687  if (NewCost.isLess(SolutionCost, TTI)) {
4688  Workspace.push_back(&F);
4689  if (Workspace.size() != Uses.size()) {
4690  SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4691  NewRegs, VisitedRegs);
4692  if (F.getNumRegs() == 1 && Workspace.size() == 1)
4693  VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4694  } else {
4695  DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
4696  dbgs() << ".\n Regs:";
4697  for (const SCEV *S : NewRegs)
4698  dbgs() << ' ' << *S;
4699  dbgs() << '\n');
4700 
4701  SolutionCost = NewCost;
4702  Solution = Workspace;
4703  }
4704  Workspace.pop_back();
4705  }
4706  }
4707 }
4708 
4709 /// Choose one formula from each use. Return the results in the given Solution
4710 /// vector.
4711 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4713  Cost SolutionCost;
4714  SolutionCost.Lose();
4715  Cost CurCost;
4717  DenseSet<const SCEV *> VisitedRegs;
4718  Workspace.reserve(Uses.size());
4719 
4720  // SolveRecurse does all the work.
4721  SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4722  CurRegs, VisitedRegs);
4723  if (Solution.empty()) {
4724  DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
4725  return;
4726  }
4727 
4728  // Ok, we've now made all our decisions.
4729  DEBUG(dbgs() << "\n"
4730  "The chosen solution requires "; SolutionCost.print(dbgs());
4731  dbgs() << ":\n";
4732  for (size_t i = 0, e = Uses.size(); i != e; ++i) {
4733  dbgs() << " ";
4734  Uses[i].print(dbgs());
4735  dbgs() << "\n"
4736  " ";
4737  Solution[i]->print(dbgs());
4738  dbgs() << '\n';
4739  });
4740 
4741  assert(Solution.size() == Uses.size() && "Malformed solution!");
4742 }
4743 
4744 /// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
4745 /// we can go while still being dominated by the input positions. This helps
4746 /// canonicalize the insert position, which encourages sharing.
4748 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4750  const {
4751  Instruction *Tentative = &*IP;
4752  while (true) {
4753  bool AllDominate = true;
4754  Instruction *BetterPos = nullptr;
4755  // Don't bother attempting to insert before a catchswitch, their basic block
4756  // cannot have other non-PHI instructions.
4757  if (isa<CatchSwitchInst>(Tentative))
4758  return IP;
4759 
4760  for (Instruction *Inst : Inputs) {
4761  if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4762  AllDominate = false;
4763  break;
4764  }
4765  // Attempt to find an insert position in the middle of the block,
4766  // instead of at the end, so that it can be used for other expansions.
4767  if (Tentative->getParent() == Inst->getParent() &&
4768  (!BetterPos || !DT.dominates(Inst, BetterPos)))
4769  BetterPos = &*std::next(BasicBlock::iterator(Inst));
4770  }
4771  if (!AllDominate)
4772  break;
4773  if (BetterPos)
4774  IP = BetterPos->getIterator();
4775  else
4776  IP = Tentative->getIterator();
4777 
4778  const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4779  unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4780 
4781  BasicBlock *IDom;
4782  for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4783  if (!Rung) return IP;
4784  Rung = Rung->getIDom();
4785  if (!Rung) return IP;
4786  IDom = Rung->getBlock();
4787 
4788  // Don't climb into a loop though.
4789  const Loop *IDomLoop = LI.getLoopFor(IDom);
4790  unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4791  if (IDomDepth <= IPLoopDepth &&
4792  (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4793  break;
4794  }
4795 
4796  Tentative = IDom->getTerminator();
4797  }
4798 
4799  return IP;
4800 }
4801 
4802 /// Determine an input position which will be dominated by the operands and
4803 /// which will dominate the result.
4805 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4806  const LSRFixup &LF,
4807  const LSRUse &LU,
4808  SCEVExpander &Rewriter) const {
4809  // Collect some instructions which must be dominated by the
4810  // expanding replacement. These must be dominated by any operands that
4811  // will be required in the expansion.
