Bug Summary

File:llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
Warning:line 5438, column 22
Called C++ object pointer is null

Annotated Source Code

Press '?' to see keyboard shortcuts

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 -fhalf-no-semantic-interposition -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-13~++20210413100635+64c24f493e5f/build-llvm/lib/Transforms/Scalar -resource-dir /usr/lib/llvm-13/lib/clang/13.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/build-llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/build-llvm/include -I /build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/lib/llvm-13/lib/clang/13.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../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-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/build-llvm/lib/Transforms/Scalar -fdebug-prefix-map=/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f=. -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -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-2021-04-14-063029-18377-1 -x c++ /build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/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())((It != RegUsesMap.end()) ? static_cast<void> (0) : __assert_fail
("It != RegUsesMap.end()", "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 291, __PRETTY_FUNCTION__))
;
292 RegSortData &RSD = It->second;
293 assert(RSD.UsedByIndices.size() > LUIdx)((RSD.UsedByIndices.size() > LUIdx) ? static_cast<void>
(0) : __assert_fail ("RSD.UsedByIndices.size() > LUIdx", "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 293, __PRETTY_FUNCTION__))
;
294 RSD.UsedByIndices.reset(LUIdx);
295}
296
297void
298RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
299 assert(LUIdx <= LastLUIdx)((LUIdx <= LastLUIdx) ? static_cast<void> (0) : __assert_fail
("LUIdx <= LastLUIdx", "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 299, __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!")((I != RegUsesMap.end() && "Unknown register!") ? static_cast
<void> (0) : __assert_fail ("I != RegUsesMap.end() && \"Unknown register!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 326, __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 // So far we did not need this case. This is easy to implement but it is
515 // useless to maintain dead code. Beside it could hurt compile time.
516 assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.")((!BaseRegs.empty() && "1*reg => reg, should not be needed."
) ? static_cast<void> (0) : __assert_fail ("!BaseRegs.empty() && \"1*reg => reg, should not be needed.\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 516, __PRETTY_FUNCTION__))
;
517
518 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
519 if (!ScaledReg) {
520 ScaledReg = BaseRegs.pop_back_val();
521 Scale = 1;
522 }
523
524 // If ScaledReg is an invariant with respect to L, find the reg from
525 // BaseRegs containing the recurrent expr related with Loop L. Swap the
526 // reg with ScaledReg.
527 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
528 if (!SAR || SAR->getLoop() != &L) {
529 auto I = find_if(BaseRegs, [&](const SCEV *S) {
530 return isa<const SCEVAddRecExpr>(S) &&
531 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
532 });
533 if (I != BaseRegs.end())
534 std::swap(ScaledReg, *I);
535 }
536}
537
538/// Get rid of the scale in the formula.
539/// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
540/// \return true if it was possible to get rid of the scale, false otherwise.
541/// \note After this operation the formula may not be in the canonical form.
542bool Formula::unscale() {
543 if (Scale != 1)
544 return false;
545 Scale = 0;
546 BaseRegs.push_back(ScaledReg);
547 ScaledReg = nullptr;
548 return true;
549}
550
551bool Formula::hasZeroEnd() const {
552 if (UnfoldedOffset || BaseOffset)
553 return false;
554 if (BaseRegs.size() != 1 || ScaledReg)
555 return false;
556 return true;
557}
558
559/// Return the total number of register operands used by this formula. This does
560/// not include register uses implied by non-constant addrec strides.
561size_t Formula::getNumRegs() const {
562 return !!ScaledReg + BaseRegs.size();
563}
564
565/// Return the type of this formula, if it has one, or null otherwise. This type
566/// is meaningless except for the bit size.
567Type *Formula::getType() const {
568 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
569 ScaledReg ? ScaledReg->getType() :
570 BaseGV ? BaseGV->getType() :
571 nullptr;
572}
573
574/// Delete the given base reg from the BaseRegs list.
575void Formula::deleteBaseReg(const SCEV *&S) {
576 if (&S != &BaseRegs.back())
577 std::swap(S, BaseRegs.back());
578 BaseRegs.pop_back();
579}
580
581/// Test if this formula references the given register.
582bool Formula::referencesReg(const SCEV *S) const {
583 return S == ScaledReg || is_contained(BaseRegs, S);
584}
585
586/// Test whether this formula uses registers which are used by uses other than
587/// the use with the given index.
588bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
589 const RegUseTracker &RegUses) const {
590 if (ScaledReg)
591 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
592 return true;
593 for (const SCEV *BaseReg : BaseRegs)
594 if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
595 return true;
596 return false;
597}
598
599#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
600void Formula::print(raw_ostream &OS) const {
601 bool First = true;
602 if (BaseGV) {
603 if (!First) OS << " + "; else First = false;
604 BaseGV->printAsOperand(OS, /*PrintType=*/false);
605 }
606 if (BaseOffset != 0) {
607 if (!First) OS << " + "; else First = false;
608 OS << BaseOffset;
609 }
610 for (const SCEV *BaseReg : BaseRegs) {
611 if (!First) OS << " + "; else First = false;
612 OS << "reg(" << *BaseReg << ')';
613 }
614 if (HasBaseReg && BaseRegs.empty()) {
615 if (!First) OS << " + "; else First = false;
616 OS << "**error: HasBaseReg**";
617 } else if (!HasBaseReg && !BaseRegs.empty()) {
618 if (!First) OS << " + "; else First = false;
619 OS << "**error: !HasBaseReg**";
620 }
621 if (Scale != 0) {
622 if (!First) OS << " + "; else First = false;
623 OS << Scale << "*reg(";
624 if (ScaledReg)
625 OS << *ScaledReg;
626 else
627 OS << "<unknown>";
628 OS << ')';
629 }
630 if (UnfoldedOffset != 0) {
631 if (!First) OS << " + ";
632 OS << "imm(" << UnfoldedOffset << ')';
633 }
634}
635
636LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Formula::dump() const {
637 print(errs()); errs() << '\n';
638}
639#endif
640
641/// Return true if the given addrec can be sign-extended without changing its
642/// value.
643static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
644 Type *WideTy =
645 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
646 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
647}
648
649/// Return true if the given add can be sign-extended without changing its
650/// value.
651static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
652 Type *WideTy =
653 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
654 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
655}
656
657/// Return true if the given mul can be sign-extended without changing its
658/// value.
659static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
660 Type *WideTy =
661 IntegerType::get(SE.getContext(),
662 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
663 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
664}
665
666/// Return an expression for LHS /s RHS, if it can be determined and if the
667/// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
668/// is true, expressions like (X * Y) /s Y are simplified to Y, ignoring that
669/// the multiplication may overflow, which is useful when the result will be
670/// used in a context where the most significant bits are ignored.
671static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
672 ScalarEvolution &SE,
673 bool IgnoreSignificantBits = false) {
674 // Handle the trivial case, which works for any SCEV type.
675 if (LHS == RHS)
676 return SE.getConstant(LHS->getType(), 1);
677
678 // Handle a few RHS special cases.
679 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
680 if (RC) {
681 const APInt &RA = RC->getAPInt();
682 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
683 // some folding.
684 if (RA.isAllOnesValue())
685 return SE.getMulExpr(LHS, RC);
686 // Handle x /s 1 as x.
687 if (RA == 1)
688 return LHS;
689 }
690
691 // Check for a division of a constant by a constant.
692 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
693 if (!RC)
694 return nullptr;
695 const APInt &LA = C->getAPInt();
696 const APInt &RA = RC->getAPInt();
697 if (LA.srem(RA) != 0)
698 return nullptr;
699 return SE.getConstant(LA.sdiv(RA));
700 }
701
702 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
703 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
704 if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
705 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
706 IgnoreSignificantBits);
707 if (!Step) return nullptr;
708 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
709 IgnoreSignificantBits);
710 if (!Start) return nullptr;
711 // FlagNW is independent of the start value, step direction, and is
712 // preserved with smaller magnitude steps.
713 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
714 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
715 }
716 return nullptr;
717 }
718
719 // Distribute the sdiv over add operands, if the add doesn't overflow.
720 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
721 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
722 SmallVector<const SCEV *, 8> Ops;
723 for (const SCEV *S : Add->operands()) {
724 const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
725 if (!Op) return nullptr;
726 Ops.push_back(Op);
727 }
728 return SE.getAddExpr(Ops);
729 }
730 return nullptr;
731 }
732
733 // Check for a multiply operand that we can pull RHS out of.
734 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
735 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
736 SmallVector<const SCEV *, 4> Ops;
737 bool Found = false;
738 for (const SCEV *S : Mul->operands()) {
739 if (!Found)
740 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
741 IgnoreSignificantBits)) {
742 S = Q;
743 Found = true;
744 }
745 Ops.push_back(S);
746 }
747 return Found ? SE.getMulExpr(Ops) : nullptr;
748 }
749 return nullptr;
750 }
751
752 // Otherwise we don't know.
753 return nullptr;
754}
755
756/// If S involves the addition of a constant integer value, return that integer
757/// value, and mutate S to point to a new SCEV with that value excluded.
758static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
759 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
760 if (C->getAPInt().getMinSignedBits() <= 64) {
761 S = SE.getConstant(C->getType(), 0);
762 return C->getValue()->getSExtValue();
763 }
764 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
765 SmallVector<const SCEV *, 8> NewOps(Add->operands());
766 int64_t Result = ExtractImmediate(NewOps.front(), SE);
767 if (Result != 0)
768 S = SE.getAddExpr(NewOps);
769 return Result;
770 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
771 SmallVector<const SCEV *, 8> NewOps(AR->operands());
772 int64_t Result = ExtractImmediate(NewOps.front(), SE);
773 if (Result != 0)
774 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
775 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
776 SCEV::FlagAnyWrap);
777 return Result;
778 }
779 return 0;
780}
781
782/// If S involves the addition of a GlobalValue address, return that symbol, and
783/// mutate S to point to a new SCEV with that value excluded.
784static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
785 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
786 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
787 S = SE.getConstant(GV->getType(), 0);
788 return GV;
789 }
790 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
791 SmallVector<const SCEV *, 8> NewOps(Add->operands());
792 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
793 if (Result)
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 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
799 if (Result)
800 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
801 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
802 SCEV::FlagAnyWrap);
803 return Result;
804 }
805 return nullptr;
806}
807
808/// Returns true if the specified instruction is using the specified value as an
809/// address.
810static bool isAddressUse(const TargetTransformInfo &TTI,
811 Instruction *Inst, Value *OperandVal) {
812 bool isAddress = isa<LoadInst>(Inst);
813 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
814 if (SI->getPointerOperand() == OperandVal)
815 isAddress = true;
816 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
817 // Addressing modes can also be folded into prefetches and a variety
818 // of intrinsics.
819 switch (II->getIntrinsicID()) {
820 case Intrinsic::memset:
821 case Intrinsic::prefetch:
822 case Intrinsic::masked_load:
823 if (II->getArgOperand(0) == OperandVal)
824 isAddress = true;
825 break;
826 case Intrinsic::masked_store:
827 if (II->getArgOperand(1) == OperandVal)
828 isAddress = true;
829 break;
830 case Intrinsic::memmove:
831 case Intrinsic::memcpy:
832 if (II->getArgOperand(0) == OperandVal ||
833 II->getArgOperand(1) == OperandVal)
834 isAddress = true;
835 break;
836 default: {
837 MemIntrinsicInfo IntrInfo;
838 if (TTI.getTgtMemIntrinsic(II, IntrInfo)) {
839 if (IntrInfo.PtrVal == OperandVal)
840 isAddress = true;
841 }
842 }
843 }
844 } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
845 if (RMW->getPointerOperand() == OperandVal)
846 isAddress = true;
847 } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
848 if (CmpX->getPointerOperand() == OperandVal)
849 isAddress = true;
850 }
851 return isAddress;
852}
853
854/// Return the type of the memory being accessed.
855static MemAccessTy getAccessType(const TargetTransformInfo &TTI,
856 Instruction *Inst, Value *OperandVal) {
857 MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
858 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
859 AccessTy.MemTy = SI->getOperand(0)->getType();
860 AccessTy.AddrSpace = SI->getPointerAddressSpace();
861 } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
862 AccessTy.AddrSpace = LI->getPointerAddressSpace();
863 } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
864 AccessTy.AddrSpace = RMW->getPointerAddressSpace();
865 } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
866 AccessTy.AddrSpace = CmpX->getPointerAddressSpace();
867 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
868 switch (II->getIntrinsicID()) {
869 case Intrinsic::prefetch:
870 case Intrinsic::memset:
871 AccessTy.AddrSpace = II->getArgOperand(0)->getType()->getPointerAddressSpace();
872 AccessTy.MemTy = OperandVal->getType();
873 break;
874 case Intrinsic::memmove:
875 case Intrinsic::memcpy:
876 AccessTy.AddrSpace = OperandVal->getType()->getPointerAddressSpace();
877 AccessTy.MemTy = OperandVal->getType();
878 break;
879 case Intrinsic::masked_load:
880 AccessTy.AddrSpace =
881 II->getArgOperand(0)->getType()->getPointerAddressSpace();
882 break;
883 case Intrinsic::masked_store:
884 AccessTy.MemTy = II->getOperand(0)->getType();
885 AccessTy.AddrSpace =
886 II->getArgOperand(1)->getType()->getPointerAddressSpace();
887 break;
888 default: {
889 MemIntrinsicInfo IntrInfo;
890 if (TTI.getTgtMemIntrinsic(II, IntrInfo) && IntrInfo.PtrVal) {
891 AccessTy.AddrSpace
892 = IntrInfo.PtrVal->getType()->getPointerAddressSpace();
893 }
894
895 break;
896 }
897 }
898 }
899
900 // All pointers have the same requirements, so canonicalize them to an
901 // arbitrary pointer type to minimize variation.
902 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
903 AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
904 PTy->getAddressSpace());
905
906 return AccessTy;
907}
908
909/// Return true if this AddRec is already a phi in its loop.
910static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
911 for (PHINode &PN : AR->getLoop()->getHeader()->phis()) {
912 if (SE.isSCEVable(PN.getType()) &&
913 (SE.getEffectiveSCEVType(PN.getType()) ==
914 SE.getEffectiveSCEVType(AR->getType())) &&
915 SE.getSCEV(&PN) == AR)
916 return true;
917 }
918 return false;
919}
920
921/// Check if expanding this expression is likely to incur significant cost. This
922/// is tricky because SCEV doesn't track which expressions are actually computed
923/// by the current IR.
924///
925/// We currently allow expansion of IV increments that involve adds,
926/// multiplication by constants, and AddRecs from existing phis.
927///
928/// TODO: Allow UDivExpr if we can find an existing IV increment that is an
929/// obvious multiple of the UDivExpr.
930static bool isHighCostExpansion(const SCEV *S,
931 SmallPtrSetImpl<const SCEV*> &Processed,
932 ScalarEvolution &SE) {
933 // Zero/One operand expressions
934 switch (S->getSCEVType()) {
935 case scUnknown:
936 case scConstant:
937 return false;
938 case scTruncate:
939 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
940 Processed, SE);
941 case scZeroExtend:
942 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
943 Processed, SE);
944 case scSignExtend:
945 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
946 Processed, SE);
947 default:
948 break;
949 }
950
951 if (!Processed.insert(S).second)
952 return false;
953
954 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
955 for (const SCEV *S : Add->operands()) {
956 if (isHighCostExpansion(S, Processed, SE))
957 return true;
958 }
959 return false;
960 }
961
962 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
963 if (Mul->getNumOperands() == 2) {
964 // Multiplication by a constant is ok
965 if (isa<SCEVConstant>(Mul->getOperand(0)))
966 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
967
968 // If we have the value of one operand, check if an existing
969 // multiplication already generates this expression.
970 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
971 Value *UVal = U->getValue();
972 for (User *UR : UVal->users()) {
973 // If U is a constant, it may be used by a ConstantExpr.
974 Instruction *UI = dyn_cast<Instruction>(UR);
975 if (UI && UI->getOpcode() == Instruction::Mul &&
976 SE.isSCEVable(UI->getType())) {
977 return SE.getSCEV(UI) == Mul;
978 }
979 }
980 }
981 }
982 }
983
984 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
985 if (isExistingPhi(AR, SE))
986 return false;
987 }
988
989 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
990 return true;
991}
992
993namespace {
994
995class LSRUse;
996
997} // end anonymous namespace
998
999/// Check if the addressing mode defined by \p F is completely
1000/// folded in \p LU at isel time.
1001/// This includes address-mode folding and special icmp tricks.
1002/// This function returns true if \p LU can accommodate what \p F
1003/// defines and up to 1 base + 1 scaled + offset.
1004/// In other words, if \p F has several base registers, this function may
1005/// still return true. Therefore, users still need to account for
1006/// additional base registers and/or unfolded offsets to derive an
1007/// accurate cost model.
1008static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1009 const LSRUse &LU, const Formula &F);
1010
1011// Get the cost of the scaling factor used in F for LU.
1012static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1013 const LSRUse &LU, const Formula &F,
1014 const Loop &L);
1015
1016namespace {
1017
1018/// This class is used to measure and compare candidate formulae.
1019class Cost {
1020 const Loop *L = nullptr;
1021 ScalarEvolution *SE = nullptr;
1022 const TargetTransformInfo *TTI = nullptr;
1023 TargetTransformInfo::LSRCost C;
1024 TTI::AddressingModeKind AMK = TTI::AMK_None;
1025
1026public:
1027 Cost() = delete;
1028 Cost(const Loop *L, ScalarEvolution &SE, const TargetTransformInfo &TTI,
1029 TTI::AddressingModeKind AMK) :
1030 L(L), SE(&SE), TTI(&TTI), AMK(AMK) {
1031 C.Insns = 0;
1032 C.NumRegs = 0;
1033 C.AddRecCost = 0;
1034 C.NumIVMuls = 0;
1035 C.NumBaseAdds = 0;
1036 C.ImmCost = 0;
1037 C.SetupCost = 0;
1038 C.ScaleCost = 0;
1039 }
1040
1041 bool isLess(Cost &Other);
1042
1043 void Lose();
1044
1045#ifndef NDEBUG
1046 // Once any of the metrics loses, they must all remain losers.
1047 bool isValid() {
1048 return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds
1049 | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u)
1050 || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds
1051 & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u);
1052 }
1053#endif
1054
1055 bool isLoser() {
1056 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1056, __PRETTY_FUNCTION__))
;
1057 return C.NumRegs == ~0u;
1058 }
1059
1060 void RateFormula(const Formula &F,
1061 SmallPtrSetImpl<const SCEV *> &Regs,
1062 const DenseSet<const SCEV *> &VisitedRegs,
1063 const LSRUse &LU,
1064 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
1065
1066 void print(raw_ostream &OS) const;
1067 void dump() const;
1068
1069private:
1070 void RateRegister(const Formula &F, const SCEV *Reg,
1071 SmallPtrSetImpl<const SCEV *> &Regs);
1072 void RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1073 SmallPtrSetImpl<const SCEV *> &Regs,
1074 SmallPtrSetImpl<const SCEV *> *LoserRegs);
1075};
1076
1077/// An operand value in an instruction which is to be replaced with some
1078/// equivalent, possibly strength-reduced, replacement.
1079struct LSRFixup {
1080 /// The instruction which will be updated.
1081 Instruction *UserInst = nullptr;
1082
1083 /// The operand of the instruction which will be replaced. The operand may be
1084 /// used more than once; every instance will be replaced.
1085 Value *OperandValToReplace = nullptr;
1086
1087 /// If this user is to use the post-incremented value of an induction
1088 /// variable, this set is non-empty and holds the loops associated with the
1089 /// induction variable.
1090 PostIncLoopSet PostIncLoops;
1091
1092 /// A constant offset to be added to the LSRUse expression. This allows
1093 /// multiple fixups to share the same LSRUse with different offsets, for
1094 /// example in an unrolled loop.
1095 int64_t Offset = 0;
1096
1097 LSRFixup() = default;
1098
1099 bool isUseFullyOutsideLoop(const Loop *L) const;
1100
1101 void print(raw_ostream &OS) const;
1102 void dump() const;
1103};
1104
1105/// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
1106/// SmallVectors of const SCEV*.
1107struct UniquifierDenseMapInfo {
1108 static SmallVector<const SCEV *, 4> getEmptyKey() {
1109 SmallVector<const SCEV *, 4> V;
1110 V.push_back(reinterpret_cast<const SCEV *>(-1));
1111 return V;
1112 }
1113
1114 static SmallVector<const SCEV *, 4> getTombstoneKey() {
1115 SmallVector<const SCEV *, 4> V;
1116 V.push_back(reinterpret_cast<const SCEV *>(-2));
1117 return V;
1118 }
1119
1120 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1121 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1122 }
1123
1124 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1125 const SmallVector<const SCEV *, 4> &RHS) {
1126 return LHS == RHS;
1127 }
1128};
1129
1130/// This class holds the state that LSR keeps for each use in IVUsers, as well
1131/// as uses invented by LSR itself. It includes information about what kinds of
1132/// things can be folded into the user, information about the user itself, and
1133/// information about how the use may be satisfied. TODO: Represent multiple
1134/// users of the same expression in common?
1135class LSRUse {
1136 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1137
1138public:
1139 /// An enum for a kind of use, indicating what types of scaled and immediate
1140 /// operands it might support.
1141 enum KindType {
1142 Basic, ///< A normal use, with no folding.
1143 Special, ///< A special case of basic, allowing -1 scales.
1144 Address, ///< An address use; folding according to TargetLowering
1145 ICmpZero ///< An equality icmp with both operands folded into one.
1146 // TODO: Add a generic icmp too?
1147 };
1148
1149 using SCEVUseKindPair = PointerIntPair<const SCEV *, 2, KindType>;
1150
1151 KindType Kind;
1152 MemAccessTy AccessTy;
1153
1154 /// The list of operands which are to be replaced.
1155 SmallVector<LSRFixup, 8> Fixups;
1156
1157 /// Keep track of the min and max offsets of the fixups.
1158 int64_t MinOffset = std::numeric_limits<int64_t>::max();
1159 int64_t MaxOffset = std::numeric_limits<int64_t>::min();
1160
1161 /// This records whether all of the fixups using this LSRUse are outside of
1162 /// the loop, in which case some special-case heuristics may be used.
1163 bool AllFixupsOutsideLoop = true;
1164
1165 /// RigidFormula is set to true to guarantee that this use will be associated
1166 /// with a single formula--the one that initially matched. Some SCEV
1167 /// expressions cannot be expanded. This allows LSR to consider the registers
1168 /// used by those expressions without the need to expand them later after
1169 /// changing the formula.
1170 bool RigidFormula = false;
1171
1172 /// This records the widest use type for any fixup using this
1173 /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1174 /// fixup widths to be equivalent, because the narrower one may be relying on
1175 /// the implicit truncation to truncate away bogus bits.
1176 Type *WidestFixupType = nullptr;
1177
1178 /// A list of ways to build a value that can satisfy this user. After the
1179 /// list is populated, one of these is selected heuristically and used to
1180 /// formulate a replacement for OperandValToReplace in UserInst.
1181 SmallVector<Formula, 12> Formulae;
1182
1183 /// The set of register candidates used by all formulae in this LSRUse.
