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LoopStrengthReduce.cpp
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1 //===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This transformation analyzes and transforms the induction variables (and
10 // computations derived from them) into forms suitable for efficient execution
11 // on the target.
12 //
13 // This pass performs a strength reduction on array references inside loops that
14 // have as one or more of their components the loop induction variable, it
15 // rewrites expressions to take advantage of scaled-index addressing modes
16 // available on the target, and it performs a variety of other optimizations
17 // related to loop induction variables.
18 //
19 // Terminology note: this code has a lot of handling for "post-increment" or
20 // "post-inc" users. This is not talking about post-increment addressing modes;
21 // it is instead talking about code like this:
22 //
23 // %i = phi [ 0, %entry ], [ %i.next, %latch ]
24 // ...
25 // %i.next = add %i, 1
26 // %c = icmp eq %i.next, %n
27 //
28 // The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
29 // it's useful to think about these as the same register, with some uses using
30 // the value of the register before the add and some using it after. In this
31 // example, the icmp is a post-increment user, since it uses %i.next, which is
32 // the value of the induction variable after the increment. The other common
33 // case of post-increment users is users outside the loop.
34 //
35 // TODO: More sophistication in the way Formulae are generated and filtered.
36 //
37 // TODO: Handle multiple loops at a time.
38 //
39 // TODO: Should the addressing mode BaseGV be changed to a ConstantExpr instead
40 // of a GlobalValue?
41 //
42 // TODO: When truncation is free, truncate ICmp users' operands to make it a
43 // smaller encoding (on x86 at least).
44 //
45 // TODO: When a negated register is used by an add (such as in a list of
46 // multiple base registers, or as the increment expression in an addrec),
47 // we may not actually need both reg and (-1 * reg) in registers; the
48 // negation can be implemented by using a sub instead of an add. The
49 // lack of support for taking this into consideration when making
50 // register pressure decisions is partly worked around by the "Special"
51 // use kind.
52 //
53 //===----------------------------------------------------------------------===//
54 
56 #include "llvm/ADT/APInt.h"
57 #include "llvm/ADT/DenseMap.h"
58 #include "llvm/ADT/DenseSet.h"
59 #include "llvm/ADT/Hashing.h"
61 #include "llvm/ADT/STLExtras.h"
62 #include "llvm/ADT/SetVector.h"
64 #include "llvm/ADT/SmallPtrSet.h"
65 #include "llvm/ADT/SmallSet.h"
66 #include "llvm/ADT/SmallVector.h"
68 #include "llvm/Analysis/IVUsers.h"
70 #include "llvm/Analysis/LoopInfo.h"
71 #include "llvm/Analysis/LoopPass.h"
78 #include "llvm/Config/llvm-config.h"
79 #include "llvm/IR/BasicBlock.h"
80 #include "llvm/IR/Constant.h"
81 #include "llvm/IR/Constants.h"
82 #include "llvm/IR/DerivedTypes.h"
83 #include "llvm/IR/Dominators.h"
84 #include "llvm/IR/GlobalValue.h"
85 #include "llvm/IR/IRBuilder.h"
86 #include "llvm/IR/InstrTypes.h"
87 #include "llvm/IR/Instruction.h"
88 #include "llvm/IR/Instructions.h"
89 #include "llvm/IR/IntrinsicInst.h"
90 #include "llvm/IR/Intrinsics.h"
91 #include "llvm/IR/Module.h"
92 #include "llvm/IR/OperandTraits.h"
93 #include "llvm/IR/Operator.h"
94 #include "llvm/IR/PassManager.h"
95 #include "llvm/IR/Type.h"
96 #include "llvm/IR/Use.h"
97 #include "llvm/IR/User.h"
98 #include "llvm/IR/Value.h"
99 #include "llvm/IR/ValueHandle.h"
100 #include "llvm/Pass.h"
101 #include "llvm/Support/Casting.h"
103 #include "llvm/Support/Compiler.h"
104 #include "llvm/Support/Debug.h"
106 #include "llvm/Support/MathExtras.h"
108 #include "llvm/Transforms/Scalar.h"
109 #include "llvm/Transforms/Utils.h"
111 #include <algorithm>
112 #include <cassert>
113 #include <cstddef>
114 #include <cstdint>
115 #include <cstdlib>
116 #include <iterator>
117 #include <limits>
118 #include <numeric>
119 #include <map>
120 #include <utility>
121 
122 using namespace llvm;
123 
124 #define DEBUG_TYPE "loop-reduce"
125 
126 /// MaxIVUsers is an arbitrary threshold that provides an early opportunity for
127 /// bail out. This threshold is far beyond the number of users that LSR can
128 /// conceivably solve, so it should not affect generated code, but catches the
129 /// worst cases before LSR burns too much compile time and stack space.
130 static const unsigned MaxIVUsers = 200;
131 
132 // Temporary flag to cleanup congruent phis after LSR phi expansion.
133 // It's currently disabled until we can determine whether it's truly useful or
134 // not. The flag should be removed after the v3.0 release.
135 // This is now needed for ivchains.
137  "enable-lsr-phielim", cl::Hidden, cl::init(true),
138  cl::desc("Enable LSR phi elimination"));
139 
140 // The flag adds instruction count to solutions cost comparision.
141 static cl::opt<bool> InsnsCost(
142  "lsr-insns-cost", cl::Hidden, cl::init(true),
143  cl::desc("Add instruction count to a LSR cost model"));
144 
145 // Flag to choose how to narrow complex lsr solution
147  "lsr-exp-narrow", cl::Hidden, cl::init(false),
148  cl::desc("Narrow LSR complex solution using"
149  " expectation of registers number"));
150 
151 // Flag to narrow search space by filtering non-optimal formulae with
152 // the same ScaledReg and Scale.
154  "lsr-filter-same-scaled-reg", cl::Hidden, cl::init(true),
155  cl::desc("Narrow LSR search space by filtering non-optimal formulae"
156  " with the same ScaledReg and Scale"));
157 
159  "lsr-backedge-indexing", cl::Hidden, cl::init(true),
160  cl::desc("Enable the generation of cross iteration indexed memops"));
161 
163  "lsr-complexity-limit", cl::Hidden,
165  cl::desc("LSR search space complexity limit"));
166 
168  "lsr-setupcost-depth-limit", cl::Hidden, cl::init(7),
169  cl::desc("The limit on recursion depth for LSRs setup cost"));
170 
171 #ifndef NDEBUG
172 // Stress test IV chain generation.
174  "stress-ivchain", cl::Hidden, cl::init(false),
175  cl::desc("Stress test LSR IV chains"));
176 #else
177 static bool StressIVChain = false;
178 #endif
179 
180 namespace {
181 
182 struct MemAccessTy {
183  /// Used in situations where the accessed memory type is unknown.
184  static const unsigned UnknownAddressSpace =
186 
187  Type *MemTy = nullptr;
188  unsigned AddrSpace = UnknownAddressSpace;
189 
190  MemAccessTy() = default;
191  MemAccessTy(Type *Ty, unsigned AS) : MemTy(Ty), AddrSpace(AS) {}
192 
193  bool operator==(MemAccessTy Other) const {
194  return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace;
195  }
196 
197  bool operator!=(MemAccessTy Other) const { return !(*this == Other); }
198 
199  static MemAccessTy getUnknown(LLVMContext &Ctx,
200  unsigned AS = UnknownAddressSpace) {
201  return MemAccessTy(Type::getVoidTy(Ctx), AS);
202  }
203 
204  Type *getType() { return MemTy; }
205 };
206 
207 /// This class holds data which is used to order reuse candidates.
208 class RegSortData {
209 public:
210  /// This represents the set of LSRUse indices which reference
211  /// a particular register.
212  SmallBitVector UsedByIndices;
213 
214  void print(raw_ostream &OS) const;
215  void dump() const;
216 };
217 
218 } // end anonymous namespace
219 
220 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
221 void RegSortData::print(raw_ostream &OS) const {
222  OS << "[NumUses=" << UsedByIndices.count() << ']';
223 }
224 
225 LLVM_DUMP_METHOD void RegSortData::dump() const {
226  print(errs()); errs() << '\n';
227 }
228 #endif
229 
230 namespace {
231 
232 /// Map register candidates to information about how they are used.
233 class RegUseTracker {
234  using RegUsesTy = DenseMap<const SCEV *, RegSortData>;
235 
236  RegUsesTy RegUsesMap;
238 
239 public:
240  void countRegister(const SCEV *Reg, size_t LUIdx);
241  void dropRegister(const SCEV *Reg, size_t LUIdx);
242  void swapAndDropUse(size_t LUIdx, size_t LastLUIdx);
243 
244  bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
245 
246  const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
247 
248  void clear();
249 
251  using const_iterator = SmallVectorImpl<const SCEV *>::const_iterator;
252 
253  iterator begin() { return RegSequence.begin(); }
254  iterator end() { return RegSequence.end(); }
255  const_iterator begin() const { return RegSequence.begin(); }
256  const_iterator end() const { return RegSequence.end(); }
257 };
258 
259 } // end anonymous namespace
260 
261 void
262 RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) {
263  std::pair<RegUsesTy::iterator, bool> Pair =
264  RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
265  RegSortData &RSD = Pair.first->second;
266  if (Pair.second)
267  RegSequence.push_back(Reg);
268  RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
269  RSD.UsedByIndices.set(LUIdx);
270 }
271 
272 void
273 RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) {
274  RegUsesTy::iterator It = RegUsesMap.find(Reg);
275  assert(It != RegUsesMap.end());
276  RegSortData &RSD = It->second;
277  assert(RSD.UsedByIndices.size() > LUIdx);
278  RSD.UsedByIndices.reset(LUIdx);
279 }
280 
281 void
282 RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
283  assert(LUIdx <= LastLUIdx);
284 
285  // Update RegUses. The data structure is not optimized for this purpose;
286  // we must iterate through it and update each of the bit vectors.
287  for (auto &Pair : RegUsesMap) {
288  SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
289  if (LUIdx < UsedByIndices.size())
290  UsedByIndices[LUIdx] =
291  LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false;
292  UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
293  }
294 }
295 
296 bool
297 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
298  RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
299  if (I == RegUsesMap.end())
300  return false;
301  const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
302  int i = UsedByIndices.find_first();
303  if (i == -1) return false;
304  if ((size_t)i != LUIdx) return true;
305  return UsedByIndices.find_next(i) != -1;
306 }
307 
308 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
309  RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
310  assert(I != RegUsesMap.end() && "Unknown register!");
311  return I->second.UsedByIndices;
312 }
313 
314 void RegUseTracker::clear() {
315  RegUsesMap.clear();
316  RegSequence.clear();
317 }
318 
319 namespace {
320 
321 /// This class holds information that describes a formula for computing
322 /// satisfying a use. It may include broken-out immediates and scaled registers.
323 struct Formula {
324  /// Global base address used for complex addressing.
325  GlobalValue *BaseGV = nullptr;
326 
327  /// Base offset for complex addressing.
328  int64_t BaseOffset = 0;
329 
330  /// Whether any complex addressing has a base register.
331  bool HasBaseReg = false;
332 
333  /// The scale of any complex addressing.
334  int64_t Scale = 0;
335 
336  /// The list of "base" registers for this use. When this is non-empty. The
337  /// canonical representation of a formula is
338  /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
339  /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
340  /// 3. The reg containing recurrent expr related with currect loop in the
341  /// formula should be put in the ScaledReg.
342  /// #1 enforces that the scaled register is always used when at least two
343  /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
344  /// #2 enforces that 1 * reg is reg.
345  /// #3 ensures invariant regs with respect to current loop can be combined
346  /// together in LSR codegen.
347  /// This invariant can be temporarily broken while building a formula.
348  /// However, every formula inserted into the LSRInstance must be in canonical
349  /// form.
351 
352  /// The 'scaled' register for this use. This should be non-null when Scale is
353  /// not zero.
354  const SCEV *ScaledReg = nullptr;
355 
356  /// An additional constant offset which added near the use. This requires a
357  /// temporary register, but the offset itself can live in an add immediate
358  /// field rather than a register.
359  int64_t UnfoldedOffset = 0;
360 
361  Formula() = default;
362 
363  void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
364 
365  bool isCanonical(const Loop &L) const;
366 
367  void canonicalize(const Loop &L);
368 
369  bool unscale();
370 
371  bool hasZeroEnd() const;
372 
373  size_t getNumRegs() const;
374  Type *getType() const;
375 
376  void deleteBaseReg(const SCEV *&S);
377 
378  bool referencesReg(const SCEV *S) const;
379  bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
380  const RegUseTracker &RegUses) const;
381 
382  void print(raw_ostream &OS) const;
383  void dump() const;
384 };
385 
386 } // end anonymous namespace
387 
388 /// Recursion helper for initialMatch.
389 static void DoInitialMatch(const SCEV *S, Loop *L,
392  ScalarEvolution &SE) {
393  // Collect expressions which properly dominate the loop header.
394  if (SE.properlyDominates(S, L->getHeader())) {
395  Good.push_back(S);
396  return;
397  }
398 
399  // Look at add operands.
400  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
401  for (const SCEV *S : Add->operands())
402  DoInitialMatch(S, L, Good, Bad, SE);
403  return;
404  }
405 
406  // Look at addrec operands.
407  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
408  if (!AR->getStart()->isZero() && AR->isAffine()) {
409  DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
410  DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
411  AR->getStepRecurrence(SE),
412  // FIXME: AR->getNoWrapFlags()
413  AR->getLoop(), SCEV::FlagAnyWrap),
414  L, Good, Bad, SE);
415  return;
416  }
417 
418  // Handle a multiplication by -1 (negation) if it didn't fold.
419  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
420  if (Mul->getOperand(0)->isAllOnesValue()) {
421  SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
422  const SCEV *NewMul = SE.getMulExpr(Ops);
423 
426  DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
427  const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
428  SE.getEffectiveSCEVType(NewMul->getType())));
429  for (const SCEV *S : MyGood)
430  Good.push_back(SE.getMulExpr(NegOne, S));
431  for (const SCEV *S : MyBad)
432  Bad.push_back(SE.getMulExpr(NegOne, S));
433  return;
434  }
435 
436  // Ok, we can't do anything interesting. Just stuff the whole thing into a
437  // register and hope for the best.
438  Bad.push_back(S);
439 }
440 
441 /// Incorporate loop-variant parts of S into this Formula, attempting to keep
442 /// all loop-invariant and loop-computable values in a single base register.
443 void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
446  DoInitialMatch(S, L, Good, Bad, SE);
447  if (!Good.empty()) {
448  const SCEV *Sum = SE.getAddExpr(Good);
449  if (!Sum->isZero())
450  BaseRegs.push_back(Sum);
451  HasBaseReg = true;
452  }
453  if (!Bad.empty()) {
454  const SCEV *Sum = SE.getAddExpr(Bad);
455  if (!Sum->isZero())
456  BaseRegs.push_back(Sum);
457  HasBaseReg = true;
458  }
459  canonicalize(*L);
460 }
461 
462 /// Check whether or not this formula satisfies the canonical
463 /// representation.
464 /// \see Formula::BaseRegs.
465 bool Formula::isCanonical(const Loop &L) const {
466  if (!ScaledReg)
467  return BaseRegs.size() <= 1;
468 
469  if (Scale != 1)
470  return true;
471 
472  if (Scale == 1 && BaseRegs.empty())
473  return false;
474 
475  const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
476  if (SAR && SAR->getLoop() == &L)
477  return true;
478 
479  // If ScaledReg is not a recurrent expr, or it is but its loop is not current
480  // loop, meanwhile BaseRegs contains a recurrent expr reg related with current
481  // loop, we want to swap the reg in BaseRegs with ScaledReg.
482  auto I =
483  find_if(make_range(BaseRegs.begin(), BaseRegs.end()), [&](const SCEV *S) {
484  return isa<const SCEVAddRecExpr>(S) &&
485  (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
486  });
487  return I == BaseRegs.end();
488 }
489 
490 /// Helper method to morph a formula into its canonical representation.
491 /// \see Formula::BaseRegs.
492 /// Every formula having more than one base register, must use the ScaledReg
493 /// field. Otherwise, we would have to do special cases everywhere in LSR
494 /// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
495 /// On the other hand, 1*reg should be canonicalized into reg.
496 void Formula::canonicalize(const Loop &L) {
497  if (isCanonical(L))
498  return;
499  // So far we did not need this case. This is easy to implement but it is
500  // useless to maintain dead code. Beside it could hurt compile time.
501  assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.");
502 
503  // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
504  if (!ScaledReg) {
505  ScaledReg = BaseRegs.back();
506  BaseRegs.pop_back();
507  Scale = 1;
508  }
509 
510  // If ScaledReg is an invariant with respect to L, find the reg from
511  // BaseRegs containing the recurrent expr related with Loop L. Swap the
512  // reg with ScaledReg.
513  const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
514  if (!SAR || SAR->getLoop() != &L) {
515  auto I = find_if(make_range(BaseRegs.begin(), BaseRegs.end()),
516  [&](const SCEV *S) {
517  return isa<const SCEVAddRecExpr>(S) &&
518  (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
519  });
520  if (I != BaseRegs.end())
521  std::swap(ScaledReg, *I);
522  }
523 }
524 
525 /// Get rid of the scale in the formula.
526 /// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
527 /// \return true if it was possible to get rid of the scale, false otherwise.
528 /// \note After this operation the formula may not be in the canonical form.
529 bool Formula::unscale() {
530  if (Scale != 1)
531  return false;
532  Scale = 0;
533  BaseRegs.push_back(ScaledReg);
534  ScaledReg = nullptr;
535  return true;
536 }
537 
538 bool Formula::hasZeroEnd() const {
539  if (UnfoldedOffset || BaseOffset)
540  return false;
541  if (BaseRegs.size() != 1 || ScaledReg)
542  return false;
543  return true;
544 }
545 
546 /// Return the total number of register operands used by this formula. This does
547 /// not include register uses implied by non-constant addrec strides.
548 size_t Formula::getNumRegs() const {
549  return !!ScaledReg + BaseRegs.size();
550 }
551 
552 /// Return the type of this formula, if it has one, or null otherwise. This type
553 /// is meaningless except for the bit size.
554 Type *Formula::getType() const {
555  return !BaseRegs.empty() ? BaseRegs.front()->getType() :
556  ScaledReg ? ScaledReg->getType() :
557  BaseGV ? BaseGV->getType() :
558  nullptr;
559 }
560 
561 /// Delete the given base reg from the BaseRegs list.
562 void Formula::deleteBaseReg(const SCEV *&S) {
563  if (&S != &BaseRegs.back())
564  std::swap(S, BaseRegs.back());
565  BaseRegs.pop_back();
566 }
567 
568 /// Test if this formula references the given register.
569 bool Formula::referencesReg(const SCEV *S) const {
570  return S == ScaledReg || is_contained(BaseRegs, S);
571 }
572 
573 /// Test whether this formula uses registers which are used by uses other than
574 /// the use with the given index.
575 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
576  const RegUseTracker &RegUses) const {
577  if (ScaledReg)
578  if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
579  return true;
580  for (const SCEV *BaseReg : BaseRegs)
581  if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
582  return true;
583  return false;
584 }
585 
586 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
587 void Formula::print(raw_ostream &OS) const {
588  bool First = true;
589  if (BaseGV) {
590  if (!First) OS << " + "; else First = false;
591  BaseGV->printAsOperand(OS, /*PrintType=*/false);
592  }
593  if (BaseOffset != 0) {
594  if (!First) OS << " + "; else First = false;
595  OS << BaseOffset;
596  }
597  for (const SCEV *BaseReg : BaseRegs) {
598  if (!First) OS << " + "; else First = false;
599  OS << "reg(" << *BaseReg << ')';
600  }
601  if (HasBaseReg && BaseRegs.empty()) {
602  if (!First) OS << " + "; else First = false;
603  OS << "**error: HasBaseReg**";
604  } else if (!HasBaseReg && !BaseRegs.empty()) {
605  if (!First) OS << " + "; else First = false;
606  OS << "**error: !HasBaseReg**";
607  }
608  if (Scale != 0) {
609  if (!First) OS << " + "; else First = false;
610  OS << Scale << "*reg(";
611  if (ScaledReg)
612  OS << *ScaledReg;
613  else
614  OS << "<unknown>";
615  OS << ')';
616  }
617  if (UnfoldedOffset != 0) {
618  if (!First) OS << " + ";
619  OS << "imm(" << UnfoldedOffset << ')';
620  }
621 }
622 
623 LLVM_DUMP_METHOD void Formula::dump() const {
624  print(errs()); errs() << '\n';
625 }
626 #endif
627 
628 /// Return true if the given addrec can be sign-extended without changing its
629 /// value.
630 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
631  Type *WideTy =
633  return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
634 }
635 
636 /// Return true if the given add can be sign-extended without changing its
637 /// value.
638 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
639  Type *WideTy =
641  return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
642 }
643 
644 /// Return true if the given mul can be sign-extended without changing its
645 /// value.
646 static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
647  Type *WideTy =
649  SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
650  return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
651 }
652 
653 /// Return an expression for LHS /s RHS, if it can be determined and if the
654 /// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
655 /// is true, expressions like (X * Y) /s Y are simplified to Y, ignoring that
656 /// the multiplication may overflow, which is useful when the result will be
657 /// used in a context where the most significant bits are ignored.
658 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
659  ScalarEvolution &SE,
660  bool IgnoreSignificantBits = false) {
661  // Handle the trivial case, which works for any SCEV type.
662  if (LHS == RHS)
663  return SE.getConstant(LHS->getType(), 1);
664 
665  // Handle a few RHS special cases.
666  const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
667  if (RC) {
668  const APInt &RA = RC->getAPInt();
669  // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
670  // some folding.
671  if (RA.isAllOnesValue())
672  return SE.getMulExpr(LHS, RC);
673  // Handle x /s 1 as x.
674  if (RA == 1)
675  return LHS;
676  }
677 
678  // Check for a division of a constant by a constant.
679  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
680  if (!RC)
681  return nullptr;
682  const APInt &LA = C->getAPInt();
683  const APInt &RA = RC->getAPInt();
684  if (LA.srem(RA) != 0)
685  return nullptr;
686  return SE.getConstant(LA.sdiv(RA));
687  }
688 
689  // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
690  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
691  if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
692  const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
693  IgnoreSignificantBits);
694  if (!Step) return nullptr;
695  const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
696  IgnoreSignificantBits);
697  if (!Start) return nullptr;
698  // FlagNW is independent of the start value, step direction, and is
699  // preserved with smaller magnitude steps.
700  // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
701  return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
702  }
703  return nullptr;
704  }
705 
706  // Distribute the sdiv over add operands, if the add doesn't overflow.
707  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
708  if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
710  for (const SCEV *S : Add->operands()) {
711  const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
712  if (!Op) return nullptr;
713  Ops.push_back(Op);
714  }
715  return SE.getAddExpr(Ops);
716  }
717  return nullptr;
718  }
719 
720  // Check for a multiply operand that we can pull RHS out of.
721  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
722  if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
724  bool Found = false;
725  for (const SCEV *S : Mul->operands()) {
726  if (!Found)
727  if (const SCEV *Q = getExactSDiv(S, RHS, SE,
728  IgnoreSignificantBits)) {
729  S = Q;
730  Found = true;
731  }
732  Ops.push_back(S);
733  }
734  return Found ? SE.getMulExpr(Ops) : nullptr;
735  }
736  return nullptr;
737  }
738 
739  // Otherwise we don't know.
740  return nullptr;
741 }
742 
743 /// If S involves the addition of a constant integer value, return that integer
744 /// value, and mutate S to point to a new SCEV with that value excluded.
745 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
746  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
747  if (C->getAPInt().getMinSignedBits() <= 64) {
748  S = SE.getConstant(C->getType(), 0);
749  return C->getValue()->getSExtValue();
750  }
751  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
752  SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
753  int64_t Result = ExtractImmediate(NewOps.front(), SE);
754  if (Result != 0)
755  S = SE.getAddExpr(NewOps);
756  return Result;
757  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
758  SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
759  int64_t Result = ExtractImmediate(NewOps.front(), SE);
760  if (Result != 0)
761  S = SE.getAddRecExpr(NewOps, AR->getLoop(),
762  // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
764  return Result;
765  }
766  return 0;
767 }
768 
769 /// If S involves the addition of a GlobalValue address, return that symbol, and
770 /// mutate S to point to a new SCEV with that value excluded.
772  if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
773  if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
774  S = SE.getConstant(GV->getType(), 0);
775  return GV;
776  }
777  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
778  SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
779  GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
780  if (Result)
781  S = SE.getAddExpr(NewOps);
782  return Result;
783  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
784  SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
785  GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
786  if (Result)
787  S = SE.getAddRecExpr(NewOps, AR->getLoop(),
788  // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
790  return Result;
791  }
792  return nullptr;
793 }
794 
795 /// Returns true if the specified instruction is using the specified value as an
796 /// address.
