Bug Summary

File:llvm/lib/Analysis/ValueTracking.cpp
Warning:line 1399, column 13
Value stored to 'L' is never read

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name ValueTracking.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -fhalf-no-semantic-interposition -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-13/lib/clang/13.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/build-llvm/lib/Analysis -I /build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis -I /build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/build-llvm/include -I /build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-13/lib/clang/13.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/build-llvm/lib/Analysis -fdebug-prefix-map=/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1=. -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2021-02-23-121308-24221-1 -x c++ /build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp
1//===- ValueTracking.cpp - Walk computations to compute properties --------===//
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 file contains routines that help analyze properties that chains of
10// computations have.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Analysis/ValueTracking.h"
15#include "llvm/ADT/APFloat.h"
16#include "llvm/ADT/APInt.h"
17#include "llvm/ADT/ArrayRef.h"
18#include "llvm/ADT/None.h"
19#include "llvm/ADT/Optional.h"
20#include "llvm/ADT/STLExtras.h"
21#include "llvm/ADT/SmallPtrSet.h"
22#include "llvm/ADT/SmallSet.h"
23#include "llvm/ADT/SmallVector.h"
24#include "llvm/ADT/StringRef.h"
25#include "llvm/ADT/iterator_range.h"
26#include "llvm/Analysis/AliasAnalysis.h"
27#include "llvm/Analysis/AssumeBundleQueries.h"
28#include "llvm/Analysis/AssumptionCache.h"
29#include "llvm/Analysis/GuardUtils.h"
30#include "llvm/Analysis/InstructionSimplify.h"
31#include "llvm/Analysis/Loads.h"
32#include "llvm/Analysis/LoopInfo.h"
33#include "llvm/Analysis/OptimizationRemarkEmitter.h"
34#include "llvm/Analysis/TargetLibraryInfo.h"
35#include "llvm/IR/Argument.h"
36#include "llvm/IR/Attributes.h"
37#include "llvm/IR/BasicBlock.h"
38#include "llvm/IR/Constant.h"
39#include "llvm/IR/ConstantRange.h"
40#include "llvm/IR/Constants.h"
41#include "llvm/IR/DerivedTypes.h"
42#include "llvm/IR/DiagnosticInfo.h"
43#include "llvm/IR/Dominators.h"
44#include "llvm/IR/Function.h"
45#include "llvm/IR/GetElementPtrTypeIterator.h"
46#include "llvm/IR/GlobalAlias.h"
47#include "llvm/IR/GlobalValue.h"
48#include "llvm/IR/GlobalVariable.h"
49#include "llvm/IR/InstrTypes.h"
50#include "llvm/IR/Instruction.h"
51#include "llvm/IR/Instructions.h"
52#include "llvm/IR/IntrinsicInst.h"
53#include "llvm/IR/Intrinsics.h"
54#include "llvm/IR/IntrinsicsAArch64.h"
55#include "llvm/IR/IntrinsicsX86.h"
56#include "llvm/IR/LLVMContext.h"
57#include "llvm/IR/Metadata.h"
58#include "llvm/IR/Module.h"
59#include "llvm/IR/Operator.h"
60#include "llvm/IR/PatternMatch.h"
61#include "llvm/IR/Type.h"
62#include "llvm/IR/User.h"
63#include "llvm/IR/Value.h"
64#include "llvm/Support/Casting.h"
65#include "llvm/Support/CommandLine.h"
66#include "llvm/Support/Compiler.h"
67#include "llvm/Support/ErrorHandling.h"
68#include "llvm/Support/KnownBits.h"
69#include "llvm/Support/MathExtras.h"
70#include <algorithm>
71#include <array>
72#include <cassert>
73#include <cstdint>
74#include <iterator>
75#include <utility>
76
77using namespace llvm;
78using namespace llvm::PatternMatch;
79
80// Controls the number of uses of the value searched for possible
81// dominating comparisons.
82static cl::opt<unsigned> DomConditionsMaxUses("dom-conditions-max-uses",
83 cl::Hidden, cl::init(20));
84
85/// Returns the bitwidth of the given scalar or pointer type. For vector types,
86/// returns the element type's bitwidth.
87static unsigned getBitWidth(Type *Ty, const DataLayout &DL) {
88 if (unsigned BitWidth = Ty->getScalarSizeInBits())
89 return BitWidth;
90
91 return DL.getPointerTypeSizeInBits(Ty);
92}
93
94namespace {
95
96// Simplifying using an assume can only be done in a particular control-flow
97// context (the context instruction provides that context). If an assume and
98// the context instruction are not in the same block then the DT helps in
99// figuring out if we can use it.
100struct Query {
101 const DataLayout &DL;
102 AssumptionCache *AC;
103 const Instruction *CxtI;
104 const DominatorTree *DT;
105
106 // Unlike the other analyses, this may be a nullptr because not all clients
107 // provide it currently.
108 OptimizationRemarkEmitter *ORE;
109
110 /// Set of assumptions that should be excluded from further queries.
111 /// This is because of the potential for mutual recursion to cause
112 /// computeKnownBits to repeatedly visit the same assume intrinsic. The
113 /// classic case of this is assume(x = y), which will attempt to determine
114 /// bits in x from bits in y, which will attempt to determine bits in y from
115 /// bits in x, etc. Regarding the mutual recursion, computeKnownBits can call
116 /// isKnownNonZero, which calls computeKnownBits and isKnownToBeAPowerOfTwo
117 /// (all of which can call computeKnownBits), and so on.
118 std::array<const Value *, MaxAnalysisRecursionDepth> Excluded;
119
120 /// If true, it is safe to use metadata during simplification.
121 InstrInfoQuery IIQ;
122
123 unsigned NumExcluded = 0;
124
125 Query(const DataLayout &DL, AssumptionCache *AC, const Instruction *CxtI,
126 const DominatorTree *DT, bool UseInstrInfo,
127 OptimizationRemarkEmitter *ORE = nullptr)
128 : DL(DL), AC(AC), CxtI(CxtI), DT(DT), ORE(ORE), IIQ(UseInstrInfo) {}
129
130 Query(const Query &Q, const Value *NewExcl)
131 : DL(Q.DL), AC(Q.AC), CxtI(Q.CxtI), DT(Q.DT), ORE(Q.ORE), IIQ(Q.IIQ),
132 NumExcluded(Q.NumExcluded) {
133 Excluded = Q.Excluded;
134 Excluded[NumExcluded++] = NewExcl;
135 assert(NumExcluded <= Excluded.size())((NumExcluded <= Excluded.size()) ? static_cast<void>
(0) : __assert_fail ("NumExcluded <= Excluded.size()", "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 135, __PRETTY_FUNCTION__))
;
136 }
137
138 bool isExcluded(const Value *Value) const {
139 if (NumExcluded == 0)
140 return false;
141 auto End = Excluded.begin() + NumExcluded;
142 return std::find(Excluded.begin(), End, Value) != End;
143 }
144};
145
146} // end anonymous namespace
147
148// Given the provided Value and, potentially, a context instruction, return
149// the preferred context instruction (if any).
150static const Instruction *safeCxtI(const Value *V, const Instruction *CxtI) {
151 // If we've been provided with a context instruction, then use that (provided
152 // it has been inserted).
153 if (CxtI && CxtI->getParent())
154 return CxtI;
155
156 // If the value is really an already-inserted instruction, then use that.
157 CxtI = dyn_cast<Instruction>(V);
158 if (CxtI && CxtI->getParent())
159 return CxtI;
160
161 return nullptr;
162}
163
164static const Instruction *safeCxtI(const Value *V1, const Value *V2, const Instruction *CxtI) {
165 // If we've been provided with a context instruction, then use that (provided
166 // it has been inserted).
167 if (CxtI && CxtI->getParent())
168 return CxtI;
169
170 // If the value is really an already-inserted instruction, then use that.
171 CxtI = dyn_cast<Instruction>(V1);
172 if (CxtI && CxtI->getParent())
173 return CxtI;
174
175 CxtI = dyn_cast<Instruction>(V2);
176 if (CxtI && CxtI->getParent())
177 return CxtI;
178
179 return nullptr;
180}
181
182static bool getShuffleDemandedElts(const ShuffleVectorInst *Shuf,
183 const APInt &DemandedElts,
184 APInt &DemandedLHS, APInt &DemandedRHS) {
185 // The length of scalable vectors is unknown at compile time, thus we
186 // cannot check their values
187 if (isa<ScalableVectorType>(Shuf->getType()))
188 return false;
189
190 int NumElts =
191 cast<FixedVectorType>(Shuf->getOperand(0)->getType())->getNumElements();
192 int NumMaskElts = cast<FixedVectorType>(Shuf->getType())->getNumElements();
193 DemandedLHS = DemandedRHS = APInt::getNullValue(NumElts);
194 if (DemandedElts.isNullValue())
195 return true;
196 // Simple case of a shuffle with zeroinitializer.
197 if (all_of(Shuf->getShuffleMask(), [](int Elt) { return Elt == 0; })) {
198 DemandedLHS.setBit(0);
199 return true;
200 }
201 for (int i = 0; i != NumMaskElts; ++i) {
202 if (!DemandedElts[i])
203 continue;
204 int M = Shuf->getMaskValue(i);
205 assert(M < (NumElts * 2) && "Invalid shuffle mask constant")((M < (NumElts * 2) && "Invalid shuffle mask constant"
) ? static_cast<void> (0) : __assert_fail ("M < (NumElts * 2) && \"Invalid shuffle mask constant\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 205, __PRETTY_FUNCTION__))
;
206
207 // For undef elements, we don't know anything about the common state of
208 // the shuffle result.
209 if (M == -1)
210 return false;
211 if (M < NumElts)
212 DemandedLHS.setBit(M % NumElts);
213 else
214 DemandedRHS.setBit(M % NumElts);
215 }
216
217 return true;
218}
219
220static void computeKnownBits(const Value *V, const APInt &DemandedElts,
221 KnownBits &Known, unsigned Depth, const Query &Q);
222
223static void computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth,
224 const Query &Q) {
225 // FIXME: We currently have no way to represent the DemandedElts of a scalable
226 // vector
227 if (isa<ScalableVectorType>(V->getType())) {
228 Known.resetAll();
229 return;
230 }
231
232 auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
233 APInt DemandedElts =
234 FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
235 computeKnownBits(V, DemandedElts, Known, Depth, Q);
236}
237
238void llvm::computeKnownBits(const Value *V, KnownBits &Known,
239 const DataLayout &DL, unsigned Depth,
240 AssumptionCache *AC, const Instruction *CxtI,
241 const DominatorTree *DT,
242 OptimizationRemarkEmitter *ORE, bool UseInstrInfo) {
243 ::computeKnownBits(V, Known, Depth,
244 Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
245}
246
247void llvm::computeKnownBits(const Value *V, const APInt &DemandedElts,
248 KnownBits &Known, const DataLayout &DL,
249 unsigned Depth, AssumptionCache *AC,
250 const Instruction *CxtI, const DominatorTree *DT,
251 OptimizationRemarkEmitter *ORE, bool UseInstrInfo) {
252 ::computeKnownBits(V, DemandedElts, Known, Depth,
253 Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
254}
255
256static KnownBits computeKnownBits(const Value *V, const APInt &DemandedElts,
257 unsigned Depth, const Query &Q);
258
259static KnownBits computeKnownBits(const Value *V, unsigned Depth,
260 const Query &Q);
261
262KnownBits llvm::computeKnownBits(const Value *V, const DataLayout &DL,
263 unsigned Depth, AssumptionCache *AC,
264 const Instruction *CxtI,
265 const DominatorTree *DT,
266 OptimizationRemarkEmitter *ORE,
267 bool UseInstrInfo) {
268 return ::computeKnownBits(
269 V, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
270}
271
272KnownBits llvm::computeKnownBits(const Value *V, const APInt &DemandedElts,
273 const DataLayout &DL, unsigned Depth,
274 AssumptionCache *AC, const Instruction *CxtI,
275 const DominatorTree *DT,
276 OptimizationRemarkEmitter *ORE,
277 bool UseInstrInfo) {
278 return ::computeKnownBits(
279 V, DemandedElts, Depth,
280 Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
281}
282
283bool llvm::haveNoCommonBitsSet(const Value *LHS, const Value *RHS,
284 const DataLayout &DL, AssumptionCache *AC,
285 const Instruction *CxtI, const DominatorTree *DT,
286 bool UseInstrInfo) {
287 assert(LHS->getType() == RHS->getType() &&((LHS->getType() == RHS->getType() && "LHS and RHS should have the same type"
) ? static_cast<void> (0) : __assert_fail ("LHS->getType() == RHS->getType() && \"LHS and RHS should have the same type\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 288, __PRETTY_FUNCTION__))
288 "LHS and RHS should have the same type")((LHS->getType() == RHS->getType() && "LHS and RHS should have the same type"
) ? static_cast<void> (0) : __assert_fail ("LHS->getType() == RHS->getType() && \"LHS and RHS should have the same type\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 288, __PRETTY_FUNCTION__))
;
289 assert(LHS->getType()->isIntOrIntVectorTy() &&((LHS->getType()->isIntOrIntVectorTy() && "LHS and RHS should be integers"
) ? static_cast<void> (0) : __assert_fail ("LHS->getType()->isIntOrIntVectorTy() && \"LHS and RHS should be integers\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 290, __PRETTY_FUNCTION__))
290 "LHS and RHS should be integers")((LHS->getType()->isIntOrIntVectorTy() && "LHS and RHS should be integers"
) ? static_cast<void> (0) : __assert_fail ("LHS->getType()->isIntOrIntVectorTy() && \"LHS and RHS should be integers\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 290, __PRETTY_FUNCTION__))
;
291 // Look for an inverted mask: (X & ~M) op (Y & M).
292 Value *M;
293 if (match(LHS, m_c_And(m_Not(m_Value(M)), m_Value())) &&
294 match(RHS, m_c_And(m_Specific(M), m_Value())))
295 return true;
296 if (match(RHS, m_c_And(m_Not(m_Value(M)), m_Value())) &&
297 match(LHS, m_c_And(m_Specific(M), m_Value())))
298 return true;
299 IntegerType *IT = cast<IntegerType>(LHS->getType()->getScalarType());
300 KnownBits LHSKnown(IT->getBitWidth());
301 KnownBits RHSKnown(IT->getBitWidth());
302 computeKnownBits(LHS, LHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
303 computeKnownBits(RHS, RHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
304 return (LHSKnown.Zero | RHSKnown.Zero).isAllOnesValue();
305}
306
307bool llvm::isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI) {
308 for (const User *U : CxtI->users()) {
309 if (const ICmpInst *IC = dyn_cast<ICmpInst>(U))
310 if (IC->isEquality())
311 if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
312 if (C->isNullValue())
313 continue;
314 return false;
315 }
316 return true;
317}
318
319static bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
320 const Query &Q);
321
322bool llvm::isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL,
323 bool OrZero, unsigned Depth,
324 AssumptionCache *AC, const Instruction *CxtI,
325 const DominatorTree *DT, bool UseInstrInfo) {
326 return ::isKnownToBeAPowerOfTwo(
327 V, OrZero, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
328}
329
330static bool isKnownNonZero(const Value *V, const APInt &DemandedElts,
331 unsigned Depth, const Query &Q);
332
333static bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q);
334
335bool llvm::isKnownNonZero(const Value *V, const DataLayout &DL, unsigned Depth,
336 AssumptionCache *AC, const Instruction *CxtI,
337 const DominatorTree *DT, bool UseInstrInfo) {
338 return ::isKnownNonZero(V, Depth,
339 Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
340}
341
342bool llvm::isKnownNonNegative(const Value *V, const DataLayout &DL,
343 unsigned Depth, AssumptionCache *AC,
344 const Instruction *CxtI, const DominatorTree *DT,
345 bool UseInstrInfo) {
346 KnownBits Known =
347 computeKnownBits(V, DL, Depth, AC, CxtI, DT, nullptr, UseInstrInfo);
348 return Known.isNonNegative();
349}
350
351bool llvm::isKnownPositive(const Value *V, const DataLayout &DL, unsigned Depth,
352 AssumptionCache *AC, const Instruction *CxtI,
353 const DominatorTree *DT, bool UseInstrInfo) {
354 if (auto *CI = dyn_cast<ConstantInt>(V))
355 return CI->getValue().isStrictlyPositive();
356
357 // TODO: We'd doing two recursive queries here. We should factor this such
358 // that only a single query is needed.
359 return isKnownNonNegative(V, DL, Depth, AC, CxtI, DT, UseInstrInfo) &&
360 isKnownNonZero(V, DL, Depth, AC, CxtI, DT, UseInstrInfo);
361}
362
363bool llvm::isKnownNegative(const Value *V, const DataLayout &DL, unsigned Depth,
364 AssumptionCache *AC, const Instruction *CxtI,
365 const DominatorTree *DT, bool UseInstrInfo) {
366 KnownBits Known =
367 computeKnownBits(V, DL, Depth, AC, CxtI, DT, nullptr, UseInstrInfo);
368 return Known.isNegative();
369}
370
371static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
372 const Query &Q);
373
374bool llvm::isKnownNonEqual(const Value *V1, const Value *V2,
375 const DataLayout &DL, AssumptionCache *AC,
376 const Instruction *CxtI, const DominatorTree *DT,
377 bool UseInstrInfo) {
378 return ::isKnownNonEqual(V1, V2, 0,
379 Query(DL, AC, safeCxtI(V2, V1, CxtI), DT,
380 UseInstrInfo, /*ORE=*/nullptr));
381}
382
383static bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth,
384 const Query &Q);
385
386bool llvm::MaskedValueIsZero(const Value *V, const APInt &Mask,
387 const DataLayout &DL, unsigned Depth,
388 AssumptionCache *AC, const Instruction *CxtI,
389 const DominatorTree *DT, bool UseInstrInfo) {
390 return ::MaskedValueIsZero(
391 V, Mask, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
392}
393
394static unsigned ComputeNumSignBits(const Value *V, const APInt &DemandedElts,
395 unsigned Depth, const Query &Q);
396
397static unsigned ComputeNumSignBits(const Value *V, unsigned Depth,
398 const Query &Q) {
399 // FIXME: We currently have no way to represent the DemandedElts of a scalable
400 // vector
401 if (isa<ScalableVectorType>(V->getType()))
402 return 1;
403
404 auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
405 APInt DemandedElts =
406 FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
407 return ComputeNumSignBits(V, DemandedElts, Depth, Q);
408}
409
410unsigned llvm::ComputeNumSignBits(const Value *V, const DataLayout &DL,
411 unsigned Depth, AssumptionCache *AC,
412 const Instruction *CxtI,
413 const DominatorTree *DT, bool UseInstrInfo) {
414 return ::ComputeNumSignBits(
415 V, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
416}
417
418static void computeKnownBitsAddSub(bool Add, const Value *Op0, const Value *Op1,
419 bool NSW, const APInt &DemandedElts,
420 KnownBits &KnownOut, KnownBits &Known2,
421 unsigned Depth, const Query &Q) {
422 computeKnownBits(Op1, DemandedElts, KnownOut, Depth + 1, Q);
423
424 // If one operand is unknown and we have no nowrap information,
425 // the result will be unknown independently of the second operand.
426 if (KnownOut.isUnknown() && !NSW)
427 return;
428
429 computeKnownBits(Op0, DemandedElts, Known2, Depth + 1, Q);
430 KnownOut = KnownBits::computeForAddSub(Add, NSW, Known2, KnownOut);
431}
432
433static void computeKnownBitsMul(const Value *Op0, const Value *Op1, bool NSW,
434 const APInt &DemandedElts, KnownBits &Known,
435 KnownBits &Known2, unsigned Depth,
436 const Query &Q) {
437 computeKnownBits(Op1, DemandedElts, Known, Depth + 1, Q);
438 computeKnownBits(Op0, DemandedElts, Known2, Depth + 1, Q);
439
440 bool isKnownNegative = false;
441 bool isKnownNonNegative = false;
442 // If the multiplication is known not to overflow, compute the sign bit.
443 if (NSW) {
444 if (Op0 == Op1) {
445 // The product of a number with itself is non-negative.
446 isKnownNonNegative = true;
447 } else {
448 bool isKnownNonNegativeOp1 = Known.isNonNegative();
449 bool isKnownNonNegativeOp0 = Known2.isNonNegative();
450 bool isKnownNegativeOp1 = Known.isNegative();
451 bool isKnownNegativeOp0 = Known2.isNegative();
452 // The product of two numbers with the same sign is non-negative.
453 isKnownNonNegative = (isKnownNegativeOp1 && isKnownNegativeOp0) ||
454 (isKnownNonNegativeOp1 && isKnownNonNegativeOp0);
455 // The product of a negative number and a non-negative number is either
456 // negative or zero.
457 if (!isKnownNonNegative)
458 isKnownNegative =
459 (isKnownNegativeOp1 && isKnownNonNegativeOp0 &&
460 Known2.isNonZero()) ||
461 (isKnownNegativeOp0 && isKnownNonNegativeOp1 && Known.isNonZero());
462 }
463 }
464
465 Known = KnownBits::computeForMul(Known, Known2);
466
467 // Only make use of no-wrap flags if we failed to compute the sign bit
468 // directly. This matters if the multiplication always overflows, in
469 // which case we prefer to follow the result of the direct computation,
470 // though as the program is invoking undefined behaviour we can choose
471 // whatever we like here.
472 if (isKnownNonNegative && !Known.isNegative())
473 Known.makeNonNegative();
474 else if (isKnownNegative && !Known.isNonNegative())
475 Known.makeNegative();
476}
477
478void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
479 KnownBits &Known) {
480 unsigned BitWidth = Known.getBitWidth();
481 unsigned NumRanges = Ranges.getNumOperands() / 2;
482 assert(NumRanges >= 1)((NumRanges >= 1) ? static_cast<void> (0) : __assert_fail
("NumRanges >= 1", "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 482, __PRETTY_FUNCTION__))
;
483
484 Known.Zero.setAllBits();
485 Known.One.setAllBits();
486
487 for (unsigned i = 0; i < NumRanges; ++i) {
488 ConstantInt *Lower =
489 mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 0));
490 ConstantInt *Upper =
491 mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 1));
492 ConstantRange Range(Lower->getValue(), Upper->getValue());
493
494 // The first CommonPrefixBits of all values in Range are equal.