1184 SmallPtrSet<const SCEV *, 4> Regs;
1185
1186 LSRUse(KindType K, MemAccessTy AT) : Kind(K), AccessTy(AT) {}
1187
1188 LSRFixup &getNewFixup() {
1189 Fixups.push_back(LSRFixup());
1190 return Fixups.back();
1191 }
1192
1193 void pushFixup(LSRFixup &f) {
1194 Fixups.push_back(f);
1195 if (f.Offset > MaxOffset)
1196 MaxOffset = f.Offset;
1197 if (f.Offset < MinOffset)
1198 MinOffset = f.Offset;
1199 }
1200
1201 bool HasFormulaWithSameRegs(const Formula &F) const;
1202 float getNotSelectedProbability(const SCEV *Reg) const;
1203 bool InsertFormula(const Formula &F, const Loop &L);
1204 void DeleteFormula(Formula &F);
1205 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1206
1207 void print(raw_ostream &OS) const;
1208 void dump() const;
1209};
1210
1211} // end anonymous namespace
1212
1213static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1214 LSRUse::KindType Kind, MemAccessTy AccessTy,
1215 GlobalValue *BaseGV, int64_t BaseOffset,
1216 bool HasBaseReg, int64_t Scale,
1217 Instruction *Fixup = nullptr);
1218
1219static unsigned getSetupCost(const SCEV *Reg, unsigned Depth) {
1220 if (isa<SCEVUnknown>(Reg) || isa<SCEVConstant>(Reg))
1221 return 1;
1222 if (Depth == 0)
1223 return 0;
1224 if (const auto *S = dyn_cast<SCEVAddRecExpr>(Reg))
1225 return getSetupCost(S->getStart(), Depth - 1);
1226 if (auto S = dyn_cast<SCEVIntegralCastExpr>(Reg))
1227 return getSetupCost(S->getOperand(), Depth - 1);
1228 if (auto S = dyn_cast<SCEVNAryExpr>(Reg))
1229 return std::accumulate(S->op_begin(), S->op_end(), 0,
1230 [&](unsigned i, const SCEV *Reg) {
1231 return i + getSetupCost(Reg, Depth - 1);
1232 });
1233 if (auto S = dyn_cast<SCEVUDivExpr>(Reg))
1234 return getSetupCost(S->getLHS(), Depth - 1) +
1235 getSetupCost(S->getRHS(), Depth - 1);
1236 return 0;
1237}
1238
1239/// Tally up interesting quantities from the given register.
1240void Cost::RateRegister(const Formula &F, const SCEV *Reg,
1241 SmallPtrSetImpl<const SCEV *> &Regs) {
1242 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1243 // If this is an addrec for another loop, it should be an invariant
1244 // with respect to L since L is the innermost loop (at least
1245 // for now LSR only handles innermost loops).
1246 if (AR->getLoop() != L) {
1247 // If the AddRec exists, consider it's register free and leave it alone.
1248 if (isExistingPhi(AR, *SE) && AMK != TTI::AMK_PostIndexed)
1249 return;
1250
1251 // It is bad to allow LSR for current loop to add induction variables
1252 // for its sibling loops.
1253 if (!AR->getLoop()->contains(L)) {
1254 Lose();
1255 return;
1256 }
1257
1258 // Otherwise, it will be an invariant with respect to Loop L.
1259 ++C.NumRegs;
1260 return;
1261 }
1262
1263 unsigned LoopCost = 1;
1264 if (TTI->isIndexedLoadLegal(TTI->MIM_PostInc, AR->getType()) ||
1265 TTI->isIndexedStoreLegal(TTI->MIM_PostInc, AR->getType())) {
1266
1267 // If the step size matches the base offset, we could use pre-indexed
1268 // addressing.
1269 if (AMK == TTI::AMK_PreIndexed) {
1270 if (auto *Step = dyn_cast<SCEVConstant>(AR->getStepRecurrence(*SE)))
1271 if (Step->getAPInt() == F.BaseOffset)
1272 LoopCost = 0;
1273 } else if (AMK == TTI::AMK_PostIndexed) {
1274 const SCEV *LoopStep = AR->getStepRecurrence(*SE);
1275 if (isa<SCEVConstant>(LoopStep)) {
1276 const SCEV *LoopStart = AR->getStart();
1277 if (!isa<SCEVConstant>(LoopStart) &&
1278 SE->isLoopInvariant(LoopStart, L))
1279 LoopCost = 0;
1280 }
1281 }
1282 }
1283 C.AddRecCost += LoopCost;
1284
1285 // Add the step value register, if it needs one.
1286 // TODO: The non-affine case isn't precisely modeled here.
1287 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1288 if (!Regs.count(AR->getOperand(1))) {
1289 RateRegister(F, AR->getOperand(1), Regs);
1290 if (isLoser())
1291 return;
1292 }
1293 }
1294 }
1295 ++C.NumRegs;
1296
1297 // Rough heuristic; favor registers which don't require extra setup
1298 // instructions in the preheader.
1299 C.SetupCost += getSetupCost(Reg, SetupCostDepthLimit);
1300 // Ensure we don't, even with the recusion limit, produce invalid costs.
1301 C.SetupCost = std::min<unsigned>(C.SetupCost, 1 << 16);
1302
1303 C.NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1304 SE->hasComputableLoopEvolution(Reg, L);
1305}
1306
1307/// Record this register in the set. If we haven't seen it before, rate
1308/// it. Optional LoserRegs provides a way to declare any formula that refers to
1309/// one of those regs an instant loser.
1310void Cost::RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1311 SmallPtrSetImpl<const SCEV *> &Regs,
1312 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1313 if (LoserRegs && LoserRegs->count(Reg)) {
1314 Lose();
1315 return;
1316 }
1317 if (Regs.insert(Reg).second) {
1318 RateRegister(F, Reg, Regs);
1319 if (LoserRegs && isLoser())
1320 LoserRegs->insert(Reg);
1321 }
1322}
1323
1324void Cost::RateFormula(const Formula &F,
1325 SmallPtrSetImpl<const SCEV *> &Regs,
1326 const DenseSet<const SCEV *> &VisitedRegs,
1327 const LSRUse &LU,
1328 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1329 assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula")((F.isCanonical(*L) && "Cost is accurate only for canonical formula"
) ? static_cast<void> (0) : __assert_fail ("F.isCanonical(*L) && \"Cost is accurate only for canonical formula\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1329, __PRETTY_FUNCTION__))
;
1330 // Tally up the registers.
1331 unsigned PrevAddRecCost = C.AddRecCost;
1332 unsigned PrevNumRegs = C.NumRegs;
1333 unsigned PrevNumBaseAdds = C.NumBaseAdds;
1334 if (const SCEV *ScaledReg = F.ScaledReg) {
1335 if (VisitedRegs.count(ScaledReg)) {
1336 Lose();
1337 return;
1338 }
1339 RatePrimaryRegister(F, ScaledReg, Regs, LoserRegs);
1340 if (isLoser())
1341 return;
1342 }
1343 for (const SCEV *BaseReg : F.BaseRegs) {
1344 if (VisitedRegs.count(BaseReg)) {
1345 Lose();
1346 return;
1347 }
1348 RatePrimaryRegister(F, BaseReg, Regs, LoserRegs);
1349 if (isLoser())
1350 return;
1351 }
1352
1353 // Determine how many (unfolded) adds we'll need inside the loop.
1354 size_t NumBaseParts = F.getNumRegs();
1355 if (NumBaseParts > 1)
1356 // Do not count the base and a possible second register if the target
1357 // allows to fold 2 registers.
1358 C.NumBaseAdds +=
1359 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(*TTI, LU, F)));
1360 C.NumBaseAdds += (F.UnfoldedOffset != 0);
1361
1362 // Accumulate non-free scaling amounts.
1363 C.ScaleCost += getScalingFactorCost(*TTI, LU, F, *L);
1364
1365 // Tally up the non-zero immediates.
1366 for (const LSRFixup &Fixup : LU.Fixups) {
1367 int64_t O = Fixup.Offset;
1368 int64_t Offset = (uint64_t)O + F.BaseOffset;
1369 if (F.BaseGV)
1370 C.ImmCost += 64; // Handle symbolic values conservatively.
1371 // TODO: This should probably be the pointer size.
1372 else if (Offset != 0)
1373 C.ImmCost += APInt(64, Offset, true).getMinSignedBits();
1374
1375 // Check with target if this offset with this instruction is
1376 // specifically not supported.
1377 if (LU.Kind == LSRUse::Address && Offset != 0 &&
1378 !isAMCompletelyFolded(*TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1379 Offset, F.HasBaseReg, F.Scale, Fixup.UserInst))
1380 C.NumBaseAdds++;
1381 }
1382
1383 // If we don't count instruction cost exit here.
1384 if (!InsnsCost) {
1385 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1385, __PRETTY_FUNCTION__))
;
1386 return;
1387 }
1388
1389 // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as
1390 // additional instruction (at least fill).
1391 // TODO: Need distinguish register class?
1392 unsigned TTIRegNum = TTI->getNumberOfRegisters(
1393 TTI->getRegisterClassForType(false, F.getType())) - 1;
1394 if (C.NumRegs > TTIRegNum) {
1395 // Cost already exceeded TTIRegNum, then only newly added register can add
1396 // new instructions.
1397 if (PrevNumRegs > TTIRegNum)
1398 C.Insns += (C.NumRegs - PrevNumRegs);
1399 else
1400 C.Insns += (C.NumRegs - TTIRegNum);
1401 }
1402
1403 // If ICmpZero formula ends with not 0, it could not be replaced by
1404 // just add or sub. We'll need to compare final result of AddRec.
1405 // That means we'll need an additional instruction. But if the target can
1406 // macro-fuse a compare with a branch, don't count this extra instruction.
1407 // For -10 + {0, +, 1}:
1408 // i = i + 1;
1409 // cmp i, 10
1410 //
1411 // For {-10, +, 1}:
1412 // i = i + 1;
1413 if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd() &&
1414 !TTI->canMacroFuseCmp())
1415 C.Insns++;
1416 // Each new AddRec adds 1 instruction to calculation.
1417 C.Insns += (C.AddRecCost - PrevAddRecCost);
1418
1419 // BaseAdds adds instructions for unfolded registers.
1420 if (LU.Kind != LSRUse::ICmpZero)
1421 C.Insns += C.NumBaseAdds - PrevNumBaseAdds;
1422 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1422, __PRETTY_FUNCTION__))
;
1423}
1424
1425/// Set this cost to a losing value.
1426void Cost::Lose() {
1427 C.Insns = std::numeric_limits<unsigned>::max();
1428 C.NumRegs = std::numeric_limits<unsigned>::max();
1429 C.AddRecCost = std::numeric_limits<unsigned>::max();
1430 C.NumIVMuls = std::numeric_limits<unsigned>::max();
1431 C.NumBaseAdds = std::numeric_limits<unsigned>::max();
1432 C.ImmCost = std::numeric_limits<unsigned>::max();
1433 C.SetupCost = std::numeric_limits<unsigned>::max();
1434 C.ScaleCost = std::numeric_limits<unsigned>::max();
1435}
1436
1437/// Choose the lower cost.
1438bool Cost::isLess(Cost &Other) {
1439 if (InsnsCost.getNumOccurrences() > 0 && InsnsCost &&
1440 C.Insns != Other.C.Insns)
1441 return C.Insns < Other.C.Insns;
1442 return TTI->isLSRCostLess(C, Other.C);
1443}
1444
1445#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1446void Cost::print(raw_ostream &OS) const {
1447 if (InsnsCost)
1448 OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s ");
1449 OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s");
1450 if (C.AddRecCost != 0)
1451 OS << ", with addrec cost " << C.AddRecCost;
1452 if (C.NumIVMuls != 0)
1453 OS << ", plus " << C.NumIVMuls << " IV mul"
1454 << (C.NumIVMuls == 1 ? "" : "s");
1455 if (C.NumBaseAdds != 0)
1456 OS << ", plus " << C.NumBaseAdds << " base add"
1457 << (C.NumBaseAdds == 1 ? "" : "s");
1458 if (C.ScaleCost != 0)
1459 OS << ", plus " << C.ScaleCost << " scale cost";
1460 if (C.ImmCost != 0)
1461 OS << ", plus " << C.ImmCost << " imm cost";
1462 if (C.SetupCost != 0)
1463 OS << ", plus " << C.SetupCost << " setup cost";
1464}
1465
1466LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Cost::dump() const {
1467 print(errs()); errs() << '\n';
1468}
1469#endif
1470
1471/// Test whether this fixup always uses its value outside of the given loop.
1472bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1473 // PHI nodes use their value in their incoming blocks.
1474 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1475 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1476 if (PN->getIncomingValue(i) == OperandValToReplace &&
1477 L->contains(PN->getIncomingBlock(i)))
1478 return false;
1479 return true;
1480 }
1481
1482 return !L->contains(UserInst);
1483}
1484
1485#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1486void LSRFixup::print(raw_ostream &OS) const {
1487 OS << "UserInst=";
1488 // Store is common and interesting enough to be worth special-casing.
1489 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1490 OS << "store ";
1491 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1492 } else if (UserInst->getType()->isVoidTy())
1493 OS << UserInst->getOpcodeName();
1494 else
1495 UserInst->printAsOperand(OS, /*PrintType=*/false);
1496
1497 OS << ", OperandValToReplace=";
1498 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1499
1500 for (const Loop *PIL : PostIncLoops) {
1501 OS << ", PostIncLoop=";
1502 PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1503 }
1504
1505 if (Offset != 0)
1506 OS << ", Offset=" << Offset;
1507}
1508
1509LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRFixup::dump() const {
1510 print(errs()); errs() << '\n';
1511}
1512#endif
1513
1514/// Test whether this use as a formula which has the same registers as the given
1515/// formula.
1516bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1517 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1518 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1519 // Unstable sort by host order ok, because this is only used for uniquifying.
1520 llvm::sort(Key);
1521 return Uniquifier.count(Key);
1522}
1523
1524/// The function returns a probability of selecting formula without Reg.
1525float LSRUse::getNotSelectedProbability(const SCEV *Reg) const {
1526 unsigned FNum = 0;
1527 for (const Formula &F : Formulae)
1528 if (F.referencesReg(Reg))
1529 FNum++;
1530 return ((float)(Formulae.size() - FNum)) / Formulae.size();
1531}
1532
1533/// If the given formula has not yet been inserted, add it to the list, and
1534/// return true. Return false otherwise. The formula must be in canonical form.
1535bool LSRUse::InsertFormula(const Formula &F, const Loop &L) {
1536 assert(F.isCanonical(L) && "Invalid canonical representation")((F.isCanonical(L) && "Invalid canonical representation"
) ? static_cast<void> (0) : __assert_fail ("F.isCanonical(L) && \"Invalid canonical representation\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1536, __PRETTY_FUNCTION__))
;
1537
1538 if (!Formulae.empty() && RigidFormula)
1539 return false;
1540
1541 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1542 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1543 // Unstable sort by host order ok, because this is only used for uniquifying.
1544 llvm::sort(Key);
1545
1546 if (!Uniquifier.insert(Key).second)
1547 return false;
1548
1549 // Using a register to hold the value of 0 is not profitable.
1550 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&(((!F.ScaledReg || !F.ScaledReg->isZero()) && "Zero allocated in a scaled register!"
) ? static_cast<void> (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1551, __PRETTY_FUNCTION__))
1551 "Zero allocated in a scaled register!")(((!F.ScaledReg || !F.ScaledReg->isZero()) && "Zero allocated in a scaled register!"
) ? static_cast<void> (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1551, __PRETTY_FUNCTION__))
;
1552#ifndef NDEBUG
1553 for (const SCEV *BaseReg : F.BaseRegs)
1554 assert(!BaseReg->isZero() && "Zero allocated in a base register!")((!BaseReg->isZero() && "Zero allocated in a base register!"
) ? static_cast<void> (0) : __assert_fail ("!BaseReg->isZero() && \"Zero allocated in a base register!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1554, __PRETTY_FUNCTION__))
;
1555#endif
1556
1557 // Add the formula to the list.
1558 Formulae.push_back(F);
1559
1560 // Record registers now being used by this use.
1561 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1562 if (F.ScaledReg)
1563 Regs.insert(F.ScaledReg);
1564
1565 return true;
1566}
1567
1568/// Remove the given formula from this use's list.
1569void LSRUse::DeleteFormula(Formula &F) {
1570 if (&F != &Formulae.back())
1571 std::swap(F, Formulae.back());
1572 Formulae.pop_back();
1573}
1574
1575/// Recompute the Regs field, and update RegUses.
1576void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1577 // Now that we've filtered out some formulae, recompute the Regs set.
1578 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1579 Regs.clear();
1580 for (const Formula &F : Formulae) {
1581 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1582 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1583 }
1584
1585 // Update the RegTracker.
1586 for (const SCEV *S : OldRegs)
1587 if (!Regs.count(S))
1588 RegUses.dropRegister(S, LUIdx);
1589}
1590
1591#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1592void LSRUse::print(raw_ostream &OS) const {
1593 OS << "LSR Use: Kind=";
1594 switch (Kind) {
1595 case Basic: OS << "Basic"; break;
1596 case Special: OS << "Special"; break;
1597 case ICmpZero: OS << "ICmpZero"; break;
1598 case Address:
1599 OS << "Address of ";
1600 if (AccessTy.MemTy->isPointerTy())
1601 OS << "pointer"; // the full pointer type could be really verbose
1602 else {
1603 OS << *AccessTy.MemTy;
1604 }
1605
1606 OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1607 }
1608
1609 OS << ", Offsets={";
1610 bool NeedComma = false;
1611 for (const LSRFixup &Fixup : Fixups) {
1612 if (NeedComma) OS << ',';
1613 OS << Fixup.Offset;
1614 NeedComma = true;
1615 }
1616 OS << '}';
1617
1618 if (AllFixupsOutsideLoop)
1619 OS << ", all-fixups-outside-loop";
1620
1621 if (WidestFixupType)
1622 OS << ", widest fixup type: " << *WidestFixupType;
1623}
1624
1625LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRUse::dump() const {
1626 print(errs()); errs() << '\n';
1627}
1628#endif
1629
1630static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1631 LSRUse::KindType Kind, MemAccessTy AccessTy,
1632 GlobalValue *BaseGV, int64_t BaseOffset,
1633 bool HasBaseReg, int64_t Scale,
1634 Instruction *Fixup/*= nullptr*/) {
1635 switch (Kind) {
1636 case LSRUse::Address:
1637 return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1638 HasBaseReg, Scale, AccessTy.AddrSpace, Fixup);
1639
1640 case LSRUse::ICmpZero:
1641 // There's not even a target hook for querying whether it would be legal to
1642 // fold a GV into an ICmp.
1643 if (BaseGV)
1644 return false;
1645
1646 // ICmp only has two operands; don't allow more than two non-trivial parts.
1647 if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1648 return false;
1649
1650 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1651 // putting the scaled register in the other operand of the icmp.
1652 if (Scale != 0 && Scale != -1)
1653 return false;
1654
1655 // If we have low-level target information, ask the target if it can fold an
1656 // integer immediate on an icmp.
1657 if (BaseOffset != 0) {
1658 // We have one of:
1659 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1660 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1661 // Offs is the ICmp immediate.
1662 if (Scale == 0)
1663 // The cast does the right thing with
1664 // std::numeric_limits<int64_t>::min().
1665 BaseOffset = -(uint64_t)BaseOffset;
1666 return TTI.isLegalICmpImmediate(BaseOffset);
1667 }
1668
1669 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1670 return true;
1671
1672 case LSRUse::Basic:
1673 // Only handle single-register values.
1674 return !BaseGV && Scale == 0 && BaseOffset == 0;
1675
1676 case LSRUse::Special:
1677 // Special case Basic to handle -1 scales.
1678 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1679 }
1680
1681 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1681)
;
1682}
1683
1684static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1685 int64_t MinOffset, int64_t MaxOffset,
1686 LSRUse::KindType Kind, MemAccessTy AccessTy,
1687 GlobalValue *BaseGV, int64_t BaseOffset,
1688 bool HasBaseReg, int64_t Scale) {
1689 // Check for overflow.
1690 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1691 (MinOffset > 0))
1692 return false;
1693 MinOffset = (uint64_t)BaseOffset + MinOffset;
1694 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1695 (MaxOffset > 0))
1696 return false;
1697 MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1698
1699 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1700 HasBaseReg, Scale) &&
1701 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1702 HasBaseReg, Scale);
1703}
1704
1705static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1706 int64_t MinOffset, int64_t MaxOffset,
1707 LSRUse::KindType Kind, MemAccessTy AccessTy,
1708 const Formula &F, const Loop &L) {
1709 // For the purpose of isAMCompletelyFolded either having a canonical formula
1710 // or a scale not equal to zero is correct.
1711 // Problems may arise from non canonical formulae having a scale == 0.
1712 // Strictly speaking it would best to just rely on canonical formulae.
1713 // However, when we generate the scaled formulae, we first check that the
1714 // scaling factor is profitable before computing the actual ScaledReg for
1715 // compile time sake.
1716 assert((F.isCanonical(L) || F.Scale != 0))(((F.isCanonical(L) || F.Scale != 0)) ? static_cast<void>
(0) : __assert_fail ("(F.isCanonical(L) || F.Scale != 0)", "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1716, __PRETTY_FUNCTION__))
;
1717 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1718 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1719}
1720
1721/// Test whether we know how to expand the current formula.
1722static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1723 int64_t MaxOffset, LSRUse::KindType Kind,
1724 MemAccessTy AccessTy, GlobalValue *BaseGV,
1725 int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1726 // We know how to expand completely foldable formulae.
1727 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1728 BaseOffset, HasBaseReg, Scale) ||
1729 // Or formulae that use a base register produced by a sum of base
1730 // registers.
1731 (Scale == 1 &&
1732 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1733 BaseGV, BaseOffset, true, 0));
1734}
1735
1736static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1737 int64_t MaxOffset, LSRUse::KindType Kind,
1738 MemAccessTy AccessTy, const Formula &F) {
1739 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1740 F.BaseOffset, F.HasBaseReg, F.Scale);
1741}
1742
1743static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1744 const LSRUse &LU, const Formula &F) {
1745 // Target may want to look at the user instructions.
1746 if (LU.Kind == LSRUse::Address && TTI.LSRWithInstrQueries()) {
1747 for (const LSRFixup &Fixup : LU.Fixups)
1748 if (!isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1749 (F.BaseOffset + Fixup.Offset), F.HasBaseReg,
1750 F.Scale, Fixup.UserInst))
1751 return false;
1752 return true;
1753 }
1754
1755 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1756 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1757 F.Scale);
1758}
1759
1760static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1761 const LSRUse &LU, const Formula &F,
1762 const Loop &L) {
1763 if (!F.Scale)
1764 return 0;
1765
1766 // If the use is not completely folded in that instruction, we will have to
1767 // pay an extra cost only for scale != 1.
1768 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1769 LU.AccessTy, F, L))
1770 return F.Scale != 1;
1771
1772 switch (LU.Kind) {
1773 case LSRUse::Address: {
1774 // Check the scaling factor cost with both the min and max offsets.
1775 int ScaleCostMinOffset = TTI.getScalingFactorCost(
1776 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1777 F.Scale, LU.AccessTy.AddrSpace);
1778 int ScaleCostMaxOffset = TTI.getScalingFactorCost(
1779 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1780 F.Scale, LU.AccessTy.AddrSpace);
1781
1782 assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&((ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >=
0 && "Legal addressing mode has an illegal cost!") ?
static_cast<void> (0) : __assert_fail ("ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && \"Legal addressing mode has an illegal cost!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1783, __PRETTY_FUNCTION__))
1783 "Legal addressing mode has an illegal cost!")((ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >=
0 && "Legal addressing mode has an illegal cost!") ?
static_cast<void> (0) : __assert_fail ("ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && \"Legal addressing mode has an illegal cost!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1783, __PRETTY_FUNCTION__))
;
1784 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1785 }
1786 case LSRUse::ICmpZero:
1787 case LSRUse::Basic:
1788 case LSRUse::Special:
1789 // The use is completely folded, i.e., everything is folded into the
1790 // instruction.
1791 return 0;
1792 }
1793
1794 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1794)
;
1795}
1796
1797static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1798 LSRUse::KindType Kind, MemAccessTy AccessTy,
1799 GlobalValue *BaseGV, int64_t BaseOffset,
1800 bool HasBaseReg) {
1801 // Fast-path: zero is always foldable.
1802 if (BaseOffset == 0 && !BaseGV) return true;
1803
1804 // Conservatively, create an address with an immediate and a
1805 // base and a scale.
1806 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1807
1808 // Canonicalize a scale of 1 to a base register if the formula doesn't
1809 // already have a base register.
