Bug Summary

File:lib/Transforms/Scalar/LoopStrengthReduce.cpp
Warning:line 5350, column 22
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name LoopStrengthReduce.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-9/lib/clang/9.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-9~svn362543/build-llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-9~svn362543/build-llvm/include -I /build/llvm-toolchain-snapshot-9~svn362543/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/include/clang/9.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-9/lib/clang/9.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-9~svn362543/build-llvm/lib/Transforms/Scalar -fdebug-prefix-map=/build/llvm-toolchain-snapshot-9~svn362543=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2019-06-05-060531-1271-1 -x c++ /build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp -faddrsig
1//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This transformation analyzes and transforms the induction variables (and
10// computations derived from them) into forms suitable for efficient execution
11// on the target.
12//
13// This pass performs a strength reduction on array references inside loops that
14// have as one or more of their components the loop induction variable, it
15// rewrites expressions to take advantage of scaled-index addressing modes
16// available on the target, and it performs a variety of other optimizations
17// related to loop induction variables.
18//
19// Terminology note: this code has a lot of handling for "post-increment" or
20// "post-inc" users. This is not talking about post-increment addressing modes;
21// it is instead talking about code like this:
22//
23// %i = phi [ 0, %entry ], [ %i.next, %latch ]
24// ...
25// %i.next = add %i, 1
26// %c = icmp eq %i.next, %n
27//
28// The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
29// it's useful to think about these as the same register, with some uses using
30// the value of the register before the add and some using it after. In this
31// example, the icmp is a post-increment user, since it uses %i.next, which is
32// the value of the induction variable after the increment. The other common
33// case of post-increment users is users outside the loop.
34//
35// TODO: More sophistication in the way Formulae are generated and filtered.
36//
37// TODO: Handle multiple loops at a time.
38//
39// TODO: Should the addressing mode BaseGV be changed to a ConstantExpr instead
40// of a GlobalValue?
41//
42// TODO: When truncation is free, truncate ICmp users' operands to make it a
43// smaller encoding (on x86 at least).
44//
45// TODO: When a negated register is used by an add (such as in a list of
46// multiple base registers, or as the increment expression in an addrec),
47// we may not actually need both reg and (-1 * reg) in registers; the
48// negation can be implemented by using a sub instead of an add. The
49// lack of support for taking this into consideration when making
50// register pressure decisions is partly worked around by the "Special"
51// use kind.
52//
53//===----------------------------------------------------------------------===//
54
55#include "llvm/Transforms/Scalar/LoopStrengthReduce.h"
56#include "llvm/ADT/APInt.h"
57#include "llvm/ADT/DenseMap.h"
58#include "llvm/ADT/DenseSet.h"
59#include "llvm/ADT/Hashing.h"
60#include "llvm/ADT/PointerIntPair.h"
61#include "llvm/ADT/STLExtras.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/iterator_range.h"
68#include "llvm/Analysis/IVUsers.h"
69#include "llvm/Analysis/LoopAnalysisManager.h"
70#include "llvm/Analysis/LoopInfo.h"
71#include "llvm/Analysis/LoopPass.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/Transforms/Utils/Local.h"
78#include "llvm/Config/llvm-config.h"
79#include "llvm/IR/BasicBlock.h"
80#include "llvm/IR/Constant.h"
81#include "llvm/IR/Constants.h"
82#include "llvm/IR/DerivedTypes.h"
83#include "llvm/IR/Dominators.h"
84#include "llvm/IR/GlobalValue.h"
85#include "llvm/IR/IRBuilder.h"
86#include "llvm/IR/InstrTypes.h"
87#include "llvm/IR/Instruction.h"
88#include "llvm/IR/Instructions.h"
89#include "llvm/IR/IntrinsicInst.h"
90#include "llvm/IR/Intrinsics.h"
91#include "llvm/IR/Module.h"
92#include "llvm/IR/OperandTraits.h"
93#include "llvm/IR/Operator.h"
94#include "llvm/IR/PassManager.h"
95#include "llvm/IR/Type.h"
96#include "llvm/IR/Use.h"
97#include "llvm/IR/User.h"
98#include "llvm/IR/Value.h"
99#include "llvm/IR/ValueHandle.h"
100#include "llvm/Pass.h"
101#include "llvm/Support/Casting.h"
102#include "llvm/Support/CommandLine.h"
103#include "llvm/Support/Compiler.h"
104#include "llvm/Support/Debug.h"
105#include "llvm/Support/ErrorHandling.h"
106#include "llvm/Support/MathExtras.h"
107#include "llvm/Support/raw_ostream.h"
108#include "llvm/Transforms/Scalar.h"
109#include "llvm/Transforms/Utils.h"
110#include "llvm/Transforms/Utils/BasicBlockUtils.h"
111#include <algorithm>
112#include <cassert>
113#include <cstddef>
114#include <cstdint>
115#include <cstdlib>
116#include <iterator>
117#include <limits>
118#include <numeric>
119#include <map>
120#include <utility>
121
122using namespace llvm;
123
124#define DEBUG_TYPE"loop-reduce" "loop-reduce"
125
126/// MaxIVUsers is an arbitrary threshold that provides an early opportunity for
127/// bail out. This threshold is far beyond the number of users that LSR can
128/// conceivably solve, so it should not affect generated code, but catches the
129/// worst cases before LSR burns too much compile time and stack space.
130static const unsigned MaxIVUsers = 200;
131
132// Temporary flag to cleanup congruent phis after LSR phi expansion.
133// It's currently disabled until we can determine whether it's truly useful or
134// not. The flag should be removed after the v3.0 release.
135// This is now needed for ivchains.
136static cl::opt<bool> EnablePhiElim(
137 "enable-lsr-phielim", cl::Hidden, cl::init(true),
138 cl::desc("Enable LSR phi elimination"));
139
140// The flag adds instruction count to solutions cost comparision.
141static cl::opt<bool> InsnsCost(
142 "lsr-insns-cost", cl::Hidden, cl::init(true),
143 cl::desc("Add instruction count to a LSR cost model"));
144
145// Flag to choose how to narrow complex lsr solution
146static cl::opt<bool> LSRExpNarrow(
147 "lsr-exp-narrow", cl::Hidden, cl::init(false),
148 cl::desc("Narrow LSR complex solution using"
149 " expectation of registers number"));
150
151// Flag to narrow search space by filtering non-optimal formulae with
152// the same ScaledReg and Scale.
153static cl::opt<bool> FilterSameScaledReg(
154 "lsr-filter-same-scaled-reg", cl::Hidden, cl::init(true),
155 cl::desc("Narrow LSR search space by filtering non-optimal formulae"
156 " with the same ScaledReg and Scale"));
157
158static cl::opt<bool> EnableBackedgeIndexing(
159 "lsr-backedge-indexing", cl::Hidden, cl::init(true),
160 cl::desc("Enable the generation of cross iteration indexed memops"));
161
162static cl::opt<unsigned> ComplexityLimit(
163 "lsr-complexity-limit", cl::Hidden,
164 cl::init(std::numeric_limits<uint16_t>::max()),
165 cl::desc("LSR search space complexity limit"));
166
167static cl::opt<unsigned> SetupCostDepthLimit(
168 "lsr-setupcost-depth-limit", cl::Hidden, cl::init(7),
169 cl::desc("The limit on recursion depth for LSRs setup cost"));
170
171#ifndef NDEBUG
172// Stress test IV chain generation.
173static cl::opt<bool> StressIVChain(
174 "stress-ivchain", cl::Hidden, cl::init(false),
175 cl::desc("Stress test LSR IV chains"));
176#else
177static bool StressIVChain = false;
178#endif
179
180namespace {
181
182struct MemAccessTy {
183 /// Used in situations where the accessed memory type is unknown.
184 static const unsigned UnknownAddressSpace =
185 std::numeric_limits<unsigned>::max();
186
187 Type *MemTy = nullptr;
188 unsigned AddrSpace = UnknownAddressSpace;
189
190 MemAccessTy() = default;
191 MemAccessTy(Type *Ty, unsigned AS) : MemTy(Ty), AddrSpace(AS) {}
192
193 bool operator==(MemAccessTy Other) const {
194 return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace;
195 }
196
197 bool operator!=(MemAccessTy Other) const { return !(*this == Other); }
198
199 static MemAccessTy getUnknown(LLVMContext &Ctx,
200 unsigned AS = UnknownAddressSpace) {
201 return MemAccessTy(Type::getVoidTy(Ctx), AS);
202 }
203
204 Type *getType() { return MemTy; }
205};
206
207/// This class holds data which is used to order reuse candidates.
208class RegSortData {
209public:
210 /// This represents the set of LSRUse indices which reference
211 /// a particular register.
212 SmallBitVector UsedByIndices;
213
214 void print(raw_ostream &OS) const;
215 void dump() const;
216};
217
218} // end anonymous namespace
219
220#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
221void RegSortData::print(raw_ostream &OS) const {
222 OS << "[NumUses=" << UsedByIndices.count() << ']';
223}
224
225LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void RegSortData::dump() const {
226 print(errs()); errs() << '\n';
227}
228#endif
229
230namespace {
231
232/// Map register candidates to information about how they are used.
233class RegUseTracker {
234 using RegUsesTy = DenseMap<const SCEV *, RegSortData>;
235
236 RegUsesTy RegUsesMap;
237 SmallVector<const SCEV *, 16> RegSequence;
238
239public:
240 void countRegister(const SCEV *Reg, size_t LUIdx);
241 void dropRegister(const SCEV *Reg, size_t LUIdx);
242 void swapAndDropUse(size_t LUIdx, size_t LastLUIdx);
243
244 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
245
246 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
247
248 void clear();
249
250 using iterator = SmallVectorImpl<const SCEV *>::iterator;
251 using const_iterator = SmallVectorImpl<const SCEV *>::const_iterator;
252
253 iterator begin() { return RegSequence.begin(); }
254 iterator end() { return RegSequence.end(); }
255 const_iterator begin() const { return RegSequence.begin(); }
256 const_iterator end() const { return RegSequence.end(); }
257};
258
259} // end anonymous namespace
260
261void
262RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) {
263 std::pair<RegUsesTy::iterator, bool> Pair =
264 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
265 RegSortData &RSD = Pair.first->second;
266 if (Pair.second)
267 RegSequence.push_back(Reg);
268 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
269 RSD.UsedByIndices.set(LUIdx);
270}
271
272void
273RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) {
274 RegUsesTy::iterator It = RegUsesMap.find(Reg);
275 assert(It != RegUsesMap.end())((It != RegUsesMap.end()) ? static_cast<void> (0) : __assert_fail
("It != RegUsesMap.end()", "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 275, __PRETTY_FUNCTION__))
;
276 RegSortData &RSD = It->second;
277 assert(RSD.UsedByIndices.size() > LUIdx)((RSD.UsedByIndices.size() > LUIdx) ? static_cast<void>
(0) : __assert_fail ("RSD.UsedByIndices.size() > LUIdx", "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 277, __PRETTY_FUNCTION__))
;
278 RSD.UsedByIndices.reset(LUIdx);
279}
280
281void
282RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
283 assert(LUIdx <= LastLUIdx)((LUIdx <= LastLUIdx) ? static_cast<void> (0) : __assert_fail
("LUIdx <= LastLUIdx", "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 283, __PRETTY_FUNCTION__))
;
284
285 // Update RegUses. The data structure is not optimized for this purpose;
286 // we must iterate through it and update each of the bit vectors.
287 for (auto &Pair : RegUsesMap) {
288 SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
289 if (LUIdx < UsedByIndices.size())
290 UsedByIndices[LUIdx] =
291 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false;
292 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
293 }
294}
295
296bool
297RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
298 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
299 if (I == RegUsesMap.end())
300 return false;
301 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
302 int i = UsedByIndices.find_first();
303 if (i == -1) return false;
304 if ((size_t)i != LUIdx) return true;
305 return UsedByIndices.find_next(i) != -1;
306}
307
308const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
309 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
310 assert(I != RegUsesMap.end() && "Unknown register!")((I != RegUsesMap.end() && "Unknown register!") ? static_cast
<void> (0) : __assert_fail ("I != RegUsesMap.end() && \"Unknown register!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 310, __PRETTY_FUNCTION__))
;
311 return I->second.UsedByIndices;
312}
313
314void RegUseTracker::clear() {
315 RegUsesMap.clear();
316 RegSequence.clear();
317}
318
319namespace {
320
321/// This class holds information that describes a formula for computing
322/// satisfying a use. It may include broken-out immediates and scaled registers.
323struct Formula {
324 /// Global base address used for complex addressing.
325 GlobalValue *BaseGV = nullptr;
326
327 /// Base offset for complex addressing.
328 int64_t BaseOffset = 0;
329
330 /// Whether any complex addressing has a base register.
331 bool HasBaseReg = false;
332
333 /// The scale of any complex addressing.
334 int64_t Scale = 0;
335
336 /// The list of "base" registers for this use. When this is non-empty. The
337 /// canonical representation of a formula is
338 /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
339 /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
340 /// 3. The reg containing recurrent expr related with currect loop in the
341 /// formula should be put in the ScaledReg.
342 /// #1 enforces that the scaled register is always used when at least two
343 /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
344 /// #2 enforces that 1 * reg is reg.
345 /// #3 ensures invariant regs with respect to current loop can be combined
346 /// together in LSR codegen.
347 /// This invariant can be temporarily broken while building a formula.
348 /// However, every formula inserted into the LSRInstance must be in canonical
349 /// form.
350 SmallVector<const SCEV *, 4> BaseRegs;
351
352 /// The 'scaled' register for this use. This should be non-null when Scale is
353 /// not zero.
354 const SCEV *ScaledReg = nullptr;
355
356 /// An additional constant offset which added near the use. This requires a
357 /// temporary register, but the offset itself can live in an add immediate
358 /// field rather than a register.
359 int64_t UnfoldedOffset = 0;
360
361 Formula() = default;
362
363 void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
364
365 bool isCanonical(const Loop &L) const;
366
367 void canonicalize(const Loop &L);
368
369 bool unscale();
370
371 bool hasZeroEnd() const;
372
373 size_t getNumRegs() const;
374 Type *getType() const;
375
376 void deleteBaseReg(const SCEV *&S);
377
378 bool referencesReg(const SCEV *S) const;
379 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
380 const RegUseTracker &RegUses) const;
381
382 void print(raw_ostream &OS) const;
383 void dump() const;
384};
385
386} // end anonymous namespace
387
388/// Recursion helper for initialMatch.
389static void DoInitialMatch(const SCEV *S, Loop *L,
390 SmallVectorImpl<const SCEV *> &Good,
391 SmallVectorImpl<const SCEV *> &Bad,
392 ScalarEvolution &SE) {
393 // Collect expressions which properly dominate the loop header.
394 if (SE.properlyDominates(S, L->getHeader())) {
395 Good.push_back(S);
396 return;
397 }
398
399 // Look at add operands.
400 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
401 for (const SCEV *S : Add->operands())
402 DoInitialMatch(S, L, Good, Bad, SE);
403 return;
404 }
405
406 // Look at addrec operands.
407 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
408 if (!AR->getStart()->isZero() && AR->isAffine()) {
409 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
410 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
411 AR->getStepRecurrence(SE),
412 // FIXME: AR->getNoWrapFlags()
413 AR->getLoop(), SCEV::FlagAnyWrap),
414 L, Good, Bad, SE);
415 return;
416 }
417
418 // Handle a multiplication by -1 (negation) if it didn't fold.
419 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
420 if (Mul->getOperand(0)->isAllOnesValue()) {
421 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
422 const SCEV *NewMul = SE.getMulExpr(Ops);
423
424 SmallVector<const SCEV *, 4> MyGood;
425 SmallVector<const SCEV *, 4> MyBad;
426 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
427 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
428 SE.getEffectiveSCEVType(NewMul->getType())));
429 for (const SCEV *S : MyGood)
430 Good.push_back(SE.getMulExpr(NegOne, S));
431 for (const SCEV *S : MyBad)
432 Bad.push_back(SE.getMulExpr(NegOne, S));
433 return;
434 }
435
436 // Ok, we can't do anything interesting. Just stuff the whole thing into a
437 // register and hope for the best.
438 Bad.push_back(S);
439}
440
441/// Incorporate loop-variant parts of S into this Formula, attempting to keep
442/// all loop-invariant and loop-computable values in a single base register.
443void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
444 SmallVector<const SCEV *, 4> Good;
445 SmallVector<const SCEV *, 4> Bad;
446 DoInitialMatch(S, L, Good, Bad, SE);
447 if (!Good.empty()) {
448 const SCEV *Sum = SE.getAddExpr(Good);
449 if (!Sum->isZero())
450 BaseRegs.push_back(Sum);
451 HasBaseReg = true;
452 }
453 if (!Bad.empty()) {
454 const SCEV *Sum = SE.getAddExpr(Bad);
455 if (!Sum->isZero())
456 BaseRegs.push_back(Sum);
457 HasBaseReg = true;
458 }
459 canonicalize(*L);
460}
461
462/// Check whether or not this formula satisfies the canonical
463/// representation.
464/// \see Formula::BaseRegs.
465bool Formula::isCanonical(const Loop &L) const {
466 if (!ScaledReg)
467 return BaseRegs.size() <= 1;
468
469 if (Scale != 1)
470 return true;
471
472 if (Scale == 1 && BaseRegs.empty())
473 return false;
474
475 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
476 if (SAR && SAR->getLoop() == &L)
477 return true;
478
479 // If ScaledReg is not a recurrent expr, or it is but its loop is not current
480 // loop, meanwhile BaseRegs contains a recurrent expr reg related with current
481 // loop, we want to swap the reg in BaseRegs with ScaledReg.
482 auto I =
483 find_if(make_range(BaseRegs.begin(), BaseRegs.end()), [&](const SCEV *S) {
484 return isa<const SCEVAddRecExpr>(S) &&
485 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
486 });
487 return I == BaseRegs.end();
488}
489
490/// Helper method to morph a formula into its canonical representation.
491/// \see Formula::BaseRegs.
492/// Every formula having more than one base register, must use the ScaledReg
493/// field. Otherwise, we would have to do special cases everywhere in LSR
494/// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
495/// On the other hand, 1*reg should be canonicalized into reg.
496void Formula::canonicalize(const Loop &L) {
497 if (isCanonical(L))
498 return;
499 // So far we did not need this case. This is easy to implement but it is
500 // useless to maintain dead code. Beside it could hurt compile time.
501 assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.")((!BaseRegs.empty() && "1*reg => reg, should not be needed."
) ? static_cast<void> (0) : __assert_fail ("!BaseRegs.empty() && \"1*reg => reg, should not be needed.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 501, __PRETTY_FUNCTION__))
;
502
503 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
504 if (!ScaledReg) {
505 ScaledReg = BaseRegs.back();
506 BaseRegs.pop_back();
507 Scale = 1;
508 }
509
510 // If ScaledReg is an invariant with respect to L, find the reg from
511 // BaseRegs containing the recurrent expr related with Loop L. Swap the
512 // reg with ScaledReg.
513 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
514 if (!SAR || SAR->getLoop() != &L) {
515 auto I = find_if(make_range(BaseRegs.begin(), BaseRegs.end()),
516 [&](const SCEV *S) {
517 return isa<const SCEVAddRecExpr>(S) &&
518 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
519 });
520 if (I != BaseRegs.end())
521 std::swap(ScaledReg, *I);
522 }
523}
524
525/// Get rid of the scale in the formula.
526/// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
527/// \return true if it was possible to get rid of the scale, false otherwise.
528/// \note After this operation the formula may not be in the canonical form.
529bool Formula::unscale() {
530 if (Scale != 1)
531 return false;
532 Scale = 0;
533 BaseRegs.push_back(ScaledReg);
534 ScaledReg = nullptr;
535 return true;
536}
537
538bool Formula::hasZeroEnd() const {
539 if (UnfoldedOffset || BaseOffset)
540 return false;
541 if (BaseRegs.size() != 1 || ScaledReg)
542 return false;
543 return true;
544}
545
546/// Return the total number of register operands used by this formula. This does
547/// not include register uses implied by non-constant addrec strides.
548size_t Formula::getNumRegs() const {
549 return !!ScaledReg + BaseRegs.size();
550}
551
552/// Return the type of this formula, if it has one, or null otherwise. This type
553/// is meaningless except for the bit size.
554Type *Formula::getType() const {
555 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
556 ScaledReg ? ScaledReg->getType() :
557 BaseGV ? BaseGV->getType() :
558 nullptr;
559}
560
561/// Delete the given base reg from the BaseRegs list.
562void Formula::deleteBaseReg(const SCEV *&S) {
563 if (&S != &BaseRegs.back())
564 std::swap(S, BaseRegs.back());
565 BaseRegs.pop_back();
566}
567
568/// Test if this formula references the given register.
569bool Formula::referencesReg(const SCEV *S) const {
570 return S == ScaledReg || is_contained(BaseRegs, S);
571}
572
573/// Test whether this formula uses registers which are used by uses other than
574/// the use with the given index.
575bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
576 const RegUseTracker &RegUses) const {
577 if (ScaledReg)
578 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
579 return true;
580 for (const SCEV *BaseReg : BaseRegs)
581 if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
582 return true;
583 return false;
584}
585
586#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
587void Formula::print(raw_ostream &OS) const {
588 bool First = true;
589 if (BaseGV) {
590 if (!First) OS << " + "; else First = false;
591 BaseGV->printAsOperand(OS, /*PrintType=*/false);
592 }
593 if (BaseOffset != 0) {
594 if (!First) OS << " + "; else First = false;
595 OS << BaseOffset;
596 }
597 for (const SCEV *BaseReg : BaseRegs) {
598 if (!First) OS << " + "; else First = false;
599 OS << "reg(" << *BaseReg << ')';
600 }
601 if (HasBaseReg && BaseRegs.empty()) {
602 if (!First) OS << " + "; else First = false;
603 OS << "**error: HasBaseReg**";
604 } else if (!HasBaseReg && !BaseRegs.empty()) {
605 if (!First) OS << " + "; else First = false;
606 OS << "**error: !HasBaseReg**";
607 }
608 if (Scale != 0) {
609 if (!First) OS << " + "; else First = false;
610 OS << Scale << "*reg(";
611 if (ScaledReg)
612 OS << *ScaledReg;
613 else
614 OS << "<unknown>";
615 OS << ')';
616 }
617 if (UnfoldedOffset != 0) {
618 if (!First) OS << " + ";
619 OS << "imm(" << UnfoldedOffset << ')';
620 }
621}
622
623LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Formula::dump() const {
624 print(errs()); errs() << '\n';
625}
626#endif
627
628/// Return true if the given addrec can be sign-extended without changing its
629/// value.
630static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
631 Type *WideTy =
632 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
633 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
634}
635
636/// Return true if the given add can be sign-extended without changing its
637/// value.
638static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
639 Type *WideTy =
640 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
641 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
642}
643
644/// Return true if the given mul can be sign-extended without changing its
645/// value.
646static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
647 Type *WideTy =
648 IntegerType::get(SE.getContext(),
649 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
650 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
651}
652
653/// Return an expression for LHS /s RHS, if it can be determined and if the
654/// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
655/// is true, expressions like (X * Y) /s Y are simplified to Y, ignoring that
656/// the multiplication may overflow, which is useful when the result will be
657/// used in a context where the most significant bits are ignored.
658static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
659 ScalarEvolution &SE,
660 bool IgnoreSignificantBits = false) {
661 // Handle the trivial case, which works for any SCEV type.
662 if (LHS == RHS)
663 return SE.getConstant(LHS->getType(), 1);
664
665 // Handle a few RHS special cases.
666 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
667 if (RC) {
668 const APInt &RA = RC->getAPInt();
669 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
670 // some folding.
671 if (RA.isAllOnesValue())
672 return SE.getMulExpr(LHS, RC);
673 // Handle x /s 1 as x.
674 if (RA == 1)
675 return LHS;
676 }
677
678 // Check for a division of a constant by a constant.
679 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
680 if (!RC)
681 return nullptr;
682 const APInt &LA = C->getAPInt();
683 const APInt &RA = RC->getAPInt();
684 if (LA.srem(RA) != 0)
685 return nullptr;
686 return SE.getConstant(LA.sdiv(RA));
687 }
688
689 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
690 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
691 if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
692 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
693 IgnoreSignificantBits);
694 if (!Step) return nullptr;
695 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
696 IgnoreSignificantBits);
697 if (!Start) return nullptr;
698 // FlagNW is independent of the start value, step direction, and is
699 // preserved with smaller magnitude steps.
700 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
701 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
702 }
703 return nullptr;
704 }
705
706 // Distribute the sdiv over add operands, if the add doesn't overflow.
707 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
708 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
709 SmallVector<const SCEV *, 8> Ops;
710 for (const SCEV *S : Add->operands()) {
711 const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
712 if (!Op) return nullptr;
713 Ops.push_back(Op);
714 }
715 return SE.getAddExpr(Ops);
716 }
717 return nullptr;
718 }
719
720 // Check for a multiply operand that we can pull RHS out of.
721 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
722 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
723 SmallVector<const SCEV *, 4> Ops;
724 bool Found = false;
725 for (const SCEV *S : Mul->operands()) {
726 if (!Found)
727 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
728 IgnoreSignificantBits)) {
729 S = Q;
730 Found = true;
731 }
732 Ops.push_back(S);
733 }
734 return Found ? SE.getMulExpr(Ops) : nullptr;
735 }
736 return nullptr;
737 }
738
739 // Otherwise we don't know.
740 return nullptr;
741}
742
743/// If S involves the addition of a constant integer value, return that integer
744/// value, and mutate S to point to a new SCEV with that value excluded.