495 unsigned CommonPrefixBits =
496 (Range.getUnsignedMax() ^ Range.getUnsignedMin()).countLeadingZeros();
497 APInt Mask = APInt::getHighBitsSet(BitWidth, CommonPrefixBits);
498 APInt UnsignedMax = Range.getUnsignedMax().zextOrTrunc(BitWidth);
499 Known.One &= UnsignedMax & Mask;
500 Known.Zero &= ~UnsignedMax & Mask;
501 }
502}
503
504static bool isEphemeralValueOf(const Instruction *I, const Value *E) {
505 SmallVector<const Value *, 16> WorkSet(1, I);
506 SmallPtrSet<const Value *, 32> Visited;
507 SmallPtrSet<const Value *, 16> EphValues;
508
509 // The instruction defining an assumption's condition itself is always
510 // considered ephemeral to that assumption (even if it has other
511 // non-ephemeral users). See r246696's test case for an example.
512 if (is_contained(I->operands(), E))
513 return true;
514
515 while (!WorkSet.empty()) {
516 const Value *V = WorkSet.pop_back_val();
517 if (!Visited.insert(V).second)
518 continue;
519
520 // If all uses of this value are ephemeral, then so is this value.
521 if (llvm::all_of(V->users(), [&](const User *U) {
522 return EphValues.count(U);
523 })) {
524 if (V == E)
525 return true;
526
527 if (V == I || isSafeToSpeculativelyExecute(V)) {
528 EphValues.insert(V);
529 if (const User *U = dyn_cast<User>(V))
530 append_range(WorkSet, U->operands());
531 }
532 }
533 }
534
535 return false;
536}
537
538// Is this an intrinsic that cannot be speculated but also cannot trap?
539bool llvm::isAssumeLikeIntrinsic(const Instruction *I) {
540 if (const IntrinsicInst *CI = dyn_cast<IntrinsicInst>(I))
541 return CI->isAssumeLikeIntrinsic();
542
543 return false;
544}
545
546bool llvm::isValidAssumeForContext(const Instruction *Inv,
547 const Instruction *CxtI,
548 const DominatorTree *DT) {
549 // There are two restrictions on the use of an assume:
550 // 1. The assume must dominate the context (or the control flow must
551 // reach the assume whenever it reaches the context).
552 // 2. The context must not be in the assume's set of ephemeral values
553 // (otherwise we will use the assume to prove that the condition
554 // feeding the assume is trivially true, thus causing the removal of
555 // the assume).
556
557 if (Inv->getParent() == CxtI->getParent()) {
558 // If Inv and CtxI are in the same block, check if the assume (Inv) is first
559 // in the BB.
560 if (Inv->comesBefore(CxtI))
561 return true;
562
563 // Don't let an assume affect itself - this would cause the problems
564 // `isEphemeralValueOf` is trying to prevent, and it would also make
565 // the loop below go out of bounds.
566 if (Inv == CxtI)
567 return false;
568
569 // The context comes first, but they're both in the same block.
570 // Make sure there is nothing in between that might interrupt
571 // the control flow, not even CxtI itself.
572 // We limit the scan distance between the assume and its context instruction
573 // to avoid a compile-time explosion. This limit is chosen arbitrarily, so
574 // it can be adjusted if needed (could be turned into a cl::opt).
575 unsigned ScanLimit = 15;
576 for (BasicBlock::const_iterator I(CxtI), IE(Inv); I != IE; ++I)
577 if (!isGuaranteedToTransferExecutionToSuccessor(&*I) || --ScanLimit == 0)
578 return false;
579
580 return !isEphemeralValueOf(Inv, CxtI);
581 }
582
583 // Inv and CxtI are in different blocks.
584 if (DT) {
585 if (DT->dominates(Inv, CxtI))
586 return true;
587 } else if (Inv->getParent() == CxtI->getParent()->getSinglePredecessor()) {
588 // We don't have a DT, but this trivially dominates.
589 return true;
590 }
591
592 return false;
593}
594
595static bool cmpExcludesZero(CmpInst::Predicate Pred, const Value *RHS) {
596 // v u> y implies v != 0.
597 if (Pred == ICmpInst::ICMP_UGT)
598 return true;
599
600 // Special-case v != 0 to also handle v != null.
601 if (Pred == ICmpInst::ICMP_NE)
602 return match(RHS, m_Zero());
603
604 // All other predicates - rely on generic ConstantRange handling.
605 const APInt *C;
606 if (!match(RHS, m_APInt(C)))
607 return false;
608
609 ConstantRange TrueValues = ConstantRange::makeExactICmpRegion(Pred, *C);
610 return !TrueValues.contains(APInt::getNullValue(C->getBitWidth()));
611}
612
613static bool isKnownNonZeroFromAssume(const Value *V, const Query &Q) {
614 // Use of assumptions is context-sensitive. If we don't have a context, we
615 // cannot use them!
616 if (!Q.AC || !Q.CxtI)
617 return false;
618
619 if (Q.CxtI && V->getType()->isPointerTy()) {
620 SmallVector<Attribute::AttrKind, 2> AttrKinds{Attribute::NonNull};
621 if (!NullPointerIsDefined(Q.CxtI->getFunction(),
622 V->getType()->getPointerAddressSpace()))
623 AttrKinds.push_back(Attribute::Dereferenceable);
624
625 if (getKnowledgeValidInContext(V, AttrKinds, Q.CxtI, Q.DT, Q.AC))
626 return true;
627 }
628
629 for (auto &AssumeVH : Q.AC->assumptionsFor(V)) {
630 if (!AssumeVH)
631 continue;
632 CallInst *I = cast<CallInst>(AssumeVH);
633 assert(I->getFunction() == Q.CxtI->getFunction() &&((I->getFunction() == Q.CxtI->getFunction() && "Got assumption for the wrong function!"
) ? static_cast<void> (0) : __assert_fail ("I->getFunction() == Q.CxtI->getFunction() && \"Got assumption for the wrong function!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 634, __PRETTY_FUNCTION__))
634 "Got assumption for the wrong function!")((I->getFunction() == Q.CxtI->getFunction() && "Got assumption for the wrong function!"
) ? static_cast<void> (0) : __assert_fail ("I->getFunction() == Q.CxtI->getFunction() && \"Got assumption for the wrong function!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 634, __PRETTY_FUNCTION__))
;
635 if (Q.isExcluded(I))
636 continue;
637
638 // Warning: This loop can end up being somewhat performance sensitive.
639 // We're running this loop for once for each value queried resulting in a
640 // runtime of ~O(#assumes * #values).
641
642 assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&((I->getCalledFunction()->getIntrinsicID() == Intrinsic
::assume && "must be an assume intrinsic") ? static_cast
<void> (0) : __assert_fail ("I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume && \"must be an assume intrinsic\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 643, __PRETTY_FUNCTION__))
643 "must be an assume intrinsic")((I->getCalledFunction()->getIntrinsicID() == Intrinsic
::assume && "must be an assume intrinsic") ? static_cast
<void> (0) : __assert_fail ("I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume && \"must be an assume intrinsic\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 643, __PRETTY_FUNCTION__))
;
644
645 Value *RHS;
646 CmpInst::Predicate Pred;
647 auto m_V = m_CombineOr(m_Specific(V), m_PtrToInt(m_Specific(V)));
648 if (!match(I->getArgOperand(0), m_c_ICmp(Pred, m_V, m_Value(RHS))))
649 return false;
650
651 if (cmpExcludesZero(Pred, RHS) && isValidAssumeForContext(I, Q.CxtI, Q.DT))
652 return true;
653 }
654
655 return false;
656}
657
658static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
659 unsigned Depth, const Query &Q) {
660 // Use of assumptions is context-sensitive. If we don't have a context, we
661 // cannot use them!
662 if (!Q.AC || !Q.CxtI)
663 return;
664
665 unsigned BitWidth = Known.getBitWidth();
666
667 // Refine Known set if the pointer alignment is set by assume bundles.
668 if (V->getType()->isPointerTy()) {
669 if (RetainedKnowledge RK = getKnowledgeValidInContext(
670 V, {Attribute::Alignment}, Q.CxtI, Q.DT, Q.AC)) {
671 Known.Zero.setLowBits(Log2_32(RK.ArgValue));
672 }
673 }
674
675 // Note that the patterns below need to be kept in sync with the code
676 // in AssumptionCache::updateAffectedValues.
677
678 for (auto &AssumeVH : Q.AC->assumptionsFor(V)) {
679 if (!AssumeVH)
680 continue;
681 CallInst *I = cast<CallInst>(AssumeVH);
682 assert(I->getParent()->getParent() == Q.CxtI->getParent()->getParent() &&((I->getParent()->getParent() == Q.CxtI->getParent()
->getParent() && "Got assumption for the wrong function!"
) ? static_cast<void> (0) : __assert_fail ("I->getParent()->getParent() == Q.CxtI->getParent()->getParent() && \"Got assumption for the wrong function!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 683, __PRETTY_FUNCTION__))
683 "Got assumption for the wrong function!")((I->getParent()->getParent() == Q.CxtI->getParent()
->getParent() && "Got assumption for the wrong function!"
) ? static_cast<void> (0) : __assert_fail ("I->getParent()->getParent() == Q.CxtI->getParent()->getParent() && \"Got assumption for the wrong function!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 683, __PRETTY_FUNCTION__))
;
684 if (Q.isExcluded(I))
685 continue;
686
687 // Warning: This loop can end up being somewhat performance sensitive.
688 // We're running this loop for once for each value queried resulting in a
689 // runtime of ~O(#assumes * #values).
690
691 assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&((I->getCalledFunction()->getIntrinsicID() == Intrinsic
::assume && "must be an assume intrinsic") ? static_cast
<void> (0) : __assert_fail ("I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume && \"must be an assume intrinsic\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 692, __PRETTY_FUNCTION__))
692 "must be an assume intrinsic")((I->getCalledFunction()->getIntrinsicID() == Intrinsic
::assume && "must be an assume intrinsic") ? static_cast
<void> (0) : __assert_fail ("I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume && \"must be an assume intrinsic\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 692, __PRETTY_FUNCTION__))
;
693
694 Value *Arg = I->getArgOperand(0);
695
696 if (Arg == V && isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
697 assert(BitWidth == 1 && "assume operand is not i1?")((BitWidth == 1 && "assume operand is not i1?") ? static_cast
<void> (0) : __assert_fail ("BitWidth == 1 && \"assume operand is not i1?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 697, __PRETTY_FUNCTION__))
;
698 Known.setAllOnes();
699 return;
700 }
701 if (match(Arg, m_Not(m_Specific(V))) &&
702 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
703 assert(BitWidth == 1 && "assume operand is not i1?")((BitWidth == 1 && "assume operand is not i1?") ? static_cast
<void> (0) : __assert_fail ("BitWidth == 1 && \"assume operand is not i1?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 703, __PRETTY_FUNCTION__))
;
704 Known.setAllZero();
705 return;
706 }
707
708 // The remaining tests are all recursive, so bail out if we hit the limit.
709 if (Depth == MaxAnalysisRecursionDepth)
710 continue;
711
712 ICmpInst *Cmp = dyn_cast<ICmpInst>(Arg);
713 if (!Cmp)
714 continue;
715
716 // Note that ptrtoint may change the bitwidth.
717 Value *A, *B;
718 auto m_V = m_CombineOr(m_Specific(V), m_PtrToInt(m_Specific(V)));
719
720 CmpInst::Predicate Pred;
721 uint64_t C;
722 switch (Cmp->getPredicate()) {
723 default:
724 break;
725 case ICmpInst::ICMP_EQ:
726 // assume(v = a)
727 if (match(Cmp, m_c_ICmp(Pred, m_V, m_Value(A))) &&
728 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
729 KnownBits RHSKnown =
730 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
731 Known.Zero |= RHSKnown.Zero;
732 Known.One |= RHSKnown.One;
733 // assume(v & b = a)
734 } else if (match(Cmp,
735 m_c_ICmp(Pred, m_c_And(m_V, m_Value(B)), m_Value(A))) &&
736 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
737 KnownBits RHSKnown =
738 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
739 KnownBits MaskKnown =
740 computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
741
742 // For those bits in the mask that are known to be one, we can propagate
743 // known bits from the RHS to V.
744 Known.Zero |= RHSKnown.Zero & MaskKnown.One;
745 Known.One |= RHSKnown.One & MaskKnown.One;
746 // assume(~(v & b) = a)
747 } else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_c_And(m_V, m_Value(B))),
748 m_Value(A))) &&
749 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
750 KnownBits RHSKnown =
751 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
752 KnownBits MaskKnown =
753 computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
754
755 // For those bits in the mask that are known to be one, we can propagate
756 // inverted known bits from the RHS to V.
757 Known.Zero |= RHSKnown.One & MaskKnown.One;
758 Known.One |= RHSKnown.Zero & MaskKnown.One;
759 // assume(v | b = a)
760 } else if (match(Cmp,
761 m_c_ICmp(Pred, m_c_Or(m_V, m_Value(B)), m_Value(A))) &&
762 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
763 KnownBits RHSKnown =
764 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
765 KnownBits BKnown =
766 computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
767
768 // For those bits in B that are known to be zero, we can propagate known
769 // bits from the RHS to V.
770 Known.Zero |= RHSKnown.Zero & BKnown.Zero;
771 Known.One |= RHSKnown.One & BKnown.Zero;
772 // assume(~(v | b) = a)
773 } else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_c_Or(m_V, m_Value(B))),
774 m_Value(A))) &&
775 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
776 KnownBits RHSKnown =
777 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
778 KnownBits BKnown =
779 computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
780
781 // For those bits in B that are known to be zero, we can propagate
782 // inverted known bits from the RHS to V.
783 Known.Zero |= RHSKnown.One & BKnown.Zero;
784 Known.One |= RHSKnown.Zero & BKnown.Zero;
785 // assume(v ^ b = a)
786 } else if (match(Cmp,
787 m_c_ICmp(Pred, m_c_Xor(m_V, m_Value(B)), m_Value(A))) &&
788 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
789 KnownBits RHSKnown =
790 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
791 KnownBits BKnown =
792 computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
793
794 // For those bits in B that are known to be zero, we can propagate known
795 // bits from the RHS to V. For those bits in B that are known to be one,
796 // we can propagate inverted known bits from the RHS to V.
797 Known.Zero |= RHSKnown.Zero & BKnown.Zero;
798 Known.One |= RHSKnown.One & BKnown.Zero;
799 Known.Zero |= RHSKnown.One & BKnown.One;
800 Known.One |= RHSKnown.Zero & BKnown.One;
801 // assume(~(v ^ b) = a)
802 } else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_c_Xor(m_V, m_Value(B))),
803 m_Value(A))) &&
804 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
805 KnownBits RHSKnown =
806 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
807 KnownBits BKnown =
808 computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
809
810 // For those bits in B that are known to be zero, we can propagate
811 // inverted known bits from the RHS to V. For those bits in B that are
812 // known to be one, we can propagate known bits from the RHS to V.
813 Known.Zero |= RHSKnown.One & BKnown.Zero;
814 Known.One |= RHSKnown.Zero & BKnown.Zero;
815 Known.Zero |= RHSKnown.Zero & BKnown.One;
816 Known.One |= RHSKnown.One & BKnown.One;
817 // assume(v << c = a)
818 } else if (match(Cmp, m_c_ICmp(Pred, m_Shl(m_V, m_ConstantInt(C)),
819 m_Value(A))) &&
820 isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
821 KnownBits RHSKnown =
822 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
823
824 // For those bits in RHS that are known, we can propagate them to known
825 // bits in V shifted to the right by C.
826 RHSKnown.Zero.lshrInPlace(C);
827 Known.Zero |= RHSKnown.Zero;
828 RHSKnown.One.lshrInPlace(C);
829 Known.One |= RHSKnown.One;
830 // assume(~(v << c) = a)
831 } else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_Shl(m_V, m_ConstantInt(C))),
832 m_Value(A))) &&
833 isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
834 KnownBits RHSKnown =
835 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
836 // For those bits in RHS that are known, we can propagate them inverted
837 // to known bits in V shifted to the right by C.
838 RHSKnown.One.lshrInPlace(C);
839 Known.Zero |= RHSKnown.One;
840 RHSKnown.Zero.lshrInPlace(C);
841 Known.One |= RHSKnown.Zero;
842 // assume(v >> c = a)
843 } else if (match(Cmp, m_c_ICmp(Pred, m_Shr(m_V, m_ConstantInt(C)),
844 m_Value(A))) &&
845 isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
846 KnownBits RHSKnown =
847 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
848 // For those bits in RHS that are known, we can propagate them to known
849 // bits in V shifted to the right by C.
850 Known.Zero |= RHSKnown.Zero << C;
851 Known.One |= RHSKnown.One << C;
852 // assume(~(v >> c) = a)
853 } else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_Shr(m_V, m_ConstantInt(C))),
854 m_Value(A))) &&
855 isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
856 KnownBits RHSKnown =
857 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
858 // For those bits in RHS that are known, we can propagate them inverted
859 // to known bits in V shifted to the right by C.
860 Known.Zero |= RHSKnown.One << C;
861 Known.One |= RHSKnown.Zero << C;
862 }
863 break;
864 case ICmpInst::ICMP_SGE:
865 // assume(v >=_s c) where c is non-negative
866 if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
867 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
868 KnownBits RHSKnown =
869 computeKnownBits(A, Depth + 1, Query(Q, I)).anyextOrTrunc(BitWidth);
870
871 if (RHSKnown.isNonNegative()) {
872 // We know that the sign bit is zero.
873 Known.makeNonNegative();
874 }
875 }
876 break;
877 case ICmpInst::ICMP_SGT:
878 // assume(v >_s c) where c is at least -1.
879 if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
880 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
881 KnownBits RHSKnown =
882 computeKnownBits(A, Depth + 1, Query(Q, I)).anyextOrTrunc(BitWidth);
883
884 if (RHSKnown.isAllOnes() || RHSKnown.isNonNegative()) {
885 // We know that the sign bit is zero.
886 Known.makeNonNegative();
887 }
888 }
889 break;
890 case ICmpInst::ICMP_SLE:
891 // assume(v <=_s c) where c is negative
892 if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
893 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
894 KnownBits RHSKnown =
895 computeKnownBits(A, Depth + 1, Query(Q, I)).anyextOrTrunc(BitWidth);
896
897 if (RHSKnown.isNegative()) {
898 // We know that the sign bit is one.
899 Known.makeNegative();
900 }
901 }
902 break;
903 case ICmpInst::ICMP_SLT:
904 // assume(v <_s c) where c is non-positive
905 if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
906 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
907 KnownBits RHSKnown =
908 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
909
910 if (RHSKnown.isZero() || RHSKnown.isNegative()) {
911 // We know that the sign bit is one.
912 Known.makeNegative();
913 }
914 }
915 break;
916 case ICmpInst::ICMP_ULE:
917 // assume(v <=_u c)
918 if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
919 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
920 KnownBits RHSKnown =
921 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
922
923 // Whatever high bits in c are zero are known to be zero.
924 Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
925 }
926 break;
927 case ICmpInst::ICMP_ULT:
928 // assume(v <_u c)
929 if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
930 isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
931 KnownBits RHSKnown =
932 computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
933
934 // If the RHS is known zero, then this assumption must be wrong (nothing
935 // is unsigned less than zero). Signal a conflict and get out of here.
936 if (RHSKnown.isZero()) {
937 Known.Zero.setAllBits();
938 Known.One.setAllBits();
939 break;
940 }
941
942 // Whatever high bits in c are zero are known to be zero (if c is a power
943 // of 2, then one more).
944 if (isKnownToBeAPowerOfTwo(A, false, Depth + 1, Query(Q, I)))
945 Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros() + 1);
946 else
947 Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
948 }
949 break;
950 }
951 }
952
953 // If assumptions conflict with each other or previous known bits, then we
954 // have a logical fallacy. It's possible that the assumption is not reachable,
955 // so this isn't a real bug. On the other hand, the program may have undefined
956 // behavior, or we might have a bug in the compiler. We can't assert/crash, so
957 // clear out the known bits, try to warn the user, and hope for the best.
958 if (Known.Zero.intersects(Known.One)) {
959 Known.resetAll();
960
961 if (Q.ORE)
962 Q.ORE->emit([&]() {
963 auto *CxtI = const_cast<Instruction *>(Q.CxtI);
964 return OptimizationRemarkAnalysis("value-tracking", "BadAssumption",
965 CxtI)
966 << "Detected conflicting code assumptions. Program may "
967 "have undefined behavior, or compiler may have "
968 "internal error.";
969 });
970 }
971}
972
973/// Compute known bits from a shift operator, including those with a
974/// non-constant shift amount. Known is the output of this function. Known2 is a
975/// pre-allocated temporary with the same bit width as Known and on return
976/// contains the known bit of the shift value source. KF is an
977/// operator-specific function that, given the known-bits and a shift amount,
978/// compute the implied known-bits of the shift operator's result respectively
979/// for that shift amount. The results from calling KF are conservatively
980/// combined for all permitted shift amounts.
981static void computeKnownBitsFromShiftOperator(
982 const Operator *I, const APInt &DemandedElts, KnownBits &Known,
983 KnownBits &Known2, unsigned Depth, const Query &Q,
984 function_ref<KnownBits(const KnownBits &, const KnownBits &)> KF) {
985 unsigned BitWidth = Known.getBitWidth();
986 computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
987 computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
988
989 // Note: We cannot use Known.Zero.getLimitedValue() here, because if
990 // BitWidth > 64 and any upper bits are known, we'll end up returning the
991 // limit value (which implies all bits are known).
992 uint64_t ShiftAmtKZ = Known.Zero.zextOrTrunc(64).getZExtValue();
993 uint64_t ShiftAmtKO = Known.One.zextOrTrunc(64).getZExtValue();
994 bool ShiftAmtIsConstant = Known.isConstant();
995 bool MaxShiftAmtIsOutOfRange = Known.getMaxValue().uge(BitWidth);
996
997 if (ShiftAmtIsConstant) {
998 Known = KF(Known2, Known);
999
1000 // If the known bits conflict, this must be an overflowing left shift, so
1001 // the shift result is poison. We can return anything we want. Choose 0 for
1002 // the best folding opportunity.
1003 if (Known.hasConflict())
1004 Known.setAllZero();
1005
1006 return;
1007 }
1008
1009 // If the shift amount could be greater than or equal to the bit-width of the
1010 // LHS, the value could be poison, but bail out because the check below is
1011 // expensive.
1012 // TODO: Should we just carry on?
1013 if (MaxShiftAmtIsOutOfRange) {
1014 Known.resetAll();
1015 return;
1016 }
1017
1018 // It would be more-clearly correct to use the two temporaries for this
1019 // calculation. Reusing the APInts here to prevent unnecessary allocations.