1810 if (!HasBaseReg && Scale == 1) {
1811 Scale = 0;
1812 HasBaseReg = true;
1813 }
1814
1815 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1816 HasBaseReg, Scale);
1817}
1818
1819static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1820 ScalarEvolution &SE, int64_t MinOffset,
1821 int64_t MaxOffset, LSRUse::KindType Kind,
1822 MemAccessTy AccessTy, const SCEV *S,
1823 bool HasBaseReg) {
1824 // Fast-path: zero is always foldable.
1825 if (S->isZero()) return true;
1826
1827 // Conservatively, create an address with an immediate and a
1828 // base and a scale.
1829 int64_t BaseOffset = ExtractImmediate(S, SE);
1830 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1831
1832 // If there's anything else involved, it's not foldable.
1833 if (!S->isZero()) return false;
1834
1835 // Fast-path: zero is always foldable.
1836 if (BaseOffset == 0 && !BaseGV) return true;
1837
1838 // Conservatively, create an address with an immediate and a
1839 // base and a scale.
1840 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1841
1842 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1843 BaseOffset, HasBaseReg, Scale);
1844}
1845
1846namespace {
1847
1848/// An individual increment in a Chain of IV increments. Relate an IV user to
1849/// an expression that computes the IV it uses from the IV used by the previous
1850/// link in the Chain.
1851///
1852/// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1853/// original IVOperand. The head of the chain's IVOperand is only valid during
1854/// chain collection, before LSR replaces IV users. During chain generation,
1855/// IncExpr can be used to find the new IVOperand that computes the same
1856/// expression.
1857struct IVInc {
1858 Instruction *UserInst;
1859 Value* IVOperand;
1860 const SCEV *IncExpr;
1861
1862 IVInc(Instruction *U, Value *O, const SCEV *E)
1863 : UserInst(U), IVOperand(O), IncExpr(E) {}
1864};
1865
1866// The list of IV increments in program order. We typically add the head of a
1867// chain without finding subsequent links.
1868struct IVChain {
1869 SmallVector<IVInc, 1> Incs;
1870 const SCEV *ExprBase = nullptr;
1871
1872 IVChain() = default;
1873 IVChain(const IVInc &Head, const SCEV *Base)
1874 : Incs(1, Head), ExprBase(Base) {}
1875
1876 using const_iterator = SmallVectorImpl<IVInc>::const_iterator;
1877
1878 // Return the first increment in the chain.
1879 const_iterator begin() const {
1880 assert(!Incs.empty())((!Incs.empty()) ? static_cast<void> (0) : __assert_fail
("!Incs.empty()", "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1880, __PRETTY_FUNCTION__))
;
1881 return std::next(Incs.begin());
1882 }
1883 const_iterator end() const {
1884 return Incs.end();
1885 }
1886
1887 // Returns true if this chain contains any increments.
1888 bool hasIncs() const { return Incs.size() >= 2; }
1889
1890 // Add an IVInc to the end of this chain.
1891 void add(const IVInc &X) { Incs.push_back(X); }
1892
1893 // Returns the last UserInst in the chain.
1894 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1895
1896 // Returns true if IncExpr can be profitably added to this chain.
1897 bool isProfitableIncrement(const SCEV *OperExpr,
1898 const SCEV *IncExpr,
1899 ScalarEvolution&);
1900};
1901
1902/// Helper for CollectChains to track multiple IV increment uses. Distinguish
1903/// between FarUsers that definitely cross IV increments and NearUsers that may
1904/// be used between IV increments.
1905struct ChainUsers {
1906 SmallPtrSet<Instruction*, 4> FarUsers;
1907 SmallPtrSet<Instruction*, 4> NearUsers;
1908};
1909
1910/// This class holds state for the main loop strength reduction logic.
1911class LSRInstance {
1912 IVUsers &IU;
1913 ScalarEvolution &SE;
1914 DominatorTree &DT;
1915 LoopInfo &LI;
1916 AssumptionCache &AC;
1917 TargetLibraryInfo &TLI;
1918 const TargetTransformInfo &TTI;
1919 Loop *const L;
1920 MemorySSAUpdater *MSSAU;
1921 TTI::AddressingModeKind AMK;
1922 bool Changed = false;
1923
1924 /// This is the insert position that the current loop's induction variable
1925 /// increment should be placed. In simple loops, this is the latch block's
1926 /// terminator. But in more complicated cases, this is a position which will
1927 /// dominate all the in-loop post-increment users.
1928 Instruction *IVIncInsertPos = nullptr;
1929
1930 /// Interesting factors between use strides.
1931 ///
1932 /// We explicitly use a SetVector which contains a SmallSet, instead of the
1933 /// default, a SmallDenseSet, because we need to use the full range of
1934 /// int64_ts, and there's currently no good way of doing that with
1935 /// SmallDenseSet.
1936 SetVector<int64_t, SmallVector<int64_t, 8>, SmallSet<int64_t, 8>> Factors;
1937
1938 /// Interesting use types, to facilitate truncation reuse.
1939 SmallSetVector<Type *, 4> Types;
1940
1941 /// The list of interesting uses.
1942 mutable SmallVector<LSRUse, 16> Uses;
1943
1944 /// Track which uses use which register candidates.
1945 RegUseTracker RegUses;
1946
1947 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1948 // have more than a few IV increment chains in a loop. Missing a Chain falls
1949 // back to normal LSR behavior for those uses.
1950 static const unsigned MaxChains = 8;
1951
1952 /// IV users can form a chain of IV increments.
1953 SmallVector<IVChain, MaxChains> IVChainVec;
1954
1955 /// IV users that belong to profitable IVChains.
1956 SmallPtrSet<Use*, MaxChains> IVIncSet;
1957
1958 void OptimizeShadowIV();
1959 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1960 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1961 void OptimizeLoopTermCond();
1962
1963 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1964 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1965 void FinalizeChain(IVChain &Chain);
1966 void CollectChains();
1967 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1968 SmallVectorImpl<WeakTrackingVH> &DeadInsts);
1969
1970 void CollectInterestingTypesAndFactors();
1971 void CollectFixupsAndInitialFormulae();
1972
1973 // Support for sharing of LSRUses between LSRFixups.
1974 using UseMapTy = DenseMap<LSRUse::SCEVUseKindPair, size_t>;
1975 UseMapTy UseMap;
1976
1977 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1978 LSRUse::KindType Kind, MemAccessTy AccessTy);
1979
1980 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
1981 MemAccessTy AccessTy);
1982
1983 void DeleteUse(LSRUse &LU, size_t LUIdx);
1984
1985 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1986
1987 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1988 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1989 void CountRegisters(const Formula &F, size_t LUIdx);
1990 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1991
1992 void CollectLoopInvariantFixupsAndFormulae();
1993
1994 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1995 unsigned Depth = 0);
1996
1997 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1998 const Formula &Base, unsigned Depth,
1999 size_t Idx, bool IsScaledReg = false);
2000 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
2001 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
2002 const Formula &Base, size_t Idx,
2003 bool IsScaledReg = false);
2004 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
2005 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
2006 const Formula &Base,
2007 const SmallVectorImpl<int64_t> &Worklist,
2008 size_t Idx, bool IsScaledReg = false);
2009 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
2010 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2011 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2012 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
2013 void GenerateCrossUseConstantOffsets();
2014 void GenerateAllReuseFormulae();
2015
2016 void FilterOutUndesirableDedicatedRegisters();
2017
2018 size_t EstimateSearchSpaceComplexity() const;
2019 void NarrowSearchSpaceByDetectingSupersets();
2020 void NarrowSearchSpaceByCollapsingUnrolledCode();
2021 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
2022 void NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
2023 void NarrowSearchSpaceByFilterPostInc();
2024 void NarrowSearchSpaceByDeletingCostlyFormulas();
2025 void NarrowSearchSpaceByPickingWinnerRegs();
2026 void NarrowSearchSpaceUsingHeuristics();
2027
2028 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
2029 Cost &SolutionCost,
2030 SmallVectorImpl<const Formula *> &Workspace,
2031 const Cost &CurCost,
2032 const SmallPtrSet<const SCEV *, 16> &CurRegs,
2033 DenseSet<const SCEV *> &VisitedRegs) const;
2034 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
2035
2036 BasicBlock::iterator
2037 HoistInsertPosition(BasicBlock::iterator IP,
2038 const SmallVectorImpl<Instruction *> &Inputs) const;
2039 BasicBlock::iterator
2040 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
2041 const LSRFixup &LF,
2042 const LSRUse &LU,
2043 SCEVExpander &Rewriter) const;
2044
2045 Value *Expand(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2046 BasicBlock::iterator IP, SCEVExpander &Rewriter,
2047 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2048 void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
2049 const Formula &F, SCEVExpander &Rewriter,
2050 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2051 void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2052 SCEVExpander &Rewriter,
2053 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2054 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
2055
2056public:
2057 LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
2058 LoopInfo &LI, const TargetTransformInfo &TTI, AssumptionCache &AC,
2059 TargetLibraryInfo &TLI, MemorySSAUpdater *MSSAU);
2060
2061 bool getChanged() const { return Changed; }
2062
2063 void print_factors_and_types(raw_ostream &OS) const;
2064 void print_fixups(raw_ostream &OS) const;
2065 void print_uses(raw_ostream &OS) const;
2066 void print(raw_ostream &OS) const;
2067 void dump() const;
2068};
2069
2070} // end anonymous namespace
2071
2072/// If IV is used in a int-to-float cast inside the loop then try to eliminate
2073/// the cast operation.
2074void LSRInstance::OptimizeShadowIV() {
2075 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2076 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2077 return;
2078
2079 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
2080 UI != E; /* empty */) {
2081 IVUsers::const_iterator CandidateUI = UI;
2082 ++UI;
2083 Instruction *ShadowUse = CandidateUI->getUser();
2084 Type *DestTy = nullptr;
2085 bool IsSigned = false;
2086
2087 /* If shadow use is a int->float cast then insert a second IV
2088 to eliminate this cast.
2089
2090 for (unsigned i = 0; i < n; ++i)
2091 foo((double)i);
2092
2093 is transformed into
2094
2095 double d = 0.0;
2096 for (unsigned i = 0; i < n; ++i, ++d)
2097 foo(d);
2098 */
2099 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
2100 IsSigned = false;
2101 DestTy = UCast->getDestTy();
2102 }
2103 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
2104 IsSigned = true;
2105 DestTy = SCast->getDestTy();
2106 }
2107 if (!DestTy) continue;
2108
2109 // If target does not support DestTy natively then do not apply
2110 // this transformation.
2111 if (!TTI.isTypeLegal(DestTy)) continue;
2112
2113 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2114 if (!PH) continue;
2115 if (PH->getNumIncomingValues() != 2) continue;
2116
2117 // If the calculation in integers overflows, the result in FP type will
2118 // differ. So we only can do this transformation if we are guaranteed to not
2119 // deal with overflowing values
2120 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PH));
2121 if (!AR) continue;
2122 if (IsSigned && !AR->hasNoSignedWrap()) continue;
2123 if (!IsSigned && !AR->hasNoUnsignedWrap()) continue;
2124
2125 Type *SrcTy = PH->getType();
2126 int Mantissa = DestTy->getFPMantissaWidth();
2127 if (Mantissa == -1) continue;
2128 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
2129 continue;
2130
2131 unsigned Entry, Latch;
2132 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2133 Entry = 0;
2134 Latch = 1;
2135 } else {
2136 Entry = 1;
2137 Latch = 0;
2138 }
2139
2140 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
2141 if (!Init) continue;
2142 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
2143 (double)Init->getSExtValue() :
2144 (double)Init->getZExtValue());
2145
2146 BinaryOperator *Incr =
2147 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
2148 if (!Incr) continue;
2149 if (Incr->getOpcode() != Instruction::Add
2150 && Incr->getOpcode() != Instruction::Sub)
2151 continue;
2152
2153 /* Initialize new IV, double d = 0.0 in above example. */
2154 ConstantInt *C = nullptr;
2155 if (Incr->getOperand(0) == PH)
2156 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2157 else if (Incr->getOperand(1) == PH)
2158 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2159 else
2160 continue;
2161
2162 if (!C) continue;
2163
2164 // Ignore negative constants, as the code below doesn't handle them
2165 // correctly. TODO: Remove this restriction.
2166 if (!C->getValue().isStrictlyPositive()) continue;
2167
2168 /* Add new PHINode. */
2169 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
2170
2171 /* create new increment. '++d' in above example. */
2172 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2173 BinaryOperator *NewIncr =
2174 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
2175 Instruction::FAdd : Instruction::FSub,
2176 NewPH, CFP, "IV.S.next.", Incr);
2177
2178 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2179 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2180
2181 /* Remove cast operation */
2182 ShadowUse->replaceAllUsesWith(NewPH);
2183 ShadowUse->eraseFromParent();
2184 Changed = true;
2185 break;
2186 }
2187}
2188
2189/// If Cond has an operand that is an expression of an IV, set the IV user and
2190/// stride information and return true, otherwise return false.
2191bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
2192 for (IVStrideUse &U : IU)
2193 if (U.getUser() == Cond) {
2194 // NOTE: we could handle setcc instructions with multiple uses here, but
2195 // InstCombine does it as well for simple uses, it's not clear that it
2196 // occurs enough in real life to handle.
2197 CondUse = &U;
2198 return true;
2199 }
2200 return false;
2201}
2202
2203/// Rewrite the loop's terminating condition if it uses a max computation.
2204///
2205/// This is a narrow solution to a specific, but acute, problem. For loops
2206/// like this:
2207///
2208/// i = 0;
2209/// do {
2210/// p[i] = 0.0;
2211/// } while (++i < n);
2212///
2213/// the trip count isn't just 'n', because 'n' might not be positive. And
2214/// unfortunately this can come up even for loops where the user didn't use
2215/// a C do-while loop. For example, seemingly well-behaved top-test loops
2216/// will commonly be lowered like this:
2217///
2218/// if (n > 0) {
2219/// i = 0;
2220/// do {
2221/// p[i] = 0.0;
2222/// } while (++i < n);
2223/// }
2224///
2225/// and then it's possible for subsequent optimization to obscure the if
2226/// test in such a way that indvars can't find it.
2227///
2228/// When indvars can't find the if test in loops like this, it creates a
2229/// max expression, which allows it to give the loop a canonical
2230/// induction variable:
2231///
2232/// i = 0;
2233/// max = n < 1 ? 1 : n;
2234/// do {
2235/// p[i] = 0.0;
2236/// } while (++i != max);
2237///
2238/// Canonical induction variables are necessary because the loop passes
2239/// are designed around them. The most obvious example of this is the
2240/// LoopInfo analysis, which doesn't remember trip count values. It
2241/// expects to be able to rediscover the trip count each time it is
2242/// needed, and it does this using a simple analysis that only succeeds if
2243/// the loop has a canonical induction variable.
2244///
2245/// However, when it comes time to generate code, the maximum operation
2246/// can be quite costly, especially if it's inside of an outer loop.
2247///
2248/// This function solves this problem by detecting this type of loop and
2249/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2250/// the instructions for the maximum computation.
2251ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
2252 // Check that the loop matches the pattern we're looking for.
2253 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2254 Cond->getPredicate() != CmpInst::ICMP_NE)
2255 return Cond;
2256
2257 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2258 if (!Sel || !Sel->hasOneUse()) return Cond;
2259
2260 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2261 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2262 return Cond;
2263 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2264
2265 // Add one to the backedge-taken count to get the trip count.
2266 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2267 if (IterationCount != SE.getSCEV(Sel)) return Cond;
2268
2269 // Check for a max calculation that matches the pattern. There's no check
2270 // for ICMP_ULE here because the comparison would be with zero, which
2271 // isn't interesting.
2272 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2273 const SCEVNAryExpr *Max = nullptr;
2274 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2275 Pred = ICmpInst::ICMP_SLE;
2276 Max = S;
2277 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2278 Pred = ICmpInst::ICMP_SLT;
2279 Max = S;
2280 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2281 Pred = ICmpInst::ICMP_ULT;
2282 Max = U;
2283 } else {
2284 // No match; bail.
2285 return Cond;
2286 }
2287
2288 // To handle a max with more than two operands, this optimization would
2289 // require additional checking and setup.
2290 if (Max->getNumOperands() != 2)
2291 return Cond;
2292
2293 const SCEV *MaxLHS = Max->getOperand(0);
2294 const SCEV *MaxRHS = Max->getOperand(1);
2295
2296 // ScalarEvolution canonicalizes constants to the left. For < and >, look
2297 // for a comparison with 1. For <= and >=, a comparison with zero.
2298 if (!MaxLHS ||
2299 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2300 return Cond;
2301
2302 // Check the relevant induction variable for conformance to
2303 // the pattern.
2304 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2305 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2306 if (!AR || !AR->isAffine() ||
2307 AR->getStart() != One ||
2308 AR->getStepRecurrence(SE) != One)
2309 return Cond;
2310
2311 assert(AR->getLoop() == L &&((AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? static_cast<void> (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2312, __PRETTY_FUNCTION__))
2312 "Loop condition operand is an addrec in a different loop!")((AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? static_cast<void> (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2312, __PRETTY_FUNCTION__))
;
2313
2314 // Check the right operand of the select, and remember it, as it will
2315 // be used in the new comparison instruction.
2316 Value *NewRHS = nullptr;
2317 if (ICmpInst::isTrueWhenEqual(Pred)) {
2318 // Look for n+1, and grab n.
2319 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2320 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2321 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2322 NewRHS = BO->getOperand(0);
2323 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2324 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2325 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2326 NewRHS = BO->getOperand(0);
2327 if (!NewRHS)
2328 return Cond;
2329 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2330 NewRHS = Sel->getOperand(1);
2331 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2332 NewRHS = Sel->getOperand(2);
2333 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2334 NewRHS = SU->getValue();
2335 else
2336 // Max doesn't match expected pattern.
2337 return Cond;
2338
2339 // Determine the new comparison opcode. It may be signed or unsigned,
2340 // and the original comparison may be either equality or inequality.
2341 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2342 Pred = CmpInst::getInversePredicate(Pred);
2343
2344 // Ok, everything looks ok to change the condition into an SLT or SGE and
2345 // delete the max calculation.
2346 ICmpInst *NewCond =
2347 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2348
2349 // Delete the max calculation instructions.
2350 Cond->replaceAllUsesWith(NewCond);
2351 CondUse->setUser(NewCond);
2352 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2353 Cond->eraseFromParent();
2354 Sel->eraseFromParent();
2355 if (Cmp->use_empty())
2356 Cmp->eraseFromParent();
2357 return NewCond;
2358}
2359
2360/// Change loop terminating condition to use the postinc iv when possible.
2361void
2362LSRInstance::OptimizeLoopTermCond() {
2363 SmallPtrSet<Instruction *, 4> PostIncs;
2364
2365 // We need a different set of heuristics for rotated and non-rotated loops.
2366 // If a loop is rotated then the latch is also the backedge, so inserting
2367 // post-inc expressions just before the latch is ideal. To reduce live ranges
2368 // it also makes sense to rewrite terminating conditions to use post-inc
2369 // expressions.
2370 //
2371 // If the loop is not rotated then the latch is not a backedge; the latch
2372 // check is done in the loop head. Adding post-inc expressions before the
2373 // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2374 // in the loop body. In this case we do *not* want to use post-inc expressions
2375 // in the latch check, and we want to insert post-inc expressions before
2376 // the backedge.
2377 BasicBlock *LatchBlock = L->getLoopLatch();
2378 SmallVector<BasicBlock*, 8> ExitingBlocks;
2379 L->getExitingBlocks(ExitingBlocks);
2380 if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2381 return LatchBlock != BB;
2382 })) {
2383 // The backedge doesn't exit the loop; treat this as a head-tested loop.
2384 IVIncInsertPos = LatchBlock->getTerminator();
2385 return;
2386 }
2387
2388 // Otherwise treat this as a rotated loop.
2389 for (BasicBlock *ExitingBlock : ExitingBlocks) {
2390 // Get the terminating condition for the loop if possible. If we
2391 // can, we want to change it to use a post-incremented version of its
2392 // induction variable, to allow coalescing the live ranges for the IV into
2393 // one register value.
2394
2395 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2396 if (!TermBr)
2397 continue;
2398 // FIXME: Overly conservative, termination condition could be an 'or' etc..
2399 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2400 continue;
2401
2402 // Search IVUsesByStride to find Cond's IVUse if there is one.
2403 IVStrideUse *CondUse = nullptr;
2404 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2405 if (!FindIVUserForCond(Cond, CondUse))
2406 continue;
2407
2408 // If the trip count is computed in terms of a max (due to ScalarEvolution
2409 // being unable to find a sufficient guard, for example), change the loop
2410 // comparison to use SLT or ULT instead of NE.
2411 // One consequence of doing this now is that it disrupts the count-down
2412 // optimization. That's not always a bad thing though, because in such
2413 // cases it may still be worthwhile to avoid a max.
2414 Cond = OptimizeMax(Cond, CondUse);
2415
2416 // If this exiting block dominates the latch block, it may also use
2417 // the post-inc value if it won't be shared with other uses.
2418 // Check for dominance.
2419 if (!DT.dominates(ExitingBlock, LatchBlock))
2420 continue;
2421
2422 // Conservatively avoid trying to use the post-inc value in non-latch
2423 // exits if there may be pre-inc users in intervening blocks.
2424 if (LatchBlock != ExitingBlock)
2425 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2426 // Test if the use is reachable from the exiting block. This dominator
2427 // query is a conservative approximation of reachability.
2428 if (&*UI != CondUse &&
2429 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2430 // Conservatively assume there may be reuse if the quotient of their
2431 // strides could be a legal scale.
2432 const SCEV *A = IU.getStride(*CondUse, L);
2433 const SCEV *B = IU.getStride(*UI, L);
2434 if (!A || !B) continue;
2435 if (SE.getTypeSizeInBits(A->getType()) !=
2436 SE.getTypeSizeInBits(B->getType())) {
2437 if (SE.getTypeSizeInBits(A->getType()) >
2438 SE.getTypeSizeInBits(B->getType()))
2439 B = SE.getSignExtendExpr(B, A->getType());
2440 else
2441 A = SE.getSignExtendExpr(A, B->getType());
2442 }
2443 if (const SCEVConstant *D =
2444 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2445 const ConstantInt *C = D->getValue();
2446 // Stride of one or negative one can have reuse with non-addresses.
2447 if (C->isOne() || C->isMinusOne())
2448 goto decline_post_inc;
2449 // Avoid weird situations.
2450 if (C->getValue().getMinSignedBits() >= 64 ||
2451 C->getValue().isMinSignedValue())
2452 goto decline_post_inc;
2453 // Check for possible scaled-address reuse.
2454 if (isAddressUse(TTI, UI->getUser(), UI->getOperandValToReplace())) {
2455 MemAccessTy AccessTy = getAccessType(
2456 TTI, UI->getUser(), UI->getOperandValToReplace());
2457 int64_t Scale = C->getSExtValue();
2458 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2459 /*BaseOffset=*/0,
2460 /*HasBaseReg=*/false, Scale,
2461 AccessTy.AddrSpace))
2462 goto decline_post_inc;
2463 Scale = -Scale;
2464 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2465 /*BaseOffset=*/0,
2466 /*HasBaseReg=*/false, Scale,
2467 AccessTy.AddrSpace))
2468 goto decline_post_inc;
2469 }
2470 }
2471 }
2472
2473 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)
2474 << *Cond << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Change loop exiting icmp to use postinc iv: "
<< *Cond << '\n'; } } while (false)
;
2475
2476 // It's possible for the setcc instruction to be anywhere in the loop, and
2477 // possible for it to have multiple users. If it is not immediately before
2478 // the exiting block branch, move it.
2479 if (&*++BasicBlock::iterator(Cond) != TermBr) {
2480 if (Cond->hasOneUse()) {
2481 Cond->moveBefore(TermBr);
2482 } else {
2483 // Clone the terminating condition and insert into the loopend.
2484 ICmpInst *OldCond = Cond;
2485 Cond = cast<ICmpInst>(Cond->clone());
2486 Cond->setName(L->getHeader()->getName() + ".termcond");
2487 ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2488
2489 // Clone the IVUse, as the old use still exists!
