Bug Summary

File:lib/Transforms/Scalar/LoopStrengthReduce.cpp
Warning:line 2914, column 16
Called C++ object pointer is null

Annotated Source Code

1//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This transformation analyzes and transforms the induction variables (and
11// computations derived from them) into forms suitable for efficient execution
12// on the target.
13//
14// This pass performs a strength reduction on array references inside loops that
15// have as one or more of their components the loop induction variable, it
16// rewrites expressions to take advantage of scaled-index addressing modes
17// available on the target, and it performs a variety of other optimizations
18// related to loop induction variables.
19//
20// Terminology note: this code has a lot of handling for "post-increment" or
21// "post-inc" users. This is not talking about post-increment addressing modes;
22// it is instead talking about code like this:
23//
24// %i = phi [ 0, %entry ], [ %i.next, %latch ]
25// ...
26// %i.next = add %i, 1
27// %c = icmp eq %i.next, %n
28//
29// The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
30// it's useful to think about these as the same register, with some uses using
31// the value of the register before the add and some using it after. In this
32// example, the icmp is a post-increment user, since it uses %i.next, which is
33// the value of the induction variable after the increment. The other common
34// case of post-increment users is users outside the loop.
35//
36// TODO: More sophistication in the way Formulae are generated and filtered.
37//
38// TODO: Handle multiple loops at a time.
39//
40// TODO: Should the addressing mode BaseGV be changed to a ConstantExpr instead
41// of a GlobalValue?
42//
43// TODO: When truncation is free, truncate ICmp users' operands to make it a
44// smaller encoding (on x86 at least).
45//
46// TODO: When a negated register is used by an add (such as in a list of
47// multiple base registers, or as the increment expression in an addrec),
48// we may not actually need both reg and (-1 * reg) in registers; the
49// negation can be implemented by using a sub instead of an add. The
50// lack of support for taking this into consideration when making
51// register pressure decisions is partly worked around by the "Special"
52// use kind.
53//
54//===----------------------------------------------------------------------===//
55
56#include "llvm/Transforms/Scalar/LoopStrengthReduce.h"
57#include "llvm/ADT/APInt.h"
58#include "llvm/ADT/DenseMap.h"
59#include "llvm/ADT/DenseSet.h"
60#include "llvm/ADT/Hashing.h"
61#include "llvm/ADT/PointerIntPair.h"
62#include "llvm/ADT/SetVector.h"
63#include "llvm/ADT/SmallBitVector.h"
64#include "llvm/ADT/SmallPtrSet.h"
65#include "llvm/ADT/SmallSet.h"
66#include "llvm/ADT/SmallVector.h"
67#include "llvm/ADT/STLExtras.h"
68#include "llvm/Analysis/IVUsers.h"
69#include "llvm/Analysis/LoopInfo.h"
70#include "llvm/Analysis/LoopPass.h"
71#include "llvm/Analysis/LoopPassManager.h"
72#include "llvm/Analysis/ScalarEvolution.h"
73#include "llvm/Analysis/ScalarEvolutionExpander.h"
74#include "llvm/Analysis/ScalarEvolutionExpressions.h"
75#include "llvm/Analysis/ScalarEvolutionNormalization.h"
76#include "llvm/Analysis/TargetTransformInfo.h"
77#include "llvm/IR/BasicBlock.h"
78#include "llvm/IR/Constant.h"
79#include "llvm/IR/Constants.h"
80#include "llvm/IR/DerivedTypes.h"
81#include "llvm/IR/Dominators.h"
82#include "llvm/IR/GlobalValue.h"
83#include "llvm/IR/Instruction.h"
84#include "llvm/IR/Instructions.h"
85#include "llvm/IR/IntrinsicInst.h"
86#include "llvm/IR/IRBuilder.h"
87#include "llvm/IR/OperandTraits.h"
88#include "llvm/IR/Operator.h"
89#include "llvm/IR/Module.h"
90#include "llvm/IR/Type.h"
91#include "llvm/IR/Value.h"
92#include "llvm/IR/ValueHandle.h"
93#include "llvm/Pass.h"
94#include "llvm/Support/Casting.h"
95#include "llvm/Support/CommandLine.h"
96#include "llvm/Support/Compiler.h"
97#include "llvm/Support/Debug.h"
98#include "llvm/Support/ErrorHandling.h"
99#include "llvm/Support/MathExtras.h"
100#include "llvm/Support/raw_ostream.h"
101#include "llvm/Transforms/Scalar.h"
102#include "llvm/Transforms/Utils/BasicBlockUtils.h"
103#include "llvm/Transforms/Utils/Local.h"
104#include <algorithm>
105#include <cassert>
106#include <cstddef>
107#include <cstdint>
108#include <cstdlib>
109#include <iterator>
110#include <map>
111#include <tuple>
112#include <utility>
113
114using namespace llvm;
115
116#define DEBUG_TYPE"loop-reduce" "loop-reduce"
117
118/// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for
119/// bail out. This threshold is far beyond the number of users that LSR can
120/// conceivably solve, so it should not affect generated code, but catches the
121/// worst cases before LSR burns too much compile time and stack space.
122static const unsigned MaxIVUsers = 200;
123
124// Temporary flag to cleanup congruent phis after LSR phi expansion.
125// It's currently disabled until we can determine whether it's truly useful or
126// not. The flag should be removed after the v3.0 release.
127// This is now needed for ivchains.
128static cl::opt<bool> EnablePhiElim(
129 "enable-lsr-phielim", cl::Hidden, cl::init(true),
130 cl::desc("Enable LSR phi elimination"));
131
132#ifndef NDEBUG
133// Stress test IV chain generation.
134static cl::opt<bool> StressIVChain(
135 "stress-ivchain", cl::Hidden, cl::init(false),
136 cl::desc("Stress test LSR IV chains"));
137#else
138static bool StressIVChain = false;
139#endif
140
141namespace {
142
143struct MemAccessTy {
144 /// Used in situations where the accessed memory type is unknown.
145 static const unsigned UnknownAddressSpace = ~0u;
146
147 Type *MemTy;
148 unsigned AddrSpace;
149
150 MemAccessTy() : MemTy(nullptr), AddrSpace(UnknownAddressSpace) {}
151
152 MemAccessTy(Type *Ty, unsigned AS) :
153 MemTy(Ty), AddrSpace(AS) {}
154
155 bool operator==(MemAccessTy Other) const {
156 return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace;
157 }
158
159 bool operator!=(MemAccessTy Other) const { return !(*this == Other); }
160
161 static MemAccessTy getUnknown(LLVMContext &Ctx) {
162 return MemAccessTy(Type::getVoidTy(Ctx), UnknownAddressSpace);
163 }
164};
165
166/// This class holds data which is used to order reuse candidates.
167class RegSortData {
168public:
169 /// This represents the set of LSRUse indices which reference
170 /// a particular register.
171 SmallBitVector UsedByIndices;
172
173 void print(raw_ostream &OS) const;
174 void dump() const;
175};
176
177} // end anonymous namespace
178
179void RegSortData::print(raw_ostream &OS) const {
180 OS << "[NumUses=" << UsedByIndices.count() << ']';
181}
182
183LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__))
184void RegSortData::dump() const {
185 print(errs()); errs() << '\n';
186}
187
188namespace {
189
190/// Map register candidates to information about how they are used.
191class RegUseTracker {
192 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
193
194 RegUsesTy RegUsesMap;
195 SmallVector<const SCEV *, 16> RegSequence;
196
197public:
198 void countRegister(const SCEV *Reg, size_t LUIdx);
199 void dropRegister(const SCEV *Reg, size_t LUIdx);
200 void swapAndDropUse(size_t LUIdx, size_t LastLUIdx);
201
202 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
203
204 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
205
206 void clear();
207
208 typedef SmallVectorImpl<const SCEV *>::iterator iterator;
209 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
210 iterator begin() { return RegSequence.begin(); }
211 iterator end() { return RegSequence.end(); }
212 const_iterator begin() const { return RegSequence.begin(); }
213 const_iterator end() const { return RegSequence.end(); }
214};
215
216} // end anonymous namespace
217
218void
219RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) {
220 std::pair<RegUsesTy::iterator, bool> Pair =
221 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
222 RegSortData &RSD = Pair.first->second;
223 if (Pair.second)
224 RegSequence.push_back(Reg);
225 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
226 RSD.UsedByIndices.set(LUIdx);
227}
228
229void
230RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) {
231 RegUsesTy::iterator It = RegUsesMap.find(Reg);
232 assert(It != RegUsesMap.end())((It != RegUsesMap.end()) ? static_cast<void> (0) : __assert_fail
("It != RegUsesMap.end()", "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 232, __PRETTY_FUNCTION__))
;
233 RegSortData &RSD = It->second;
234 assert(RSD.UsedByIndices.size() > LUIdx)((RSD.UsedByIndices.size() > LUIdx) ? static_cast<void>
(0) : __assert_fail ("RSD.UsedByIndices.size() > LUIdx", "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 234, __PRETTY_FUNCTION__))
;
235 RSD.UsedByIndices.reset(LUIdx);
236}
237
238void
239RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
240 assert(LUIdx <= LastLUIdx)((LUIdx <= LastLUIdx) ? static_cast<void> (0) : __assert_fail
("LUIdx <= LastLUIdx", "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 240, __PRETTY_FUNCTION__))
;
241
242 // Update RegUses. The data structure is not optimized for this purpose;
243 // we must iterate through it and update each of the bit vectors.
244 for (auto &Pair : RegUsesMap) {
245 SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
246 if (LUIdx < UsedByIndices.size())
247 UsedByIndices[LUIdx] =
248 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false;
249 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
250 }
251}
252
253bool
254RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
255 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
256 if (I == RegUsesMap.end())
257 return false;
258 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
259 int i = UsedByIndices.find_first();
260 if (i == -1) return false;
261 if ((size_t)i != LUIdx) return true;
262 return UsedByIndices.find_next(i) != -1;
263}
264
265const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
266 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
267 assert(I != RegUsesMap.end() && "Unknown register!")((I != RegUsesMap.end() && "Unknown register!") ? static_cast
<void> (0) : __assert_fail ("I != RegUsesMap.end() && \"Unknown register!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 267, __PRETTY_FUNCTION__))
;
268 return I->second.UsedByIndices;
269}
270
271void RegUseTracker::clear() {
272 RegUsesMap.clear();
273 RegSequence.clear();
274}
275
276namespace {
277
278/// This class holds information that describes a formula for computing
279/// satisfying a use. It may include broken-out immediates and scaled registers.
280struct Formula {
281 /// Global base address used for complex addressing.
282 GlobalValue *BaseGV;
283
284 /// Base offset for complex addressing.
285 int64_t BaseOffset;
286
287 /// Whether any complex addressing has a base register.
288 bool HasBaseReg;
289
290 /// The scale of any complex addressing.
291 int64_t Scale;
292
293 /// The list of "base" registers for this use. When this is non-empty. The
294 /// canonical representation of a formula is
295 /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
296 /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
297 /// #1 enforces that the scaled register is always used when at least two
298 /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
299 /// #2 enforces that 1 * reg is reg.
300 /// This invariant can be temporarly broken while building a formula.
301 /// However, every formula inserted into the LSRInstance must be in canonical
302 /// form.
303 SmallVector<const SCEV *, 4> BaseRegs;
304
305 /// The 'scaled' register for this use. This should be non-null when Scale is
306 /// not zero.
307 const SCEV *ScaledReg;
308
309 /// An additional constant offset which added near the use. This requires a
310 /// temporary register, but the offset itself can live in an add immediate
311 /// field rather than a register.
312 int64_t UnfoldedOffset;
313
314 Formula()
315 : BaseGV(nullptr), BaseOffset(0), HasBaseReg(false), Scale(0),
316 ScaledReg(nullptr), UnfoldedOffset(0) {}
317
318 void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
319
320 bool isCanonical() const;
321
322 void canonicalize();
323
324 bool unscale();
325
326 size_t getNumRegs() const;
327 Type *getType() const;
328
329 void deleteBaseReg(const SCEV *&S);
330
331 bool referencesReg(const SCEV *S) const;
332 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
333 const RegUseTracker &RegUses) const;
334
335 void print(raw_ostream &OS) const;
336 void dump() const;
337};
338
339} // end anonymous namespace
340
341/// Recursion helper for initialMatch.
342static void DoInitialMatch(const SCEV *S, Loop *L,
343 SmallVectorImpl<const SCEV *> &Good,
344 SmallVectorImpl<const SCEV *> &Bad,
345 ScalarEvolution &SE) {
346 // Collect expressions which properly dominate the loop header.
347 if (SE.properlyDominates(S, L->getHeader())) {
348 Good.push_back(S);
349 return;
350 }
351
352 // Look at add operands.
353 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
354 for (const SCEV *S : Add->operands())
355 DoInitialMatch(S, L, Good, Bad, SE);
356 return;
357 }
358
359 // Look at addrec operands.
360 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
361 if (!AR->getStart()->isZero() && AR->isAffine()) {
362 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
363 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
364 AR->getStepRecurrence(SE),
365 // FIXME: AR->getNoWrapFlags()
366 AR->getLoop(), SCEV::FlagAnyWrap),
367 L, Good, Bad, SE);
368 return;
369 }
370
371 // Handle a multiplication by -1 (negation) if it didn't fold.
372 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
373 if (Mul->getOperand(0)->isAllOnesValue()) {
374 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
375 const SCEV *NewMul = SE.getMulExpr(Ops);
376
377 SmallVector<const SCEV *, 4> MyGood;
378 SmallVector<const SCEV *, 4> MyBad;
379 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
380 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
381 SE.getEffectiveSCEVType(NewMul->getType())));
382 for (const SCEV *S : MyGood)
383 Good.push_back(SE.getMulExpr(NegOne, S));
384 for (const SCEV *S : MyBad)
385 Bad.push_back(SE.getMulExpr(NegOne, S));
386 return;
387 }
388
389 // Ok, we can't do anything interesting. Just stuff the whole thing into a
390 // register and hope for the best.
391 Bad.push_back(S);
392}
393
394/// Incorporate loop-variant parts of S into this Formula, attempting to keep
395/// all loop-invariant and loop-computable values in a single base register.
396void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
397 SmallVector<const SCEV *, 4> Good;
398 SmallVector<const SCEV *, 4> Bad;
399 DoInitialMatch(S, L, Good, Bad, SE);
400 if (!Good.empty()) {
401 const SCEV *Sum = SE.getAddExpr(Good);
402 if (!Sum->isZero())
403 BaseRegs.push_back(Sum);
404 HasBaseReg = true;
405 }
406 if (!Bad.empty()) {
407 const SCEV *Sum = SE.getAddExpr(Bad);
408 if (!Sum->isZero())
409 BaseRegs.push_back(Sum);
410 HasBaseReg = true;
411 }
412 canonicalize();
413}
414
415/// \brief Check whether or not this formula statisfies the canonical
416/// representation.
417/// \see Formula::BaseRegs.
418bool Formula::isCanonical() const {
419 if (ScaledReg)
420 return Scale != 1 || !BaseRegs.empty();
421 return BaseRegs.size() <= 1;
422}
423
424/// \brief Helper method to morph a formula into its canonical representation.
425/// \see Formula::BaseRegs.
426/// Every formula having more than one base register, must use the ScaledReg
427/// field. Otherwise, we would have to do special cases everywhere in LSR
428/// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
429/// On the other hand, 1*reg should be canonicalized into reg.
430void Formula::canonicalize() {
431 if (isCanonical())
432 return;
433 // So far we did not need this case. This is easy to implement but it is
434 // useless to maintain dead code. Beside it could hurt compile time.
435 assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.")((!BaseRegs.empty() && "1*reg => reg, should not be needed."
) ? static_cast<void> (0) : __assert_fail ("!BaseRegs.empty() && \"1*reg => reg, should not be needed.\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 435, __PRETTY_FUNCTION__))
;
436 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
437 ScaledReg = BaseRegs.back();
438 BaseRegs.pop_back();
439 Scale = 1;
440 size_t BaseRegsSize = BaseRegs.size();
441 size_t Try = 0;
442 // If ScaledReg is an invariant, try to find a variant expression.
443 while (Try < BaseRegsSize && !isa<SCEVAddRecExpr>(ScaledReg))
444 std::swap(ScaledReg, BaseRegs[Try++]);
445}
446
447/// \brief Get rid of the scale in the formula.
448/// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
449/// \return true if it was possible to get rid of the scale, false otherwise.
450/// \note After this operation the formula may not be in the canonical form.
451bool Formula::unscale() {
452 if (Scale != 1)
453 return false;
454 Scale = 0;
455 BaseRegs.push_back(ScaledReg);
456 ScaledReg = nullptr;
457 return true;
458}
459
460/// Return the total number of register operands used by this formula. This does
461/// not include register uses implied by non-constant addrec strides.
462size_t Formula::getNumRegs() const {
463 return !!ScaledReg + BaseRegs.size();
464}
465
466/// Return the type of this formula, if it has one, or null otherwise. This type
467/// is meaningless except for the bit size.
468Type *Formula::getType() const {
469 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
470 ScaledReg ? ScaledReg->getType() :
471 BaseGV ? BaseGV->getType() :
472 nullptr;
473}
474
475/// Delete the given base reg from the BaseRegs list.
476void Formula::deleteBaseReg(const SCEV *&S) {
477 if (&S != &BaseRegs.back())
478 std::swap(S, BaseRegs.back());
479 BaseRegs.pop_back();
480}
481
482/// Test if this formula references the given register.
483bool Formula::referencesReg(const SCEV *S) const {
484 return S == ScaledReg || is_contained(BaseRegs, S);
485}
486
487/// Test whether this formula uses registers which are used by uses other than
488/// the use with the given index.
489bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
490 const RegUseTracker &RegUses) const {
491 if (ScaledReg)
492 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
493 return true;
494 for (const SCEV *BaseReg : BaseRegs)
495 if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
496 return true;
497 return false;
498}
499
500void Formula::print(raw_ostream &OS) const {
501 bool First = true;
502 if (BaseGV) {
503 if (!First) OS << " + "; else First = false;
504 BaseGV->printAsOperand(OS, /*PrintType=*/false);
505 }
506 if (BaseOffset != 0) {
507 if (!First) OS << " + "; else First = false;
508 OS << BaseOffset;
509 }
510 for (const SCEV *BaseReg : BaseRegs) {
511 if (!First) OS << " + "; else First = false;
512 OS << "reg(" << *BaseReg << ')';
513 }
514 if (HasBaseReg && BaseRegs.empty()) {
515 if (!First) OS << " + "; else First = false;
516 OS << "**error: HasBaseReg**";
517 } else if (!HasBaseReg && !BaseRegs.empty()) {
518 if (!First) OS << " + "; else First = false;
519 OS << "**error: !HasBaseReg**";
520 }
521 if (Scale != 0) {
522 if (!First) OS << " + "; else First = false;
523 OS << Scale << "*reg(";
524 if (ScaledReg)
525 OS << *ScaledReg;
526 else
527 OS << "<unknown>";
528 OS << ')';
529 }
530 if (UnfoldedOffset != 0) {
531 if (!First) OS << " + ";
532 OS << "imm(" << UnfoldedOffset << ')';
533 }
534}
535
536LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__))
537void Formula::dump() const {
538 print(errs()); errs() << '\n';
539}
540
541/// Return true if the given addrec can be sign-extended without changing its
542/// value.
543static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
544 Type *WideTy =
545 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
546 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
547}
548
549/// Return true if the given add can be sign-extended without changing its
550/// value.
551static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
552 Type *WideTy =
553 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
554 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
555}
556
557/// Return true if the given mul can be sign-extended without changing its
558/// value.
559static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
560 Type *WideTy =
561 IntegerType::get(SE.getContext(),
562 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
563 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
564}
565
566/// Return an expression for LHS /s RHS, if it can be determined and if the
567/// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
568/// is true, expressions like (X * Y) /s Y are simplified to Y, ignoring that
569/// the multiplication may overflow, which is useful when the result will be
570/// used in a context where the most significant bits are ignored.
571static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
572 ScalarEvolution &SE,
573 bool IgnoreSignificantBits = false) {
574 // Handle the trivial case, which works for any SCEV type.
575 if (LHS == RHS)
576 return SE.getConstant(LHS->getType(), 1);
577
578 // Handle a few RHS special cases.
579 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
580 if (RC) {
581 const APInt &RA = RC->getAPInt();
582 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
583 // some folding.
584 if (RA.isAllOnesValue())
585 return SE.getMulExpr(LHS, RC);
586 // Handle x /s 1 as x.
587 if (RA == 1)
588 return LHS;
589 }
590
591 // Check for a division of a constant by a constant.
592 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
593 if (!RC)
594 return nullptr;
595 const APInt &LA = C->getAPInt();
596 const APInt &RA = RC->getAPInt();
597 if (LA.srem(RA) != 0)
598 return nullptr;
599 return SE.getConstant(LA.sdiv(RA));
600 }
601
602 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
603 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
604 if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
605 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
606 IgnoreSignificantBits);
607 if (!Step) return nullptr;
608 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
609 IgnoreSignificantBits);
610 if (!Start) return nullptr;
611 // FlagNW is independent of the start value, step direction, and is
612 // preserved with smaller magnitude steps.
613 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
614 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
615 }
616 return nullptr;
617 }
618
619 // Distribute the sdiv over add operands, if the add doesn't overflow.
620 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
621 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
622 SmallVector<const SCEV *, 8> Ops;
623 for (const SCEV *S : Add->operands()) {
624 const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
625 if (!Op) return nullptr;
626 Ops.push_back(Op);
627 }
628 return SE.getAddExpr(Ops);
629 }
630 return nullptr;
631 }
632
633 // Check for a multiply operand that we can pull RHS out of.
634 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
635 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
636 SmallVector<const SCEV *, 4> Ops;
637 bool Found = false;
638 for (const SCEV *S : Mul->operands()) {
639 if (!Found)
640 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
641 IgnoreSignificantBits)) {
642 S = Q;
643 Found = true;
644 }
645 Ops.push_back(S);
646 }
647 return Found ? SE.getMulExpr(Ops) : nullptr;
648 }
649 return nullptr;
650 }
651
652 // Otherwise we don't know.
653 return nullptr;
654}
655
656/// If S involves the addition of a constant integer value, return that integer
657/// value, and mutate S to point to a new SCEV with that value excluded.
658static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
659 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
660 if (C->getAPInt().getMinSignedBits() <= 64) {
661 S = SE.getConstant(C->getType(), 0);
662 return C->getValue()->getSExtValue();
663 }
664 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
665 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
666 int64_t Result = ExtractImmediate(NewOps.front(), SE);
667 if (Result != 0)
668 S = SE.getAddExpr(NewOps);
669 return Result;
670 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
671 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
672 int64_t Result = ExtractImmediate(NewOps.front(), SE);
673 if (Result != 0)
674 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
675 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
676 SCEV::FlagAnyWrap);
677 return Result;
678 }
679 return 0;
680}
681
682/// If S involves the addition of a GlobalValue address, return that symbol, and
683/// mutate S to point to a new SCEV with that value excluded.