745static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
746 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
747 if (C->getAPInt().getMinSignedBits() <= 64) {
748 S = SE.getConstant(C->getType(), 0);
749 return C->getValue()->getSExtValue();
750 }
751 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
752 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
753 int64_t Result = ExtractImmediate(NewOps.front(), SE);
754 if (Result != 0)
755 S = SE.getAddExpr(NewOps);
756 return Result;
757 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
758 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
759 int64_t Result = ExtractImmediate(NewOps.front(), SE);
760 if (Result != 0)
761 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
762 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
763 SCEV::FlagAnyWrap);
764 return Result;
765 }
766 return 0;
767}
768
769/// If S involves the addition of a GlobalValue address, return that symbol, and
770/// mutate S to point to a new SCEV with that value excluded.
771static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
772 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
773 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
774 S = SE.getConstant(GV->getType(), 0);
775 return GV;
776 }
777 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
778 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
779 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
780 if (Result)
781 S = SE.getAddExpr(NewOps);
782 return Result;
783 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
784 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
785 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
786 if (Result)
787 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
788 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
789 SCEV::FlagAnyWrap);
790 return Result;
791 }
792 return nullptr;
793}
794
795/// Returns true if the specified instruction is using the specified value as an
796/// address.
797static bool isAddressUse(const TargetTransformInfo &TTI,
798 Instruction *Inst, Value *OperandVal) {
799 bool isAddress = isa<LoadInst>(Inst);
800 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
801 if (SI->getPointerOperand() == OperandVal)
802 isAddress = true;
803 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
804 // Addressing modes can also be folded into prefetches and a variety
805 // of intrinsics.
806 switch (II->getIntrinsicID()) {
807 case Intrinsic::memset:
808 case Intrinsic::prefetch:
809 if (II->getArgOperand(0) == OperandVal)
810 isAddress = true;
811 break;
812 case Intrinsic::memmove:
813 case Intrinsic::memcpy:
814 if (II->getArgOperand(0) == OperandVal ||
815 II->getArgOperand(1) == OperandVal)
816 isAddress = true;
817 break;
818 default: {
819 MemIntrinsicInfo IntrInfo;
820 if (TTI.getTgtMemIntrinsic(II, IntrInfo)) {
821 if (IntrInfo.PtrVal == OperandVal)
822 isAddress = true;
823 }
824 }
825 }
826 } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
827 if (RMW->getPointerOperand() == OperandVal)
828 isAddress = true;
829 } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
830 if (CmpX->getPointerOperand() == OperandVal)
831 isAddress = true;
832 }
833 return isAddress;
834}
835
836/// Return the type of the memory being accessed.
837static MemAccessTy getAccessType(const TargetTransformInfo &TTI,
838 Instruction *Inst, Value *OperandVal) {
839 MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
840 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
841 AccessTy.MemTy = SI->getOperand(0)->getType();
842 AccessTy.AddrSpace = SI->getPointerAddressSpace();
843 } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
844 AccessTy.AddrSpace = LI->getPointerAddressSpace();
845 } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
846 AccessTy.AddrSpace = RMW->getPointerAddressSpace();
847 } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
848 AccessTy.AddrSpace = CmpX->getPointerAddressSpace();
849 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
850 switch (II->getIntrinsicID()) {
851 case Intrinsic::prefetch:
852 case Intrinsic::memset:
853 AccessTy.AddrSpace = II->getArgOperand(0)->getType()->getPointerAddressSpace();
854 AccessTy.MemTy = OperandVal->getType();
855 break;
856 case Intrinsic::memmove:
857 case Intrinsic::memcpy:
858 AccessTy.AddrSpace = OperandVal->getType()->getPointerAddressSpace();
859 AccessTy.MemTy = OperandVal->getType();
860 break;
861 default: {
862 MemIntrinsicInfo IntrInfo;
863 if (TTI.getTgtMemIntrinsic(II, IntrInfo) && IntrInfo.PtrVal) {
864 AccessTy.AddrSpace
865 = IntrInfo.PtrVal->getType()->getPointerAddressSpace();
866 }
867
868 break;
869 }
870 }
871 }
872
873 // All pointers have the same requirements, so canonicalize them to an
874 // arbitrary pointer type to minimize variation.
875 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
876 AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
877 PTy->getAddressSpace());
878
879 return AccessTy;
880}
881
882/// Return true if this AddRec is already a phi in its loop.
883static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
884 for (PHINode &PN : AR->getLoop()->getHeader()->phis()) {
885 if (SE.isSCEVable(PN.getType()) &&
886 (SE.getEffectiveSCEVType(PN.getType()) ==
887 SE.getEffectiveSCEVType(AR->getType())) &&
888 SE.getSCEV(&PN) == AR)
889 return true;
890 }
891 return false;
892}
893
894/// Check if expanding this expression is likely to incur significant cost. This
895/// is tricky because SCEV doesn't track which expressions are actually computed
896/// by the current IR.
897///
898/// We currently allow expansion of IV increments that involve adds,
899/// multiplication by constants, and AddRecs from existing phis.
900///
901/// TODO: Allow UDivExpr if we can find an existing IV increment that is an
902/// obvious multiple of the UDivExpr.
903static bool isHighCostExpansion(const SCEV *S,
904 SmallPtrSetImpl<const SCEV*> &Processed,
905 ScalarEvolution &SE) {
906 // Zero/One operand expressions
907 switch (S->getSCEVType()) {
908 case scUnknown:
909 case scConstant:
910 return false;
911 case scTruncate:
912 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
913 Processed, SE);
914 case scZeroExtend:
915 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
916 Processed, SE);
917 case scSignExtend:
918 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
919 Processed, SE);
920 }
921
922 if (!Processed.insert(S).second)
923 return false;
924
925 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
926 for (const SCEV *S : Add->operands()) {
927 if (isHighCostExpansion(S, Processed, SE))
928 return true;
929 }
930 return false;
931 }
932
933 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
934 if (Mul->getNumOperands() == 2) {
935 // Multiplication by a constant is ok
936 if (isa<SCEVConstant>(Mul->getOperand(0)))
937 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
938
939 // If we have the value of one operand, check if an existing
940 // multiplication already generates this expression.
941 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
942 Value *UVal = U->getValue();
943 for (User *UR : UVal->users()) {
944 // If U is a constant, it may be used by a ConstantExpr.
945 Instruction *UI = dyn_cast<Instruction>(UR);
946 if (UI && UI->getOpcode() == Instruction::Mul &&
947 SE.isSCEVable(UI->getType())) {
948 return SE.getSCEV(UI) == Mul;
949 }
950 }
951 }
952 }
953 }
954
955 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
956 if (isExistingPhi(AR, SE))
957 return false;
958 }
959
960 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
961 return true;
962}
963
964/// If any of the instructions in the specified set are trivially dead, delete
965/// them and see if this makes any of their operands subsequently dead.
966static bool
967DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
968 bool Changed = false;
969
970 while (!DeadInsts.empty()) {
971 Value *V = DeadInsts.pop_back_val();
972 Instruction *I = dyn_cast_or_null<Instruction>(V);
973
974 if (!I || !isInstructionTriviallyDead(I))
975 continue;
976
977 for (Use &O : I->operands())
978 if (Instruction *U = dyn_cast<Instruction>(O)) {
979 O = nullptr;
980 if (U->use_empty())
981 DeadInsts.emplace_back(U);
982 }
983
984 I->eraseFromParent();
985 Changed = true;
986 }
987
988 return Changed;
989}
990
991namespace {
992
993class LSRUse;
994
995} // end anonymous namespace
996
997/// Check if the addressing mode defined by \p F is completely
998/// folded in \p LU at isel time.
999/// This includes address-mode folding and special icmp tricks.
1000/// This function returns true if \p LU can accommodate what \p F
1001/// defines and up to 1 base + 1 scaled + offset.
1002/// In other words, if \p F has several base registers, this function may
1003/// still return true. Therefore, users still need to account for
1004/// additional base registers and/or unfolded offsets to derive an
1005/// accurate cost model.
1006static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1007 const LSRUse &LU, const Formula &F);
1008
1009// Get the cost of the scaling factor used in F for LU.
1010static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1011 const LSRUse &LU, const Formula &F,
1012 const Loop &L);
1013
1014namespace {
1015
1016/// This class is used to measure and compare candidate formulae.
1017class Cost {
1018 const Loop *L = nullptr;
1019 ScalarEvolution *SE = nullptr;
1020 const TargetTransformInfo *TTI = nullptr;
1021 TargetTransformInfo::LSRCost C;
1022
1023public:
1024 Cost() = delete;
1025 Cost(const Loop *L, ScalarEvolution &SE, const TargetTransformInfo &TTI) :
1026 L(L), SE(&SE), TTI(&TTI) {
1027 C.Insns = 0;
1028 C.NumRegs = 0;
1029 C.AddRecCost = 0;
1030 C.NumIVMuls = 0;
1031 C.NumBaseAdds = 0;
1032 C.ImmCost = 0;
1033 C.SetupCost = 0;
1034 C.ScaleCost = 0;
1035 }
1036
1037 bool isLess(Cost &Other);
1038
1039 void Lose();
1040
1041#ifndef NDEBUG
1042 // Once any of the metrics loses, they must all remain losers.
1043 bool isValid() {
1044 return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds
1045 | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u)
1046 || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds
1047 & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u);
1048 }
1049#endif
1050
1051 bool isLoser() {
1052 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1052, __PRETTY_FUNCTION__))
;
1053 return C.NumRegs == ~0u;
1054 }
1055
1056 void RateFormula(const Formula &F,
1057 SmallPtrSetImpl<const SCEV *> &Regs,
1058 const DenseSet<const SCEV *> &VisitedRegs,
1059 const LSRUse &LU,
1060 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
1061
1062 void print(raw_ostream &OS) const;
1063 void dump() const;
1064
1065private:
1066 void RateRegister(const Formula &F, const SCEV *Reg,
1067 SmallPtrSetImpl<const SCEV *> &Regs);
1068 void RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1069 SmallPtrSetImpl<const SCEV *> &Regs,
1070 SmallPtrSetImpl<const SCEV *> *LoserRegs);
1071};
1072
1073/// An operand value in an instruction which is to be replaced with some
1074/// equivalent, possibly strength-reduced, replacement.
1075struct LSRFixup {
1076 /// The instruction which will be updated.
1077 Instruction *UserInst = nullptr;
1078
1079 /// The operand of the instruction which will be replaced. The operand may be
1080 /// used more than once; every instance will be replaced.
1081 Value *OperandValToReplace = nullptr;
1082
1083 /// If this user is to use the post-incremented value of an induction
1084 /// variable, this set is non-empty and holds the loops associated with the
1085 /// induction variable.
1086 PostIncLoopSet PostIncLoops;
1087
1088 /// A constant offset to be added to the LSRUse expression. This allows
1089 /// multiple fixups to share the same LSRUse with different offsets, for
1090 /// example in an unrolled loop.
1091 int64_t Offset = 0;
1092
1093 LSRFixup() = default;
1094
1095 bool isUseFullyOutsideLoop(const Loop *L) const;
1096
1097 void print(raw_ostream &OS) const;
1098 void dump() const;
1099};
1100
1101/// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
1102/// SmallVectors of const SCEV*.
1103struct UniquifierDenseMapInfo {
1104 static SmallVector<const SCEV *, 4> getEmptyKey() {
1105 SmallVector<const SCEV *, 4> V;
1106 V.push_back(reinterpret_cast<const SCEV *>(-1));
1107 return V;
1108 }
1109
1110 static SmallVector<const SCEV *, 4> getTombstoneKey() {
1111 SmallVector<const SCEV *, 4> V;
1112 V.push_back(reinterpret_cast<const SCEV *>(-2));
1113 return V;
1114 }
1115
1116 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1117 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1118 }
1119
1120 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1121 const SmallVector<const SCEV *, 4> &RHS) {
1122 return LHS == RHS;
1123 }
1124};
1125
1126/// This class holds the state that LSR keeps for each use in IVUsers, as well
1127/// as uses invented by LSR itself. It includes information about what kinds of
1128/// things can be folded into the user, information about the user itself, and
1129/// information about how the use may be satisfied. TODO: Represent multiple
1130/// users of the same expression in common?
1131class LSRUse {
1132 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1133
1134public:
1135 /// An enum for a kind of use, indicating what types of scaled and immediate
1136 /// operands it might support.
1137 enum KindType {
1138 Basic, ///< A normal use, with no folding.
1139 Special, ///< A special case of basic, allowing -1 scales.
1140 Address, ///< An address use; folding according to TargetLowering
1141 ICmpZero ///< An equality icmp with both operands folded into one.
1142 // TODO: Add a generic icmp too?
1143 };
1144
1145 using SCEVUseKindPair = PointerIntPair<const SCEV *, 2, KindType>;
1146
1147 KindType Kind;
1148 MemAccessTy AccessTy;
1149
1150 /// The list of operands which are to be replaced.
1151 SmallVector<LSRFixup, 8> Fixups;
1152
1153 /// Keep track of the min and max offsets of the fixups.
1154 int64_t MinOffset = std::numeric_limits<int64_t>::max();
1155 int64_t MaxOffset = std::numeric_limits<int64_t>::min();
1156
1157 /// This records whether all of the fixups using this LSRUse are outside of
1158 /// the loop, in which case some special-case heuristics may be used.
1159 bool AllFixupsOutsideLoop = true;
1160
1161 /// RigidFormula is set to true to guarantee that this use will be associated
1162 /// with a single formula--the one that initially matched. Some SCEV
1163 /// expressions cannot be expanded. This allows LSR to consider the registers
1164 /// used by those expressions without the need to expand them later after
1165 /// changing the formula.
1166 bool RigidFormula = false;
1167
1168 /// This records the widest use type for any fixup using this
1169 /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1170 /// fixup widths to be equivalent, because the narrower one may be relying on
1171 /// the implicit truncation to truncate away bogus bits.
1172 Type *WidestFixupType = nullptr;
1173
1174 /// A list of ways to build a value that can satisfy this user. After the
1175 /// list is populated, one of these is selected heuristically and used to
1176 /// formulate a replacement for OperandValToReplace in UserInst.
1177 SmallVector<Formula, 12> Formulae;
1178
1179 /// The set of register candidates used by all formulae in this LSRUse.
1180 SmallPtrSet<const SCEV *, 4> Regs;
1181
1182 LSRUse(KindType K, MemAccessTy AT) : Kind(K), AccessTy(AT) {}
1183
1184 LSRFixup &getNewFixup() {
1185 Fixups.push_back(LSRFixup());
1186 return Fixups.back();
1187 }
1188
1189 void pushFixup(LSRFixup &f) {
1190 Fixups.push_back(f);
1191 if (f.Offset > MaxOffset)
1192 MaxOffset = f.Offset;
1193 if (f.Offset < MinOffset)
1194 MinOffset = f.Offset;
1195 }
1196
1197 bool HasFormulaWithSameRegs(const Formula &F) const;
1198 float getNotSelectedProbability(const SCEV *Reg) const;
1199 bool InsertFormula(const Formula &F, const Loop &L);
1200 void DeleteFormula(Formula &F);
1201 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1202
1203 void print(raw_ostream &OS) const;
1204 void dump() const;
1205};
1206
1207} // end anonymous namespace
1208
1209static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1210 LSRUse::KindType Kind, MemAccessTy AccessTy,
1211 GlobalValue *BaseGV, int64_t BaseOffset,
1212 bool HasBaseReg, int64_t Scale,
1213 Instruction *Fixup = nullptr);
1214
1215static unsigned getSetupCost(const SCEV *Reg, unsigned Depth) {
1216 if (isa<SCEVUnknown>(Reg) || isa<SCEVConstant>(Reg))
1217 return 1;
1218 if (Depth == 0)
1219 return 0;
1220 if (const auto *S = dyn_cast<SCEVAddRecExpr>(Reg))
1221 return getSetupCost(S->getStart(), Depth - 1);
1222 if (auto S = dyn_cast<SCEVCastExpr>(Reg))
1223 return getSetupCost(S->getOperand(), Depth - 1);
1224 if (auto S = dyn_cast<SCEVNAryExpr>(Reg))
1225 return std::accumulate(S->op_begin(), S->op_end(), 0,
1226 [&](unsigned i, const SCEV *Reg) {
1227 return i + getSetupCost(Reg, Depth - 1);
1228 });
1229 if (auto S = dyn_cast<SCEVUDivExpr>(Reg))
1230 return getSetupCost(S->getLHS(), Depth - 1) +
1231 getSetupCost(S->getRHS(), Depth - 1);
1232 return 0;
1233}
1234
1235/// Tally up interesting quantities from the given register.
1236void Cost::RateRegister(const Formula &F, const SCEV *Reg,
1237 SmallPtrSetImpl<const SCEV *> &Regs) {
1238 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1239 // If this is an addrec for another loop, it should be an invariant
1240 // with respect to L since L is the innermost loop (at least
1241 // for now LSR only handles innermost loops).
1242 if (AR->getLoop() != L) {
1243 // If the AddRec exists, consider it's register free and leave it alone.
1244 if (isExistingPhi(AR, *SE))
1245 return;
1246
1247 // It is bad to allow LSR for current loop to add induction variables
1248 // for its sibling loops.
1249 if (!AR->getLoop()->contains(L)) {
1250 Lose();
1251 return;
1252 }
1253
1254 // Otherwise, it will be an invariant with respect to Loop L.
1255 ++C.NumRegs;
1256 return;
1257 }
1258
1259 unsigned LoopCost = 1;
1260 if (TTI->isIndexedLoadLegal(TTI->MIM_PostInc, AR->getType()) ||
1261 TTI->isIndexedStoreLegal(TTI->MIM_PostInc, AR->getType())) {
1262
1263 // If the step size matches the base offset, we could use pre-indexed
1264 // addressing.
1265 if (TTI->shouldFavorBackedgeIndex(L)) {
1266 if (auto *Step = dyn_cast<SCEVConstant>(AR->getStepRecurrence(*SE)))
1267 if (Step->getAPInt() == F.BaseOffset)
1268 LoopCost = 0;
1269 }
1270
1271 if (TTI->shouldFavorPostInc()) {
1272 const SCEV *LoopStep = AR->getStepRecurrence(*SE);
1273 if (isa<SCEVConstant>(LoopStep)) {
1274 const SCEV *LoopStart = AR->getStart();
1275 if (!isa<SCEVConstant>(LoopStart) &&
1276 SE->isLoopInvariant(LoopStart, L))
1277 LoopCost = 0;
1278 }
1279 }
1280 }
1281 C.AddRecCost += LoopCost;
1282
1283 // Add the step value register, if it needs one.
1284 // TODO: The non-affine case isn't precisely modeled here.
1285 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1286 if (!Regs.count(AR->getOperand(1))) {
1287 RateRegister(F, AR->getOperand(1), Regs);
1288 if (isLoser())
1289 return;
1290 }
1291 }
1292 }
1293 ++C.NumRegs;
1294
1295 // Rough heuristic; favor registers which don't require extra setup
1296 // instructions in the preheader.
1297 C.SetupCost += getSetupCost(Reg, SetupCostDepthLimit);
1298 // Ensure we don't, even with the recusion limit, produce invalid costs.
1299 C.SetupCost = std::min<unsigned>(C.SetupCost, 1 << 16);
1300
1301 C.NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1302 SE->hasComputableLoopEvolution(Reg, L);
1303}
1304
1305/// Record this register in the set. If we haven't seen it before, rate
1306/// it. Optional LoserRegs provides a way to declare any formula that refers to
1307/// one of those regs an instant loser.
1308void Cost::RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1309 SmallPtrSetImpl<const SCEV *> &Regs,
1310 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1311 if (LoserRegs && LoserRegs->count(Reg)) {
1312 Lose();
1313 return;
1314 }
1315 if (Regs.insert(Reg).second) {
1316 RateRegister(F, Reg, Regs);
1317 if (LoserRegs && isLoser())
1318 LoserRegs->insert(Reg);
1319 }
1320}
1321
1322void Cost::RateFormula(const Formula &F,
1323 SmallPtrSetImpl<const SCEV *> &Regs,
1324 const DenseSet<const SCEV *> &VisitedRegs,
1325 const LSRUse &LU,
1326 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1327 assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula")((F.isCanonical(*L) && "Cost is accurate only for canonical formula"
) ? static_cast<void> (0) : __assert_fail ("F.isCanonical(*L) && \"Cost is accurate only for canonical formula\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1327, __PRETTY_FUNCTION__))
;
1328 // Tally up the registers.
1329 unsigned PrevAddRecCost = C.AddRecCost;
1330 unsigned PrevNumRegs = C.NumRegs;
1331 unsigned PrevNumBaseAdds = C.NumBaseAdds;
1332 if (const SCEV *ScaledReg = F.ScaledReg) {
1333 if (VisitedRegs.count(ScaledReg)) {
1334 Lose();
1335 return;
1336 }
1337 RatePrimaryRegister(F, ScaledReg, Regs, LoserRegs);
1338 if (isLoser())
1339 return;
1340 }
1341 for (const SCEV *BaseReg : F.BaseRegs) {
1342 if (VisitedRegs.count(BaseReg)) {
1343 Lose();
1344 return;
1345 }
1346 RatePrimaryRegister(F, BaseReg, Regs, LoserRegs);
1347 if (isLoser())
1348 return;
1349 }
1350
1351 // Determine how many (unfolded) adds we'll need inside the loop.
1352 size_t NumBaseParts = F.getNumRegs();
1353 if (NumBaseParts > 1)
1354 // Do not count the base and a possible second register if the target
1355 // allows to fold 2 registers.
1356 C.NumBaseAdds +=
1357 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(*TTI, LU, F)));
1358 C.NumBaseAdds += (F.UnfoldedOffset != 0);
1359
1360 // Accumulate non-free scaling amounts.
1361 C.ScaleCost += getScalingFactorCost(*TTI, LU, F, *L);
1362
1363 // Tally up the non-zero immediates.
1364 for (const LSRFixup &Fixup : LU.Fixups) {
1365 int64_t O = Fixup.Offset;
1366 int64_t Offset = (uint64_t)O + F.BaseOffset;
1367 if (F.BaseGV)
1368 C.ImmCost += 64; // Handle symbolic values conservatively.
1369 // TODO: This should probably be the pointer size.
1370 else if (Offset != 0)
1371 C.ImmCost += APInt(64, Offset, true).getMinSignedBits();
1372
1373 // Check with target if this offset with this instruction is
1374 // specifically not supported.
1375 if (LU.Kind == LSRUse::Address && Offset != 0 &&
1376 !isAMCompletelyFolded(*TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1377 Offset, F.HasBaseReg, F.Scale, Fixup.UserInst))
1378 C.NumBaseAdds++;
1379 }
1380
1381 // If we don't count instruction cost exit here.
1382 if (!InsnsCost) {
1383 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1383, __PRETTY_FUNCTION__))
;
1384 return;
1385 }
1386
1387 // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as
1388 // additional instruction (at least fill).
1389 unsigned TTIRegNum = TTI->getNumberOfRegisters(false) - 1;
1390 if (C.NumRegs > TTIRegNum) {
1391 // Cost already exceeded TTIRegNum, then only newly added register can add
1392 // new instructions.
1393 if (PrevNumRegs > TTIRegNum)
1394 C.Insns += (C.NumRegs - PrevNumRegs);
1395 else
1396 C.Insns += (C.NumRegs - TTIRegNum);
1397 }
1398
1399 // If ICmpZero formula ends with not 0, it could not be replaced by
1400 // just add or sub. We'll need to compare final result of AddRec.
1401 // That means we'll need an additional instruction. But if the target can
1402 // macro-fuse a compare with a branch, don't count this extra instruction.
1403 // For -10 + {0, +, 1}:
1404 // i = i + 1;
1405 // cmp i, 10
1406 //
1407 // For {-10, +, 1}:
1408 // i = i + 1;
1409 if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd() &&
1410 !TTI->canMacroFuseCmp())
1411 C.Insns++;
1412 // Each new AddRec adds 1 instruction to calculation.
1413 C.Insns += (C.AddRecCost - PrevAddRecCost);
1414
1415 // BaseAdds adds instructions for unfolded registers.
1416 if (LU.Kind != LSRUse::ICmpZero)
1417 C.Insns += C.NumBaseAdds - PrevNumBaseAdds;
1418 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1418, __PRETTY_FUNCTION__))
;
1419}
1420
1421/// Set this cost to a losing value.
1422void Cost::Lose() {
1423 C.Insns = std::numeric_limits<unsigned>::max();
1424 C.NumRegs = std::numeric_limits<unsigned>::max();
1425 C.AddRecCost = std::numeric_limits<unsigned>::max();
1426 C.NumIVMuls = std::numeric_limits<unsigned>::max();
1427 C.NumBaseAdds = std::numeric_limits<unsigned>::max();
1428 C.ImmCost = std::numeric_limits<unsigned>::max();
1429 C.SetupCost = std::numeric_limits<unsigned>::max();
1430 C.ScaleCost = std::numeric_limits<unsigned>::max();
1431}
1432
1433/// Choose the lower cost.
1434bool Cost::isLess(Cost &Other) {
1435 if (InsnsCost.getNumOccurrences() > 0 && InsnsCost &&
1436 C.Insns != Other.C.Insns)
1437 return C.Insns < Other.C.Insns;
1438 return TTI->isLSRCostLess(C, Other.C);
1439}
1440
1441#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1442void Cost::print(raw_ostream &OS) const {
1443 if (InsnsCost)
1444 OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s ");
1445 OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s");
1446 if (C.AddRecCost != 0)
1447 OS << ", with addrec cost " << C.AddRecCost;
1448 if (C.NumIVMuls != 0)
1449 OS << ", plus " << C.NumIVMuls << " IV mul"
1450 << (C.NumIVMuls == 1 ? "" : "s");
1451 if (C.NumBaseAdds != 0)
1452 OS << ", plus " << C.NumBaseAdds << " base add"
1453 << (C.NumBaseAdds == 1 ? "" : "s");
1454 if (C.ScaleCost != 0)
1455 OS << ", plus " << C.ScaleCost << " scale cost";
1456 if (C.ImmCost != 0)
1457 OS << ", plus " << C.ImmCost << " imm cost";
1458 if (C.SetupCost != 0)
1459 OS << ", plus " << C.SetupCost << " setup cost";
1460}
1461
1462LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Cost::dump() const {
1463 print(errs()); errs() << '\n';
1464}
1465#endif
1466
1467/// Test whether this fixup always uses its value outside of the given loop.