2490 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2491 TermBr->replaceUsesOfWith(OldCond, Cond);
2492 }
2493 }
2494
2495 // If we get to here, we know that we can transform the setcc instruction to
2496 // use the post-incremented version of the IV, allowing us to coalesce the
2497 // live ranges for the IV correctly.
2498 CondUse->transformToPostInc(L);
2499 Changed = true;
2500
2501 PostIncs.insert(Cond);
2502 decline_post_inc:;
2503 }
2504
2505 // Determine an insertion point for the loop induction variable increment. It
2506 // must dominate all the post-inc comparisons we just set up, and it must
2507 // dominate the loop latch edge.
2508 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2509 for (Instruction *Inst : PostIncs) {
2510 BasicBlock *BB =
2511 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2512 Inst->getParent());
2513 if (BB == Inst->getParent())
2514 IVIncInsertPos = Inst;
2515 else if (BB != IVIncInsertPos->getParent())
2516 IVIncInsertPos = BB->getTerminator();
2517 }
2518}
2519
2520/// Determine if the given use can accommodate a fixup at the given offset and
2521/// other details. If so, update the use and return true.
2522bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2523 bool HasBaseReg, LSRUse::KindType Kind,
2524 MemAccessTy AccessTy) {
2525 int64_t NewMinOffset = LU.MinOffset;
2526 int64_t NewMaxOffset = LU.MaxOffset;
2527 MemAccessTy NewAccessTy = AccessTy;
2528
2529 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2530 // something conservative, however this can pessimize in the case that one of
2531 // the uses will have all its uses outside the loop, for example.
2532 if (LU.Kind != Kind)
2533 return false;
2534
2535 // Check for a mismatched access type, and fall back conservatively as needed.
2536 // TODO: Be less conservative when the type is similar and can use the same
2537 // addressing modes.
2538 if (Kind == LSRUse::Address) {
2539 if (AccessTy.MemTy != LU.AccessTy.MemTy) {
2540 NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(),
2541 AccessTy.AddrSpace);
2542 }
2543 }
2544
2545 // Conservatively assume HasBaseReg is true for now.
2546 if (NewOffset < LU.MinOffset) {
2547 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2548 LU.MaxOffset - NewOffset, HasBaseReg))
2549 return false;
2550 NewMinOffset = NewOffset;
2551 } else if (NewOffset > LU.MaxOffset) {
2552 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2553 NewOffset - LU.MinOffset, HasBaseReg))
2554 return false;
2555 NewMaxOffset = NewOffset;
2556 }
2557
2558 // Update the use.
2559 LU.MinOffset = NewMinOffset;
2560 LU.MaxOffset = NewMaxOffset;
2561 LU.AccessTy = NewAccessTy;
2562 return true;
2563}
2564
2565/// Return an LSRUse index and an offset value for a fixup which needs the given
2566/// expression, with the given kind and optional access type. Either reuse an
2567/// existing use or create a new one, as needed.
2568std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2569 LSRUse::KindType Kind,
2570 MemAccessTy AccessTy) {
2571 const SCEV *Copy = Expr;
2572 int64_t Offset = ExtractImmediate(Expr, SE);
2573
2574 // Basic uses can't accept any offset, for example.
2575 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2576 Offset, /*HasBaseReg=*/ true)) {
2577 Expr = Copy;
2578 Offset = 0;
2579 }
2580
2581 std::pair<UseMapTy::iterator, bool> P =
2582 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2583 if (!P.second) {
2584 // A use already existed with this base.
2585 size_t LUIdx = P.first->second;
2586 LSRUse &LU = Uses[LUIdx];
2587 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2588 // Reuse this use.
2589 return std::make_pair(LUIdx, Offset);
2590 }
2591
2592 // Create a new use.
2593 size_t LUIdx = Uses.size();
2594 P.first->second = LUIdx;
2595 Uses.push_back(LSRUse(Kind, AccessTy));
2596 LSRUse &LU = Uses[LUIdx];
2597
2598 LU.MinOffset = Offset;
2599 LU.MaxOffset = Offset;
2600 return std::make_pair(LUIdx, Offset);
2601}
2602
2603/// Delete the given use from the Uses list.
2604void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2605 if (&LU != &Uses.back())
2606 std::swap(LU, Uses.back());
2607 Uses.pop_back();
2608
2609 // Update RegUses.
2610 RegUses.swapAndDropUse(LUIdx, Uses.size());
2611}
2612
2613/// Look for a use distinct from OrigLU which is has a formula that has the same
2614/// registers as the given formula.
2615LSRUse *
2616LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2617 const LSRUse &OrigLU) {
2618 // Search all uses for the formula. This could be more clever.
2619 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2620 LSRUse &LU = Uses[LUIdx];
2621 // Check whether this use is close enough to OrigLU, to see whether it's
2622 // worthwhile looking through its formulae.
2623 // Ignore ICmpZero uses because they may contain formulae generated by
2624 // GenerateICmpZeroScales, in which case adding fixup offsets may
2625 // be invalid.
2626 if (&LU != &OrigLU &&
2627 LU.Kind != LSRUse::ICmpZero &&
2628 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2629 LU.WidestFixupType == OrigLU.WidestFixupType &&
2630 LU.HasFormulaWithSameRegs(OrigF)) {
2631 // Scan through this use's formulae.
2632 for (const Formula &F : LU.Formulae) {
2633 // Check to see if this formula has the same registers and symbols
2634 // as OrigF.
2635 if (F.BaseRegs == OrigF.BaseRegs &&
2636 F.ScaledReg == OrigF.ScaledReg &&
2637 F.BaseGV == OrigF.BaseGV &&
2638 F.Scale == OrigF.Scale &&
2639 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2640 if (F.BaseOffset == 0)
2641 return &LU;
2642 // This is the formula where all the registers and symbols matched;
2643 // there aren't going to be any others. Since we declined it, we
2644 // can skip the rest of the formulae and proceed to the next LSRUse.
2645 break;
2646 }
2647 }
2648 }
2649 }
2650
2651 // Nothing looked good.
2652 return nullptr;
2653}
2654
2655void LSRInstance::CollectInterestingTypesAndFactors() {
2656 SmallSetVector<const SCEV *, 4> Strides;
2657
2658 // Collect interesting types and strides.
2659 SmallVector<const SCEV *, 4> Worklist;
2660 for (const IVStrideUse &U : IU) {
2661 const SCEV *Expr = IU.getExpr(U);
2662
2663 // Collect interesting types.
2664 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2665
2666 // Add strides for mentioned loops.
2667 Worklist.push_back(Expr);
2668 do {
2669 const SCEV *S = Worklist.pop_back_val();
2670 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2671 if (AR->getLoop() == L)
2672 Strides.insert(AR->getStepRecurrence(SE));
2673 Worklist.push_back(AR->getStart());
2674 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2675 Worklist.append(Add->op_begin(), Add->op_end());
2676 }
2677 } while (!Worklist.empty());
2678 }
2679
2680 // Compute interesting factors from the set of interesting strides.
2681 for (SmallSetVector<const SCEV *, 4>::const_iterator
2682 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2683 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2684 std::next(I); NewStrideIter != E; ++NewStrideIter) {
2685 const SCEV *OldStride = *I;
2686 const SCEV *NewStride = *NewStrideIter;
2687
2688 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2689 SE.getTypeSizeInBits(NewStride->getType())) {
2690 if (SE.getTypeSizeInBits(OldStride->getType()) >
2691 SE.getTypeSizeInBits(NewStride->getType()))
2692 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2693 else
2694 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2695 }
2696 if (const SCEVConstant *Factor =
2697 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2698 SE, true))) {
2699 if (Factor->getAPInt().getMinSignedBits() <= 64)
2700 Factors.insert(Factor->getAPInt().getSExtValue());
2701 } else if (const SCEVConstant *Factor =
2702 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2703 NewStride,
2704 SE, true))) {
2705 if (Factor->getAPInt().getMinSignedBits() <= 64)
2706 Factors.insert(Factor->getAPInt().getSExtValue());
2707 }
2708 }
2709
2710 // If all uses use the same type, don't bother looking for truncation-based
2711 // reuse.
2712 if (Types.size() == 1)
2713 Types.clear();
2714
2715 LLVM_DEBUG(print_factors_and_types(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_factors_and_types(dbgs()); } } while
(false)
;
2716}
2717
2718/// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2719/// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2720/// IVStrideUses, we could partially skip this.
2721static User::op_iterator
2722findIVOperand(User::op_iterator OI, User::op_iterator OE,
2723 Loop *L, ScalarEvolution &SE) {
2724 for(; OI != OE; ++OI) {
2725 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2726 if (!SE.isSCEVable(Oper->getType()))
2727 continue;
2728
2729 if (const SCEVAddRecExpr *AR =
2730 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2731 if (AR->getLoop() == L)
2732 break;
2733 }
2734 }
2735 }
2736 return OI;
2737}
2738
2739/// IVChain logic must consistently peek base TruncInst operands, so wrap it in
2740/// a convenient helper.
2741static Value *getWideOperand(Value *Oper) {
2742 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2743 return Trunc->getOperand(0);
2744 return Oper;
2745}
2746
2747/// Return true if we allow an IV chain to include both types.
2748static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2749 Type *LType = LVal->getType();
2750 Type *RType = RVal->getType();
2751 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy() &&
2752 // Different address spaces means (possibly)
2753 // different types of the pointer implementation,
2754 // e.g. i16 vs i32 so disallow that.
2755 (LType->getPointerAddressSpace() ==
2756 RType->getPointerAddressSpace()));
2757}
2758
2759/// Return an approximation of this SCEV expression's "base", or NULL for any
2760/// constant. Returning the expression itself is conservative. Returning a
2761/// deeper subexpression is more precise and valid as long as it isn't less
2762/// complex than another subexpression. For expressions involving multiple
2763/// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2764/// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2765/// IVInc==b-a.
2766///
2767/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2768/// SCEVUnknown, we simply return the rightmost SCEV operand.
2769static const SCEV *getExprBase(const SCEV *S) {
2770 switch (S->getSCEVType()) {
2771 default: // uncluding scUnknown.
2772 return S;
2773 case scConstant:
2774 return nullptr;
2775 case scTruncate:
2776 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2777 case scZeroExtend:
2778 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2779 case scSignExtend:
2780 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2781 case scAddExpr: {
2782 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2783 // there's nothing more complex.
2784 // FIXME: not sure if we want to recognize negation.
2785 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2786 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2787 E(Add->op_begin()); I != E; ++I) {
2788 const SCEV *SubExpr = *I;
2789 if (SubExpr->getSCEVType() == scAddExpr)
2790 return getExprBase(SubExpr);
2791
2792 if (SubExpr->getSCEVType() != scMulExpr)
2793 return SubExpr;
2794 }
2795 return S; // all operands are scaled, be conservative.
2796 }
2797 case scAddRecExpr:
2798 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2799 }
2800 llvm_unreachable("Unknown SCEV kind!")::llvm::llvm_unreachable_internal("Unknown SCEV kind!", "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2800)
;
2801}
2802
2803/// Return true if the chain increment is profitable to expand into a loop
2804/// invariant value, which may require its own register. A profitable chain
2805/// increment will be an offset relative to the same base. We allow such offsets
2806/// to potentially be used as chain increment as long as it's not obviously
2807/// expensive to expand using real instructions.
2808bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2809 const SCEV *IncExpr,
2810 ScalarEvolution &SE) {
2811 // Aggressively form chains when -stress-ivchain.
2812 if (StressIVChain)
2813 return true;
2814
2815 // Do not replace a constant offset from IV head with a nonconstant IV
2816 // increment.
2817 if (!isa<SCEVConstant>(IncExpr)) {
2818 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2819 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2820 return false;
2821 }
2822
2823 SmallPtrSet<const SCEV*, 8> Processed;
2824 return !isHighCostExpansion(IncExpr, Processed, SE);
2825}
2826
2827/// Return true if the number of registers needed for the chain is estimated to
2828/// be less than the number required for the individual IV users. First prohibit
2829/// any IV users that keep the IV live across increments (the Users set should
2830/// be empty). Next count the number and type of increments in the chain.
2831///
2832/// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2833/// effectively use postinc addressing modes. Only consider it profitable it the
2834/// increments can be computed in fewer registers when chained.
2835///
2836/// TODO: Consider IVInc free if it's already used in another chains.
2837static bool isProfitableChain(IVChain &Chain,
2838 SmallPtrSetImpl<Instruction *> &Users,
2839 ScalarEvolution &SE,
2840 const TargetTransformInfo &TTI) {
2841 if (StressIVChain)
2842 return true;
2843
2844 if (!Chain.hasIncs())
2845 return false;
2846
2847 if (!Users.empty()) {
2848 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)
2849 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)
2850 : 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)
;
2851 return false;
2852 }
2853 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")((!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? static_cast<void> (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2853, __PRETTY_FUNCTION__))
;
2854
2855 // The chain itself may require a register, so intialize cost to 1.
2856 int cost = 1;
2857
2858 // A complete chain likely eliminates the need for keeping the original IV in
2859 // a register. LSR does not currently know how to form a complete chain unless
2860 // the header phi already exists.
2861 if (isa<PHINode>(Chain.tailUserInst())
2862 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2863 --cost;
2864 }
2865 const SCEV *LastIncExpr = nullptr;
2866 unsigned NumConstIncrements = 0;
2867 unsigned NumVarIncrements = 0;
2868 unsigned NumReusedIncrements = 0;
2869
2870 if (TTI.isProfitableLSRChainElement(Chain.Incs[0].UserInst))
2871 return true;
2872
2873 for (const IVInc &Inc : Chain) {
2874 if (TTI.isProfitableLSRChainElement(Inc.UserInst))
2875 return true;
2876 if (Inc.IncExpr->isZero())
2877 continue;
2878
2879 // Incrementing by zero or some constant is neutral. We assume constants can
2880 // be folded into an addressing mode or an add's immediate operand.
2881 if (isa<SCEVConstant>(Inc.IncExpr)) {
2882 ++NumConstIncrements;
2883 continue;
2884 }
2885
2886 if (Inc.IncExpr == LastIncExpr)
2887 ++NumReusedIncrements;
2888 else
2889 ++NumVarIncrements;
2890
2891 LastIncExpr = Inc.IncExpr;
2892 }
2893 // An IV chain with a single increment is handled by LSR's postinc
2894 // uses. However, a chain with multiple increments requires keeping the IV's
2895 // value live longer than it needs to be if chained.
2896 if (NumConstIncrements > 1)
2897 --cost;
2898
2899 // Materializing increment expressions in the preheader that didn't exist in
2900 // the original code may cost a register. For example, sign-extended array
2901 // indices can produce ridiculous increments like this:
2902 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2903 cost += NumVarIncrements;
2904
2905 // Reusing variable increments likely saves a register to hold the multiple of
2906 // the stride.
2907 cost -= NumReusedIncrements;
2908
2909 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)
2910 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " Cost: " << cost << "\n"
; } } while (false)
;
2911
2912 return cost < 0;
2913}
2914
2915/// Add this IV user to an existing chain or make it the head of a new chain.
2916void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2917 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2918 // When IVs are used as types of varying widths, they are generally converted
2919 // to a wider type with some uses remaining narrow under a (free) trunc.
2920 Value *const NextIV = getWideOperand(IVOper);
2921 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2922 const SCEV *const OperExprBase = getExprBase(OperExpr);
2923
2924 // Visit all existing chains. Check if its IVOper can be computed as a
2925 // profitable loop invariant increment from the last link in the Chain.
2926 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2927 const SCEV *LastIncExpr = nullptr;
2928 for (; ChainIdx < NChains; ++ChainIdx) {
2929 IVChain &Chain = IVChainVec[ChainIdx];
2930
2931 // Prune the solution space aggressively by checking that both IV operands
2932 // are expressions that operate on the same unscaled SCEVUnknown. This
2933 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2934 // first avoids creating extra SCEV expressions.
2935 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2936 continue;
2937
2938 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2939 if (!isCompatibleIVType(PrevIV, NextIV))
2940 continue;
2941
2942 // A phi node terminates a chain.
2943 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2944 continue;
2945
2946 // The increment must be loop-invariant so it can be kept in a register.
2947 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2948 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2949 if (!SE.isLoopInvariant(IncExpr, L))
2950 continue;
2951
2952 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2953 LastIncExpr = IncExpr;
2954 break;
2955 }
2956 }
2957 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2958 // bother for phi nodes, because they must be last in the chain.
2959 if (ChainIdx == NChains) {
2960 if (isa<PHINode>(UserInst))
2961 return;
2962 if (NChains >= MaxChains && !StressIVChain) {
2963 LLVM_DEBUG(dbgs() << "IV Chain Limit\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain Limit\n"; } } while
(false)
;
2964 return;
2965 }
2966 LastIncExpr = OperExpr;
2967 // IVUsers may have skipped over sign/zero extensions. We don't currently
2968 // attempt to form chains involving extensions unless they can be hoisted
2969 // into this loop's AddRec.
2970 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2971 return;
2972 ++NChains;
2973 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2974 OperExprBase));
2975 ChainUsersVec.resize(NChains);
2976 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)
2977 << ") IV=" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Head: (" << *UserInst << ") IV=" <<
*LastIncExpr << "\n"; } } while (false)
;
2978 } else {
2979 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)
2980 << ") IV+" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Inc: (" << *UserInst << ") IV+" <<
*LastIncExpr << "\n"; } } while (false)
;
2981 // Add this IV user to the end of the chain.
2982 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2983 }
2984 IVChain &Chain = IVChainVec[ChainIdx];
2985
2986 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2987 // This chain's NearUsers become FarUsers.
2988 if (!LastIncExpr->isZero()) {
2989 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2990 NearUsers.end());
2991 NearUsers.clear();
2992 }
2993
2994 // All other uses of IVOperand become near uses of the chain.
2995 // We currently ignore intermediate values within SCEV expressions, assuming
2996 // they will eventually be used be the current chain, or can be computed
2997 // from one of the chain increments. To be more precise we could
2998 // transitively follow its user and only add leaf IV users to the set.
2999 for (User *U : IVOper->users()) {
3000 Instruction *OtherUse = dyn_cast<Instruction>(U);
3001 if (!OtherUse)
3002 continue;
3003 // Uses in the chain will no longer be uses if the chain is formed.
3004 // Include the head of the chain in this iteration (not Chain.begin()).
3005 IVChain::const_iterator IncIter = Chain.Incs.begin();
3006 IVChain::const_iterator IncEnd = Chain.Incs.end();
3007 for( ; IncIter != IncEnd; ++IncIter) {
3008 if (IncIter->UserInst == OtherUse)
3009 break;
3010 }
3011 if (IncIter != IncEnd)
3012 continue;
3013
3014 if (SE.isSCEVable(OtherUse->getType())
3015 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
3016 && IU.isIVUserOrOperand(OtherUse)) {
3017 continue;
3018 }
3019 NearUsers.insert(OtherUse);
3020 }
3021
3022 // Since this user is part of the chain, it's no longer considered a use
3023 // of the chain.
3024 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
3025}
3026
3027/// Populate the vector of Chains.
3028///
3029/// This decreases ILP at the architecture level. Targets with ample registers,
3030/// multiple memory ports, and no register renaming probably don't want
3031/// this. However, such targets should probably disable LSR altogether.
3032///
3033/// The job of LSR is to make a reasonable choice of induction variables across
3034/// the loop. Subsequent passes can easily "unchain" computation exposing more
3035/// ILP *within the loop* if the target wants it.
3036///
3037/// Finding the best IV chain is potentially a scheduling problem. Since LSR
3038/// will not reorder memory operations, it will recognize this as a chain, but
3039/// will generate redundant IV increments. Ideally this would be corrected later
3040/// by a smart scheduler:
3041/// = A[i]
3042/// = A[i+x]
3043/// A[i] =
3044/// A[i+x] =
3045///
3046/// TODO: Walk the entire domtree within this loop, not just the path to the
3047/// loop latch. This will discover chains on side paths, but requires
3048/// maintaining multiple copies of the Chains state.
3049void LSRInstance::CollectChains() {
3050 LLVM_DEBUG(dbgs() << "Collecting IV Chains.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Collecting IV Chains.\n";
} } while (false)
;
3051 SmallVector<ChainUsers, 8> ChainUsersVec;
3052
3053 SmallVector<BasicBlock *,8> LatchPath;
3054 BasicBlock *LoopHeader = L->getHeader();
3055 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
3056 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
3057 LatchPath.push_back(Rung->getBlock());
3058 }
3059 LatchPath.push_back(LoopHeader);
3060
3061 // Walk the instruction stream from the loop header to the loop latch.
3062 for (BasicBlock *BB : reverse(LatchPath)) {
3063 for (Instruction &I : *BB) {
3064 // Skip instructions that weren't seen by IVUsers analysis.
3065 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
3066 continue;
3067
3068 // Ignore users that are part of a SCEV expression. This way we only
3069 // consider leaf IV Users. This effectively rediscovers a portion of
3070 // IVUsers analysis but in program order this time.
3071 if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
3072 continue;
3073
3074 // Remove this instruction from any NearUsers set it may be in.
3075 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
3076 ChainIdx < NChains; ++ChainIdx) {
3077 ChainUsersVec[ChainIdx].NearUsers.erase(&I);
3078 }
3079 // Search for operands that can be chained.
3080 SmallPtrSet<Instruction*, 4> UniqueOperands;
3081 User::op_iterator IVOpEnd = I.op_end();
3082 User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
3083 while (IVOpIter != IVOpEnd) {
3084 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
3085 if (UniqueOperands.insert(IVOpInst).second)
3086 ChainInstruction(&I, IVOpInst, ChainUsersVec);
3087 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3088 }
3089 } // Continue walking down the instructions.
3090 } // Continue walking down the domtree.
3091 // Visit phi backedges to determine if the chain can generate the IV postinc.
3092 for (PHINode &PN : L->getHeader()->phis()) {
3093 if (!SE.isSCEVable(PN.getType()))
3094 continue;
3095
3096 Instruction *IncV =
3097 dyn_cast<Instruction>(PN.getIncomingValueForBlock(L->getLoopLatch()));
3098 if (IncV)
3099 ChainInstruction(&PN, IncV, ChainUsersVec);
3100 }
3101 // Remove any unprofitable chains.
3102 unsigned ChainIdx = 0;
3103 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
3104 UsersIdx < NChains; ++UsersIdx) {
3105 if (!isProfitableChain(IVChainVec[UsersIdx],
3106 ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
3107 continue;
3108 // Preserve the chain at UsesIdx.
3109 if (ChainIdx != UsersIdx)
3110 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
3111 FinalizeChain(IVChainVec[ChainIdx]);
3112 ++ChainIdx;
3113 }
3114 IVChainVec.resize(ChainIdx);
3115}
3116
3117void LSRInstance::FinalizeChain(IVChain &Chain) {
3118 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")((!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? static_cast<void> (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3118, __PRETTY_FUNCTION__))
;
3119 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)
;
3120
3121 for (const IVInc &Inc : Chain) {
3122 LLVM_DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Inc: " << *
Inc.UserInst << "\n"; } } while (false)
;
3123 auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
3124 assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand")((UseI != Inc.UserInst->op_end() && "cannot find IV operand"
) ? static_cast<void> (0) : __assert_fail ("UseI != Inc.UserInst->op_end() && \"cannot find IV operand\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3124, __PRETTY_FUNCTION__))
;
3125 IVIncSet.insert(UseI);
3126 }
3127}
3128
3129/// Return true if the IVInc can be folded into an addressing mode.
3130static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
3131 Value *Operand, const TargetTransformInfo &TTI) {
3132 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
3133 if (!IncConst || !isAddressUse(TTI, UserInst, Operand))
3134 return false;
3135
3136 if (IncConst->getAPInt().getMinSignedBits() > 64)
3137 return false;
3138
3139 MemAccessTy AccessTy = getAccessType(TTI, UserInst, Operand);
3140 int64_t IncOffset = IncConst->getValue()->getSExtValue();
3141 if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
3142 IncOffset, /*HasBaseReg=*/false))
3143 return false;
3144
3145 return true;
3146}
3147
3148/// Generate an add or subtract for each IVInc in a chain to materialize the IV
3149/// user's operand from the previous IV user's operand.