684static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
685 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
686 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
687 S = SE.getConstant(GV->getType(), 0);
688 return GV;
689 }
690 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
691 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
692 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
693 if (Result)
694 S = SE.getAddExpr(NewOps);
695 return Result;
696 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
697 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
698 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
699 if (Result)
700 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
701 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
702 SCEV::FlagAnyWrap);
703 return Result;
704 }
705 return nullptr;
706}
707
708/// Returns true if the specified instruction is using the specified value as an
709/// address.
710static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
711 bool isAddress = isa<LoadInst>(Inst);
712 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
713 if (SI->getOperand(1) == OperandVal)
714 isAddress = true;
715 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
716 // Addressing modes can also be folded into prefetches and a variety
717 // of intrinsics.
718 switch (II->getIntrinsicID()) {
719 default: break;
720 case Intrinsic::prefetch:
721 if (II->getArgOperand(0) == OperandVal)
722 isAddress = true;
723 break;
724 }
725 }
726 return isAddress;
727}
728
729/// Return the type of the memory being accessed.
730static MemAccessTy getAccessType(const Instruction *Inst) {
731 MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
732 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
733 AccessTy.MemTy = SI->getOperand(0)->getType();
734 AccessTy.AddrSpace = SI->getPointerAddressSpace();
735 } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
736 AccessTy.AddrSpace = LI->getPointerAddressSpace();
737 }
738
739 // All pointers have the same requirements, so canonicalize them to an
740 // arbitrary pointer type to minimize variation.
741 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
742 AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
743 PTy->getAddressSpace());
744
745 return AccessTy;
746}
747
748/// Return true if this AddRec is already a phi in its loop.
749static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
750 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
751 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
752 if (SE.isSCEVable(PN->getType()) &&
753 (SE.getEffectiveSCEVType(PN->getType()) ==
754 SE.getEffectiveSCEVType(AR->getType())) &&
755 SE.getSCEV(PN) == AR)
756 return true;
757 }
758 return false;
759}
760
761/// Check if expanding this expression is likely to incur significant cost. This
762/// is tricky because SCEV doesn't track which expressions are actually computed
763/// by the current IR.
764///
765/// We currently allow expansion of IV increments that involve adds,
766/// multiplication by constants, and AddRecs from existing phis.
767///
768/// TODO: Allow UDivExpr if we can find an existing IV increment that is an
769/// obvious multiple of the UDivExpr.
770static bool isHighCostExpansion(const SCEV *S,
771 SmallPtrSetImpl<const SCEV*> &Processed,
772 ScalarEvolution &SE) {
773 // Zero/One operand expressions
774 switch (S->getSCEVType()) {
775 case scUnknown:
776 case scConstant:
777 return false;
778 case scTruncate:
779 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
780 Processed, SE);
781 case scZeroExtend:
782 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
783 Processed, SE);
784 case scSignExtend:
785 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
786 Processed, SE);
787 }
788
789 if (!Processed.insert(S).second)
790 return false;
791
792 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
793 for (const SCEV *S : Add->operands()) {
794 if (isHighCostExpansion(S, Processed, SE))
795 return true;
796 }
797 return false;
798 }
799
800 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
801 if (Mul->getNumOperands() == 2) {
802 // Multiplication by a constant is ok
803 if (isa<SCEVConstant>(Mul->getOperand(0)))
804 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
805
806 // If we have the value of one operand, check if an existing
807 // multiplication already generates this expression.
808 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
809 Value *UVal = U->getValue();
810 for (User *UR : UVal->users()) {
811 // If U is a constant, it may be used by a ConstantExpr.
812 Instruction *UI = dyn_cast<Instruction>(UR);
813 if (UI && UI->getOpcode() == Instruction::Mul &&
814 SE.isSCEVable(UI->getType())) {
815 return SE.getSCEV(UI) == Mul;
816 }
817 }
818 }
819 }
820 }
821
822 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
823 if (isExistingPhi(AR, SE))
824 return false;
825 }
826
827 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
828 return true;
829}
830
831/// If any of the instructions is the specified set are trivially dead, delete
832/// them and see if this makes any of their operands subsequently dead.
833static bool
834DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
835 bool Changed = false;
836
837 while (!DeadInsts.empty()) {
838 Value *V = DeadInsts.pop_back_val();
839 Instruction *I = dyn_cast_or_null<Instruction>(V);
840
841 if (!I || !isInstructionTriviallyDead(I))
842 continue;
843
844 for (Use &O : I->operands())
845 if (Instruction *U = dyn_cast<Instruction>(O)) {
846 O = nullptr;
847 if (U->use_empty())
848 DeadInsts.emplace_back(U);
849 }
850
851 I->eraseFromParent();
852 Changed = true;
853 }
854
855 return Changed;
856}
857
858namespace {
859
860class LSRUse;
861
862} // end anonymous namespace
863
864/// \brief Check if the addressing mode defined by \p F is completely
865/// folded in \p LU at isel time.
866/// This includes address-mode folding and special icmp tricks.
867/// This function returns true if \p LU can accommodate what \p F
868/// defines and up to 1 base + 1 scaled + offset.
869/// In other words, if \p F has several base registers, this function may
870/// still return true. Therefore, users still need to account for
871/// additional base registers and/or unfolded offsets to derive an
872/// accurate cost model.
873static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
874 const LSRUse &LU, const Formula &F);
875// Get the cost of the scaling factor used in F for LU.
876static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
877 const LSRUse &LU, const Formula &F);
878
879namespace {
880
881/// This class is used to measure and compare candidate formulae.
882class Cost {
883 /// TODO: Some of these could be merged. Also, a lexical ordering
884 /// isn't always optimal.
885 unsigned NumRegs;
886 unsigned AddRecCost;
887 unsigned NumIVMuls;
888 unsigned NumBaseAdds;
889 unsigned ImmCost;
890 unsigned SetupCost;
891 unsigned ScaleCost;
892
893public:
894 Cost()
895 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
896 SetupCost(0), ScaleCost(0) {}
897
898 bool operator<(const Cost &Other) const;
899
900 void Lose();
901
902#ifndef NDEBUG
903 // Once any of the metrics loses, they must all remain losers.
904 bool isValid() {
905 return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds
906 | ImmCost | SetupCost | ScaleCost) != ~0u)
907 || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds
908 & ImmCost & SetupCost & ScaleCost) == ~0u);
909 }
910#endif
911
912 bool isLoser() {
913 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 913, __PRETTY_FUNCTION__))
;
914 return NumRegs == ~0u;
915 }
916
917 void RateFormula(const TargetTransformInfo &TTI,
918 const Formula &F,
919 SmallPtrSetImpl<const SCEV *> &Regs,
920 const DenseSet<const SCEV *> &VisitedRegs,
921 const Loop *L,
922 ScalarEvolution &SE, DominatorTree &DT,
923 const LSRUse &LU,
924 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
925
926 void print(raw_ostream &OS) const;
927 void dump() const;
928
929private:
930 void RateRegister(const SCEV *Reg,
931 SmallPtrSetImpl<const SCEV *> &Regs,
932 const Loop *L,
933 ScalarEvolution &SE, DominatorTree &DT);
934 void RatePrimaryRegister(const SCEV *Reg,
935 SmallPtrSetImpl<const SCEV *> &Regs,
936 const Loop *L,
937 ScalarEvolution &SE, DominatorTree &DT,
938 SmallPtrSetImpl<const SCEV *> *LoserRegs);
939};
940
941/// An operand value in an instruction which is to be replaced with some
942/// equivalent, possibly strength-reduced, replacement.
943struct LSRFixup {
944 /// The instruction which will be updated.
945 Instruction *UserInst;
946
947 /// The operand of the instruction which will be replaced. The operand may be
948 /// used more than once; every instance will be replaced.
949 Value *OperandValToReplace;
950
951 /// If this user is to use the post-incremented value of an induction
952 /// variable, this variable is non-null and holds the loop associated with the
953 /// induction variable.
954 PostIncLoopSet PostIncLoops;
955
956 /// A constant offset to be added to the LSRUse expression. This allows
957 /// multiple fixups to share the same LSRUse with different offsets, for
958 /// example in an unrolled loop.
959 int64_t Offset;
960
961 bool isUseFullyOutsideLoop(const Loop *L) const;
962
963 LSRFixup();
964
965 void print(raw_ostream &OS) const;
966 void dump() const;
967};
968
969/// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
970/// SmallVectors of const SCEV*.
971struct UniquifierDenseMapInfo {
972 static SmallVector<const SCEV *, 4> getEmptyKey() {
973 SmallVector<const SCEV *, 4> V;
974 V.push_back(reinterpret_cast<const SCEV *>(-1));
975 return V;
976 }
977
978 static SmallVector<const SCEV *, 4> getTombstoneKey() {
979 SmallVector<const SCEV *, 4> V;
980 V.push_back(reinterpret_cast<const SCEV *>(-2));
981 return V;
982 }
983
984 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
985 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
986 }
987
988 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
989 const SmallVector<const SCEV *, 4> &RHS) {
990 return LHS == RHS;
991 }
992};
993
994/// This class holds the state that LSR keeps for each use in IVUsers, as well
995/// as uses invented by LSR itself. It includes information about what kinds of
996/// things can be folded into the user, information about the user itself, and
997/// information about how the use may be satisfied. TODO: Represent multiple
998/// users of the same expression in common?
999class LSRUse {
1000 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1001
1002public:
1003 /// An enum for a kind of use, indicating what types of scaled and immediate
1004 /// operands it might support.
1005 enum KindType {
1006 Basic, ///< A normal use, with no folding.
1007 Special, ///< A special case of basic, allowing -1 scales.
1008 Address, ///< An address use; folding according to TargetLowering
1009 ICmpZero ///< An equality icmp with both operands folded into one.
1010 // TODO: Add a generic icmp too?
1011 };
1012
1013 typedef PointerIntPair<const SCEV *, 2, KindType> SCEVUseKindPair;
1014
1015 KindType Kind;
1016 MemAccessTy AccessTy;
1017
1018 /// The list of operands which are to be replaced.
1019 SmallVector<LSRFixup, 8> Fixups;
1020
1021 /// Keep track of the min and max offsets of the fixups.
1022 int64_t MinOffset;
1023 int64_t MaxOffset;
1024
1025 /// This records whether all of the fixups using this LSRUse are outside of
1026 /// the loop, in which case some special-case heuristics may be used.
1027 bool AllFixupsOutsideLoop;
1028
1029 /// RigidFormula is set to true to guarantee that this use will be associated
1030 /// with a single formula--the one that initially matched. Some SCEV
1031 /// expressions cannot be expanded. This allows LSR to consider the registers
1032 /// used by those expressions without the need to expand them later after
1033 /// changing the formula.
1034 bool RigidFormula;
1035
1036 /// This records the widest use type for any fixup using this
1037 /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1038 /// fixup widths to be equivalent, because the narrower one may be relying on
1039 /// the implicit truncation to truncate away bogus bits.
1040 Type *WidestFixupType;
1041
1042 /// A list of ways to build a value that can satisfy this user. After the
1043 /// list is populated, one of these is selected heuristically and used to
1044 /// formulate a replacement for OperandValToReplace in UserInst.
1045 SmallVector<Formula, 12> Formulae;
1046
1047 /// The set of register candidates used by all formulae in this LSRUse.
1048 SmallPtrSet<const SCEV *, 4> Regs;
1049
1050 LSRUse(KindType K, MemAccessTy AT)
1051 : Kind(K), AccessTy(AT), MinOffset(INT64_MAX(9223372036854775807L)), MaxOffset(INT64_MIN(-9223372036854775807L -1)),
1052 AllFixupsOutsideLoop(true), RigidFormula(false),
1053 WidestFixupType(nullptr) {}
1054
1055 LSRFixup &getNewFixup() {
1056 Fixups.push_back(LSRFixup());
1057 return Fixups.back();
1058 }
1059
1060 void pushFixup(LSRFixup &f) {
1061 Fixups.push_back(f);
1062 if (f.Offset > MaxOffset)
1063 MaxOffset = f.Offset;
1064 if (f.Offset < MinOffset)
1065 MinOffset = f.Offset;
1066 }
1067
1068 bool HasFormulaWithSameRegs(const Formula &F) const;
1069 bool InsertFormula(const Formula &F);
1070 void DeleteFormula(Formula &F);
1071 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1072
1073 void print(raw_ostream &OS) const;
1074 void dump() const;
1075};
1076
1077} // end anonymous namespace
1078
1079/// Tally up interesting quantities from the given register.
1080void Cost::RateRegister(const SCEV *Reg,
1081 SmallPtrSetImpl<const SCEV *> &Regs,
1082 const Loop *L,
1083 ScalarEvolution &SE, DominatorTree &DT) {
1084 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1085 // If this is an addrec for another loop, don't second-guess its addrec phi
1086 // nodes. LSR isn't currently smart enough to reason about more than one
1087 // loop at a time. LSR has already run on inner loops, will not run on outer
1088 // loops, and cannot be expected to change sibling loops.
1089 if (AR->getLoop() != L) {
1090 // If the AddRec exists, consider it's register free and leave it alone.
1091 if (isExistingPhi(AR, SE))
1092 return;
1093
1094 // Otherwise, do not consider this formula at all.
1095 Lose();
1096 return;
1097 }
1098 AddRecCost += 1; /// TODO: This should be a function of the stride.
1099
1100 // Add the step value register, if it needs one.
1101 // TODO: The non-affine case isn't precisely modeled here.
1102 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1103 if (!Regs.count(AR->getOperand(1))) {
1104 RateRegister(AR->getOperand(1), Regs, L, SE, DT);
1105 if (isLoser())
1106 return;
1107 }
1108 }
1109 }
1110 ++NumRegs;
1111
1112 // Rough heuristic; favor registers which don't require extra setup
1113 // instructions in the preheader.
1114 if (!isa<SCEVUnknown>(Reg) &&
1115 !isa<SCEVConstant>(Reg) &&
1116 !(isa<SCEVAddRecExpr>(Reg) &&
1117 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
1118 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
1119 ++SetupCost;
1120
1121 NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1122 SE.hasComputableLoopEvolution(Reg, L);
1123}
1124
1125/// Record this register in the set. If we haven't seen it before, rate
1126/// it. Optional LoserRegs provides a way to declare any formula that refers to
1127/// one of those regs an instant loser.
1128void Cost::RatePrimaryRegister(const SCEV *Reg,
1129 SmallPtrSetImpl<const SCEV *> &Regs,
1130 const Loop *L,
1131 ScalarEvolution &SE, DominatorTree &DT,
1132 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1133 if (LoserRegs && LoserRegs->count(Reg)) {
1134 Lose();
1135 return;
1136 }
1137 if (Regs.insert(Reg).second) {
1138 RateRegister(Reg, Regs, L, SE, DT);
1139 if (LoserRegs && isLoser())
1140 LoserRegs->insert(Reg);
1141 }
1142}
1143
1144void Cost::RateFormula(const TargetTransformInfo &TTI,
1145 const Formula &F,
1146 SmallPtrSetImpl<const SCEV *> &Regs,
1147 const DenseSet<const SCEV *> &VisitedRegs,
1148 const Loop *L,
1149 ScalarEvolution &SE, DominatorTree &DT,
1150 const LSRUse &LU,
1151 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1152 assert(F.isCanonical() && "Cost is accurate only for canonical formula")((F.isCanonical() && "Cost is accurate only for canonical formula"
) ? static_cast<void> (0) : __assert_fail ("F.isCanonical() && \"Cost is accurate only for canonical formula\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1152, __PRETTY_FUNCTION__))
;
1153 // Tally up the registers.
1154 if (const SCEV *ScaledReg = F.ScaledReg) {
1155 if (VisitedRegs.count(ScaledReg)) {
1156 Lose();
1157 return;
1158 }
1159 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs);
1160 if (isLoser())
1161 return;
1162 }
1163 for (const SCEV *BaseReg : F.BaseRegs) {
1164 if (VisitedRegs.count(BaseReg)) {
1165 Lose();
1166 return;
1167 }
1168 RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs);
1169 if (isLoser())
1170 return;
1171 }
1172
1173 // Determine how many (unfolded) adds we'll need inside the loop.
1174 size_t NumBaseParts = F.getNumRegs();
1175 if (NumBaseParts > 1)
1176 // Do not count the base and a possible second register if the target
1177 // allows to fold 2 registers.
1178 NumBaseAdds +=
1179 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(TTI, LU, F)));
1180 NumBaseAdds += (F.UnfoldedOffset != 0);
1181
1182 // Accumulate non-free scaling amounts.
1183 ScaleCost += getScalingFactorCost(TTI, LU, F);
1184
1185 // Tally up the non-zero immediates.
1186 for (const LSRFixup &Fixup : LU.Fixups) {
1187 int64_t O = Fixup.Offset;
1188 int64_t Offset = (uint64_t)O + F.BaseOffset;
1189 if (F.BaseGV)
1190 ImmCost += 64; // Handle symbolic values conservatively.
1191 // TODO: This should probably be the pointer size.
1192 else if (Offset != 0)
1193 ImmCost += APInt(64, Offset, true).getMinSignedBits();
1194
1195 // Check with target if this offset with this instruction is
1196 // specifically not supported.
1197 if ((isa<LoadInst>(Fixup.UserInst) || isa<StoreInst>(Fixup.UserInst)) &&
1198 !TTI.isFoldableMemAccessOffset(Fixup.UserInst, Offset))
1199 NumBaseAdds++;
1200 }
1201 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1201, __PRETTY_FUNCTION__))
;
1202}
1203
1204/// Set this cost to a losing value.
1205void Cost::Lose() {
1206 NumRegs = ~0u;
1207 AddRecCost = ~0u;
1208 NumIVMuls = ~0u;
1209 NumBaseAdds = ~0u;
1210 ImmCost = ~0u;
1211 SetupCost = ~0u;
1212 ScaleCost = ~0u;
1213}
1214
1215/// Choose the lower cost.
1216bool Cost::operator<(const Cost &Other) const {
1217 return std::tie(NumRegs, AddRecCost, NumIVMuls, NumBaseAdds, ScaleCost,
1218 ImmCost, SetupCost) <
1219 std::tie(Other.NumRegs, Other.AddRecCost, Other.NumIVMuls,
1220 Other.NumBaseAdds, Other.ScaleCost, Other.ImmCost,
1221 Other.SetupCost);
1222}
1223
1224void Cost::print(raw_ostream &OS) const {
1225 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
1226 if (AddRecCost != 0)
1227 OS << ", with addrec cost " << AddRecCost;
1228 if (NumIVMuls != 0)
1229 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
1230 if (NumBaseAdds != 0)
1231 OS << ", plus " << NumBaseAdds << " base add"
1232 << (NumBaseAdds == 1 ? "" : "s");
1233 if (ScaleCost != 0)
1234 OS << ", plus " << ScaleCost << " scale cost";
1235 if (ImmCost != 0)
1236 OS << ", plus " << ImmCost << " imm cost";
1237 if (SetupCost != 0)
1238 OS << ", plus " << SetupCost << " setup cost";
1239}
1240
1241LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__))
1242void Cost::dump() const {
1243 print(errs()); errs() << '\n';
1244}
1245
1246LSRFixup::LSRFixup()
1247 : UserInst(nullptr), OperandValToReplace(nullptr),
1248 Offset(0) {}
1249
1250/// Test whether this fixup always uses its value outside of the given loop.
1251bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1252 // PHI nodes use their value in their incoming blocks.
1253 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1254 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1255 if (PN->getIncomingValue(i) == OperandValToReplace &&
1256 L->contains(PN->getIncomingBlock(i)))
1257 return false;
1258 return true;
1259 }
1260
1261 return !L->contains(UserInst);
1262}
1263
1264void LSRFixup::print(raw_ostream &OS) const {
1265 OS << "UserInst=";
1266 // Store is common and interesting enough to be worth special-casing.
1267 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1268 OS << "store ";
1269 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1270 } else if (UserInst->getType()->isVoidTy())
1271 OS << UserInst->getOpcodeName();
1272 else
1273 UserInst->printAsOperand(OS, /*PrintType=*/false);
1274
1275 OS << ", OperandValToReplace=";
1276 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1277
1278 for (const Loop *PIL : PostIncLoops) {
1279 OS << ", PostIncLoop=";
1280 PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1281 }
1282
1283 if (Offset != 0)
1284 OS << ", Offset=" << Offset;
1285}
1286
1287LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__))
1288void LSRFixup::dump() const {
1289 print(errs()); errs() << '\n';
1290}
1291
1292/// Test whether this use as a formula which has the same registers as the given
1293/// formula.
1294bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1295 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1296 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1297 // Unstable sort by host order ok, because this is only used for uniquifying.
1298 std::sort(Key.begin(), Key.end());
1299 return Uniquifier.count(Key);
1300}
1301
1302/// If the given formula has not yet been inserted, add it to the list, and
1303/// return true. Return false otherwise. The formula must be in canonical form.
1304bool LSRUse::InsertFormula(const Formula &F) {
1305 assert(F.isCanonical() && "Invalid canonical representation")((F.isCanonical() && "Invalid canonical representation"
) ? static_cast<void> (0) : __assert_fail ("F.isCanonical() && \"Invalid canonical representation\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1305, __PRETTY_FUNCTION__))
;
1306
1307 if (!Formulae.empty() && RigidFormula)
1308 return false;
1309
1310 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1311 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1312 // Unstable sort by host order ok, because this is only used for uniquifying.
1313 std::sort(Key.begin(), Key.end());
1314
1315 if (!Uniquifier.insert(Key).second)
1316 return false;
1317
1318 // Using a register to hold the value of 0 is not profitable.
1319 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&(((!F.ScaledReg || !F.ScaledReg->isZero()) && "Zero allocated in a scaled register!"
) ? static_cast<void> (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1320, __PRETTY_FUNCTION__))
1320 "Zero allocated in a scaled register!")(((!F.ScaledReg || !F.ScaledReg->isZero()) && "Zero allocated in a scaled register!"
) ? static_cast<void> (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1320, __PRETTY_FUNCTION__))
;
1321#ifndef NDEBUG
1322 for (const SCEV *BaseReg : F.BaseRegs)
1323 assert(!BaseReg->isZero() && "Zero allocated in a base register!")((!BaseReg->isZero() && "Zero allocated in a base register!"
) ? static_cast<void> (0) : __assert_fail ("!BaseReg->isZero() && \"Zero allocated in a base register!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1323, __PRETTY_FUNCTION__))
;
1324#endif
1325
1326 // Add the formula to the list.
1327 Formulae.push_back(F);
1328
1329 // Record registers now being used by this use.
1330 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1331 if (F.ScaledReg)
1332 Regs.insert(F.ScaledReg);
1333
1334 return true;
1335}
1336
1337/// Remove the given formula from this use's list.
1338void LSRUse::DeleteFormula(Formula &F) {
1339 if (&F != &Formulae.back())
1340 std::swap(F, Formulae.back());
1341 Formulae.pop_back();
1342}
1343
1344/// Recompute the Regs field, and update RegUses.
1345void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1346 // Now that we've filtered out some formulae, recompute the Regs set.
1347 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1348 Regs.clear();
1349 for (const Formula &F : Formulae) {
1350 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1351 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1352 }
1353
1354 // Update the RegTracker.