4813  if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4814  Inputs.push_back(I);
4815  if (LU.Kind == LSRUse::ICmpZero)
4816  if (Instruction *I =
4817  dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4818  Inputs.push_back(I);
4819  if (LF.PostIncLoops.count(L)) {
4820  if (LF.isUseFullyOutsideLoop(L))
4821  Inputs.push_back(L->getLoopLatch()->getTerminator());
4822  else
4823  Inputs.push_back(IVIncInsertPos);
4824  }
4825  // The expansion must also be dominated by the increment positions of any
4826  // loops it for which it is using post-inc mode.
4827  for (const Loop *PIL : LF.PostIncLoops) {
4828  if (PIL == L) continue;
4829 
4830  // Be dominated by the loop exit.
4831  SmallVector<BasicBlock *, 4> ExitingBlocks;
4832  PIL->getExitingBlocks(ExitingBlocks);
4833  if (!ExitingBlocks.empty()) {
4834  BasicBlock *BB = ExitingBlocks[0];
4835  for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4836  BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4837  Inputs.push_back(BB->getTerminator());
4838  }
4839  }
4840 
4841  assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad()
4842  && !isa<DbgInfoIntrinsic>(LowestIP) &&
4843  "Insertion point must be a normal instruction");
4844 
4845  // Then, climb up the immediate dominator tree as far as we can go while
4846  // still being dominated by the input positions.
4847  BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4848 
4849  // Don't insert instructions before PHI nodes.
4850  while (isa<PHINode>(IP)) ++IP;
4851 
4852  // Ignore landingpad instructions.
4853  while (IP->isEHPad()) ++IP;
4854 
4855  // Ignore debug intrinsics.
4856  while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4857 
4858  // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4859  // IP consistent across expansions and allows the previously inserted
4860  // instructions to be reused by subsequent expansion.
4861  while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
4862  ++IP;
4863 
4864  return IP;
4865 }
4866 
4867 /// Emit instructions for the leading candidate expression for this LSRUse (this
4868 /// is called "expanding").
4869 Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF,
4870  const Formula &F, BasicBlock::iterator IP,
4871  SCEVExpander &Rewriter,
4872  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
4873  if (LU.RigidFormula)
4874  return LF.OperandValToReplace;
4875 
4876  // Determine an input position which will be dominated by the operands and
4877  // which will dominate the result.
4878  IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4879  Rewriter.setInsertPoint(&*IP);
4880 
4881  // Inform the Rewriter if we have a post-increment use, so that it can
4882  // perform an advantageous expansion.
4883  Rewriter.setPostInc(LF.PostIncLoops);
4884 
4885  // This is the type that the user actually needs.
4886  Type *OpTy = LF.OperandValToReplace->getType();
4887  // This will be the type that we'll initially expand to.
4888  Type *Ty = F.getType();
4889  if (!Ty)
4890  // No type known; just expand directly to the ultimate type.
4891  Ty = OpTy;
4892  else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
4893  // Expand directly to the ultimate type if it's the right size.
4894  Ty = OpTy;
4895  // This is the type to do integer arithmetic in.
4896  Type *IntTy = SE.getEffectiveSCEVType(Ty);
4897 
4898  // Build up a list of operands to add together to form the full base.
4900 
4901  // Expand the BaseRegs portion.
4902  for (const SCEV *Reg : F.BaseRegs) {
4903  assert(!Reg->isZero() && "Zero allocated in a base register!");
4904 
4905  // If we're expanding for a post-inc user, make the post-inc adjustment.
4906  Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE);
4907  Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
4908  }
4909 
4910  // Expand the ScaledReg portion.
4911  Value *ICmpScaledV = nullptr;
4912  if (F.Scale != 0) {
4913  const SCEV *ScaledS = F.ScaledReg;
4914 
4915  // If we're expanding for a post-inc user, make the post-inc adjustment.
4916  PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4917  ScaledS = denormalizeForPostIncUse(ScaledS, Loops, SE);
4918 
4919  if (LU.Kind == LSRUse::ICmpZero) {
4920  // Expand ScaleReg as if it was part of the base regs.
4921  if (F.Scale == 1)
4922  Ops.push_back(
4923  SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
4924  else {
4925  // An interesting way of "folding" with an icmp is to use a negated
4926  // scale, which we'll implement by inserting it into the other operand
4927  // of the icmp.