3150void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
3151 SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
3152 // Find the new IVOperand for the head of the chain. It may have been replaced
3153 // by LSR.
3154 const IVInc &Head = Chain.Incs[0];
3155 User::op_iterator IVOpEnd = Head.UserInst->op_end();
3156 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
3157 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
3158 IVOpEnd, L, SE);
3159 Value *IVSrc = nullptr;
3160 while (IVOpIter != IVOpEnd) {
3161 IVSrc = getWideOperand(*IVOpIter);
3162
3163 // If this operand computes the expression that the chain needs, we may use
3164 // it. (Check this after setting IVSrc which is used below.)
3165 //
3166 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
3167 // narrow for the chain, so we can no longer use it. We do allow using a
3168 // wider phi, assuming the LSR checked for free truncation. In that case we
3169 // should already have a truncate on this operand such that
3170 // getSCEV(IVSrc) == IncExpr.
3171 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
3172 || SE.getSCEV(IVSrc) == Head.IncExpr) {
3173 break;
3174 }
3175 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3176 }
3177 if (IVOpIter == IVOpEnd) {
3178 // Gracefully give up on this chain.
3179 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)
;
3180 return;
3181 }
3182 assert(IVSrc && "Failed to find IV chain source")((IVSrc && "Failed to find IV chain source") ? static_cast
<void> (0) : __assert_fail ("IVSrc && \"Failed to find IV chain source\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3182, __PRETTY_FUNCTION__))
;
3183
3184 LLVM_DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generate chain at: " <<
*IVSrc << "\n"; } } while (false)
;
3185 Type *IVTy = IVSrc->getType();
3186 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
3187 const SCEV *LeftOverExpr = nullptr;
3188 for (const IVInc &Inc : Chain) {
3189 Instruction *InsertPt = Inc.UserInst;
3190 if (isa<PHINode>(InsertPt))
3191 InsertPt = L->getLoopLatch()->getTerminator();
3192
3193 // IVOper will replace the current IV User's operand. IVSrc is the IV
3194 // value currently held in a register.
3195 Value *IVOper = IVSrc;
3196 if (!Inc.IncExpr->isZero()) {
3197 // IncExpr was the result of subtraction of two narrow values, so must
3198 // be signed.
3199 const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
3200 LeftOverExpr = LeftOverExpr ?
3201 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
3202 }
3203 if (LeftOverExpr && !LeftOverExpr->isZero()) {
3204 // Expand the IV increment.
3205 Rewriter.clearPostInc();
3206 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
3207 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
3208 SE.getUnknown(IncV));
3209 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
3210
3211 // If an IV increment can't be folded, use it as the next IV value.
3212 if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
3213 assert(IVTy == IVOper->getType() && "inconsistent IV increment type")((IVTy == IVOper->getType() && "inconsistent IV increment type"
) ? static_cast<void> (0) : __assert_fail ("IVTy == IVOper->getType() && \"inconsistent IV increment type\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3213, __PRETTY_FUNCTION__))
;
3214 IVSrc = IVOper;
3215 LeftOverExpr = nullptr;
3216 }
3217 }
3218 Type *OperTy = Inc.IVOperand->getType();
3219 if (IVTy != OperTy) {
3220 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&((SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy
) && "cannot extend a chained IV") ? static_cast<void
> (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3221, __PRETTY_FUNCTION__))
3221 "cannot extend a chained IV")((SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy
) && "cannot extend a chained IV") ? static_cast<void
> (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3221, __PRETTY_FUNCTION__))
;
3222 IRBuilder<> Builder(InsertPt);
3223 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
3224 }
3225 Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
3226 if (auto *OperandIsInstr = dyn_cast<Instruction>(Inc.IVOperand))
3227 DeadInsts.emplace_back(OperandIsInstr);
3228 }
3229 // If LSR created a new, wider phi, we may also replace its postinc. We only
3230 // do this if we also found a wide value for the head of the chain.
3231 if (isa<PHINode>(Chain.tailUserInst())) {
3232 for (PHINode &Phi : L->getHeader()->phis()) {
3233 if (!isCompatibleIVType(&Phi, IVSrc))
3234 continue;
3235 Instruction *PostIncV = dyn_cast<Instruction>(
3236 Phi.getIncomingValueForBlock(L->getLoopLatch()));
3237 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
3238 continue;
3239 Value *IVOper = IVSrc;
3240 Type *PostIncTy = PostIncV->getType();
3241 if (IVTy != PostIncTy) {
3242 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types")((PostIncTy->isPointerTy() && "mixing int/ptr IV types"
) ? static_cast<void> (0) : __assert_fail ("PostIncTy->isPointerTy() && \"mixing int/ptr IV types\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3242, __PRETTY_FUNCTION__))
;
3243 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
3244 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
3245 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
3246 }
3247 Phi.replaceUsesOfWith(PostIncV, IVOper);
3248 DeadInsts.emplace_back(PostIncV);
3249 }
3250 }
3251}
3252
3253void LSRInstance::CollectFixupsAndInitialFormulae() {
3254 BranchInst *ExitBranch = nullptr;
3255 bool SaveCmp = TTI.canSaveCmp(L, &ExitBranch, &SE, &LI, &DT, &AC, &TLI);
3256
3257 for (const IVStrideUse &U : IU) {
3258 Instruction *UserInst = U.getUser();
3259 // Skip IV users that are part of profitable IV Chains.
3260 User::op_iterator UseI =
3261 find(UserInst->operands(), U.getOperandValToReplace());
3262 assert(UseI != UserInst->op_end() && "cannot find IV operand")((UseI != UserInst->op_end() && "cannot find IV operand"
) ? static_cast<void> (0) : __assert_fail ("UseI != UserInst->op_end() && \"cannot find IV operand\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3262, __PRETTY_FUNCTION__))
;
3263 if (IVIncSet.count(UseI)) {
3264 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)
;
3265 continue;
3266 }
3267
3268 LSRUse::KindType Kind = LSRUse::Basic;
3269 MemAccessTy AccessTy;
3270 if (isAddressUse(TTI, UserInst, U.getOperandValToReplace())) {
3271 Kind = LSRUse::Address;
3272 AccessTy = getAccessType(TTI, UserInst, U.getOperandValToReplace());
3273 }
3274
3275 const SCEV *S = IU.getExpr(U);
3276 PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3277
3278 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3279 // (N - i == 0), and this allows (N - i) to be the expression that we work
3280 // with rather than just N or i, so we can consider the register
3281 // requirements for both N and i at the same time. Limiting this code to
3282 // equality icmps is not a problem because all interesting loops use
3283 // equality icmps, thanks to IndVarSimplify.
3284 if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst)) {
3285 // If CI can be saved in some target, like replaced inside hardware loop
3286 // in PowerPC, no need to generate initial formulae for it.
3287 if (SaveCmp && CI == dyn_cast<ICmpInst>(ExitBranch->getCondition()))
3288 continue;
3289 if (CI->isEquality()) {
3290 // Swap the operands if needed to put the OperandValToReplace on the
3291 // left, for consistency.
3292 Value *NV = CI->getOperand(1);
3293 if (NV == U.getOperandValToReplace()) {
3294 CI->setOperand(1, CI->getOperand(0));
3295 CI->setOperand(0, NV);
3296 NV = CI->getOperand(1);
3297 Changed = true;
3298 }
3299
3300 // x == y --> x - y == 0
3301 const SCEV *N = SE.getSCEV(NV);
3302 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3303 // S is normalized, so normalize N before folding it into S
3304 // to keep the result normalized.
3305 N = normalizeForPostIncUse(N, TmpPostIncLoops, SE);
3306 Kind = LSRUse::ICmpZero;
3307 S = SE.getMinusSCEV(N, S);
3308 }
3309
3310 // -1 and the negations of all interesting strides (except the negation
3311 // of -1) are now also interesting.
3312 for (size_t i = 0, e = Factors.size(); i != e; ++i)
3313 if (Factors[i] != -1)
3314 Factors.insert(-(uint64_t)Factors[i]);
3315 Factors.insert(-1);
3316 }
3317 }
3318
3319 // Get or create an LSRUse.
3320 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3321 size_t LUIdx = P.first;
3322 int64_t Offset = P.second;
3323 LSRUse &LU = Uses[LUIdx];
3324
3325 // Record the fixup.
3326 LSRFixup &LF = LU.getNewFixup();
3327 LF.UserInst = UserInst;
3328 LF.OperandValToReplace = U.getOperandValToReplace();
3329 LF.PostIncLoops = TmpPostIncLoops;
3330 LF.Offset = Offset;
3331 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3332
3333 if (!LU.WidestFixupType ||
3334 SE.getTypeSizeInBits(LU.WidestFixupType) <
3335 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3336 LU.WidestFixupType = LF.OperandValToReplace->getType();
3337
3338 // If this is the first use of this LSRUse, give it a formula.
3339 if (LU.Formulae.empty()) {
3340 InsertInitialFormula(S, LU, LUIdx);
3341 CountRegisters(LU.Formulae.back(), LUIdx);
3342 }
3343 }
3344
3345 LLVM_DEBUG(print_fixups(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_fixups(dbgs()); } } while (false)
;
3346}
3347
3348/// Insert a formula for the given expression into the given use, separating out
3349/// loop-variant portions from loop-invariant and loop-computable portions.
3350void
3351LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3352 // Mark uses whose expressions cannot be expanded.
3353 if (!isSafeToExpand(S, SE))
3354 LU.RigidFormula = true;
3355
3356 Formula F;
3357 F.initialMatch(S, L, SE);
3358 bool Inserted = InsertFormula(LU, LUIdx, F);
3359 assert(Inserted && "Initial formula already exists!")((Inserted && "Initial formula already exists!") ? static_cast
<void> (0) : __assert_fail ("Inserted && \"Initial formula already exists!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3359, __PRETTY_FUNCTION__))
; (void)Inserted;
3360}
3361
3362/// Insert a simple single-register formula for the given expression into the
3363/// given use.
3364void
3365LSRInstance::InsertSupplementalFormula(const SCEV *S,
3366 LSRUse &LU, size_t LUIdx) {
3367 Formula F;
3368 F.BaseRegs.push_back(S);
3369 F.HasBaseReg = true;
3370 bool Inserted = InsertFormula(LU, LUIdx, F);
3371 assert(Inserted && "Supplemental formula already exists!")((Inserted && "Supplemental formula already exists!")
? static_cast<void> (0) : __assert_fail ("Inserted && \"Supplemental formula already exists!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3371, __PRETTY_FUNCTION__))
; (void)Inserted;
3372}
3373
3374/// Note which registers are used by the given formula, updating RegUses.
3375void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3376 if (F.ScaledReg)
3377 RegUses.countRegister(F.ScaledReg, LUIdx);
3378 for (const SCEV *BaseReg : F.BaseRegs)
3379 RegUses.countRegister(BaseReg, LUIdx);
3380}
3381
3382/// If the given formula has not yet been inserted, add it to the list, and
3383/// return true. Return false otherwise.
3384bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3385 // Do not insert formula that we will not be able to expand.
3386 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Formula is illegal") ? static_cast<void>
(0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3387, __PRETTY_FUNCTION__))
3387 "Formula is illegal")((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Formula is illegal") ? static_cast<void>
(0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3387, __PRETTY_FUNCTION__))
;
3388
3389 if (!LU.InsertFormula(F, *L))
3390 return false;
3391
3392 CountRegisters(F, LUIdx);
3393 return true;
3394}
3395
3396/// Check for other uses of loop-invariant values which we're tracking. These
3397/// other uses will pin these values in registers, making them less profitable
3398/// for elimination.
3399/// TODO: This currently misses non-constant addrec step registers.
3400/// TODO: Should this give more weight to users inside the loop?
3401void
3402LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3403 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3404 SmallPtrSet<const SCEV *, 32> Visited;
3405
3406 while (!Worklist.empty()) {
3407 const SCEV *S = Worklist.pop_back_val();
3408
3409 // Don't process the same SCEV twice
3410 if (!Visited.insert(S).second)
3411 continue;
3412
3413 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3414 Worklist.append(N->op_begin(), N->op_end());
3415 else if (const SCEVIntegralCastExpr *C = dyn_cast<SCEVIntegralCastExpr>(S))
3416 Worklist.push_back(C->getOperand());
3417 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3418 Worklist.push_back(D->getLHS());
3419 Worklist.push_back(D->getRHS());
3420 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3421 const Value *V = US->getValue();
3422 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3423 // Look for instructions defined outside the loop.
3424 if (L->contains(Inst)) continue;
3425 } else if (isa<UndefValue>(V))
3426 // Undef doesn't have a live range, so it doesn't matter.
3427 continue;
3428 for (const Use &U : V->uses()) {
3429 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3430 // Ignore non-instructions.
3431 if (!UserInst)
3432 continue;
3433 // Don't bother if the instruction is an EHPad.
3434 if (UserInst->isEHPad())
3435 continue;
3436 // Ignore instructions in other functions (as can happen with
3437 // Constants).
3438 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3439 continue;
3440 // Ignore instructions not dominated by the loop.
3441 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3442 UserInst->getParent() :
3443 cast<PHINode>(UserInst)->getIncomingBlock(
3444 PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3445 if (!DT.dominates(L->getHeader(), UseBB))
3446 continue;
3447 // Don't bother if the instruction is in a BB which ends in an EHPad.
3448 if (UseBB->getTerminator()->isEHPad())
3449 continue;
3450 // Don't bother rewriting PHIs in catchswitch blocks.
3451 if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator()))
3452 continue;
3453 // Ignore uses which are part of other SCEV expressions, to avoid
3454 // analyzing them multiple times.
3455 if (SE.isSCEVable(UserInst->getType())) {
3456 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3457 // If the user is a no-op, look through to its uses.
3458 if (!isa<SCEVUnknown>(UserS))
3459 continue;
3460 if (UserS == US) {
3461 Worklist.push_back(
3462 SE.getUnknown(const_cast<Instruction *>(UserInst)));
3463 continue;
3464 }
3465 }
3466 // Ignore icmp instructions which are already being analyzed.
3467 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3468 unsigned OtherIdx = !U.getOperandNo();
3469 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3470 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3471 continue;
3472 }
3473
3474 std::pair<size_t, int64_t> P = getUse(
3475 S, LSRUse::Basic, MemAccessTy());
3476 size_t LUIdx = P.first;
3477 int64_t Offset = P.second;
3478 LSRUse &LU = Uses[LUIdx];
3479 LSRFixup &LF = LU.getNewFixup();
3480 LF.UserInst = const_cast<Instruction *>(UserInst);
3481 LF.OperandValToReplace = U;
3482 LF.Offset = Offset;
3483 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3484 if (!LU.WidestFixupType ||
3485 SE.getTypeSizeInBits(LU.WidestFixupType) <
3486 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3487 LU.WidestFixupType = LF.OperandValToReplace->getType();
3488 InsertSupplementalFormula(US, LU, LUIdx);
3489 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3490 break;
3491 }
3492 }
3493 }
3494}
3495
3496/// Split S into subexpressions which can be pulled out into separate
3497/// registers. If C is non-null, multiply each subexpression by C.
3498///
3499/// Return remainder expression after factoring the subexpressions captured by
3500/// Ops. If Ops is complete, return NULL.
3501static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3502 SmallVectorImpl<const SCEV *> &Ops,
3503 const Loop *L,
3504 ScalarEvolution &SE,
3505 unsigned Depth = 0) {
3506 // Arbitrarily cap recursion to protect compile time.
3507 if (Depth >= 3)
3508 return S;
3509
3510 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3511 // Break out add operands.
3512 for (const SCEV *S : Add->operands()) {
3513 const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3514 if (Remainder)
3515 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3516 }
3517 return nullptr;
3518 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3519 // Split a non-zero base out of an addrec.
3520 if (AR->getStart()->isZero() || !AR->isAffine())
3521 return S;
3522
3523 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3524 C, Ops, L, SE, Depth+1);
3525 // Split the non-zero AddRec unless it is part of a nested recurrence that
3526 // does not pertain to this loop.
3527 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3528 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3529 Remainder = nullptr;
3530 }
3531 if (Remainder != AR->getStart()) {
3532 if (!Remainder)
3533 Remainder = SE.getConstant(AR->getType(), 0);
3534 return SE.getAddRecExpr(Remainder,
3535 AR->getStepRecurrence(SE),
3536 AR->getLoop(),
3537 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3538 SCEV::FlagAnyWrap);
3539 }
3540 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3541 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3542 if (Mul->getNumOperands() != 2)
3543 return S;
3544 if (const SCEVConstant *Op0 =
3545 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3546 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3547 const SCEV *Remainder =
3548 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3549 if (Remainder)
3550 Ops.push_back(SE.getMulExpr(C, Remainder));
3551 return nullptr;
3552 }
3553 }
3554 return S;
3555}
3556
3557/// Return true if the SCEV represents a value that may end up as a
3558/// post-increment operation.
3559static bool mayUsePostIncMode(const TargetTransformInfo &TTI,
3560 LSRUse &LU, const SCEV *S, const Loop *L,
3561 ScalarEvolution &SE) {
3562 if (LU.Kind != LSRUse::Address ||
3563 !LU.AccessTy.getType()->isIntOrIntVectorTy())
3564 return false;
3565 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S);
3566 if (!AR)
3567 return false;
3568 const SCEV *LoopStep = AR->getStepRecurrence(SE);
3569 if (!isa<SCEVConstant>(LoopStep))
3570 return false;
3571 // Check if a post-indexed load/store can be used.
3572 if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) ||
3573 TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) {
3574 const SCEV *LoopStart = AR->getStart();
3575 if (!isa<SCEVConstant>(LoopStart) && SE.isLoopInvariant(LoopStart, L))
3576 return true;
3577 }
3578 return false;
3579}
3580
3581/// Helper function for LSRInstance::GenerateReassociations.
3582void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3583 const Formula &Base,
3584 unsigned Depth, size_t Idx,
3585 bool IsScaledReg) {
3586 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3587 // Don't generate reassociations for the base register of a value that
3588 // may generate a post-increment operator. The reason is that the
3589 // reassociations cause extra base+register formula to be created,
3590 // and possibly chosen, but the post-increment is more efficient.
3591 if (AMK == TTI::AMK_PostIndexed && mayUsePostIncMode(TTI, LU, BaseReg, L, SE))
3592 return;
3593 SmallVector<const SCEV *, 8> AddOps;
3594 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3595 if (Remainder)
3596 AddOps.push_back(Remainder);
3597
3598 if (AddOps.size() == 1)
3599 return;
3600
3601 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3602 JE = AddOps.end();
3603 J != JE; ++J) {
3604 // Loop-variant "unknown" values are uninteresting; we won't be able to
3605 // do anything meaningful with them.
3606 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3607 continue;
3608
3609 // Don't pull a constant into a register if the constant could be folded
3610 // into an immediate field.
3611 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3612 LU.AccessTy, *J, Base.getNumRegs() > 1))
3613 continue;
3614
3615 // Collect all operands except *J.
3616 SmallVector<const SCEV *, 8> InnerAddOps(
3617 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3618 InnerAddOps.append(std::next(J),
3619 ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3620
3621 // Don't leave just a constant behind in a register if the constant could
3622 // be folded into an immediate field.
3623 if (InnerAddOps.size() == 1 &&
3624 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3625 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3626 continue;
3627
3628 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3629 if (InnerSum->isZero())
3630 continue;
3631 Formula F = Base;
3632
3633 // Add the remaining pieces of the add back into the new formula.
3634 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3635 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3636 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3637 InnerSumSC->getValue()->getZExtValue())) {
3638 F.UnfoldedOffset =
3639 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3640 if (IsScaledReg)
3641 F.ScaledReg = nullptr;
3642 else
3643 F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3644 } else if (IsScaledReg)
3645 F.ScaledReg = InnerSum;
3646 else
3647 F.BaseRegs[Idx] = InnerSum;
3648
3649 // Add J as its own register, or an unfolded immediate.
3650 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3651 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3652 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3653 SC->getValue()->getZExtValue()))
3654 F.UnfoldedOffset =
3655 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3656 else
3657 F.BaseRegs.push_back(*J);
3658 // We may have changed the number of register in base regs, adjust the
3659 // formula accordingly.
3660 F.canonicalize(*L);
3661
3662 if (InsertFormula(LU, LUIdx, F))
3663 // If that formula hadn't been seen before, recurse to find more like
3664 // it.
3665 // Add check on Log16(AddOps.size()) - same as Log2_32(AddOps.size()) >> 2)
3666 // Because just Depth is not enough to bound compile time.
3667 // This means that every time AddOps.size() is greater 16^x we will add
3668 // x to Depth.
3669 GenerateReassociations(LU, LUIdx, LU.Formulae.back(),
3670 Depth + 1 + (Log2_32(AddOps.size()) >> 2));
3671 }
3672}
3673
3674/// Split out subexpressions from adds and the bases of addrecs.
3675void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3676 Formula Base, unsigned Depth) {
3677 assert(Base.isCanonical(*L) && "Input must be in the canonical form")((Base.isCanonical(*L) && "Input must be in the canonical form"
) ? static_cast<void> (0) : __assert_fail ("Base.isCanonical(*L) && \"Input must be in the canonical form\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3677, __PRETTY_FUNCTION__))
;
3678 // Arbitrarily cap recursion to protect compile time.
3679 if (Depth >= 3)
3680 return;
3681
3682 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3683 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3684
3685 if (Base.Scale == 1)
3686 GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3687 /* Idx */ -1, /* IsScaledReg */ true);
3688}
3689
3690/// Generate a formula consisting of all of the loop-dominating registers added
3691/// into a single register.
3692void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3693 Formula Base) {
3694 // This method is only interesting on a plurality of registers.
3695 if (Base.BaseRegs.size() + (Base.Scale == 1) +
3696 (Base.UnfoldedOffset != 0) <= 1)
3697 return;
3698
3699 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3700 // processing the formula.
3701 Base.unscale();
3702 SmallVector<const SCEV *, 4> Ops;
3703 Formula NewBase = Base;
3704 NewBase.BaseRegs.clear();
3705 Type *CombinedIntegerType = nullptr;
3706 for (const SCEV *BaseReg : Base.BaseRegs) {
3707 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3708 !SE.hasComputableLoopEvolution(BaseReg, L)) {
3709 if (!CombinedIntegerType)
3710 CombinedIntegerType = SE.getEffectiveSCEVType(BaseReg->getType());
3711 Ops.push_back(BaseReg);
3712 }
3713 else
3714 NewBase.BaseRegs.push_back(BaseReg);
3715 }
3716
3717 // If no register is relevant, we're done.
3718 if (Ops.size() == 0)
3719 return;
3720
3721 // Utility function for generating the required variants of the combined
3722 // registers.
3723 auto GenerateFormula = [&](const SCEV *Sum) {
3724 Formula F = NewBase;
3725
3726 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3727 // opportunity to fold something. For now, just ignore such cases
3728 // rather than proceed with zero in a register.
3729 if (Sum->isZero())
3730 return;
3731
3732 F.BaseRegs.push_back(Sum);
3733 F.canonicalize(*L);
3734 (void)InsertFormula(LU, LUIdx, F);
3735 };
3736
3737 // If we collected at least two registers, generate a formula combining them.
3738 if (Ops.size() > 1) {
3739 SmallVector<const SCEV *, 4> OpsCopy(Ops); // Don't let SE modify Ops.
3740 GenerateFormula(SE.getAddExpr(OpsCopy));
3741 }
3742
3743 // If we have an unfolded offset, generate a formula combining it with the
3744 // registers collected.
3745 if (NewBase.UnfoldedOffset) {
3746 assert(CombinedIntegerType && "Missing a type for the unfolded offset")((CombinedIntegerType && "Missing a type for the unfolded offset"
) ? static_cast<void> (0) : __assert_fail ("CombinedIntegerType && \"Missing a type for the unfolded offset\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3746, __PRETTY_FUNCTION__))
;
3747 Ops.push_back(SE.getConstant(CombinedIntegerType, NewBase.UnfoldedOffset,
3748 true));
3749 NewBase.UnfoldedOffset = 0;
3750 GenerateFormula(SE.getAddExpr(Ops));
3751 }
3752}
3753
3754/// Helper function for LSRInstance::GenerateSymbolicOffsets.