797 static bool isAddressUse(const TargetTransformInfo &TTI,
798  Instruction *Inst, Value *OperandVal) {
799  bool isAddress = isa<LoadInst>(Inst);
800  if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
801  if (SI->getPointerOperand() == OperandVal)
802  isAddress = true;
803  } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
804  // Addressing modes can also be folded into prefetches and a variety
805  // of intrinsics.
806  switch (II->getIntrinsicID()) {
807  case Intrinsic::memset:
808  case Intrinsic::prefetch:
809  if (II->getArgOperand(0) == OperandVal)
810  isAddress = true;
811  break;
812  case Intrinsic::memmove:
813  case Intrinsic::memcpy:
814  if (II->getArgOperand(0) == OperandVal ||
815  II->getArgOperand(1) == OperandVal)
816  isAddress = true;
817  break;
818  default: {
819  MemIntrinsicInfo IntrInfo;
820  if (TTI.getTgtMemIntrinsic(II, IntrInfo)) {
821  if (IntrInfo.PtrVal == OperandVal)
822  isAddress = true;
823  }
824  }
825  }
826  } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
827  if (RMW->getPointerOperand() == OperandVal)
828  isAddress = true;
829  } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
830  if (CmpX->getPointerOperand() == OperandVal)
831  isAddress = true;
832  }
833  return isAddress;
834 }
835 
836 /// Return the type of the memory being accessed.
837 static MemAccessTy getAccessType(const TargetTransformInfo &TTI,
838  Instruction *Inst, Value *OperandVal) {
839  MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
840  if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
841  AccessTy.MemTy = SI->getOperand(0)->getType();
842  AccessTy.AddrSpace = SI->getPointerAddressSpace();
843  } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
844  AccessTy.AddrSpace = LI->getPointerAddressSpace();
845  } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
846  AccessTy.AddrSpace = RMW->getPointerAddressSpace();
847  } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
848  AccessTy.AddrSpace = CmpX->getPointerAddressSpace();
849  } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
850  switch (II->getIntrinsicID()) {
851  case Intrinsic::prefetch:
852  case Intrinsic::memset:
853  AccessTy.AddrSpace = II->getArgOperand(0)->getType()->getPointerAddressSpace();
854  AccessTy.MemTy = OperandVal->getType();
855  break;
856  case Intrinsic::memmove:
857  case Intrinsic::memcpy:
858  AccessTy.AddrSpace = OperandVal->getType()->getPointerAddressSpace();
859  AccessTy.MemTy = OperandVal->getType();
860  break;
861  default: {
862  MemIntrinsicInfo IntrInfo;
863  if (TTI.getTgtMemIntrinsic(II, IntrInfo) && IntrInfo.PtrVal) {
864  AccessTy.AddrSpace
865  = IntrInfo.PtrVal->getType()->getPointerAddressSpace();
866  }
867 
868  break;
869  }
870  }
871  }
872 
873  // All pointers have the same requirements, so canonicalize them to an
874  // arbitrary pointer type to minimize variation.
875  if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
876  AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
877  PTy->getAddressSpace());
878 
879  return AccessTy;
880 }
881 
882 /// Return true if this AddRec is already a phi in its loop.
883 static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
884  for (PHINode &PN : AR->getLoop()->getHeader()->phis()) {
885  if (SE.isSCEVable(PN.getType()) &&
886  (SE.getEffectiveSCEVType(PN.getType()) ==
887  SE.getEffectiveSCEVType(AR->getType())) &&
888  SE.getSCEV(&PN) == AR)
889  return true;
890  }
891  return false;
892 }
893 
894 /// Check if expanding this expression is likely to incur significant cost. This
895 /// is tricky because SCEV doesn't track which expressions are actually computed
896 /// by the current IR.
897 ///
898 /// We currently allow expansion of IV increments that involve adds,
899 /// multiplication by constants, and AddRecs from existing phis.
900 ///
901 /// TODO: Allow UDivExpr if we can find an existing IV increment that is an
902 /// obvious multiple of the UDivExpr.
903 static bool isHighCostExpansion(const SCEV *S,
904  SmallPtrSetImpl<const SCEV*> &Processed,
905  ScalarEvolution &SE) {
906  // Zero/One operand expressions
907  switch (S->getSCEVType()) {
908  case scUnknown:
909  case scConstant:
910  return false;
911  case scTruncate:
912  return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
913  Processed, SE);
914  case scZeroExtend:
915  return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
916  Processed, SE);
917  case scSignExtend:
918  return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
919  Processed, SE);
920  }
921 
922  if (!Processed.insert(S).second)
923  return false;
924 
925  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
926  for (const SCEV *S : Add->operands()) {
927  if (isHighCostExpansion(S, Processed, SE))
928  return true;
929  }
930  return false;
931  }
932 
933  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
934  if (Mul->getNumOperands() == 2) {
935  // Multiplication by a constant is ok
936  if (isa<SCEVConstant>(Mul->getOperand(0)))
937  return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
938 
939  // If we have the value of one operand, check if an existing
940  // multiplication already generates this expression.
941  if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
942  Value *UVal = U->getValue();
943  for (User *UR : UVal->users()) {
944  // If U is a constant, it may be used by a ConstantExpr.
945  Instruction *UI = dyn_cast<Instruction>(UR);
946  if (UI && UI->getOpcode() == Instruction::Mul &&
947  SE.isSCEVable(UI->getType())) {
948  return SE.getSCEV(UI) == Mul;
949  }
950  }
951  }
952  }
953  }
954 
955  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
956  if (isExistingPhi(AR, SE))
957  return false;
958  }
959 
960  // Fow now, consider any other type of expression (div/mul/min/max) high cost.
961  return true;
962 }
963 
964 /// If any of the instructions in the specified set are trivially dead, delete
965 /// them and see if this makes any of their operands subsequently dead.
966 static bool
968  bool Changed = false;
969 
970  while (!DeadInsts.empty()) {
971  Value *V = DeadInsts.pop_back_val();
972  Instruction *I = dyn_cast_or_null<Instruction>(V);
973 
974  if (!I || !isInstructionTriviallyDead(I))
975  continue;
976 
977  for (Use &O : I->operands())
978  if (Instruction *U = dyn_cast<Instruction>(O)) {
979  O = nullptr;
980  if (U->use_empty())
981  DeadInsts.emplace_back(U);
982  }
983 
984  I->eraseFromParent();
985  Changed = true;
986  }
987 
988  return Changed;
989 }
990 
991 namespace {
992 
993 class LSRUse;
994 
995 } // end anonymous namespace
996 
997 /// Check if the addressing mode defined by \p F is completely
998 /// folded in \p LU at isel time.
999 /// This includes address-mode folding and special icmp tricks.
1000 /// This function returns true if \p LU can accommodate what \p F
1001 /// defines and up to 1 base + 1 scaled + offset.
1002 /// In other words, if \p F has several base registers, this function may
1003 /// still return true. Therefore, users still need to account for
1004 /// additional base registers and/or unfolded offsets to derive an
1005 /// accurate cost model.
1006 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1007  const LSRUse &LU, const Formula &F);
1008 
1009 // Get the cost of the scaling factor used in F for LU.
1010 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1011  const LSRUse &LU, const Formula &F,
1012  const Loop &L);
1013 
1014 namespace {
1015 
1016 /// This class is used to measure and compare candidate formulae.
1017 class Cost {
1018  const Loop *L = nullptr;
1019  ScalarEvolution *SE = nullptr;
1020  const TargetTransformInfo *TTI = nullptr;
1022 
1023 public:
1024  Cost() = delete;
1025  Cost(const Loop *L, ScalarEvolution &SE, const TargetTransformInfo &TTI) :
1026  L(L), SE(&SE), TTI(&TTI) {
1027  C.Insns = 0;
1028  C.NumRegs = 0;
1029  C.AddRecCost = 0;
1030  C.NumIVMuls = 0;
1031  C.NumBaseAdds = 0;
1032  C.ImmCost = 0;
1033  C.SetupCost = 0;
1034  C.ScaleCost = 0;
1035  }
1036 
1037  bool isLess(Cost &Other);
1038 
1039  void Lose();
1040 
1041 #ifndef NDEBUG
1042  // Once any of the metrics loses, they must all remain losers.
1043  bool isValid() {
1044  return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds
1045  | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u)
1046  || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds
1047  & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u);
1048  }
1049 #endif
1050 
1051  bool isLoser() {
1052  assert(isValid() && "invalid cost");
1053  return C.NumRegs == ~0u;
1054  }
1055 
1056  void RateFormula(const Formula &F,
1058  const DenseSet<const SCEV *> &VisitedRegs,
1059  const LSRUse &LU,
1060  SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
1061 
1062  void print(raw_ostream &OS) const;
1063  void dump() const;
1064 
1065 private:
1066  void RateRegister(const Formula &F, const SCEV *Reg,
1068  void RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1070  SmallPtrSetImpl<const SCEV *> *LoserRegs);
1071 };
1072 
1073 /// An operand value in an instruction which is to be replaced with some
1074 /// equivalent, possibly strength-reduced, replacement.
1075 struct LSRFixup {
1076  /// The instruction which will be updated.
1077  Instruction *UserInst = nullptr;
1078 
1079  /// The operand of the instruction which will be replaced. The operand may be
1080  /// used more than once; every instance will be replaced.
1081  Value *OperandValToReplace = nullptr;
1082 
1083  /// If this user is to use the post-incremented value of an induction
1084  /// variable, this set is non-empty and holds the loops associated with the
1085  /// induction variable.
1086  PostIncLoopSet PostIncLoops;
1087 
1088  /// A constant offset to be added to the LSRUse expression. This allows
1089  /// multiple fixups to share the same LSRUse with different offsets, for
1090  /// example in an unrolled loop.
1091  int64_t Offset = 0;
1092 
1093  LSRFixup() = default;
1094 
1095  bool isUseFullyOutsideLoop(const Loop *L) const;
1096 
1097  void print(raw_ostream &OS) const;
1098  void dump() const;
1099 };
1100 
1101 /// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
1102 /// SmallVectors of const SCEV*.
1103 struct UniquifierDenseMapInfo {
1104  static SmallVector<const SCEV *, 4> getEmptyKey() {
1106  V.push_back(reinterpret_cast<const SCEV *>(-1));
1107  return V;
1108  }
1109 
1110  static SmallVector<const SCEV *, 4> getTombstoneKey() {
1112  V.push_back(reinterpret_cast<const SCEV *>(-2));
1113  return V;
1114  }
1115 
1116  static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1117  return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1118  }
1119 
1120  static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1121  const SmallVector<const SCEV *, 4> &RHS) {
1122  return LHS == RHS;
1123  }
1124 };
1125 
1126 /// This class holds the state that LSR keeps for each use in IVUsers, as well
1127 /// as uses invented by LSR itself. It includes information about what kinds of
1128 /// things can be folded into the user, information about the user itself, and
1129 /// information about how the use may be satisfied. TODO: Represent multiple
1130 /// users of the same expression in common?
1131 class LSRUse {
1132  DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1133 
1134 public:
1135  /// An enum for a kind of use, indicating what types of scaled and immediate
1136  /// operands it might support.
1137  enum KindType {
1138  Basic, ///< A normal use, with no folding.
1139  Special, ///< A special case of basic, allowing -1 scales.
1140  Address, ///< An address use; folding according to TargetLowering
1141  ICmpZero ///< An equality icmp with both operands folded into one.
1142  // TODO: Add a generic icmp too?
1143  };
1144 
1145  using SCEVUseKindPair = PointerIntPair<const SCEV *, 2, KindType>;
1146 
1147  KindType Kind;
1148  MemAccessTy AccessTy;
1149 
1150  /// The list of operands which are to be replaced.
1152 
1153  /// Keep track of the min and max offsets of the fixups.
1154  int64_t MinOffset = std::numeric_limits<int64_t>::max();
1155  int64_t MaxOffset = std::numeric_limits<int64_t>::min();
1156 
1157  /// This records whether all of the fixups using this LSRUse are outside of
1158  /// the loop, in which case some special-case heuristics may be used.
1159  bool AllFixupsOutsideLoop = true;
1160 
1161  /// RigidFormula is set to true to guarantee that this use will be associated
1162  /// with a single formula--the one that initially matched. Some SCEV
1163  /// expressions cannot be expanded. This allows LSR to consider the registers
1164  /// used by those expressions without the need to expand them later after
1165  /// changing the formula.
1166  bool RigidFormula = false;
1167 
1168  /// This records the widest use type for any fixup using this
1169  /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1170  /// fixup widths to be equivalent, because the narrower one may be relying on
1171  /// the implicit truncation to truncate away bogus bits.
1172  Type *WidestFixupType = nullptr;
1173 
1174  /// A list of ways to build a value that can satisfy this user. After the
1175  /// list is populated, one of these is selected heuristically and used to
1176  /// formulate a replacement for OperandValToReplace in UserInst.
1177  SmallVector<Formula, 12> Formulae;
1178 
1179  /// The set of register candidates used by all formulae in this LSRUse.
1181 
1182  LSRUse(KindType K, MemAccessTy AT) : Kind(K), AccessTy(AT) {}
1183 
1184  LSRFixup &getNewFixup() {
1185  Fixups.push_back(LSRFixup());
1186  return Fixups.back();
1187  }
1188 
1189  void pushFixup(LSRFixup &f) {
1190  Fixups.push_back(f);
1191  if (f.Offset > MaxOffset)
1192  MaxOffset = f.Offset;
1193  if (f.Offset < MinOffset)
1194  MinOffset = f.Offset;
1195  }
1196 
1197  bool HasFormulaWithSameRegs(const Formula &F) const;
1198  float getNotSelectedProbability(const SCEV *Reg) const;
1199  bool InsertFormula(const Formula &F, const Loop &L);
1200  void DeleteFormula(Formula &F);
1201  void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1202 
1203  void print(raw_ostream &OS) const;
1204  void dump() const;
1205 };
1206 
1207 } // end anonymous namespace
1208 
1209 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1210  LSRUse::KindType Kind, MemAccessTy AccessTy,
1211  GlobalValue *BaseGV, int64_t BaseOffset,
1212  bool HasBaseReg, int64_t Scale,
1213  Instruction *Fixup = nullptr);
1214 
1215 static unsigned getSetupCost(const SCEV *Reg, unsigned Depth) {
1216  if (isa<SCEVUnknown>(Reg) || isa<SCEVConstant>(Reg))
1217  return 1;
1218  if (Depth == 0)
1219  return 0;
1220  if (const auto *S = dyn_cast<SCEVAddRecExpr>(Reg))
1221  return getSetupCost(S->getStart(), Depth - 1);
1222  if (auto S = dyn_cast<SCEVCastExpr>(Reg))
1223  return getSetupCost(S->getOperand(), Depth - 1);
1224  if (auto S = dyn_cast<SCEVNAryExpr>(Reg))
1225  return std::accumulate(S->op_begin(), S->op_end(), 0,
1226  [&](unsigned i, const SCEV *Reg) {
1227  return i + getSetupCost(Reg, Depth - 1);
1228  });
1229  if (auto S = dyn_cast<SCEVUDivExpr>(Reg))
1230  return getSetupCost(S->getLHS(), Depth - 1) +
1231  getSetupCost(S->getRHS(), Depth - 1);
1232  return 0;
1233 }
1234 
1235 /// Tally up interesting quantities from the given register.
1236 void Cost::RateRegister(const Formula &F, const SCEV *Reg,
1238  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1239  // If this is an addrec for another loop, it should be an invariant
1240  // with respect to L since L is the innermost loop (at least
1241  // for now LSR only handles innermost loops).
1242  if (AR->getLoop() != L) {
1243  // If the AddRec exists, consider it's register free and leave it alone.
1244  if (isExistingPhi(AR, *SE))
1245  return;
1246 
1247  // It is bad to allow LSR for current loop to add induction variables
1248  // for its sibling loops.
1249  if (!AR->getLoop()->contains(L)) {
1250  Lose();
1251  return;
1252  }
1253 
1254  // Otherwise, it will be an invariant with respect to Loop L.
1255  ++C.NumRegs;
1256  return;
1257  }
1258 
1259  unsigned LoopCost = 1;
1260  if (TTI->isIndexedLoadLegal(TTI->MIM_PostInc, AR->getType()) ||
1261  TTI->isIndexedStoreLegal(TTI->MIM_PostInc, AR->getType())) {
1262 
1263  // If the step size matches the base offset, we could use pre-indexed
1264  // addressing.
1265  if (TTI->shouldFavorBackedgeIndex(L)) {
1266  if (auto *Step = dyn_cast<SCEVConstant>(AR->getStepRecurrence(*SE)))
1267  if (Step->getAPInt() == F.BaseOffset)
1268  LoopCost = 0;
1269  }
1270 
1271  if (TTI->shouldFavorPostInc()) {
1272  const SCEV *LoopStep = AR->getStepRecurrence(*SE);
1273  if (isa<SCEVConstant>(LoopStep)) {
1274  const SCEV *LoopStart = AR->getStart();
1275  if (!isa<SCEVConstant>(LoopStart) &&
1276  SE->isLoopInvariant(LoopStart, L))
1277  LoopCost = 0;
1278  }
1279  }
1280  }
1281  C.AddRecCost += LoopCost;
1282 
1283  // Add the step value register, if it needs one.
1284  // TODO: The non-affine case isn't precisely modeled here.
1285  if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1286  if (!Regs.count(AR->getOperand(1))) {
1287  RateRegister(F, AR->getOperand(1), Regs);
1288  if (isLoser())
1289  return;
1290  }
1291  }
1292  }
1293  ++C.NumRegs;
1294 
1295  // Rough heuristic; favor registers which don't require extra setup
1296  // instructions in the preheader.
1297  C.SetupCost += getSetupCost(Reg, SetupCostDepthLimit);
1298  // Ensure we don't, even with the recusion limit, produce invalid costs.
1299  C.SetupCost = std::min<unsigned>(C.SetupCost, 1 << 16);
1300 
1301  C.NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1302  SE->hasComputableLoopEvolution(Reg, L);
1303 }
1304 
1305 /// Record this register in the set. If we haven't seen it before, rate
1306 /// it. Optional LoserRegs provides a way to declare any formula that refers to
1307 /// one of those regs an instant loser.
1308 void Cost::RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1310  SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1311  if (LoserRegs && LoserRegs->count(Reg)) {
1312  Lose();
1313  return;
1314  }
1315  if (Regs.insert(Reg).second) {
1316  RateRegister(F, Reg, Regs);
1317  if (LoserRegs && isLoser())
1318  LoserRegs->insert(Reg);
1319  }
1320 }
1321 
1322 void Cost::RateFormula(const Formula &F,
1324  const DenseSet<const SCEV *> &VisitedRegs,
1325  const LSRUse &LU,
1326  SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1327  assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula");
1328  // Tally up the registers.
1329  unsigned PrevAddRecCost = C.AddRecCost;
1330  unsigned PrevNumRegs = C.NumRegs;
1331  unsigned PrevNumBaseAdds = C.NumBaseAdds;
1332  if (const SCEV *ScaledReg = F.ScaledReg) {
1333  if (VisitedRegs.count(ScaledReg)) {
1334  Lose();
1335  return;
1336  }
1337  RatePrimaryRegister(F, ScaledReg, Regs, LoserRegs);
1338  if (isLoser())
1339  return;
1340  }
1341  for (const SCEV *BaseReg : F.BaseRegs) {
1342  if (VisitedRegs.count(BaseReg)) {
1343  Lose();
1344  return;
1345  }
1346  RatePrimaryRegister(F, BaseReg, Regs, LoserRegs);
1347  if (isLoser())
1348  return;
1349  }
1350 
1351  // Determine how many (unfolded) adds we'll need inside the loop.
1352  size_t NumBaseParts = F.getNumRegs();
1353  if (NumBaseParts > 1)
1354  // Do not count the base and a possible second register if the target
1355  // allows to fold 2 registers.
1356  C.NumBaseAdds +=
1357  NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(*TTI, LU, F)));
1358  C.NumBaseAdds += (F.UnfoldedOffset != 0);
1359 
1360  // Accumulate non-free scaling amounts.
1361  C.ScaleCost += getScalingFactorCost(*TTI, LU, F, *L);
1362 
1363  // Tally up the non-zero immediates.
1364  for (const LSRFixup &Fixup : LU.Fixups) {
1365  int64_t O = Fixup.Offset;
1366  int64_t Offset = (uint64_t)O + F.BaseOffset;
1367  if (F.BaseGV)
1368  C.ImmCost += 64; // Handle symbolic values conservatively.
1369  // TODO: This should probably be the pointer size.
1370  else if (Offset != 0)
1371  C.ImmCost += APInt(64, Offset, true).getMinSignedBits();
1372 
1373  // Check with target if this offset with this instruction is
1374  // specifically not supported.
1375  if (LU.Kind == LSRUse::Address && Offset != 0 &&
1376  !isAMCompletelyFolded(*TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1377  Offset, F.HasBaseReg, F.Scale, Fixup.UserInst))
1378  C.NumBaseAdds++;
1379  }
1380 
1381  // If we don't count instruction cost exit here.
1382  if (!InsnsCost) {
1383  assert(isValid() && "invalid cost");
1384  return;
1385  }
1386 
1387  // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as
1388  // additional instruction (at least fill).
1389  unsigned TTIRegNum = TTI->getNumberOfRegisters(false) - 1;
1390  if (C.NumRegs > TTIRegNum) {
1391  // Cost already exceeded TTIRegNum, then only newly added register can add
1392  // new instructions.
1393  if (PrevNumRegs > TTIRegNum)
1394  C.Insns += (C.NumRegs - PrevNumRegs);
1395  else
1396  C.Insns += (C.NumRegs - TTIRegNum);
1397  }
1398 
1399  // If ICmpZero formula ends with not 0, it could not be replaced by
1400  // just add or sub. We'll need to compare final result of AddRec.
1401  // That means we'll need an additional instruction. But if the target can
1402  // macro-fuse a compare with a branch, don't count this extra instruction.
1403  // For -10 + {0, +, 1}:
1404  // i = i + 1;
1405  // cmp i, 10
1406  //
1407  // For {-10, +, 1}:
1408  // i = i + 1;
1409  if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd() &&
1410  !TTI->canMacroFuseCmp())
1411  C.Insns++;
1412  // Each new AddRec adds 1 instruction to calculation.
1413  C.Insns += (C.AddRecCost - PrevAddRecCost);
1414 
1415  // BaseAdds adds instructions for unfolded registers.
1416  if (LU.Kind != LSRUse::ICmpZero)
1417  C.Insns += C.NumBaseAdds - PrevNumBaseAdds;
1418  assert(isValid() && "invalid cost");
1419 }
1420 
1421 /// Set this cost to a losing value.
1422 void Cost::Lose() {
1425  C.AddRecCost = std::numeric_limits<unsigned>::max();
1426  C.NumIVMuls = std::numeric_limits<unsigned>::max();
1427  C.NumBaseAdds = std::numeric_limits<unsigned>::max();
1429  C.SetupCost = std::numeric_limits<unsigned>::max();
1430  C.ScaleCost = std::numeric_limits<unsigned>::max();
1431 }
1432 
1433 /// Choose the lower cost.
1434 bool Cost::isLess(Cost &Other) {
1435  if (InsnsCost.getNumOccurrences() > 0 && InsnsCost &&
1436  C.Insns != Other.C.Insns)
1437  return C.Insns < Other.C.Insns;
1438  return TTI->isLSRCostLess(C, Other.C);
1439 }
1440 
1441 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1442 void Cost::print(raw_ostream &OS) const {
1443  if (InsnsCost)
1444  OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s ");
1445  OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s");
1446  if (C.AddRecCost != 0)
1447  OS << ", with addrec cost " << C.AddRecCost;
1448  if (C.NumIVMuls != 0)
1449  OS << ", plus " << C.NumIVMuls << " IV mul"
1450  << (C.NumIVMuls == 1 ? "" : "s");
1451  if (C.NumBaseAdds != 0)
1452  OS << ", plus " << C.NumBaseAdds << " base add"
1453  << (C.NumBaseAdds == 1 ? "" : "s");
1454  if (C.ScaleCost != 0)
1455  OS << ", plus " << C.ScaleCost << " scale cost";
1456  if (C.ImmCost != 0)
1457  OS << ", plus " << C.ImmCost << " imm cost";
1458  if (C.SetupCost != 0)
1459  OS << ", plus " << C.SetupCost << " setup cost";
1460 }
1461 
1462 LLVM_DUMP_METHOD void Cost::dump() const {
1463  print(errs()); errs() << '\n';
1464 }
1465 #endif
1466 
1467 /// Test whether this fixup always uses its value outside of the given loop.
1468 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1469  // PHI nodes use their value in their incoming blocks.
1470  if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1471  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1472  if (PN->getIncomingValue(i) == OperandValToReplace &&
1473  L->contains(PN->getIncomingBlock(i)))
1474  return false;
1475  return true;
1476  }
1477 
1478  return !L->contains(UserInst);
1479 }
1480 
1481 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1482 void LSRFixup::print(raw_ostream &OS) const {
1483  OS << "UserInst=";
1484  // Store is common and interesting enough to be worth special-casing.
