Bug Summary

File:llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
Warning:line 5262, column 16
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -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 -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/build-llvm -resource-dir /usr/lib/llvm-14/lib/clang/14.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar -I include -I /build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/include -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-14/lib/clang/14.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-command-line-argument -Wno-unknown-warning-option -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/build-llvm -ferror-limit 19 -fvisibility-inlines-hidden -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2021-09-26-234817-15343-1 -x c++ /build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
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/AssumptionCache.h"
69#include "llvm/Analysis/IVUsers.h"
70#include "llvm/Analysis/LoopAnalysisManager.h"
71#include "llvm/Analysis/LoopInfo.h"
72#include "llvm/Analysis/LoopPass.h"
73#include "llvm/Analysis/MemorySSA.h"
74#include "llvm/Analysis/MemorySSAUpdater.h"
75#include "llvm/Analysis/ScalarEvolution.h"
76#include "llvm/Analysis/ScalarEvolutionExpressions.h"
77#include "llvm/Analysis/ScalarEvolutionNormalization.h"
78#include "llvm/Analysis/TargetLibraryInfo.h"
79#include "llvm/Analysis/TargetTransformInfo.h"
80#include "llvm/Analysis/ValueTracking.h"
81#include "llvm/Config/llvm-config.h"
82#include "llvm/IR/BasicBlock.h"
83#include "llvm/IR/Constant.h"
84#include "llvm/IR/Constants.h"
85#include "llvm/IR/DebugInfoMetadata.h"
86#include "llvm/IR/DerivedTypes.h"
87#include "llvm/IR/Dominators.h"
88#include "llvm/IR/GlobalValue.h"
89#include "llvm/IR/IRBuilder.h"
90#include "llvm/IR/InstrTypes.h"
91#include "llvm/IR/Instruction.h"
92#include "llvm/IR/Instructions.h"
93#include "llvm/IR/IntrinsicInst.h"
94#include "llvm/IR/Intrinsics.h"
95#include "llvm/IR/Module.h"
96#include "llvm/IR/OperandTraits.h"
97#include "llvm/IR/Operator.h"
98#include "llvm/IR/PassManager.h"
99#include "llvm/IR/Type.h"
100#include "llvm/IR/Use.h"
101#include "llvm/IR/User.h"
102#include "llvm/IR/Value.h"
103#include "llvm/IR/ValueHandle.h"
104#include "llvm/InitializePasses.h"
105#include "llvm/Pass.h"
106#include "llvm/Support/Casting.h"
107#include "llvm/Support/CommandLine.h"
108#include "llvm/Support/Compiler.h"
109#include "llvm/Support/Debug.h"
110#include "llvm/Support/ErrorHandling.h"
111#include "llvm/Support/MathExtras.h"
112#include "llvm/Support/raw_ostream.h"
113#include "llvm/Transforms/Scalar.h"
114#include "llvm/Transforms/Utils.h"
115#include "llvm/Transforms/Utils/BasicBlockUtils.h"
116#include "llvm/Transforms/Utils/Local.h"
117#include "llvm/Transforms/Utils/ScalarEvolutionExpander.h"
118#include <algorithm>
119#include <cassert>
120#include <cstddef>
121#include <cstdint>
122#include <cstdlib>
123#include <iterator>
124#include <limits>
125#include <map>
126#include <numeric>
127#include <utility>
128
129using namespace llvm;
130
131#define DEBUG_TYPE"loop-reduce" "loop-reduce"
132
133/// MaxIVUsers is an arbitrary threshold that provides an early opportunity for
134/// bail out. This threshold is far beyond the number of users that LSR can
135/// conceivably solve, so it should not affect generated code, but catches the
136/// worst cases before LSR burns too much compile time and stack space.
137static const unsigned MaxIVUsers = 200;
138
139// Temporary flag to cleanup congruent phis after LSR phi expansion.
140// It's currently disabled until we can determine whether it's truly useful or
141// not. The flag should be removed after the v3.0 release.
142// This is now needed for ivchains.
143static cl::opt<bool> EnablePhiElim(
144 "enable-lsr-phielim", cl::Hidden, cl::init(true),
145 cl::desc("Enable LSR phi elimination"));
146
147// The flag adds instruction count to solutions cost comparision.
148static cl::opt<bool> InsnsCost(
149 "lsr-insns-cost", cl::Hidden, cl::init(true),
150 cl::desc("Add instruction count to a LSR cost model"));
151
152// Flag to choose how to narrow complex lsr solution
153static cl::opt<bool> LSRExpNarrow(
154 "lsr-exp-narrow", cl::Hidden, cl::init(false),
155 cl::desc("Narrow LSR complex solution using"
156 " expectation of registers number"));
157
158// Flag to narrow search space by filtering non-optimal formulae with
159// the same ScaledReg and Scale.
160static cl::opt<bool> FilterSameScaledReg(
161 "lsr-filter-same-scaled-reg", cl::Hidden, cl::init(true),
162 cl::desc("Narrow LSR search space by filtering non-optimal formulae"
163 " with the same ScaledReg and Scale"));
164
165static cl::opt<TTI::AddressingModeKind> PreferredAddresingMode(
166 "lsr-preferred-addressing-mode", cl::Hidden, cl::init(TTI::AMK_None),
167 cl::desc("A flag that overrides the target's preferred addressing mode."),
168 cl::values(clEnumValN(TTI::AMK_None,llvm::cl::OptionEnumValue { "none", int(TTI::AMK_None), "Don't prefer any addressing mode"
}
169 "none",llvm::cl::OptionEnumValue { "none", int(TTI::AMK_None), "Don't prefer any addressing mode"
}
170 "Don't prefer any addressing mode")llvm::cl::OptionEnumValue { "none", int(TTI::AMK_None), "Don't prefer any addressing mode"
}
,
171 clEnumValN(TTI::AMK_PreIndexed,llvm::cl::OptionEnumValue { "preindexed", int(TTI::AMK_PreIndexed
), "Prefer pre-indexed addressing mode" }
172 "preindexed",llvm::cl::OptionEnumValue { "preindexed", int(TTI::AMK_PreIndexed
), "Prefer pre-indexed addressing mode" }
173 "Prefer pre-indexed addressing mode")llvm::cl::OptionEnumValue { "preindexed", int(TTI::AMK_PreIndexed
), "Prefer pre-indexed addressing mode" }
,
174 clEnumValN(TTI::AMK_PostIndexed,llvm::cl::OptionEnumValue { "postindexed", int(TTI::AMK_PostIndexed
), "Prefer post-indexed addressing mode" }
175 "postindexed",llvm::cl::OptionEnumValue { "postindexed", int(TTI::AMK_PostIndexed
), "Prefer post-indexed addressing mode" }
176 "Prefer post-indexed addressing mode")llvm::cl::OptionEnumValue { "postindexed", int(TTI::AMK_PostIndexed
), "Prefer post-indexed addressing mode" }
));
177
178static cl::opt<unsigned> ComplexityLimit(
179 "lsr-complexity-limit", cl::Hidden,
180 cl::init(std::numeric_limits<uint16_t>::max()),
181 cl::desc("LSR search space complexity limit"));
182
183static cl::opt<unsigned> SetupCostDepthLimit(
184 "lsr-setupcost-depth-limit", cl::Hidden, cl::init(7),
185 cl::desc("The limit on recursion depth for LSRs setup cost"));
186
187#ifndef NDEBUG
188// Stress test IV chain generation.
189static cl::opt<bool> StressIVChain(
190 "stress-ivchain", cl::Hidden, cl::init(false),
191 cl::desc("Stress test LSR IV chains"));
192#else
193static bool StressIVChain = false;
194#endif
195
196namespace {
197
198struct MemAccessTy {
199 /// Used in situations where the accessed memory type is unknown.
200 static const unsigned UnknownAddressSpace =
201 std::numeric_limits<unsigned>::max();
202
203 Type *MemTy = nullptr;
204 unsigned AddrSpace = UnknownAddressSpace;
205
206 MemAccessTy() = default;
207 MemAccessTy(Type *Ty, unsigned AS) : MemTy(Ty), AddrSpace(AS) {}
208
209 bool operator==(MemAccessTy Other) const {
210 return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace;
211 }
212
213 bool operator!=(MemAccessTy Other) const { return !(*this == Other); }
214
215 static MemAccessTy getUnknown(LLVMContext &Ctx,
216 unsigned AS = UnknownAddressSpace) {
217 return MemAccessTy(Type::getVoidTy(Ctx), AS);
218 }
219
220 Type *getType() { return MemTy; }
221};
222
223/// This class holds data which is used to order reuse candidates.
224class RegSortData {
225public:
226 /// This represents the set of LSRUse indices which reference
227 /// a particular register.
228 SmallBitVector UsedByIndices;
229
230 void print(raw_ostream &OS) const;
231 void dump() const;
232};
233
234} // end anonymous namespace
235
236#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
237void RegSortData::print(raw_ostream &OS) const {
238 OS << "[NumUses=" << UsedByIndices.count() << ']';
239}
240
241LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void RegSortData::dump() const {
242 print(errs()); errs() << '\n';
243}
244#endif
245
246namespace {
247
248/// Map register candidates to information about how they are used.
249class RegUseTracker {
250 using RegUsesTy = DenseMap<const SCEV *, RegSortData>;
251
252 RegUsesTy RegUsesMap;
253 SmallVector<const SCEV *, 16> RegSequence;
254
255public:
256 void countRegister(const SCEV *Reg, size_t LUIdx);
257 void dropRegister(const SCEV *Reg, size_t LUIdx);
258 void swapAndDropUse(size_t LUIdx, size_t LastLUIdx);
259
260 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
261
262 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
263
264 void clear();
265
266 using iterator = SmallVectorImpl<const SCEV *>::iterator;
267 using const_iterator = SmallVectorImpl<const SCEV *>::const_iterator;
268
269 iterator begin() { return RegSequence.begin(); }
270 iterator end() { return RegSequence.end(); }
271 const_iterator begin() const { return RegSequence.begin(); }
272 const_iterator end() const { return RegSequence.end(); }
273};
274
275} // end anonymous namespace
276
277void
278RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) {
279 std::pair<RegUsesTy::iterator, bool> Pair =
280 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
281 RegSortData &RSD = Pair.first->second;
282 if (Pair.second)
283 RegSequence.push_back(Reg);
284 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
285 RSD.UsedByIndices.set(LUIdx);
286}
287
288void
289RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) {
290 RegUsesTy::iterator It = RegUsesMap.find(Reg);
291 assert(It != RegUsesMap.end())(static_cast <bool> (It != RegUsesMap.end()) ? void (0)
: __assert_fail ("It != RegUsesMap.end()", "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 291, __extension__ __PRETTY_FUNCTION__))
;
292 RegSortData &RSD = It->second;
293 assert(RSD.UsedByIndices.size() > LUIdx)(static_cast <bool> (RSD.UsedByIndices.size() > LUIdx
) ? void (0) : __assert_fail ("RSD.UsedByIndices.size() > LUIdx"
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 293, __extension__ __PRETTY_FUNCTION__))
;
294 RSD.UsedByIndices.reset(LUIdx);
295}
296
297void
298RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
299 assert(LUIdx <= LastLUIdx)(static_cast <bool> (LUIdx <= LastLUIdx) ? void (0) :
__assert_fail ("LUIdx <= LastLUIdx", "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 299, __extension__ __PRETTY_FUNCTION__))
;
300
301 // Update RegUses. The data structure is not optimized for this purpose;
302 // we must iterate through it and update each of the bit vectors.
303 for (auto &Pair : RegUsesMap) {
304 SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
305 if (LUIdx < UsedByIndices.size())
306 UsedByIndices[LUIdx] =
307 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false;
308 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
309 }
310}
311
312bool
313RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
314 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
315 if (I == RegUsesMap.end())
316 return false;
317 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
318 int i = UsedByIndices.find_first();
319 if (i == -1) return false;
320 if ((size_t)i != LUIdx) return true;
321 return UsedByIndices.find_next(i) != -1;
322}
323
324const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
325 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
326 assert(I != RegUsesMap.end() && "Unknown register!")(static_cast <bool> (I != RegUsesMap.end() && "Unknown register!"
) ? void (0) : __assert_fail ("I != RegUsesMap.end() && \"Unknown register!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 326, __extension__ __PRETTY_FUNCTION__))
;
327 return I->second.UsedByIndices;
328}
329
330void RegUseTracker::clear() {
331 RegUsesMap.clear();
332 RegSequence.clear();
333}
334
335namespace {
336
337/// This class holds information that describes a formula for computing
338/// satisfying a use. It may include broken-out immediates and scaled registers.
339struct Formula {
340 /// Global base address used for complex addressing.
341 GlobalValue *BaseGV = nullptr;
342
343 /// Base offset for complex addressing.
344 int64_t BaseOffset = 0;
345
346 /// Whether any complex addressing has a base register.
347 bool HasBaseReg = false;
348
349 /// The scale of any complex addressing.
350 int64_t Scale = 0;
351
352 /// The list of "base" registers for this use. When this is non-empty. The
353 /// canonical representation of a formula is
354 /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
355 /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
356 /// 3. The reg containing recurrent expr related with currect loop in the
357 /// formula should be put in the ScaledReg.
358 /// #1 enforces that the scaled register is always used when at least two
359 /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
360 /// #2 enforces that 1 * reg is reg.
361 /// #3 ensures invariant regs with respect to current loop can be combined
362 /// together in LSR codegen.
363 /// This invariant can be temporarily broken while building a formula.
364 /// However, every formula inserted into the LSRInstance must be in canonical
365 /// form.
366 SmallVector<const SCEV *, 4> BaseRegs;
367
368 /// The 'scaled' register for this use. This should be non-null when Scale is
369 /// not zero.
370 const SCEV *ScaledReg = nullptr;
371
372 /// An additional constant offset which added near the use. This requires a
373 /// temporary register, but the offset itself can live in an add immediate
374 /// field rather than a register.
375 int64_t UnfoldedOffset = 0;
376
377 Formula() = default;
378
379 void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
380
381 bool isCanonical(const Loop &L) const;
382
383 void canonicalize(const Loop &L);
384
385 bool unscale();
386
387 bool hasZeroEnd() const;
388
389 size_t getNumRegs() const;
390 Type *getType() const;
391
392 void deleteBaseReg(const SCEV *&S);
393
394 bool referencesReg(const SCEV *S) const;
395 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
396 const RegUseTracker &RegUses) const;
397
398 void print(raw_ostream &OS) const;
399 void dump() const;
400};
401
402} // end anonymous namespace
403
404/// Recursion helper for initialMatch.
405static void DoInitialMatch(const SCEV *S, Loop *L,
406 SmallVectorImpl<const SCEV *> &Good,
407 SmallVectorImpl<const SCEV *> &Bad,
408 ScalarEvolution &SE) {
409 // Collect expressions which properly dominate the loop header.
410 if (SE.properlyDominates(S, L->getHeader())) {
411 Good.push_back(S);
412 return;
413 }
414
415 // Look at add operands.
416 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
417 for (const SCEV *S : Add->operands())
418 DoInitialMatch(S, L, Good, Bad, SE);
419 return;
420 }
421
422 // Look at addrec operands.
423 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
424 if (!AR->getStart()->isZero() && AR->isAffine()) {
425 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
426 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
427 AR->getStepRecurrence(SE),
428 // FIXME: AR->getNoWrapFlags()
429 AR->getLoop(), SCEV::FlagAnyWrap),
430 L, Good, Bad, SE);
431 return;
432 }
433
434 // Handle a multiplication by -1 (negation) if it didn't fold.
435 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
436 if (Mul->getOperand(0)->isAllOnesValue()) {
437 SmallVector<const SCEV *, 4> Ops(drop_begin(Mul->operands()));
438 const SCEV *NewMul = SE.getMulExpr(Ops);
439
440 SmallVector<const SCEV *, 4> MyGood;
441 SmallVector<const SCEV *, 4> MyBad;
442 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
443 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
444 SE.getEffectiveSCEVType(NewMul->getType())));
445 for (const SCEV *S : MyGood)
446 Good.push_back(SE.getMulExpr(NegOne, S));
447 for (const SCEV *S : MyBad)
448 Bad.push_back(SE.getMulExpr(NegOne, S));
449 return;
450 }
451
452 // Ok, we can't do anything interesting. Just stuff the whole thing into a
453 // register and hope for the best.
454 Bad.push_back(S);
455}
456
457/// Incorporate loop-variant parts of S into this Formula, attempting to keep
458/// all loop-invariant and loop-computable values in a single base register.
459void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
460 SmallVector<const SCEV *, 4> Good;
461 SmallVector<const SCEV *, 4> Bad;
462 DoInitialMatch(S, L, Good, Bad, SE);
463 if (!Good.empty()) {
464 const SCEV *Sum = SE.getAddExpr(Good);
465 if (!Sum->isZero())
466 BaseRegs.push_back(Sum);
467 HasBaseReg = true;
468 }
469 if (!Bad.empty()) {
470 const SCEV *Sum = SE.getAddExpr(Bad);
471 if (!Sum->isZero())
472 BaseRegs.push_back(Sum);
473 HasBaseReg = true;
474 }
475 canonicalize(*L);
476}
477
478/// Check whether or not this formula satisfies the canonical
479/// representation.
480/// \see Formula::BaseRegs.
481bool Formula::isCanonical(const Loop &L) const {
482 if (!ScaledReg)
483 return BaseRegs.size() <= 1;
484
485 if (Scale != 1)
486 return true;
487
488 if (Scale == 1 && BaseRegs.empty())
489 return false;
490
491 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
492 if (SAR && SAR->getLoop() == &L)
493 return true;
494
495 // If ScaledReg is not a recurrent expr, or it is but its loop is not current
496 // loop, meanwhile BaseRegs contains a recurrent expr reg related with current
497 // loop, we want to swap the reg in BaseRegs with ScaledReg.
498 auto I = find_if(BaseRegs, [&](const SCEV *S) {
499 return isa<const SCEVAddRecExpr>(S) &&
500 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
501 });
502 return I == BaseRegs.end();
503}
504
505/// Helper method to morph a formula into its canonical representation.
506/// \see Formula::BaseRegs.
507/// Every formula having more than one base register, must use the ScaledReg
508/// field. Otherwise, we would have to do special cases everywhere in LSR
509/// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
510/// On the other hand, 1*reg should be canonicalized into reg.
511void Formula::canonicalize(const Loop &L) {
512 if (isCanonical(L))
513 return;
514
515 if (BaseRegs.empty()) {
516 // No base reg? Use scale reg with scale = 1 as such.
517 assert(ScaledReg && "Expected 1*reg => reg")(static_cast <bool> (ScaledReg && "Expected 1*reg => reg"
) ? void (0) : __assert_fail ("ScaledReg && \"Expected 1*reg => reg\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 517, __extension__ __PRETTY_FUNCTION__))
;
518 assert(Scale == 1 && "Expected 1*reg => reg")(static_cast <bool> (Scale == 1 && "Expected 1*reg => reg"
) ? void (0) : __assert_fail ("Scale == 1 && \"Expected 1*reg => reg\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 518, __extension__ __PRETTY_FUNCTION__))
;
519 BaseRegs.push_back(ScaledReg);
520 Scale = 0;
521 ScaledReg = nullptr;
522 return;
523 }
524
525 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
526 if (!ScaledReg) {
527 ScaledReg = BaseRegs.pop_back_val();
528 Scale = 1;
529 }
530
531 // If ScaledReg is an invariant with respect to L, find the reg from
532 // BaseRegs containing the recurrent expr related with Loop L. Swap the
533 // reg with ScaledReg.
534 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
535 if (!SAR || SAR->getLoop() != &L) {
536 auto I = find_if(BaseRegs, [&](const SCEV *S) {
537 return isa<const SCEVAddRecExpr>(S) &&
538 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
539 });
540 if (I != BaseRegs.end())
541 std::swap(ScaledReg, *I);
542 }
543 assert(isCanonical(L) && "Failed to canonicalize?")(static_cast <bool> (isCanonical(L) && "Failed to canonicalize?"
) ? void (0) : __assert_fail ("isCanonical(L) && \"Failed to canonicalize?\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 543, __extension__ __PRETTY_FUNCTION__))
;
544}
545
546/// Get rid of the scale in the formula.
547/// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
548/// \return true if it was possible to get rid of the scale, false otherwise.
549/// \note After this operation the formula may not be in the canonical form.
550bool Formula::unscale() {
551 if (Scale != 1)
552 return false;
553 Scale = 0;
554 BaseRegs.push_back(ScaledReg);
555 ScaledReg = nullptr;
556 return true;
557}
558
559bool Formula::hasZeroEnd() const {
560 if (UnfoldedOffset || BaseOffset)
561 return false;
562 if (BaseRegs.size() != 1 || ScaledReg)
563 return false;
564 return true;
565}
566
567/// Return the total number of register operands used by this formula. This does
568/// not include register uses implied by non-constant addrec strides.
569size_t Formula::getNumRegs() const {
570 return !!ScaledReg + BaseRegs.size();
571}
572
573/// Return the type of this formula, if it has one, or null otherwise. This type
574/// is meaningless except for the bit size.
575Type *Formula::getType() const {
576 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
577 ScaledReg ? ScaledReg->getType() :
578 BaseGV ? BaseGV->getType() :
579 nullptr;
580}
581
582/// Delete the given base reg from the BaseRegs list.
583void Formula::deleteBaseReg(const SCEV *&S) {
584 if (&S != &BaseRegs.back())
585 std::swap(S, BaseRegs.back());
586 BaseRegs.pop_back();
587}
588
589/// Test if this formula references the given register.
590bool Formula::referencesReg(const SCEV *S) const {
591 return S == ScaledReg || is_contained(BaseRegs, S);
592}
593
594/// Test whether this formula uses registers which are used by uses other than
595/// the use with the given index.
596bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
597 const RegUseTracker &RegUses) const {
598 if (ScaledReg)
599 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
600 return true;
601 for (const SCEV *BaseReg : BaseRegs)
602 if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
603 return true;
604 return false;
605}
606
607#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
608void Formula::print(raw_ostream &OS) const {
609 bool First = true;
610 if (BaseGV) {
611 if (!First) OS << " + "; else First = false;
612 BaseGV->printAsOperand(OS, /*PrintType=*/false);
613 }
614 if (BaseOffset != 0) {
615 if (!First) OS << " + "; else First = false;
616 OS << BaseOffset;
617 }
618 for (const SCEV *BaseReg : BaseRegs) {
619 if (!First) OS << " + "; else First = false;
620 OS << "reg(" << *BaseReg << ')';
621 }
622 if (HasBaseReg && BaseRegs.empty()) {
623 if (!First) OS << " + "; else First = false;
624 OS << "**error: HasBaseReg**";
625 } else if (!HasBaseReg && !BaseRegs.empty()) {
626 if (!First) OS << " + "; else First = false;
627 OS << "**error: !HasBaseReg**";
628 }
629 if (Scale != 0) {
630 if (!First) OS << " + "; else First = false;
631 OS << Scale << "*reg(";
632 if (ScaledReg)
633 OS << *ScaledReg;
634 else
635 OS << "<unknown>";
636 OS << ')';
637 }
638 if (UnfoldedOffset != 0) {
639 if (!First) OS << " + ";
640 OS << "imm(" << UnfoldedOffset << ')';
641 }
642}
643
644LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Formula::dump() const {
645 print(errs()); errs() << '\n';
646}
647#endif
648
649/// Return true if the given addrec can be sign-extended without changing its
650/// value.
651static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
652 Type *WideTy =
653 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
654 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
655}
656
657/// Return true if the given add can be sign-extended without changing its
658/// value.
659static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
660 Type *WideTy =
661 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
662 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
663}
664
665/// Return true if the given mul can be sign-extended without changing its
666/// value.
667static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
668 Type *WideTy =
669 IntegerType::get(SE.getContext(),
670 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
671 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
672}
673
674/// Return an expression for LHS /s RHS, if it can be determined and if the
675/// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
676/// is true, expressions like (X * Y) /s Y are simplified to X, ignoring that
677/// the multiplication may overflow, which is useful when the result will be
678/// used in a context where the most significant bits are ignored.
679static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
680 ScalarEvolution &SE,
681 bool IgnoreSignificantBits = false) {
682 // Handle the trivial case, which works for any SCEV type.
683 if (LHS == RHS)
684 return SE.getConstant(LHS->getType(), 1);
685
686 // Handle a few RHS special cases.
687 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
688 if (RC) {
689 const APInt &RA = RC->getAPInt();
690 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
691 // some folding.
692 if (RA.isAllOnesValue()) {
693 if (LHS->getType()->isPointerTy())
694 return nullptr;
695 return SE.getMulExpr(LHS, RC);
696 }
697 // Handle x /s 1 as x.
698 if (RA == 1)
699 return LHS;
700 }
701
702 // Check for a division of a constant by a constant.
703 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
704 if (!RC)
705 return nullptr;
706 const APInt &LA = C->getAPInt();
707 const APInt &RA = RC->getAPInt();
708 if (LA.srem(RA) != 0)
709 return nullptr;
710 return SE.getConstant(LA.sdiv(RA));
711 }
712
713 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
714 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
715 if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
716 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
717 IgnoreSignificantBits);
718 if (!Step) return nullptr;
719 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
720 IgnoreSignificantBits);
721 if (!Start) return nullptr;
722 // FlagNW is independent of the start value, step direction, and is
723 // preserved with smaller magnitude steps.
724 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
725 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
726 }
727 return nullptr;
728 }
729
730 // Distribute the sdiv over add operands, if the add doesn't overflow.
731 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
732 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
733 SmallVector<const SCEV *, 8> Ops;
734 for (const SCEV *S : Add->operands()) {
735 const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
736 if (!Op) return nullptr;
737 Ops.push_back(Op);
738 }
739 return SE.getAddExpr(Ops);
740 }
741 return nullptr;
742 }
743
744 // Check for a multiply operand that we can pull RHS out of.
745 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
746 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
747 // Handle special case C1*X*Y /s C2*X*Y.