3755void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3756 const Formula &Base, size_t Idx,
3757 bool IsScaledReg) {
3758 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3759 GlobalValue *GV = ExtractSymbol(G, SE);
3760 if (G->isZero() || !GV)
3761 return;
3762 Formula F = Base;
3763 F.BaseGV = GV;
3764 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3765 return;
3766 if (IsScaledReg)
3767 F.ScaledReg = G;
3768 else
3769 F.BaseRegs[Idx] = G;
3770 (void)InsertFormula(LU, LUIdx, F);
3771}
3772
3773/// Generate reuse formulae using symbolic offsets.
3774void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3775 Formula Base) {
3776 // We can't add a symbolic offset if the address already contains one.
3777 if (Base.BaseGV) return;
3778
3779 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3780 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3781 if (Base.Scale == 1)
3782 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3783 /* IsScaledReg */ true);
3784}
3785
3786/// Helper function for LSRInstance::GenerateConstantOffsets.
3787void LSRInstance::GenerateConstantOffsetsImpl(
3788 LSRUse &LU, unsigned LUIdx, const Formula &Base,
3789 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3790
3791 auto GenerateOffset = [&](const SCEV *G, int64_t Offset) {
3792 Formula F = Base;
3793 F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3794
3795 if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind,
3796 LU.AccessTy, F)) {
3797 // Add the offset to the base register.
3798 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3799 // If it cancelled out, drop the base register, otherwise update it.
3800 if (NewG->isZero()) {
3801 if (IsScaledReg) {
3802 F.Scale = 0;
3803 F.ScaledReg = nullptr;
3804 } else
3805 F.deleteBaseReg(F.BaseRegs[Idx]);
3806 F.canonicalize(*L);
3807 } else if (IsScaledReg)
3808 F.ScaledReg = NewG;
3809 else
3810 F.BaseRegs[Idx] = NewG;
3811
3812 (void)InsertFormula(LU, LUIdx, F);
3813 }
3814 };
3815
3816 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3817
3818 // With constant offsets and constant steps, we can generate pre-inc
3819 // accesses by having the offset equal the step. So, for access #0 with a
3820 // step of 8, we generate a G - 8 base which would require the first access
3821 // to be ((G - 8) + 8),+,8. The pre-indexed access then updates the pointer
3822 // for itself and hopefully becomes the base for other accesses. This means
3823 // means that a single pre-indexed access can be generated to become the new
3824 // base pointer for each iteration of the loop, resulting in no extra add/sub
3825 // instructions for pointer updating.
3826 if (AMK == TTI::AMK_PreIndexed && LU.Kind == LSRUse::Address) {
3827 if (auto *GAR = dyn_cast<SCEVAddRecExpr>(G)) {
3828 if (auto *StepRec =
3829 dyn_cast<SCEVConstant>(GAR->getStepRecurrence(SE))) {
3830 const APInt &StepInt = StepRec->getAPInt();
3831 int64_t Step = StepInt.isNegative() ?
3832 StepInt.getSExtValue() : StepInt.getZExtValue();
3833
3834 for (int64_t Offset : Worklist) {
3835 Offset -= Step;
3836 GenerateOffset(G, Offset);
3837 }
3838 }
3839 }
3840 }
3841 for (int64_t Offset : Worklist)
3842 GenerateOffset(G, Offset);
3843
3844 int64_t Imm = ExtractImmediate(G, SE);
3845 if (G->isZero() || Imm == 0)
3846 return;
3847 Formula F = Base;
3848 F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3849 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3850 return;
3851 if (IsScaledReg) {
3852 F.ScaledReg = G;
3853 } else {
3854 F.BaseRegs[Idx] = G;
3855 // We may generate non canonical Formula if G is a recurrent expr reg
3856 // related with current loop while F.ScaledReg is not.
3857 F.canonicalize(*L);
3858 }
3859 (void)InsertFormula(LU, LUIdx, F);
3860}
3861
3862/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3863void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3864 Formula Base) {
3865 // TODO: For now, just add the min and max offset, because it usually isn't
3866 // worthwhile looking at everything inbetween.
3867 SmallVector<int64_t, 2> Worklist;
3868 Worklist.push_back(LU.MinOffset);
3869 if (LU.MaxOffset != LU.MinOffset)
3870 Worklist.push_back(LU.MaxOffset);
3871
3872 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3873 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3874 if (Base.Scale == 1)
3875 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3876 /* IsScaledReg */ true);
3877}
3878
3879/// For ICmpZero, check to see if we can scale up the comparison. For example, x
3880/// == y -> x*c == y*c.
3881void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3882 Formula Base) {
3883 if (LU.Kind != LSRUse::ICmpZero) return;
3884
3885 // Determine the integer type for the base formula.
3886 Type *IntTy = Base.getType();
3887 if (!IntTy) return;
3888 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3889
3890 // Don't do this if there is more than one offset.
3891 if (LU.MinOffset != LU.MaxOffset) return;
3892
3893 // Check if transformation is valid. It is illegal to multiply pointer.
3894 if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
3895 return;
3896 for (const SCEV *BaseReg : Base.BaseRegs)
3897 if (BaseReg->getType()->isPointerTy())
3898 return;
3899 assert(!Base.BaseGV && "ICmpZero use is not legal!")((!Base.BaseGV && "ICmpZero use is not legal!") ? static_cast
<void> (0) : __assert_fail ("!Base.BaseGV && \"ICmpZero use is not legal!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3899, __PRETTY_FUNCTION__))
;
3900
3901 // Check each interesting stride.
3902 for (int64_t Factor : Factors) {
3903 // Check that the multiplication doesn't overflow.
3904 if (Base.BaseOffset == std::numeric_limits<int64_t>::min() && Factor == -1)
3905 continue;
3906 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3907 if (NewBaseOffset / Factor != Base.BaseOffset)
3908 continue;
3909 // If the offset will be truncated at this use, check that it is in bounds.
3910 if (!IntTy->isPointerTy() &&
3911 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3912 continue;
3913
3914 // Check that multiplying with the use offset doesn't overflow.
3915 int64_t Offset = LU.MinOffset;
3916 if (Offset == std::numeric_limits<int64_t>::min() && Factor == -1)
3917 continue;
3918 Offset = (uint64_t)Offset * Factor;
3919 if (Offset / Factor != LU.MinOffset)
3920 continue;
3921 // If the offset will be truncated at this use, check that it is in bounds.
3922 if (!IntTy->isPointerTy() &&
3923 !ConstantInt::isValueValidForType(IntTy, Offset))
3924 continue;
3925
3926 Formula F = Base;
3927 F.BaseOffset = NewBaseOffset;
3928
3929 // Check that this scale is legal.
3930 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3931 continue;
3932
3933 // Compensate for the use having MinOffset built into it.
3934 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3935
3936 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3937
3938 // Check that multiplying with each base register doesn't overflow.
3939 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3940 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3941 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3942 goto next;
3943 }
3944
3945 // Check that multiplying with the scaled register doesn't overflow.
3946 if (F.ScaledReg) {
3947 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3948 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3949 continue;
3950 }
3951
3952 // Check that multiplying with the unfolded offset doesn't overflow.
3953 if (F.UnfoldedOffset != 0) {
3954 if (F.UnfoldedOffset == std::numeric_limits<int64_t>::min() &&
3955 Factor == -1)
3956 continue;
3957 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3958 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3959 continue;
3960 // If the offset will be truncated, check that it is in bounds.
3961 if (!IntTy->isPointerTy() &&
3962 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3963 continue;
3964 }
3965
3966 // If we make it here and it's legal, add it.
3967 (void)InsertFormula(LU, LUIdx, F);
3968 next:;
3969 }
3970}
3971
3972/// Generate stride factor reuse formulae by making use of scaled-offset address
3973/// modes, for example.
3974void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3975 // Determine the integer type for the base formula.
3976 Type *IntTy = Base.getType();
3977 if (!IntTy) return;
3978
3979 // If this Formula already has a scaled register, we can't add another one.
3980 // Try to unscale the formula to generate a better scale.
3981 if (Base.Scale != 0 && !Base.unscale())
3982 return;
3983
3984 assert(Base.Scale == 0 && "unscale did not did its job!")((Base.Scale == 0 && "unscale did not did its job!") ?
static_cast<void> (0) : __assert_fail ("Base.Scale == 0 && \"unscale did not did its job!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3984, __PRETTY_FUNCTION__))
;
3985
3986 // Check each interesting stride.
3987 for (int64_t Factor : Factors) {
3988 Base.Scale = Factor;
3989 Base.HasBaseReg = Base.BaseRegs.size() > 1;
3990 // Check whether this scale is going to be legal.
3991 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3992 Base)) {
3993 // As a special-case, handle special out-of-loop Basic users specially.
3994 // TODO: Reconsider this special case.
3995 if (LU.Kind == LSRUse::Basic &&
3996 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3997 LU.AccessTy, Base) &&
3998 LU.AllFixupsOutsideLoop)
3999 LU.Kind = LSRUse::Special;
4000 else
4001 continue;
4002 }
4003 // For an ICmpZero, negating a solitary base register won't lead to
4004 // new solutions.
4005 if (LU.Kind == LSRUse::ICmpZero &&
4006 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
4007 continue;
4008 // For each addrec base reg, if its loop is current loop, apply the scale.
4009 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
4010 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]);
4011 if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) {
4012 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
4013 if (FactorS->isZero())
4014 continue;
4015 // Divide out the factor, ignoring high bits, since we'll be
4016 // scaling the value back up in the end.
4017 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
4018 // TODO: This could be optimized to avoid all the copying.
4019 Formula F = Base;
4020 F.ScaledReg = Quotient;
4021 F.deleteBaseReg(F.BaseRegs[i]);
4022 // The canonical representation of 1*reg is reg, which is already in
4023 // Base. In that case, do not try to insert the formula, it will be
4024 // rejected anyway.
4025 if (F.Scale == 1 && (F.BaseRegs.empty() ||
4026 (AR->getLoop() != L && LU.AllFixupsOutsideLoop)))
4027 continue;
4028 // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate
4029 // non canonical Formula with ScaledReg's loop not being L.
4030 if (F.Scale == 1 && LU.AllFixupsOutsideLoop)
4031 F.canonicalize(*L);
4032 (void)InsertFormula(LU, LUIdx, F);
4033 }
4034 }
4035 }
4036 }
4037}
4038
4039/// Generate reuse formulae from different IV types.
4040void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
4041 // Don't bother truncating symbolic values.
4042 if (Base.BaseGV) return;
4043
4044 // Determine the integer type for the base formula.
4045 Type *DstTy = Base.getType();
4046 if (!DstTy) return;
4047 DstTy = SE.getEffectiveSCEVType(DstTy);
4048
4049 for (Type *SrcTy : Types) {
4050 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
4051 Formula F = Base;
4052
4053 // Sometimes SCEV is able to prove zero during ext transform. It may
4054 // happen if SCEV did not do all possible transforms while creating the
4055 // initial node (maybe due to depth limitations), but it can do them while
4056 // taking ext.
4057 if (F.ScaledReg) {
4058 const SCEV *NewScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
4059 if (NewScaledReg->isZero())
4060 continue;
4061 F.ScaledReg = NewScaledReg;
4062 }
4063 bool HasZeroBaseReg = false;
4064 for (const SCEV *&BaseReg : F.BaseRegs) {
4065 const SCEV *NewBaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
4066 if (NewBaseReg->isZero()) {
4067 HasZeroBaseReg = true;
4068 break;
4069 }
4070 BaseReg = NewBaseReg;
4071 }
4072 if (HasZeroBaseReg)
4073 continue;
4074
4075 // TODO: This assumes we've done basic processing on all uses and
4076 // have an idea what the register usage is.
4077 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
4078 continue;
4079
4080 F.canonicalize(*L);
4081 (void)InsertFormula(LU, LUIdx, F);
4082 }
4083 }
4084}
4085
4086namespace {
4087
4088/// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
4089/// modifications so that the search phase doesn't have to worry about the data
4090/// structures moving underneath it.
4091struct WorkItem {
4092 size_t LUIdx;
4093 int64_t Imm;
4094 const SCEV *OrigReg;
4095
4096 WorkItem(size_t LI, int64_t I, const SCEV *R)
4097 : LUIdx(LI), Imm(I), OrigReg(R) {}
4098
4099 void print(raw_ostream &OS) const;
4100 void dump() const;
4101};
4102
4103} // end anonymous namespace
4104
4105#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
4106void WorkItem::print(raw_ostream &OS) const {
4107 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
4108 << " , add offset " << Imm;
4109}
4110
4111LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void WorkItem::dump() const {
4112 print(errs()); errs() << '\n';
4113}
4114#endif
4115
4116/// Look for registers which are a constant distance apart and try to form reuse
4117/// opportunities between them.
4118void LSRInstance::GenerateCrossUseConstantOffsets() {
4119 // Group the registers by their value without any added constant offset.
4120 using ImmMapTy = std::map<int64_t, const SCEV *>;
4121
4122 DenseMap<const SCEV *, ImmMapTy> Map;
4123 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
4124 SmallVector<const SCEV *, 8> Sequence;
4125 for (const SCEV *Use : RegUses) {
4126 const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
4127 int64_t Imm = ExtractImmediate(Reg, SE);
4128 auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
4129 if (Pair.second)
4130 Sequence.push_back(Reg);
4131 Pair.first->second.insert(std::make_pair(Imm, Use));
4132 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
4133 }
4134
4135 // Now examine each set of registers with the same base value. Build up
4136 // a list of work to do and do the work in a separate step so that we're
4137 // not adding formulae and register counts while we're searching.
4138 SmallVector<WorkItem, 32> WorkItems;
4139 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
4140 for (const SCEV *Reg : Sequence) {
4141 const ImmMapTy &Imms = Map.find(Reg)->second;
4142
4143 // It's not worthwhile looking for reuse if there's only one offset.
4144 if (Imms.size() == 1)
4145 continue;
4146
4147 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)
4148 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)
4149 : 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)
4150 << ' ' << 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)
4151 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)
;
4152
4153 // Examine each offset.
4154 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
4155 J != JE; ++J) {
4156 const SCEV *OrigReg = J->second;
4157
4158 int64_t JImm = J->first;
4159 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
4160
4161 if (!isa<SCEVConstant>(OrigReg) &&
4162 UsedByIndicesMap[Reg].count() == 1) {
4163 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)
4164 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Skipping cross-use reuse for "
<< *OrigReg << '\n'; } } while (false)
;
4165 continue;
4166 }
4167
4168 // Conservatively examine offsets between this orig reg a few selected
4169 // other orig regs.
4170 int64_t First = Imms.begin()->first;
4171 int64_t Last = std::prev(Imms.end())->first;
4172 // Compute (First + Last) / 2 without overflow using the fact that
4173 // First + Last = 2 * (First + Last) + (First ^ Last).
4174 int64_t Avg = (First & Last) + ((First ^ Last) >> 1);
4175 // If the result is negative and First is odd and Last even (or vice versa),
4176 // we rounded towards -inf. Add 1 in that case, to round towards 0.
4177 Avg = Avg + ((First ^ Last) & ((uint64_t)Avg >> 63));
4178 ImmMapTy::const_iterator OtherImms[] = {
4179 Imms.begin(), std::prev(Imms.end()),
4180 Imms.lower_bound(Avg)};
4181 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
4182 ImmMapTy::const_iterator M = OtherImms[i];
4183 if (M == J || M == JE) continue;
4184
4185 // Compute the difference between the two.
4186 int64_t Imm = (uint64_t)JImm - M->first;
4187 for (unsigned LUIdx : UsedByIndices.set_bits())
4188 // Make a memo of this use, offset, and register tuple.
4189 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
4190 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
4191 }
4192 }
4193 }
4194
4195 Map.clear();
4196 Sequence.clear();
4197 UsedByIndicesMap.clear();
4198 UniqueItems.clear();
4199
4200 // Now iterate through the worklist and add new formulae.
4201 for (const WorkItem &WI : WorkItems) {
4202 size_t LUIdx = WI.LUIdx;
4203 LSRUse &LU = Uses[LUIdx];
4204 int64_t Imm = WI.Imm;
4205 const SCEV *OrigReg = WI.OrigReg;
4206
4207 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
4208 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
4209 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
4210
4211 // TODO: Use a more targeted data structure.
4212 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
4213 Formula F = LU.Formulae[L];
4214 // FIXME: The code for the scaled and unscaled registers looks
4215 // very similar but slightly different. Investigate if they
4216 // could be merged. That way, we would not have to unscale the
4217 // Formula.
4218 F.unscale();
4219 // Use the immediate in the scaled register.
4220 if (F.ScaledReg == OrigReg) {
4221 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
4222 // Don't create 50 + reg(-50).
4223 if (F.referencesReg(SE.getSCEV(
4224 ConstantInt::get(IntTy, -(uint64_t)Offset))))
4225 continue;
4226 Formula NewF = F;
4227 NewF.BaseOffset = Offset;
4228 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4229 NewF))
4230 continue;
4231 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
4232
4233 // If the new scale is a constant in a register, and adding the constant
4234 // value to the immediate would produce a value closer to zero than the
4235 // immediate itself, then the formula isn't worthwhile.
4236 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
4237 if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
4238 (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
4239 .ule(std::abs(NewF.BaseOffset)))
4240 continue;
4241
4242 // OK, looks good.
4243 NewF.canonicalize(*this->L);
4244 (void)InsertFormula(LU, LUIdx, NewF);
4245 } else {
4246 // Use the immediate in a base register.
4247 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
4248 const SCEV *BaseReg = F.BaseRegs[N];
4249 if (BaseReg != OrigReg)
4250 continue;
4251 Formula NewF = F;
4252 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
4253 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
4254 LU.Kind, LU.AccessTy, NewF)) {
4255 if (AMK == TTI::AMK_PostIndexed &&
4256 mayUsePostIncMode(TTI, LU, OrigReg, this->L, SE))
4257 continue;
4258 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
4259 continue;
4260 NewF = F;
4261 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
4262 }
4263 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
4264
4265 // If the new formula has a constant in a register, and adding the
4266 // constant value to the immediate would produce a value closer to
4267 // zero than the immediate itself, then the formula isn't worthwhile.
4268 for (const SCEV *NewReg : NewF.BaseRegs)
4269 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
4270 if ((C->getAPInt() + NewF.BaseOffset)
4271 .abs()
4272 .slt(std::abs(NewF.BaseOffset)) &&
4273 (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
4274 countTrailingZeros<uint64_t>(NewF.BaseOffset))
4275 goto skip_formula;
4276
4277 // Ok, looks good.
4278 NewF.canonicalize(*this->L);
4279 (void)InsertFormula(LU, LUIdx, NewF);
4280 break;
4281 skip_formula:;
4282 }
4283 }
4284 }
4285 }
4286}
4287
4288/// Generate formulae for each use.
4289void
4290LSRInstance::GenerateAllReuseFormulae() {
4291 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
4292 // queries are more precise.
4293 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4294 LSRUse &LU = Uses[LUIdx];
4295 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4296 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
4297 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4298 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
4299 }
4300 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4301 LSRUse &LU = Uses[LUIdx];
4302 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4303 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
4304 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4305 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
4306 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4307 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
4308 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4309 GenerateScales(LU, LUIdx, LU.Formulae[i]);
4310 }
4311 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4312 LSRUse &LU = Uses[LUIdx];
4313 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4314 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
4315 }
4316
4317 GenerateCrossUseConstantOffsets();
4318
4319 LLVM_DEBUG(dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
4320 "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)
4321 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
;
4322}
4323
4324/// If there are multiple formulae with the same set of registers used
4325/// by other uses, pick the best one and delete the others.
4326void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
4327 DenseSet<const SCEV *> VisitedRegs;
4328 SmallPtrSet<const SCEV *, 16> Regs;
4329 SmallPtrSet<const SCEV *, 16> LoserRegs;
4330#ifndef NDEBUG
4331 bool ChangedFormulae = false;
4332#endif
4333
4334 // Collect the best formula for each unique set of shared registers. This
4335 // is reset for each use.
4336 using BestFormulaeTy =
4337 DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>;
4338
4339 BestFormulaeTy BestFormulae;
4340
4341 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4342 LSRUse &LU = Uses[LUIdx];
4343 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)
4344 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4345
4346 bool Any = false;
4347 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
4348 FIdx != NumForms; ++FIdx) {
4349 Formula &F = LU.Formulae[FIdx];
4350
4351 // Some formulas are instant losers. For example, they may depend on
4352 // nonexistent AddRecs from other loops. These need to be filtered
4353 // immediately, otherwise heuristics could choose them over others leading
4354 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
4355 // avoids the need to recompute this information across formulae using the
4356 // same bad AddRec. Passing LoserRegs is also essential unless we remove
4357 // the corresponding bad register from the Regs set.
4358 Cost CostF(L, SE, TTI, AMK);
4359 Regs.clear();
4360 CostF.RateFormula(F, Regs, VisitedRegs, LU, &LoserRegs);
4361 if (CostF.isLoser()) {
4362 // During initial formula generation, undesirable formulae are generated
4363 // by uses within other loops that have some non-trivial address mode or
4364 // use the postinc form of the IV. LSR needs to provide these formulae
4365 // as the basis of rediscovering the desired formula that uses an AddRec
4366 // corresponding to the existing phi. Once all formulae have been
4367 // generated, these initial losers may be pruned.
4368 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)
4369 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering loser "; F.print
(dbgs()); dbgs() << "\n"; } } while (false)
;
4370 }
4371 else {
4372 SmallVector<const SCEV *, 4> Key;
4373 for (const SCEV *Reg : F.BaseRegs) {
4374 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
4375 Key.push_back(Reg);
4376 }
4377 if (F.ScaledReg &&
4378 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
4379 Key.push_back(F.ScaledReg);
4380 // Unstable sort by host order ok, because this is only used for
4381 // uniquifying.
4382 llvm::sort(Key);
4383
4384 std::pair<BestFormulaeTy::const_iterator, bool> P =
4385 BestFormulae.insert(std::make_pair(Key, FIdx));
4386 if (P.second)
4387 continue;
4388
4389 Formula &Best = LU.Formulae[P.first->second];
4390
4391 Cost CostBest(L, SE, TTI, AMK);
4392 Regs.clear();
4393 CostBest.RateFormula(Best, Regs, VisitedRegs, LU);
4394 if (CostF.isLess(CostBest))
4395 std::swap(F, Best);
4396 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)
4397 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)
4398 " 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)
4399 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)
;
4400 }
4401#ifndef NDEBUG
4402 ChangedFormulae = true;
4403#endif
4404 LU.DeleteFormula(F);
4405 --FIdx;
4406 --NumForms;
4407 Any = true;
4408 }
4409
4410 // Now that we've filtered out some formulae, recompute the Regs set.
4411 if (Any)
4412 LU.RecomputeRegs(LUIdx, RegUses);
4413
4414 // Reset this to prepare for the next use.
4415 BestFormulae.clear();
4416 }
4417
4418 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)
4419 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)
4420 "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)
4421 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)
4422 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4423}
4424
4425/// Estimate the worst-case number of solutions the solver might have to
4426/// consider. It almost never considers this many solutions because it prune the
4427/// search space, but the pruning isn't always sufficient.
4428size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4429 size_t Power = 1;
4430 for (const LSRUse &LU : Uses) {
4431 size_t FSize = LU.Formulae.size();
4432 if (FSize >= ComplexityLimit) {
4433 Power = ComplexityLimit;
4434 break;
4435 }
4436 Power *= FSize;
4437 if (Power >= ComplexityLimit)
4438 break;
4439 }
4440 return Power;
4441}
4442
4443/// When one formula uses a superset of the registers of another formula, it
4444/// won't help reduce register pressure (though it may not necessarily hurt
4445/// register pressure); remove it to simplify the system.