1485  if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1486  OS << "store ";
1487  Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1488  } else if (UserInst->getType()->isVoidTy())
1489  OS << UserInst->getOpcodeName();
1490  else
1491  UserInst->printAsOperand(OS, /*PrintType=*/false);
1492 
1493  OS << ", OperandValToReplace=";
1494  OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1495 
1496  for (const Loop *PIL : PostIncLoops) {
1497  OS << ", PostIncLoop=";
1498  PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1499  }
1500 
1501  if (Offset != 0)
1502  OS << ", Offset=" << Offset;
1503 }
1504 
1505 LLVM_DUMP_METHOD void LSRFixup::dump() const {
1506  print(errs()); errs() << '\n';
1507 }
1508 #endif
1509 
1510 /// Test whether this use as a formula which has the same registers as the given
1511 /// formula.
1512 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1513  SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1514  if (F.ScaledReg) Key.push_back(F.ScaledReg);
1515  // Unstable sort by host order ok, because this is only used for uniquifying.
1516  llvm::sort(Key);
1517  return Uniquifier.count(Key);
1518 }
1519 
1520 /// The function returns a probability of selecting formula without Reg.
1521 float LSRUse::getNotSelectedProbability(const SCEV *Reg) const {
1522  unsigned FNum = 0;
1523  for (const Formula &F : Formulae)
1524  if (F.referencesReg(Reg))
1525  FNum++;
1526  return ((float)(Formulae.size() - FNum)) / Formulae.size();
1527 }
1528 
1529 /// If the given formula has not yet been inserted, add it to the list, and
1530 /// return true. Return false otherwise. The formula must be in canonical form.
1531 bool LSRUse::InsertFormula(const Formula &F, const Loop &L) {
1532  assert(F.isCanonical(L) && "Invalid canonical representation");
1533 
1534  if (!Formulae.empty() && RigidFormula)
1535  return false;
1536 
1537  SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1538  if (F.ScaledReg) Key.push_back(F.ScaledReg);
1539  // Unstable sort by host order ok, because this is only used for uniquifying.
1540  llvm::sort(Key);
1541 
1542  if (!Uniquifier.insert(Key).second)
1543  return false;
1544 
1545  // Using a register to hold the value of 0 is not profitable.
1546  assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1547  "Zero allocated in a scaled register!");
1548 #ifndef NDEBUG
1549  for (const SCEV *BaseReg : F.BaseRegs)
1550  assert(!BaseReg->isZero() && "Zero allocated in a base register!");
1551 #endif
1552 
1553  // Add the formula to the list.
1554  Formulae.push_back(F);
1555 
1556  // Record registers now being used by this use.
1557  Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1558  if (F.ScaledReg)
1559  Regs.insert(F.ScaledReg);
1560 
1561  return true;
1562 }
1563 
1564 /// Remove the given formula from this use's list.
1565 void LSRUse::DeleteFormula(Formula &F) {
1566  if (&F != &Formulae.back())
1567  std::swap(F, Formulae.back());
1568  Formulae.pop_back();
1569 }
1570 
1571 /// Recompute the Regs field, and update RegUses.
1572 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1573  // Now that we've filtered out some formulae, recompute the Regs set.
1574  SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1575  Regs.clear();
1576  for (const Formula &F : Formulae) {
1577  if (F.ScaledReg) Regs.insert(F.ScaledReg);
1578  Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1579  }
1580 
1581  // Update the RegTracker.
1582  for (const SCEV *S : OldRegs)
1583  if (!Regs.count(S))
1584  RegUses.dropRegister(S, LUIdx);
1585 }
1586 
1587 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1588 void LSRUse::print(raw_ostream &OS) const {
1589  OS << "LSR Use: Kind=";
1590  switch (Kind) {
1591  case Basic: OS << "Basic"; break;
1592  case Special: OS << "Special"; break;
1593  case ICmpZero: OS << "ICmpZero"; break;
1594  case Address:
1595  OS << "Address of ";
1596  if (AccessTy.MemTy->isPointerTy())
1597  OS << "pointer"; // the full pointer type could be really verbose
1598  else {
1599  OS << *AccessTy.MemTy;
1600  }
1601 
1602  OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1603  }
1604 
1605  OS << ", Offsets={";
1606  bool NeedComma = false;
1607  for (const LSRFixup &Fixup : Fixups) {
1608  if (NeedComma) OS << ',';
1609  OS << Fixup.Offset;
1610  NeedComma = true;
1611  }
1612  OS << '}';
1613 
1614  if (AllFixupsOutsideLoop)
1615  OS << ", all-fixups-outside-loop";
1616 
1617  if (WidestFixupType)
1618  OS << ", widest fixup type: " << *WidestFixupType;
1619 }
1620 
1621 LLVM_DUMP_METHOD void LSRUse::dump() const {
1622  print(errs()); errs() << '\n';
1623 }
1624 #endif
1625 
1627  LSRUse::KindType Kind, MemAccessTy AccessTy,
1628  GlobalValue *BaseGV, int64_t BaseOffset,
1629  bool HasBaseReg, int64_t Scale,
1630  Instruction *Fixup/*= nullptr*/) {
1631  switch (Kind) {
1632  case LSRUse::Address:
1633  return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1634  HasBaseReg, Scale, AccessTy.AddrSpace, Fixup);
1635 
1636  case LSRUse::ICmpZero:
1637  // There's not even a target hook for querying whether it would be legal to
1638  // fold a GV into an ICmp.
1639  if (BaseGV)
1640  return false;
1641 
1642  // ICmp only has two operands; don't allow more than two non-trivial parts.
1643  if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1644  return false;
1645 
1646  // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1647  // putting the scaled register in the other operand of the icmp.
1648  if (Scale != 0 && Scale != -1)
1649  return false;
1650 
1651  // If we have low-level target information, ask the target if it can fold an
1652  // integer immediate on an icmp.
1653  if (BaseOffset != 0) {
1654  // We have one of:
1655  // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1656  // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1657  // Offs is the ICmp immediate.
1658  if (Scale == 0)
1659  // The cast does the right thing with
1660  // std::numeric_limits<int64_t>::min().
1661  BaseOffset = -(uint64_t)BaseOffset;
1662  return TTI.isLegalICmpImmediate(BaseOffset);
1663  }
1664 
1665  // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1666  return true;
1667 
1668  case LSRUse::Basic:
1669  // Only handle single-register values.
1670  return !BaseGV && Scale == 0 && BaseOffset == 0;
1671 
1672  case LSRUse::Special:
1673  // Special case Basic to handle -1 scales.
1674  return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1675  }
1676 
1677  llvm_unreachable("Invalid LSRUse Kind!");
1678 }
1679 
1681  int64_t MinOffset, int64_t MaxOffset,
1682  LSRUse::KindType Kind, MemAccessTy AccessTy,
1683  GlobalValue *BaseGV, int64_t BaseOffset,
1684  bool HasBaseReg, int64_t Scale) {
1685  // Check for overflow.
1686  if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1687  (MinOffset > 0))
1688  return false;
1689  MinOffset = (uint64_t)BaseOffset + MinOffset;
1690  if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1691  (MaxOffset > 0))
1692  return false;
1693  MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1694 
1695  return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1696  HasBaseReg, Scale) &&
1697  isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1698  HasBaseReg, Scale);
1699 }
1700 
1702  int64_t MinOffset, int64_t MaxOffset,
1703  LSRUse::KindType Kind, MemAccessTy AccessTy,
1704  const Formula &F, const Loop &L) {
1705  // For the purpose of isAMCompletelyFolded either having a canonical formula
1706  // or a scale not equal to zero is correct.
1707  // Problems may arise from non canonical formulae having a scale == 0.
1708  // Strictly speaking it would best to just rely on canonical formulae.
1709  // However, when we generate the scaled formulae, we first check that the
1710  // scaling factor is profitable before computing the actual ScaledReg for
1711  // compile time sake.
1712  assert((F.isCanonical(L) || F.Scale != 0));
1713  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1714  F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1715 }
1716 
1717 /// Test whether we know how to expand the current formula.
1718 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1719  int64_t MaxOffset, LSRUse::KindType Kind,
1720  MemAccessTy AccessTy, GlobalValue *BaseGV,
1721  int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1722  // We know how to expand completely foldable formulae.
1723  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1724  BaseOffset, HasBaseReg, Scale) ||
1725  // Or formulae that use a base register produced by a sum of base
1726  // registers.
1727  (Scale == 1 &&
1728  isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1729  BaseGV, BaseOffset, true, 0));
1730 }
1731 
1732 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1733  int64_t MaxOffset, LSRUse::KindType Kind,
1734  MemAccessTy AccessTy, const Formula &F) {
1735  return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1736  F.BaseOffset, F.HasBaseReg, F.Scale);
1737 }
1738 
1740  const LSRUse &LU, const Formula &F) {
1741  // Target may want to look at the user instructions.
1742  if (LU.Kind == LSRUse::Address && TTI.LSRWithInstrQueries()) {
1743  for (const LSRFixup &Fixup : LU.Fixups)
1744  if (!isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1745  (F.BaseOffset + Fixup.Offset), F.HasBaseReg,
1746  F.Scale, Fixup.UserInst))
1747  return false;
1748  return true;
1749  }
1750 
1751  return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1752  LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1753  F.Scale);
1754 }
1755 
1756 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1757  const LSRUse &LU, const Formula &F,
1758  const Loop &L) {
1759  if (!F.Scale)
1760  return 0;
1761 
1762  // If the use is not completely folded in that instruction, we will have to
1763  // pay an extra cost only for scale != 1.
1764  if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1765  LU.AccessTy, F, L))
1766  return F.Scale != 1;
1767 
1768  switch (LU.Kind) {
1769  case LSRUse::Address: {
1770  // Check the scaling factor cost with both the min and max offsets.
1771  int ScaleCostMinOffset = TTI.getScalingFactorCost(
1772  LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1773  F.Scale, LU.AccessTy.AddrSpace);
1774  int ScaleCostMaxOffset = TTI.getScalingFactorCost(
1775  LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1776  F.Scale, LU.AccessTy.AddrSpace);
1777 
1778  assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&
1779  "Legal addressing mode has an illegal cost!");
1780  return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1781  }
1782  case LSRUse::ICmpZero:
1783  case LSRUse::Basic:
1784  case LSRUse::Special:
1785  // The use is completely folded, i.e., everything is folded into the
1786  // instruction.
1787  return 0;
1788  }
1789 
1790  llvm_unreachable("Invalid LSRUse Kind!");
1791 }
1792 
1793 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1794  LSRUse::KindType Kind, MemAccessTy AccessTy,
1795  GlobalValue *BaseGV, int64_t BaseOffset,
1796  bool HasBaseReg) {
1797  // Fast-path: zero is always foldable.
1798  if (BaseOffset == 0 && !BaseGV) return true;
1799 
1800  // Conservatively, create an address with an immediate and a
1801  // base and a scale.
1802  int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1803 
1804  // Canonicalize a scale of 1 to a base register if the formula doesn't
1805  // already have a base register.
1806  if (!HasBaseReg && Scale == 1) {
1807  Scale = 0;
1808  HasBaseReg = true;
1809  }
1810 
1811  return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1812  HasBaseReg, Scale);
1813 }
1814 
1815 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1816  ScalarEvolution &SE, int64_t MinOffset,
1817  int64_t MaxOffset, LSRUse::KindType Kind,
1818  MemAccessTy AccessTy, const SCEV *S,
1819  bool HasBaseReg) {
1820  // Fast-path: zero is always foldable.
1821  if (S->isZero()) return true;
1822 
1823  // Conservatively, create an address with an immediate and a
1824  // base and a scale.
1825  int64_t BaseOffset = ExtractImmediate(S, SE);
1826  GlobalValue *BaseGV = ExtractSymbol(S, SE);
1827 
1828  // If there's anything else involved, it's not foldable.
1829  if (!S->isZero()) return false;
1830 
1831  // Fast-path: zero is always foldable.
1832  if (BaseOffset == 0 && !BaseGV) return true;
1833 
1834  // Conservatively, create an address with an immediate and a
1835  // base and a scale.
1836  int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1837 
1838  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1839  BaseOffset, HasBaseReg, Scale);
1840 }
1841 
1842 namespace {
1843 
1844 /// An individual increment in a Chain of IV increments. Relate an IV user to
1845 /// an expression that computes the IV it uses from the IV used by the previous
1846 /// link in the Chain.
1847 ///
1848 /// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1849 /// original IVOperand. The head of the chain's IVOperand is only valid during
1850 /// chain collection, before LSR replaces IV users. During chain generation,
1851 /// IncExpr can be used to find the new IVOperand that computes the same
1852 /// expression.
1853 struct IVInc {
1854  Instruction *UserInst;
1855  Value* IVOperand;
1856  const SCEV *IncExpr;
1857 
1858  IVInc(Instruction *U, Value *O, const SCEV *E)
1859  : UserInst(U), IVOperand(O), IncExpr(E) {}
1860 };
1861 
1862 // The list of IV increments in program order. We typically add the head of a
1863 // chain without finding subsequent links.
1864 struct IVChain {
1865  SmallVector<IVInc, 1> Incs;
1866  const SCEV *ExprBase = nullptr;
1867 
1868  IVChain() = default;
1869  IVChain(const IVInc &Head, const SCEV *Base)
1870  : Incs(1, Head), ExprBase(Base) {}
1871 
1872  using const_iterator = SmallVectorImpl<IVInc>::const_iterator;
1873 
1874  // Return the first increment in the chain.
1875  const_iterator begin() const {
1876  assert(!Incs.empty());
1877  return std::next(Incs.begin());
1878  }
1879  const_iterator end() const {
1880  return Incs.end();
1881  }
1882 
1883  // Returns true if this chain contains any increments.
1884  bool hasIncs() const { return Incs.size() >= 2; }
1885 
1886  // Add an IVInc to the end of this chain.
1887  void add(const IVInc &X) { Incs.push_back(X); }
1888 
1889  // Returns the last UserInst in the chain.
1890  Instruction *tailUserInst() const { return Incs.back().UserInst; }
1891 
1892  // Returns true if IncExpr can be profitably added to this chain.
1893  bool isProfitableIncrement(const SCEV *OperExpr,
1894  const SCEV *IncExpr,
1895  ScalarEvolution&);
1896 };
1897 
1898 /// Helper for CollectChains to track multiple IV increment uses. Distinguish
1899 /// between FarUsers that definitely cross IV increments and NearUsers that may
1900 /// be used between IV increments.
1901 struct ChainUsers {
1903  SmallPtrSet<Instruction*, 4> NearUsers;
1904 };
1905 
1906 /// This class holds state for the main loop strength reduction logic.
1907 class LSRInstance {
1908  IVUsers &IU;
1909  ScalarEvolution &SE;
1910  DominatorTree &DT;
1911  LoopInfo &LI;
1912  AssumptionCache &AC;
1913  TargetLibraryInfo &LibInfo;
1914  const TargetTransformInfo &TTI;
1915  Loop *const L;
1916  bool FavorBackedgeIndex = false;
1917  bool Changed = false;
1918 
1919  /// This is the insert position that the current loop's induction variable
1920  /// increment should be placed. In simple loops, this is the latch block's
1921  /// terminator. But in more complicated cases, this is a position which will
1922  /// dominate all the in-loop post-increment users.
1923  Instruction *IVIncInsertPos = nullptr;
1924 
1925  /// Interesting factors between use strides.
1926  ///
1927  /// We explicitly use a SetVector which contains a SmallSet, instead of the
1928  /// default, a SmallDenseSet, because we need to use the full range of
1929  /// int64_ts, and there's currently no good way of doing that with
1930  /// SmallDenseSet.
1932 
1933  /// Interesting use types, to facilitate truncation reuse.
1935 
1936  /// The list of interesting uses.
1937  mutable SmallVector<LSRUse, 16> Uses;
1938 
1939  /// Track which uses use which register candidates.
1940  RegUseTracker RegUses;
1941 
1942  // Limit the number of chains to avoid quadratic behavior. We don't expect to
1943  // have more than a few IV increment chains in a loop. Missing a Chain falls
1944  // back to normal LSR behavior for those uses.
1945  static const unsigned MaxChains = 8;
1946 
1947  /// IV users can form a chain of IV increments.
1949 
1950  /// IV users that belong to profitable IVChains.
1952 
1953  void OptimizeShadowIV();
1954  bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1955  ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1956  void OptimizeLoopTermCond();
1957 
1958  void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1959  SmallVectorImpl<ChainUsers> &ChainUsersVec);
1960  void FinalizeChain(IVChain &Chain);
1961  void CollectChains();
1962  void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1963  SmallVectorImpl<WeakTrackingVH> &DeadInsts);
1964 
1965  void CollectInterestingTypesAndFactors();
1966  void CollectFixupsAndInitialFormulae();
1967 
1968  // Support for sharing of LSRUses between LSRFixups.
1970  UseMapTy UseMap;
1971 
1972  bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1973  LSRUse::KindType Kind, MemAccessTy AccessTy);
1974 
1975  std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
1976  MemAccessTy AccessTy);
1977 
1978  void DeleteUse(LSRUse &LU, size_t LUIdx);
1979 
1980  LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1981 
1982  void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1983  void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1984  void CountRegisters(const Formula &F, size_t LUIdx);
1985  bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1986 
1987  void CollectLoopInvariantFixupsAndFormulae();
1988 
1989  void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1990  unsigned Depth = 0);
1991 
1992  void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1993  const Formula &Base, unsigned Depth,
1994  size_t Idx, bool IsScaledReg = false);
1995  void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1996  void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1997  const Formula &Base, size_t Idx,
1998  bool IsScaledReg = false);
1999  void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
2000  void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
2001  const Formula &Base,
2002  const SmallVectorImpl<int64_t> &Worklist,
2003  size_t Idx, bool IsScaledReg = false);
2004  void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
2005  void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2006  void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2007  void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
2008  void GenerateCrossUseConstantOffsets();
2009  void GenerateAllReuseFormulae();
2010 
2011  void FilterOutUndesirableDedicatedRegisters();
2012 
2013  size_t EstimateSearchSpaceComplexity() const;
2014  void NarrowSearchSpaceByDetectingSupersets();
2015  void NarrowSearchSpaceByCollapsingUnrolledCode();
2016  void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
2017  void NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
2018  void NarrowSearchSpaceByDeletingCostlyFormulas();
2019  void NarrowSearchSpaceByPickingWinnerRegs();
2020  void NarrowSearchSpaceUsingHeuristics();
2021 
2022  void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
2023  Cost &SolutionCost,
2025  const Cost &CurCost,
2026  const SmallPtrSet<const SCEV *, 16> &CurRegs,
2027  DenseSet<const SCEV *> &VisitedRegs) const;
2028  void Solve(SmallVectorImpl<const Formula *> &Solution) const;
2029 
2031  HoistInsertPosition(BasicBlock::iterator IP,
2032  const SmallVectorImpl<Instruction *> &Inputs) const;
2034  AdjustInsertPositionForExpand(BasicBlock::iterator IP,
2035  const LSRFixup &LF,
2036  const LSRUse &LU,
2037  SCEVExpander &Rewriter) const;
2038 
2039  Value *Expand(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2040  BasicBlock::iterator IP, SCEVExpander &Rewriter,
2041  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2042  void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
2043  const Formula &F, SCEVExpander &Rewriter,
2044  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2045  void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2046  SCEVExpander &Rewriter,
2047  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2048  void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
2049 
2050 public:
2051  LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
2052  LoopInfo &LI, const TargetTransformInfo &TTI, AssumptionCache &AC,
2053  TargetLibraryInfo &LibInfo);
2054 
2055  bool getChanged() const { return Changed; }
2056 
2057  void print_factors_and_types(raw_ostream &OS) const;
2058  void print_fixups(raw_ostream &OS) const;
2059  void print_uses(raw_ostream &OS) const;
2060  void print(raw_ostream &OS) const;
2061  void dump() const;
2062 };
2063 
2064 } // end anonymous namespace
2065 
2066 /// If IV is used in a int-to-float cast inside the loop then try to eliminate
2067 /// the cast operation.
2068 void LSRInstance::OptimizeShadowIV() {
2069  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2070  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2071  return;
2072 
2073  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
2074  UI != E; /* empty */) {
2075  IVUsers::const_iterator CandidateUI = UI;
2076  ++UI;
2077  Instruction *ShadowUse = CandidateUI->getUser();
2078  Type *DestTy = nullptr;
2079  bool IsSigned = false;
2080 
2081  /* If shadow use is a int->float cast then insert a second IV
2082  to eliminate this cast.
2083 
2084  for (unsigned i = 0; i < n; ++i)
2085  foo((double)i);
2086 
2087  is transformed into
2088 
2089  double d = 0.0;
2090  for (unsigned i = 0; i < n; ++i, ++d)
2091  foo(d);
2092  */
2093  if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
2094  IsSigned = false;
2095  DestTy = UCast->getDestTy();
2096  }
2097  else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
2098  IsSigned = true;
2099  DestTy = SCast->getDestTy();
2100  }
2101  if (!DestTy) continue;
2102 
2103  // If target does not support DestTy natively then do not apply
2104  // this transformation.
2105  if (!TTI.isTypeLegal(DestTy)) continue;
2106 
2107  PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2108  if (!PH) continue;
2109  if (PH->getNumIncomingValues() != 2) continue;
2110 
2111  // If the calculation in integers overflows, the result in FP type will
2112  // differ. So we only can do this transformation if we are guaranteed to not
2113  // deal with overflowing values
2114  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PH));
2115  if (!AR) continue;
2116  if (IsSigned && !AR->hasNoSignedWrap()) continue;
2117  if (!IsSigned && !AR->hasNoUnsignedWrap()) continue;
2118 
2119  Type *SrcTy = PH->getType();
2120  int Mantissa = DestTy->getFPMantissaWidth();
2121  if (Mantissa == -1) continue;
2122  if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
2123  continue;
2124 
2125  unsigned Entry, Latch;
2126  if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2127  Entry = 0;
2128  Latch = 1;
2129  } else {
2130  Entry = 1;
2131  Latch = 0;
2132  }
2133 
2135  if (!Init) continue;
2136  Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
2137  (double)Init->getSExtValue() :
2138  (double)Init->getZExtValue());
2139 
2140  BinaryOperator *Incr =
2142  if (!Incr) continue;
2143  if (Incr->getOpcode() != Instruction::Add
2144  && Incr->getOpcode() != Instruction::Sub)
2145  continue;
2146 
2147  /* Initialize new IV, double d = 0.0 in above example. */
2148  ConstantInt *C = nullptr;
2149  if (Incr->getOperand(0) == PH)
2150  C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2151  else if (Incr->getOperand(1) == PH)
2152  C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2153  else
2154  continue;
2155 
2156  if (!C) continue;
2157 
2158  // Ignore negative constants, as the code below doesn't handle them
2159  // correctly. TODO: Remove this restriction.
2160  if (!C->getValue().isStrictlyPositive()) continue;
2161 
2162  /* Add new PHINode. */
2163  PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
2164 
2165  /* create new increment. '++d' in above example. */
2166  Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2167  BinaryOperator *NewIncr =
2168  BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
2169  Instruction::FAdd : Instruction::FSub,
2170  NewPH, CFP, "IV.S.next.", Incr);
2171 
2172  NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2173  NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2174 
2175  /* Remove cast operation */
2176  ShadowUse->replaceAllUsesWith(NewPH);
2177  ShadowUse->eraseFromParent();
2178  Changed = true;
2179  break;
2180  }
2181 }
2182 
2183 /// If Cond has an operand that is an expression of an IV, set the IV user and
2184 /// stride information and return true, otherwise return false.
2185 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
2186  for (IVStrideUse &U : IU)
2187  if (U.getUser() == Cond) {
2188  // NOTE: we could handle setcc instructions with multiple uses here, but
2189  // InstCombine does it as well for simple uses, it's not clear that it
2190  // occurs enough in real life to handle.
2191  CondUse = &U;
2192  return true;
2193  }
2194  return false;
2195 }
2196 
2197 /// Rewrite the loop's terminating condition if it uses a max computation.
2198 ///
2199 /// This is a narrow solution to a specific, but acute, problem. For loops
2200 /// like this:
2201 ///
2202 /// i = 0;
2203 /// do {
2204 /// p[i] = 0.0;
2205 /// } while (++i < n);
2206 ///
2207 /// the trip count isn't just 'n', because 'n' might not be positive. And
2208 /// unfortunately this can come up even for loops where the user didn't use
2209 /// a C do-while loop. For example, seemingly well-behaved top-test loops
2210 /// will commonly be lowered like this:
2211 ///
2212 /// if (n > 0) {
2213 /// i = 0;
2214 /// do {
2215 /// p[i] = 0.0;
2216 /// } while (++i < n);
2217 /// }
2218 ///
2219 /// and then it's possible for subsequent optimization to obscure the if
2220 /// test in such a way that indvars can't find it.