1020 Known.resetAll();
1021
1022 // If we know the shifter operand is nonzero, we can sometimes infer more
1023 // known bits. However this is expensive to compute, so be lazy about it and
1024 // only compute it when absolutely necessary.
1025 Optional<bool> ShifterOperandIsNonZero;
1026
1027 // Early exit if we can't constrain any well-defined shift amount.
1028 if (!(ShiftAmtKZ & (PowerOf2Ceil(BitWidth) - 1)) &&
1029 !(ShiftAmtKO & (PowerOf2Ceil(BitWidth) - 1))) {
1030 ShifterOperandIsNonZero =
1031 isKnownNonZero(I->getOperand(1), DemandedElts, Depth + 1, Q);
1032 if (!*ShifterOperandIsNonZero)
1033 return;
1034 }
1035
1036 Known.Zero.setAllBits();
1037 Known.One.setAllBits();
1038 for (unsigned ShiftAmt = 0; ShiftAmt < BitWidth; ++ShiftAmt) {
1039 // Combine the shifted known input bits only for those shift amounts
1040 // compatible with its known constraints.
1041 if ((ShiftAmt & ~ShiftAmtKZ) != ShiftAmt)
1042 continue;
1043 if ((ShiftAmt | ShiftAmtKO) != ShiftAmt)
1044 continue;
1045 // If we know the shifter is nonzero, we may be able to infer more known
1046 // bits. This check is sunk down as far as possible to avoid the expensive
1047 // call to isKnownNonZero if the cheaper checks above fail.
1048 if (ShiftAmt == 0) {
1049 if (!ShifterOperandIsNonZero.hasValue())
1050 ShifterOperandIsNonZero =
1051 isKnownNonZero(I->getOperand(1), DemandedElts, Depth + 1, Q);
1052 if (*ShifterOperandIsNonZero)
1053 continue;
1054 }
1055
1056 Known = KnownBits::commonBits(
1057 Known, KF(Known2, KnownBits::makeConstant(APInt(32, ShiftAmt))));
1058 }
1059
1060 // If the known bits conflict, the result is poison. Return a 0 and hope the
1061 // caller can further optimize that.
1062 if (Known.hasConflict())
1063 Known.setAllZero();
1064}
1065
1066static void computeKnownBitsFromOperator(const Operator *I,
1067 const APInt &DemandedElts,
1068 KnownBits &Known, unsigned Depth,
1069 const Query &Q) {
1070 unsigned BitWidth = Known.getBitWidth();
1071
1072 KnownBits Known2(BitWidth);
1073 switch (I->getOpcode()) {
1074 default: break;
1075 case Instruction::Load:
1076 if (MDNode *MD =
1077 Q.IIQ.getMetadata(cast<LoadInst>(I), LLVMContext::MD_range))
1078 computeKnownBitsFromRangeMetadata(*MD, Known);
1079 break;
1080 case Instruction::And: {
1081 // If either the LHS or the RHS are Zero, the result is zero.
1082 computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
1083 computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
1084
1085 Known &= Known2;
1086
1087 // and(x, add (x, -1)) is a common idiom that always clears the low bit;
1088 // here we handle the more general case of adding any odd number by
1089 // matching the form add(x, add(x, y)) where y is odd.
1090 // TODO: This could be generalized to clearing any bit set in y where the
1091 // following bit is known to be unset in y.
1092 Value *X = nullptr, *Y = nullptr;
1093 if (!Known.Zero[0] && !Known.One[0] &&
1094 match(I, m_c_BinOp(m_Value(X), m_Add(m_Deferred(X), m_Value(Y))))) {
1095 Known2.resetAll();
1096 computeKnownBits(Y, DemandedElts, Known2, Depth + 1, Q);
1097 if (Known2.countMinTrailingOnes() > 0)
1098 Known.Zero.setBit(0);
1099 }
1100 break;
1101 }
1102 case Instruction::Or:
1103 computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
1104 computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
1105
1106 Known |= Known2;
1107 break;
1108 case Instruction::Xor:
1109 computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
1110 computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
1111
1112 Known ^= Known2;
1113 break;
1114 case Instruction::Mul: {
1115 bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
1116 computeKnownBitsMul(I->getOperand(0), I->getOperand(1), NSW, DemandedElts,
1117 Known, Known2, Depth, Q);
1118 break;
1119 }
1120 case Instruction::UDiv: {
1121 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1122 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1123 Known = KnownBits::udiv(Known, Known2);
1124 break;
1125 }
1126 case Instruction::Select: {
1127 const Value *LHS = nullptr, *RHS = nullptr;
1128 SelectPatternFlavor SPF = matchSelectPattern(I, LHS, RHS).Flavor;
1129 if (SelectPatternResult::isMinOrMax(SPF)) {
1130 computeKnownBits(RHS, Known, Depth + 1, Q);
1131 computeKnownBits(LHS, Known2, Depth + 1, Q);
1132 switch (SPF) {
1133 default:
1134 llvm_unreachable("Unhandled select pattern flavor!")::llvm::llvm_unreachable_internal("Unhandled select pattern flavor!"
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1134)
;
1135 case SPF_SMAX:
1136 Known = KnownBits::smax(Known, Known2);
1137 break;
1138 case SPF_SMIN:
1139 Known = KnownBits::smin(Known, Known2);
1140 break;
1141 case SPF_UMAX:
1142 Known = KnownBits::umax(Known, Known2);
1143 break;
1144 case SPF_UMIN:
1145 Known = KnownBits::umin(Known, Known2);
1146 break;
1147 }
1148 break;
1149 }
1150
1151 computeKnownBits(I->getOperand(2), Known, Depth + 1, Q);
1152 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1153
1154 // Only known if known in both the LHS and RHS.
1155 Known = KnownBits::commonBits(Known, Known2);
1156
1157 if (SPF == SPF_ABS) {
1158 // RHS from matchSelectPattern returns the negation part of abs pattern.
1159 // If the negate has an NSW flag we can assume the sign bit of the result
1160 // will be 0 because that makes abs(INT_MIN) undefined.
1161 if (match(RHS, m_Neg(m_Specific(LHS))) &&
1162 Q.IIQ.hasNoSignedWrap(cast<Instruction>(RHS)))
1163 Known.Zero.setSignBit();
1164 }
1165
1166 break;
1167 }
1168 case Instruction::FPTrunc:
1169 case Instruction::FPExt:
1170 case Instruction::FPToUI:
1171 case Instruction::FPToSI:
1172 case Instruction::SIToFP:
1173 case Instruction::UIToFP:
1174 break; // Can't work with floating point.
1175 case Instruction::PtrToInt:
1176 case Instruction::IntToPtr:
1177 // Fall through and handle them the same as zext/trunc.
1178 LLVM_FALLTHROUGH[[gnu::fallthrough]];
1179 case Instruction::ZExt:
1180 case Instruction::Trunc: {
1181 Type *SrcTy = I->getOperand(0)->getType();
1182
1183 unsigned SrcBitWidth;
1184 // Note that we handle pointer operands here because of inttoptr/ptrtoint
1185 // which fall through here.
1186 Type *ScalarTy = SrcTy->getScalarType();
1187 SrcBitWidth = ScalarTy->isPointerTy() ?
1188 Q.DL.getPointerTypeSizeInBits(ScalarTy) :
1189 Q.DL.getTypeSizeInBits(ScalarTy);
1190
1191 assert(SrcBitWidth && "SrcBitWidth can't be zero")((SrcBitWidth && "SrcBitWidth can't be zero") ? static_cast
<void> (0) : __assert_fail ("SrcBitWidth && \"SrcBitWidth can't be zero\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1191, __PRETTY_FUNCTION__))
;
1192 Known = Known.anyextOrTrunc(SrcBitWidth);
1193 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1194 Known = Known.zextOrTrunc(BitWidth);
1195 break;
1196 }
1197 case Instruction::BitCast: {
1198 Type *SrcTy = I->getOperand(0)->getType();
1199 if (SrcTy->isIntOrPtrTy() &&
1200 // TODO: For now, not handling conversions like:
1201 // (bitcast i64 %x to <2 x i32>)
1202 !I->getType()->isVectorTy()) {
1203 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1204 break;
1205 }
1206 break;
1207 }
1208 case Instruction::SExt: {
1209 // Compute the bits in the result that are not present in the input.
1210 unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
1211
1212 Known = Known.trunc(SrcBitWidth);
1213 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1214 // If the sign bit of the input is known set or clear, then we know the
1215 // top bits of the result.
1216 Known = Known.sext(BitWidth);
1217 break;
1218 }
1219 case Instruction::Shl: {
1220 bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
1221 auto KF = [NSW](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
1222 KnownBits Result = KnownBits::shl(KnownVal, KnownAmt);
1223 // If this shift has "nsw" keyword, then the result is either a poison
1224 // value or has the same sign bit as the first operand.
1225 if (NSW) {
1226 if (KnownVal.Zero.isSignBitSet())
1227 Result.Zero.setSignBit();
1228 if (KnownVal.One.isSignBitSet())
1229 Result.One.setSignBit();
1230 }
1231 return Result;
1232 };
1233 computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
1234 KF);
1235 // Trailing zeros of a right-shifted constant never decrease.
1236 const APInt *C;
1237 if (match(I->getOperand(0), m_APInt(C)))
1238 Known.Zero.setLowBits(C->countTrailingZeros());
1239 break;
1240 }
1241 case Instruction::LShr: {
1242 auto KF = [](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
1243 return KnownBits::lshr(KnownVal, KnownAmt);
1244 };
1245 computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
1246 KF);
1247 // Leading zeros of a left-shifted constant never decrease.
1248 const APInt *C;
1249 if (match(I->getOperand(0), m_APInt(C)))
1250 Known.Zero.setHighBits(C->countLeadingZeros());
1251 break;
1252 }
1253 case Instruction::AShr: {
1254 auto KF = [](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
1255 return KnownBits::ashr(KnownVal, KnownAmt);
1256 };
1257 computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
1258 KF);
1259 break;
1260 }
1261 case Instruction::Sub: {
1262 bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
1263 computeKnownBitsAddSub(false, I->getOperand(0), I->getOperand(1), NSW,
1264 DemandedElts, Known, Known2, Depth, Q);
1265 break;
1266 }
1267 case Instruction::Add: {
1268 bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
1269 computeKnownBitsAddSub(true, I->getOperand(0), I->getOperand(1), NSW,
1270 DemandedElts, Known, Known2, Depth, Q);
1271 break;
1272 }
1273 case Instruction::SRem:
1274 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1275 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1276 Known = KnownBits::srem(Known, Known2);
1277 break;
1278
1279 case Instruction::URem:
1280 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1281 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1282 Known = KnownBits::urem(Known, Known2);
1283 break;
1284 case Instruction::Alloca:
1285 Known.Zero.setLowBits(Log2(cast<AllocaInst>(I)->getAlign()));
1286 break;
1287 case Instruction::GetElementPtr: {
1288 // Analyze all of the subscripts of this getelementptr instruction
1289 // to determine if we can prove known low zero bits.
1290 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1291 // Accumulate the constant indices in a separate variable
1292 // to minimize the number of calls to computeForAddSub.
1293 APInt AccConstIndices(BitWidth, 0, /*IsSigned*/ true);
1294
1295 gep_type_iterator GTI = gep_type_begin(I);
1296 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) {
1297 // TrailZ can only become smaller, short-circuit if we hit zero.
1298 if (Known.isUnknown())
1299 break;
1300
1301 Value *Index = I->getOperand(i);
1302
1303 // Handle case when index is zero.
1304 Constant *CIndex = dyn_cast<Constant>(Index);
1305 if (CIndex && CIndex->isZeroValue())
1306 continue;
1307
1308 if (StructType *STy = GTI.getStructTypeOrNull()) {
1309 // Handle struct member offset arithmetic.
1310
1311 assert(CIndex &&((CIndex && "Access to structure field must be known at compile time"
) ? static_cast<void> (0) : __assert_fail ("CIndex && \"Access to structure field must be known at compile time\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1312, __PRETTY_FUNCTION__))
1312 "Access to structure field must be known at compile time")((CIndex && "Access to structure field must be known at compile time"
) ? static_cast<void> (0) : __assert_fail ("CIndex && \"Access to structure field must be known at compile time\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1312, __PRETTY_FUNCTION__))
;
1313
1314 if (CIndex->getType()->isVectorTy())
1315 Index = CIndex->getSplatValue();
1316
1317 unsigned Idx = cast<ConstantInt>(Index)->getZExtValue();
1318 const StructLayout *SL = Q.DL.getStructLayout(STy);
1319 uint64_t Offset = SL->getElementOffset(Idx);
1320 AccConstIndices += Offset;
1321 continue;
1322 }
1323
1324 // Handle array index arithmetic.
1325 Type *IndexedTy = GTI.getIndexedType();
1326 if (!IndexedTy->isSized()) {
1327 Known.resetAll();
1328 break;
1329 }
1330
1331 unsigned IndexBitWidth = Index->getType()->getScalarSizeInBits();
1332 KnownBits IndexBits(IndexBitWidth);
1333 computeKnownBits(Index, IndexBits, Depth + 1, Q);
1334 TypeSize IndexTypeSize = Q.DL.getTypeAllocSize(IndexedTy);
1335 uint64_t TypeSizeInBytes = IndexTypeSize.getKnownMinSize();
1336 KnownBits ScalingFactor(IndexBitWidth);
1337 // Multiply by current sizeof type.
1338 // &A[i] == A + i * sizeof(*A[i]).
1339 if (IndexTypeSize.isScalable()) {
1340 // For scalable types the only thing we know about sizeof is
1341 // that this is a multiple of the minimum size.
1342 ScalingFactor.Zero.setLowBits(countTrailingZeros(TypeSizeInBytes));
1343 } else if (IndexBits.isConstant()) {
1344 APInt IndexConst = IndexBits.getConstant();
1345 APInt ScalingFactor(IndexBitWidth, TypeSizeInBytes);
1346 IndexConst *= ScalingFactor;
1347 AccConstIndices += IndexConst.sextOrTrunc(BitWidth);
1348 continue;
1349 } else {
1350 ScalingFactor =
1351 KnownBits::makeConstant(APInt(IndexBitWidth, TypeSizeInBytes));
1352 }
1353 IndexBits = KnownBits::computeForMul(IndexBits, ScalingFactor);
1354
1355 // If the offsets have a different width from the pointer, according
1356 // to the language reference we need to sign-extend or truncate them
1357 // to the width of the pointer.
1358 IndexBits = IndexBits.sextOrTrunc(BitWidth);
1359
1360 // Note that inbounds does *not* guarantee nsw for the addition, as only
1361 // the offset is signed, while the base address is unsigned.
1362 Known = KnownBits::computeForAddSub(
1363 /*Add=*/true, /*NSW=*/false, Known, IndexBits);
1364 }
1365 if (!Known.isUnknown() && !AccConstIndices.isNullValue()) {
1366 KnownBits Index = KnownBits::makeConstant(AccConstIndices);
1367 Known = KnownBits::computeForAddSub(
1368 /*Add=*/true, /*NSW=*/false, Known, Index);
1369 }
1370 break;
1371 }
1372 case Instruction::PHI: {
1373 const PHINode *P = cast<PHINode>(I);
1374 // Handle the case of a simple two-predecessor recurrence PHI.
1375 // There's a lot more that could theoretically be done here, but
1376 // this is sufficient to catch some interesting cases.
1377 if (P->getNumIncomingValues() == 2) {
1378 for (unsigned i = 0; i != 2; ++i) {
1379 Value *L = P->getIncomingValue(i);
1380 Value *R = P->getIncomingValue(!i);
1381 Instruction *RInst = P->getIncomingBlock(!i)->getTerminator();
1382 Instruction *LInst = P->getIncomingBlock(i)->getTerminator();
1383 Operator *LU = dyn_cast<Operator>(L);
1384 if (!LU)
1385 continue;
1386 unsigned Opcode = LU->getOpcode();
1387
1388
1389 // If this is a shift recurrence, we know the bits being shifted in.
1390 // We can combine that with information about the start value of the
1391 // recurrence to conclude facts about the result.
1392 if (Opcode == Instruction::LShr ||
1393 Opcode == Instruction::AShr ||
1394 Opcode == Instruction::Shl) {
1395 Value *LL = LU->getOperand(0);
1396 Value *LR = LU->getOperand(1);
1397 // Find a recurrence.
1398 if (LL == I)
1399 L = LR;
Value stored to 'L' is never read
1400 else
1401 continue; // Check for recurrence with L and R flipped.
1402
1403 // We have matched a recurrence of the form:
1404 // %iv = [R, %entry], [%iv.next, %backedge]
1405 // %iv.next = shift_op %iv, L
1406
1407 // Recurse with the phi context to avoid concern about whether facts
1408 // inferred hold at original context instruction. TODO: It may be
1409 // correct to use the original context. IF warranted, explore and
1410 // add sufficient tests to cover.
1411 Query RecQ = Q;
1412 RecQ.CxtI = P;
1413 computeKnownBits(R, DemandedElts, Known2, Depth + 1, RecQ);
1414 switch (Opcode) {
1415 case Instruction::Shl:
1416 // A shl recurrence will only increase the tailing zeros
1417 Known.Zero.setLowBits(Known2.countMinTrailingZeros());
1418 break;
1419 case Instruction::LShr:
1420 // A lshr recurrence will preserve the leading zeros of the
1421 // start value
1422 Known.Zero.setHighBits(Known2.countMinLeadingZeros());
1423 break;
1424 case Instruction::AShr:
1425 // An ashr recurrence will extend the initial sign bit
1426 Known.Zero.setHighBits(Known2.countMinLeadingZeros());
1427 Known.One.setHighBits(Known2.countMinLeadingOnes());
1428 break;
1429 };
1430 }
1431
1432 // Check for operations that have the property that if
1433 // both their operands have low zero bits, the result
1434 // will have low zero bits.
1435 if (Opcode == Instruction::Add ||
1436 Opcode == Instruction::Sub ||
1437 Opcode == Instruction::And ||
1438 Opcode == Instruction::Or ||
1439 Opcode == Instruction::Mul) {
1440 Value *LL = LU->getOperand(0);
1441 Value *LR = LU->getOperand(1);
1442 // Find a recurrence.
1443 if (LL == I)
1444 L = LR;
1445 else if (LR == I)
1446 L = LL;
1447 else
1448 continue; // Check for recurrence with L and R flipped.
1449
1450 // Change the context instruction to the "edge" that flows into the
1451 // phi. This is important because that is where the value is actually
1452 // "evaluated" even though it is used later somewhere else. (see also
1453 // D69571).
1454 Query RecQ = Q;
1455
1456 // Ok, we have a PHI of the form L op= R. Check for low
1457 // zero bits.
1458 RecQ.CxtI = RInst;
1459 computeKnownBits(R, Known2, Depth + 1, RecQ);
1460
1461 // We need to take the minimum number of known bits
1462 KnownBits Known3(BitWidth);
1463 RecQ.CxtI = LInst;
1464 computeKnownBits(L, Known3, Depth + 1, RecQ);
1465
1466 Known.Zero.setLowBits(std::min(Known2.countMinTrailingZeros(),
1467 Known3.countMinTrailingZeros()));
1468
1469 auto *OverflowOp = dyn_cast<OverflowingBinaryOperator>(LU);
1470 if (OverflowOp && Q.IIQ.hasNoSignedWrap(OverflowOp)) {
1471 // If initial value of recurrence is nonnegative, and we are adding
1472 // a nonnegative number with nsw, the result can only be nonnegative
1473 // or poison value regardless of the number of times we execute the
1474 // add in phi recurrence. If initial value is negative and we are
1475 // adding a negative number with nsw, the result can only be
1476 // negative or poison value. Similar arguments apply to sub and mul.
1477 //
1478 // (add non-negative, non-negative) --> non-negative
1479 // (add negative, negative) --> negative
1480 if (Opcode == Instruction::Add) {
1481 if (Known2.isNonNegative() && Known3.isNonNegative())
1482 Known.makeNonNegative();
1483 else if (Known2.isNegative() && Known3.isNegative())
1484 Known.makeNegative();
1485 }
1486
1487 // (sub nsw non-negative, negative) --> non-negative
1488 // (sub nsw negative, non-negative) --> negative
1489 else if (Opcode == Instruction::Sub && LL == I) {
1490 if (Known2.isNonNegative() && Known3.isNegative())
1491 Known.makeNonNegative();
1492 else if (Known2.isNegative() && Known3.isNonNegative())
1493 Known.makeNegative();
1494 }
1495
1496 // (mul nsw non-negative, non-negative) --> non-negative
1497 else if (Opcode == Instruction::Mul && Known2.isNonNegative() &&
1498 Known3.isNonNegative())
1499 Known.makeNonNegative();
1500 }
1501
1502 break;
1503 }
1504 }
1505 }
1506
1507 // Unreachable blocks may have zero-operand PHI nodes.
1508 if (P->getNumIncomingValues() == 0)
1509 break;
1510
1511 // Otherwise take the unions of the known bit sets of the operands,
1512 // taking conservative care to avoid excessive recursion.
1513 if (Depth < MaxAnalysisRecursionDepth - 1 && !Known.Zero && !Known.One) {
1514 // Skip if every incoming value references to ourself.
1515 if (dyn_cast_or_null<UndefValue>(P->hasConstantValue()))
1516 break;
1517
1518 Known.Zero.setAllBits();
1519 Known.One.setAllBits();
1520 for (unsigned u = 0, e = P->getNumIncomingValues(); u < e; ++u) {
1521 Value *IncValue = P->getIncomingValue(u);
1522 // Skip direct self references.
1523 if (IncValue == P) continue;
1524
1525 // Change the context instruction to the "edge" that flows into the
1526 // phi. This is important because that is where the value is actually
1527 // "evaluated" even though it is used later somewhere else. (see also
1528 // D69571).
1529 Query RecQ = Q;
1530 RecQ.CxtI = P->getIncomingBlock(u)->getTerminator();
1531
1532 Known2 = KnownBits(BitWidth);
1533 // Recurse, but cap the recursion to one level, because we don't
1534 // want to waste time spinning around in loops.
1535 computeKnownBits(IncValue, Known2, MaxAnalysisRecursionDepth - 1, RecQ);
1536 Known = KnownBits::commonBits(Known, Known2);
1537 // If all bits have been ruled out, there's no need to check
1538 // more operands.
1539 if (Known.isUnknown())
1540 break;
1541 }
1542 }
1543 break;
1544 }
1545 case Instruction::Call:
1546 case Instruction::Invoke:
1547 // If range metadata is attached to this call, set known bits from that,
1548 // and then intersect with known bits based on other properties of the
1549 // function.