1355 for (const SCEV *S : OldRegs)
1356 if (!Regs.count(S))
1357 RegUses.dropRegister(S, LUIdx);
1358}
1359
1360void LSRUse::print(raw_ostream &OS) const {
1361 OS << "LSR Use: Kind=";
1362 switch (Kind) {
1363 case Basic: OS << "Basic"; break;
1364 case Special: OS << "Special"; break;
1365 case ICmpZero: OS << "ICmpZero"; break;
1366 case Address:
1367 OS << "Address of ";
1368 if (AccessTy.MemTy->isPointerTy())
1369 OS << "pointer"; // the full pointer type could be really verbose
1370 else {
1371 OS << *AccessTy.MemTy;
1372 }
1373
1374 OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1375 }
1376
1377 OS << ", Offsets={";
1378 bool NeedComma = false;
1379 for (const LSRFixup &Fixup : Fixups) {
1380 if (NeedComma) OS << ',';
1381 OS << Fixup.Offset;
1382 NeedComma = true;
1383 }
1384 OS << '}';
1385
1386 if (AllFixupsOutsideLoop)
1387 OS << ", all-fixups-outside-loop";
1388
1389 if (WidestFixupType)
1390 OS << ", widest fixup type: " << *WidestFixupType;
1391}
1392
1393LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__))
1394void LSRUse::dump() const {
1395 print(errs()); errs() << '\n';
1396}
1397
1398static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1399 LSRUse::KindType Kind, MemAccessTy AccessTy,
1400 GlobalValue *BaseGV, int64_t BaseOffset,
1401 bool HasBaseReg, int64_t Scale) {
1402 switch (Kind) {
1403 case LSRUse::Address:
1404 return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1405 HasBaseReg, Scale, AccessTy.AddrSpace);
1406
1407 case LSRUse::ICmpZero:
1408 // There's not even a target hook for querying whether it would be legal to
1409 // fold a GV into an ICmp.
1410 if (BaseGV)
1411 return false;
1412
1413 // ICmp only has two operands; don't allow more than two non-trivial parts.
1414 if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1415 return false;
1416
1417 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1418 // putting the scaled register in the other operand of the icmp.
1419 if (Scale != 0 && Scale != -1)
1420 return false;
1421
1422 // If we have low-level target information, ask the target if it can fold an
1423 // integer immediate on an icmp.
1424 if (BaseOffset != 0) {
1425 // We have one of:
1426 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1427 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1428 // Offs is the ICmp immediate.
1429 if (Scale == 0)
1430 // The cast does the right thing with INT64_MIN.
1431 BaseOffset = -(uint64_t)BaseOffset;
1432 return TTI.isLegalICmpImmediate(BaseOffset);
1433 }
1434
1435 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1436 return true;
1437
1438 case LSRUse::Basic:
1439 // Only handle single-register values.
1440 return !BaseGV && Scale == 0 && BaseOffset == 0;
1441
1442 case LSRUse::Special:
1443 // Special case Basic to handle -1 scales.
1444 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1445 }
1446
1447 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1447)
;
1448}
1449
1450static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1451 int64_t MinOffset, int64_t MaxOffset,
1452 LSRUse::KindType Kind, MemAccessTy AccessTy,
1453 GlobalValue *BaseGV, int64_t BaseOffset,
1454 bool HasBaseReg, int64_t Scale) {
1455 // Check for overflow.
1456 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1457 (MinOffset > 0))
1458 return false;
1459 MinOffset = (uint64_t)BaseOffset + MinOffset;
1460 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1461 (MaxOffset > 0))
1462 return false;
1463 MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1464
1465 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1466 HasBaseReg, Scale) &&
1467 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1468 HasBaseReg, Scale);
1469}
1470
1471static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1472 int64_t MinOffset, int64_t MaxOffset,
1473 LSRUse::KindType Kind, MemAccessTy AccessTy,
1474 const Formula &F) {
1475 // For the purpose of isAMCompletelyFolded either having a canonical formula
1476 // or a scale not equal to zero is correct.
1477 // Problems may arise from non canonical formulae having a scale == 0.
1478 // Strictly speaking it would best to just rely on canonical formulae.
1479 // However, when we generate the scaled formulae, we first check that the
1480 // scaling factor is profitable before computing the actual ScaledReg for
1481 // compile time sake.
1482 assert((F.isCanonical() || F.Scale != 0))(((F.isCanonical() || F.Scale != 0)) ? static_cast<void>
(0) : __assert_fail ("(F.isCanonical() || F.Scale != 0)", "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1482, __PRETTY_FUNCTION__))
;
1483 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1484 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1485}
1486
1487/// Test whether we know how to expand the current formula.
1488static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1489 int64_t MaxOffset, LSRUse::KindType Kind,
1490 MemAccessTy AccessTy, GlobalValue *BaseGV,
1491 int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1492 // We know how to expand completely foldable formulae.
1493 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1494 BaseOffset, HasBaseReg, Scale) ||
1495 // Or formulae that use a base register produced by a sum of base
1496 // registers.
1497 (Scale == 1 &&
1498 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1499 BaseGV, BaseOffset, true, 0));
1500}
1501
1502static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1503 int64_t MaxOffset, LSRUse::KindType Kind,
1504 MemAccessTy AccessTy, const Formula &F) {
1505 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1506 F.BaseOffset, F.HasBaseReg, F.Scale);
1507}
1508
1509static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1510 const LSRUse &LU, const Formula &F) {
1511 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1512 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1513 F.Scale);
1514}
1515
1516static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1517 const LSRUse &LU, const Formula &F) {
1518 if (!F.Scale)
1519 return 0;
1520
1521 // If the use is not completely folded in that instruction, we will have to
1522 // pay an extra cost only for scale != 1.
1523 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1524 LU.AccessTy, F))
1525 return F.Scale != 1;
1526
1527 switch (LU.Kind) {
1528 case LSRUse::Address: {
1529 // Check the scaling factor cost with both the min and max offsets.
1530 int ScaleCostMinOffset = TTI.getScalingFactorCost(
1531 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1532 F.Scale, LU.AccessTy.AddrSpace);
1533 int ScaleCostMaxOffset = TTI.getScalingFactorCost(
1534 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1535 F.Scale, LU.AccessTy.AddrSpace);
1536
1537 assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&((ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >=
0 && "Legal addressing mode has an illegal cost!") ?
static_cast<void> (0) : __assert_fail ("ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && \"Legal addressing mode has an illegal cost!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1538, __PRETTY_FUNCTION__))
1538 "Legal addressing mode has an illegal cost!")((ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >=
0 && "Legal addressing mode has an illegal cost!") ?
static_cast<void> (0) : __assert_fail ("ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && \"Legal addressing mode has an illegal cost!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1538, __PRETTY_FUNCTION__))
;
1539 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1540 }
1541 case LSRUse::ICmpZero:
1542 case LSRUse::Basic:
1543 case LSRUse::Special:
1544 // The use is completely folded, i.e., everything is folded into the
1545 // instruction.
1546 return 0;
1547 }
1548
1549 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1549)
;
1550}
1551
1552static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1553 LSRUse::KindType Kind, MemAccessTy AccessTy,
1554 GlobalValue *BaseGV, int64_t BaseOffset,
1555 bool HasBaseReg) {
1556 // Fast-path: zero is always foldable.
1557 if (BaseOffset == 0 && !BaseGV) return true;
1558
1559 // Conservatively, create an address with an immediate and a
1560 // base and a scale.
1561 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1562
1563 // Canonicalize a scale of 1 to a base register if the formula doesn't
1564 // already have a base register.
1565 if (!HasBaseReg && Scale == 1) {
1566 Scale = 0;
1567 HasBaseReg = true;
1568 }
1569
1570 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1571 HasBaseReg, Scale);
1572}
1573
1574static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1575 ScalarEvolution &SE, int64_t MinOffset,
1576 int64_t MaxOffset, LSRUse::KindType Kind,
1577 MemAccessTy AccessTy, const SCEV *S,
1578 bool HasBaseReg) {
1579 // Fast-path: zero is always foldable.
1580 if (S->isZero()) return true;
1581
1582 // Conservatively, create an address with an immediate and a
1583 // base and a scale.
1584 int64_t BaseOffset = ExtractImmediate(S, SE);
1585 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1586
1587 // If there's anything else involved, it's not foldable.
1588 if (!S->isZero()) return false;
1589
1590 // Fast-path: zero is always foldable.
1591 if (BaseOffset == 0 && !BaseGV) return true;
1592
1593 // Conservatively, create an address with an immediate and a
1594 // base and a scale.
1595 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1596
1597 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1598 BaseOffset, HasBaseReg, Scale);
1599}
1600
1601namespace {
1602
1603/// An individual increment in a Chain of IV increments. Relate an IV user to
1604/// an expression that computes the IV it uses from the IV used by the previous
1605/// link in the Chain.
1606///
1607/// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1608/// original IVOperand. The head of the chain's IVOperand is only valid during
1609/// chain collection, before LSR replaces IV users. During chain generation,
1610/// IncExpr can be used to find the new IVOperand that computes the same
1611/// expression.
1612struct IVInc {
1613 Instruction *UserInst;
1614 Value* IVOperand;
1615 const SCEV *IncExpr;
1616
1617 IVInc(Instruction *U, Value *O, const SCEV *E):
1618 UserInst(U), IVOperand(O), IncExpr(E) {}
1619};
1620
1621// The list of IV increments in program order. We typically add the head of a
1622// chain without finding subsequent links.
1623struct IVChain {
1624 SmallVector<IVInc,1> Incs;
1625 const SCEV *ExprBase;
1626
1627 IVChain() : ExprBase(nullptr) {}
1628
1629 IVChain(const IVInc &Head, const SCEV *Base)
1630 : Incs(1, Head), ExprBase(Base) {}
1631
1632 typedef SmallVectorImpl<IVInc>::const_iterator const_iterator;
1633
1634 // Return the first increment in the chain.
1635 const_iterator begin() const {
1636 assert(!Incs.empty())((!Incs.empty()) ? static_cast<void> (0) : __assert_fail
("!Incs.empty()", "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1636, __PRETTY_FUNCTION__))
;
1637 return std::next(Incs.begin());
1638 }
1639 const_iterator end() const {
1640 return Incs.end();
1641 }
1642
1643 // Returns true if this chain contains any increments.
1644 bool hasIncs() const { return Incs.size() >= 2; }
1645
1646 // Add an IVInc to the end of this chain.
1647 void add(const IVInc &X) { Incs.push_back(X); }
1648
1649 // Returns the last UserInst in the chain.
1650 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1651
1652 // Returns true if IncExpr can be profitably added to this chain.
1653 bool isProfitableIncrement(const SCEV *OperExpr,
1654 const SCEV *IncExpr,
1655 ScalarEvolution&);
1656};
1657
1658/// Helper for CollectChains to track multiple IV increment uses. Distinguish
1659/// between FarUsers that definitely cross IV increments and NearUsers that may
1660/// be used between IV increments.
1661struct ChainUsers {
1662 SmallPtrSet<Instruction*, 4> FarUsers;
1663 SmallPtrSet<Instruction*, 4> NearUsers;
1664};
1665
1666/// This class holds state for the main loop strength reduction logic.
1667class LSRInstance {
1668 IVUsers &IU;
1669 ScalarEvolution &SE;
1670 DominatorTree &DT;
1671 LoopInfo &LI;
1672 const TargetTransformInfo &TTI;
1673 Loop *const L;
1674 bool Changed;
1675
1676 /// This is the insert position that the current loop's induction variable
1677 /// increment should be placed. In simple loops, this is the latch block's
1678 /// terminator. But in more complicated cases, this is a position which will
1679 /// dominate all the in-loop post-increment users.
1680 Instruction *IVIncInsertPos;
1681
1682 /// Interesting factors between use strides.
1683 ///
1684 /// We explicitly use a SetVector which contains a SmallSet, instead of the
1685 /// default, a SmallDenseSet, because we need to use the full range of
1686 /// int64_ts, and there's currently no good way of doing that with
1687 /// SmallDenseSet.
1688 SetVector<int64_t, SmallVector<int64_t, 8>, SmallSet<int64_t, 8>> Factors;
1689
1690 /// Interesting use types, to facilitate truncation reuse.
1691 SmallSetVector<Type *, 4> Types;
1692
1693 /// The list of interesting uses.
1694 SmallVector<LSRUse, 16> Uses;
1695
1696 /// Track which uses use which register candidates.
1697 RegUseTracker RegUses;
1698
1699 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1700 // have more than a few IV increment chains in a loop. Missing a Chain falls
1701 // back to normal LSR behavior for those uses.
1702 static const unsigned MaxChains = 8;
1703
1704 /// IV users can form a chain of IV increments.
1705 SmallVector<IVChain, MaxChains> IVChainVec;
1706
1707 /// IV users that belong to profitable IVChains.
1708 SmallPtrSet<Use*, MaxChains> IVIncSet;
1709
1710 void OptimizeShadowIV();
1711 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1712 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1713 void OptimizeLoopTermCond();
1714
1715 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1716 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1717 void FinalizeChain(IVChain &Chain);
1718 void CollectChains();
1719 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1720 SmallVectorImpl<WeakVH> &DeadInsts);
1721
1722 void CollectInterestingTypesAndFactors();
1723 void CollectFixupsAndInitialFormulae();
1724
1725 // Support for sharing of LSRUses between LSRFixups.
1726 typedef DenseMap<LSRUse::SCEVUseKindPair, size_t> UseMapTy;
1727 UseMapTy UseMap;
1728
1729 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1730 LSRUse::KindType Kind, MemAccessTy AccessTy);
1731
1732 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
1733 MemAccessTy AccessTy);
1734
1735 void DeleteUse(LSRUse &LU, size_t LUIdx);
1736
1737 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1738
1739 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1740 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1741 void CountRegisters(const Formula &F, size_t LUIdx);
1742 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1743
1744 void CollectLoopInvariantFixupsAndFormulae();
1745
1746 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1747 unsigned Depth = 0);
1748
1749 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1750 const Formula &Base, unsigned Depth,
1751 size_t Idx, bool IsScaledReg = false);
1752 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1753 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1754 const Formula &Base, size_t Idx,
1755 bool IsScaledReg = false);
1756 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1757 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1758 const Formula &Base,
1759 const SmallVectorImpl<int64_t> &Worklist,
1760 size_t Idx, bool IsScaledReg = false);
1761 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1762 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1763 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1764 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1765 void GenerateCrossUseConstantOffsets();
1766 void GenerateAllReuseFormulae();
1767
1768 void FilterOutUndesirableDedicatedRegisters();
1769
1770 size_t EstimateSearchSpaceComplexity() const;
1771 void NarrowSearchSpaceByDetectingSupersets();
1772 void NarrowSearchSpaceByCollapsingUnrolledCode();
1773 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1774 void NarrowSearchSpaceByPickingWinnerRegs();
1775 void NarrowSearchSpaceUsingHeuristics();
1776
1777 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1778 Cost &SolutionCost,
1779 SmallVectorImpl<const Formula *> &Workspace,
1780 const Cost &CurCost,
1781 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1782 DenseSet<const SCEV *> &VisitedRegs) const;
1783 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1784
1785 BasicBlock::iterator
1786 HoistInsertPosition(BasicBlock::iterator IP,
1787 const SmallVectorImpl<Instruction *> &Inputs) const;
1788 BasicBlock::iterator
1789 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1790 const LSRFixup &LF,
1791 const LSRUse &LU,
1792 SCEVExpander &Rewriter) const;
1793
1794 Value *Expand(const LSRUse &LU, const LSRFixup &LF,
1795 const Formula &F,
1796 BasicBlock::iterator IP,
1797 SCEVExpander &Rewriter,
1798 SmallVectorImpl<WeakVH> &DeadInsts) const;
1799 void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
1800 const Formula &F,
1801 SCEVExpander &Rewriter,
1802 SmallVectorImpl<WeakVH> &DeadInsts) const;
1803 void Rewrite(const LSRUse &LU, const LSRFixup &LF,
1804 const Formula &F,
1805 SCEVExpander &Rewriter,
1806 SmallVectorImpl<WeakVH> &DeadInsts) const;
1807 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
1808
1809public:
1810 LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
1811 LoopInfo &LI, const TargetTransformInfo &TTI);
1812
1813 bool getChanged() const { return Changed; }
1814
1815 void print_factors_and_types(raw_ostream &OS) const;
1816 void print_fixups(raw_ostream &OS) const;
1817 void print_uses(raw_ostream &OS) const;
1818 void print(raw_ostream &OS) const;
1819 void dump() const;
1820};
1821
1822} // end anonymous namespace
1823
1824/// If IV is used in a int-to-float cast inside the loop then try to eliminate
1825/// the cast operation.
1826void LSRInstance::OptimizeShadowIV() {
1827 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1828 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1829 return;
1830
1831 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1832 UI != E; /* empty */) {
1833 IVUsers::const_iterator CandidateUI = UI;
1834 ++UI;
1835 Instruction *ShadowUse = CandidateUI->getUser();
1836 Type *DestTy = nullptr;
1837 bool IsSigned = false;
1838
1839 /* If shadow use is a int->float cast then insert a second IV
1840 to eliminate this cast.
1841
1842 for (unsigned i = 0; i < n; ++i)
1843 foo((double)i);
1844
1845 is transformed into
1846
1847 double d = 0.0;
1848 for (unsigned i = 0; i < n; ++i, ++d)
1849 foo(d);
1850 */
1851 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
1852 IsSigned = false;
1853 DestTy = UCast->getDestTy();
1854 }
1855 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
1856 IsSigned = true;
1857 DestTy = SCast->getDestTy();
1858 }
1859 if (!DestTy) continue;
1860
1861 // If target does not support DestTy natively then do not apply
1862 // this transformation.
1863 if (!TTI.isTypeLegal(DestTy)) continue;
1864
1865 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1866 if (!PH) continue;
1867 if (PH->getNumIncomingValues() != 2) continue;
1868
1869 Type *SrcTy = PH->getType();
1870 int Mantissa = DestTy->getFPMantissaWidth();
1871 if (Mantissa == -1) continue;
1872 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1873 continue;
1874
1875 unsigned Entry, Latch;
1876 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1877 Entry = 0;
1878 Latch = 1;
1879 } else {
1880 Entry = 1;
1881 Latch = 0;
1882 }
1883
1884 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1885 if (!Init) continue;
1886 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
1887 (double)Init->getSExtValue() :
1888 (double)Init->getZExtValue());
1889
1890 BinaryOperator *Incr =
1891 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1892 if (!Incr) continue;
1893 if (Incr->getOpcode() != Instruction::Add
1894 && Incr->getOpcode() != Instruction::Sub)
1895 continue;
1896
1897 /* Initialize new IV, double d = 0.0 in above example. */
1898 ConstantInt *C = nullptr;
1899 if (Incr->getOperand(0) == PH)
1900 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1901 else if (Incr->getOperand(1) == PH)
1902 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1903 else
1904 continue;
1905
1906 if (!C) continue;
1907
1908 // Ignore negative constants, as the code below doesn't handle them
1909 // correctly. TODO: Remove this restriction.
1910 if (!C->getValue().isStrictlyPositive()) continue;
1911
1912 /* Add new PHINode. */
1913 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
1914
1915 /* create new increment. '++d' in above example. */
1916 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1917 BinaryOperator *NewIncr =
1918 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1919 Instruction::FAdd : Instruction::FSub,
1920 NewPH, CFP, "IV.S.next.", Incr);
1921
1922 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1923 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1924
1925 /* Remove cast operation */
1926 ShadowUse->replaceAllUsesWith(NewPH);
1927 ShadowUse->eraseFromParent();
1928 Changed = true;
1929 break;
1930 }
1931}
1932
1933/// If Cond has an operand that is an expression of an IV, set the IV user and
1934/// stride information and return true, otherwise return false.
1935bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
1936 for (IVStrideUse &U : IU)
1937 if (U.getUser() == Cond) {
1938 // NOTE: we could handle setcc instructions with multiple uses here, but
1939 // InstCombine does it as well for simple uses, it's not clear that it
1940 // occurs enough in real life to handle.
1941 CondUse = &U;
1942 return true;
1943 }
1944 return false;
1945}
1946
1947/// Rewrite the loop's terminating condition if it uses a max computation.
1948///
1949/// This is a narrow solution to a specific, but acute, problem. For loops
1950/// like this:
1951///
1952/// i = 0;
1953/// do {
1954/// p[i] = 0.0;
1955/// } while (++i < n);
1956///
1957/// the trip count isn't just 'n', because 'n' might not be positive. And
1958/// unfortunately this can come up even for loops where the user didn't use
1959/// a C do-while loop. For example, seemingly well-behaved top-test loops
1960/// will commonly be lowered like this:
1961//
1962/// if (n > 0) {
1963/// i = 0;
1964/// do {
1965/// p[i] = 0.0;
1966/// } while (++i < n);
1967/// }
1968///
1969/// and then it's possible for subsequent optimization to obscure the if
1970/// test in such a way that indvars can't find it.
1971///
1972/// When indvars can't find the if test in loops like this, it creates a
1973/// max expression, which allows it to give the loop a canonical
1974/// induction variable:
1975///
1976/// i = 0;
1977/// max = n < 1 ? 1 : n;
1978/// do {
1979/// p[i] = 0.0;
1980/// } while (++i != max);
1981///
1982/// Canonical induction variables are necessary because the loop passes
1983/// are designed around them. The most obvious example of this is the
1984/// LoopInfo analysis, which doesn't remember trip count values. It
1985/// expects to be able to rediscover the trip count each time it is
1986/// needed, and it does this using a simple analysis that only succeeds if
1987/// the loop has a canonical induction variable.
1988///
1989/// However, when it comes time to generate code, the maximum operation
1990/// can be quite costly, especially if it's inside of an outer loop.
1991///
1992/// This function solves this problem by detecting this type of loop and
1993/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1994/// the instructions for the maximum computation.
1995///
1996ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1997 // Check that the loop matches the pattern we're looking for.
1998 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1999 Cond->getPredicate() != CmpInst::ICMP_NE)
2000 return Cond;
2001
2002 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2003 if (!Sel || !Sel->hasOneUse()) return Cond;
2004
2005 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2006 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2007 return Cond;
2008 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2009
2010 // Add one to the backedge-taken count to get the trip count.
2011 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2012 if (IterationCount != SE.getSCEV(Sel)) return Cond;
2013
2014 // Check for a max calculation that matches the pattern. There's no check
2015 // for ICMP_ULE here because the comparison would be with zero, which
2016 // isn't interesting.
2017 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2018 const SCEVNAryExpr *Max = nullptr;
2019 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2020 Pred = ICmpInst::ICMP_SLE;
2021 Max = S;
2022 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2023 Pred = ICmpInst::ICMP_SLT;
2024 Max = S;
2025 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2026 Pred = ICmpInst::ICMP_ULT;
2027 Max = U;
2028 } else {
2029 // No match; bail.
2030 return Cond;
2031 }
2032
2033 // To handle a max with more than two operands, this optimization would
2034 // require additional checking and setup.
