Bug Summary

File:llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
Warning:line 5514, column 22
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name LoopStrengthReduce.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/build-llvm -resource-dir /usr/lib/llvm-14/lib/clang/14.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/llvm/lib/Transforms/Scalar -I include -I /build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/llvm/include -D _FORTIFY_SOURCE=2 -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-14/lib/clang/14.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fmacro-prefix-map=/build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/build-llvm=build-llvm -fmacro-prefix-map=/build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/= -fcoverage-prefix-map=/build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/build-llvm=build-llvm -fcoverage-prefix-map=/build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/= -O3 -Wno-unused-command-line-argument -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/build-llvm -fdebug-prefix-map=/build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/build-llvm=build-llvm -fdebug-prefix-map=/build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/= -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2022-01-19-134126-35450-1 -x c++ /build/llvm-toolchain-snapshot-14~++20220119111520+da61cb019eb2/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/// Limit the size of expression that SCEV-based salvaging will attempt to
140/// translate into a DIExpression.
141/// Choose a maximum size such that debuginfo is not excessively increased and
142/// the salvaging is not too expensive for the compiler.
143static const unsigned MaxSCEVSalvageExpressionSize = 64;
144
145// Temporary flag to cleanup congruent phis after LSR phi expansion.
146// It's currently disabled until we can determine whether it's truly useful or
147// not. The flag should be removed after the v3.0 release.
148// This is now needed for ivchains.
149static cl::opt<bool> EnablePhiElim(
150 "enable-lsr-phielim", cl::Hidden, cl::init(true),
151 cl::desc("Enable LSR phi elimination"));
152
153// The flag adds instruction count to solutions cost comparision.
154static cl::opt<bool> InsnsCost(
155 "lsr-insns-cost", cl::Hidden, cl::init(true),
156 cl::desc("Add instruction count to a LSR cost model"));
157
158// Flag to choose how to narrow complex lsr solution
159static cl::opt<bool> LSRExpNarrow(
160 "lsr-exp-narrow", cl::Hidden, cl::init(false),
161 cl::desc("Narrow LSR complex solution using"
162 " expectation of registers number"));
163
164// Flag to narrow search space by filtering non-optimal formulae with
165// the same ScaledReg and Scale.
166static cl::opt<bool> FilterSameScaledReg(
167 "lsr-filter-same-scaled-reg", cl::Hidden, cl::init(true),
168 cl::desc("Narrow LSR search space by filtering non-optimal formulae"
169 " with the same ScaledReg and Scale"));
170
171static cl::opt<TTI::AddressingModeKind> PreferredAddresingMode(
172 "lsr-preferred-addressing-mode", cl::Hidden, cl::init(TTI::AMK_None),
173 cl::desc("A flag that overrides the target's preferred addressing mode."),
174 cl::values(clEnumValN(TTI::AMK_None,llvm::cl::OptionEnumValue { "none", int(TTI::AMK_None), "Don't prefer any addressing mode"
}
175 "none",llvm::cl::OptionEnumValue { "none", int(TTI::AMK_None), "Don't prefer any addressing mode"
}
176 "Don't prefer any addressing mode")llvm::cl::OptionEnumValue { "none", int(TTI::AMK_None), "Don't prefer any addressing mode"
}
,
177 clEnumValN(TTI::AMK_PreIndexed,llvm::cl::OptionEnumValue { "preindexed", int(TTI::AMK_PreIndexed
), "Prefer pre-indexed addressing mode" }
178 "preindexed",llvm::cl::OptionEnumValue { "preindexed", int(TTI::AMK_PreIndexed
), "Prefer pre-indexed addressing mode" }
179 "Prefer pre-indexed addressing mode")llvm::cl::OptionEnumValue { "preindexed", int(TTI::AMK_PreIndexed
), "Prefer pre-indexed addressing mode" }
,
180 clEnumValN(TTI::AMK_PostIndexed,llvm::cl::OptionEnumValue { "postindexed", int(TTI::AMK_PostIndexed
), "Prefer post-indexed addressing mode" }
181 "postindexed",llvm::cl::OptionEnumValue { "postindexed", int(TTI::AMK_PostIndexed
), "Prefer post-indexed addressing mode" }
182 "Prefer post-indexed addressing mode")llvm::cl::OptionEnumValue { "postindexed", int(TTI::AMK_PostIndexed
), "Prefer post-indexed addressing mode" }
));
183
184static cl::opt<unsigned> ComplexityLimit(
185 "lsr-complexity-limit", cl::Hidden,
186 cl::init(std::numeric_limits<uint16_t>::max()),
187 cl::desc("LSR search space complexity limit"));
188
189static cl::opt<unsigned> SetupCostDepthLimit(
190 "lsr-setupcost-depth-limit", cl::Hidden, cl::init(7),
191 cl::desc("The limit on recursion depth for LSRs setup cost"));
192
193#ifndef NDEBUG
194// Stress test IV chain generation.
195static cl::opt<bool> StressIVChain(
196 "stress-ivchain", cl::Hidden, cl::init(false),
197 cl::desc("Stress test LSR IV chains"));
198#else
199static bool StressIVChain = false;
200#endif
201
202namespace {
203
204struct MemAccessTy {
205 /// Used in situations where the accessed memory type is unknown.
206 static const unsigned UnknownAddressSpace =
207 std::numeric_limits<unsigned>::max();
208
209 Type *MemTy = nullptr;
210 unsigned AddrSpace = UnknownAddressSpace;
211
212 MemAccessTy() = default;
213 MemAccessTy(Type *Ty, unsigned AS) : MemTy(Ty), AddrSpace(AS) {}
214
215 bool operator==(MemAccessTy Other) const {
216 return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace;
217 }
218
219 bool operator!=(MemAccessTy Other) const { return !(*this == Other); }
220
221 static MemAccessTy getUnknown(LLVMContext &Ctx,
222 unsigned AS = UnknownAddressSpace) {
223 return MemAccessTy(Type::getVoidTy(Ctx), AS);
224 }
225
226 Type *getType() { return MemTy; }
227};
228
229/// This class holds data which is used to order reuse candidates.
230class RegSortData {
231public:
232 /// This represents the set of LSRUse indices which reference
233 /// a particular register.
234 SmallBitVector UsedByIndices;
235
236 void print(raw_ostream &OS) const;
237 void dump() const;
238};
239
240} // end anonymous namespace
241
242#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
243void RegSortData::print(raw_ostream &OS) const {
244 OS << "[NumUses=" << UsedByIndices.count() << ']';
245}
246
247LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void RegSortData::dump() const {
248 print(errs()); errs() << '\n';
249}
250#endif
251
252namespace {
253
254/// Map register candidates to information about how they are used.
255class RegUseTracker {
256 using RegUsesTy = DenseMap<const SCEV *, RegSortData>;
257
258 RegUsesTy RegUsesMap;
259 SmallVector<const SCEV *, 16> RegSequence;
260
261public:
262 void countRegister(const SCEV *Reg, size_t LUIdx);
263 void dropRegister(const SCEV *Reg, size_t LUIdx);
264 void swapAndDropUse(size_t LUIdx, size_t LastLUIdx);
265
266 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
267
268 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
269
270 void clear();
271
272 using iterator = SmallVectorImpl<const SCEV *>::iterator;
273 using const_iterator = SmallVectorImpl<const SCEV *>::const_iterator;
274
275 iterator begin() { return RegSequence.begin(); }
276 iterator end() { return RegSequence.end(); }
277 const_iterator begin() const { return RegSequence.begin(); }
278 const_iterator end() const { return RegSequence.end(); }
279};
280
281} // end anonymous namespace
282
283void
284RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) {
285 std::pair<RegUsesTy::iterator, bool> Pair =
286 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
287 RegSortData &RSD = Pair.first->second;
288 if (Pair.second)
289 RegSequence.push_back(Reg);
290 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
291 RSD.UsedByIndices.set(LUIdx);
292}
293
294void
295RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) {
296 RegUsesTy::iterator It = RegUsesMap.find(Reg);
297 assert(It != RegUsesMap.end())(static_cast <bool> (It != RegUsesMap.end()) ? void (0)
: __assert_fail ("It != RegUsesMap.end()", "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 297, __extension__ __PRETTY_FUNCTION__))
;
298 RegSortData &RSD = It->second;
299 assert(RSD.UsedByIndices.size() > LUIdx)(static_cast <bool> (RSD.UsedByIndices.size() > LUIdx
) ? void (0) : __assert_fail ("RSD.UsedByIndices.size() > LUIdx"
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 299, __extension__
__PRETTY_FUNCTION__))
;
300 RSD.UsedByIndices.reset(LUIdx);
301}
302
303void
304RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
305 assert(LUIdx <= LastLUIdx)(static_cast <bool> (LUIdx <= LastLUIdx) ? void (0) :
__assert_fail ("LUIdx <= LastLUIdx", "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 305, __extension__ __PRETTY_FUNCTION__))
;
306
307 // Update RegUses. The data structure is not optimized for this purpose;
308 // we must iterate through it and update each of the bit vectors.
309 for (auto &Pair : RegUsesMap) {
310 SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
311 if (LUIdx < UsedByIndices.size())
312 UsedByIndices[LUIdx] =
313 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false;
314 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
315 }
316}
317
318bool
319RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
320 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
321 if (I == RegUsesMap.end())
322 return false;
323 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
324 int i = UsedByIndices.find_first();
325 if (i == -1) return false;
326 if ((size_t)i != LUIdx) return true;
327 return UsedByIndices.find_next(i) != -1;
328}
329
330const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
331 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
332 assert(I != RegUsesMap.end() && "Unknown register!")(static_cast <bool> (I != RegUsesMap.end() && "Unknown register!"
) ? void (0) : __assert_fail ("I != RegUsesMap.end() && \"Unknown register!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 332, __extension__
__PRETTY_FUNCTION__))
;
333 return I->second.UsedByIndices;
334}
335
336void RegUseTracker::clear() {
337 RegUsesMap.clear();
338 RegSequence.clear();
339}
340
341namespace {
342
343/// This class holds information that describes a formula for computing
344/// satisfying a use. It may include broken-out immediates and scaled registers.
345struct Formula {
346 /// Global base address used for complex addressing.
347 GlobalValue *BaseGV = nullptr;
348
349 /// Base offset for complex addressing.
350 int64_t BaseOffset = 0;
351
352 /// Whether any complex addressing has a base register.
353 bool HasBaseReg = false;
354
355 /// The scale of any complex addressing.
356 int64_t Scale = 0;
357
358 /// The list of "base" registers for this use. When this is non-empty. The
359 /// canonical representation of a formula is
360 /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
361 /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
362 /// 3. The reg containing recurrent expr related with currect loop in the
363 /// formula should be put in the ScaledReg.
364 /// #1 enforces that the scaled register is always used when at least two
365 /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
366 /// #2 enforces that 1 * reg is reg.
367 /// #3 ensures invariant regs with respect to current loop can be combined
368 /// together in LSR codegen.
369 /// This invariant can be temporarily broken while building a formula.
370 /// However, every formula inserted into the LSRInstance must be in canonical
371 /// form.
372 SmallVector<const SCEV *, 4> BaseRegs;
373
374 /// The 'scaled' register for this use. This should be non-null when Scale is
375 /// not zero.
376 const SCEV *ScaledReg = nullptr;
377
378 /// An additional constant offset which added near the use. This requires a
379 /// temporary register, but the offset itself can live in an add immediate
380 /// field rather than a register.
381 int64_t UnfoldedOffset = 0;
382
383 Formula() = default;
384
385 void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
386
387 bool isCanonical(const Loop &L) const;
388
389 void canonicalize(const Loop &L);
390
391 bool unscale();
392
393 bool hasZeroEnd() const;
394
395 size_t getNumRegs() const;
396 Type *getType() const;
397
398 void deleteBaseReg(const SCEV *&S);
399
400 bool referencesReg(const SCEV *S) const;
401 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
402 const RegUseTracker &RegUses) const;
403
404 void print(raw_ostream &OS) const;
405 void dump() const;
406};
407
408} // end anonymous namespace
409
410/// Recursion helper for initialMatch.
411static void DoInitialMatch(const SCEV *S, Loop *L,
412 SmallVectorImpl<const SCEV *> &Good,
413 SmallVectorImpl<const SCEV *> &Bad,
414 ScalarEvolution &SE) {
415 // Collect expressions which properly dominate the loop header.
416 if (SE.properlyDominates(S, L->getHeader())) {
417 Good.push_back(S);
418 return;
419 }
420
421 // Look at add operands.
422 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
423 for (const SCEV *S : Add->operands())
424 DoInitialMatch(S, L, Good, Bad, SE);
425 return;
426 }
427
428 // Look at addrec operands.
429 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
430 if (!AR->getStart()->isZero() && AR->isAffine()) {
431 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
432 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
433 AR->getStepRecurrence(SE),
434 // FIXME: AR->getNoWrapFlags()
435 AR->getLoop(), SCEV::FlagAnyWrap),
436 L, Good, Bad, SE);
437 return;
438 }
439
440 // Handle a multiplication by -1 (negation) if it didn't fold.
441 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
442 if (Mul->getOperand(0)->isAllOnesValue()) {
443 SmallVector<const SCEV *, 4> Ops(drop_begin(Mul->operands()));
444 const SCEV *NewMul = SE.getMulExpr(Ops);
445
446 SmallVector<const SCEV *, 4> MyGood;
447 SmallVector<const SCEV *, 4> MyBad;
448 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
449 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
450 SE.getEffectiveSCEVType(NewMul->getType())));
451 for (const SCEV *S : MyGood)
452 Good.push_back(SE.getMulExpr(NegOne, S));
453 for (const SCEV *S : MyBad)
454 Bad.push_back(SE.getMulExpr(NegOne, S));
455 return;
456 }
457
458 // Ok, we can't do anything interesting. Just stuff the whole thing into a
459 // register and hope for the best.
460 Bad.push_back(S);
461}
462
463/// Incorporate loop-variant parts of S into this Formula, attempting to keep
464/// all loop-invariant and loop-computable values in a single base register.
465void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
466 SmallVector<const SCEV *, 4> Good;
467 SmallVector<const SCEV *, 4> Bad;
468 DoInitialMatch(S, L, Good, Bad, SE);
469 if (!Good.empty()) {
470 const SCEV *Sum = SE.getAddExpr(Good);
471 if (!Sum->isZero())
472 BaseRegs.push_back(Sum);
473 HasBaseReg = true;
474 }
475 if (!Bad.empty()) {
476 const SCEV *Sum = SE.getAddExpr(Bad);
477 if (!Sum->isZero())
478 BaseRegs.push_back(Sum);
479 HasBaseReg = true;
480 }
481 canonicalize(*L);
482}
483
484/// Check whether or not this formula satisfies the canonical
485/// representation.
486/// \see Formula::BaseRegs.
487bool Formula::isCanonical(const Loop &L) const {
488 if (!ScaledReg)
489 return BaseRegs.size() <= 1;
490
491 if (Scale != 1)
492 return true;
493
494 if (Scale == 1 && BaseRegs.empty())
495 return false;
496
497 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
498 if (SAR && SAR->getLoop() == &L)
499 return true;
500
501 // If ScaledReg is not a recurrent expr, or it is but its loop is not current
502 // loop, meanwhile BaseRegs contains a recurrent expr reg related with current
503 // loop, we want to swap the reg in BaseRegs with ScaledReg.
504 auto I = find_if(BaseRegs, [&](const SCEV *S) {
505 return isa<const SCEVAddRecExpr>(S) &&
506 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
507 });
508 return I == BaseRegs.end();
509}
510
511/// Helper method to morph a formula into its canonical representation.
512/// \see Formula::BaseRegs.
513/// Every formula having more than one base register, must use the ScaledReg
514/// field. Otherwise, we would have to do special cases everywhere in LSR
515/// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
516/// On the other hand, 1*reg should be canonicalized into reg.
517void Formula::canonicalize(const Loop &L) {
518 if (isCanonical(L))
519 return;
520
521 if (BaseRegs.empty()) {
522 // No base reg? Use scale reg with scale = 1 as such.
523 assert(ScaledReg && "Expected 1*reg => reg")(static_cast <bool> (ScaledReg && "Expected 1*reg => reg"
) ? void (0) : __assert_fail ("ScaledReg && \"Expected 1*reg => reg\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 523, __extension__
__PRETTY_FUNCTION__))
;
524 assert(Scale == 1 && "Expected 1*reg => reg")(static_cast <bool> (Scale == 1 && "Expected 1*reg => reg"
) ? void (0) : __assert_fail ("Scale == 1 && \"Expected 1*reg => reg\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 524, __extension__
__PRETTY_FUNCTION__))
;
525 BaseRegs.push_back(ScaledReg);
526 Scale = 0;
527 ScaledReg = nullptr;
528 return;
529 }
530
531 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
532 if (!ScaledReg) {
533 ScaledReg = BaseRegs.pop_back_val();
534 Scale = 1;
535 }
536
537 // If ScaledReg is an invariant with respect to L, find the reg from
538 // BaseRegs containing the recurrent expr related with Loop L. Swap the
539 // reg with ScaledReg.
540 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
541 if (!SAR || SAR->getLoop() != &L) {
542 auto I = find_if(BaseRegs, [&](const SCEV *S) {
543 return isa<const SCEVAddRecExpr>(S) &&
544 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
545 });
546 if (I != BaseRegs.end())
547 std::swap(ScaledReg, *I);
548 }
549 assert(isCanonical(L) && "Failed to canonicalize?")(static_cast <bool> (isCanonical(L) && "Failed to canonicalize?"
) ? void (0) : __assert_fail ("isCanonical(L) && \"Failed to canonicalize?\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 549, __extension__
__PRETTY_FUNCTION__))
;
550}
551
552/// Get rid of the scale in the formula.
553/// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
554/// \return true if it was possible to get rid of the scale, false otherwise.
555/// \note After this operation the formula may not be in the canonical form.
556bool Formula::unscale() {
557 if (Scale != 1)
558 return false;
559 Scale = 0;
560 BaseRegs.push_back(ScaledReg);
561 ScaledReg = nullptr;
562 return true;
563}
564
565bool Formula::hasZeroEnd() const {
566 if (UnfoldedOffset || BaseOffset)
567 return false;
568 if (BaseRegs.size() != 1 || ScaledReg)
569 return false;
570 return true;
571}
572
573/// Return the total number of register operands used by this formula. This does
574/// not include register uses implied by non-constant addrec strides.
575size_t Formula::getNumRegs() const {
576 return !!ScaledReg + BaseRegs.size();
577}
578
579/// Return the type of this formula, if it has one, or null otherwise. This type
580/// is meaningless except for the bit size.
581Type *Formula::getType() const {
582 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
583 ScaledReg ? ScaledReg->getType() :
584 BaseGV ? BaseGV->getType() :
585 nullptr;
586}
587
588/// Delete the given base reg from the BaseRegs list.
589void Formula::deleteBaseReg(const SCEV *&S) {
590 if (&S != &BaseRegs.back())
591 std::swap(S, BaseRegs.back());
592 BaseRegs.pop_back();
593}
594
595/// Test if this formula references the given register.
596bool Formula::referencesReg(const SCEV *S) const {
597 return S == ScaledReg || is_contained(BaseRegs, S);
598}
599
600/// Test whether this formula uses registers which are used by uses other than
601/// the use with the given index.
602bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
603 const RegUseTracker &RegUses) const {
604 if (ScaledReg)
605 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
606 return true;
607 for (const SCEV *BaseReg : BaseRegs)
608 if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
609 return true;
610 return false;
611}
612
613#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
614void Formula::print(raw_ostream &OS) const {
615 bool First = true;
616 if (BaseGV) {
617 if (!First) OS << " + "; else First = false;
618 BaseGV->printAsOperand(OS, /*PrintType=*/false);
619 }
620 if (BaseOffset != 0) {
621 if (!First) OS << " + "; else First = false;
622 OS << BaseOffset;
623 }
624 for (const SCEV *BaseReg : BaseRegs) {
625 if (!First) OS << " + "; else First = false;
626 OS << "reg(" << *BaseReg << ')';
627 }
628 if (HasBaseReg && BaseRegs.empty()) {
629 if (!First) OS << " + "; else First = false;
630 OS << "**error: HasBaseReg**";
631 } else if (!HasBaseReg && !BaseRegs.empty()) {
632 if (!First) OS << " + "; else First = false;
633 OS << "**error: !HasBaseReg**";
634 }
635 if (Scale != 0) {
636 if (!First) OS << " + "; else First = false;
637 OS << Scale << "*reg(";
638 if (ScaledReg)
639 OS << *ScaledReg;
640 else
641 OS << "<unknown>";
642 OS << ')';
643 }
644 if (UnfoldedOffset != 0) {
645 if (!First) OS << " + ";
646 OS << "imm(" << UnfoldedOffset << ')';
647 }
648}
649
650LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Formula::dump() const {
651 print(errs()); errs() << '\n';
652}
653#endif
654
655/// Return true if the given addrec can be sign-extended without changing its
656/// value.
657static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
658 Type *WideTy =
659 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
660 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
661}
662
663/// Return true if the given add can be sign-extended without changing its
664/// value.
665static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
666 Type *WideTy =
667 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
668 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
669}
670
671/// Return true if the given mul can be sign-extended without changing its
672/// value.
673static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
674 Type *WideTy =
675 IntegerType::get(SE.getContext(),
676 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
677 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
678}
679
680/// Return an expression for LHS /s RHS, if it can be determined and if the
681/// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
682/// is true, expressions like (X * Y) /s Y are simplified to X, ignoring that
683/// the multiplication may overflow, which is useful when the result will be
684/// used in a context where the most significant bits are ignored.
685static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
686 ScalarEvolution &SE,
687 bool IgnoreSignificantBits = false) {
688 // Handle the trivial case, which works for any SCEV type.
689 if (LHS == RHS)
690 return SE.getConstant(LHS->getType(), 1);
691
692 // Handle a few RHS special cases.
693 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
694 if (RC) {
695 const APInt &RA = RC->getAPInt();
696 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
697 // some folding.
698 if (RA.isAllOnes()) {
699 if (LHS->getType()->isPointerTy())
700 return nullptr;
701 return SE.getMulExpr(LHS, RC);
702 }
703 // Handle x /s 1 as x.
704 if (RA == 1)
705 return LHS;
706 }
707
708 // Check for a division of a constant by a constant.
709 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
710 if (!RC)
711 return nullptr;
712 const APInt &LA = C->getAPInt();
713 const APInt &RA = RC->getAPInt();
714 if (LA.srem(RA) != 0)
715 return nullptr;
716 return SE.getConstant(LA.sdiv(RA));
717 }
718
719 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
720 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
721 if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
722 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
723 IgnoreSignificantBits);
724 if (!Step) return nullptr;
725 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
726 IgnoreSignificantBits);
727 if (!Start) return nullptr;
728 // FlagNW is independent of the start value, step direction, and is
729 // preserved with smaller magnitude steps.
730 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
731 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
732 }
733 return nullptr;
734 }
735
736 // Distribute the sdiv over add operands, if the add doesn't overflow.
737 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
738 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
739 SmallVector<const SCEV *, 8> Ops;
740 for (const SCEV *S : Add->operands()) {
741 const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
742 if (!Op) return nullptr;
743 Ops.push_back(Op);
744 }
745 return SE.getAddExpr(Ops);
746 }
747 return nullptr;
748 }
749
750 // Check for a multiply operand that we can pull RHS out of.
751 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
752 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
753 // Handle special case C1*X*Y /s C2*X*Y.
754 if (const SCEVMulExpr *MulRHS = dyn_cast<SCEVMulExpr>(RHS)) {
755 if (IgnoreSignificantBits || isMulSExtable(MulRHS, SE)) {
756 const SCEVConstant *LC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
757 const SCEVConstant *RC =
758 dyn_cast<SCEVConstant>(MulRHS->getOperand(0));
759 if (LC && RC) {
760 SmallVector<const SCEV *, 4> LOps(drop_begin(Mul->operands()));
761 SmallVector<const SCEV *, 4> ROps(drop_begin(MulRHS->operands()));
762 if (LOps == ROps)
763 return getExactSDiv(LC, RC, SE, IgnoreSignificantBits);
764 }
765 }
766 }
767
768 SmallVector<const SCEV *, 4> Ops;
769 bool Found = false;
770 for (const SCEV *S : Mul->operands()) {
771 if (!Found)
772 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
773 IgnoreSignificantBits)) {
774 S = Q;
775 Found = true;
776 }
777 Ops.push_back(S);
778 }
779 return Found ? SE.getMulExpr(Ops) : nullptr;
780 }
781 return nullptr;
782 }
783
784 // Otherwise we don't know.
785 return nullptr;
786}
787
788/// If S involves the addition of a constant integer value, return that integer
789/// value, and mutate S to point to a new SCEV with that value excluded.
790static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
791 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
792 if (C->getAPInt().getMinSignedBits() <= 64) {
793 S = SE.getConstant(C->getType(), 0);
794 return C->getValue()->getSExtValue();
795 }
796 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
797 SmallVector<const SCEV *, 8> NewOps(Add->operands());
798 int64_t Result = ExtractImmediate(NewOps.front(), SE);
799 if (Result != 0)
800 S = SE.getAddExpr(NewOps);
801 return Result;
802 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
803 SmallVector<const SCEV *, 8> NewOps(AR->operands());
804 int64_t Result = ExtractImmediate(NewOps.front(), SE);
805 if (Result != 0)
806 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
807 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
808 SCEV::FlagAnyWrap);
809 return Result;
810 }
811 return 0;
812}
813
814/// If S involves the addition of a GlobalValue address, return that symbol, and
815/// mutate S to point to a new SCEV with that value excluded.
816static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
817 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
818 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
819 S = SE.getConstant(GV->getType(), 0);
820 return GV;
821 }
822 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
823 SmallVector<const SCEV *, 8> NewOps(Add->operands());
824 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
825 if (Result)
826 S = SE.getAddExpr(NewOps);
827 return Result;
828 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
829 SmallVector<const SCEV *, 8> NewOps(AR->operands());
830 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
831 if (Result)
832 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
833 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
834 SCEV::FlagAnyWrap);
835 return Result;
836 }
837 return nullptr;
838}
839
840/// Returns true if the specified instruction is using the specified value as an
841/// address.