748 if (const SCEVMulExpr *MulRHS = dyn_cast<SCEVMulExpr>(RHS)) {
749 if (IgnoreSignificantBits || isMulSExtable(MulRHS, SE)) {
750 const SCEVConstant *LC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
751 const SCEVConstant *RC =
752 dyn_cast<SCEVConstant>(MulRHS->getOperand(0));
753 if (LC && RC) {
754 SmallVector<const SCEV *, 4> LOps(drop_begin(Mul->operands()));
755 SmallVector<const SCEV *, 4> ROps(drop_begin(MulRHS->operands()));
756 if (LOps == ROps)
757 return getExactSDiv(LC, RC, SE, IgnoreSignificantBits);
758 }
759 }
760 }
761
762 SmallVector<const SCEV *, 4> Ops;
763 bool Found = false;
764 for (const SCEV *S : Mul->operands()) {
765 if (!Found)
766 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
767 IgnoreSignificantBits)) {
768 S = Q;
769 Found = true;
770 }
771 Ops.push_back(S);
772 }
773 return Found ? SE.getMulExpr(Ops) : nullptr;
774 }
775 return nullptr;
776 }
777
778 // Otherwise we don't know.
779 return nullptr;
780}
781
782/// If S involves the addition of a constant integer value, return that integer
783/// value, and mutate S to point to a new SCEV with that value excluded.
784static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
785 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
786 if (C->getAPInt().getMinSignedBits() <= 64) {
787 S = SE.getConstant(C->getType(), 0);
788 return C->getValue()->getSExtValue();
789 }
790 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
791 SmallVector<const SCEV *, 8> NewOps(Add->operands());
792 int64_t Result = ExtractImmediate(NewOps.front(), SE);
793 if (Result != 0)
794 S = SE.getAddExpr(NewOps);
795 return Result;
796 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
797 SmallVector<const SCEV *, 8> NewOps(AR->operands());
798 int64_t Result = ExtractImmediate(NewOps.front(), SE);
799 if (Result != 0)
800 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
801 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
802 SCEV::FlagAnyWrap);
803 return Result;
804 }
805 return 0;
806}
807
808/// If S involves the addition of a GlobalValue address, return that symbol, and
809/// mutate S to point to a new SCEV with that value excluded.
810static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
811 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
812 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
813 S = SE.getConstant(GV->getType(), 0);
814 return GV;
815 }
816 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
817 SmallVector<const SCEV *, 8> NewOps(Add->operands());
818 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
819 if (Result)
820 S = SE.getAddExpr(NewOps);
821 return Result;
822 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
823 SmallVector<const SCEV *, 8> NewOps(AR->operands());
824 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
825 if (Result)
826 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
827 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
828 SCEV::FlagAnyWrap);
829 return Result;
830 }
831 return nullptr;
832}
833
834/// Returns true if the specified instruction is using the specified value as an
835/// address.
836static bool isAddressUse(const TargetTransformInfo &TTI,
837 Instruction *Inst, Value *OperandVal) {
838 bool isAddress = isa<LoadInst>(Inst);
839 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
840 if (SI->getPointerOperand() == OperandVal)
841 isAddress = true;
842 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
843 // Addressing modes can also be folded into prefetches and a variety
844 // of intrinsics.
845 switch (II->getIntrinsicID()) {
846 case Intrinsic::memset:
847 case Intrinsic::prefetch:
848 case Intrinsic::masked_load:
849 if (II->getArgOperand(0) == OperandVal)
850 isAddress = true;
851 break;
852 case Intrinsic::masked_store:
853 if (II->getArgOperand(1) == OperandVal)
854 isAddress = true;
855 break;
856 case Intrinsic::memmove:
857 case Intrinsic::memcpy:
858 if (II->getArgOperand(0) == OperandVal ||
859 II->getArgOperand(1) == OperandVal)
860 isAddress = true;
861 break;
862 default: {
863 MemIntrinsicInfo IntrInfo;
864 if (TTI.getTgtMemIntrinsic(II, IntrInfo)) {
865 if (IntrInfo.PtrVal == OperandVal)
866 isAddress = true;
867 }
868 }
869 }
870 } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
871 if (RMW->getPointerOperand() == OperandVal)
872 isAddress = true;
873 } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
874 if (CmpX->getPointerOperand() == OperandVal)
875 isAddress = true;
876 }
877 return isAddress;
878}
879
880/// Return the type of the memory being accessed.
881static MemAccessTy getAccessType(const TargetTransformInfo &TTI,
882 Instruction *Inst, Value *OperandVal) {
883 MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
884 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
885 AccessTy.MemTy = SI->getOperand(0)->getType();
886 AccessTy.AddrSpace = SI->getPointerAddressSpace();
887 } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
888 AccessTy.AddrSpace = LI->getPointerAddressSpace();
889 } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
890 AccessTy.AddrSpace = RMW->getPointerAddressSpace();
891 } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
892 AccessTy.AddrSpace = CmpX->getPointerAddressSpace();
893 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
894 switch (II->getIntrinsicID()) {
895 case Intrinsic::prefetch:
896 case Intrinsic::memset:
897 AccessTy.AddrSpace = II->getArgOperand(0)->getType()->getPointerAddressSpace();
898 AccessTy.MemTy = OperandVal->getType();
899 break;
900 case Intrinsic::memmove:
901 case Intrinsic::memcpy:
902 AccessTy.AddrSpace = OperandVal->getType()->getPointerAddressSpace();
903 AccessTy.MemTy = OperandVal->getType();
904 break;
905 case Intrinsic::masked_load:
906 AccessTy.AddrSpace =
907 II->getArgOperand(0)->getType()->getPointerAddressSpace();
908 break;
909 case Intrinsic::masked_store:
910 AccessTy.MemTy = II->getOperand(0)->getType();
911 AccessTy.AddrSpace =
912 II->getArgOperand(1)->getType()->getPointerAddressSpace();
913 break;
914 default: {
915 MemIntrinsicInfo IntrInfo;
916 if (TTI.getTgtMemIntrinsic(II, IntrInfo) && IntrInfo.PtrVal) {
917 AccessTy.AddrSpace
918 = IntrInfo.PtrVal->getType()->getPointerAddressSpace();
919 }
920
921 break;
922 }
923 }
924 }
925
926 // All pointers have the same requirements, so canonicalize them to an
927 // arbitrary pointer type to minimize variation.
928 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
929 AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
930 PTy->getAddressSpace());
931
932 return AccessTy;
933}
934
935/// Return true if this AddRec is already a phi in its loop.
936static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
937 for (PHINode &PN : AR->getLoop()->getHeader()->phis()) {
938 if (SE.isSCEVable(PN.getType()) &&
939 (SE.getEffectiveSCEVType(PN.getType()) ==
940 SE.getEffectiveSCEVType(AR->getType())) &&
941 SE.getSCEV(&PN) == AR)
942 return true;
943 }
944 return false;
945}
946
947/// Check if expanding this expression is likely to incur significant cost. This
948/// is tricky because SCEV doesn't track which expressions are actually computed
949/// by the current IR.
950///
951/// We currently allow expansion of IV increments that involve adds,
952/// multiplication by constants, and AddRecs from existing phis.
953///
954/// TODO: Allow UDivExpr if we can find an existing IV increment that is an
955/// obvious multiple of the UDivExpr.
956static bool isHighCostExpansion(const SCEV *S,
957 SmallPtrSetImpl<const SCEV*> &Processed,
958 ScalarEvolution &SE) {
959 // Zero/One operand expressions
960 switch (S->getSCEVType()) {
961 case scUnknown:
962 case scConstant:
963 return false;
964 case scTruncate:
965 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
966 Processed, SE);
967 case scZeroExtend:
968 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
969 Processed, SE);
970 case scSignExtend:
971 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
972 Processed, SE);
973 default:
974 break;
975 }
976
977 if (!Processed.insert(S).second)
978 return false;
979
980 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
981 for (const SCEV *S : Add->operands()) {
982 if (isHighCostExpansion(S, Processed, SE))
983 return true;
984 }
985 return false;
986 }
987
988 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
989 if (Mul->getNumOperands() == 2) {
990 // Multiplication by a constant is ok
991 if (isa<SCEVConstant>(Mul->getOperand(0)))
992 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
993
994 // If we have the value of one operand, check if an existing
995 // multiplication already generates this expression.
996 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
997 Value *UVal = U->getValue();
998 for (User *UR : UVal->users()) {
999 // If U is a constant, it may be used by a ConstantExpr.
1000 Instruction *UI = dyn_cast<Instruction>(UR);
1001 if (UI && UI->getOpcode() == Instruction::Mul &&
1002 SE.isSCEVable(UI->getType())) {
1003 return SE.getSCEV(UI) == Mul;
1004 }
1005 }
1006 }
1007 }
1008 }
1009
1010 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
1011 if (isExistingPhi(AR, SE))
1012 return false;
1013 }
1014
1015 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
1016 return true;
1017}
1018
1019namespace {
1020
1021class LSRUse;
1022
1023} // end anonymous namespace
1024
1025/// Check if the addressing mode defined by \p F is completely
1026/// folded in \p LU at isel time.
1027/// This includes address-mode folding and special icmp tricks.
1028/// This function returns true if \p LU can accommodate what \p F
1029/// defines and up to 1 base + 1 scaled + offset.
1030/// In other words, if \p F has several base registers, this function may
1031/// still return true. Therefore, users still need to account for
1032/// additional base registers and/or unfolded offsets to derive an
1033/// accurate cost model.
1034static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1035 const LSRUse &LU, const Formula &F);
1036
1037// Get the cost of the scaling factor used in F for LU.
1038static InstructionCost getScalingFactorCost(const TargetTransformInfo &TTI,
1039 const LSRUse &LU, const Formula &F,
1040 const Loop &L);
1041
1042namespace {
1043
1044/// This class is used to measure and compare candidate formulae.
1045class Cost {
1046 const Loop *L = nullptr;
1047 ScalarEvolution *SE = nullptr;
1048 const TargetTransformInfo *TTI = nullptr;
1049 TargetTransformInfo::LSRCost C;
1050 TTI::AddressingModeKind AMK = TTI::AMK_None;
1051
1052public:
1053 Cost() = delete;
1054 Cost(const Loop *L, ScalarEvolution &SE, const TargetTransformInfo &TTI,
1055 TTI::AddressingModeKind AMK) :
1056 L(L), SE(&SE), TTI(&TTI), AMK(AMK) {
1057 C.Insns = 0;
1058 C.NumRegs = 0;
1059 C.AddRecCost = 0;
1060 C.NumIVMuls = 0;
1061 C.NumBaseAdds = 0;
1062 C.ImmCost = 0;
1063 C.SetupCost = 0;
1064 C.ScaleCost = 0;
1065 }
1066
1067 bool isLess(Cost &Other);
1068
1069 void Lose();
1070
1071#ifndef NDEBUG
1072 // Once any of the metrics loses, they must all remain losers.
1073 bool isValid() {
1074 return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds
1075 | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u)
1076 || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds
1077 & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u);
1078 }
1079#endif
1080
1081 bool isLoser() {
1082 assert(isValid() && "invalid cost")(static_cast <bool> (isValid() && "invalid cost"
) ? void (0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1082, __extension__ __PRETTY_FUNCTION__))
;
1083 return C.NumRegs == ~0u;
1084 }
1085
1086 void RateFormula(const Formula &F,
1087 SmallPtrSetImpl<const SCEV *> &Regs,
1088 const DenseSet<const SCEV *> &VisitedRegs,
1089 const LSRUse &LU,
1090 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
1091
1092 void print(raw_ostream &OS) const;
1093 void dump() const;
1094
1095private:
1096 void RateRegister(const Formula &F, const SCEV *Reg,
1097 SmallPtrSetImpl<const SCEV *> &Regs);
1098 void RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1099 SmallPtrSetImpl<const SCEV *> &Regs,
1100 SmallPtrSetImpl<const SCEV *> *LoserRegs);
1101};
1102
1103/// An operand value in an instruction which is to be replaced with some
1104/// equivalent, possibly strength-reduced, replacement.
1105struct LSRFixup {
1106 /// The instruction which will be updated.
1107 Instruction *UserInst = nullptr;
1108
1109 /// The operand of the instruction which will be replaced. The operand may be
1110 /// used more than once; every instance will be replaced.
1111 Value *OperandValToReplace = nullptr;
1112
1113 /// If this user is to use the post-incremented value of an induction
1114 /// variable, this set is non-empty and holds the loops associated with the
1115 /// induction variable.
1116 PostIncLoopSet PostIncLoops;
1117
1118 /// A constant offset to be added to the LSRUse expression. This allows
1119 /// multiple fixups to share the same LSRUse with different offsets, for
1120 /// example in an unrolled loop.
1121 int64_t Offset = 0;
1122
1123 LSRFixup() = default;
1124
1125 bool isUseFullyOutsideLoop(const Loop *L) const;
1126
1127 void print(raw_ostream &OS) const;
1128 void dump() const;
1129};
1130
1131/// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
1132/// SmallVectors of const SCEV*.
1133struct UniquifierDenseMapInfo {
1134 static SmallVector<const SCEV *, 4> getEmptyKey() {
1135 SmallVector<const SCEV *, 4> V;
1136 V.push_back(reinterpret_cast<const SCEV *>(-1));
1137 return V;
1138 }
1139
1140 static SmallVector<const SCEV *, 4> getTombstoneKey() {
1141 SmallVector<const SCEV *, 4> V;
1142 V.push_back(reinterpret_cast<const SCEV *>(-2));
1143 return V;
1144 }
1145
1146 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1147 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1148 }
1149
1150 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1151 const SmallVector<const SCEV *, 4> &RHS) {
1152 return LHS == RHS;
1153 }
1154};
1155
1156/// This class holds the state that LSR keeps for each use in IVUsers, as well
1157/// as uses invented by LSR itself. It includes information about what kinds of
1158/// things can be folded into the user, information about the user itself, and
1159/// information about how the use may be satisfied. TODO: Represent multiple
1160/// users of the same expression in common?
1161class LSRUse {
1162 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1163
1164public:
1165 /// An enum for a kind of use, indicating what types of scaled and immediate
1166 /// operands it might support.
1167 enum KindType {
1168 Basic, ///< A normal use, with no folding.
1169 Special, ///< A special case of basic, allowing -1 scales.
1170 Address, ///< An address use; folding according to TargetLowering
1171 ICmpZero ///< An equality icmp with both operands folded into one.
1172 // TODO: Add a generic icmp too?
1173 };
1174
1175 using SCEVUseKindPair = PointerIntPair<const SCEV *, 2, KindType>;
1176
1177 KindType Kind;
1178 MemAccessTy AccessTy;
1179
1180 /// The list of operands which are to be replaced.
1181 SmallVector<LSRFixup, 8> Fixups;
1182
1183 /// Keep track of the min and max offsets of the fixups.
1184 int64_t MinOffset = std::numeric_limits<int64_t>::max();
1185 int64_t MaxOffset = std::numeric_limits<int64_t>::min();
1186
1187 /// This records whether all of the fixups using this LSRUse are outside of
1188 /// the loop, in which case some special-case heuristics may be used.
1189 bool AllFixupsOutsideLoop = true;
1190
1191 /// RigidFormula is set to true to guarantee that this use will be associated
1192 /// with a single formula--the one that initially matched. Some SCEV
1193 /// expressions cannot be expanded. This allows LSR to consider the registers
1194 /// used by those expressions without the need to expand them later after
1195 /// changing the formula.
1196 bool RigidFormula = false;
1197
1198 /// This records the widest use type for any fixup using this
1199 /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1200 /// fixup widths to be equivalent, because the narrower one may be relying on
1201 /// the implicit truncation to truncate away bogus bits.
1202 Type *WidestFixupType = nullptr;
1203
1204 /// A list of ways to build a value that can satisfy this user. After the
1205 /// list is populated, one of these is selected heuristically and used to
1206 /// formulate a replacement for OperandValToReplace in UserInst.
1207 SmallVector<Formula, 12> Formulae;
1208
1209 /// The set of register candidates used by all formulae in this LSRUse.
1210 SmallPtrSet<const SCEV *, 4> Regs;
1211
1212 LSRUse(KindType K, MemAccessTy AT) : Kind(K), AccessTy(AT) {}
1213
1214 LSRFixup &getNewFixup() {
1215 Fixups.push_back(LSRFixup());
1216 return Fixups.back();
1217 }
1218
1219 void pushFixup(LSRFixup &f) {
1220 Fixups.push_back(f);
1221 if (f.Offset > MaxOffset)
1222 MaxOffset = f.Offset;
1223 if (f.Offset < MinOffset)
1224 MinOffset = f.Offset;
1225 }
1226
1227 bool HasFormulaWithSameRegs(const Formula &F) const;
1228 float getNotSelectedProbability(const SCEV *Reg) const;
1229 bool InsertFormula(const Formula &F, const Loop &L);
1230 void DeleteFormula(Formula &F);
1231 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1232
1233 void print(raw_ostream &OS) const;
1234 void dump() const;
1235};
1236
1237} // end anonymous namespace
1238
1239static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1240 LSRUse::KindType Kind, MemAccessTy AccessTy,
1241 GlobalValue *BaseGV, int64_t BaseOffset,
1242 bool HasBaseReg, int64_t Scale,
1243 Instruction *Fixup = nullptr);
1244
1245static unsigned getSetupCost(const SCEV *Reg, unsigned Depth) {
1246 if (isa<SCEVUnknown>(Reg) || isa<SCEVConstant>(Reg))
1247 return 1;
1248 if (Depth == 0)
1249 return 0;
1250 if (const auto *S = dyn_cast<SCEVAddRecExpr>(Reg))
1251 return getSetupCost(S->getStart(), Depth - 1);
1252 if (auto S = dyn_cast<SCEVIntegralCastExpr>(Reg))
1253 return getSetupCost(S->getOperand(), Depth - 1);
1254 if (auto S = dyn_cast<SCEVNAryExpr>(Reg))
1255 return std::accumulate(S->op_begin(), S->op_end(), 0,
1256 [&](unsigned i, const SCEV *Reg) {
1257 return i + getSetupCost(Reg, Depth - 1);
1258 });
1259 if (auto S = dyn_cast<SCEVUDivExpr>(Reg))
1260 return getSetupCost(S->getLHS(), Depth - 1) +
1261 getSetupCost(S->getRHS(), Depth - 1);
1262 return 0;
1263}
1264
1265/// Tally up interesting quantities from the given register.
1266void Cost::RateRegister(const Formula &F, const SCEV *Reg,
1267 SmallPtrSetImpl<const SCEV *> &Regs) {
1268 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1269 // If this is an addrec for another loop, it should be an invariant
1270 // with respect to L since L is the innermost loop (at least
1271 // for now LSR only handles innermost loops).
1272 if (AR->getLoop() != L) {
1273 // If the AddRec exists, consider it's register free and leave it alone.
1274 if (isExistingPhi(AR, *SE) && AMK != TTI::AMK_PostIndexed)
1275 return;
1276
1277 // It is bad to allow LSR for current loop to add induction variables
1278 // for its sibling loops.
1279 if (!AR->getLoop()->contains(L)) {
1280 Lose();
1281 return;
1282 }
1283
1284 // Otherwise, it will be an invariant with respect to Loop L.
1285 ++C.NumRegs;
1286 return;
1287 }
1288
1289 unsigned LoopCost = 1;
1290 if (TTI->isIndexedLoadLegal(TTI->MIM_PostInc, AR->getType()) ||
1291 TTI->isIndexedStoreLegal(TTI->MIM_PostInc, AR->getType())) {
1292
1293 // If the step size matches the base offset, we could use pre-indexed
1294 // addressing.
1295 if (AMK == TTI::AMK_PreIndexed) {
1296 if (auto *Step = dyn_cast<SCEVConstant>(AR->getStepRecurrence(*SE)))
1297 if (Step->getAPInt() == F.BaseOffset)
1298 LoopCost = 0;
1299 } else if (AMK == TTI::AMK_PostIndexed) {
1300 const SCEV *LoopStep = AR->getStepRecurrence(*SE);
1301 if (isa<SCEVConstant>(LoopStep)) {
1302 const SCEV *LoopStart = AR->getStart();
1303 if (!isa<SCEVConstant>(LoopStart) &&
1304 SE->isLoopInvariant(LoopStart, L))
1305 LoopCost = 0;
1306 }
1307 }
1308 }
1309 C.AddRecCost += LoopCost;
1310
1311 // Add the step value register, if it needs one.
1312 // TODO: The non-affine case isn't precisely modeled here.
1313 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1314 if (!Regs.count(AR->getOperand(1))) {
1315 RateRegister(F, AR->getOperand(1), Regs);
1316 if (isLoser())
1317 return;
1318 }
1319 }
1320 }
1321 ++C.NumRegs;
1322
1323 // Rough heuristic; favor registers which don't require extra setup
1324 // instructions in the preheader.
1325 C.SetupCost += getSetupCost(Reg, SetupCostDepthLimit);
1326 // Ensure we don't, even with the recusion limit, produce invalid costs.
1327 C.SetupCost = std::min<unsigned>(C.SetupCost, 1 << 16);
1328
1329 C.NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1330 SE->hasComputableLoopEvolution(Reg, L);
1331}
1332
1333/// Record this register in the set. If we haven't seen it before, rate
1334/// it. Optional LoserRegs provides a way to declare any formula that refers to
1335/// one of those regs an instant loser.
1336void Cost::RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1337 SmallPtrSetImpl<const SCEV *> &Regs,
1338 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1339 if (LoserRegs && LoserRegs->count(Reg)) {
1340 Lose();
1341 return;
1342 }
1343 if (Regs.insert(Reg).second) {
1344 RateRegister(F, Reg, Regs);
1345 if (LoserRegs && isLoser())
1346 LoserRegs->insert(Reg);
1347 }
1348}
1349
1350void Cost::RateFormula(const Formula &F,
1351 SmallPtrSetImpl<const SCEV *> &Regs,
1352 const DenseSet<const SCEV *> &VisitedRegs,
1353 const LSRUse &LU,
1354 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1355 assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula")(static_cast <bool> (F.isCanonical(*L) && "Cost is accurate only for canonical formula"
) ? void (0) : __assert_fail ("F.isCanonical(*L) && \"Cost is accurate only for canonical formula\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1355, __extension__ __PRETTY_FUNCTION__))
;
1356 // Tally up the registers.
1357 unsigned PrevAddRecCost = C.AddRecCost;
1358 unsigned PrevNumRegs = C.NumRegs;
1359 unsigned PrevNumBaseAdds = C.NumBaseAdds;
1360 if (const SCEV *ScaledReg = F.ScaledReg) {
1361 if (VisitedRegs.count(ScaledReg)) {
1362 Lose();
1363 return;
1364 }
1365 RatePrimaryRegister(F, ScaledReg, Regs, LoserRegs);
1366 if (isLoser())
1367 return;
1368 }
1369 for (const SCEV *BaseReg : F.BaseRegs) {
1370 if (VisitedRegs.count(BaseReg)) {
1371 Lose();
1372 return;
1373 }
1374 RatePrimaryRegister(F, BaseReg, Regs, LoserRegs);
1375 if (isLoser())
1376 return;
1377 }
1378
1379 // Determine how many (unfolded) adds we'll need inside the loop.
1380 size_t NumBaseParts = F.getNumRegs();
1381 if (NumBaseParts > 1)
1382 // Do not count the base and a possible second register if the target
1383 // allows to fold 2 registers.
1384 C.NumBaseAdds +=
1385 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(*TTI, LU, F)));
1386 C.NumBaseAdds += (F.UnfoldedOffset != 0);
1387
1388 // Accumulate non-free scaling amounts.
1389 C.ScaleCost += *getScalingFactorCost(*TTI, LU, F, *L).getValue();
1390
1391 // Tally up the non-zero immediates.
1392 for (const LSRFixup &Fixup : LU.Fixups) {
1393 int64_t O = Fixup.Offset;
1394 int64_t Offset = (uint64_t)O + F.BaseOffset;
1395 if (F.BaseGV)
1396 C.ImmCost += 64; // Handle symbolic values conservatively.
1397 // TODO: This should probably be the pointer size.
1398 else if (Offset != 0)
1399 C.ImmCost += APInt(64, Offset, true).getMinSignedBits();
1400
1401 // Check with target if this offset with this instruction is
1402 // specifically not supported.
1403 if (LU.Kind == LSRUse::Address && Offset != 0 &&
1404 !isAMCompletelyFolded(*TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1405 Offset, F.HasBaseReg, F.Scale, Fixup.UserInst))
1406 C.NumBaseAdds++;
1407 }
1408
1409 // If we don't count instruction cost exit here.
1410 if (!InsnsCost) {
1411 assert(isValid() && "invalid cost")(static_cast <bool> (isValid() && "invalid cost"
) ? void (0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1411, __extension__ __PRETTY_FUNCTION__))
;
1412 return;
1413 }
1414
1415 // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as
1416 // additional instruction (at least fill).
1417 // TODO: Need distinguish register class?
1418 unsigned TTIRegNum = TTI->getNumberOfRegisters(
1419 TTI->getRegisterClassForType(false, F.getType())) - 1;
1420 if (C.NumRegs > TTIRegNum) {
1421 // Cost already exceeded TTIRegNum, then only newly added register can add
1422 // new instructions.
1423 if (PrevNumRegs > TTIRegNum)
1424 C.Insns += (C.NumRegs - PrevNumRegs);
1425 else
1426 C.Insns += (C.NumRegs - TTIRegNum);
1427 }
1428
1429 // If ICmpZero formula ends with not 0, it could not be replaced by
1430 // just add or sub. We'll need to compare final result of AddRec.
1431 // That means we'll need an additional instruction. But if the target can
1432 // macro-fuse a compare with a branch, don't count this extra instruction.
1433 // For -10 + {0, +, 1}:
1434 // i = i + 1;
1435 // cmp i, 10
1436 //
1437 // For {-10, +, 1}:
1438 // i = i + 1;
1439 if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd() &&
1440 !TTI->canMacroFuseCmp())
1441 C.Insns++;
1442 // Each new AddRec adds 1 instruction to calculation.
1443 C.Insns += (C.AddRecCost - PrevAddRecCost);
1444
1445 // BaseAdds adds instructions for unfolded registers.
1446 if (LU.Kind != LSRUse::ICmpZero)
1447 C.Insns += C.NumBaseAdds - PrevNumBaseAdds;
1448 assert(isValid() && "invalid cost")(static_cast <bool> (isValid() && "invalid cost"
) ? void (0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1448, __extension__ __PRETTY_FUNCTION__))
;
1449}
1450
1451/// Set this cost to a losing value.