4446void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4447 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4448 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)
;
4449
4450 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)
4451 "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)
4452 "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)
;
4453
4454 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4455 LSRUse &LU = Uses[LUIdx];
4456 bool Any = false;
4457 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4458 Formula &F = LU.Formulae[i];
4459 // Look for a formula with a constant or GV in a register. If the use
4460 // also has a formula with that same value in an immediate field,
4461 // delete the one that uses a register.
4462 for (SmallVectorImpl<const SCEV *>::const_iterator
4463 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4464 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4465 Formula NewF = F;
4466 //FIXME: Formulas should store bitwidth to do wrapping properly.
4467 // See PR41034.
4468 NewF.BaseOffset += (uint64_t)C->getValue()->getSExtValue();
4469 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4470 (I - F.BaseRegs.begin()));
4471 if (LU.HasFormulaWithSameRegs(NewF)) {
4472 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4473 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4474 LU.DeleteFormula(F);
4475 --i;
4476 --e;
4477 Any = true;
4478 break;
4479 }
4480 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4481 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4482 if (!F.BaseGV) {
4483 Formula NewF = F;
4484 NewF.BaseGV = GV;
4485 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4486 (I - F.BaseRegs.begin()));
4487 if (LU.HasFormulaWithSameRegs(NewF)) {
4488 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4489 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4490 LU.DeleteFormula(F);
4491 --i;
4492 --e;
4493 Any = true;
4494 break;
4495 }
4496 }
4497 }
4498 }
4499 }
4500 if (Any)
4501 LU.RecomputeRegs(LUIdx, RegUses);
4502 }
4503
4504 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)
;
4505 }
4506}
4507
4508/// When there are many registers for expressions like A, A+1, A+2, etc.,
4509/// allocate a single register for them.
4510void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4511 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4512 return;
4513
4514 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)
4515 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)
4516 "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)
4517 "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)
;
4518
4519 // This is especially useful for unrolled loops.
4520
4521 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4522 LSRUse &LU = Uses[LUIdx];
4523 for (const Formula &F : LU.Formulae) {
4524 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4525 continue;
4526
4527 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4528 if (!LUThatHas)
4529 continue;
4530
4531 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4532 LU.Kind, LU.AccessTy))
4533 continue;
4534
4535 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)
;
4536
4537 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4538
4539 // Transfer the fixups of LU to LUThatHas.
4540 for (LSRFixup &Fixup : LU.Fixups) {
4541 Fixup.Offset += F.BaseOffset;
4542 LUThatHas->pushFixup(Fixup);
4543 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)
;
4544 }
4545
4546 // Delete formulae from the new use which are no longer legal.
4547 bool Any = false;
4548 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4549 Formula &F = LUThatHas->Formulae[i];
4550 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4551 LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4552 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)
;
4553 LUThatHas->DeleteFormula(F);
4554 --i;
4555 --e;
4556 Any = true;
4557 }
4558 }
4559
4560 if (Any)
4561 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4562
4563 // Delete the old use.
4564 DeleteUse(LU, LUIdx);
4565 --LUIdx;
4566 --NumUses;
4567 break;
4568 }
4569 }
4570
4571 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)
;
4572}
4573
4574/// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4575/// we've done more filtering, as it may be able to find more formulae to
4576/// eliminate.
4577void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4578 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4579 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)
;
4580
4581 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)
4582 "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)
;
4583
4584 FilterOutUndesirableDedicatedRegisters();
4585
4586 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)
;
4587 }
4588}
4589
4590/// If a LSRUse has multiple formulae with the same ScaledReg and Scale.
4591/// Pick the best one and delete the others.
4592/// This narrowing heuristic is to keep as many formulae with different
4593/// Scale and ScaledReg pair as possible while narrowing the search space.
4594/// The benefit is that it is more likely to find out a better solution
4595/// from a formulae set with more Scale and ScaledReg variations than
4596/// a formulae set with the same Scale and ScaledReg. The picking winner
4597/// reg heuristic will often keep the formulae with the same Scale and
4598/// ScaledReg and filter others, and we want to avoid that if possible.
4599void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() {
4600 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4601 return;
4602
4603 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)
4604 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)
4605 "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)
4606 "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)
;
4607
4608 // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse.
4609 using BestFormulaeTy = DenseMap<std::pair<const SCEV *, int64_t>, size_t>;
4610
4611 BestFormulaeTy BestFormulae;
4612#ifndef NDEBUG
4613 bool ChangedFormulae = false;
4614#endif
4615 DenseSet<const SCEV *> VisitedRegs;
4616 SmallPtrSet<const SCEV *, 16> Regs;
4617
4618 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4619 LSRUse &LU = Uses[LUIdx];
4620 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)
4621 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4622
4623 // Return true if Formula FA is better than Formula FB.
4624 auto IsBetterThan = [&](Formula &FA, Formula &FB) {
4625 // First we will try to choose the Formula with fewer new registers.
4626 // For a register used by current Formula, the more the register is
4627 // shared among LSRUses, the less we increase the register number
4628 // counter of the formula.
4629 size_t FARegNum = 0;
4630 for (const SCEV *Reg : FA.BaseRegs) {
4631 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4632 FARegNum += (NumUses - UsedByIndices.count() + 1);
4633 }
4634 size_t FBRegNum = 0;
4635 for (const SCEV *Reg : FB.BaseRegs) {
4636 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4637 FBRegNum += (NumUses - UsedByIndices.count() + 1);
4638 }
4639 if (FARegNum != FBRegNum)
4640 return FARegNum < FBRegNum;
4641
4642 // If the new register numbers are the same, choose the Formula with
4643 // less Cost.
4644 Cost CostFA(L, SE, TTI, AMK);
4645 Cost CostFB(L, SE, TTI, AMK);
4646 Regs.clear();
4647 CostFA.RateFormula(FA, Regs, VisitedRegs, LU);
4648 Regs.clear();
4649 CostFB.RateFormula(FB, Regs, VisitedRegs, LU);
4650 return CostFA.isLess(CostFB);
4651 };
4652
4653 bool Any = false;
4654 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4655 ++FIdx) {
4656 Formula &F = LU.Formulae[FIdx];
4657 if (!F.ScaledReg)
4658 continue;
4659 auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx});
4660 if (P.second)
4661 continue;
4662
4663 Formula &Best = LU.Formulae[P.first->second];
4664 if (IsBetterThan(F, Best))
4665 std::swap(F, Best);
4666 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)
4667 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)
4668 " 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)
4669 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)
;
4670#ifndef NDEBUG
4671 ChangedFormulae = true;
4672#endif
4673 LU.DeleteFormula(F);
4674 --FIdx;
4675 --NumForms;
4676 Any = true;
4677 }
4678 if (Any)
4679 LU.RecomputeRegs(LUIdx, RegUses);
4680
4681 // Reset this to prepare for the next use.
4682 BestFormulae.clear();
4683 }
4684
4685 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)
4686 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)
4687 "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)
4688 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)
4689 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4690}
4691
4692/// If we are over the complexity limit, filter out any post-inc prefering
4693/// variables to only post-inc values.
4694void LSRInstance::NarrowSearchSpaceByFilterPostInc() {
4695 if (AMK != TTI::AMK_PostIndexed)
4696 return;
4697 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4698 return;
4699
4700 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)
4701 "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)
4702 "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)
;
4703
4704 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4705 LSRUse &LU = Uses[LUIdx];
4706
4707 if (LU.Kind != LSRUse::Address)
4708 continue;
4709 if (!TTI.isIndexedLoadLegal(TTI.MIM_PostInc, LU.AccessTy.getType()) &&
4710 !TTI.isIndexedStoreLegal(TTI.MIM_PostInc, LU.AccessTy.getType()))
4711 continue;
4712
4713 size_t MinRegs = std::numeric_limits<size_t>::max();
4714 for (const Formula &F : LU.Formulae)
4715 MinRegs = std::min(F.getNumRegs(), MinRegs);
4716
4717 bool Any = false;
4718 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4719 ++FIdx) {
4720 Formula &F = LU.Formulae[FIdx];
4721 if (F.getNumRegs() > MinRegs) {
4722 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)
4723 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n"; } } while (false)
;
4724 LU.DeleteFormula(F);
4725 --FIdx;
4726 --NumForms;
4727 Any = true;
4728 }
4729 }
4730 if (Any)
4731 LU.RecomputeRegs(LUIdx, RegUses);
4732
4733 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4734 break;
4735 }
4736
4737 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)
;
4738}
4739
4740/// The function delete formulas with high registers number expectation.
4741/// Assuming we don't know the value of each formula (already delete
4742/// all inefficient), generate probability of not selecting for each
4743/// register.
4744/// For example,
4745/// Use1:
4746/// reg(a) + reg({0,+,1})
4747/// reg(a) + reg({-1,+,1}) + 1
4748/// reg({a,+,1})
4749/// Use2:
4750/// reg(b) + reg({0,+,1})
4751/// reg(b) + reg({-1,+,1}) + 1
4752/// reg({b,+,1})
4753/// Use3:
4754/// reg(c) + reg(b) + reg({0,+,1})
4755/// reg(c) + reg({b,+,1})
4756///
4757/// Probability of not selecting
4758/// Use1 Use2 Use3
4759/// reg(a) (1/3) * 1 * 1
4760/// reg(b) 1 * (1/3) * (1/2)
4761/// reg({0,+,1}) (2/3) * (2/3) * (1/2)
4762/// reg({-1,+,1}) (2/3) * (2/3) * 1
4763/// reg({a,+,1}) (2/3) * 1 * 1
4764/// reg({b,+,1}) 1 * (2/3) * (2/3)
4765/// reg(c) 1 * 1 * 0
4766///
4767/// Now count registers number mathematical expectation for each formula:
4768/// Note that for each use we exclude probability if not selecting for the use.
4769/// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding
4770/// probabilty 1/3 of not selecting for Use1).
4771/// Use1:
4772/// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted
4773/// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted
4774/// reg({a,+,1}) 1
4775/// Use2:
4776/// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted
4777/// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted
4778/// reg({b,+,1}) 2/3
4779/// Use3:
4780/// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted
4781/// reg(c) + reg({b,+,1}) 1 + 2/3
4782void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() {
4783 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4784 return;
4785 // Ok, we have too many of formulae on our hands to conveniently handle.
4786 // Use a rough heuristic to thin out the list.
4787
4788 // Set of Regs wich will be 100% used in final solution.
4789 // Used in each formula of a solution (in example above this is reg(c)).
4790 // We can skip them in calculations.
4791 SmallPtrSet<const SCEV *, 4> UniqRegs;
4792 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)
;
4793
4794 // Map each register to probability of not selecting
4795 DenseMap <const SCEV *, float> RegNumMap;
4796 for (const SCEV *Reg : RegUses) {
4797 if (UniqRegs.count(Reg))
4798 continue;
4799 float PNotSel = 1;
4800 for (const LSRUse &LU : Uses) {
4801 if (!LU.Regs.count(Reg))
4802 continue;
4803 float P = LU.getNotSelectedProbability(Reg);
4804 if (P != 0.0)
4805 PNotSel *= P;
4806 else
4807 UniqRegs.insert(Reg);
4808 }
4809 RegNumMap.insert(std::make_pair(Reg, PNotSel));
4810 }
4811
4812 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by deleting costly formulas\n"
; } } while (false)
4813 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)
;
4814
4815 // Delete formulas where registers number expectation is high.
4816 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4817 LSRUse &LU = Uses[LUIdx];
4818 // If nothing to delete - continue.
4819 if (LU.Formulae.size() < 2)
4820 continue;
4821 // This is temporary solution to test performance. Float should be
4822 // replaced with round independent type (based on integers) to avoid
4823 // different results for different target builds.
4824 float FMinRegNum = LU.Formulae[0].getNumRegs();
4825 float FMinARegNum = LU.Formulae[0].getNumRegs();
4826 size_t MinIdx = 0;
4827 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4828 Formula &F = LU.Formulae[i];
4829 float FRegNum = 0;
4830 float FARegNum = 0;
4831 for (const SCEV *BaseReg : F.BaseRegs) {
4832 if (UniqRegs.count(BaseReg))
4833 continue;
4834 FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4835 if (isa<SCEVAddRecExpr>(BaseReg))
4836 FARegNum +=
4837 RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4838 }
4839 if (const SCEV *ScaledReg = F.ScaledReg) {
4840 if (!UniqRegs.count(ScaledReg)) {
4841 FRegNum +=
4842 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4843 if (isa<SCEVAddRecExpr>(ScaledReg))
4844 FARegNum +=
4845 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4846 }
4847 }
4848 if (FMinRegNum > FRegNum ||
4849 (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) {
4850 FMinRegNum = FRegNum;
4851 FMinARegNum = FARegNum;
4852 MinIdx = i;
4853 }
4854 }
4855 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)
4856 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)
;
4857 if (MinIdx != 0)
4858 std::swap(LU.Formulae[MinIdx], LU.Formulae[0]);
4859 while (LU.Formulae.size() != 1) {
4860 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
)
4861 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; LU.Formulae
.back().print(dbgs()); dbgs() << '\n'; } } while (false
)
;
4862 LU.Formulae.pop_back();
4863 }
4864 LU.RecomputeRegs(LUIdx, RegUses);
4865 assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula")((LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula"
) ? static_cast<void> (0) : __assert_fail ("LU.Formulae.size() == 1 && \"Should be exactly 1 min regs formula\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4865, __PRETTY_FUNCTION__))
;
4866 Formula &F = LU.Formulae[0];
4867 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)
;
4868 // When we choose the formula, the regs become unique.
4869 UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
4870 if (F.ScaledReg)
4871 UniqRegs.insert(F.ScaledReg);
4872 }
4873 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)
;
4874}
4875
4876/// Pick a register which seems likely to be profitable, and then in any use
4877/// which has any reference to that register, delete all formulae which do not
4878/// reference that register.
4879void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4880 // With all other options exhausted, loop until the system is simple
4881 // enough to handle.
4882 SmallPtrSet<const SCEV *, 4> Taken;
4883 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4884 // Ok, we have too many of formulae on our hands to conveniently handle.
4885 // Use a rough heuristic to thin out the list.
4886 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)
;
4887
4888 // Pick the register which is used by the most LSRUses, which is likely
4889 // to be a good reuse register candidate.
4890 const SCEV *Best = nullptr;
4891 unsigned BestNum = 0;
4892 for (const SCEV *Reg : RegUses) {
4893 if (Taken.count(Reg))
4894 continue;
4895 if (!Best) {
4896 Best = Reg;
4897 BestNum = RegUses.getUsedByIndices(Reg).count();
4898 } else {
4899 unsigned Count = RegUses.getUsedByIndices(Reg).count();
4900 if (Count > BestNum) {
4901 Best = Reg;
4902 BestNum = Count;
4903 }
4904 }
4905 }
4906 assert(Best && "Failed to find best LSRUse candidate")((Best && "Failed to find best LSRUse candidate") ? static_cast
<void> (0) : __assert_fail ("Best && \"Failed to find best LSRUse candidate\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4906, __PRETTY_FUNCTION__))
;
4907
4908 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)
4909 << " 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)
;
4910 Taken.insert(Best);
4911
4912 // In any use with formulae which references this register, delete formulae
4913 // which don't reference it.
4914 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4915 LSRUse &LU = Uses[LUIdx];
4916 if (!LU.Regs.count(Best)) continue;
4917
4918 bool Any = false;
4919 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4920 Formula &F = LU.Formulae[i];
4921 if (!F.referencesReg(Best)) {
4922 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)
;
4923 LU.DeleteFormula(F);
4924 --e;
4925 --i;
4926 Any = true;
4927 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?")((e != 0 && "Use has no formulae left! Is Regs inconsistent?"
) ? static_cast<void> (0) : __assert_fail ("e != 0 && \"Use has no formulae left! Is Regs inconsistent?\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4927, __PRETTY_FUNCTION__))
;
4928 continue;
4929 }
4930 }
4931
4932 if (Any)
4933 LU.RecomputeRegs(LUIdx, RegUses);
4934 }
4935
4936 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)
;
4937 }
4938}
4939
4940/// If there are an extraordinary number of formulae to choose from, use some
4941/// rough heuristics to prune down the number of formulae. This keeps the main
4942/// solver from taking an extraordinary amount of time in some worst-case
4943/// scenarios.
4944void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4945 NarrowSearchSpaceByDetectingSupersets();
4946 NarrowSearchSpaceByCollapsingUnrolledCode();
4947 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4948 if (FilterSameScaledReg)
4949 NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
4950 NarrowSearchSpaceByFilterPostInc();
4951 if (LSRExpNarrow)
4952 NarrowSearchSpaceByDeletingCostlyFormulas();
4953 else
4954 NarrowSearchSpaceByPickingWinnerRegs();
4955}
4956
4957/// This is the recursive solver.
4958void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4959 Cost &SolutionCost,
4960 SmallVectorImpl<const Formula *> &Workspace,
4961 const Cost &CurCost,
4962 const SmallPtrSet<const SCEV *, 16> &CurRegs,
4963 DenseSet<const SCEV *> &VisitedRegs) const {
4964 // Some ideas:
4965 // - prune more:
4966 // - use more aggressive filtering
4967 // - sort the formula so that the most profitable solutions are found first
4968 // - sort the uses too
4969 // - search faster:
4970 // - don't compute a cost, and then compare. compare while computing a cost
4971 // and bail early.
4972 // - track register sets with SmallBitVector
4973
4974 const LSRUse &LU = Uses[Workspace.size()];
4975
4976 // If this use references any register that's already a part of the
4977 // in-progress solution, consider it a requirement that a formula must
4978 // reference that register in order to be considered. This prunes out
4979 // unprofitable searching.
4980 SmallSetVector<const SCEV *, 4> ReqRegs;
4981 for (const SCEV *S : CurRegs)
4982 if (LU.Regs.count(S))
4983 ReqRegs.insert(S);
4984
4985 SmallPtrSet<const SCEV *, 16> NewRegs;
4986 Cost NewCost(L, SE, TTI, AMK);
4987 for (const Formula &F : LU.Formulae) {
4988 // Ignore formulae which may not be ideal in terms of register reuse of
4989 // ReqRegs. The formula should use all required registers before
4990 // introducing new ones.
4991 // This can sometimes (notably when trying to favour postinc) lead to
4992 // sub-optimial decisions. There it is best left to the cost modelling to
4993 // get correct.
4994 if (AMK != TTI::AMK_PostIndexed || LU.Kind != LSRUse::Address) {
4995 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4996 for (const SCEV *Reg : ReqRegs) {
4997 if ((F.ScaledReg && F.ScaledReg == Reg) ||
4998 is_contained(F.BaseRegs, Reg)) {
4999 --NumReqRegsToFind;
5000 if (NumReqRegsToFind == 0)
5001 break;
5002 }
5003 }
5004 if (NumReqRegsToFind != 0) {
5005 // If none of the formulae satisfied the required registers, then we could
5006 // clear ReqRegs and try again. Currently, we simply give up in this case.
5007 continue;
5008 }
5009 }
5010
5011 // Evaluate the cost of the current formula. If it's already worse than
5012 // the current best, prune the search at that point.
5013 NewCost = CurCost;
5014 NewRegs = CurRegs;
5015 NewCost.RateFormula(F, NewRegs, VisitedRegs, LU);
5016 if (NewCost.isLess(SolutionCost)) {
5017 Workspace.push_back(&F);
5018 if (Workspace.size() != Uses.size()) {
5019 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
5020 NewRegs, VisitedRegs);
5021 if (F.getNumRegs() == 1 && Workspace.size() == 1)
5022 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
5023 } else {
5024 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)
5025 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)
5026 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)
5027 << "- " << *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)
5028 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)
;
5029
5030 SolutionCost = NewCost;
5031 Solution = Workspace;
5032 }
5033 Workspace.pop_back();
5034 }
5035 }
5036}
5037
5038/// Choose one formula from each use. Return the results in the given Solution
5039/// vector.
5040void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
5041 SmallVector<const Formula *, 8> Workspace;
5042 Cost SolutionCost(L, SE, TTI, AMK);
5043 SolutionCost.Lose();
5044 Cost CurCost(L, SE, TTI, AMK);
5045 SmallPtrSet<const SCEV *, 16> CurRegs;
5046 DenseSet<const SCEV *> VisitedRegs;
5047 Workspace.reserve(Uses.size());
5048
5049 // SolveRecurse does all the work.
5050 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
5051 CurRegs, VisitedRegs);
5052 if (Solution.empty()) {
5053 LLVM_DEBUG(dbgs() << "\nNo Satisfactory Solution\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nNo Satisfactory Solution\n"
; } } while (false)
;
5054 return;
5055 }
5056
5057 // Ok, we've now made all our decisions.
5058 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
)
5059 "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
)
5060 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
)
5061 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
)
5062 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
)
5063 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
)
5064 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
)
5065 " ";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
)
5066 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
)
5067 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
)
5068 })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
)
;
5069
5070 assert(Solution.size() == Uses.size() && "Malformed solution!")((Solution.size() == Uses.size() && "Malformed solution!"
) ? static_cast<void> (0) : __assert_fail ("Solution.size() == Uses.size() && \"Malformed solution!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5070, __PRETTY_FUNCTION__))
;
5071}
5072
5073/// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
5074/// we can go while still being dominated by the input positions. This helps
5075/// canonicalize the insert position, which encourages sharing.
5076BasicBlock::iterator
5077LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
5078 const SmallVectorImpl<Instruction *> &Inputs)
5079 const {
5080 Instruction *Tentative = &*IP;
5081 while (true) {
5082 bool AllDominate = true;
5083 Instruction *BetterPos = nullptr;
5084 // Don't bother attempting to insert before a catchswitch, their basic block
5085 // cannot have other non-PHI instructions.
5086 if (isa<CatchSwitchInst>(Tentative))
5087 return IP;
5088
5089 for (Instruction *Inst : Inputs) {
5090 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
5091 AllDominate = false;
5092 break;
5093 }
5094 // Attempt to find an insert position in the middle of the block,
5095 // instead of at the end, so that it can be used for other expansions.
5096 if (Tentative->getParent() == Inst->getParent() &&
5097 (!BetterPos || !DT.dominates(Inst, BetterPos)))
5098 BetterPos = &*std::next(BasicBlock::iterator(Inst));
5099 }
5100 if (!AllDominate)
5101 break;
5102 if (BetterPos)
5103 IP = BetterPos->getIterator();
5104 else
5105 IP = Tentative->getIterator();
5106
5107 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
5108 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
5109
5110 BasicBlock *IDom;
5111 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
5112 if (!Rung) return IP;
5113 Rung = Rung->getIDom();
5114 if (!Rung) return IP;
5115 IDom = Rung->getBlock();
5116
5117 // Don't climb into a loop though.
5118 const Loop *IDomLoop = LI.getLoopFor(IDom);
5119 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
5120 if (IDomDepth <= IPLoopDepth &&
5121 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
5122 break;
5123 }
5124
5125 Tentative = IDom->getTerminator();
5126 }
5127
5128 return IP;
5129}
5130
5131/// Determine an input position which will be dominated by the operands and
5132/// which will dominate the result.
5133BasicBlock::iterator
5134LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
5135 const LSRFixup &LF,
5136 const LSRUse &LU,
5137 SCEVExpander &Rewriter) const {
5138 // Collect some instructions which must be dominated by the
5139 // expanding replacement. These must be dominated by any operands that
5140 // will be required in the expansion.
5141 SmallVector<Instruction *, 4> Inputs;
5142 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
5143 Inputs.push_back(I);
5144 if (LU.Kind == LSRUse::ICmpZero)
5145 if (Instruction *I =
5146 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
5147 Inputs.push_back(I);
5148 if (LF.PostIncLoops.count(L)) {
5149 if (LF.isUseFullyOutsideLoop(L))
5150 Inputs.push_back(L->getLoopLatch()->getTerminator());
5151 else
5152 Inputs.push_back(IVIncInsertPos);
5153 }
5154 // The expansion must also be dominated by the increment positions of any
5155 // loops it for which it is using post-inc mode.