842static bool isAddressUse(const TargetTransformInfo &TTI,
843 Instruction *Inst, Value *OperandVal) {
844 bool isAddress = isa<LoadInst>(Inst);
845 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
846 if (SI->getPointerOperand() == OperandVal)
847 isAddress = true;
848 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
849 // Addressing modes can also be folded into prefetches and a variety
850 // of intrinsics.
851 switch (II->getIntrinsicID()) {
852 case Intrinsic::memset:
853 case Intrinsic::prefetch:
854 case Intrinsic::masked_load:
855 if (II->getArgOperand(0) == OperandVal)
856 isAddress = true;
857 break;
858 case Intrinsic::masked_store:
859 if (II->getArgOperand(1) == OperandVal)
860 isAddress = true;
861 break;
862 case Intrinsic::memmove:
863 case Intrinsic::memcpy:
864 if (II->getArgOperand(0) == OperandVal ||
865 II->getArgOperand(1) == OperandVal)
866 isAddress = true;
867 break;
868 default: {
869 MemIntrinsicInfo IntrInfo;
870 if (TTI.getTgtMemIntrinsic(II, IntrInfo)) {
871 if (IntrInfo.PtrVal == OperandVal)
872 isAddress = true;
873 }
874 }
875 }
876 } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
877 if (RMW->getPointerOperand() == OperandVal)
878 isAddress = true;
879 } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
880 if (CmpX->getPointerOperand() == OperandVal)
881 isAddress = true;
882 }
883 return isAddress;
884}
885
886/// Return the type of the memory being accessed.
887static MemAccessTy getAccessType(const TargetTransformInfo &TTI,
888 Instruction *Inst, Value *OperandVal) {
889 MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
890 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
891 AccessTy.MemTy = SI->getOperand(0)->getType();
892 AccessTy.AddrSpace = SI->getPointerAddressSpace();
893 } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
894 AccessTy.AddrSpace = LI->getPointerAddressSpace();
895 } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
896 AccessTy.AddrSpace = RMW->getPointerAddressSpace();
897 } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
898 AccessTy.AddrSpace = CmpX->getPointerAddressSpace();
899 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
900 switch (II->getIntrinsicID()) {
901 case Intrinsic::prefetch:
902 case Intrinsic::memset:
903 AccessTy.AddrSpace = II->getArgOperand(0)->getType()->getPointerAddressSpace();
904 AccessTy.MemTy = OperandVal->getType();
905 break;
906 case Intrinsic::memmove:
907 case Intrinsic::memcpy:
908 AccessTy.AddrSpace = OperandVal->getType()->getPointerAddressSpace();
909 AccessTy.MemTy = OperandVal->getType();
910 break;
911 case Intrinsic::masked_load:
912 AccessTy.AddrSpace =
913 II->getArgOperand(0)->getType()->getPointerAddressSpace();
914 break;
915 case Intrinsic::masked_store:
916 AccessTy.MemTy = II->getOperand(0)->getType();
917 AccessTy.AddrSpace =
918 II->getArgOperand(1)->getType()->getPointerAddressSpace();
919 break;
920 default: {
921 MemIntrinsicInfo IntrInfo;
922 if (TTI.getTgtMemIntrinsic(II, IntrInfo) && IntrInfo.PtrVal) {
923 AccessTy.AddrSpace
924 = IntrInfo.PtrVal->getType()->getPointerAddressSpace();
925 }
926
927 break;
928 }
929 }
930 }
931
932 // All pointers have the same requirements, so canonicalize them to an
933 // arbitrary pointer type to minimize variation.
934 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
935 AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
936 PTy->getAddressSpace());
937
938 return AccessTy;
939}
940
941/// Return true if this AddRec is already a phi in its loop.
942static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
943 for (PHINode &PN : AR->getLoop()->getHeader()->phis()) {
944 if (SE.isSCEVable(PN.getType()) &&
945 (SE.getEffectiveSCEVType(PN.getType()) ==
946 SE.getEffectiveSCEVType(AR->getType())) &&
947 SE.getSCEV(&PN) == AR)
948 return true;
949 }
950 return false;
951}
952
953/// Check if expanding this expression is likely to incur significant cost. This
954/// is tricky because SCEV doesn't track which expressions are actually computed
955/// by the current IR.
956///
957/// We currently allow expansion of IV increments that involve adds,
958/// multiplication by constants, and AddRecs from existing phis.
959///
960/// TODO: Allow UDivExpr if we can find an existing IV increment that is an
961/// obvious multiple of the UDivExpr.
962static bool isHighCostExpansion(const SCEV *S,
963 SmallPtrSetImpl<const SCEV*> &Processed,
964 ScalarEvolution &SE) {
965 // Zero/One operand expressions
966 switch (S->getSCEVType()) {
967 case scUnknown:
968 case scConstant:
969 return false;
970 case scTruncate:
971 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
972 Processed, SE);
973 case scZeroExtend:
974 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
975 Processed, SE);
976 case scSignExtend:
977 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
978 Processed, SE);
979 default:
980 break;
981 }
982
983 if (!Processed.insert(S).second)
984 return false;
985
986 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
987 for (const SCEV *S : Add->operands()) {
988 if (isHighCostExpansion(S, Processed, SE))
989 return true;
990 }
991 return false;
992 }
993
994 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
995 if (Mul->getNumOperands() == 2) {
996 // Multiplication by a constant is ok
997 if (isa<SCEVConstant>(Mul->getOperand(0)))
998 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
999
1000 // If we have the value of one operand, check if an existing
1001 // multiplication already generates this expression.
1002 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
1003 Value *UVal = U->getValue();
1004 for (User *UR : UVal->users()) {
1005 // If U is a constant, it may be used by a ConstantExpr.
1006 Instruction *UI = dyn_cast<Instruction>(UR);
1007 if (UI && UI->getOpcode() == Instruction::Mul &&
1008 SE.isSCEVable(UI->getType())) {
1009 return SE.getSCEV(UI) == Mul;
1010 }
1011 }
1012 }
1013 }
1014 }
1015
1016 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
1017 if (isExistingPhi(AR, SE))
1018 return false;
1019 }
1020
1021 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
1022 return true;
1023}
1024
1025namespace {
1026
1027class LSRUse;
1028
1029} // end anonymous namespace
1030
1031/// Check if the addressing mode defined by \p F is completely
1032/// folded in \p LU at isel time.
1033/// This includes address-mode folding and special icmp tricks.
1034/// This function returns true if \p LU can accommodate what \p F
1035/// defines and up to 1 base + 1 scaled + offset.
1036/// In other words, if \p F has several base registers, this function may
1037/// still return true. Therefore, users still need to account for
1038/// additional base registers and/or unfolded offsets to derive an
1039/// accurate cost model.
1040static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1041 const LSRUse &LU, const Formula &F);
1042
1043// Get the cost of the scaling factor used in F for LU.
1044static InstructionCost getScalingFactorCost(const TargetTransformInfo &TTI,
1045 const LSRUse &LU, const Formula &F,
1046 const Loop &L);
1047
1048namespace {
1049
1050/// This class is used to measure and compare candidate formulae.
1051class Cost {
1052 const Loop *L = nullptr;
1053 ScalarEvolution *SE = nullptr;
1054 const TargetTransformInfo *TTI = nullptr;
1055 TargetTransformInfo::LSRCost C;
1056 TTI::AddressingModeKind AMK = TTI::AMK_None;
1057
1058public:
1059 Cost() = delete;
1060 Cost(const Loop *L, ScalarEvolution &SE, const TargetTransformInfo &TTI,
1061 TTI::AddressingModeKind AMK) :
1062 L(L), SE(&SE), TTI(&TTI), AMK(AMK) {
1063 C.Insns = 0;
1064 C.NumRegs = 0;
1065 C.AddRecCost = 0;
1066 C.NumIVMuls = 0;
1067 C.NumBaseAdds = 0;
1068 C.ImmCost = 0;
1069 C.SetupCost = 0;
1070 C.ScaleCost = 0;
1071 }
1072
1073 bool isLess(Cost &Other);
1074
1075 void Lose();
1076
1077#ifndef NDEBUG
1078 // Once any of the metrics loses, they must all remain losers.
1079 bool isValid() {
1080 return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds
1081 | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u)
1082 || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds
1083 & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u);
1084 }
1085#endif
1086
1087 bool isLoser() {
1088 assert(isValid() && "invalid cost")(static_cast <bool> (isValid() && "invalid cost"
) ? void (0) : __assert_fail ("isValid() && \"invalid cost\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1088, __extension__
__PRETTY_FUNCTION__))
;
1089 return C.NumRegs == ~0u;
1090 }
1091
1092 void RateFormula(const Formula &F,
1093 SmallPtrSetImpl<const SCEV *> &Regs,
1094 const DenseSet<const SCEV *> &VisitedRegs,
1095 const LSRUse &LU,
1096 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
1097
1098 void print(raw_ostream &OS) const;
1099 void dump() const;
1100
1101private:
1102 void RateRegister(const Formula &F, const SCEV *Reg,
1103 SmallPtrSetImpl<const SCEV *> &Regs);
1104 void RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1105 SmallPtrSetImpl<const SCEV *> &Regs,
1106 SmallPtrSetImpl<const SCEV *> *LoserRegs);
1107};
1108
1109/// An operand value in an instruction which is to be replaced with some
1110/// equivalent, possibly strength-reduced, replacement.
1111struct LSRFixup {
1112 /// The instruction which will be updated.
1113 Instruction *UserInst = nullptr;
1114
1115 /// The operand of the instruction which will be replaced. The operand may be
1116 /// used more than once; every instance will be replaced.
1117 Value *OperandValToReplace = nullptr;
1118
1119 /// If this user is to use the post-incremented value of an induction
1120 /// variable, this set is non-empty and holds the loops associated with the
1121 /// induction variable.
1122 PostIncLoopSet PostIncLoops;
1123
1124 /// A constant offset to be added to the LSRUse expression. This allows
1125 /// multiple fixups to share the same LSRUse with different offsets, for
1126 /// example in an unrolled loop.
1127 int64_t Offset = 0;
1128
1129 LSRFixup() = default;
1130
1131 bool isUseFullyOutsideLoop(const Loop *L) const;
1132
1133 void print(raw_ostream &OS) const;
1134 void dump() const;
1135};
1136
1137/// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
1138/// SmallVectors of const SCEV*.
1139struct UniquifierDenseMapInfo {
1140 static SmallVector<const SCEV *, 4> getEmptyKey() {
1141 SmallVector<const SCEV *, 4> V;
1142 V.push_back(reinterpret_cast<const SCEV *>(-1));
1143 return V;
1144 }
1145
1146 static SmallVector<const SCEV *, 4> getTombstoneKey() {
1147 SmallVector<const SCEV *, 4> V;
1148 V.push_back(reinterpret_cast<const SCEV *>(-2));
1149 return V;
1150 }
1151
1152 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1153 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1154 }
1155
1156 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1157 const SmallVector<const SCEV *, 4> &RHS) {
1158 return LHS == RHS;
1159 }
1160};
1161
1162/// This class holds the state that LSR keeps for each use in IVUsers, as well
1163/// as uses invented by LSR itself. It includes information about what kinds of
1164/// things can be folded into the user, information about the user itself, and
1165/// information about how the use may be satisfied. TODO: Represent multiple
1166/// users of the same expression in common?
1167class LSRUse {
1168 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1169
1170public:
1171 /// An enum for a kind of use, indicating what types of scaled and immediate
1172 /// operands it might support.
1173 enum KindType {
1174 Basic, ///< A normal use, with no folding.
1175 Special, ///< A special case of basic, allowing -1 scales.
1176 Address, ///< An address use; folding according to TargetLowering
1177 ICmpZero ///< An equality icmp with both operands folded into one.
1178 // TODO: Add a generic icmp too?
1179 };
1180
1181 using SCEVUseKindPair = PointerIntPair<const SCEV *, 2, KindType>;
1182
1183 KindType Kind;
1184 MemAccessTy AccessTy;
1185
1186 /// The list of operands which are to be replaced.
1187 SmallVector<LSRFixup, 8> Fixups;
1188
1189 /// Keep track of the min and max offsets of the fixups.
1190 int64_t MinOffset = std::numeric_limits<int64_t>::max();
1191 int64_t MaxOffset = std::numeric_limits<int64_t>::min();
1192
1193 /// This records whether all of the fixups using this LSRUse are outside of
1194 /// the loop, in which case some special-case heuristics may be used.
1195 bool AllFixupsOutsideLoop = true;
1196
1197 /// RigidFormula is set to true to guarantee that this use will be associated
1198 /// with a single formula--the one that initially matched. Some SCEV
1199 /// expressions cannot be expanded. This allows LSR to consider the registers
1200 /// used by those expressions without the need to expand them later after
1201 /// changing the formula.
1202 bool RigidFormula = false;
1203
1204 /// This records the widest use type for any fixup using this
1205 /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1206 /// fixup widths to be equivalent, because the narrower one may be relying on
1207 /// the implicit truncation to truncate away bogus bits.
1208 Type *WidestFixupType = nullptr;
1209
1210 /// A list of ways to build a value that can satisfy this user. After the
1211 /// list is populated, one of these is selected heuristically and used to
1212 /// formulate a replacement for OperandValToReplace in UserInst.
1213 SmallVector<Formula, 12> Formulae;
1214
1215 /// The set of register candidates used by all formulae in this LSRUse.
1216 SmallPtrSet<const SCEV *, 4> Regs;
1217
1218 LSRUse(KindType K, MemAccessTy AT) : Kind(K), AccessTy(AT) {}
1219
1220 LSRFixup &getNewFixup() {
1221 Fixups.push_back(LSRFixup());
1222 return Fixups.back();
1223 }
1224
1225 void pushFixup(LSRFixup &f) {
1226 Fixups.push_back(f);
1227 if (f.Offset > MaxOffset)
1228 MaxOffset = f.Offset;
1229 if (f.Offset < MinOffset)
1230 MinOffset = f.Offset;
1231 }
1232
1233 bool HasFormulaWithSameRegs(const Formula &F) const;
1234 float getNotSelectedProbability(const SCEV *Reg) const;
1235 bool InsertFormula(const Formula &F, const Loop &L);
1236 void DeleteFormula(Formula &F);
1237 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1238
1239 void print(raw_ostream &OS) const;
1240 void dump() const;
1241};
1242
1243} // end anonymous namespace
1244
1245static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1246 LSRUse::KindType Kind, MemAccessTy AccessTy,
1247 GlobalValue *BaseGV, int64_t BaseOffset,
1248 bool HasBaseReg, int64_t Scale,
1249 Instruction *Fixup = nullptr);
1250
1251static unsigned getSetupCost(const SCEV *Reg, unsigned Depth) {
1252 if (isa<SCEVUnknown>(Reg) || isa<SCEVConstant>(Reg))
1253 return 1;
1254 if (Depth == 0)
1255 return 0;
1256 if (const auto *S = dyn_cast<SCEVAddRecExpr>(Reg))
1257 return getSetupCost(S->getStart(), Depth - 1);
1258 if (auto S = dyn_cast<SCEVIntegralCastExpr>(Reg))
1259 return getSetupCost(S->getOperand(), Depth - 1);
1260 if (auto S = dyn_cast<SCEVNAryExpr>(Reg))
1261 return std::accumulate(S->op_begin(), S->op_end(), 0,
1262 [&](unsigned i, const SCEV *Reg) {
1263 return i + getSetupCost(Reg, Depth - 1);
1264 });
1265 if (auto S = dyn_cast<SCEVUDivExpr>(Reg))
1266 return getSetupCost(S->getLHS(), Depth - 1) +
1267 getSetupCost(S->getRHS(), Depth - 1);
1268 return 0;
1269}
1270
1271/// Tally up interesting quantities from the given register.
1272void Cost::RateRegister(const Formula &F, const SCEV *Reg,
1273 SmallPtrSetImpl<const SCEV *> &Regs) {
1274 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1275 // If this is an addrec for another loop, it should be an invariant
1276 // with respect to L since L is the innermost loop (at least
1277 // for now LSR only handles innermost loops).
1278 if (AR->getLoop() != L) {
1279 // If the AddRec exists, consider it's register free and leave it alone.
1280 if (isExistingPhi(AR, *SE) && AMK != TTI::AMK_PostIndexed)
1281 return;
1282
1283 // It is bad to allow LSR for current loop to add induction variables
1284 // for its sibling loops.
1285 if (!AR->getLoop()->contains(L)) {
1286 Lose();
1287 return;
1288 }
1289
1290 // Otherwise, it will be an invariant with respect to Loop L.
1291 ++C.NumRegs;
1292 return;
1293 }
1294
1295 unsigned LoopCost = 1;
1296 if (TTI->isIndexedLoadLegal(TTI->MIM_PostInc, AR->getType()) ||
1297 TTI->isIndexedStoreLegal(TTI->MIM_PostInc, AR->getType())) {
1298
1299 // If the step size matches the base offset, we could use pre-indexed
1300 // addressing.
1301 if (AMK == TTI::AMK_PreIndexed) {
1302 if (auto *Step = dyn_cast<SCEVConstant>(AR->getStepRecurrence(*SE)))
1303 if (Step->getAPInt() == F.BaseOffset)
1304 LoopCost = 0;
1305 } else if (AMK == TTI::AMK_PostIndexed) {
1306 const SCEV *LoopStep = AR->getStepRecurrence(*SE);
1307 if (isa<SCEVConstant>(LoopStep)) {
1308 const SCEV *LoopStart = AR->getStart();
1309 if (!isa<SCEVConstant>(LoopStart) &&
1310 SE->isLoopInvariant(LoopStart, L))
1311 LoopCost = 0;
1312 }
1313 }
1314 }
1315 C.AddRecCost += LoopCost;
1316
1317 // Add the step value register, if it needs one.
1318 // TODO: The non-affine case isn't precisely modeled here.
1319 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1320 if (!Regs.count(AR->getOperand(1))) {
1321 RateRegister(F, AR->getOperand(1), Regs);
1322 if (isLoser())
1323 return;
1324 }
1325 }
1326 }
1327 ++C.NumRegs;
1328
1329 // Rough heuristic; favor registers which don't require extra setup
1330 // instructions in the preheader.
1331 C.SetupCost += getSetupCost(Reg, SetupCostDepthLimit);
1332 // Ensure we don't, even with the recusion limit, produce invalid costs.
1333 C.SetupCost = std::min<unsigned>(C.SetupCost, 1 << 16);
1334
1335 C.NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1336 SE->hasComputableLoopEvolution(Reg, L);
1337}
1338
1339/// Record this register in the set. If we haven't seen it before, rate
1340/// it. Optional LoserRegs provides a way to declare any formula that refers to
1341/// one of those regs an instant loser.
1342void Cost::RatePrimaryRegister(const Formula &F, const SCEV *Reg,
1343 SmallPtrSetImpl<const SCEV *> &Regs,
1344 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1345 if (LoserRegs && LoserRegs->count(Reg)) {
1346 Lose();
1347 return;
1348 }
1349 if (Regs.insert(Reg).second) {
1350 RateRegister(F, Reg, Regs);
1351 if (LoserRegs && isLoser())
1352 LoserRegs->insert(Reg);
1353 }
1354}
1355
1356void Cost::RateFormula(const Formula &F,
1357 SmallPtrSetImpl<const SCEV *> &Regs,
1358 const DenseSet<const SCEV *> &VisitedRegs,
1359 const LSRUse &LU,
1360 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1361 assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula")(static_cast <bool> (F.isCanonical(*L) && "Cost is accurate only for canonical formula"
) ? void (0) : __assert_fail ("F.isCanonical(*L) && \"Cost is accurate only for canonical formula\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1361, __extension__
__PRETTY_FUNCTION__))
;
1362 // Tally up the registers.
1363 unsigned PrevAddRecCost = C.AddRecCost;
1364 unsigned PrevNumRegs = C.NumRegs;
1365 unsigned PrevNumBaseAdds = C.NumBaseAdds;
1366 if (const SCEV *ScaledReg = F.ScaledReg) {
1367 if (VisitedRegs.count(ScaledReg)) {
1368 Lose();
1369 return;
1370 }
1371 RatePrimaryRegister(F, ScaledReg, Regs, LoserRegs);
1372 if (isLoser())
1373 return;
1374 }
1375 for (const SCEV *BaseReg : F.BaseRegs) {
1376 if (VisitedRegs.count(BaseReg)) {
1377 Lose();
1378 return;
1379 }
1380 RatePrimaryRegister(F, BaseReg, Regs, LoserRegs);
1381 if (isLoser())
1382 return;
1383 }
1384
1385 // Determine how many (unfolded) adds we'll need inside the loop.
1386 size_t NumBaseParts = F.getNumRegs();
1387 if (NumBaseParts > 1)
1388 // Do not count the base and a possible second register if the target
1389 // allows to fold 2 registers.
1390 C.NumBaseAdds +=
1391 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(*TTI, LU, F)));
1392 C.NumBaseAdds += (F.UnfoldedOffset != 0);
1393
1394 // Accumulate non-free scaling amounts.
1395 C.ScaleCost += *getScalingFactorCost(*TTI, LU, F, *L).getValue();
1396
1397 // Tally up the non-zero immediates.
1398 for (const LSRFixup &Fixup : LU.Fixups) {
1399 int64_t O = Fixup.Offset;
1400 int64_t Offset = (uint64_t)O + F.BaseOffset;
1401 if (F.BaseGV)
1402 C.ImmCost += 64; // Handle symbolic values conservatively.
1403 // TODO: This should probably be the pointer size.
1404 else if (Offset != 0)
1405 C.ImmCost += APInt(64, Offset, true).getMinSignedBits();
1406
1407 // Check with target if this offset with this instruction is
1408 // specifically not supported.
1409 if (LU.Kind == LSRUse::Address && Offset != 0 &&
1410 !isAMCompletelyFolded(*TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1411 Offset, F.HasBaseReg, F.Scale, Fixup.UserInst))
1412 C.NumBaseAdds++;
1413 }
1414
1415 // If we don't count instruction cost exit here.
1416 if (!InsnsCost) {
1417 assert(isValid() && "invalid cost")(static_cast <bool> (isValid() && "invalid cost"
) ? void (0) : __assert_fail ("isValid() && \"invalid cost\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1417, __extension__
__PRETTY_FUNCTION__))
;
1418 return;
1419 }
1420
1421 // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as
1422 // additional instruction (at least fill).
1423 // TODO: Need distinguish register class?
1424 unsigned TTIRegNum = TTI->getNumberOfRegisters(
1425 TTI->getRegisterClassForType(false, F.getType())) - 1;
1426 if (C.NumRegs > TTIRegNum) {
1427 // Cost already exceeded TTIRegNum, then only newly added register can add
1428 // new instructions.
1429 if (PrevNumRegs > TTIRegNum)
1430 C.Insns += (C.NumRegs - PrevNumRegs);
1431 else
1432 C.Insns += (C.NumRegs - TTIRegNum);
1433 }
1434
1435 // If ICmpZero formula ends with not 0, it could not be replaced by
1436 // just add or sub. We'll need to compare final result of AddRec.
1437 // That means we'll need an additional instruction. But if the target can
1438 // macro-fuse a compare with a branch, don't count this extra instruction.
1439 // For -10 + {0, +, 1}:
1440 // i = i + 1;
1441 // cmp i, 10
1442 //
1443 // For {-10, +, 1}:
1444 // i = i + 1;
1445 if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd() &&
1446 !TTI->canMacroFuseCmp())
1447 C.Insns++;
1448 // Each new AddRec adds 1 instruction to calculation.
1449 C.Insns += (C.AddRecCost - PrevAddRecCost);
1450
1451 // BaseAdds adds instructions for unfolded registers.
1452 if (LU.Kind != LSRUse::ICmpZero)
1453 C.Insns += C.NumBaseAdds - PrevNumBaseAdds;
1454 assert(isValid() && "invalid cost")(static_cast <bool> (isValid() && "invalid cost"
) ? void (0) : __assert_fail ("isValid() && \"invalid cost\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1454, __extension__
__PRETTY_FUNCTION__))
;
1455}
1456
1457/// Set this cost to a losing value.
1458void Cost::Lose() {
1459 C.Insns = std::numeric_limits<unsigned>::max();
1460 C.NumRegs = std::numeric_limits<unsigned>::max();
1461 C.AddRecCost = std::numeric_limits<unsigned>::max();
1462 C.NumIVMuls = std::numeric_limits<unsigned>::max();
1463 C.NumBaseAdds = std::numeric_limits<unsigned>::max();
1464 C.ImmCost = std::numeric_limits<unsigned>::max();
1465 C.SetupCost = std::numeric_limits<unsigned>::max();
1466 C.ScaleCost = std::numeric_limits<unsigned>::max();
1467}
1468
1469/// Choose the lower cost.
1470bool Cost::isLess(Cost &Other) {
1471 if (InsnsCost.getNumOccurrences() > 0 && InsnsCost &&
1472 C.Insns != Other.C.Insns)
1473 return C.Insns < Other.C.Insns;
1474 return TTI->isLSRCostLess(C, Other.C);
1475}
1476
1477#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1478void Cost::print(raw_ostream &OS) const {
1479 if (InsnsCost)
1480 OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s ");
1481 OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s");
1482 if (C.AddRecCost != 0)
1483 OS << ", with addrec cost " << C.AddRecCost;
1484 if (C.NumIVMuls != 0)
1485 OS << ", plus " << C.NumIVMuls << " IV mul"
1486 << (C.NumIVMuls == 1 ? "" : "s");
1487 if (C.NumBaseAdds != 0)
1488 OS << ", plus " << C.NumBaseAdds << " base add"
1489 << (C.NumBaseAdds == 1 ? "" : "s");
1490 if (C.ScaleCost != 0)
1491 OS << ", plus " << C.ScaleCost << " scale cost";
1492 if (C.ImmCost != 0)
1493 OS << ", plus " << C.ImmCost << " imm cost";
1494 if (C.SetupCost != 0)
1495 OS << ", plus " << C.SetupCost << " setup cost";
1496}
1497
1498LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Cost::dump() const {
1499 print(errs()); errs() << '\n';
1500}
1501#endif
1502
1503/// Test whether this fixup always uses its value outside of the given loop.