1452void Cost::Lose() {
1453 C.Insns = std::numeric_limits<unsigned>::max();
1454 C.NumRegs = std::numeric_limits<unsigned>::max();
1455 C.AddRecCost = std::numeric_limits<unsigned>::max();
1456 C.NumIVMuls = std::numeric_limits<unsigned>::max();
1457 C.NumBaseAdds = std::numeric_limits<unsigned>::max();
1458 C.ImmCost = std::numeric_limits<unsigned>::max();
1459 C.SetupCost = std::numeric_limits<unsigned>::max();
1460 C.ScaleCost = std::numeric_limits<unsigned>::max();
1461}
1462
1463/// Choose the lower cost.
1464bool Cost::isLess(Cost &Other) {
1465 if (InsnsCost.getNumOccurrences() > 0 && InsnsCost &&
1466 C.Insns != Other.C.Insns)
1467 return C.Insns < Other.C.Insns;
1468 return TTI->isLSRCostLess(C, Other.C);
1469}
1470
1471#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1472void Cost::print(raw_ostream &OS) const {
1473 if (InsnsCost)
1474 OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s ");
1475 OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s");
1476 if (C.AddRecCost != 0)
1477 OS << ", with addrec cost " << C.AddRecCost;
1478 if (C.NumIVMuls != 0)
1479 OS << ", plus " << C.NumIVMuls << " IV mul"
1480 << (C.NumIVMuls == 1 ? "" : "s");
1481 if (C.NumBaseAdds != 0)
1482 OS << ", plus " << C.NumBaseAdds << " base add"
1483 << (C.NumBaseAdds == 1 ? "" : "s");
1484 if (C.ScaleCost != 0)
1485 OS << ", plus " << C.ScaleCost << " scale cost";
1486 if (C.ImmCost != 0)
1487 OS << ", plus " << C.ImmCost << " imm cost";
1488 if (C.SetupCost != 0)
1489 OS << ", plus " << C.SetupCost << " setup cost";
1490}
1491
1492LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Cost::dump() const {
1493 print(errs()); errs() << '\n';
1494}
1495#endif
1496
1497/// Test whether this fixup always uses its value outside of the given loop.
1498bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1499 // PHI nodes use their value in their incoming blocks.
1500 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1501 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1502 if (PN->getIncomingValue(i) == OperandValToReplace &&
1503 L->contains(PN->getIncomingBlock(i)))
1504 return false;
1505 return true;
1506 }
1507
1508 return !L->contains(UserInst);
1509}
1510
1511#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1512void LSRFixup::print(raw_ostream &OS) const {
1513 OS << "UserInst=";
1514 // Store is common and interesting enough to be worth special-casing.
1515 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1516 OS << "store ";
1517 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1518 } else if (UserInst->getType()->isVoidTy())
1519 OS << UserInst->getOpcodeName();
1520 else
1521 UserInst->printAsOperand(OS, /*PrintType=*/false);
1522
1523 OS << ", OperandValToReplace=";
1524 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1525
1526 for (const Loop *PIL : PostIncLoops) {
1527 OS << ", PostIncLoop=";
1528 PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1529 }
1530
1531 if (Offset != 0)
1532 OS << ", Offset=" << Offset;
1533}
1534
1535LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRFixup::dump() const {
1536 print(errs()); errs() << '\n';
1537}
1538#endif
1539
1540/// Test whether this use as a formula which has the same registers as the given
1541/// formula.
1542bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1543 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1544 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1545 // Unstable sort by host order ok, because this is only used for uniquifying.
1546 llvm::sort(Key);
1547 return Uniquifier.count(Key);
1548}
1549
1550/// The function returns a probability of selecting formula without Reg.
1551float LSRUse::getNotSelectedProbability(const SCEV *Reg) const {
1552 unsigned FNum = 0;
1553 for (const Formula &F : Formulae)
1554 if (F.referencesReg(Reg))
1555 FNum++;
1556 return ((float)(Formulae.size() - FNum)) / Formulae.size();
1557}
1558
1559/// If the given formula has not yet been inserted, add it to the list, and
1560/// return true. Return false otherwise. The formula must be in canonical form.
1561bool LSRUse::InsertFormula(const Formula &F, const Loop &L) {
1562 assert(F.isCanonical(L) && "Invalid canonical representation")(static_cast <bool> (F.isCanonical(L) && "Invalid canonical representation"
) ? void (0) : __assert_fail ("F.isCanonical(L) && \"Invalid canonical representation\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1562, __extension__ __PRETTY_FUNCTION__))
;
1563
1564 if (!Formulae.empty() && RigidFormula)
1565 return false;
1566
1567 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1568 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1569 // Unstable sort by host order ok, because this is only used for uniquifying.
1570 llvm::sort(Key);
1571
1572 if (!Uniquifier.insert(Key).second)
1573 return false;
1574
1575 // Using a register to hold the value of 0 is not profitable.
1576 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&(static_cast <bool> ((!F.ScaledReg || !F.ScaledReg->
isZero()) && "Zero allocated in a scaled register!") ?
void (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1577, __extension__ __PRETTY_FUNCTION__))
1577 "Zero allocated in a scaled register!")(static_cast <bool> ((!F.ScaledReg || !F.ScaledReg->
isZero()) && "Zero allocated in a scaled register!") ?
void (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1577, __extension__ __PRETTY_FUNCTION__))
;
1578#ifndef NDEBUG
1579 for (const SCEV *BaseReg : F.BaseRegs)
1580 assert(!BaseReg->isZero() && "Zero allocated in a base register!")(static_cast <bool> (!BaseReg->isZero() && "Zero allocated in a base register!"
) ? void (0) : __assert_fail ("!BaseReg->isZero() && \"Zero allocated in a base register!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1580, __extension__ __PRETTY_FUNCTION__))
;
1581#endif
1582
1583 // Add the formula to the list.
1584 Formulae.push_back(F);
1585
1586 // Record registers now being used by this use.
1587 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1588 if (F.ScaledReg)
1589 Regs.insert(F.ScaledReg);
1590
1591 return true;
1592}
1593
1594/// Remove the given formula from this use's list.
1595void LSRUse::DeleteFormula(Formula &F) {
1596 if (&F != &Formulae.back())
1597 std::swap(F, Formulae.back());
1598 Formulae.pop_back();
1599}
1600
1601/// Recompute the Regs field, and update RegUses.
1602void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1603 // Now that we've filtered out some formulae, recompute the Regs set.
1604 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1605 Regs.clear();
1606 for (const Formula &F : Formulae) {
1607 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1608 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1609 }
1610
1611 // Update the RegTracker.
1612 for (const SCEV *S : OldRegs)
1613 if (!Regs.count(S))
1614 RegUses.dropRegister(S, LUIdx);
1615}
1616
1617#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1618void LSRUse::print(raw_ostream &OS) const {
1619 OS << "LSR Use: Kind=";
1620 switch (Kind) {
1621 case Basic: OS << "Basic"; break;
1622 case Special: OS << "Special"; break;
1623 case ICmpZero: OS << "ICmpZero"; break;
1624 case Address:
1625 OS << "Address of ";
1626 if (AccessTy.MemTy->isPointerTy())
1627 OS << "pointer"; // the full pointer type could be really verbose
1628 else {
1629 OS << *AccessTy.MemTy;
1630 }
1631
1632 OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1633 }
1634
1635 OS << ", Offsets={";
1636 bool NeedComma = false;
1637 for (const LSRFixup &Fixup : Fixups) {
1638 if (NeedComma) OS << ',';
1639 OS << Fixup.Offset;
1640 NeedComma = true;
1641 }
1642 OS << '}';
1643
1644 if (AllFixupsOutsideLoop)
1645 OS << ", all-fixups-outside-loop";
1646
1647 if (WidestFixupType)
1648 OS << ", widest fixup type: " << *WidestFixupType;
1649}
1650
1651LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRUse::dump() const {
1652 print(errs()); errs() << '\n';
1653}
1654#endif
1655
1656static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1657 LSRUse::KindType Kind, MemAccessTy AccessTy,
1658 GlobalValue *BaseGV, int64_t BaseOffset,
1659 bool HasBaseReg, int64_t Scale,
1660 Instruction *Fixup/*= nullptr*/) {
1661 switch (Kind) {
1662 case LSRUse::Address:
1663 return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1664 HasBaseReg, Scale, AccessTy.AddrSpace, Fixup);
1665
1666 case LSRUse::ICmpZero:
1667 // There's not even a target hook for querying whether it would be legal to
1668 // fold a GV into an ICmp.
1669 if (BaseGV)
1670 return false;
1671
1672 // ICmp only has two operands; don't allow more than two non-trivial parts.
1673 if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1674 return false;
1675
1676 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1677 // putting the scaled register in the other operand of the icmp.
1678 if (Scale != 0 && Scale != -1)
1679 return false;
1680
1681 // If we have low-level target information, ask the target if it can fold an
1682 // integer immediate on an icmp.
1683 if (BaseOffset != 0) {
1684 // We have one of:
1685 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1686 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1687 // Offs is the ICmp immediate.
1688 if (Scale == 0)
1689 // The cast does the right thing with
1690 // std::numeric_limits<int64_t>::min().
1691 BaseOffset = -(uint64_t)BaseOffset;
1692 return TTI.isLegalICmpImmediate(BaseOffset);
1693 }
1694
1695 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1696 return true;
1697
1698 case LSRUse::Basic:
1699 // Only handle single-register values.
1700 return !BaseGV && Scale == 0 && BaseOffset == 0;
1701
1702 case LSRUse::Special:
1703 // Special case Basic to handle -1 scales.
1704 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1705 }
1706
1707 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1707)
;
1708}
1709
1710static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1711 int64_t MinOffset, int64_t MaxOffset,
1712 LSRUse::KindType Kind, MemAccessTy AccessTy,
1713 GlobalValue *BaseGV, int64_t BaseOffset,
1714 bool HasBaseReg, int64_t Scale) {
1715 // Check for overflow.
1716 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1717 (MinOffset > 0))
1718 return false;
1719 MinOffset = (uint64_t)BaseOffset + MinOffset;
1720 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1721 (MaxOffset > 0))
1722 return false;
1723 MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1724
1725 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1726 HasBaseReg, Scale) &&
1727 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1728 HasBaseReg, Scale);
1729}
1730
1731static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1732 int64_t MinOffset, int64_t MaxOffset,
1733 LSRUse::KindType Kind, MemAccessTy AccessTy,
1734 const Formula &F, const Loop &L) {
1735 // For the purpose of isAMCompletelyFolded either having a canonical formula
1736 // or a scale not equal to zero is correct.
1737 // Problems may arise from non canonical formulae having a scale == 0.
1738 // Strictly speaking it would best to just rely on canonical formulae.
1739 // However, when we generate the scaled formulae, we first check that the
1740 // scaling factor is profitable before computing the actual ScaledReg for
1741 // compile time sake.
1742 assert((F.isCanonical(L) || F.Scale != 0))(static_cast <bool> ((F.isCanonical(L) || F.Scale != 0)
) ? void (0) : __assert_fail ("(F.isCanonical(L) || F.Scale != 0)"
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1742, __extension__ __PRETTY_FUNCTION__))
;
1743 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1744 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1745}
1746
1747/// Test whether we know how to expand the current formula.
1748static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1749 int64_t MaxOffset, LSRUse::KindType Kind,
1750 MemAccessTy AccessTy, GlobalValue *BaseGV,
1751 int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1752 // We know how to expand completely foldable formulae.
1753 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1754 BaseOffset, HasBaseReg, Scale) ||
1755 // Or formulae that use a base register produced by a sum of base
1756 // registers.
1757 (Scale == 1 &&
1758 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1759 BaseGV, BaseOffset, true, 0));
1760}
1761
1762static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1763 int64_t MaxOffset, LSRUse::KindType Kind,
1764 MemAccessTy AccessTy, const Formula &F) {
1765 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1766 F.BaseOffset, F.HasBaseReg, F.Scale);
1767}
1768
1769static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1770 const LSRUse &LU, const Formula &F) {
1771 // Target may want to look at the user instructions.
1772 if (LU.Kind == LSRUse::Address && TTI.LSRWithInstrQueries()) {
1773 for (const LSRFixup &Fixup : LU.Fixups)
1774 if (!isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1775 (F.BaseOffset + Fixup.Offset), F.HasBaseReg,
1776 F.Scale, Fixup.UserInst))
1777 return false;
1778 return true;
1779 }
1780
1781 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1782 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1783 F.Scale);
1784}
1785
1786static InstructionCost getScalingFactorCost(const TargetTransformInfo &TTI,
1787 const LSRUse &LU, const Formula &F,
1788 const Loop &L) {
1789 if (!F.Scale)
1790 return 0;
1791
1792 // If the use is not completely folded in that instruction, we will have to
1793 // pay an extra cost only for scale != 1.
1794 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1795 LU.AccessTy, F, L))
1796 return F.Scale != 1;
1797
1798 switch (LU.Kind) {
1799 case LSRUse::Address: {
1800 // Check the scaling factor cost with both the min and max offsets.
1801 InstructionCost ScaleCostMinOffset = TTI.getScalingFactorCost(
1802 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1803 F.Scale, LU.AccessTy.AddrSpace);
1804 InstructionCost ScaleCostMaxOffset = TTI.getScalingFactorCost(
1805 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1806 F.Scale, LU.AccessTy.AddrSpace);
1807
1808 assert(ScaleCostMinOffset.isValid() && ScaleCostMaxOffset.isValid() &&(static_cast <bool> (ScaleCostMinOffset.isValid() &&
ScaleCostMaxOffset.isValid() && "Legal addressing mode has an illegal cost!"
) ? void (0) : __assert_fail ("ScaleCostMinOffset.isValid() && ScaleCostMaxOffset.isValid() && \"Legal addressing mode has an illegal cost!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1809, __extension__ __PRETTY_FUNCTION__))
1809 "Legal addressing mode has an illegal cost!")(static_cast <bool> (ScaleCostMinOffset.isValid() &&
ScaleCostMaxOffset.isValid() && "Legal addressing mode has an illegal cost!"
) ? void (0) : __assert_fail ("ScaleCostMinOffset.isValid() && ScaleCostMaxOffset.isValid() && \"Legal addressing mode has an illegal cost!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1809, __extension__ __PRETTY_FUNCTION__))
;
1810 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1811 }
1812 case LSRUse::ICmpZero:
1813 case LSRUse::Basic:
1814 case LSRUse::Special:
1815 // The use is completely folded, i.e., everything is folded into the
1816 // instruction.
1817 return 0;
1818 }
1819
1820 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1820)
;
1821}
1822
1823static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1824 LSRUse::KindType Kind, MemAccessTy AccessTy,
1825 GlobalValue *BaseGV, int64_t BaseOffset,
1826 bool HasBaseReg) {
1827 // Fast-path: zero is always foldable.
1828 if (BaseOffset == 0 && !BaseGV) return true;
1829
1830 // Conservatively, create an address with an immediate and a
1831 // base and a scale.
1832 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1833
1834 // Canonicalize a scale of 1 to a base register if the formula doesn't
1835 // already have a base register.
1836 if (!HasBaseReg && Scale == 1) {
1837 Scale = 0;
1838 HasBaseReg = true;
1839 }
1840
1841 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1842 HasBaseReg, Scale);
1843}
1844
1845static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1846 ScalarEvolution &SE, int64_t MinOffset,
1847 int64_t MaxOffset, LSRUse::KindType Kind,
1848 MemAccessTy AccessTy, const SCEV *S,
1849 bool HasBaseReg) {
1850 // Fast-path: zero is always foldable.
1851 if (S->isZero()) return true;
1852
1853 // Conservatively, create an address with an immediate and a
1854 // base and a scale.
1855 int64_t BaseOffset = ExtractImmediate(S, SE);
1856 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1857
1858 // If there's anything else involved, it's not foldable.
1859 if (!S->isZero()) return false;
1860
1861 // Fast-path: zero is always foldable.
1862 if (BaseOffset == 0 && !BaseGV) return true;
1863
1864 // Conservatively, create an address with an immediate and a
1865 // base and a scale.
1866 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1867
1868 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1869 BaseOffset, HasBaseReg, Scale);
1870}
1871
1872namespace {
1873
1874/// An individual increment in a Chain of IV increments. Relate an IV user to
1875/// an expression that computes the IV it uses from the IV used by the previous
1876/// link in the Chain.
1877///
1878/// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1879/// original IVOperand. The head of the chain's IVOperand is only valid during
1880/// chain collection, before LSR replaces IV users. During chain generation,
1881/// IncExpr can be used to find the new IVOperand that computes the same
1882/// expression.
1883struct IVInc {
1884 Instruction *UserInst;
1885 Value* IVOperand;
1886 const SCEV *IncExpr;
1887
1888 IVInc(Instruction *U, Value *O, const SCEV *E)
1889 : UserInst(U), IVOperand(O), IncExpr(E) {}
1890};
1891
1892// The list of IV increments in program order. We typically add the head of a
1893// chain without finding subsequent links.
1894struct IVChain {
1895 SmallVector<IVInc, 1> Incs;
1896 const SCEV *ExprBase = nullptr;
1897
1898 IVChain() = default;
1899 IVChain(const IVInc &Head, const SCEV *Base)
1900 : Incs(1, Head), ExprBase(Base) {}
1901
1902 using const_iterator = SmallVectorImpl<IVInc>::const_iterator;
1903
1904 // Return the first increment in the chain.
1905 const_iterator begin() const {
1906 assert(!Incs.empty())(static_cast <bool> (!Incs.empty()) ? void (0) : __assert_fail
("!Incs.empty()", "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1906, __extension__ __PRETTY_FUNCTION__))
;
1907 return std::next(Incs.begin());
1908 }
1909 const_iterator end() const {
1910 return Incs.end();
1911 }
1912
1913 // Returns true if this chain contains any increments.
1914 bool hasIncs() const { return Incs.size() >= 2; }
1915
1916 // Add an IVInc to the end of this chain.
1917 void add(const IVInc &X) { Incs.push_back(X); }
1918
1919 // Returns the last UserInst in the chain.
1920 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1921
1922 // Returns true if IncExpr can be profitably added to this chain.
1923 bool isProfitableIncrement(const SCEV *OperExpr,
1924 const SCEV *IncExpr,
1925 ScalarEvolution&);
1926};
1927
1928/// Helper for CollectChains to track multiple IV increment uses. Distinguish
1929/// between FarUsers that definitely cross IV increments and NearUsers that may
1930/// be used between IV increments.
1931struct ChainUsers {
1932 SmallPtrSet<Instruction*, 4> FarUsers;
1933 SmallPtrSet<Instruction*, 4> NearUsers;
1934};
1935
1936/// This class holds state for the main loop strength reduction logic.
1937class LSRInstance {
1938 IVUsers &IU;
1939 ScalarEvolution &SE;
1940 DominatorTree &DT;
1941 LoopInfo &LI;
1942 AssumptionCache &AC;
1943 TargetLibraryInfo &TLI;
1944 const TargetTransformInfo &TTI;
1945 Loop *const L;
1946 MemorySSAUpdater *MSSAU;
1947 TTI::AddressingModeKind AMK;
1948 bool Changed = false;
1949
1950 /// This is the insert position that the current loop's induction variable
1951 /// increment should be placed. In simple loops, this is the latch block's
1952 /// terminator. But in more complicated cases, this is a position which will
1953 /// dominate all the in-loop post-increment users.
1954 Instruction *IVIncInsertPos = nullptr;
1955
1956 /// Interesting factors between use strides.
1957 ///
1958 /// We explicitly use a SetVector which contains a SmallSet, instead of the
1959 /// default, a SmallDenseSet, because we need to use the full range of
1960 /// int64_ts, and there's currently no good way of doing that with
1961 /// SmallDenseSet.
1962 SetVector<int64_t, SmallVector<int64_t, 8>, SmallSet<int64_t, 8>> Factors;
1963
1964 /// Interesting use types, to facilitate truncation reuse.
1965 SmallSetVector<Type *, 4> Types;
1966
1967 /// The list of interesting uses.
1968 mutable SmallVector<LSRUse, 16> Uses;
1969
1970 /// Track which uses use which register candidates.
1971 RegUseTracker RegUses;
1972
1973 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1974 // have more than a few IV increment chains in a loop. Missing a Chain falls
1975 // back to normal LSR behavior for those uses.
1976 static const unsigned MaxChains = 8;
1977
1978 /// IV users can form a chain of IV increments.
1979 SmallVector<IVChain, MaxChains> IVChainVec;
1980
1981 /// IV users that belong to profitable IVChains.
1982 SmallPtrSet<Use*, MaxChains> IVIncSet;
1983
1984 /// Induction variables that were generated and inserted by the SCEV Expander.
1985 SmallVector<llvm::WeakVH, 2> ScalarEvolutionIVs;
1986
1987 void OptimizeShadowIV();
1988 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1989 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1990 void OptimizeLoopTermCond();
1991
1992 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1993 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1994 void FinalizeChain(IVChain &Chain);
1995 void CollectChains();
1996 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1997 SmallVectorImpl<WeakTrackingVH> &DeadInsts);
1998
1999 void CollectInterestingTypesAndFactors();
2000 void CollectFixupsAndInitialFormulae();
2001
2002 // Support for sharing of LSRUses between LSRFixups.
2003 using UseMapTy = DenseMap<LSRUse::SCEVUseKindPair, size_t>;
2004 UseMapTy UseMap;
2005
2006 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
2007 LSRUse::KindType Kind, MemAccessTy AccessTy);
2008
2009 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
2010 MemAccessTy AccessTy);
2011
2012 void DeleteUse(LSRUse &LU, size_t LUIdx);
2013
2014 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
2015
2016 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
2017 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
2018 void CountRegisters(const Formula &F, size_t LUIdx);
2019 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
2020
2021 void CollectLoopInvariantFixupsAndFormulae();
2022
2023 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
2024 unsigned Depth = 0);
2025
2026 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
2027 const Formula &Base, unsigned Depth,
2028 size_t Idx, bool IsScaledReg = false);
2029 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
2030 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
2031 const Formula &Base, size_t Idx,
2032 bool IsScaledReg = false);
2033 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
2034 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
2035 const Formula &Base,
2036 const SmallVectorImpl<int64_t> &Worklist,
2037 size_t Idx, bool IsScaledReg = false);
2038 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
2039 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2040 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2041 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
2042 void GenerateCrossUseConstantOffsets();
2043 void GenerateAllReuseFormulae();
2044
2045 void FilterOutUndesirableDedicatedRegisters();
2046
2047 size_t EstimateSearchSpaceComplexity() const;
2048 void NarrowSearchSpaceByDetectingSupersets();
2049 void NarrowSearchSpaceByCollapsingUnrolledCode();
2050 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
2051 void NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
2052 void NarrowSearchSpaceByFilterPostInc();
2053 void NarrowSearchSpaceByDeletingCostlyFormulas();
2054 void NarrowSearchSpaceByPickingWinnerRegs();
2055 void NarrowSearchSpaceUsingHeuristics();
2056
2057 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
2058 Cost &SolutionCost,
2059 SmallVectorImpl<const Formula *> &Workspace,
2060 const Cost &CurCost,
2061 const SmallPtrSet<const SCEV *, 16> &CurRegs,
2062 DenseSet<const SCEV *> &VisitedRegs) const;
2063 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
2064
2065 BasicBlock::iterator
2066 HoistInsertPosition(BasicBlock::iterator IP,
2067 const SmallVectorImpl<Instruction *> &Inputs) const;
2068 BasicBlock::iterator
2069 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
2070 const LSRFixup &LF,
2071 const LSRUse &LU,
2072 SCEVExpander &Rewriter) const;
2073
2074 Value *Expand(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2075 BasicBlock::iterator IP, SCEVExpander &Rewriter,
2076 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2077 void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
2078 const Formula &F, SCEVExpander &Rewriter,
2079 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2080 void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2081 SCEVExpander &Rewriter,
2082 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2083 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
2084
2085public:
2086 LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
2087 LoopInfo &LI, const TargetTransformInfo &TTI, AssumptionCache &AC,
2088 TargetLibraryInfo &TLI, MemorySSAUpdater *MSSAU);
2089
2090 bool getChanged() const { return Changed; }
2091 const SmallVectorImpl<WeakVH> &getScalarEvolutionIVs() const {
2092 return ScalarEvolutionIVs;
2093 }
2094
2095 void print_factors_and_types(raw_ostream &OS) const;
2096 void print_fixups(raw_ostream &OS) const;
2097 void print_uses(raw_ostream &OS) const;
2098 void print(raw_ostream &OS) const;
2099 void dump() const;
2100};
2101
2102} // end anonymous namespace
2103
2104/// If IV is used in a int-to-float cast inside the loop then try to eliminate
2105/// the cast operation.
2106void LSRInstance::OptimizeShadowIV() {
2107 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2108 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2109 return;
2110
2111 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
2112 UI != E; /* empty */) {
2113 IVUsers::const_iterator CandidateUI = UI;
2114 ++UI;
2115 Instruction *ShadowUse = CandidateUI->getUser();
2116 Type *DestTy = nullptr;
2117 bool IsSigned = false;
2118
2119 /* If shadow use is a int->float cast then insert a second IV
2120 to eliminate this cast.
2121
2122 for (unsigned i = 0; i < n; ++i)
2123 foo((double)i);
2124
2125 is transformed into
2126
2127 double d = 0.0;
2128 for (unsigned i = 0; i < n; ++i, ++d)
2129 foo(d);
2130 */
2131 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
2132 IsSigned = false;
2133 DestTy = UCast->getDestTy();
2134 }
2135 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
2136 IsSigned = true;
2137 DestTy = SCast->getDestTy();
2138 }
2139 if (!DestTy) continue;
2140
2141 // If target does not support DestTy natively then do not apply
2142 // this transformation.