1550 if (MDNode *MD =
1551 Q.IIQ.getMetadata(cast<Instruction>(I), LLVMContext::MD_range))
1552 computeKnownBitsFromRangeMetadata(*MD, Known);
1553 if (const Value *RV = cast<CallBase>(I)->getReturnedArgOperand()) {
1554 computeKnownBits(RV, Known2, Depth + 1, Q);
1555 Known.Zero |= Known2.Zero;
1556 Known.One |= Known2.One;
1557 }
1558 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
1559 switch (II->getIntrinsicID()) {
1560 default: break;
1561 case Intrinsic::abs: {
1562 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1563 bool IntMinIsPoison = match(II->getArgOperand(1), m_One());
1564 Known = Known2.abs(IntMinIsPoison);
1565 break;
1566 }
1567 case Intrinsic::bitreverse:
1568 computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
1569 Known.Zero |= Known2.Zero.reverseBits();
1570 Known.One |= Known2.One.reverseBits();
1571 break;
1572 case Intrinsic::bswap:
1573 computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
1574 Known.Zero |= Known2.Zero.byteSwap();
1575 Known.One |= Known2.One.byteSwap();
1576 break;
1577 case Intrinsic::ctlz: {
1578 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1579 // If we have a known 1, its position is our upper bound.
1580 unsigned PossibleLZ = Known2.countMaxLeadingZeros();
1581 // If this call is undefined for 0, the result will be less than 2^n.
1582 if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
1583 PossibleLZ = std::min(PossibleLZ, BitWidth - 1);
1584 unsigned LowBits = Log2_32(PossibleLZ)+1;
1585 Known.Zero.setBitsFrom(LowBits);
1586 break;
1587 }
1588 case Intrinsic::cttz: {
1589 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1590 // If we have a known 1, its position is our upper bound.
1591 unsigned PossibleTZ = Known2.countMaxTrailingZeros();
1592 // If this call is undefined for 0, the result will be less than 2^n.
1593 if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
1594 PossibleTZ = std::min(PossibleTZ, BitWidth - 1);
1595 unsigned LowBits = Log2_32(PossibleTZ)+1;
1596 Known.Zero.setBitsFrom(LowBits);
1597 break;
1598 }
1599 case Intrinsic::ctpop: {
1600 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1601 // We can bound the space the count needs. Also, bits known to be zero
1602 // can't contribute to the population.
1603 unsigned BitsPossiblySet = Known2.countMaxPopulation();
1604 unsigned LowBits = Log2_32(BitsPossiblySet)+1;
1605 Known.Zero.setBitsFrom(LowBits);
1606 // TODO: we could bound KnownOne using the lower bound on the number
1607 // of bits which might be set provided by popcnt KnownOne2.
1608 break;
1609 }
1610 case Intrinsic::fshr:
1611 case Intrinsic::fshl: {
1612 const APInt *SA;
1613 if (!match(I->getOperand(2), m_APInt(SA)))
1614 break;
1615
1616 // Normalize to funnel shift left.
1617 uint64_t ShiftAmt = SA->urem(BitWidth);
1618 if (II->getIntrinsicID() == Intrinsic::fshr)
1619 ShiftAmt = BitWidth - ShiftAmt;
1620
1621 KnownBits Known3(BitWidth);
1622 computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
1623 computeKnownBits(I->getOperand(1), Known3, Depth + 1, Q);
1624
1625 Known.Zero =
1626 Known2.Zero.shl(ShiftAmt) | Known3.Zero.lshr(BitWidth - ShiftAmt);
1627 Known.One =
1628 Known2.One.shl(ShiftAmt) | Known3.One.lshr(BitWidth - ShiftAmt);
1629 break;
1630 }
1631 case Intrinsic::uadd_sat:
1632 case Intrinsic::usub_sat: {
1633 bool IsAdd = II->getIntrinsicID() == Intrinsic::uadd_sat;
1634 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1635 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1636
1637 // Add: Leading ones of either operand are preserved.
1638 // Sub: Leading zeros of LHS and leading ones of RHS are preserved
1639 // as leading zeros in the result.
1640 unsigned LeadingKnown;
1641 if (IsAdd)
1642 LeadingKnown = std::max(Known.countMinLeadingOnes(),
1643 Known2.countMinLeadingOnes());
1644 else
1645 LeadingKnown = std::max(Known.countMinLeadingZeros(),
1646 Known2.countMinLeadingOnes());
1647
1648 Known = KnownBits::computeForAddSub(
1649 IsAdd, /* NSW */ false, Known, Known2);
1650
1651 // We select between the operation result and all-ones/zero
1652 // respectively, so we can preserve known ones/zeros.
1653 if (IsAdd) {
1654 Known.One.setHighBits(LeadingKnown);
1655 Known.Zero.clearAllBits();
1656 } else {
1657 Known.Zero.setHighBits(LeadingKnown);
1658 Known.One.clearAllBits();
1659 }
1660 break;
1661 }
1662 case Intrinsic::umin:
1663 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1664 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1665 Known = KnownBits::umin(Known, Known2);
1666 break;
1667 case Intrinsic::umax:
1668 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1669 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1670 Known = KnownBits::umax(Known, Known2);
1671 break;
1672 case Intrinsic::smin:
1673 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1674 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1675 Known = KnownBits::smin(Known, Known2);
1676 break;
1677 case Intrinsic::smax:
1678 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1679 computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
1680 Known = KnownBits::smax(Known, Known2);
1681 break;
1682 case Intrinsic::x86_sse42_crc32_64_64:
1683 Known.Zero.setBitsFrom(32);
1684 break;
1685 }
1686 }
1687 break;
1688 case Instruction::ShuffleVector: {
1689 auto *Shuf = dyn_cast<ShuffleVectorInst>(I);
1690 // FIXME: Do we need to handle ConstantExpr involving shufflevectors?
1691 if (!Shuf) {
1692 Known.resetAll();
1693 return;
1694 }
1695 // For undef elements, we don't know anything about the common state of
1696 // the shuffle result.
1697 APInt DemandedLHS, DemandedRHS;
1698 if (!getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS)) {
1699 Known.resetAll();
1700 return;
1701 }
1702 Known.One.setAllBits();
1703 Known.Zero.setAllBits();
1704 if (!!DemandedLHS) {
1705 const Value *LHS = Shuf->getOperand(0);
1706 computeKnownBits(LHS, DemandedLHS, Known, Depth + 1, Q);
1707 // If we don't know any bits, early out.
1708 if (Known.isUnknown())
1709 break;
1710 }
1711 if (!!DemandedRHS) {
1712 const Value *RHS = Shuf->getOperand(1);
1713 computeKnownBits(RHS, DemandedRHS, Known2, Depth + 1, Q);
1714 Known = KnownBits::commonBits(Known, Known2);
1715 }
1716 break;
1717 }
1718 case Instruction::InsertElement: {
1719 const Value *Vec = I->getOperand(0);
1720 const Value *Elt = I->getOperand(1);
1721 auto *CIdx = dyn_cast<ConstantInt>(I->getOperand(2));
1722 // Early out if the index is non-constant or out-of-range.
1723 unsigned NumElts = DemandedElts.getBitWidth();
1724 if (!CIdx || CIdx->getValue().uge(NumElts)) {
1725 Known.resetAll();
1726 return;
1727 }
1728 Known.One.setAllBits();
1729 Known.Zero.setAllBits();
1730 unsigned EltIdx = CIdx->getZExtValue();
1731 // Do we demand the inserted element?
1732 if (DemandedElts[EltIdx]) {
1733 computeKnownBits(Elt, Known, Depth + 1, Q);
1734 // If we don't know any bits, early out.
1735 if (Known.isUnknown())
1736 break;
1737 }
1738 // We don't need the base vector element that has been inserted.
1739 APInt DemandedVecElts = DemandedElts;
1740 DemandedVecElts.clearBit(EltIdx);
1741 if (!!DemandedVecElts) {
1742 computeKnownBits(Vec, DemandedVecElts, Known2, Depth + 1, Q);
1743 Known = KnownBits::commonBits(Known, Known2);
1744 }
1745 break;
1746 }
1747 case Instruction::ExtractElement: {
1748 // Look through extract element. If the index is non-constant or
1749 // out-of-range demand all elements, otherwise just the extracted element.
1750 const Value *Vec = I->getOperand(0);
1751 const Value *Idx = I->getOperand(1);
1752 auto *CIdx = dyn_cast<ConstantInt>(Idx);
1753 if (isa<ScalableVectorType>(Vec->getType())) {
1754 // FIXME: there's probably *something* we can do with scalable vectors
1755 Known.resetAll();
1756 break;
1757 }
1758 unsigned NumElts = cast<FixedVectorType>(Vec->getType())->getNumElements();
1759 APInt DemandedVecElts = APInt::getAllOnesValue(NumElts);
1760 if (CIdx && CIdx->getValue().ult(NumElts))
1761 DemandedVecElts = APInt::getOneBitSet(NumElts, CIdx->getZExtValue());
1762 computeKnownBits(Vec, DemandedVecElts, Known, Depth + 1, Q);
1763 break;
1764 }
1765 case Instruction::ExtractValue:
1766 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I->getOperand(0))) {
1767 const ExtractValueInst *EVI = cast<ExtractValueInst>(I);
1768 if (EVI->getNumIndices() != 1) break;
1769 if (EVI->getIndices()[0] == 0) {
1770 switch (II->getIntrinsicID()) {
1771 default: break;
1772 case Intrinsic::uadd_with_overflow:
1773 case Intrinsic::sadd_with_overflow:
1774 computeKnownBitsAddSub(true, II->getArgOperand(0),
1775 II->getArgOperand(1), false, DemandedElts,
1776 Known, Known2, Depth, Q);
1777 break;
1778 case Intrinsic::usub_with_overflow:
1779 case Intrinsic::ssub_with_overflow:
1780 computeKnownBitsAddSub(false, II->getArgOperand(0),
1781 II->getArgOperand(1), false, DemandedElts,
1782 Known, Known2, Depth, Q);
1783 break;
1784 case Intrinsic::umul_with_overflow:
1785 case Intrinsic::smul_with_overflow:
1786 computeKnownBitsMul(II->getArgOperand(0), II->getArgOperand(1), false,
1787 DemandedElts, Known, Known2, Depth, Q);
1788 break;
1789 }
1790 }
1791 }
1792 break;
1793 case Instruction::Freeze:
1794 if (isGuaranteedNotToBePoison(I->getOperand(0), Q.AC, Q.CxtI, Q.DT,
1795 Depth + 1))
1796 computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
1797 break;
1798 }
1799}
1800
1801/// Determine which bits of V are known to be either zero or one and return
1802/// them.
1803KnownBits computeKnownBits(const Value *V, const APInt &DemandedElts,
1804 unsigned Depth, const Query &Q) {
1805 KnownBits Known(getBitWidth(V->getType(), Q.DL));
1806 computeKnownBits(V, DemandedElts, Known, Depth, Q);
1807 return Known;
1808}
1809
1810/// Determine which bits of V are known to be either zero or one and return
1811/// them.
1812KnownBits computeKnownBits(const Value *V, unsigned Depth, const Query &Q) {
1813 KnownBits Known(getBitWidth(V->getType(), Q.DL));
1814 computeKnownBits(V, Known, Depth, Q);
1815 return Known;
1816}
1817
1818/// Determine which bits of V are known to be either zero or one and return
1819/// them in the Known bit set.
1820///
1821/// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that
1822/// we cannot optimize based on the assumption that it is zero without changing
1823/// it to be an explicit zero. If we don't change it to zero, other code could
1824/// optimized based on the contradictory assumption that it is non-zero.
1825/// Because instcombine aggressively folds operations with undef args anyway,
1826/// this won't lose us code quality.
1827///
1828/// This function is defined on values with integer type, values with pointer
1829/// type, and vectors of integers. In the case
1830/// where V is a vector, known zero, and known one values are the
1831/// same width as the vector element, and the bit is set only if it is true
1832/// for all of the demanded elements in the vector specified by DemandedElts.
1833void computeKnownBits(const Value *V, const APInt &DemandedElts,
1834 KnownBits &Known, unsigned Depth, const Query &Q) {
1835 if (!DemandedElts || isa<ScalableVectorType>(V->getType())) {
1836 // No demanded elts or V is a scalable vector, better to assume we don't
1837 // know anything.
1838 Known.resetAll();
1839 return;
1840 }
1841
1842 assert(V && "No Value?")((V && "No Value?") ? static_cast<void> (0) : __assert_fail
("V && \"No Value?\"", "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1842, __PRETTY_FUNCTION__))
;
1843 assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth")((Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth"
) ? static_cast<void> (0) : __assert_fail ("Depth <= MaxAnalysisRecursionDepth && \"Limit Search Depth\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1843, __PRETTY_FUNCTION__))
;
1844
1845#ifndef NDEBUG
1846 Type *Ty = V->getType();
1847 unsigned BitWidth = Known.getBitWidth();
1848
1849 assert((Ty->isIntOrIntVectorTy(BitWidth) || Ty->isPtrOrPtrVectorTy()) &&(((Ty->isIntOrIntVectorTy(BitWidth) || Ty->isPtrOrPtrVectorTy
()) && "Not integer or pointer type!") ? static_cast<
void> (0) : __assert_fail ("(Ty->isIntOrIntVectorTy(BitWidth) || Ty->isPtrOrPtrVectorTy()) && \"Not integer or pointer type!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1850, __PRETTY_FUNCTION__))
1850 "Not integer or pointer type!")(((Ty->isIntOrIntVectorTy(BitWidth) || Ty->isPtrOrPtrVectorTy
()) && "Not integer or pointer type!") ? static_cast<
void> (0) : __assert_fail ("(Ty->isIntOrIntVectorTy(BitWidth) || Ty->isPtrOrPtrVectorTy()) && \"Not integer or pointer type!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1850, __PRETTY_FUNCTION__))
;
1851
1852 if (auto *FVTy = dyn_cast<FixedVectorType>(Ty)) {
1853 assert(((FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements"
) ? static_cast<void> (0) : __assert_fail ("FVTy->getNumElements() == DemandedElts.getBitWidth() && \"DemandedElt width should equal the fixed vector number of elements\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1855, __PRETTY_FUNCTION__))
1854 FVTy->getNumElements() == DemandedElts.getBitWidth() &&((FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements"
) ? static_cast<void> (0) : __assert_fail ("FVTy->getNumElements() == DemandedElts.getBitWidth() && \"DemandedElt width should equal the fixed vector number of elements\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1855, __PRETTY_FUNCTION__))
1855 "DemandedElt width should equal the fixed vector number of elements")((FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements"
) ? static_cast<void> (0) : __assert_fail ("FVTy->getNumElements() == DemandedElts.getBitWidth() && \"DemandedElt width should equal the fixed vector number of elements\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1855, __PRETTY_FUNCTION__))
;
1856 } else {
1857 assert(DemandedElts == APInt(1, 1) &&((DemandedElts == APInt(1, 1) && "DemandedElt width should be 1 for scalars"
) ? static_cast<void> (0) : __assert_fail ("DemandedElts == APInt(1, 1) && \"DemandedElt width should be 1 for scalars\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1858, __PRETTY_FUNCTION__))
1858 "DemandedElt width should be 1 for scalars")((DemandedElts == APInt(1, 1) && "DemandedElt width should be 1 for scalars"
) ? static_cast<void> (0) : __assert_fail ("DemandedElts == APInt(1, 1) && \"DemandedElt width should be 1 for scalars\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1858, __PRETTY_FUNCTION__))
;
1859 }
1860
1861 Type *ScalarTy = Ty->getScalarType();
1862 if (ScalarTy->isPointerTy()) {
1863 assert(BitWidth == Q.DL.getPointerTypeSizeInBits(ScalarTy) &&((BitWidth == Q.DL.getPointerTypeSizeInBits(ScalarTy) &&
"V and Known should have same BitWidth") ? static_cast<void
> (0) : __assert_fail ("BitWidth == Q.DL.getPointerTypeSizeInBits(ScalarTy) && \"V and Known should have same BitWidth\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1864, __PRETTY_FUNCTION__))
1864 "V and Known should have same BitWidth")((BitWidth == Q.DL.getPointerTypeSizeInBits(ScalarTy) &&
"V and Known should have same BitWidth") ? static_cast<void
> (0) : __assert_fail ("BitWidth == Q.DL.getPointerTypeSizeInBits(ScalarTy) && \"V and Known should have same BitWidth\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1864, __PRETTY_FUNCTION__))
;
1865 } else {
1866 assert(BitWidth == Q.DL.getTypeSizeInBits(ScalarTy) &&((BitWidth == Q.DL.getTypeSizeInBits(ScalarTy) && "V and Known should have same BitWidth"
) ? static_cast<void> (0) : __assert_fail ("BitWidth == Q.DL.getTypeSizeInBits(ScalarTy) && \"V and Known should have same BitWidth\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1867, __PRETTY_FUNCTION__))
1867 "V and Known should have same BitWidth")((BitWidth == Q.DL.getTypeSizeInBits(ScalarTy) && "V and Known should have same BitWidth"
) ? static_cast<void> (0) : __assert_fail ("BitWidth == Q.DL.getTypeSizeInBits(ScalarTy) && \"V and Known should have same BitWidth\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1867, __PRETTY_FUNCTION__))
;
1868 }
1869#endif
1870
1871 const APInt *C;
1872 if (match(V, m_APInt(C))) {
1873 // We know all of the bits for a scalar constant or a splat vector constant!
1874 Known = KnownBits::makeConstant(*C);
1875 return;
1876 }
1877 // Null and aggregate-zero are all-zeros.
1878 if (isa<ConstantPointerNull>(V) || isa<ConstantAggregateZero>(V)) {
1879 Known.setAllZero();
1880 return;
1881 }
1882 // Handle a constant vector by taking the intersection of the known bits of
1883 // each element.
1884 if (const ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(V)) {
1885 // We know that CDV must be a vector of integers. Take the intersection of
1886 // each element.
1887 Known.Zero.setAllBits(); Known.One.setAllBits();
1888 for (unsigned i = 0, e = CDV->getNumElements(); i != e; ++i) {
1889 if (!DemandedElts[i])
1890 continue;
1891 APInt Elt = CDV->getElementAsAPInt(i);
1892 Known.Zero &= ~Elt;
1893 Known.One &= Elt;
1894 }
1895 return;
1896 }
1897
1898 if (const auto *CV = dyn_cast<ConstantVector>(V)) {
1899 // We know that CV must be a vector of integers. Take the intersection of
1900 // each element.
1901 Known.Zero.setAllBits(); Known.One.setAllBits();
1902 for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
1903 if (!DemandedElts[i])
1904 continue;
1905 Constant *Element = CV->getAggregateElement(i);
1906 auto *ElementCI = dyn_cast_or_null<ConstantInt>(Element);
1907 if (!ElementCI) {
1908 Known.resetAll();
1909 return;
1910 }
1911 const APInt &Elt = ElementCI->getValue();
1912 Known.Zero &= ~Elt;
1913 Known.One &= Elt;
1914 }
1915 return;
1916 }
1917
1918 // Start out not knowing anything.
1919 Known.resetAll();
1920
1921 // We can't imply anything about undefs.
1922 if (isa<UndefValue>(V))
1923 return;
1924
1925 // There's no point in looking through other users of ConstantData for
1926 // assumptions. Confirm that we've handled them all.
1927 assert(!isa<ConstantData>(V) && "Unhandled constant data!")((!isa<ConstantData>(V) && "Unhandled constant data!"
) ? static_cast<void> (0) : __assert_fail ("!isa<ConstantData>(V) && \"Unhandled constant data!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1927, __PRETTY_FUNCTION__))
;
1928
1929 // All recursive calls that increase depth must come after this.
1930 if (Depth == MaxAnalysisRecursionDepth)
1931 return;
1932
1933 // A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
1934 // the bits of its aliasee.
1935 if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
1936 if (!GA->isInterposable())
1937 computeKnownBits(GA->getAliasee(), Known, Depth + 1, Q);
1938 return;
1939 }
1940
1941 if (const Operator *I = dyn_cast<Operator>(V))
1942 computeKnownBitsFromOperator(I, DemandedElts, Known, Depth, Q);
1943
1944 // Aligned pointers have trailing zeros - refine Known.Zero set
1945 if (isa<PointerType>(V->getType())) {
1946 Align Alignment = V->getPointerAlignment(Q.DL);
1947 Known.Zero.setLowBits(Log2(Alignment));
1948 }
1949
1950 // computeKnownBitsFromAssume strictly refines Known.
1951 // Therefore, we run them after computeKnownBitsFromOperator.
1952
1953 // Check whether a nearby assume intrinsic can determine some known bits.
1954 computeKnownBitsFromAssume(V, Known, Depth, Q);
1955
1956 assert((Known.Zero & Known.One) == 0 && "Bits known to be one AND zero?")(((Known.Zero & Known.One) == 0 && "Bits known to be one AND zero?"
) ? static_cast<void> (0) : __assert_fail ("(Known.Zero & Known.One) == 0 && \"Bits known to be one AND zero?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1956, __PRETTY_FUNCTION__))
;
1957}
1958
1959/// Return true if the given value is known to have exactly one
1960/// bit set when defined. For vectors return true if every element is known to
1961/// be a power of two when defined. Supports values with integer or pointer
1962/// types and vectors of integers.
1963bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
1964 const Query &Q) {
1965 assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth")((Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth"
) ? static_cast<void> (0) : __assert_fail ("Depth <= MaxAnalysisRecursionDepth && \"Limit Search Depth\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 1965, __PRETTY_FUNCTION__))
;
1966
1967 // Attempt to match against constants.
1968 if (OrZero && match(V, m_Power2OrZero()))
1969 return true;
1970 if (match(V, m_Power2()))
1971 return true;
1972
1973 // 1 << X is clearly a power of two if the one is not shifted off the end. If
1974 // it is shifted off the end then the result is undefined.
1975 if (match(V, m_Shl(m_One(), m_Value())))
1976 return true;
1977
1978 // (signmask) >>l X is clearly a power of two if the one is not shifted off
1979 // the bottom. If it is shifted off the bottom then the result is undefined.
1980 if (match(V, m_LShr(m_SignMask(), m_Value())))
1981 return true;
1982
1983 // The remaining tests are all recursive, so bail out if we hit the limit.
1984 if (Depth++ == MaxAnalysisRecursionDepth)
1985 return false;
1986
1987 Value *X = nullptr, *Y = nullptr;
1988 // A shift left or a logical shift right of a power of two is a power of two
1989 // or zero.