1504bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1505 // PHI nodes use their value in their incoming blocks.
1506 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1507 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1508 if (PN->getIncomingValue(i) == OperandValToReplace &&
1509 L->contains(PN->getIncomingBlock(i)))
1510 return false;
1511 return true;
1512 }
1513
1514 return !L->contains(UserInst);
1515}
1516
1517#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1518void LSRFixup::print(raw_ostream &OS) const {
1519 OS << "UserInst=";
1520 // Store is common and interesting enough to be worth special-casing.
1521 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1522 OS << "store ";
1523 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1524 } else if (UserInst->getType()->isVoidTy())
1525 OS << UserInst->getOpcodeName();
1526 else
1527 UserInst->printAsOperand(OS, /*PrintType=*/false);
1528
1529 OS << ", OperandValToReplace=";
1530 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1531
1532 for (const Loop *PIL : PostIncLoops) {
1533 OS << ", PostIncLoop=";
1534 PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1535 }
1536
1537 if (Offset != 0)
1538 OS << ", Offset=" << Offset;
1539}
1540
1541LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRFixup::dump() const {
1542 print(errs()); errs() << '\n';
1543}
1544#endif
1545
1546/// Test whether this use as a formula which has the same registers as the given
1547/// formula.
1548bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1549 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1550 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1551 // Unstable sort by host order ok, because this is only used for uniquifying.
1552 llvm::sort(Key);
1553 return Uniquifier.count(Key);
1554}
1555
1556/// The function returns a probability of selecting formula without Reg.
1557float LSRUse::getNotSelectedProbability(const SCEV *Reg) const {
1558 unsigned FNum = 0;
1559 for (const Formula &F : Formulae)
1560 if (F.referencesReg(Reg))
1561 FNum++;
1562 return ((float)(Formulae.size() - FNum)) / Formulae.size();
1563}
1564
1565/// If the given formula has not yet been inserted, add it to the list, and
1566/// return true. Return false otherwise. The formula must be in canonical form.
1567bool LSRUse::InsertFormula(const Formula &F, const Loop &L) {
1568 assert(F.isCanonical(L) && "Invalid canonical representation")(static_cast <bool> (F.isCanonical(L) && "Invalid canonical representation"
) ? void (0) : __assert_fail ("F.isCanonical(L) && \"Invalid canonical representation\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1568, __extension__
__PRETTY_FUNCTION__))
;
1569
1570 if (!Formulae.empty() && RigidFormula)
1571 return false;
1572
1573 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1574 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1575 // Unstable sort by host order ok, because this is only used for uniquifying.
1576 llvm::sort(Key);
1577
1578 if (!Uniquifier.insert(Key).second)
1579 return false;
1580
1581 // Using a register to hold the value of 0 is not profitable.
1582 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&(static_cast <bool> ((!F.ScaledReg || !F.ScaledReg->
isZero()) && "Zero allocated in a scaled register!") ?
void (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1583, __extension__
__PRETTY_FUNCTION__))
1583 "Zero allocated in a scaled register!")(static_cast <bool> ((!F.ScaledReg || !F.ScaledReg->
isZero()) && "Zero allocated in a scaled register!") ?
void (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1583, __extension__
__PRETTY_FUNCTION__))
;
1584#ifndef NDEBUG
1585 for (const SCEV *BaseReg : F.BaseRegs)
1586 assert(!BaseReg->isZero() && "Zero allocated in a base register!")(static_cast <bool> (!BaseReg->isZero() && "Zero allocated in a base register!"
) ? void (0) : __assert_fail ("!BaseReg->isZero() && \"Zero allocated in a base register!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1586, __extension__
__PRETTY_FUNCTION__))
;
1587#endif
1588
1589 // Add the formula to the list.
1590 Formulae.push_back(F);
1591
1592 // Record registers now being used by this use.
1593 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1594 if (F.ScaledReg)
1595 Regs.insert(F.ScaledReg);
1596
1597 return true;
1598}
1599
1600/// Remove the given formula from this use's list.
1601void LSRUse::DeleteFormula(Formula &F) {
1602 if (&F != &Formulae.back())
1603 std::swap(F, Formulae.back());
1604 Formulae.pop_back();
1605}
1606
1607/// Recompute the Regs field, and update RegUses.
1608void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1609 // Now that we've filtered out some formulae, recompute the Regs set.
1610 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1611 Regs.clear();
1612 for (const Formula &F : Formulae) {
1613 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1614 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1615 }
1616
1617 // Update the RegTracker.
1618 for (const SCEV *S : OldRegs)
1619 if (!Regs.count(S))
1620 RegUses.dropRegister(S, LUIdx);
1621}
1622
1623#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1624void LSRUse::print(raw_ostream &OS) const {
1625 OS << "LSR Use: Kind=";
1626 switch (Kind) {
1627 case Basic: OS << "Basic"; break;
1628 case Special: OS << "Special"; break;
1629 case ICmpZero: OS << "ICmpZero"; break;
1630 case Address:
1631 OS << "Address of ";
1632 if (AccessTy.MemTy->isPointerTy())
1633 OS << "pointer"; // the full pointer type could be really verbose
1634 else {
1635 OS << *AccessTy.MemTy;
1636 }
1637
1638 OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1639 }
1640
1641 OS << ", Offsets={";
1642 bool NeedComma = false;
1643 for (const LSRFixup &Fixup : Fixups) {
1644 if (NeedComma) OS << ',';
1645 OS << Fixup.Offset;
1646 NeedComma = true;
1647 }
1648 OS << '}';
1649
1650 if (AllFixupsOutsideLoop)
1651 OS << ", all-fixups-outside-loop";
1652
1653 if (WidestFixupType)
1654 OS << ", widest fixup type: " << *WidestFixupType;
1655}
1656
1657LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRUse::dump() const {
1658 print(errs()); errs() << '\n';
1659}
1660#endif
1661
1662static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1663 LSRUse::KindType Kind, MemAccessTy AccessTy,
1664 GlobalValue *BaseGV, int64_t BaseOffset,
1665 bool HasBaseReg, int64_t Scale,
1666 Instruction *Fixup/*= nullptr*/) {
1667 switch (Kind) {
1668 case LSRUse::Address:
1669 return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1670 HasBaseReg, Scale, AccessTy.AddrSpace, Fixup);
1671
1672 case LSRUse::ICmpZero:
1673 // There's not even a target hook for querying whether it would be legal to
1674 // fold a GV into an ICmp.
1675 if (BaseGV)
1676 return false;
1677
1678 // ICmp only has two operands; don't allow more than two non-trivial parts.
1679 if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1680 return false;
1681
1682 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1683 // putting the scaled register in the other operand of the icmp.
1684 if (Scale != 0 && Scale != -1)
1685 return false;
1686
1687 // If we have low-level target information, ask the target if it can fold an
1688 // integer immediate on an icmp.
1689 if (BaseOffset != 0) {
1690 // We have one of:
1691 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1692 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1693 // Offs is the ICmp immediate.
1694 if (Scale == 0)
1695 // The cast does the right thing with
1696 // std::numeric_limits<int64_t>::min().
1697 BaseOffset = -(uint64_t)BaseOffset;
1698 return TTI.isLegalICmpImmediate(BaseOffset);
1699 }
1700
1701 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1702 return true;
1703
1704 case LSRUse::Basic:
1705 // Only handle single-register values.
1706 return !BaseGV && Scale == 0 && BaseOffset == 0;
1707
1708 case LSRUse::Special:
1709 // Special case Basic to handle -1 scales.
1710 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1711 }
1712
1713 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1713)
;
1714}
1715
1716static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1717 int64_t MinOffset, int64_t MaxOffset,
1718 LSRUse::KindType Kind, MemAccessTy AccessTy,
1719 GlobalValue *BaseGV, int64_t BaseOffset,
1720 bool HasBaseReg, int64_t Scale) {
1721 // Check for overflow.
1722 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1723 (MinOffset > 0))
1724 return false;
1725 MinOffset = (uint64_t)BaseOffset + MinOffset;
1726 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1727 (MaxOffset > 0))
1728 return false;
1729 MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1730
1731 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1732 HasBaseReg, Scale) &&
1733 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1734 HasBaseReg, Scale);
1735}
1736
1737static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1738 int64_t MinOffset, int64_t MaxOffset,
1739 LSRUse::KindType Kind, MemAccessTy AccessTy,
1740 const Formula &F, const Loop &L) {
1741 // For the purpose of isAMCompletelyFolded either having a canonical formula
1742 // or a scale not equal to zero is correct.
1743 // Problems may arise from non canonical formulae having a scale == 0.
1744 // Strictly speaking it would best to just rely on canonical formulae.
1745 // However, when we generate the scaled formulae, we first check that the
1746 // scaling factor is profitable before computing the actual ScaledReg for
1747 // compile time sake.
1748 assert((F.isCanonical(L) || F.Scale != 0))(static_cast <bool> ((F.isCanonical(L) || F.Scale != 0)
) ? void (0) : __assert_fail ("(F.isCanonical(L) || F.Scale != 0)"
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1748, __extension__
__PRETTY_FUNCTION__))
;
1749 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1750 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1751}
1752
1753/// Test whether we know how to expand the current formula.
1754static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1755 int64_t MaxOffset, LSRUse::KindType Kind,
1756 MemAccessTy AccessTy, GlobalValue *BaseGV,
1757 int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1758 // We know how to expand completely foldable formulae.
1759 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1760 BaseOffset, HasBaseReg, Scale) ||
1761 // Or formulae that use a base register produced by a sum of base
1762 // registers.
1763 (Scale == 1 &&
1764 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1765 BaseGV, BaseOffset, true, 0));
1766}
1767
1768static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1769 int64_t MaxOffset, LSRUse::KindType Kind,
1770 MemAccessTy AccessTy, const Formula &F) {
1771 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1772 F.BaseOffset, F.HasBaseReg, F.Scale);
1773}
1774
1775static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1776 const LSRUse &LU, const Formula &F) {
1777 // Target may want to look at the user instructions.
1778 if (LU.Kind == LSRUse::Address && TTI.LSRWithInstrQueries()) {
1779 for (const LSRFixup &Fixup : LU.Fixups)
1780 if (!isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1781 (F.BaseOffset + Fixup.Offset), F.HasBaseReg,
1782 F.Scale, Fixup.UserInst))
1783 return false;
1784 return true;
1785 }
1786
1787 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1788 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1789 F.Scale);
1790}
1791
1792static InstructionCost getScalingFactorCost(const TargetTransformInfo &TTI,
1793 const LSRUse &LU, const Formula &F,
1794 const Loop &L) {
1795 if (!F.Scale)
1796 return 0;
1797
1798 // If the use is not completely folded in that instruction, we will have to
1799 // pay an extra cost only for scale != 1.
1800 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1801 LU.AccessTy, F, L))
1802 return F.Scale != 1;
1803
1804 switch (LU.Kind) {
1805 case LSRUse::Address: {
1806 // Check the scaling factor cost with both the min and max offsets.
1807 InstructionCost ScaleCostMinOffset = TTI.getScalingFactorCost(
1808 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1809 F.Scale, LU.AccessTy.AddrSpace);
1810 InstructionCost ScaleCostMaxOffset = TTI.getScalingFactorCost(
1811 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1812 F.Scale, LU.AccessTy.AddrSpace);
1813
1814 assert(ScaleCostMinOffset.isValid() && ScaleCostMaxOffset.isValid() &&(static_cast <bool> (ScaleCostMinOffset.isValid() &&
ScaleCostMaxOffset.isValid() && "Legal addressing mode has an illegal cost!"
) ? void (0) : __assert_fail ("ScaleCostMinOffset.isValid() && ScaleCostMaxOffset.isValid() && \"Legal addressing mode has an illegal cost!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1815, __extension__
__PRETTY_FUNCTION__))
1815 "Legal addressing mode has an illegal cost!")(static_cast <bool> (ScaleCostMinOffset.isValid() &&
ScaleCostMaxOffset.isValid() && "Legal addressing mode has an illegal cost!"
) ? void (0) : __assert_fail ("ScaleCostMinOffset.isValid() && ScaleCostMaxOffset.isValid() && \"Legal addressing mode has an illegal cost!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 1815, __extension__
__PRETTY_FUNCTION__))
;
1816 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1817 }
1818 case LSRUse::ICmpZero:
1819 case LSRUse::Basic:
1820 case LSRUse::Special:
1821 // The use is completely folded, i.e., everything is folded into the
1822 // instruction.
1823 return 0;
1824 }
1825
1826 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1826)
;
1827}
1828
1829static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1830 LSRUse::KindType Kind, MemAccessTy AccessTy,
1831 GlobalValue *BaseGV, int64_t BaseOffset,
1832 bool HasBaseReg) {
1833 // Fast-path: zero is always foldable.
1834 if (BaseOffset == 0 && !BaseGV) return true;
1835
1836 // Conservatively, create an address with an immediate and a
1837 // base and a scale.
1838 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1839
1840 // Canonicalize a scale of 1 to a base register if the formula doesn't
1841 // already have a base register.
1842 if (!HasBaseReg && Scale == 1) {
1843 Scale = 0;
1844 HasBaseReg = true;
1845 }
1846
1847 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1848 HasBaseReg, Scale);
1849}
1850
1851static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1852 ScalarEvolution &SE, int64_t MinOffset,
1853 int64_t MaxOffset, LSRUse::KindType Kind,
1854 MemAccessTy AccessTy, const SCEV *S,
1855 bool HasBaseReg) {
1856 // Fast-path: zero is always foldable.
1857 if (S->isZero()) return true;
1858
1859 // Conservatively, create an address with an immediate and a
1860 // base and a scale.
1861 int64_t BaseOffset = ExtractImmediate(S, SE);
1862 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1863
1864 // If there's anything else involved, it's not foldable.
1865 if (!S->isZero()) return false;
1866
1867 // Fast-path: zero is always foldable.
1868 if (BaseOffset == 0 && !BaseGV) return true;
1869
1870 // Conservatively, create an address with an immediate and a
1871 // base and a scale.
1872 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1873
1874 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1875 BaseOffset, HasBaseReg, Scale);
1876}
1877
1878namespace {
1879
1880/// An individual increment in a Chain of IV increments. Relate an IV user to
1881/// an expression that computes the IV it uses from the IV used by the previous
1882/// link in the Chain.
1883///
1884/// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1885/// original IVOperand. The head of the chain's IVOperand is only valid during
1886/// chain collection, before LSR replaces IV users. During chain generation,
1887/// IncExpr can be used to find the new IVOperand that computes the same
1888/// expression.
1889struct IVInc {
1890 Instruction *UserInst;
1891 Value* IVOperand;
1892 const SCEV *IncExpr;
1893
1894 IVInc(Instruction *U, Value *O, const SCEV *E)
1895 : UserInst(U), IVOperand(O), IncExpr(E) {}
1896};
1897
1898// The list of IV increments in program order. We typically add the head of a
1899// chain without finding subsequent links.
1900struct IVChain {
1901 SmallVector<IVInc, 1> Incs;
1902 const SCEV *ExprBase = nullptr;
1903
1904 IVChain() = default;
1905 IVChain(const IVInc &Head, const SCEV *Base)
1906 : Incs(1, Head), ExprBase(Base) {}
1907
1908 using const_iterator = SmallVectorImpl<IVInc>::const_iterator;
1909
1910 // Return the first increment in the chain.
1911 const_iterator begin() const {
1912 assert(!Incs.empty())(static_cast <bool> (!Incs.empty()) ? void (0) : __assert_fail
("!Incs.empty()", "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1912, __extension__ __PRETTY_FUNCTION__))
;
1913 return std::next(Incs.begin());
1914 }
1915 const_iterator end() const {
1916 return Incs.end();
1917 }
1918
1919 // Returns true if this chain contains any increments.
1920 bool hasIncs() const { return Incs.size() >= 2; }
1921
1922 // Add an IVInc to the end of this chain.
1923 void add(const IVInc &X) { Incs.push_back(X); }
1924
1925 // Returns the last UserInst in the chain.
1926 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1927
1928 // Returns true if IncExpr can be profitably added to this chain.
1929 bool isProfitableIncrement(const SCEV *OperExpr,
1930 const SCEV *IncExpr,
1931 ScalarEvolution&);
1932};
1933
1934/// Helper for CollectChains to track multiple IV increment uses. Distinguish
1935/// between FarUsers that definitely cross IV increments and NearUsers that may
1936/// be used between IV increments.
1937struct ChainUsers {
1938 SmallPtrSet<Instruction*, 4> FarUsers;
1939 SmallPtrSet<Instruction*, 4> NearUsers;
1940};
1941
1942/// This class holds state for the main loop strength reduction logic.
1943class LSRInstance {
1944 IVUsers &IU;
1945 ScalarEvolution &SE;
1946 DominatorTree &DT;
1947 LoopInfo &LI;
1948 AssumptionCache &AC;
1949 TargetLibraryInfo &TLI;
1950 const TargetTransformInfo &TTI;
1951 Loop *const L;
1952 MemorySSAUpdater *MSSAU;
1953 TTI::AddressingModeKind AMK;
1954 bool Changed = false;
1955
1956 /// This is the insert position that the current loop's induction variable
1957 /// increment should be placed. In simple loops, this is the latch block's
1958 /// terminator. But in more complicated cases, this is a position which will
1959 /// dominate all the in-loop post-increment users.
1960 Instruction *IVIncInsertPos = nullptr;
1961
1962 /// Interesting factors between use strides.
1963 ///
1964 /// We explicitly use a SetVector which contains a SmallSet, instead of the
1965 /// default, a SmallDenseSet, because we need to use the full range of
1966 /// int64_ts, and there's currently no good way of doing that with
1967 /// SmallDenseSet.
1968 SetVector<int64_t, SmallVector<int64_t, 8>, SmallSet<int64_t, 8>> Factors;
1969
1970 /// Interesting use types, to facilitate truncation reuse.
1971 SmallSetVector<Type *, 4> Types;
1972
1973 /// The list of interesting uses.
1974 mutable SmallVector<LSRUse, 16> Uses;
1975
1976 /// Track which uses use which register candidates.
1977 RegUseTracker RegUses;
1978
1979 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1980 // have more than a few IV increment chains in a loop. Missing a Chain falls
1981 // back to normal LSR behavior for those uses.
1982 static const unsigned MaxChains = 8;
1983
1984 /// IV users can form a chain of IV increments.
1985 SmallVector<IVChain, MaxChains> IVChainVec;
1986
1987 /// IV users that belong to profitable IVChains.
1988 SmallPtrSet<Use*, MaxChains> IVIncSet;
1989
1990 /// Induction variables that were generated and inserted by the SCEV Expander.
1991 SmallVector<llvm::WeakVH, 2> ScalarEvolutionIVs;
1992
1993 void OptimizeShadowIV();
1994 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1995 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1996 void OptimizeLoopTermCond();
1997
1998 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1999 SmallVectorImpl<ChainUsers> &ChainUsersVec);
2000 void FinalizeChain(IVChain &Chain);
2001 void CollectChains();
2002 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
2003 SmallVectorImpl<WeakTrackingVH> &DeadInsts);
2004
2005 void CollectInterestingTypesAndFactors();
2006 void CollectFixupsAndInitialFormulae();
2007
2008 // Support for sharing of LSRUses between LSRFixups.
2009 using UseMapTy = DenseMap<LSRUse::SCEVUseKindPair, size_t>;
2010 UseMapTy UseMap;
2011
2012 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
2013 LSRUse::KindType Kind, MemAccessTy AccessTy);
2014
2015 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
2016 MemAccessTy AccessTy);
2017
2018 void DeleteUse(LSRUse &LU, size_t LUIdx);
2019
2020 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
2021
2022 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
2023 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
2024 void CountRegisters(const Formula &F, size_t LUIdx);
2025 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
2026
2027 void CollectLoopInvariantFixupsAndFormulae();
2028
2029 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
2030 unsigned Depth = 0);
2031
2032 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
2033 const Formula &Base, unsigned Depth,
2034 size_t Idx, bool IsScaledReg = false);
2035 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
2036 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
2037 const Formula &Base, size_t Idx,
2038 bool IsScaledReg = false);
2039 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
2040 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
2041 const Formula &Base,
2042 const SmallVectorImpl<int64_t> &Worklist,
2043 size_t Idx, bool IsScaledReg = false);
2044 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
2045 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2046 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
2047 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
2048 void GenerateCrossUseConstantOffsets();
2049 void GenerateAllReuseFormulae();
2050
2051 void FilterOutUndesirableDedicatedRegisters();
2052
2053 size_t EstimateSearchSpaceComplexity() const;
2054 void NarrowSearchSpaceByDetectingSupersets();
2055 void NarrowSearchSpaceByCollapsingUnrolledCode();
2056 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
2057 void NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
2058 void NarrowSearchSpaceByFilterPostInc();
2059 void NarrowSearchSpaceByDeletingCostlyFormulas();
2060 void NarrowSearchSpaceByPickingWinnerRegs();
2061 void NarrowSearchSpaceUsingHeuristics();
2062
2063 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
2064 Cost &SolutionCost,
2065 SmallVectorImpl<const Formula *> &Workspace,
2066 const Cost &CurCost,
2067 const SmallPtrSet<const SCEV *, 16> &CurRegs,
2068 DenseSet<const SCEV *> &VisitedRegs) const;
2069 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
2070
2071 BasicBlock::iterator
2072 HoistInsertPosition(BasicBlock::iterator IP,
2073 const SmallVectorImpl<Instruction *> &Inputs) const;
2074 BasicBlock::iterator
2075 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
2076 const LSRFixup &LF,
2077 const LSRUse &LU,
2078 SCEVExpander &Rewriter) const;
2079
2080 Value *Expand(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2081 BasicBlock::iterator IP, SCEVExpander &Rewriter,
2082 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2083 void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
2084 const Formula &F, SCEVExpander &Rewriter,
2085 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2086 void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2087 SCEVExpander &Rewriter,
2088 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2089 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
2090
2091public:
2092 LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
2093 LoopInfo &LI, const TargetTransformInfo &TTI, AssumptionCache &AC,
2094 TargetLibraryInfo &TLI, MemorySSAUpdater *MSSAU);
2095
2096 bool getChanged() const { return Changed; }
2097 const SmallVectorImpl<WeakVH> &getScalarEvolutionIVs() const {
2098 return ScalarEvolutionIVs;
2099 }
2100
2101 void print_factors_and_types(raw_ostream &OS) const;
2102 void print_fixups(raw_ostream &OS) const;
2103 void print_uses(raw_ostream &OS) const;
2104 void print(raw_ostream &OS) const;
2105 void dump() const;
2106};
2107
2108} // end anonymous namespace
2109
2110/// If IV is used in a int-to-float cast inside the loop then try to eliminate
2111/// the cast operation.
2112void LSRInstance::OptimizeShadowIV() {
2113 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2114 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2115 return;
2116
2117 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
2118 UI != E; /* empty */) {
2119 IVUsers::const_iterator CandidateUI = UI;
2120 ++UI;
2121 Instruction *ShadowUse = CandidateUI->getUser();
2122 Type *DestTy = nullptr;
2123 bool IsSigned = false;
2124
2125 /* If shadow use is a int->float cast then insert a second IV
2126 to eliminate this cast.
2127
2128 for (unsigned i = 0; i < n; ++i)
2129 foo((double)i);
2130
2131 is transformed into
2132
2133 double d = 0.0;
2134 for (unsigned i = 0; i < n; ++i, ++d)
2135 foo(d);
2136 */
2137 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
2138 IsSigned = false;
2139 DestTy = UCast->getDestTy();
2140 }
2141 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
2142 IsSigned = true;
2143 DestTy = SCast->getDestTy();
2144 }
2145 if (!DestTy) continue;
2146
2147 // If target does not support DestTy natively then do not apply
2148 // this transformation.
2149 if (!TTI.isTypeLegal(DestTy)) continue;
2150
2151 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2152 if (!PH) continue;
2153 if (PH->getNumIncomingValues() != 2) continue;
2154
2155 // If the calculation in integers overflows, the result in FP type will
2156 // differ. So we only can do this transformation if we are guaranteed to not
2157 // deal with overflowing values
2158 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PH));
2159 if (!AR) continue;
2160 if (IsSigned && !AR->hasNoSignedWrap()) continue;
2161 if (!IsSigned && !AR->hasNoUnsignedWrap()) continue;
2162
2163 Type *SrcTy = PH->getType();
2164 int Mantissa = DestTy->getFPMantissaWidth();
2165 if (Mantissa == -1) continue;
2166 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
2167 continue;
2168
2169 unsigned Entry, Latch;
2170 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2171 Entry = 0;
2172 Latch = 1;
2173 } else {
2174 Entry = 1;
2175 Latch = 0;
2176 }
2177
2178 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
2179 if (!Init) continue;
2180 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
2181 (double)Init->getSExtValue() :
2182 (double)Init->getZExtValue());
2183
2184 BinaryOperator *Incr =
2185 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
2186 if (!Incr) continue;
2187 if (Incr->getOpcode() != Instruction::Add
2188 && Incr->getOpcode() != Instruction::Sub)
2189 continue;
2190
2191 /* Initialize new IV, double d = 0.0 in above example. */
2192 ConstantInt *C = nullptr;
2193 if (Incr->getOperand(0) == PH)
2194 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2195 else if (Incr->getOperand(1) == PH)
2196 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2197 else
2198 continue;
2199
2200 if (!C) continue;
2201
2202 // Ignore negative constants, as the code below doesn't handle them
2203 // correctly. TODO: Remove this restriction.