2143 if (!TTI.isTypeLegal(DestTy)) continue;
2144
2145 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2146 if (!PH) continue;
2147 if (PH->getNumIncomingValues() != 2) continue;
2148
2149 // If the calculation in integers overflows, the result in FP type will
2150 // differ. So we only can do this transformation if we are guaranteed to not
2151 // deal with overflowing values
2152 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PH));
2153 if (!AR) continue;
2154 if (IsSigned && !AR->hasNoSignedWrap()) continue;
2155 if (!IsSigned && !AR->hasNoUnsignedWrap()) continue;
2156
2157 Type *SrcTy = PH->getType();
2158 int Mantissa = DestTy->getFPMantissaWidth();
2159 if (Mantissa == -1) continue;
2160 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
2161 continue;
2162
2163 unsigned Entry, Latch;
2164 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2165 Entry = 0;
2166 Latch = 1;
2167 } else {
2168 Entry = 1;
2169 Latch = 0;
2170 }
2171
2172 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
2173 if (!Init) continue;
2174 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
2175 (double)Init->getSExtValue() :
2176 (double)Init->getZExtValue());
2177
2178 BinaryOperator *Incr =
2179 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
2180 if (!Incr) continue;
2181 if (Incr->getOpcode() != Instruction::Add
2182 && Incr->getOpcode() != Instruction::Sub)
2183 continue;
2184
2185 /* Initialize new IV, double d = 0.0 in above example. */
2186 ConstantInt *C = nullptr;
2187 if (Incr->getOperand(0) == PH)
2188 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2189 else if (Incr->getOperand(1) == PH)
2190 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2191 else
2192 continue;
2193
2194 if (!C) continue;
2195
2196 // Ignore negative constants, as the code below doesn't handle them
2197 // correctly. TODO: Remove this restriction.
2198 if (!C->getValue().isStrictlyPositive()) continue;
2199
2200 /* Add new PHINode. */
2201 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
2202
2203 /* create new increment. '++d' in above example. */
2204 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2205 BinaryOperator *NewIncr =
2206 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
2207 Instruction::FAdd : Instruction::FSub,
2208 NewPH, CFP, "IV.S.next.", Incr);
2209
2210 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2211 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2212
2213 /* Remove cast operation */
2214 ShadowUse->replaceAllUsesWith(NewPH);
2215 ShadowUse->eraseFromParent();
2216 Changed = true;
2217 break;
2218 }
2219}
2220
2221/// If Cond has an operand that is an expression of an IV, set the IV user and
2222/// stride information and return true, otherwise return false.
2223bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
2224 for (IVStrideUse &U : IU)
2225 if (U.getUser() == Cond) {
2226 // NOTE: we could handle setcc instructions with multiple uses here, but
2227 // InstCombine does it as well for simple uses, it's not clear that it
2228 // occurs enough in real life to handle.
2229 CondUse = &U;
2230 return true;
2231 }
2232 return false;
2233}
2234
2235/// Rewrite the loop's terminating condition if it uses a max computation.
2236///
2237/// This is a narrow solution to a specific, but acute, problem. For loops
2238/// like this:
2239///
2240/// i = 0;
2241/// do {
2242/// p[i] = 0.0;
2243/// } while (++i < n);
2244///
2245/// the trip count isn't just 'n', because 'n' might not be positive. And
2246/// unfortunately this can come up even for loops where the user didn't use
2247/// a C do-while loop. For example, seemingly well-behaved top-test loops
2248/// will commonly be lowered like this:
2249///
2250/// if (n > 0) {
2251/// i = 0;
2252/// do {
2253/// p[i] = 0.0;
2254/// } while (++i < n);
2255/// }
2256///
2257/// and then it's possible for subsequent optimization to obscure the if
2258/// test in such a way that indvars can't find it.
2259///
2260/// When indvars can't find the if test in loops like this, it creates a
2261/// max expression, which allows it to give the loop a canonical
2262/// induction variable:
2263///
2264/// i = 0;
2265/// max = n < 1 ? 1 : n;
2266/// do {
2267/// p[i] = 0.0;
2268/// } while (++i != max);
2269///
2270/// Canonical induction variables are necessary because the loop passes
2271/// are designed around them. The most obvious example of this is the
2272/// LoopInfo analysis, which doesn't remember trip count values. It
2273/// expects to be able to rediscover the trip count each time it is
2274/// needed, and it does this using a simple analysis that only succeeds if
2275/// the loop has a canonical induction variable.
2276///
2277/// However, when it comes time to generate code, the maximum operation
2278/// can be quite costly, especially if it's inside of an outer loop.
2279///
2280/// This function solves this problem by detecting this type of loop and
2281/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2282/// the instructions for the maximum computation.
2283ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
2284 // Check that the loop matches the pattern we're looking for.
2285 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2286 Cond->getPredicate() != CmpInst::ICMP_NE)
2287 return Cond;
2288
2289 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2290 if (!Sel || !Sel->hasOneUse()) return Cond;
2291
2292 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2293 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2294 return Cond;
2295 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2296
2297 // Add one to the backedge-taken count to get the trip count.
2298 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2299 if (IterationCount != SE.getSCEV(Sel)) return Cond;
2300
2301 // Check for a max calculation that matches the pattern. There's no check
2302 // for ICMP_ULE here because the comparison would be with zero, which
2303 // isn't interesting.
2304 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2305 const SCEVNAryExpr *Max = nullptr;
2306 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2307 Pred = ICmpInst::ICMP_SLE;
2308 Max = S;
2309 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2310 Pred = ICmpInst::ICMP_SLT;
2311 Max = S;
2312 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2313 Pred = ICmpInst::ICMP_ULT;
2314 Max = U;
2315 } else {
2316 // No match; bail.
2317 return Cond;
2318 }
2319
2320 // To handle a max with more than two operands, this optimization would
2321 // require additional checking and setup.
2322 if (Max->getNumOperands() != 2)
2323 return Cond;
2324
2325 const SCEV *MaxLHS = Max->getOperand(0);
2326 const SCEV *MaxRHS = Max->getOperand(1);
2327
2328 // ScalarEvolution canonicalizes constants to the left. For < and >, look
2329 // for a comparison with 1. For <= and >=, a comparison with zero.
2330 if (!MaxLHS ||
2331 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2332 return Cond;
2333
2334 // Check the relevant induction variable for conformance to
2335 // the pattern.
2336 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2337 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2338 if (!AR || !AR->isAffine() ||
2339 AR->getStart() != One ||
2340 AR->getStepRecurrence(SE) != One)
2341 return Cond;
2342
2343 assert(AR->getLoop() == L &&(static_cast <bool> (AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? void (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2344, __extension__ __PRETTY_FUNCTION__))
2344 "Loop condition operand is an addrec in a different loop!")(static_cast <bool> (AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? void (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2344, __extension__ __PRETTY_FUNCTION__))
;
2345
2346 // Check the right operand of the select, and remember it, as it will
2347 // be used in the new comparison instruction.
2348 Value *NewRHS = nullptr;
2349 if (ICmpInst::isTrueWhenEqual(Pred)) {
2350 // Look for n+1, and grab n.
2351 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2352 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2353 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2354 NewRHS = BO->getOperand(0);
2355 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2356 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2357 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2358 NewRHS = BO->getOperand(0);
2359 if (!NewRHS)
2360 return Cond;
2361 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2362 NewRHS = Sel->getOperand(1);
2363 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2364 NewRHS = Sel->getOperand(2);
2365 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2366 NewRHS = SU->getValue();
2367 else
2368 // Max doesn't match expected pattern.
2369 return Cond;
2370
2371 // Determine the new comparison opcode. It may be signed or unsigned,
2372 // and the original comparison may be either equality or inequality.
2373 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2374 Pred = CmpInst::getInversePredicate(Pred);
2375
2376 // Ok, everything looks ok to change the condition into an SLT or SGE and
2377 // delete the max calculation.
2378 ICmpInst *NewCond =
2379 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2380
2381 // Delete the max calculation instructions.
2382 NewCond->setDebugLoc(Cond->getDebugLoc());
2383 Cond->replaceAllUsesWith(NewCond);
2384 CondUse->setUser(NewCond);
2385 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2386 Cond->eraseFromParent();
2387 Sel->eraseFromParent();
2388 if (Cmp->use_empty())
2389 Cmp->eraseFromParent();
2390 return NewCond;
2391}
2392
2393/// Change loop terminating condition to use the postinc iv when possible.
2394void
2395LSRInstance::OptimizeLoopTermCond() {
2396 SmallPtrSet<Instruction *, 4> PostIncs;
2397
2398 // We need a different set of heuristics for rotated and non-rotated loops.
2399 // If a loop is rotated then the latch is also the backedge, so inserting
2400 // post-inc expressions just before the latch is ideal. To reduce live ranges
2401 // it also makes sense to rewrite terminating conditions to use post-inc
2402 // expressions.
2403 //
2404 // If the loop is not rotated then the latch is not a backedge; the latch
2405 // check is done in the loop head. Adding post-inc expressions before the
2406 // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2407 // in the loop body. In this case we do *not* want to use post-inc expressions
2408 // in the latch check, and we want to insert post-inc expressions before
2409 // the backedge.
2410 BasicBlock *LatchBlock = L->getLoopLatch();
2411 SmallVector<BasicBlock*, 8> ExitingBlocks;
2412 L->getExitingBlocks(ExitingBlocks);
2413 if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2414 return LatchBlock != BB;
2415 })) {
2416 // The backedge doesn't exit the loop; treat this as a head-tested loop.
2417 IVIncInsertPos = LatchBlock->getTerminator();
2418 return;
2419 }
2420
2421 // Otherwise treat this as a rotated loop.
2422 for (BasicBlock *ExitingBlock : ExitingBlocks) {
2423 // Get the terminating condition for the loop if possible. If we
2424 // can, we want to change it to use a post-incremented version of its
2425 // induction variable, to allow coalescing the live ranges for the IV into
2426 // one register value.
2427
2428 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2429 if (!TermBr)
2430 continue;
2431 // FIXME: Overly conservative, termination condition could be an 'or' etc..
2432 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2433 continue;
2434
2435 // Search IVUsesByStride to find Cond's IVUse if there is one.
2436 IVStrideUse *CondUse = nullptr;
2437 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2438 if (!FindIVUserForCond(Cond, CondUse))
2439 continue;
2440
2441 // If the trip count is computed in terms of a max (due to ScalarEvolution
2442 // being unable to find a sufficient guard, for example), change the loop
2443 // comparison to use SLT or ULT instead of NE.
2444 // One consequence of doing this now is that it disrupts the count-down
2445 // optimization. That's not always a bad thing though, because in such
2446 // cases it may still be worthwhile to avoid a max.
2447 Cond = OptimizeMax(Cond, CondUse);
2448
2449 // If this exiting block dominates the latch block, it may also use
2450 // the post-inc value if it won't be shared with other uses.
2451 // Check for dominance.
2452 if (!DT.dominates(ExitingBlock, LatchBlock))
2453 continue;
2454
2455 // Conservatively avoid trying to use the post-inc value in non-latch
2456 // exits if there may be pre-inc users in intervening blocks.
2457 if (LatchBlock != ExitingBlock)
2458 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2459 // Test if the use is reachable from the exiting block. This dominator
2460 // query is a conservative approximation of reachability.
2461 if (&*UI != CondUse &&
2462 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2463 // Conservatively assume there may be reuse if the quotient of their
2464 // strides could be a legal scale.
2465 const SCEV *A = IU.getStride(*CondUse, L);
2466 const SCEV *B = IU.getStride(*UI, L);
2467 if (!A || !B) continue;
2468 if (SE.getTypeSizeInBits(A->getType()) !=
2469 SE.getTypeSizeInBits(B->getType())) {
2470 if (SE.getTypeSizeInBits(A->getType()) >
2471 SE.getTypeSizeInBits(B->getType()))
2472 B = SE.getSignExtendExpr(B, A->getType());
2473 else
2474 A = SE.getSignExtendExpr(A, B->getType());
2475 }
2476 if (const SCEVConstant *D =
2477 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2478 const ConstantInt *C = D->getValue();
2479 // Stride of one or negative one can have reuse with non-addresses.
2480 if (C->isOne() || C->isMinusOne())
2481 goto decline_post_inc;
2482 // Avoid weird situations.
2483 if (C->getValue().getMinSignedBits() >= 64 ||
2484 C->getValue().isMinSignedValue())
2485 goto decline_post_inc;
2486 // Check for possible scaled-address reuse.
2487 if (isAddressUse(TTI, UI->getUser(), UI->getOperandValToReplace())) {
2488 MemAccessTy AccessTy = getAccessType(
2489 TTI, UI->getUser(), UI->getOperandValToReplace());
2490 int64_t Scale = C->getSExtValue();
2491 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2492 /*BaseOffset=*/0,
2493 /*HasBaseReg=*/false, Scale,
2494 AccessTy.AddrSpace))
2495 goto decline_post_inc;
2496 Scale = -Scale;
2497 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2498 /*BaseOffset=*/0,
2499 /*HasBaseReg=*/false, Scale,
2500 AccessTy.AddrSpace))
2501 goto decline_post_inc;
2502 }
2503 }
2504 }
2505
2506 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)
2507 << *Cond << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Change loop exiting icmp to use postinc iv: "
<< *Cond << '\n'; } } while (false)
;
2508
2509 // It's possible for the setcc instruction to be anywhere in the loop, and
2510 // possible for it to have multiple users. If it is not immediately before
2511 // the exiting block branch, move it.
2512 if (Cond->getNextNonDebugInstruction() != TermBr) {
2513 if (Cond->hasOneUse()) {
2514 Cond->moveBefore(TermBr);
2515 } else {
2516 // Clone the terminating condition and insert into the loopend.
2517 ICmpInst *OldCond = Cond;
2518 Cond = cast<ICmpInst>(Cond->clone());
2519 Cond->setName(L->getHeader()->getName() + ".termcond");
2520 ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2521
2522 // Clone the IVUse, as the old use still exists!
2523 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2524 TermBr->replaceUsesOfWith(OldCond, Cond);
2525 }
2526 }
2527
2528 // If we get to here, we know that we can transform the setcc instruction to
2529 // use the post-incremented version of the IV, allowing us to coalesce the
2530 // live ranges for the IV correctly.
2531 CondUse->transformToPostInc(L);
2532 Changed = true;
2533
2534 PostIncs.insert(Cond);
2535 decline_post_inc:;
2536 }
2537
2538 // Determine an insertion point for the loop induction variable increment. It
2539 // must dominate all the post-inc comparisons we just set up, and it must
2540 // dominate the loop latch edge.
2541 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2542 for (Instruction *Inst : PostIncs) {
2543 BasicBlock *BB =
2544 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2545 Inst->getParent());
2546 if (BB == Inst->getParent())
2547 IVIncInsertPos = Inst;
2548 else if (BB != IVIncInsertPos->getParent())
2549 IVIncInsertPos = BB->getTerminator();
2550 }
2551}
2552
2553/// Determine if the given use can accommodate a fixup at the given offset and
2554/// other details. If so, update the use and return true.
2555bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2556 bool HasBaseReg, LSRUse::KindType Kind,
2557 MemAccessTy AccessTy) {
2558 int64_t NewMinOffset = LU.MinOffset;
2559 int64_t NewMaxOffset = LU.MaxOffset;
2560 MemAccessTy NewAccessTy = AccessTy;
2561
2562 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2563 // something conservative, however this can pessimize in the case that one of
2564 // the uses will have all its uses outside the loop, for example.
2565 if (LU.Kind != Kind)
2566 return false;
2567
2568 // Check for a mismatched access type, and fall back conservatively as needed.
2569 // TODO: Be less conservative when the type is similar and can use the same
2570 // addressing modes.
2571 if (Kind == LSRUse::Address) {
2572 if (AccessTy.MemTy != LU.AccessTy.MemTy) {
2573 NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(),
2574 AccessTy.AddrSpace);
2575 }
2576 }
2577
2578 // Conservatively assume HasBaseReg is true for now.
2579 if (NewOffset < LU.MinOffset) {
2580 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2581 LU.MaxOffset - NewOffset, HasBaseReg))
2582 return false;
2583 NewMinOffset = NewOffset;
2584 } else if (NewOffset > LU.MaxOffset) {
2585 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2586 NewOffset - LU.MinOffset, HasBaseReg))
2587 return false;
2588 NewMaxOffset = NewOffset;
2589 }
2590
2591 // Update the use.
2592 LU.MinOffset = NewMinOffset;
2593 LU.MaxOffset = NewMaxOffset;
2594 LU.AccessTy = NewAccessTy;
2595 return true;
2596}
2597
2598/// Return an LSRUse index and an offset value for a fixup which needs the given
2599/// expression, with the given kind and optional access type. Either reuse an
2600/// existing use or create a new one, as needed.
2601std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2602 LSRUse::KindType Kind,
2603 MemAccessTy AccessTy) {
2604 const SCEV *Copy = Expr;
2605 int64_t Offset = ExtractImmediate(Expr, SE);
2606
2607 // Basic uses can't accept any offset, for example.
2608 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2609 Offset, /*HasBaseReg=*/ true)) {
2610 Expr = Copy;
2611 Offset = 0;
2612 }
2613
2614 std::pair<UseMapTy::iterator, bool> P =
2615 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2616 if (!P.second) {
2617 // A use already existed with this base.
2618 size_t LUIdx = P.first->second;
2619 LSRUse &LU = Uses[LUIdx];
2620 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2621 // Reuse this use.
2622 return std::make_pair(LUIdx, Offset);
2623 }
2624
2625 // Create a new use.
2626 size_t LUIdx = Uses.size();
2627 P.first->second = LUIdx;
2628 Uses.push_back(LSRUse(Kind, AccessTy));
2629 LSRUse &LU = Uses[LUIdx];
2630
2631 LU.MinOffset = Offset;
2632 LU.MaxOffset = Offset;
2633 return std::make_pair(LUIdx, Offset);
2634}
2635
2636/// Delete the given use from the Uses list.
2637void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2638 if (&LU != &Uses.back())
2639 std::swap(LU, Uses.back());
2640 Uses.pop_back();
2641
2642 // Update RegUses.
2643 RegUses.swapAndDropUse(LUIdx, Uses.size());
2644}
2645
2646/// Look for a use distinct from OrigLU which is has a formula that has the same
2647/// registers as the given formula.
2648LSRUse *
2649LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2650 const LSRUse &OrigLU) {
2651 // Search all uses for the formula. This could be more clever.
2652 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2653 LSRUse &LU = Uses[LUIdx];
2654 // Check whether this use is close enough to OrigLU, to see whether it's
2655 // worthwhile looking through its formulae.
2656 // Ignore ICmpZero uses because they may contain formulae generated by
2657 // GenerateICmpZeroScales, in which case adding fixup offsets may
2658 // be invalid.
2659 if (&LU != &OrigLU &&
2660 LU.Kind != LSRUse::ICmpZero &&
2661 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2662 LU.WidestFixupType == OrigLU.WidestFixupType &&
2663 LU.HasFormulaWithSameRegs(OrigF)) {
2664 // Scan through this use's formulae.
2665 for (const Formula &F : LU.Formulae) {
2666 // Check to see if this formula has the same registers and symbols
2667 // as OrigF.
2668 if (F.BaseRegs == OrigF.BaseRegs &&
2669 F.ScaledReg == OrigF.ScaledReg &&
2670 F.BaseGV == OrigF.BaseGV &&
2671 F.Scale == OrigF.Scale &&
2672 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2673 if (F.BaseOffset == 0)
2674 return &LU;
2675 // This is the formula where all the registers and symbols matched;
2676 // there aren't going to be any others. Since we declined it, we
2677 // can skip the rest of the formulae and proceed to the next LSRUse.
2678 break;
2679 }
2680 }
2681 }
2682 }
2683
2684 // Nothing looked good.
2685 return nullptr;
2686}
2687
2688void LSRInstance::CollectInterestingTypesAndFactors() {
2689 SmallSetVector<const SCEV *, 4> Strides;
2690
2691 // Collect interesting types and strides.
2692 SmallVector<const SCEV *, 4> Worklist;
2693 for (const IVStrideUse &U : IU) {
2694 const SCEV *Expr = IU.getExpr(U);
2695
2696 // Collect interesting types.
2697 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2698
2699 // Add strides for mentioned loops.
2700 Worklist.push_back(Expr);
2701 do {
2702 const SCEV *S = Worklist.pop_back_val();
2703 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2704 if (AR->getLoop() == L)
2705 Strides.insert(AR->getStepRecurrence(SE));
2706 Worklist.push_back(AR->getStart());
2707 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2708 Worklist.append(Add->op_begin(), Add->op_end());
2709 }
2710 } while (!Worklist.empty());
2711 }
2712
2713 // Compute interesting factors from the set of interesting strides.
2714 for (SmallSetVector<const SCEV *, 4>::const_iterator
2715 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2716 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2717 std::next(I); NewStrideIter != E; ++NewStrideIter) {
2718 const SCEV *OldStride = *I;
2719 const SCEV *NewStride = *NewStrideIter;
2720
2721 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2722 SE.getTypeSizeInBits(NewStride->getType())) {
2723 if (SE.getTypeSizeInBits(OldStride->getType()) >
2724 SE.getTypeSizeInBits(NewStride->getType()))
2725 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2726 else
2727 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2728 }
2729 if (const SCEVConstant *Factor =
2730 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2731 SE, true))) {
2732 if (Factor->getAPInt().getMinSignedBits() <= 64 && !Factor->isZero())
2733 Factors.insert(Factor->getAPInt().getSExtValue());
2734 } else if (const SCEVConstant *Factor =
2735 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2736 NewStride,
2737 SE, true))) {
2738 if (Factor->getAPInt().getMinSignedBits() <= 64 && !Factor->isZero())
2739 Factors.insert(Factor->getAPInt().getSExtValue());
2740 }
2741 }
2742
2743 // If all uses use the same type, don't bother looking for truncation-based
2744 // reuse.
2745 if (Types.size() == 1)
2746 Types.clear();
2747
2748 LLVM_DEBUG(print_factors_and_types(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_factors_and_types(dbgs()); } } while
(false)
;
2749}
2750
2751/// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2752/// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2753/// IVStrideUses, we could partially skip this.
2754static User::op_iterator
2755findIVOperand(User::op_iterator OI, User::op_iterator OE,
2756 Loop *L, ScalarEvolution &SE) {
2757 for(; OI != OE; ++OI) {
2758 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2759 if (!SE.isSCEVable(Oper->getType()))
2760 continue;
2761
2762 if (const SCEVAddRecExpr *AR =
2763 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2764 if (AR->getLoop() == L)
2765 break;
2766 }
2767 }
2768 }
2769 return OI;
2770}
2771
2772/// IVChain logic must consistently peek base TruncInst operands, so wrap it in
2773/// a convenient helper.
2774static Value *getWideOperand(Value *Oper) {
2775 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2776 return Trunc->getOperand(0);
2777 return Oper;
2778}
2779
2780/// Return true if we allow an IV chain to include both types.
2781static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2782 Type *LType = LVal->getType();
2783 Type *RType = RVal->getType();
2784 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy() &&
2785 // Different address spaces means (possibly)
2786 // different types of the pointer implementation,
2787 // e.g. i16 vs i32 so disallow that.
2788 (LType->getPointerAddressSpace() ==
2789 RType->getPointerAddressSpace()));
2790}
2791
2792/// Return an approximation of this SCEV expression's "base", or NULL for any
2793/// constant. Returning the expression itself is conservative. Returning a
2794/// deeper subexpression is more precise and valid as long as it isn't less
2795/// complex than another subexpression. For expressions involving multiple
2796/// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2797/// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2798/// IVInc==b-a.
2799///
2800/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2801/// SCEVUnknown, we simply return the rightmost SCEV operand.
2802static const SCEV *getExprBase(const SCEV *S) {
2803 switch (S->getSCEVType()) {
2804 default: // uncluding scUnknown.
2805 return S;
2806 case scConstant:
2807 return nullptr;
2808 case scTruncate:
2809 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2810 case scZeroExtend:
2811 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2812 case scSignExtend:
2813 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2814 case scAddExpr: {
2815 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2816 // there's nothing more complex.
2817 // FIXME: not sure if we want to recognize negation.
2818 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2819 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2820 E(Add->op_begin()); I != E; ++I) {
2821 const SCEV *SubExpr = *I;
2822 if (SubExpr->getSCEVType() == scAddExpr)
2823 return getExprBase(SubExpr);
2824
2825 if (SubExpr->getSCEVType() != scMulExpr)
2826 return SubExpr;
2827 }
2828 return S; // all operands are scaled, be conservative.
2829 }
2830 case scAddRecExpr:
2831 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2832 }
2833 llvm_unreachable("Unknown SCEV kind!")::llvm::llvm_unreachable_internal("Unknown SCEV kind!", "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2833)
;
2834}
2835
2836/// Return true if the chain increment is profitable to expand into a loop
2837/// invariant value, which may require its own register. A profitable chain
2838/// increment will be an offset relative to the same base. We allow such offsets
2839/// to potentially be used as chain increment as long as it's not obviously
2840/// expensive to expand using real instructions.
2841bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2842 const SCEV *IncExpr,
2843 ScalarEvolution &SE) {
2844 // Aggressively form chains when -stress-ivchain.
2845 if (StressIVChain)
2846 return true;
2847
2848 // Do not replace a constant offset from IV head with a nonconstant IV
2849 // increment.
2850 if (!isa<SCEVConstant>(IncExpr)) {
2851 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2852 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2853 return false;
2854 }
2855
2856 SmallPtrSet<const SCEV*, 8> Processed;
2857 return !isHighCostExpansion(IncExpr, Processed, SE);
2858}
2859
2860/// Return true if the number of registers needed for the chain is estimated to
2861/// be less than the number required for the individual IV users. First prohibit
2862/// any IV users that keep the IV live across increments (the Users set should
2863/// be empty). Next count the number and type of increments in the chain.
2864///
2865/// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2866/// effectively use postinc addressing modes. Only consider it profitable it the
2867/// increments can be computed in fewer registers when chained.
2868///
2869/// TODO: Consider IVInc free if it's already used in another chains.
2870static bool isProfitableChain(IVChain &Chain,
2871 SmallPtrSetImpl<Instruction *> &Users,
2872 ScalarEvolution &SE,
2873 const TargetTransformInfo &TTI) {
2874 if (StressIVChain)
2875 return true;
2876
2877 if (!Chain.hasIncs())
2878 return false;
2879
2880 if (!Users.empty()) {
2881 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)
2882 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)
2883 : 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)
;
2884 return false;
2885 }
2886 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")(static_cast <bool> (!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? void (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2886, __extension__ __PRETTY_FUNCTION__))
;
2887
2888 // The chain itself may require a register, so intialize cost to 1.