1990 if (OrZero && (match(V, m_Shl(m_Value(X), m_Value())) ||
1991 match(V, m_LShr(m_Value(X), m_Value()))))
1992 return isKnownToBeAPowerOfTwo(X, /*OrZero*/ true, Depth, Q);
1993
1994 if (const ZExtInst *ZI = dyn_cast<ZExtInst>(V))
1995 return isKnownToBeAPowerOfTwo(ZI->getOperand(0), OrZero, Depth, Q);
1996
1997 if (const SelectInst *SI = dyn_cast<SelectInst>(V))
1998 return isKnownToBeAPowerOfTwo(SI->getTrueValue(), OrZero, Depth, Q) &&
1999 isKnownToBeAPowerOfTwo(SI->getFalseValue(), OrZero, Depth, Q);
2000
2001 if (OrZero && match(V, m_And(m_Value(X), m_Value(Y)))) {
2002 // A power of two and'd with anything is a power of two or zero.
2003 if (isKnownToBeAPowerOfTwo(X, /*OrZero*/ true, Depth, Q) ||
2004 isKnownToBeAPowerOfTwo(Y, /*OrZero*/ true, Depth, Q))
2005 return true;
2006 // X & (-X) is always a power of two or zero.
2007 if (match(X, m_Neg(m_Specific(Y))) || match(Y, m_Neg(m_Specific(X))))
2008 return true;
2009 return false;
2010 }
2011
2012 // Adding a power-of-two or zero to the same power-of-two or zero yields
2013 // either the original power-of-two, a larger power-of-two or zero.
2014 if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
2015 const OverflowingBinaryOperator *VOBO = cast<OverflowingBinaryOperator>(V);
2016 if (OrZero || Q.IIQ.hasNoUnsignedWrap(VOBO) ||
2017 Q.IIQ.hasNoSignedWrap(VOBO)) {
2018 if (match(X, m_And(m_Specific(Y), m_Value())) ||
2019 match(X, m_And(m_Value(), m_Specific(Y))))
2020 if (isKnownToBeAPowerOfTwo(Y, OrZero, Depth, Q))
2021 return true;
2022 if (match(Y, m_And(m_Specific(X), m_Value())) ||
2023 match(Y, m_And(m_Value(), m_Specific(X))))
2024 if (isKnownToBeAPowerOfTwo(X, OrZero, Depth, Q))
2025 return true;
2026
2027 unsigned BitWidth = V->getType()->getScalarSizeInBits();
2028 KnownBits LHSBits(BitWidth);
2029 computeKnownBits(X, LHSBits, Depth, Q);
2030
2031 KnownBits RHSBits(BitWidth);
2032 computeKnownBits(Y, RHSBits, Depth, Q);
2033 // If i8 V is a power of two or zero:
2034 // ZeroBits: 1 1 1 0 1 1 1 1
2035 // ~ZeroBits: 0 0 0 1 0 0 0 0
2036 if ((~(LHSBits.Zero & RHSBits.Zero)).isPowerOf2())
2037 // If OrZero isn't set, we cannot give back a zero result.
2038 // Make sure either the LHS or RHS has a bit set.
2039 if (OrZero || RHSBits.One.getBoolValue() || LHSBits.One.getBoolValue())
2040 return true;
2041 }
2042 }
2043
2044 // An exact divide or right shift can only shift off zero bits, so the result
2045 // is a power of two only if the first operand is a power of two and not
2046 // copying a sign bit (sdiv int_min, 2).
2047 if (match(V, m_Exact(m_LShr(m_Value(), m_Value()))) ||
2048 match(V, m_Exact(m_UDiv(m_Value(), m_Value())))) {
2049 return isKnownToBeAPowerOfTwo(cast<Operator>(V)->getOperand(0), OrZero,
2050 Depth, Q);
2051 }
2052
2053 return false;
2054}
2055
2056/// Test whether a GEP's result is known to be non-null.
2057///
2058/// Uses properties inherent in a GEP to try to determine whether it is known
2059/// to be non-null.
2060///
2061/// Currently this routine does not support vector GEPs.
2062static bool isGEPKnownNonNull(const GEPOperator *GEP, unsigned Depth,
2063 const Query &Q) {
2064 const Function *F = nullptr;
2065 if (const Instruction *I = dyn_cast<Instruction>(GEP))
2066 F = I->getFunction();
2067
2068 if (!GEP->isInBounds() ||
2069 NullPointerIsDefined(F, GEP->getPointerAddressSpace()))
2070 return false;
2071
2072 // FIXME: Support vector-GEPs.
2073 assert(GEP->getType()->isPointerTy() && "We only support plain pointer GEP")((GEP->getType()->isPointerTy() && "We only support plain pointer GEP"
) ? static_cast<void> (0) : __assert_fail ("GEP->getType()->isPointerTy() && \"We only support plain pointer GEP\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2073, __PRETTY_FUNCTION__))
;
2074
2075 // If the base pointer is non-null, we cannot walk to a null address with an
2076 // inbounds GEP in address space zero.
2077 if (isKnownNonZero(GEP->getPointerOperand(), Depth, Q))
2078 return true;
2079
2080 // Walk the GEP operands and see if any operand introduces a non-zero offset.
2081 // If so, then the GEP cannot produce a null pointer, as doing so would
2082 // inherently violate the inbounds contract within address space zero.
2083 for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
2084 GTI != GTE; ++GTI) {
2085 // Struct types are easy -- they must always be indexed by a constant.
2086 if (StructType *STy = GTI.getStructTypeOrNull()) {
2087 ConstantInt *OpC = cast<ConstantInt>(GTI.getOperand());
2088 unsigned ElementIdx = OpC->getZExtValue();
2089 const StructLayout *SL = Q.DL.getStructLayout(STy);
2090 uint64_t ElementOffset = SL->getElementOffset(ElementIdx);
2091 if (ElementOffset > 0)
2092 return true;
2093 continue;
2094 }
2095
2096 // If we have a zero-sized type, the index doesn't matter. Keep looping.
2097 if (Q.DL.getTypeAllocSize(GTI.getIndexedType()).getKnownMinSize() == 0)
2098 continue;
2099
2100 // Fast path the constant operand case both for efficiency and so we don't
2101 // increment Depth when just zipping down an all-constant GEP.
2102 if (ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand())) {
2103 if (!OpC->isZero())
2104 return true;
2105 continue;
2106 }
2107
2108 // We post-increment Depth here because while isKnownNonZero increments it
2109 // as well, when we pop back up that increment won't persist. We don't want
2110 // to recurse 10k times just because we have 10k GEP operands. We don't
2111 // bail completely out because we want to handle constant GEPs regardless
2112 // of depth.
2113 if (Depth++ >= MaxAnalysisRecursionDepth)
2114 continue;
2115
2116 if (isKnownNonZero(GTI.getOperand(), Depth, Q))
2117 return true;
2118 }
2119
2120 return false;
2121}
2122
2123static bool isKnownNonNullFromDominatingCondition(const Value *V,
2124 const Instruction *CtxI,
2125 const DominatorTree *DT) {
2126 if (isa<Constant>(V))
2127 return false;
2128
2129 if (!CtxI || !DT)
2130 return false;
2131
2132 unsigned NumUsesExplored = 0;
2133 for (auto *U : V->users()) {
2134 // Avoid massive lists
2135 if (NumUsesExplored >= DomConditionsMaxUses)
2136 break;
2137 NumUsesExplored++;
2138
2139 // If the value is used as an argument to a call or invoke, then argument
2140 // attributes may provide an answer about null-ness.
2141 if (const auto *CB = dyn_cast<CallBase>(U))
2142 if (auto *CalledFunc = CB->getCalledFunction())
2143 for (const Argument &Arg : CalledFunc->args())
2144 if (CB->getArgOperand(Arg.getArgNo()) == V &&
2145 Arg.hasNonNullAttr(/* AllowUndefOrPoison */ false) &&
2146 DT->dominates(CB, CtxI))
2147 return true;
2148
2149 // If the value is used as a load/store, then the pointer must be non null.
2150 if (V == getLoadStorePointerOperand(U)) {
2151 const Instruction *I = cast<Instruction>(U);
2152 if (!NullPointerIsDefined(I->getFunction(),
2153 V->getType()->getPointerAddressSpace()) &&
2154 DT->dominates(I, CtxI))
2155 return true;
2156 }
2157
2158 // Consider only compare instructions uniquely controlling a branch
2159 Value *RHS;
2160 CmpInst::Predicate Pred;
2161 if (!match(U, m_c_ICmp(Pred, m_Specific(V), m_Value(RHS))))
2162 continue;
2163
2164 bool NonNullIfTrue;
2165 if (cmpExcludesZero(Pred, RHS))
2166 NonNullIfTrue = true;
2167 else if (cmpExcludesZero(CmpInst::getInversePredicate(Pred), RHS))
2168 NonNullIfTrue = false;
2169 else
2170 continue;
2171
2172 SmallVector<const User *, 4> WorkList;
2173 SmallPtrSet<const User *, 4> Visited;
2174 for (auto *CmpU : U->users()) {
2175 assert(WorkList.empty() && "Should be!")((WorkList.empty() && "Should be!") ? static_cast<
void> (0) : __assert_fail ("WorkList.empty() && \"Should be!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2175, __PRETTY_FUNCTION__))
;
2176 if (Visited.insert(CmpU).second)
2177 WorkList.push_back(CmpU);
2178
2179 while (!WorkList.empty()) {
2180 auto *Curr = WorkList.pop_back_val();
2181
2182 // If a user is an AND, add all its users to the work list. We only
2183 // propagate "pred != null" condition through AND because it is only
2184 // correct to assume that all conditions of AND are met in true branch.
2185 // TODO: Support similar logic of OR and EQ predicate?
2186 if (NonNullIfTrue)
2187 if (match(Curr, m_LogicalAnd(m_Value(), m_Value()))) {
2188 for (auto *CurrU : Curr->users())
2189 if (Visited.insert(CurrU).second)
2190 WorkList.push_back(CurrU);
2191 continue;
2192 }
2193
2194 if (const BranchInst *BI = dyn_cast<BranchInst>(Curr)) {
2195 assert(BI->isConditional() && "uses a comparison!")((BI->isConditional() && "uses a comparison!") ? static_cast
<void> (0) : __assert_fail ("BI->isConditional() && \"uses a comparison!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2195, __PRETTY_FUNCTION__))
;
2196
2197 BasicBlock *NonNullSuccessor =
2198 BI->getSuccessor(NonNullIfTrue ? 0 : 1);
2199 BasicBlockEdge Edge(BI->getParent(), NonNullSuccessor);
2200 if (Edge.isSingleEdge() && DT->dominates(Edge, CtxI->getParent()))
2201 return true;
2202 } else if (NonNullIfTrue && isGuard(Curr) &&
2203 DT->dominates(cast<Instruction>(Curr), CtxI)) {
2204 return true;
2205 }
2206 }
2207 }
2208 }
2209
2210 return false;
2211}
2212
2213/// Does the 'Range' metadata (which must be a valid MD_range operand list)
2214/// ensure that the value it's attached to is never Value? 'RangeType' is
2215/// is the type of the value described by the range.
2216static bool rangeMetadataExcludesValue(const MDNode* Ranges, const APInt& Value) {
2217 const unsigned NumRanges = Ranges->getNumOperands() / 2;
2218 assert(NumRanges >= 1)((NumRanges >= 1) ? static_cast<void> (0) : __assert_fail
("NumRanges >= 1", "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2218, __PRETTY_FUNCTION__))
;
2219 for (unsigned i = 0; i < NumRanges; ++i) {
2220 ConstantInt *Lower =
2221 mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 0));
2222 ConstantInt *Upper =
2223 mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 1));
2224 ConstantRange Range(Lower->getValue(), Upper->getValue());
2225 if (Range.contains(Value))
2226 return false;
2227 }
2228 return true;
2229}
2230
2231/// Return true if the given value is known to be non-zero when defined. For
2232/// vectors, return true if every demanded element is known to be non-zero when
2233/// defined. For pointers, if the context instruction and dominator tree are
2234/// specified, perform context-sensitive analysis and return true if the
2235/// pointer couldn't possibly be null at the specified instruction.
2236/// Supports values with integer or pointer type and vectors of integers.
2237bool isKnownNonZero(const Value *V, const APInt &DemandedElts, unsigned Depth,
2238 const Query &Q) {
2239 // FIXME: We currently have no way to represent the DemandedElts of a scalable
2240 // vector
2241 if (isa<ScalableVectorType>(V->getType()))
2242 return false;
2243
2244 if (auto *C = dyn_cast<Constant>(V)) {
2245 if (C->isNullValue())
2246 return false;
2247 if (isa<ConstantInt>(C))
2248 // Must be non-zero due to null test above.
2249 return true;
2250
2251 if (auto *CE = dyn_cast<ConstantExpr>(C)) {
2252 // See the comment for IntToPtr/PtrToInt instructions below.
2253 if (CE->getOpcode() == Instruction::IntToPtr ||
2254 CE->getOpcode() == Instruction::PtrToInt)
2255 if (Q.DL.getTypeSizeInBits(CE->getOperand(0)->getType())
2256 .getFixedSize() <=
2257 Q.DL.getTypeSizeInBits(CE->getType()).getFixedSize())
2258 return isKnownNonZero(CE->getOperand(0), Depth, Q);
2259 }
2260
2261 // For constant vectors, check that all elements are undefined or known
2262 // non-zero to determine that the whole vector is known non-zero.
2263 if (auto *VecTy = dyn_cast<FixedVectorType>(C->getType())) {
2264 for (unsigned i = 0, e = VecTy->getNumElements(); i != e; ++i) {
2265 if (!DemandedElts[i])
2266 continue;
2267 Constant *Elt = C->getAggregateElement(i);
2268 if (!Elt || Elt->isNullValue())
2269 return false;
2270 if (!isa<UndefValue>(Elt) && !isa<ConstantInt>(Elt))
2271 return false;
2272 }
2273 return true;
2274 }
2275
2276 // A global variable in address space 0 is non null unless extern weak
2277 // or an absolute symbol reference. Other address spaces may have null as a
2278 // valid address for a global, so we can't assume anything.
2279 if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
2280 if (!GV->isAbsoluteSymbolRef() && !GV->hasExternalWeakLinkage() &&
2281 GV->getType()->getAddressSpace() == 0)
2282 return true;
2283 } else
2284 return false;
2285 }
2286
2287 if (auto *I = dyn_cast<Instruction>(V)) {
2288 if (MDNode *Ranges = Q.IIQ.getMetadata(I, LLVMContext::MD_range)) {
2289 // If the possible ranges don't contain zero, then the value is
2290 // definitely non-zero.
2291 if (auto *Ty = dyn_cast<IntegerType>(V->getType())) {
2292 const APInt ZeroValue(Ty->getBitWidth(), 0);
2293 if (rangeMetadataExcludesValue(Ranges, ZeroValue))
2294 return true;
2295 }
2296 }
2297 }
2298
2299 if (isKnownNonZeroFromAssume(V, Q))
2300 return true;
2301
2302 // Some of the tests below are recursive, so bail out if we hit the limit.
2303 if (Depth++ >= MaxAnalysisRecursionDepth)
2304 return false;
2305
2306 // Check for pointer simplifications.
2307
2308 if (PointerType *PtrTy = dyn_cast<PointerType>(V->getType())) {
2309 // Alloca never returns null, malloc might.
2310 if (isa<AllocaInst>(V) && Q.DL.getAllocaAddrSpace() == 0)
2311 return true;
2312
2313 // A byval, inalloca may not be null in a non-default addres space. A
2314 // nonnull argument is assumed never 0.
2315 if (const Argument *A = dyn_cast<Argument>(V)) {
2316 if (((A->hasPassPointeeByValueCopyAttr() &&
2317 !NullPointerIsDefined(A->getParent(), PtrTy->getAddressSpace())) ||
2318 A->hasNonNullAttr()))
2319 return true;
2320 }
2321
2322 // A Load tagged with nonnull metadata is never null.
2323 if (const LoadInst *LI = dyn_cast<LoadInst>(V))
2324 if (Q.IIQ.getMetadata(LI, LLVMContext::MD_nonnull))
2325 return true;
2326
2327 if (const auto *Call = dyn_cast<CallBase>(V)) {
2328 if (Call->isReturnNonNull())
2329 return true;
2330 if (const auto *RP = getArgumentAliasingToReturnedPointer(Call, true))
2331 return isKnownNonZero(RP, Depth, Q);
2332 }
2333 }
2334
2335 if (isKnownNonNullFromDominatingCondition(V, Q.CxtI, Q.DT))
2336 return true;
2337
2338 // Check for recursive pointer simplifications.
2339 if (V->getType()->isPointerTy()) {
2340 // Look through bitcast operations, GEPs, and int2ptr instructions as they
2341 // do not alter the value, or at least not the nullness property of the
2342 // value, e.g., int2ptr is allowed to zero/sign extend the value.
2343 //
2344 // Note that we have to take special care to avoid looking through
2345 // truncating casts, e.g., int2ptr/ptr2int with appropriate sizes, as well
2346 // as casts that can alter the value, e.g., AddrSpaceCasts.
2347 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V))
2348 return isGEPKnownNonNull(GEP, Depth, Q);
2349
2350 if (auto *BCO = dyn_cast<BitCastOperator>(V))
2351 return isKnownNonZero(BCO->getOperand(0), Depth, Q);
2352
2353 if (auto *I2P = dyn_cast<IntToPtrInst>(V))
2354 if (Q.DL.getTypeSizeInBits(I2P->getSrcTy()).getFixedSize() <=
2355 Q.DL.getTypeSizeInBits(I2P->getDestTy()).getFixedSize())
2356 return isKnownNonZero(I2P->getOperand(0), Depth, Q);
2357 }
2358
2359 // Similar to int2ptr above, we can look through ptr2int here if the cast
2360 // is a no-op or an extend and not a truncate.
2361 if (auto *P2I = dyn_cast<PtrToIntInst>(V))
2362 if (Q.DL.getTypeSizeInBits(P2I->getSrcTy()).getFixedSize() <=
2363 Q.DL.getTypeSizeInBits(P2I->getDestTy()).getFixedSize())
2364 return isKnownNonZero(P2I->getOperand(0), Depth, Q);
2365
2366 unsigned BitWidth = getBitWidth(V->getType()->getScalarType(), Q.DL);
2367
2368 // X | Y != 0 if X != 0 or Y != 0.
2369 Value *X = nullptr, *Y = nullptr;
2370 if (match(V, m_Or(m_Value(X), m_Value(Y))))
2371 return isKnownNonZero(X, DemandedElts, Depth, Q) ||
2372 isKnownNonZero(Y, DemandedElts, Depth, Q);
2373
2374 // ext X != 0 if X != 0.
2375 if (isa<SExtInst>(V) || isa<ZExtInst>(V))
2376 return isKnownNonZero(cast<Instruction>(V)->getOperand(0), Depth, Q);
2377
2378 // shl X, Y != 0 if X is odd. Note that the value of the shift is undefined
2379 // if the lowest bit is shifted off the end.
2380 if (match(V, m_Shl(m_Value(X), m_Value(Y)))) {
2381 // shl nuw can't remove any non-zero bits.
2382 const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
2383 if (Q.IIQ.hasNoUnsignedWrap(BO))
2384 return isKnownNonZero(X, Depth, Q);
2385
2386 KnownBits Known(BitWidth);
2387 computeKnownBits(X, DemandedElts, Known, Depth, Q);
2388 if (Known.One[0])
2389 return true;
2390 }
2391 // shr X, Y != 0 if X is negative. Note that the value of the shift is not
2392 // defined if the sign bit is shifted off the end.
2393 else if (match(V, m_Shr(m_Value(X), m_Value(Y)))) {
2394 // shr exact can only shift out zero bits.
2395 const PossiblyExactOperator *BO = cast<PossiblyExactOperator>(V);
2396 if (BO->isExact())
2397 return isKnownNonZero(X, Depth, Q);
2398
2399 KnownBits Known = computeKnownBits(X, DemandedElts, Depth, Q);
2400 if (Known.isNegative())
2401 return true;
2402
2403 // If the shifter operand is a constant, and all of the bits shifted
2404 // out are known to be zero, and X is known non-zero then at least one
2405 // non-zero bit must remain.
2406 if (ConstantInt *Shift = dyn_cast<ConstantInt>(Y)) {
2407 auto ShiftVal = Shift->getLimitedValue(BitWidth - 1);
2408 // Is there a known one in the portion not shifted out?
2409 if (Known.countMaxLeadingZeros() < BitWidth - ShiftVal)
2410 return true;
2411 // Are all the bits to be shifted out known zero?
2412 if (Known.countMinTrailingZeros() >= ShiftVal)
2413 return isKnownNonZero(X, DemandedElts, Depth, Q);
2414 }
2415 }
2416 // div exact can only produce a zero if the dividend is zero.
2417 else if (match(V, m_Exact(m_IDiv(m_Value(X), m_Value())))) {
2418 return isKnownNonZero(X, DemandedElts, Depth, Q);
2419 }
2420 // X + Y.
2421 else if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
2422 KnownBits XKnown = computeKnownBits(X, DemandedElts, Depth, Q);
2423 KnownBits YKnown = computeKnownBits(Y, DemandedElts, Depth, Q);
2424
2425 // If X and Y are both non-negative (as signed values) then their sum is not
2426 // zero unless both X and Y are zero.
2427 if (XKnown.isNonNegative() && YKnown.isNonNegative())
2428 if (isKnownNonZero(X, DemandedElts, Depth, Q) ||
2429 isKnownNonZero(Y, DemandedElts, Depth, Q))
2430 return true;
2431
2432 // If X and Y are both negative (as signed values) then their sum is not
2433 // zero unless both X and Y equal INT_MIN.
2434 if (XKnown.isNegative() && YKnown.isNegative()) {
2435 APInt Mask = APInt::getSignedMaxValue(BitWidth);
2436 // The sign bit of X is set. If some other bit is set then X is not equal
2437 // to INT_MIN.
2438 if (XKnown.One.intersects(Mask))
2439 return true;
2440 // The sign bit of Y is set. If some other bit is set then Y is not equal
2441 // to INT_MIN.
2442 if (YKnown.One.intersects(Mask))
2443 return true;
2444 }
2445
2446 // The sum of a non-negative number and a power of two is not zero.
2447 if (XKnown.isNonNegative() &&
2448 isKnownToBeAPowerOfTwo(Y, /*OrZero*/ false, Depth, Q))
2449 return true;
2450 if (YKnown.isNonNegative() &&
2451 isKnownToBeAPowerOfTwo(X, /*OrZero*/ false, Depth, Q))
2452 return true;
2453 }
2454 // X * Y.