2221 ///
2222 /// When indvars can't find the if test in loops like this, it creates a
2223 /// max expression, which allows it to give the loop a canonical
2224 /// induction variable:
2225 ///
2226 /// i = 0;
2227 /// max = n < 1 ? 1 : n;
2228 /// do {
2229 /// p[i] = 0.0;
2230 /// } while (++i != max);
2231 ///
2232 /// Canonical induction variables are necessary because the loop passes
2233 /// are designed around them. The most obvious example of this is the
2234 /// LoopInfo analysis, which doesn't remember trip count values. It
2235 /// expects to be able to rediscover the trip count each time it is
2236 /// needed, and it does this using a simple analysis that only succeeds if
2237 /// the loop has a canonical induction variable.
2238 ///
2239 /// However, when it comes time to generate code, the maximum operation
2240 /// can be quite costly, especially if it's inside of an outer loop.
2241 ///
2242 /// This function solves this problem by detecting this type of loop and
2243 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2244 /// the instructions for the maximum computation.
2245 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
2246  // Check that the loop matches the pattern we're looking for.
2247  if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2248  Cond->getPredicate() != CmpInst::ICMP_NE)
2249  return Cond;
2250 
2251  SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2252  if (!Sel || !Sel->hasOneUse()) return Cond;
2253 
2254  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2255  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2256  return Cond;
2257  const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2258 
2259  // Add one to the backedge-taken count to get the trip count.
2260  const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2261  if (IterationCount != SE.getSCEV(Sel)) return Cond;
2262 
2263  // Check for a max calculation that matches the pattern. There's no check
2264  // for ICMP_ULE here because the comparison would be with zero, which
2265  // isn't interesting.
2267  const SCEVNAryExpr *Max = nullptr;
2268  if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2269  Pred = ICmpInst::ICMP_SLE;
2270  Max = S;
2271  } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2272  Pred = ICmpInst::ICMP_SLT;
2273  Max = S;
2274  } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2275  Pred = ICmpInst::ICMP_ULT;
2276  Max = U;
2277  } else {
2278  // No match; bail.
2279  return Cond;
2280  }
2281 
2282  // To handle a max with more than two operands, this optimization would
2283  // require additional checking and setup.
2284  if (Max->getNumOperands() != 2)
2285  return Cond;
2286 
2287  const SCEV *MaxLHS = Max->getOperand(0);
2288  const SCEV *MaxRHS = Max->getOperand(1);
2289 
2290  // ScalarEvolution canonicalizes constants to the left. For < and >, look
2291  // for a comparison with 1. For <= and >=, a comparison with zero.
2292  if (!MaxLHS ||
2293  (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2294  return Cond;
2295 
2296  // Check the relevant induction variable for conformance to
2297  // the pattern.
2298  const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2299  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2300  if (!AR || !AR->isAffine() ||
2301  AR->getStart() != One ||
2302  AR->getStepRecurrence(SE) != One)
2303  return Cond;
2304 
2305  assert(AR->getLoop() == L &&
2306  "Loop condition operand is an addrec in a different loop!");
2307 
2308  // Check the right operand of the select, and remember it, as it will
2309  // be used in the new comparison instruction.
2310  Value *NewRHS = nullptr;
2311  if (ICmpInst::isTrueWhenEqual(Pred)) {
2312  // Look for n+1, and grab n.
2313  if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2314  if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2315  if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2316  NewRHS = BO->getOperand(0);
2317  if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2318  if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2319  if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2320  NewRHS = BO->getOperand(0);
2321  if (!NewRHS)
2322  return Cond;
2323  } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2324  NewRHS = Sel->getOperand(1);
2325  else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2326  NewRHS = Sel->getOperand(2);
2327  else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2328  NewRHS = SU->getValue();
2329  else
2330  // Max doesn't match expected pattern.
2331  return Cond;
2332 
2333  // Determine the new comparison opcode. It may be signed or unsigned,
2334  // and the original comparison may be either equality or inequality.
2335  if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2336  Pred = CmpInst::getInversePredicate(Pred);
2337 
2338  // Ok, everything looks ok to change the condition into an SLT or SGE and
2339  // delete the max calculation.
2340  ICmpInst *NewCond =
2341  new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2342 
2343  // Delete the max calculation instructions.
2344  Cond->replaceAllUsesWith(NewCond);
2345  CondUse->setUser(NewCond);
2346  Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2347  Cond->eraseFromParent();
2348  Sel->eraseFromParent();
2349  if (Cmp->use_empty())
2350  Cmp->eraseFromParent();
2351  return NewCond;
2352 }
2353 
2354 /// Change loop terminating condition to use the postinc iv when possible.
2355 void
2356 LSRInstance::OptimizeLoopTermCond() {
2358 
2359  // We need a different set of heuristics for rotated and non-rotated loops.
2360  // If a loop is rotated then the latch is also the backedge, so inserting
2361  // post-inc expressions just before the latch is ideal. To reduce live ranges
2362  // it also makes sense to rewrite terminating conditions to use post-inc
2363  // expressions.
2364  //
2365  // If the loop is not rotated then the latch is not a backedge; the latch
2366  // check is done in the loop head. Adding post-inc expressions before the
2367  // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2368  // in the loop body. In this case we do *not* want to use post-inc expressions
2369  // in the latch check, and we want to insert post-inc expressions before
2370  // the backedge.
2371  BasicBlock *LatchBlock = L->getLoopLatch();
2372  SmallVector<BasicBlock*, 8> ExitingBlocks;
2373  L->getExitingBlocks(ExitingBlocks);
2374  if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2375  return LatchBlock != BB;
2376  })) {
2377  // The backedge doesn't exit the loop; treat this as a head-tested loop.
2378  IVIncInsertPos = LatchBlock->getTerminator();
2379  return;
2380  }
2381 
2382  // Otherwise treat this as a rotated loop.
2383  for (BasicBlock *ExitingBlock : ExitingBlocks) {
2384  // Get the terminating condition for the loop if possible. If we
2385  // can, we want to change it to use a post-incremented version of its
2386  // induction variable, to allow coalescing the live ranges for the IV into
2387  // one register value.
2388 
2389  BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2390  if (!TermBr)
2391  continue;
2392  // FIXME: Overly conservative, termination condition could be an 'or' etc..
2393  if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2394  continue;
2395 
2396  // Search IVUsesByStride to find Cond's IVUse if there is one.
2397  IVStrideUse *CondUse = nullptr;
2398  ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2399  if (!FindIVUserForCond(Cond, CondUse))
2400  continue;
2401 
2402  // If the trip count is computed in terms of a max (due to ScalarEvolution
2403  // being unable to find a sufficient guard, for example), change the loop
2404  // comparison to use SLT or ULT instead of NE.
2405  // One consequence of doing this now is that it disrupts the count-down
2406  // optimization. That's not always a bad thing though, because in such
2407  // cases it may still be worthwhile to avoid a max.
2408  Cond = OptimizeMax(Cond, CondUse);
2409 
2410  // If this exiting block dominates the latch block, it may also use
2411  // the post-inc value if it won't be shared with other uses.
2412  // Check for dominance.
2413  if (!DT.dominates(ExitingBlock, LatchBlock))
2414  continue;
2415 
2416  // Conservatively avoid trying to use the post-inc value in non-latch
2417  // exits if there may be pre-inc users in intervening blocks.
2418  if (LatchBlock != ExitingBlock)
2419  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2420  // Test if the use is reachable from the exiting block. This dominator
2421  // query is a conservative approximation of reachability.
2422  if (&*UI != CondUse &&
2423  !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2424  // Conservatively assume there may be reuse if the quotient of their
2425  // strides could be a legal scale.
2426  const SCEV *A = IU.getStride(*CondUse, L);
2427  const SCEV *B = IU.getStride(*UI, L);
2428  if (!A || !B) continue;
2429  if (SE.getTypeSizeInBits(A->getType()) !=
2430  SE.getTypeSizeInBits(B->getType())) {
2431  if (SE.getTypeSizeInBits(A->getType()) >
2432  SE.getTypeSizeInBits(B->getType()))
2433  B = SE.getSignExtendExpr(B, A->getType());
2434  else
2435  A = SE.getSignExtendExpr(A, B->getType());
2436  }
2437  if (const SCEVConstant *D =
2438  dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2439  const ConstantInt *C = D->getValue();
2440  // Stride of one or negative one can have reuse with non-addresses.
2441  if (C->isOne() || C->isMinusOne())
2442  goto decline_post_inc;
2443  // Avoid weird situations.
2444  if (C->getValue().getMinSignedBits() >= 64 ||
2445  C->getValue().isMinSignedValue())
2446  goto decline_post_inc;
2447  // Check for possible scaled-address reuse.
2448  if (isAddressUse(TTI, UI->getUser(), UI->getOperandValToReplace())) {
2449  MemAccessTy AccessTy = getAccessType(
2450  TTI, UI->getUser(), UI->getOperandValToReplace());
2451  int64_t Scale = C->getSExtValue();
2452  if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2453  /*BaseOffset=*/0,
2454  /*HasBaseReg=*/false, Scale,
2455  AccessTy.AddrSpace))
2456  goto decline_post_inc;
2457  Scale = -Scale;
2458  if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2459  /*BaseOffset=*/0,
2460  /*HasBaseReg=*/false, Scale,
2461  AccessTy.AddrSpace))
2462  goto decline_post_inc;
2463  }
2464  }
2465  }
2466 
2467  LLVM_DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
2468  << *Cond << '\n');
2469 
2470  // It's possible for the setcc instruction to be anywhere in the loop, and
2471  // possible for it to have multiple users. If it is not immediately before
2472  // the exiting block branch, move it.
2473  if (&*++BasicBlock::iterator(Cond) != TermBr) {
2474  if (Cond->hasOneUse()) {
2475  Cond->moveBefore(TermBr);
2476  } else {
2477  // Clone the terminating condition and insert into the loopend.
2478  ICmpInst *OldCond = Cond;
2479  Cond = cast<ICmpInst>(Cond->clone());
2480  Cond->setName(L->getHeader()->getName() + ".termcond");
2481  ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2482 
2483  // Clone the IVUse, as the old use still exists!
2484  CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2485  TermBr->replaceUsesOfWith(OldCond, Cond);
2486  }
2487  }
2488 
2489  // If we get to here, we know that we can transform the setcc instruction to
2490  // use the post-incremented version of the IV, allowing us to coalesce the
2491  // live ranges for the IV correctly.
2492  CondUse->transformToPostInc(L);
2493  Changed = true;
2494 
2495  PostIncs.insert(Cond);
2496  decline_post_inc:;
2497  }
2498 
2499  // Determine an insertion point for the loop induction variable increment. It
2500  // must dominate all the post-inc comparisons we just set up, and it must
2501  // dominate the loop latch edge.
2502  IVIncInsertPos = L->getLoopLatch()->getTerminator();
2503  for (Instruction *Inst : PostIncs) {
2504  BasicBlock *BB =
2505  DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2506  Inst->getParent());
2507  if (BB == Inst->getParent())
2508  IVIncInsertPos = Inst;
2509  else if (BB != IVIncInsertPos->getParent())
2510  IVIncInsertPos = BB->getTerminator();
2511  }
2512 }
2513 
2514 /// Determine if the given use can accommodate a fixup at the given offset and
2515 /// other details. If so, update the use and return true.
2516 bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2517  bool HasBaseReg, LSRUse::KindType Kind,
2518  MemAccessTy AccessTy) {
2519  int64_t NewMinOffset = LU.MinOffset;
2520  int64_t NewMaxOffset = LU.MaxOffset;
2521  MemAccessTy NewAccessTy = AccessTy;
2522 
2523  // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2524  // something conservative, however this can pessimize in the case that one of
2525  // the uses will have all its uses outside the loop, for example.
2526  if (LU.Kind != Kind)
2527  return false;
2528 
2529  // Check for a mismatched access type, and fall back conservatively as needed.
2530  // TODO: Be less conservative when the type is similar and can use the same
2531  // addressing modes.
2532  if (Kind == LSRUse::Address) {
2533  if (AccessTy.MemTy != LU.AccessTy.MemTy) {
2534  NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(),
2535  AccessTy.AddrSpace);
2536  }
2537  }
2538 
2539  // Conservatively assume HasBaseReg is true for now.
2540  if (NewOffset < LU.MinOffset) {
2541  if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2542  LU.MaxOffset - NewOffset, HasBaseReg))
2543  return false;
2544  NewMinOffset = NewOffset;
2545  } else if (NewOffset > LU.MaxOffset) {
2546  if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2547  NewOffset - LU.MinOffset, HasBaseReg))
2548  return false;
2549  NewMaxOffset = NewOffset;
2550  }
2551 
2552  // Update the use.
2553  LU.MinOffset = NewMinOffset;
2554  LU.MaxOffset = NewMaxOffset;
2555  LU.AccessTy = NewAccessTy;
2556  return true;
2557 }
2558 
2559 /// Return an LSRUse index and an offset value for a fixup which needs the given
2560 /// expression, with the given kind and optional access type. Either reuse an
2561 /// existing use or create a new one, as needed.
2562 std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2563  LSRUse::KindType Kind,
2564  MemAccessTy AccessTy) {
2565  const SCEV *Copy = Expr;
2566  int64_t Offset = ExtractImmediate(Expr, SE);
2567 
2568  // Basic uses can't accept any offset, for example.
2569  if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2570  Offset, /*HasBaseReg=*/ true)) {
2571  Expr = Copy;
2572  Offset = 0;
2573  }
2574 
2575  std::pair<UseMapTy::iterator, bool> P =
2576  UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2577  if (!P.second) {
2578  // A use already existed with this base.
2579  size_t LUIdx = P.first->second;
2580  LSRUse &LU = Uses[LUIdx];
2581  if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2582  // Reuse this use.
2583  return std::make_pair(LUIdx, Offset);
2584  }
2585 
2586  // Create a new use.
2587  size_t LUIdx = Uses.size();
2588  P.first->second = LUIdx;
2589  Uses.push_back(LSRUse(Kind, AccessTy));
2590  LSRUse &LU = Uses[LUIdx];
2591 
2592  LU.MinOffset = Offset;
2593  LU.MaxOffset = Offset;
2594  return std::make_pair(LUIdx, Offset);
2595 }
2596 
2597 /// Delete the given use from the Uses list.
2598 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2599  if (&LU != &Uses.back())
2600  std::swap(LU, Uses.back());
2601  Uses.pop_back();
2602 
2603  // Update RegUses.
2604  RegUses.swapAndDropUse(LUIdx, Uses.size());
2605 }
2606 
2607 /// Look for a use distinct from OrigLU which is has a formula that has the same
2608 /// registers as the given formula.
2609 LSRUse *
2610 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2611  const LSRUse &OrigLU) {
2612  // Search all uses for the formula. This could be more clever.
2613  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2614  LSRUse &LU = Uses[LUIdx];
2615  // Check whether this use is close enough to OrigLU, to see whether it's
2616  // worthwhile looking through its formulae.
2617  // Ignore ICmpZero uses because they may contain formulae generated by
2618  // GenerateICmpZeroScales, in which case adding fixup offsets may
2619  // be invalid.
2620  if (&LU != &OrigLU &&
2621  LU.Kind != LSRUse::ICmpZero &&
2622  LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2623  LU.WidestFixupType == OrigLU.WidestFixupType &&
2624  LU.HasFormulaWithSameRegs(OrigF)) {
2625  // Scan through this use's formulae.
2626  for (const Formula &F : LU.Formulae) {
2627  // Check to see if this formula has the same registers and symbols
2628  // as OrigF.
2629  if (F.BaseRegs == OrigF.BaseRegs &&
2630  F.ScaledReg == OrigF.ScaledReg &&
2631  F.BaseGV == OrigF.BaseGV &&
2632  F.Scale == OrigF.Scale &&
2633  F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2634  if (F.BaseOffset == 0)
2635  return &LU;
2636  // This is the formula where all the registers and symbols matched;
2637  // there aren't going to be any others. Since we declined it, we
2638  // can skip the rest of the formulae and proceed to the next LSRUse.
2639  break;
2640  }
2641  }
2642  }
2643  }
2644 
2645  // Nothing looked good.
2646  return nullptr;
2647 }
2648 
2649 void LSRInstance::CollectInterestingTypesAndFactors() {
2651 
2652  // Collect interesting types and strides.
2654  for (const IVStrideUse &U : IU) {
2655  const SCEV *Expr = IU.getExpr(U);
2656 
2657  // Collect interesting types.
2658  Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2659 
2660  // Add strides for mentioned loops.
2661  Worklist.push_back(Expr);
2662  do {
2663  const SCEV *S = Worklist.pop_back_val();
2664  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2665  if (AR->getLoop() == L)
2666  Strides.insert(AR->getStepRecurrence(SE));
2667  Worklist.push_back(AR->getStart());
2668  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2669  Worklist.append(Add->op_begin(), Add->op_end());
2670  }
2671  } while (!Worklist.empty());
2672  }
2673 
2674  // Compute interesting factors from the set of interesting strides.
2676  I = Strides.begin(), E = Strides.end(); I != E; ++I)
2678  std::next(I); NewStrideIter != E; ++NewStrideIter) {
2679  const SCEV *OldStride = *I;
2680  const SCEV *NewStride = *NewStrideIter;
2681 
2682  if (SE.getTypeSizeInBits(OldStride->getType()) !=
2683  SE.getTypeSizeInBits(NewStride->getType())) {
2684  if (SE.getTypeSizeInBits(OldStride->getType()) >
2685  SE.getTypeSizeInBits(NewStride->getType()))
2686  NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2687  else
2688  OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2689  }
2690  if (const SCEVConstant *Factor =
2691  dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2692  SE, true))) {
2693  if (Factor->getAPInt().getMinSignedBits() <= 64)
2694  Factors.insert(Factor->getAPInt().getSExtValue());
2695  } else if (const SCEVConstant *Factor =
2696  dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2697  NewStride,
2698  SE, true))) {
2699  if (Factor->getAPInt().getMinSignedBits() <= 64)
2700  Factors.insert(Factor->getAPInt().getSExtValue());
2701  }
2702  }
2703 
2704  // If all uses use the same type, don't bother looking for truncation-based
2705  // reuse.
2706  if (Types.size() == 1)
2707  Types.clear();
2708 
2709  LLVM_DEBUG(print_factors_and_types(dbgs()));
2710 }
2711 
2712 /// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2713 /// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2714 /// IVStrideUses, we could partially skip this.
2715 static User::op_iterator
2717  Loop *L, ScalarEvolution &SE) {
2718  for(; OI != OE; ++OI) {
2719  if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2720  if (!SE.isSCEVable(Oper->getType()))
2721  continue;
2722 
2723  if (const SCEVAddRecExpr *AR =
2724  dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2725  if (AR->getLoop() == L)
2726  break;
2727  }
2728  }
2729  }
2730  return OI;
2731 }
2732 
2733 /// IVChain logic must consistently peek base TruncInst operands, so wrap it in
2734 /// a convenient helper.
2735 static Value *getWideOperand(Value *Oper) {
2736  if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2737  return Trunc->getOperand(0);
2738  return Oper;
2739 }
2740 
2741 /// Return true if we allow an IV chain to include both types.
2742 static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2743  Type *LType = LVal->getType();
2744  Type *RType = RVal->getType();
2745  return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy() &&
2746  // Different address spaces means (possibly)
2747  // different types of the pointer implementation,
2748  // e.g. i16 vs i32 so disallow that.
2749  (LType->getPointerAddressSpace() ==
2750  RType->getPointerAddressSpace()));
2751 }
2752 
2753 /// Return an approximation of this SCEV expression's "base", or NULL for any
2754 /// constant. Returning the expression itself is conservative. Returning a
2755 /// deeper subexpression is more precise and valid as long as it isn't less
2756 /// complex than another subexpression. For expressions involving multiple
2757 /// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2758 /// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2759 /// IVInc==b-a.
2760 ///
2761 /// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2762 /// SCEVUnknown, we simply return the rightmost SCEV operand.
2763 static const SCEV *getExprBase(const SCEV *S) {
2764  switch (S->getSCEVType()) {
2765  default: // uncluding scUnknown.
2766  return S;
2767  case scConstant:
2768  return nullptr;
2769  case scTruncate:
2770  return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2771  case scZeroExtend:
2772  return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2773  case scSignExtend:
2774  return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2775  case scAddExpr: {
2776  // Skip over scaled operands (scMulExpr) to follow add operands as long as
2777  // there's nothing more complex.
2778  // FIXME: not sure if we want to recognize negation.
2779  const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2780  for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2781  E(Add->op_begin()); I != E; ++I) {
2782  const SCEV *SubExpr = *I;
2783  if (SubExpr->getSCEVType() == scAddExpr)
2784  return getExprBase(SubExpr);
2785 
2786  if (SubExpr->getSCEVType() != scMulExpr)
2787  return SubExpr;
2788  }
2789  return S; // all operands are scaled, be conservative.
2790  }
2791  case scAddRecExpr:
2792  return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2793  }
2794 }
2795 
2796 /// Return true if the chain increment is profitable to expand into a loop
2797 /// invariant value, which may require its own register. A profitable chain
2798 /// increment will be an offset relative to the same base. We allow such offsets
2799 /// to potentially be used as chain increment as long as it's not obviously
2800 /// expensive to expand using real instructions.
2801 bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2802  const SCEV *IncExpr,
2803  ScalarEvolution &SE) {
2804  // Aggressively form chains when -stress-ivchain.
2805  if (StressIVChain)
2806  return true;
2807 
2808  // Do not replace a constant offset from IV head with a nonconstant IV
2809  // increment.
2810  if (!isa<SCEVConstant>(IncExpr)) {
2811  const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2812  if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2813  return false;
2814  }
2815 
2816  SmallPtrSet<const SCEV*, 8> Processed;
2817  return !isHighCostExpansion(IncExpr, Processed, SE);
2818 }
2819 
2820 /// Return true if the number of registers needed for the chain is estimated to
2821 /// be less than the number required for the individual IV users. First prohibit
2822 /// any IV users that keep the IV live across increments (the Users set should
2823 /// be empty). Next count the number and type of increments in the chain.
2824 ///
2825 /// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2826 /// effectively use postinc addressing modes. Only consider it profitable it the
2827 /// increments can be computed in fewer registers when chained.
2828 ///
2829 /// TODO: Consider IVInc free if it's already used in another chains.
2830 static bool
2832  ScalarEvolution &SE) {
2833  if (StressIVChain)
2834  return true;
2835 
2836  if (!Chain.hasIncs())
2837  return false;
2838 
2839  if (!Users.empty()) {
2840  LLVM_DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";
2841  for (Instruction *Inst
2842  : Users) { dbgs() << " " << *Inst << "\n"; });
2843  return false;
2844  }
2845  assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2846 
2847  // The chain itself may require a register, so intialize cost to 1.
2848  int cost = 1;
2849 
2850  // A complete chain likely eliminates the need for keeping the original IV in
2851  // a register. LSR does not currently know how to form a complete chain unless
2852  // the header phi already exists.
2853  if (isa<PHINode>(Chain.tailUserInst())
2854  && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2855  --cost;
2856  }
2857  const SCEV *LastIncExpr = nullptr;
2858  unsigned NumConstIncrements = 0;
2859  unsigned NumVarIncrements = 0;
2860  unsigned NumReusedIncrements = 0;
2861  for (const IVInc &Inc : Chain) {
2862  if (Inc.IncExpr->isZero())
2863  continue;
2864 
2865  // Incrementing by zero or some constant is neutral. We assume constants can
2866  // be folded into an addressing mode or an add's immediate operand.
2867  if (isa<SCEVConstant>(Inc.IncExpr)) {
2868  ++NumConstIncrements;
2869  continue;
2870  }
2871 
2872  if (Inc.IncExpr == LastIncExpr)
2873  ++NumReusedIncrements;
2874  else
2875  ++NumVarIncrements;
2876 
2877  LastIncExpr = Inc.IncExpr;
2878  }
2879  // An IV chain with a single increment is handled by LSR's postinc
2880  // uses. However, a chain with multiple increments requires keeping the IV's
2881  // value live longer than it needs to be if chained.
2882  if (NumConstIncrements > 1)
2883  --cost;
2884 
2885  // Materializing increment expressions in the preheader that didn't exist in
2886  // the original code may cost a register. For example, sign-extended array
2887  // indices can produce ridiculous increments like this:
2888  // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2889  cost += NumVarIncrements;
2890 
2891  // Reusing variable increments likely saves a register to hold the multiple of
2892  // the stride.
2893  cost -= NumReusedIncrements;
2894 
2895  LLVM_DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost
2896  << "\n");
2897 
2898  return cost < 0;
2899 }
2900 
2901 /// Add this IV user to an existing chain or make it the head of a new chain.
2902 void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2903  SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2904  // When IVs are used as types of varying widths, they are generally converted
2905  // to a wider type with some uses remaining narrow under a (free) trunc.
2906  Value *const NextIV = getWideOperand(IVOper);
2907  const SCEV *const OperExpr = SE.getSCEV(NextIV);
2908  const SCEV *const OperExprBase = getExprBase(OperExpr);
2909 
2910  // Visit all existing chains. Check if its IVOper can be computed as a
2911  // profitable loop invariant increment from the last link in the Chain.