2889 int cost = 1;
2890
2891 // A complete chain likely eliminates the need for keeping the original IV in
2892 // a register. LSR does not currently know how to form a complete chain unless
2893 // the header phi already exists.
2894 if (isa<PHINode>(Chain.tailUserInst())
2895 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2896 --cost;
2897 }
2898 const SCEV *LastIncExpr = nullptr;
2899 unsigned NumConstIncrements = 0;
2900 unsigned NumVarIncrements = 0;
2901 unsigned NumReusedIncrements = 0;
2902
2903 if (TTI.isProfitableLSRChainElement(Chain.Incs[0].UserInst))
2904 return true;
2905
2906 for (const IVInc &Inc : Chain) {
2907 if (TTI.isProfitableLSRChainElement(Inc.UserInst))
2908 return true;
2909 if (Inc.IncExpr->isZero())
2910 continue;
2911
2912 // Incrementing by zero or some constant is neutral. We assume constants can
2913 // be folded into an addressing mode or an add's immediate operand.
2914 if (isa<SCEVConstant>(Inc.IncExpr)) {
2915 ++NumConstIncrements;
2916 continue;
2917 }
2918
2919 if (Inc.IncExpr == LastIncExpr)
2920 ++NumReusedIncrements;
2921 else
2922 ++NumVarIncrements;
2923
2924 LastIncExpr = Inc.IncExpr;
2925 }
2926 // An IV chain with a single increment is handled by LSR's postinc
2927 // uses. However, a chain with multiple increments requires keeping the IV's
2928 // value live longer than it needs to be if chained.
2929 if (NumConstIncrements > 1)
2930 --cost;
2931
2932 // Materializing increment expressions in the preheader that didn't exist in
2933 // the original code may cost a register. For example, sign-extended array
2934 // indices can produce ridiculous increments like this:
2935 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2936 cost += NumVarIncrements;
2937
2938 // Reusing variable increments likely saves a register to hold the multiple of
2939 // the stride.
2940 cost -= NumReusedIncrements;
2941
2942 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)
2943 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " Cost: " << cost << "\n"
; } } while (false)
;
2944
2945 return cost < 0;
2946}
2947
2948/// Add this IV user to an existing chain or make it the head of a new chain.
2949void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2950 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2951 // When IVs are used as types of varying widths, they are generally converted
2952 // to a wider type with some uses remaining narrow under a (free) trunc.
2953 Value *const NextIV = getWideOperand(IVOper);
2954 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2955 const SCEV *const OperExprBase = getExprBase(OperExpr);
2956
2957 // Visit all existing chains. Check if its IVOper can be computed as a
2958 // profitable loop invariant increment from the last link in the Chain.
2959 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2960 const SCEV *LastIncExpr = nullptr;
2961 for (; ChainIdx < NChains; ++ChainIdx) {
2962 IVChain &Chain = IVChainVec[ChainIdx];
2963
2964 // Prune the solution space aggressively by checking that both IV operands
2965 // are expressions that operate on the same unscaled SCEVUnknown. This
2966 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2967 // first avoids creating extra SCEV expressions.
2968 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2969 continue;
2970
2971 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2972 if (!isCompatibleIVType(PrevIV, NextIV))
2973 continue;
2974
2975 // A phi node terminates a chain.
2976 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2977 continue;
2978
2979 // The increment must be loop-invariant so it can be kept in a register.
2980 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2981 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2982 if (isa<SCEVCouldNotCompute>(IncExpr) || !SE.isLoopInvariant(IncExpr, L))
2983 continue;
2984
2985 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2986 LastIncExpr = IncExpr;
2987 break;
2988 }
2989 }
2990 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2991 // bother for phi nodes, because they must be last in the chain.
2992 if (ChainIdx == NChains) {
2993 if (isa<PHINode>(UserInst))
2994 return;
2995 if (NChains >= MaxChains && !StressIVChain) {
2996 LLVM_DEBUG(dbgs() << "IV Chain Limit\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain Limit\n"; } } while
(false)
;
2997 return;
2998 }
2999 LastIncExpr = OperExpr;
3000 // IVUsers may have skipped over sign/zero extensions. We don't currently
3001 // attempt to form chains involving extensions unless they can be hoisted
3002 // into this loop's AddRec.
3003 if (!isa<SCEVAddRecExpr>(LastIncExpr))
3004 return;
3005 ++NChains;
3006 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
3007 OperExprBase));
3008 ChainUsersVec.resize(NChains);
3009 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)
3010 << ") IV=" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Head: (" << *UserInst << ") IV=" <<
*LastIncExpr << "\n"; } } while (false)
;
3011 } else {
3012 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)
3013 << ") IV+" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Inc: (" << *UserInst << ") IV+" <<
*LastIncExpr << "\n"; } } while (false)
;
3014 // Add this IV user to the end of the chain.
3015 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
3016 }
3017 IVChain &Chain = IVChainVec[ChainIdx];
3018
3019 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
3020 // This chain's NearUsers become FarUsers.
3021 if (!LastIncExpr->isZero()) {
3022 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
3023 NearUsers.end());
3024 NearUsers.clear();
3025 }
3026
3027 // All other uses of IVOperand become near uses of the chain.
3028 // We currently ignore intermediate values within SCEV expressions, assuming
3029 // they will eventually be used be the current chain, or can be computed
3030 // from one of the chain increments. To be more precise we could
3031 // transitively follow its user and only add leaf IV users to the set.
3032 for (User *U : IVOper->users()) {
3033 Instruction *OtherUse = dyn_cast<Instruction>(U);
3034 if (!OtherUse)
3035 continue;
3036 // Uses in the chain will no longer be uses if the chain is formed.
3037 // Include the head of the chain in this iteration (not Chain.begin()).
3038 IVChain::const_iterator IncIter = Chain.Incs.begin();
3039 IVChain::const_iterator IncEnd = Chain.Incs.end();
3040 for( ; IncIter != IncEnd; ++IncIter) {
3041 if (IncIter->UserInst == OtherUse)
3042 break;
3043 }
3044 if (IncIter != IncEnd)
3045 continue;
3046
3047 if (SE.isSCEVable(OtherUse->getType())
3048 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
3049 && IU.isIVUserOrOperand(OtherUse)) {
3050 continue;
3051 }
3052 NearUsers.insert(OtherUse);
3053 }
3054
3055 // Since this user is part of the chain, it's no longer considered a use
3056 // of the chain.
3057 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
3058}
3059
3060/// Populate the vector of Chains.
3061///
3062/// This decreases ILP at the architecture level. Targets with ample registers,
3063/// multiple memory ports, and no register renaming probably don't want
3064/// this. However, such targets should probably disable LSR altogether.
3065///
3066/// The job of LSR is to make a reasonable choice of induction variables across
3067/// the loop. Subsequent passes can easily "unchain" computation exposing more
3068/// ILP *within the loop* if the target wants it.
3069///
3070/// Finding the best IV chain is potentially a scheduling problem. Since LSR
3071/// will not reorder memory operations, it will recognize this as a chain, but
3072/// will generate redundant IV increments. Ideally this would be corrected later
3073/// by a smart scheduler:
3074/// = A[i]
3075/// = A[i+x]
3076/// A[i] =
3077/// A[i+x] =
3078///
3079/// TODO: Walk the entire domtree within this loop, not just the path to the
3080/// loop latch. This will discover chains on side paths, but requires
3081/// maintaining multiple copies of the Chains state.
3082void LSRInstance::CollectChains() {
3083 LLVM_DEBUG(dbgs() << "Collecting IV Chains.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Collecting IV Chains.\n";
} } while (false)
;
3084 SmallVector<ChainUsers, 8> ChainUsersVec;
3085
3086 SmallVector<BasicBlock *,8> LatchPath;
3087 BasicBlock *LoopHeader = L->getHeader();
3088 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
3089 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
3090 LatchPath.push_back(Rung->getBlock());
3091 }
3092 LatchPath.push_back(LoopHeader);
3093
3094 // Walk the instruction stream from the loop header to the loop latch.
3095 for (BasicBlock *BB : reverse(LatchPath)) {
3096 for (Instruction &I : *BB) {
3097 // Skip instructions that weren't seen by IVUsers analysis.
3098 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
3099 continue;
3100
3101 // Ignore users that are part of a SCEV expression. This way we only
3102 // consider leaf IV Users. This effectively rediscovers a portion of
3103 // IVUsers analysis but in program order this time.
3104 if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
3105 continue;
3106
3107 // Remove this instruction from any NearUsers set it may be in.
3108 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
3109 ChainIdx < NChains; ++ChainIdx) {
3110 ChainUsersVec[ChainIdx].NearUsers.erase(&I);
3111 }
3112 // Search for operands that can be chained.
3113 SmallPtrSet<Instruction*, 4> UniqueOperands;
3114 User::op_iterator IVOpEnd = I.op_end();
3115 User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
3116 while (IVOpIter != IVOpEnd) {
3117 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
3118 if (UniqueOperands.insert(IVOpInst).second)
3119 ChainInstruction(&I, IVOpInst, ChainUsersVec);
3120 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3121 }
3122 } // Continue walking down the instructions.
3123 } // Continue walking down the domtree.
3124 // Visit phi backedges to determine if the chain can generate the IV postinc.
3125 for (PHINode &PN : L->getHeader()->phis()) {
3126 if (!SE.isSCEVable(PN.getType()))
3127 continue;
3128
3129 Instruction *IncV =
3130 dyn_cast<Instruction>(PN.getIncomingValueForBlock(L->getLoopLatch()));
3131 if (IncV)
3132 ChainInstruction(&PN, IncV, ChainUsersVec);
3133 }
3134 // Remove any unprofitable chains.
3135 unsigned ChainIdx = 0;
3136 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
3137 UsersIdx < NChains; ++UsersIdx) {
3138 if (!isProfitableChain(IVChainVec[UsersIdx],
3139 ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
3140 continue;
3141 // Preserve the chain at UsesIdx.
3142 if (ChainIdx != UsersIdx)
3143 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
3144 FinalizeChain(IVChainVec[ChainIdx]);
3145 ++ChainIdx;
3146 }
3147 IVChainVec.resize(ChainIdx);
3148}
3149
3150void LSRInstance::FinalizeChain(IVChain &Chain) {
3151 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")(static_cast <bool> (!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? void (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3151, __extension__ __PRETTY_FUNCTION__))
;
3152 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)
;
3153
3154 for (const IVInc &Inc : Chain) {
3155 LLVM_DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Inc: " << *
Inc.UserInst << "\n"; } } while (false)
;
3156 auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
3157 assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand")(static_cast <bool> (UseI != Inc.UserInst->op_end() &&
"cannot find IV operand") ? void (0) : __assert_fail ("UseI != Inc.UserInst->op_end() && \"cannot find IV operand\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3157, __extension__ __PRETTY_FUNCTION__))
;
3158 IVIncSet.insert(UseI);
3159 }
3160}
3161
3162/// Return true if the IVInc can be folded into an addressing mode.
3163static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
3164 Value *Operand, const TargetTransformInfo &TTI) {
3165 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
3166 if (!IncConst || !isAddressUse(TTI, UserInst, Operand))
3167 return false;
3168
3169 if (IncConst->getAPInt().getMinSignedBits() > 64)
3170 return false;
3171
3172 MemAccessTy AccessTy = getAccessType(TTI, UserInst, Operand);
3173 int64_t IncOffset = IncConst->getValue()->getSExtValue();
3174 if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
3175 IncOffset, /*HasBaseReg=*/false))
3176 return false;
3177
3178 return true;
3179}
3180
3181/// Generate an add or subtract for each IVInc in a chain to materialize the IV
3182/// user's operand from the previous IV user's operand.
3183void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
3184 SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
3185 // Find the new IVOperand for the head of the chain. It may have been replaced
3186 // by LSR.
3187 const IVInc &Head = Chain.Incs[0];
3188 User::op_iterator IVOpEnd = Head.UserInst->op_end();
3189 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
3190 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
3191 IVOpEnd, L, SE);
3192 Value *IVSrc = nullptr;
3193 while (IVOpIter != IVOpEnd) {
3194 IVSrc = getWideOperand(*IVOpIter);
3195
3196 // If this operand computes the expression that the chain needs, we may use
3197 // it. (Check this after setting IVSrc which is used below.)
3198 //
3199 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
3200 // narrow for the chain, so we can no longer use it. We do allow using a
3201 // wider phi, assuming the LSR checked for free truncation. In that case we
3202 // should already have a truncate on this operand such that
3203 // getSCEV(IVSrc) == IncExpr.
3204 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
3205 || SE.getSCEV(IVSrc) == Head.IncExpr) {
3206 break;
3207 }
3208 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3209 }
3210 if (IVOpIter == IVOpEnd) {
3211 // Gracefully give up on this chain.
3212 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)
;
3213 return;
3214 }
3215 assert(IVSrc && "Failed to find IV chain source")(static_cast <bool> (IVSrc && "Failed to find IV chain source"
) ? void (0) : __assert_fail ("IVSrc && \"Failed to find IV chain source\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3215, __extension__ __PRETTY_FUNCTION__))
;
3216
3217 LLVM_DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generate chain at: " <<
*IVSrc << "\n"; } } while (false)
;
3218 Type *IVTy = IVSrc->getType();
3219 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
3220 const SCEV *LeftOverExpr = nullptr;
3221 for (const IVInc &Inc : Chain) {
3222 Instruction *InsertPt = Inc.UserInst;
3223 if (isa<PHINode>(InsertPt))
3224 InsertPt = L->getLoopLatch()->getTerminator();
3225
3226 // IVOper will replace the current IV User's operand. IVSrc is the IV
3227 // value currently held in a register.
3228 Value *IVOper = IVSrc;
3229 if (!Inc.IncExpr->isZero()) {
3230 // IncExpr was the result of subtraction of two narrow values, so must
3231 // be signed.
3232 const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
3233 LeftOverExpr = LeftOverExpr ?
3234 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
3235 }
3236 if (LeftOverExpr && !LeftOverExpr->isZero()) {
3237 // Expand the IV increment.
3238 Rewriter.clearPostInc();
3239 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
3240 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
3241 SE.getUnknown(IncV));
3242 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
3243
3244 // If an IV increment can't be folded, use it as the next IV value.
3245 if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
3246 assert(IVTy == IVOper->getType() && "inconsistent IV increment type")(static_cast <bool> (IVTy == IVOper->getType() &&
"inconsistent IV increment type") ? void (0) : __assert_fail
("IVTy == IVOper->getType() && \"inconsistent IV increment type\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3246, __extension__ __PRETTY_FUNCTION__))
;
3247 IVSrc = IVOper;
3248 LeftOverExpr = nullptr;
3249 }
3250 }
3251 Type *OperTy = Inc.IVOperand->getType();
3252 if (IVTy != OperTy) {
3253 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&(static_cast <bool> (SE.getTypeSizeInBits(IVTy) >= SE
.getTypeSizeInBits(OperTy) && "cannot extend a chained IV"
) ? void (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3254, __extension__ __PRETTY_FUNCTION__))
3254 "cannot extend a chained IV")(static_cast <bool> (SE.getTypeSizeInBits(IVTy) >= SE
.getTypeSizeInBits(OperTy) && "cannot extend a chained IV"
) ? void (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3254, __extension__ __PRETTY_FUNCTION__))
;
3255 IRBuilder<> Builder(InsertPt);
3256 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
3257 }
3258 Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
3259 if (auto *OperandIsInstr = dyn_cast<Instruction>(Inc.IVOperand))
3260 DeadInsts.emplace_back(OperandIsInstr);
3261 }
3262 // If LSR created a new, wider phi, we may also replace its postinc. We only
3263 // do this if we also found a wide value for the head of the chain.
3264 if (isa<PHINode>(Chain.tailUserInst())) {
3265 for (PHINode &Phi : L->getHeader()->phis()) {
3266 if (!isCompatibleIVType(&Phi, IVSrc))
3267 continue;
3268 Instruction *PostIncV = dyn_cast<Instruction>(
3269 Phi.getIncomingValueForBlock(L->getLoopLatch()));
3270 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
3271 continue;
3272 Value *IVOper = IVSrc;
3273 Type *PostIncTy = PostIncV->getType();
3274 if (IVTy != PostIncTy) {
3275 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types")(static_cast <bool> (PostIncTy->isPointerTy() &&
"mixing int/ptr IV types") ? void (0) : __assert_fail ("PostIncTy->isPointerTy() && \"mixing int/ptr IV types\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3275, __extension__ __PRETTY_FUNCTION__))
;
3276 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
3277 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
3278 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
3279 }
3280 Phi.replaceUsesOfWith(PostIncV, IVOper);
3281 DeadInsts.emplace_back(PostIncV);
3282 }
3283 }
3284}
3285
3286void LSRInstance::CollectFixupsAndInitialFormulae() {
3287 BranchInst *ExitBranch = nullptr;
3288 bool SaveCmp = TTI.canSaveCmp(L, &ExitBranch, &SE, &LI, &DT, &AC, &TLI);
3289
3290 for (const IVStrideUse &U : IU) {
3291 Instruction *UserInst = U.getUser();
3292 // Skip IV users that are part of profitable IV Chains.
3293 User::op_iterator UseI =
3294 find(UserInst->operands(), U.getOperandValToReplace());
3295 assert(UseI != UserInst->op_end() && "cannot find IV operand")(static_cast <bool> (UseI != UserInst->op_end() &&
"cannot find IV operand") ? void (0) : __assert_fail ("UseI != UserInst->op_end() && \"cannot find IV operand\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3295, __extension__ __PRETTY_FUNCTION__))
;
3296 if (IVIncSet.count(UseI)) {
3297 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)
;
3298 continue;
3299 }
3300
3301 LSRUse::KindType Kind = LSRUse::Basic;
3302 MemAccessTy AccessTy;
3303 if (isAddressUse(TTI, UserInst, U.getOperandValToReplace())) {
3304 Kind = LSRUse::Address;
3305 AccessTy = getAccessType(TTI, UserInst, U.getOperandValToReplace());
3306 }
3307
3308 const SCEV *S = IU.getExpr(U);
3309 PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3310
3311 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3312 // (N - i == 0), and this allows (N - i) to be the expression that we work
3313 // with rather than just N or i, so we can consider the register
3314 // requirements for both N and i at the same time. Limiting this code to
3315 // equality icmps is not a problem because all interesting loops use
3316 // equality icmps, thanks to IndVarSimplify.
3317 if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst)) {
3318 // If CI can be saved in some target, like replaced inside hardware loop
3319 // in PowerPC, no need to generate initial formulae for it.
3320 if (SaveCmp && CI == dyn_cast<ICmpInst>(ExitBranch->getCondition()))
3321 continue;
3322 if (CI->isEquality()) {
3323 // Swap the operands if needed to put the OperandValToReplace on the
3324 // left, for consistency.
3325 Value *NV = CI->getOperand(1);
3326 if (NV == U.getOperandValToReplace()) {
3327 CI->setOperand(1, CI->getOperand(0));
3328 CI->setOperand(0, NV);
3329 NV = CI->getOperand(1);
3330 Changed = true;
3331 }
3332
3333 // x == y --> x - y == 0
3334 const SCEV *N = SE.getSCEV(NV);
3335 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE) &&
3336 (!NV->getType()->isPointerTy() ||
3337 SE.getPointerBase(N) == SE.getPointerBase(S))) {
3338 // S is normalized, so normalize N before folding it into S
3339 // to keep the result normalized.
3340 N = normalizeForPostIncUse(N, TmpPostIncLoops, SE);
3341 Kind = LSRUse::ICmpZero;
3342 S = SE.getMinusSCEV(N, S);
3343 }
3344
3345 // -1 and the negations of all interesting strides (except the negation
3346 // of -1) are now also interesting.
3347 for (size_t i = 0, e = Factors.size(); i != e; ++i)
3348 if (Factors[i] != -1)
3349 Factors.insert(-(uint64_t)Factors[i]);
3350 Factors.insert(-1);
3351 }
3352 }
3353
3354 // Get or create an LSRUse.
3355 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3356 size_t LUIdx = P.first;
3357 int64_t Offset = P.second;
3358 LSRUse &LU = Uses[LUIdx];
3359
3360 // Record the fixup.
3361 LSRFixup &LF = LU.getNewFixup();
3362 LF.UserInst = UserInst;
3363 LF.OperandValToReplace = U.getOperandValToReplace();
3364 LF.PostIncLoops = TmpPostIncLoops;
3365 LF.Offset = Offset;
3366 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3367
3368 if (!LU.WidestFixupType ||
3369 SE.getTypeSizeInBits(LU.WidestFixupType) <
3370 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3371 LU.WidestFixupType = LF.OperandValToReplace->getType();
3372
3373 // If this is the first use of this LSRUse, give it a formula.
3374 if (LU.Formulae.empty()) {
3375 InsertInitialFormula(S, LU, LUIdx);
3376 CountRegisters(LU.Formulae.back(), LUIdx);
3377 }
3378 }
3379
3380 LLVM_DEBUG(print_fixups(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_fixups(dbgs()); } } while (false)
;
3381}
3382
3383/// Insert a formula for the given expression into the given use, separating out
3384/// loop-variant portions from loop-invariant and loop-computable portions.
3385void
3386LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3387 // Mark uses whose expressions cannot be expanded.
3388 if (!isSafeToExpand(S, SE))
3389 LU.RigidFormula = true;
3390
3391 Formula F;
3392 F.initialMatch(S, L, SE);
3393 bool Inserted = InsertFormula(LU, LUIdx, F);
3394 assert(Inserted && "Initial formula already exists!")(static_cast <bool> (Inserted && "Initial formula already exists!"
) ? void (0) : __assert_fail ("Inserted && \"Initial formula already exists!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3394, __extension__ __PRETTY_FUNCTION__))
; (void)Inserted;
3395}
3396
3397/// Insert a simple single-register formula for the given expression into the
3398/// given use.
3399void
3400LSRInstance::InsertSupplementalFormula(const SCEV *S,
3401 LSRUse &LU, size_t LUIdx) {
3402 Formula F;
3403 F.BaseRegs.push_back(S);
3404 F.HasBaseReg = true;
3405 bool Inserted = InsertFormula(LU, LUIdx, F);
3406 assert(Inserted && "Supplemental formula already exists!")(static_cast <bool> (Inserted && "Supplemental formula already exists!"
) ? void (0) : __assert_fail ("Inserted && \"Supplemental formula already exists!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3406, __extension__ __PRETTY_FUNCTION__))
; (void)Inserted;
3407}
3408
3409/// Note which registers are used by the given formula, updating RegUses.
3410void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3411 if (F.ScaledReg)
3412 RegUses.countRegister(F.ScaledReg, LUIdx);
3413 for (const SCEV *BaseReg : F.BaseRegs)
3414 RegUses.countRegister(BaseReg, LUIdx);
3415}
3416
3417/// If the given formula has not yet been inserted, add it to the list, and
3418/// return true. Return false otherwise.
3419bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3420 // Do not insert formula that we will not be able to expand.
3421 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&(static_cast <bool> (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset
, LU.Kind, LU.AccessTy, F) && "Formula is illegal") ?
void (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3422, __extension__ __PRETTY_FUNCTION__))
3422 "Formula is illegal")(static_cast <bool> (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset
, LU.Kind, LU.AccessTy, F) && "Formula is illegal") ?
void (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3422, __extension__ __PRETTY_FUNCTION__))
;
3423
3424 if (!LU.InsertFormula(F, *L))
3425 return false;
3426
3427 CountRegisters(F, LUIdx);
3428 return true;
3429}
3430
3431/// Check for other uses of loop-invariant values which we're tracking. These
3432/// other uses will pin these values in registers, making them less profitable
3433/// for elimination.
3434/// TODO: This currently misses non-constant addrec step registers.
3435/// TODO: Should this give more weight to users inside the loop?
3436void
3437LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3438 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3439 SmallPtrSet<const SCEV *, 32> Visited;
3440
3441 while (!Worklist.empty()) {
3442 const SCEV *S = Worklist.pop_back_val();
3443
3444 // Don't process the same SCEV twice
3445 if (!Visited.insert(S).second)
3446 continue;
3447
3448 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3449 Worklist.append(N->op_begin(), N->op_end());
3450 else if (const SCEVIntegralCastExpr *C = dyn_cast<SCEVIntegralCastExpr>(S))
3451 Worklist.push_back(C->getOperand());
3452 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3453 Worklist.push_back(D->getLHS());
3454 Worklist.push_back(D->getRHS());
3455 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3456 const Value *V = US->getValue();
3457 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3458 // Look for instructions defined outside the loop.
3459 if (L->contains(Inst)) continue;
3460 } else if (isa<UndefValue>(V))
3461 // Undef doesn't have a live range, so it doesn't matter.
3462 continue;
3463 for (const Use &U : V->uses()) {
3464 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3465 // Ignore non-instructions.
3466 if (!UserInst)
3467 continue;
3468 // Don't bother if the instruction is an EHPad.
3469 if (UserInst->isEHPad())
3470 continue;
3471 // Ignore instructions in other functions (as can happen with
3472 // Constants).
3473 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3474 continue;
3475 // Ignore instructions not dominated by the loop.
3476 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3477 UserInst->getParent() :
3478 cast<PHINode>(UserInst)->getIncomingBlock(
3479 PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3480 if (!DT.dominates(L->getHeader(), UseBB))
3481 continue;
3482 // Don't bother if the instruction is in a BB which ends in an EHPad.
3483 if (UseBB->getTerminator()->isEHPad())
3484 continue;
3485 // Don't bother rewriting PHIs in catchswitch blocks.
3486 if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator()))
3487 continue;
3488 // Ignore uses which are part of other SCEV expressions, to avoid
3489 // analyzing them multiple times.
3490 if (SE.isSCEVable(UserInst->getType())) {
3491 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3492 // If the user is a no-op, look through to its uses.
3493 if (!isa<SCEVUnknown>(UserS))
3494 continue;
3495 if (UserS == US) {
3496 Worklist.push_back(
3497 SE.getUnknown(const_cast<Instruction *>(UserInst)));
3498 continue;
3499 }
3500 }
3501 // Ignore icmp instructions which are already being analyzed.