2455 else if (match(V, m_Mul(m_Value(X), m_Value(Y)))) {
2456 const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
2457 // If X and Y are non-zero then so is X * Y as long as the multiplication
2458 // does not overflow.
2459 if ((Q.IIQ.hasNoSignedWrap(BO) || Q.IIQ.hasNoUnsignedWrap(BO)) &&
2460 isKnownNonZero(X, DemandedElts, Depth, Q) &&
2461 isKnownNonZero(Y, DemandedElts, Depth, Q))
2462 return true;
2463 }
2464 // (C ? X : Y) != 0 if X != 0 and Y != 0.
2465 else if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
2466 if (isKnownNonZero(SI->getTrueValue(), DemandedElts, Depth, Q) &&
2467 isKnownNonZero(SI->getFalseValue(), DemandedElts, Depth, Q))
2468 return true;
2469 }
2470 // PHI
2471 else if (const PHINode *PN = dyn_cast<PHINode>(V)) {
2472 // Try and detect a recurrence that monotonically increases from a
2473 // starting value, as these are common as induction variables.
2474 if (PN->getNumIncomingValues() == 2) {
2475 Value *Start = PN->getIncomingValue(0);
2476 Value *Induction = PN->getIncomingValue(1);
2477 if (isa<ConstantInt>(Induction) && !isa<ConstantInt>(Start))
2478 std::swap(Start, Induction);
2479 if (ConstantInt *C = dyn_cast<ConstantInt>(Start)) {
2480 if (!C->isZero() && !C->isNegative()) {
2481 ConstantInt *X;
2482 if (Q.IIQ.UseInstrInfo &&
2483 (match(Induction, m_NSWAdd(m_Specific(PN), m_ConstantInt(X))) ||
2484 match(Induction, m_NUWAdd(m_Specific(PN), m_ConstantInt(X)))) &&
2485 !X->isNegative())
2486 return true;
2487 }
2488 }
2489 }
2490 // Check if all incoming values are non-zero using recursion.
2491 Query RecQ = Q;
2492 unsigned NewDepth = std::max(Depth, MaxAnalysisRecursionDepth - 1);
2493 return llvm::all_of(PN->operands(), [&](const Use &U) {
2494 if (U.get() == PN)
2495 return true;
2496 RecQ.CxtI = PN->getIncomingBlock(U)->getTerminator();
2497 return isKnownNonZero(U.get(), DemandedElts, NewDepth, RecQ);
2498 });
2499 }
2500 // ExtractElement
2501 else if (const auto *EEI = dyn_cast<ExtractElementInst>(V)) {
2502 const Value *Vec = EEI->getVectorOperand();
2503 const Value *Idx = EEI->getIndexOperand();
2504 auto *CIdx = dyn_cast<ConstantInt>(Idx);
2505 if (auto *VecTy = dyn_cast<FixedVectorType>(Vec->getType())) {
2506 unsigned NumElts = VecTy->getNumElements();
2507 APInt DemandedVecElts = APInt::getAllOnesValue(NumElts);
2508 if (CIdx && CIdx->getValue().ult(NumElts))
2509 DemandedVecElts = APInt::getOneBitSet(NumElts, CIdx->getZExtValue());
2510 return isKnownNonZero(Vec, DemandedVecElts, Depth, Q);
2511 }
2512 }
2513 // Freeze
2514 else if (const FreezeInst *FI = dyn_cast<FreezeInst>(V)) {
2515 auto *Op = FI->getOperand(0);
2516 if (isKnownNonZero(Op, Depth, Q) &&
2517 isGuaranteedNotToBePoison(Op, Q.AC, Q.CxtI, Q.DT, Depth))
2518 return true;
2519 }
2520
2521 KnownBits Known(BitWidth);
2522 computeKnownBits(V, DemandedElts, Known, Depth, Q);
2523 return Known.One != 0;
2524}
2525
2526bool isKnownNonZero(const Value* V, unsigned Depth, const Query& Q) {
2527 // FIXME: We currently have no way to represent the DemandedElts of a scalable
2528 // vector
2529 if (isa<ScalableVectorType>(V->getType()))
2530 return false;
2531
2532 auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
2533 APInt DemandedElts =
2534 FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
2535 return isKnownNonZero(V, DemandedElts, Depth, Q);
2536}
2537
2538/// Return true if V2 == V1 + X, where X is known non-zero.
2539static bool isAddOfNonZero(const Value *V1, const Value *V2, unsigned Depth,
2540 const Query &Q) {
2541 const BinaryOperator *BO = dyn_cast<BinaryOperator>(V1);
2542 if (!BO || BO->getOpcode() != Instruction::Add)
2543 return false;
2544 Value *Op = nullptr;
2545 if (V2 == BO->getOperand(0))
2546 Op = BO->getOperand(1);
2547 else if (V2 == BO->getOperand(1))
2548 Op = BO->getOperand(0);
2549 else
2550 return false;
2551 return isKnownNonZero(Op, Depth + 1, Q);
2552}
2553
2554
2555/// Return true if it is known that V1 != V2.
2556static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
2557 const Query &Q) {
2558 if (V1 == V2)
2559 return false;
2560 if (V1->getType() != V2->getType())
2561 // We can't look through casts yet.
2562 return false;
2563
2564 if (Depth >= MaxAnalysisRecursionDepth)
2565 return false;
2566
2567 // See if we can recurse through (exactly one of) our operands. This
2568 // requires our operation be 1-to-1 and map every input value to exactly
2569 // one output value. Such an operation is invertible.
2570 auto *O1 = dyn_cast<Operator>(V1);
2571 auto *O2 = dyn_cast<Operator>(V2);
2572 if (O1 && O2 && O1->getOpcode() == O2->getOpcode()) {
2573 switch (O1->getOpcode()) {
2574 default: break;
2575 case Instruction::Add:
2576 case Instruction::Sub:
2577 // Assume operand order has been canonicalized
2578 if (O1->getOperand(0) == O2->getOperand(0))
2579 return isKnownNonEqual(O1->getOperand(1), O2->getOperand(1),
2580 Depth + 1, Q);
2581 if (O1->getOperand(1) == O2->getOperand(1))
2582 return isKnownNonEqual(O1->getOperand(0), O2->getOperand(0),
2583 Depth + 1, Q);
2584 break;
2585 case Instruction::Mul: {
2586 // invertible if A * B == (A * B) mod 2^N where A, and B are integers
2587 // and N is the bitwdith. The nsw case is non-obvious, but proven by
2588 // alive2: https://alive2.llvm.org/ce/z/Z6D5qK
2589 auto *OBO1 = cast<OverflowingBinaryOperator>(O1);
2590 auto *OBO2 = cast<OverflowingBinaryOperator>(O2);
2591 if ((!OBO1->hasNoUnsignedWrap() || !OBO2->hasNoUnsignedWrap()) &&
2592 (!OBO1->hasNoSignedWrap() || !OBO2->hasNoSignedWrap()))
2593 break;
2594
2595 // Assume operand order has been canonicalized
2596 if (O1->getOperand(1) == O2->getOperand(1) &&
2597 isa<ConstantInt>(O1->getOperand(1)) &&
2598 !cast<ConstantInt>(O1->getOperand(1))->isZero())
2599 return isKnownNonEqual(O1->getOperand(0), O2->getOperand(0),
2600 Depth + 1, Q);
2601 break;
2602 }
2603 case Instruction::SExt:
2604 case Instruction::ZExt:
2605 if (O1->getOperand(0)->getType() == O2->getOperand(0)->getType())
2606 return isKnownNonEqual(O1->getOperand(0), O2->getOperand(0),
2607 Depth + 1, Q);
2608 break;
2609 };
2610 }
2611
2612 if (isAddOfNonZero(V1, V2, Depth, Q) || isAddOfNonZero(V2, V1, Depth, Q))
2613 return true;
2614
2615 if (V1->getType()->isIntOrIntVectorTy()) {
2616 // Are any known bits in V1 contradictory to known bits in V2? If V1
2617 // has a known zero where V2 has a known one, they must not be equal.
2618 KnownBits Known1 = computeKnownBits(V1, Depth, Q);
2619 KnownBits Known2 = computeKnownBits(V2, Depth, Q);
2620
2621 if (Known1.Zero.intersects(Known2.One) ||
2622 Known2.Zero.intersects(Known1.One))
2623 return true;
2624 }
2625 return false;
2626}
2627
2628/// Return true if 'V & Mask' is known to be zero. We use this predicate to
2629/// simplify operations downstream. Mask is known to be zero for bits that V
2630/// cannot have.
2631///
2632/// This function is defined on values with integer type, values with pointer
2633/// type, and vectors of integers. In the case
2634/// where V is a vector, the mask, known zero, and known one values are the
2635/// same width as the vector element, and the bit is set only if it is true
2636/// for all of the elements in the vector.
2637bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth,
2638 const Query &Q) {
2639 KnownBits Known(Mask.getBitWidth());
2640 computeKnownBits(V, Known, Depth, Q);
2641 return Mask.isSubsetOf(Known.Zero);
2642}
2643
2644// Match a signed min+max clamp pattern like smax(smin(In, CHigh), CLow).
2645// Returns the input and lower/upper bounds.
2646static bool isSignedMinMaxClamp(const Value *Select, const Value *&In,
2647 const APInt *&CLow, const APInt *&CHigh) {
2648 assert(isa<Operator>(Select) &&((isa<Operator>(Select) && cast<Operator>
(Select)->getOpcode() == Instruction::Select && "Input should be a Select!"
) ? static_cast<void> (0) : __assert_fail ("isa<Operator>(Select) && cast<Operator>(Select)->getOpcode() == Instruction::Select && \"Input should be a Select!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2650, __PRETTY_FUNCTION__))
2649 cast<Operator>(Select)->getOpcode() == Instruction::Select &&((isa<Operator>(Select) && cast<Operator>
(Select)->getOpcode() == Instruction::Select && "Input should be a Select!"
) ? static_cast<void> (0) : __assert_fail ("isa<Operator>(Select) && cast<Operator>(Select)->getOpcode() == Instruction::Select && \"Input should be a Select!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2650, __PRETTY_FUNCTION__))
2650 "Input should be a Select!")((isa<Operator>(Select) && cast<Operator>
(Select)->getOpcode() == Instruction::Select && "Input should be a Select!"
) ? static_cast<void> (0) : __assert_fail ("isa<Operator>(Select) && cast<Operator>(Select)->getOpcode() == Instruction::Select && \"Input should be a Select!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2650, __PRETTY_FUNCTION__))
;
2651
2652 const Value *LHS = nullptr, *RHS = nullptr;
2653 SelectPatternFlavor SPF = matchSelectPattern(Select, LHS, RHS).Flavor;
2654 if (SPF != SPF_SMAX && SPF != SPF_SMIN)
2655 return false;
2656
2657 if (!match(RHS, m_APInt(CLow)))
2658 return false;
2659
2660 const Value *LHS2 = nullptr, *RHS2 = nullptr;
2661 SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2).Flavor;
2662 if (getInverseMinMaxFlavor(SPF) != SPF2)
2663 return false;
2664
2665 if (!match(RHS2, m_APInt(CHigh)))
2666 return false;
2667
2668 if (SPF == SPF_SMIN)
2669 std::swap(CLow, CHigh);
2670
2671 In = LHS2;
2672 return CLow->sle(*CHigh);
2673}
2674
2675/// For vector constants, loop over the elements and find the constant with the
2676/// minimum number of sign bits. Return 0 if the value is not a vector constant
2677/// or if any element was not analyzed; otherwise, return the count for the
2678/// element with the minimum number of sign bits.
2679static unsigned computeNumSignBitsVectorConstant(const Value *V,
2680 const APInt &DemandedElts,
2681 unsigned TyBits) {
2682 const auto *CV = dyn_cast<Constant>(V);
2683 if (!CV || !isa<FixedVectorType>(CV->getType()))
2684 return 0;
2685
2686 unsigned MinSignBits = TyBits;
2687 unsigned NumElts = cast<FixedVectorType>(CV->getType())->getNumElements();
2688 for (unsigned i = 0; i != NumElts; ++i) {
2689 if (!DemandedElts[i])
2690 continue;
2691 // If we find a non-ConstantInt, bail out.
2692 auto *Elt = dyn_cast_or_null<ConstantInt>(CV->getAggregateElement(i));
2693 if (!Elt)
2694 return 0;
2695
2696 MinSignBits = std::min(MinSignBits, Elt->getValue().getNumSignBits());
2697 }
2698
2699 return MinSignBits;
2700}
2701
2702static unsigned ComputeNumSignBitsImpl(const Value *V,
2703 const APInt &DemandedElts,
2704 unsigned Depth, const Query &Q);
2705
2706static unsigned ComputeNumSignBits(const Value *V, const APInt &DemandedElts,
2707 unsigned Depth, const Query &Q) {
2708 unsigned Result = ComputeNumSignBitsImpl(V, DemandedElts, Depth, Q);
2709 assert(Result > 0 && "At least one sign bit needs to be present!")((Result > 0 && "At least one sign bit needs to be present!"
) ? static_cast<void> (0) : __assert_fail ("Result > 0 && \"At least one sign bit needs to be present!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2709, __PRETTY_FUNCTION__))
;
2710 return Result;
2711}
2712
2713/// Return the number of times the sign bit of the register is replicated into
2714/// the other bits. We know that at least 1 bit is always equal to the sign bit
2715/// (itself), but other cases can give us information. For example, immediately
2716/// after an "ashr X, 2", we know that the top 3 bits are all equal to each
2717/// other, so we return 3. For vectors, return the number of sign bits for the
2718/// vector element with the minimum number of known sign bits of the demanded
2719/// elements in the vector specified by DemandedElts.
2720static unsigned ComputeNumSignBitsImpl(const Value *V,
2721 const APInt &DemandedElts,
2722 unsigned Depth, const Query &Q) {
2723 Type *Ty = V->getType();
2724
2725 // FIXME: We currently have no way to represent the DemandedElts of a scalable
2726 // vector
2727 if (isa<ScalableVectorType>(Ty))
2728 return 1;
2729
2730#ifndef NDEBUG
2731 assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth")((Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth"
) ? static_cast<void> (0) : __assert_fail ("Depth <= MaxAnalysisRecursionDepth && \"Limit Search Depth\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2731, __PRETTY_FUNCTION__))
;
2732
2733 if (auto *FVTy = dyn_cast<FixedVectorType>(Ty)) {
2734 assert(((FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements"
) ? static_cast<void> (0) : __assert_fail ("FVTy->getNumElements() == DemandedElts.getBitWidth() && \"DemandedElt width should equal the fixed vector number of elements\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2736, __PRETTY_FUNCTION__))
2735 FVTy->getNumElements() == DemandedElts.getBitWidth() &&((FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements"
) ? static_cast<void> (0) : __assert_fail ("FVTy->getNumElements() == DemandedElts.getBitWidth() && \"DemandedElt width should equal the fixed vector number of elements\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2736, __PRETTY_FUNCTION__))
2736 "DemandedElt width should equal the fixed vector number of elements")((FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements"
) ? static_cast<void> (0) : __assert_fail ("FVTy->getNumElements() == DemandedElts.getBitWidth() && \"DemandedElt width should equal the fixed vector number of elements\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2736, __PRETTY_FUNCTION__))
;
2737 } else {
2738 assert(DemandedElts == APInt(1, 1) &&((DemandedElts == APInt(1, 1) && "DemandedElt width should be 1 for scalars"
) ? static_cast<void> (0) : __assert_fail ("DemandedElts == APInt(1, 1) && \"DemandedElt width should be 1 for scalars\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2739, __PRETTY_FUNCTION__))
2739 "DemandedElt width should be 1 for scalars")((DemandedElts == APInt(1, 1) && "DemandedElt width should be 1 for scalars"
) ? static_cast<void> (0) : __assert_fail ("DemandedElts == APInt(1, 1) && \"DemandedElt width should be 1 for scalars\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 2739, __PRETTY_FUNCTION__))
;
2740 }
2741#endif
2742
2743 // We return the minimum number of sign bits that are guaranteed to be present
2744 // in V, so for undef we have to conservatively return 1. We don't have the
2745 // same behavior for poison though -- that's a FIXME today.
2746
2747 Type *ScalarTy = Ty->getScalarType();
2748 unsigned TyBits = ScalarTy->isPointerTy() ?
2749 Q.DL.getPointerTypeSizeInBits(ScalarTy) :
2750 Q.DL.getTypeSizeInBits(ScalarTy);
2751
2752 unsigned Tmp, Tmp2;
2753 unsigned FirstAnswer = 1;
2754
2755 // Note that ConstantInt is handled by the general computeKnownBits case
2756 // below.
2757
2758 if (Depth == MaxAnalysisRecursionDepth)
2759 return 1;
2760
2761 if (auto *U = dyn_cast<Operator>(V)) {
2762 switch (Operator::getOpcode(V)) {
2763 default: break;
2764 case Instruction::SExt:
2765 Tmp = TyBits - U->getOperand(0)->getType()->getScalarSizeInBits();
2766 return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q) + Tmp;
2767
2768 case Instruction::SDiv: {
2769 const APInt *Denominator;
2770 // sdiv X, C -> adds log(C) sign bits.
2771 if (match(U->getOperand(1), m_APInt(Denominator))) {
2772
2773 // Ignore non-positive denominator.
2774 if (!Denominator->isStrictlyPositive())
2775 break;
2776
2777 // Calculate the incoming numerator bits.
2778 unsigned NumBits = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2779
2780 // Add floor(log(C)) bits to the numerator bits.
2781 return std::min(TyBits, NumBits + Denominator->logBase2());
2782 }
2783 break;
2784 }
2785
2786 case Instruction::SRem: {
2787 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2788
2789 const APInt *Denominator;
2790 // srem X, C -> we know that the result is within [-C+1,C) when C is a
2791 // positive constant. This let us put a lower bound on the number of sign
2792 // bits.
2793 if (match(U->getOperand(1), m_APInt(Denominator))) {
2794
2795 // Ignore non-positive denominator.
2796 if (Denominator->isStrictlyPositive()) {
2797 // Calculate the leading sign bit constraints by examining the
2798 // denominator. Given that the denominator is positive, there are two
2799 // cases:
2800 //
2801 // 1. The numerator is positive. The result range is [0,C) and
2802 // [0,C) u< (1 << ceilLogBase2(C)).
2803 //
2804 // 2. The numerator is negative. Then the result range is (-C,0] and
2805 // integers in (-C,0] are either 0 or >u (-1 << ceilLogBase2(C)).
2806 //
2807 // Thus a lower bound on the number of sign bits is `TyBits -
2808 // ceilLogBase2(C)`.
2809
2810 unsigned ResBits = TyBits - Denominator->ceilLogBase2();
2811 Tmp = std::max(Tmp, ResBits);
2812 }
2813 }
2814 return Tmp;
2815 }
2816
2817 case Instruction::AShr: {
2818 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2819 // ashr X, C -> adds C sign bits. Vectors too.
2820 const APInt *ShAmt;
2821 if (match(U->getOperand(1), m_APInt(ShAmt))) {
2822 if (ShAmt->uge(TyBits))
2823 break; // Bad shift.
2824 unsigned ShAmtLimited = ShAmt->getZExtValue();
2825 Tmp += ShAmtLimited;
2826 if (Tmp > TyBits) Tmp = TyBits;
2827 }
2828 return Tmp;
2829 }
2830 case Instruction::Shl: {
2831 const APInt *ShAmt;
2832 if (match(U->getOperand(1), m_APInt(ShAmt))) {
2833 // shl destroys sign bits.
2834 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2835 if (ShAmt->uge(TyBits) || // Bad shift.
2836 ShAmt->uge(Tmp)) break; // Shifted all sign bits out.
2837 Tmp2 = ShAmt->getZExtValue();
2838 return Tmp - Tmp2;
2839 }
2840 break;
2841 }
2842 case Instruction::And:
2843 case Instruction::Or:
2844 case Instruction::Xor: // NOT is handled here.
2845 // Logical binary ops preserve the number of sign bits at the worst.
2846 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2847 if (Tmp != 1) {
2848 Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2849 FirstAnswer = std::min(Tmp, Tmp2);
2850 // We computed what we know about the sign bits as our first
2851 // answer. Now proceed to the generic code that uses
2852 // computeKnownBits, and pick whichever answer is better.
2853 }
2854 break;
2855
2856 case Instruction::Select: {
2857 // If we have a clamp pattern, we know that the number of sign bits will
2858 // be the minimum of the clamp min/max range.
2859 const Value *X;
2860 const APInt *CLow, *CHigh;
2861 if (isSignedMinMaxClamp(U, X, CLow, CHigh))
2862 return std::min(CLow->getNumSignBits(), CHigh->getNumSignBits());
2863
2864 Tmp = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2865 if (Tmp == 1) break;
2866 Tmp2 = ComputeNumSignBits(U->getOperand(2), Depth + 1, Q);
2867 return std::min(Tmp, Tmp2);
2868 }
2869
2870 case Instruction::Add:
2871 // Add can have at most one carry bit. Thus we know that the output
2872 // is, at worst, one more bit than the inputs.
2873 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2874 if (Tmp == 1) break;
2875
2876 // Special case decrementing a value (ADD X, -1):
2877 if (const auto *CRHS = dyn_cast<Constant>(U->getOperand(1)))
2878 if (CRHS->isAllOnesValue()) {
2879 KnownBits Known(TyBits);
2880 computeKnownBits(U->getOperand(0), Known, Depth + 1, Q);
2881
2882 // If the input is known to be 0 or 1, the output is 0/-1, which is
2883 // all sign bits set.
2884 if ((Known.Zero | 1).isAllOnesValue())
2885 return TyBits;
2886
2887 // If we are subtracting one from a positive number, there is no carry
2888 // out of the result.
2889 if (Known.isNonNegative())
2890 return Tmp;
2891 }
2892
2893 Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2894 if (Tmp2 == 1) break;
2895 return std::min(Tmp, Tmp2) - 1;
2896
2897 case Instruction::Sub:
2898 Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2899 if (Tmp2 == 1) break;
2900
2901 // Handle NEG.
2902 if (const auto *CLHS = dyn_cast<Constant>(U->getOperand(0)))
2903 if (CLHS->isNullValue()) {
2904 KnownBits Known(TyBits);
2905 computeKnownBits(U->getOperand(1), Known, Depth + 1, Q);
2906 // If the input is known to be 0 or 1, the output is 0/-1, which is
2907 // all sign bits set.
2908 if ((Known.Zero | 1).isAllOnesValue())
2909 return TyBits;
2910
2911 // If the input is known to be positive (the sign bit is known clear),
2912 // the output of the NEG has the same number of sign bits as the
2913 // input.