2204 if (!C->getValue().isStrictlyPositive()) continue;
2205
2206 /* Add new PHINode. */
2207 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
2208
2209 /* create new increment. '++d' in above example. */
2210 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2211 BinaryOperator *NewIncr =
2212 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
2213 Instruction::FAdd : Instruction::FSub,
2214 NewPH, CFP, "IV.S.next.", Incr);
2215
2216 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2217 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2218
2219 /* Remove cast operation */
2220 ShadowUse->replaceAllUsesWith(NewPH);
2221 ShadowUse->eraseFromParent();
2222 Changed = true;
2223 break;
2224 }
2225}
2226
2227/// If Cond has an operand that is an expression of an IV, set the IV user and
2228/// stride information and return true, otherwise return false.
2229bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
2230 for (IVStrideUse &U : IU)
2231 if (U.getUser() == Cond) {
2232 // NOTE: we could handle setcc instructions with multiple uses here, but
2233 // InstCombine does it as well for simple uses, it's not clear that it
2234 // occurs enough in real life to handle.
2235 CondUse = &U;
2236 return true;
2237 }
2238 return false;
2239}
2240
2241/// Rewrite the loop's terminating condition if it uses a max computation.
2242///
2243/// This is a narrow solution to a specific, but acute, problem. For loops
2244/// like this:
2245///
2246/// i = 0;
2247/// do {
2248/// p[i] = 0.0;
2249/// } while (++i < n);
2250///
2251/// the trip count isn't just 'n', because 'n' might not be positive. And
2252/// unfortunately this can come up even for loops where the user didn't use
2253/// a C do-while loop. For example, seemingly well-behaved top-test loops
2254/// will commonly be lowered like this:
2255///
2256/// if (n > 0) {
2257/// i = 0;
2258/// do {
2259/// p[i] = 0.0;
2260/// } while (++i < n);
2261/// }
2262///
2263/// and then it's possible for subsequent optimization to obscure the if
2264/// test in such a way that indvars can't find it.
2265///
2266/// When indvars can't find the if test in loops like this, it creates a
2267/// max expression, which allows it to give the loop a canonical
2268/// induction variable:
2269///
2270/// i = 0;
2271/// max = n < 1 ? 1 : n;
2272/// do {
2273/// p[i] = 0.0;
2274/// } while (++i != max);
2275///
2276/// Canonical induction variables are necessary because the loop passes
2277/// are designed around them. The most obvious example of this is the
2278/// LoopInfo analysis, which doesn't remember trip count values. It
2279/// expects to be able to rediscover the trip count each time it is
2280/// needed, and it does this using a simple analysis that only succeeds if
2281/// the loop has a canonical induction variable.
2282///
2283/// However, when it comes time to generate code, the maximum operation
2284/// can be quite costly, especially if it's inside of an outer loop.
2285///
2286/// This function solves this problem by detecting this type of loop and
2287/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2288/// the instructions for the maximum computation.
2289ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
2290 // Check that the loop matches the pattern we're looking for.
2291 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2292 Cond->getPredicate() != CmpInst::ICMP_NE)
2293 return Cond;
2294
2295 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2296 if (!Sel || !Sel->hasOneUse()) return Cond;
2297
2298 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2299 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2300 return Cond;
2301 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2302
2303 // Add one to the backedge-taken count to get the trip count.
2304 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2305 if (IterationCount != SE.getSCEV(Sel)) return Cond;
2306
2307 // Check for a max calculation that matches the pattern. There's no check
2308 // for ICMP_ULE here because the comparison would be with zero, which
2309 // isn't interesting.
2310 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2311 const SCEVNAryExpr *Max = nullptr;
2312 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2313 Pred = ICmpInst::ICMP_SLE;
2314 Max = S;
2315 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2316 Pred = ICmpInst::ICMP_SLT;
2317 Max = S;
2318 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2319 Pred = ICmpInst::ICMP_ULT;
2320 Max = U;
2321 } else {
2322 // No match; bail.
2323 return Cond;
2324 }
2325
2326 // To handle a max with more than two operands, this optimization would
2327 // require additional checking and setup.
2328 if (Max->getNumOperands() != 2)
2329 return Cond;
2330
2331 const SCEV *MaxLHS = Max->getOperand(0);
2332 const SCEV *MaxRHS = Max->getOperand(1);
2333
2334 // ScalarEvolution canonicalizes constants to the left. For < and >, look
2335 // for a comparison with 1. For <= and >=, a comparison with zero.
2336 if (!MaxLHS ||
2337 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2338 return Cond;
2339
2340 // Check the relevant induction variable for conformance to
2341 // the pattern.
2342 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2343 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2344 if (!AR || !AR->isAffine() ||
2345 AR->getStart() != One ||
2346 AR->getStepRecurrence(SE) != One)
2347 return Cond;
2348
2349 assert(AR->getLoop() == L &&(static_cast <bool> (AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? void (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 2350, __extension__
__PRETTY_FUNCTION__))
2350 "Loop condition operand is an addrec in a different loop!")(static_cast <bool> (AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? void (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 2350, __extension__
__PRETTY_FUNCTION__))
;
2351
2352 // Check the right operand of the select, and remember it, as it will
2353 // be used in the new comparison instruction.
2354 Value *NewRHS = nullptr;
2355 if (ICmpInst::isTrueWhenEqual(Pred)) {
2356 // Look for n+1, and grab n.
2357 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2358 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2359 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2360 NewRHS = BO->getOperand(0);
2361 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2362 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2363 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2364 NewRHS = BO->getOperand(0);
2365 if (!NewRHS)
2366 return Cond;
2367 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2368 NewRHS = Sel->getOperand(1);
2369 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2370 NewRHS = Sel->getOperand(2);
2371 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2372 NewRHS = SU->getValue();
2373 else
2374 // Max doesn't match expected pattern.
2375 return Cond;
2376
2377 // Determine the new comparison opcode. It may be signed or unsigned,
2378 // and the original comparison may be either equality or inequality.
2379 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2380 Pred = CmpInst::getInversePredicate(Pred);
2381
2382 // Ok, everything looks ok to change the condition into an SLT or SGE and
2383 // delete the max calculation.
2384 ICmpInst *NewCond =
2385 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2386
2387 // Delete the max calculation instructions.
2388 NewCond->setDebugLoc(Cond->getDebugLoc());
2389 Cond->replaceAllUsesWith(NewCond);
2390 CondUse->setUser(NewCond);
2391 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2392 Cond->eraseFromParent();
2393 Sel->eraseFromParent();
2394 if (Cmp->use_empty())
2395 Cmp->eraseFromParent();
2396 return NewCond;
2397}
2398
2399/// Change loop terminating condition to use the postinc iv when possible.
2400void
2401LSRInstance::OptimizeLoopTermCond() {
2402 SmallPtrSet<Instruction *, 4> PostIncs;
2403
2404 // We need a different set of heuristics for rotated and non-rotated loops.
2405 // If a loop is rotated then the latch is also the backedge, so inserting
2406 // post-inc expressions just before the latch is ideal. To reduce live ranges
2407 // it also makes sense to rewrite terminating conditions to use post-inc
2408 // expressions.
2409 //
2410 // If the loop is not rotated then the latch is not a backedge; the latch
2411 // check is done in the loop head. Adding post-inc expressions before the
2412 // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2413 // in the loop body. In this case we do *not* want to use post-inc expressions
2414 // in the latch check, and we want to insert post-inc expressions before
2415 // the backedge.
2416 BasicBlock *LatchBlock = L->getLoopLatch();
2417 SmallVector<BasicBlock*, 8> ExitingBlocks;
2418 L->getExitingBlocks(ExitingBlocks);
2419 if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2420 return LatchBlock != BB;
2421 })) {
2422 // The backedge doesn't exit the loop; treat this as a head-tested loop.
2423 IVIncInsertPos = LatchBlock->getTerminator();
2424 return;
2425 }
2426
2427 // Otherwise treat this as a rotated loop.
2428 for (BasicBlock *ExitingBlock : ExitingBlocks) {
2429 // Get the terminating condition for the loop if possible. If we
2430 // can, we want to change it to use a post-incremented version of its
2431 // induction variable, to allow coalescing the live ranges for the IV into
2432 // one register value.
2433
2434 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2435 if (!TermBr)
2436 continue;
2437 // FIXME: Overly conservative, termination condition could be an 'or' etc..
2438 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2439 continue;
2440
2441 // Search IVUsesByStride to find Cond's IVUse if there is one.
2442 IVStrideUse *CondUse = nullptr;
2443 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2444 if (!FindIVUserForCond(Cond, CondUse))
2445 continue;
2446
2447 // If the trip count is computed in terms of a max (due to ScalarEvolution
2448 // being unable to find a sufficient guard, for example), change the loop
2449 // comparison to use SLT or ULT instead of NE.
2450 // One consequence of doing this now is that it disrupts the count-down
2451 // optimization. That's not always a bad thing though, because in such
2452 // cases it may still be worthwhile to avoid a max.
2453 Cond = OptimizeMax(Cond, CondUse);
2454
2455 // If this exiting block dominates the latch block, it may also use
2456 // the post-inc value if it won't be shared with other uses.
2457 // Check for dominance.
2458 if (!DT.dominates(ExitingBlock, LatchBlock))
2459 continue;
2460
2461 // Conservatively avoid trying to use the post-inc value in non-latch
2462 // exits if there may be pre-inc users in intervening blocks.
2463 if (LatchBlock != ExitingBlock)
2464 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2465 // Test if the use is reachable from the exiting block. This dominator
2466 // query is a conservative approximation of reachability.
2467 if (&*UI != CondUse &&
2468 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2469 // Conservatively assume there may be reuse if the quotient of their
2470 // strides could be a legal scale.
2471 const SCEV *A = IU.getStride(*CondUse, L);
2472 const SCEV *B = IU.getStride(*UI, L);
2473 if (!A || !B) continue;
2474 if (SE.getTypeSizeInBits(A->getType()) !=
2475 SE.getTypeSizeInBits(B->getType())) {
2476 if (SE.getTypeSizeInBits(A->getType()) >
2477 SE.getTypeSizeInBits(B->getType()))
2478 B = SE.getSignExtendExpr(B, A->getType());
2479 else
2480 A = SE.getSignExtendExpr(A, B->getType());
2481 }
2482 if (const SCEVConstant *D =
2483 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2484 const ConstantInt *C = D->getValue();
2485 // Stride of one or negative one can have reuse with non-addresses.
2486 if (C->isOne() || C->isMinusOne())
2487 goto decline_post_inc;
2488 // Avoid weird situations.
2489 if (C->getValue().getMinSignedBits() >= 64 ||
2490 C->getValue().isMinSignedValue())
2491 goto decline_post_inc;
2492 // Check for possible scaled-address reuse.
2493 if (isAddressUse(TTI, UI->getUser(), UI->getOperandValToReplace())) {
2494 MemAccessTy AccessTy = getAccessType(
2495 TTI, UI->getUser(), UI->getOperandValToReplace());
2496 int64_t Scale = C->getSExtValue();
2497 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2498 /*BaseOffset=*/0,
2499 /*HasBaseReg=*/false, Scale,
2500 AccessTy.AddrSpace))
2501 goto decline_post_inc;
2502 Scale = -Scale;
2503 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2504 /*BaseOffset=*/0,
2505 /*HasBaseReg=*/false, Scale,
2506 AccessTy.AddrSpace))
2507 goto decline_post_inc;
2508 }
2509 }
2510 }
2511
2512 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)
2513 << *Cond << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Change loop exiting icmp to use postinc iv: "
<< *Cond << '\n'; } } while (false)
;
2514
2515 // It's possible for the setcc instruction to be anywhere in the loop, and
2516 // possible for it to have multiple users. If it is not immediately before
2517 // the exiting block branch, move it.
2518 if (Cond->getNextNonDebugInstruction() != TermBr) {
2519 if (Cond->hasOneUse()) {
2520 Cond->moveBefore(TermBr);
2521 } else {
2522 // Clone the terminating condition and insert into the loopend.
2523 ICmpInst *OldCond = Cond;
2524 Cond = cast<ICmpInst>(Cond->clone());
2525 Cond->setName(L->getHeader()->getName() + ".termcond");
2526 ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2527
2528 // Clone the IVUse, as the old use still exists!
2529 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2530 TermBr->replaceUsesOfWith(OldCond, Cond);
2531 }
2532 }
2533
2534 // If we get to here, we know that we can transform the setcc instruction to
2535 // use the post-incremented version of the IV, allowing us to coalesce the
2536 // live ranges for the IV correctly.
2537 CondUse->transformToPostInc(L);
2538 Changed = true;
2539
2540 PostIncs.insert(Cond);
2541 decline_post_inc:;
2542 }
2543
2544 // Determine an insertion point for the loop induction variable increment. It
2545 // must dominate all the post-inc comparisons we just set up, and it must
2546 // dominate the loop latch edge.
2547 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2548 for (Instruction *Inst : PostIncs) {
2549 BasicBlock *BB =
2550 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2551 Inst->getParent());
2552 if (BB == Inst->getParent())
2553 IVIncInsertPos = Inst;
2554 else if (BB != IVIncInsertPos->getParent())
2555 IVIncInsertPos = BB->getTerminator();
2556 }
2557}
2558
2559/// Determine if the given use can accommodate a fixup at the given offset and
2560/// other details. If so, update the use and return true.
2561bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2562 bool HasBaseReg, LSRUse::KindType Kind,
2563 MemAccessTy AccessTy) {
2564 int64_t NewMinOffset = LU.MinOffset;
2565 int64_t NewMaxOffset = LU.MaxOffset;
2566 MemAccessTy NewAccessTy = AccessTy;
2567
2568 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2569 // something conservative, however this can pessimize in the case that one of
2570 // the uses will have all its uses outside the loop, for example.
2571 if (LU.Kind != Kind)
2572 return false;
2573
2574 // Check for a mismatched access type, and fall back conservatively as needed.
2575 // TODO: Be less conservative when the type is similar and can use the same
2576 // addressing modes.
2577 if (Kind == LSRUse::Address) {
2578 if (AccessTy.MemTy != LU.AccessTy.MemTy) {
2579 NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(),
2580 AccessTy.AddrSpace);
2581 }
2582 }
2583
2584 // Conservatively assume HasBaseReg is true for now.
2585 if (NewOffset < LU.MinOffset) {
2586 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2587 LU.MaxOffset - NewOffset, HasBaseReg))
2588 return false;
2589 NewMinOffset = NewOffset;
2590 } else if (NewOffset > LU.MaxOffset) {
2591 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2592 NewOffset - LU.MinOffset, HasBaseReg))
2593 return false;
2594 NewMaxOffset = NewOffset;
2595 }
2596
2597 // Update the use.
2598 LU.MinOffset = NewMinOffset;
2599 LU.MaxOffset = NewMaxOffset;
2600 LU.AccessTy = NewAccessTy;
2601 return true;
2602}
2603
2604/// Return an LSRUse index and an offset value for a fixup which needs the given
2605/// expression, with the given kind and optional access type. Either reuse an
2606/// existing use or create a new one, as needed.
2607std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2608 LSRUse::KindType Kind,
2609 MemAccessTy AccessTy) {
2610 const SCEV *Copy = Expr;
2611 int64_t Offset = ExtractImmediate(Expr, SE);
2612
2613 // Basic uses can't accept any offset, for example.
2614 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2615 Offset, /*HasBaseReg=*/ true)) {
2616 Expr = Copy;
2617 Offset = 0;
2618 }
2619
2620 std::pair<UseMapTy::iterator, bool> P =
2621 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2622 if (!P.second) {
2623 // A use already existed with this base.
2624 size_t LUIdx = P.first->second;
2625 LSRUse &LU = Uses[LUIdx];
2626 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2627 // Reuse this use.
2628 return std::make_pair(LUIdx, Offset);
2629 }
2630
2631 // Create a new use.
2632 size_t LUIdx = Uses.size();
2633 P.first->second = LUIdx;
2634 Uses.push_back(LSRUse(Kind, AccessTy));
2635 LSRUse &LU = Uses[LUIdx];
2636
2637 LU.MinOffset = Offset;
2638 LU.MaxOffset = Offset;
2639 return std::make_pair(LUIdx, Offset);
2640}
2641
2642/// Delete the given use from the Uses list.
2643void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2644 if (&LU != &Uses.back())
2645 std::swap(LU, Uses.back());
2646 Uses.pop_back();
2647
2648 // Update RegUses.
2649 RegUses.swapAndDropUse(LUIdx, Uses.size());
2650}
2651
2652/// Look for a use distinct from OrigLU which is has a formula that has the same
2653/// registers as the given formula.
2654LSRUse *
2655LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2656 const LSRUse &OrigLU) {
2657 // Search all uses for the formula. This could be more clever.
2658 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2659 LSRUse &LU = Uses[LUIdx];
2660 // Check whether this use is close enough to OrigLU, to see whether it's
2661 // worthwhile looking through its formulae.
2662 // Ignore ICmpZero uses because they may contain formulae generated by
2663 // GenerateICmpZeroScales, in which case adding fixup offsets may
2664 // be invalid.
2665 if (&LU != &OrigLU &&
2666 LU.Kind != LSRUse::ICmpZero &&
2667 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2668 LU.WidestFixupType == OrigLU.WidestFixupType &&
2669 LU.HasFormulaWithSameRegs(OrigF)) {
2670 // Scan through this use's formulae.
2671 for (const Formula &F : LU.Formulae) {
2672 // Check to see if this formula has the same registers and symbols
2673 // as OrigF.
2674 if (F.BaseRegs == OrigF.BaseRegs &&
2675 F.ScaledReg == OrigF.ScaledReg &&
2676 F.BaseGV == OrigF.BaseGV &&
2677 F.Scale == OrigF.Scale &&
2678 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2679 if (F.BaseOffset == 0)
2680 return &LU;
2681 // This is the formula where all the registers and symbols matched;
2682 // there aren't going to be any others. Since we declined it, we
2683 // can skip the rest of the formulae and proceed to the next LSRUse.
2684 break;
2685 }
2686 }
2687 }
2688 }
2689
2690 // Nothing looked good.
2691 return nullptr;
2692}
2693
2694void LSRInstance::CollectInterestingTypesAndFactors() {
2695 SmallSetVector<const SCEV *, 4> Strides;
2696
2697 // Collect interesting types and strides.
2698 SmallVector<const SCEV *, 4> Worklist;
2699 for (const IVStrideUse &U : IU) {
2700 const SCEV *Expr = IU.getExpr(U);
2701
2702 // Collect interesting types.
2703 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2704
2705 // Add strides for mentioned loops.
2706 Worklist.push_back(Expr);
2707 do {
2708 const SCEV *S = Worklist.pop_back_val();
2709 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2710 if (AR->getLoop() == L)
2711 Strides.insert(AR->getStepRecurrence(SE));
2712 Worklist.push_back(AR->getStart());
2713 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2714 Worklist.append(Add->op_begin(), Add->op_end());
2715 }
2716 } while (!Worklist.empty());
2717 }
2718
2719 // Compute interesting factors from the set of interesting strides.
2720 for (SmallSetVector<const SCEV *, 4>::const_iterator
2721 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2722 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2723 std::next(I); NewStrideIter != E; ++NewStrideIter) {
2724 const SCEV *OldStride = *I;
2725 const SCEV *NewStride = *NewStrideIter;
2726
2727 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2728 SE.getTypeSizeInBits(NewStride->getType())) {
2729 if (SE.getTypeSizeInBits(OldStride->getType()) >
2730 SE.getTypeSizeInBits(NewStride->getType()))
2731 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2732 else
2733 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2734 }
2735 if (const SCEVConstant *Factor =
2736 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2737 SE, true))) {
2738 if (Factor->getAPInt().getMinSignedBits() <= 64 && !Factor->isZero())
2739 Factors.insert(Factor->getAPInt().getSExtValue());
2740 } else if (const SCEVConstant *Factor =
2741 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2742 NewStride,
2743 SE, true))) {
2744 if (Factor->getAPInt().getMinSignedBits() <= 64 && !Factor->isZero())
2745 Factors.insert(Factor->getAPInt().getSExtValue());
2746 }
2747 }
2748
2749 // If all uses use the same type, don't bother looking for truncation-based
2750 // reuse.
2751 if (Types.size() == 1)
2752 Types.clear();
2753
2754 LLVM_DEBUG(print_factors_and_types(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_factors_and_types(dbgs()); } } while
(false)
;
2755}
2756
2757/// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2758/// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2759/// IVStrideUses, we could partially skip this.
2760static User::op_iterator
2761findIVOperand(User::op_iterator OI, User::op_iterator OE,
2762 Loop *L, ScalarEvolution &SE) {
2763 for(; OI != OE; ++OI) {
2764 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2765 if (!SE.isSCEVable(Oper->getType()))
2766 continue;
2767
2768 if (const SCEVAddRecExpr *AR =
2769 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2770 if (AR->getLoop() == L)
2771 break;
2772 }
2773 }
2774 }
2775 return OI;
2776}
2777
2778/// IVChain logic must consistently peek base TruncInst operands, so wrap it in
2779/// a convenient helper.
2780static Value *getWideOperand(Value *Oper) {
2781 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2782 return Trunc->getOperand(0);
2783 return Oper;
2784}
2785
2786/// Return true if we allow an IV chain to include both types.
2787static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2788 Type *LType = LVal->getType();
2789 Type *RType = RVal->getType();
2790 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy() &&
2791 // Different address spaces means (possibly)
2792 // different types of the pointer implementation,
2793 // e.g. i16 vs i32 so disallow that.
2794 (LType->getPointerAddressSpace() ==
2795 RType->getPointerAddressSpace()));
2796}
2797
2798/// Return an approximation of this SCEV expression's "base", or NULL for any
2799/// constant. Returning the expression itself is conservative. Returning a
2800/// deeper subexpression is more precise and valid as long as it isn't less
2801/// complex than another subexpression. For expressions involving multiple
2802/// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2803/// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2804/// IVInc==b-a.
2805///
2806/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2807/// SCEVUnknown, we simply return the rightmost SCEV operand.
2808static const SCEV *getExprBase(const SCEV *S) {
2809 switch (S->getSCEVType()) {
2810 default: // uncluding scUnknown.
2811 return S;
2812 case scConstant:
2813 return nullptr;
2814 case scTruncate:
2815 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2816 case scZeroExtend:
2817 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2818 case scSignExtend:
2819 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2820 case scAddExpr: {
2821 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2822 // there's nothing more complex.
2823 // FIXME: not sure if we want to recognize negation.
2824 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2825 for (const SCEV *SubExpr : reverse(Add->operands())) {
2826 if (SubExpr->getSCEVType() == scAddExpr)
2827 return getExprBase(SubExpr);
2828
2829 if (SubExpr->getSCEVType() != scMulExpr)
2830 return SubExpr;
2831 }
2832 return S; // all operands are scaled, be conservative.
2833 }
2834 case scAddRecExpr:
2835 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2836 }
2837 llvm_unreachable("Unknown SCEV kind!")::llvm::llvm_unreachable_internal("Unknown SCEV kind!", "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2837)
;
2838}
2839
2840/// Return true if the chain increment is profitable to expand into a loop
2841/// invariant value, which may require its own register. A profitable chain
2842/// increment will be an offset relative to the same base. We allow such offsets
2843/// to potentially be used as chain increment as long as it's not obviously
2844/// expensive to expand using real instructions.
2845bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2846 const SCEV *IncExpr,
2847 ScalarEvolution &SE) {
2848 // Aggressively form chains when -stress-ivchain.
2849 if (StressIVChain)
2850 return true;
2851
2852 // Do not replace a constant offset from IV head with a nonconstant IV
2853 // increment.
2854 if (!isa<SCEVConstant>(IncExpr)) {
2855 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2856 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2857 return false;
2858 }
2859
2860 SmallPtrSet<const SCEV*, 8> Processed;
2861 return !isHighCostExpansion(IncExpr, Processed, SE);
2862}
2863
2864/// Return true if the number of registers needed for the chain is estimated to
2865/// be less than the number required for the individual IV users. First prohibit
2866/// any IV users that keep the IV live across increments (the Users set should
2867/// be empty). Next count the number and type of increments in the chain.
2868///
2869/// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2870/// effectively use postinc addressing modes. Only consider it profitable it the
2871/// increments can be computed in fewer registers when chained.
2872///
2873/// TODO: Consider IVInc free if it's already used in another chains.
2874static bool isProfitableChain(IVChain &Chain,
2875 SmallPtrSetImpl<Instruction *> &Users,
2876 ScalarEvolution &SE,
2877 const TargetTransformInfo &TTI) {
2878 if (StressIVChain)
2879 return true;
2880
2881 if (!Chain.hasIncs())
2882 return false;
2883
2884 if (!Users.empty()) {
2885 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)
2886 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)
2887 : 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)
;
2888 return false;
2889 }
2890 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")(static_cast <bool> (!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? void (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 2890, __extension__
__PRETTY_FUNCTION__))
;
2891
2892 // The chain itself may require a register, so intialize cost to 1.
2893 int cost = 1;
2894
2895 // A complete chain likely eliminates the need for keeping the original IV in
2896 // a register. LSR does not currently know how to form a complete chain unless
2897 // the header phi already exists.
2898 if (isa<PHINode>(Chain.tailUserInst())
2899 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2900 --cost;
2901 }
2902 const SCEV *LastIncExpr = nullptr;
2903 unsigned NumConstIncrements = 0;
2904 unsigned NumVarIncrements = 0;
2905 unsigned NumReusedIncrements = 0;
2906
2907 if (TTI.isProfitableLSRChainElement(Chain.Incs[0].UserInst))
2908 return true;
2909
2910 for (const IVInc &Inc : Chain) {
2911 if (TTI.isProfitableLSRChainElement(Inc.UserInst))
2912 return true;
2913 if (Inc.IncExpr->isZero())
2914 continue;
2915
2916 // Incrementing by zero or some constant is neutral. We assume constants can
2917 // be folded into an addressing mode or an add's immediate operand.
2918 if (isa<SCEVConstant>(Inc.IncExpr)) {
2919 ++NumConstIncrements;
2920 continue;
2921 }
2922
2923 if (Inc.IncExpr == LastIncExpr)
2924 ++NumReusedIncrements;
2925 else
2926 ++NumVarIncrements;
2927
2928 LastIncExpr = Inc.IncExpr;
2929 }
2930 // An IV chain with a single increment is handled by LSR's postinc
2931 // uses. However, a chain with multiple increments requires keeping the IV's
2932 // value live longer than it needs to be if chained.