2912  unsigned ChainIdx = 0, NChains = IVChainVec.size();
2913  const SCEV *LastIncExpr = nullptr;
2914  for (; ChainIdx < NChains; ++ChainIdx) {
2915  IVChain &Chain = IVChainVec[ChainIdx];
2916 
2917  // Prune the solution space aggressively by checking that both IV operands
2918  // are expressions that operate on the same unscaled SCEVUnknown. This
2919  // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2920  // first avoids creating extra SCEV expressions.
2921  if (!StressIVChain && Chain.ExprBase != OperExprBase)
2922  continue;
2923 
2924  Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2925  if (!isCompatibleIVType(PrevIV, NextIV))
2926  continue;
2927 
2928  // A phi node terminates a chain.
2929  if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2930  continue;
2931 
2932  // The increment must be loop-invariant so it can be kept in a register.
2933  const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2934  const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2935  if (!SE.isLoopInvariant(IncExpr, L))
2936  continue;
2937 
2938  if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2939  LastIncExpr = IncExpr;
2940  break;
2941  }
2942  }
2943  // If we haven't found a chain, create a new one, unless we hit the max. Don't
2944  // bother for phi nodes, because they must be last in the chain.
2945  if (ChainIdx == NChains) {
2946  if (isa<PHINode>(UserInst))
2947  return;
2948  if (NChains >= MaxChains && !StressIVChain) {
2949  LLVM_DEBUG(dbgs() << "IV Chain Limit\n");
2950  return;
2951  }
2952  LastIncExpr = OperExpr;
2953  // IVUsers may have skipped over sign/zero extensions. We don't currently
2954  // attempt to form chains involving extensions unless they can be hoisted
2955  // into this loop's AddRec.
2956  if (!isa<SCEVAddRecExpr>(LastIncExpr))
2957  return;
2958  ++NChains;
2959  IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2960  OperExprBase));
2961  ChainUsersVec.resize(NChains);
2962  LLVM_DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst
2963  << ") IV=" << *LastIncExpr << "\n");
2964  } else {
2965  LLVM_DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst
2966  << ") IV+" << *LastIncExpr << "\n");
2967  // Add this IV user to the end of the chain.
2968  IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2969  }
2970  IVChain &Chain = IVChainVec[ChainIdx];
2971 
2972  SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2973  // This chain's NearUsers become FarUsers.
2974  if (!LastIncExpr->isZero()) {
2975  ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2976  NearUsers.end());
2977  NearUsers.clear();
2978  }
2979 
2980  // All other uses of IVOperand become near uses of the chain.
2981  // We currently ignore intermediate values within SCEV expressions, assuming
2982  // they will eventually be used be the current chain, or can be computed
2983  // from one of the chain increments. To be more precise we could
2984  // transitively follow its user and only add leaf IV users to the set.
2985  for (User *U : IVOper->users()) {
2986  Instruction *OtherUse = dyn_cast<Instruction>(U);
2987  if (!OtherUse)
2988  continue;
2989  // Uses in the chain will no longer be uses if the chain is formed.
2990  // Include the head of the chain in this iteration (not Chain.begin()).
2991  IVChain::const_iterator IncIter = Chain.Incs.begin();
2992  IVChain::const_iterator IncEnd = Chain.Incs.end();
2993  for( ; IncIter != IncEnd; ++IncIter) {
2994  if (IncIter->UserInst == OtherUse)
2995  break;
2996  }
2997  if (IncIter != IncEnd)
2998  continue;
2999 
3000  if (SE.isSCEVable(OtherUse->getType())
3001  && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
3002  && IU.isIVUserOrOperand(OtherUse)) {
3003  continue;
3004  }
3005  NearUsers.insert(OtherUse);
3006  }
3007 
3008  // Since this user is part of the chain, it's no longer considered a use
3009  // of the chain.
3010  ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
3011 }
3012 
3013 /// Populate the vector of Chains.
3014 ///
3015 /// This decreases ILP at the architecture level. Targets with ample registers,
3016 /// multiple memory ports, and no register renaming probably don't want
3017 /// this. However, such targets should probably disable LSR altogether.
3018 ///
3019 /// The job of LSR is to make a reasonable choice of induction variables across
3020 /// the loop. Subsequent passes can easily "unchain" computation exposing more
3021 /// ILP *within the loop* if the target wants it.
3022 ///
3023 /// Finding the best IV chain is potentially a scheduling problem. Since LSR
3024 /// will not reorder memory operations, it will recognize this as a chain, but
3025 /// will generate redundant IV increments. Ideally this would be corrected later
3026 /// by a smart scheduler:
3027 /// = A[i]
3028 /// = A[i+x]
3029 /// A[i] =
3030 /// A[i+x] =
3031 ///
3032 /// TODO: Walk the entire domtree within this loop, not just the path to the
3033 /// loop latch. This will discover chains on side paths, but requires
3034 /// maintaining multiple copies of the Chains state.
3035 void LSRInstance::CollectChains() {
3036  LLVM_DEBUG(dbgs() << "Collecting IV Chains.\n");
3037  SmallVector<ChainUsers, 8> ChainUsersVec;
3038 
3039  SmallVector<BasicBlock *,8> LatchPath;
3040  BasicBlock *LoopHeader = L->getHeader();
3041  for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
3042  Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
3043  LatchPath.push_back(Rung->getBlock());
3044  }
3045  LatchPath.push_back(LoopHeader);
3046 
3047  // Walk the instruction stream from the loop header to the loop latch.
3048  for (BasicBlock *BB : reverse(LatchPath)) {
3049  for (Instruction &I : *BB) {
3050  // Skip instructions that weren't seen by IVUsers analysis.
3051  if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
3052  continue;
3053 
3054  // Ignore users that are part of a SCEV expression. This way we only
3055  // consider leaf IV Users. This effectively rediscovers a portion of
3056  // IVUsers analysis but in program order this time.
3057  if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
3058  continue;
3059 
3060  // Remove this instruction from any NearUsers set it may be in.
3061  for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
3062  ChainIdx < NChains; ++ChainIdx) {
3063  ChainUsersVec[ChainIdx].NearUsers.erase(&I);
3064  }
3065  // Search for operands that can be chained.
3066  SmallPtrSet<Instruction*, 4> UniqueOperands;
3067  User::op_iterator IVOpEnd = I.op_end();
3068  User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
3069  while (IVOpIter != IVOpEnd) {
3070  Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
3071  if (UniqueOperands.insert(IVOpInst).second)
3072  ChainInstruction(&I, IVOpInst, ChainUsersVec);
3073  IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3074  }
3075  } // Continue walking down the instructions.
3076  } // Continue walking down the domtree.
3077  // Visit phi backedges to determine if the chain can generate the IV postinc.
3078  for (PHINode &PN : L->getHeader()->phis()) {
3079  if (!SE.isSCEVable(PN.getType()))
3080  continue;
3081 
3082  Instruction *IncV =
3083  dyn_cast<Instruction>(PN.getIncomingValueForBlock(L->getLoopLatch()));
3084  if (IncV)
3085  ChainInstruction(&PN, IncV, ChainUsersVec);
3086  }
3087  // Remove any unprofitable chains.
3088  unsigned ChainIdx = 0;
3089  for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
3090  UsersIdx < NChains; ++UsersIdx) {
3091  if (!isProfitableChain(IVChainVec[UsersIdx],
3092  ChainUsersVec[UsersIdx].FarUsers, SE))
3093  continue;
3094  // Preserve the chain at UsesIdx.
3095  if (ChainIdx != UsersIdx)
3096  IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
3097  FinalizeChain(IVChainVec[ChainIdx]);
3098  ++ChainIdx;
3099  }
3100  IVChainVec.resize(ChainIdx);
3101 }
3102 
3103 void LSRInstance::FinalizeChain(IVChain &Chain) {
3104  assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
3105  LLVM_DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n");
3106 
3107  for (const IVInc &Inc : Chain) {
3108  LLVM_DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n");
3109  auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
3110  assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand");
3111  IVIncSet.insert(UseI);
3112  }
3113 }
3114 
3115 /// Return true if the IVInc can be folded into an addressing mode.
3116 static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
3117  Value *Operand, const TargetTransformInfo &TTI) {
3118  const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
3119  if (!IncConst || !isAddressUse(TTI, UserInst, Operand))
3120  return false;
3121 
3122  if (IncConst->getAPInt().getMinSignedBits() > 64)
3123  return false;
3124 
3125  MemAccessTy AccessTy = getAccessType(TTI, UserInst, Operand);
3126  int64_t IncOffset = IncConst->getValue()->getSExtValue();
3127  if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
3128  IncOffset, /*HasBaseReg=*/false))
3129  return false;
3130 
3131  return true;
3132 }
3133 
3134 /// Generate an add or subtract for each IVInc in a chain to materialize the IV
3135 /// user's operand from the previous IV user's operand.
3136 void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
3137  SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
3138  // Find the new IVOperand for the head of the chain. It may have been replaced
3139  // by LSR.
3140  const IVInc &Head = Chain.Incs[0];
3141  User::op_iterator IVOpEnd = Head.UserInst->op_end();
3142  // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
3143  User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
3144  IVOpEnd, L, SE);
3145  Value *IVSrc = nullptr;
3146  while (IVOpIter != IVOpEnd) {
3147  IVSrc = getWideOperand(*IVOpIter);
3148 
3149  // If this operand computes the expression that the chain needs, we may use
3150  // it. (Check this after setting IVSrc which is used below.)
3151  //
3152  // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
3153  // narrow for the chain, so we can no longer use it. We do allow using a
3154  // wider phi, assuming the LSR checked for free truncation. In that case we
3155  // should already have a truncate on this operand such that
3156  // getSCEV(IVSrc) == IncExpr.
3157  if (SE.getSCEV(*IVOpIter) == Head.IncExpr
3158  || SE.getSCEV(IVSrc) == Head.IncExpr) {
3159  break;
3160  }
3161  IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3162  }
3163  if (IVOpIter == IVOpEnd) {
3164  // Gracefully give up on this chain.
3165  LLVM_DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
3166  return;
3167  }
3168 
3169  LLVM_DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
3170  Type *IVTy = IVSrc->getType();
3171  Type *IntTy = SE.getEffectiveSCEVType(IVTy);
3172  const SCEV *LeftOverExpr = nullptr;
3173  for (const IVInc &Inc : Chain) {
3174  Instruction *InsertPt = Inc.UserInst;
3175  if (isa<PHINode>(InsertPt))
3176  InsertPt = L->getLoopLatch()->getTerminator();
3177 
3178  // IVOper will replace the current IV User's operand. IVSrc is the IV
3179  // value currently held in a register.
3180  Value *IVOper = IVSrc;
3181  if (!Inc.IncExpr->isZero()) {
3182  // IncExpr was the result of subtraction of two narrow values, so must
3183  // be signed.
3184  const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
3185  LeftOverExpr = LeftOverExpr ?
3186  SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
3187  }
3188  if (LeftOverExpr && !LeftOverExpr->isZero()) {
3189  // Expand the IV increment.
3190  Rewriter.clearPostInc();
3191  Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
3192  const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
3193  SE.getUnknown(IncV));
3194  IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
3195 
3196  // If an IV increment can't be folded, use it as the next IV value.
3197  if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
3198  assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
3199  IVSrc = IVOper;
3200  LeftOverExpr = nullptr;
3201  }
3202  }
3203  Type *OperTy = Inc.IVOperand->getType();
3204  if (IVTy != OperTy) {
3205  assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
3206  "cannot extend a chained IV");
3207  IRBuilder<> Builder(InsertPt);
3208  IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
3209  }
3210  Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
3211  DeadInsts.emplace_back(Inc.IVOperand);
3212  }
3213  // If LSR created a new, wider phi, we may also replace its postinc. We only
3214  // do this if we also found a wide value for the head of the chain.
3215  if (isa<PHINode>(Chain.tailUserInst())) {
3216  for (PHINode &Phi : L->getHeader()->phis()) {
3217  if (!isCompatibleIVType(&Phi, IVSrc))
3218  continue;
3219  Instruction *PostIncV = dyn_cast<Instruction>(
3220  Phi.getIncomingValueForBlock(L->getLoopLatch()));
3221  if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
3222  continue;
3223  Value *IVOper = IVSrc;
3224  Type *PostIncTy = PostIncV->getType();
3225  if (IVTy != PostIncTy) {
3226  assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
3227  IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
3228  Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
3229  IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
3230  }
3231  Phi.replaceUsesOfWith(PostIncV, IVOper);
3232  DeadInsts.emplace_back(PostIncV);
3233  }
3234  }
3235 }
3236 
3237 void LSRInstance::CollectFixupsAndInitialFormulae() {
3238  BranchInst *ExitBranch = nullptr;
3239  bool SaveCmp = TTI.canSaveCmp(L, &ExitBranch, &SE, &LI, &DT, &AC, &LibInfo);
3240 
3241  for (const IVStrideUse &U : IU) {
3242  Instruction *UserInst = U.getUser();
3243  // Skip IV users that are part of profitable IV Chains.
3244  User::op_iterator UseI =
3245  find(UserInst->operands(), U.getOperandValToReplace());
3246  assert(UseI != UserInst->op_end() && "cannot find IV operand");
3247  if (IVIncSet.count(UseI)) {
3248  LLVM_DEBUG(dbgs() << "Use is in profitable chain: " << **UseI << '\n');
3249  continue;
3250  }
3251 
3252  LSRUse::KindType Kind = LSRUse::Basic;
3253  MemAccessTy AccessTy;
3254  if (isAddressUse(TTI, UserInst, U.getOperandValToReplace())) {
3255  Kind = LSRUse::Address;
3256  AccessTy = getAccessType(TTI, UserInst, U.getOperandValToReplace());
3257  }
3258 
3259  const SCEV *S = IU.getExpr(U);
3260  PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3261 
3262  // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3263  // (N - i == 0), and this allows (N - i) to be the expression that we work
3264  // with rather than just N or i, so we can consider the register
3265  // requirements for both N and i at the same time. Limiting this code to
3266  // equality icmps is not a problem because all interesting loops use
3267  // equality icmps, thanks to IndVarSimplify.
3268  if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst)) {
3269  // If CI can be saved in some target, like replaced inside hardware loop
3270  // in PowerPC, no need to generate initial formulae for it.
3271  if (SaveCmp && CI == dyn_cast<ICmpInst>(ExitBranch->getCondition()))
3272  continue;
3273  if (CI->isEquality()) {
3274  // Swap the operands if needed to put the OperandValToReplace on the
3275  // left, for consistency.
3276  Value *NV = CI->getOperand(1);
3277  if (NV == U.getOperandValToReplace()) {
3278  CI->setOperand(1, CI->getOperand(0));
3279  CI->setOperand(0, NV);
3280  NV = CI->getOperand(1);
3281  Changed = true;
3282  }
3283 
3284  // x == y --> x - y == 0
3285  const SCEV *N = SE.getSCEV(NV);
3286  if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3287  // S is normalized, so normalize N before folding it into S
3288  // to keep the result normalized.
3289  N = normalizeForPostIncUse(N, TmpPostIncLoops, SE);
3290  Kind = LSRUse::ICmpZero;
3291  S = SE.getMinusSCEV(N, S);
3292  }
3293 
3294  // -1 and the negations of all interesting strides (except the negation
3295  // of -1) are now also interesting.
3296  for (size_t i = 0, e = Factors.size(); i != e; ++i)
3297  if (Factors[i] != -1)
3298  Factors.insert(-(uint64_t)Factors[i]);
3299  Factors.insert(-1);
3300  }
3301  }
3302 
3303  // Get or create an LSRUse.
3304  std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3305  size_t LUIdx = P.first;
3306  int64_t Offset = P.second;
3307  LSRUse &LU = Uses[LUIdx];
3308 
3309  // Record the fixup.
3310  LSRFixup &LF = LU.getNewFixup();
3311  LF.UserInst = UserInst;
3312  LF.OperandValToReplace = U.getOperandValToReplace();
3313  LF.PostIncLoops = TmpPostIncLoops;
3314  LF.Offset = Offset;
3315  LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3316 
3317  if (!LU.WidestFixupType ||
3318  SE.getTypeSizeInBits(LU.WidestFixupType) <
3319  SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3320  LU.WidestFixupType = LF.OperandValToReplace->getType();
3321 
3322  // If this is the first use of this LSRUse, give it a formula.
3323  if (LU.Formulae.empty()) {
3324  InsertInitialFormula(S, LU, LUIdx);
3325  CountRegisters(LU.Formulae.back(), LUIdx);
3326  }
3327  }
3328 
3329  LLVM_DEBUG(print_fixups(dbgs()));
3330 }
3331 
3332 /// Insert a formula for the given expression into the given use, separating out
3333 /// loop-variant portions from loop-invariant and loop-computable portions.
3334 void
3335 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3336  // Mark uses whose expressions cannot be expanded.
3337  if (!isSafeToExpand(S, SE))
3338  LU.RigidFormula = true;
3339 
3340  Formula F;
3341  F.initialMatch(S, L, SE);
3342  bool Inserted = InsertFormula(LU, LUIdx, F);
3343  assert(Inserted && "Initial formula already exists!"); (void)Inserted;
3344 }
3345 
3346 /// Insert a simple single-register formula for the given expression into the
3347 /// given use.
3348 void
3349 LSRInstance::InsertSupplementalFormula(const SCEV *S,
3350  LSRUse &LU, size_t LUIdx) {
3351  Formula F;
3352  F.BaseRegs.push_back(S);
3353  F.HasBaseReg = true;
3354  bool Inserted = InsertFormula(LU, LUIdx, F);
3355  assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
3356 }
3357 
3358 /// Note which registers are used by the given formula, updating RegUses.
3359 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3360  if (F.ScaledReg)
3361  RegUses.countRegister(F.ScaledReg, LUIdx);
3362  for (const SCEV *BaseReg : F.BaseRegs)
3363  RegUses.countRegister(BaseReg, LUIdx);
3364 }
3365 
3366 /// If the given formula has not yet been inserted, add it to the list, and
3367 /// return true. Return false otherwise.
3368 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3369  // Do not insert formula that we will not be able to expand.
3370  assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&
3371  "Formula is illegal");
3372 
3373  if (!LU.InsertFormula(F, *L))
3374  return false;
3375 
3376  CountRegisters(F, LUIdx);
3377  return true;
3378 }
3379 
3380 /// Check for other uses of loop-invariant values which we're tracking. These
3381 /// other uses will pin these values in registers, making them less profitable
3382 /// for elimination.
3383 /// TODO: This currently misses non-constant addrec step registers.
3384 /// TODO: Should this give more weight to users inside the loop?
3385 void
3386 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3387  SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3389 
3390  while (!Worklist.empty()) {
3391  const SCEV *S = Worklist.pop_back_val();
3392 
3393  // Don't process the same SCEV twice
3394  if (!Visited.insert(S).second)
3395  continue;
3396 
3397  if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3398  Worklist.append(N->op_begin(), N->op_end());
3399  else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3400  Worklist.push_back(C->getOperand());
3401  else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3402  Worklist.push_back(D->getLHS());
3403  Worklist.push_back(D->getRHS());
3404  } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3405  const Value *V = US->getValue();
3406  if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3407  // Look for instructions defined outside the loop.
3408  if (L->contains(Inst)) continue;
3409  } else if (isa<UndefValue>(V))
3410  // Undef doesn't have a live range, so it doesn't matter.
3411  continue;
3412  for (const Use &U : V->uses()) {
3413  const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3414  // Ignore non-instructions.
3415  if (!UserInst)
3416  continue;
3417  // Ignore instructions in other functions (as can happen with
3418  // Constants).
3419  if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3420  continue;
3421  // Ignore instructions not dominated by the loop.
3422  const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3423  UserInst->getParent() :
3424  cast<PHINode>(UserInst)->getIncomingBlock(
3425  PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3426  if (!DT.dominates(L->getHeader(), UseBB))
3427  continue;
3428  // Don't bother if the instruction is in a BB which ends in an EHPad.
3429  if (UseBB->getTerminator()->isEHPad())
3430  continue;
3431  // Don't bother rewriting PHIs in catchswitch blocks.
3432  if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator()))
3433  continue;
3434  // Ignore uses which are part of other SCEV expressions, to avoid
3435  // analyzing them multiple times.
3436  if (SE.isSCEVable(UserInst->getType())) {
3437  const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3438  // If the user is a no-op, look through to its uses.
3439  if (!isa<SCEVUnknown>(UserS))
3440  continue;
3441  if (UserS == US) {
3442  Worklist.push_back(
3443  SE.getUnknown(const_cast<Instruction *>(UserInst)));
3444  continue;
3445  }
3446  }
3447  // Ignore icmp instructions which are already being analyzed.
3448  if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3449  unsigned OtherIdx = !U.getOperandNo();
3450  Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3451  if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3452  continue;
3453  }
3454 
3455  std::pair<size_t, int64_t> P = getUse(
3456  S, LSRUse::Basic, MemAccessTy());
3457  size_t LUIdx = P.first;
3458  int64_t Offset = P.second;
3459  LSRUse &LU = Uses[LUIdx];
3460  LSRFixup &LF = LU.getNewFixup();
3461  LF.UserInst = const_cast<Instruction *>(UserInst);
3462  LF.OperandValToReplace = U;
3463  LF.Offset = Offset;
3464  LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3465  if (!LU.WidestFixupType ||
3466  SE.getTypeSizeInBits(LU.WidestFixupType) <
3467  SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3468  LU.WidestFixupType = LF.OperandValToReplace->getType();
3469  InsertSupplementalFormula(US, LU, LUIdx);
3470  CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3471  break;
3472  }
3473  }
3474  }
3475 }
3476 
3477 /// Split S into subexpressions which can be pulled out into separate
3478 /// registers. If C is non-null, multiply each subexpression by C.
3479 ///
3480 /// Return remainder expression after factoring the subexpressions captured by
3481 /// Ops. If Ops is complete, return NULL.
3482 static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3484  const Loop *L,
3485  ScalarEvolution &SE,
3486  unsigned Depth = 0) {
3487  // Arbitrarily cap recursion to protect compile time.
3488  if (Depth >= 3)
3489  return S;
3490 
3491  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3492  // Break out add operands.
3493  for (const SCEV *S : Add->operands()) {
3494  const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3495  if (Remainder)
3496  Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3497  }
3498  return nullptr;
3499  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3500  // Split a non-zero base out of an addrec.
3501  if (AR->getStart()->isZero() || !AR->isAffine())
3502  return S;
3503 
3504  const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3505  C, Ops, L, SE, Depth+1);
3506  // Split the non-zero AddRec unless it is part of a nested recurrence that
3507  // does not pertain to this loop.
3508  if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3509  Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3510  Remainder = nullptr;
3511  }
3512  if (Remainder != AR->getStart()) {
3513  if (!Remainder)
3514  Remainder = SE.getConstant(AR->getType(), 0);
3515  return SE.getAddRecExpr(Remainder,
3516  AR->getStepRecurrence(SE),
3517  AR->getLoop(),
3518  //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3520  }
3521  } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3522  // Break (C * (a + b + c)) into C*a + C*b + C*c.
3523  if (Mul->getNumOperands() != 2)
3524  return S;
3525  if (const SCEVConstant *Op0 =
3526  dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3527  C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3528  const SCEV *Remainder =
3529  CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3530  if (Remainder)
3531  Ops.push_back(SE.getMulExpr(C, Remainder));
3532  return nullptr;
3533  }
3534  }
3535  return S;
3536 }
3537 
3538 /// Return true if the SCEV represents a value that may end up as a
3539 /// post-increment operation.
3541  LSRUse &LU, const SCEV *S, const Loop *L,
3542  ScalarEvolution &SE) {
3543  if (LU.Kind != LSRUse::Address ||
3544  !LU.AccessTy.getType()->isIntOrIntVectorTy())
3545  return false;
3546  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S);
3547  if (!AR)
3548  return false;
3549  const SCEV *LoopStep = AR->getStepRecurrence(SE);
3550  if (!isa<SCEVConstant>(LoopStep))
3551  return false;
3552  if (LU.AccessTy.getType()->getScalarSizeInBits() !=
3553  LoopStep->getType()->getScalarSizeInBits())
3554  return false;
3555  // Check if a post-indexed load/store can be used.
3556  if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) ||
3557  TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) {
3558  const SCEV *LoopStart = AR->getStart();
3559  if (!isa<SCEVConstant>(LoopStart) && SE.isLoopInvariant(LoopStart, L))
3560  return true;
3561  }
3562  return false;
3563 }
3564 
3565 /// Helper function for LSRInstance::GenerateReassociations.
3566 void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3567  const Formula &Base,
3568  unsigned Depth, size_t Idx,
3569  bool IsScaledReg) {
3570  const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3571  // Don't generate reassociations for the base register of a value that
3572  // may generate a post-increment operator. The reason is that the
3573  // reassociations cause extra base+register formula to be created,
3574  // and possibly chosen, but the post-increment is more efficient.