4928  assert(F.Scale == -1 &&
4929  "The only scale supported by ICmpZero uses is -1!");
4930  ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
4931  }
4932  } else {
4933  // Otherwise just expand the scaled register and an explicit scale,
4934  // which is expected to be matched as part of the address.
4935 
4936  // Flush the operand list to suppress SCEVExpander hoisting address modes.
4937  // Unless the addressing mode will not be folded.
4938  if (!Ops.empty() && LU.Kind == LSRUse::Address &&
4939  isAMCompletelyFolded(TTI, LU, F)) {
4940  Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
4941  Ops.clear();
4942  Ops.push_back(SE.getUnknown(FullV));
4943  }
4944  ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
4945  if (F.Scale != 1)
4946  ScaledS =
4947  SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
4948  Ops.push_back(ScaledS);
4949  }
4950  }
4951 
4952  // Expand the GV portion.
4953  if (F.BaseGV) {
4954  // Flush the operand list to suppress SCEVExpander hoisting.
4955  if (!Ops.empty()) {
4956  Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
4957  Ops.clear();
4958  Ops.push_back(SE.getUnknown(FullV));
4959  }
4960  Ops.push_back(SE.getUnknown(F.BaseGV));
4961  }
4962 
4963  // Flush the operand list to suppress SCEVExpander hoisting of both folded and
4964  // unfolded offsets. LSR assumes they both live next to their uses.
4965  if (!Ops.empty()) {
4966  Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
4967  Ops.clear();
4968  Ops.push_back(SE.getUnknown(FullV));
4969  }
4970 
4971  // Expand the immediate portion.
4972  int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
4973  if (Offset != 0) {
4974  if (LU.Kind == LSRUse::ICmpZero) {
4975  // The other interesting way of "folding" with an ICmpZero is to use a
4976  // negated immediate.
4977  if (!ICmpScaledV)
4978  ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
4979  else {
4980  Ops.push_back(SE.getUnknown(ICmpScaledV));
4981  ICmpScaledV = ConstantInt::get(IntTy, Offset);
4982  }
4983  } else {
4984  // Just add the immediate values. These again are expected to be matched
4985  // as part of the address.
4986  Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
4987  }
4988  }
4989 
4990  // Expand the unfolded offset portion.
4991  int64_t UnfoldedOffset = F.UnfoldedOffset;
4992  if (UnfoldedOffset != 0) {
4993  // Just add the immediate values.
4995  UnfoldedOffset)));
4996  }
4997 
4998  // Emit instructions summing all the operands.
4999  const SCEV *FullS = Ops.empty() ?
5000  SE.getConstant(IntTy, 0) :
5001  SE.getAddExpr(Ops);
5002  Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
5003 
5004  // We're done expanding now, so reset the rewriter.
5005  Rewriter.clearPostInc();
5006 
5007  // An ICmpZero Formula represents an ICmp which we're handling as a
5008  // comparison against zero. Now that we've expanded an expression for that
5009  // form, update the ICmp's other operand.
5010  if (LU.Kind == LSRUse::ICmpZero) {
5011  ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
5012  DeadInsts.emplace_back(CI->getOperand(1));
5013  assert(!F.BaseGV && "ICmp does not support folding a global value and "
5014  "a scale at the same time!");
5015  if (F.Scale == -1) {
5016  if (ICmpScaledV->getType() != OpTy) {
5017  Instruction *Cast =
5018  CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
5019  OpTy, false),
5020  ICmpScaledV, OpTy, "tmp", CI);
5021  ICmpScaledV = Cast;
5022  }
5023  CI->setOperand(1, ICmpScaledV);
5024  } else {
5025  // A scale of 1 means that the scale has been expanded as part of the
5026  // base regs.
5027  assert((F.Scale == 0 || F.Scale == 1) &&
5028  "ICmp does not support folding a global value and "
5029  "a scale at the same time!");
5031  -(uint64_t)Offset);
5032  if (C->getType() != OpTy)
5034  OpTy, false),
5035  C, OpTy);
5036 
5037  CI->setOperand(1, C);
5038  }
5039  }
5040 
5041  return FullV;
5042 }
5043 
5044 /// Helper for Rewrite. PHI nodes are special because the use of their operands
5045 /// effectively happens in their predecessor blocks, so the expression may need
5046 /// to be expanded in multiple places.