2035 if (Max->getNumOperands() != 2)
2036 return Cond;
2037
2038 const SCEV *MaxLHS = Max->getOperand(0);
2039 const SCEV *MaxRHS = Max->getOperand(1);
2040
2041 // ScalarEvolution canonicalizes constants to the left. For < and >, look
2042 // for a comparison with 1. For <= and >=, a comparison with zero.
2043 if (!MaxLHS ||
2044 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2045 return Cond;
2046
2047 // Check the relevant induction variable for conformance to
2048 // the pattern.
2049 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2050 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2051 if (!AR || !AR->isAffine() ||
2052 AR->getStart() != One ||
2053 AR->getStepRecurrence(SE) != One)
2054 return Cond;
2055
2056 assert(AR->getLoop() == L &&((AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? static_cast<void> (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2057, __PRETTY_FUNCTION__))
2057 "Loop condition operand is an addrec in a different loop!")((AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? static_cast<void> (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2057, __PRETTY_FUNCTION__))
;
2058
2059 // Check the right operand of the select, and remember it, as it will
2060 // be used in the new comparison instruction.
2061 Value *NewRHS = nullptr;
2062 if (ICmpInst::isTrueWhenEqual(Pred)) {
2063 // Look for n+1, and grab n.
2064 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2065 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2066 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2067 NewRHS = BO->getOperand(0);
2068 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2069 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2070 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2071 NewRHS = BO->getOperand(0);
2072 if (!NewRHS)
2073 return Cond;
2074 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2075 NewRHS = Sel->getOperand(1);
2076 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2077 NewRHS = Sel->getOperand(2);
2078 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2079 NewRHS = SU->getValue();
2080 else
2081 // Max doesn't match expected pattern.
2082 return Cond;
2083
2084 // Determine the new comparison opcode. It may be signed or unsigned,
2085 // and the original comparison may be either equality or inequality.
2086 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2087 Pred = CmpInst::getInversePredicate(Pred);
2088
2089 // Ok, everything looks ok to change the condition into an SLT or SGE and
2090 // delete the max calculation.
2091 ICmpInst *NewCond =
2092 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2093
2094 // Delete the max calculation instructions.
2095 Cond->replaceAllUsesWith(NewCond);
2096 CondUse->setUser(NewCond);
2097 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2098 Cond->eraseFromParent();
2099 Sel->eraseFromParent();
2100 if (Cmp->use_empty())
2101 Cmp->eraseFromParent();
2102 return NewCond;
2103}
2104
2105/// Change loop terminating condition to use the postinc iv when possible.
2106void
2107LSRInstance::OptimizeLoopTermCond() {
2108 SmallPtrSet<Instruction *, 4> PostIncs;
2109
2110 // We need a different set of heuristics for rotated and non-rotated loops.
2111 // If a loop is rotated then the latch is also the backedge, so inserting
2112 // post-inc expressions just before the latch is ideal. To reduce live ranges
2113 // it also makes sense to rewrite terminating conditions to use post-inc
2114 // expressions.
2115 //
2116 // If the loop is not rotated then the latch is not a backedge; the latch
2117 // check is done in the loop head. Adding post-inc expressions before the
2118 // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2119 // in the loop body. In this case we do *not* want to use post-inc expressions
2120 // in the latch check, and we want to insert post-inc expressions before
2121 // the backedge.
2122 BasicBlock *LatchBlock = L->getLoopLatch();
2123 SmallVector<BasicBlock*, 8> ExitingBlocks;
2124 L->getExitingBlocks(ExitingBlocks);
2125 if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2126 return LatchBlock != BB;
2127 })) {
2128 // The backedge doesn't exit the loop; treat this as a head-tested loop.
2129 IVIncInsertPos = LatchBlock->getTerminator();
2130 return;
2131 }
2132
2133 // Otherwise treat this as a rotated loop.
2134 for (BasicBlock *ExitingBlock : ExitingBlocks) {
2135
2136 // Get the terminating condition for the loop if possible. If we
2137 // can, we want to change it to use a post-incremented version of its
2138 // induction variable, to allow coalescing the live ranges for the IV into
2139 // one register value.
2140
2141 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2142 if (!TermBr)
2143 continue;
2144 // FIXME: Overly conservative, termination condition could be an 'or' etc..
2145 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2146 continue;
2147
2148 // Search IVUsesByStride to find Cond's IVUse if there is one.
2149 IVStrideUse *CondUse = nullptr;
2150 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2151 if (!FindIVUserForCond(Cond, CondUse))
2152 continue;
2153
2154 // If the trip count is computed in terms of a max (due to ScalarEvolution
2155 // being unable to find a sufficient guard, for example), change the loop
2156 // comparison to use SLT or ULT instead of NE.
2157 // One consequence of doing this now is that it disrupts the count-down
2158 // optimization. That's not always a bad thing though, because in such
2159 // cases it may still be worthwhile to avoid a max.
2160 Cond = OptimizeMax(Cond, CondUse);
2161
2162 // If this exiting block dominates the latch block, it may also use
2163 // the post-inc value if it won't be shared with other uses.
2164 // Check for dominance.
2165 if (!DT.dominates(ExitingBlock, LatchBlock))
2166 continue;
2167
2168 // Conservatively avoid trying to use the post-inc value in non-latch
2169 // exits if there may be pre-inc users in intervening blocks.
2170 if (LatchBlock != ExitingBlock)
2171 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2172 // Test if the use is reachable from the exiting block. This dominator
2173 // query is a conservative approximation of reachability.
2174 if (&*UI != CondUse &&
2175 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2176 // Conservatively assume there may be reuse if the quotient of their
2177 // strides could be a legal scale.
2178 const SCEV *A = IU.getStride(*CondUse, L);
2179 const SCEV *B = IU.getStride(*UI, L);
2180 if (!A || !B) continue;
2181 if (SE.getTypeSizeInBits(A->getType()) !=
2182 SE.getTypeSizeInBits(B->getType())) {
2183 if (SE.getTypeSizeInBits(A->getType()) >
2184 SE.getTypeSizeInBits(B->getType()))
2185 B = SE.getSignExtendExpr(B, A->getType());
2186 else
2187 A = SE.getSignExtendExpr(A, B->getType());
2188 }
2189 if (const SCEVConstant *D =
2190 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2191 const ConstantInt *C = D->getValue();
2192 // Stride of one or negative one can have reuse with non-addresses.
2193 if (C->isOne() || C->isAllOnesValue())
2194 goto decline_post_inc;
2195 // Avoid weird situations.
2196 if (C->getValue().getMinSignedBits() >= 64 ||
2197 C->getValue().isMinSignedValue())
2198 goto decline_post_inc;
2199 // Check for possible scaled-address reuse.
2200 MemAccessTy AccessTy = getAccessType(UI->getUser());
2201 int64_t Scale = C->getSExtValue();
2202 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2203 /*BaseOffset=*/0,
2204 /*HasBaseReg=*/false, Scale,
2205 AccessTy.AddrSpace))
2206 goto decline_post_inc;
2207 Scale = -Scale;
2208 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2209 /*BaseOffset=*/0,
2210 /*HasBaseReg=*/false, Scale,
2211 AccessTy.AddrSpace))
2212 goto decline_post_inc;
2213 }
2214 }
2215
2216 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Change loop exiting icmp to use postinc iv: "
<< *Cond << '\n'; } } while (false)
2217 << *Cond << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Change loop exiting icmp to use postinc iv: "
<< *Cond << '\n'; } } while (false)
;
2218
2219 // It's possible for the setcc instruction to be anywhere in the loop, and
2220 // possible for it to have multiple users. If it is not immediately before
2221 // the exiting block branch, move it.
2222 if (&*++BasicBlock::iterator(Cond) != TermBr) {
2223 if (Cond->hasOneUse()) {
2224 Cond->moveBefore(TermBr);
2225 } else {
2226 // Clone the terminating condition and insert into the loopend.
2227 ICmpInst *OldCond = Cond;
2228 Cond = cast<ICmpInst>(Cond->clone());
2229 Cond->setName(L->getHeader()->getName() + ".termcond");
2230 ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2231
2232 // Clone the IVUse, as the old use still exists!
2233 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2234 TermBr->replaceUsesOfWith(OldCond, Cond);
2235 }
2236 }
2237
2238 // If we get to here, we know that we can transform the setcc instruction to
2239 // use the post-incremented version of the IV, allowing us to coalesce the
2240 // live ranges for the IV correctly.
2241 CondUse->transformToPostInc(L);
2242 Changed = true;
2243
2244 PostIncs.insert(Cond);
2245 decline_post_inc:;
2246 }
2247
2248 // Determine an insertion point for the loop induction variable increment. It
2249 // must dominate all the post-inc comparisons we just set up, and it must
2250 // dominate the loop latch edge.
2251 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2252 for (Instruction *Inst : PostIncs) {
2253 BasicBlock *BB =
2254 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2255 Inst->getParent());
2256 if (BB == Inst->getParent())
2257 IVIncInsertPos = Inst;
2258 else if (BB != IVIncInsertPos->getParent())
2259 IVIncInsertPos = BB->getTerminator();
2260 }
2261}
2262
2263/// Determine if the given use can accommodate a fixup at the given offset and
2264/// other details. If so, update the use and return true.
2265bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2266 bool HasBaseReg, LSRUse::KindType Kind,
2267 MemAccessTy AccessTy) {
2268 int64_t NewMinOffset = LU.MinOffset;
2269 int64_t NewMaxOffset = LU.MaxOffset;
2270 MemAccessTy NewAccessTy = AccessTy;
2271
2272 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2273 // something conservative, however this can pessimize in the case that one of
2274 // the uses will have all its uses outside the loop, for example.
2275 if (LU.Kind != Kind)
2276 return false;
2277
2278 // Check for a mismatched access type, and fall back conservatively as needed.
2279 // TODO: Be less conservative when the type is similar and can use the same
2280 // addressing modes.
2281 if (Kind == LSRUse::Address) {
2282 if (AccessTy != LU.AccessTy)
2283 NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext());
2284 }
2285
2286 // Conservatively assume HasBaseReg is true for now.
2287 if (NewOffset < LU.MinOffset) {
2288 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2289 LU.MaxOffset - NewOffset, HasBaseReg))
2290 return false;
2291 NewMinOffset = NewOffset;
2292 } else if (NewOffset > LU.MaxOffset) {
2293 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2294 NewOffset - LU.MinOffset, HasBaseReg))
2295 return false;
2296 NewMaxOffset = NewOffset;
2297 }
2298
2299 // Update the use.
2300 LU.MinOffset = NewMinOffset;
2301 LU.MaxOffset = NewMaxOffset;
2302 LU.AccessTy = NewAccessTy;
2303 return true;
2304}
2305
2306/// Return an LSRUse index and an offset value for a fixup which needs the given
2307/// expression, with the given kind and optional access type. Either reuse an
2308/// existing use or create a new one, as needed.
2309std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2310 LSRUse::KindType Kind,
2311 MemAccessTy AccessTy) {
2312 const SCEV *Copy = Expr;
2313 int64_t Offset = ExtractImmediate(Expr, SE);
2314
2315 // Basic uses can't accept any offset, for example.
2316 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2317 Offset, /*HasBaseReg=*/ true)) {
2318 Expr = Copy;
2319 Offset = 0;
2320 }
2321
2322 std::pair<UseMapTy::iterator, bool> P =
2323 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2324 if (!P.second) {
2325 // A use already existed with this base.
2326 size_t LUIdx = P.first->second;
2327 LSRUse &LU = Uses[LUIdx];
2328 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2329 // Reuse this use.
2330 return std::make_pair(LUIdx, Offset);
2331 }
2332
2333 // Create a new use.
2334 size_t LUIdx = Uses.size();
2335 P.first->second = LUIdx;
2336 Uses.push_back(LSRUse(Kind, AccessTy));
2337 LSRUse &LU = Uses[LUIdx];
2338
2339 LU.MinOffset = Offset;
2340 LU.MaxOffset = Offset;
2341 return std::make_pair(LUIdx, Offset);
2342}
2343
2344/// Delete the given use from the Uses list.
2345void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2346 if (&LU != &Uses.back())
2347 std::swap(LU, Uses.back());
2348 Uses.pop_back();
2349
2350 // Update RegUses.
2351 RegUses.swapAndDropUse(LUIdx, Uses.size());
2352}
2353
2354/// Look for a use distinct from OrigLU which is has a formula that has the same
2355/// registers as the given formula.
2356LSRUse *
2357LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2358 const LSRUse &OrigLU) {
2359 // Search all uses for the formula. This could be more clever.
2360 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2361 LSRUse &LU = Uses[LUIdx];
2362 // Check whether this use is close enough to OrigLU, to see whether it's
2363 // worthwhile looking through its formulae.
2364 // Ignore ICmpZero uses because they may contain formulae generated by
2365 // GenerateICmpZeroScales, in which case adding fixup offsets may
2366 // be invalid.
2367 if (&LU != &OrigLU &&
2368 LU.Kind != LSRUse::ICmpZero &&
2369 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2370 LU.WidestFixupType == OrigLU.WidestFixupType &&
2371 LU.HasFormulaWithSameRegs(OrigF)) {
2372 // Scan through this use's formulae.
2373 for (const Formula &F : LU.Formulae) {
2374 // Check to see if this formula has the same registers and symbols
2375 // as OrigF.
2376 if (F.BaseRegs == OrigF.BaseRegs &&
2377 F.ScaledReg == OrigF.ScaledReg &&
2378 F.BaseGV == OrigF.BaseGV &&
2379 F.Scale == OrigF.Scale &&
2380 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2381 if (F.BaseOffset == 0)
2382 return &LU;
2383 // This is the formula where all the registers and symbols matched;
2384 // there aren't going to be any others. Since we declined it, we
2385 // can skip the rest of the formulae and proceed to the next LSRUse.
2386 break;
2387 }
2388 }
2389 }
2390 }
2391
2392 // Nothing looked good.
2393 return nullptr;
2394}
2395
2396void LSRInstance::CollectInterestingTypesAndFactors() {
2397 SmallSetVector<const SCEV *, 4> Strides;
2398
2399 // Collect interesting types and strides.
2400 SmallVector<const SCEV *, 4> Worklist;
2401 for (const IVStrideUse &U : IU) {
2402 const SCEV *Expr = IU.getExpr(U);
2403
2404 // Collect interesting types.
2405 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2406
2407 // Add strides for mentioned loops.
2408 Worklist.push_back(Expr);
2409 do {
2410 const SCEV *S = Worklist.pop_back_val();
2411 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2412 if (AR->getLoop() == L)
2413 Strides.insert(AR->getStepRecurrence(SE));
2414 Worklist.push_back(AR->getStart());
2415 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2416 Worklist.append(Add->op_begin(), Add->op_end());
2417 }
2418 } while (!Worklist.empty());
2419 }
2420
2421 // Compute interesting factors from the set of interesting strides.
2422 for (SmallSetVector<const SCEV *, 4>::const_iterator
2423 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2424 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2425 std::next(I); NewStrideIter != E; ++NewStrideIter) {
2426 const SCEV *OldStride = *I;
2427 const SCEV *NewStride = *NewStrideIter;
2428
2429 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2430 SE.getTypeSizeInBits(NewStride->getType())) {
2431 if (SE.getTypeSizeInBits(OldStride->getType()) >
2432 SE.getTypeSizeInBits(NewStride->getType()))
2433 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2434 else
2435 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2436 }
2437 if (const SCEVConstant *Factor =
2438 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2439 SE, true))) {
2440 if (Factor->getAPInt().getMinSignedBits() <= 64)
2441 Factors.insert(Factor->getAPInt().getSExtValue());
2442 } else if (const SCEVConstant *Factor =
2443 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2444 NewStride,
2445 SE, true))) {
2446 if (Factor->getAPInt().getMinSignedBits() <= 64)
2447 Factors.insert(Factor->getAPInt().getSExtValue());
2448 }
2449 }
2450
2451 // If all uses use the same type, don't bother looking for truncation-based
2452 // reuse.
2453 if (Types.size() == 1)
2454 Types.clear();
2455
2456 DEBUG(print_factors_and_types(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_factors_and_types(dbgs()); } } while
(false)
;
2457}
2458
2459/// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2460/// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2461/// IVStrideUses, we could partially skip this.
2462static User::op_iterator
2463findIVOperand(User::op_iterator OI, User::op_iterator OE,
2464 Loop *L, ScalarEvolution &SE) {
2465 for(; OI != OE; ++OI) {
2466 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2467 if (!SE.isSCEVable(Oper->getType()))
2468 continue;
2469
2470 if (const SCEVAddRecExpr *AR =
2471 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2472 if (AR->getLoop() == L)
2473 break;
2474 }
2475 }
2476 }
2477 return OI;
2478}
2479
2480/// IVChain logic must consistenctly peek base TruncInst operands, so wrap it in
2481/// a convenient helper.
2482static Value *getWideOperand(Value *Oper) {
2483 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2484 return Trunc->getOperand(0);
2485 return Oper;
2486}
2487
2488/// Return true if we allow an IV chain to include both types.
2489static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2490 Type *LType = LVal->getType();
2491 Type *RType = RVal->getType();
2492 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy());
2493}
2494
2495/// Return an approximation of this SCEV expression's "base", or NULL for any
2496/// constant. Returning the expression itself is conservative. Returning a
2497/// deeper subexpression is more precise and valid as long as it isn't less
2498/// complex than another subexpression. For expressions involving multiple
2499/// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2500/// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2501/// IVInc==b-a.
2502///
2503/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2504/// SCEVUnknown, we simply return the rightmost SCEV operand.
2505static const SCEV *getExprBase(const SCEV *S) {
2506 switch (S->getSCEVType()) {
2507 default: // uncluding scUnknown.
2508 return S;
2509 case scConstant:
2510 return nullptr;
2511 case scTruncate:
2512 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2513 case scZeroExtend:
2514 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2515 case scSignExtend:
2516 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2517 case scAddExpr: {
2518 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2519 // there's nothing more complex.
2520 // FIXME: not sure if we want to recognize negation.
2521 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2522 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2523 E(Add->op_begin()); I != E; ++I) {
2524 const SCEV *SubExpr = *I;
2525 if (SubExpr->getSCEVType() == scAddExpr)
2526 return getExprBase(SubExpr);
2527
2528 if (SubExpr->getSCEVType() != scMulExpr)
2529 return SubExpr;
2530 }
2531 return S; // all operands are scaled, be conservative.
2532 }
2533 case scAddRecExpr:
2534 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2535 }
2536}
2537
2538/// Return true if the chain increment is profitable to expand into a loop
2539/// invariant value, which may require its own register. A profitable chain
2540/// increment will be an offset relative to the same base. We allow such offsets
2541/// to potentially be used as chain increment as long as it's not obviously
2542/// expensive to expand using real instructions.
2543bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2544 const SCEV *IncExpr,
2545 ScalarEvolution &SE) {
2546 // Aggressively form chains when -stress-ivchain.
2547 if (StressIVChain)
2548 return true;
2549
2550 // Do not replace a constant offset from IV head with a nonconstant IV
2551 // increment.
2552 if (!isa<SCEVConstant>(IncExpr)) {
2553 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2554 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2555 return false;
2556 }
2557
2558 SmallPtrSet<const SCEV*, 8> Processed;
2559 return !isHighCostExpansion(IncExpr, Processed, SE);
2560}
2561
2562/// Return true if the number of registers needed for the chain is estimated to
2563/// be less than the number required for the individual IV users. First prohibit
2564/// any IV users that keep the IV live across increments (the Users set should
2565/// be empty). Next count the number and type of increments in the chain.
2566///
2567/// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2568/// effectively use postinc addressing modes. Only consider it profitable it the
2569/// increments can be computed in fewer registers when chained.
2570///
2571/// TODO: Consider IVInc free if it's already used in another chains.
2572static bool
2573isProfitableChain(IVChain &Chain, SmallPtrSetImpl<Instruction*> &Users,
2574 ScalarEvolution &SE, const TargetTransformInfo &TTI) {
2575 if (StressIVChain)
2576 return true;
2577
2578 if (!Chain.hasIncs())
2579 return false;
2580
2581 if (!Users.empty()) {
2582 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " users:\n"; for (Instruction *Inst
: Users) { dbgs() << " " << *Inst << "\n"
; }; } } while (false)
2583 for (Instruction *Inst : Users) {do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " users:\n"; for (Instruction *Inst
: Users) { dbgs() << " " << *Inst << "\n"
; }; } } while (false)
2584 dbgs() << " " << *Inst << "\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " users:\n"; for (Instruction *Inst
: Users) { dbgs() << " " << *Inst << "\n"
; }; } } while (false)
2585 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " users:\n"; for (Instruction *Inst
: Users) { dbgs() << " " << *Inst << "\n"
; }; } } while (false)
;
2586 return false;
2587 }
2588 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")((!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? static_cast<void> (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2588, __PRETTY_FUNCTION__))
;
2589
2590 // The chain itself may require a register, so intialize cost to 1.
2591 int cost = 1;
2592
2593 // A complete chain likely eliminates the need for keeping the original IV in
2594 // a register. LSR does not currently know how to form a complete chain unless
2595 // the header phi already exists.
2596 if (isa<PHINode>(Chain.tailUserInst())
2597 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2598 --cost;
2599 }
2600 const SCEV *LastIncExpr = nullptr;
2601 unsigned NumConstIncrements = 0;
2602 unsigned NumVarIncrements = 0;
2603 unsigned NumReusedIncrements = 0;
2604 for (const IVInc &Inc : Chain) {
2605 if (Inc.IncExpr->isZero())
2606 continue;
2607
2608 // Incrementing by zero or some constant is neutral. We assume constants can
2609 // be folded into an addressing mode or an add's immediate operand.
2610 if (isa<SCEVConstant>(Inc.IncExpr)) {
2611 ++NumConstIncrements;
2612 continue;
2613 }
2614
2615 if (Inc.IncExpr == LastIncExpr)
2616 ++NumReusedIncrements;
2617 else
2618 ++NumVarIncrements;
2619
2620 LastIncExpr = Inc.IncExpr;
2621 }
2622 // An IV chain with a single increment is handled by LSR's postinc
2623 // uses. However, a chain with multiple increments requires keeping the IV's
2624 // value live longer than it needs to be if chained.
2625 if (NumConstIncrements > 1)
2626 --cost;
2627
2628 // Materializing increment expressions in the preheader that didn't exist in
2629 // the original code may cost a register. For example, sign-extended array
2630 // indices can produce ridiculous increments like this:
2631 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2632 cost += NumVarIncrements;
2633
2634 // Reusing variable increments likely saves a register to hold the multiple of
2635 // the stride.
2636 cost -= NumReusedIncrements;
2637
2638 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << costdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " Cost: " << cost << "\n"
; } } while (false)
2639 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " Cost: " << cost << "\n"
; } } while (false)
;
2640
2641 return cost < 0;
2642}
2643
2644/// Add this IV user to an existing chain or make it the head of a new chain.
2645void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2646 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2647 // When IVs are used as types of varying widths, they are generally converted
2648 // to a wider type with some uses remaining narrow under a (free) trunc.
2649 Value *const NextIV = getWideOperand(IVOper);
2650 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2651 const SCEV *const OperExprBase = getExprBase(OperExpr);
2652
2653 // Visit all existing chains. Check if its IVOper can be computed as a
2654 // profitable loop invariant increment from the last link in the Chain.