2933 if (NumConstIncrements > 1)
2934 --cost;
2935
2936 // Materializing increment expressions in the preheader that didn't exist in
2937 // the original code may cost a register. For example, sign-extended array
2938 // indices can produce ridiculous increments like this:
2939 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2940 cost += NumVarIncrements;
2941
2942 // Reusing variable increments likely saves a register to hold the multiple of
2943 // the stride.
2944 cost -= NumReusedIncrements;
2945
2946 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)
2947 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " Cost: " << cost << "\n"
; } } while (false)
;
2948
2949 return cost < 0;
2950}
2951
2952/// Add this IV user to an existing chain or make it the head of a new chain.
2953void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2954 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2955 // When IVs are used as types of varying widths, they are generally converted
2956 // to a wider type with some uses remaining narrow under a (free) trunc.
2957 Value *const NextIV = getWideOperand(IVOper);
2958 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2959 const SCEV *const OperExprBase = getExprBase(OperExpr);
2960
2961 // Visit all existing chains. Check if its IVOper can be computed as a
2962 // profitable loop invariant increment from the last link in the Chain.
2963 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2964 const SCEV *LastIncExpr = nullptr;
2965 for (; ChainIdx < NChains; ++ChainIdx) {
2966 IVChain &Chain = IVChainVec[ChainIdx];
2967
2968 // Prune the solution space aggressively by checking that both IV operands
2969 // are expressions that operate on the same unscaled SCEVUnknown. This
2970 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2971 // first avoids creating extra SCEV expressions.
2972 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2973 continue;
2974
2975 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2976 if (!isCompatibleIVType(PrevIV, NextIV))
2977 continue;
2978
2979 // A phi node terminates a chain.
2980 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2981 continue;
2982
2983 // The increment must be loop-invariant so it can be kept in a register.
2984 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2985 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2986 if (isa<SCEVCouldNotCompute>(IncExpr) || !SE.isLoopInvariant(IncExpr, L))
2987 continue;
2988
2989 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2990 LastIncExpr = IncExpr;
2991 break;
2992 }
2993 }
2994 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2995 // bother for phi nodes, because they must be last in the chain.
2996 if (ChainIdx == NChains) {
2997 if (isa<PHINode>(UserInst))
2998 return;
2999 if (NChains >= MaxChains && !StressIVChain) {
3000 LLVM_DEBUG(dbgs() << "IV Chain Limit\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain Limit\n"; } } while
(false)
;
3001 return;
3002 }
3003 LastIncExpr = OperExpr;
3004 // IVUsers may have skipped over sign/zero extensions. We don't currently
3005 // attempt to form chains involving extensions unless they can be hoisted
3006 // into this loop's AddRec.
3007 if (!isa<SCEVAddRecExpr>(LastIncExpr))
3008 return;
3009 ++NChains;
3010 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
3011 OperExprBase));
3012 ChainUsersVec.resize(NChains);
3013 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)
3014 << ") IV=" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Head: (" << *UserInst << ") IV=" <<
*LastIncExpr << "\n"; } } while (false)
;
3015 } else {
3016 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)
3017 << ") IV+" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Inc: (" << *UserInst << ") IV+" <<
*LastIncExpr << "\n"; } } while (false)
;
3018 // Add this IV user to the end of the chain.
3019 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
3020 }
3021 IVChain &Chain = IVChainVec[ChainIdx];
3022
3023 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
3024 // This chain's NearUsers become FarUsers.
3025 if (!LastIncExpr->isZero()) {
3026 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
3027 NearUsers.end());
3028 NearUsers.clear();
3029 }
3030
3031 // All other uses of IVOperand become near uses of the chain.
3032 // We currently ignore intermediate values within SCEV expressions, assuming
3033 // they will eventually be used be the current chain, or can be computed
3034 // from one of the chain increments. To be more precise we could
3035 // transitively follow its user and only add leaf IV users to the set.
3036 for (User *U : IVOper->users()) {
3037 Instruction *OtherUse = dyn_cast<Instruction>(U);
3038 if (!OtherUse)
3039 continue;
3040 // Uses in the chain will no longer be uses if the chain is formed.
3041 // Include the head of the chain in this iteration (not Chain.begin()).
3042 IVChain::const_iterator IncIter = Chain.Incs.begin();
3043 IVChain::const_iterator IncEnd = Chain.Incs.end();
3044 for( ; IncIter != IncEnd; ++IncIter) {
3045 if (IncIter->UserInst == OtherUse)
3046 break;
3047 }
3048 if (IncIter != IncEnd)
3049 continue;
3050
3051 if (SE.isSCEVable(OtherUse->getType())
3052 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
3053 && IU.isIVUserOrOperand(OtherUse)) {
3054 continue;
3055 }
3056 NearUsers.insert(OtherUse);
3057 }
3058
3059 // Since this user is part of the chain, it's no longer considered a use
3060 // of the chain.
3061 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
3062}
3063
3064/// Populate the vector of Chains.
3065///
3066/// This decreases ILP at the architecture level. Targets with ample registers,
3067/// multiple memory ports, and no register renaming probably don't want
3068/// this. However, such targets should probably disable LSR altogether.
3069///
3070/// The job of LSR is to make a reasonable choice of induction variables across
3071/// the loop. Subsequent passes can easily "unchain" computation exposing more
3072/// ILP *within the loop* if the target wants it.
3073///
3074/// Finding the best IV chain is potentially a scheduling problem. Since LSR
3075/// will not reorder memory operations, it will recognize this as a chain, but
3076/// will generate redundant IV increments. Ideally this would be corrected later
3077/// by a smart scheduler:
3078/// = A[i]
3079/// = A[i+x]
3080/// A[i] =
3081/// A[i+x] =
3082///
3083/// TODO: Walk the entire domtree within this loop, not just the path to the
3084/// loop latch. This will discover chains on side paths, but requires
3085/// maintaining multiple copies of the Chains state.
3086void LSRInstance::CollectChains() {
3087 LLVM_DEBUG(dbgs() << "Collecting IV Chains.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Collecting IV Chains.\n";
} } while (false)
;
3088 SmallVector<ChainUsers, 8> ChainUsersVec;
3089
3090 SmallVector<BasicBlock *,8> LatchPath;
3091 BasicBlock *LoopHeader = L->getHeader();
3092 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
3093 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
3094 LatchPath.push_back(Rung->getBlock());
3095 }
3096 LatchPath.push_back(LoopHeader);
3097
3098 // Walk the instruction stream from the loop header to the loop latch.
3099 for (BasicBlock *BB : reverse(LatchPath)) {
3100 for (Instruction &I : *BB) {
3101 // Skip instructions that weren't seen by IVUsers analysis.
3102 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
3103 continue;
3104
3105 // Ignore users that are part of a SCEV expression. This way we only
3106 // consider leaf IV Users. This effectively rediscovers a portion of
3107 // IVUsers analysis but in program order this time.
3108 if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
3109 continue;
3110
3111 // Remove this instruction from any NearUsers set it may be in.
3112 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
3113 ChainIdx < NChains; ++ChainIdx) {
3114 ChainUsersVec[ChainIdx].NearUsers.erase(&I);
3115 }
3116 // Search for operands that can be chained.
3117 SmallPtrSet<Instruction*, 4> UniqueOperands;
3118 User::op_iterator IVOpEnd = I.op_end();
3119 User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
3120 while (IVOpIter != IVOpEnd) {
3121 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
3122 if (UniqueOperands.insert(IVOpInst).second)
3123 ChainInstruction(&I, IVOpInst, ChainUsersVec);
3124 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3125 }
3126 } // Continue walking down the instructions.
3127 } // Continue walking down the domtree.
3128 // Visit phi backedges to determine if the chain can generate the IV postinc.
3129 for (PHINode &PN : L->getHeader()->phis()) {
3130 if (!SE.isSCEVable(PN.getType()))
3131 continue;
3132
3133 Instruction *IncV =
3134 dyn_cast<Instruction>(PN.getIncomingValueForBlock(L->getLoopLatch()));
3135 if (IncV)
3136 ChainInstruction(&PN, IncV, ChainUsersVec);
3137 }
3138 // Remove any unprofitable chains.
3139 unsigned ChainIdx = 0;
3140 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
3141 UsersIdx < NChains; ++UsersIdx) {
3142 if (!isProfitableChain(IVChainVec[UsersIdx],
3143 ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
3144 continue;
3145 // Preserve the chain at UsesIdx.
3146 if (ChainIdx != UsersIdx)
3147 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
3148 FinalizeChain(IVChainVec[ChainIdx]);
3149 ++ChainIdx;
3150 }
3151 IVChainVec.resize(ChainIdx);
3152}
3153
3154void LSRInstance::FinalizeChain(IVChain &Chain) {
3155 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")(static_cast <bool> (!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? void (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3155, __extension__
__PRETTY_FUNCTION__))
;
3156 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)
;
3157
3158 for (const IVInc &Inc : Chain) {
3159 LLVM_DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Inc: " << *
Inc.UserInst << "\n"; } } while (false)
;
3160 auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
3161 assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand")(static_cast <bool> (UseI != Inc.UserInst->op_end() &&
"cannot find IV operand") ? void (0) : __assert_fail ("UseI != Inc.UserInst->op_end() && \"cannot find IV operand\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3161, __extension__
__PRETTY_FUNCTION__))
;
3162 IVIncSet.insert(UseI);
3163 }
3164}
3165
3166/// Return true if the IVInc can be folded into an addressing mode.
3167static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
3168 Value *Operand, const TargetTransformInfo &TTI) {
3169 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
3170 if (!IncConst || !isAddressUse(TTI, UserInst, Operand))
3171 return false;
3172
3173 if (IncConst->getAPInt().getMinSignedBits() > 64)
3174 return false;
3175
3176 MemAccessTy AccessTy = getAccessType(TTI, UserInst, Operand);
3177 int64_t IncOffset = IncConst->getValue()->getSExtValue();
3178 if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
3179 IncOffset, /*HasBaseReg=*/false))
3180 return false;
3181
3182 return true;
3183}
3184
3185/// Generate an add or subtract for each IVInc in a chain to materialize the IV
3186/// user's operand from the previous IV user's operand.
3187void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
3188 SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
3189 // Find the new IVOperand for the head of the chain. It may have been replaced
3190 // by LSR.
3191 const IVInc &Head = Chain.Incs[0];
3192 User::op_iterator IVOpEnd = Head.UserInst->op_end();
3193 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
3194 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
3195 IVOpEnd, L, SE);
3196 Value *IVSrc = nullptr;
3197 while (IVOpIter != IVOpEnd) {
3198 IVSrc = getWideOperand(*IVOpIter);
3199
3200 // If this operand computes the expression that the chain needs, we may use
3201 // it. (Check this after setting IVSrc which is used below.)
3202 //
3203 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
3204 // narrow for the chain, so we can no longer use it. We do allow using a
3205 // wider phi, assuming the LSR checked for free truncation. In that case we
3206 // should already have a truncate on this operand such that
3207 // getSCEV(IVSrc) == IncExpr.
3208 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
3209 || SE.getSCEV(IVSrc) == Head.IncExpr) {
3210 break;
3211 }
3212 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3213 }
3214 if (IVOpIter == IVOpEnd) {
3215 // Gracefully give up on this chain.
3216 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)
;
3217 return;
3218 }
3219 assert(IVSrc && "Failed to find IV chain source")(static_cast <bool> (IVSrc && "Failed to find IV chain source"
) ? void (0) : __assert_fail ("IVSrc && \"Failed to find IV chain source\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3219, __extension__
__PRETTY_FUNCTION__))
;
3220
3221 LLVM_DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generate chain at: " <<
*IVSrc << "\n"; } } while (false)
;
3222 Type *IVTy = IVSrc->getType();
3223 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
3224 const SCEV *LeftOverExpr = nullptr;
3225 for (const IVInc &Inc : Chain) {
3226 Instruction *InsertPt = Inc.UserInst;
3227 if (isa<PHINode>(InsertPt))
3228 InsertPt = L->getLoopLatch()->getTerminator();
3229
3230 // IVOper will replace the current IV User's operand. IVSrc is the IV
3231 // value currently held in a register.
3232 Value *IVOper = IVSrc;
3233 if (!Inc.IncExpr->isZero()) {
3234 // IncExpr was the result of subtraction of two narrow values, so must
3235 // be signed.
3236 const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
3237 LeftOverExpr = LeftOverExpr ?
3238 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
3239 }
3240 if (LeftOverExpr && !LeftOverExpr->isZero()) {
3241 // Expand the IV increment.
3242 Rewriter.clearPostInc();
3243 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
3244 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
3245 SE.getUnknown(IncV));
3246 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
3247
3248 // If an IV increment can't be folded, use it as the next IV value.
3249 if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
3250 assert(IVTy == IVOper->getType() && "inconsistent IV increment type")(static_cast <bool> (IVTy == IVOper->getType() &&
"inconsistent IV increment type") ? void (0) : __assert_fail
("IVTy == IVOper->getType() && \"inconsistent IV increment type\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3250, __extension__
__PRETTY_FUNCTION__))
;
3251 IVSrc = IVOper;
3252 LeftOverExpr = nullptr;
3253 }
3254 }
3255 Type *OperTy = Inc.IVOperand->getType();
3256 if (IVTy != OperTy) {
3257 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&(static_cast <bool> (SE.getTypeSizeInBits(IVTy) >= SE
.getTypeSizeInBits(OperTy) && "cannot extend a chained IV"
) ? void (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3258, __extension__
__PRETTY_FUNCTION__))
3258 "cannot extend a chained IV")(static_cast <bool> (SE.getTypeSizeInBits(IVTy) >= SE
.getTypeSizeInBits(OperTy) && "cannot extend a chained IV"
) ? void (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3258, __extension__
__PRETTY_FUNCTION__))
;
3259 IRBuilder<> Builder(InsertPt);
3260 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
3261 }
3262 Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
3263 if (auto *OperandIsInstr = dyn_cast<Instruction>(Inc.IVOperand))
3264 DeadInsts.emplace_back(OperandIsInstr);
3265 }
3266 // If LSR created a new, wider phi, we may also replace its postinc. We only
3267 // do this if we also found a wide value for the head of the chain.
3268 if (isa<PHINode>(Chain.tailUserInst())) {
3269 for (PHINode &Phi : L->getHeader()->phis()) {
3270 if (!isCompatibleIVType(&Phi, IVSrc))
3271 continue;
3272 Instruction *PostIncV = dyn_cast<Instruction>(
3273 Phi.getIncomingValueForBlock(L->getLoopLatch()));
3274 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
3275 continue;
3276 Value *IVOper = IVSrc;
3277 Type *PostIncTy = PostIncV->getType();
3278 if (IVTy != PostIncTy) {
3279 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types")(static_cast <bool> (PostIncTy->isPointerTy() &&
"mixing int/ptr IV types") ? void (0) : __assert_fail ("PostIncTy->isPointerTy() && \"mixing int/ptr IV types\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3279, __extension__
__PRETTY_FUNCTION__))
;
3280 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
3281 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
3282 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
3283 }
3284 Phi.replaceUsesOfWith(PostIncV, IVOper);
3285 DeadInsts.emplace_back(PostIncV);
3286 }
3287 }
3288}
3289
3290void LSRInstance::CollectFixupsAndInitialFormulae() {
3291 BranchInst *ExitBranch = nullptr;
3292 bool SaveCmp = TTI.canSaveCmp(L, &ExitBranch, &SE, &LI, &DT, &AC, &TLI);
3293
3294 for (const IVStrideUse &U : IU) {
3295 Instruction *UserInst = U.getUser();
3296 // Skip IV users that are part of profitable IV Chains.
3297 User::op_iterator UseI =
3298 find(UserInst->operands(), U.getOperandValToReplace());
3299 assert(UseI != UserInst->op_end() && "cannot find IV operand")(static_cast <bool> (UseI != UserInst->op_end() &&
"cannot find IV operand") ? void (0) : __assert_fail ("UseI != UserInst->op_end() && \"cannot find IV operand\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3299, __extension__
__PRETTY_FUNCTION__))
;
3300 if (IVIncSet.count(UseI)) {
3301 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)
;
3302 continue;
3303 }
3304
3305 LSRUse::KindType Kind = LSRUse::Basic;
3306 MemAccessTy AccessTy;
3307 if (isAddressUse(TTI, UserInst, U.getOperandValToReplace())) {
3308 Kind = LSRUse::Address;
3309 AccessTy = getAccessType(TTI, UserInst, U.getOperandValToReplace());
3310 }
3311
3312 const SCEV *S = IU.getExpr(U);
3313 PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3314
3315 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3316 // (N - i == 0), and this allows (N - i) to be the expression that we work
3317 // with rather than just N or i, so we can consider the register
3318 // requirements for both N and i at the same time. Limiting this code to
3319 // equality icmps is not a problem because all interesting loops use
3320 // equality icmps, thanks to IndVarSimplify.
3321 if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst)) {
3322 // If CI can be saved in some target, like replaced inside hardware loop
3323 // in PowerPC, no need to generate initial formulae for it.
3324 if (SaveCmp && CI == dyn_cast<ICmpInst>(ExitBranch->getCondition()))
3325 continue;
3326 if (CI->isEquality()) {
3327 // Swap the operands if needed to put the OperandValToReplace on the
3328 // left, for consistency.
3329 Value *NV = CI->getOperand(1);
3330 if (NV == U.getOperandValToReplace()) {
3331 CI->setOperand(1, CI->getOperand(0));
3332 CI->setOperand(0, NV);
3333 NV = CI->getOperand(1);
3334 Changed = true;
3335 }
3336
3337 // x == y --> x - y == 0
3338 const SCEV *N = SE.getSCEV(NV);
3339 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE) &&
3340 (!NV->getType()->isPointerTy() ||
3341 SE.getPointerBase(N) == SE.getPointerBase(S))) {
3342 // S is normalized, so normalize N before folding it into S
3343 // to keep the result normalized.
3344 N = normalizeForPostIncUse(N, TmpPostIncLoops, SE);
3345 Kind = LSRUse::ICmpZero;
3346 S = SE.getMinusSCEV(N, S);
3347 }
3348
3349 // -1 and the negations of all interesting strides (except the negation
3350 // of -1) are now also interesting.
3351 for (size_t i = 0, e = Factors.size(); i != e; ++i)
3352 if (Factors[i] != -1)
3353 Factors.insert(-(uint64_t)Factors[i]);
3354 Factors.insert(-1);
3355 }
3356 }
3357
3358 // Get or create an LSRUse.
3359 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3360 size_t LUIdx = P.first;
3361 int64_t Offset = P.second;
3362 LSRUse &LU = Uses[LUIdx];
3363
3364 // Record the fixup.
3365 LSRFixup &LF = LU.getNewFixup();
3366 LF.UserInst = UserInst;
3367 LF.OperandValToReplace = U.getOperandValToReplace();
3368 LF.PostIncLoops = TmpPostIncLoops;
3369 LF.Offset = Offset;
3370 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3371
3372 if (!LU.WidestFixupType ||
3373 SE.getTypeSizeInBits(LU.WidestFixupType) <
3374 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3375 LU.WidestFixupType = LF.OperandValToReplace->getType();
3376
3377 // If this is the first use of this LSRUse, give it a formula.
3378 if (LU.Formulae.empty()) {
3379 InsertInitialFormula(S, LU, LUIdx);
3380 CountRegisters(LU.Formulae.back(), LUIdx);
3381 }
3382 }
3383
3384 LLVM_DEBUG(print_fixups(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_fixups(dbgs()); } } while (false)
;
3385}
3386
3387/// Insert a formula for the given expression into the given use, separating out
3388/// loop-variant portions from loop-invariant and loop-computable portions.
3389void
3390LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3391 // Mark uses whose expressions cannot be expanded.
3392 if (!isSafeToExpand(S, SE, /*CanonicalMode*/ false))
3393 LU.RigidFormula = true;
3394
3395 Formula F;
3396 F.initialMatch(S, L, SE);
3397 bool Inserted = InsertFormula(LU, LUIdx, F);
3398 assert(Inserted && "Initial formula already exists!")(static_cast <bool> (Inserted && "Initial formula already exists!"
) ? void (0) : __assert_fail ("Inserted && \"Initial formula already exists!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3398, __extension__
__PRETTY_FUNCTION__))
; (void)Inserted;
3399}
3400
3401/// Insert a simple single-register formula for the given expression into the
3402/// given use.
3403void
3404LSRInstance::InsertSupplementalFormula(const SCEV *S,
3405 LSRUse &LU, size_t LUIdx) {
3406 Formula F;
3407 F.BaseRegs.push_back(S);
3408 F.HasBaseReg = true;
3409 bool Inserted = InsertFormula(LU, LUIdx, F);
3410 assert(Inserted && "Supplemental formula already exists!")(static_cast <bool> (Inserted && "Supplemental formula already exists!"
) ? void (0) : __assert_fail ("Inserted && \"Supplemental formula already exists!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3410, __extension__
__PRETTY_FUNCTION__))
; (void)Inserted;
3411}
3412
3413/// Note which registers are used by the given formula, updating RegUses.
3414void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3415 if (F.ScaledReg)
3416 RegUses.countRegister(F.ScaledReg, LUIdx);
3417 for (const SCEV *BaseReg : F.BaseRegs)
3418 RegUses.countRegister(BaseReg, LUIdx);
3419}
3420
3421/// If the given formula has not yet been inserted, add it to the list, and
3422/// return true. Return false otherwise.
3423bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3424 // Do not insert formula that we will not be able to expand.
3425 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&(static_cast <bool> (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset
, LU.Kind, LU.AccessTy, F) && "Formula is illegal") ?
void (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3426, __extension__
__PRETTY_FUNCTION__))
3426 "Formula is illegal")(static_cast <bool> (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset
, LU.Kind, LU.AccessTy, F) && "Formula is illegal") ?
void (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3426, __extension__
__PRETTY_FUNCTION__))
;
3427
3428 if (!LU.InsertFormula(F, *L))
3429 return false;
3430
3431 CountRegisters(F, LUIdx);
3432 return true;
3433}
3434
3435/// Check for other uses of loop-invariant values which we're tracking. These
3436/// other uses will pin these values in registers, making them less profitable
3437/// for elimination.
3438/// TODO: This currently misses non-constant addrec step registers.
3439/// TODO: Should this give more weight to users inside the loop?
3440void
3441LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3442 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3443 SmallPtrSet<const SCEV *, 32> Visited;
3444
3445 while (!Worklist.empty()) {
3446 const SCEV *S = Worklist.pop_back_val();
3447
3448 // Don't process the same SCEV twice
3449 if (!Visited.insert(S).second)
3450 continue;
3451
3452 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3453 Worklist.append(N->op_begin(), N->op_end());
3454 else if (const SCEVIntegralCastExpr *C = dyn_cast<SCEVIntegralCastExpr>(S))
3455 Worklist.push_back(C->getOperand());
3456 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3457 Worklist.push_back(D->getLHS());
3458 Worklist.push_back(D->getRHS());
3459 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3460 const Value *V = US->getValue();
3461 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3462 // Look for instructions defined outside the loop.
3463 if (L->contains(Inst)) continue;
3464 } else if (isa<UndefValue>(V))
3465 // Undef doesn't have a live range, so it doesn't matter.
3466 continue;
3467 for (const Use &U : V->uses()) {
3468 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3469 // Ignore non-instructions.
3470 if (!UserInst)
3471 continue;
3472 // Don't bother if the instruction is an EHPad.
3473 if (UserInst->isEHPad())
3474 continue;
3475 // Ignore instructions in other functions (as can happen with
3476 // Constants).
3477 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3478 continue;
3479 // Ignore instructions not dominated by the loop.
3480 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3481 UserInst->getParent() :
3482 cast<PHINode>(UserInst)->getIncomingBlock(
3483 PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3484 if (!DT.dominates(L->getHeader(), UseBB))
3485 continue;
3486 // Don't bother if the instruction is in a BB which ends in an EHPad.
3487 if (UseBB->getTerminator()->isEHPad())
3488 continue;
3489
3490 // Ignore cases in which the currently-examined value could come from
3491 // a basic block terminated with an EHPad. This checks all incoming
3492 // blocks of the phi node since it is possible that the same incoming
3493 // value comes from multiple basic blocks, only some of which may end
3494 // in an EHPad. If any of them do, a subsequent rewrite attempt by this
3495 // pass would try to insert instructions into an EHPad, hitting an
3496 // assertion.
3497 if (isa<PHINode>(UserInst)) {
3498 const auto *PhiNode = cast<PHINode>(UserInst);
3499 bool HasIncompatibleEHPTerminatedBlock = false;
3500 llvm::Value *ExpectedValue = U;
3501 for (unsigned int I = 0; I < PhiNode->getNumIncomingValues(); I++) {
3502 if (PhiNode->getIncomingValue(I) == ExpectedValue) {
3503 if (PhiNode->getIncomingBlock(I)->getTerminator()->isEHPad()) {
3504 HasIncompatibleEHPTerminatedBlock = true;
3505 break;
3506 }
3507 }
3508 }
3509 if (HasIncompatibleEHPTerminatedBlock) {
3510 continue;
3511 }
3512 }
3513
3514 // Don't bother rewriting PHIs in catchswitch blocks.
3515 if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator()))
3516 continue;
3517 // Ignore uses which are part of other SCEV expressions, to avoid
3518 // analyzing them multiple times.
3519 if (SE.isSCEVable(UserInst->getType())) {
3520 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3521 // If the user is a no-op, look through to its uses.
3522 if (!isa<SCEVUnknown>(UserS))
3523 continue;
3524 if (UserS == US) {
3525 Worklist.push_back(
3526 SE.getUnknown(const_cast<Instruction *>(UserInst)));
3527 continue;
3528 }
3529 }
3530 // Ignore icmp instructions which are already being analyzed.