5047 void LSRInstance::RewriteForPHI(
5048  PHINode *PN, const LSRUse &LU, const LSRFixup &LF, const Formula &F,
5049  SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5051  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
5052  if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
5053  BasicBlock *BB = PN->getIncomingBlock(i);
5054 
5055  // If this is a critical edge, split the edge so that we do not insert
5056  // the code on all predecessor/successor paths. We do this unless this
5057  // is the canonical backedge for this loop, which complicates post-inc
5058  // users.
5059  if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
5060  !isa<IndirectBrInst>(BB->getTerminator()) &&
5061  !isa<CatchSwitchInst>(BB->getTerminator())) {
5062  BasicBlock *Parent = PN->getParent();
5063  Loop *PNLoop = LI.getLoopFor(Parent);
5064  if (!PNLoop || Parent != PNLoop->getHeader()) {
5065  // Split the critical edge.
5066  BasicBlock *NewBB = nullptr;
5067  if (!Parent->isLandingPad()) {
5068  NewBB = SplitCriticalEdge(BB, Parent,
5070  .setMergeIdenticalEdges()
5071  .setDontDeleteUselessPHIs());
5072  } else {
5074  SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
5075  NewBB = NewBBs[0];
5076  }
5077  // If NewBB==NULL, then SplitCriticalEdge refused to split because all
5078  // phi predecessors are identical. The simple thing to do is skip
5079  // splitting in this case rather than complicate the API.
5080  if (NewBB) {
5081  // If PN is outside of the loop and BB is in the loop, we want to
5082  // move the block to be immediately before the PHI block, not
5083  // immediately after BB.
5084  if (L->contains(BB) && !L->contains(PN))
5085  NewBB->moveBefore(PN->getParent());
5086 
5087  // Splitting the edge can reduce the number of PHI entries we have.
5088  e = PN->getNumIncomingValues();
5089  BB = NewBB;
5090  i = PN->getBasicBlockIndex(BB);
5091  }
5092  }
5093  }
5094 
5095  std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
5096  Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
5097  if (!Pair.second)
5098  PN->setIncomingValue(i, Pair.first->second);
5099  else {
5100  Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
5101  Rewriter, DeadInsts);
5102 
5103  // If this is reuse-by-noop-cast, insert the noop cast.
5104  Type *OpTy = LF.OperandValToReplace->getType();
5105  if (FullV->getType() != OpTy)
5106  FullV =
5108  OpTy, false),
5109  FullV, LF.OperandValToReplace->getType(),
5110  "tmp", BB->getTerminator());
5111 
5112  PN->setIncomingValue(i, FullV);
5113  Pair.first->second = FullV;
5114  }
5115  }
5116 }
5117 
5118 /// Emit instructions for the leading candidate expression for this LSRUse (this
5119 /// is called "expanding"), and update the UserInst to reference the newly
5120 /// expanded value.
5121 void LSRInstance::Rewrite(const LSRUse &LU, const LSRFixup &LF,
5122  const Formula &F, SCEVExpander &Rewriter,
5123  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5124  // First, find an insertion point that dominates UserInst. For PHI nodes,
5125  // find the nearest block which dominates all the relevant uses.
5126  if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
5127  RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
5128  } else {
5129  Value *FullV =
5130  Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
5131 
5132  // If this is reuse-by-noop-cast, insert the noop cast.
5133  Type *OpTy = LF.OperandValToReplace->getType();
5134  if (FullV->getType() != OpTy) {
5135  Instruction *Cast =
5136  CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
5137  FullV, OpTy, "tmp", LF.UserInst);
5138  FullV = Cast;
5139  }
5140 
5141  // Update the user. ICmpZero is handled specially here (for now) because
5142  // Expand may have updated one of the operands of the icmp already, and
5143  // its new value may happen to be equal to LF.OperandValToReplace, in
5144  // which case doing replaceUsesOfWith leads to replacing both operands
5145  // with the same value. TODO: Reorganize this.