1468bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1469 // PHI nodes use their value in their incoming blocks.
1470 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1471 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1472 if (PN->getIncomingValue(i) == OperandValToReplace &&
1473 L->contains(PN->getIncomingBlock(i)))
1474 return false;
1475 return true;
1476 }
1477
1478 return !L->contains(UserInst);
1479}
1480
1481#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1482void LSRFixup::print(raw_ostream &OS) const {
1483 OS << "UserInst=";
1484 // Store is common and interesting enough to be worth special-casing.
1485 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1486 OS << "store ";
1487 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1488 } else if (UserInst->getType()->isVoidTy())
1489 OS << UserInst->getOpcodeName();
1490 else
1491 UserInst->printAsOperand(OS, /*PrintType=*/false);
1492
1493 OS << ", OperandValToReplace=";
1494 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1495
1496 for (const Loop *PIL : PostIncLoops) {
1497 OS << ", PostIncLoop=";
1498 PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1499 }
1500
1501 if (Offset != 0)
1502 OS << ", Offset=" << Offset;
1503}
1504
1505LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRFixup::dump() const {
1506 print(errs()); errs() << '\n';
1507}
1508#endif
1509
1510/// Test whether this use as a formula which has the same registers as the given
1511/// formula.
1512bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1513 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1514 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1515 // Unstable sort by host order ok, because this is only used for uniquifying.
1516 llvm::sort(Key);
1517 return Uniquifier.count(Key);
1518}
1519
1520/// The function returns a probability of selecting formula without Reg.
1521float LSRUse::getNotSelectedProbability(const SCEV *Reg) const {
1522 unsigned FNum = 0;
1523 for (const Formula &F : Formulae)
1524 if (F.referencesReg(Reg))
1525 FNum++;
1526 return ((float)(Formulae.size() - FNum)) / Formulae.size();
1527}
1528
1529/// If the given formula has not yet been inserted, add it to the list, and
1530/// return true. Return false otherwise. The formula must be in canonical form.
1531bool LSRUse::InsertFormula(const Formula &F, const Loop &L) {
1532 assert(F.isCanonical(L) && "Invalid canonical representation")((F.isCanonical(L) && "Invalid canonical representation"
) ? static_cast<void> (0) : __assert_fail ("F.isCanonical(L) && \"Invalid canonical representation\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1532, __PRETTY_FUNCTION__))
;
1533
1534 if (!Formulae.empty() && RigidFormula)
1535 return false;
1536
1537 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1538 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1539 // Unstable sort by host order ok, because this is only used for uniquifying.
1540 llvm::sort(Key);
1541
1542 if (!Uniquifier.insert(Key).second)
1543 return false;
1544
1545 // Using a register to hold the value of 0 is not profitable.
1546 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&(((!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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1547, __PRETTY_FUNCTION__))
1547 "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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1547, __PRETTY_FUNCTION__))
;
1548#ifndef NDEBUG
1549 for (const SCEV *BaseReg : F.BaseRegs)
1550 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1550, __PRETTY_FUNCTION__))
;
1551#endif
1552
1553 // Add the formula to the list.
1554 Formulae.push_back(F);
1555
1556 // Record registers now being used by this use.
1557 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1558 if (F.ScaledReg)
1559 Regs.insert(F.ScaledReg);
1560
1561 return true;
1562}
1563
1564/// Remove the given formula from this use's list.
1565void LSRUse::DeleteFormula(Formula &F) {
1566 if (&F != &Formulae.back())
1567 std::swap(F, Formulae.back());
1568 Formulae.pop_back();
1569}
1570
1571/// Recompute the Regs field, and update RegUses.
1572void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1573 // Now that we've filtered out some formulae, recompute the Regs set.
1574 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1575 Regs.clear();
1576 for (const Formula &F : Formulae) {
1577 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1578 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1579 }
1580
1581 // Update the RegTracker.
1582 for (const SCEV *S : OldRegs)
1583 if (!Regs.count(S))
1584 RegUses.dropRegister(S, LUIdx);
1585}
1586
1587#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1588void LSRUse::print(raw_ostream &OS) const {
1589 OS << "LSR Use: Kind=";
1590 switch (Kind) {
1591 case Basic: OS << "Basic"; break;
1592 case Special: OS << "Special"; break;
1593 case ICmpZero: OS << "ICmpZero"; break;
1594 case Address:
1595 OS << "Address of ";
1596 if (AccessTy.MemTy->isPointerTy())
1597 OS << "pointer"; // the full pointer type could be really verbose
1598 else {
1599 OS << *AccessTy.MemTy;
1600 }
1601
1602 OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1603 }
1604
1605 OS << ", Offsets={";
1606 bool NeedComma = false;
1607 for (const LSRFixup &Fixup : Fixups) {
1608 if (NeedComma) OS << ',';
1609 OS << Fixup.Offset;
1610 NeedComma = true;
1611 }
1612 OS << '}';
1613
1614 if (AllFixupsOutsideLoop)
1615 OS << ", all-fixups-outside-loop";
1616
1617 if (WidestFixupType)
1618 OS << ", widest fixup type: " << *WidestFixupType;
1619}
1620
1621LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRUse::dump() const {
1622 print(errs()); errs() << '\n';
1623}
1624#endif
1625
1626static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1627 LSRUse::KindType Kind, MemAccessTy AccessTy,
1628 GlobalValue *BaseGV, int64_t BaseOffset,
1629 bool HasBaseReg, int64_t Scale,
1630 Instruction *Fixup/*= nullptr*/) {
1631 switch (Kind) {
1632 case LSRUse::Address:
1633 return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1634 HasBaseReg, Scale, AccessTy.AddrSpace, Fixup);
1635
1636 case LSRUse::ICmpZero:
1637 // There's not even a target hook for querying whether it would be legal to
1638 // fold a GV into an ICmp.
1639 if (BaseGV)
1640 return false;
1641
1642 // ICmp only has two operands; don't allow more than two non-trivial parts.
1643 if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1644 return false;
1645
1646 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1647 // putting the scaled register in the other operand of the icmp.
1648 if (Scale != 0 && Scale != -1)
1649 return false;
1650
1651 // If we have low-level target information, ask the target if it can fold an
1652 // integer immediate on an icmp.
1653 if (BaseOffset != 0) {
1654 // We have one of:
1655 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1656 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1657 // Offs is the ICmp immediate.
1658 if (Scale == 0)
1659 // The cast does the right thing with
1660 // std::numeric_limits<int64_t>::min().
1661 BaseOffset = -(uint64_t)BaseOffset;
1662 return TTI.isLegalICmpImmediate(BaseOffset);
1663 }
1664
1665 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1666 return true;
1667
1668 case LSRUse::Basic:
1669 // Only handle single-register values.
1670 return !BaseGV && Scale == 0 && BaseOffset == 0;
1671
1672 case LSRUse::Special:
1673 // Special case Basic to handle -1 scales.
1674 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1675 }
1676
1677 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1677)
;
1678}
1679
1680static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1681 int64_t MinOffset, int64_t MaxOffset,
1682 LSRUse::KindType Kind, MemAccessTy AccessTy,
1683 GlobalValue *BaseGV, int64_t BaseOffset,
1684 bool HasBaseReg, int64_t Scale) {
1685 // Check for overflow.
1686 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1687 (MinOffset > 0))
1688 return false;
1689 MinOffset = (uint64_t)BaseOffset + MinOffset;
1690 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1691 (MaxOffset > 0))
1692 return false;
1693 MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1694
1695 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1696 HasBaseReg, Scale) &&
1697 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1698 HasBaseReg, Scale);
1699}
1700
1701static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1702 int64_t MinOffset, int64_t MaxOffset,
1703 LSRUse::KindType Kind, MemAccessTy AccessTy,
1704 const Formula &F, const Loop &L) {
1705 // For the purpose of isAMCompletelyFolded either having a canonical formula
1706 // or a scale not equal to zero is correct.
1707 // Problems may arise from non canonical formulae having a scale == 0.
1708 // Strictly speaking it would best to just rely on canonical formulae.
1709 // However, when we generate the scaled formulae, we first check that the
1710 // scaling factor is profitable before computing the actual ScaledReg for
1711 // compile time sake.
1712 assert((F.isCanonical(L) || F.Scale != 0))(((F.isCanonical(L) || F.Scale != 0)) ? static_cast<void>
(0) : __assert_fail ("(F.isCanonical(L) || F.Scale != 0)", "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1712, __PRETTY_FUNCTION__))
;
1713 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1714 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1715}
1716
1717/// Test whether we know how to expand the current formula.
1718static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1719 int64_t MaxOffset, LSRUse::KindType Kind,
1720 MemAccessTy AccessTy, GlobalValue *BaseGV,
1721 int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1722 // We know how to expand completely foldable formulae.
1723 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1724 BaseOffset, HasBaseReg, Scale) ||
1725 // Or formulae that use a base register produced by a sum of base
1726 // registers.
1727 (Scale == 1 &&
1728 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1729 BaseGV, BaseOffset, true, 0));
1730}
1731
1732static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1733 int64_t MaxOffset, LSRUse::KindType Kind,
1734 MemAccessTy AccessTy, const Formula &F) {
1735 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1736 F.BaseOffset, F.HasBaseReg, F.Scale);
1737}
1738
1739static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1740 const LSRUse &LU, const Formula &F) {
1741 // Target may want to look at the user instructions.
1742 if (LU.Kind == LSRUse::Address && TTI.LSRWithInstrQueries()) {
1743 for (const LSRFixup &Fixup : LU.Fixups)
1744 if (!isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1745 (F.BaseOffset + Fixup.Offset), F.HasBaseReg,
1746 F.Scale, Fixup.UserInst))
1747 return false;
1748 return true;
1749 }
1750
1751 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1752 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1753 F.Scale);
1754}
1755
1756static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1757 const LSRUse &LU, const Formula &F,
1758 const Loop &L) {
1759 if (!F.Scale)
1760 return 0;
1761
1762 // If the use is not completely folded in that instruction, we will have to
1763 // pay an extra cost only for scale != 1.
1764 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1765 LU.AccessTy, F, L))
1766 return F.Scale != 1;
1767
1768 switch (LU.Kind) {
1769 case LSRUse::Address: {
1770 // Check the scaling factor cost with both the min and max offsets.
1771 int ScaleCostMinOffset = TTI.getScalingFactorCost(
1772 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1773 F.Scale, LU.AccessTy.AddrSpace);
1774 int ScaleCostMaxOffset = TTI.getScalingFactorCost(
1775 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1776 F.Scale, LU.AccessTy.AddrSpace);
1777
1778 assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&((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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1779, __PRETTY_FUNCTION__))
1779 "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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1779, __PRETTY_FUNCTION__))
;
1780 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1781 }
1782 case LSRUse::ICmpZero:
1783 case LSRUse::Basic:
1784 case LSRUse::Special:
1785 // The use is completely folded, i.e., everything is folded into the
1786 // instruction.
1787 return 0;
1788 }
1789
1790 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1790)
;
1791}
1792
1793static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1794 LSRUse::KindType Kind, MemAccessTy AccessTy,
1795 GlobalValue *BaseGV, int64_t BaseOffset,
1796 bool HasBaseReg) {
1797 // Fast-path: zero is always foldable.
1798 if (BaseOffset == 0 && !BaseGV) return true;
1799
1800 // Conservatively, create an address with an immediate and a
1801 // base and a scale.
1802 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1803
1804 // Canonicalize a scale of 1 to a base register if the formula doesn't
1805 // already have a base register.
1806 if (!HasBaseReg && Scale == 1) {
1807 Scale = 0;
1808 HasBaseReg = true;
1809 }
1810
1811 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1812 HasBaseReg, Scale);
1813}
1814
1815static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1816 ScalarEvolution &SE, int64_t MinOffset,
1817 int64_t MaxOffset, LSRUse::KindType Kind,
1818 MemAccessTy AccessTy, const SCEV *S,
1819 bool HasBaseReg) {
1820 // Fast-path: zero is always foldable.
1821 if (S->isZero()) return true;
1822
1823 // Conservatively, create an address with an immediate and a
1824 // base and a scale.
1825 int64_t BaseOffset = ExtractImmediate(S, SE);
1826 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1827
1828 // If there's anything else involved, it's not foldable.
1829 if (!S->isZero()) return false;
1830
1831 // Fast-path: zero is always foldable.
1832 if (BaseOffset == 0 && !BaseGV) return true;
1833
1834 // Conservatively, create an address with an immediate and a
1835 // base and a scale.
1836 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1837
1838 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1839 BaseOffset, HasBaseReg, Scale);
1840}
1841
1842namespace {
1843
1844/// An individual increment in a Chain of IV increments. Relate an IV user to
1845/// an expression that computes the IV it uses from the IV used by the previous
1846/// link in the Chain.
1847///
1848/// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1849/// original IVOperand. The head of the chain's IVOperand is only valid during
1850/// chain collection, before LSR replaces IV users. During chain generation,
1851/// IncExpr can be used to find the new IVOperand that computes the same
1852/// expression.
1853struct IVInc {
1854 Instruction *UserInst;
1855 Value* IVOperand;
1856 const SCEV *IncExpr;
1857
1858 IVInc(Instruction *U, Value *O, const SCEV *E)
1859 : UserInst(U), IVOperand(O), IncExpr(E) {}
1860};
1861
1862// The list of IV increments in program order. We typically add the head of a
1863// chain without finding subsequent links.
1864struct IVChain {
1865 SmallVector<IVInc, 1> Incs;
1866 const SCEV *ExprBase = nullptr;
1867
1868 IVChain() = default;
1869 IVChain(const IVInc &Head, const SCEV *Base)
1870 : Incs(1, Head), ExprBase(Base) {}
1871
1872 using const_iterator = SmallVectorImpl<IVInc>::const_iterator;
1873
1874 // Return the first increment in the chain.
1875 const_iterator begin() const {
1876 assert(!Incs.empty())((!Incs.empty()) ? static_cast<void> (0) : __assert_fail
("!Incs.empty()", "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1876, __PRETTY_FUNCTION__))
;
1877 return std::next(Incs.begin());
1878 }
1879 const_iterator end() const {
1880 return Incs.end();
1881 }
1882
1883 // Returns true if this chain contains any increments.
1884 bool hasIncs() const { return Incs.size() >= 2; }
1885
1886 // Add an IVInc to the end of this chain.
1887 void add(const IVInc &X) { Incs.push_back(X); }
1888
1889 // Returns the last UserInst in the chain.
1890 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1891
1892 // Returns true if IncExpr can be profitably added to this chain.
1893 bool isProfitableIncrement(const SCEV *OperExpr,
1894 const SCEV *IncExpr,
1895 ScalarEvolution&);
1896};
1897
1898/// Helper for CollectChains to track multiple IV increment uses. Distinguish
1899/// between FarUsers that definitely cross IV increments and NearUsers that may
1900/// be used between IV increments.
1901struct ChainUsers {
1902 SmallPtrSet<Instruction*, 4> FarUsers;
1903 SmallPtrSet<Instruction*, 4> NearUsers;
1904};
1905
1906/// This class holds state for the main loop strength reduction logic.
1907class LSRInstance {
1908 IVUsers &IU;
1909 ScalarEvolution &SE;
1910 DominatorTree &DT;
1911 LoopInfo &LI;
1912 const TargetTransformInfo &TTI;
1913 Loop *const L;
1914 bool FavorBackedgeIndex = false;
1915 bool Changed = false;
1916
1917 /// This is the insert position that the current loop's induction variable
1918 /// increment should be placed. In simple loops, this is the latch block's
1919 /// terminator. But in more complicated cases, this is a position which will
1920 /// dominate all the in-loop post-increment users.
1921 Instruction *IVIncInsertPos = nullptr;
1922
1923 /// Interesting factors between use strides.
1924 ///
1925 /// We explicitly use a SetVector which contains a SmallSet, instead of the
1926 /// default, a SmallDenseSet, because we need to use the full range of
1927 /// int64_ts, and there's currently no good way of doing that with
1928 /// SmallDenseSet.
1929 SetVector<int64_t, SmallVector<int64_t, 8>, SmallSet<int64_t, 8>> Factors;
1930
1931 /// Interesting use types, to facilitate truncation reuse.
1932 SmallSetVector<Type *, 4> Types;
1933
1934 /// The list of interesting uses.
1935 mutable SmallVector<LSRUse, 16> Uses;
1936
1937 /// Track which uses use which register candidates.
1938 RegUseTracker RegUses;
1939
1940 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1941 // have more than a few IV increment chains in a loop. Missing a Chain falls
1942 // back to normal LSR behavior for those uses.
1943 static const unsigned MaxChains = 8;
1944
1945 /// IV users can form a chain of IV increments.
1946 SmallVector<IVChain, MaxChains> IVChainVec;
1947
1948 /// IV users that belong to profitable IVChains.
1949 SmallPtrSet<Use*, MaxChains> IVIncSet;
1950
1951 void OptimizeShadowIV();
1952 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1953 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1954 void OptimizeLoopTermCond();
1955
1956 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1957 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1958 void FinalizeChain(IVChain &Chain);
1959 void CollectChains();
1960 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1961 SmallVectorImpl<WeakTrackingVH> &DeadInsts);
1962
1963 void CollectInterestingTypesAndFactors();
1964 void CollectFixupsAndInitialFormulae();
1965
1966 // Support for sharing of LSRUses between LSRFixups.
1967 using UseMapTy = DenseMap<LSRUse::SCEVUseKindPair, size_t>;
1968 UseMapTy UseMap;
1969
1970 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1971 LSRUse::KindType Kind, MemAccessTy AccessTy);
1972
1973 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
1974 MemAccessTy AccessTy);
1975
1976 void DeleteUse(LSRUse &LU, size_t LUIdx);
1977
1978 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1979
1980 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1981 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1982 void CountRegisters(const Formula &F, size_t LUIdx);
1983 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1984
1985 void CollectLoopInvariantFixupsAndFormulae();
1986
1987 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1988 unsigned Depth = 0);
1989
1990 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1991 const Formula &Base, unsigned Depth,
1992 size_t Idx, bool IsScaledReg = false);
1993 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1994 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1995 const Formula &Base, size_t Idx,
1996 bool IsScaledReg = false);
1997 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1998 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1999 const Formula &Base,
2000 const SmallVectorImpl<int64_t> &Worklist,
2001 size_t Idx, bool IsScaledReg = false);
2002 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
2003 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2004 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2005 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
2006 void GenerateCrossUseConstantOffsets();
2007 void GenerateAllReuseFormulae();
2008
2009 void FilterOutUndesirableDedicatedRegisters();
2010
2011 size_t EstimateSearchSpaceComplexity() const;
2012 void NarrowSearchSpaceByDetectingSupersets();
2013 void NarrowSearchSpaceByCollapsingUnrolledCode();
2014 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
2015 void NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
2016 void NarrowSearchSpaceByDeletingCostlyFormulas();
2017 void NarrowSearchSpaceByPickingWinnerRegs();
2018 void NarrowSearchSpaceUsingHeuristics();
2019
2020 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
2021 Cost &SolutionCost,
2022 SmallVectorImpl<const Formula *> &Workspace,
2023 const Cost &CurCost,
2024 const SmallPtrSet<const SCEV *, 16> &CurRegs,
2025 DenseSet<const SCEV *> &VisitedRegs) const;
2026 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
2027
2028 BasicBlock::iterator
2029 HoistInsertPosition(BasicBlock::iterator IP,
2030 const SmallVectorImpl<Instruction *> &Inputs) const;
2031 BasicBlock::iterator
2032 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
2033 const LSRFixup &LF,
2034 const LSRUse &LU,
2035 SCEVExpander &Rewriter) const;
2036
2037 Value *Expand(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2038 BasicBlock::iterator IP, SCEVExpander &Rewriter,
2039 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2040 void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
2041 const Formula &F, SCEVExpander &Rewriter,
2042 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2043 void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2044 SCEVExpander &Rewriter,
2045 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2046 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
2047
2048public:
2049 LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
2050 LoopInfo &LI, const TargetTransformInfo &TTI);
2051
2052 bool getChanged() const { return Changed; }
2053
2054 void print_factors_and_types(raw_ostream &OS) const;
2055 void print_fixups(raw_ostream &OS) const;
2056 void print_uses(raw_ostream &OS) const;
2057 void print(raw_ostream &OS) const;
2058 void dump() const;
2059};
2060
2061} // end anonymous namespace
2062
2063/// If IV is used in a int-to-float cast inside the loop then try to eliminate
2064/// the cast operation.
2065void LSRInstance::OptimizeShadowIV() {
2066 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2067 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2068 return;
2069
2070 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
2071 UI != E; /* empty */) {
2072 IVUsers::const_iterator CandidateUI = UI;
2073 ++UI;
2074 Instruction *ShadowUse = CandidateUI->getUser();
2075 Type *DestTy = nullptr;
2076 bool IsSigned = false;
2077
2078 /* If shadow use is a int->float cast then insert a second IV
2079 to eliminate this cast.
2080
2081 for (unsigned i = 0; i < n; ++i)
2082 foo((double)i);
2083
2084 is transformed into
2085
2086 double d = 0.0;
2087 for (unsigned i = 0; i < n; ++i, ++d)
2088 foo(d);
2089 */
2090 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
2091 IsSigned = false;
2092 DestTy = UCast->getDestTy();
2093 }
2094 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
2095 IsSigned = true;
2096 DestTy = SCast->getDestTy();
2097 }
2098 if (!DestTy) continue;
2099
2100 // If target does not support DestTy natively then do not apply
2101 // this transformation.
2102 if (!TTI.isTypeLegal(DestTy)) continue;
2103
2104 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2105 if (!PH) continue;
2106 if (PH->getNumIncomingValues() != 2) continue;
2107
2108 // If the calculation in integers overflows, the result in FP type will
2109 // differ. So we only can do this transformation if we are guaranteed to not
2110 // deal with overflowing values
2111 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PH));
2112 if (!AR) continue;
2113 if (IsSigned && !AR->hasNoSignedWrap()) continue;
2114 if (!IsSigned && !AR->hasNoUnsignedWrap()) continue;
2115
2116 Type *SrcTy = PH->getType();
2117 int Mantissa = DestTy->getFPMantissaWidth();
2118 if (Mantissa == -1) continue;
2119 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
2120 continue;
2121
2122 unsigned Entry, Latch;
2123 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2124 Entry = 0;
2125 Latch = 1;
2126 } else {
2127 Entry = 1;
2128 Latch = 0;
2129 }
2130
2131 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
2132 if (!Init) continue;
2133 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
2134 (double)Init->getSExtValue() :
2135 (double)Init->getZExtValue());
2136
2137 BinaryOperator *Incr =
2138 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
2139 if (!Incr) continue;
2140 if (Incr->getOpcode() != Instruction::Add
2141 && Incr->getOpcode() != Instruction::Sub)
2142 continue;
2143
2144 /* Initialize new IV, double d = 0.0 in above example. */
2145 ConstantInt *C = nullptr;
2146 if (Incr->getOperand(0) == PH)
2147 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2148 else if (Incr->getOperand(1) == PH)
2149 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2150 else
2151 continue;
2152
2153 if (!C) continue;
2154
2155 // Ignore negative constants, as the code below doesn't handle them
2156 // correctly. TODO: Remove this restriction.
2157 if (!C->getValue().isStrictlyPositive()) continue;
2158
2159 /* Add new PHINode. */
2160 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
2161
2162 /* create new increment. '++d' in above example. */
2163 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2164 BinaryOperator *NewIncr =
2165 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
2166 Instruction::FAdd : Instruction::FSub,
2167 NewPH, CFP, "IV.S.next.", Incr);
2168
2169 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2170 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2171
2172 /* Remove cast operation */
2173 ShadowUse->replaceAllUsesWith(NewPH);
2174 ShadowUse->eraseFromParent();
2175 Changed = true;
2176 break;
2177 }
2178}
2179
2180/// If Cond has an operand that is an expression of an IV, set the IV user and
2181/// stride information and return true, otherwise return false.
2182bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
2183 for (IVStrideUse &U : IU)
2184 if (U.getUser() == Cond) {
2185 // NOTE: we could handle setcc instructions with multiple uses here, but
2186 // InstCombine does it as well for simple uses, it's not clear that it
2187 // occurs enough in real life to handle.
2188 CondUse = &U;
2189 return true;
2190 }
2191 return false;
2192}
2193
2194/// Rewrite the loop's terminating condition if it uses a max computation.
2195///
2196/// This is a narrow solution to a specific, but acute, problem. For loops
2197/// like this:
2198///
2199/// i = 0;
2200/// do {
2201/// p[i] = 0.0;
2202/// } while (++i < n);
2203///
2204/// the trip count isn't just 'n', because 'n' might not be positive. And
2205/// unfortunately this can come up even for loops where the user didn't use
2206/// a C do-while loop. For example, seemingly well-behaved top-test loops
2207/// will commonly be lowered like this:
2208///
2209/// if (n > 0) {
2210/// i = 0;
2211/// do {
2212/// p[i] = 0.0;
2213/// } while (++i < n);
2214/// }
2215///
2216/// and then it's possible for subsequent optimization to obscure the if
2217/// test in such a way that indvars can't find it.