3531 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3532 unsigned OtherIdx = !U.getOperandNo();
3533 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3534 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3535 continue;
3536 }
3537
3538 std::pair<size_t, int64_t> P = getUse(
3539 S, LSRUse::Basic, MemAccessTy());
3540 size_t LUIdx = P.first;
3541 int64_t Offset = P.second;
3542 LSRUse &LU = Uses[LUIdx];
3543 LSRFixup &LF = LU.getNewFixup();
3544 LF.UserInst = const_cast<Instruction *>(UserInst);
3545 LF.OperandValToReplace = U;
3546 LF.Offset = Offset;
3547 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3548 if (!LU.WidestFixupType ||
3549 SE.getTypeSizeInBits(LU.WidestFixupType) <
3550 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3551 LU.WidestFixupType = LF.OperandValToReplace->getType();
3552 InsertSupplementalFormula(US, LU, LUIdx);
3553 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3554 break;
3555 }
3556 }
3557 }
3558}
3559
3560/// Split S into subexpressions which can be pulled out into separate
3561/// registers. If C is non-null, multiply each subexpression by C.
3562///
3563/// Return remainder expression after factoring the subexpressions captured by
3564/// Ops. If Ops is complete, return NULL.
3565static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3566 SmallVectorImpl<const SCEV *> &Ops,
3567 const Loop *L,
3568 ScalarEvolution &SE,
3569 unsigned Depth = 0) {
3570 // Arbitrarily cap recursion to protect compile time.
3571 if (Depth >= 3)
3572 return S;
3573
3574 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3575 // Break out add operands.
3576 for (const SCEV *S : Add->operands()) {
3577 const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3578 if (Remainder)
3579 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3580 }
3581 return nullptr;
3582 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3583 // Split a non-zero base out of an addrec.
3584 if (AR->getStart()->isZero() || !AR->isAffine())
3585 return S;
3586
3587 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3588 C, Ops, L, SE, Depth+1);
3589 // Split the non-zero AddRec unless it is part of a nested recurrence that
3590 // does not pertain to this loop.
3591 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3592 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3593 Remainder = nullptr;
3594 }
3595 if (Remainder != AR->getStart()) {
3596 if (!Remainder)
3597 Remainder = SE.getConstant(AR->getType(), 0);
3598 return SE.getAddRecExpr(Remainder,
3599 AR->getStepRecurrence(SE),
3600 AR->getLoop(),
3601 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3602 SCEV::FlagAnyWrap);
3603 }
3604 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3605 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3606 if (Mul->getNumOperands() != 2)
3607 return S;
3608 if (const SCEVConstant *Op0 =
3609 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3610 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3611 const SCEV *Remainder =
3612 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3613 if (Remainder)
3614 Ops.push_back(SE.getMulExpr(C, Remainder));
3615 return nullptr;
3616 }
3617 }
3618 return S;
3619}
3620
3621/// Return true if the SCEV represents a value that may end up as a
3622/// post-increment operation.
3623static bool mayUsePostIncMode(const TargetTransformInfo &TTI,
3624 LSRUse &LU, const SCEV *S, const Loop *L,
3625 ScalarEvolution &SE) {
3626 if (LU.Kind != LSRUse::Address ||
3627 !LU.AccessTy.getType()->isIntOrIntVectorTy())
3628 return false;
3629 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S);
3630 if (!AR)
3631 return false;
3632 const SCEV *LoopStep = AR->getStepRecurrence(SE);
3633 if (!isa<SCEVConstant>(LoopStep))
3634 return false;
3635 // Check if a post-indexed load/store can be used.
3636 if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) ||
3637 TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) {
3638 const SCEV *LoopStart = AR->getStart();
3639 if (!isa<SCEVConstant>(LoopStart) && SE.isLoopInvariant(LoopStart, L))
3640 return true;
3641 }
3642 return false;
3643}
3644
3645/// Helper function for LSRInstance::GenerateReassociations.
3646void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3647 const Formula &Base,
3648 unsigned Depth, size_t Idx,
3649 bool IsScaledReg) {
3650 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3651 // Don't generate reassociations for the base register of a value that
3652 // may generate a post-increment operator. The reason is that the
3653 // reassociations cause extra base+register formula to be created,
3654 // and possibly chosen, but the post-increment is more efficient.
3655 if (AMK == TTI::AMK_PostIndexed && mayUsePostIncMode(TTI, LU, BaseReg, L, SE))
3656 return;
3657 SmallVector<const SCEV *, 8> AddOps;
3658 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3659 if (Remainder)
3660 AddOps.push_back(Remainder);
3661
3662 if (AddOps.size() == 1)
3663 return;
3664
3665 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3666 JE = AddOps.end();
3667 J != JE; ++J) {
3668 // Loop-variant "unknown" values are uninteresting; we won't be able to
3669 // do anything meaningful with them.
3670 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3671 continue;
3672
3673 // Don't pull a constant into a register if the constant could be folded
3674 // into an immediate field.
3675 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3676 LU.AccessTy, *J, Base.getNumRegs() > 1))
3677 continue;
3678
3679 // Collect all operands except *J.
3680 SmallVector<const SCEV *, 8> InnerAddOps(
3681 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3682 InnerAddOps.append(std::next(J),
3683 ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3684
3685 // Don't leave just a constant behind in a register if the constant could
3686 // be folded into an immediate field.
3687 if (InnerAddOps.size() == 1 &&
3688 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3689 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3690 continue;
3691
3692 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3693 if (InnerSum->isZero())
3694 continue;
3695 Formula F = Base;
3696
3697 // Add the remaining pieces of the add back into the new formula.
3698 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3699 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3700 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3701 InnerSumSC->getValue()->getZExtValue())) {
3702 F.UnfoldedOffset =
3703 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3704 if (IsScaledReg)
3705 F.ScaledReg = nullptr;
3706 else
3707 F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3708 } else if (IsScaledReg)
3709 F.ScaledReg = InnerSum;
3710 else
3711 F.BaseRegs[Idx] = InnerSum;
3712
3713 // Add J as its own register, or an unfolded immediate.
3714 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3715 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3716 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3717 SC->getValue()->getZExtValue()))
3718 F.UnfoldedOffset =
3719 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3720 else
3721 F.BaseRegs.push_back(*J);
3722 // We may have changed the number of register in base regs, adjust the
3723 // formula accordingly.
3724 F.canonicalize(*L);
3725
3726 if (InsertFormula(LU, LUIdx, F))
3727 // If that formula hadn't been seen before, recurse to find more like
3728 // it.
3729 // Add check on Log16(AddOps.size()) - same as Log2_32(AddOps.size()) >> 2)
3730 // Because just Depth is not enough to bound compile time.
3731 // This means that every time AddOps.size() is greater 16^x we will add
3732 // x to Depth.
3733 GenerateReassociations(LU, LUIdx, LU.Formulae.back(),
3734 Depth + 1 + (Log2_32(AddOps.size()) >> 2));
3735 }
3736}
3737
3738/// Split out subexpressions from adds and the bases of addrecs.
3739void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3740 Formula Base, unsigned Depth) {
3741 assert(Base.isCanonical(*L) && "Input must be in the canonical form")(static_cast <bool> (Base.isCanonical(*L) && "Input must be in the canonical form"
) ? void (0) : __assert_fail ("Base.isCanonical(*L) && \"Input must be in the canonical form\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3741, __extension__
__PRETTY_FUNCTION__))
;
3742 // Arbitrarily cap recursion to protect compile time.
3743 if (Depth >= 3)
3744 return;
3745
3746 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3747 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3748
3749 if (Base.Scale == 1)
3750 GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3751 /* Idx */ -1, /* IsScaledReg */ true);
3752}
3753
3754/// Generate a formula consisting of all of the loop-dominating registers added
3755/// into a single register.
3756void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3757 Formula Base) {
3758 // This method is only interesting on a plurality of registers.
3759 if (Base.BaseRegs.size() + (Base.Scale == 1) +
3760 (Base.UnfoldedOffset != 0) <= 1)
3761 return;
3762
3763 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3764 // processing the formula.
3765 Base.unscale();
3766 SmallVector<const SCEV *, 4> Ops;
3767 Formula NewBase = Base;
3768 NewBase.BaseRegs.clear();
3769 Type *CombinedIntegerType = nullptr;
3770 for (const SCEV *BaseReg : Base.BaseRegs) {
3771 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3772 !SE.hasComputableLoopEvolution(BaseReg, L)) {
3773 if (!CombinedIntegerType)
3774 CombinedIntegerType = SE.getEffectiveSCEVType(BaseReg->getType());
3775 Ops.push_back(BaseReg);
3776 }
3777 else
3778 NewBase.BaseRegs.push_back(BaseReg);
3779 }
3780
3781 // If no register is relevant, we're done.
3782 if (Ops.size() == 0)
3783 return;
3784
3785 // Utility function for generating the required variants of the combined
3786 // registers.
3787 auto GenerateFormula = [&](const SCEV *Sum) {
3788 Formula F = NewBase;
3789
3790 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3791 // opportunity to fold something. For now, just ignore such cases
3792 // rather than proceed with zero in a register.
3793 if (Sum->isZero())
3794 return;
3795
3796 F.BaseRegs.push_back(Sum);
3797 F.canonicalize(*L);
3798 (void)InsertFormula(LU, LUIdx, F);
3799 };
3800
3801 // If we collected at least two registers, generate a formula combining them.
3802 if (Ops.size() > 1) {
3803 SmallVector<const SCEV *, 4> OpsCopy(Ops); // Don't let SE modify Ops.
3804 GenerateFormula(SE.getAddExpr(OpsCopy));
3805 }
3806
3807 // If we have an unfolded offset, generate a formula combining it with the
3808 // registers collected.
3809 if (NewBase.UnfoldedOffset) {
3810 assert(CombinedIntegerType && "Missing a type for the unfolded offset")(static_cast <bool> (CombinedIntegerType && "Missing a type for the unfolded offset"
) ? void (0) : __assert_fail ("CombinedIntegerType && \"Missing a type for the unfolded offset\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3810, __extension__
__PRETTY_FUNCTION__))
;
3811 Ops.push_back(SE.getConstant(CombinedIntegerType, NewBase.UnfoldedOffset,
3812 true));
3813 NewBase.UnfoldedOffset = 0;
3814 GenerateFormula(SE.getAddExpr(Ops));
3815 }
3816}
3817
3818/// Helper function for LSRInstance::GenerateSymbolicOffsets.
3819void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3820 const Formula &Base, size_t Idx,
3821 bool IsScaledReg) {
3822 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3823 GlobalValue *GV = ExtractSymbol(G, SE);
3824 if (G->isZero() || !GV)
3825 return;
3826 Formula F = Base;
3827 F.BaseGV = GV;
3828 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3829 return;
3830 if (IsScaledReg)
3831 F.ScaledReg = G;
3832 else
3833 F.BaseRegs[Idx] = G;
3834 (void)InsertFormula(LU, LUIdx, F);
3835}
3836
3837/// Generate reuse formulae using symbolic offsets.
3838void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3839 Formula Base) {
3840 // We can't add a symbolic offset if the address already contains one.
3841 if (Base.BaseGV) return;
3842
3843 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3844 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3845 if (Base.Scale == 1)
3846 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3847 /* IsScaledReg */ true);
3848}
3849
3850/// Helper function for LSRInstance::GenerateConstantOffsets.
3851void LSRInstance::GenerateConstantOffsetsImpl(
3852 LSRUse &LU, unsigned LUIdx, const Formula &Base,
3853 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3854
3855 auto GenerateOffset = [&](const SCEV *G, int64_t Offset) {
3856 Formula F = Base;
3857 F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3858
3859 if (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F)) {
3860 // Add the offset to the base register.
3861 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3862 // If it cancelled out, drop the base register, otherwise update it.
3863 if (NewG->isZero()) {
3864 if (IsScaledReg) {
3865 F.Scale = 0;
3866 F.ScaledReg = nullptr;
3867 } else
3868 F.deleteBaseReg(F.BaseRegs[Idx]);
3869 F.canonicalize(*L);
3870 } else if (IsScaledReg)
3871 F.ScaledReg = NewG;
3872 else
3873 F.BaseRegs[Idx] = NewG;
3874
3875 (void)InsertFormula(LU, LUIdx, F);
3876 }
3877 };
3878
3879 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3880
3881 // With constant offsets and constant steps, we can generate pre-inc
3882 // accesses by having the offset equal the step. So, for access #0 with a
3883 // step of 8, we generate a G - 8 base which would require the first access
3884 // to be ((G - 8) + 8),+,8. The pre-indexed access then updates the pointer
3885 // for itself and hopefully becomes the base for other accesses. This means
3886 // means that a single pre-indexed access can be generated to become the new
3887 // base pointer for each iteration of the loop, resulting in no extra add/sub
3888 // instructions for pointer updating.
3889 if (AMK == TTI::AMK_PreIndexed && LU.Kind == LSRUse::Address) {
3890 if (auto *GAR = dyn_cast<SCEVAddRecExpr>(G)) {
3891 if (auto *StepRec =
3892 dyn_cast<SCEVConstant>(GAR->getStepRecurrence(SE))) {
3893 const APInt &StepInt = StepRec->getAPInt();
3894 int64_t Step = StepInt.isNegative() ?
3895 StepInt.getSExtValue() : StepInt.getZExtValue();
3896
3897 for (int64_t Offset : Worklist) {
3898 Offset -= Step;
3899 GenerateOffset(G, Offset);
3900 }
3901 }
3902 }
3903 }
3904 for (int64_t Offset : Worklist)
3905 GenerateOffset(G, Offset);
3906
3907 int64_t Imm = ExtractImmediate(G, SE);
3908 if (G->isZero() || Imm == 0)
3909 return;
3910 Formula F = Base;
3911 F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3912 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3913 return;
3914 if (IsScaledReg) {
3915 F.ScaledReg = G;
3916 } else {
3917 F.BaseRegs[Idx] = G;
3918 // We may generate non canonical Formula if G is a recurrent expr reg
3919 // related with current loop while F.ScaledReg is not.
3920 F.canonicalize(*L);
3921 }
3922 (void)InsertFormula(LU, LUIdx, F);
3923}
3924
3925/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3926void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3927 Formula Base) {
3928 // TODO: For now, just add the min and max offset, because it usually isn't
3929 // worthwhile looking at everything inbetween.
3930 SmallVector<int64_t, 2> Worklist;
3931 Worklist.push_back(LU.MinOffset);
3932 if (LU.MaxOffset != LU.MinOffset)
3933 Worklist.push_back(LU.MaxOffset);
3934
3935 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3936 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3937 if (Base.Scale == 1)
3938 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3939 /* IsScaledReg */ true);
3940}
3941
3942/// For ICmpZero, check to see if we can scale up the comparison. For example, x
3943/// == y -> x*c == y*c.
3944void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3945 Formula Base) {
3946 if (LU.Kind != LSRUse::ICmpZero) return;
3947
3948 // Determine the integer type for the base formula.
3949 Type *IntTy = Base.getType();
3950 if (!IntTy) return;
3951 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3952
3953 // Don't do this if there is more than one offset.
3954 if (LU.MinOffset != LU.MaxOffset) return;
3955
3956 // Check if transformation is valid. It is illegal to multiply pointer.
3957 if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
3958 return;
3959 for (const SCEV *BaseReg : Base.BaseRegs)
3960 if (BaseReg->getType()->isPointerTy())
3961 return;
3962 assert(!Base.BaseGV && "ICmpZero use is not legal!")(static_cast <bool> (!Base.BaseGV && "ICmpZero use is not legal!"
) ? void (0) : __assert_fail ("!Base.BaseGV && \"ICmpZero use is not legal!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3962, __extension__
__PRETTY_FUNCTION__))
;
3963
3964 // Check each interesting stride.
3965 for (int64_t Factor : Factors) {
3966 // Check that Factor can be represented by IntTy
3967 if (!ConstantInt::isValueValidForType(IntTy, Factor))
3968 continue;
3969 // Check that the multiplication doesn't overflow.
3970 if (Base.BaseOffset == std::numeric_limits<int64_t>::min() && Factor == -1)
3971 continue;
3972 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3973 assert(Factor != 0 && "Zero factor not expected!")(static_cast <bool> (Factor != 0 && "Zero factor not expected!"
) ? void (0) : __assert_fail ("Factor != 0 && \"Zero factor not expected!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 3973, __extension__
__PRETTY_FUNCTION__))
;
3974 if (NewBaseOffset / Factor != Base.BaseOffset)
3975 continue;
3976 // If the offset will be truncated at this use, check that it is in bounds.
3977 if (!IntTy->isPointerTy() &&
3978 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3979 continue;
3980
3981 // Check that multiplying with the use offset doesn't overflow.
3982 int64_t Offset = LU.MinOffset;
3983 if (Offset == std::numeric_limits<int64_t>::min() && Factor == -1)
3984 continue;
3985 Offset = (uint64_t)Offset * Factor;
3986 if (Offset / Factor != LU.MinOffset)
3987 continue;
3988 // If the offset will be truncated at this use, check that it is in bounds.
3989 if (!IntTy->isPointerTy() &&
3990 !ConstantInt::isValueValidForType(IntTy, Offset))
3991 continue;
3992
3993 Formula F = Base;
3994 F.BaseOffset = NewBaseOffset;
3995
3996 // Check that this scale is legal.
3997 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3998 continue;
3999
4000 // Compensate for the use having MinOffset built into it.
4001 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
4002
4003 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
4004
4005 // Check that multiplying with each base register doesn't overflow.
4006 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
4007 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
4008 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
4009 goto next;
4010 }
4011
4012 // Check that multiplying with the scaled register doesn't overflow.
4013 if (F.ScaledReg) {
4014 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
4015 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
4016 continue;
4017 }
4018
4019 // Check that multiplying with the unfolded offset doesn't overflow.
4020 if (F.UnfoldedOffset != 0) {
4021 if (F.UnfoldedOffset == std::numeric_limits<int64_t>::min() &&
4022 Factor == -1)
4023 continue;
4024 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
4025 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
4026 continue;
4027 // If the offset will be truncated, check that it is in bounds.
4028 if (!IntTy->isPointerTy() &&
4029 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
4030 continue;
4031 }
4032
4033 // If we make it here and it's legal, add it.
4034 (void)InsertFormula(LU, LUIdx, F);
4035 next:;
4036 }
4037}
4038
4039/// Generate stride factor reuse formulae by making use of scaled-offset address
4040/// modes, for example.
4041void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
4042 // Determine the integer type for the base formula.
4043 Type *IntTy = Base.getType();
4044 if (!IntTy) return;
4045
4046 // If this Formula already has a scaled register, we can't add another one.
4047 // Try to unscale the formula to generate a better scale.
4048 if (Base.Scale != 0 && !Base.unscale())
4049 return;
4050
4051 assert(Base.Scale == 0 && "unscale did not did its job!")(static_cast <bool> (Base.Scale == 0 && "unscale did not did its job!"
) ? void (0) : __assert_fail ("Base.Scale == 0 && \"unscale did not did its job!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 4051, __extension__
__PRETTY_FUNCTION__))
;
4052
4053 // Check each interesting stride.
4054 for (int64_t Factor : Factors) {
4055 Base.Scale = Factor;
4056 Base.HasBaseReg = Base.BaseRegs.size() > 1;
4057 // Check whether this scale is going to be legal.
4058 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4059 Base)) {
4060 // As a special-case, handle special out-of-loop Basic users specially.
4061 // TODO: Reconsider this special case.
4062 if (LU.Kind == LSRUse::Basic &&
4063 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
4064 LU.AccessTy, Base) &&
4065 LU.AllFixupsOutsideLoop)
4066 LU.Kind = LSRUse::Special;
4067 else
4068 continue;
4069 }
4070 // For an ICmpZero, negating a solitary base register won't lead to
4071 // new solutions.
4072 if (LU.Kind == LSRUse::ICmpZero &&
4073 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
4074 continue;
4075 // For each addrec base reg, if its loop is current loop, apply the scale.
4076 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
4077 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]);
4078 if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) {
4079 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
4080 if (FactorS->isZero())
4081 continue;
4082 // Divide out the factor, ignoring high bits, since we'll be
4083 // scaling the value back up in the end.
4084 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
4085 // TODO: This could be optimized to avoid all the copying.
4086 Formula F = Base;
4087 F.ScaledReg = Quotient;
4088 F.deleteBaseReg(F.BaseRegs[i]);
4089 // The canonical representation of 1*reg is reg, which is already in
4090 // Base. In that case, do not try to insert the formula, it will be
4091 // rejected anyway.
4092 if (F.Scale == 1 && (F.BaseRegs.empty() ||
4093 (AR->getLoop() != L && LU.AllFixupsOutsideLoop)))
4094 continue;
4095 // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate
4096 // non canonical Formula with ScaledReg's loop not being L.
4097 if (F.Scale == 1 && LU.AllFixupsOutsideLoop)
4098 F.canonicalize(*L);
4099 (void)InsertFormula(LU, LUIdx, F);
4100 }
4101 }
4102 }
4103 }
4104}
4105
4106/// Generate reuse formulae from different IV types.
4107void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
4108 // Don't bother truncating symbolic values.
4109 if (Base.BaseGV) return;
4110
4111 // Determine the integer type for the base formula.
4112 Type *DstTy = Base.getType();
4113 if (!DstTy) return;
4114 if (DstTy->isPointerTy())
4115 return;
4116
4117 // It is invalid to extend a pointer type so exit early if ScaledReg or
4118 // any of the BaseRegs are pointers.
4119 if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
4120 return;
4121 if (any_of(Base.BaseRegs,
4122 [](const SCEV *S) { return S->getType()->isPointerTy(); }))
4123 return;
4124
4125 for (Type *SrcTy : Types) {
4126 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
4127 Formula F = Base;
4128
4129 // Sometimes SCEV is able to prove zero during ext transform. It may
4130 // happen if SCEV did not do all possible transforms while creating the
4131 // initial node (maybe due to depth limitations), but it can do them while
4132 // taking ext.
4133 if (F.ScaledReg) {
4134 const SCEV *NewScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
4135 if (NewScaledReg->isZero())
4136 continue;
4137 F.ScaledReg = NewScaledReg;
4138 }
4139 bool HasZeroBaseReg = false;
4140 for (const SCEV *&BaseReg : F.BaseRegs) {
4141 const SCEV *NewBaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
4142 if (NewBaseReg->isZero()) {
4143 HasZeroBaseReg = true;
4144 break;
4145 }
4146 BaseReg = NewBaseReg;
4147 }
4148 if (HasZeroBaseReg)
4149 continue;
4150
4151 // TODO: This assumes we've done basic processing on all uses and
4152 // have an idea what the register usage is.
4153 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
4154 continue;
4155
4156 F.canonicalize(*L);
4157 (void)InsertFormula(LU, LUIdx, F);
4158 }
4159 }
4160}
4161
4162namespace {
4163
4164/// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
4165/// modifications so that the search phase doesn't have to worry about the data
4166/// structures moving underneath it.
4167struct WorkItem {
4168 size_t LUIdx;
4169 int64_t Imm;
4170 const SCEV *OrigReg;
4171
4172 WorkItem(size_t LI, int64_t I, const SCEV *R)
4173 : LUIdx(LI), Imm(I), OrigReg(R) {}
4174
4175 void print(raw_ostream &OS) const;
4176 void dump() const;
4177};
4178
4179} // end anonymous namespace
4180
4181#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
4182void WorkItem::print(raw_ostream &OS) const {
4183 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
4184 << " , add offset " << Imm;
4185}
4186
4187LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void WorkItem::dump() const {
4188 print(errs()); errs() << '\n';
4189}
4190#endif
4191
4192/// Look for registers which are a constant distance apart and try to form reuse
4193/// opportunities between them.
4194void LSRInstance::GenerateCrossUseConstantOffsets() {
4195 // Group the registers by their value without any added constant offset.
4196 using ImmMapTy = std::map<int64_t, const SCEV *>;
4197
4198 DenseMap<const SCEV *, ImmMapTy> Map;
4199 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
4200 SmallVector<const SCEV *, 8> Sequence;
4201 for (const SCEV *Use : RegUses) {
4202 const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
4203 int64_t Imm = ExtractImmediate(Reg, SE);
4204 auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
4205 if (Pair.second)
4206 Sequence.push_back(Reg);
4207 Pair.first->second.insert(std::make_pair(Imm, Use));
4208 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
4209 }
4210
4211 // Now examine each set of registers with the same base value. Build up
4212 // a list of work to do and do the work in a separate step so that we're
4213 // not adding formulae and register counts while we're searching.
4214 SmallVector<WorkItem, 32> WorkItems;
4215 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
4216 for (const SCEV *Reg : Sequence) {
4217 const ImmMapTy &Imms = Map.find(Reg)->second;
4218
4219 // It's not worthwhile looking for reuse if there's only one offset.
4220 if (Imms.size() == 1)
4221 continue;
4222
4223 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)
4224 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)
4225 : 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)
4226 << ' ' << 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)
4227 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)
;
4228
4229 // Examine each offset.
4230 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
4231 J != JE; ++J) {
4232 const SCEV *OrigReg = J->second;
4233
4234 int64_t JImm = J->first;
4235 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
4236
4237 if (!isa<SCEVConstant>(OrigReg) &&
4238 UsedByIndicesMap[Reg].count() == 1) {
4239 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)
4240 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Skipping cross-use reuse for "
<< *OrigReg << '\n'; } } while (false)
;
4241 continue;
4242 }
4243
4244 // Conservatively examine offsets between this orig reg a few selected
4245 // other orig regs.
4246 int64_t First = Imms.begin()->first;
4247 int64_t Last = std::prev(Imms.end())->first;
4248 // Compute (First + Last) / 2 without overflow using the fact that
4249 // First + Last = 2 * (First + Last) + (First ^ Last).
4250 int64_t Avg = (First & Last) + ((First ^ Last) >> 1);
4251 // If the result is negative and First is odd and Last even (or vice versa),
4252 // we rounded towards -inf. Add 1 in that case, to round towards 0.