5146  if (LU.Kind == LSRUse::ICmpZero)
5147  LF.UserInst->setOperand(0, FullV);
5148  else
5149  LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
5150  }
5151 
5152  DeadInsts.emplace_back(LF.OperandValToReplace);
5153 }
5154 
5155 /// Rewrite all the fixup locations with new values, following the chosen
5156 /// solution.
5157 void LSRInstance::ImplementSolution(
5158  const SmallVectorImpl<const Formula *> &Solution) {
5159  // Keep track of instructions we may have made dead, so that
5160  // we can remove them after we are done working.
5162 
5164  "lsr");
5165 #ifndef NDEBUG
5166  Rewriter.setDebugType(DEBUG_TYPE);
5167 #endif
5168  Rewriter.disableCanonicalMode();
5169  Rewriter.enableLSRMode();
5170  Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
5171 
5172  // Mark phi nodes that terminate chains so the expander tries to reuse them.
5173  for (const IVChain &Chain : IVChainVec) {
5174  if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
5175  Rewriter.setChainedPhi(PN);
5176  }
5177 
5178  // Expand the new value definitions and update the users.
5179  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5180  for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
5181  Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
5182  Changed = true;
5183  }
5184 
5185  for (const IVChain &Chain : IVChainVec) {
5186  GenerateIVChain(Chain, Rewriter, DeadInsts);
5187  Changed = true;
5188  }
5189  // Clean up after ourselves. This must be done before deleting any
5190  // instructions.
5191  Rewriter.clear();
5192 
5193  Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
5194 }
5195 
5196 LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5197  DominatorTree &DT, LoopInfo &LI,
5198  const TargetTransformInfo &TTI)
5199  : IU(IU), SE(SE), DT(DT), LI(LI), TTI(TTI), L(L), Changed(false),
5200  IVIncInsertPos(nullptr) {
5201  // If LoopSimplify form is not available, stay out of trouble.
5202  if (!L->isLoopSimplifyForm())
5203  return;
5204 
5205  // If there's no interesting work to be done, bail early.
5206  if (IU.empty()) return;
5207 
5208  // If there's too much analysis to be done, bail early. We won't be able to
5209  // model the problem anyway.
5210  unsigned NumUsers = 0;
5211  for (const IVStrideUse &U : IU) {
5212  if (++NumUsers > MaxIVUsers) {
5213  (void)U;
5214  DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << U << "\n");
5215  return;
5216  }
5217  // Bail out if we have a PHI on an EHPad that gets a value from a
5218  // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is
5219  // no good place to stick any instructions.
5220  if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
5221  auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
5222  if (isa<FuncletPadInst>(FirstNonPHI) ||
5223  isa<CatchSwitchInst>(FirstNonPHI))
5224  for (BasicBlock *PredBB : PN->blocks())
5225  if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
5226  return;
5227  }
5228  }
5229 
5230 #ifndef NDEBUG
5231  // All dominating loops must have preheaders, or SCEVExpander may not be able
5232  // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
5233  //
5234  // IVUsers analysis should only create users that are dominated by simple loop
5235  // headers. Since this loop should dominate all of its users, its user list
5236  // should be empty if this loop itself is not within a simple loop nest.
5237  for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
5238  Rung; Rung = Rung->getIDom()) {
5239  BasicBlock *BB = Rung->getBlock();
5240  const Loop *DomLoop = LI.getLoopFor(BB);
5241  if (DomLoop && DomLoop->getHeader() == BB) {
5242  assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
5243  }
5244  }
5245 #endif // DEBUG
5246 
5247  DEBUG(dbgs() << "\nLSR on loop ";
5248  L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false);
5249  dbgs() << ":\n");
5250 
5251  // First, perform some low-level loop optimizations.
5252  OptimizeShadowIV();
5253  OptimizeLoopTermCond();
5254 
5255  // If loop preparation eliminates all interesting IV users, bail.
5256  if (IU.empty()) return;
5257 
5258  // Skip nested loops until we can model them better with formulae.
5259  if (!L->empty()) {
5260  DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
5261  return;
5262  }
5263 
5264  // Start collecting data and preparing for the solver.