2218///
2219/// When indvars can't find the if test in loops like this, it creates a
2220/// max expression, which allows it to give the loop a canonical
2221/// induction variable:
2222///
2223/// i = 0;
2224/// max = n < 1 ? 1 : n;
2225/// do {
2226/// p[i] = 0.0;
2227/// } while (++i != max);
2228///
2229/// Canonical induction variables are necessary because the loop passes
2230/// are designed around them. The most obvious example of this is the
2231/// LoopInfo analysis, which doesn't remember trip count values. It
2232/// expects to be able to rediscover the trip count each time it is
2233/// needed, and it does this using a simple analysis that only succeeds if
2234/// the loop has a canonical induction variable.
2235///
2236/// However, when it comes time to generate code, the maximum operation
2237/// can be quite costly, especially if it's inside of an outer loop.
2238///
2239/// This function solves this problem by detecting this type of loop and
2240/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2241/// the instructions for the maximum computation.
2242ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
2243 // Check that the loop matches the pattern we're looking for.
2244 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2245 Cond->getPredicate() != CmpInst::ICMP_NE)
2246 return Cond;
2247
2248 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2249 if (!Sel || !Sel->hasOneUse()) return Cond;
2250
2251 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2252 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2253 return Cond;
2254 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2255
2256 // Add one to the backedge-taken count to get the trip count.
2257 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2258 if (IterationCount != SE.getSCEV(Sel)) return Cond;
2259
2260 // Check for a max calculation that matches the pattern. There's no check
2261 // for ICMP_ULE here because the comparison would be with zero, which
2262 // isn't interesting.
2263 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2264 const SCEVNAryExpr *Max = nullptr;
2265 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2266 Pred = ICmpInst::ICMP_SLE;
2267 Max = S;
2268 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2269 Pred = ICmpInst::ICMP_SLT;
2270 Max = S;
2271 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2272 Pred = ICmpInst::ICMP_ULT;
2273 Max = U;
2274 } else {
2275 // No match; bail.
2276 return Cond;
2277 }
2278
2279 // To handle a max with more than two operands, this optimization would
2280 // require additional checking and setup.
2281 if (Max->getNumOperands() != 2)
2282 return Cond;
2283
2284 const SCEV *MaxLHS = Max->getOperand(0);
2285 const SCEV *MaxRHS = Max->getOperand(1);
2286
2287 // ScalarEvolution canonicalizes constants to the left. For < and >, look
2288 // for a comparison with 1. For <= and >=, a comparison with zero.
2289 if (!MaxLHS ||
2290 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2291 return Cond;
2292
2293 // Check the relevant induction variable for conformance to
2294 // the pattern.
2295 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2296 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2297 if (!AR || !AR->isAffine() ||
2298 AR->getStart() != One ||
2299 AR->getStepRecurrence(SE) != One)
2300 return Cond;
2301
2302 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2303, __PRETTY_FUNCTION__))
2303 "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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2303, __PRETTY_FUNCTION__))
;
2304
2305 // Check the right operand of the select, and remember it, as it will
2306 // be used in the new comparison instruction.
2307 Value *NewRHS = nullptr;
2308 if (ICmpInst::isTrueWhenEqual(Pred)) {
2309 // Look for n+1, and grab n.
2310 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2311 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2312 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2313 NewRHS = BO->getOperand(0);
2314 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2315 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2316 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2317 NewRHS = BO->getOperand(0);
2318 if (!NewRHS)
2319 return Cond;
2320 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2321 NewRHS = Sel->getOperand(1);
2322 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2323 NewRHS = Sel->getOperand(2);
2324 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2325 NewRHS = SU->getValue();
2326 else
2327 // Max doesn't match expected pattern.
2328 return Cond;
2329
2330 // Determine the new comparison opcode. It may be signed or unsigned,
2331 // and the original comparison may be either equality or inequality.
2332 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2333 Pred = CmpInst::getInversePredicate(Pred);
2334
2335 // Ok, everything looks ok to change the condition into an SLT or SGE and
2336 // delete the max calculation.
2337 ICmpInst *NewCond =
2338 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2339
2340 // Delete the max calculation instructions.
2341 Cond->replaceAllUsesWith(NewCond);
2342 CondUse->setUser(NewCond);
2343 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2344 Cond->eraseFromParent();
2345 Sel->eraseFromParent();
2346 if (Cmp->use_empty())
2347 Cmp->eraseFromParent();
2348 return NewCond;
2349}
2350
2351/// Change loop terminating condition to use the postinc iv when possible.
2352void
2353LSRInstance::OptimizeLoopTermCond() {
2354 SmallPtrSet<Instruction *, 4> PostIncs;
2355
2356 // We need a different set of heuristics for rotated and non-rotated loops.
2357 // If a loop is rotated then the latch is also the backedge, so inserting
2358 // post-inc expressions just before the latch is ideal. To reduce live ranges
2359 // it also makes sense to rewrite terminating conditions to use post-inc
2360 // expressions.
2361 //
2362 // If the loop is not rotated then the latch is not a backedge; the latch
2363 // check is done in the loop head. Adding post-inc expressions before the
2364 // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2365 // in the loop body. In this case we do *not* want to use post-inc expressions
2366 // in the latch check, and we want to insert post-inc expressions before
2367 // the backedge.
2368 BasicBlock *LatchBlock = L->getLoopLatch();
2369 SmallVector<BasicBlock*, 8> ExitingBlocks;
2370 L->getExitingBlocks(ExitingBlocks);
2371 if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2372 return LatchBlock != BB;
2373 })) {
2374 // The backedge doesn't exit the loop; treat this as a head-tested loop.
2375 IVIncInsertPos = LatchBlock->getTerminator();
2376 return;
2377 }
2378
2379 // Otherwise treat this as a rotated loop.
2380 for (BasicBlock *ExitingBlock : ExitingBlocks) {
2381 // Get the terminating condition for the loop if possible. If we
2382 // can, we want to change it to use a post-incremented version of its
2383 // induction variable, to allow coalescing the live ranges for the IV into
2384 // one register value.
2385
2386 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2387 if (!TermBr)
2388 continue;
2389 // FIXME: Overly conservative, termination condition could be an 'or' etc..
2390 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2391 continue;
2392
2393 // Search IVUsesByStride to find Cond's IVUse if there is one.
2394 IVStrideUse *CondUse = nullptr;
2395 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2396 if (!FindIVUserForCond(Cond, CondUse))
2397 continue;
2398
2399 // If the trip count is computed in terms of a max (due to ScalarEvolution
2400 // being unable to find a sufficient guard, for example), change the loop
2401 // comparison to use SLT or ULT instead of NE.
2402 // One consequence of doing this now is that it disrupts the count-down
2403 // optimization. That's not always a bad thing though, because in such
2404 // cases it may still be worthwhile to avoid a max.
2405 Cond = OptimizeMax(Cond, CondUse);
2406
2407 // If this exiting block dominates the latch block, it may also use
2408 // the post-inc value if it won't be shared with other uses.
2409 // Check for dominance.
2410 if (!DT.dominates(ExitingBlock, LatchBlock))
2411 continue;
2412
2413 // Conservatively avoid trying to use the post-inc value in non-latch
2414 // exits if there may be pre-inc users in intervening blocks.
2415 if (LatchBlock != ExitingBlock)
2416 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2417 // Test if the use is reachable from the exiting block. This dominator
2418 // query is a conservative approximation of reachability.
2419 if (&*UI != CondUse &&
2420 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2421 // Conservatively assume there may be reuse if the quotient of their
2422 // strides could be a legal scale.
2423 const SCEV *A = IU.getStride(*CondUse, L);
2424 const SCEV *B = IU.getStride(*UI, L);
2425 if (!A || !B) continue;
2426 if (SE.getTypeSizeInBits(A->getType()) !=
2427 SE.getTypeSizeInBits(B->getType())) {
2428 if (SE.getTypeSizeInBits(A->getType()) >
2429 SE.getTypeSizeInBits(B->getType()))
2430 B = SE.getSignExtendExpr(B, A->getType());
2431 else
2432 A = SE.getSignExtendExpr(A, B->getType());
2433 }
2434 if (const SCEVConstant *D =
2435 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2436 const ConstantInt *C = D->getValue();
2437 // Stride of one or negative one can have reuse with non-addresses.
2438 if (C->isOne() || C->isMinusOne())
2439 goto decline_post_inc;
2440 // Avoid weird situations.
2441 if (C->getValue().getMinSignedBits() >= 64 ||
2442 C->getValue().isMinSignedValue())
2443 goto decline_post_inc;
2444 // Check for possible scaled-address reuse.
2445 if (isAddressUse(TTI, UI->getUser(), UI->getOperandValToReplace())) {
2446 MemAccessTy AccessTy = getAccessType(
2447 TTI, UI->getUser(), UI->getOperandValToReplace());
2448 int64_t Scale = C->getSExtValue();
2449 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2450 /*BaseOffset=*/0,
2451 /*HasBaseReg=*/false, Scale,
2452 AccessTy.AddrSpace))
2453 goto decline_post_inc;
2454 Scale = -Scale;
2455 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2456 /*BaseOffset=*/0,
2457 /*HasBaseReg=*/false, Scale,
2458 AccessTy.AddrSpace))
2459 goto decline_post_inc;
2460 }
2461 }
2462 }
2463
2464 LLVM_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)
2465 << *Cond << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Change loop exiting icmp to use postinc iv: "
<< *Cond << '\n'; } } while (false)
;
2466
2467 // It's possible for the setcc instruction to be anywhere in the loop, and
2468 // possible for it to have multiple users. If it is not immediately before
2469 // the exiting block branch, move it.
2470 if (&*++BasicBlock::iterator(Cond) != TermBr) {
2471 if (Cond->hasOneUse()) {
2472 Cond->moveBefore(TermBr);
2473 } else {
2474 // Clone the terminating condition and insert into the loopend.
2475 ICmpInst *OldCond = Cond;
2476 Cond = cast<ICmpInst>(Cond->clone());
2477 Cond->setName(L->getHeader()->getName() + ".termcond");
2478 ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2479
2480 // Clone the IVUse, as the old use still exists!
2481 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2482 TermBr->replaceUsesOfWith(OldCond, Cond);
2483 }
2484 }
2485
2486 // If we get to here, we know that we can transform the setcc instruction to
2487 // use the post-incremented version of the IV, allowing us to coalesce the
2488 // live ranges for the IV correctly.
2489 CondUse->transformToPostInc(L);
2490 Changed = true;
2491
2492 PostIncs.insert(Cond);
2493 decline_post_inc:;
2494 }
2495
2496 // Determine an insertion point for the loop induction variable increment. It
2497 // must dominate all the post-inc comparisons we just set up, and it must
2498 // dominate the loop latch edge.
2499 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2500 for (Instruction *Inst : PostIncs) {
2501 BasicBlock *BB =
2502 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2503 Inst->getParent());
2504 if (BB == Inst->getParent())
2505 IVIncInsertPos = Inst;
2506 else if (BB != IVIncInsertPos->getParent())
2507 IVIncInsertPos = BB->getTerminator();
2508 }
2509}
2510
2511/// Determine if the given use can accommodate a fixup at the given offset and
2512/// other details. If so, update the use and return true.
2513bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2514 bool HasBaseReg, LSRUse::KindType Kind,
2515 MemAccessTy AccessTy) {
2516 int64_t NewMinOffset = LU.MinOffset;
2517 int64_t NewMaxOffset = LU.MaxOffset;
2518 MemAccessTy NewAccessTy = AccessTy;
2519
2520 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2521 // something conservative, however this can pessimize in the case that one of
2522 // the uses will have all its uses outside the loop, for example.
2523 if (LU.Kind != Kind)
2524 return false;
2525
2526 // Check for a mismatched access type, and fall back conservatively as needed.
2527 // TODO: Be less conservative when the type is similar and can use the same
2528 // addressing modes.
2529 if (Kind == LSRUse::Address) {
2530 if (AccessTy.MemTy != LU.AccessTy.MemTy) {
2531 NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(),
2532 AccessTy.AddrSpace);
2533 }
2534 }
2535
2536 // Conservatively assume HasBaseReg is true for now.
2537 if (NewOffset < LU.MinOffset) {
2538 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2539 LU.MaxOffset - NewOffset, HasBaseReg))
2540 return false;
2541 NewMinOffset = NewOffset;
2542 } else if (NewOffset > LU.MaxOffset) {
2543 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2544 NewOffset - LU.MinOffset, HasBaseReg))
2545 return false;
2546 NewMaxOffset = NewOffset;
2547 }
2548
2549 // Update the use.
2550 LU.MinOffset = NewMinOffset;
2551 LU.MaxOffset = NewMaxOffset;
2552 LU.AccessTy = NewAccessTy;
2553 return true;
2554}
2555
2556/// Return an LSRUse index and an offset value for a fixup which needs the given
2557/// expression, with the given kind and optional access type. Either reuse an
2558/// existing use or create a new one, as needed.
2559std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2560 LSRUse::KindType Kind,
2561 MemAccessTy AccessTy) {
2562 const SCEV *Copy = Expr;
2563 int64_t Offset = ExtractImmediate(Expr, SE);
2564
2565 // Basic uses can't accept any offset, for example.
2566 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2567 Offset, /*HasBaseReg=*/ true)) {
2568 Expr = Copy;
2569 Offset = 0;
2570 }
2571
2572 std::pair<UseMapTy::iterator, bool> P =
2573 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2574 if (!P.second) {
2575 // A use already existed with this base.
2576 size_t LUIdx = P.first->second;
2577 LSRUse &LU = Uses[LUIdx];
2578 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2579 // Reuse this use.
2580 return std::make_pair(LUIdx, Offset);
2581 }
2582
2583 // Create a new use.
2584 size_t LUIdx = Uses.size();
2585 P.first->second = LUIdx;
2586 Uses.push_back(LSRUse(Kind, AccessTy));
2587 LSRUse &LU = Uses[LUIdx];
2588
2589 LU.MinOffset = Offset;
2590 LU.MaxOffset = Offset;
2591 return std::make_pair(LUIdx, Offset);
2592}
2593
2594/// Delete the given use from the Uses list.
2595void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2596 if (&LU != &Uses.back())
2597 std::swap(LU, Uses.back());
2598 Uses.pop_back();
2599
2600 // Update RegUses.
2601 RegUses.swapAndDropUse(LUIdx, Uses.size());
2602}
2603
2604/// Look for a use distinct from OrigLU which is has a formula that has the same
2605/// registers as the given formula.
2606LSRUse *
2607LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2608 const LSRUse &OrigLU) {
2609 // Search all uses for the formula. This could be more clever.
2610 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2611 LSRUse &LU = Uses[LUIdx];
2612 // Check whether this use is close enough to OrigLU, to see whether it's
2613 // worthwhile looking through its formulae.
2614 // Ignore ICmpZero uses because they may contain formulae generated by
2615 // GenerateICmpZeroScales, in which case adding fixup offsets may
2616 // be invalid.
2617 if (&LU != &OrigLU &&
2618 LU.Kind != LSRUse::ICmpZero &&
2619 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2620 LU.WidestFixupType == OrigLU.WidestFixupType &&
2621 LU.HasFormulaWithSameRegs(OrigF)) {
2622 // Scan through this use's formulae.
2623 for (const Formula &F : LU.Formulae) {
2624 // Check to see if this formula has the same registers and symbols
2625 // as OrigF.
2626 if (F.BaseRegs == OrigF.BaseRegs &&
2627 F.ScaledReg == OrigF.ScaledReg &&
2628 F.BaseGV == OrigF.BaseGV &&
2629 F.Scale == OrigF.Scale &&
2630 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2631 if (F.BaseOffset == 0)
2632 return &LU;
2633 // This is the formula where all the registers and symbols matched;
2634 // there aren't going to be any others. Since we declined it, we
2635 // can skip the rest of the formulae and proceed to the next LSRUse.
2636 break;
2637 }
2638 }
2639 }
2640 }
2641
2642 // Nothing looked good.
2643 return nullptr;
2644}
2645
2646void LSRInstance::CollectInterestingTypesAndFactors() {
2647 SmallSetVector<const SCEV *, 4> Strides;
2648
2649 // Collect interesting types and strides.
2650 SmallVector<const SCEV *, 4> Worklist;
2651 for (const IVStrideUse &U : IU) {
2652 const SCEV *Expr = IU.getExpr(U);
2653
2654 // Collect interesting types.
2655 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2656
2657 // Add strides for mentioned loops.
2658 Worklist.push_back(Expr);
2659 do {
2660 const SCEV *S = Worklist.pop_back_val();
2661 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2662 if (AR->getLoop() == L)
2663 Strides.insert(AR->getStepRecurrence(SE));
2664 Worklist.push_back(AR->getStart());
2665 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2666 Worklist.append(Add->op_begin(), Add->op_end());
2667 }
2668 } while (!Worklist.empty());
2669 }
2670
2671 // Compute interesting factors from the set of interesting strides.
2672 for (SmallSetVector<const SCEV *, 4>::const_iterator
2673 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2674 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2675 std::next(I); NewStrideIter != E; ++NewStrideIter) {
2676 const SCEV *OldStride = *I;
2677 const SCEV *NewStride = *NewStrideIter;
2678
2679 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2680 SE.getTypeSizeInBits(NewStride->getType())) {
2681 if (SE.getTypeSizeInBits(OldStride->getType()) >
2682 SE.getTypeSizeInBits(NewStride->getType()))
2683 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2684 else
2685 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2686 }
2687 if (const SCEVConstant *Factor =
2688 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2689 SE, true))) {
2690 if (Factor->getAPInt().getMinSignedBits() <= 64)
2691 Factors.insert(Factor->getAPInt().getSExtValue());
2692 } else if (const SCEVConstant *Factor =
2693 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2694 NewStride,
2695 SE, true))) {
2696 if (Factor->getAPInt().getMinSignedBits() <= 64)
2697 Factors.insert(Factor->getAPInt().getSExtValue());
2698 }
2699 }
2700
2701 // If all uses use the same type, don't bother looking for truncation-based
2702 // reuse.
2703 if (Types.size() == 1)
2704 Types.clear();
2705
2706 LLVM_DEBUG(print_factors_and_types(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_factors_and_types(dbgs()); } } while
(false)
;
2707}
2708
2709/// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2710/// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2711/// IVStrideUses, we could partially skip this.
2712static User::op_iterator
2713findIVOperand(User::op_iterator OI, User::op_iterator OE,
2714 Loop *L, ScalarEvolution &SE) {
2715 for(; OI != OE; ++OI) {
2716 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2717 if (!SE.isSCEVable(Oper->getType()))
2718 continue;
2719
2720 if (const SCEVAddRecExpr *AR =
2721 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2722 if (AR->getLoop() == L)
2723 break;
2724 }
2725 }
2726 }
2727 return OI;
2728}
2729
2730/// IVChain logic must consistently peek base TruncInst operands, so wrap it in
2731/// a convenient helper.
2732static Value *getWideOperand(Value *Oper) {
2733 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2734 return Trunc->getOperand(0);
2735 return Oper;
2736}
2737
2738/// Return true if we allow an IV chain to include both types.
2739static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2740 Type *LType = LVal->getType();
2741 Type *RType = RVal->getType();
2742 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy() &&
2743 // Different address spaces means (possibly)
2744 // different types of the pointer implementation,
2745 // e.g. i16 vs i32 so disallow that.
2746 (LType->getPointerAddressSpace() ==
2747 RType->getPointerAddressSpace()));
2748}
2749
2750/// Return an approximation of this SCEV expression's "base", or NULL for any
2751/// constant. Returning the expression itself is conservative. Returning a
2752/// deeper subexpression is more precise and valid as long as it isn't less
2753/// complex than another subexpression. For expressions involving multiple
2754/// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2755/// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2756/// IVInc==b-a.
2757///
2758/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2759/// SCEVUnknown, we simply return the rightmost SCEV operand.
2760static const SCEV *getExprBase(const SCEV *S) {
2761 switch (S->getSCEVType()) {
2762 default: // uncluding scUnknown.
2763 return S;
2764 case scConstant:
2765 return nullptr;
2766 case scTruncate:
2767 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2768 case scZeroExtend:
2769 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2770 case scSignExtend:
2771 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2772 case scAddExpr: {
2773 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2774 // there's nothing more complex.
2775 // FIXME: not sure if we want to recognize negation.
2776 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2777 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2778 E(Add->op_begin()); I != E; ++I) {
2779 const SCEV *SubExpr = *I;
2780 if (SubExpr->getSCEVType() == scAddExpr)
2781 return getExprBase(SubExpr);
2782
2783 if (SubExpr->getSCEVType() != scMulExpr)
2784 return SubExpr;
2785 }
2786 return S; // all operands are scaled, be conservative.
2787 }
2788 case scAddRecExpr:
2789 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2790 }
2791}
2792
2793/// Return true if the chain increment is profitable to expand into a loop
2794/// invariant value, which may require its own register. A profitable chain
2795/// increment will be an offset relative to the same base. We allow such offsets
2796/// to potentially be used as chain increment as long as it's not obviously
2797/// expensive to expand using real instructions.
2798bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2799 const SCEV *IncExpr,
2800 ScalarEvolution &SE) {
2801 // Aggressively form chains when -stress-ivchain.
2802 if (StressIVChain)
2803 return true;
2804
2805 // Do not replace a constant offset from IV head with a nonconstant IV
2806 // increment.
2807 if (!isa<SCEVConstant>(IncExpr)) {
2808 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2809 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2810 return false;
2811 }
2812
2813 SmallPtrSet<const SCEV*, 8> Processed;
2814 return !isHighCostExpansion(IncExpr, Processed, SE);
2815}
2816
2817/// Return true if the number of registers needed for the chain is estimated to
2818/// be less than the number required for the individual IV users. First prohibit
2819/// any IV users that keep the IV live across increments (the Users set should
2820/// be empty). Next count the number and type of increments in the chain.
2821///
2822/// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2823/// effectively use postinc addressing modes. Only consider it profitable it the
2824/// increments can be computed in fewer registers when chained.
2825///
2826/// TODO: Consider IVInc free if it's already used in another chains.
2827static bool
2828isProfitableChain(IVChain &Chain, SmallPtrSetImpl<Instruction*> &Users,
2829 ScalarEvolution &SE) {
2830 if (StressIVChain)
2831 return true;
2832
2833 if (!Chain.hasIncs())
2834 return false;
2835
2836 if (!Users.empty()) {
2837 LLVM_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)
2838 for (Instruction *Instdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " users:\n"; for (Instruction *Inst
: Users) { dbgs() << " " << *Inst << "\n"
; }; } } while (false)
2839 : Users) { 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)
;
2840 return false;
2841 }
2842 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2842, __PRETTY_FUNCTION__))
;
2843
2844 // The chain itself may require a register, so intialize cost to 1.
2845 int cost = 1;
2846
2847 // A complete chain likely eliminates the need for keeping the original IV in
2848 // a register. LSR does not currently know how to form a complete chain unless
2849 // the header phi already exists.
2850 if (isa<PHINode>(Chain.tailUserInst())
2851 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2852 --cost;
2853 }
2854 const SCEV *LastIncExpr = nullptr;
2855 unsigned NumConstIncrements = 0;
2856 unsigned NumVarIncrements = 0;
2857 unsigned NumReusedIncrements = 0;
2858 for (const IVInc &Inc : Chain) {
2859 if (Inc.IncExpr->isZero())
2860 continue;
2861
2862 // Incrementing by zero or some constant is neutral. We assume constants can
2863 // be folded into an addressing mode or an add's immediate operand.
2864 if (isa<SCEVConstant>(Inc.IncExpr)) {
2865 ++NumConstIncrements;
2866 continue;
2867 }
2868
2869 if (Inc.IncExpr == LastIncExpr)
2870 ++NumReusedIncrements;
2871 else
2872 ++NumVarIncrements;
2873
2874 LastIncExpr = Inc.IncExpr;
2875 }
2876 // An IV chain with a single increment is handled by LSR's postinc
2877 // uses. However, a chain with multiple increments requires keeping the IV's
2878 // value live longer than it needs to be if chained.
2879 if (NumConstIncrements > 1)
2880 --cost;
2881
2882 // Materializing increment expressions in the preheader that didn't exist in
2883 // the original code may cost a register. For example, sign-extended array
2884 // indices can produce ridiculous increments like this:
2885 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2886 cost += NumVarIncrements;
2887
2888 // Reusing variable increments likely saves a register to hold the multiple of
2889 // the stride.
2890 cost -= NumReusedIncrements;
2891
2892 LLVM_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)
2893 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " Cost: " << cost << "\n"
; } } while (false)
;
2894
2895 return cost < 0;
2896}
2897
2898/// Add this IV user to an existing chain or make it the head of a new chain.
2899void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2900 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2901 // When IVs are used as types of varying widths, they are generally converted
2902 // to a wider type with some uses remaining narrow under a (free) trunc.
2903 Value *const NextIV = getWideOperand(IVOper);
2904 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2905 const SCEV *const OperExprBase = getExprBase(OperExpr);
2906
2907 // Visit all existing chains. Check if its IVOper can be computed as a
2908 // profitable loop invariant increment from the last link in the Chain.
2909 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2910 const SCEV *LastIncExpr = nullptr;
2911 for (; ChainIdx < NChains; ++ChainIdx) {
2912 IVChain &Chain = IVChainVec[ChainIdx];
2913
2914 // Prune the solution space aggressively by checking that both IV operands
2915 // are expressions that operate on the same unscaled SCEVUnknown. This
2916 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2917 // first avoids creating extra SCEV expressions.
2918 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2919 continue;
2920
2921 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2922 if (!isCompatibleIVType(PrevIV, NextIV))
2923 continue;
2924
2925 // A phi node terminates a chain.
2926 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2927 continue;
2928
2929 // The increment must be loop-invariant so it can be kept in a register.
2930 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2931 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2932 if (!SE.isLoopInvariant(IncExpr, L))
2933 continue;
2934
2935 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2936 LastIncExpr = IncExpr;
2937 break;
2938 }
2939 }
2940 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2941 // bother for phi nodes, because they must be last in the chain.