4253 Avg = Avg + ((First ^ Last) & ((uint64_t)Avg >> 63));
4254 ImmMapTy::const_iterator OtherImms[] = {
4255 Imms.begin(), std::prev(Imms.end()),
4256 Imms.lower_bound(Avg)};
4257 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
4258 ImmMapTy::const_iterator M = OtherImms[i];
4259 if (M == J || M == JE) continue;
4260
4261 // Compute the difference between the two.
4262 int64_t Imm = (uint64_t)JImm - M->first;
4263 for (unsigned LUIdx : UsedByIndices.set_bits())
4264 // Make a memo of this use, offset, and register tuple.
4265 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
4266 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
4267 }
4268 }
4269 }
4270
4271 Map.clear();
4272 Sequence.clear();
4273 UsedByIndicesMap.clear();
4274 UniqueItems.clear();
4275
4276 // Now iterate through the worklist and add new formulae.
4277 for (const WorkItem &WI : WorkItems) {
4278 size_t LUIdx = WI.LUIdx;
4279 LSRUse &LU = Uses[LUIdx];
4280 int64_t Imm = WI.Imm;
4281 const SCEV *OrigReg = WI.OrigReg;
4282
4283 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
4284 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
4285 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
4286
4287 // TODO: Use a more targeted data structure.
4288 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
4289 Formula F = LU.Formulae[L];
4290 // FIXME: The code for the scaled and unscaled registers looks
4291 // very similar but slightly different. Investigate if they
4292 // could be merged. That way, we would not have to unscale the
4293 // Formula.
4294 F.unscale();
4295 // Use the immediate in the scaled register.
4296 if (F.ScaledReg == OrigReg) {
4297 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
4298 // Don't create 50 + reg(-50).
4299 if (F.referencesReg(SE.getSCEV(
4300 ConstantInt::get(IntTy, -(uint64_t)Offset))))
4301 continue;
4302 Formula NewF = F;
4303 NewF.BaseOffset = Offset;
4304 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4305 NewF))
4306 continue;
4307 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
4308
4309 // If the new scale is a constant in a register, and adding the constant
4310 // value to the immediate would produce a value closer to zero than the
4311 // immediate itself, then the formula isn't worthwhile.
4312 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
4313 if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
4314 (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
4315 .ule(std::abs(NewF.BaseOffset)))
4316 continue;
4317
4318 // OK, looks good.
4319 NewF.canonicalize(*this->L);
4320 (void)InsertFormula(LU, LUIdx, NewF);
4321 } else {
4322 // Use the immediate in a base register.
4323 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
4324 const SCEV *BaseReg = F.BaseRegs[N];
4325 if (BaseReg != OrigReg)
4326 continue;
4327 Formula NewF = F;
4328 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
4329 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
4330 LU.Kind, LU.AccessTy, NewF)) {
4331 if (AMK == TTI::AMK_PostIndexed &&
4332 mayUsePostIncMode(TTI, LU, OrigReg, this->L, SE))
4333 continue;
4334 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
4335 continue;
4336 NewF = F;
4337 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
4338 }
4339 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
4340
4341 // If the new formula has a constant in a register, and adding the
4342 // constant value to the immediate would produce a value closer to
4343 // zero than the immediate itself, then the formula isn't worthwhile.
4344 for (const SCEV *NewReg : NewF.BaseRegs)
4345 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
4346 if ((C->getAPInt() + NewF.BaseOffset)
4347 .abs()
4348 .slt(std::abs(NewF.BaseOffset)) &&
4349 (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
4350 countTrailingZeros<uint64_t>(NewF.BaseOffset))
4351 goto skip_formula;
4352
4353 // Ok, looks good.
4354 NewF.canonicalize(*this->L);
4355 (void)InsertFormula(LU, LUIdx, NewF);
4356 break;
4357 skip_formula:;
4358 }
4359 }
4360 }
4361 }
4362}
4363
4364/// Generate formulae for each use.
4365void
4366LSRInstance::GenerateAllReuseFormulae() {
4367 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
4368 // queries are more precise.
4369 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4370 LSRUse &LU = Uses[LUIdx];
4371 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4372 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
4373 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4374 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
4375 }
4376 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4377 LSRUse &LU = Uses[LUIdx];
4378 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4379 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
4380 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4381 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
4382 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4383 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
4384 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4385 GenerateScales(LU, LUIdx, LU.Formulae[i]);
4386 }
4387 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4388 LSRUse &LU = Uses[LUIdx];
4389 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4390 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
4391 }
4392
4393 GenerateCrossUseConstantOffsets();
4394
4395 LLVM_DEBUG(dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
4396 "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)
4397 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
;
4398}
4399
4400/// If there are multiple formulae with the same set of registers used
4401/// by other uses, pick the best one and delete the others.
4402void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
4403 DenseSet<const SCEV *> VisitedRegs;
4404 SmallPtrSet<const SCEV *, 16> Regs;
4405 SmallPtrSet<const SCEV *, 16> LoserRegs;
4406#ifndef NDEBUG
4407 bool ChangedFormulae = false;
4408#endif
4409
4410 // Collect the best formula for each unique set of shared registers. This
4411 // is reset for each use.
4412 using BestFormulaeTy =
4413 DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>;
4414
4415 BestFormulaeTy BestFormulae;
4416
4417 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4418 LSRUse &LU = Uses[LUIdx];
4419 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)
4420 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4421
4422 bool Any = false;
4423 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
4424 FIdx != NumForms; ++FIdx) {
4425 Formula &F = LU.Formulae[FIdx];
4426
4427 // Some formulas are instant losers. For example, they may depend on
4428 // nonexistent AddRecs from other loops. These need to be filtered
4429 // immediately, otherwise heuristics could choose them over others leading
4430 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
4431 // avoids the need to recompute this information across formulae using the
4432 // same bad AddRec. Passing LoserRegs is also essential unless we remove
4433 // the corresponding bad register from the Regs set.
4434 Cost CostF(L, SE, TTI, AMK);
4435 Regs.clear();
4436 CostF.RateFormula(F, Regs, VisitedRegs, LU, &LoserRegs);
4437 if (CostF.isLoser()) {
4438 // During initial formula generation, undesirable formulae are generated
4439 // by uses within other loops that have some non-trivial address mode or
4440 // use the postinc form of the IV. LSR needs to provide these formulae
4441 // as the basis of rediscovering the desired formula that uses an AddRec
4442 // corresponding to the existing phi. Once all formulae have been
4443 // generated, these initial losers may be pruned.
4444 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)
4445 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering loser "; F.print
(dbgs()); dbgs() << "\n"; } } while (false)
;
4446 }
4447 else {
4448 SmallVector<const SCEV *, 4> Key;
4449 for (const SCEV *Reg : F.BaseRegs) {
4450 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
4451 Key.push_back(Reg);
4452 }
4453 if (F.ScaledReg &&
4454 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
4455 Key.push_back(F.ScaledReg);
4456 // Unstable sort by host order ok, because this is only used for
4457 // uniquifying.
4458 llvm::sort(Key);
4459
4460 std::pair<BestFormulaeTy::const_iterator, bool> P =
4461 BestFormulae.insert(std::make_pair(Key, FIdx));
4462 if (P.second)
4463 continue;
4464
4465 Formula &Best = LU.Formulae[P.first->second];
4466
4467 Cost CostBest(L, SE, TTI, AMK);
4468 Regs.clear();
4469 CostBest.RateFormula(Best, Regs, VisitedRegs, LU);
4470 if (CostF.isLess(CostBest))
4471 std::swap(F, Best);
4472 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)
4473 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)
4474 " 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)
4475 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)
;
4476 }
4477#ifndef NDEBUG
4478 ChangedFormulae = true;
4479#endif
4480 LU.DeleteFormula(F);
4481 --FIdx;
4482 --NumForms;
4483 Any = true;
4484 }
4485
4486 // Now that we've filtered out some formulae, recompute the Regs set.
4487 if (Any)
4488 LU.RecomputeRegs(LUIdx, RegUses);
4489
4490 // Reset this to prepare for the next use.
4491 BestFormulae.clear();
4492 }
4493
4494 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)
4495 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)
4496 "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)
4497 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)
4498 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4499}
4500
4501/// Estimate the worst-case number of solutions the solver might have to
4502/// consider. It almost never considers this many solutions because it prune the
4503/// search space, but the pruning isn't always sufficient.
4504size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4505 size_t Power = 1;
4506 for (const LSRUse &LU : Uses) {
4507 size_t FSize = LU.Formulae.size();
4508 if (FSize >= ComplexityLimit) {
4509 Power = ComplexityLimit;
4510 break;
4511 }
4512 Power *= FSize;
4513 if (Power >= ComplexityLimit)
4514 break;
4515 }
4516 return Power;
4517}
4518
4519/// When one formula uses a superset of the registers of another formula, it
4520/// won't help reduce register pressure (though it may not necessarily hurt
4521/// register pressure); remove it to simplify the system.
4522void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4523 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4524 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)
;
4525
4526 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)
4527 "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)
4528 "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)
;
4529
4530 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4531 LSRUse &LU = Uses[LUIdx];
4532 bool Any = false;
4533 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4534 Formula &F = LU.Formulae[i];
4535 // Look for a formula with a constant or GV in a register. If the use
4536 // also has a formula with that same value in an immediate field,
4537 // delete the one that uses a register.
4538 for (SmallVectorImpl<const SCEV *>::const_iterator
4539 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4540 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4541 Formula NewF = F;
4542 //FIXME: Formulas should store bitwidth to do wrapping properly.
4543 // See PR41034.
4544 NewF.BaseOffset += (uint64_t)C->getValue()->getSExtValue();
4545 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4546 (I - F.BaseRegs.begin()));
4547 if (LU.HasFormulaWithSameRegs(NewF)) {
4548 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4549 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4550 LU.DeleteFormula(F);
4551 --i;
4552 --e;
4553 Any = true;
4554 break;
4555 }
4556 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4557 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4558 if (!F.BaseGV) {
4559 Formula NewF = F;
4560 NewF.BaseGV = GV;
4561 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4562 (I - F.BaseRegs.begin()));
4563 if (LU.HasFormulaWithSameRegs(NewF)) {
4564 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4565 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4566 LU.DeleteFormula(F);
4567 --i;
4568 --e;
4569 Any = true;
4570 break;
4571 }
4572 }
4573 }
4574 }
4575 }
4576 if (Any)
4577 LU.RecomputeRegs(LUIdx, RegUses);
4578 }
4579
4580 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)
;
4581 }
4582}
4583
4584/// When there are many registers for expressions like A, A+1, A+2, etc.,
4585/// allocate a single register for them.
4586void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4587 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4588 return;
4589
4590 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)
4591 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)
4592 "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)
4593 "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)
;
4594
4595 // This is especially useful for unrolled loops.
4596
4597 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4598 LSRUse &LU = Uses[LUIdx];
4599 for (const Formula &F : LU.Formulae) {
4600 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4601 continue;
4602
4603 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4604 if (!LUThatHas)
4605 continue;
4606
4607 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4608 LU.Kind, LU.AccessTy))
4609 continue;
4610
4611 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)
;
4612
4613 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4614
4615 // Transfer the fixups of LU to LUThatHas.
4616 for (LSRFixup &Fixup : LU.Fixups) {
4617 Fixup.Offset += F.BaseOffset;
4618 LUThatHas->pushFixup(Fixup);
4619 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)
;
4620 }
4621
4622 // Delete formulae from the new use which are no longer legal.
4623 bool Any = false;
4624 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4625 Formula &F = LUThatHas->Formulae[i];
4626 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4627 LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4628 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)
;
4629 LUThatHas->DeleteFormula(F);
4630 --i;
4631 --e;
4632 Any = true;
4633 }
4634 }
4635
4636 if (Any)
4637 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4638
4639 // Delete the old use.
4640 DeleteUse(LU, LUIdx);
4641 --LUIdx;
4642 --NumUses;
4643 break;
4644 }
4645 }
4646
4647 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)
;
4648}
4649
4650/// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4651/// we've done more filtering, as it may be able to find more formulae to
4652/// eliminate.
4653void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4654 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4655 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)
;
4656
4657 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)
4658 "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)
;
4659
4660 FilterOutUndesirableDedicatedRegisters();
4661
4662 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)
;
4663 }
4664}
4665
4666/// If a LSRUse has multiple formulae with the same ScaledReg and Scale.
4667/// Pick the best one and delete the others.
4668/// This narrowing heuristic is to keep as many formulae with different
4669/// Scale and ScaledReg pair as possible while narrowing the search space.
4670/// The benefit is that it is more likely to find out a better solution
4671/// from a formulae set with more Scale and ScaledReg variations than
4672/// a formulae set with the same Scale and ScaledReg. The picking winner
4673/// reg heuristic will often keep the formulae with the same Scale and
4674/// ScaledReg and filter others, and we want to avoid that if possible.
4675void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() {
4676 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4677 return;
4678
4679 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)
4680 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)
4681 "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)
4682 "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)
;
4683
4684 // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse.
4685 using BestFormulaeTy = DenseMap<std::pair<const SCEV *, int64_t>, size_t>;
4686
4687 BestFormulaeTy BestFormulae;
4688#ifndef NDEBUG
4689 bool ChangedFormulae = false;
4690#endif
4691 DenseSet<const SCEV *> VisitedRegs;
4692 SmallPtrSet<const SCEV *, 16> Regs;
4693
4694 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4695 LSRUse &LU = Uses[LUIdx];
4696 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)
4697 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4698
4699 // Return true if Formula FA is better than Formula FB.
4700 auto IsBetterThan = [&](Formula &FA, Formula &FB) {
4701 // First we will try to choose the Formula with fewer new registers.
4702 // For a register used by current Formula, the more the register is
4703 // shared among LSRUses, the less we increase the register number
4704 // counter of the formula.
4705 size_t FARegNum = 0;
4706 for (const SCEV *Reg : FA.BaseRegs) {
4707 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4708 FARegNum += (NumUses - UsedByIndices.count() + 1);
4709 }
4710 size_t FBRegNum = 0;
4711 for (const SCEV *Reg : FB.BaseRegs) {
4712 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4713 FBRegNum += (NumUses - UsedByIndices.count() + 1);
4714 }
4715 if (FARegNum != FBRegNum)
4716 return FARegNum < FBRegNum;
4717
4718 // If the new register numbers are the same, choose the Formula with
4719 // less Cost.
4720 Cost CostFA(L, SE, TTI, AMK);
4721 Cost CostFB(L, SE, TTI, AMK);
4722 Regs.clear();
4723 CostFA.RateFormula(FA, Regs, VisitedRegs, LU);
4724 Regs.clear();
4725 CostFB.RateFormula(FB, Regs, VisitedRegs, LU);
4726 return CostFA.isLess(CostFB);
4727 };
4728
4729 bool Any = false;
4730 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4731 ++FIdx) {
4732 Formula &F = LU.Formulae[FIdx];
4733 if (!F.ScaledReg)
4734 continue;
4735 auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx});
4736 if (P.second)
4737 continue;
4738
4739 Formula &Best = LU.Formulae[P.first->second];
4740 if (IsBetterThan(F, Best))
4741 std::swap(F, Best);
4742 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)
4743 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)
4744 " 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)
4745 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)
;
4746#ifndef NDEBUG
4747 ChangedFormulae = true;
4748#endif
4749 LU.DeleteFormula(F);
4750 --FIdx;
4751 --NumForms;
4752 Any = true;
4753 }
4754 if (Any)
4755 LU.RecomputeRegs(LUIdx, RegUses);
4756
4757 // Reset this to prepare for the next use.
4758 BestFormulae.clear();
4759 }
4760
4761 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)
4762 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)
4763 "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)
4764 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)
4765 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4766}
4767
4768/// If we are over the complexity limit, filter out any post-inc prefering
4769/// variables to only post-inc values.
4770void LSRInstance::NarrowSearchSpaceByFilterPostInc() {
4771 if (AMK != TTI::AMK_PostIndexed)
4772 return;
4773 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4774 return;
4775
4776 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)
4777 "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)
4778 "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)
;
4779
4780 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4781 LSRUse &LU = Uses[LUIdx];
4782
4783 if (LU.Kind != LSRUse::Address)
4784 continue;
4785 if (!TTI.isIndexedLoadLegal(TTI.MIM_PostInc, LU.AccessTy.getType()) &&
4786 !TTI.isIndexedStoreLegal(TTI.MIM_PostInc, LU.AccessTy.getType()))
4787 continue;
4788
4789 size_t MinRegs = std::numeric_limits<size_t>::max();
4790 for (const Formula &F : LU.Formulae)
4791 MinRegs = std::min(F.getNumRegs(), MinRegs);
4792
4793 bool Any = false;
4794 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4795 ++FIdx) {
4796 Formula &F = LU.Formulae[FIdx];
4797 if (F.getNumRegs() > MinRegs) {
4798 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)
4799 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n"; } } while (false)
;
4800 LU.DeleteFormula(F);
4801 --FIdx;
4802 --NumForms;
4803 Any = true;
4804 }
4805 }
4806 if (Any)
4807 LU.RecomputeRegs(LUIdx, RegUses);
4808
4809 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4810 break;
4811 }
4812
4813 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)
;
4814}
4815
4816/// The function delete formulas with high registers number expectation.
4817/// Assuming we don't know the value of each formula (already delete
4818/// all inefficient), generate probability of not selecting for each
4819/// register.
4820/// For example,
4821/// Use1:
4822/// reg(a) + reg({0,+,1})
4823/// reg(a) + reg({-1,+,1}) + 1
4824/// reg({a,+,1})
4825/// Use2:
4826/// reg(b) + reg({0,+,1})
4827/// reg(b) + reg({-1,+,1}) + 1
4828/// reg({b,+,1})
4829/// Use3:
4830/// reg(c) + reg(b) + reg({0,+,1})
4831/// reg(c) + reg({b,+,1})
4832///
4833/// Probability of not selecting
4834/// Use1 Use2 Use3
4835/// reg(a) (1/3) * 1 * 1
4836/// reg(b) 1 * (1/3) * (1/2)
4837/// reg({0,+,1}) (2/3) * (2/3) * (1/2)
4838/// reg({-1,+,1}) (2/3) * (2/3) * 1
4839/// reg({a,+,1}) (2/3) * 1 * 1
4840/// reg({b,+,1}) 1 * (2/3) * (2/3)
4841/// reg(c) 1 * 1 * 0
4842///
4843/// Now count registers number mathematical expectation for each formula:
4844/// Note that for each use we exclude probability if not selecting for the use.
4845/// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding
4846/// probabilty 1/3 of not selecting for Use1).
4847/// Use1:
4848/// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted
4849/// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted
4850/// reg({a,+,1}) 1
4851/// Use2:
4852/// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted
4853/// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted
4854/// reg({b,+,1}) 2/3
4855/// Use3:
4856/// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted
4857/// reg(c) + reg({b,+,1}) 1 + 2/3
4858void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() {
4859 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4860 return;
4861 // Ok, we have too many of formulae on our hands to conveniently handle.
4862 // Use a rough heuristic to thin out the list.
4863
4864 // Set of Regs wich will be 100% used in final solution.
4865 // Used in each formula of a solution (in example above this is reg(c)).
4866 // We can skip them in calculations.
4867 SmallPtrSet<const SCEV *, 4> UniqRegs;
4868 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)
;
4869
4870 // Map each register to probability of not selecting
4871 DenseMap <const SCEV *, float> RegNumMap;
4872 for (const SCEV *Reg : RegUses) {
4873 if (UniqRegs.count(Reg))
4874 continue;
4875 float PNotSel = 1;
4876 for (const LSRUse &LU : Uses) {
4877 if (!LU.Regs.count(Reg))
4878 continue;
4879 float P = LU.getNotSelectedProbability(Reg);
4880 if (P != 0.0)
4881 PNotSel *= P;
4882 else
4883 UniqRegs.insert(Reg);
4884 }
4885 RegNumMap.insert(std::make_pair(Reg, PNotSel));
4886 }
4887
4888 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by deleting costly formulas\n"
; } } while (false)
4889 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)
;
4890
4891 // Delete formulas where registers number expectation is high.
4892 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4893 LSRUse &LU = Uses[LUIdx];
4894 // If nothing to delete - continue.
4895 if (LU.Formulae.size() < 2)
4896 continue;
4897 // This is temporary solution to test performance. Float should be
4898 // replaced with round independent type (based on integers) to avoid
4899 // different results for different target builds.
4900 float FMinRegNum = LU.Formulae[0].getNumRegs();
4901 float FMinARegNum = LU.Formulae[0].getNumRegs();
4902 size_t MinIdx = 0;
4903 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4904 Formula &F = LU.Formulae[i];
4905 float FRegNum = 0;
4906 float FARegNum = 0;
4907 for (const SCEV *BaseReg : F.BaseRegs) {
4908 if (UniqRegs.count(BaseReg))
4909 continue;
4910 FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4911 if (isa<SCEVAddRecExpr>(BaseReg))
4912 FARegNum +=
4913 RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4914 }
4915 if (const SCEV *ScaledReg = F.ScaledReg) {
4916 if (!UniqRegs.count(ScaledReg)) {
4917 FRegNum +=
4918 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4919 if (isa<SCEVAddRecExpr>(ScaledReg))
4920 FARegNum +=
4921 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4922 }
4923 }
4924 if (FMinRegNum > FRegNum ||
4925 (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) {
4926 FMinRegNum = FRegNum;
4927 FMinARegNum = FARegNum;
4928 MinIdx = i;
4929 }
4930 }
4931 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)
4932 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)
;
4933 if (MinIdx != 0)
4934 std::swap(LU.Formulae[MinIdx], LU.Formulae[0]);
4935 while (LU.Formulae.size() != 1) {
4936 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
)
4937 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; LU.Formulae
.back().print(dbgs()); dbgs() << '\n'; } } while (false
)
;
4938 LU.Formulae.pop_back();
4939 }
4940 LU.RecomputeRegs(LUIdx, RegUses);
4941 assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula")(static_cast <bool> (LU.Formulae.size() == 1 &&
"Should be exactly 1 min regs formula") ? void (0) : __assert_fail
("LU.Formulae.size() == 1 && \"Should be exactly 1 min regs formula\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 4941, __extension__
__PRETTY_FUNCTION__))
;
4942 Formula &F = LU.Formulae[0];
4943 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)
;
4944 // When we choose the formula, the regs become unique.
4945 UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
4946 if (F.ScaledReg)
4947 UniqRegs.insert(F.ScaledReg);
4948 }
4949 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)
;
4950}
4951
4952/// Pick a register which seems likely to be profitable, and then in any use
4953/// which has any reference to that register, delete all formulae which do not
4954/// reference that register.
4955void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4956 // With all other options exhausted, loop until the system is simple
4957 // enough to handle.
4958 SmallPtrSet<const SCEV *, 4> Taken;
4959 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4960 // Ok, we have too many of formulae on our hands to conveniently handle.
4961 // Use a rough heuristic to thin out the list.
4962 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)
;
4963
4964 // Pick the register which is used by the most LSRUses, which is likely
4965 // to be a good reuse register candidate.
4966 const SCEV *Best = nullptr;
4967 unsigned BestNum = 0;
4968 for (const SCEV *Reg : RegUses) {
4969 if (Taken.count(Reg))
4970 continue;
4971 if (!Best) {
4972 Best = Reg;
4973 BestNum = RegUses.getUsedByIndices(Reg).count();
4974 } else {
4975 unsigned Count = RegUses.getUsedByIndices(Reg).count();
4976 if (Count > BestNum) {
4977 Best = Reg;
4978 BestNum = Count;
4979 }
4980 }
4981 }
4982 assert(Best && "Failed to find best LSRUse candidate")(static_cast <bool> (Best && "Failed to find best LSRUse candidate"
) ? void (0) : __assert_fail ("Best && \"Failed to find best LSRUse candidate\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 4982, __extension__
__PRETTY_FUNCTION__))
;
4983
4984 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)
4985 << " 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)
;
4986 Taken.insert(Best);
4987
4988 // In any use with formulae which references this register, delete formulae
4989 // which don't reference it.
4990 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4991 LSRUse &LU = Uses[LUIdx];
4992 if (!LU.Regs.count(Best)) continue;
4993
4994 bool Any = false;
4995 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4996 Formula &F = LU.Formulae[i];
4997 if (!F.referencesReg(Best)) {
4998 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)
;
4999 LU.DeleteFormula(F);
5000 --e;
5001 --i;
5002 Any = true;
5003 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?")(static_cast <bool> (e != 0 && "Use has no formulae left! Is Regs inconsistent?"
) ? void (0) : __assert_fail ("e != 0 && \"Use has no formulae left! Is Regs inconsistent?\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5003, __extension__
__PRETTY_FUNCTION__))
;
5004 continue;
5005 }
5006 }
5007
5008 if (Any)
5009 LU.RecomputeRegs(LUIdx, RegUses);
5010 }
5011
5012 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)
;
5013 }
5014}
5015
5016/// If there are an extraordinary number of formulae to choose from, use some
5017/// rough heuristics to prune down the number of formulae. This keeps the main
5018/// solver from taking an extraordinary amount of time in some worst-case
5019/// scenarios.
5020void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
5021 NarrowSearchSpaceByDetectingSupersets();
5022 NarrowSearchSpaceByCollapsingUnrolledCode();
5023 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
5024 if (FilterSameScaledReg)
5025 NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
5026 NarrowSearchSpaceByFilterPostInc();
5027 if (LSRExpNarrow)
5028 NarrowSearchSpaceByDeletingCostlyFormulas();
5029 else
5030 NarrowSearchSpaceByPickingWinnerRegs();
5031}
5032
5033/// This is the recursive solver.
5034void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
5035 Cost &SolutionCost,
5036 SmallVectorImpl<const Formula *> &Workspace,
5037 const Cost &CurCost,
5038 const SmallPtrSet<const SCEV *, 16> &CurRegs,
5039 DenseSet<const SCEV *> &VisitedRegs) const {
5040 // Some ideas:
5041 // - prune more:
5042 // - use more aggressive filtering
5043 // - sort the formula so that the most profitable solutions are found first
5044 // - sort the uses too
5045 // - search faster:
5046 // - don't compute a cost, and then compare. compare while computing a cost
5047 // and bail early.