5265  CollectChains();
5266  CollectInterestingTypesAndFactors();
5267  CollectFixupsAndInitialFormulae();
5268  CollectLoopInvariantFixupsAndFormulae();
5269 
5270  assert(!Uses.empty() && "IVUsers reported at least one use");
5271  DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
5272  print_uses(dbgs()));
5273 
5274  // Now use the reuse data to generate a bunch of interesting ways
5275  // to formulate the values needed for the uses.
5276  GenerateAllReuseFormulae();
5277 
5278  FilterOutUndesirableDedicatedRegisters();
5279  NarrowSearchSpaceUsingHeuristics();
5280 
5282  Solve(Solution);
5283 
5284  // Release memory that is no longer needed.
5285  Factors.clear();
5286  Types.clear();
5287  RegUses.clear();
5288 
5289  if (Solution.empty())
5290  return;
5291 
5292 #ifndef NDEBUG
5293  // Formulae should be legal.
5294  for (const LSRUse &LU : Uses) {
5295  for (const Formula &F : LU.Formulae)
5296  assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
5297  F) && "Illegal formula generated!");
5298  };
5299 #endif
5300 
5301  // Now that we've decided what we want, make it so.
5302  ImplementSolution(Solution);
5303 }
5304 
5305 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
5306  if (Factors.empty() && Types.empty()) return;
5307 
5308  OS << "LSR has identified the following interesting factors and types: ";
5309  bool First = true;
5310 
5311  for (int64_t Factor : Factors) {
5312  if (!First) OS << ", ";
5313  First = false;
5314  OS << '*' << Factor;
5315  }
5316 
5317  for (Type *Ty : Types) {
5318  if (!First) OS << ", ";
5319  First = false;
5320  OS << '(' << *Ty << ')';
5321  }
5322  OS << '\n';
5323 }
5324 
5325 void LSRInstance::print_fixups(raw_ostream &OS) const {
5326  OS << "LSR is examining the following fixup sites:\n";
5327  for (const LSRUse &LU : Uses)
5328  for (const LSRFixup &LF : LU.Fixups) {
5329  dbgs() << " ";
5330  LF.print(OS);
5331  OS << '\n';
5332  }
5333 }
5334 
5335 void LSRInstance::print_uses(raw_ostream &OS) const {
5336  OS << "LSR is examining the following uses:\n";
5337  for (const LSRUse &LU : Uses) {
5338  dbgs() << " ";
5339  LU.print(OS);
5340  OS << '\n';
5341  for (const Formula &F : LU.Formulae) {
5342  OS << " ";
5343  F.print(OS);
5344  OS << '\n';
5345  }
5346  }
5347 }
5348 
5349 void LSRInstance::print(raw_ostream &OS) const {
5350  print_factors_and_types(OS);
5351  print_fixups(OS);
5352  print_uses(OS);
5353 }
5354 
5355 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5356 LLVM_DUMP_METHOD void LSRInstance::dump() const {
5357  print(errs()); errs() << '\n';
5358 }
5359 #endif
5360 
5361 namespace {
5362 
5363 class LoopStrengthReduce : public LoopPass {
5364 public:
5365  static char ID; // Pass ID, replacement for typeid
5366 
5367  LoopStrengthReduce();
5368 
5369 private:
5370  bool runOnLoop(Loop *L, LPPassManager &LPM) override;
5371  void getAnalysisUsage(AnalysisUsage &AU) const override;
5372 };
5373 
5374 } // end anonymous namespace
5375 
5376 LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
5378 }
5379 
5380 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
5381  // We split critical edges, so we change the CFG. However, we do update
5382  // many analyses if they are around.
5384 
5392  // Requiring LoopSimplify a second time here prevents IVUsers from running
5393  // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5398 }
5399 
5401  DominatorTree &DT, LoopInfo &LI,
5402  const TargetTransformInfo &TTI) {
5403  bool Changed = false;
5404 
5405  // Run the main LSR transformation.
5406  Changed |= LSRInstance(L, IU, SE, DT, LI, TTI).getChanged();
5407 
5408  // Remove any extra phis created by processing inner loops.