3502 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3503 unsigned OtherIdx = !U.getOperandNo();
3504 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3505 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3506 continue;
3507 }
3508
3509 std::pair<size_t, int64_t> P = getUse(
3510 S, LSRUse::Basic, MemAccessTy());
3511 size_t LUIdx = P.first;
3512 int64_t Offset = P.second;
3513 LSRUse &LU = Uses[LUIdx];
3514 LSRFixup &LF = LU.getNewFixup();
3515 LF.UserInst = const_cast<Instruction *>(UserInst);
3516 LF.OperandValToReplace = U;
3517 LF.Offset = Offset;
3518 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3519 if (!LU.WidestFixupType ||
3520 SE.getTypeSizeInBits(LU.WidestFixupType) <
3521 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3522 LU.WidestFixupType = LF.OperandValToReplace->getType();
3523 InsertSupplementalFormula(US, LU, LUIdx);
3524 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3525 break;
3526 }
3527 }
3528 }
3529}
3530
3531/// Split S into subexpressions which can be pulled out into separate
3532/// registers. If C is non-null, multiply each subexpression by C.
3533///
3534/// Return remainder expression after factoring the subexpressions captured by
3535/// Ops. If Ops is complete, return NULL.
3536static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3537 SmallVectorImpl<const SCEV *> &Ops,
3538 const Loop *L,
3539 ScalarEvolution &SE,
3540 unsigned Depth = 0) {
3541 // Arbitrarily cap recursion to protect compile time.
3542 if (Depth >= 3)
3543 return S;
3544
3545 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3546 // Break out add operands.
3547 for (const SCEV *S : Add->operands()) {
3548 const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3549 if (Remainder)
3550 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3551 }
3552 return nullptr;
3553 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3554 // Split a non-zero base out of an addrec.
3555 if (AR->getStart()->isZero() || !AR->isAffine())
3556 return S;
3557
3558 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3559 C, Ops, L, SE, Depth+1);
3560 // Split the non-zero AddRec unless it is part of a nested recurrence that
3561 // does not pertain to this loop.
3562 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3563 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3564 Remainder = nullptr;
3565 }
3566 if (Remainder != AR->getStart()) {
3567 if (!Remainder)
3568 Remainder = SE.getConstant(AR->getType(), 0);
3569 return SE.getAddRecExpr(Remainder,
3570 AR->getStepRecurrence(SE),
3571 AR->getLoop(),
3572 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3573 SCEV::FlagAnyWrap);
3574 }
3575 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3576 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3577 if (Mul->getNumOperands() != 2)
3578 return S;
3579 if (const SCEVConstant *Op0 =
3580 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3581 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3582 const SCEV *Remainder =
3583 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3584 if (Remainder)
3585 Ops.push_back(SE.getMulExpr(C, Remainder));
3586 return nullptr;
3587 }
3588 }
3589 return S;
3590}
3591
3592/// Return true if the SCEV represents a value that may end up as a
3593/// post-increment operation.
3594static bool mayUsePostIncMode(const TargetTransformInfo &TTI,
3595 LSRUse &LU, const SCEV *S, const Loop *L,
3596 ScalarEvolution &SE) {
3597 if (LU.Kind != LSRUse::Address ||
3598 !LU.AccessTy.getType()->isIntOrIntVectorTy())
3599 return false;
3600 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S);
3601 if (!AR)
3602 return false;
3603 const SCEV *LoopStep = AR->getStepRecurrence(SE);
3604 if (!isa<SCEVConstant>(LoopStep))
3605 return false;
3606 // Check if a post-indexed load/store can be used.
3607 if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) ||
3608 TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) {
3609 const SCEV *LoopStart = AR->getStart();
3610 if (!isa<SCEVConstant>(LoopStart) && SE.isLoopInvariant(LoopStart, L))
3611 return true;
3612 }
3613 return false;
3614}
3615
3616/// Helper function for LSRInstance::GenerateReassociations.
3617void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3618 const Formula &Base,
3619 unsigned Depth, size_t Idx,
3620 bool IsScaledReg) {
3621 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3622 // Don't generate reassociations for the base register of a value that
3623 // may generate a post-increment operator. The reason is that the
3624 // reassociations cause extra base+register formula to be created,
3625 // and possibly chosen, but the post-increment is more efficient.
3626 if (AMK == TTI::AMK_PostIndexed && mayUsePostIncMode(TTI, LU, BaseReg, L, SE))
3627 return;
3628 SmallVector<const SCEV *, 8> AddOps;
3629 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3630 if (Remainder)
3631 AddOps.push_back(Remainder);
3632
3633 if (AddOps.size() == 1)
3634 return;
3635
3636 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3637 JE = AddOps.end();
3638 J != JE; ++J) {
3639 // Loop-variant "unknown" values are uninteresting; we won't be able to
3640 // do anything meaningful with them.
3641 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3642 continue;
3643
3644 // Don't pull a constant into a register if the constant could be folded
3645 // into an immediate field.
3646 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3647 LU.AccessTy, *J, Base.getNumRegs() > 1))
3648 continue;
3649
3650 // Collect all operands except *J.
3651 SmallVector<const SCEV *, 8> InnerAddOps(
3652 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3653 InnerAddOps.append(std::next(J),
3654 ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3655
3656 // Don't leave just a constant behind in a register if the constant could
3657 // be folded into an immediate field.
3658 if (InnerAddOps.size() == 1 &&
3659 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3660 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3661 continue;
3662
3663 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3664 if (InnerSum->isZero())
3665 continue;
3666 Formula F = Base;
3667
3668 // Add the remaining pieces of the add back into the new formula.
3669 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3670 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3671 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3672 InnerSumSC->getValue()->getZExtValue())) {
3673 F.UnfoldedOffset =
3674 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3675 if (IsScaledReg)
3676 F.ScaledReg = nullptr;
3677 else
3678 F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3679 } else if (IsScaledReg)
3680 F.ScaledReg = InnerSum;
3681 else
3682 F.BaseRegs[Idx] = InnerSum;
3683
3684 // Add J as its own register, or an unfolded immediate.
3685 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3686 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3687 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3688 SC->getValue()->getZExtValue()))
3689 F.UnfoldedOffset =
3690 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3691 else
3692 F.BaseRegs.push_back(*J);
3693 // We may have changed the number of register in base regs, adjust the
3694 // formula accordingly.
3695 F.canonicalize(*L);
3696
3697 if (InsertFormula(LU, LUIdx, F))
3698 // If that formula hadn't been seen before, recurse to find more like
3699 // it.
3700 // Add check on Log16(AddOps.size()) - same as Log2_32(AddOps.size()) >> 2)
3701 // Because just Depth is not enough to bound compile time.
3702 // This means that every time AddOps.size() is greater 16^x we will add
3703 // x to Depth.
3704 GenerateReassociations(LU, LUIdx, LU.Formulae.back(),
3705 Depth + 1 + (Log2_32(AddOps.size()) >> 2));
3706 }
3707}
3708
3709/// Split out subexpressions from adds and the bases of addrecs.
3710void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3711 Formula Base, unsigned Depth) {
3712 assert(Base.isCanonical(*L) && "Input must be in the canonical form")(static_cast <bool> (Base.isCanonical(*L) && "Input must be in the canonical form"
) ? void (0) : __assert_fail ("Base.isCanonical(*L) && \"Input must be in the canonical form\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3712, __extension__ __PRETTY_FUNCTION__))
;
3713 // Arbitrarily cap recursion to protect compile time.
3714 if (Depth >= 3)
3715 return;
3716
3717 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3718 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3719
3720 if (Base.Scale == 1)
3721 GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3722 /* Idx */ -1, /* IsScaledReg */ true);
3723}
3724
3725/// Generate a formula consisting of all of the loop-dominating registers added
3726/// into a single register.
3727void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3728 Formula Base) {
3729 // This method is only interesting on a plurality of registers.
3730 if (Base.BaseRegs.size() + (Base.Scale == 1) +
3731 (Base.UnfoldedOffset != 0) <= 1)
3732 return;
3733
3734 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3735 // processing the formula.
3736 Base.unscale();
3737 SmallVector<const SCEV *, 4> Ops;
3738 Formula NewBase = Base;
3739 NewBase.BaseRegs.clear();
3740 Type *CombinedIntegerType = nullptr;
3741 for (const SCEV *BaseReg : Base.BaseRegs) {
3742 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3743 !SE.hasComputableLoopEvolution(BaseReg, L)) {
3744 if (!CombinedIntegerType)
3745 CombinedIntegerType = SE.getEffectiveSCEVType(BaseReg->getType());
3746 Ops.push_back(BaseReg);
3747 }
3748 else
3749 NewBase.BaseRegs.push_back(BaseReg);
3750 }
3751
3752 // If no register is relevant, we're done.
3753 if (Ops.size() == 0)
3754 return;
3755
3756 // Utility function for generating the required variants of the combined
3757 // registers.
3758 auto GenerateFormula = [&](const SCEV *Sum) {
3759 Formula F = NewBase;
3760
3761 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3762 // opportunity to fold something. For now, just ignore such cases
3763 // rather than proceed with zero in a register.
3764 if (Sum->isZero())
3765 return;
3766
3767 F.BaseRegs.push_back(Sum);
3768 F.canonicalize(*L);
3769 (void)InsertFormula(LU, LUIdx, F);
3770 };
3771
3772 // If we collected at least two registers, generate a formula combining them.
3773 if (Ops.size() > 1) {
3774 SmallVector<const SCEV *, 4> OpsCopy(Ops); // Don't let SE modify Ops.
3775 GenerateFormula(SE.getAddExpr(OpsCopy));
3776 }
3777
3778 // If we have an unfolded offset, generate a formula combining it with the
3779 // registers collected.
3780 if (NewBase.UnfoldedOffset) {
3781 assert(CombinedIntegerType && "Missing a type for the unfolded offset")(static_cast <bool> (CombinedIntegerType && "Missing a type for the unfolded offset"
) ? void (0) : __assert_fail ("CombinedIntegerType && \"Missing a type for the unfolded offset\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3781, __extension__ __PRETTY_FUNCTION__))
;
3782 Ops.push_back(SE.getConstant(CombinedIntegerType, NewBase.UnfoldedOffset,
3783 true));
3784 NewBase.UnfoldedOffset = 0;
3785 GenerateFormula(SE.getAddExpr(Ops));
3786 }
3787}
3788
3789/// Helper function for LSRInstance::GenerateSymbolicOffsets.
3790void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3791 const Formula &Base, size_t Idx,
3792 bool IsScaledReg) {
3793 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3794 GlobalValue *GV = ExtractSymbol(G, SE);
3795 if (G->isZero() || !GV)
3796 return;
3797 Formula F = Base;
3798 F.BaseGV = GV;
3799 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3800 return;
3801 if (IsScaledReg)
3802 F.ScaledReg = G;
3803 else
3804 F.BaseRegs[Idx] = G;
3805 (void)InsertFormula(LU, LUIdx, F);
3806}
3807
3808/// Generate reuse formulae using symbolic offsets.
3809void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3810 Formula Base) {
3811 // We can't add a symbolic offset if the address already contains one.
3812 if (Base.BaseGV) return;
3813
3814 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3815 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3816 if (Base.Scale == 1)
3817 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3818 /* IsScaledReg */ true);
3819}
3820
3821/// Helper function for LSRInstance::GenerateConstantOffsets.
3822void LSRInstance::GenerateConstantOffsetsImpl(
3823 LSRUse &LU, unsigned LUIdx, const Formula &Base,
3824 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3825
3826 auto GenerateOffset = [&](const SCEV *G, int64_t Offset) {
3827 Formula F = Base;
3828 F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3829
3830 if (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F)) {
3831 // Add the offset to the base register.
3832 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3833 // If it cancelled out, drop the base register, otherwise update it.
3834 if (NewG->isZero()) {
3835 if (IsScaledReg) {
3836 F.Scale = 0;
3837 F.ScaledReg = nullptr;
3838 } else
3839 F.deleteBaseReg(F.BaseRegs[Idx]);
3840 F.canonicalize(*L);
3841 } else if (IsScaledReg)
3842 F.ScaledReg = NewG;
3843 else
3844 F.BaseRegs[Idx] = NewG;
3845
3846 (void)InsertFormula(LU, LUIdx, F);
3847 }
3848 };
3849
3850 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3851
3852 // With constant offsets and constant steps, we can generate pre-inc
3853 // accesses by having the offset equal the step. So, for access #0 with a
3854 // step of 8, we generate a G - 8 base which would require the first access
3855 // to be ((G - 8) + 8),+,8. The pre-indexed access then updates the pointer
3856 // for itself and hopefully becomes the base for other accesses. This means
3857 // means that a single pre-indexed access can be generated to become the new
3858 // base pointer for each iteration of the loop, resulting in no extra add/sub
3859 // instructions for pointer updating.
3860 if (AMK == TTI::AMK_PreIndexed && LU.Kind == LSRUse::Address) {
3861 if (auto *GAR = dyn_cast<SCEVAddRecExpr>(G)) {
3862 if (auto *StepRec =
3863 dyn_cast<SCEVConstant>(GAR->getStepRecurrence(SE))) {
3864 const APInt &StepInt = StepRec->getAPInt();
3865 int64_t Step = StepInt.isNegative() ?
3866 StepInt.getSExtValue() : StepInt.getZExtValue();
3867
3868 for (int64_t Offset : Worklist) {
3869 Offset -= Step;
3870 GenerateOffset(G, Offset);
3871 }
3872 }
3873 }
3874 }
3875 for (int64_t Offset : Worklist)
3876 GenerateOffset(G, Offset);
3877
3878 int64_t Imm = ExtractImmediate(G, SE);
3879 if (G->isZero() || Imm == 0)
3880 return;
3881 Formula F = Base;
3882 F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3883 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3884 return;
3885 if (IsScaledReg) {
3886 F.ScaledReg = G;
3887 } else {
3888 F.BaseRegs[Idx] = G;
3889 // We may generate non canonical Formula if G is a recurrent expr reg
3890 // related with current loop while F.ScaledReg is not.
3891 F.canonicalize(*L);
3892 }
3893 (void)InsertFormula(LU, LUIdx, F);
3894}
3895
3896/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3897void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3898 Formula Base) {
3899 // TODO: For now, just add the min and max offset, because it usually isn't
3900 // worthwhile looking at everything inbetween.
3901 SmallVector<int64_t, 2> Worklist;
3902 Worklist.push_back(LU.MinOffset);
3903 if (LU.MaxOffset != LU.MinOffset)
3904 Worklist.push_back(LU.MaxOffset);
3905
3906 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3907 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3908 if (Base.Scale == 1)
3909 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3910 /* IsScaledReg */ true);
3911}
3912
3913/// For ICmpZero, check to see if we can scale up the comparison. For example, x
3914/// == y -> x*c == y*c.
3915void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3916 Formula Base) {
3917 if (LU.Kind != LSRUse::ICmpZero) return;
3918
3919 // Determine the integer type for the base formula.
3920 Type *IntTy = Base.getType();
3921 if (!IntTy) return;
3922 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3923
3924 // Don't do this if there is more than one offset.
3925 if (LU.MinOffset != LU.MaxOffset) return;
3926
3927 // Check if transformation is valid. It is illegal to multiply pointer.
3928 if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
3929 return;
3930 for (const SCEV *BaseReg : Base.BaseRegs)
3931 if (BaseReg->getType()->isPointerTy())
3932 return;
3933 assert(!Base.BaseGV && "ICmpZero use is not legal!")(static_cast <bool> (!Base.BaseGV && "ICmpZero use is not legal!"
) ? void (0) : __assert_fail ("!Base.BaseGV && \"ICmpZero use is not legal!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3933, __extension__ __PRETTY_FUNCTION__))
;
3934
3935 // Check each interesting stride.
3936 for (int64_t Factor : Factors) {
3937 // Check that Factor can be represented by IntTy
3938 if (!ConstantInt::isValueValidForType(IntTy, Factor))
3939 continue;
3940 // Check that the multiplication doesn't overflow.
3941 if (Base.BaseOffset == std::numeric_limits<int64_t>::min() && Factor == -1)
3942 continue;
3943 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3944 assert(Factor != 0 && "Zero factor not expected!")(static_cast <bool> (Factor != 0 && "Zero factor not expected!"
) ? void (0) : __assert_fail ("Factor != 0 && \"Zero factor not expected!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3944, __extension__ __PRETTY_FUNCTION__))
;
3945 if (NewBaseOffset / Factor != Base.BaseOffset)
3946 continue;
3947 // If the offset will be truncated at this use, check that it is in bounds.
3948 if (!IntTy->isPointerTy() &&
3949 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3950 continue;
3951
3952 // Check that multiplying with the use offset doesn't overflow.
3953 int64_t Offset = LU.MinOffset;
3954 if (Offset == std::numeric_limits<int64_t>::min() && Factor == -1)
3955 continue;
3956 Offset = (uint64_t)Offset * Factor;
3957 if (Offset / Factor != LU.MinOffset)
3958 continue;
3959 // If the offset will be truncated at this use, check that it is in bounds.
3960 if (!IntTy->isPointerTy() &&
3961 !ConstantInt::isValueValidForType(IntTy, Offset))
3962 continue;
3963
3964 Formula F = Base;
3965 F.BaseOffset = NewBaseOffset;
3966
3967 // Check that this scale is legal.
3968 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3969 continue;
3970
3971 // Compensate for the use having MinOffset built into it.
3972 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3973
3974 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3975
3976 // Check that multiplying with each base register doesn't overflow.
3977 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3978 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3979 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3980 goto next;
3981 }
3982
3983 // Check that multiplying with the scaled register doesn't overflow.
3984 if (F.ScaledReg) {
3985 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3986 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3987 continue;
3988 }
3989
3990 // Check that multiplying with the unfolded offset doesn't overflow.
3991 if (F.UnfoldedOffset != 0) {
3992 if (F.UnfoldedOffset == std::numeric_limits<int64_t>::min() &&
3993 Factor == -1)
3994 continue;
3995 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3996 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3997 continue;
3998 // If the offset will be truncated, check that it is in bounds.
3999 if (!IntTy->isPointerTy() &&
4000 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
4001 continue;
4002 }
4003
4004 // If we make it here and it's legal, add it.
4005 (void)InsertFormula(LU, LUIdx, F);
4006 next:;
4007 }
4008}
4009
4010/// Generate stride factor reuse formulae by making use of scaled-offset address
4011/// modes, for example.
4012void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
4013 // Determine the integer type for the base formula.
4014 Type *IntTy = Base.getType();
4015 if (!IntTy) return;
4016
4017 // If this Formula already has a scaled register, we can't add another one.
4018 // Try to unscale the formula to generate a better scale.
4019 if (Base.Scale != 0 && !Base.unscale())
4020 return;
4021
4022 assert(Base.Scale == 0 && "unscale did not did its job!")(static_cast <bool> (Base.Scale == 0 && "unscale did not did its job!"
) ? void (0) : __assert_fail ("Base.Scale == 0 && \"unscale did not did its job!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4022, __extension__ __PRETTY_FUNCTION__))
;
4023
4024 // Check each interesting stride.
4025 for (int64_t Factor : Factors) {
4026 Base.Scale = Factor;
4027 Base.HasBaseReg = Base.BaseRegs.size() > 1;
4028 // Check whether this scale is going to be legal.
4029 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4030 Base)) {
4031 // As a special-case, handle special out-of-loop Basic users specially.
4032 // TODO: Reconsider this special case.
4033 if (LU.Kind == LSRUse::Basic &&
4034 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
4035 LU.AccessTy, Base) &&
4036 LU.AllFixupsOutsideLoop)
4037 LU.Kind = LSRUse::Special;
4038 else
4039 continue;
4040 }
4041 // For an ICmpZero, negating a solitary base register won't lead to
4042 // new solutions.
4043 if (LU.Kind == LSRUse::ICmpZero &&
4044 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
4045 continue;
4046 // For each addrec base reg, if its loop is current loop, apply the scale.
4047 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
4048 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]);
4049 if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) {
4050 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
4051 if (FactorS->isZero())
4052 continue;
4053 // Divide out the factor, ignoring high bits, since we'll be
4054 // scaling the value back up in the end.
4055 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
4056 // TODO: This could be optimized to avoid all the copying.
4057 Formula F = Base;
4058 F.ScaledReg = Quotient;
4059 F.deleteBaseReg(F.BaseRegs[i]);
4060 // The canonical representation of 1*reg is reg, which is already in
4061 // Base. In that case, do not try to insert the formula, it will be
4062 // rejected anyway.
4063 if (F.Scale == 1 && (F.BaseRegs.empty() ||
4064 (AR->getLoop() != L && LU.AllFixupsOutsideLoop)))
4065 continue;
4066 // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate
4067 // non canonical Formula with ScaledReg's loop not being L.
4068 if (F.Scale == 1 && LU.AllFixupsOutsideLoop)
4069 F.canonicalize(*L);
4070 (void)InsertFormula(LU, LUIdx, F);
4071 }
4072 }
4073 }
4074 }
4075}
4076
4077/// Generate reuse formulae from different IV types.
4078void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
4079 // Don't bother truncating symbolic values.
4080 if (Base.BaseGV) return;
4081
4082 // Determine the integer type for the base formula.
4083 Type *DstTy = Base.getType();
4084 if (!DstTy) return;
4085 if (DstTy->isPointerTy())
4086 return;
4087
4088 // It is invalid to extend a pointer type so exit early if ScaledReg or
4089 // any of the BaseRegs are pointers.
4090 if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
4091 return;
4092 if (any_of(Base.BaseRegs,
4093 [](const SCEV *S) { return S->getType()->isPointerTy(); }))
4094 return;
4095
4096 for (Type *SrcTy : Types) {
4097 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
4098 Formula F = Base;
4099
4100 // Sometimes SCEV is able to prove zero during ext transform. It may
4101 // happen if SCEV did not do all possible transforms while creating the
4102 // initial node (maybe due to depth limitations), but it can do them while
4103 // taking ext.
4104 if (F.ScaledReg) {
4105 const SCEV *NewScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
4106 if (NewScaledReg->isZero())
4107 continue;
4108 F.ScaledReg = NewScaledReg;
4109 }
4110 bool HasZeroBaseReg = false;
4111 for (const SCEV *&BaseReg : F.BaseRegs) {
4112 const SCEV *NewBaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
4113 if (NewBaseReg->isZero()) {
4114 HasZeroBaseReg = true;
4115 break;
4116 }
4117 BaseReg = NewBaseReg;
4118 }
4119 if (HasZeroBaseReg)
4120 continue;
4121
4122 // TODO: This assumes we've done basic processing on all uses and
4123 // have an idea what the register usage is.
4124 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
4125 continue;
4126
4127 F.canonicalize(*L);
4128 (void)InsertFormula(LU, LUIdx, F);
4129 }
4130 }
4131}
4132
4133namespace {
4134
4135/// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
4136/// modifications so that the search phase doesn't have to worry about the data
4137/// structures moving underneath it.
4138struct WorkItem {
4139 size_t LUIdx;
4140 int64_t Imm;
4141 const SCEV *OrigReg;
4142
4143 WorkItem(size_t LI, int64_t I, const SCEV *R)
4144 : LUIdx(LI), Imm(I), OrigReg(R) {}
4145
4146 void print(raw_ostream &OS) const;
4147 void dump() const;
4148};
4149
4150} // end anonymous namespace
4151
4152#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
4153void WorkItem::print(raw_ostream &OS) const {
4154 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
4155 << " , add offset " << Imm;
4156}
4157
4158LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void WorkItem::dump() const {
4159 print(errs()); errs() << '\n';
4160}
4161#endif
4162
4163/// Look for registers which are a constant distance apart and try to form reuse
4164/// opportunities between them.
4165void LSRInstance::GenerateCrossUseConstantOffsets() {
4166 // Group the registers by their value without any added constant offset.
4167 using ImmMapTy = std::map<int64_t, const SCEV *>;
4168
4169 DenseMap<const SCEV *, ImmMapTy> Map;
4170 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
4171 SmallVector<const SCEV *, 8> Sequence;
4172 for (const SCEV *Use : RegUses) {
4173 const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
4174 int64_t Imm = ExtractImmediate(Reg, SE);
4175 auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
4176 if (Pair.second)
4177 Sequence.push_back(Reg);
4178 Pair.first->second.insert(std::make_pair(Imm, Use));
4179 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
4180 }
4181
4182 // Now examine each set of registers with the same base value. Build up
4183 // a list of work to do and do the work in a separate step so that we're
4184 // not adding formulae and register counts while we're searching.
4185 SmallVector<WorkItem, 32> WorkItems;
4186 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
4187 for (const SCEV *Reg : Sequence) {
4188 const ImmMapTy &Imms = Map.find(Reg)->second;
4189
4190 // It's not worthwhile looking for reuse if there's only one offset.
4191 if (Imms.size() == 1)
4192 continue;
4193
4194 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)
4195 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)
4196 : 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)
4197 << ' ' << 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)
4198 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)
;
4199
4200 // Examine each offset.
4201 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
4202 J != JE; ++J) {
4203 const SCEV *OrigReg = J->second;
4204
4205 int64_t JImm = J->first;
4206 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
4207
4208 if (!isa<SCEVConstant>(OrigReg) &&
4209 UsedByIndicesMap[Reg].count() == 1) {
4210 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)
4211 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Skipping cross-use reuse for "
<< *OrigReg << '\n'; } } while (false)
;
4212 continue;
4213 }
4214
4215 // Conservatively examine offsets between this orig reg a few selected
4216 // other orig regs.
4217 int64_t First = Imms.begin()->first;
4218 int64_t Last = std::prev(Imms.end())->first;
4219 // Compute (First + Last) / 2 without overflow using the fact that
4220 // First + Last = 2 * (First + Last) + (First ^ Last).
4221 int64_t Avg = (First & Last) + ((First ^ Last) >> 1);
4222 // If the result is negative and First is odd and Last even (or vice versa),
4223 // we rounded towards -inf. Add 1 in that case, to round towards 0.