5048 // - track register sets with SmallBitVector
5049
5050 const LSRUse &LU = Uses[Workspace.size()];
5051
5052 // If this use references any register that's already a part of the
5053 // in-progress solution, consider it a requirement that a formula must
5054 // reference that register in order to be considered. This prunes out
5055 // unprofitable searching.
5056 SmallSetVector<const SCEV *, 4> ReqRegs;
5057 for (const SCEV *S : CurRegs)
5058 if (LU.Regs.count(S))
5059 ReqRegs.insert(S);
5060
5061 SmallPtrSet<const SCEV *, 16> NewRegs;
5062 Cost NewCost(L, SE, TTI, AMK);
5063 for (const Formula &F : LU.Formulae) {
5064 // Ignore formulae which may not be ideal in terms of register reuse of
5065 // ReqRegs. The formula should use all required registers before
5066 // introducing new ones.
5067 // This can sometimes (notably when trying to favour postinc) lead to
5068 // sub-optimial decisions. There it is best left to the cost modelling to
5069 // get correct.
5070 if (AMK != TTI::AMK_PostIndexed || LU.Kind != LSRUse::Address) {
5071 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
5072 for (const SCEV *Reg : ReqRegs) {
5073 if ((F.ScaledReg && F.ScaledReg == Reg) ||
5074 is_contained(F.BaseRegs, Reg)) {
5075 --NumReqRegsToFind;
5076 if (NumReqRegsToFind == 0)
5077 break;
5078 }
5079 }
5080 if (NumReqRegsToFind != 0) {
5081 // If none of the formulae satisfied the required registers, then we could
5082 // clear ReqRegs and try again. Currently, we simply give up in this case.
5083 continue;
5084 }
5085 }
5086
5087 // Evaluate the cost of the current formula. If it's already worse than
5088 // the current best, prune the search at that point.
5089 NewCost = CurCost;
5090 NewRegs = CurRegs;
5091 NewCost.RateFormula(F, NewRegs, VisitedRegs, LU);
5092 if (NewCost.isLess(SolutionCost)) {
5093 Workspace.push_back(&F);
5094 if (Workspace.size() != Uses.size()) {
5095 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
5096 NewRegs, VisitedRegs);
5097 if (F.getNumRegs() == 1 && Workspace.size() == 1)
5098 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
5099 } else {
5100 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)
5101 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)
5102 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)
5103 << "- " << *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)
5104 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)
;
5105
5106 SolutionCost = NewCost;
5107 Solution = Workspace;
5108 }
5109 Workspace.pop_back();
5110 }
5111 }
5112}
5113
5114/// Choose one formula from each use. Return the results in the given Solution
5115/// vector.
5116void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
5117 SmallVector<const Formula *, 8> Workspace;
5118 Cost SolutionCost(L, SE, TTI, AMK);
5119 SolutionCost.Lose();
5120 Cost CurCost(L, SE, TTI, AMK);
5121 SmallPtrSet<const SCEV *, 16> CurRegs;
5122 DenseSet<const SCEV *> VisitedRegs;
5123 Workspace.reserve(Uses.size());
5124
5125 // SolveRecurse does all the work.
5126 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
5127 CurRegs, VisitedRegs);
5128 if (Solution.empty()) {
5129 LLVM_DEBUG(dbgs() << "\nNo Satisfactory Solution\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nNo Satisfactory Solution\n"
; } } while (false)
;
5130 return;
5131 }
5132
5133 // Ok, we've now made all our decisions.
5134 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
)
5135 "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
)
5136 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
)
5137 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
)
5138 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
)
5139 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
)
5140 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
)
5141 " ";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
)
5142 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
)
5143 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
)
5144 })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
)
;
5145
5146 assert(Solution.size() == Uses.size() && "Malformed solution!")(static_cast <bool> (Solution.size() == Uses.size() &&
"Malformed solution!") ? void (0) : __assert_fail ("Solution.size() == Uses.size() && \"Malformed solution!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5146, __extension__
__PRETTY_FUNCTION__))
;
5147}
5148
5149/// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
5150/// we can go while still being dominated by the input positions. This helps
5151/// canonicalize the insert position, which encourages sharing.
5152BasicBlock::iterator
5153LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
5154 const SmallVectorImpl<Instruction *> &Inputs)
5155 const {
5156 Instruction *Tentative = &*IP;
5157 while (true) {
5158 bool AllDominate = true;
5159 Instruction *BetterPos = nullptr;
5160 // Don't bother attempting to insert before a catchswitch, their basic block
5161 // cannot have other non-PHI instructions.
5162 if (isa<CatchSwitchInst>(Tentative))
5163 return IP;
5164
5165 for (Instruction *Inst : Inputs) {
5166 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
5167 AllDominate = false;
5168 break;
5169 }
5170 // Attempt to find an insert position in the middle of the block,
5171 // instead of at the end, so that it can be used for other expansions.
5172 if (Tentative->getParent() == Inst->getParent() &&
5173 (!BetterPos || !DT.dominates(Inst, BetterPos)))
5174 BetterPos = &*std::next(BasicBlock::iterator(Inst));
5175 }
5176 if (!AllDominate)
5177 break;
5178 if (BetterPos)
5179 IP = BetterPos->getIterator();
5180 else
5181 IP = Tentative->getIterator();
5182
5183 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
5184 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
5185
5186 BasicBlock *IDom;
5187 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
5188 if (!Rung) return IP;
5189 Rung = Rung->getIDom();
5190 if (!Rung) return IP;
5191 IDom = Rung->getBlock();
5192
5193 // Don't climb into a loop though.
5194 const Loop *IDomLoop = LI.getLoopFor(IDom);
5195 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
5196 if (IDomDepth <= IPLoopDepth &&
5197 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
5198 break;
5199 }
5200
5201 Tentative = IDom->getTerminator();
5202 }
5203
5204 return IP;
5205}
5206
5207/// Determine an input position which will be dominated by the operands and
5208/// which will dominate the result.
5209BasicBlock::iterator
5210LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
5211 const LSRFixup &LF,
5212 const LSRUse &LU,
5213 SCEVExpander &Rewriter) const {
5214 // Collect some instructions which must be dominated by the
5215 // expanding replacement. These must be dominated by any operands that
5216 // will be required in the expansion.
5217 SmallVector<Instruction *, 4> Inputs;
5218 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
5219 Inputs.push_back(I);
5220 if (LU.Kind == LSRUse::ICmpZero)
5221 if (Instruction *I =
5222 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
5223 Inputs.push_back(I);
5224 if (LF.PostIncLoops.count(L)) {
5225 if (LF.isUseFullyOutsideLoop(L))
5226 Inputs.push_back(L->getLoopLatch()->getTerminator());
5227 else
5228 Inputs.push_back(IVIncInsertPos);
5229 }
5230 // The expansion must also be dominated by the increment positions of any
5231 // loops it for which it is using post-inc mode.
5232 for (const Loop *PIL : LF.PostIncLoops) {
5233 if (PIL == L) continue;
5234
5235 // Be dominated by the loop exit.
5236 SmallVector<BasicBlock *, 4> ExitingBlocks;
5237 PIL->getExitingBlocks(ExitingBlocks);
5238 if (!ExitingBlocks.empty()) {
5239 BasicBlock *BB = ExitingBlocks[0];
5240 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
5241 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
5242 Inputs.push_back(BB->getTerminator());
5243 }
5244 }
5245
5246 assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad()(static_cast <bool> (!isa<PHINode>(LowestIP) &&
!LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>
(LowestIP) && "Insertion point must be a normal instruction"
) ? void (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5248, __extension__
__PRETTY_FUNCTION__))
5247 && !isa<DbgInfoIntrinsic>(LowestIP) &&(static_cast <bool> (!isa<PHINode>(LowestIP) &&
!LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>
(LowestIP) && "Insertion point must be a normal instruction"
) ? void (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5248, __extension__
__PRETTY_FUNCTION__))
5248 "Insertion point must be a normal instruction")(static_cast <bool> (!isa<PHINode>(LowestIP) &&
!LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>
(LowestIP) && "Insertion point must be a normal instruction"
) ? void (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5248, __extension__
__PRETTY_FUNCTION__))
;
5249
5250 // Then, climb up the immediate dominator tree as far as we can go while
5251 // still being dominated by the input positions.
5252 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
5253
5254 // Don't insert instructions before PHI nodes.
5255 while (isa<PHINode>(IP)) ++IP;
5256
5257 // Ignore landingpad instructions.
5258 while (IP->isEHPad()) ++IP;
5259
5260 // Ignore debug intrinsics.
5261 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
5262
5263 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
5264 // IP consistent across expansions and allows the previously inserted
5265 // instructions to be reused by subsequent expansion.
5266 while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
5267 ++IP;
5268
5269 return IP;
5270}
5271
5272/// Emit instructions for the leading candidate expression for this LSRUse (this
5273/// is called "expanding").
5274Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF,
5275 const Formula &F, BasicBlock::iterator IP,
5276 SCEVExpander &Rewriter,
5277 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5278 if (LU.RigidFormula)
5279 return LF.OperandValToReplace;
5280
5281 // Determine an input position which will be dominated by the operands and
5282 // which will dominate the result.
5283 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
5284 Rewriter.setInsertPoint(&*IP);
5285
5286 // Inform the Rewriter if we have a post-increment use, so that it can
5287 // perform an advantageous expansion.
5288 Rewriter.setPostInc(LF.PostIncLoops);
5289
5290 // This is the type that the user actually needs.
5291 Type *OpTy = LF.OperandValToReplace->getType();
5292 // This will be the type that we'll initially expand to.
5293 Type *Ty = F.getType();
5294 if (!Ty)
5295 // No type known; just expand directly to the ultimate type.
5296 Ty = OpTy;
5297 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
5298 // Expand directly to the ultimate type if it's the right size.
5299 Ty = OpTy;
5300 // This is the type to do integer arithmetic in.
5301 Type *IntTy = SE.getEffectiveSCEVType(Ty);
5302
5303 // Build up a list of operands to add together to form the full base.
5304 SmallVector<const SCEV *, 8> Ops;
5305
5306 // Expand the BaseRegs portion.
5307 for (const SCEV *Reg : F.BaseRegs) {
5308 assert(!Reg->isZero() && "Zero allocated in a base register!")(static_cast <bool> (!Reg->isZero() && "Zero allocated in a base register!"
) ? void (0) : __assert_fail ("!Reg->isZero() && \"Zero allocated in a base register!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5308, __extension__
__PRETTY_FUNCTION__))
;
5309
5310 // If we're expanding for a post-inc user, make the post-inc adjustment.
5311 Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE);
5312 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
5313 }
5314
5315 // Expand the ScaledReg portion.
5316 Value *ICmpScaledV = nullptr;
5317 if (F.Scale != 0) {
5318 const SCEV *ScaledS = F.ScaledReg;
5319
5320 // If we're expanding for a post-inc user, make the post-inc adjustment.
5321 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
5322 ScaledS = denormalizeForPostIncUse(ScaledS, Loops, SE);
5323
5324 if (LU.Kind == LSRUse::ICmpZero) {
5325 // Expand ScaleReg as if it was part of the base regs.
5326 if (F.Scale == 1)
5327 Ops.push_back(
5328 SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
5329 else {
5330 // An interesting way of "folding" with an icmp is to use a negated
5331 // scale, which we'll implement by inserting it into the other operand
5332 // of the icmp.
5333 assert(F.Scale == -1 &&(static_cast <bool> (F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? void (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5334, __extension__
__PRETTY_FUNCTION__))
5334 "The only scale supported by ICmpZero uses is -1!")(static_cast <bool> (F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? void (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5334, __extension__
__PRETTY_FUNCTION__))
;
5335 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
5336 }
5337 } else {
5338 // Otherwise just expand the scaled register and an explicit scale,
5339 // which is expected to be matched as part of the address.
5340
5341 // Flush the operand list to suppress SCEVExpander hoisting address modes.
5342 // Unless the addressing mode will not be folded.
5343 if (!Ops.empty() && LU.Kind == LSRUse::Address &&
5344 isAMCompletelyFolded(TTI, LU, F)) {
5345 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), nullptr);
5346 Ops.clear();
5347 Ops.push_back(SE.getUnknown(FullV));
5348 }
5349 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
5350 if (F.Scale != 1)
5351 ScaledS =
5352 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
5353 Ops.push_back(ScaledS);
5354 }
5355 }
5356
5357 // Expand the GV portion.
5358 if (F.BaseGV) {
5359 // Flush the operand list to suppress SCEVExpander hoisting.
5360 if (!Ops.empty()) {
5361 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), IntTy);
5362 Ops.clear();
5363 Ops.push_back(SE.getUnknown(FullV));
5364 }
5365 Ops.push_back(SE.getUnknown(F.BaseGV));
5366 }
5367
5368 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
5369 // unfolded offsets. LSR assumes they both live next to their uses.
5370 if (!Ops.empty()) {
5371 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5372 Ops.clear();
5373 Ops.push_back(SE.getUnknown(FullV));
5374 }
5375
5376 // Expand the immediate portion.
5377 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
5378 if (Offset != 0) {
5379 if (LU.Kind == LSRUse::ICmpZero) {
5380 // The other interesting way of "folding" with an ICmpZero is to use a
5381 // negated immediate.
5382 if (!ICmpScaledV)
5383 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
5384 else {
5385 Ops.push_back(SE.getUnknown(ICmpScaledV));
5386 ICmpScaledV = ConstantInt::get(IntTy, Offset);
5387 }
5388 } else {
5389 // Just add the immediate values. These again are expected to be matched
5390 // as part of the address.
5391 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
5392 }
5393 }
5394
5395 // Expand the unfolded offset portion.
5396 int64_t UnfoldedOffset = F.UnfoldedOffset;
5397 if (UnfoldedOffset != 0) {
5398 // Just add the immediate values.
5399 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
5400 UnfoldedOffset)));
5401 }
5402
5403 // Emit instructions summing all the operands.
5404 const SCEV *FullS = Ops.empty() ?
5405 SE.getConstant(IntTy, 0) :
5406 SE.getAddExpr(Ops);
5407 Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
5408
5409 // We're done expanding now, so reset the rewriter.
5410 Rewriter.clearPostInc();
5411
5412 // An ICmpZero Formula represents an ICmp which we're handling as a
5413 // comparison against zero. Now that we've expanded an expression for that
5414 // form, update the ICmp's other operand.
5415 if (LU.Kind == LSRUse::ICmpZero) {
5416 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
5417 if (auto *OperandIsInstr = dyn_cast<Instruction>(CI->getOperand(1)))
5418 DeadInsts.emplace_back(OperandIsInstr);
5419 assert(!F.BaseGV && "ICmp does not support folding a global value and "(static_cast <bool> (!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? void (0) : __assert_fail ("!F.BaseGV && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5420, __extension__
__PRETTY_FUNCTION__))
5420 "a scale at the same time!")(static_cast <bool> (!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? void (0) : __assert_fail ("!F.BaseGV && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5420, __extension__
__PRETTY_FUNCTION__))
;
5421 if (F.Scale == -1) {
5422 if (ICmpScaledV->getType() != OpTy) {
5423 Instruction *Cast =
5424 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
5425 OpTy, false),
5426 ICmpScaledV, OpTy, "tmp", CI);
5427 ICmpScaledV = Cast;
5428 }
5429 CI->setOperand(1, ICmpScaledV);
5430 } else {
5431 // A scale of 1 means that the scale has been expanded as part of the
5432 // base regs.
5433 assert((F.Scale == 0 || F.Scale == 1) &&(static_cast <bool> ((F.Scale == 0 || F.Scale == 1) &&
"ICmp does not support folding a global value and " "a scale at the same time!"
) ? void (0) : __assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5435, __extension__
__PRETTY_FUNCTION__))
5434 "ICmp does not support folding a global value and "(static_cast <bool> ((F.Scale == 0 || F.Scale == 1) &&
"ICmp does not support folding a global value and " "a scale at the same time!"
) ? void (0) : __assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5435, __extension__
__PRETTY_FUNCTION__))
5435 "a scale at the same time!")(static_cast <bool> ((F.Scale == 0 || F.Scale == 1) &&
"ICmp does not support folding a global value and " "a scale at the same time!"
) ? void (0) : __assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp", 5435, __extension__
__PRETTY_FUNCTION__))
;
5436 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
5437 -(uint64_t)Offset);
5438 if (C->getType() != OpTy)
5439 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
5440 OpTy, false),
5441 C, OpTy);
5442
5443 CI->setOperand(1, C);
5444 }
5445 }
5446
5447 return FullV;
5448}
5449
5450/// Helper for Rewrite. PHI nodes are special because the use of their operands
5451/// effectively happens in their predecessor blocks, so the expression may need
5452/// to be expanded in multiple places.
5453void LSRInstance::RewriteForPHI(
5454 PHINode *PN, const LSRUse &LU, const LSRFixup &LF, const Formula &F,
5455 SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5456 DenseMap<BasicBlock *, Value *> Inserted;
5457 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
5458 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
3
Assuming pointer value is null
4
Taking true branch
5459 bool needUpdateFixups = false;
5460 BasicBlock *BB = PN->getIncomingBlock(i);
5461
5462 // If this is a critical edge, split the edge so that we do not insert
5463 // the code on all predecessor/successor paths. We do this unless this
5464 // is the canonical backedge for this loop, which complicates post-inc
5465 // users.
5466 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
5
Assuming 'e' is equal to 1
6
Taking false branch
5467 !isa<IndirectBrInst>(BB->getTerminator()) &&
5468 !isa<CatchSwitchInst>(BB->getTerminator())) {
5469 BasicBlock *Parent = PN->getParent();
5470 Loop *PNLoop = LI.getLoopFor(Parent);
5471 if (!PNLoop || Parent != PNLoop->getHeader()) {
5472 // Split the critical edge.
5473 BasicBlock *NewBB = nullptr;
5474 if (!Parent->isLandingPad()) {
5475 NewBB =
5476 SplitCriticalEdge(BB, Parent,
5477 CriticalEdgeSplittingOptions(&DT, &LI, MSSAU)
5478 .setMergeIdenticalEdges()
5479 .setKeepOneInputPHIs());
5480 } else {
5481 SmallVector<BasicBlock*, 2> NewBBs;
5482 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
5483 NewBB = NewBBs[0];
5484 }
5485 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
5486 // phi predecessors are identical. The simple thing to do is skip
5487 // splitting in this case rather than complicate the API.
5488 if (NewBB) {
5489 // If PN is outside of the loop and BB is in the loop, we want to
5490 // move the block to be immediately before the PHI block, not
5491 // immediately after BB.
5492 if (L->contains(BB) && !L->contains(PN))
5493 NewBB->moveBefore(PN->getParent());
5494
5495 // Splitting the edge can reduce the number of PHI entries we have.
5496 e = PN->getNumIncomingValues();
5497 BB = NewBB;
5498 i = PN->getBasicBlockIndex(BB);
5499
5500 needUpdateFixups = true;
5501 }
5502 }
5503 }
5504
5505 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
5506 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
5507 if (!Pair.second)
7
Assuming field 'second' is true
8
Taking false branch
5508 PN->setIncomingValue(i, Pair.first->second);
5509 else {
5510 Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
5511 Rewriter, DeadInsts);
5512
5513 // If this is reuse-by-noop-cast, insert the noop cast.
5514 Type *OpTy = LF.OperandValToReplace->getType();
9
Called C++ object pointer is null
5515 if (FullV->getType() != OpTy)
5516 FullV =
5517 CastInst::Create(CastInst::getCastOpcode(FullV, false,
5518 OpTy, false),
5519 FullV, LF.OperandValToReplace->getType(),
5520 "tmp", BB->getTerminator());
5521
5522 PN->setIncomingValue(i, FullV);
5523 Pair.first->second = FullV;
5524 }
5525
5526 // If LSR splits critical edge and phi node has other pending
5527 // fixup operands, we need to update those pending fixups. Otherwise
5528 // formulae will not be implemented completely and some instructions
5529 // will not be eliminated.
5530 if (needUpdateFixups) {
5531 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5532 for (LSRFixup &Fixup : Uses[LUIdx].Fixups)
5533 // If fixup is supposed to rewrite some operand in the phi
5534 // that was just updated, it may be already moved to
5535 // another phi node. Such fixup requires update.
5536 if (Fixup.UserInst == PN) {
5537 // Check if the operand we try to replace still exists in the
5538 // original phi.
5539 bool foundInOriginalPHI = false;
5540 for (const auto &val : PN->incoming_values())
5541 if (val == Fixup.OperandValToReplace) {
5542 foundInOriginalPHI = true;
5543 break;
5544 }
5545
5546 // If fixup operand found in original PHI - nothing to do.
5547 if (foundInOriginalPHI)
5548 continue;
5549
5550 // Otherwise it might be moved to another PHI and requires update.
5551 // If fixup operand not found in any of the incoming blocks that
5552 // means we have already rewritten it - nothing to do.
5553 for (const auto &Block : PN->blocks())
5554 for (BasicBlock::iterator I = Block->begin(); isa<PHINode>(I);
5555 ++I) {
5556 PHINode *NewPN = cast<PHINode>(I);
5557 for (const auto &val : NewPN->incoming_values())
5558 if (val == Fixup.OperandValToReplace)
5559 Fixup.UserInst = NewPN;
5560 }
5561 }
5562 }
5563 }
5564}
5565
5566/// Emit instructions for the leading candidate expression for this LSRUse (this
5567/// is called "expanding"), and update the UserInst to reference the newly
5568/// expanded value.
5569void LSRInstance::Rewrite(const LSRUse &LU, const LSRFixup &LF,
5570 const Formula &F, SCEVExpander &Rewriter,
5571 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5572 // First, find an insertion point that dominates UserInst. For PHI nodes,
5573 // find the nearest block which dominates all the relevant uses.
5574 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
5575 RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
5576 } else {
5577 Value *FullV =
5578 Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
5579
5580 // If this is reuse-by-noop-cast, insert the noop cast.
5581 Type *OpTy = LF.OperandValToReplace->getType();
5582 if (FullV->getType() != OpTy) {
5583 Instruction *Cast =
5584 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
5585 FullV, OpTy, "tmp", LF.UserInst);
5586 FullV = Cast;
5587 }
5588
5589 // Update the user. ICmpZero is handled specially here (for now) because
5590 // Expand may have updated one of the operands of the icmp already, and
5591 // its new value may happen to be equal to LF.OperandValToReplace, in
5592 // which case doing replaceUsesOfWith leads to replacing both operands
5593 // with the same value. TODO: Reorganize this.
5594 if (LU.Kind == LSRUse::ICmpZero)
5595 LF.UserInst->setOperand(0, FullV);
5596 else
5597 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
5598 }
5599
5600 if (auto *OperandIsInstr = dyn_cast<Instruction>(LF.OperandValToReplace))
5601 DeadInsts.emplace_back(OperandIsInstr);
5602}
5603
5604/// Rewrite all the fixup locations with new values, following the chosen
5605/// solution.
5606void LSRInstance::ImplementSolution(
5607 const SmallVectorImpl<const Formula *> &Solution) {
5608 // Keep track of instructions we may have made dead, so that
5609 // we can remove them after we are done working.
5610 SmallVector<WeakTrackingVH, 16> DeadInsts;
5611
5612 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(), "lsr",
5613 false);
5614#ifndef NDEBUG
5615 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5616#endif
5617 Rewriter.disableCanonicalMode();
5618 Rewriter.enableLSRMode();
5619 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
5620
5621 // Mark phi nodes that terminate chains so the expander tries to reuse them.
5622 for (const IVChain &Chain : IVChainVec) {
5623 if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
5624 Rewriter.setChainedPhi(PN);
5625 }
5626
5627 // Expand the new value definitions and update the users.
5628 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5629 for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
5630 Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
5631 Changed = true;
5632 }
5633
5634 for (const IVChain &Chain : IVChainVec) {
5635 GenerateIVChain(Chain, Rewriter, DeadInsts);
5636 Changed = true;
5637 }
5638
5639 for (const WeakVH &IV : Rewriter.getInsertedIVs())
5640 if (IV && dyn_cast<Instruction>(&*IV)->getParent())
5641 ScalarEvolutionIVs.push_back(IV);
5642
5643 // Clean up after ourselves. This must be done before deleting any
5644 // instructions.
5645 Rewriter.clear();
5646
5647 Changed |= RecursivelyDeleteTriviallyDeadInstructionsPermissive(DeadInsts,
5648 &TLI, MSSAU);
5649
5650 // In our cost analysis above, we assume that each addrec consumes exactly
5651 // one register, and arrange to have increments inserted just before the
5652 // latch to maximimize the chance this is true. However, if we reused
5653 // existing IVs, we now need to move the increments to match our
5654 // expectations. Otherwise, our cost modeling results in us having a
5655 // chosen a non-optimal result for the actual schedule. (And yes, this
5656 // scheduling decision does impact later codegen.)
5657 for (PHINode &PN : L->getHeader()->phis()) {
5658 BinaryOperator *BO = nullptr;
5659 Value *Start = nullptr, *Step = nullptr;
5660 if (!matchSimpleRecurrence(&PN, BO, Start, Step))
5661 continue;
5662
5663 switch (BO->getOpcode()) {
5664 case Instruction::Sub:
5665 if (BO->getOperand(0) != &PN)
5666 // sub is non-commutative - match handling elsewhere in LSR
5667 continue;
5668 break;
5669 case Instruction::Add:
5670 break;
5671 default:
5672 continue;
5673 };
5674
5675 if (!isa<Constant>(Step))
5676 // If not a constant step, might increase register pressure
5677 // (We assume constants have been canonicalized to RHS)
5678 continue;
5679
5680 if (BO->getParent() == IVIncInsertPos->getParent())
5681 // Only bother moving across blocks. Isel can handle block local case.
5682 continue;
5683
5684 // Can we legally schedule inc at the desired point?
5685 if (!llvm::all_of(BO->uses(),
5686 [&](Use &U) {return DT.dominates(IVIncInsertPos, U);}))
5687 continue;
5688 BO->moveBefore(IVIncInsertPos);
5689 Changed = true;