5156 for (const Loop *PIL : LF.PostIncLoops) {
5157 if (PIL == L) continue;
5158
5159 // Be dominated by the loop exit.
5160 SmallVector<BasicBlock *, 4> ExitingBlocks;
5161 PIL->getExitingBlocks(ExitingBlocks);
5162 if (!ExitingBlocks.empty()) {
5163 BasicBlock *BB = ExitingBlocks[0];
5164 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
5165 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
5166 Inputs.push_back(BB->getTerminator());
5167 }
5168 }
5169
5170 assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad()((!isa<PHINode>(LowestIP) && !LowestIP->isEHPad
() && !isa<DbgInfoIntrinsic>(LowestIP) &&
"Insertion point must be a normal instruction") ? static_cast
<void> (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5172, __PRETTY_FUNCTION__))
5171 && !isa<DbgInfoIntrinsic>(LowestIP) &&((!isa<PHINode>(LowestIP) && !LowestIP->isEHPad
() && !isa<DbgInfoIntrinsic>(LowestIP) &&
"Insertion point must be a normal instruction") ? static_cast
<void> (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5172, __PRETTY_FUNCTION__))
5172 "Insertion point must be a normal instruction")((!isa<PHINode>(LowestIP) && !LowestIP->isEHPad
() && !isa<DbgInfoIntrinsic>(LowestIP) &&
"Insertion point must be a normal instruction") ? static_cast
<void> (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5172, __PRETTY_FUNCTION__))
;
5173
5174 // Then, climb up the immediate dominator tree as far as we can go while
5175 // still being dominated by the input positions.
5176 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
5177
5178 // Don't insert instructions before PHI nodes.
5179 while (isa<PHINode>(IP)) ++IP;
5180
5181 // Ignore landingpad instructions.
5182 while (IP->isEHPad()) ++IP;
5183
5184 // Ignore debug intrinsics.
5185 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
5186
5187 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
5188 // IP consistent across expansions and allows the previously inserted
5189 // instructions to be reused by subsequent expansion.
5190 while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
5191 ++IP;
5192
5193 return IP;
5194}
5195
5196/// Emit instructions for the leading candidate expression for this LSRUse (this
5197/// is called "expanding").
5198Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF,
5199 const Formula &F, BasicBlock::iterator IP,
5200 SCEVExpander &Rewriter,
5201 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5202 if (LU.RigidFormula)
5203 return LF.OperandValToReplace;
5204
5205 // Determine an input position which will be dominated by the operands and
5206 // which will dominate the result.
5207 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
5208 Rewriter.setInsertPoint(&*IP);
5209
5210 // Inform the Rewriter if we have a post-increment use, so that it can
5211 // perform an advantageous expansion.
5212 Rewriter.setPostInc(LF.PostIncLoops);
5213
5214 // This is the type that the user actually needs.
5215 Type *OpTy = LF.OperandValToReplace->getType();
5216 // This will be the type that we'll initially expand to.
5217 Type *Ty = F.getType();
5218 if (!Ty)
5219 // No type known; just expand directly to the ultimate type.
5220 Ty = OpTy;
5221 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
5222 // Expand directly to the ultimate type if it's the right size.
5223 Ty = OpTy;
5224 // This is the type to do integer arithmetic in.
5225 Type *IntTy = SE.getEffectiveSCEVType(Ty);
5226
5227 // Build up a list of operands to add together to form the full base.
5228 SmallVector<const SCEV *, 8> Ops;
5229
5230 // Expand the BaseRegs portion.
5231 for (const SCEV *Reg : F.BaseRegs) {
5232 assert(!Reg->isZero() && "Zero allocated in a base register!")((!Reg->isZero() && "Zero allocated in a base register!"
) ? static_cast<void> (0) : __assert_fail ("!Reg->isZero() && \"Zero allocated in a base register!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5232, __PRETTY_FUNCTION__))
;
5233
5234 // If we're expanding for a post-inc user, make the post-inc adjustment.
5235 Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE);
5236 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
5237 }
5238
5239 // Expand the ScaledReg portion.
5240 Value *ICmpScaledV = nullptr;
5241 if (F.Scale != 0) {
5242 const SCEV *ScaledS = F.ScaledReg;
5243
5244 // If we're expanding for a post-inc user, make the post-inc adjustment.
5245 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
5246 ScaledS = denormalizeForPostIncUse(ScaledS, Loops, SE);
5247
5248 if (LU.Kind == LSRUse::ICmpZero) {
5249 // Expand ScaleReg as if it was part of the base regs.
5250 if (F.Scale == 1)
5251 Ops.push_back(
5252 SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
5253 else {
5254 // An interesting way of "folding" with an icmp is to use a negated
5255 // scale, which we'll implement by inserting it into the other operand
5256 // of the icmp.
5257 assert(F.Scale == -1 &&((F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? static_cast<void> (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5258, __PRETTY_FUNCTION__))
5258 "The only scale supported by ICmpZero uses is -1!")((F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? static_cast<void> (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5258, __PRETTY_FUNCTION__))
;
5259 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
5260 }
5261 } else {
5262 // Otherwise just expand the scaled register and an explicit scale,
5263 // which is expected to be matched as part of the address.
5264
5265 // Flush the operand list to suppress SCEVExpander hoisting address modes.
5266 // Unless the addressing mode will not be folded.
5267 if (!Ops.empty() && LU.Kind == LSRUse::Address &&
5268 isAMCompletelyFolded(TTI, LU, F)) {
5269 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), nullptr);
5270 Ops.clear();
5271 Ops.push_back(SE.getUnknown(FullV));
5272 }
5273 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
5274 if (F.Scale != 1)
5275 ScaledS =
5276 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
5277 Ops.push_back(ScaledS);
5278 }
5279 }
5280
5281 // Expand the GV portion.
5282 if (F.BaseGV) {
5283 // Flush the operand list to suppress SCEVExpander hoisting.
5284 if (!Ops.empty()) {
5285 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5286 Ops.clear();
5287 Ops.push_back(SE.getUnknown(FullV));
5288 }
5289 Ops.push_back(SE.getUnknown(F.BaseGV));
5290 }
5291
5292 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
5293 // unfolded offsets. LSR assumes they both live next to their uses.
5294 if (!Ops.empty()) {
5295 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5296 Ops.clear();
5297 Ops.push_back(SE.getUnknown(FullV));
5298 }
5299
5300 // Expand the immediate portion.
5301 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
5302 if (Offset != 0) {
5303 if (LU.Kind == LSRUse::ICmpZero) {
5304 // The other interesting way of "folding" with an ICmpZero is to use a
5305 // negated immediate.
5306 if (!ICmpScaledV)
5307 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
5308 else {
5309 Ops.push_back(SE.getUnknown(ICmpScaledV));
5310 ICmpScaledV = ConstantInt::get(IntTy, Offset);
5311 }
5312 } else {
5313 // Just add the immediate values. These again are expected to be matched
5314 // as part of the address.
5315 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
5316 }
5317 }
5318
5319 // Expand the unfolded offset portion.
5320 int64_t UnfoldedOffset = F.UnfoldedOffset;
5321 if (UnfoldedOffset != 0) {
5322 // Just add the immediate values.
5323 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
5324 UnfoldedOffset)));
5325 }
5326
5327 // Emit instructions summing all the operands.
5328 const SCEV *FullS = Ops.empty() ?
5329 SE.getConstant(IntTy, 0) :
5330 SE.getAddExpr(Ops);
5331 Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
5332
5333 // We're done expanding now, so reset the rewriter.
5334 Rewriter.clearPostInc();
5335
5336 // An ICmpZero Formula represents an ICmp which we're handling as a
5337 // comparison against zero. Now that we've expanded an expression for that
5338 // form, update the ICmp's other operand.
5339 if (LU.Kind == LSRUse::ICmpZero) {
5340 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
5341 if (auto *OperandIsInstr = dyn_cast<Instruction>(CI->getOperand(1)))
5342 DeadInsts.emplace_back(OperandIsInstr);
5343 assert(!F.BaseGV && "ICmp does not support folding a global value and "((!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("!F.BaseGV && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5344, __PRETTY_FUNCTION__))
5344 "a scale at the same time!")((!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("!F.BaseGV && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5344, __PRETTY_FUNCTION__))
;
5345 if (F.Scale == -1) {
5346 if (ICmpScaledV->getType() != OpTy) {
5347 Instruction *Cast =
5348 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
5349 OpTy, false),
5350 ICmpScaledV, OpTy, "tmp", CI);
5351 ICmpScaledV = Cast;
5352 }
5353 CI->setOperand(1, ICmpScaledV);
5354 } else {
5355 // A scale of 1 means that the scale has been expanded as part of the
5356 // base regs.
5357 assert((F.Scale == 0 || F.Scale == 1) &&(((F.Scale == 0 || F.Scale == 1) && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5359, __PRETTY_FUNCTION__))
5358 "ICmp does not support folding a global value and "(((F.Scale == 0 || F.Scale == 1) && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5359, __PRETTY_FUNCTION__))
5359 "a scale at the same time!")(((F.Scale == 0 || F.Scale == 1) && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5359, __PRETTY_FUNCTION__))
;
5360 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
5361 -(uint64_t)Offset);
5362 if (C->getType() != OpTy)
5363 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
5364 OpTy, false),
5365 C, OpTy);
5366
5367 CI->setOperand(1, C);
5368 }
5369 }
5370
5371 return FullV;
5372}
5373
5374/// Helper for Rewrite. PHI nodes are special because the use of their operands
5375/// effectively happens in their predecessor blocks, so the expression may need
5376/// to be expanded in multiple places.
5377void LSRInstance::RewriteForPHI(
5378 PHINode *PN, const LSRUse &LU, const LSRFixup &LF, const Formula &F,
5379 SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5380 DenseMap<BasicBlock *, Value *> Inserted;
5381 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
5382 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
3
Assuming pointer value is null
4
Taking true branch
5383 bool needUpdateFixups = false;
5384 BasicBlock *BB = PN->getIncomingBlock(i);
5385
5386 // If this is a critical edge, split the edge so that we do not insert
5387 // the code on all predecessor/successor paths. We do this unless this
5388 // is the canonical backedge for this loop, which complicates post-inc
5389 // users.
5390 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
5
Assuming 'e' is equal to 1
6
Taking false branch
5391 !isa<IndirectBrInst>(BB->getTerminator()) &&
5392 !isa<CatchSwitchInst>(BB->getTerminator())) {
5393 BasicBlock *Parent = PN->getParent();
5394 Loop *PNLoop = LI.getLoopFor(Parent);
5395 if (!PNLoop || Parent != PNLoop->getHeader()) {
5396 // Split the critical edge.
5397 BasicBlock *NewBB = nullptr;
5398 if (!Parent->isLandingPad()) {
5399 NewBB =
5400 SplitCriticalEdge(BB, Parent,
5401 CriticalEdgeSplittingOptions(&DT, &LI, MSSAU)
5402 .setMergeIdenticalEdges()
5403 .setKeepOneInputPHIs());
5404 } else {
5405 SmallVector<BasicBlock*, 2> NewBBs;
5406 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
5407 NewBB = NewBBs[0];
5408 }
5409 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
5410 // phi predecessors are identical. The simple thing to do is skip
5411 // splitting in this case rather than complicate the API.
5412 if (NewBB) {
5413 // If PN is outside of the loop and BB is in the loop, we want to
5414 // move the block to be immediately before the PHI block, not
5415 // immediately after BB.
5416 if (L->contains(BB) && !L->contains(PN))
5417 NewBB->moveBefore(PN->getParent());
5418
5419 // Splitting the edge can reduce the number of PHI entries we have.
5420 e = PN->getNumIncomingValues();
5421 BB = NewBB;
5422 i = PN->getBasicBlockIndex(BB);
5423
5424 needUpdateFixups = true;
5425 }
5426 }
5427 }
5428
5429 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
5430 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
5431 if (!Pair.second)
7
Assuming field 'second' is true
8
Taking false branch
5432 PN->setIncomingValue(i, Pair.first->second);
5433 else {
5434 Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
5435 Rewriter, DeadInsts);
5436
5437 // If this is reuse-by-noop-cast, insert the noop cast.
5438 Type *OpTy = LF.OperandValToReplace->getType();
9
Called C++ object pointer is null
5439 if (FullV->getType() != OpTy)
5440 FullV =
5441 CastInst::Create(CastInst::getCastOpcode(FullV, false,
5442 OpTy, false),
5443 FullV, LF.OperandValToReplace->getType(),
5444 "tmp", BB->getTerminator());
5445
5446 PN->setIncomingValue(i, FullV);
5447 Pair.first->second = FullV;
5448 }
5449
5450 // If LSR splits critical edge and phi node has other pending
5451 // fixup operands, we need to update those pending fixups. Otherwise
5452 // formulae will not be implemented completely and some instructions
5453 // will not be eliminated.
5454 if (needUpdateFixups) {
5455 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5456 for (LSRFixup &Fixup : Uses[LUIdx].Fixups)
5457 // If fixup is supposed to rewrite some operand in the phi
5458 // that was just updated, it may be already moved to
5459 // another phi node. Such fixup requires update.
5460 if (Fixup.UserInst == PN) {
5461 // Check if the operand we try to replace still exists in the
5462 // original phi.
5463 bool foundInOriginalPHI = false;
5464 for (const auto &val : PN->incoming_values())
5465 if (val == Fixup.OperandValToReplace) {
5466 foundInOriginalPHI = true;
5467 break;
5468 }
5469
5470 // If fixup operand found in original PHI - nothing to do.
5471 if (foundInOriginalPHI)
5472 continue;
5473
5474 // Otherwise it might be moved to another PHI and requires update.
5475 // If fixup operand not found in any of the incoming blocks that
5476 // means we have already rewritten it - nothing to do.
5477 for (const auto &Block : PN->blocks())
5478 for (BasicBlock::iterator I = Block->begin(); isa<PHINode>(I);
5479 ++I) {
5480 PHINode *NewPN = cast<PHINode>(I);
5481 for (const auto &val : NewPN->incoming_values())
5482 if (val == Fixup.OperandValToReplace)
5483 Fixup.UserInst = NewPN;
5484 }
5485 }
5486 }
5487 }
5488}
5489
5490/// Emit instructions for the leading candidate expression for this LSRUse (this
5491/// is called "expanding"), and update the UserInst to reference the newly
5492/// expanded value.
5493void LSRInstance::Rewrite(const LSRUse &LU, const LSRFixup &LF,
5494 const Formula &F, SCEVExpander &Rewriter,
5495 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5496 // First, find an insertion point that dominates UserInst. For PHI nodes,
5497 // find the nearest block which dominates all the relevant uses.
5498 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
5499 RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
5500 } else {
5501 Value *FullV =
5502 Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
5503
5504 // If this is reuse-by-noop-cast, insert the noop cast.
5505 Type *OpTy = LF.OperandValToReplace->getType();
5506 if (FullV->getType() != OpTy) {
5507 Instruction *Cast =
5508 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
5509 FullV, OpTy, "tmp", LF.UserInst);
5510 FullV = Cast;
5511 }
5512
5513 // Update the user. ICmpZero is handled specially here (for now) because
5514 // Expand may have updated one of the operands of the icmp already, and
5515 // its new value may happen to be equal to LF.OperandValToReplace, in
5516 // which case doing replaceUsesOfWith leads to replacing both operands
5517 // with the same value. TODO: Reorganize this.
5518 if (LU.Kind == LSRUse::ICmpZero)
5519 LF.UserInst->setOperand(0, FullV);
5520 else
5521 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
5522 }
5523
5524 if (auto *OperandIsInstr = dyn_cast<Instruction>(LF.OperandValToReplace))
5525 DeadInsts.emplace_back(OperandIsInstr);
5526}
5527
5528/// Rewrite all the fixup locations with new values, following the chosen
5529/// solution.
5530void LSRInstance::ImplementSolution(
5531 const SmallVectorImpl<const Formula *> &Solution) {
5532 // Keep track of instructions we may have made dead, so that
5533 // we can remove them after we are done working.
5534 SmallVector<WeakTrackingVH, 16> DeadInsts;
5535
5536 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(), "lsr",
5537 false);
5538#ifndef NDEBUG
5539 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5540#endif
5541 Rewriter.disableCanonicalMode();
5542 Rewriter.enableLSRMode();
5543 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
5544
5545 // Mark phi nodes that terminate chains so the expander tries to reuse them.
5546 for (const IVChain &Chain : IVChainVec) {
5547 if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
5548 Rewriter.setChainedPhi(PN);
5549 }
5550
5551 // Expand the new value definitions and update the users.
5552 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5553 for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
5554 Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
5555 Changed = true;
5556 }
5557
5558 for (const IVChain &Chain : IVChainVec) {
5559 GenerateIVChain(Chain, Rewriter, DeadInsts);
5560 Changed = true;
5561 }
5562 // Clean up after ourselves. This must be done before deleting any
5563 // instructions.
5564 Rewriter.clear();
5565
5566 Changed |= RecursivelyDeleteTriviallyDeadInstructionsPermissive(DeadInsts,
5567 &TLI, MSSAU);
5568
5569 // In our cost analysis above, we assume that each addrec consumes exactly
5570 // one register, and arrange to have increments inserted just before the
5571 // latch to maximimize the chance this is true. However, if we reused
5572 // existing IVs, we now need to move the increments to match our
5573 // expectations. Otherwise, our cost modeling results in us having a
5574 // chosen a non-optimal result for the actual schedule. (And yes, this
5575 // scheduling decision does impact later codegen.)
5576 for (PHINode &PN : L->getHeader()->phis()) {
5577 BinaryOperator *BO = nullptr;
5578 Value *Start = nullptr, *Step = nullptr;
5579 if (!matchSimpleRecurrence(&PN, BO, Start, Step))
5580 continue;
5581
5582 switch (BO->getOpcode()) {
5583 case Instruction::Sub:
5584 if (BO->getOperand(0) != &PN)
5585 // sub is non-commutative - match handling elsewhere in LSR
5586 continue;
5587 break;
5588 case Instruction::Add:
5589 break;
5590 default:
5591 continue;
5592 };
5593
5594 if (!isa<Constant>(Step))
5595 // If not a constant step, might increase register pressure
5596 // (We assume constants have been canonicalized to RHS)
5597 continue;
5598
5599 if (BO->getParent() == IVIncInsertPos->getParent())
5600 // Only bother moving across blocks. Isel can handle block local case.
5601 continue;
5602
5603 // Can we legally schedule inc at the desired point?
5604 if (!llvm::all_of(BO->uses(),
5605 [&](Use &U) {return DT.dominates(IVIncInsertPos, U);}))
5606 continue;
5607 BO->moveBefore(IVIncInsertPos);
5608 Changed = true;
5609 }
5610
5611
5612}
5613
5614LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5615 DominatorTree &DT, LoopInfo &LI,
5616 const TargetTransformInfo &TTI, AssumptionCache &AC,
5617 TargetLibraryInfo &TLI, MemorySSAUpdater *MSSAU)
5618 : IU(IU), SE(SE), DT(DT), LI(LI), AC(AC), TLI(TLI), TTI(TTI), L(L),
5619 MSSAU(MSSAU), AMK(PreferredAddresingMode.getNumOccurrences() > 0 ?
5620 PreferredAddresingMode : TTI.getPreferredAddressingMode(L, &SE)) {
5621 // If LoopSimplify form is not available, stay out of trouble.
5622 if (!L->isLoopSimplifyForm())
5623 return;
5624
5625 // If there's no interesting work to be done, bail early.
5626 if (IU.empty()) return;
5627
5628 // If there's too much analysis to be done, bail early. We won't be able to
5629 // model the problem anyway.
5630 unsigned NumUsers = 0;
5631 for (const IVStrideUse &U : IU) {
5632 if (++NumUsers > MaxIVUsers) {
5633 (void)U;
5634 LLVM_DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << Udo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping loop, too many IV Users in "
<< U << "\n"; } } while (false)
5635 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping loop, too many IV Users in "
<< U << "\n"; } } while (false)
;
5636 return;
5637 }
5638 // Bail out if we have a PHI on an EHPad that gets a value from a
5639 // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is
5640 // no good place to stick any instructions.
5641 if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
5642 auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
5643 if (isa<FuncletPadInst>(FirstNonPHI) ||
5644 isa<CatchSwitchInst>(FirstNonPHI))
5645 for (BasicBlock *PredBB : PN->blocks())
5646 if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
5647 return;
5648 }
5649 }
5650
5651#ifndef NDEBUG
5652 // All dominating loops must have preheaders, or SCEVExpander may not be able
5653 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
5654 //
5655 // IVUsers analysis should only create users that are dominated by simple loop
5656 // headers. Since this loop should dominate all of its users, its user list
5657 // should be empty if this loop itself is not within a simple loop nest.
5658 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
5659 Rung; Rung = Rung->getIDom()) {
5660 BasicBlock *BB = Rung->getBlock();
5661 const Loop *DomLoop = LI.getLoopFor(BB);
5662 if (DomLoop && DomLoop->getHeader() == BB) {
5663 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest")((DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest"
) ? static_cast<void> (0) : __assert_fail ("DomLoop->getLoopPreheader() && \"LSR needs a simplified loop nest\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5663, __PRETTY_FUNCTION__))
;
5664 }
5665 }
5666#endif // DEBUG
5667
5668 LLVM_DEBUG(dbgs() << "\nLSR on loop ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
5669 L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false);do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
5670 dbgs() << ":\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
;
5671
5672 // First, perform some low-level loop optimizations.
5673 OptimizeShadowIV();
5674 OptimizeLoopTermCond();
5675
5676 // If loop preparation eliminates all interesting IV users, bail.
5677 if (IU.empty()) return;
5678
5679 // Skip nested loops until we can model them better with formulae.
5680 if (!L->isInnermost()) {
5681 LLVM_DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping outer loop "
<< *L << "\n"; } } while (false)
;
5682 return;
5683 }
5684
5685 // Start collecting data and preparing for the solver.
5686 // If number of registers is not the major cost, we cannot benefit from the
5687 // current profitable chain optimization which is based on number of
5688 // registers.
5689 // FIXME: add profitable chain optimization for other kinds major cost, for
5690 // example number of instructions.
5691 if (TTI.isNumRegsMajorCostOfLSR() || StressIVChain)
5692 CollectChains();
5693 CollectInterestingTypesAndFactors();
5694 CollectFixupsAndInitialFormulae();
5695 CollectLoopInvariantFixupsAndFormulae();
5696
5697 if (Uses.empty())
5698 return;
5699
5700 LLVM_DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR found " << Uses
.size() << " uses:\n"; print_uses(dbgs()); } } while (false
)
5701 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR found " << Uses
.size() << " uses:\n"; print_uses(dbgs()); } } while (false
)
;
5702
5703 // Now use the reuse data to generate a bunch of interesting ways
5704 // to formulate the values needed for the uses.
5705 GenerateAllReuseFormulae();
5706
5707 FilterOutUndesirableDedicatedRegisters();
5708 NarrowSearchSpaceUsingHeuristics();
5709
5710 SmallVector<const Formula *, 8> Solution;
5711 Solve(Solution);
5712
5713 // Release memory that is no longer needed.
5714 Factors.clear();
5715 Types.clear();
5716 RegUses.clear();
5717
5718 if (Solution.empty())
5719 return;
5720
5721#ifndef NDEBUG
5722 // Formulae should be legal.
5723 for (const LSRUse &LU : Uses) {
5724 for (const Formula &F : LU.Formulae)
5725 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Illegal formula generated!") ? static_cast<
void> (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Illegal formula generated!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5726, __PRETTY_FUNCTION__))
5726 F) && "Illegal formula generated!")((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Illegal formula generated!") ? static_cast<
void> (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Illegal formula generated!\""
, "/build/llvm-toolchain-snapshot-13~++20210413100635+64c24f493e5f/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5726, __PRETTY_FUNCTION__))
;
5727 };
5728#endif
5729
5730 // Now that we've decided what we want, make it so.
5731 ImplementSolution(Solution);
5732}
5733
5734#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5735void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
5736 if (Factors.empty() && Types.empty()) return;
5737
5738