3575  if (TTI.shouldFavorPostInc() && mayUsePostIncMode(TTI, LU, BaseReg, L, SE))
3576  return;
3578  const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3579  if (Remainder)
3580  AddOps.push_back(Remainder);
3581 
3582  if (AddOps.size() == 1)
3583  return;
3584 
3586  JE = AddOps.end();
3587  J != JE; ++J) {
3588  // Loop-variant "unknown" values are uninteresting; we won't be able to
3589  // do anything meaningful with them.
3590  if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3591  continue;
3592 
3593  // Don't pull a constant into a register if the constant could be folded
3594  // into an immediate field.
3595  if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3596  LU.AccessTy, *J, Base.getNumRegs() > 1))
3597  continue;
3598 
3599  // Collect all operands except *J.
3600  SmallVector<const SCEV *, 8> InnerAddOps(
3601  ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3602  InnerAddOps.append(std::next(J),
3603  ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3604 
3605  // Don't leave just a constant behind in a register if the constant could
3606  // be folded into an immediate field.
3607  if (InnerAddOps.size() == 1 &&
3608  isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3609  LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3610  continue;
3611 
3612  const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3613  if (InnerSum->isZero())
3614  continue;
3615  Formula F = Base;
3616 
3617  // Add the remaining pieces of the add back into the new formula.
3618  const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3619  if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3620  TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3621  InnerSumSC->getValue()->getZExtValue())) {
3622  F.UnfoldedOffset =
3623  (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3624  if (IsScaledReg)
3625  F.ScaledReg = nullptr;
3626  else
3627  F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3628  } else if (IsScaledReg)
3629  F.ScaledReg = InnerSum;
3630  else
3631  F.BaseRegs[Idx] = InnerSum;
3632 
3633  // Add J as its own register, or an unfolded immediate.
3634  const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3635  if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3636  TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3637  SC->getValue()->getZExtValue()))
3638  F.UnfoldedOffset =
3639  (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3640  else
3641  F.BaseRegs.push_back(*J);
3642  // We may have changed the number of register in base regs, adjust the
3643  // formula accordingly.
3644  F.canonicalize(*L);
3645 
3646  if (InsertFormula(LU, LUIdx, F))
3647  // If that formula hadn't been seen before, recurse to find more like
3648  // it.
3649  // Add check on Log16(AddOps.size()) - same as Log2_32(AddOps.size()) >> 2)
3650  // Because just Depth is not enough to bound compile time.
3651  // This means that every time AddOps.size() is greater 16^x we will add
3652  // x to Depth.
3653  GenerateReassociations(LU, LUIdx, LU.Formulae.back(),
3654  Depth + 1 + (Log2_32(AddOps.size()) >> 2));
3655  }
3656 }
3657 
3658 /// Split out subexpressions from adds and the bases of addrecs.
3659 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3660  Formula Base, unsigned Depth) {
3661  assert(Base.isCanonical(*L) && "Input must be in the canonical form");
3662  // Arbitrarily cap recursion to protect compile time.
3663  if (Depth >= 3)
3664  return;
3665 
3666  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3667  GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3668 
3669  if (Base.Scale == 1)
3670  GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3671  /* Idx */ -1, /* IsScaledReg */ true);
3672 }
3673 
3674 /// Generate a formula consisting of all of the loop-dominating registers added
3675 /// into a single register.
3676 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3677  Formula Base) {
3678  // This method is only interesting on a plurality of registers.
3679  if (Base.BaseRegs.size() + (Base.Scale == 1) +
3680  (Base.UnfoldedOffset != 0) <= 1)
3681  return;
3682 
3683  // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3684  // processing the formula.
3685  Base.unscale();
3687  Formula NewBase = Base;
3688  NewBase.BaseRegs.clear();
3689  Type *CombinedIntegerType = nullptr;
3690  for (const SCEV *BaseReg : Base.BaseRegs) {
3691  if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3692  !SE.hasComputableLoopEvolution(BaseReg, L)) {
3693  if (!CombinedIntegerType)
3694  CombinedIntegerType = SE.getEffectiveSCEVType(BaseReg->getType());
3695  Ops.push_back(BaseReg);
3696  }
3697  else
3698  NewBase.BaseRegs.push_back(BaseReg);
3699  }
3700 
3701  // If no register is relevant, we're done.
3702  if (Ops.size() == 0)
3703  return;
3704 
3705  // Utility function for generating the required variants of the combined
3706  // registers.
3707  auto GenerateFormula = [&](const SCEV *Sum) {
3708  Formula F = NewBase;
3709 
3710  // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3711  // opportunity to fold something. For now, just ignore such cases
3712  // rather than proceed with zero in a register.
3713  if (Sum->isZero())
3714  return;
3715 
3716  F.BaseRegs.push_back(Sum);
3717  F.canonicalize(*L);
3718  (void)InsertFormula(LU, LUIdx, F);
3719  };
3720 
3721  // If we collected at least two registers, generate a formula combining them.
3722  if (Ops.size() > 1) {
3723  SmallVector<const SCEV *, 4> OpsCopy(Ops); // Don't let SE modify Ops.
3724  GenerateFormula(SE.getAddExpr(OpsCopy));
3725  }
3726 
3727  // If we have an unfolded offset, generate a formula combining it with the
3728  // registers collected.
3729  if (NewBase.UnfoldedOffset) {
3730  assert(CombinedIntegerType && "Missing a type for the unfolded offset");
3731  Ops.push_back(SE.getConstant(CombinedIntegerType, NewBase.UnfoldedOffset,
3732  true));
3733  NewBase.UnfoldedOffset = 0;
3734  GenerateFormula(SE.getAddExpr(Ops));
3735  }
3736 }
3737 
3738 /// Helper function for LSRInstance::GenerateSymbolicOffsets.
3739 void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3740  const Formula &Base, size_t Idx,
3741  bool IsScaledReg) {
3742  const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3743  GlobalValue *GV = ExtractSymbol(G, SE);
3744  if (G->isZero() || !GV)
3745  return;
3746  Formula F = Base;
3747  F.BaseGV = GV;
3748  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3749  return;
3750  if (IsScaledReg)
3751  F.ScaledReg = G;
3752  else
3753  F.BaseRegs[Idx] = G;
3754  (void)InsertFormula(LU, LUIdx, F);
3755 }
3756 
3757 /// Generate reuse formulae using symbolic offsets.
3758 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3759  Formula Base) {
3760  // We can't add a symbolic offset if the address already contains one.
3761  if (Base.BaseGV) return;
3762 
3763  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3764  GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3765  if (Base.Scale == 1)
3766  GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3767  /* IsScaledReg */ true);
3768 }
3769 
3770 /// Helper function for LSRInstance::GenerateConstantOffsets.
3771 void LSRInstance::GenerateConstantOffsetsImpl(
3772  LSRUse &LU, unsigned LUIdx, const Formula &Base,
3773  const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3774 
3775  auto GenerateOffset = [&](const SCEV *G, int64_t Offset) {
3776  Formula F = Base;
3777  F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3778 
3779  if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind,
3780  LU.AccessTy, F)) {
3781  // Add the offset to the base register.
3782  const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3783  // If it cancelled out, drop the base register, otherwise update it.
3784  if (NewG->isZero()) {
3785  if (IsScaledReg) {
3786  F.Scale = 0;
3787  F.ScaledReg = nullptr;
3788  } else
3789  F.deleteBaseReg(F.BaseRegs[Idx]);
3790  F.canonicalize(*L);
3791  } else if (IsScaledReg)
3792  F.ScaledReg = NewG;
3793  else
3794  F.BaseRegs[Idx] = NewG;
3795 
3796  (void)InsertFormula(LU, LUIdx, F);
3797  }
3798  };
3799 
3800  const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3801 
3802  // With constant offsets and constant steps, we can generate pre-inc
3803  // accesses by having the offset equal the step. So, for access #0 with a
3804  // step of 8, we generate a G - 8 base which would require the first access
3805  // to be ((G - 8) + 8),+,8. The pre-indexed access then updates the pointer
3806  // for itself and hopefully becomes the base for other accesses. This means
3807  // means that a single pre-indexed access can be generated to become the new
3808  // base pointer for each iteration of the loop, resulting in no extra add/sub
3809  // instructions for pointer updating.
3810  if (FavorBackedgeIndex && LU.Kind == LSRUse::Address) {
3811  if (auto *GAR = dyn_cast<SCEVAddRecExpr>(G)) {
3812  if (auto *StepRec =
3813  dyn_cast<SCEVConstant>(GAR->getStepRecurrence(SE))) {
3814  const APInt &StepInt = StepRec->getAPInt();
3815  int64_t Step = StepInt.isNegative() ?
3816  StepInt.getSExtValue() : StepInt.getZExtValue();
3817 
3818  for (int64_t Offset : Worklist) {
3819  Offset -= Step;
3820  GenerateOffset(G, Offset);
3821  }
3822  }
3823  }
3824  }
3825  for (int64_t Offset : Worklist)
3826  GenerateOffset(G, Offset);
3827 
3828  int64_t Imm = ExtractImmediate(G, SE);
3829  if (G->isZero() || Imm == 0)
3830  return;
3831  Formula F = Base;
3832  F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3833  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3834  return;
3835  if (IsScaledReg)
3836  F.ScaledReg = G;
3837  else
3838  F.BaseRegs[Idx] = G;
3839  (void)InsertFormula(LU, LUIdx, F);
3840 }
3841 
3842 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3843 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3844  Formula Base) {
3845  // TODO: For now, just add the min and max offset, because it usually isn't
3846  // worthwhile looking at everything inbetween.
3847  SmallVector<int64_t, 2> Worklist;
3848  Worklist.push_back(LU.MinOffset);
3849  if (LU.MaxOffset != LU.MinOffset)
3850  Worklist.push_back(LU.MaxOffset);
3851 
3852  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3853  GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3854  if (Base.Scale == 1)
3855  GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3856  /* IsScaledReg */ true);
3857 }
3858 
3859 /// For ICmpZero, check to see if we can scale up the comparison. For example, x
3860 /// == y -> x*c == y*c.
3861 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3862  Formula Base) {
3863  if (LU.Kind != LSRUse::ICmpZero) return;
3864 
3865  // Determine the integer type for the base formula.
3866  Type *IntTy = Base.getType();
3867  if (!IntTy) return;
3868  if (SE.getTypeSizeInBits(IntTy) > 64) return;
3869 
3870  // Don't do this if there is more than one offset.
3871  if (LU.MinOffset != LU.MaxOffset) return;
3872 
3873  // Check if transformation is valid. It is illegal to multiply pointer.
3874  if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
3875  return;
3876  for (const SCEV *BaseReg : Base.BaseRegs)
3877  if (BaseReg->getType()->isPointerTy())
3878  return;
3879  assert(!Base.BaseGV && "ICmpZero use is not legal!");
3880 
3881  // Check each interesting stride.
3882  for (int64_t Factor : Factors) {
3883  // Check that the multiplication doesn't overflow.
3884  if (Base.BaseOffset == std::numeric_limits<int64_t>::min() && Factor == -1)
3885  continue;
3886  int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3887  if (NewBaseOffset / Factor != Base.BaseOffset)
3888  continue;
3889  // If the offset will be truncated at this use, check that it is in bounds.
3890  if (!IntTy->isPointerTy() &&
3891  !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3892  continue;
3893 
3894  // Check that multiplying with the use offset doesn't overflow.
3895  int64_t Offset = LU.MinOffset;
3896  if (Offset == std::numeric_limits<int64_t>::min() && Factor == -1)
3897  continue;
3898  Offset = (uint64_t)Offset * Factor;
3899  if (Offset / Factor != LU.MinOffset)
3900  continue;
3901  // If the offset will be truncated at this use, check that it is in bounds.
3902  if (!IntTy->isPointerTy() &&
3903  !ConstantInt::isValueValidForType(IntTy, Offset))
3904  continue;
3905 
3906  Formula F = Base;
3907  F.BaseOffset = NewBaseOffset;
3908 
3909  // Check that this scale is legal.
3910  if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3911  continue;
3912 
3913  // Compensate for the use having MinOffset built into it.
3914  F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3915 
3916  const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3917 
3918  // Check that multiplying with each base register doesn't overflow.
3919  for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3920  F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3921  if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3922  goto next;
3923  }
3924 
3925  // Check that multiplying with the scaled register doesn't overflow.
3926  if (F.ScaledReg) {
3927  F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3928  if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3929  continue;
3930  }
3931 
3932  // Check that multiplying with the unfolded offset doesn't overflow.
3933  if (F.UnfoldedOffset != 0) {
3934  if (F.UnfoldedOffset == std::numeric_limits<int64_t>::min() &&
3935  Factor == -1)
3936  continue;
3937  F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3938  if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3939  continue;
3940  // If the offset will be truncated, check that it is in bounds.
3941  if (!IntTy->isPointerTy() &&
3942  !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3943  continue;
3944  }
3945 
3946  // If we make it here and it's legal, add it.
3947  (void)InsertFormula(LU, LUIdx, F);
3948  next:;
3949  }
3950 }
3951 
3952 /// Generate stride factor reuse formulae by making use of scaled-offset address
3953 /// modes, for example.
3954 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3955  // Determine the integer type for the base formula.
3956  Type *IntTy = Base.getType();
3957  if (!IntTy) return;
3958 
3959  // If this Formula already has a scaled register, we can't add another one.
3960  // Try to unscale the formula to generate a better scale.
3961  if (Base.Scale != 0 && !Base.unscale())
3962  return;
3963 
3964  assert(Base.Scale == 0 && "unscale did not did its job!");
3965 
3966  // Check each interesting stride.
3967  for (int64_t Factor : Factors) {
3968  Base.Scale = Factor;
3969  Base.HasBaseReg = Base.BaseRegs.size() > 1;
3970  // Check whether this scale is going to be legal.
3971  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3972  Base)) {
3973  // As a special-case, handle special out-of-loop Basic users specially.
3974  // TODO: Reconsider this special case.
3975  if (LU.Kind == LSRUse::Basic &&
3976  isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3977  LU.AccessTy, Base) &&
3978  LU.AllFixupsOutsideLoop)
3979  LU.Kind = LSRUse::Special;
3980  else
3981  continue;
3982  }
3983  // For an ICmpZero, negating a solitary base register won't lead to
3984  // new solutions.
3985  if (LU.Kind == LSRUse::ICmpZero &&
3986  !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3987  continue;
3988  // For each addrec base reg, if its loop is current loop, apply the scale.
3989  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3990  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]);
3991  if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) {
3992  const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3993  if (FactorS->isZero())
3994  continue;
3995  // Divide out the factor, ignoring high bits, since we'll be
3996  // scaling the value back up in the end.
3997  if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3998  // TODO: This could be optimized to avoid all the copying.
3999  Formula F = Base;
4000  F.ScaledReg = Quotient;
4001  F.deleteBaseReg(F.BaseRegs[i]);
4002  // The canonical representation of 1*reg is reg, which is already in
4003  // Base. In that case, do not try to insert the formula, it will be
4004  // rejected anyway.
4005  if (F.Scale == 1 && (F.BaseRegs.empty() ||
4006  (AR->getLoop() != L && LU.AllFixupsOutsideLoop)))
4007  continue;
4008  // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate
4009  // non canonical Formula with ScaledReg's loop not being L.
4010  if (F.Scale == 1 && LU.AllFixupsOutsideLoop)
4011  F.canonicalize(*L);
4012  (void)InsertFormula(LU, LUIdx, F);
4013  }
4014  }
4015  }
4016  }
4017 }
4018 
4019 /// Generate reuse formulae from different IV types.
4020 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
4021  // Don't bother truncating symbolic values.
4022  if (Base.BaseGV) return;
4023 
4024  // Determine the integer type for the base formula.
4025  Type *DstTy = Base.getType();
4026  if (!DstTy) return;
4027  DstTy = SE.getEffectiveSCEVType(DstTy);
4028 
4029  for (Type *SrcTy : Types) {
4030  if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
4031  Formula F = Base;
4032 
4033  // Sometimes SCEV is able to prove zero during ext transform. It may
4034  // happen if SCEV did not do all possible transforms while creating the
4035  // initial node (maybe due to depth limitations), but it can do them while
4036  // taking ext.
4037  if (F.ScaledReg) {
4038  const SCEV *NewScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
4039  if (NewScaledReg->isZero())
4040  continue;
4041  F.ScaledReg = NewScaledReg;
4042  }
4043  bool HasZeroBaseReg = false;
4044  for (const SCEV *&BaseReg : F.BaseRegs) {
4045  const SCEV *NewBaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
4046  if (NewBaseReg->isZero()) {
4047  HasZeroBaseReg = true;
4048  break;
4049  }
4050  BaseReg = NewBaseReg;
4051  }
4052  if (HasZeroBaseReg)
4053  continue;
4054 
4055  // TODO: This assumes we've done basic processing on all uses and
4056  // have an idea what the register usage is.
4057  if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
4058  continue;
4059 
4060  F.canonicalize(*L);
4061  (void)InsertFormula(LU, LUIdx, F);
4062  }
4063  }
4064 }
4065 
4066 namespace {
4067 
4068 /// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
4069 /// modifications so that the search phase doesn't have to worry about the data
4070 /// structures moving underneath it.
4071 struct WorkItem {
4072  size_t LUIdx;
4073  int64_t Imm;
4074  const SCEV *OrigReg;
4075 
4076  WorkItem(size_t LI, int64_t I, const SCEV *R)
4077  : LUIdx(LI), Imm(I), OrigReg(R) {}
4078 
4079  void print(raw_ostream &OS) const;
4080  void dump() const;
4081 };
4082 
4083 } // end anonymous namespace
4084 
4085 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
4086 void WorkItem::print(raw_ostream &OS) const {
4087  OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
4088  << " , add offset " << Imm;
4089 }
4090 
4091 LLVM_DUMP_METHOD void WorkItem::dump() const {
4092  print(errs()); errs() << '\n';
4093 }
4094 #endif
4095 
4096 /// Look for registers which are a constant distance apart and try to form reuse
4097 /// opportunities between them.
4098 void LSRInstance::GenerateCrossUseConstantOffsets() {
4099  // Group the registers by their value without any added constant offset.
4100  using ImmMapTy = std::map<int64_t, const SCEV *>;
4101 
4103  DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
4105  for (const SCEV *Use : RegUses) {
4106  const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
4107  int64_t Imm = ExtractImmediate(Reg, SE);
4108  auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
4109  if (Pair.second)
4110  Sequence.push_back(Reg);
4111  Pair.first->second.insert(std::make_pair(Imm, Use));
4112  UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
4113  }
4114 
4115  // Now examine each set of registers with the same base value. Build up
4116  // a list of work to do and do the work in a separate step so that we're
4117  // not adding formulae and register counts while we're searching.
4118  SmallVector<WorkItem, 32> WorkItems;
4119  SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
4120  for (const SCEV *Reg : Sequence) {
4121  const ImmMapTy &Imms = Map.find(Reg)->second;
4122 
4123  // It's not worthwhile looking for reuse if there's only one offset.
4124  if (Imms.size() == 1)
4125  continue;
4126 
4127  LLVM_DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
4128  for (const auto &Entry
4129  : Imms) dbgs()
4130  << ' ' << Entry.first;
4131  dbgs() << '\n');
4132 
4133  // Examine each offset.
4134  for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
4135  J != JE; ++J) {
4136  const SCEV *OrigReg = J->second;
4137 
4138  int64_t JImm = J->first;
4139  const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
4140 
4141  if (!isa<SCEVConstant>(OrigReg) &&
4142  UsedByIndicesMap[Reg].count() == 1) {
4143  LLVM_DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg
4144  << '\n');
4145  continue;
4146  }
4147 
4148  // Conservatively examine offsets between this orig reg a few selected
4149  // other orig regs.
4150  int64_t First = Imms.begin()->first;
4151  int64_t Last = std::prev(Imms.end())->first;
4152  // Compute (First + Last) / 2 without overflow using the fact that
4153  // First + Last = 2 * (First + Last) + (First ^ Last).
4154  int64_t Avg = (First & Last) + ((First ^ Last) >> 1);
4155  // If the result is negative and First is odd and Last even (or vice versa),
4156  // we rounded towards -inf. Add 1 in that case, to round towards 0.
4157  Avg = Avg + ((First ^ Last) & ((uint64_t)Avg >> 63));
4158  ImmMapTy::const_iterator OtherImms[] = {
4159  Imms.begin(), std::prev(Imms.end()),
4160  Imms.lower_bound(Avg)};
4161  for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
4162  ImmMapTy::const_iterator M = OtherImms[i];
4163  if (M == J || M == JE) continue;
4164 
4165  // Compute the difference between the two.
4166  int64_t Imm = (uint64_t)JImm - M->first;
4167  for (unsigned LUIdx : UsedByIndices.set_bits())
4168  // Make a memo of this use, offset, and register tuple.
4169  if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
4170  WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
4171  }
4172  }
4173  }
4174 
4175  Map.clear();
4176  Sequence.clear();
4177  UsedByIndicesMap.clear();
4178  UniqueItems.clear();
4179 
4180  // Now iterate through the worklist and add new formulae.
4181  for (const WorkItem &WI : WorkItems) {
4182  size_t LUIdx = WI.LUIdx;
4183  LSRUse &LU = Uses[LUIdx];
4184  int64_t Imm = WI.Imm;
4185  const SCEV *OrigReg = WI.OrigReg;
4186 
4187  Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
4188  const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
4189  unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
4190 
4191  // TODO: Use a more targeted data structure.
4192  for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
4193  Formula F = LU.Formulae[L];
4194  // FIXME: The code for the scaled and unscaled registers looks
4195  // very similar but slightly different. Investigate if they
4196  // could be merged. That way, we would not have to unscale the
4197  // Formula.
4198  F.unscale();
4199  // Use the immediate in the scaled register.
4200  if (F.ScaledReg == OrigReg) {
4201  int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
4202  // Don't create 50 + reg(-50).
4203  if (F.referencesReg(SE.getSCEV(
4204  ConstantInt::get(IntTy, -(uint64_t)Offset))))
4205  continue;
4206  Formula NewF = F;
4207  NewF.BaseOffset = Offset;
4208  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4209  NewF))
4210  continue;
4211  NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
4212 
4213  // If the new scale is a constant in a register, and adding the constant
4214  // value to the immediate would produce a value closer to zero than the
4215  // immediate itself, then the formula isn't worthwhile.
4216  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
4217  if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
4218  (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
4219  .ule(std::abs(NewF.BaseOffset)))
4220  continue;
4221 
4222  // OK, looks good.
4223  NewF.canonicalize(*this->L);
4224  (void)InsertFormula(LU, LUIdx, NewF);
4225  } else {
4226  // Use the immediate in a base register.
4227  for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
4228  const SCEV *BaseReg = F.BaseRegs[N];
4229  if (BaseReg != OrigReg)
4230  continue;
4231  Formula NewF = F;
4232  NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
4233  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
4234  LU.Kind, LU.AccessTy, NewF)) {
4235  if (TTI.shouldFavorPostInc() &&
4236  mayUsePostIncMode(TTI, LU, OrigReg, this->L, SE))
4237  continue;
4238  if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
4239  continue;
4240  NewF = F;
4241  NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
4242  }
4243  NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
4244 
4245  // If the new formula has a constant in a register, and adding the
4246  // constant value to the immediate would produce a value closer to
4247  // zero than the immediate itself, then the formula isn't worthwhile.
4248  for (const SCEV *NewReg : NewF.BaseRegs)
4249  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
4250  if ((C->getAPInt() + NewF.BaseOffset)
4251  .abs()
4252  .slt(std::abs(NewF.BaseOffset)) &&
4253  (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
4254  countTrailingZeros<uint64_t>(NewF.BaseOffset))
4255  goto skip_formula;
4256 
4257  // Ok, looks good.
4258  NewF.canonicalize(*this->L);
4259  (void)InsertFormula(LU, LUIdx, NewF);
4260  break;
4261  skip_formula:;
4262  }
4263  }
4264  }
4265  }
4266 }
4267 
4268 /// Generate formulae for each use.
4269 void
4270 LSRInstance::GenerateAllReuseFormulae() {
4271  // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
4272  // queries are more precise.
4273  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4274  LSRUse &LU = Uses[LUIdx];
4275  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4276  GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
4277  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4278  GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
4279  }
4280  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4281  LSRUse &LU = Uses[LUIdx];
4282  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4283  GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
4284  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4285  GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
4286  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4287  GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
4288  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4289  GenerateScales(LU, LUIdx, LU.Formulae[i]);
4290  }
4291  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4292  LSRUse &LU = Uses[LUIdx];
4293  for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4294  GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
4295  }
4296 
4297  GenerateCrossUseConstantOffsets();
4298 
4299  LLVM_DEBUG(dbgs() << "\n"
4300  "After generating reuse formulae:\n";
4301  print_uses(dbgs()));
4302 }
4303 
4304 /// If there are multiple formulae with the same set of registers used
4305 /// by other uses, pick the best one and delete the others.