2655 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2656 const SCEV *LastIncExpr = nullptr;
2657 for (; ChainIdx < NChains; ++ChainIdx) {
2658 IVChain &Chain = IVChainVec[ChainIdx];
2659
2660 // Prune the solution space aggressively by checking that both IV operands
2661 // are expressions that operate on the same unscaled SCEVUnknown. This
2662 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2663 // first avoids creating extra SCEV expressions.
2664 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2665 continue;
2666
2667 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2668 if (!isCompatibleIVType(PrevIV, NextIV))
2669 continue;
2670
2671 // A phi node terminates a chain.
2672 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2673 continue;
2674
2675 // The increment must be loop-invariant so it can be kept in a register.
2676 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2677 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2678 if (!SE.isLoopInvariant(IncExpr, L))
2679 continue;
2680
2681 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2682 LastIncExpr = IncExpr;
2683 break;
2684 }
2685 }
2686 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2687 // bother for phi nodes, because they must be last in the chain.
2688 if (ChainIdx == NChains) {
2689 if (isa<PHINode>(UserInst))
2690 return;
2691 if (NChains >= MaxChains && !StressIVChain) {
2692 DEBUG(dbgs() << "IV Chain Limit\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain Limit\n"; } } while
(false)
;
2693 return;
2694 }
2695 LastIncExpr = OperExpr;
2696 // IVUsers may have skipped over sign/zero extensions. We don't currently
2697 // attempt to form chains involving extensions unless they can be hoisted
2698 // into this loop's AddRec.
2699 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2700 return;
2701 ++NChains;
2702 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2703 OperExprBase));
2704 ChainUsersVec.resize(NChains);
2705 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInstdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Head: (" << *UserInst << ") IV=" <<
*LastIncExpr << "\n"; } } while (false)
2706 << ") IV=" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Head: (" << *UserInst << ") IV=" <<
*LastIncExpr << "\n"; } } while (false)
;
2707 } else {
2708 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInstdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Inc: (" << *UserInst << ") IV+" <<
*LastIncExpr << "\n"; } } while (false)
2709 << ") IV+" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Inc: (" << *UserInst << ") IV+" <<
*LastIncExpr << "\n"; } } while (false)
;
2710 // Add this IV user to the end of the chain.
2711 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2712 }
2713 IVChain &Chain = IVChainVec[ChainIdx];
2714
2715 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2716 // This chain's NearUsers become FarUsers.
2717 if (!LastIncExpr->isZero()) {
2718 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2719 NearUsers.end());
2720 NearUsers.clear();
2721 }
2722
2723 // All other uses of IVOperand become near uses of the chain.
2724 // We currently ignore intermediate values within SCEV expressions, assuming
2725 // they will eventually be used be the current chain, or can be computed
2726 // from one of the chain increments. To be more precise we could
2727 // transitively follow its user and only add leaf IV users to the set.
2728 for (User *U : IVOper->users()) {
2729 Instruction *OtherUse = dyn_cast<Instruction>(U);
2730 if (!OtherUse)
2731 continue;
2732 // Uses in the chain will no longer be uses if the chain is formed.
2733 // Include the head of the chain in this iteration (not Chain.begin()).
2734 IVChain::const_iterator IncIter = Chain.Incs.begin();
2735 IVChain::const_iterator IncEnd = Chain.Incs.end();
2736 for( ; IncIter != IncEnd; ++IncIter) {
2737 if (IncIter->UserInst == OtherUse)
2738 break;
2739 }
2740 if (IncIter != IncEnd)
2741 continue;
2742
2743 if (SE.isSCEVable(OtherUse->getType())
2744 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2745 && IU.isIVUserOrOperand(OtherUse)) {
2746 continue;
2747 }
2748 NearUsers.insert(OtherUse);
2749 }
2750
2751 // Since this user is part of the chain, it's no longer considered a use
2752 // of the chain.
2753 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2754}
2755
2756/// Populate the vector of Chains.
2757///
2758/// This decreases ILP at the architecture level. Targets with ample registers,
2759/// multiple memory ports, and no register renaming probably don't want
2760/// this. However, such targets should probably disable LSR altogether.
2761///
2762/// The job of LSR is to make a reasonable choice of induction variables across
2763/// the loop. Subsequent passes can easily "unchain" computation exposing more
2764/// ILP *within the loop* if the target wants it.
2765///
2766/// Finding the best IV chain is potentially a scheduling problem. Since LSR
2767/// will not reorder memory operations, it will recognize this as a chain, but
2768/// will generate redundant IV increments. Ideally this would be corrected later
2769/// by a smart scheduler:
2770/// = A[i]
2771/// = A[i+x]
2772/// A[i] =
2773/// A[i+x] =
2774///
2775/// TODO: Walk the entire domtree within this loop, not just the path to the
2776/// loop latch. This will discover chains on side paths, but requires
2777/// maintaining multiple copies of the Chains state.
2778void LSRInstance::CollectChains() {
2779 DEBUG(dbgs() << "Collecting IV Chains.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Collecting IV Chains.\n";
} } while (false)
;
2780 SmallVector<ChainUsers, 8> ChainUsersVec;
2781
2782 SmallVector<BasicBlock *,8> LatchPath;
2783 BasicBlock *LoopHeader = L->getHeader();
2784 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
2785 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
2786 LatchPath.push_back(Rung->getBlock());
2787 }
2788 LatchPath.push_back(LoopHeader);
2789
2790 // Walk the instruction stream from the loop header to the loop latch.
2791 for (BasicBlock *BB : reverse(LatchPath)) {
2792 for (Instruction &I : *BB) {
2793 // Skip instructions that weren't seen by IVUsers analysis.
2794 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
2795 continue;
2796
2797 // Ignore users that are part of a SCEV expression. This way we only
2798 // consider leaf IV Users. This effectively rediscovers a portion of
2799 // IVUsers analysis but in program order this time.
2800 if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
2801 continue;
2802
2803 // Remove this instruction from any NearUsers set it may be in.
2804 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
2805 ChainIdx < NChains; ++ChainIdx) {
2806 ChainUsersVec[ChainIdx].NearUsers.erase(&I);
2807 }
2808 // Search for operands that can be chained.
2809 SmallPtrSet<Instruction*, 4> UniqueOperands;
2810 User::op_iterator IVOpEnd = I.op_end();
2811 User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
2812 while (IVOpIter != IVOpEnd) {
2813 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
2814 if (UniqueOperands.insert(IVOpInst).second)
2815 ChainInstruction(&I, IVOpInst, ChainUsersVec);
2816 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
2817 }
2818 } // Continue walking down the instructions.
2819 } // Continue walking down the domtree.
2820 // Visit phi backedges to determine if the chain can generate the IV postinc.
2821 for (BasicBlock::iterator I = L->getHeader()->begin();
2822 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
2823 if (!SE.isSCEVable(PN->getType()))
2824 continue;
2825
2826 Instruction *IncV =
2827 dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch()));
2828 if (IncV)
2829 ChainInstruction(PN, IncV, ChainUsersVec);
2830 }
2831 // Remove any unprofitable chains.
2832 unsigned ChainIdx = 0;
2833 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
2834 UsersIdx < NChains; ++UsersIdx) {
2835 if (!isProfitableChain(IVChainVec[UsersIdx],
2836 ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
2837 continue;
2838 // Preserve the chain at UsesIdx.
2839 if (ChainIdx != UsersIdx)
2840 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
2841 FinalizeChain(IVChainVec[ChainIdx]);
2842 ++ChainIdx;
2843 }
2844 IVChainVec.resize(ChainIdx);
2845}
2846
2847void LSRInstance::FinalizeChain(IVChain &Chain) {
2848 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")((!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? static_cast<void> (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2848, __PRETTY_FUNCTION__))
;
2849 DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Final Chain: " << *
Chain.Incs[0].UserInst << "\n"; } } while (false)
;
2850
2851 for (const IVInc &Inc : Chain) {
2852 DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Inc: " << *
Inc.UserInst << "\n"; } } while (false)
;
2853 auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
2854 assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand")((UseI != Inc.UserInst->op_end() && "cannot find IV operand"
) ? static_cast<void> (0) : __assert_fail ("UseI != Inc.UserInst->op_end() && \"cannot find IV operand\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2854, __PRETTY_FUNCTION__))
;
2855 IVIncSet.insert(UseI);
2856 }
2857}
2858
2859/// Return true if the IVInc can be folded into an addressing mode.
2860static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
2861 Value *Operand, const TargetTransformInfo &TTI) {
2862 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
2863 if (!IncConst || !isAddressUse(UserInst, Operand))
2864 return false;
2865
2866 if (IncConst->getAPInt().getMinSignedBits() > 64)
2867 return false;
2868
2869 MemAccessTy AccessTy = getAccessType(UserInst);
2870 int64_t IncOffset = IncConst->getValue()->getSExtValue();
2871 if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
2872 IncOffset, /*HaseBaseReg=*/false))
2873 return false;
2874
2875 return true;
2876}
2877
2878/// Generate an add or subtract for each IVInc in a chain to materialize the IV
2879/// user's operand from the previous IV user's operand.
2880void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
2881 SmallVectorImpl<WeakVH> &DeadInsts) {
2882 // Find the new IVOperand for the head of the chain. It may have been replaced
2883 // by LSR.
2884 const IVInc &Head = Chain.Incs[0];
2885 User::op_iterator IVOpEnd = Head.UserInst->op_end();
2886 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
2887 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
2888 IVOpEnd, L, SE);
2889 Value *IVSrc = nullptr;
1
'IVSrc' initialized to a null pointer value
2890 while (IVOpIter != IVOpEnd) {
2
Loop condition is false. Execution continues on line 2907
2891 IVSrc = getWideOperand(*IVOpIter);
2892
2893 // If this operand computes the expression that the chain needs, we may use
2894 // it. (Check this after setting IVSrc which is used below.)
2895 //
2896 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
2897 // narrow for the chain, so we can no longer use it. We do allow using a
2898 // wider phi, assuming the LSR checked for free truncation. In that case we
2899 // should already have a truncate on this operand such that
2900 // getSCEV(IVSrc) == IncExpr.
2901 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
2902 || SE.getSCEV(IVSrc) == Head.IncExpr) {
2903 break;
2904 }
2905 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
2906 }
2907 if (IVOpIter == IVOpEnd) {
3
Taking false branch
2908 // Gracefully give up on this chain.
2909 DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Concealed chain head: " <<
*Head.UserInst << "\n"; } } while (false)
;
2910 return;
2911 }
2912
2913 DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generate chain at: " <<
*IVSrc << "\n"; } } while (false)
;
2914 Type *IVTy = IVSrc->getType();
4
Called C++ object pointer is null
2915 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
2916 const SCEV *LeftOverExpr = nullptr;
2917 for (const IVInc &Inc : Chain) {
2918 Instruction *InsertPt = Inc.UserInst;
2919 if (isa<PHINode>(InsertPt))
2920 InsertPt = L->getLoopLatch()->getTerminator();
2921
2922 // IVOper will replace the current IV User's operand. IVSrc is the IV
2923 // value currently held in a register.
2924 Value *IVOper = IVSrc;
2925 if (!Inc.IncExpr->isZero()) {
2926 // IncExpr was the result of subtraction of two narrow values, so must
2927 // be signed.
2928 const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
2929 LeftOverExpr = LeftOverExpr ?
2930 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
2931 }
2932 if (LeftOverExpr && !LeftOverExpr->isZero()) {
2933 // Expand the IV increment.
2934 Rewriter.clearPostInc();
2935 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
2936 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
2937 SE.getUnknown(IncV));
2938 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
2939
2940 // If an IV increment can't be folded, use it as the next IV value.
2941 if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
2942 assert(IVTy == IVOper->getType() && "inconsistent IV increment type")((IVTy == IVOper->getType() && "inconsistent IV increment type"
) ? static_cast<void> (0) : __assert_fail ("IVTy == IVOper->getType() && \"inconsistent IV increment type\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2942, __PRETTY_FUNCTION__))
;
2943 IVSrc = IVOper;
2944 LeftOverExpr = nullptr;
2945 }
2946 }
2947 Type *OperTy = Inc.IVOperand->getType();
2948 if (IVTy != OperTy) {
2949 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&((SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy
) && "cannot extend a chained IV") ? static_cast<void
> (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2950, __PRETTY_FUNCTION__))
2950 "cannot extend a chained IV")((SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy
) && "cannot extend a chained IV") ? static_cast<void
> (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2950, __PRETTY_FUNCTION__))
;
2951 IRBuilder<> Builder(InsertPt);
2952 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
2953 }
2954 Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
2955 DeadInsts.emplace_back(Inc.IVOperand);
2956 }
2957 // If LSR created a new, wider phi, we may also replace its postinc. We only
2958 // do this if we also found a wide value for the head of the chain.
2959 if (isa<PHINode>(Chain.tailUserInst())) {
2960 for (BasicBlock::iterator I = L->getHeader()->begin();
2961 PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
2962 if (!isCompatibleIVType(Phi, IVSrc))
2963 continue;
2964 Instruction *PostIncV = dyn_cast<Instruction>(
2965 Phi->getIncomingValueForBlock(L->getLoopLatch()));
2966 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
2967 continue;
2968 Value *IVOper = IVSrc;
2969 Type *PostIncTy = PostIncV->getType();
2970 if (IVTy != PostIncTy) {
2971 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types")((PostIncTy->isPointerTy() && "mixing int/ptr IV types"
) ? static_cast<void> (0) : __assert_fail ("PostIncTy->isPointerTy() && \"mixing int/ptr IV types\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2971, __PRETTY_FUNCTION__))
;
2972 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
2973 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
2974 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
2975 }
2976 Phi->replaceUsesOfWith(PostIncV, IVOper);
2977 DeadInsts.emplace_back(PostIncV);
2978 }
2979 }
2980}
2981
2982void LSRInstance::CollectFixupsAndInitialFormulae() {
2983 for (const IVStrideUse &U : IU) {
2984 Instruction *UserInst = U.getUser();
2985 // Skip IV users that are part of profitable IV Chains.
2986 User::op_iterator UseI =
2987 find(UserInst->operands(), U.getOperandValToReplace());
2988 assert(UseI != UserInst->op_end() && "cannot find IV operand")((UseI != UserInst->op_end() && "cannot find IV operand"
) ? static_cast<void> (0) : __assert_fail ("UseI != UserInst->op_end() && \"cannot find IV operand\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2988, __PRETTY_FUNCTION__))
;
2989 if (IVIncSet.count(UseI))
2990 continue;
2991
2992 LSRUse::KindType Kind = LSRUse::Basic;
2993 MemAccessTy AccessTy;
2994 if (isAddressUse(UserInst, U.getOperandValToReplace())) {
2995 Kind = LSRUse::Address;
2996 AccessTy = getAccessType(UserInst);
2997 }
2998
2999 const SCEV *S = IU.getExpr(U);
3000 PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3001
3002 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3003 // (N - i == 0), and this allows (N - i) to be the expression that we work
3004 // with rather than just N or i, so we can consider the register
3005 // requirements for both N and i at the same time. Limiting this code to
3006 // equality icmps is not a problem because all interesting loops use
3007 // equality icmps, thanks to IndVarSimplify.
3008 if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst))
3009 if (CI->isEquality()) {
3010 // Swap the operands if needed to put the OperandValToReplace on the
3011 // left, for consistency.
3012 Value *NV = CI->getOperand(1);
3013 if (NV == U.getOperandValToReplace()) {
3014 CI->setOperand(1, CI->getOperand(0));
3015 CI->setOperand(0, NV);
3016 NV = CI->getOperand(1);
3017 Changed = true;
3018 }
3019
3020 // x == y --> x - y == 0
3021 const SCEV *N = SE.getSCEV(NV);
3022 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3023 // S is normalized, so normalize N before folding it into S
3024 // to keep the result normalized.
3025 N = TransformForPostIncUse(Normalize, N, CI, nullptr,
3026 TmpPostIncLoops, SE, DT);
3027 Kind = LSRUse::ICmpZero;
3028 S = SE.getMinusSCEV(N, S);
3029 }
3030
3031 // -1 and the negations of all interesting strides (except the negation
3032 // of -1) are now also interesting.
3033 for (size_t i = 0, e = Factors.size(); i != e; ++i)
3034 if (Factors[i] != -1)
3035 Factors.insert(-(uint64_t)Factors[i]);
3036 Factors.insert(-1);
3037 }
3038
3039 // Get or create an LSRUse.
3040 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3041 size_t LUIdx = P.first;
3042 int64_t Offset = P.second;
3043 LSRUse &LU = Uses[LUIdx];
3044
3045 // Record the fixup.
3046 LSRFixup &LF = LU.getNewFixup();
3047 LF.UserInst = UserInst;
3048 LF.OperandValToReplace = U.getOperandValToReplace();
3049 LF.PostIncLoops = TmpPostIncLoops;
3050 LF.Offset = Offset;
3051 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3052
3053 if (!LU.WidestFixupType ||
3054 SE.getTypeSizeInBits(LU.WidestFixupType) <
3055 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3056 LU.WidestFixupType = LF.OperandValToReplace->getType();
3057
3058 // If this is the first use of this LSRUse, give it a formula.
3059 if (LU.Formulae.empty()) {
3060 InsertInitialFormula(S, LU, LUIdx);
3061 CountRegisters(LU.Formulae.back(), LUIdx);
3062 }
3063 }
3064
3065 DEBUG(print_fixups(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_fixups(dbgs()); } } while (false)
;
3066}
3067
3068/// Insert a formula for the given expression into the given use, separating out
3069/// loop-variant portions from loop-invariant and loop-computable portions.
3070void
3071LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3072 // Mark uses whose expressions cannot be expanded.
3073 if (!isSafeToExpand(S, SE))
3074 LU.RigidFormula = true;
3075
3076 Formula F;
3077 F.initialMatch(S, L, SE);
3078 bool Inserted = InsertFormula(LU, LUIdx, F);
3079 assert(Inserted && "Initial formula already exists!")((Inserted && "Initial formula already exists!") ? static_cast
<void> (0) : __assert_fail ("Inserted && \"Initial formula already exists!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3079, __PRETTY_FUNCTION__))
; (void)Inserted;
3080}
3081
3082/// Insert a simple single-register formula for the given expression into the
3083/// given use.
3084void
3085LSRInstance::InsertSupplementalFormula(const SCEV *S,
3086 LSRUse &LU, size_t LUIdx) {
3087 Formula F;
3088 F.BaseRegs.push_back(S);
3089 F.HasBaseReg = true;
3090 bool Inserted = InsertFormula(LU, LUIdx, F);
3091 assert(Inserted && "Supplemental formula already exists!")((Inserted && "Supplemental formula already exists!")
? static_cast<void> (0) : __assert_fail ("Inserted && \"Supplemental formula already exists!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3091, __PRETTY_FUNCTION__))
; (void)Inserted;
3092}
3093
3094/// Note which registers are used by the given formula, updating RegUses.
3095void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3096 if (F.ScaledReg)
3097 RegUses.countRegister(F.ScaledReg, LUIdx);
3098 for (const SCEV *BaseReg : F.BaseRegs)
3099 RegUses.countRegister(BaseReg, LUIdx);
3100}
3101
3102/// If the given formula has not yet been inserted, add it to the list, and
3103/// return true. Return false otherwise.
3104bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3105 // Do not insert formula that we will not be able to expand.
3106 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Formula is illegal") ? static_cast<void>
(0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3107, __PRETTY_FUNCTION__))
3107 "Formula is illegal")((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Formula is illegal") ? static_cast<void>
(0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3107, __PRETTY_FUNCTION__))
;
3108 if (!LU.InsertFormula(F))
3109 return false;
3110
3111 CountRegisters(F, LUIdx);
3112 return true;
3113}
3114
3115/// Check for other uses of loop-invariant values which we're tracking. These
3116/// other uses will pin these values in registers, making them less profitable
3117/// for elimination.
3118/// TODO: This currently misses non-constant addrec step registers.
3119/// TODO: Should this give more weight to users inside the loop?
3120void
3121LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3122 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3123 SmallPtrSet<const SCEV *, 32> Visited;
3124
3125 while (!Worklist.empty()) {
3126 const SCEV *S = Worklist.pop_back_val();
3127
3128 // Don't process the same SCEV twice
3129 if (!Visited.insert(S).second)
3130 continue;
3131
3132 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3133 Worklist.append(N->op_begin(), N->op_end());
3134 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3135 Worklist.push_back(C->getOperand());
3136 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3137 Worklist.push_back(D->getLHS());
3138 Worklist.push_back(D->getRHS());
3139 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3140 const Value *V = US->getValue();
3141 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3142 // Look for instructions defined outside the loop.
3143 if (L->contains(Inst)) continue;
3144 } else if (isa<UndefValue>(V))
3145 // Undef doesn't have a live range, so it doesn't matter.
3146 continue;
3147 for (const Use &U : V->uses()) {
3148 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3149 // Ignore non-instructions.
3150 if (!UserInst)
3151 continue;
3152 // Ignore instructions in other functions (as can happen with
3153 // Constants).
3154 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3155 continue;
3156 // Ignore instructions not dominated by the loop.
3157 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3158 UserInst->getParent() :
3159 cast<PHINode>(UserInst)->getIncomingBlock(
3160 PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3161 if (!DT.dominates(L->getHeader(), UseBB))
3162 continue;
3163 // Don't bother if the instruction is in a BB which ends in an EHPad.
3164 if (UseBB->getTerminator()->isEHPad())
3165 continue;
3166 // Ignore uses which are part of other SCEV expressions, to avoid
3167 // analyzing them multiple times.
3168 if (SE.isSCEVable(UserInst->getType())) {
3169 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3170 // If the user is a no-op, look through to its uses.
3171 if (!isa<SCEVUnknown>(UserS))
3172 continue;
3173 if (UserS == US) {
3174 Worklist.push_back(
3175 SE.getUnknown(const_cast<Instruction *>(UserInst)));
3176 continue;
3177 }
3178 }
3179 // Ignore icmp instructions which are already being analyzed.
3180 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3181 unsigned OtherIdx = !U.getOperandNo();
3182 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3183 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3184 continue;
3185 }
3186
3187 std::pair<size_t, int64_t> P = getUse(
3188 S, LSRUse::Basic, MemAccessTy());
3189 size_t LUIdx = P.first;
3190 int64_t Offset = P.second;
3191 LSRUse &LU = Uses[LUIdx];
3192 LSRFixup &LF = LU.getNewFixup();
3193 LF.UserInst = const_cast<Instruction *>(UserInst);
3194 LF.OperandValToReplace = U;
3195 LF.Offset = Offset;
3196 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3197 if (!LU.WidestFixupType ||
3198 SE.getTypeSizeInBits(LU.WidestFixupType) <
3199 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3200 LU.WidestFixupType = LF.OperandValToReplace->getType();
3201 InsertSupplementalFormula(US, LU, LUIdx);
3202 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3203 break;
3204 }
3205 }
3206 }
3207}
3208
3209/// Split S into subexpressions which can be pulled out into separate
3210/// registers. If C is non-null, multiply each subexpression by C.
3211///
3212/// Return remainder expression after factoring the subexpressions captured by
3213/// Ops. If Ops is complete, return NULL.