5409  Changed |= DeleteDeadPHIs(L->getHeader());
5410  if (EnablePhiElim && L->isLoopSimplifyForm()) {
5412  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
5413  SCEVExpander Rewriter(SE, DL, "lsr");
5414 #ifndef NDEBUG
5415  Rewriter.setDebugType(DEBUG_TYPE);
5416 #endif
5417  unsigned numFolded = Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, &TTI);
5418  if (numFolded) {
5419  Changed = true;
5421  DeleteDeadPHIs(L->getHeader());
5422  }
5423  }
5424  return Changed;
5425 }
5426 
5427 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5428  if (skipLoop(L))
5429  return false;
5430 
5431  auto &IU = getAnalysis<IVUsersWrapperPass>().getIU();
5432  auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
5433  auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
5434  auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
5435  const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
5436  *L->getHeader()->getParent());
5437  return ReduceLoopStrength(L, IU, SE, DT, LI, TTI);
5438 }
5439 
5442  LPMUpdater &) {
5443  if (!ReduceLoopStrength(&L, AM.getResult<IVUsersAnalysis>(L, AR), AR.SE,
5444  AR.DT, AR.LI, AR.TTI))
5445  return PreservedAnalyses::all();
5446 
5448 }
5449 
5450 char LoopStrengthReduce::ID = 0;
5451 INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
5452  "Loop Strength Reduction", false, false)
5458 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
5459 INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
5460  "Loop Strength Reduction", false, false)
5461 
5462 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:1172
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:69
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:243
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
iterator_range< use_iterator > uses()
Definition: Value.h:350
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:149
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
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:234
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
This header provides classes for managing a pipeline of passes over loops in LLVM IR...
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:1590
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:96
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:101
static cl::opt< bool > InsnsCost("lsr-insns-cost", cl::Hidden, cl::init(false), cl::desc("Add instruction count to a LSR cost model"))
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:885
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:818
void resize(unsigned N, bool t=false)
Grow or shrink the bitvector.
static void dump(StringRef Title, SpillInfo const &Spills)
Definition: CoroFrame.cpp:285
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...
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
void reserve(size_type N)
Definition: SmallVector.h:380
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:345
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:252
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:176
#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:958
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:585
void clearPostInc()
Disable all post-inc expansion.
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
static User::op_iterator findIVOperand(User::op_iterator OI, User::op_iterator OE, Loop *L, ScalarEvolution &SE)
Helper for CollectChains that finds an IV operand (computed by an AddRec in this loop) within [OI...
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:42
LLVMContext & getContext() const
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:664
Reg
All possible values of the reg field in the ModR/M byte.
void setName(const Twine &Name)
Change the name of the value.
Definition: Value.cpp:284
This node represents multiplication of some number of SCEVs.
ELFYAML::ELF_STO Other
Definition: ELFYAML.cpp:695
This file implements a class to represent arbitrary precision integral constant values and operations...
const APInt & getAPInt() const
BlockT * getHeader() const
Definition: LoopInfo.h:103
ConstantInt * getValue() const
auto reverse(ContainerTy &&C, typename std::enable_if< has_rbegin< ContainerTy >::value >::type *=nullptr) -> decltype(make_range(C.rbegin(), C.rend()))
Definition: STLExtras.h:250
bool isOne() const
This is just a convenience method to make client code smaller for a common case.
Definition: Constants.h:201
Instruction * clone() const
Create a copy of &#39;this&#39; instruction that is identical in all ways except the following: ...
#define F(x, y, z)
Definition: MD5.cpp:55
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
bool isTruncateFree(Type *Ty1, Type *Ty2) const
Return true if it&#39;s free to truncate a value of type Ty1 to type Ty2.
bool insert(const value_type &X)
Insert a new element into the SetVector.
Definition: SetVector.h:142
void clear()
Definition: SmallSet.h:119
static bool isEqual(const Function &Caller, const Function &Callee)
This node represents a polynomial recurrence on the trip count of the specified loop.
const RegList & Regs
iterator begin()
Get an iterator to the beginning of the SetVector.
Definition: SetVector.h:83
bool DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI=nullptr)
Examine each PHI in the given block and delete it if it is dead.