4224 Avg = Avg + ((First ^ Last) & ((uint64_t)Avg >> 63));
4225 ImmMapTy::const_iterator OtherImms[] = {
4226 Imms.begin(), std::prev(Imms.end()),
4227 Imms.lower_bound(Avg)};
4228 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
4229 ImmMapTy::const_iterator M = OtherImms[i];
4230 if (M == J || M == JE) continue;
4231
4232 // Compute the difference between the two.
4233 int64_t Imm = (uint64_t)JImm - M->first;
4234 for (unsigned LUIdx : UsedByIndices.set_bits())
4235 // Make a memo of this use, offset, and register tuple.
4236 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
4237 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
4238 }
4239 }
4240 }
4241
4242 Map.clear();
4243 Sequence.clear();
4244 UsedByIndicesMap.clear();
4245 UniqueItems.clear();
4246
4247 // Now iterate through the worklist and add new formulae.
4248 for (const WorkItem &WI : WorkItems) {
4249 size_t LUIdx = WI.LUIdx;
4250 LSRUse &LU = Uses[LUIdx];
4251 int64_t Imm = WI.Imm;
4252 const SCEV *OrigReg = WI.OrigReg;
4253
4254 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
4255 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
4256 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
4257
4258 // TODO: Use a more targeted data structure.
4259 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
4260 Formula F = LU.Formulae[L];
4261 // FIXME: The code for the scaled and unscaled registers looks
4262 // very similar but slightly different. Investigate if they
4263 // could be merged. That way, we would not have to unscale the
4264 // Formula.
4265 F.unscale();
4266 // Use the immediate in the scaled register.
4267 if (F.ScaledReg == OrigReg) {
4268 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
4269 // Don't create 50 + reg(-50).
4270 if (F.referencesReg(SE.getSCEV(
4271 ConstantInt::get(IntTy, -(uint64_t)Offset))))
4272 continue;
4273 Formula NewF = F;
4274 NewF.BaseOffset = Offset;
4275 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4276 NewF))
4277 continue;
4278 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
4279
4280 // If the new scale is a constant in a register, and adding the constant
4281 // value to the immediate would produce a value closer to zero than the
4282 // immediate itself, then the formula isn't worthwhile.
4283 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
4284 if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
4285 (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
4286 .ule(std::abs(NewF.BaseOffset)))
4287 continue;
4288
4289 // OK, looks good.
4290 NewF.canonicalize(*this->L);
4291 (void)InsertFormula(LU, LUIdx, NewF);
4292 } else {
4293 // Use the immediate in a base register.
4294 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
4295 const SCEV *BaseReg = F.BaseRegs[N];
4296 if (BaseReg != OrigReg)
4297 continue;
4298 Formula NewF = F;
4299 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
4300 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
4301 LU.Kind, LU.AccessTy, NewF)) {
4302 if (AMK == TTI::AMK_PostIndexed &&
4303 mayUsePostIncMode(TTI, LU, OrigReg, this->L, SE))
4304 continue;
4305 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
4306 continue;
4307 NewF = F;
4308 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
4309 }
4310 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
4311
4312 // If the new formula has a constant in a register, and adding the
4313 // constant value to the immediate would produce a value closer to
4314 // zero than the immediate itself, then the formula isn't worthwhile.
4315 for (const SCEV *NewReg : NewF.BaseRegs)
4316 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
4317 if ((C->getAPInt() + NewF.BaseOffset)
4318 .abs()
4319 .slt(std::abs(NewF.BaseOffset)) &&
4320 (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
4321 countTrailingZeros<uint64_t>(NewF.BaseOffset))
4322 goto skip_formula;
4323
4324 // Ok, looks good.
4325 NewF.canonicalize(*this->L);
4326 (void)InsertFormula(LU, LUIdx, NewF);
4327 break;
4328 skip_formula:;
4329 }
4330 }
4331 }
4332 }
4333}
4334
4335/// Generate formulae for each use.
4336void
4337LSRInstance::GenerateAllReuseFormulae() {
4338 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
4339 // queries are more precise.
4340 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4341 LSRUse &LU = Uses[LUIdx];
4342 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4343 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
4344 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4345 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
4346 }
4347 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4348 LSRUse &LU = Uses[LUIdx];
4349 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4350 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
4351 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4352 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
4353 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4354 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
4355 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4356 GenerateScales(LU, LUIdx, LU.Formulae[i]);
4357 }
4358 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4359 LSRUse &LU = Uses[LUIdx];
4360 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4361 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
4362 }
4363
4364 GenerateCrossUseConstantOffsets();
4365
4366 LLVM_DEBUG(dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
4367 "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)
4368 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
;
4369}
4370
4371/// If there are multiple formulae with the same set of registers used
4372/// by other uses, pick the best one and delete the others.
4373void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
4374 DenseSet<const SCEV *> VisitedRegs;
4375 SmallPtrSet<const SCEV *, 16> Regs;
4376 SmallPtrSet<const SCEV *, 16> LoserRegs;
4377#ifndef NDEBUG
4378 bool ChangedFormulae = false;
4379#endif
4380
4381 // Collect the best formula for each unique set of shared registers. This
4382 // is reset for each use.
4383 using BestFormulaeTy =
4384 DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>;
4385
4386 BestFormulaeTy BestFormulae;
4387
4388 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4389 LSRUse &LU = Uses[LUIdx];
4390 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)
4391 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4392
4393 bool Any = false;
4394 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
4395 FIdx != NumForms; ++FIdx) {
4396 Formula &F = LU.Formulae[FIdx];
4397
4398 // Some formulas are instant losers. For example, they may depend on
4399 // nonexistent AddRecs from other loops. These need to be filtered
4400 // immediately, otherwise heuristics could choose them over others leading
4401 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
4402 // avoids the need to recompute this information across formulae using the
4403 // same bad AddRec. Passing LoserRegs is also essential unless we remove
4404 // the corresponding bad register from the Regs set.
4405 Cost CostF(L, SE, TTI, AMK);
4406 Regs.clear();
4407 CostF.RateFormula(F, Regs, VisitedRegs, LU, &LoserRegs);
4408 if (CostF.isLoser()) {
4409 // During initial formula generation, undesirable formulae are generated
4410 // by uses within other loops that have some non-trivial address mode or
4411 // use the postinc form of the IV. LSR needs to provide these formulae
4412 // as the basis of rediscovering the desired formula that uses an AddRec
4413 // corresponding to the existing phi. Once all formulae have been
4414 // generated, these initial losers may be pruned.
4415 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)
4416 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering loser "; F.print
(dbgs()); dbgs() << "\n"; } } while (false)
;
4417 }
4418 else {
4419 SmallVector<const SCEV *, 4> Key;
4420 for (const SCEV *Reg : F.BaseRegs) {
4421 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
4422 Key.push_back(Reg);
4423 }
4424 if (F.ScaledReg &&
4425 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
4426 Key.push_back(F.ScaledReg);
4427 // Unstable sort by host order ok, because this is only used for
4428 // uniquifying.
4429 llvm::sort(Key);
4430
4431 std::pair<BestFormulaeTy::const_iterator, bool> P =
4432 BestFormulae.insert(std::make_pair(Key, FIdx));
4433 if (P.second)
4434 continue;
4435
4436 Formula &Best = LU.Formulae[P.first->second];
4437
4438 Cost CostBest(L, SE, TTI, AMK);
4439 Regs.clear();
4440 CostBest.RateFormula(Best, Regs, VisitedRegs, LU);
4441 if (CostF.isLess(CostBest))
4442 std::swap(F, Best);
4443 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)
4444 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)
4445 " 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)
4446 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)
;
4447 }
4448#ifndef NDEBUG
4449 ChangedFormulae = true;
4450#endif
4451 LU.DeleteFormula(F);
4452 --FIdx;
4453 --NumForms;
4454 Any = true;
4455 }
4456
4457 // Now that we've filtered out some formulae, recompute the Regs set.
4458 if (Any)
4459 LU.RecomputeRegs(LUIdx, RegUses);
4460
4461 // Reset this to prepare for the next use.
4462 BestFormulae.clear();
4463 }
4464
4465 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)
4466 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)
4467 "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)
4468 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)
4469 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4470}
4471
4472/// Estimate the worst-case number of solutions the solver might have to
4473/// consider. It almost never considers this many solutions because it prune the
4474/// search space, but the pruning isn't always sufficient.
4475size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4476 size_t Power = 1;
4477 for (const LSRUse &LU : Uses) {
4478 size_t FSize = LU.Formulae.size();
4479 if (FSize >= ComplexityLimit) {
4480 Power = ComplexityLimit;
4481 break;
4482 }
4483 Power *= FSize;
4484 if (Power >= ComplexityLimit)
4485 break;
4486 }
4487 return Power;
4488}
4489
4490/// When one formula uses a superset of the registers of another formula, it
4491/// won't help reduce register pressure (though it may not necessarily hurt
4492/// register pressure); remove it to simplify the system.
4493void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4494 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4495 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)
;
4496
4497 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)
4498 "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)
4499 "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)
;
4500
4501 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4502 LSRUse &LU = Uses[LUIdx];
4503 bool Any = false;
4504 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4505 Formula &F = LU.Formulae[i];
4506 // Look for a formula with a constant or GV in a register. If the use
4507 // also has a formula with that same value in an immediate field,
4508 // delete the one that uses a register.
4509 for (SmallVectorImpl<const SCEV *>::const_iterator
4510 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4511 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4512 Formula NewF = F;
4513 //FIXME: Formulas should store bitwidth to do wrapping properly.
4514 // See PR41034.
4515 NewF.BaseOffset += (uint64_t)C->getValue()->getSExtValue();
4516 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4517 (I - F.BaseRegs.begin()));
4518 if (LU.HasFormulaWithSameRegs(NewF)) {
4519 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4520 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4521 LU.DeleteFormula(F);
4522 --i;
4523 --e;
4524 Any = true;
4525 break;
4526 }
4527 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4528 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4529 if (!F.BaseGV) {
4530 Formula NewF = F;
4531 NewF.BaseGV = GV;
4532 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4533 (I - F.BaseRegs.begin()));
4534 if (LU.HasFormulaWithSameRegs(NewF)) {
4535 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4536 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4537 LU.DeleteFormula(F);
4538 --i;
4539 --e;
4540 Any = true;
4541 break;
4542 }
4543 }
4544 }
4545 }
4546 }
4547 if (Any)
4548 LU.RecomputeRegs(LUIdx, RegUses);
4549 }
4550
4551 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)
;
4552 }
4553}
4554
4555/// When there are many registers for expressions like A, A+1, A+2, etc.,
4556/// allocate a single register for them.
4557void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4558 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4559 return;
4560
4561 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)
4562 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)
4563 "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)
4564 "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)
;
4565
4566 // This is especially useful for unrolled loops.
4567
4568 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4569 LSRUse &LU = Uses[LUIdx];
4570 for (const Formula &F : LU.Formulae) {
4571 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4572 continue;
4573
4574 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4575 if (!LUThatHas)
4576 continue;
4577
4578 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4579 LU.Kind, LU.AccessTy))
4580 continue;
4581
4582 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)
;
4583
4584 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4585
4586 // Transfer the fixups of LU to LUThatHas.
4587 for (LSRFixup &Fixup : LU.Fixups) {
4588 Fixup.Offset += F.BaseOffset;
4589 LUThatHas->pushFixup(Fixup);
4590 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)
;
4591 }
4592
4593 // Delete formulae from the new use which are no longer legal.
4594 bool Any = false;
4595 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4596 Formula &F = LUThatHas->Formulae[i];
4597 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4598 LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4599 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)
;
4600 LUThatHas->DeleteFormula(F);
4601 --i;
4602 --e;
4603 Any = true;
4604 }
4605 }
4606
4607 if (Any)
4608 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4609
4610 // Delete the old use.
4611 DeleteUse(LU, LUIdx);
4612 --LUIdx;
4613 --NumUses;
4614 break;
4615 }
4616 }
4617
4618 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)
;
4619}
4620
4621/// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4622/// we've done more filtering, as it may be able to find more formulae to
4623/// eliminate.
4624void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4625 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4626 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)
;
4627
4628 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)
4629 "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)
;
4630
4631 FilterOutUndesirableDedicatedRegisters();
4632
4633 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)
;
4634 }
4635}
4636
4637/// If a LSRUse has multiple formulae with the same ScaledReg and Scale.
4638/// Pick the best one and delete the others.
4639/// This narrowing heuristic is to keep as many formulae with different
4640/// Scale and ScaledReg pair as possible while narrowing the search space.
4641/// The benefit is that it is more likely to find out a better solution
4642/// from a formulae set with more Scale and ScaledReg variations than
4643/// a formulae set with the same Scale and ScaledReg. The picking winner
4644/// reg heuristic will often keep the formulae with the same Scale and
4645/// ScaledReg and filter others, and we want to avoid that if possible.
4646void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() {
4647 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4648 return;
4649
4650 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)
4651 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)
4652 "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)
4653 "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)
;
4654
4655 // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse.
4656 using BestFormulaeTy = DenseMap<std::pair<const SCEV *, int64_t>, size_t>;
4657
4658 BestFormulaeTy BestFormulae;
4659#ifndef NDEBUG
4660 bool ChangedFormulae = false;
4661#endif
4662 DenseSet<const SCEV *> VisitedRegs;
4663 SmallPtrSet<const SCEV *, 16> Regs;
4664
4665 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4666 LSRUse &LU = Uses[LUIdx];
4667 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)
4668 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4669
4670 // Return true if Formula FA is better than Formula FB.
4671 auto IsBetterThan = [&](Formula &FA, Formula &FB) {
4672 // First we will try to choose the Formula with fewer new registers.
4673 // For a register used by current Formula, the more the register is
4674 // shared among LSRUses, the less we increase the register number
4675 // counter of the formula.
4676 size_t FARegNum = 0;
4677 for (const SCEV *Reg : FA.BaseRegs) {
4678 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4679 FARegNum += (NumUses - UsedByIndices.count() + 1);
4680 }
4681 size_t FBRegNum = 0;
4682 for (const SCEV *Reg : FB.BaseRegs) {
4683 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4684 FBRegNum += (NumUses - UsedByIndices.count() + 1);
4685 }
4686 if (FARegNum != FBRegNum)
4687 return FARegNum < FBRegNum;
4688
4689 // If the new register numbers are the same, choose the Formula with
4690 // less Cost.
4691 Cost CostFA(L, SE, TTI, AMK);
4692 Cost CostFB(L, SE, TTI, AMK);
4693 Regs.clear();
4694 CostFA.RateFormula(FA, Regs, VisitedRegs, LU);
4695 Regs.clear();
4696 CostFB.RateFormula(FB, Regs, VisitedRegs, LU);
4697 return CostFA.isLess(CostFB);
4698 };
4699
4700 bool Any = false;
4701 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4702 ++FIdx) {
4703 Formula &F = LU.Formulae[FIdx];
4704 if (!F.ScaledReg)
4705 continue;
4706 auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx});
4707 if (P.second)
4708 continue;
4709
4710 Formula &Best = LU.Formulae[P.first->second];
4711 if (IsBetterThan(F, Best))
4712 std::swap(F, Best);
4713 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)
4714 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)
4715 " 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)
4716 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)
;
4717#ifndef NDEBUG
4718 ChangedFormulae = true;
4719#endif
4720 LU.DeleteFormula(F);
4721 --FIdx;
4722 --NumForms;
4723 Any = true;
4724 }
4725 if (Any)
4726 LU.RecomputeRegs(LUIdx, RegUses);
4727
4728 // Reset this to prepare for the next use.
4729 BestFormulae.clear();
4730 }
4731
4732 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)
4733 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)
4734 "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)
4735 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)
4736 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4737}
4738
4739/// If we are over the complexity limit, filter out any post-inc prefering
4740/// variables to only post-inc values.
4741void LSRInstance::NarrowSearchSpaceByFilterPostInc() {
4742 if (AMK != TTI::AMK_PostIndexed)
4743 return;
4744 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4745 return;
4746
4747 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"
"Narrowing the search space by choosing the lowest " "register Formula for PostInc Uses.\n"
; } } while (false)
4748 "Narrowing the search space by choosing the lowest "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by choosing the lowest " "register Formula for PostInc Uses.\n"
; } } while (false)
4749 "register Formula for PostInc Uses.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by choosing the lowest " "register Formula for PostInc Uses.\n"
; } } while (false)
;
4750
4751 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4752 LSRUse &LU = Uses[LUIdx];
4753
4754 if (LU.Kind != LSRUse::Address)
4755 continue;
4756 if (!TTI.isIndexedLoadLegal(TTI.MIM_PostInc, LU.AccessTy.getType()) &&
4757 !TTI.isIndexedStoreLegal(TTI.MIM_PostInc, LU.AccessTy.getType()))
4758 continue;
4759
4760 size_t MinRegs = std::numeric_limits<size_t>::max();
4761 for (const Formula &F : LU.Formulae)
4762 MinRegs = std::min(F.getNumRegs(), MinRegs);
4763
4764 bool Any = false;
4765 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4766 ++FIdx) {
4767 Formula &F = LU.Formulae[FIdx];
4768 if (F.getNumRegs() > MinRegs) {
4769 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"; } } while (false)
4770 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n"; } } while (false)
;
4771 LU.DeleteFormula(F);
4772 --FIdx;
4773 --NumForms;
4774 Any = true;
4775 }
4776 }
4777 if (Any)
4778 LU.RecomputeRegs(LUIdx, RegUses);
4779
4780 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4781 break;
4782 }
4783
4784 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)
;
4785}
4786
4787/// The function delete formulas with high registers number expectation.
4788/// Assuming we don't know the value of each formula (already delete
4789/// all inefficient), generate probability of not selecting for each
4790/// register.
4791/// For example,
4792/// Use1:
4793/// reg(a) + reg({0,+,1})
4794/// reg(a) + reg({-1,+,1}) + 1
4795/// reg({a,+,1})
4796/// Use2:
4797/// reg(b) + reg({0,+,1})
4798/// reg(b) + reg({-1,+,1}) + 1
4799/// reg({b,+,1})
4800/// Use3:
4801/// reg(c) + reg(b) + reg({0,+,1})
4802/// reg(c) + reg({b,+,1})
4803///
4804/// Probability of not selecting
4805/// Use1 Use2 Use3
4806/// reg(a) (1/3) * 1 * 1
4807/// reg(b) 1 * (1/3) * (1/2)
4808/// reg({0,+,1}) (2/3) * (2/3) * (1/2)
4809/// reg({-1,+,1}) (2/3) * (2/3) * 1
4810/// reg({a,+,1}) (2/3) * 1 * 1
4811/// reg({b,+,1}) 1 * (2/3) * (2/3)
4812/// reg(c) 1 * 1 * 0
4813///
4814/// Now count registers number mathematical expectation for each formula:
4815/// Note that for each use we exclude probability if not selecting for the use.
4816/// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding
4817/// probabilty 1/3 of not selecting for Use1).
4818/// Use1:
4819/// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted
4820/// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted
4821/// reg({a,+,1}) 1
4822/// Use2:
4823/// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted
4824/// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted
4825/// reg({b,+,1}) 2/3
4826/// Use3:
4827/// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted
4828/// reg(c) + reg({b,+,1}) 1 + 2/3
4829void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() {
4830 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4831 return;
4832 // Ok, we have too many of formulae on our hands to conveniently handle.
4833 // Use a rough heuristic to thin out the list.
4834
4835 // Set of Regs wich will be 100% used in final solution.
4836 // Used in each formula of a solution (in example above this is reg(c)).
4837 // We can skip them in calculations.
4838 SmallPtrSet<const SCEV *, 4> UniqRegs;
4839 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)
;
4840
4841 // Map each register to probability of not selecting
4842 DenseMap <const SCEV *, float> RegNumMap;
4843 for (const SCEV *Reg : RegUses) {
4844 if (UniqRegs.count(Reg))
4845 continue;
4846 float PNotSel = 1;
4847 for (const LSRUse &LU : Uses) {
4848 if (!LU.Regs.count(Reg))
4849 continue;
4850 float P = LU.getNotSelectedProbability(Reg);
4851 if (P != 0.0)
4852 PNotSel *= P;
4853 else
4854 UniqRegs.insert(Reg);
4855 }
4856 RegNumMap.insert(std::make_pair(Reg, PNotSel));
4857 }
4858
4859 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by deleting costly formulas\n"
; } } while (false)
4860 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)
;
4861
4862 // Delete formulas where registers number expectation is high.
4863 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4864 LSRUse &LU = Uses[LUIdx];
4865 // If nothing to delete - continue.
4866 if (LU.Formulae.size() < 2)
4867 continue;
4868 // This is temporary solution to test performance. Float should be
4869 // replaced with round independent type (based on integers) to avoid
4870 // different results for different target builds.
4871 float FMinRegNum = LU.Formulae[0].getNumRegs();
4872 float FMinARegNum = LU.Formulae[0].getNumRegs();
4873 size_t MinIdx = 0;
4874 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4875 Formula &F = LU.Formulae[i];
4876 float FRegNum = 0;
4877 float FARegNum = 0;
4878 for (const SCEV *BaseReg : F.BaseRegs) {
4879 if (UniqRegs.count(BaseReg))
4880 continue;
4881 FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4882 if (isa<SCEVAddRecExpr>(BaseReg))
4883 FARegNum +=
4884 RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4885 }
4886 if (const SCEV *ScaledReg = F.ScaledReg) {
4887 if (!UniqRegs.count(ScaledReg)) {
4888 FRegNum +=
4889 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4890 if (isa<SCEVAddRecExpr>(ScaledReg))
4891 FARegNum +=
4892 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4893 }
4894 }
4895 if (FMinRegNum > FRegNum ||
4896 (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) {
4897 FMinRegNum = FRegNum;
4898 FMinARegNum = FARegNum;
4899 MinIdx = i;
4900 }
4901 }
4902 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)
4903 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)
;
4904 if (MinIdx != 0)
4905 std::swap(LU.Formulae[MinIdx], LU.Formulae[0]);
4906 while (LU.Formulae.size() != 1) {
4907 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
)
4908 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; LU.Formulae
.back().print(dbgs()); dbgs() << '\n'; } } while (false
)
;
4909 LU.Formulae.pop_back();
4910 }
4911 LU.RecomputeRegs(LUIdx, RegUses);
4912 assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula")(static_cast <bool> (LU.Formulae.size() == 1 &&
"Should be exactly 1 min regs formula") ? void (0) : __assert_fail
("LU.Formulae.size() == 1 && \"Should be exactly 1 min regs formula\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4912, __extension__ __PRETTY_FUNCTION__))
;
4913 Formula &F = LU.Formulae[0];
4914 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)
;
4915 // When we choose the formula, the regs become unique.
4916 UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
4917 if (F.ScaledReg)
4918 UniqRegs.insert(F.ScaledReg);
4919 }
4920 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)
;
4921}
4922
4923/// Pick a register which seems likely to be profitable, and then in any use
4924/// which has any reference to that register, delete all formulae which do not
4925/// reference that register.
4926void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4927 // With all other options exhausted, loop until the system is simple
4928 // enough to handle.
4929 SmallPtrSet<const SCEV *, 4> Taken;
4930 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4931 // Ok, we have too many of formulae on our hands to conveniently handle.
4932 // Use a rough heuristic to thin out the list.
4933 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)
;
4934
4935 // Pick the register which is used by the most LSRUses, which is likely
4936 // to be a good reuse register candidate.
4937 const SCEV *Best = nullptr;
4938 unsigned BestNum = 0;
4939 for (const SCEV *Reg : RegUses) {
4940 if (Taken.count(Reg))
4941 continue;
4942 if (!Best) {
4943 Best = Reg;
4944 BestNum = RegUses.getUsedByIndices(Reg).count();
4945 } else {
4946 unsigned Count = RegUses.getUsedByIndices(Reg).count();
4947 if (Count > BestNum) {
4948 Best = Reg;
4949 BestNum = Count;
4950 }
4951 }
4952 }
4953 assert(Best && "Failed to find best LSRUse candidate")(static_cast <bool> (Best && "Failed to find best LSRUse candidate"
) ? void (0) : __assert_fail ("Best && \"Failed to find best LSRUse candidate\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4953, __extension__ __PRETTY_FUNCTION__))
;
4954
4955 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)
4956 << " 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)
;
4957 Taken.insert(Best);
4958
4959 // In any use with formulae which references this register, delete formulae
4960 // which don't reference it.
4961 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4962 LSRUse &LU = Uses[LUIdx];
4963 if (!LU.Regs.count(Best)) continue;
4964
4965 bool Any = false;
4966 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4967 Formula &F = LU.Formulae[i];
4968 if (!F.referencesReg(Best)) {
4969 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)
;
4970 LU.DeleteFormula(F);
4971 --e;
4972 --i;
4973 Any = true;
4974 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?")(static_cast <bool> (e != 0 && "Use has no formulae left! Is Regs inconsistent?"
) ? void (0) : __assert_fail ("e != 0 && \"Use has no formulae left! Is Regs inconsistent?\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4974, __extension__ __PRETTY_FUNCTION__))
;
4975 continue;
4976 }
4977 }
4978
4979 if (Any)
4980 LU.RecomputeRegs(LUIdx, RegUses);
4981 }
4982
4983 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)
;
4984 }
4985}
4986
4987/// If there are an extraordinary number of formulae to choose from, use some
4988/// rough heuristics to prune down the number of formulae. This keeps the main
4989/// solver from taking an extraordinary amount of time in some worst-case
4990/// scenarios.
4991void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4992 NarrowSearchSpaceByDetectingSupersets();
4993 NarrowSearchSpaceByCollapsingUnrolledCode();
4994 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4995 if (FilterSameScaledReg)
4996 NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
4997 NarrowSearchSpaceByFilterPostInc();
4998 if (LSRExpNarrow)
4999 NarrowSearchSpaceByDeletingCostlyFormulas();
5000 else
5001 NarrowSearchSpaceByPickingWinnerRegs();
5002}
5003
5004/// This is the recursive solver.
5005void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
5006 Cost &SolutionCost,
5007 SmallVectorImpl<const Formula *> &Workspace,
5008 const Cost &CurCost,
5009 const SmallPtrSet<const SCEV *, 16> &CurRegs,
5010 DenseSet<const SCEV *> &VisitedRegs) const {
5011 // Some ideas:
5012 // - prune more:
5013 // - use more aggressive filtering
5014 // - sort the formula so that the most profitable solutions are found first
5015 // - sort the uses too
5016 // - search faster:
5017 // - don't compute a cost, and then compare. compare while computing a cost
5018 // and bail early.