3214static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3215 SmallVectorImpl<const SCEV *> &Ops,
3216 const Loop *L,
3217 ScalarEvolution &SE,
3218 unsigned Depth = 0) {
3219 // Arbitrarily cap recursion to protect compile time.
3220 if (Depth >= 3)
3221 return S;
3222
3223 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3224 // Break out add operands.
3225 for (const SCEV *S : Add->operands()) {
3226 const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3227 if (Remainder)
3228 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3229 }
3230 return nullptr;
3231 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3232 // Split a non-zero base out of an addrec.
3233 if (AR->getStart()->isZero() || !AR->isAffine())
3234 return S;
3235
3236 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3237 C, Ops, L, SE, Depth+1);
3238 // Split the non-zero AddRec unless it is part of a nested recurrence that
3239 // does not pertain to this loop.
3240 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3241 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3242 Remainder = nullptr;
3243 }
3244 if (Remainder != AR->getStart()) {
3245 if (!Remainder)
3246 Remainder = SE.getConstant(AR->getType(), 0);
3247 return SE.getAddRecExpr(Remainder,
3248 AR->getStepRecurrence(SE),
3249 AR->getLoop(),
3250 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3251 SCEV::FlagAnyWrap);
3252 }
3253 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3254 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3255 if (Mul->getNumOperands() != 2)
3256 return S;
3257 if (const SCEVConstant *Op0 =
3258 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3259 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3260 const SCEV *Remainder =
3261 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3262 if (Remainder)
3263 Ops.push_back(SE.getMulExpr(C, Remainder));
3264 return nullptr;
3265 }
3266 }
3267 return S;
3268}
3269
3270/// \brief Helper function for LSRInstance::GenerateReassociations.
3271void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3272 const Formula &Base,
3273 unsigned Depth, size_t Idx,
3274 bool IsScaledReg) {
3275 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3276 SmallVector<const SCEV *, 8> AddOps;
3277 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3278 if (Remainder)
3279 AddOps.push_back(Remainder);
3280
3281 if (AddOps.size() == 1)
3282 return;
3283
3284 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3285 JE = AddOps.end();
3286 J != JE; ++J) {
3287
3288 // Loop-variant "unknown" values are uninteresting; we won't be able to
3289 // do anything meaningful with them.
3290 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3291 continue;
3292
3293 // Don't pull a constant into a register if the constant could be folded
3294 // into an immediate field.
3295 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3296 LU.AccessTy, *J, Base.getNumRegs() > 1))
3297 continue;
3298
3299 // Collect all operands except *J.
3300 SmallVector<const SCEV *, 8> InnerAddOps(
3301 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3302 InnerAddOps.append(std::next(J),
3303 ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3304
3305 // Don't leave just a constant behind in a register if the constant could
3306 // be folded into an immediate field.
3307 if (InnerAddOps.size() == 1 &&
3308 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3309 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3310 continue;
3311
3312 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3313 if (InnerSum->isZero())
3314 continue;
3315 Formula F = Base;
3316
3317 // Add the remaining pieces of the add back into the new formula.
3318 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3319 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3320 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3321 InnerSumSC->getValue()->getZExtValue())) {
3322 F.UnfoldedOffset =
3323 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3324 if (IsScaledReg)
3325 F.ScaledReg = nullptr;
3326 else
3327 F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3328 } else if (IsScaledReg)
3329 F.ScaledReg = InnerSum;
3330 else
3331 F.BaseRegs[Idx] = InnerSum;
3332
3333 // Add J as its own register, or an unfolded immediate.
3334 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3335 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3336 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3337 SC->getValue()->getZExtValue()))
3338 F.UnfoldedOffset =
3339 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3340 else
3341 F.BaseRegs.push_back(*J);
3342 // We may have changed the number of register in base regs, adjust the
3343 // formula accordingly.
3344 F.canonicalize();
3345
3346 if (InsertFormula(LU, LUIdx, F))
3347 // If that formula hadn't been seen before, recurse to find more like
3348 // it.
3349 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth + 1);
3350 }
3351}
3352
3353/// Split out subexpressions from adds and the bases of addrecs.
3354void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3355 Formula Base, unsigned Depth) {
3356 assert(Base.isCanonical() && "Input must be in the canonical form")((Base.isCanonical() && "Input must be in the canonical form"
) ? static_cast<void> (0) : __assert_fail ("Base.isCanonical() && \"Input must be in the canonical form\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3356, __PRETTY_FUNCTION__))
;
3357 // Arbitrarily cap recursion to protect compile time.
3358 if (Depth >= 3)
3359 return;
3360
3361 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3362 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3363
3364 if (Base.Scale == 1)
3365 GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3366 /* Idx */ -1, /* IsScaledReg */ true);
3367}
3368
3369/// Generate a formula consisting of all of the loop-dominating registers added
3370/// into a single register.
3371void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3372 Formula Base) {
3373 // This method is only interesting on a plurality of registers.
3374 if (Base.BaseRegs.size() + (Base.Scale == 1) <= 1)
3375 return;
3376
3377 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3378 // processing the formula.
3379 Base.unscale();
3380 Formula F = Base;
3381 F.BaseRegs.clear();
3382 SmallVector<const SCEV *, 4> Ops;
3383 for (const SCEV *BaseReg : Base.BaseRegs) {
3384 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3385 !SE.hasComputableLoopEvolution(BaseReg, L))
3386 Ops.push_back(BaseReg);
3387 else
3388 F.BaseRegs.push_back(BaseReg);
3389 }
3390 if (Ops.size() > 1) {
3391 const SCEV *Sum = SE.getAddExpr(Ops);
3392 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3393 // opportunity to fold something. For now, just ignore such cases
3394 // rather than proceed with zero in a register.
3395 if (!Sum->isZero()) {
3396 F.BaseRegs.push_back(Sum);
3397 F.canonicalize();
3398 (void)InsertFormula(LU, LUIdx, F);
3399 }
3400 }
3401}
3402
3403/// \brief Helper function for LSRInstance::GenerateSymbolicOffsets.
3404void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3405 const Formula &Base, size_t Idx,
3406 bool IsScaledReg) {
3407 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3408 GlobalValue *GV = ExtractSymbol(G, SE);
3409 if (G->isZero() || !GV)
3410 return;
3411 Formula F = Base;
3412 F.BaseGV = GV;
3413 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3414 return;
3415 if (IsScaledReg)
3416 F.ScaledReg = G;
3417 else
3418 F.BaseRegs[Idx] = G;
3419 (void)InsertFormula(LU, LUIdx, F);
3420}
3421
3422/// Generate reuse formulae using symbolic offsets.
3423void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3424 Formula Base) {
3425 // We can't add a symbolic offset if the address already contains one.
3426 if (Base.BaseGV) return;
3427
3428 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3429 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3430 if (Base.Scale == 1)
3431 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3432 /* IsScaledReg */ true);
3433}
3434
3435/// \brief Helper function for LSRInstance::GenerateConstantOffsets.
3436void LSRInstance::GenerateConstantOffsetsImpl(
3437 LSRUse &LU, unsigned LUIdx, const Formula &Base,
3438 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3439 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3440 for (int64_t Offset : Worklist) {
3441 Formula F = Base;
3442 F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3443 if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind,
3444 LU.AccessTy, F)) {
3445 // Add the offset to the base register.
3446 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3447 // If it cancelled out, drop the base register, otherwise update it.
3448 if (NewG->isZero()) {
3449 if (IsScaledReg) {
3450 F.Scale = 0;
3451 F.ScaledReg = nullptr;
3452 } else
3453 F.deleteBaseReg(F.BaseRegs[Idx]);
3454 F.canonicalize();
3455 } else if (IsScaledReg)
3456 F.ScaledReg = NewG;
3457 else
3458 F.BaseRegs[Idx] = NewG;
3459
3460 (void)InsertFormula(LU, LUIdx, F);
3461 }
3462 }
3463
3464 int64_t Imm = ExtractImmediate(G, SE);
3465 if (G->isZero() || Imm == 0)
3466 return;
3467 Formula F = Base;
3468 F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3469 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3470 return;
3471 if (IsScaledReg)
3472 F.ScaledReg = G;
3473 else
3474 F.BaseRegs[Idx] = G;
3475 (void)InsertFormula(LU, LUIdx, F);
3476}
3477
3478/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3479void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3480 Formula Base) {
3481 // TODO: For now, just add the min and max offset, because it usually isn't
3482 // worthwhile looking at everything inbetween.
3483 SmallVector<int64_t, 2> Worklist;
3484 Worklist.push_back(LU.MinOffset);
3485 if (LU.MaxOffset != LU.MinOffset)
3486 Worklist.push_back(LU.MaxOffset);
3487
3488 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3489 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3490 if (Base.Scale == 1)
3491 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3492 /* IsScaledReg */ true);
3493}
3494
3495/// For ICmpZero, check to see if we can scale up the comparison. For example, x
3496/// == y -> x*c == y*c.
3497void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3498 Formula Base) {
3499 if (LU.Kind != LSRUse::ICmpZero) return;
3500
3501 // Determine the integer type for the base formula.
3502 Type *IntTy = Base.getType();
3503 if (!IntTy) return;
3504 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3505
3506 // Don't do this if there is more than one offset.
3507 if (LU.MinOffset != LU.MaxOffset) return;
3508
3509 assert(!Base.BaseGV && "ICmpZero use is not legal!")((!Base.BaseGV && "ICmpZero use is not legal!") ? static_cast
<void> (0) : __assert_fail ("!Base.BaseGV && \"ICmpZero use is not legal!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3509, __PRETTY_FUNCTION__))
;
3510
3511 // Check each interesting stride.
3512 for (int64_t Factor : Factors) {
3513 // Check that the multiplication doesn't overflow.
3514 if (Base.BaseOffset == INT64_MIN(-9223372036854775807L -1) && Factor == -1)
3515 continue;
3516 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3517 if (NewBaseOffset / Factor != Base.BaseOffset)
3518 continue;
3519 // If the offset will be truncated at this use, check that it is in bounds.
3520 if (!IntTy->isPointerTy() &&
3521 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3522 continue;
3523
3524 // Check that multiplying with the use offset doesn't overflow.
3525 int64_t Offset = LU.MinOffset;
3526 if (Offset == INT64_MIN(-9223372036854775807L -1) && Factor == -1)
3527 continue;
3528 Offset = (uint64_t)Offset * Factor;
3529 if (Offset / Factor != LU.MinOffset)
3530 continue;
3531 // If the offset will be truncated at this use, check that it is in bounds.
3532 if (!IntTy->isPointerTy() &&
3533 !ConstantInt::isValueValidForType(IntTy, Offset))
3534 continue;
3535
3536 Formula F = Base;
3537 F.BaseOffset = NewBaseOffset;
3538
3539 // Check that this scale is legal.
3540 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3541 continue;
3542
3543 // Compensate for the use having MinOffset built into it.
3544 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3545
3546 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3547
3548 // Check that multiplying with each base register doesn't overflow.
3549 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3550 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3551 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3552 goto next;
3553 }
3554
3555 // Check that multiplying with the scaled register doesn't overflow.
3556 if (F.ScaledReg) {
3557 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3558 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3559 continue;
3560 }
3561
3562 // Check that multiplying with the unfolded offset doesn't overflow.
3563 if (F.UnfoldedOffset != 0) {
3564 if (F.UnfoldedOffset == INT64_MIN(-9223372036854775807L -1) && Factor == -1)
3565 continue;
3566 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3567 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3568 continue;
3569 // If the offset will be truncated, check that it is in bounds.
3570 if (!IntTy->isPointerTy() &&
3571 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3572 continue;
3573 }
3574
3575 // If we make it here and it's legal, add it.
3576 (void)InsertFormula(LU, LUIdx, F);
3577 next:;
3578 }
3579}
3580
3581/// Generate stride factor reuse formulae by making use of scaled-offset address
3582/// modes, for example.
3583void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3584 // Determine the integer type for the base formula.
3585 Type *IntTy = Base.getType();
3586 if (!IntTy) return;
3587
3588 // If this Formula already has a scaled register, we can't add another one.
3589 // Try to unscale the formula to generate a better scale.
3590 if (Base.Scale != 0 && !Base.unscale())
3591 return;
3592
3593 assert(Base.Scale == 0 && "unscale did not did its job!")((Base.Scale == 0 && "unscale did not did its job!") ?
static_cast<void> (0) : __assert_fail ("Base.Scale == 0 && \"unscale did not did its job!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3593, __PRETTY_FUNCTION__))
;
3594
3595 // Check each interesting stride.
3596 for (int64_t Factor : Factors) {
3597 Base.Scale = Factor;
3598 Base.HasBaseReg = Base.BaseRegs.size() > 1;
3599 // Check whether this scale is going to be legal.
3600 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3601 Base)) {
3602 // As a special-case, handle special out-of-loop Basic users specially.
3603 // TODO: Reconsider this special case.
3604 if (LU.Kind == LSRUse::Basic &&
3605 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3606 LU.AccessTy, Base) &&
3607 LU.AllFixupsOutsideLoop)
3608 LU.Kind = LSRUse::Special;
3609 else
3610 continue;
3611 }
3612 // For an ICmpZero, negating a solitary base register won't lead to
3613 // new solutions.
3614 if (LU.Kind == LSRUse::ICmpZero &&
3615 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3616 continue;
3617 // For each addrec base reg, apply the scale, if possible.
3618 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3619 if (const SCEVAddRecExpr *AR =
3620 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
3621 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3622 if (FactorS->isZero())
3623 continue;
3624 // Divide out the factor, ignoring high bits, since we'll be
3625 // scaling the value back up in the end.
3626 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3627 // TODO: This could be optimized to avoid all the copying.
3628 Formula F = Base;
3629 F.ScaledReg = Quotient;
3630 F.deleteBaseReg(F.BaseRegs[i]);
3631 // The canonical representation of 1*reg is reg, which is already in
3632 // Base. In that case, do not try to insert the formula, it will be
3633 // rejected anyway.
3634 if (F.Scale == 1 && F.BaseRegs.empty())
3635 continue;
3636 (void)InsertFormula(LU, LUIdx, F);
3637 }
3638 }
3639 }
3640}
3641
3642/// Generate reuse formulae from different IV types.
3643void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3644 // Don't bother truncating symbolic values.
3645 if (Base.BaseGV) return;
3646
3647 // Determine the integer type for the base formula.
3648 Type *DstTy = Base.getType();
3649 if (!DstTy) return;
3650 DstTy = SE.getEffectiveSCEVType(DstTy);
3651
3652 for (Type *SrcTy : Types) {
3653 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
3654 Formula F = Base;
3655
3656 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
3657 for (const SCEV *&BaseReg : F.BaseRegs)
3658 BaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
3659
3660 // TODO: This assumes we've done basic processing on all uses and
3661 // have an idea what the register usage is.
3662 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3663 continue;
3664
3665 (void)InsertFormula(LU, LUIdx, F);
3666 }
3667 }
3668}
3669
3670namespace {
3671
3672/// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
3673/// modifications so that the search phase doesn't have to worry about the data
3674/// structures moving underneath it.
3675struct WorkItem {
3676 size_t LUIdx;
3677 int64_t Imm;
3678 const SCEV *OrigReg;
3679
3680 WorkItem(size_t LI, int64_t I, const SCEV *R)
3681 : LUIdx(LI), Imm(I), OrigReg(R) {}
3682
3683 void print(raw_ostream &OS) const;
3684 void dump() const;
3685};
3686
3687} // end anonymous namespace
3688
3689void WorkItem::print(raw_ostream &OS) const {
3690 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3691 << " , add offset " << Imm;
3692}
3693
3694LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__))
3695void WorkItem::dump() const {
3696 print(errs()); errs() << '\n';
3697}
3698
3699/// Look for registers which are a constant distance apart and try to form reuse
3700/// opportunities between them.
3701void LSRInstance::GenerateCrossUseConstantOffsets() {
3702 // Group the registers by their value without any added constant offset.
3703 typedef std::map<int64_t, const SCEV *> ImmMapTy;
3704 DenseMap<const SCEV *, ImmMapTy> Map;
3705 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3706 SmallVector<const SCEV *, 8> Sequence;
3707 for (const SCEV *Use : RegUses) {
3708 const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
3709 int64_t Imm = ExtractImmediate(Reg, SE);
3710 auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
3711 if (Pair.second)
3712 Sequence.push_back(Reg);
3713 Pair.first->second.insert(std::make_pair(Imm, Use));
3714 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
3715 }
3716
3717 // Now examine each set of registers with the same base value. Build up
3718 // a list of work to do and do the work in a separate step so that we're
3719 // not adding formulae and register counts while we're searching.
3720 SmallVector<WorkItem, 32> WorkItems;
3721 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3722 for (const SCEV *Reg : Sequence) {
3723 const ImmMapTy &Imms = Map.find(Reg)->second;
3724
3725 // It's not worthwhile looking for reuse if there's only one offset.
3726 if (Imms.size() == 1)
3727 continue;
3728
3729 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generating cross-use offsets for "
<< *Reg << ':'; for (const auto &Entry : Imms
) dbgs() << ' ' << Entry.first; dbgs() << '\n'
; } } while (false)
3730 for (const auto &Entry : Imms)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generating cross-use offsets for "
<< *Reg << ':'; for (const auto &Entry : Imms
) dbgs() << ' ' << Entry.first; dbgs() << '\n'
; } } while (false)
3731 dbgs() << ' ' << Entry.first;do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generating cross-use offsets for "
<< *Reg << ':'; for (const auto &Entry : Imms
) dbgs() << ' ' << Entry.first; dbgs() << '\n'
; } } while (false)
3732 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generating cross-use offsets for "
<< *Reg << ':'; for (const auto &Entry : Imms
) dbgs() << ' ' << Entry.first; dbgs() << '\n'
; } } while (false)
;
3733
3734 // Examine each offset.
3735 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3736 J != JE; ++J) {
3737 const SCEV *OrigReg = J->second;
3738
3739 int64_t JImm = J->first;
3740 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
3741
3742 if (!isa<SCEVConstant>(OrigReg) &&
3743 UsedByIndicesMap[Reg].count() == 1) {
3744 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Skipping cross-use reuse for "
<< *OrigReg << '\n'; } } while (false)
;
3745 continue;
3746 }
3747
3748 // Conservatively examine offsets between this orig reg a few selected
3749 // other orig regs.
3750 ImmMapTy::const_iterator OtherImms[] = {
3751 Imms.begin(), std::prev(Imms.end()),
3752 Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) /
3753 2)
3754 };
3755 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
3756 ImmMapTy::const_iterator M = OtherImms[i];
3757 if (M == J || M == JE) continue;
3758
3759 // Compute the difference between the two.
3760 int64_t Imm = (uint64_t)JImm - M->first;
3761 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
3762 LUIdx = UsedByIndices.find_next(LUIdx))
3763 // Make a memo of this use, offset, and register tuple.
3764 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
3765 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
3766 }
3767 }
3768 }
3769
3770 Map.clear();
3771 Sequence.clear();
3772 UsedByIndicesMap.clear();
3773 UniqueItems.clear();
3774
3775 // Now iterate through the worklist and add new formulae.
3776 for (const WorkItem &WI : WorkItems) {
3777 size_t LUIdx = WI.LUIdx;
3778 LSRUse &LU = Uses[LUIdx];
3779 int64_t Imm = WI.Imm;
3780 const SCEV *OrigReg = WI.OrigReg;
3781
3782 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
3783 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
3784 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
3785
3786 // TODO: Use a more targeted data structure.
3787 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
3788 Formula F = LU.Formulae[L];
3789 // FIXME: The code for the scaled and unscaled registers looks
3790 // very similar but slightly different. Investigate if they
3791 // could be merged. That way, we would not have to unscale the
3792 // Formula.
3793 F.unscale();
3794 // Use the immediate in the scaled register.
3795 if (F.ScaledReg == OrigReg) {
3796 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
3797 // Don't create 50 + reg(-50).
3798 if (F.referencesReg(SE.getSCEV(
3799 ConstantInt::get(IntTy, -(uint64_t)Offset))))
3800 continue;
3801 Formula NewF = F;
3802 NewF.BaseOffset = Offset;
3803 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3804 NewF))
3805 continue;
3806 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
3807
3808 // If the new scale is a constant in a register, and adding the constant
3809 // value to the immediate would produce a value closer to zero than the
3810 // immediate itself, then the formula isn't worthwhile.
3811 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
3812 if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
3813 (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
3814 .ule(std::abs(NewF.BaseOffset)))
3815 continue;
3816
3817 // OK, looks good.
3818 NewF.canonicalize();
3819 (void)InsertFormula(LU, LUIdx, NewF);
3820 } else {
3821 // Use the immediate in a base register.
3822 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
3823 const SCEV *BaseReg = F.BaseRegs[N];
3824 if (BaseReg != OrigReg)
3825 continue;
3826 Formula NewF = F;
3827 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
3828 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
3829 LU.Kind, LU.AccessTy, NewF)) {
3830 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
3831 continue;
3832 NewF = F;
3833 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
3834 }
3835 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
3836
3837 // If the new formula has a constant in a register, and adding the
3838 // constant value to the immediate would produce a value closer to
3839 // zero than the immediate itself, then the formula isn't worthwhile.
3840 for (const SCEV *NewReg : NewF.BaseRegs)
3841 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
3842 if ((C->getAPInt() + NewF.BaseOffset)
3843 .abs()
3844 .slt(std::abs(NewF.BaseOffset)) &&
3845 (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
3846 countTrailingZeros<uint64_t>(NewF.BaseOffset))
3847 goto skip_formula;
3848
3849 // Ok, looks good.
3850 NewF.canonicalize();
3851 (void)InsertFormula(LU, LUIdx, NewF);
3852 break;
3853 skip_formula:;
3854 }
3855 }
3856 }
3857 }
3858}
3859
3860/// Generate formulae for each use.
3861void
3862LSRInstance::GenerateAllReuseFormulae() {
3863 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
3864 // queries are more precise.
3865 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3866 LSRUse &LU = Uses[LUIdx];
3867 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3868 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
3869 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3870 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
3871 }
3872 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3873 LSRUse &LU = Uses[LUIdx];
3874 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3875 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
3876 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3877 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
3878 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3879 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
3880 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3881 GenerateScales(LU, LUIdx, LU.Formulae[i]);
3882 }
3883 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3884 LSRUse &LU = Uses[LUIdx];
3885 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3886 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
3887 }
3888
3889 GenerateCrossUseConstantOffsets();
3890
3891 DEBUG(dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
3892 "After generating reuse formulae:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
3893 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
;
3894}
3895
3896/// If there are multiple formulae with the same set of registers used
3897/// by other uses, pick the best one and delete the others.
3898void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
3899 DenseSet<const SCEV *> VisitedRegs;
3900 SmallPtrSet<const SCEV *, 16> Regs;
3901 SmallPtrSet<const SCEV *, 16> LoserRegs;
3902#ifndef NDEBUG
3903 bool ChangedFormulae = false;
3904#endif
3905
3906 // Collect the best formula for each unique set of shared registers. This
3907 // is reset for each use.