2942 if (ChainIdx == NChains) {
2943 if (isa<PHINode>(UserInst))
2944 return;
2945 if (NChains >= MaxChains && !StressIVChain) {
2946 LLVM_DEBUG(dbgs() << "IV Chain Limit\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain Limit\n"; } } while
(false)
;
2947 return;
2948 }
2949 LastIncExpr = OperExpr;
2950 // IVUsers may have skipped over sign/zero extensions. We don't currently
2951 // attempt to form chains involving extensions unless they can be hoisted
2952 // into this loop's AddRec.
2953 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2954 return;
2955 ++NChains;
2956 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2957 OperExprBase));
2958 ChainUsersVec.resize(NChains);
2959 LLVM_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)
2960 << ") IV=" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Head: (" << *UserInst << ") IV=" <<
*LastIncExpr << "\n"; } } while (false)
;
2961 } else {
2962 LLVM_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)
2963 << ") IV+" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Inc: (" << *UserInst << ") IV+" <<
*LastIncExpr << "\n"; } } while (false)
;
2964 // Add this IV user to the end of the chain.
2965 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2966 }
2967 IVChain &Chain = IVChainVec[ChainIdx];
2968
2969 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2970 // This chain's NearUsers become FarUsers.
2971 if (!LastIncExpr->isZero()) {
2972 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2973 NearUsers.end());
2974 NearUsers.clear();
2975 }
2976
2977 // All other uses of IVOperand become near uses of the chain.
2978 // We currently ignore intermediate values within SCEV expressions, assuming
2979 // they will eventually be used be the current chain, or can be computed
2980 // from one of the chain increments. To be more precise we could
2981 // transitively follow its user and only add leaf IV users to the set.
2982 for (User *U : IVOper->users()) {
2983 Instruction *OtherUse = dyn_cast<Instruction>(U);
2984 if (!OtherUse)
2985 continue;
2986 // Uses in the chain will no longer be uses if the chain is formed.
2987 // Include the head of the chain in this iteration (not Chain.begin()).
2988 IVChain::const_iterator IncIter = Chain.Incs.begin();
2989 IVChain::const_iterator IncEnd = Chain.Incs.end();
2990 for( ; IncIter != IncEnd; ++IncIter) {
2991 if (IncIter->UserInst == OtherUse)
2992 break;
2993 }
2994 if (IncIter != IncEnd)
2995 continue;
2996
2997 if (SE.isSCEVable(OtherUse->getType())
2998 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2999 && IU.isIVUserOrOperand(OtherUse)) {
3000 continue;
3001 }
3002 NearUsers.insert(OtherUse);
3003 }
3004
3005 // Since this user is part of the chain, it's no longer considered a use
3006 // of the chain.
3007 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
3008}
3009
3010/// Populate the vector of Chains.
3011///
3012/// This decreases ILP at the architecture level. Targets with ample registers,
3013/// multiple memory ports, and no register renaming probably don't want
3014/// this. However, such targets should probably disable LSR altogether.
3015///
3016/// The job of LSR is to make a reasonable choice of induction variables across
3017/// the loop. Subsequent passes can easily "unchain" computation exposing more
3018/// ILP *within the loop* if the target wants it.
3019///
3020/// Finding the best IV chain is potentially a scheduling problem. Since LSR
3021/// will not reorder memory operations, it will recognize this as a chain, but
3022/// will generate redundant IV increments. Ideally this would be corrected later
3023/// by a smart scheduler:
3024/// = A[i]
3025/// = A[i+x]
3026/// A[i] =
3027/// A[i+x] =
3028///
3029/// TODO: Walk the entire domtree within this loop, not just the path to the
3030/// loop latch. This will discover chains on side paths, but requires
3031/// maintaining multiple copies of the Chains state.
3032void LSRInstance::CollectChains() {
3033 LLVM_DEBUG(dbgs() << "Collecting IV Chains.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Collecting IV Chains.\n";
} } while (false)
;
3034 SmallVector<ChainUsers, 8> ChainUsersVec;
3035
3036 SmallVector<BasicBlock *,8> LatchPath;
3037 BasicBlock *LoopHeader = L->getHeader();
3038 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
3039 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
3040 LatchPath.push_back(Rung->getBlock());
3041 }
3042 LatchPath.push_back(LoopHeader);
3043
3044 // Walk the instruction stream from the loop header to the loop latch.
3045 for (BasicBlock *BB : reverse(LatchPath)) {
3046 for (Instruction &I : *BB) {
3047 // Skip instructions that weren't seen by IVUsers analysis.
3048 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
3049 continue;
3050
3051 // Ignore users that are part of a SCEV expression. This way we only
3052 // consider leaf IV Users. This effectively rediscovers a portion of
3053 // IVUsers analysis but in program order this time.
3054 if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
3055 continue;
3056
3057 // Remove this instruction from any NearUsers set it may be in.
3058 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
3059 ChainIdx < NChains; ++ChainIdx) {
3060 ChainUsersVec[ChainIdx].NearUsers.erase(&I);
3061 }
3062 // Search for operands that can be chained.
3063 SmallPtrSet<Instruction*, 4> UniqueOperands;
3064 User::op_iterator IVOpEnd = I.op_end();
3065 User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
3066 while (IVOpIter != IVOpEnd) {
3067 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
3068 if (UniqueOperands.insert(IVOpInst).second)
3069 ChainInstruction(&I, IVOpInst, ChainUsersVec);
3070 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3071 }
3072 } // Continue walking down the instructions.
3073 } // Continue walking down the domtree.
3074 // Visit phi backedges to determine if the chain can generate the IV postinc.
3075 for (PHINode &PN : L->getHeader()->phis()) {
3076 if (!SE.isSCEVable(PN.getType()))
3077 continue;
3078
3079 Instruction *IncV =
3080 dyn_cast<Instruction>(PN.getIncomingValueForBlock(L->getLoopLatch()));
3081 if (IncV)
3082 ChainInstruction(&PN, IncV, ChainUsersVec);
3083 }
3084 // Remove any unprofitable chains.
3085 unsigned ChainIdx = 0;
3086 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
3087 UsersIdx < NChains; ++UsersIdx) {
3088 if (!isProfitableChain(IVChainVec[UsersIdx],
3089 ChainUsersVec[UsersIdx].FarUsers, SE))
3090 continue;
3091 // Preserve the chain at UsesIdx.
3092 if (ChainIdx != UsersIdx)
3093 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
3094 FinalizeChain(IVChainVec[ChainIdx]);
3095 ++ChainIdx;
3096 }
3097 IVChainVec.resize(ChainIdx);
3098}
3099
3100void LSRInstance::FinalizeChain(IVChain &Chain) {
3101 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3101, __PRETTY_FUNCTION__))
;
3102 LLVM_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)
;
3103
3104 for (const IVInc &Inc : Chain) {
3105 LLVM_DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Inc: " << *
Inc.UserInst << "\n"; } } while (false)
;
3106 auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
3107 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3107, __PRETTY_FUNCTION__))
;
3108 IVIncSet.insert(UseI);
3109 }
3110}
3111
3112/// Return true if the IVInc can be folded into an addressing mode.
3113static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
3114 Value *Operand, const TargetTransformInfo &TTI) {
3115 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
3116 if (!IncConst || !isAddressUse(TTI, UserInst, Operand))
3117 return false;
3118
3119 if (IncConst->getAPInt().getMinSignedBits() > 64)
3120 return false;
3121
3122 MemAccessTy AccessTy = getAccessType(TTI, UserInst, Operand);
3123 int64_t IncOffset = IncConst->getValue()->getSExtValue();
3124 if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
3125 IncOffset, /*HaseBaseReg=*/false))
3126 return false;
3127
3128 return true;
3129}
3130
3131/// Generate an add or subtract for each IVInc in a chain to materialize the IV
3132/// user's operand from the previous IV user's operand.
3133void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
3134 SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
3135 // Find the new IVOperand for the head of the chain. It may have been replaced
3136 // by LSR.
3137 const IVInc &Head = Chain.Incs[0];
3138 User::op_iterator IVOpEnd = Head.UserInst->op_end();
3139 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
3140 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
3141 IVOpEnd, L, SE);
3142 Value *IVSrc = nullptr;
3143 while (IVOpIter != IVOpEnd) {
3144 IVSrc = getWideOperand(*IVOpIter);
3145
3146 // If this operand computes the expression that the chain needs, we may use
3147 // it. (Check this after setting IVSrc which is used below.)
3148 //
3149 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
3150 // narrow for the chain, so we can no longer use it. We do allow using a
3151 // wider phi, assuming the LSR checked for free truncation. In that case we
3152 // should already have a truncate on this operand such that
3153 // getSCEV(IVSrc) == IncExpr.
3154 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
3155 || SE.getSCEV(IVSrc) == Head.IncExpr) {
3156 break;
3157 }
3158 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3159 }
3160 if (IVOpIter == IVOpEnd) {
3161 // Gracefully give up on this chain.
3162 LLVM_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)
;
3163 return;
3164 }
3165
3166 LLVM_DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generate chain at: " <<
*IVSrc << "\n"; } } while (false)
;
3167 Type *IVTy = IVSrc->getType();
3168 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
3169 const SCEV *LeftOverExpr = nullptr;
3170 for (const IVInc &Inc : Chain) {
3171 Instruction *InsertPt = Inc.UserInst;
3172 if (isa<PHINode>(InsertPt))
3173 InsertPt = L->getLoopLatch()->getTerminator();
3174
3175 // IVOper will replace the current IV User's operand. IVSrc is the IV
3176 // value currently held in a register.
3177 Value *IVOper = IVSrc;
3178 if (!Inc.IncExpr->isZero()) {
3179 // IncExpr was the result of subtraction of two narrow values, so must
3180 // be signed.
3181 const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
3182 LeftOverExpr = LeftOverExpr ?
3183 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
3184 }
3185 if (LeftOverExpr && !LeftOverExpr->isZero()) {
3186 // Expand the IV increment.
3187 Rewriter.clearPostInc();
3188 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
3189 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
3190 SE.getUnknown(IncV));
3191 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
3192
3193 // If an IV increment can't be folded, use it as the next IV value.
3194 if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
3195 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3195, __PRETTY_FUNCTION__))
;
3196 IVSrc = IVOper;
3197 LeftOverExpr = nullptr;
3198 }
3199 }
3200 Type *OperTy = Inc.IVOperand->getType();
3201 if (IVTy != OperTy) {
3202 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3203, __PRETTY_FUNCTION__))
3203 "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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3203, __PRETTY_FUNCTION__))
;
3204 IRBuilder<> Builder(InsertPt);
3205 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
3206 }
3207 Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
3208 DeadInsts.emplace_back(Inc.IVOperand);
3209 }
3210 // If LSR created a new, wider phi, we may also replace its postinc. We only
3211 // do this if we also found a wide value for the head of the chain.
3212 if (isa<PHINode>(Chain.tailUserInst())) {
3213 for (PHINode &Phi : L->getHeader()->phis()) {
3214 if (!isCompatibleIVType(&Phi, IVSrc))
3215 continue;
3216 Instruction *PostIncV = dyn_cast<Instruction>(
3217 Phi.getIncomingValueForBlock(L->getLoopLatch()));
3218 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
3219 continue;
3220 Value *IVOper = IVSrc;
3221 Type *PostIncTy = PostIncV->getType();
3222 if (IVTy != PostIncTy) {
3223 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3223, __PRETTY_FUNCTION__))
;
3224 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
3225 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
3226 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
3227 }
3228 Phi.replaceUsesOfWith(PostIncV, IVOper);
3229 DeadInsts.emplace_back(PostIncV);
3230 }
3231 }
3232}
3233
3234void LSRInstance::CollectFixupsAndInitialFormulae() {
3235 for (const IVStrideUse &U : IU) {
3236 Instruction *UserInst = U.getUser();
3237 // Skip IV users that are part of profitable IV Chains.
3238 User::op_iterator UseI =
3239 find(UserInst->operands(), U.getOperandValToReplace());
3240 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3240, __PRETTY_FUNCTION__))
;
3241 if (IVIncSet.count(UseI)) {
3242 LLVM_DEBUG(dbgs() << "Use is in profitable chain: " << **UseI << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Use is in profitable chain: "
<< **UseI << '\n'; } } while (false)
;
3243 continue;
3244 }
3245
3246 LSRUse::KindType Kind = LSRUse::Basic;
3247 MemAccessTy AccessTy;
3248 if (isAddressUse(TTI, UserInst, U.getOperandValToReplace())) {
3249 Kind = LSRUse::Address;
3250 AccessTy = getAccessType(TTI, UserInst, U.getOperandValToReplace());
3251 }
3252
3253 const SCEV *S = IU.getExpr(U);
3254 PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3255
3256 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3257 // (N - i == 0), and this allows (N - i) to be the expression that we work
3258 // with rather than just N or i, so we can consider the register
3259 // requirements for both N and i at the same time. Limiting this code to
3260 // equality icmps is not a problem because all interesting loops use
3261 // equality icmps, thanks to IndVarSimplify.
3262 if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst))
3263 if (CI->isEquality()) {
3264 // Swap the operands if needed to put the OperandValToReplace on the
3265 // left, for consistency.
3266 Value *NV = CI->getOperand(1);
3267 if (NV == U.getOperandValToReplace()) {
3268 CI->setOperand(1, CI->getOperand(0));
3269 CI->setOperand(0, NV);
3270 NV = CI->getOperand(1);
3271 Changed = true;
3272 }
3273
3274 // x == y --> x - y == 0
3275 const SCEV *N = SE.getSCEV(NV);
3276 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3277 // S is normalized, so normalize N before folding it into S
3278 // to keep the result normalized.
3279 N = normalizeForPostIncUse(N, TmpPostIncLoops, SE);
3280 Kind = LSRUse::ICmpZero;
3281 S = SE.getMinusSCEV(N, S);
3282 }
3283
3284 // -1 and the negations of all interesting strides (except the negation
3285 // of -1) are now also interesting.
3286 for (size_t i = 0, e = Factors.size(); i != e; ++i)
3287 if (Factors[i] != -1)
3288 Factors.insert(-(uint64_t)Factors[i]);
3289 Factors.insert(-1);
3290 }
3291
3292 // Get or create an LSRUse.
3293 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3294 size_t LUIdx = P.first;
3295 int64_t Offset = P.second;
3296 LSRUse &LU = Uses[LUIdx];
3297
3298 // Record the fixup.
3299 LSRFixup &LF = LU.getNewFixup();
3300 LF.UserInst = UserInst;
3301 LF.OperandValToReplace = U.getOperandValToReplace();
3302 LF.PostIncLoops = TmpPostIncLoops;
3303 LF.Offset = Offset;
3304 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3305
3306 if (!LU.WidestFixupType ||
3307 SE.getTypeSizeInBits(LU.WidestFixupType) <
3308 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3309 LU.WidestFixupType = LF.OperandValToReplace->getType();
3310
3311 // If this is the first use of this LSRUse, give it a formula.
3312 if (LU.Formulae.empty()) {
3313 InsertInitialFormula(S, LU, LUIdx);
3314 CountRegisters(LU.Formulae.back(), LUIdx);
3315 }
3316 }
3317
3318 LLVM_DEBUG(print_fixups(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_fixups(dbgs()); } } while (false)
;
3319}
3320
3321/// Insert a formula for the given expression into the given use, separating out
3322/// loop-variant portions from loop-invariant and loop-computable portions.
3323void
3324LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3325 // Mark uses whose expressions cannot be expanded.
3326 if (!isSafeToExpand(S, SE))
3327 LU.RigidFormula = true;
3328
3329 Formula F;
3330 F.initialMatch(S, L, SE);
3331 bool Inserted = InsertFormula(LU, LUIdx, F);
3332 assert(Inserted && "Initial formula already exists!")((Inserted && "Initial formula already exists!") ? static_cast
<void> (0) : __assert_fail ("Inserted && \"Initial formula already exists!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3332, __PRETTY_FUNCTION__))
; (void)Inserted;
3333}
3334
3335/// Insert a simple single-register formula for the given expression into the
3336/// given use.
3337void
3338LSRInstance::InsertSupplementalFormula(const SCEV *S,
3339 LSRUse &LU, size_t LUIdx) {
3340 Formula F;
3341 F.BaseRegs.push_back(S);
3342 F.HasBaseReg = true;
3343 bool Inserted = InsertFormula(LU, LUIdx, F);
3344 assert(Inserted && "Supplemental formula already exists!")((Inserted && "Supplemental formula already exists!")
? static_cast<void> (0) : __assert_fail ("Inserted && \"Supplemental formula already exists!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3344, __PRETTY_FUNCTION__))
; (void)Inserted;
3345}
3346
3347/// Note which registers are used by the given formula, updating RegUses.
3348void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3349 if (F.ScaledReg)
3350 RegUses.countRegister(F.ScaledReg, LUIdx);
3351 for (const SCEV *BaseReg : F.BaseRegs)
3352 RegUses.countRegister(BaseReg, LUIdx);
3353}
3354
3355/// If the given formula has not yet been inserted, add it to the list, and
3356/// return true. Return false otherwise.
3357bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3358 // Do not insert formula that we will not be able to expand.
3359 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3360, __PRETTY_FUNCTION__))
3360 "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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3360, __PRETTY_FUNCTION__))
;
3361
3362 if (!LU.InsertFormula(F, *L))
3363 return false;
3364
3365 CountRegisters(F, LUIdx);
3366 return true;
3367}
3368
3369/// Check for other uses of loop-invariant values which we're tracking. These
3370/// other uses will pin these values in registers, making them less profitable
3371/// for elimination.
3372/// TODO: This currently misses non-constant addrec step registers.
3373/// TODO: Should this give more weight to users inside the loop?
3374void
3375LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3376 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3377 SmallPtrSet<const SCEV *, 32> Visited;
3378
3379 while (!Worklist.empty()) {
3380 const SCEV *S = Worklist.pop_back_val();
3381
3382 // Don't process the same SCEV twice
3383 if (!Visited.insert(S).second)
3384 continue;
3385
3386 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3387 Worklist.append(N->op_begin(), N->op_end());
3388 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3389 Worklist.push_back(C->getOperand());
3390 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3391 Worklist.push_back(D->getLHS());
3392 Worklist.push_back(D->getRHS());
3393 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3394 const Value *V = US->getValue();
3395 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3396 // Look for instructions defined outside the loop.
3397 if (L->contains(Inst)) continue;
3398 } else if (isa<UndefValue>(V))
3399 // Undef doesn't have a live range, so it doesn't matter.
3400 continue;
3401 for (const Use &U : V->uses()) {
3402 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3403 // Ignore non-instructions.
3404 if (!UserInst)
3405 continue;
3406 // Ignore instructions in other functions (as can happen with
3407 // Constants).
3408 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3409 continue;
3410 // Ignore instructions not dominated by the loop.
3411 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3412 UserInst->getParent() :
3413 cast<PHINode>(UserInst)->getIncomingBlock(
3414 PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3415 if (!DT.dominates(L->getHeader(), UseBB))
3416 continue;
3417 // Don't bother if the instruction is in a BB which ends in an EHPad.
3418 if (UseBB->getTerminator()->isEHPad())
3419 continue;
3420 // Don't bother rewriting PHIs in catchswitch blocks.
3421 if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator()))
3422 continue;
3423 // Ignore uses which are part of other SCEV expressions, to avoid
3424 // analyzing them multiple times.
3425 if (SE.isSCEVable(UserInst->getType())) {
3426 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3427 // If the user is a no-op, look through to its uses.
3428 if (!isa<SCEVUnknown>(UserS))
3429 continue;
3430 if (UserS == US) {
3431 Worklist.push_back(
3432 SE.getUnknown(const_cast<Instruction *>(UserInst)));
3433 continue;
3434 }
3435 }
3436 // Ignore icmp instructions which are already being analyzed.
3437 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3438 unsigned OtherIdx = !U.getOperandNo();
3439 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3440 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3441 continue;
3442 }
3443
3444 std::pair<size_t, int64_t> P = getUse(
3445 S, LSRUse::Basic, MemAccessTy());
3446 size_t LUIdx = P.first;
3447 int64_t Offset = P.second;
3448 LSRUse &LU = Uses[LUIdx];
3449 LSRFixup &LF = LU.getNewFixup();
3450 LF.UserInst = const_cast<Instruction *>(UserInst);
3451 LF.OperandValToReplace = U;
3452 LF.Offset = Offset;
3453 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3454 if (!LU.WidestFixupType ||
3455 SE.getTypeSizeInBits(LU.WidestFixupType) <
3456 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3457 LU.WidestFixupType = LF.OperandValToReplace->getType();
3458 InsertSupplementalFormula(US, LU, LUIdx);
3459 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3460 break;
3461 }
3462 }
3463 }
3464}
3465
3466/// Split S into subexpressions which can be pulled out into separate
3467/// registers. If C is non-null, multiply each subexpression by C.
3468///
3469/// Return remainder expression after factoring the subexpressions captured by
3470/// Ops. If Ops is complete, return NULL.
3471static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3472 SmallVectorImpl<const SCEV *> &Ops,
3473 const Loop *L,
3474 ScalarEvolution &SE,
3475 unsigned Depth = 0) {
3476 // Arbitrarily cap recursion to protect compile time.
3477 if (Depth >= 3)
3478 return S;
3479
3480 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3481 // Break out add operands.
3482 for (const SCEV *S : Add->operands()) {
3483 const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3484 if (Remainder)
3485 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3486 }
3487 return nullptr;
3488 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3489 // Split a non-zero base out of an addrec.
3490 if (AR->getStart()->isZero() || !AR->isAffine())
3491 return S;
3492
3493 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3494 C, Ops, L, SE, Depth+1);
3495 // Split the non-zero AddRec unless it is part of a nested recurrence that
3496 // does not pertain to this loop.
3497 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3498 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3499 Remainder = nullptr;
3500 }
3501 if (Remainder != AR->getStart()) {
3502 if (!Remainder)
3503 Remainder = SE.getConstant(AR->getType(), 0);
3504 return SE.getAddRecExpr(Remainder,
3505 AR->getStepRecurrence(SE),
3506 AR->getLoop(),
3507 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3508 SCEV::FlagAnyWrap);
3509 }
3510 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3511 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3512 if (Mul->getNumOperands() != 2)
3513 return S;
3514 if (const SCEVConstant *Op0 =
3515 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3516 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3517 const SCEV *Remainder =
3518 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3519 if (Remainder)
3520 Ops.push_back(SE.getMulExpr(C, Remainder));
3521 return nullptr;
3522 }
3523 }
3524 return S;
3525}
3526
3527/// Return true if the SCEV represents a value that may end up as a
3528/// post-increment operation.
3529static bool mayUsePostIncMode(const TargetTransformInfo &TTI,
3530 LSRUse &LU, const SCEV *S, const Loop *L,
3531 ScalarEvolution &SE) {
3532 if (LU.Kind != LSRUse::Address ||
3533 !LU.AccessTy.getType()->isIntOrIntVectorTy())
3534 return false;
3535 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S);
3536 if (!AR)
3537 return false;
3538 const SCEV *LoopStep = AR->getStepRecurrence(SE);
3539 if (!isa<SCEVConstant>(LoopStep))
3540 return false;
3541 if (LU.AccessTy.getType()->getScalarSizeInBits() !=
3542 LoopStep->getType()->getScalarSizeInBits())
3543 return false;
3544 // Check if a post-indexed load/store can be used.
3545 if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) ||
3546 TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) {
3547 const SCEV *LoopStart = AR->getStart();
3548 if (!isa<SCEVConstant>(LoopStart) && SE.isLoopInvariant(LoopStart, L))
3549 return true;
3550 }
3551 return false;
3552}
3553
3554/// Helper function for LSRInstance::GenerateReassociations.
3555void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3556 const Formula &Base,
3557 unsigned Depth, size_t Idx,
3558 bool IsScaledReg) {
3559 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3560 // Don't generate reassociations for the base register of a value that
3561 // may generate a post-increment operator. The reason is that the
3562 // reassociations cause extra base+register formula to be created,
3563 // and possibly chosen, but the post-increment is more efficient.
3564 if (TTI.shouldFavorPostInc() && mayUsePostIncMode(TTI, LU, BaseReg, L, SE))
3565 return;
3566 SmallVector<const SCEV *, 8> AddOps;
3567 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3568 if (Remainder)
3569 AddOps.push_back(Remainder);
3570
3571 if (AddOps.size() == 1)
3572 return;
3573
3574 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3575 JE = AddOps.end();
3576 J != JE; ++J) {
3577 // Loop-variant "unknown" values are uninteresting; we won't be able to
3578 // do anything meaningful with them.
3579 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3580 continue;
3581
3582 // Don't pull a constant into a register if the constant could be folded
3583 // into an immediate field.
3584 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3585 LU.AccessTy, *J, Base.getNumRegs() > 1))
3586 continue;
3587
3588 // Collect all operands except *J.
3589 SmallVector<const SCEV *, 8> InnerAddOps(
3590 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3591 InnerAddOps.append(std::next(J),
3592 ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3593
3594 // Don't leave just a constant behind in a register if the constant could
3595 // be folded into an immediate field.
3596 if (InnerAddOps.size() == 1 &&
3597 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3598 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3599 continue;
3600
3601 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3602 if (InnerSum->isZero())
3603 continue;
3604 Formula F = Base;
3605
3606 // Add the remaining pieces of the add back into the new formula.
3607 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3608 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3609 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3610 InnerSumSC->getValue()->getZExtValue())) {
3611 F.UnfoldedOffset =
3612 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3613 if (IsScaledReg)
3614 F.ScaledReg = nullptr;
3615 else
3616 F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3617 } else if (IsScaledReg)
3618 F.ScaledReg = InnerSum;
3619 else
3620 F.BaseRegs[Idx] = InnerSum;
3621
3622 // Add J as its own register, or an unfolded immediate.