4306 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
4307  DenseSet<const SCEV *> VisitedRegs;
4310 #ifndef NDEBUG
4311  bool ChangedFormulae = false;
4312 #endif
4313 
4314  // Collect the best formula for each unique set of shared registers. This
4315  // is reset for each use.
4316  using BestFormulaeTy =
4317  DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>;
4318 
4319  BestFormulaeTy BestFormulae;
4320 
4321  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4322  LSRUse &LU = Uses[LUIdx];
4323  LLVM_DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs());
4324  dbgs() << '\n');
4325 
4326  bool Any = false;
4327  for (size_t FIdx = 0, NumForms = LU.Formulae.size();
4328  FIdx != NumForms; ++FIdx) {
4329  Formula &F = LU.Formulae[FIdx];
4330 
4331  // Some formulas are instant losers. For example, they may depend on
4332  // nonexistent AddRecs from other loops. These need to be filtered
4333  // immediately, otherwise heuristics could choose them over others leading
4334  // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
4335  // avoids the need to recompute this information across formulae using the
4336  // same bad AddRec. Passing LoserRegs is also essential unless we remove
4337  // the corresponding bad register from the Regs set.
4338  Cost CostF(L, SE, TTI);
4339  Regs.clear();
4340  CostF.RateFormula(F, Regs, VisitedRegs, LU, &LoserRegs);
4341  if (CostF.isLoser()) {
4342  // During initial formula generation, undesirable formulae are generated
4343  // by uses within other loops that have some non-trivial address mode or
4344  // use the postinc form of the IV. LSR needs to provide these formulae
4345  // as the basis of rediscovering the desired formula that uses an AddRec
4346  // corresponding to the existing phi. Once all formulae have been
4347  // generated, these initial losers may be pruned.
4348  LLVM_DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());
4349  dbgs() << "\n");
4350  }
4351  else {
4353  for (const SCEV *Reg : F.BaseRegs) {
4354  if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
4355  Key.push_back(Reg);
4356  }
4357  if (F.ScaledReg &&
4358  RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
4359  Key.push_back(F.ScaledReg);
4360  // Unstable sort by host order ok, because this is only used for
4361  // uniquifying.
4362  llvm::sort(Key);
4363 
4364  std::pair<BestFormulaeTy::const_iterator, bool> P =
4365  BestFormulae.insert(std::make_pair(Key, FIdx));
4366  if (P.second)
4367  continue;
4368 
4369  Formula &Best = LU.Formulae[P.first->second];
4370 
4371  Cost CostBest(L, SE, TTI);
4372  Regs.clear();
4373  CostBest.RateFormula(Best, Regs, VisitedRegs, LU);
4374  if (CostF.isLess(CostBest))
4375  std::swap(F, Best);
4376  LLVM_DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
4377  dbgs() << "\n"
4378  " in favor of formula ";
4379  Best.print(dbgs()); dbgs() << '\n');
4380  }
4381 #ifndef NDEBUG
4382  ChangedFormulae = true;
4383 #endif
4384  LU.DeleteFormula(F);
4385  --FIdx;
4386  --NumForms;
4387  Any = true;
4388  }
4389 
4390  // Now that we've filtered out some formulae, recompute the Regs set.
4391  if (Any)
4392  LU.RecomputeRegs(LUIdx, RegUses);
4393 
4394  // Reset this to prepare for the next use.
4395  BestFormulae.clear();
4396  }
4397 
4398  LLVM_DEBUG(if (ChangedFormulae) {
4399  dbgs() << "\n"
4400  "After filtering out undesirable candidates:\n";
4401  print_uses(dbgs());
4402  });
4403 }
4404 
4405 /// Estimate the worst-case number of solutions the solver might have to
4406 /// consider. It almost never considers this many solutions because it prune the
4407 /// search space, but the pruning isn't always sufficient.
4408 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4409  size_t Power = 1;
4410  for (const LSRUse &LU : Uses) {
4411  size_t FSize = LU.Formulae.size();
4412  if (FSize >= ComplexityLimit) {
4413  Power = ComplexityLimit;
4414  break;
4415  }
4416  Power *= FSize;
4417  if (Power >= ComplexityLimit)
4418  break;
4419  }
4420  return Power;
4421 }
4422 
4423 /// When one formula uses a superset of the registers of another formula, it
4424 /// won't help reduce register pressure (though it may not necessarily hurt
4425 /// register pressure); remove it to simplify the system.
4426 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4427  if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4428  LLVM_DEBUG(dbgs() << "The search space is too complex.\n");
4429 
4430  LLVM_DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
4431  "which use a superset of registers used by other "
4432  "formulae.\n");
4433 
4434  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4435  LSRUse &LU = Uses[LUIdx];
4436  bool Any = false;
4437  for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4438  Formula &F = LU.Formulae[i];
4439  // Look for a formula with a constant or GV in a register. If the use
4440  // also has a formula with that same value in an immediate field,
4441  // delete the one that uses a register.
4443  I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4444  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4445  Formula NewF = F;
4446  //FIXME: Formulas should store bitwidth to do wrapping properly.
4447  // See PR41034.
4448  NewF.BaseOffset += (uint64_t)C->getValue()->getSExtValue();
4449  NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4450  (I - F.BaseRegs.begin()));
4451  if (LU.HasFormulaWithSameRegs(NewF)) {
4452  LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4453  dbgs() << '\n');
4454  LU.DeleteFormula(F);
4455  --i;
4456  --e;
4457  Any = true;
4458  break;
4459  }
4460  } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4461  if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4462  if (!F.BaseGV) {
4463  Formula NewF = F;
4464  NewF.BaseGV = GV;
4465  NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4466  (I - F.BaseRegs.begin()));
4467  if (LU.HasFormulaWithSameRegs(NewF)) {
4468  LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4469  dbgs() << '\n');
4470  LU.DeleteFormula(F);
4471  --i;
4472  --e;
4473  Any = true;
4474  break;
4475  }
4476  }
4477  }
4478  }
4479  }
4480  if (Any)
4481  LU.RecomputeRegs(LUIdx, RegUses);
4482  }
4483 
4484  LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4485  }
4486 }
4487 
4488 /// When there are many registers for expressions like A, A+1, A+2, etc.,
4489 /// allocate a single register for them.
4490 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4491  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4492  return;
4493 
4494  LLVM_DEBUG(
4495  dbgs() << "The search space is too complex.\n"
4496  "Narrowing the search space by assuming that uses separated "
4497  "by a constant offset will use the same registers.\n");
4498 
4499  // This is especially useful for unrolled loops.
4500 
4501  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4502  LSRUse &LU = Uses[LUIdx];
4503  for (const Formula &F : LU.Formulae) {
4504  if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4505  continue;
4506 
4507  LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4508  if (!LUThatHas)
4509  continue;
4510 
4511  if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4512  LU.Kind, LU.AccessTy))
4513  continue;
4514 
4515  LLVM_DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n');
4516 
4517  LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4518 
4519  // Transfer the fixups of LU to LUThatHas.
4520  for (LSRFixup &Fixup : LU.Fixups) {
4521  Fixup.Offset += F.BaseOffset;
4522  LUThatHas->pushFixup(Fixup);
4523  LLVM_DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n');
4524  }
4525 
4526  // Delete formulae from the new use which are no longer legal.
4527  bool Any = false;
4528  for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4529  Formula &F = LUThatHas->Formulae[i];
4530  if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4531  LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4532  LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4533  LUThatHas->DeleteFormula(F);
4534  --i;
4535  --e;
4536  Any = true;
4537  }
4538  }
4539 
4540  if (Any)
4541  LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4542 
4543  // Delete the old use.
4544  DeleteUse(LU, LUIdx);
4545  --LUIdx;
4546  --NumUses;
4547  break;
4548  }
4549  }
4550 
4551  LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4552 }
4553 
4554 /// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4555 /// we've done more filtering, as it may be able to find more formulae to
4556 /// eliminate.
4557 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4558  if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4559  LLVM_DEBUG(dbgs() << "The search space is too complex.\n");
4560 
4561  LLVM_DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
4562  "undesirable dedicated registers.\n");
4563 
4564  FilterOutUndesirableDedicatedRegisters();
4565 
4566  LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4567  }
4568 }
4569 
4570 /// If a LSRUse has multiple formulae with the same ScaledReg and Scale.
4571 /// Pick the best one and delete the others.
4572 /// This narrowing heuristic is to keep as many formulae with different
4573 /// Scale and ScaledReg pair as possible while narrowing the search space.
4574 /// The benefit is that it is more likely to find out a better solution
4575 /// from a formulae set with more Scale and ScaledReg variations than
4576 /// a formulae set with the same Scale and ScaledReg. The picking winner
4577 /// reg heuristic will often keep the formulae with the same Scale and
4578 /// ScaledReg and filter others, and we want to avoid that if possible.
4579 void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() {
4580  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4581  return;
4582 
4583  LLVM_DEBUG(
4584  dbgs() << "The search space is too complex.\n"
4585  "Narrowing the search space by choosing the best Formula "
4586  "from the Formulae with the same Scale and ScaledReg.\n");
4587 
4588  // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse.
4589  using BestFormulaeTy = DenseMap<std::pair<const SCEV *, int64_t>, size_t>;
4590 
4591  BestFormulaeTy BestFormulae;
4592 #ifndef NDEBUG
4593  bool ChangedFormulae = false;
4594 #endif
4595  DenseSet<const SCEV *> VisitedRegs;
4597 
4598  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4599  LSRUse &LU = Uses[LUIdx];
4600  LLVM_DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs());
4601  dbgs() << '\n');
4602 
4603  // Return true if Formula FA is better than Formula FB.
4604  auto IsBetterThan = [&](Formula &FA, Formula &FB) {
4605  // First we will try to choose the Formula with fewer new registers.
4606  // For a register used by current Formula, the more the register is
4607  // shared among LSRUses, the less we increase the register number
4608  // counter of the formula.
4609  size_t FARegNum = 0;
4610  for (const SCEV *Reg : FA.BaseRegs) {
4611  const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4612  FARegNum += (NumUses - UsedByIndices.count() + 1);
4613  }
4614  size_t FBRegNum = 0;
4615  for (const SCEV *Reg : FB.BaseRegs) {
4616  const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4617  FBRegNum += (NumUses - UsedByIndices.count() + 1);
4618  }
4619  if (FARegNum != FBRegNum)
4620  return FARegNum < FBRegNum;
4621 
4622  // If the new register numbers are the same, choose the Formula with
4623  // less Cost.
4624  Cost CostFA(L, SE, TTI);
4625  Cost CostFB(L, SE, TTI);
4626  Regs.clear();
4627  CostFA.RateFormula(FA, Regs, VisitedRegs, LU);
4628  Regs.clear();
4629  CostFB.RateFormula(FB, Regs, VisitedRegs, LU);
4630  return CostFA.isLess(CostFB);
4631  };
4632 
4633  bool Any = false;
4634  for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4635  ++FIdx) {
4636  Formula &F = LU.Formulae[FIdx];
4637  if (!F.ScaledReg)
4638  continue;
4639  auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx});
4640  if (P.second)
4641  continue;
4642 
4643  Formula &Best = LU.Formulae[P.first->second];
4644  if (IsBetterThan(F, Best))
4645  std::swap(F, Best);
4646  LLVM_DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
4647  dbgs() << "\n"
4648  " in favor of formula ";
4649  Best.print(dbgs()); dbgs() << '\n');
4650 #ifndef NDEBUG
4651  ChangedFormulae = true;
4652 #endif
4653  LU.DeleteFormula(F);
4654  --FIdx;
4655  --NumForms;
4656  Any = true;
4657  }
4658  if (Any)
4659  LU.RecomputeRegs(LUIdx, RegUses);
4660 
4661  // Reset this to prepare for the next use.
4662  BestFormulae.clear();
4663  }
4664 
4665  LLVM_DEBUG(if (ChangedFormulae) {
4666  dbgs() << "\n"
4667  "After filtering out undesirable candidates:\n";
4668  print_uses(dbgs());
4669  });
4670 }
4671 
4672 /// The function delete formulas with high registers number expectation.
4673 /// Assuming we don't know the value of each formula (already delete
4674 /// all inefficient), generate probability of not selecting for each
4675 /// register.
4676 /// For example,
4677 /// Use1:
4678 /// reg(a) + reg({0,+,1})
4679 /// reg(a) + reg({-1,+,1}) + 1
4680 /// reg({a,+,1})
4681 /// Use2:
4682 /// reg(b) + reg({0,+,1})
4683 /// reg(b) + reg({-1,+,1}) + 1
4684 /// reg({b,+,1})
4685 /// Use3:
4686 /// reg(c) + reg(b) + reg({0,+,1})
4687 /// reg(c) + reg({b,+,1})
4688 ///
4689 /// Probability of not selecting
4690 /// Use1 Use2 Use3
4691 /// reg(a) (1/3) * 1 * 1
4692 /// reg(b) 1 * (1/3) * (1/2)
4693 /// reg({0,+,1}) (2/3) * (2/3) * (1/2)
4694 /// reg({-1,+,1}) (2/3) * (2/3) * 1
4695 /// reg({a,+,1}) (2/3) * 1 * 1
4696 /// reg({b,+,1}) 1 * (2/3) * (2/3)
4697 /// reg(c) 1 * 1 * 0
4698 ///
4699 /// Now count registers number mathematical expectation for each formula:
4700 /// Note that for each use we exclude probability if not selecting for the use.
4701 /// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding
4702 /// probabilty 1/3 of not selecting for Use1).
4703 /// Use1:
4704 /// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted
4705 /// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted
4706 /// reg({a,+,1}) 1
4707 /// Use2:
4708 /// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted
4709 /// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted
4710 /// reg({b,+,1}) 2/3
4711 /// Use3:
4712 /// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted
4713 /// reg(c) + reg({b,+,1}) 1 + 2/3
4714 void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() {
4715  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4716  return;
4717  // Ok, we have too many of formulae on our hands to conveniently handle.
4718  // Use a rough heuristic to thin out the list.
4719 
4720  // Set of Regs wich will be 100% used in final solution.
4721  // Used in each formula of a solution (in example above this is reg(c)).
4722  // We can skip them in calculations.
4724  LLVM_DEBUG(dbgs() << "The search space is too complex.\n");
4725 
4726  // Map each register to probability of not selecting
4728  for (const SCEV *Reg : RegUses) {
4729  if (UniqRegs.count(Reg))
4730  continue;
4731  float PNotSel = 1;
4732  for (const LSRUse &LU : Uses) {
4733  if (!LU.Regs.count(Reg))
4734  continue;
4735  float P = LU.getNotSelectedProbability(Reg);
4736  if (P != 0.0)
4737  PNotSel *= P;
4738  else
4739  UniqRegs.insert(Reg);
4740  }
4741  RegNumMap.insert(std::make_pair(Reg, PNotSel));
4742  }
4743 
4744  LLVM_DEBUG(
4745  dbgs() << "Narrowing the search space by deleting costly formulas\n");
4746 
4747  // Delete formulas where registers number expectation is high.
4748  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4749  LSRUse &LU = Uses[LUIdx];
4750  // If nothing to delete - continue.
4751  if (LU.Formulae.size() < 2)
4752  continue;
4753  // This is temporary solution to test performance. Float should be
4754  // replaced with round independent type (based on integers) to avoid
4755  // different results for different target builds.
4756  float FMinRegNum = LU.Formulae[0].getNumRegs();
4757  float FMinARegNum = LU.Formulae[0].getNumRegs();
4758  size_t MinIdx = 0;
4759  for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4760  Formula &F = LU.Formulae[i];
4761  float FRegNum = 0;
4762  float FARegNum = 0;
4763  for (const SCEV *BaseReg : F.BaseRegs) {
4764  if (UniqRegs.count(BaseReg))
4765  continue;
4766  FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4767  if (isa<SCEVAddRecExpr>(BaseReg))
4768  FARegNum +=
4769  RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4770  }
4771  if (const SCEV *ScaledReg = F.ScaledReg) {
4772  if (!UniqRegs.count(ScaledReg)) {
4773  FRegNum +=
4774  RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4775  if (isa<SCEVAddRecExpr>(ScaledReg))
4776  FARegNum +=
4777  RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4778  }
4779  }
4780  if (FMinRegNum > FRegNum ||
4781  (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) {
4782  FMinRegNum = FRegNum;
4783  FMinARegNum = FARegNum;
4784  MinIdx = i;
4785  }
4786  }
4787  LLVM_DEBUG(dbgs() << " The formula "; LU.Formulae[MinIdx].print(dbgs());
4788  dbgs() << " with min reg num " << FMinRegNum << '\n');
4789  if (MinIdx != 0)
4790  std::swap(LU.Formulae[MinIdx], LU.Formulae[0]);
4791  while (LU.Formulae.size() != 1) {
4792  LLVM_DEBUG(dbgs() << " Deleting "; LU.Formulae.back().print(dbgs());
4793  dbgs() << '\n');
4794  LU.Formulae.pop_back();
4795  }
4796  LU.RecomputeRegs(LUIdx, RegUses);
4797  assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula");
4798  Formula &F = LU.Formulae[0];
4799  LLVM_DEBUG(dbgs() << " Leaving only "; F.print(dbgs()); dbgs() << '\n');
4800  // When we choose the formula, the regs become unique.
4801  UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
4802  if (F.ScaledReg)
4803  UniqRegs.insert(F.ScaledReg);
4804  }
4805  LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4806 }
4807 
4808 /// Pick a register which seems likely to be profitable, and then in any use
4809 /// which has any reference to that register, delete all formulae which do not
4810 /// reference that register.
4811 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4812  // With all other options exhausted, loop until the system is simple
4813  // enough to handle.
4815  while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4816  // Ok, we have too many of formulae on our hands to conveniently handle.
4817  // Use a rough heuristic to thin out the list.
4818  LLVM_DEBUG(dbgs() << "The search space is too complex.\n");
4819 
4820  // Pick the register which is used by the most LSRUses, which is likely
4821  // to be a good reuse register candidate.
4822  const SCEV *Best = nullptr;
4823  unsigned BestNum = 0;
4824  for (const SCEV *Reg : RegUses) {
4825  if (Taken.count(Reg))
4826  continue;
4827  if (!Best) {
4828  Best = Reg;
4829  BestNum = RegUses.getUsedByIndices(Reg).count();
4830  } else {
4831  unsigned Count = RegUses.getUsedByIndices(Reg).count();
4832  if (Count > BestNum) {
4833  Best = Reg;
4834  BestNum = Count;
4835  }
4836  }
4837  }
4838 
4839  LLVM_DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
4840  << " will yield profitable reuse.\n");
4841  Taken.insert(Best);
4842 
4843  // In any use with formulae which references this register, delete formulae
4844  // which don't reference it.
4845  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4846  LSRUse &LU = Uses[LUIdx];
4847  if (!LU.Regs.count(Best)) continue;
4848 
4849  bool Any = false;
4850  for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4851  Formula &F = LU.Formulae[i];
4852  if (!F.referencesReg(Best)) {
4853  LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4854  LU.DeleteFormula(F);
4855  --e;
4856  --i;
4857  Any = true;
4858  assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
4859  continue;
4860  }
4861  }
4862 
4863  if (Any)
4864  LU.RecomputeRegs(LUIdx, RegUses);
4865  }
4866 
4867  LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4868  }
4869 }
4870 
4871 /// If there are an extraordinary number of formulae to choose from, use some
4872 /// rough heuristics to prune down the number of formulae. This keeps the main
4873 /// solver from taking an extraordinary amount of time in some worst-case
4874 /// scenarios.
4875 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4876  NarrowSearchSpaceByDetectingSupersets();
4877  NarrowSearchSpaceByCollapsingUnrolledCode();
4878  NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4879  if (FilterSameScaledReg)
4880  NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
4881  if (LSRExpNarrow)
4882  NarrowSearchSpaceByDeletingCostlyFormulas();
4883  else
4884  NarrowSearchSpaceByPickingWinnerRegs();
4885 }
4886 
4887 /// This is the recursive solver.
4888 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4889  Cost &SolutionCost,
4891  const Cost &CurCost,
4892  const SmallPtrSet<const SCEV *, 16> &CurRegs,
4893  DenseSet<const SCEV *> &VisitedRegs) const {
4894  // Some ideas:
4895  // - prune more:
4896  // - use more aggressive filtering
4897  // - sort the formula so that the most profitable solutions are found first
4898  // - sort the uses too
4899  // - search faster:
4900  // - don't compute a cost, and then compare. compare while computing a cost
4901  // and bail early.
4902  // - track register sets with SmallBitVector
4903 
4904  const LSRUse &LU = Uses[Workspace.size()];
4905 
4906  // If this use references any register that's already a part of the
4907  // in-progress solution, consider it a requirement that a formula must
4908  // reference that register in order to be considered. This prunes out
4909  // unprofitable searching.
4911  for (const SCEV *S : CurRegs)
4912  if (LU.Regs.count(S))
4913  ReqRegs.insert(S);
4914 
4916  Cost NewCost(L, SE, TTI);
4917  for (const Formula &F : LU.Formulae) {
4918  // Ignore formulae which may not be ideal in terms of register reuse of
4919  // ReqRegs. The formula should use all required registers before
4920  // introducing new ones.
4921  int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4922  for (const SCEV *Reg : ReqRegs) {
4923  if ((F.ScaledReg && F.ScaledReg == Reg) ||
4924  is_contained(F.BaseRegs, Reg)) {
4925  --NumReqRegsToFind;
4926  if (NumReqRegsToFind == 0)
4927  break;
4928  }
4929  }
4930  if (NumReqRegsToFind != 0) {
4931  // If none of the formulae satisfied the required registers, then we could
4932  // clear ReqRegs and try again. Currently, we simply give up in this case.
4933  continue;
4934  }
4935 
4936  // Evaluate the cost of the current formula. If it's already worse than
4937  // the current best, prune the search at that point.
4938  NewCost = CurCost;
4939  NewRegs = CurRegs;
4940  NewCost.RateFormula(F, NewRegs, VisitedRegs, LU);
4941  if (NewCost.isLess(SolutionCost)) {
4942  Workspace.push_back(&F);
4943  if (Workspace.size() != Uses.size()) {
4944  SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4945  NewRegs, VisitedRegs);
4946  if (F.getNumRegs() == 1 && Workspace.size() == 1)
4947  VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4948  } else {
4949  LLVM_DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
4950  dbgs() << ".\nRegs:\n";
4951  for (const SCEV *S : NewRegs) dbgs()
4952  << "- " << *S << "\n";
4953  dbgs() << '\n');
4954 
4955  SolutionCost = NewCost;
4956  Solution = Workspace;
4957  }
4958  Workspace.pop_back();
4959  }
4960  }
4961 }
4962 
4963 /// Choose one formula from each use. Return the results in the given Solution
4964 /// vector.
4965 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4967  Cost SolutionCost(L, SE, TTI);
4968  SolutionCost.Lose();
4969  Cost CurCost(L, SE, TTI);
4971  DenseSet<const SCEV *> VisitedRegs;
4972  Workspace.reserve(Uses.size());
4973 
4974  // SolveRecurse does all the work.
4975  SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4976  CurRegs, VisitedRegs);
4977  if (Solution.empty()) {
4978  LLVM_DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
4979  return;
4980  }
4981 
4982  // Ok, we've now made all our decisions.
4983  LLVM_DEBUG(dbgs() << "\n"
4984  "The chosen solution requires ";
4985  SolutionCost.print(dbgs()); dbgs() << ":\n";
4986  for (size_t i = 0, e = Uses.size(); i != e; ++i) {
4987  dbgs() << " ";
4988  Uses[i].print(dbgs());
4989  dbgs() << "\n"
4990  " ";
4991  Solution[i]->print(dbgs());
4992  dbgs() << '\n';
4993  });
4994 
4995  assert(Solution.size() == Uses.size() && "Malformed solution!");
4996 }
4997 
4998 /// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
4999 /// we can go while still being dominated by the input positions. This helps
5000 /// canonicalize the insert position, which encourages sharing.
5002 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
5003  const SmallVectorImpl<Instruction *> &Inputs)
5004  const {
5005  Instruction *Tentative = &*IP;
5006  while (true) {
5007  bool AllDominate = true;
5008  Instruction *BetterPos = nullptr;
5009  // Don't bother attempting to insert before a catchswitch, their basic block
5010  // cannot have other non-PHI instructions.
5011  if (isa<CatchSwitchInst>(Tentative))
5012  return IP;
5013 
5014  for (Instruction *Inst : Inputs) {
5015  if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
5016  AllDominate = false;
5017  break;
5018  }
5019  // Attempt to find an insert position in the middle of the block,
5020  // instead of at the end, so that it can be used for other expansions.
5021  if (Tentative->getParent() == Inst->getParent() &&
5022  (!BetterPos || !DT.dominates(Inst, BetterPos)))
5023  BetterPos = &*std::next(BasicBlock::iterator(Inst));
5024  }
5025  if (!AllDominate)
5026  break;
5027  if (BetterPos)
5028  IP = BetterPos->getIterator();
5029  else
5030  IP = Tentative->getIterator();
5031 
5032  const Loop *IPLoop = LI.getLoopFor(IP->getParent());
5033  unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
5034 
5035  BasicBlock *IDom;
5036  for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
5037  if (!Rung) return IP;
5038  Rung = Rung->getIDom();
5039  if (!Rung) return IP;
5040  IDom = Rung->getBlock();
5041 
5042  // Don't climb into a loop though.