3908 typedef DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>
3909 BestFormulaeTy;
3910 BestFormulaeTy BestFormulae;
3911
3912 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3913 LSRUse &LU = Uses[LUIdx];
3914 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
3915
3916 bool Any = false;
3917 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
3918 FIdx != NumForms; ++FIdx) {
3919 Formula &F = LU.Formulae[FIdx];
3920
3921 // Some formulas are instant losers. For example, they may depend on
3922 // nonexistent AddRecs from other loops. These need to be filtered
3923 // immediately, otherwise heuristics could choose them over others leading
3924 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
3925 // avoids the need to recompute this information across formulae using the
3926 // same bad AddRec. Passing LoserRegs is also essential unless we remove
3927 // the corresponding bad register from the Regs set.
3928 Cost CostF;
3929 Regs.clear();
3930 CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, SE, DT, LU, &LoserRegs);
3931 if (CostF.isLoser()) {
3932 // During initial formula generation, undesirable formulae are generated
3933 // by uses within other loops that have some non-trivial address mode or
3934 // use the postinc form of the IV. LSR needs to provide these formulae
3935 // as the basis of rediscovering the desired formula that uses an AddRec
3936 // corresponding to the existing phi. Once all formulae have been
3937 // generated, these initial losers may be pruned.
3938 DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering loser "; F.print
(dbgs()); dbgs() << "\n"; } } while (false)
3939 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering loser "; F.print
(dbgs()); dbgs() << "\n"; } } while (false)
;
3940 }
3941 else {
3942 SmallVector<const SCEV *, 4> Key;
3943 for (const SCEV *Reg : F.BaseRegs) {
3944 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
3945 Key.push_back(Reg);
3946 }
3947 if (F.ScaledReg &&
3948 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
3949 Key.push_back(F.ScaledReg);
3950 // Unstable sort by host order ok, because this is only used for
3951 // uniquifying.
3952 std::sort(Key.begin(), Key.end());
3953
3954 std::pair<BestFormulaeTy::const_iterator, bool> P =
3955 BestFormulae.insert(std::make_pair(Key, FIdx));
3956 if (P.second)
3957 continue;
3958
3959 Formula &Best = LU.Formulae[P.first->second];
3960
3961 Cost CostBest;
3962 Regs.clear();
3963 CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, SE, DT, LU);
3964 if (CostF < CostBest)
3965 std::swap(F, Best);
3966 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
3967 dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
3968 " in favor of formula "; Best.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
3969 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
;
3970 }
3971#ifndef NDEBUG
3972 ChangedFormulae = true;
3973#endif
3974 LU.DeleteFormula(F);
3975 --FIdx;
3976 --NumForms;
3977 Any = true;
3978 }
3979
3980 // Now that we've filtered out some formulae, recompute the Regs set.
3981 if (Any)
3982 LU.RecomputeRegs(LUIdx, RegUses);
3983
3984 // Reset this to prepare for the next use.
3985 BestFormulae.clear();
3986 }
3987
3988 DEBUG(if (ChangedFormulae) {do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
3989 dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
3990 "After filtering out undesirable candidates:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
3991 print_uses(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
3992 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
3993}
3994
3995// This is a rough guess that seems to work fairly well.
3996static const size_t ComplexityLimit = UINT16_MAX(65535);
3997
3998/// Estimate the worst-case number of solutions the solver might have to
3999/// consider. It almost never considers this many solutions because it prune the
4000/// search space, but the pruning isn't always sufficient.
4001size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4002 size_t Power = 1;
4003 for (const LSRUse &LU : Uses) {
4004 size_t FSize = LU.Formulae.size();
4005 if (FSize >= ComplexityLimit) {
4006 Power = ComplexityLimit;
4007 break;
4008 }
4009 Power *= FSize;
4010 if (Power >= ComplexityLimit)
4011 break;
4012 }
4013 return Power;
4014}
4015
4016/// When one formula uses a superset of the registers of another formula, it
4017/// won't help reduce register pressure (though it may not necessarily hurt
4018/// register pressure); remove it to simplify the system.
4019void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4020 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4021 DEBUG(dbgs() << "The search space is too complex.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
; } } while (false)
;
4022
4023 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by eliminating formulae "
"which use a superset of registers used by other " "formulae.\n"
; } } while (false)
4024 "which use a superset of registers used by other "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by eliminating formulae "
"which use a superset of registers used by other " "formulae.\n"
; } } while (false)
4025 "formulae.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by eliminating formulae "
"which use a superset of registers used by other " "formulae.\n"
; } } while (false)
;
4026
4027 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4028 LSRUse &LU = Uses[LUIdx];
4029 bool Any = false;
4030 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4031 Formula &F = LU.Formulae[i];
4032 // Look for a formula with a constant or GV in a register. If the use
4033 // also has a formula with that same value in an immediate field,
4034 // delete the one that uses a register.
4035 for (SmallVectorImpl<const SCEV *>::const_iterator
4036 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4037 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4038 Formula NewF = F;
4039 NewF.BaseOffset += C->getValue()->getSExtValue();
4040 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4041 (I - F.BaseRegs.begin()));
4042 if (LU.HasFormulaWithSameRegs(NewF)) {
4043 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4044 LU.DeleteFormula(F);
4045 --i;
4046 --e;
4047 Any = true;
4048 break;
4049 }
4050 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4051 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4052 if (!F.BaseGV) {
4053 Formula NewF = F;
4054 NewF.BaseGV = GV;
4055 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4056 (I - F.BaseRegs.begin()));
4057 if (LU.HasFormulaWithSameRegs(NewF)) {
4058 DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4059 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4060 LU.DeleteFormula(F);
4061 --i;
4062 --e;
4063 Any = true;
4064 break;
4065 }
4066 }
4067 }
4068 }
4069 }
4070 if (Any)
4071 LU.RecomputeRegs(LUIdx, RegUses);
4072 }
4073
4074 DEBUG(dbgs() << "After pre-selection:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
4075 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4076 }
4077}
4078
4079/// When there are many registers for expressions like A, A+1, A+2, etc.,
4080/// allocate a single register for them.
4081void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4082 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4083 return;
4084
4085 DEBUG(dbgs() << "The search space is too complex.\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by assuming that uses separated "
"by a constant offset will use the same registers.\n"; } } while
(false)
4086 "Narrowing the search space by assuming that uses separated "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by assuming that uses separated "
"by a constant offset will use the same registers.\n"; } } while
(false)
4087 "by a constant offset will use the same registers.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by assuming that uses separated "
"by a constant offset will use the same registers.\n"; } } while
(false)
;
4088
4089 // This is especially useful for unrolled loops.
4090
4091 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4092 LSRUse &LU = Uses[LUIdx];
4093 for (const Formula &F : LU.Formulae) {
4094 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4095 continue;
4096
4097 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4098 if (!LUThatHas)
4099 continue;
4100
4101 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4102 LU.Kind, LU.AccessTy))
4103 continue;
4104
4105 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4106
4107 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4108
4109 // Transfer the fixups of LU to LUThatHas.
4110 for (LSRFixup &Fixup : LU.Fixups) {
4111 Fixup.Offset += F.BaseOffset;
4112 LUThatHas->pushFixup(Fixup);
4113 DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New fixup has offset " <<
Fixup.Offset << '\n'; } } while (false)
;
4114 }
4115
4116 // Delete formulae from the new use which are no longer legal.
4117 bool Any = false;
4118 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4119 Formula &F = LUThatHas->Formulae[i];
4120 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4121 LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4122 DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4123 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4124 LUThatHas->DeleteFormula(F);
4125 --i;
4126 --e;
4127 Any = true;
4128 }
4129 }
4130
4131 if (Any)
4132 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4133
4134 // Delete the old use.
4135 DeleteUse(LU, LUIdx);
4136 --LUIdx;
4137 --NumUses;
4138 break;
4139 }
4140 }
4141
4142 DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4143}
4144
4145/// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4146/// we've done more filtering, as it may be able to find more formulae to
4147/// eliminate.
4148void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4149 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4150 DEBUG(dbgs() << "The search space is too complex.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
; } } while (false)
;
4151
4152 DEBUG(dbgs() << "Narrowing the search space by re-filtering out "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by re-filtering out "
"undesirable dedicated registers.\n"; } } while (false)
4153 "undesirable dedicated registers.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by re-filtering out "
"undesirable dedicated registers.\n"; } } while (false)
;
4154
4155 FilterOutUndesirableDedicatedRegisters();
4156
4157 DEBUG(dbgs() << "After pre-selection:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
4158 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4159 }
4160}
4161
4162/// Pick a register which seems likely to be profitable, and then in any use
4163/// which has any reference to that register, delete all formulae which do not
4164/// reference that register.
4165void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4166 // With all other options exhausted, loop until the system is simple
4167 // enough to handle.
4168 SmallPtrSet<const SCEV *, 4> Taken;
4169 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4170 // Ok, we have too many of formulae on our hands to conveniently handle.
4171 // Use a rough heuristic to thin out the list.
4172 DEBUG(dbgs() << "The search space is too complex.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
; } } while (false)
;
4173
4174 // Pick the register which is used by the most LSRUses, which is likely
4175 // to be a good reuse register candidate.
4176 const SCEV *Best = nullptr;
4177 unsigned BestNum = 0;
4178 for (const SCEV *Reg : RegUses) {
4179 if (Taken.count(Reg))
4180 continue;
4181 if (!Best) {
4182 Best = Reg;
4183 BestNum = RegUses.getUsedByIndices(Reg).count();
4184 } else {
4185 unsigned Count = RegUses.getUsedByIndices(Reg).count();
4186 if (Count > BestNum) {
4187 Best = Reg;
4188 BestNum = Count;
4189 }
4190 }
4191 }
4192
4193 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Bestdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by assuming "
<< *Best << " will yield profitable reuse.\n"; }
} while (false)
4194 << " will yield profitable reuse.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by assuming "
<< *Best << " will yield profitable reuse.\n"; }
} while (false)
;
4195 Taken.insert(Best);
4196
4197 // In any use with formulae which references this register, delete formulae
4198 // which don't reference it.
4199 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4200 LSRUse &LU = Uses[LUIdx];
4201 if (!LU.Regs.count(Best)) continue;
4202
4203 bool Any = false;
4204 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4205 Formula &F = LU.Formulae[i];
4206 if (!F.referencesReg(Best)) {
4207 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4208 LU.DeleteFormula(F);
4209 --e;
4210 --i;
4211 Any = true;
4212 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?")((e != 0 && "Use has no formulae left! Is Regs inconsistent?"
) ? static_cast<void> (0) : __assert_fail ("e != 0 && \"Use has no formulae left! Is Regs inconsistent?\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4212, __PRETTY_FUNCTION__))
;
4213 continue;
4214 }
4215 }
4216
4217 if (Any)
4218 LU.RecomputeRegs(LUIdx, RegUses);
4219 }
4220
4221 DEBUG(dbgs() << "After pre-selection:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
4222 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4223 }
4224}
4225
4226/// If there are an extraordinary number of formulae to choose from, use some
4227/// rough heuristics to prune down the number of formulae. This keeps the main
4228/// solver from taking an extraordinary amount of time in some worst-case
4229/// scenarios.
4230void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4231 NarrowSearchSpaceByDetectingSupersets();
4232 NarrowSearchSpaceByCollapsingUnrolledCode();
4233 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4234 NarrowSearchSpaceByPickingWinnerRegs();
4235}
4236
4237/// This is the recursive solver.
4238void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4239 Cost &SolutionCost,
4240 SmallVectorImpl<const Formula *> &Workspace,
4241 const Cost &CurCost,
4242 const SmallPtrSet<const SCEV *, 16> &CurRegs,
4243 DenseSet<const SCEV *> &VisitedRegs) const {
4244 // Some ideas:
4245 // - prune more:
4246 // - use more aggressive filtering
4247 // - sort the formula so that the most profitable solutions are found first
4248 // - sort the uses too
4249 // - search faster:
4250 // - don't compute a cost, and then compare. compare while computing a cost
4251 // and bail early.
4252 // - track register sets with SmallBitVector
4253
4254 const LSRUse &LU = Uses[Workspace.size()];
4255
4256 // If this use references any register that's already a part of the
4257 // in-progress solution, consider it a requirement that a formula must
4258 // reference that register in order to be considered. This prunes out
4259 // unprofitable searching.
4260 SmallSetVector<const SCEV *, 4> ReqRegs;
4261 for (const SCEV *S : CurRegs)
4262 if (LU.Regs.count(S))
4263 ReqRegs.insert(S);
4264
4265 SmallPtrSet<const SCEV *, 16> NewRegs;
4266 Cost NewCost;
4267 for (const Formula &F : LU.Formulae) {
4268 // Ignore formulae which may not be ideal in terms of register reuse of
4269 // ReqRegs. The formula should use all required registers before
4270 // introducing new ones.
4271 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4272 for (const SCEV *Reg : ReqRegs) {
4273 if ((F.ScaledReg && F.ScaledReg == Reg) ||
4274 is_contained(F.BaseRegs, Reg)) {
4275 --NumReqRegsToFind;
4276 if (NumReqRegsToFind == 0)
4277 break;
4278 }
4279 }
4280 if (NumReqRegsToFind != 0) {
4281 // If none of the formulae satisfied the required registers, then we could
4282 // clear ReqRegs and try again. Currently, we simply give up in this case.
4283 continue;
4284 }
4285
4286 // Evaluate the cost of the current formula. If it's already worse than
4287 // the current best, prune the search at that point.
4288 NewCost = CurCost;
4289 NewRegs = CurRegs;
4290 NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, SE, DT, LU);
4291 if (NewCost < SolutionCost) {
4292 Workspace.push_back(&F);
4293 if (Workspace.size() != Uses.size()) {
4294 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4295 NewRegs, VisitedRegs);
4296 if (F.getNumRegs() == 1 && Workspace.size() == 1)
4297 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4298 } else {
4299 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
4300 dbgs() << ".\n Regs:";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
4301 for (const SCEV *S : NewRegs)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
4302 dbgs() << ' ' << *S;do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
4303 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
;
4304
4305 SolutionCost = NewCost;
4306 Solution = Workspace;
4307 }
4308 Workspace.pop_back();
4309 }
4310 }
4311}
4312
4313/// Choose one formula from each use. Return the results in the given Solution
4314/// vector.
4315void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4316 SmallVector<const Formula *, 8> Workspace;
4317 Cost SolutionCost;
4318 SolutionCost.Lose();
4319 Cost CurCost;
4320 SmallPtrSet<const SCEV *, 16> CurRegs;
4321 DenseSet<const SCEV *> VisitedRegs;
4322 Workspace.reserve(Uses.size());
4323
4324 // SolveRecurse does all the work.
4325 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4326 CurRegs, VisitedRegs);
4327 if (Solution.empty()) {
4328 DEBUG(dbgs() << "\nNo Satisfactory Solution\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nNo Satisfactory Solution\n"
; } } while (false)
;
4329 return;
4330 }
4331
4332 // Ok, we've now made all our decisions.
4333 DEBUG(dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4334 "The chosen solution requires "; SolutionCost.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4335 dbgs() << ":\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4336 for (size_t i = 0, e = Uses.size(); i != e; ++i) {do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4337 dbgs() << " ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4338 Uses[i].print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4339 dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4340 " ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4341 Solution[i]->print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4342 dbgs() << '\n';do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4343 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
;
4344
4345 assert(Solution.size() == Uses.size() && "Malformed solution!")((Solution.size() == Uses.size() && "Malformed solution!"
) ? static_cast<void> (0) : __assert_fail ("Solution.size() == Uses.size() && \"Malformed solution!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4345, __PRETTY_FUNCTION__))
;
4346}
4347
4348/// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
4349/// we can go while still being dominated by the input positions. This helps
4350/// canonicalize the insert position, which encourages sharing.
4351BasicBlock::iterator
4352LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4353 const SmallVectorImpl<Instruction *> &Inputs)
4354 const {
4355 Instruction *Tentative = &*IP;
4356 while (true) {
4357 bool AllDominate = true;
4358 Instruction *BetterPos = nullptr;
4359 // Don't bother attempting to insert before a catchswitch, their basic block
4360 // cannot have other non-PHI instructions.
4361 if (isa<CatchSwitchInst>(Tentative))
4362 return IP;
4363
4364 for (Instruction *Inst : Inputs) {
4365 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4366 AllDominate = false;
4367 break;
4368 }
4369 // Attempt to find an insert position in the middle of the block,
4370 // instead of at the end, so that it can be used for other expansions.
4371 if (Tentative->getParent() == Inst->getParent() &&
4372 (!BetterPos || !DT.dominates(Inst, BetterPos)))
4373 BetterPos = &*std::next(BasicBlock::iterator(Inst));
4374 }
4375 if (!AllDominate)
4376 break;
4377 if (BetterPos)
4378 IP = BetterPos->getIterator();
4379 else
4380 IP = Tentative->getIterator();
4381
4382 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4383 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4384
4385 BasicBlock *IDom;
4386 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4387 if (!Rung) return IP;
4388 Rung = Rung->getIDom();
4389 if (!Rung) return IP;
4390 IDom = Rung->getBlock();
4391
4392 // Don't climb into a loop though.
4393 const Loop *IDomLoop = LI.getLoopFor(IDom);
4394 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4395 if (IDomDepth <= IPLoopDepth &&
4396 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4397 break;
4398 }
4399
4400 Tentative = IDom->getTerminator();
4401 }
4402
4403 return IP;
4404}
4405
4406/// Determine an input position which will be dominated by the operands and
4407/// which will dominate the result.
4408BasicBlock::iterator
4409LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4410 const LSRFixup &LF,
4411 const LSRUse &LU,
4412 SCEVExpander &Rewriter) const {
4413 // Collect some instructions which must be dominated by the
4414 // expanding replacement. These must be dominated by any operands that
4415 // will be required in the expansion.
4416 SmallVector<Instruction *, 4> Inputs;
4417 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4418 Inputs.push_back(I);
4419 if (LU.Kind == LSRUse::ICmpZero)
4420 if (Instruction *I =
4421 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4422 Inputs.push_back(I);
4423 if (LF.PostIncLoops.count(L)) {
4424 if (LF.isUseFullyOutsideLoop(L))
4425 Inputs.push_back(L->getLoopLatch()->getTerminator());
4426 else
4427 Inputs.push_back(IVIncInsertPos);
4428 }
4429 // The expansion must also be dominated by the increment positions of any
4430 // loops it for which it is using post-inc mode.
4431 for (const Loop *PIL : LF.PostIncLoops) {
4432 if (PIL == L) continue;
4433
4434 // Be dominated by the loop exit.
4435 SmallVector<BasicBlock *, 4> ExitingBlocks;
4436 PIL->getExitingBlocks(ExitingBlocks);
4437 if (!ExitingBlocks.empty()) {
4438 BasicBlock *BB = ExitingBlocks[0];
4439 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4440 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4441 Inputs.push_back(BB->getTerminator());
4442 }
4443 }
4444
4445 assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad()((!isa<PHINode>(LowestIP) && !LowestIP->isEHPad
() && !isa<DbgInfoIntrinsic>(LowestIP) &&
"Insertion point must be a normal instruction") ? static_cast
<void> (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4447, __PRETTY_FUNCTION__))
4446 && !isa<DbgInfoIntrinsic>(LowestIP) &&((!isa<PHINode>(LowestIP) && !LowestIP->isEHPad
() && !isa<DbgInfoIntrinsic>(LowestIP) &&
"Insertion point must be a normal instruction") ? static_cast
<void> (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4447, __PRETTY_FUNCTION__))
4447 "Insertion point must be a normal instruction")((!isa<PHINode>(LowestIP) && !LowestIP->isEHPad
() && !isa<DbgInfoIntrinsic>(LowestIP) &&
"Insertion point must be a normal instruction") ? static_cast
<void> (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4447, __PRETTY_FUNCTION__))
;
4448
4449 // Then, climb up the immediate dominator tree as far as we can go while
4450 // still being dominated by the input positions.
4451 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4452
4453 // Don't insert instructions before PHI nodes.
4454 while (isa<PHINode>(IP)) ++IP;
4455
4456 // Ignore landingpad instructions.
4457 while (IP->isEHPad()) ++IP;
4458
4459 // Ignore debug intrinsics.
4460 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4461
4462 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4463 // IP consistent across expansions and allows the previously inserted
4464 // instructions to be reused by subsequent expansion.
4465 while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
4466 ++IP;
4467
4468 return IP;
4469}
4470
4471/// Emit instructions for the leading candidate expression for this LSRUse (this
4472/// is called "expanding").
4473Value *LSRInstance::Expand(const LSRUse &LU,
4474 const LSRFixup &LF,
4475 const Formula &F,
4476 BasicBlock::iterator IP,
4477 SCEVExpander &Rewriter,
4478 SmallVectorImpl<WeakVH> &DeadInsts) const {
4479 if (LU.RigidFormula)
4480 return LF.OperandValToReplace;
4481
4482 // Determine an input position which will be dominated by the operands and
4483 // which will dominate the result.
4484 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4485 Rewriter.setInsertPoint(&*IP);
4486
4487 // Inform the Rewriter if we have a post-increment use, so that it can
4488 // perform an advantageous expansion.
4489 Rewriter.setPostInc(LF.PostIncLoops);
4490
4491 // This is the type that the user actually needs.
4492 Type *OpTy = LF.OperandValToReplace->getType();
4493 // This will be the type that we'll initially expand to.
4494 Type *Ty = F.getType();
4495 if (!Ty)
4496 // No type known; just expand directly to the ultimate type.
4497 Ty = OpTy;
4498 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
4499 // Expand directly to the ultimate type if it's the right size.
4500 Ty = OpTy;
4501 // This is the type to do integer arithmetic in.
4502 Type *IntTy = SE.getEffectiveSCEVType(Ty);
4503
4504 // Build up a list of operands to add together to form the full base.
4505 SmallVector<const SCEV *, 8> Ops;
4506
4507 // Expand the BaseRegs portion.
4508 for (const SCEV *Reg : F.BaseRegs) {
4509 assert(!Reg->isZero() && "Zero allocated in a base register!")((!Reg->isZero() && "Zero allocated in a base register!"
) ? static_cast<void> (0) : __assert_fail ("!Reg->isZero() && \"Zero allocated in a base register!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4509, __PRETTY_FUNCTION__))
;
4510
4511 // If we're expanding for a post-inc user, make the post-inc adjustment.
4512 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4513 Reg = TransformForPostIncUse(Denormalize, Reg,
4514 LF.UserInst, LF.OperandValToReplace,
4515 Loops, SE, DT);
4516
4517 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
4518 }
4519
4520 // Expand the ScaledReg portion.
4521 Value *ICmpScaledV = nullptr;
4522 if (F.Scale != 0) {
4523 const SCEV *ScaledS = F.ScaledReg;
4524
4525 // If we're expanding for a post-inc user, make the post-inc adjustment.
4526 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4527 ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
4528 LF.UserInst, LF.OperandValToReplace,
4529 Loops, SE, DT);
4530
4531 if (LU.Kind == LSRUse::ICmpZero) {
4532 // Expand ScaleReg as if it was part of the base regs.
4533 if (F.Scale == 1)
4534 Ops.push_back(
4535 SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
4536 else {
4537 // An interesting way of "folding" with an icmp is to use a negated
4538 // scale, which we'll implement by inserting it into the other operand
4539 // of the icmp.