2914 if (Known.isNonNegative())
2915 return Tmp2;
2916
2917 // Otherwise, we treat this like a SUB.
2918 }
2919
2920 // Sub can have at most one carry bit. Thus we know that the output
2921 // is, at worst, one more bit than the inputs.
2922 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2923 if (Tmp == 1) break;
2924 return std::min(Tmp, Tmp2) - 1;
2925
2926 case Instruction::Mul: {
2927 // The output of the Mul can be at most twice the valid bits in the
2928 // inputs.
2929 unsigned SignBitsOp0 = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2930 if (SignBitsOp0 == 1) break;
2931 unsigned SignBitsOp1 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
2932 if (SignBitsOp1 == 1) break;
2933 unsigned OutValidBits =
2934 (TyBits - SignBitsOp0 + 1) + (TyBits - SignBitsOp1 + 1);
2935 return OutValidBits > TyBits ? 1 : TyBits - OutValidBits + 1;
2936 }
2937
2938 case Instruction::PHI: {
2939 const PHINode *PN = cast<PHINode>(U);
2940 unsigned NumIncomingValues = PN->getNumIncomingValues();
2941 // Don't analyze large in-degree PHIs.
2942 if (NumIncomingValues > 4) break;
2943 // Unreachable blocks may have zero-operand PHI nodes.
2944 if (NumIncomingValues == 0) break;
2945
2946 // Take the minimum of all incoming values. This can't infinitely loop
2947 // because of our depth threshold.
2948 Query RecQ = Q;
2949 Tmp = TyBits;
2950 for (unsigned i = 0, e = NumIncomingValues; i != e; ++i) {
2951 if (Tmp == 1) return Tmp;
2952 RecQ.CxtI = PN->getIncomingBlock(i)->getTerminator();
2953 Tmp = std::min(
2954 Tmp, ComputeNumSignBits(PN->getIncomingValue(i), Depth + 1, RecQ));
2955 }
2956 return Tmp;
2957 }
2958
2959 case Instruction::Trunc:
2960 // FIXME: it's tricky to do anything useful for this, but it is an
2961 // important case for targets like X86.
2962 break;
2963
2964 case Instruction::ExtractElement:
2965 // Look through extract element. At the moment we keep this simple and
2966 // skip tracking the specific element. But at least we might find
2967 // information valid for all elements of the vector (for example if vector
2968 // is sign extended, shifted, etc).
2969 return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
2970
2971 case Instruction::ShuffleVector: {
2972 // Collect the minimum number of sign bits that are shared by every vector
2973 // element referenced by the shuffle.
2974 auto *Shuf = dyn_cast<ShuffleVectorInst>(U);
2975 if (!Shuf) {
2976 // FIXME: Add support for shufflevector constant expressions.
2977 return 1;
2978 }
2979 APInt DemandedLHS, DemandedRHS;
2980 // For undef elements, we don't know anything about the common state of
2981 // the shuffle result.
2982 if (!getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS))
2983 return 1;
2984 Tmp = std::numeric_limits<unsigned>::max();
2985 if (!!DemandedLHS) {
2986 const Value *LHS = Shuf->getOperand(0);
2987 Tmp = ComputeNumSignBits(LHS, DemandedLHS, Depth + 1, Q);
2988 }
2989 // If we don't know anything, early out and try computeKnownBits
2990 // fall-back.
2991 if (Tmp == 1)
2992 break;
2993 if (!!DemandedRHS) {
2994 const Value *RHS = Shuf->getOperand(1);
2995 Tmp2 = ComputeNumSignBits(RHS, DemandedRHS, Depth + 1, Q);
2996 Tmp = std::min(Tmp, Tmp2);
2997 }
2998 // If we don't know anything, early out and try computeKnownBits
2999 // fall-back.
3000 if (Tmp == 1)
3001 break;
3002 assert(Tmp <= TyBits && "Failed to determine minimum sign bits")((Tmp <= TyBits && "Failed to determine minimum sign bits"
) ? static_cast<void> (0) : __assert_fail ("Tmp <= TyBits && \"Failed to determine minimum sign bits\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3002, __PRETTY_FUNCTION__))
;
3003 return Tmp;
3004 }
3005 case Instruction::Call: {
3006 if (const auto *II = dyn_cast<IntrinsicInst>(U)) {
3007 switch (II->getIntrinsicID()) {
3008 default: break;
3009 case Intrinsic::abs:
3010 Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
3011 if (Tmp == 1) break;
3012
3013 // Absolute value reduces number of sign bits by at most 1.
3014 return Tmp - 1;
3015 }
3016 }
3017 }
3018 }
3019 }
3020
3021 // Finally, if we can prove that the top bits of the result are 0's or 1's,
3022 // use this information.
3023
3024 // If we can examine all elements of a vector constant successfully, we're
3025 // done (we can't do any better than that). If not, keep trying.
3026 if (unsigned VecSignBits =
3027 computeNumSignBitsVectorConstant(V, DemandedElts, TyBits))
3028 return VecSignBits;
3029
3030 KnownBits Known(TyBits);
3031 computeKnownBits(V, DemandedElts, Known, Depth, Q);
3032
3033 // If we know that the sign bit is either zero or one, determine the number of
3034 // identical bits in the top of the input value.
3035 return std::max(FirstAnswer, Known.countMinSignBits());
3036}
3037
3038/// This function computes the integer multiple of Base that equals V.
3039/// If successful, it returns true and returns the multiple in
3040/// Multiple. If unsuccessful, it returns false. It looks
3041/// through SExt instructions only if LookThroughSExt is true.
3042bool llvm::ComputeMultiple(Value *V, unsigned Base, Value *&Multiple,
3043 bool LookThroughSExt, unsigned Depth) {
3044 assert(V && "No Value?")((V && "No Value?") ? static_cast<void> (0) : __assert_fail
("V && \"No Value?\"", "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3044, __PRETTY_FUNCTION__))
;
3045 assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth")((Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth"
) ? static_cast<void> (0) : __assert_fail ("Depth <= MaxAnalysisRecursionDepth && \"Limit Search Depth\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3045, __PRETTY_FUNCTION__))
;
3046 assert(V->getType()->isIntegerTy() && "Not integer or pointer type!")((V->getType()->isIntegerTy() && "Not integer or pointer type!"
) ? static_cast<void> (0) : __assert_fail ("V->getType()->isIntegerTy() && \"Not integer or pointer type!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3046, __PRETTY_FUNCTION__))
;
3047
3048 Type *T = V->getType();
3049
3050 ConstantInt *CI = dyn_cast<ConstantInt>(V);
3051
3052 if (Base == 0)
3053 return false;
3054
3055 if (Base == 1) {
3056 Multiple = V;
3057 return true;
3058 }
3059
3060 ConstantExpr *CO = dyn_cast<ConstantExpr>(V);
3061 Constant *BaseVal = ConstantInt::get(T, Base);
3062 if (CO && CO == BaseVal) {
3063 // Multiple is 1.
3064 Multiple = ConstantInt::get(T, 1);
3065 return true;
3066 }
3067
3068 if (CI && CI->getZExtValue() % Base == 0) {
3069 Multiple = ConstantInt::get(T, CI->getZExtValue() / Base);
3070 return true;
3071 }
3072
3073 if (Depth == MaxAnalysisRecursionDepth) return false;
3074
3075 Operator *I = dyn_cast<Operator>(V);
3076 if (!I) return false;
3077
3078 switch (I->getOpcode()) {
3079 default: break;
3080 case Instruction::SExt:
3081 if (!LookThroughSExt) return false;
3082 // otherwise fall through to ZExt
3083 LLVM_FALLTHROUGH[[gnu::fallthrough]];
3084 case Instruction::ZExt:
3085 return ComputeMultiple(I->getOperand(0), Base, Multiple,
3086 LookThroughSExt, Depth+1);
3087 case Instruction::Shl:
3088 case Instruction::Mul: {
3089 Value *Op0 = I->getOperand(0);
3090 Value *Op1 = I->getOperand(1);
3091
3092 if (I->getOpcode() == Instruction::Shl) {
3093 ConstantInt *Op1CI = dyn_cast<ConstantInt>(Op1);
3094 if (!Op1CI) return false;
3095 // Turn Op0 << Op1 into Op0 * 2^Op1
3096 APInt Op1Int = Op1CI->getValue();
3097 uint64_t BitToSet = Op1Int.getLimitedValue(Op1Int.getBitWidth() - 1);
3098 APInt API(Op1Int.getBitWidth(), 0);
3099 API.setBit(BitToSet);
3100 Op1 = ConstantInt::get(V->getContext(), API);
3101 }
3102
3103 Value *Mul0 = nullptr;
3104 if (ComputeMultiple(Op0, Base, Mul0, LookThroughSExt, Depth+1)) {
3105 if (Constant *Op1C = dyn_cast<Constant>(Op1))
3106 if (Constant *MulC = dyn_cast<Constant>(Mul0)) {
3107 if (Op1C->getType()->getPrimitiveSizeInBits().getFixedSize() <
3108 MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
3109 Op1C = ConstantExpr::getZExt(Op1C, MulC->getType());
3110 if (Op1C->getType()->getPrimitiveSizeInBits().getFixedSize() >
3111 MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
3112 MulC = ConstantExpr::getZExt(MulC, Op1C->getType());
3113
3114 // V == Base * (Mul0 * Op1), so return (Mul0 * Op1)
3115 Multiple = ConstantExpr::getMul(MulC, Op1C);
3116 return true;
3117 }
3118
3119 if (ConstantInt *Mul0CI = dyn_cast<ConstantInt>(Mul0))
3120 if (Mul0CI->getValue() == 1) {
3121 // V == Base * Op1, so return Op1
3122 Multiple = Op1;
3123 return true;
3124 }
3125 }
3126
3127 Value *Mul1 = nullptr;
3128 if (ComputeMultiple(Op1, Base, Mul1, LookThroughSExt, Depth+1)) {
3129 if (Constant *Op0C = dyn_cast<Constant>(Op0))
3130 if (Constant *MulC = dyn_cast<Constant>(Mul1)) {
3131 if (Op0C->getType()->getPrimitiveSizeInBits().getFixedSize() <
3132 MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
3133 Op0C = ConstantExpr::getZExt(Op0C, MulC->getType());
3134 if (Op0C->getType()->getPrimitiveSizeInBits().getFixedSize() >
3135 MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
3136 MulC = ConstantExpr::getZExt(MulC, Op0C->getType());
3137
3138 // V == Base * (Mul1 * Op0), so return (Mul1 * Op0)
3139 Multiple = ConstantExpr::getMul(MulC, Op0C);
3140 return true;
3141 }
3142
3143 if (ConstantInt *Mul1CI = dyn_cast<ConstantInt>(Mul1))
3144 if (Mul1CI->getValue() == 1) {
3145 // V == Base * Op0, so return Op0
3146 Multiple = Op0;
3147 return true;
3148 }
3149 }
3150 }
3151 }
3152
3153 // We could not determine if V is a multiple of Base.
3154 return false;
3155}
3156
3157Intrinsic::ID llvm::getIntrinsicForCallSite(const CallBase &CB,
3158 const TargetLibraryInfo *TLI) {
3159 const Function *F = CB.getCalledFunction();
3160 if (!F)
3161 return Intrinsic::not_intrinsic;
3162
3163 if (F->isIntrinsic())
3164 return F->getIntrinsicID();
3165
3166 // We are going to infer semantics of a library function based on mapping it
3167 // to an LLVM intrinsic. Check that the library function is available from
3168 // this callbase and in this environment.
3169 LibFunc Func;
3170 if (F->hasLocalLinkage() || !TLI || !TLI->getLibFunc(CB, Func) ||
3171 !CB.onlyReadsMemory())
3172 return Intrinsic::not_intrinsic;
3173
3174 switch (Func) {
3175 default:
3176 break;
3177 case LibFunc_sin:
3178 case LibFunc_sinf:
3179 case LibFunc_sinl:
3180 return Intrinsic::sin;
3181 case LibFunc_cos:
3182 case LibFunc_cosf:
3183 case LibFunc_cosl:
3184 return Intrinsic::cos;
3185 case LibFunc_exp:
3186 case LibFunc_expf:
3187 case LibFunc_expl:
3188 return Intrinsic::exp;
3189 case LibFunc_exp2:
3190 case LibFunc_exp2f:
3191 case LibFunc_exp2l:
3192 return Intrinsic::exp2;
3193 case LibFunc_log:
3194 case LibFunc_logf:
3195 case LibFunc_logl:
3196 return Intrinsic::log;
3197 case LibFunc_log10:
3198 case LibFunc_log10f:
3199 case LibFunc_log10l:
3200 return Intrinsic::log10;
3201 case LibFunc_log2:
3202 case LibFunc_log2f:
3203 case LibFunc_log2l:
3204 return Intrinsic::log2;
3205 case LibFunc_fabs:
3206 case LibFunc_fabsf:
3207 case LibFunc_fabsl:
3208 return Intrinsic::fabs;
3209 case LibFunc_fmin:
3210 case LibFunc_fminf:
3211 case LibFunc_fminl:
3212 return Intrinsic::minnum;
3213 case LibFunc_fmax:
3214 case LibFunc_fmaxf:
3215 case LibFunc_fmaxl:
3216 return Intrinsic::maxnum;
3217 case LibFunc_copysign:
3218 case LibFunc_copysignf:
3219 case LibFunc_copysignl:
3220 return Intrinsic::copysign;
3221 case LibFunc_floor:
3222 case LibFunc_floorf:
3223 case LibFunc_floorl:
3224 return Intrinsic::floor;
3225 case LibFunc_ceil:
3226 case LibFunc_ceilf:
3227 case LibFunc_ceill:
3228 return Intrinsic::ceil;
3229 case LibFunc_trunc:
3230 case LibFunc_truncf:
3231 case LibFunc_truncl:
3232 return Intrinsic::trunc;
3233 case LibFunc_rint:
3234 case LibFunc_rintf:
3235 case LibFunc_rintl:
3236 return Intrinsic::rint;
3237 case LibFunc_nearbyint:
3238 case LibFunc_nearbyintf:
3239 case LibFunc_nearbyintl:
3240 return Intrinsic::nearbyint;
3241 case LibFunc_round:
3242 case LibFunc_roundf:
3243 case LibFunc_roundl:
3244 return Intrinsic::round;
3245 case LibFunc_roundeven:
3246 case LibFunc_roundevenf:
3247 case LibFunc_roundevenl:
3248 return Intrinsic::roundeven;
3249 case LibFunc_pow:
3250 case LibFunc_powf:
3251 case LibFunc_powl:
3252 return Intrinsic::pow;
3253 case LibFunc_sqrt:
3254 case LibFunc_sqrtf:
3255 case LibFunc_sqrtl:
3256 return Intrinsic::sqrt;
3257 }
3258
3259 return Intrinsic::not_intrinsic;
3260}
3261
3262/// Return true if we can prove that the specified FP value is never equal to
3263/// -0.0.
3264/// NOTE: Do not check 'nsz' here because that fast-math-flag does not guarantee
3265/// that a value is not -0.0. It only guarantees that -0.0 may be treated
3266/// the same as +0.0 in floating-point ops.
3267///
3268/// NOTE: this function will need to be revisited when we support non-default
3269/// rounding modes!
3270bool llvm::CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI,
3271 unsigned Depth) {
3272 if (auto *CFP = dyn_cast<ConstantFP>(V))
3273 return !CFP->getValueAPF().isNegZero();
3274
3275 if (Depth == MaxAnalysisRecursionDepth)
3276 return false;
3277
3278 auto *Op = dyn_cast<Operator>(V);
3279 if (!Op)
3280 return false;
3281
3282 // (fadd x, 0.0) is guaranteed to return +0.0, not -0.0.
3283 if (match(Op, m_FAdd(m_Value(), m_PosZeroFP())))
3284 return true;
3285
3286 // sitofp and uitofp turn into +0.0 for zero.
3287 if (isa<SIToFPInst>(Op) || isa<UIToFPInst>(Op))
3288 return true;
3289
3290 if (auto *Call = dyn_cast<CallInst>(Op)) {
3291 Intrinsic::ID IID = getIntrinsicForCallSite(*Call, TLI);
3292 switch (IID) {
3293 default:
3294 break;
3295 // sqrt(-0.0) = -0.0, no other negative results are possible.
3296 case Intrinsic::sqrt:
3297 case Intrinsic::canonicalize:
3298 return CannotBeNegativeZero(Call->getArgOperand(0), TLI, Depth + 1);
3299 // fabs(x) != -0.0
3300 case Intrinsic::fabs:
3301 return true;
3302 }
3303 }
3304
3305 return false;
3306}
3307
3308/// If \p SignBitOnly is true, test for a known 0 sign bit rather than a
3309/// standard ordered compare. e.g. make -0.0 olt 0.0 be true because of the sign
3310/// bit despite comparing equal.
3311static bool cannotBeOrderedLessThanZeroImpl(const Value *V,
3312 const TargetLibraryInfo *TLI,
3313 bool SignBitOnly,
3314 unsigned Depth) {
3315 // TODO: This function does not do the right thing when SignBitOnly is true
3316 // and we're lowering to a hypothetical IEEE 754-compliant-but-evil platform
3317 // which flips the sign bits of NaNs. See
3318 // https://llvm.org/bugs/show_bug.cgi?id=31702.
3319
3320 if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
3321 return !CFP->getValueAPF().isNegative() ||
3322 (!SignBitOnly && CFP->getValueAPF().isZero());
3323 }
3324
3325 // Handle vector of constants.
3326 if (auto *CV = dyn_cast<Constant>(V)) {
3327 if (auto *CVFVTy = dyn_cast<FixedVectorType>(CV->getType())) {
3328 unsigned NumElts = CVFVTy->getNumElements();
3329 for (unsigned i = 0; i != NumElts; ++i) {
3330 auto *CFP = dyn_cast_or_null<ConstantFP>(CV->getAggregateElement(i));
3331 if (!CFP)
3332 return false;
3333 if (CFP->getValueAPF().isNegative() &&
3334 (SignBitOnly || !CFP->getValueAPF().isZero()))
3335 return false;
3336 }
3337
3338 // All non-negative ConstantFPs.
3339 return true;
3340 }
3341 }
3342
3343 if (Depth == MaxAnalysisRecursionDepth)
3344 return false;
3345
3346 const Operator *I = dyn_cast<Operator>(V);
3347 if (!I)
3348 return false;
3349
3350 switch (I->getOpcode()) {
3351 default:
3352 break;
3353 // Unsigned integers are always nonnegative.
3354 case Instruction::UIToFP:
3355 return true;
3356 case Instruction::FMul:
3357 case Instruction::FDiv:
3358 // X * X is always non-negative or a NaN.
3359 // X / X is always exactly 1.0 or a NaN.
3360 if (I->getOperand(0) == I->getOperand(1) &&
3361 (!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()))
3362 return true;
3363
3364 LLVM_FALLTHROUGH[[gnu::fallthrough]];
3365 case Instruction::FAdd:
3366 case Instruction::FRem:
3367 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
3368 Depth + 1) &&
3369 cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
3370 Depth + 1);
3371 case Instruction::Select:
3372 return cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
3373 Depth + 1) &&
3374 cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
3375 Depth + 1);
3376 case Instruction::FPExt:
3377 case Instruction::FPTrunc:
3378 // Widening/narrowing never change sign.
3379 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
3380 Depth + 1);
3381 case Instruction::ExtractElement:
3382 // Look through extract element. At the moment we keep this simple and skip
3383 // tracking the specific element. But at least we might find information
3384 // valid for all elements of the vector.
3385 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
3386 Depth + 1);
3387 case Instruction::Call:
3388 const auto *CI = cast<CallInst>(I);
3389 Intrinsic::ID IID = getIntrinsicForCallSite(*CI, TLI);
3390 switch (IID) {
3391 default:
3392 break;
3393 case Intrinsic::maxnum: {
3394 Value *V0 = I->getOperand(0), *V1 = I->getOperand(1);
3395 auto isPositiveNum = [&](Value *V) {
3396 if (SignBitOnly) {
3397 // With SignBitOnly, this is tricky because the result of
3398 // maxnum(+0.0, -0.0) is unspecified. Just check if the operand is
3399 // a constant strictly greater than 0.0.
3400 const APFloat *C;
3401 return match(V, m_APFloat(C)) &&
3402 *C > APFloat::getZero(C->getSemantics());
3403 }
3404
3405 // -0.0 compares equal to 0.0, so if this operand is at least -0.0,
3406 // maxnum can't be ordered-less-than-zero.
3407 return isKnownNeverNaN(V, TLI) &&
3408 cannotBeOrderedLessThanZeroImpl(V, TLI, false, Depth + 1);
3409 };
3410
3411 // TODO: This could be improved. We could also check that neither operand
3412 // has its sign bit set (and at least 1 is not-NAN?).
3413 return isPositiveNum(V0) || isPositiveNum(V1);
3414 }
3415
3416 case Intrinsic::maximum:
3417 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
3418 Depth + 1) ||
3419 cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
3420 Depth + 1);
3421 case Intrinsic::minnum:
3422 case Intrinsic::minimum:
3423 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
3424 Depth + 1) &&
3425 cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
3426 Depth + 1);
3427 case Intrinsic::exp:
3428 case Intrinsic::exp2:
3429 case Intrinsic::fabs:
3430 return true;
3431
3432 case Intrinsic::sqrt:
3433 // sqrt(x) is always >= -0 or NaN. Moreover, sqrt(x) == -0 iff x == -0.
3434 if (!SignBitOnly)
3435 return true;
3436 return CI->hasNoNaNs() && (CI->hasNoSignedZeros() ||
3437 CannotBeNegativeZero(CI->getOperand(0), TLI));
3438
3439 case Intrinsic::powi:
3440 if (ConstantInt *Exponent = dyn_cast<ConstantInt>(I->getOperand(1))) {
3441 // powi(x,n) is non-negative if n is even.
3442 if (Exponent->getBitWidth() <= 64 && Exponent->getSExtValue() % 2u == 0)
3443 return true;
3444 }
3445 // TODO: This is not correct. Given that exp is an integer, here are the
3446 // ways that pow can return a negative value:
3447 //
3448 // pow(x, exp) --> negative if exp is odd and x is negative.
3449 // pow(-0, exp) --> -inf if exp is negative odd.
3450 // pow(-0, exp) --> -0 if exp is positive odd.
3451 // pow(-inf, exp) --> -0 if exp is negative odd.
3452 // pow(-inf, exp) --> -inf if exp is positive odd.