3623 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3624 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3625 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3626 SC->getValue()->getZExtValue()))
3627 F.UnfoldedOffset =
3628 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3629 else
3630 F.BaseRegs.push_back(*J);
3631 // We may have changed the number of register in base regs, adjust the
3632 // formula accordingly.
3633 F.canonicalize(*L);
3634
3635 if (InsertFormula(LU, LUIdx, F))
3636 // If that formula hadn't been seen before, recurse to find more like
3637 // it.
3638 // Add check on Log16(AddOps.size()) - same as Log2_32(AddOps.size()) >> 2)
3639 // Because just Depth is not enough to bound compile time.
3640 // This means that every time AddOps.size() is greater 16^x we will add
3641 // x to Depth.
3642 GenerateReassociations(LU, LUIdx, LU.Formulae.back(),
3643 Depth + 1 + (Log2_32(AddOps.size()) >> 2));
3644 }
3645}
3646
3647/// Split out subexpressions from adds and the bases of addrecs.
3648void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3649 Formula Base, unsigned Depth) {
3650 assert(Base.isCanonical(*L) && "Input must be in the canonical form")((Base.isCanonical(*L) && "Input must be in the canonical form"
) ? static_cast<void> (0) : __assert_fail ("Base.isCanonical(*L) && \"Input must be in the canonical form\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3650, __PRETTY_FUNCTION__))
;
3651 // Arbitrarily cap recursion to protect compile time.
3652 if (Depth >= 3)
3653 return;
3654
3655 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3656 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3657
3658 if (Base.Scale == 1)
3659 GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3660 /* Idx */ -1, /* IsScaledReg */ true);
3661}
3662
3663/// Generate a formula consisting of all of the loop-dominating registers added
3664/// into a single register.
3665void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3666 Formula Base) {
3667 // This method is only interesting on a plurality of registers.
3668 if (Base.BaseRegs.size() + (Base.Scale == 1) +
3669 (Base.UnfoldedOffset != 0) <= 1)
3670 return;
3671
3672 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3673 // processing the formula.
3674 Base.unscale();
3675 SmallVector<const SCEV *, 4> Ops;
3676 Formula NewBase = Base;
3677 NewBase.BaseRegs.clear();
3678 Type *CombinedIntegerType = nullptr;
3679 for (const SCEV *BaseReg : Base.BaseRegs) {
3680 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3681 !SE.hasComputableLoopEvolution(BaseReg, L)) {
3682 if (!CombinedIntegerType)
3683 CombinedIntegerType = SE.getEffectiveSCEVType(BaseReg->getType());
3684 Ops.push_back(BaseReg);
3685 }
3686 else
3687 NewBase.BaseRegs.push_back(BaseReg);
3688 }
3689
3690 // If no register is relevant, we're done.
3691 if (Ops.size() == 0)
3692 return;
3693
3694 // Utility function for generating the required variants of the combined
3695 // registers.
3696 auto GenerateFormula = [&](const SCEV *Sum) {
3697 Formula F = NewBase;
3698
3699 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3700 // opportunity to fold something. For now, just ignore such cases
3701 // rather than proceed with zero in a register.
3702 if (Sum->isZero())
3703 return;
3704
3705 F.BaseRegs.push_back(Sum);
3706 F.canonicalize(*L);
3707 (void)InsertFormula(LU, LUIdx, F);
3708 };
3709
3710 // If we collected at least two registers, generate a formula combining them.
3711 if (Ops.size() > 1) {
3712 SmallVector<const SCEV *, 4> OpsCopy(Ops); // Don't let SE modify Ops.
3713 GenerateFormula(SE.getAddExpr(OpsCopy));
3714 }
3715
3716 // If we have an unfolded offset, generate a formula combining it with the
3717 // registers collected.
3718 if (NewBase.UnfoldedOffset) {
3719 assert(CombinedIntegerType && "Missing a type for the unfolded offset")((CombinedIntegerType && "Missing a type for the unfolded offset"
) ? static_cast<void> (0) : __assert_fail ("CombinedIntegerType && \"Missing a type for the unfolded offset\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3719, __PRETTY_FUNCTION__))
;
3720 Ops.push_back(SE.getConstant(CombinedIntegerType, NewBase.UnfoldedOffset,
3721 true));
3722 NewBase.UnfoldedOffset = 0;
3723 GenerateFormula(SE.getAddExpr(Ops));
3724 }
3725}
3726
3727/// Helper function for LSRInstance::GenerateSymbolicOffsets.
3728void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3729 const Formula &Base, size_t Idx,
3730 bool IsScaledReg) {
3731 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3732 GlobalValue *GV = ExtractSymbol(G, SE);
3733 if (G->isZero() || !GV)
3734 return;
3735 Formula F = Base;
3736 F.BaseGV = GV;
3737 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3738 return;
3739 if (IsScaledReg)
3740 F.ScaledReg = G;
3741 else
3742 F.BaseRegs[Idx] = G;
3743 (void)InsertFormula(LU, LUIdx, F);
3744}
3745
3746/// Generate reuse formulae using symbolic offsets.
3747void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3748 Formula Base) {
3749 // We can't add a symbolic offset if the address already contains one.
3750 if (Base.BaseGV) return;
3751
3752 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3753 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3754 if (Base.Scale == 1)
3755 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3756 /* IsScaledReg */ true);
3757}
3758
3759/// Helper function for LSRInstance::GenerateConstantOffsets.
3760void LSRInstance::GenerateConstantOffsetsImpl(
3761 LSRUse &LU, unsigned LUIdx, const Formula &Base,
3762 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3763
3764 auto GenerateOffset = [&](const SCEV *G, int64_t Offset) {
3765 Formula F = Base;
3766 F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3767
3768 if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind,
3769 LU.AccessTy, F)) {
3770 // Add the offset to the base register.
3771 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3772 // If it cancelled out, drop the base register, otherwise update it.
3773 if (NewG->isZero()) {
3774 if (IsScaledReg) {
3775 F.Scale = 0;
3776 F.ScaledReg = nullptr;
3777 } else
3778 F.deleteBaseReg(F.BaseRegs[Idx]);
3779 F.canonicalize(*L);
3780 } else if (IsScaledReg)
3781 F.ScaledReg = NewG;
3782 else
3783 F.BaseRegs[Idx] = NewG;
3784
3785 (void)InsertFormula(LU, LUIdx, F);
3786 }
3787 };
3788
3789 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3790
3791 // With constant offsets and constant steps, we can generate pre-inc
3792 // accesses by having the offset equal the step. So, for access #0 with a
3793 // step of 8, we generate a G - 8 base which would require the first access
3794 // to be ((G - 8) + 8),+,8. The pre-indexed access then updates the pointer
3795 // for itself and hopefully becomes the base for other accesses. This means
3796 // means that a single pre-indexed access can be generated to become the new
3797 // base pointer for each iteration of the loop, resulting in no extra add/sub
3798 // instructions for pointer updating.
3799 if (FavorBackedgeIndex && LU.Kind == LSRUse::Address) {
3800 if (auto *GAR = dyn_cast<SCEVAddRecExpr>(G)) {
3801 if (auto *StepRec =
3802 dyn_cast<SCEVConstant>(GAR->getStepRecurrence(SE))) {
3803 const APInt &StepInt = StepRec->getAPInt();
3804 int64_t Step = StepInt.isNegative() ?
3805 StepInt.getSExtValue() : StepInt.getZExtValue();
3806
3807 for (int64_t Offset : Worklist) {
3808 Offset -= Step;
3809 GenerateOffset(G, Offset);
3810 }
3811 }
3812 }
3813 }
3814 for (int64_t Offset : Worklist)
3815 GenerateOffset(G, Offset);
3816
3817 int64_t Imm = ExtractImmediate(G, SE);
3818 if (G->isZero() || Imm == 0)
3819 return;
3820 Formula F = Base;
3821 F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3822 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3823 return;
3824 if (IsScaledReg)
3825 F.ScaledReg = G;
3826 else
3827 F.BaseRegs[Idx] = G;
3828 (void)InsertFormula(LU, LUIdx, F);
3829}
3830
3831/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3832void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3833 Formula Base) {
3834 // TODO: For now, just add the min and max offset, because it usually isn't
3835 // worthwhile looking at everything inbetween.
3836 SmallVector<int64_t, 2> Worklist;
3837 Worklist.push_back(LU.MinOffset);
3838 if (LU.MaxOffset != LU.MinOffset)
3839 Worklist.push_back(LU.MaxOffset);
3840
3841 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3842 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3843 if (Base.Scale == 1)
3844 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3845 /* IsScaledReg */ true);
3846}
3847
3848/// For ICmpZero, check to see if we can scale up the comparison. For example, x
3849/// == y -> x*c == y*c.
3850void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3851 Formula Base) {
3852 if (LU.Kind != LSRUse::ICmpZero) return;
3853
3854 // Determine the integer type for the base formula.
3855 Type *IntTy = Base.getType();
3856 if (!IntTy) return;
3857 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3858
3859 // Don't do this if there is more than one offset.
3860 if (LU.MinOffset != LU.MaxOffset) return;
3861
3862 // Check if transformation is valid. It is illegal to multiply pointer.
3863 if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
3864 return;
3865 for (const SCEV *BaseReg : Base.BaseRegs)
3866 if (BaseReg->getType()->isPointerTy())
3867 return;
3868 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3868, __PRETTY_FUNCTION__))
;
3869
3870 // Check each interesting stride.
3871 for (int64_t Factor : Factors) {
3872 // Check that the multiplication doesn't overflow.
3873 if (Base.BaseOffset == std::numeric_limits<int64_t>::min() && Factor == -1)
3874 continue;
3875 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3876 if (NewBaseOffset / Factor != Base.BaseOffset)
3877 continue;
3878 // If the offset will be truncated at this use, check that it is in bounds.
3879 if (!IntTy->isPointerTy() &&
3880 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3881 continue;
3882
3883 // Check that multiplying with the use offset doesn't overflow.
3884 int64_t Offset = LU.MinOffset;
3885 if (Offset == std::numeric_limits<int64_t>::min() && Factor == -1)
3886 continue;
3887 Offset = (uint64_t)Offset * Factor;
3888 if (Offset / Factor != LU.MinOffset)
3889 continue;
3890 // If the offset will be truncated at this use, check that it is in bounds.
3891 if (!IntTy->isPointerTy() &&
3892 !ConstantInt::isValueValidForType(IntTy, Offset))
3893 continue;
3894
3895 Formula F = Base;
3896 F.BaseOffset = NewBaseOffset;
3897
3898 // Check that this scale is legal.
3899 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3900 continue;
3901
3902 // Compensate for the use having MinOffset built into it.
3903 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3904
3905 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3906
3907 // Check that multiplying with each base register doesn't overflow.
3908 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3909 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3910 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3911 goto next;
3912 }
3913
3914 // Check that multiplying with the scaled register doesn't overflow.
3915 if (F.ScaledReg) {
3916 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3917 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3918 continue;
3919 }
3920
3921 // Check that multiplying with the unfolded offset doesn't overflow.
3922 if (F.UnfoldedOffset != 0) {
3923 if (F.UnfoldedOffset == std::numeric_limits<int64_t>::min() &&
3924 Factor == -1)
3925 continue;
3926 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3927 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3928 continue;
3929 // If the offset will be truncated, check that it is in bounds.
3930 if (!IntTy->isPointerTy() &&
3931 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3932 continue;
3933 }
3934
3935 // If we make it here and it's legal, add it.
3936 (void)InsertFormula(LU, LUIdx, F);
3937 next:;
3938 }
3939}
3940
3941/// Generate stride factor reuse formulae by making use of scaled-offset address
3942/// modes, for example.
3943void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3944 // Determine the integer type for the base formula.
3945 Type *IntTy = Base.getType();
3946 if (!IntTy) return;
3947
3948 // If this Formula already has a scaled register, we can't add another one.
3949 // Try to unscale the formula to generate a better scale.
3950 if (Base.Scale != 0 && !Base.unscale())
3951 return;
3952
3953 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3953, __PRETTY_FUNCTION__))
;
3954
3955 // Check each interesting stride.
3956 for (int64_t Factor : Factors) {
3957 Base.Scale = Factor;
3958 Base.HasBaseReg = Base.BaseRegs.size() > 1;
3959 // Check whether this scale is going to be legal.
3960 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3961 Base)) {
3962 // As a special-case, handle special out-of-loop Basic users specially.
3963 // TODO: Reconsider this special case.
3964 if (LU.Kind == LSRUse::Basic &&
3965 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3966 LU.AccessTy, Base) &&
3967 LU.AllFixupsOutsideLoop)
3968 LU.Kind = LSRUse::Special;
3969 else
3970 continue;
3971 }
3972 // For an ICmpZero, negating a solitary base register won't lead to
3973 // new solutions.
3974 if (LU.Kind == LSRUse::ICmpZero &&
3975 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3976 continue;
3977 // For each addrec base reg, if its loop is current loop, apply the scale.
3978 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3979 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]);
3980 if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) {
3981 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3982 if (FactorS->isZero())
3983 continue;
3984 // Divide out the factor, ignoring high bits, since we'll be
3985 // scaling the value back up in the end.
3986 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3987 // TODO: This could be optimized to avoid all the copying.
3988 Formula F = Base;
3989 F.ScaledReg = Quotient;
3990 F.deleteBaseReg(F.BaseRegs[i]);
3991 // The canonical representation of 1*reg is reg, which is already in
3992 // Base. In that case, do not try to insert the formula, it will be
3993 // rejected anyway.
3994 if (F.Scale == 1 && (F.BaseRegs.empty() ||
3995 (AR->getLoop() != L && LU.AllFixupsOutsideLoop)))
3996 continue;
3997 // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate
3998 // non canonical Formula with ScaledReg's loop not being L.
3999 if (F.Scale == 1 && LU.AllFixupsOutsideLoop)
4000 F.canonicalize(*L);
4001 (void)InsertFormula(LU, LUIdx, F);
4002 }
4003 }
4004 }
4005 }
4006}
4007
4008/// Generate reuse formulae from different IV types.
4009void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
4010 // Don't bother truncating symbolic values.
4011 if (Base.BaseGV) return;
4012
4013 // Determine the integer type for the base formula.
4014 Type *DstTy = Base.getType();
4015 if (!DstTy) return;
4016 DstTy = SE.getEffectiveSCEVType(DstTy);
4017
4018 for (Type *SrcTy : Types) {
4019 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
4020 Formula F = Base;
4021
4022 // Sometimes SCEV is able to prove zero during ext transform. It may
4023 // happen if SCEV did not do all possible transforms while creating the
4024 // initial node (maybe due to depth limitations), but it can do them while
4025 // taking ext.
4026 if (F.ScaledReg) {
4027 const SCEV *NewScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
4028 if (NewScaledReg->isZero())
4029 continue;
4030 F.ScaledReg = NewScaledReg;
4031 }
4032 bool HasZeroBaseReg = false;
4033 for (const SCEV *&BaseReg : F.BaseRegs) {
4034 const SCEV *NewBaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
4035 if (NewBaseReg->isZero()) {
4036 HasZeroBaseReg = true;
4037 break;
4038 }
4039 BaseReg = NewBaseReg;
4040 }
4041 if (HasZeroBaseReg)
4042 continue;
4043
4044 // TODO: This assumes we've done basic processing on all uses and
4045 // have an idea what the register usage is.
4046 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
4047 continue;
4048
4049 F.canonicalize(*L);
4050 (void)InsertFormula(LU, LUIdx, F);
4051 }
4052 }
4053}
4054
4055namespace {
4056
4057/// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
4058/// modifications so that the search phase doesn't have to worry about the data
4059/// structures moving underneath it.
4060struct WorkItem {
4061 size_t LUIdx;
4062 int64_t Imm;
4063 const SCEV *OrigReg;
4064
4065 WorkItem(size_t LI, int64_t I, const SCEV *R)
4066 : LUIdx(LI), Imm(I), OrigReg(R) {}
4067
4068 void print(raw_ostream &OS) const;
4069 void dump() const;
4070};
4071
4072} // end anonymous namespace
4073
4074#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
4075void WorkItem::print(raw_ostream &OS) const {
4076 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
4077 << " , add offset " << Imm;
4078}
4079
4080LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void WorkItem::dump() const {
4081 print(errs()); errs() << '\n';
4082}
4083#endif
4084
4085/// Look for registers which are a constant distance apart and try to form reuse
4086/// opportunities between them.
4087void LSRInstance::GenerateCrossUseConstantOffsets() {
4088 // Group the registers by their value without any added constant offset.
4089 using ImmMapTy = std::map<int64_t, const SCEV *>;
4090
4091 DenseMap<const SCEV *, ImmMapTy> Map;
4092 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
4093 SmallVector<const SCEV *, 8> Sequence;
4094 for (const SCEV *Use : RegUses) {
4095 const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
4096 int64_t Imm = ExtractImmediate(Reg, SE);
4097 auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
4098 if (Pair.second)
4099 Sequence.push_back(Reg);
4100 Pair.first->second.insert(std::make_pair(Imm, Use));
4101 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
4102 }
4103
4104 // Now examine each set of registers with the same base value. Build up
4105 // a list of work to do and do the work in a separate step so that we're
4106 // not adding formulae and register counts while we're searching.
4107 SmallVector<WorkItem, 32> WorkItems;
4108 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
4109 for (const SCEV *Reg : Sequence) {
4110 const ImmMapTy &Imms = Map.find(Reg)->second;
4111
4112 // It's not worthwhile looking for reuse if there's only one offset.
4113 if (Imms.size() == 1)
4114 continue;
4115
4116 LLVM_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)
4117 for (const auto &Entrydo { 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)
4118 : Imms) dbgs()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)
4119 << ' ' << 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)
4120 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)
;
4121
4122 // Examine each offset.
4123 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
4124 J != JE; ++J) {
4125 const SCEV *OrigReg = J->second;
4126
4127 int64_t JImm = J->first;
4128 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
4129
4130 if (!isa<SCEVConstant>(OrigReg) &&
4131 UsedByIndicesMap[Reg].count() == 1) {
4132 LLVM_DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigRegdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Skipping cross-use reuse for "
<< *OrigReg << '\n'; } } while (false)
4133 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Skipping cross-use reuse for "
<< *OrigReg << '\n'; } } while (false)
;
4134 continue;
4135 }
4136
4137 // Conservatively examine offsets between this orig reg a few selected
4138 // other orig regs.
4139 int64_t First = Imms.begin()->first;
4140 int64_t Last = std::prev(Imms.end())->first;
4141 // Compute (First + Last) / 2 without overflow using the fact that
4142 // First + Last = 2 * (First + Last) + (First ^ Last).
4143 int64_t Avg = (First & Last) + ((First ^ Last) >> 1);
4144 // If the result is negative and First is odd and Last even (or vice versa),
4145 // we rounded towards -inf. Add 1 in that case, to round towards 0.
4146 Avg = Avg + ((First ^ Last) & ((uint64_t)Avg >> 63));
4147 ImmMapTy::const_iterator OtherImms[] = {
4148 Imms.begin(), std::prev(Imms.end()),
4149 Imms.lower_bound(Avg)};
4150 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
4151 ImmMapTy::const_iterator M = OtherImms[i];
4152 if (M == J || M == JE) continue;
4153
4154 // Compute the difference between the two.
4155 int64_t Imm = (uint64_t)JImm - M->first;
4156 for (unsigned LUIdx : UsedByIndices.set_bits())
4157 // Make a memo of this use, offset, and register tuple.
4158 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
4159 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
4160 }
4161 }
4162 }
4163
4164 Map.clear();
4165 Sequence.clear();
4166 UsedByIndicesMap.clear();
4167 UniqueItems.clear();
4168
4169 // Now iterate through the worklist and add new formulae.
4170 for (const WorkItem &WI : WorkItems) {
4171 size_t LUIdx = WI.LUIdx;
4172 LSRUse &LU = Uses[LUIdx];
4173 int64_t Imm = WI.Imm;
4174 const SCEV *OrigReg = WI.OrigReg;
4175
4176 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
4177 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
4178 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
4179
4180 // TODO: Use a more targeted data structure.
4181 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
4182 Formula F = LU.Formulae[L];
4183 // FIXME: The code for the scaled and unscaled registers looks
4184 // very similar but slightly different. Investigate if they
4185 // could be merged. That way, we would not have to unscale the
4186 // Formula.
4187 F.unscale();
4188 // Use the immediate in the scaled register.
4189 if (F.ScaledReg == OrigReg) {
4190 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
4191 // Don't create 50 + reg(-50).
4192 if (F.referencesReg(SE.getSCEV(
4193 ConstantInt::get(IntTy, -(uint64_t)Offset))))
4194 continue;
4195 Formula NewF = F;
4196 NewF.BaseOffset = Offset;
4197 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4198 NewF))
4199 continue;
4200 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
4201
4202 // If the new scale is a constant in a register, and adding the constant
4203 // value to the immediate would produce a value closer to zero than the
4204 // immediate itself, then the formula isn't worthwhile.
4205 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
4206 if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
4207 (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
4208 .ule(std::abs(NewF.BaseOffset)))
4209 continue;
4210
4211 // OK, looks good.
4212 NewF.canonicalize(*this->L);
4213 (void)InsertFormula(LU, LUIdx, NewF);
4214 } else {
4215 // Use the immediate in a base register.
4216 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
4217 const SCEV *BaseReg = F.BaseRegs[N];
4218 if (BaseReg != OrigReg)
4219 continue;
4220 Formula NewF = F;
4221 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
4222 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
4223 LU.Kind, LU.AccessTy, NewF)) {
4224 if (TTI.shouldFavorPostInc() &&
4225 mayUsePostIncMode(TTI, LU, OrigReg, this->L, SE))
4226 continue;
4227 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
4228 continue;
4229 NewF = F;
4230 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
4231 }
4232 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
4233
4234 // If the new formula has a constant in a register, and adding the
4235 // constant value to the immediate would produce a value closer to
4236 // zero than the immediate itself, then the formula isn't worthwhile.
4237 for (const SCEV *NewReg : NewF.BaseRegs)
4238 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
4239 if ((C->getAPInt() + NewF.BaseOffset)
4240 .abs()
4241 .slt(std::abs(NewF.BaseOffset)) &&
4242 (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
4243 countTrailingZeros<uint64_t>(NewF.BaseOffset))
4244 goto skip_formula;
4245
4246 // Ok, looks good.
4247 NewF.canonicalize(*this->L);
4248 (void)InsertFormula(LU, LUIdx, NewF);
4249 break;
4250 skip_formula:;
4251 }
4252 }
4253 }
4254 }
4255}
4256
4257/// Generate formulae for each use.
4258void
4259LSRInstance::GenerateAllReuseFormulae() {
4260 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
4261 // queries are more precise.
4262 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4263 LSRUse &LU = Uses[LUIdx];
4264 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4265 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
4266 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4267 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
4268 }
4269 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4270 LSRUse &LU = Uses[LUIdx];
4271 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4272 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
4273 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4274 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
4275 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4276 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
4277 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4278 GenerateScales(LU, LUIdx, LU.Formulae[i]);
4279 }
4280 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4281 LSRUse &LU = Uses[LUIdx];
4282 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4283 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
4284 }
4285
4286 GenerateCrossUseConstantOffsets();
4287
4288 LLVM_DEBUG(dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
4289 "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)
4290 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
;
4291}
4292
4293/// If there are multiple formulae with the same set of registers used
4294/// by other uses, pick the best one and delete the others.
4295void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
4296 DenseSet<const SCEV *> VisitedRegs;
4297 SmallPtrSet<const SCEV *, 16> Regs;
4298 SmallPtrSet<const SCEV *, 16> LoserRegs;
4299#ifndef NDEBUG
4300 bool ChangedFormulae = false;
4301#endif
4302
4303 // Collect the best formula for each unique set of shared registers. This
4304 // is reset for each use.
4305 using BestFormulaeTy =
4306 DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>;
4307
4308 BestFormulaeTy BestFormulae;
4309
4310 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4311 LSRUse &LU = Uses[LUIdx];
4312 LLVM_DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
4313 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4314
4315 bool Any = false;
4316 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
4317 FIdx != NumForms; ++FIdx) {
4318 Formula &F = LU.Formulae[FIdx];
4319
4320 // Some formulas are instant losers. For example, they may depend on
4321 // nonexistent AddRecs from other loops. These need to be filtered
4322 // immediately, otherwise heuristics could choose them over others leading
4323 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
4324 // avoids the need to recompute this information across formulae using the
4325 // same bad AddRec. Passing LoserRegs is also essential unless we remove
4326 // the corresponding bad register from the Regs set.
4327 Cost CostF(L, SE, TTI);
4328 Regs.clear();
4329 CostF.RateFormula(F, Regs, VisitedRegs, LU, &LoserRegs);
4330 if (CostF.isLoser()) {
4331 // During initial formula generation, undesirable formulae are generated
4332 // by uses within other loops that have some non-trivial address mode or
4333 // use the postinc form of the IV. LSR needs to provide these formulae
4334 // as the basis of rediscovering the desired formula that uses an AddRec
4335 // corresponding to the existing phi. Once all formulae have been
4336 // generated, these initial losers may be pruned.
4337 LLVM_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)
4338 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering loser "; F.print
(dbgs()); dbgs() << "\n"; } } while (false)
;
4339 }
4340 else {
4341 SmallVector<const SCEV *, 4> Key;
4342 for (const SCEV *Reg : F.BaseRegs) {
4343 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
4344 Key.push_back(Reg);
4345 }
4346 if (F.ScaledReg &&
4347 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
4348 Key.push_back(F.ScaledReg);
4349 // Unstable sort by host order ok, because this is only used for
4350 // uniquifying.