5043  const Loop *IDomLoop = LI.getLoopFor(IDom);
5044  unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
5045  if (IDomDepth <= IPLoopDepth &&
5046  (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
5047  break;
5048  }
5049 
5050  Tentative = IDom->getTerminator();
5051  }
5052 
5053  return IP;
5054 }
5055 
5056 /// Determine an input position which will be dominated by the operands and
5057 /// which will dominate the result.
5059 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
5060  const LSRFixup &LF,
5061  const LSRUse &LU,
5062  SCEVExpander &Rewriter) const {
5063  // Collect some instructions which must be dominated by the
5064  // expanding replacement. These must be dominated by any operands that
5065  // will be required in the expansion.
5067  if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
5068  Inputs.push_back(I);
5069  if (LU.Kind == LSRUse::ICmpZero)
5070  if (Instruction *I =
5071  dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
5072  Inputs.push_back(I);
5073  if (LF.PostIncLoops.count(L)) {
5074  if (LF.isUseFullyOutsideLoop(L))
5075  Inputs.push_back(L->getLoopLatch()->getTerminator());
5076  else
5077  Inputs.push_back(IVIncInsertPos);
5078  }
5079  // The expansion must also be dominated by the increment positions of any
5080  // loops it for which it is using post-inc mode.
5081  for (const Loop *PIL : LF.PostIncLoops) {
5082  if (PIL == L) continue;
5083 
5084  // Be dominated by the loop exit.
5085  SmallVector<BasicBlock *, 4> ExitingBlocks;
5086  PIL->getExitingBlocks(ExitingBlocks);
5087  if (!ExitingBlocks.empty()) {
5088  BasicBlock *BB = ExitingBlocks[0];
5089  for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
5090  BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
5091  Inputs.push_back(BB->getTerminator());
5092  }
5093  }
5094 
5095  assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad()
5096  && !isa<DbgInfoIntrinsic>(LowestIP) &&
5097  "Insertion point must be a normal instruction");
5098 
5099  // Then, climb up the immediate dominator tree as far as we can go while
5100  // still being dominated by the input positions.
5101  BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
5102 
5103  // Don't insert instructions before PHI nodes.
5104  while (isa<PHINode>(IP)) ++IP;
5105 
5106  // Ignore landingpad instructions.
5107  while (IP->isEHPad()) ++IP;
5108 
5109  // Ignore debug intrinsics.
5110  while (isa<DbgInfoIntrinsic>(IP)) ++IP;
5111 
5112  // Set IP below instructions recently inserted by SCEVExpander. This keeps the
5113  // IP consistent across expansions and allows the previously inserted
5114  // instructions to be reused by subsequent expansion.
5115  while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
5116  ++IP;
5117 
5118  return IP;
5119 }
5120 
5121 /// Emit instructions for the leading candidate expression for this LSRUse (this
5122 /// is called "expanding").
5123 Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF,
5124  const Formula &F, BasicBlock::iterator IP,
5125  SCEVExpander &Rewriter,
5126  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5127  if (LU.RigidFormula)
5128  return LF.OperandValToReplace;
5129 
5130  // Determine an input position which will be dominated by the operands and
5131  // which will dominate the result.
5132  IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
5133  Rewriter.setInsertPoint(&*IP);
5134 
5135  // Inform the Rewriter if we have a post-increment use, so that it can
5136  // perform an advantageous expansion.
5137  Rewriter.setPostInc(LF.PostIncLoops);
5138 
5139  // This is the type that the user actually needs.
5140  Type *OpTy = LF.OperandValToReplace->getType();
5141  // This will be the type that we'll initially expand to.
5142  Type *Ty = F.getType();
5143  if (!Ty)
5144  // No type known; just expand directly to the ultimate type.
5145  Ty = OpTy;
5146  else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
5147  // Expand directly to the ultimate type if it's the right size.
5148  Ty = OpTy;
5149  // This is the type to do integer arithmetic in.
5150  Type *IntTy = SE.getEffectiveSCEVType(Ty);
5151 
5152  // Build up a list of operands to add together to form the full base.
5154 
5155  // Expand the BaseRegs portion.
5156  for (const SCEV *Reg : F.BaseRegs) {
5157  assert(!Reg->isZero() && "Zero allocated in a base register!");
5158 
5159  // If we're expanding for a post-inc user, make the post-inc adjustment.
5160  Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE);
5161  Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
5162  }
5163 
5164  // Expand the ScaledReg portion.
5165  Value *ICmpScaledV = nullptr;
5166  if (F.Scale != 0) {
5167  const SCEV *ScaledS = F.ScaledReg;
5168 
5169  // If we're expanding for a post-inc user, make the post-inc adjustment.
5170  PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
5171  ScaledS = denormalizeForPostIncUse(ScaledS, Loops, SE);
5172 
5173  if (LU.Kind == LSRUse::ICmpZero) {
5174  // Expand ScaleReg as if it was part of the base regs.
5175  if (F.Scale == 1)
5176  Ops.push_back(
5177  SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
5178  else {
5179  // An interesting way of "folding" with an icmp is to use a negated
5180  // scale, which we'll implement by inserting it into the other operand
5181  // of the icmp.
5182  assert(F.Scale == -1 &&
5183  "The only scale supported by ICmpZero uses is -1!");
5184  ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
5185  }
5186  } else {
5187  // Otherwise just expand the scaled register and an explicit scale,
5188  // which is expected to be matched as part of the address.
5189 
5190  // Flush the operand list to suppress SCEVExpander hoisting address modes.
5191  // Unless the addressing mode will not be folded.
5192  if (!Ops.empty() && LU.Kind == LSRUse::Address &&
5193  isAMCompletelyFolded(TTI, LU, F)) {
5194  Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), nullptr);
5195  Ops.clear();
5196  Ops.push_back(SE.getUnknown(FullV));
5197  }
5198  ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
5199  if (F.Scale != 1)
5200  ScaledS =
5201  SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
5202  Ops.push_back(ScaledS);
5203  }
5204  }
5205 
5206  // Expand the GV portion.
5207  if (F.BaseGV) {
5208  // Flush the operand list to suppress SCEVExpander hoisting.
5209  if (!Ops.empty()) {
5210  Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5211  Ops.clear();
5212  Ops.push_back(SE.getUnknown(FullV));
5213  }
5214  Ops.push_back(SE.getUnknown(F.BaseGV));
5215  }
5216 
5217  // Flush the operand list to suppress SCEVExpander hoisting of both folded and
5218  // unfolded offsets. LSR assumes they both live next to their uses.
5219  if (!Ops.empty()) {
5220  Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5221  Ops.clear();
5222  Ops.push_back(SE.getUnknown(FullV));
5223  }
5224 
5225  // Expand the immediate portion.
5226  int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
5227  if (Offset != 0) {
5228  if (LU.Kind == LSRUse::ICmpZero) {
5229  // The other interesting way of "folding" with an ICmpZero is to use a
5230  // negated immediate.
5231  if (!ICmpScaledV)
5232  ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
5233  else {
5234  Ops.push_back(SE.getUnknown(ICmpScaledV));
5235  ICmpScaledV = ConstantInt::get(IntTy, Offset);
5236  }
5237  } else {
5238  // Just add the immediate values. These again are expected to be matched
5239  // as part of the address.
5240  Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
5241  }
5242  }
5243 
5244  // Expand the unfolded offset portion.
5245  int64_t UnfoldedOffset = F.UnfoldedOffset;
5246  if (UnfoldedOffset != 0) {
5247  // Just add the immediate values.
5249  UnfoldedOffset)));
5250  }
5251 
5252  // Emit instructions summing all the operands.
5253  const SCEV *FullS = Ops.empty() ?
5254  SE.getConstant(IntTy, 0) :
5255  SE.getAddExpr(Ops);
5256  Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
5257 
5258  // We're done expanding now, so reset the rewriter.
5259  Rewriter.clearPostInc();
5260 
5261  // An ICmpZero Formula represents an ICmp which we're handling as a
5262  // comparison against zero. Now that we've expanded an expression for that
5263  // form, update the ICmp's other operand.
5264  if (LU.Kind == LSRUse::ICmpZero) {
5265  ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
5266  DeadInsts.emplace_back(CI->getOperand(1));
5267  assert(!F.BaseGV && "ICmp does not support folding a global value and "
5268  "a scale at the same time!");
5269  if (F.Scale == -1) {
5270  if (ICmpScaledV->getType() != OpTy) {
5271  Instruction *Cast =
5272  CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
5273  OpTy, false),
5274  ICmpScaledV, OpTy, "tmp", CI);
5275  ICmpScaledV = Cast;
5276  }
5277  CI->setOperand(1, ICmpScaledV);
5278  } else {
5279  // A scale of 1 means that the scale has been expanded as part of the
5280  // base regs.
5281  assert((F.Scale == 0 || F.Scale == 1) &&
5282  "ICmp does not support folding a global value and "
5283  "a scale at the same time!");
5285  -(uint64_t)Offset);
5286  if (C->getType() != OpTy)
5288  OpTy, false),
5289  C, OpTy);
5290 
5291  CI->setOperand(1, C);
5292  }
5293  }
5294 
5295  return FullV;
5296 }
5297 
5298 /// Helper for Rewrite. PHI nodes are special because the use of their operands
5299 /// effectively happens in their predecessor blocks, so the expression may need
5300 /// to be expanded in multiple places.
5301 void LSRInstance::RewriteForPHI(
5302  PHINode *PN, const LSRUse &LU, const LSRFixup &LF, const Formula &F,
5303  SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5305  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
5306  if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
5307  bool needUpdateFixups = false;
5308  BasicBlock *BB = PN->getIncomingBlock(i);
5309 
5310  // If this is a critical edge, split the edge so that we do not insert
5311  // the code on all predecessor/successor paths. We do this unless this
5312  // is the canonical backedge for this loop, which complicates post-inc
5313  // users.
5314  if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
5315  !isa<IndirectBrInst>(BB->getTerminator()) &&
5316  !isa<CatchSwitchInst>(BB->getTerminator())) {
5317  BasicBlock *Parent = PN->getParent();
5318  Loop *PNLoop = LI.getLoopFor(Parent);
5319  if (!PNLoop || Parent != PNLoop->getHeader()) {
5320  // Split the critical edge.
5321  BasicBlock *NewBB = nullptr;
5322  if (!Parent->isLandingPad()) {
5323  NewBB = SplitCriticalEdge(BB, Parent,
5325  .setMergeIdenticalEdges()
5326  .setKeepOneInputPHIs());
5327  } else {
5329  SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
5330  NewBB = NewBBs[0];
5331  }
5332  // If NewBB==NULL, then SplitCriticalEdge refused to split because all
5333  // phi predecessors are identical. The simple thing to do is skip
5334  // splitting in this case rather than complicate the API.
5335  if (NewBB) {
5336  // If PN is outside of the loop and BB is in the loop, we want to
5337  // move the block to be immediately before the PHI block, not
5338  // immediately after BB.
5339  if (L->contains(BB) && !L->contains(PN))
5340  NewBB->moveBefore(PN->getParent());
5341 
5342  // Splitting the edge can reduce the number of PHI entries we have.
5343  e = PN->getNumIncomingValues();
5344  BB = NewBB;
5345  i = PN->getBasicBlockIndex(BB);
5346 
5347  needUpdateFixups = true;
5348  }
5349  }
5350  }
5351 
5352  std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
5353  Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
5354  if (!Pair.second)
5355  PN->setIncomingValue(i, Pair.first->second);
5356  else {
5357  Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
5358  Rewriter, DeadInsts);
5359 
5360  // If this is reuse-by-noop-cast, insert the noop cast.
5361  Type *OpTy = LF.OperandValToReplace->getType();
5362  if (FullV->getType() != OpTy)
5363  FullV =
5365  OpTy, false),
5366  FullV, LF.OperandValToReplace->getType(),
5367  "tmp", BB->getTerminator());
5368 
5369  PN->setIncomingValue(i, FullV);
5370  Pair.first->second = FullV;
5371  }
5372 
5373  // If LSR splits critical edge and phi node has other pending
5374  // fixup operands, we need to update those pending fixups. Otherwise
5375  // formulae will not be implemented completely and some instructions
5376  // will not be eliminated.
5377  if (needUpdateFixups) {
5378  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5379  for (LSRFixup &Fixup : Uses[LUIdx].Fixups)
5380  // If fixup is supposed to rewrite some operand in the phi
5381  // that was just updated, it may be already moved to
5382  // another phi node. Such fixup requires update.
5383  if (Fixup.UserInst == PN) {
5384  // Check if the operand we try to replace still exists in the
5385  // original phi.
5386  bool foundInOriginalPHI = false;
5387  for (const auto &val : PN->incoming_values())
5388  if (val == Fixup.OperandValToReplace) {
5389  foundInOriginalPHI = true;
5390  break;
5391  }
5392 
5393  // If fixup operand found in original PHI - nothing to do.
5394  if (foundInOriginalPHI)
5395  continue;
5396 
5397  // Otherwise it might be moved to another PHI and requires update.
5398  // If fixup operand not found in any of the incoming blocks that
5399  // means we have already rewritten it - nothing to do.
5400  for (const auto &Block : PN->blocks())
5401  for (BasicBlock::iterator I = Block->begin(); isa<PHINode>(I);
5402  ++I) {
5403  PHINode *NewPN = cast<PHINode>(I);
5404  for (const auto &val : NewPN->incoming_values())
5405  if (val == Fixup.OperandValToReplace)
5406  Fixup.UserInst = NewPN;
5407  }
5408  }
5409  }
5410  }
5411 }
5412 
5413 /// Emit instructions for the leading candidate expression for this LSRUse (this
5414 /// is called "expanding"), and update the UserInst to reference the newly
5415 /// expanded value.
5416 void LSRInstance::Rewrite(const LSRUse &LU, const LSRFixup &LF,
5417  const Formula &F, SCEVExpander &Rewriter,
5418  SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5419  // First, find an insertion point that dominates UserInst. For PHI nodes,
5420  // find the nearest block which dominates all the relevant uses.
5421  if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
5422  RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
5423  } else {
5424  Value *FullV =
5425  Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
5426 
5427  // If this is reuse-by-noop-cast, insert the noop cast.
5428  Type *OpTy = LF.OperandValToReplace->getType();
5429  if (FullV->getType() != OpTy) {
5430  Instruction *Cast =
5431  CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
5432  FullV, OpTy, "tmp", LF.UserInst);
5433  FullV = Cast;
5434  }
5435 
5436  // Update the user. ICmpZero is handled specially here (for now) because
5437  // Expand may have updated one of the operands of the icmp already, and
5438  // its new value may happen to be equal to LF.OperandValToReplace, in
5439  // which case doing replaceUsesOfWith leads to replacing both operands
5440  // with the same value. TODO: Reorganize this.
5441  if (LU.Kind == LSRUse::ICmpZero)
5442  LF.UserInst->setOperand(0, FullV);
5443  else
5444  LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
5445  }
5446 
5447  DeadInsts.emplace_back(LF.OperandValToReplace);
5448 }
5449 
5450 /// Rewrite all the fixup locations with new values, following the chosen
5451 /// solution.
5452 void LSRInstance::ImplementSolution(
5453  const SmallVectorImpl<const Formula *> &Solution) {
5454  // Keep track of instructions we may have made dead, so that
5455  // we can remove them after we are done working.
5457 
5459  "lsr");
5460 #ifndef NDEBUG
5461  Rewriter.setDebugType(DEBUG_TYPE);
5462 #endif
5463  Rewriter.disableCanonicalMode();
5464  Rewriter.enableLSRMode();
5465  Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
5466 
5467  // Mark phi nodes that terminate chains so the expander tries to reuse them.
5468  for (const IVChain &Chain : IVChainVec) {
5469  if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
5470  Rewriter.setChainedPhi(PN);
5471  }
5472 
5473  // Expand the new value definitions and update the users.
5474  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5475  for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
5476  Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
5477  Changed = true;
5478  }
5479 
5480  for (const IVChain &Chain : IVChainVec) {
5481  GenerateIVChain(Chain, Rewriter, DeadInsts);
5482  Changed = true;
5483  }
5484  // Clean up after ourselves. This must be done before deleting any
5485  // instructions.
5486  Rewriter.clear();
5487 
5488  Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
5489 }
5490 
5491 LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5492  DominatorTree &DT, LoopInfo &LI,
5493  const TargetTransformInfo &TTI, AssumptionCache &AC,
5494  TargetLibraryInfo &LibInfo)
5495  : IU(IU), SE(SE), DT(DT), LI(LI), AC(AC), LibInfo(LibInfo), TTI(TTI), L(L),
5496  FavorBackedgeIndex(EnableBackedgeIndexing &&
5497  TTI.shouldFavorBackedgeIndex(L)) {
5498  // If LoopSimplify form is not available, stay out of trouble.
5499  if (!L->isLoopSimplifyForm())
5500  return;
5501 
5502  // If there's no interesting work to be done, bail early.
5503  if (IU.empty()) return;
5504 
5505  // If there's too much analysis to be done, bail early. We won't be able to
5506  // model the problem anyway.
5507  unsigned NumUsers = 0;
5508  for (const IVStrideUse &U : IU) {
5509  if (++NumUsers > MaxIVUsers) {
5510  (void)U;
5511  LLVM_DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << U
5512  << "\n");
5513  return;
5514  }
5515  // Bail out if we have a PHI on an EHPad that gets a value from a
5516  // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is
5517  // no good place to stick any instructions.
5518  if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
5519  auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
5520  if (isa<FuncletPadInst>(FirstNonPHI) ||
5521  isa<CatchSwitchInst>(FirstNonPHI))
5522  for (BasicBlock *PredBB : PN->blocks())
5523  if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
5524  return;
5525  }
5526  }
5527 
5528 #ifndef NDEBUG
5529  // All dominating loops must have preheaders, or SCEVExpander may not be able
5530  // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
5531  //
5532  // IVUsers analysis should only create users that are dominated by simple loop
5533  // headers. Since this loop should dominate all of its users, its user list
5534  // should be empty if this loop itself is not within a simple loop nest.
5535  for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
5536  Rung; Rung = Rung->getIDom()) {
5537  BasicBlock *BB = Rung->getBlock();
5538  const Loop *DomLoop = LI.getLoopFor(BB);
5539  if (DomLoop && DomLoop->getHeader() == BB) {
5540  assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
5541  }
5542  }
5543 #endif // DEBUG
5544 
5545  LLVM_DEBUG(dbgs() << "\nLSR on loop ";
5546  L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false);
5547  dbgs() << ":\n");
5548 
5549  // First, perform some low-level loop optimizations.
5550  OptimizeShadowIV();
5551  OptimizeLoopTermCond();
5552 
5553  // If loop preparation eliminates all interesting IV users, bail.
5554  if (IU.empty()) return;
5555 
5556  // Skip nested loops until we can model them better with formulae.
5557  if (!L->empty()) {
5558  LLVM_DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
5559  return;
5560  }
5561 
5562  // Start collecting data and preparing for the solver.
5563  CollectChains();
5564  CollectInterestingTypesAndFactors();
5565  CollectFixupsAndInitialFormulae();
5566  CollectLoopInvariantFixupsAndFormulae();
5567 
5568  if (Uses.empty())
5569  return;
5570 
5571  LLVM_DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
5572  print_uses(dbgs()));
5573 
5574  // Now use the reuse data to generate a bunch of interesting ways
5575  // to formulate the values needed for the uses.
5576  GenerateAllReuseFormulae();
5577 
5578  FilterOutUndesirableDedicatedRegisters();
5579  NarrowSearchSpaceUsingHeuristics();
5580 
5582  Solve(Solution);
5583 
5584  // Release memory that is no longer needed.
5585  Factors.clear();
5586  Types.clear();
5587  RegUses.clear();
5588 
5589  if (Solution.empty())
5590  return;
5591 
5592 #ifndef NDEBUG
5593  // Formulae should be legal.
5594  for (const LSRUse &LU : Uses) {
5595  for (const Formula &F : LU.Formulae)
5596  assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
5597  F) && "Illegal formula generated!");
5598  };
5599 #endif
5600 
5601  // Now that we've decided what we want, make it so.
5602  ImplementSolution(Solution);
5603 }
5604 
5605 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5606 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
5607  if (Factors.empty() && Types.empty()) return;
5608 
5609  OS << "LSR has identified the following interesting factors and types: ";
5610  bool First = true;
5611 
5612  for (int64_t Factor : Factors) {
5613  if (!First) OS << ", ";
5614  First = false;
5615  OS << '*' << Factor;
5616  }
5617 
5618  for (Type *Ty : Types) {
5619  if (!First) OS << ", ";
5620  First = false;
5621  OS << '(' << *Ty << ')';
5622  }
5623  OS << '\n';
5624 }
5625 
5626 void LSRInstance::print_fixups(raw_ostream &OS) const {
5627  OS << "LSR is examining the following fixup sites:\n";
5628  for (const LSRUse &LU : Uses)
5629  for (const LSRFixup &LF : LU.Fixups) {
5630  dbgs() << " ";
5631  LF.print(OS);
5632  OS << '\n';
5633  }
5634 }
5635 
5636 void LSRInstance::print_uses(raw_ostream &OS) const {
5637  OS << "LSR is examining the following uses:\n";
5638  for (const LSRUse &LU : Uses) {
5639  dbgs() << " ";
5640  LU.print(OS);
5641  OS << '\n';
5642  for (const Formula &F : LU.Formulae) {
5643  OS << " ";
5644  F.print(OS);
5645  OS << '\n';
5646  }
5647  }
5648 }
5649 
5650 void LSRInstance::print(raw_ostream &OS) const {
5651  print_factors_and_types(OS);
5652  print_fixups(OS);
5653  print_uses(OS);
5654 }
5655 
5656 LLVM_DUMP_METHOD void LSRInstance::dump() const {
5657  print(errs()); errs() << '\n';
5658 }
5659 #endif
5660 
5661 namespace {
5662 
5663 class LoopStrengthReduce : public LoopPass {
5664 public:
5665  static char ID; // Pass ID, replacement for typeid
5666 
5667  LoopStrengthReduce();
5668 
5669 private:
5670  bool runOnLoop(Loop *L, LPPassManager &LPM) override;
5671  void getAnalysisUsage(AnalysisUsage &AU) const override;
5672 };
5673 
5674 } // end anonymous namespace
5675 
5676 LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
5678 }
5679 
5680 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
5681  // We split critical edges, so we change the CFG. However, we do update
5682  // many analyses if they are around.
5684 
5694  // Requiring LoopSimplify a second time here prevents IVUsers from running
5695  // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5700 }
5701 
5703  DominatorTree &DT, LoopInfo &LI,
5704  const TargetTransformInfo &TTI,
5705  AssumptionCache &AC,
5706  TargetLibraryInfo &LibInfo) {
5707 
5708  bool Changed = false;
5709 
5710  // Run the main LSR transformation.
5711  Changed |= LSRInstance(L, IU, SE, DT, LI, TTI, AC, LibInfo).getChanged();
5712 
5713  // Remove any extra phis created by processing inner loops.
5714  Changed |= DeleteDeadPHIs(L->getHeader());
5715  if (EnablePhiElim && L->isLoopSimplifyForm()) {
5717  const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
5718  SCEVExpander Rewriter(SE, DL, "lsr");
5719 #ifndef NDEBUG
5720  Rewriter.setDebugType(DEBUG_TYPE);
5721 #endif
5722  unsigned numFolded = Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, &TTI);
5723  if (numFolded) {
5724  Changed = true;
5726  DeleteDeadPHIs(L->getHeader());
5727  }
5728  }
5729  return Changed;
5730 }
5731 
5732 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5733  if (skipLoop(L))
5734  return false;
5735 
5736  auto &IU = getAnalysis<IVUsersWrapperPass>().getIU();
5737  auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
5738  auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
5739  auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
5740  const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
5741  *L->getHeader()->getParent());
5742  auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(
5743  *L->getHeader()->getParent());
5744  auto &LibInfo = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(
5745  *L->getHeader()->getParent());
5746  return ReduceLoopStrength(L, IU, SE, DT, LI, TTI, AC, LibInfo);
5747 }
5748 
5751  LPMUpdater &) {
5752  if (!ReduceLoopStrength(&L, AM.getResult<IVUsersAnalysis>(L, AR), AR.SE,
5753  AR.DT, AR.LI, AR.TTI, AR.AC, AR.TLI))
5754  return PreservedAnalyses::all();
5755 
5757 }
5758 
5759 char LoopStrengthReduce::ID = 0;
5760 
5761 INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
5762  "Loop Strength Reduction", false, false)
5768 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
5769 INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
5770  "Loop Strength Reduction", false, false)
5771 
5772 Pass *llvm::createLoopStrengthReducePass() { return new LoopStrengthReduce(); }
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:80