5019 // - track register sets with SmallBitVector
5020
5021 const LSRUse &LU = Uses[Workspace.size()];
5022
5023 // If this use references any register that's already a part of the
5024 // in-progress solution, consider it a requirement that a formula must
5025 // reference that register in order to be considered. This prunes out
5026 // unprofitable searching.
5027 SmallSetVector<const SCEV *, 4> ReqRegs;
5028 for (const SCEV *S : CurRegs)
5029 if (LU.Regs.count(S))
5030 ReqRegs.insert(S);
5031
5032 SmallPtrSet<const SCEV *, 16> NewRegs;
5033 Cost NewCost(L, SE, TTI, AMK);
5034 for (const Formula &F : LU.Formulae) {
5035 // Ignore formulae which may not be ideal in terms of register reuse of
5036 // ReqRegs. The formula should use all required registers before
5037 // introducing new ones.
5038 // This can sometimes (notably when trying to favour postinc) lead to
5039 // sub-optimial decisions. There it is best left to the cost modelling to
5040 // get correct.
5041 if (AMK != TTI::AMK_PostIndexed || LU.Kind != LSRUse::Address) {
5042 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
5043 for (const SCEV *Reg : ReqRegs) {
5044 if ((F.ScaledReg && F.ScaledReg == Reg) ||
5045 is_contained(F.BaseRegs, Reg)) {
5046 --NumReqRegsToFind;
5047 if (NumReqRegsToFind == 0)
5048 break;
5049 }
5050 }
5051 if (NumReqRegsToFind != 0) {
5052 // If none of the formulae satisfied the required registers, then we could
5053 // clear ReqRegs and try again. Currently, we simply give up in this case.
5054 continue;
5055 }
5056 }
5057
5058 // Evaluate the cost of the current formula. If it's already worse than
5059 // the current best, prune the search at that point.
5060 NewCost = CurCost;
5061 NewRegs = CurRegs;
5062 NewCost.RateFormula(F, NewRegs, VisitedRegs, LU);
5063 if (NewCost.isLess(SolutionCost)) {
5064 Workspace.push_back(&F);
5065 if (Workspace.size() != Uses.size()) {
5066 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
5067 NewRegs, VisitedRegs);
5068 if (F.getNumRegs() == 1 && Workspace.size() == 1)
5069 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
5070 } else {
5071 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)
5072 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)
5073 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)
5074 << "- " << *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)
5075 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)
;
5076
5077 SolutionCost = NewCost;
5078 Solution = Workspace;
5079 }
5080 Workspace.pop_back();
5081 }
5082 }
5083}
5084
5085/// Choose one formula from each use. Return the results in the given Solution
5086/// vector.
5087void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
5088 SmallVector<const Formula *, 8> Workspace;
5089 Cost SolutionCost(L, SE, TTI, AMK);
5090 SolutionCost.Lose();
5091 Cost CurCost(L, SE, TTI, AMK);
5092 SmallPtrSet<const SCEV *, 16> CurRegs;
5093 DenseSet<const SCEV *> VisitedRegs;
5094 Workspace.reserve(Uses.size());
5095
5096 // SolveRecurse does all the work.
5097 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
5098 CurRegs, VisitedRegs);
5099 if (Solution.empty()) {
5100 LLVM_DEBUG(dbgs() << "\nNo Satisfactory Solution\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nNo Satisfactory Solution\n"
; } } while (false)
;
5101 return;
5102 }
5103
5104 // Ok, we've now made all our decisions.
5105 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
)
5106 "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
)
5107 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
)
5108 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
)
5109 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
)
5110 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
)
5111 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
)
5112 " ";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
)
5113 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
)
5114 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
)
5115 })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
)
;
5116
5117 assert(Solution.size() == Uses.size() && "Malformed solution!")(static_cast <bool> (Solution.size() == Uses.size() &&
"Malformed solution!") ? void (0) : __assert_fail ("Solution.size() == Uses.size() && \"Malformed solution!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5117, __extension__ __PRETTY_FUNCTION__))
;
5118}
5119
5120/// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
5121/// we can go while still being dominated by the input positions. This helps
5122/// canonicalize the insert position, which encourages sharing.
5123BasicBlock::iterator
5124LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
5125 const SmallVectorImpl<Instruction *> &Inputs)
5126 const {
5127 Instruction *Tentative = &*IP;
5128 while (true) {
5129 bool AllDominate = true;
5130 Instruction *BetterPos = nullptr;
5131 // Don't bother attempting to insert before a catchswitch, their basic block
5132 // cannot have other non-PHI instructions.
5133 if (isa<CatchSwitchInst>(Tentative))
5134 return IP;
5135
5136 for (Instruction *Inst : Inputs) {
5137 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
5138 AllDominate = false;
5139 break;
5140 }
5141 // Attempt to find an insert position in the middle of the block,
5142 // instead of at the end, so that it can be used for other expansions.
5143 if (Tentative->getParent() == Inst->getParent() &&
5144 (!BetterPos || !DT.dominates(Inst, BetterPos)))
5145 BetterPos = &*std::next(BasicBlock::iterator(Inst));
5146 }
5147 if (!AllDominate)
5148 break;
5149 if (BetterPos)
5150 IP = BetterPos->getIterator();
5151 else
5152 IP = Tentative->getIterator();
5153
5154 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
5155 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
5156
5157 BasicBlock *IDom;
5158 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
5159 if (!Rung) return IP;
5160 Rung = Rung->getIDom();
5161 if (!Rung) return IP;
5162 IDom = Rung->getBlock();
5163
5164 // Don't climb into a loop though.
5165 const Loop *IDomLoop = LI.getLoopFor(IDom);
5166 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
5167 if (IDomDepth <= IPLoopDepth &&
5168 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
5169 break;
5170 }
5171
5172 Tentative = IDom->getTerminator();
5173 }
5174
5175 return IP;
5176}
5177
5178/// Determine an input position which will be dominated by the operands and
5179/// which will dominate the result.
5180BasicBlock::iterator
5181LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
5182 const LSRFixup &LF,
5183 const LSRUse &LU,
5184 SCEVExpander &Rewriter) const {
5185 // Collect some instructions which must be dominated by the
5186 // expanding replacement. These must be dominated by any operands that
5187 // will be required in the expansion.
5188 SmallVector<Instruction *, 4> Inputs;
5189 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
5190 Inputs.push_back(I);
5191 if (LU.Kind == LSRUse::ICmpZero)
5192 if (Instruction *I =
5193 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
5194 Inputs.push_back(I);
5195 if (LF.PostIncLoops.count(L)) {
5196 if (LF.isUseFullyOutsideLoop(L))
5197 Inputs.push_back(L->getLoopLatch()->getTerminator());
5198 else
5199 Inputs.push_back(IVIncInsertPos);
5200 }
5201 // The expansion must also be dominated by the increment positions of any
5202 // loops it for which it is using post-inc mode.
5203 for (const Loop *PIL : LF.PostIncLoops) {
5204 if (PIL == L) continue;
5205
5206 // Be dominated by the loop exit.
5207 SmallVector<BasicBlock *, 4> ExitingBlocks;
5208 PIL->getExitingBlocks(ExitingBlocks);
5209 if (!ExitingBlocks.empty()) {
5210 BasicBlock *BB = ExitingBlocks[0];
5211 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
5212 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
5213 Inputs.push_back(BB->getTerminator());
5214 }
5215 }
5216
5217 assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad()(static_cast <bool> (!isa<PHINode>(LowestIP) &&
!LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>
(LowestIP) && "Insertion point must be a normal instruction"
) ? void (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5219, __extension__ __PRETTY_FUNCTION__))
5218 && !isa<DbgInfoIntrinsic>(LowestIP) &&(static_cast <bool> (!isa<PHINode>(LowestIP) &&
!LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>
(LowestIP) && "Insertion point must be a normal instruction"
) ? void (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5219, __extension__ __PRETTY_FUNCTION__))
5219 "Insertion point must be a normal instruction")(static_cast <bool> (!isa<PHINode>(LowestIP) &&
!LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>
(LowestIP) && "Insertion point must be a normal instruction"
) ? void (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5219, __extension__ __PRETTY_FUNCTION__))
;
5220
5221 // Then, climb up the immediate dominator tree as far as we can go while
5222 // still being dominated by the input positions.
5223 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
5224
5225 // Don't insert instructions before PHI nodes.
5226 while (isa<PHINode>(IP)) ++IP;
5227
5228 // Ignore landingpad instructions.
5229 while (IP->isEHPad()) ++IP;
5230
5231 // Ignore debug intrinsics.
5232 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
5233
5234 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
5235 // IP consistent across expansions and allows the previously inserted
5236 // instructions to be reused by subsequent expansion.
5237 while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
5238 ++IP;
5239
5240 return IP;
5241}
5242
5243/// Emit instructions for the leading candidate expression for this LSRUse (this
5244/// is called "expanding").
5245Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF,
5246 const Formula &F, BasicBlock::iterator IP,
5247 SCEVExpander &Rewriter,
5248 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5249 if (LU.RigidFormula)
10
Assuming field 'RigidFormula' is false
11
Taking false branch
5250 return LF.OperandValToReplace;
5251
5252 // Determine an input position which will be dominated by the operands and
5253 // which will dominate the result.
5254 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
5255 Rewriter.setInsertPoint(&*IP);
5256
5257 // Inform the Rewriter if we have a post-increment use, so that it can
5258 // perform an advantageous expansion.
5259 Rewriter.setPostInc(LF.PostIncLoops);
5260
5261 // This is the type that the user actually needs.
5262 Type *OpTy = LF.OperandValToReplace->getType();
12
Called C++ object pointer is null
5263 // This will be the type that we'll initially expand to.
5264 Type *Ty = F.getType();
5265 if (!Ty)
5266 // No type known; just expand directly to the ultimate type.
5267 Ty = OpTy;
5268 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
5269 // Expand directly to the ultimate type if it's the right size.
5270 Ty = OpTy;
5271 // This is the type to do integer arithmetic in.
5272 Type *IntTy = SE.getEffectiveSCEVType(Ty);
5273
5274 // Build up a list of operands to add together to form the full base.
5275 SmallVector<const SCEV *, 8> Ops;
5276
5277 // Expand the BaseRegs portion.
5278 for (const SCEV *Reg : F.BaseRegs) {
5279 assert(!Reg->isZero() && "Zero allocated in a base register!")(static_cast <bool> (!Reg->isZero() && "Zero allocated in a base register!"
) ? void (0) : __assert_fail ("!Reg->isZero() && \"Zero allocated in a base register!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5279, __extension__ __PRETTY_FUNCTION__))
;
5280
5281 // If we're expanding for a post-inc user, make the post-inc adjustment.
5282 Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE);
5283 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
5284 }
5285
5286 // Expand the ScaledReg portion.
5287 Value *ICmpScaledV = nullptr;
5288 if (F.Scale != 0) {
5289 const SCEV *ScaledS = F.ScaledReg;
5290
5291 // If we're expanding for a post-inc user, make the post-inc adjustment.
5292 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
5293 ScaledS = denormalizeForPostIncUse(ScaledS, Loops, SE);
5294
5295 if (LU.Kind == LSRUse::ICmpZero) {
5296 // Expand ScaleReg as if it was part of the base regs.
5297 if (F.Scale == 1)
5298 Ops.push_back(
5299 SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
5300 else {
5301 // An interesting way of "folding" with an icmp is to use a negated
5302 // scale, which we'll implement by inserting it into the other operand
5303 // of the icmp.
5304 assert(F.Scale == -1 &&(static_cast <bool> (F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? void (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5305, __extension__ __PRETTY_FUNCTION__))
5305 "The only scale supported by ICmpZero uses is -1!")(static_cast <bool> (F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? void (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5305, __extension__ __PRETTY_FUNCTION__))
;
5306 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
5307 }
5308 } else {
5309 // Otherwise just expand the scaled register and an explicit scale,
5310 // which is expected to be matched as part of the address.
5311
5312 // Flush the operand list to suppress SCEVExpander hoisting address modes.
5313 // Unless the addressing mode will not be folded.
5314 if (!Ops.empty() && LU.Kind == LSRUse::Address &&
5315 isAMCompletelyFolded(TTI, LU, F)) {
5316 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), nullptr);
5317 Ops.clear();
5318 Ops.push_back(SE.getUnknown(FullV));
5319 }
5320 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
5321 if (F.Scale != 1)
5322 ScaledS =
5323 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
5324 Ops.push_back(ScaledS);
5325 }
5326 }
5327
5328 // Expand the GV portion.
5329 if (F.BaseGV) {
5330 // Flush the operand list to suppress SCEVExpander hoisting.
5331 if (!Ops.empty()) {
5332 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), IntTy);
5333 Ops.clear();
5334 Ops.push_back(SE.getUnknown(FullV));
5335 }
5336 Ops.push_back(SE.getUnknown(F.BaseGV));
5337 }
5338
5339 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
5340 // unfolded offsets. LSR assumes they both live next to their uses.
5341 if (!Ops.empty()) {
5342 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5343 Ops.clear();
5344 Ops.push_back(SE.getUnknown(FullV));
5345 }
5346
5347 // Expand the immediate portion.
5348 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
5349 if (Offset != 0) {
5350 if (LU.Kind == LSRUse::ICmpZero) {
5351 // The other interesting way of "folding" with an ICmpZero is to use a
5352 // negated immediate.
5353 if (!ICmpScaledV)
5354 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
5355 else {
5356 Ops.push_back(SE.getUnknown(ICmpScaledV));
5357 ICmpScaledV = ConstantInt::get(IntTy, Offset);
5358 }
5359 } else {
5360 // Just add the immediate values. These again are expected to be matched
5361 // as part of the address.
5362 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
5363 }
5364 }
5365
5366 // Expand the unfolded offset portion.
5367 int64_t UnfoldedOffset = F.UnfoldedOffset;
5368 if (UnfoldedOffset != 0) {
5369 // Just add the immediate values.
5370 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
5371 UnfoldedOffset)));
5372 }
5373
5374 // Emit instructions summing all the operands.
5375 const SCEV *FullS = Ops.empty() ?
5376 SE.getConstant(IntTy, 0) :
5377 SE.getAddExpr(Ops);
5378 Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
5379
5380 // We're done expanding now, so reset the rewriter.
5381 Rewriter.clearPostInc();
5382
5383 // An ICmpZero Formula represents an ICmp which we're handling as a
5384 // comparison against zero. Now that we've expanded an expression for that
5385 // form, update the ICmp's other operand.
5386 if (LU.Kind == LSRUse::ICmpZero) {
5387 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
5388 if (auto *OperandIsInstr = dyn_cast<Instruction>(CI->getOperand(1)))
5389 DeadInsts.emplace_back(OperandIsInstr);
5390 assert(!F.BaseGV && "ICmp does not support folding a global value and "(static_cast <bool> (!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? 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-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5391, __extension__ __PRETTY_FUNCTION__))
5391 "a scale at the same time!")(static_cast <bool> (!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? 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-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5391, __extension__ __PRETTY_FUNCTION__))
;
5392 if (F.Scale == -1) {
5393 if (ICmpScaledV->getType() != OpTy) {
5394 Instruction *Cast =
5395 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
5396 OpTy, false),
5397 ICmpScaledV, OpTy, "tmp", CI);
5398 ICmpScaledV = Cast;
5399 }
5400 CI->setOperand(1, ICmpScaledV);
5401 } else {
5402 // A scale of 1 means that the scale has been expanded as part of the
5403 // base regs.
5404 assert((F.Scale == 0 || F.Scale == 1) &&(static_cast <bool> ((F.Scale == 0 || F.Scale == 1) &&
"ICmp does not support folding a global value and " "a scale at the same time!"
) ? 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-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5406, __extension__ __PRETTY_FUNCTION__))
5405 "ICmp does not support folding a global value and "(static_cast <bool> ((F.Scale == 0 || F.Scale == 1) &&
"ICmp does not support folding a global value and " "a scale at the same time!"
) ? 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-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5406, __extension__ __PRETTY_FUNCTION__))
5406 "a scale at the same time!")(static_cast <bool> ((F.Scale == 0 || F.Scale == 1) &&
"ICmp does not support folding a global value and " "a scale at the same time!"
) ? 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-14~++20210926122410+d23fd8ae8906/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5406, __extension__ __PRETTY_FUNCTION__))
;
5407 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
5408 -(uint64_t)Offset);
5409 if (C->getType() != OpTy)
5410 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
5411 OpTy, false),
5412 C, OpTy);
5413
5414 CI->setOperand(1, C);
5415 }
5416 }
5417
5418 return FullV;
5419}
5420
5421/// Helper for Rewrite. PHI nodes are special because the use of their operands
5422/// effectively happens in their predecessor blocks, so the expression may need
5423/// to be expanded in multiple places.
5424void LSRInstance::RewriteForPHI(
5425 PHINode *PN, const LSRUse &LU, const LSRFixup &LF, const Formula &F,
5426 SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5427 DenseMap<BasicBlock *, Value *> Inserted;
5428 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
5429 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
3
Assuming pointer value is null
4
Taking true branch
5430 bool needUpdateFixups = false;
5431 BasicBlock *BB = PN->getIncomingBlock(i);
5432
5433 // If this is a critical edge, split the edge so that we do not insert
5434 // the code on all predecessor/successor paths. We do this unless this
5435 // is the canonical backedge for this loop, which complicates post-inc
5436 // users.
5437 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
5
Assuming 'e' is equal to 1
6
Taking false branch
5438 !isa<IndirectBrInst>(BB->getTerminator()) &&
5439 !isa<CatchSwitchInst>(BB->getTerminator())) {
5440 BasicBlock *Parent = PN->getParent();
5441 Loop *PNLoop = LI.getLoopFor(Parent);
5442 if (!PNLoop || Parent != PNLoop->getHeader()) {
5443 // Split the critical edge.
5444 BasicBlock *NewBB = nullptr;
5445 if (!Parent->isLandingPad()) {
5446 NewBB =
5447 SplitCriticalEdge(BB, Parent,
5448 CriticalEdgeSplittingOptions(&DT, &LI, MSSAU)
5449 .setMergeIdenticalEdges()
5450 .setKeepOneInputPHIs());
5451 } else {
5452 SmallVector<BasicBlock*, 2> NewBBs;
5453 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
5454 NewBB = NewBBs[0];
5455 }
5456 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
5457 // phi predecessors are identical. The simple thing to do is skip
5458 // splitting in this case rather than complicate the API.
5459 if (NewBB) {
5460 // If PN is outside of the loop and BB is in the loop, we want to
5461 // move the block to be immediately before the PHI block, not
5462 // immediately after BB.
5463 if (L->contains(BB) && !L->contains(PN))
5464 NewBB->moveBefore(PN->getParent());
5465
5466 // Splitting the edge can reduce the number of PHI entries we have.
5467 e = PN->getNumIncomingValues();
5468 BB = NewBB;
5469 i = PN->getBasicBlockIndex(BB);
5470
5471 needUpdateFixups = true;
5472 }
5473 }
5474 }
5475
5476 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
5477 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
5478 if (!Pair.second)
7
Assuming field 'second' is true
8
Taking false branch
5479 PN->setIncomingValue(i, Pair.first->second);
5480 else {
5481 Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
9
Calling 'LSRInstance::Expand'
5482 Rewriter, DeadInsts);
5483
5484 // If this is reuse-by-noop-cast, insert the noop cast.
5485 Type *OpTy = LF.OperandValToReplace->getType();
5486 if (FullV->getType() != OpTy)
5487 FullV =
5488 CastInst::Create(CastInst::getCastOpcode(FullV, false,
5489 OpTy, false),
5490 FullV, LF.OperandValToReplace->getType(),
5491 "tmp", BB->getTerminator());
5492
5493 PN->setIncomingValue(i, FullV);
5494 Pair.first->second = FullV;
5495 }
5496
5497 // If LSR splits critical edge and phi node has other pending
5498 // fixup operands, we need to update those pending fixups. Otherwise
5499 // formulae will not be implemented completely and some instructions
5500 // will not be eliminated.
5501 if (needUpdateFixups) {
5502 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5503 for (LSRFixup &Fixup : Uses[LUIdx].Fixups)
5504 // If fixup is supposed to rewrite some operand in the phi
5505 // that was just updated, it may be already moved to
5506 // another phi node. Such fixup requires update.
5507 if (Fixup.UserInst == PN) {
5508 // Check if the operand we try to replace still exists in the
5509 // original phi.
5510 bool foundInOriginalPHI = false;
5511 for (const auto &val : PN->incoming_values())
5512 if (val == Fixup.OperandValToReplace) {
5513 foundInOriginalPHI = true;
5514 break;
5515 }
5516
5517 // If fixup operand found in original PHI - nothing to do.
5518 if (foundInOriginalPHI)
5519 continue;
5520
5521 // Otherwise it might be moved to another PHI and requires update.
5522 // If fixup operand not found in any of the incoming blocks that
5523 // means we have already rewritten it - nothing to do.
5524 for (const auto &Block : PN->blocks())
5525 for (BasicBlock::iterator I = Block->begin(); isa<PHINode>(I);
5526 ++I) {
5527 PHINode *NewPN = cast<PHINode>(I);
5528 for (const auto &val : NewPN->incoming_values())
5529 if (val == Fixup.OperandValToReplace)
5530 Fixup.UserInst = NewPN;
5531 }
5532 }
5533 }
5534 }
5535}
5536
5537/// Emit instructions for the leading candidate expression for this LSRUse (this
5538/// is called "expanding"), and update the UserInst to reference the newly
5539/// expanded value.
5540void LSRInstance::Rewrite(const LSRUse &LU, const LSRFixup &LF,
5541 const Formula &F, SCEVExpander &Rewriter,
5542 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5543 // First, find an insertion point that dominates UserInst. For PHI nodes,
5544 // find the nearest block which dominates all the relevant uses.
5545 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
5546 RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
5547 } else {
5548 Value *FullV =
5549 Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
5550
5551 // If this is reuse-by-noop-cast, insert the noop cast.
5552 Type *OpTy = LF.OperandValToReplace->getType();
5553 if (FullV->getType() != OpTy) {
5554 Instruction *Cast =
5555 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
5556 FullV, OpTy, "tmp", LF.UserInst);
5557 FullV = Cast;
5558 }
5559
5560 // Update the user. ICmpZero is handled specially here (for now) because
5561 // Expand may have updated one of the operands of the icmp already, and
5562 // its new value may happen to be equal to LF.OperandValToReplace, in
5563 // which case doing replaceUsesOfWith leads to replacing both operands
5564 // with the same value. TODO: Reorganize this.
5565 if (LU.Kind == LSRUse::ICmpZero)
5566 LF.UserInst->setOperand(0, FullV);
5567 else
5568 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
5569 }
5570
5571 if (auto *OperandIsInstr = dyn_cast<Instruction>(LF.OperandValToReplace))
5572 DeadInsts.emplace_back(OperandIsInstr);
5573}
5574
5575/// Rewrite all the fixup locations with new values, following the chosen
5576/// solution.
5577void LSRInstance::ImplementSolution(
5578 const SmallVectorImpl<const Formula *> &Solution) {
5579 // Keep track of instructions we may have made dead, so that
5580 // we can remove them after we are done working.
5581 SmallVector<WeakTrackingVH, 16> DeadInsts;
5582
5583 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(), "lsr",
5584 false);
5585#ifndef NDEBUG
5586 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5587#endif
5588 Rewriter.disableCanonicalMode();
5589 Rewriter.enableLSRMode();
5590 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
5591
5592 // Mark phi nodes that terminate chains so the expander tries to reuse them.
5593 for (const IVChain &Chain : IVChainVec) {
5594 if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
5595 Rewriter.setChainedPhi(PN);
5596 }
5597
5598 // Expand the new value definitions and update the users.
5599 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5600 for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
5601 Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
5602 Changed = true;
5603 }
5604
5605 for (const IVChain &Chain : IVChainVec) {
5606 GenerateIVChain(Chain, Rewriter, DeadInsts);
5607 Changed = true;
5608 }
5609
5610 for (const WeakVH &IV : Rewriter.getInsertedIVs())
5611 if (IV && dyn_cast<Instruction>(&*IV)->getParent())
5612 ScalarEvolutionIVs.push_back(IV);
5613
5614 // Clean up after ourselves. This must be done before deleting any
5615 // instructions.
5616 Rewriter.clear();
5617
5618 Changed |= RecursivelyDeleteTriviallyDeadInstructionsPermissive(DeadInsts,
5619 &TLI, MSSAU);
5620
5621 // In our cost analysis above, we assume that each addrec consumes exactly
5622 // one register, and arrange to have increments inserted just before the
5623 // latch to maximimize the chance this is true. However, if we reused
5624 // existing IVs, we now need to move the increments to match our
5625 // expectations. Otherwise, our cost modeling results in us having a
5626 // chosen a non-optimal result for the actual schedule. (And yes, this
5627 // scheduling decision does impact later codegen.)
5628 for (PHINode &PN : L->getHeader()->phis()) {
5629 BinaryOperator *BO = nullptr;
5630 Value *Start = nullptr, *Step = nullptr;
5631 if (!matchSimpleRecurrence(&PN, BO, Start, Step))
5632 continue;
5633
5634 switch (BO->getOpcode()) {
5635 case Instruction::Sub:
5636 if (BO->getOperand(0) != &PN)
5637 // sub is non-commutative - match handling elsewhere in LSR
5638 continue;
5639 break;
5640 case Instruction::Add:
5641 break;
5642 default:
5643 continue;
5644 };
5645
5646 if (!isa<Constant>(Step))
5647 // If not a constant step, might increase register pressure
5648 // (We assume constants have been canonicalized to RHS)
5649 continue;
5650
5651 if (BO->getParent() == IVIncInsertPos->getParent())
5652 // Only bother moving across blocks. Isel can handle block local case.
5653 continue;
5654
5655 // Can we legally schedule inc at the desired point?
5656 if (!llvm::all_of(BO->uses(),
5657 [&](Use &U) {return DT.dominates(IVIncInsertPos, U);}))
5658 continue;
5659 BO->moveBefore(IVIncInsertPos);
5660 Changed = true;
5661 }