4351 llvm::sort(Key);
4352
4353 std::pair<BestFormulaeTy::const_iterator, bool> P =
4354 BestFormulae.insert(std::make_pair(Key, FIdx));
4355 if (P.second)
4356 continue;
4357
4358 Formula &Best = LU.Formulae[P.first->second];
4359
4360 Cost CostBest(L, SE, TTI);
4361 Regs.clear();
4362 CostBest.RateFormula(Best, Regs, VisitedRegs, LU);
4363 if (CostF.isLess(CostBest))
4364 std::swap(F, Best);
4365 LLVM_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)
4366 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)
4367 " in favor of formula ";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)
4368 Best.print(dbgs()); 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)
;
4369 }
4370#ifndef NDEBUG
4371 ChangedFormulae = true;
4372#endif
4373 LU.DeleteFormula(F);
4374 --FIdx;
4375 --NumForms;
4376 Any = true;
4377 }
4378
4379 // Now that we've filtered out some formulae, recompute the Regs set.
4380 if (Any)
4381 LU.RecomputeRegs(LUIdx, RegUses);
4382
4383 // Reset this to prepare for the next use.
4384 BestFormulae.clear();
4385 }
4386
4387 LLVM_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)
4388 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)
4389 "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)
4390 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)
4391 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4392}
4393
4394/// Estimate the worst-case number of solutions the solver might have to
4395/// consider. It almost never considers this many solutions because it prune the
4396/// search space, but the pruning isn't always sufficient.
4397size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4398 size_t Power = 1;
4399 for (const LSRUse &LU : Uses) {
4400 size_t FSize = LU.Formulae.size();
4401 if (FSize >= ComplexityLimit) {
4402 Power = ComplexityLimit;
4403 break;
4404 }
4405 Power *= FSize;
4406 if (Power >= ComplexityLimit)
4407 break;
4408 }
4409 return Power;
4410}
4411
4412/// When one formula uses a superset of the registers of another formula, it
4413/// won't help reduce register pressure (though it may not necessarily hurt
4414/// register pressure); remove it to simplify the system.
4415void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4416 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4417 LLVM_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)
;
4418
4419 LLVM_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)
4420 "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)
4421 "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)
;
4422
4423 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4424 LSRUse &LU = Uses[LUIdx];
4425 bool Any = false;
4426 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4427 Formula &F = LU.Formulae[i];
4428 // Look for a formula with a constant or GV in a register. If the use
4429 // also has a formula with that same value in an immediate field,
4430 // delete the one that uses a register.
4431 for (SmallVectorImpl<const SCEV *>::const_iterator
4432 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4433 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4434 Formula NewF = F;
4435 //FIXME: Formulas should store bitwidth to do wrapping properly.
4436 // See PR41034.
4437 NewF.BaseOffset += (uint64_t)C->getValue()->getSExtValue();
4438 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4439 (I - F.BaseRegs.begin()));
4440 if (LU.HasFormulaWithSameRegs(NewF)) {
4441 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4442 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4443 LU.DeleteFormula(F);
4444 --i;
4445 --e;
4446 Any = true;
4447 break;
4448 }
4449 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4450 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4451 if (!F.BaseGV) {
4452 Formula NewF = F;
4453 NewF.BaseGV = GV;
4454 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4455 (I - F.BaseRegs.begin()));
4456 if (LU.HasFormulaWithSameRegs(NewF)) {
4457 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4458 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4459 LU.DeleteFormula(F);
4460 --i;
4461 --e;
4462 Any = true;
4463 break;
4464 }
4465 }
4466 }
4467 }
4468 }
4469 if (Any)
4470 LU.RecomputeRegs(LUIdx, RegUses);
4471 }
4472
4473 LLVM_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)
;
4474 }
4475}
4476
4477/// When there are many registers for expressions like A, A+1, A+2, etc.,
4478/// allocate a single register for them.
4479void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4480 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4481 return;
4482
4483 LLVM_DEBUG(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)
4484 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)
4485 "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)
4486 "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)
;
4487
4488 // This is especially useful for unrolled loops.
4489
4490 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4491 LSRUse &LU = Uses[LUIdx];
4492 for (const Formula &F : LU.Formulae) {
4493 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4494 continue;
4495
4496 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4497 if (!LUThatHas)
4498 continue;
4499
4500 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4501 LU.Kind, LU.AccessTy))
4502 continue;
4503
4504 LLVM_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)
;
4505
4506 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4507
4508 // Transfer the fixups of LU to LUThatHas.
4509 for (LSRFixup &Fixup : LU.Fixups) {
4510 Fixup.Offset += F.BaseOffset;
4511 LUThatHas->pushFixup(Fixup);
4512 LLVM_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)
;
4513 }
4514
4515 // Delete formulae from the new use which are no longer legal.
4516 bool Any = false;
4517 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4518 Formula &F = LUThatHas->Formulae[i];
4519 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4520 LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4521 LLVM_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)
;
4522 LUThatHas->DeleteFormula(F);
4523 --i;
4524 --e;
4525 Any = true;
4526 }
4527 }
4528
4529 if (Any)
4530 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4531
4532 // Delete the old use.
4533 DeleteUse(LU, LUIdx);
4534 --LUIdx;
4535 --NumUses;
4536 break;
4537 }
4538 }
4539
4540 LLVM_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)
;
4541}
4542
4543/// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4544/// we've done more filtering, as it may be able to find more formulae to
4545/// eliminate.
4546void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4547 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4548 LLVM_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)
;
4549
4550 LLVM_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)
4551 "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)
;
4552
4553 FilterOutUndesirableDedicatedRegisters();
4554
4555 LLVM_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)
;
4556 }
4557}
4558
4559/// If a LSRUse has multiple formulae with the same ScaledReg and Scale.
4560/// Pick the best one and delete the others.
4561/// This narrowing heuristic is to keep as many formulae with different
4562/// Scale and ScaledReg pair as possible while narrowing the search space.
4563/// The benefit is that it is more likely to find out a better solution
4564/// from a formulae set with more Scale and ScaledReg variations than
4565/// a formulae set with the same Scale and ScaledReg. The picking winner
4566/// reg heuristic will often keep the formulae with the same Scale and
4567/// ScaledReg and filter others, and we want to avoid that if possible.
4568void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() {
4569 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4570 return;
4571
4572 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by choosing the best Formula " "from the Formulae with the same Scale and ScaledReg.\n"
; } } while (false)
4573 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 choosing the best Formula " "from the Formulae with the same Scale and ScaledReg.\n"
; } } while (false)
4574 "Narrowing the search space by choosing the best Formula "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by choosing the best Formula " "from the Formulae with the same Scale and ScaledReg.\n"
; } } while (false)
4575 "from the Formulae with the same Scale and ScaledReg.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by choosing the best Formula " "from the Formulae with the same Scale and ScaledReg.\n"
; } } while (false)
;
4576
4577 // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse.
4578 using BestFormulaeTy = DenseMap<std::pair<const SCEV *, int64_t>, size_t>;
4579
4580 BestFormulaeTy BestFormulae;
4581#ifndef NDEBUG
4582 bool ChangedFormulae = false;
4583#endif
4584 DenseSet<const SCEV *> VisitedRegs;
4585 SmallPtrSet<const SCEV *, 16> Regs;
4586
4587 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4588 LSRUse &LU = Uses[LUIdx];
4589 LLVM_DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
4590 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4591
4592 // Return true if Formula FA is better than Formula FB.
4593 auto IsBetterThan = [&](Formula &FA, Formula &FB) {
4594 // First we will try to choose the Formula with fewer new registers.
4595 // For a register used by current Formula, the more the register is
4596 // shared among LSRUses, the less we increase the register number
4597 // counter of the formula.
4598 size_t FARegNum = 0;
4599 for (const SCEV *Reg : FA.BaseRegs) {
4600 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4601 FARegNum += (NumUses - UsedByIndices.count() + 1);
4602 }
4603 size_t FBRegNum = 0;
4604 for (const SCEV *Reg : FB.BaseRegs) {
4605 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4606 FBRegNum += (NumUses - UsedByIndices.count() + 1);
4607 }
4608 if (FARegNum != FBRegNum)
4609 return FARegNum < FBRegNum;
4610
4611 // If the new register numbers are the same, choose the Formula with
4612 // less Cost.
4613 Cost CostFA(L, SE, TTI);
4614 Cost CostFB(L, SE, TTI);
4615 Regs.clear();
4616 CostFA.RateFormula(FA, Regs, VisitedRegs, LU);
4617 Regs.clear();
4618 CostFB.RateFormula(FB, Regs, VisitedRegs, LU);
4619 return CostFA.isLess(CostFB);
4620 };
4621
4622 bool Any = false;
4623 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4624 ++FIdx) {
4625 Formula &F = LU.Formulae[FIdx];
4626 if (!F.ScaledReg)
4627 continue;
4628 auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx});
4629 if (P.second)
4630 continue;
4631
4632 Formula &Best = LU.Formulae[P.first->second];
4633 if (IsBetterThan(F, Best))
4634 std::swap(F, Best);
4635 LLVM_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)
4636 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)
4637 " in favor of formula ";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)
4638 Best.print(dbgs()); 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)
;
4639#ifndef NDEBUG
4640 ChangedFormulae = true;
4641#endif
4642 LU.DeleteFormula(F);
4643 --FIdx;
4644 --NumForms;
4645 Any = true;
4646 }
4647 if (Any)
4648 LU.RecomputeRegs(LUIdx, RegUses);
4649
4650 // Reset this to prepare for the next use.
4651 BestFormulae.clear();
4652 }
4653
4654 LLVM_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)
4655 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)
4656 "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)
4657 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)
4658 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4659}
4660
4661/// The function delete formulas with high registers number expectation.
4662/// Assuming we don't know the value of each formula (already delete
4663/// all inefficient), generate probability of not selecting for each
4664/// register.
4665/// For example,
4666/// Use1:
4667/// reg(a) + reg({0,+,1})
4668/// reg(a) + reg({-1,+,1}) + 1
4669/// reg({a,+,1})
4670/// Use2:
4671/// reg(b) + reg({0,+,1})
4672/// reg(b) + reg({-1,+,1}) + 1
4673/// reg({b,+,1})
4674/// Use3:
4675/// reg(c) + reg(b) + reg({0,+,1})
4676/// reg(c) + reg({b,+,1})
4677///
4678/// Probability of not selecting
4679/// Use1 Use2 Use3
4680/// reg(a) (1/3) * 1 * 1
4681/// reg(b) 1 * (1/3) * (1/2)
4682/// reg({0,+,1}) (2/3) * (2/3) * (1/2)
4683/// reg({-1,+,1}) (2/3) * (2/3) * 1
4684/// reg({a,+,1}) (2/3) * 1 * 1
4685/// reg({b,+,1}) 1 * (2/3) * (2/3)
4686/// reg(c) 1 * 1 * 0
4687///
4688/// Now count registers number mathematical expectation for each formula:
4689/// Note that for each use we exclude probability if not selecting for the use.
4690/// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding
4691/// probabilty 1/3 of not selecting for Use1).
4692/// Use1:
4693/// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted
4694/// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted
4695/// reg({a,+,1}) 1
4696/// Use2:
4697/// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted
4698/// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted
4699/// reg({b,+,1}) 2/3
4700/// Use3:
4701/// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted
4702/// reg(c) + reg({b,+,1}) 1 + 2/3
4703void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() {
4704 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4705 return;
4706 // Ok, we have too many of formulae on our hands to conveniently handle.
4707 // Use a rough heuristic to thin out the list.
4708
4709 // Set of Regs wich will be 100% used in final solution.
4710 // Used in each formula of a solution (in example above this is reg(c)).
4711 // We can skip them in calculations.
4712 SmallPtrSet<const SCEV *, 4> UniqRegs;
4713 LLVM_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)
;
4714
4715 // Map each register to probability of not selecting
4716 DenseMap <const SCEV *, float> RegNumMap;
4717 for (const SCEV *Reg : RegUses) {
4718 if (UniqRegs.count(Reg))
4719 continue;
4720 float PNotSel = 1;
4721 for (const LSRUse &LU : Uses) {
4722 if (!LU.Regs.count(Reg))
4723 continue;
4724 float P = LU.getNotSelectedProbability(Reg);
4725 if (P != 0.0)
4726 PNotSel *= P;
4727 else
4728 UniqRegs.insert(Reg);
4729 }
4730 RegNumMap.insert(std::make_pair(Reg, PNotSel));
4731 }
4732
4733 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by deleting costly formulas\n"
; } } while (false)
4734 dbgs() << "Narrowing the search space by deleting costly formulas\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by deleting costly formulas\n"
; } } while (false)
;
4735
4736 // Delete formulas where registers number expectation is high.
4737 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4738 LSRUse &LU = Uses[LUIdx];
4739 // If nothing to delete - continue.
4740 if (LU.Formulae.size() < 2)
4741 continue;
4742 // This is temporary solution to test performance. Float should be
4743 // replaced with round independent type (based on integers) to avoid
4744 // different results for different target builds.
4745 float FMinRegNum = LU.Formulae[0].getNumRegs();
4746 float FMinARegNum = LU.Formulae[0].getNumRegs();
4747 size_t MinIdx = 0;
4748 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4749 Formula &F = LU.Formulae[i];
4750 float FRegNum = 0;
4751 float FARegNum = 0;
4752 for (const SCEV *BaseReg : F.BaseRegs) {
4753 if (UniqRegs.count(BaseReg))
4754 continue;
4755 FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4756 if (isa<SCEVAddRecExpr>(BaseReg))
4757 FARegNum +=
4758 RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4759 }
4760 if (const SCEV *ScaledReg = F.ScaledReg) {
4761 if (!UniqRegs.count(ScaledReg)) {
4762 FRegNum +=
4763 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4764 if (isa<SCEVAddRecExpr>(ScaledReg))
4765 FARegNum +=
4766 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4767 }
4768 }
4769 if (FMinRegNum > FRegNum ||
4770 (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) {
4771 FMinRegNum = FRegNum;
4772 FMinARegNum = FARegNum;
4773 MinIdx = i;
4774 }
4775 }
4776 LLVM_DEBUG(dbgs() << " The formula "; LU.Formulae[MinIdx].print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " The formula "; LU.Formulae
[MinIdx].print(dbgs()); dbgs() << " with min reg num " <<
FMinRegNum << '\n'; } } while (false)
4777 dbgs() << " with min reg num " << FMinRegNum << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " The formula "; LU.Formulae
[MinIdx].print(dbgs()); dbgs() << " with min reg num " <<
FMinRegNum << '\n'; } } while (false)
;
4778 if (MinIdx != 0)
4779 std::swap(LU.Formulae[MinIdx], LU.Formulae[0]);
4780 while (LU.Formulae.size() != 1) {
4781 LLVM_DEBUG(dbgs() << " Deleting "; LU.Formulae.back().print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; LU.Formulae
.back().print(dbgs()); dbgs() << '\n'; } } while (false
)
4782 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; LU.Formulae
.back().print(dbgs()); dbgs() << '\n'; } } while (false
)
;
4783 LU.Formulae.pop_back();
4784 }
4785 LU.RecomputeRegs(LUIdx, RegUses);
4786 assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula")((LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula"
) ? static_cast<void> (0) : __assert_fail ("LU.Formulae.size() == 1 && \"Should be exactly 1 min regs formula\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4786, __PRETTY_FUNCTION__))
;
4787 Formula &F = LU.Formulae[0];
4788 LLVM_DEBUG(dbgs() << " Leaving only "; F.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Leaving only "; F.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4789 // When we choose the formula, the regs become unique.
4790 UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
4791 if (F.ScaledReg)
4792 UniqRegs.insert(F.ScaledReg);
4793 }
4794 LLVM_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)
;
4795}
4796
4797/// Pick a register which seems likely to be profitable, and then in any use
4798/// which has any reference to that register, delete all formulae which do not
4799/// reference that register.
4800void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4801 // With all other options exhausted, loop until the system is simple
4802 // enough to handle.
4803 SmallPtrSet<const SCEV *, 4> Taken;
4804 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4805 // Ok, we have too many of formulae on our hands to conveniently handle.
4806 // Use a rough heuristic to thin out the list.
4807 LLVM_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)
;
4808
4809 // Pick the register which is used by the most LSRUses, which is likely
4810 // to be a good reuse register candidate.
4811 const SCEV *Best = nullptr;
4812 unsigned BestNum = 0;
4813 for (const SCEV *Reg : RegUses) {
4814 if (Taken.count(Reg))
4815 continue;
4816 if (!Best) {
4817 Best = Reg;
4818 BestNum = RegUses.getUsedByIndices(Reg).count();
4819 } else {
4820 unsigned Count = RegUses.getUsedByIndices(Reg).count();
4821 if (Count > BestNum) {
4822 Best = Reg;
4823 BestNum = Count;
4824 }
4825 }
4826 }
4827
4828 LLVM_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)
4829 << " 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)
;
4830 Taken.insert(Best);
4831
4832 // In any use with formulae which references this register, delete formulae
4833 // which don't reference it.
4834 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4835 LSRUse &LU = Uses[LUIdx];
4836 if (!LU.Regs.count(Best)) continue;
4837
4838 bool Any = false;
4839 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4840 Formula &F = LU.Formulae[i];
4841 if (!F.referencesReg(Best)) {
4842 LLVM_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)
;
4843 LU.DeleteFormula(F);
4844 --e;
4845 --i;
4846 Any = true;
4847 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?\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4847, __PRETTY_FUNCTION__))
;
4848 continue;
4849 }
4850 }
4851
4852 if (Any)
4853 LU.RecomputeRegs(LUIdx, RegUses);
4854 }
4855
4856 LLVM_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)
;
4857 }
4858}
4859
4860/// If there are an extraordinary number of formulae to choose from, use some
4861/// rough heuristics to prune down the number of formulae. This keeps the main
4862/// solver from taking an extraordinary amount of time in some worst-case
4863/// scenarios.
4864void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4865 NarrowSearchSpaceByDetectingSupersets();
4866 NarrowSearchSpaceByCollapsingUnrolledCode();
4867 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4868 if (FilterSameScaledReg)
4869 NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
4870 if (LSRExpNarrow)
4871 NarrowSearchSpaceByDeletingCostlyFormulas();
4872 else
4873 NarrowSearchSpaceByPickingWinnerRegs();
4874}
4875
4876/// This is the recursive solver.
4877void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4878 Cost &SolutionCost,
4879 SmallVectorImpl<const Formula *> &Workspace,
4880 const Cost &CurCost,
4881 const SmallPtrSet<const SCEV *, 16> &CurRegs,
4882 DenseSet<const SCEV *> &VisitedRegs) const {
4883 // Some ideas:
4884 // - prune more:
4885 // - use more aggressive filtering
4886 // - sort the formula so that the most profitable solutions are found first
4887 // - sort the uses too
4888 // - search faster:
4889 // - don't compute a cost, and then compare. compare while computing a cost
4890 // and bail early.
4891 // - track register sets with SmallBitVector
4892
4893 const LSRUse &LU = Uses[Workspace.size()];
4894
4895 // If this use references any register that's already a part of the
4896 // in-progress solution, consider it a requirement that a formula must
4897 // reference that register in order to be considered. This prunes out
4898 // unprofitable searching.
4899 SmallSetVector<const SCEV *, 4> ReqRegs;
4900 for (const SCEV *S : CurRegs)
4901 if (LU.Regs.count(S))
4902 ReqRegs.insert(S);
4903
4904 SmallPtrSet<const SCEV *, 16> NewRegs;
4905 Cost NewCost(L, SE, TTI);
4906 for (const Formula &F : LU.Formulae) {
4907 // Ignore formulae which may not be ideal in terms of register reuse of
4908 // ReqRegs. The formula should use all required registers before
4909 // introducing new ones.
4910 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4911 for (const SCEV *Reg : ReqRegs) {
4912 if ((F.ScaledReg && F.ScaledReg == Reg) ||
4913 is_contained(F.BaseRegs, Reg)) {
4914 --NumReqRegsToFind;
4915 if (NumReqRegsToFind == 0)
4916 break;
4917 }
4918 }
4919 if (NumReqRegsToFind != 0) {
4920 // If none of the formulae satisfied the required registers, then we could
4921 // clear ReqRegs and try again. Currently, we simply give up in this case.
4922 continue;
4923 }
4924
4925 // Evaluate the cost of the current formula. If it's already worse than
4926 // the current best, prune the search at that point.
4927 NewCost = CurCost;
4928 NewRegs = CurRegs;
4929 NewCost.RateFormula(F, NewRegs, VisitedRegs, LU);
4930 if (NewCost.isLess(SolutionCost)) {
4931 Workspace.push_back(&F);
4932 if (Workspace.size() != Uses.size()) {
4933 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4934 NewRegs, VisitedRegs);
4935 if (F.getNumRegs() == 1 && Workspace.size() == 1)
4936 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4937 } else {
4938 LLVM_DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\nRegs:\n"; for (const SCEV *S : NewRegs
) dbgs() << "- " << *S << "\n"; dbgs() <<
'\n'; } } while (false)
4939 dbgs() << ".\nRegs:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\nRegs:\n"; for (const SCEV *S : NewRegs
) dbgs() << "- " << *S << "\n"; dbgs() <<
'\n'; } } while (false)
4940 for (const SCEV *S : NewRegs) dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\nRegs:\n"; for (const SCEV *S : NewRegs
) dbgs() << "- " << *S << "\n"; dbgs() <<
'\n'; } } while (false)
4941 << "- " << *S << "\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\nRegs:\n"; for (const SCEV *S : NewRegs
) dbgs() << "- " << *S << "\n"; dbgs() <<
'\n'; } } while (false)
4942 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\nRegs:\n"; for (const SCEV *S : NewRegs
) dbgs() << "- " << *S << "\n"; dbgs() <<
'\n'; } } while (false)
;
4943
4944 SolutionCost = NewCost;
4945 Solution = Workspace;
4946 }
4947 Workspace.pop_back();
4948 }
4949 }
4950}
4951
4952/// Choose one formula from each use. Return the results in the given Solution
4953/// vector.
4954void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4955 SmallVector<const Formula *, 8> Workspace;
4956 Cost SolutionCost(L, SE, TTI);
4957 SolutionCost.Lose();
4958 Cost CurCost(L, SE, TTI);
4959 SmallPtrSet<const SCEV *, 16> CurRegs;
4960 DenseSet<const SCEV *> VisitedRegs;
4961 Workspace.reserve(Uses.size());
4962
4963 // SolveRecurse does all the work.
4964 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4965 CurRegs, VisitedRegs);
4966 if (Solution.empty()) {
4967 LLVM_DEBUG(dbgs() << "\nNo Satisfactory Solution\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nNo Satisfactory Solution\n"
; } } while (false)
;
4968 return;
4969 }
4970
4971 // Ok, we've now made all our decisions.
4972 LLVM_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
)
4973 "The chosen solution requires ";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
)
4974 SolutionCost.print(dbgs()); 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
)
4975 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
)
4976 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
)
4977 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
)
4978 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
)
4979 " ";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
)
4980 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
)
4981 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
)
4982 })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
)
;
4983
4984 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4984, __PRETTY_FUNCTION__))
;
4985}
4986
4987/// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
4988/// we can go while still being dominated by the input positions. This helps
4989/// canonicalize the insert position, which encourages sharing.
4990BasicBlock::iterator
4991LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4992 const SmallVectorImpl<Instruction *> &Inputs)
4993 const {
4994 Instruction *Tentative = &*IP;
4995 while (true) {
4996 bool AllDominate = true;
4997 Instruction *BetterPos = nullptr;
4998 // Don't bother attempting to insert before a catchswitch, their basic block
4999 // cannot have other non-PHI instructions.
5000 if (isa<CatchSwitchInst>(Tentative))
5001 return IP;
5002
5003 for (Instruction *Inst : Inputs) {
5004 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
5005 AllDominate = false;
5006 break;
5007 }
5008 // Attempt to find an insert position in the middle of the block,
5009 // instead of at the end, so that it can be used for other expansions.
5010 if (Tentative->getParent() == Inst->getParent() &&
5011 (!BetterPos || !DT.dominates(Inst, BetterPos)))
5012 BetterPos = &*std::next(BasicBlock::iterator(Inst));
5013 }
5014 if (!AllDominate)
5015 break;
5016 if (BetterPos)
5017 IP = BetterPos->getIterator();
5018 else
5019 IP = Tentative->getIterator();
5020
5021 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
5022 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
5023
5024 BasicBlock *IDom;
5025 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
5026 if (!Rung) return IP;
5027 Rung = Rung->getIDom();
5028 if (!Rung) return IP;
5029 IDom = Rung->getBlock();
5030
5031 // Don't climb into a loop though.
5032 const Loop *IDomLoop = LI.getLoopFor(IDom);
5033 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
5034 if (IDomDepth <= IPLoopDepth &&
5035 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
5036 break;
5037 }
5038
5039 Tentative = IDom->getTerminator();
5040 }
5041
5042 return IP;
5043}
5044
5045/// Determine an input position which will be dominated by the operands and
5046/// which will dominate the result.
5047BasicBlock::iterator
5048LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
5049 const LSRFixup &LF,
5050 const LSRUse &LU,
5051 SCEVExpander &Rewriter) const {
5052 // Collect some instructions which must be dominated by the
5053 // expanding replacement. These must be dominated by any operands that
5054 // will be required in the expansion.
5055 SmallVector<Instruction *, 4> Inputs;
5056 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
5057 Inputs.push_back(I);
5058 if (LU.Kind == LSRUse::ICmpZero)
5059 if (Instruction *I =
5060 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
5061 Inputs.push_back(I);
5062 if (LF.PostIncLoops.count(L)) {
5063 if (LF.isUseFullyOutsideLoop(L))
5064 Inputs.push_back(L->getLoopLatch()->getTerminator());
5065 else
5066 Inputs.push_back(IVIncInsertPos);
5067 }
5068 // The expansion must also be dominated by the increment positions of any
5069 // loops it for which it is using post-inc mode.