4540 assert(F.Scale == -1 &&((F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? static_cast<void> (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4541, __PRETTY_FUNCTION__))
4541 "The only scale supported by ICmpZero uses is -1!")((F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? static_cast<void> (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4541, __PRETTY_FUNCTION__))
;
4542 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
4543 }
4544 } else {
4545 // Otherwise just expand the scaled register and an explicit scale,
4546 // which is expected to be matched as part of the address.
4547
4548 // Flush the operand list to suppress SCEVExpander hoisting address modes.
4549 // Unless the addressing mode will not be folded.
4550 if (!Ops.empty() && LU.Kind == LSRUse::Address &&
4551 isAMCompletelyFolded(TTI, LU, F)) {
4552 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
4553 Ops.clear();
4554 Ops.push_back(SE.getUnknown(FullV));
4555 }
4556 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
4557 if (F.Scale != 1)
4558 ScaledS =
4559 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
4560 Ops.push_back(ScaledS);
4561 }
4562 }
4563
4564 // Expand the GV portion.
4565 if (F.BaseGV) {
4566 // Flush the operand list to suppress SCEVExpander hoisting.
4567 if (!Ops.empty()) {
4568 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
4569 Ops.clear();
4570 Ops.push_back(SE.getUnknown(FullV));
4571 }
4572 Ops.push_back(SE.getUnknown(F.BaseGV));
4573 }
4574
4575 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
4576 // unfolded offsets. LSR assumes they both live next to their uses.
4577 if (!Ops.empty()) {
4578 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
4579 Ops.clear();
4580 Ops.push_back(SE.getUnknown(FullV));
4581 }
4582
4583 // Expand the immediate portion.
4584 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
4585 if (Offset != 0) {
4586 if (LU.Kind == LSRUse::ICmpZero) {
4587 // The other interesting way of "folding" with an ICmpZero is to use a
4588 // negated immediate.
4589 if (!ICmpScaledV)
4590 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
4591 else {
4592 Ops.push_back(SE.getUnknown(ICmpScaledV));
4593 ICmpScaledV = ConstantInt::get(IntTy, Offset);
4594 }
4595 } else {
4596 // Just add the immediate values. These again are expected to be matched
4597 // as part of the address.
4598 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
4599 }
4600 }
4601
4602 // Expand the unfolded offset portion.
4603 int64_t UnfoldedOffset = F.UnfoldedOffset;
4604 if (UnfoldedOffset != 0) {
4605 // Just add the immediate values.
4606 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
4607 UnfoldedOffset)));
4608 }
4609
4610 // Emit instructions summing all the operands.
4611 const SCEV *FullS = Ops.empty() ?
4612 SE.getConstant(IntTy, 0) :
4613 SE.getAddExpr(Ops);
4614 Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
4615
4616 // We're done expanding now, so reset the rewriter.
4617 Rewriter.clearPostInc();
4618
4619 // An ICmpZero Formula represents an ICmp which we're handling as a
4620 // comparison against zero. Now that we've expanded an expression for that
4621 // form, update the ICmp's other operand.
4622 if (LU.Kind == LSRUse::ICmpZero) {
4623 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
4624 DeadInsts.emplace_back(CI->getOperand(1));
4625 assert(!F.BaseGV && "ICmp does not support folding a global value and "((!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("!F.BaseGV && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4626, __PRETTY_FUNCTION__))
4626 "a scale at the same time!")((!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("!F.BaseGV && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4626, __PRETTY_FUNCTION__))
;
4627 if (F.Scale == -1) {
4628 if (ICmpScaledV->getType() != OpTy) {
4629 Instruction *Cast =
4630 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
4631 OpTy, false),
4632 ICmpScaledV, OpTy, "tmp", CI);
4633 ICmpScaledV = Cast;
4634 }
4635 CI->setOperand(1, ICmpScaledV);
4636 } else {
4637 // A scale of 1 means that the scale has been expanded as part of the
4638 // base regs.
4639 assert((F.Scale == 0 || F.Scale == 1) &&(((F.Scale == 0 || F.Scale == 1) && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4641, __PRETTY_FUNCTION__))
4640 "ICmp does not support folding a global value and "(((F.Scale == 0 || F.Scale == 1) && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4641, __PRETTY_FUNCTION__))
4641 "a scale at the same time!")(((F.Scale == 0 || F.Scale == 1) && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4641, __PRETTY_FUNCTION__))
;
4642 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
4643 -(uint64_t)Offset);
4644 if (C->getType() != OpTy)
4645 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4646 OpTy, false),
4647 C, OpTy);
4648
4649 CI->setOperand(1, C);
4650 }
4651 }
4652
4653 return FullV;
4654}
4655
4656/// Helper for Rewrite. PHI nodes are special because the use of their operands
4657/// effectively happens in their predecessor blocks, so the expression may need
4658/// to be expanded in multiple places.
4659void LSRInstance::RewriteForPHI(PHINode *PN,
4660 const LSRUse &LU,
4661 const LSRFixup &LF,
4662 const Formula &F,
4663 SCEVExpander &Rewriter,
4664 SmallVectorImpl<WeakVH> &DeadInsts) const {
4665 DenseMap<BasicBlock *, Value *> Inserted;
4666 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
4667 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
4668 BasicBlock *BB = PN->getIncomingBlock(i);
4669
4670 // If this is a critical edge, split the edge so that we do not insert
4671 // the code on all predecessor/successor paths. We do this unless this
4672 // is the canonical backedge for this loop, which complicates post-inc
4673 // users.
4674 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
4675 !isa<IndirectBrInst>(BB->getTerminator())) {
4676 BasicBlock *Parent = PN->getParent();
4677 Loop *PNLoop = LI.getLoopFor(Parent);
4678 if (!PNLoop || Parent != PNLoop->getHeader()) {
4679 // Split the critical edge.
4680 BasicBlock *NewBB = nullptr;
4681 if (!Parent->isLandingPad()) {
4682 NewBB = SplitCriticalEdge(BB, Parent,
4683 CriticalEdgeSplittingOptions(&DT, &LI)
4684 .setMergeIdenticalEdges()
4685 .setDontDeleteUselessPHIs());
4686 } else {
4687 SmallVector<BasicBlock*, 2> NewBBs;
4688 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
4689 NewBB = NewBBs[0];
4690 }
4691 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
4692 // phi predecessors are identical. The simple thing to do is skip
4693 // splitting in this case rather than complicate the API.
4694 if (NewBB) {
4695 // If PN is outside of the loop and BB is in the loop, we want to
4696 // move the block to be immediately before the PHI block, not
4697 // immediately after BB.
4698 if (L->contains(BB) && !L->contains(PN))
4699 NewBB->moveBefore(PN->getParent());
4700
4701 // Splitting the edge can reduce the number of PHI entries we have.
4702 e = PN->getNumIncomingValues();
4703 BB = NewBB;
4704 i = PN->getBasicBlockIndex(BB);
4705 }
4706 }
4707 }
4708
4709 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
4710 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
4711 if (!Pair.second)
4712 PN->setIncomingValue(i, Pair.first->second);
4713 else {
4714 Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
4715 Rewriter, DeadInsts);
4716
4717 // If this is reuse-by-noop-cast, insert the noop cast.
4718 Type *OpTy = LF.OperandValToReplace->getType();
4719 if (FullV->getType() != OpTy)
4720 FullV =
4721 CastInst::Create(CastInst::getCastOpcode(FullV, false,
4722 OpTy, false),
4723 FullV, LF.OperandValToReplace->getType(),
4724 "tmp", BB->getTerminator());
4725
4726 PN->setIncomingValue(i, FullV);
4727 Pair.first->second = FullV;
4728 }
4729 }
4730}
4731
4732/// Emit instructions for the leading candidate expression for this LSRUse (this
4733/// is called "expanding"), and update the UserInst to reference the newly
4734/// expanded value.
4735void LSRInstance::Rewrite(const LSRUse &LU,
4736 const LSRFixup &LF,
4737 const Formula &F,
4738 SCEVExpander &Rewriter,
4739 SmallVectorImpl<WeakVH> &DeadInsts) const {
4740 // First, find an insertion point that dominates UserInst. For PHI nodes,
4741 // find the nearest block which dominates all the relevant uses.
4742 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
4743 RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
4744 } else {
4745 Value *FullV =
4746 Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
4747
4748 // If this is reuse-by-noop-cast, insert the noop cast.
4749 Type *OpTy = LF.OperandValToReplace->getType();
4750 if (FullV->getType() != OpTy) {
4751 Instruction *Cast =
4752 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
4753 FullV, OpTy, "tmp", LF.UserInst);
4754 FullV = Cast;
4755 }
4756
4757 // Update the user. ICmpZero is handled specially here (for now) because
4758 // Expand may have updated one of the operands of the icmp already, and
4759 // its new value may happen to be equal to LF.OperandValToReplace, in
4760 // which case doing replaceUsesOfWith leads to replacing both operands
4761 // with the same value. TODO: Reorganize this.
4762 if (LU.Kind == LSRUse::ICmpZero)
4763 LF.UserInst->setOperand(0, FullV);
4764 else
4765 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
4766 }
4767
4768 DeadInsts.emplace_back(LF.OperandValToReplace);
4769}
4770
4771/// Rewrite all the fixup locations with new values, following the chosen
4772/// solution.
4773void LSRInstance::ImplementSolution(
4774 const SmallVectorImpl<const Formula *> &Solution) {
4775 // Keep track of instructions we may have made dead, so that
4776 // we can remove them after we are done working.
4777 SmallVector<WeakVH, 16> DeadInsts;
4778
4779 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(),
4780 "lsr");
4781#ifndef NDEBUG
4782 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
4783#endif
4784 Rewriter.disableCanonicalMode();
4785 Rewriter.enableLSRMode();
4786 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
4787
4788 // Mark phi nodes that terminate chains so the expander tries to reuse them.
4789 for (const IVChain &Chain : IVChainVec) {
4790 if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
4791 Rewriter.setChainedPhi(PN);
4792 }
4793
4794 // Expand the new value definitions and update the users.
4795 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
4796 for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
4797 Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
4798 Changed = true;
4799 }
4800
4801 for (const IVChain &Chain : IVChainVec) {
4802 GenerateIVChain(Chain, Rewriter, DeadInsts);
4803 Changed = true;
4804 }
4805 // Clean up after ourselves. This must be done before deleting any
4806 // instructions.
4807 Rewriter.clear();
4808
4809 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
4810}
4811
4812LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
4813 DominatorTree &DT, LoopInfo &LI,
4814 const TargetTransformInfo &TTI)
4815 : IU(IU), SE(SE), DT(DT), LI(LI), TTI(TTI), L(L), Changed(false),
4816 IVIncInsertPos(nullptr) {
4817 // If LoopSimplify form is not available, stay out of trouble.
4818 if (!L->isLoopSimplifyForm())
4819 return;
4820
4821 // If there's no interesting work to be done, bail early.
4822 if (IU.empty()) return;
4823
4824 // If there's too much analysis to be done, bail early. We won't be able to
4825 // model the problem anyway.
4826 unsigned NumUsers = 0;
4827 for (const IVStrideUse &U : IU) {
4828 if (++NumUsers > MaxIVUsers) {
4829 (void)U;
4830 DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << U << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping loop, too many IV Users in "
<< U << "\n"; } } while (false)
;
4831 return;
4832 }
4833 // Bail out if we have a PHI on an EHPad that gets a value from a
4834 // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is
4835 // no good place to stick any instructions.
4836 if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
4837 auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
4838 if (isa<FuncletPadInst>(FirstNonPHI) ||
4839 isa<CatchSwitchInst>(FirstNonPHI))
4840 for (BasicBlock *PredBB : PN->blocks())
4841 if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
4842 return;
4843 }
4844 }
4845
4846#ifndef NDEBUG
4847 // All dominating loops must have preheaders, or SCEVExpander may not be able
4848 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
4849 //
4850 // IVUsers analysis should only create users that are dominated by simple loop
4851 // headers. Since this loop should dominate all of its users, its user list
4852 // should be empty if this loop itself is not within a simple loop nest.
4853 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
4854 Rung; Rung = Rung->getIDom()) {
4855 BasicBlock *BB = Rung->getBlock();
4856 const Loop *DomLoop = LI.getLoopFor(BB);
4857 if (DomLoop && DomLoop->getHeader() == BB) {
4858 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest")((DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest"
) ? static_cast<void> (0) : __assert_fail ("DomLoop->getLoopPreheader() && \"LSR needs a simplified loop nest\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4858, __PRETTY_FUNCTION__))
;
4859 }
4860 }
4861#endif // DEBUG
4862
4863 DEBUG(dbgs() << "\nLSR on loop ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
4864 L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false);do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
4865 dbgs() << ":\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
;
4866
4867 // First, perform some low-level loop optimizations.
4868 OptimizeShadowIV();
4869 OptimizeLoopTermCond();
4870
4871 // If loop preparation eliminates all interesting IV users, bail.
4872 if (IU.empty()) return;
4873
4874 // Skip nested loops until we can model them better with formulae.
4875 if (!L->empty()) {
4876 DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping outer loop "
<< *L << "\n"; } } while (false)
;
4877 return;
4878 }
4879
4880 // Start collecting data and preparing for the solver.
4881 CollectChains();
4882 CollectInterestingTypesAndFactors();
4883 CollectFixupsAndInitialFormulae();
4884 CollectLoopInvariantFixupsAndFormulae();
4885
4886 assert(!Uses.empty() && "IVUsers reported at least one use")((!Uses.empty() && "IVUsers reported at least one use"
) ? static_cast<void> (0) : __assert_fail ("!Uses.empty() && \"IVUsers reported at least one use\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4886, __PRETTY_FUNCTION__))
;
4887 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR found " << Uses
.size() << " uses:\n"; print_uses(dbgs()); } } while (false
)
4888 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR found " << Uses
.size() << " uses:\n"; print_uses(dbgs()); } } while (false
)
;
4889
4890 // Now use the reuse data to generate a bunch of interesting ways
4891 // to formulate the values needed for the uses.
4892 GenerateAllReuseFormulae();
4893
4894 FilterOutUndesirableDedicatedRegisters();
4895 NarrowSearchSpaceUsingHeuristics();
4896
4897 SmallVector<const Formula *, 8> Solution;
4898 Solve(Solution);
4899
4900 // Release memory that is no longer needed.
4901 Factors.clear();
4902 Types.clear();
4903 RegUses.clear();
4904
4905 if (Solution.empty())
4906 return;
4907
4908#ifndef NDEBUG
4909 // Formulae should be legal.
4910 for (const LSRUse &LU : Uses) {
4911 for (const Formula &F : LU.Formulae)
4912 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Illegal formula generated!") ? static_cast<
void> (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Illegal formula generated!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4913, __PRETTY_FUNCTION__))
4913 F) && "Illegal formula generated!")((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Illegal formula generated!") ? static_cast<
void> (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Illegal formula generated!\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4913, __PRETTY_FUNCTION__))
;
4914 };
4915#endif
4916
4917 // Now that we've decided what we want, make it so.
4918 ImplementSolution(Solution);
4919}
4920
4921void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
4922 if (Factors.empty() && Types.empty()) return;
4923
4924 OS << "LSR has identified the following interesting factors and types: ";
4925 bool First = true;
4926
4927 for (int64_t Factor : Factors) {
4928 if (!First) OS << ", ";
4929 First = false;
4930 OS << '*' << Factor;
4931 }
4932
4933 for (Type *Ty : Types) {
4934 if (!First) OS << ", ";
4935 First = false;
4936 OS << '(' << *Ty << ')';
4937 }
4938 OS << '\n';
4939}
4940
4941void LSRInstance::print_fixups(raw_ostream &OS) const {
4942 OS << "LSR is examining the following fixup sites:\n";
4943 for (const LSRUse &LU : Uses)
4944 for (const LSRFixup &LF : LU.Fixups) {
4945 dbgs() << " ";
4946 LF.print(OS);
4947 OS << '\n';
4948 }
4949}
4950
4951void LSRInstance::print_uses(raw_ostream &OS) const {
4952 OS << "LSR is examining the following uses:\n";
4953 for (const LSRUse &LU : Uses) {
4954 dbgs() << " ";
4955 LU.print(OS);
4956 OS << '\n';
4957 for (const Formula &F : LU.Formulae) {
4958 OS << " ";
4959 F.print(OS);
4960 OS << '\n';
4961 }
4962 }
4963}
4964
4965void LSRInstance::print(raw_ostream &OS) const {
4966 print_factors_and_types(OS);
4967 print_fixups(OS);
4968 print_uses(OS);
4969}
4970
4971LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__))
4972void LSRInstance::dump() const {
4973 print(errs()); errs() << '\n';
4974}
4975
4976namespace {
4977
4978class LoopStrengthReduce : public LoopPass {
4979public:
4980 static char ID; // Pass ID, replacement for typeid
4981
4982 LoopStrengthReduce();
4983
4984private:
4985 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
4986 void getAnalysisUsage(AnalysisUsage &AU) const override;
4987};
4988
4989} // end anonymous namespace
4990
4991LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
4992 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
4993}
4994
4995void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
4996 // We split critical edges, so we change the CFG. However, we do update
4997 // many analyses if they are around.
4998 AU.addPreservedID(LoopSimplifyID);
4999
5000 AU.addRequired<LoopInfoWrapperPass>();
5001 AU.addPreserved<LoopInfoWrapperPass>();
5002 AU.addRequiredID(LoopSimplifyID);
5003 AU.addRequired<DominatorTreeWrapperPass>();
5004 AU.addPreserved<DominatorTreeWrapperPass>();
5005 AU.addRequired<ScalarEvolutionWrapperPass>();
5006 AU.addPreserved<ScalarEvolutionWrapperPass>();
5007 // Requiring LoopSimplify a second time here prevents IVUsers from running
5008 // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5009 AU.addRequiredID(LoopSimplifyID);
5010 AU.addRequired<IVUsersWrapperPass>();
5011 AU.addPreserved<IVUsersWrapperPass>();
5012 AU.addRequired<TargetTransformInfoWrapperPass>();
5013}
5014
5015static bool ReduceLoopStrength(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5016 DominatorTree &DT, LoopInfo &LI,
5017 const TargetTransformInfo &TTI) {
5018 bool Changed = false;
5019
5020 // Run the main LSR transformation.
5021 Changed |= LSRInstance(L, IU, SE, DT, LI, TTI).getChanged();
5022
5023 // Remove any extra phis created by processing inner loops.
5024 Changed |= DeleteDeadPHIs(L->getHeader());
5025 if (EnablePhiElim && L->isLoopSimplifyForm()) {
5026 SmallVector<WeakVH, 16> DeadInsts;
5027 const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
5028 SCEVExpander Rewriter(SE, DL, "lsr");
5029#ifndef NDEBUG
5030 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5031#endif
5032 unsigned numFolded = Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, &TTI);
5033 if (numFolded) {
5034 Changed = true;
5035 DeleteTriviallyDeadInstructions(DeadInsts);
5036 DeleteDeadPHIs(L->getHeader());
5037 }
5038 }
5039 return Changed;
5040}
5041
5042bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5043 if (skipLoop(L))
5044 return false;
5045
5046 auto &IU = getAnalysis<IVUsersWrapperPass>().getIU();
5047 auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
5048 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
5049 auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
5050 const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
5051 *L->getHeader()->getParent());
5052 return ReduceLoopStrength(L, IU, SE, DT, LI, TTI);
5053}
5054
5055PreservedAnalyses LoopStrengthReducePass::run(Loop &L,
5056 LoopAnalysisManager &AM) {
5057 const auto &FAM =
5058 AM.getResult<FunctionAnalysisManagerLoopProxy>(L).getManager();
5059 Function *F = L.getHeader()->getParent();
5060
5061 auto &IU = AM.getResult<IVUsersAnalysis>(L);
5062 auto *SE = FAM.getCachedResult<ScalarEvolutionAnalysis>(*F);
5063 auto *DT = FAM.getCachedResult<DominatorTreeAnalysis>(*F);
5064 auto *LI = FAM.getCachedResult<LoopAnalysis>(*F);
5065 auto *TTI = FAM.getCachedResult<TargetIRAnalysis>(*F);
5066 assert((SE && DT && LI && TTI) &&(((SE && DT && LI && TTI) && "Analyses for Loop Strength Reduce not available"
) ? static_cast<void> (0) : __assert_fail ("(SE && DT && LI && TTI) && \"Analyses for Loop Strength Reduce not available\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5067, __PRETTY_FUNCTION__))
5067 "Analyses for Loop Strength Reduce not available")(((SE && DT && LI && TTI) && "Analyses for Loop Strength Reduce not available"
) ? static_cast<void> (0) : __assert_fail ("(SE && DT && LI && TTI) && \"Analyses for Loop Strength Reduce not available\""
, "/tmp/buildd/llvm-toolchain-snapshot-4.0~svn290870/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5067, __PRETTY_FUNCTION__))
;
5068
5069 if (!ReduceLoopStrength(&L, IU, *SE, *DT, *LI, *TTI))
5070 return PreservedAnalyses::all();
5071
5072 return getLoopPassPreservedAnalyses();
5073}
5074
5075char LoopStrengthReduce::ID = 0;
5076INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",static void *initializeLoopStrengthReducePassOnce(PassRegistry
&Registry) {
5077 "Loop Strength Reduction", false, false)static void *initializeLoopStrengthReducePassOnce(PassRegistry
&Registry) {
5078INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry);
5079INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
5080INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)initializeScalarEvolutionWrapperPassPass(Registry);
5081INITIALIZE_PASS_DEPENDENCY(IVUsersWrapperPass)initializeIVUsersWrapperPassPass(Registry);
5082INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry);
5083INITIALIZE_PASS_DEPENDENCY(LoopSimplify)initializeLoopSimplifyPass(Registry);
5084INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",PassInfo *PI = new PassInfo( "Loop Strength Reduction", "loop-reduce"
, &LoopStrengthReduce::ID, PassInfo::NormalCtor_t(callDefaultCtor
<LoopStrengthReduce>), false, false); Registry.registerPass
(*PI, true); return PI; } static once_flag InitializeLoopStrengthReducePassFlag
; void llvm::initializeLoopStrengthReducePass(PassRegistry &
Registry) { llvm::call_once(InitializeLoopStrengthReducePassFlag
, initializeLoopStrengthReducePassOnce, std::ref(Registry)); }
5085 "Loop Strength Reduction", false, false)PassInfo *PI = new PassInfo( "Loop Strength Reduction", "loop-reduce"
, &LoopStrengthReduce::ID, PassInfo::NormalCtor_t(callDefaultCtor
<LoopStrengthReduce>), false, false); Registry.registerPass
(*PI, true); return PI; } static once_flag InitializeLoopStrengthReducePassFlag
; void llvm::initializeLoopStrengthReducePass(PassRegistry &
Registry) { llvm::call_once(InitializeLoopStrengthReducePassFlag
, initializeLoopStrengthReducePassOnce, std::ref(Registry)); }
5086
5087Pass *llvm::createLoopStrengthReducePass() { return new LoopStrengthReduce(); }