5070 for (const Loop *PIL : LF.PostIncLoops) {
5071 if (PIL == L) continue;
5072
5073 // Be dominated by the loop exit.
5074 SmallVector<BasicBlock *, 4> ExitingBlocks;
5075 PIL->getExitingBlocks(ExitingBlocks);
5076 if (!ExitingBlocks.empty()) {
5077 BasicBlock *BB = ExitingBlocks[0];
5078 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
5079 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
5080 Inputs.push_back(BB->getTerminator());
5081 }
5082 }
5083
5084 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5086, __PRETTY_FUNCTION__))
5085 && !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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5086, __PRETTY_FUNCTION__))
5086 "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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5086, __PRETTY_FUNCTION__))
;
5087
5088 // Then, climb up the immediate dominator tree as far as we can go while
5089 // still being dominated by the input positions.
5090 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
5091
5092 // Don't insert instructions before PHI nodes.
5093 while (isa<PHINode>(IP)) ++IP;
5094
5095 // Ignore landingpad instructions.
5096 while (IP->isEHPad()) ++IP;
5097
5098 // Ignore debug intrinsics.
5099 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
5100
5101 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
5102 // IP consistent across expansions and allows the previously inserted
5103 // instructions to be reused by subsequent expansion.
5104 while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
5105 ++IP;
5106
5107 return IP;
5108}
5109
5110/// Emit instructions for the leading candidate expression for this LSRUse (this
5111/// is called "expanding").
5112Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF,
5113 const Formula &F, BasicBlock::iterator IP,
5114 SCEVExpander &Rewriter,
5115 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5116 if (LU.RigidFormula)
5117 return LF.OperandValToReplace;
5118
5119 // Determine an input position which will be dominated by the operands and
5120 // which will dominate the result.
5121 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
5122 Rewriter.setInsertPoint(&*IP);
5123
5124 // Inform the Rewriter if we have a post-increment use, so that it can
5125 // perform an advantageous expansion.
5126 Rewriter.setPostInc(LF.PostIncLoops);
5127
5128 // This is the type that the user actually needs.
5129 Type *OpTy = LF.OperandValToReplace->getType();
5130 // This will be the type that we'll initially expand to.
5131 Type *Ty = F.getType();
5132 if (!Ty)
5133 // No type known; just expand directly to the ultimate type.
5134 Ty = OpTy;
5135 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
5136 // Expand directly to the ultimate type if it's the right size.
5137 Ty = OpTy;
5138 // This is the type to do integer arithmetic in.
5139 Type *IntTy = SE.getEffectiveSCEVType(Ty);
5140
5141 // Build up a list of operands to add together to form the full base.
5142 SmallVector<const SCEV *, 8> Ops;
5143
5144 // Expand the BaseRegs portion.
5145 for (const SCEV *Reg : F.BaseRegs) {
5146 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5146, __PRETTY_FUNCTION__))
;
5147
5148 // If we're expanding for a post-inc user, make the post-inc adjustment.
5149 Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE);
5150 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
5151 }
5152
5153 // Expand the ScaledReg portion.
5154 Value *ICmpScaledV = nullptr;
5155 if (F.Scale != 0) {
5156 const SCEV *ScaledS = F.ScaledReg;
5157
5158 // If we're expanding for a post-inc user, make the post-inc adjustment.
5159 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
5160 ScaledS = denormalizeForPostIncUse(ScaledS, Loops, SE);
5161
5162 if (LU.Kind == LSRUse::ICmpZero) {
5163 // Expand ScaleReg as if it was part of the base regs.
5164 if (F.Scale == 1)
5165 Ops.push_back(
5166 SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
5167 else {
5168 // An interesting way of "folding" with an icmp is to use a negated
5169 // scale, which we'll implement by inserting it into the other operand
5170 // of the icmp.
5171 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5172, __PRETTY_FUNCTION__))
5172 "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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5172, __PRETTY_FUNCTION__))
;
5173 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
5174 }
5175 } else {
5176 // Otherwise just expand the scaled register and an explicit scale,
5177 // which is expected to be matched as part of the address.
5178
5179 // Flush the operand list to suppress SCEVExpander hoisting address modes.
5180 // Unless the addressing mode will not be folded.
5181 if (!Ops.empty() && LU.Kind == LSRUse::Address &&
5182 isAMCompletelyFolded(TTI, LU, F)) {
5183 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), nullptr);
5184 Ops.clear();
5185 Ops.push_back(SE.getUnknown(FullV));
5186 }
5187 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
5188 if (F.Scale != 1)
5189 ScaledS =
5190 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
5191 Ops.push_back(ScaledS);
5192 }
5193 }
5194
5195 // Expand the GV portion.
5196 if (F.BaseGV) {
5197 // Flush the operand list to suppress SCEVExpander hoisting.
5198 if (!Ops.empty()) {
5199 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5200 Ops.clear();
5201 Ops.push_back(SE.getUnknown(FullV));
5202 }
5203 Ops.push_back(SE.getUnknown(F.BaseGV));
5204 }
5205
5206 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
5207 // unfolded offsets. LSR assumes they both live next to their uses.
5208 if (!Ops.empty()) {
5209 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5210 Ops.clear();
5211 Ops.push_back(SE.getUnknown(FullV));
5212 }
5213
5214 // Expand the immediate portion.
5215 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
5216 if (Offset != 0) {
5217 if (LU.Kind == LSRUse::ICmpZero) {
5218 // The other interesting way of "folding" with an ICmpZero is to use a
5219 // negated immediate.
5220 if (!ICmpScaledV)
5221 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
5222 else {
5223 Ops.push_back(SE.getUnknown(ICmpScaledV));
5224 ICmpScaledV = ConstantInt::get(IntTy, Offset);
5225 }
5226 } else {
5227 // Just add the immediate values. These again are expected to be matched
5228 // as part of the address.
5229 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
5230 }
5231 }
5232
5233 // Expand the unfolded offset portion.
5234 int64_t UnfoldedOffset = F.UnfoldedOffset;
5235 if (UnfoldedOffset != 0) {
5236 // Just add the immediate values.
5237 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
5238 UnfoldedOffset)));
5239 }
5240
5241 // Emit instructions summing all the operands.
5242 const SCEV *FullS = Ops.empty() ?
5243 SE.getConstant(IntTy, 0) :
5244 SE.getAddExpr(Ops);
5245 Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
5246
5247 // We're done expanding now, so reset the rewriter.
5248 Rewriter.clearPostInc();
5249
5250 // An ICmpZero Formula represents an ICmp which we're handling as a
5251 // comparison against zero. Now that we've expanded an expression for that
5252 // form, update the ICmp's other operand.
5253 if (LU.Kind == LSRUse::ICmpZero) {
5254 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
5255 DeadInsts.emplace_back(CI->getOperand(1));
5256 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5257, __PRETTY_FUNCTION__))
5257 "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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5257, __PRETTY_FUNCTION__))
;
5258 if (F.Scale == -1) {
5259 if (ICmpScaledV->getType() != OpTy) {
5260 Instruction *Cast =
5261 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
5262 OpTy, false),
5263 ICmpScaledV, OpTy, "tmp", CI);
5264 ICmpScaledV = Cast;
5265 }
5266 CI->setOperand(1, ICmpScaledV);
5267 } else {
5268 // A scale of 1 means that the scale has been expanded as part of the
5269 // base regs.
5270 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5272, __PRETTY_FUNCTION__))
5271 "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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5272, __PRETTY_FUNCTION__))
5272 "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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5272, __PRETTY_FUNCTION__))
;
5273 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
5274 -(uint64_t)Offset);
5275 if (C->getType() != OpTy)
5276 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
5277 OpTy, false),
5278 C, OpTy);
5279
5280 CI->setOperand(1, C);
5281 }
5282 }
5283
5284 return FullV;
5285}
5286
5287/// Helper for Rewrite. PHI nodes are special because the use of their operands
5288/// effectively happens in their predecessor blocks, so the expression may need
5289/// to be expanded in multiple places.
5290void LSRInstance::RewriteForPHI(
5291 PHINode *PN, const LSRUse &LU, const LSRFixup &LF, const Formula &F,
5292 SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5293 DenseMap<BasicBlock *, Value *> Inserted;
5294 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1
Assuming 'i' is not equal to 'e'
2
Loop condition is true. Entering loop body
5295 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
3
Assuming pointer value is null
4
Taking true branch
5296 bool needUpdateFixups = false;
5297 BasicBlock *BB = PN->getIncomingBlock(i);
5298
5299 // If this is a critical edge, split the edge so that we do not insert
5300 // the code on all predecessor/successor paths. We do this unless this
5301 // is the canonical backedge for this loop, which complicates post-inc
5302 // users.
5303 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
5
Assuming 'e' is equal to 1
6
Taking false branch
5304 !isa<IndirectBrInst>(BB->getTerminator()) &&
5305 !isa<CatchSwitchInst>(BB->getTerminator())) {
5306 BasicBlock *Parent = PN->getParent();
5307 Loop *PNLoop = LI.getLoopFor(Parent);
5308 if (!PNLoop || Parent != PNLoop->getHeader()) {
5309 // Split the critical edge.
5310 BasicBlock *NewBB = nullptr;
5311 if (!Parent->isLandingPad()) {
5312 NewBB = SplitCriticalEdge(BB, Parent,
5313 CriticalEdgeSplittingOptions(&DT, &LI)
5314 .setMergeIdenticalEdges()
5315 .setKeepOneInputPHIs());
5316 } else {
5317 SmallVector<BasicBlock*, 2> NewBBs;
5318 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
5319 NewBB = NewBBs[0];
5320 }
5321 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
5322 // phi predecessors are identical. The simple thing to do is skip
5323 // splitting in this case rather than complicate the API.
5324 if (NewBB) {
5325 // If PN is outside of the loop and BB is in the loop, we want to
5326 // move the block to be immediately before the PHI block, not
5327 // immediately after BB.
5328 if (L->contains(BB) && !L->contains(PN))
5329 NewBB->moveBefore(PN->getParent());
5330
5331 // Splitting the edge can reduce the number of PHI entries we have.
5332 e = PN->getNumIncomingValues();
5333 BB = NewBB;
5334 i = PN->getBasicBlockIndex(BB);
5335
5336 needUpdateFixups = true;
5337 }
5338 }
5339 }
5340
5341 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
5342 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
5343 if (!Pair.second)
7
Assuming the condition is false
8
Taking false branch
5344 PN->setIncomingValue(i, Pair.first->second);
5345 else {
5346 Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
5347 Rewriter, DeadInsts);
5348
5349 // If this is reuse-by-noop-cast, insert the noop cast.
5350 Type *OpTy = LF.OperandValToReplace->getType();
9
Called C++ object pointer is null
5351 if (FullV->getType() != OpTy)
5352 FullV =
5353 CastInst::Create(CastInst::getCastOpcode(FullV, false,
5354 OpTy, false),
5355 FullV, LF.OperandValToReplace->getType(),
5356 "tmp", BB->getTerminator());
5357
5358 PN->setIncomingValue(i, FullV);
5359 Pair.first->second = FullV;
5360 }
5361
5362 // If LSR splits critical edge and phi node has other pending
5363 // fixup operands, we need to update those pending fixups. Otherwise
5364 // formulae will not be implemented completely and some instructions
5365 // will not be eliminated.
5366 if (needUpdateFixups) {
5367 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5368 for (LSRFixup &Fixup : Uses[LUIdx].Fixups)
5369 // If fixup is supposed to rewrite some operand in the phi
5370 // that was just updated, it may be already moved to
5371 // another phi node. Such fixup requires update.
5372 if (Fixup.UserInst == PN) {
5373 // Check if the operand we try to replace still exists in the
5374 // original phi.
5375 bool foundInOriginalPHI = false;
5376 for (const auto &val : PN->incoming_values())
5377 if (val == Fixup.OperandValToReplace) {
5378 foundInOriginalPHI = true;
5379 break;
5380 }
5381
5382 // If fixup operand found in original PHI - nothing to do.
5383 if (foundInOriginalPHI)
5384 continue;
5385
5386 // Otherwise it might be moved to another PHI and requires update.
5387 // If fixup operand not found in any of the incoming blocks that
5388 // means we have already rewritten it - nothing to do.
5389 for (const auto &Block : PN->blocks())
5390 for (BasicBlock::iterator I = Block->begin(); isa<PHINode>(I);
5391 ++I) {
5392 PHINode *NewPN = cast<PHINode>(I);
5393 for (const auto &val : NewPN->incoming_values())
5394 if (val == Fixup.OperandValToReplace)
5395 Fixup.UserInst = NewPN;
5396 }
5397 }
5398 }
5399 }
5400}
5401
5402/// Emit instructions for the leading candidate expression for this LSRUse (this
5403/// is called "expanding"), and update the UserInst to reference the newly
5404/// expanded value.
5405void LSRInstance::Rewrite(const LSRUse &LU, const LSRFixup &LF,
5406 const Formula &F, SCEVExpander &Rewriter,
5407 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5408 // First, find an insertion point that dominates UserInst. For PHI nodes,
5409 // find the nearest block which dominates all the relevant uses.
5410 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
5411 RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
5412 } else {
5413 Value *FullV =
5414 Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
5415
5416 // If this is reuse-by-noop-cast, insert the noop cast.
5417 Type *OpTy = LF.OperandValToReplace->getType();
5418 if (FullV->getType() != OpTy) {
5419 Instruction *Cast =
5420 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
5421 FullV, OpTy, "tmp", LF.UserInst);
5422 FullV = Cast;
5423 }
5424
5425 // Update the user. ICmpZero is handled specially here (for now) because
5426 // Expand may have updated one of the operands of the icmp already, and
5427 // its new value may happen to be equal to LF.OperandValToReplace, in
5428 // which case doing replaceUsesOfWith leads to replacing both operands
5429 // with the same value. TODO: Reorganize this.
5430 if (LU.Kind == LSRUse::ICmpZero)
5431 LF.UserInst->setOperand(0, FullV);
5432 else
5433 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
5434 }
5435
5436 DeadInsts.emplace_back(LF.OperandValToReplace);
5437}
5438
5439/// Rewrite all the fixup locations with new values, following the chosen
5440/// solution.
5441void LSRInstance::ImplementSolution(
5442 const SmallVectorImpl<const Formula *> &Solution) {
5443 // Keep track of instructions we may have made dead, so that
5444 // we can remove them after we are done working.
5445 SmallVector<WeakTrackingVH, 16> DeadInsts;
5446
5447 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(),
5448 "lsr");
5449#ifndef NDEBUG
5450 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5451#endif
5452 Rewriter.disableCanonicalMode();
5453 Rewriter.enableLSRMode();
5454 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
5455
5456 // Mark phi nodes that terminate chains so the expander tries to reuse them.
5457 for (const IVChain &Chain : IVChainVec) {
5458 if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
5459 Rewriter.setChainedPhi(PN);
5460 }
5461
5462 // Expand the new value definitions and update the users.
5463 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5464 for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
5465 Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
5466 Changed = true;
5467 }
5468
5469 for (const IVChain &Chain : IVChainVec) {
5470 GenerateIVChain(Chain, Rewriter, DeadInsts);
5471 Changed = true;
5472 }
5473 // Clean up after ourselves. This must be done before deleting any
5474 // instructions.
5475 Rewriter.clear();
5476
5477 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
5478}
5479
5480LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5481 DominatorTree &DT, LoopInfo &LI,
5482 const TargetTransformInfo &TTI)
5483 : IU(IU), SE(SE), DT(DT), LI(LI), TTI(TTI), L(L),
5484 FavorBackedgeIndex(EnableBackedgeIndexing &&
5485 TTI.shouldFavorBackedgeIndex(L)) {
5486 // If LoopSimplify form is not available, stay out of trouble.
5487 if (!L->isLoopSimplifyForm())
5488 return;
5489
5490 // If there's no interesting work to be done, bail early.
5491 if (IU.empty()) return;
5492
5493 // If there's too much analysis to be done, bail early. We won't be able to
5494 // model the problem anyway.
5495 unsigned NumUsers = 0;
5496 for (const IVStrideUse &U : IU) {
5497 if (++NumUsers > MaxIVUsers) {
5498 (void)U;
5499 LLVM_DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << Udo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping loop, too many IV Users in "
<< U << "\n"; } } while (false)
5500 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping loop, too many IV Users in "
<< U << "\n"; } } while (false)
;
5501 return;
5502 }
5503 // Bail out if we have a PHI on an EHPad that gets a value from a
5504 // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is
5505 // no good place to stick any instructions.
5506 if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
5507 auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
5508 if (isa<FuncletPadInst>(FirstNonPHI) ||
5509 isa<CatchSwitchInst>(FirstNonPHI))
5510 for (BasicBlock *PredBB : PN->blocks())
5511 if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
5512 return;
5513 }
5514 }
5515
5516#ifndef NDEBUG
5517 // All dominating loops must have preheaders, or SCEVExpander may not be able
5518 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
5519 //
5520 // IVUsers analysis should only create users that are dominated by simple loop
5521 // headers. Since this loop should dominate all of its users, its user list
5522 // should be empty if this loop itself is not within a simple loop nest.
5523 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
5524 Rung; Rung = Rung->getIDom()) {
5525 BasicBlock *BB = Rung->getBlock();
5526 const Loop *DomLoop = LI.getLoopFor(BB);
5527 if (DomLoop && DomLoop->getHeader() == BB) {
5528 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\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5528, __PRETTY_FUNCTION__))
;
5529 }
5530 }
5531#endif // DEBUG
5532
5533 LLVM_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)
5534 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)
5535 dbgs() << ":\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
;
5536
5537 // First, perform some low-level loop optimizations.
5538 OptimizeShadowIV();
5539 OptimizeLoopTermCond();
5540
5541 // If loop preparation eliminates all interesting IV users, bail.
5542 if (IU.empty()) return;
5543
5544 // Skip nested loops until we can model them better with formulae.
5545 if (!L->empty()) {
5546 LLVM_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)
;
5547 return;
5548 }
5549
5550 // Start collecting data and preparing for the solver.
5551 CollectChains();
5552 CollectInterestingTypesAndFactors();
5553 CollectFixupsAndInitialFormulae();
5554 CollectLoopInvariantFixupsAndFormulae();
5555
5556 if (Uses.empty())
5557 return;
5558
5559 LLVM_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
)
5560 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR found " << Uses
.size() << " uses:\n"; print_uses(dbgs()); } } while (false
)
;
5561
5562 // Now use the reuse data to generate a bunch of interesting ways
5563 // to formulate the values needed for the uses.
5564 GenerateAllReuseFormulae();
5565
5566 FilterOutUndesirableDedicatedRegisters();
5567 NarrowSearchSpaceUsingHeuristics();
5568
5569 SmallVector<const Formula *, 8> Solution;
5570 Solve(Solution);
5571
5572 // Release memory that is no longer needed.
5573 Factors.clear();
5574 Types.clear();
5575 RegUses.clear();
5576
5577 if (Solution.empty())
5578 return;
5579
5580#ifndef NDEBUG
5581 // Formulae should be legal.
5582 for (const LSRUse &LU : Uses) {
5583 for (const Formula &F : LU.Formulae)
5584 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5585, __PRETTY_FUNCTION__))
5585 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!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5585, __PRETTY_FUNCTION__))
;
5586 };
5587#endif
5588
5589 // Now that we've decided what we want, make it so.
5590 ImplementSolution(Solution);
5591}
5592
5593#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5594void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
5595 if (Factors.empty() && Types.empty()) return;
5596
5597 OS << "LSR has identified the following interesting factors and types: ";
5598 bool First = true;
5599
5600 for (int64_t Factor : Factors) {
5601 if (!First) OS << ", ";
5602 First = false;
5603 OS << '*' << Factor;
5604 }
5605
5606 for (Type *Ty : Types) {
5607 if (!First) OS << ", ";
5608 First = false;
5609 OS << '(' << *Ty << ')';
5610 }
5611 OS << '\n';
5612}
5613
5614void LSRInstance::print_fixups(raw_ostream &OS) const {
5615 OS << "LSR is examining the following fixup sites:\n";
5616 for (const LSRUse &LU : Uses)
5617 for (const LSRFixup &LF : LU.Fixups) {
5618 dbgs() << " ";
5619 LF.print(OS);
5620 OS << '\n';
5621 }
5622}
5623
5624void LSRInstance::print_uses(raw_ostream &OS) const {
5625 OS << "LSR is examining the following uses:\n";
5626 for (const LSRUse &LU : Uses) {
5627 dbgs() << " ";
5628 LU.print(OS);
5629 OS << '\n';
5630 for (const Formula &F : LU.Formulae) {
5631 OS << " ";
5632 F.print(OS);
5633 OS << '\n';
5634 }
5635 }
5636}
5637
5638void LSRInstance::print(raw_ostream &OS) const {
5639 print_factors_and_types(OS);
5640 print_fixups(OS);
5641 print_uses(OS);
5642}
5643
5644LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRInstance::dump() const {
5645 print(errs()); errs() << '\n';
5646}
5647#endif
5648
5649namespace {
5650
5651class LoopStrengthReduce : public LoopPass {
5652public:
5653 static char ID; // Pass ID, replacement for typeid
5654
5655 LoopStrengthReduce();
5656
5657private:
5658 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
5659 void getAnalysisUsage(AnalysisUsage &AU) const override;
5660};
5661
5662} // end anonymous namespace
5663
5664LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
5665 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
5666}
5667
5668void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
5669 // We split critical edges, so we change the CFG. However, we do update
5670 // many analyses if they are around.
5671 AU.addPreservedID(LoopSimplifyID);
5672
5673 AU.addRequired<LoopInfoWrapperPass>();
5674 AU.addPreserved<LoopInfoWrapperPass>();
5675 AU.addRequiredID(LoopSimplifyID);
5676 AU.addRequired<DominatorTreeWrapperPass>();
5677 AU.addPreserved<DominatorTreeWrapperPass>();
5678 AU.addRequired<ScalarEvolutionWrapperPass>();
5679 AU.addPreserved<ScalarEvolutionWrapperPass>();
5680 // Requiring LoopSimplify a second time here prevents IVUsers from running
5681 // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5682 AU.addRequiredID(LoopSimplifyID);
5683 AU.addRequired<IVUsersWrapperPass>();
5684 AU.addPreserved<IVUsersWrapperPass>();
5685 AU.addRequired<TargetTransformInfoWrapperPass>();
5686}
5687
5688static bool ReduceLoopStrength(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5689 DominatorTree &DT, LoopInfo &LI,
5690 const TargetTransformInfo &TTI) {
5691 bool Changed = false;
5692
5693 // Run the main LSR transformation.
5694 Changed |= LSRInstance(L, IU, SE, DT, LI, TTI).getChanged();
5695
5696 // Remove any extra phis created by processing inner loops.
5697 Changed |= DeleteDeadPHIs(L->getHeader());
5698 if (EnablePhiElim && L->isLoopSimplifyForm()) {
5699 SmallVector<WeakTrackingVH, 16> DeadInsts;
5700 const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
5701 SCEVExpander Rewriter(SE, DL, "lsr");
5702#ifndef NDEBUG
5703 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5704#endif
5705 unsigned numFolded = Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, &TTI);
5706 if (numFolded) {
5707 Changed = true;
5708 DeleteTriviallyDeadInstructions(DeadInsts);
5709 DeleteDeadPHIs(L->getHeader());
5710 }
5711 }
5712 return Changed;
5713}
5714
5715bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5716 if (skipLoop(L))
5717 return false;
5718
5719 auto &IU = getAnalysis<IVUsersWrapperPass>().getIU();
5720 auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
5721 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
5722 auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
5723 const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
5724 *L->getHeader()->getParent());
5725 return ReduceLoopStrength(L, IU, SE, DT, LI, TTI);
5726}
5727
5728PreservedAnalyses LoopStrengthReducePass::run(Loop &L, LoopAnalysisManager &AM,
5729 LoopStandardAnalysisResults &AR,
5730 LPMUpdater &) {
5731 if (!ReduceLoopStrength(&L, AM.getResult<IVUsersAnalysis>(L, AR), AR.SE,
5732 AR.DT, AR.LI, AR.TTI))
5733 return PreservedAnalyses::all();
5734
5735 return getLoopPassPreservedAnalyses();
5736}
5737
5738char LoopStrengthReduce::ID = 0;
5739
5740INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",static void *initializeLoopStrengthReducePassOnce(PassRegistry
&Registry) {
5741 "Loop Strength Reduction", false, false)static void *initializeLoopStrengthReducePassOnce(PassRegistry
&Registry) {
5742INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry);
5743INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
5744INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)initializeScalarEvolutionWrapperPassPass(Registry);
5745INITIALIZE_PASS_DEPENDENCY(IVUsersWrapperPass)initializeIVUsersWrapperPassPass(Registry);
5746INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry);
5747INITIALIZE_PASS_DEPENDENCY(LoopSimplify)initializeLoopSimplifyPass(Registry);
5748INITIALIZE_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 llvm::once_flag InitializeLoopStrengthReducePassFlag
; void llvm::initializeLoopStrengthReducePass(PassRegistry &
Registry) { llvm::call_once(InitializeLoopStrengthReducePassFlag
, initializeLoopStrengthReducePassOnce, std::ref(Registry)); }
5749 "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 llvm::once_flag InitializeLoopStrengthReducePassFlag
; void llvm::initializeLoopStrengthReducePass(PassRegistry &
Registry) { llvm::call_once(InitializeLoopStrengthReducePassFlag
, initializeLoopStrengthReducePassOnce, std::ref(Registry)); }
5750
5751Pass *llvm::createLoopStrengthReducePass() { return new LoopStrengthReduce(); }