3453 //
3454 // Therefore, if !SignBitOnly, we can return true if x >= +0 or x is NaN,
3455 // but we must return false if x == -0. Unfortunately we do not currently
3456 // have a way of expressing this constraint. See details in
3457 // https://llvm.org/bugs/show_bug.cgi?id=31702.
3458 return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
3459 Depth + 1);
3460
3461 case Intrinsic::fma:
3462 case Intrinsic::fmuladd:
3463 // x*x+y is non-negative if y is non-negative.
3464 return I->getOperand(0) == I->getOperand(1) &&
3465 (!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()) &&
3466 cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
3467 Depth + 1);
3468 }
3469 break;
3470 }
3471 return false;
3472}
3473
3474bool llvm::CannotBeOrderedLessThanZero(const Value *V,
3475 const TargetLibraryInfo *TLI) {
3476 return cannotBeOrderedLessThanZeroImpl(V, TLI, false, 0);
3477}
3478
3479bool llvm::SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI) {
3480 return cannotBeOrderedLessThanZeroImpl(V, TLI, true, 0);
3481}
3482
3483bool llvm::isKnownNeverInfinity(const Value *V, const TargetLibraryInfo *TLI,
3484 unsigned Depth) {
3485 assert(V->getType()->isFPOrFPVectorTy() && "Querying for Inf on non-FP type")((V->getType()->isFPOrFPVectorTy() && "Querying for Inf on non-FP type"
) ? static_cast<void> (0) : __assert_fail ("V->getType()->isFPOrFPVectorTy() && \"Querying for Inf on non-FP type\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3485, __PRETTY_FUNCTION__))
;
3486
3487 // If we're told that infinities won't happen, assume they won't.
3488 if (auto *FPMathOp = dyn_cast<FPMathOperator>(V))
3489 if (FPMathOp->hasNoInfs())
3490 return true;
3491
3492 // Handle scalar constants.
3493 if (auto *CFP = dyn_cast<ConstantFP>(V))
3494 return !CFP->isInfinity();
3495
3496 if (Depth == MaxAnalysisRecursionDepth)
3497 return false;
3498
3499 if (auto *Inst = dyn_cast<Instruction>(V)) {
3500 switch (Inst->getOpcode()) {
3501 case Instruction::Select: {
3502 return isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1) &&
3503 isKnownNeverInfinity(Inst->getOperand(2), TLI, Depth + 1);
3504 }
3505 case Instruction::SIToFP:
3506 case Instruction::UIToFP: {
3507 // Get width of largest magnitude integer (remove a bit if signed).
3508 // This still works for a signed minimum value because the largest FP
3509 // value is scaled by some fraction close to 2.0 (1.0 + 0.xxxx).
3510 int IntSize = Inst->getOperand(0)->getType()->getScalarSizeInBits();
3511 if (Inst->getOpcode() == Instruction::SIToFP)
3512 --IntSize;
3513
3514 // If the exponent of the largest finite FP value can hold the largest
3515 // integer, the result of the cast must be finite.
3516 Type *FPTy = Inst->getType()->getScalarType();
3517 return ilogb(APFloat::getLargest(FPTy->getFltSemantics())) >= IntSize;
3518 }
3519 default:
3520 break;
3521 }
3522 }
3523
3524 // try to handle fixed width vector constants
3525 auto *VFVTy = dyn_cast<FixedVectorType>(V->getType());
3526 if (VFVTy && isa<Constant>(V)) {
3527 // For vectors, verify that each element is not infinity.
3528 unsigned NumElts = VFVTy->getNumElements();
3529 for (unsigned i = 0; i != NumElts; ++i) {
3530 Constant *Elt = cast<Constant>(V)->getAggregateElement(i);
3531 if (!Elt)
3532 return false;
3533 if (isa<UndefValue>(Elt))
3534 continue;
3535 auto *CElt = dyn_cast<ConstantFP>(Elt);
3536 if (!CElt || CElt->isInfinity())
3537 return false;
3538 }
3539 // All elements were confirmed non-infinity or undefined.
3540 return true;
3541 }
3542
3543 // was not able to prove that V never contains infinity
3544 return false;
3545}
3546
3547bool llvm::isKnownNeverNaN(const Value *V, const TargetLibraryInfo *TLI,
3548 unsigned Depth) {
3549 assert(V->getType()->isFPOrFPVectorTy() && "Querying for NaN on non-FP type")((V->getType()->isFPOrFPVectorTy() && "Querying for NaN on non-FP type"
) ? static_cast<void> (0) : __assert_fail ("V->getType()->isFPOrFPVectorTy() && \"Querying for NaN on non-FP type\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3549, __PRETTY_FUNCTION__))
;
3550
3551 // If we're told that NaNs won't happen, assume they won't.
3552 if (auto *FPMathOp = dyn_cast<FPMathOperator>(V))
3553 if (FPMathOp->hasNoNaNs())
3554 return true;
3555
3556 // Handle scalar constants.
3557 if (auto *CFP = dyn_cast<ConstantFP>(V))
3558 return !CFP->isNaN();
3559
3560 if (Depth == MaxAnalysisRecursionDepth)
3561 return false;
3562
3563 if (auto *Inst = dyn_cast<Instruction>(V)) {
3564 switch (Inst->getOpcode()) {
3565 case Instruction::FAdd:
3566 case Instruction::FSub:
3567 // Adding positive and negative infinity produces NaN.
3568 return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1) &&
3569 isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
3570 (isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1) ||
3571 isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1));
3572
3573 case Instruction::FMul:
3574 // Zero multiplied with infinity produces NaN.
3575 // FIXME: If neither side can be zero fmul never produces NaN.
3576 return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1) &&
3577 isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1) &&
3578 isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
3579 isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1);
3580
3581 case Instruction::FDiv:
3582 case Instruction::FRem:
3583 // FIXME: Only 0/0, Inf/Inf, Inf REM x and x REM 0 produce NaN.
3584 return false;
3585
3586 case Instruction::Select: {
3587 return isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
3588 isKnownNeverNaN(Inst->getOperand(2), TLI, Depth + 1);
3589 }
3590 case Instruction::SIToFP:
3591 case Instruction::UIToFP:
3592 return true;
3593 case Instruction::FPTrunc:
3594 case Instruction::FPExt:
3595 return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1);
3596 default:
3597 break;
3598 }
3599 }
3600
3601 if (const auto *II = dyn_cast<IntrinsicInst>(V)) {
3602 switch (II->getIntrinsicID()) {
3603 case Intrinsic::canonicalize:
3604 case Intrinsic::fabs:
3605 case Intrinsic::copysign:
3606 case Intrinsic::exp:
3607 case Intrinsic::exp2:
3608 case Intrinsic::floor:
3609 case Intrinsic::ceil:
3610 case Intrinsic::trunc:
3611 case Intrinsic::rint:
3612 case Intrinsic::nearbyint:
3613 case Intrinsic::round:
3614 case Intrinsic::roundeven:
3615 return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1);
3616 case Intrinsic::sqrt:
3617 return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1) &&
3618 CannotBeOrderedLessThanZero(II->getArgOperand(0), TLI);
3619 case Intrinsic::minnum:
3620 case Intrinsic::maxnum:
3621 // If either operand is not NaN, the result is not NaN.
3622 return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1) ||
3623 isKnownNeverNaN(II->getArgOperand(1), TLI, Depth + 1);
3624 default:
3625 return false;
3626 }
3627 }
3628
3629 // Try to handle fixed width vector constants
3630 auto *VFVTy = dyn_cast<FixedVectorType>(V->getType());
3631 if (VFVTy && isa<Constant>(V)) {
3632 // For vectors, verify that each element is not NaN.
3633 unsigned NumElts = VFVTy->getNumElements();
3634 for (unsigned i = 0; i != NumElts; ++i) {
3635 Constant *Elt = cast<Constant>(V)->getAggregateElement(i);
3636 if (!Elt)
3637 return false;
3638 if (isa<UndefValue>(Elt))
3639 continue;
3640 auto *CElt = dyn_cast<ConstantFP>(Elt);
3641 if (!CElt || CElt->isNaN())
3642 return false;
3643 }
3644 // All elements were confirmed not-NaN or undefined.
3645 return true;
3646 }
3647
3648 // Was not able to prove that V never contains NaN
3649 return false;
3650}
3651
3652Value *llvm::isBytewiseValue(Value *V, const DataLayout &DL) {
3653
3654 // All byte-wide stores are splatable, even of arbitrary variables.
3655 if (V->getType()->isIntegerTy(8))
3656 return V;
3657
3658 LLVMContext &Ctx = V->getContext();
3659
3660 // Undef don't care.
3661 auto *UndefInt8 = UndefValue::get(Type::getInt8Ty(Ctx));
3662 if (isa<UndefValue>(V))
3663 return UndefInt8;
3664
3665 // Return Undef for zero-sized type.
3666 if (!DL.getTypeStoreSize(V->getType()).isNonZero())
3667 return UndefInt8;
3668
3669 Constant *C = dyn_cast<Constant>(V);
3670 if (!C) {
3671 // Conceptually, we could handle things like:
3672 // %a = zext i8 %X to i16
3673 // %b = shl i16 %a, 8
3674 // %c = or i16 %a, %b
3675 // but until there is an example that actually needs this, it doesn't seem
3676 // worth worrying about.
3677 return nullptr;
3678 }
3679
3680 // Handle 'null' ConstantArrayZero etc.
3681 if (C->isNullValue())
3682 return Constant::getNullValue(Type::getInt8Ty(Ctx));
3683
3684 // Constant floating-point values can be handled as integer values if the
3685 // corresponding integer value is "byteable". An important case is 0.0.
3686 if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
3687 Type *Ty = nullptr;
3688 if (CFP->getType()->isHalfTy())
3689 Ty = Type::getInt16Ty(Ctx);
3690 else if (CFP->getType()->isFloatTy())
3691 Ty = Type::getInt32Ty(Ctx);
3692 else if (CFP->getType()->isDoubleTy())
3693 Ty = Type::getInt64Ty(Ctx);
3694 // Don't handle long double formats, which have strange constraints.
3695 return Ty ? isBytewiseValue(ConstantExpr::getBitCast(CFP, Ty), DL)
3696 : nullptr;
3697 }
3698
3699 // We can handle constant integers that are multiple of 8 bits.
3700 if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
3701 if (CI->getBitWidth() % 8 == 0) {
3702 assert(CI->getBitWidth() > 8 && "8 bits should be handled above!")((CI->getBitWidth() > 8 && "8 bits should be handled above!"
) ? static_cast<void> (0) : __assert_fail ("CI->getBitWidth() > 8 && \"8 bits should be handled above!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3702, __PRETTY_FUNCTION__))
;
3703 if (!CI->getValue().isSplat(8))
3704 return nullptr;
3705 return ConstantInt::get(Ctx, CI->getValue().trunc(8));
3706 }
3707 }
3708
3709 if (auto *CE = dyn_cast<ConstantExpr>(C)) {
3710 if (CE->getOpcode() == Instruction::IntToPtr) {
3711 if (auto *PtrTy = dyn_cast<PointerType>(CE->getType())) {
3712 unsigned BitWidth = DL.getPointerSizeInBits(PtrTy->getAddressSpace());
3713 return isBytewiseValue(
3714 ConstantExpr::getIntegerCast(CE->getOperand(0),
3715 Type::getIntNTy(Ctx, BitWidth), false),
3716 DL);
3717 }
3718 }
3719 }
3720
3721 auto Merge = [&](Value *LHS, Value *RHS) -> Value * {
3722 if (LHS == RHS)
3723 return LHS;
3724 if (!LHS || !RHS)
3725 return nullptr;
3726 if (LHS == UndefInt8)
3727 return RHS;
3728 if (RHS == UndefInt8)
3729 return LHS;
3730 return nullptr;
3731 };
3732
3733 if (ConstantDataSequential *CA = dyn_cast<ConstantDataSequential>(C)) {
3734 Value *Val = UndefInt8;
3735 for (unsigned I = 0, E = CA->getNumElements(); I != E; ++I)
3736 if (!(Val = Merge(Val, isBytewiseValue(CA->getElementAsConstant(I), DL))))
3737 return nullptr;
3738 return Val;
3739 }
3740
3741 if (isa<ConstantAggregate>(C)) {
3742 Value *Val = UndefInt8;
3743 for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I)
3744 if (!(Val = Merge(Val, isBytewiseValue(C->getOperand(I), DL))))
3745 return nullptr;
3746 return Val;
3747 }
3748
3749 // Don't try to handle the handful of other constants.
3750 return nullptr;
3751}
3752
3753// This is the recursive version of BuildSubAggregate. It takes a few different
3754// arguments. Idxs is the index within the nested struct From that we are
3755// looking at now (which is of type IndexedType). IdxSkip is the number of
3756// indices from Idxs that should be left out when inserting into the resulting
3757// struct. To is the result struct built so far, new insertvalue instructions
3758// build on that.
3759static Value *BuildSubAggregate(Value *From, Value* To, Type *IndexedType,
3760 SmallVectorImpl<unsigned> &Idxs,
3761 unsigned IdxSkip,
3762 Instruction *InsertBefore) {
3763 StructType *STy = dyn_cast<StructType>(IndexedType);
3764 if (STy) {
3765 // Save the original To argument so we can modify it
3766 Value *OrigTo = To;
3767 // General case, the type indexed by Idxs is a struct
3768 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
3769 // Process each struct element recursively
3770 Idxs.push_back(i);
3771 Value *PrevTo = To;
3772 To = BuildSubAggregate(From, To, STy->getElementType(i), Idxs, IdxSkip,
3773 InsertBefore);
3774 Idxs.pop_back();
3775 if (!To) {
3776 // Couldn't find any inserted value for this index? Cleanup
3777 while (PrevTo != OrigTo) {
3778 InsertValueInst* Del = cast<InsertValueInst>(PrevTo);
3779 PrevTo = Del->getAggregateOperand();
3780 Del->eraseFromParent();
3781 }
3782 // Stop processing elements
3783 break;
3784 }
3785 }
3786 // If we successfully found a value for each of our subaggregates
3787 if (To)
3788 return To;
3789 }
3790 // Base case, the type indexed by SourceIdxs is not a struct, or not all of
3791 // the struct's elements had a value that was inserted directly. In the latter
3792 // case, perhaps we can't determine each of the subelements individually, but
3793 // we might be able to find the complete struct somewhere.
3794
3795 // Find the value that is at that particular spot
3796 Value *V = FindInsertedValue(From, Idxs);
3797
3798 if (!V)
3799 return nullptr;
3800
3801 // Insert the value in the new (sub) aggregate
3802 return InsertValueInst::Create(To, V, makeArrayRef(Idxs).slice(IdxSkip),
3803 "tmp", InsertBefore);
3804}
3805
3806// This helper takes a nested struct and extracts a part of it (which is again a
3807// struct) into a new value. For example, given the struct:
3808// { a, { b, { c, d }, e } }
3809// and the indices "1, 1" this returns
3810// { c, d }.
3811//
3812// It does this by inserting an insertvalue for each element in the resulting
3813// struct, as opposed to just inserting a single struct. This will only work if
3814// each of the elements of the substruct are known (ie, inserted into From by an
3815// insertvalue instruction somewhere).
3816//
3817// All inserted insertvalue instructions are inserted before InsertBefore
3818static Value *BuildSubAggregate(Value *From, ArrayRef<unsigned> idx_range,
3819 Instruction *InsertBefore) {
3820 assert(InsertBefore && "Must have someplace to insert!")((InsertBefore && "Must have someplace to insert!") ?
static_cast<void> (0) : __assert_fail ("InsertBefore && \"Must have someplace to insert!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3820, __PRETTY_FUNCTION__))
;
3821 Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(),
3822 idx_range);
3823 Value *To = UndefValue::get(IndexedType);
3824 SmallVector<unsigned, 10> Idxs(idx_range.begin(), idx_range.end());
3825 unsigned IdxSkip = Idxs.size();
3826
3827 return BuildSubAggregate(From, To, IndexedType, Idxs, IdxSkip, InsertBefore);
3828}
3829
3830/// Given an aggregate and a sequence of indices, see if the scalar value
3831/// indexed is already around as a register, for example if it was inserted
3832/// directly into the aggregate.
3833///
3834/// If InsertBefore is not null, this function will duplicate (modified)
3835/// insertvalues when a part of a nested struct is extracted.
3836Value *llvm::FindInsertedValue(Value *V, ArrayRef<unsigned> idx_range,
3837 Instruction *InsertBefore) {
3838 // Nothing to index? Just return V then (this is useful at the end of our
3839 // recursion).
3840 if (idx_range.empty())
3841 return V;
3842 // We have indices, so V should have an indexable type.
3843 assert((V->getType()->isStructTy() || V->getType()->isArrayTy()) &&(((V->getType()->isStructTy() || V->getType()->isArrayTy
()) && "Not looking at a struct or array?") ? static_cast
<void> (0) : __assert_fail ("(V->getType()->isStructTy() || V->getType()->isArrayTy()) && \"Not looking at a struct or array?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3844, __PRETTY_FUNCTION__))
3844 "Not looking at a struct or array?")(((V->getType()->isStructTy() || V->getType()->isArrayTy
()) && "Not looking at a struct or array?") ? static_cast
<void> (0) : __assert_fail ("(V->getType()->isStructTy() || V->getType()->isArrayTy()) && \"Not looking at a struct or array?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3844, __PRETTY_FUNCTION__))
;
3845 assert(ExtractValueInst::getIndexedType(V->getType(), idx_range) &&((ExtractValueInst::getIndexedType(V->getType(), idx_range
) && "Invalid indices for type?") ? static_cast<void
> (0) : __assert_fail ("ExtractValueInst::getIndexedType(V->getType(), idx_range) && \"Invalid indices for type?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3846, __PRETTY_FUNCTION__))
3846 "Invalid indices for type?")((ExtractValueInst::getIndexedType(V->getType(), idx_range
) && "Invalid indices for type?") ? static_cast<void
> (0) : __assert_fail ("ExtractValueInst::getIndexedType(V->getType(), idx_range) && \"Invalid indices for type?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3846, __PRETTY_FUNCTION__))
;
3847
3848 if (Constant *C = dyn_cast<Constant>(V)) {
3849 C = C->getAggregateElement(idx_range[0]);
3850 if (!C) return nullptr;
3851 return FindInsertedValue(C, idx_range.slice(1), InsertBefore);
3852 }
3853
3854 if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) {
3855 // Loop the indices for the insertvalue instruction in parallel with the
3856 // requested indices
3857 const unsigned *req_idx = idx_range.begin();
3858 for (const unsigned *i = I->idx_begin(), *e = I->idx_end();
3859 i != e; ++i, ++req_idx) {
3860 if (req_idx == idx_range.end()) {
3861 // We can't handle this without inserting insertvalues
3862 if (!InsertBefore)
3863 return nullptr;
3864
3865 // The requested index identifies a part of a nested aggregate. Handle
3866 // this specially. For example,
3867 // %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0
3868 // %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1
3869 // %C = extractvalue {i32, { i32, i32 } } %B, 1
3870 // This can be changed into
3871 // %A = insertvalue {i32, i32 } undef, i32 10, 0
3872 // %C = insertvalue {i32, i32 } %A, i32 11, 1
3873 // which allows the unused 0,0 element from the nested struct to be
3874 // removed.
3875 return BuildSubAggregate(V, makeArrayRef(idx_range.begin(), req_idx),
3876 InsertBefore);
3877 }
3878
3879 // This insert value inserts something else than what we are looking for.
3880 // See if the (aggregate) value inserted into has the value we are
3881 // looking for, then.
3882 if (*req_idx != *i)
3883 return FindInsertedValue(I->getAggregateOperand(), idx_range,
3884 InsertBefore);
3885 }
3886 // If we end up here, the indices of the insertvalue match with those
3887 // requested (though possibly only partially). Now we recursively look at
3888 // the inserted value, passing any remaining indices.
3889 return FindInsertedValue(I->getInsertedValueOperand(),
3890 makeArrayRef(req_idx, idx_range.end()),
3891 InsertBefore);
3892 }
3893
3894 if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) {
3895 // If we're extracting a value from an aggregate that was extracted from
3896 // something else, we can extract from that something else directly instead.
3897 // However, we will need to chain I's indices with the requested indices.
3898
3899 // Calculate the number of indices required
3900 unsigned size = I->getNumIndices() + idx_range.size();
3901 // Allocate some space to put the new indices in
3902 SmallVector<unsigned, 5> Idxs;
3903 Idxs.reserve(size);
3904 // Add indices from the extract value instruction
3905 Idxs.append(I->idx_begin(), I->idx_end());
3906
3907 // Add requested indices
3908 Idxs.append(idx_range.begin(), idx_range.end());
3909
3910 assert(Idxs.size() == size((Idxs.size() == size && "Number of indices added not correct?"
) ? static_cast<void> (0) : __assert_fail ("Idxs.size() == size && \"Number of indices added not correct?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3911, __PRETTY_FUNCTION__))
3911 && "Number of indices added not correct?")((Idxs.size() == size && "Number of indices added not correct?"
) ? static_cast<void> (0) : __assert_fail ("Idxs.size() == size && \"Number of indices added not correct?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3911, __PRETTY_FUNCTION__))
;
3912
3913 return FindInsertedValue(I->getAggregateOperand(), Idxs, InsertBefore);
3914 }
3915 // Otherwise, we don't know (such as, extracting from a function return value
3916 // or load instruction)
3917 return nullptr;
3918}
3919
3920bool llvm::isGEPBasedOnPointerToString(const GEPOperator *GEP,
3921 unsigned CharSize) {
3922 // Make sure the GEP has exactly three arguments.
3923 if (GEP->getNumOperands() != 3)
3924 return false;
3925
3926 // Make sure the index-ee is a pointer to array of \p CharSize integers.
3927 // CharSize.
3928 ArrayType *AT = dyn_cast<ArrayType>(GEP->getSourceElementType());
3929 if (!AT || !AT->getElementType()->isIntegerTy(CharSize))
3930 return false;
3931
3932 // Check to make sure that the first operand of the GEP is an integer and
3933 // has value 0 so that we are sure we're indexing into the initializer.
3934 const ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1));
3935 if (!FirstIdx || !FirstIdx->isZero())
3936 return false;
3937
3938 return true;
3939}
3940
3941bool llvm::getConstantDataArrayInfo(const Value *V,
3942 ConstantDataArraySlice &Slice,
3943 unsigned ElementSize, uint64_t Offset) {
3944 assert(V)((V) ? static_cast<void> (0) : __assert_fail ("V", "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 3944, __PRETTY_FUNCTION__))
;
3945
3946 // Look through bitcast instructions and geps.
3947 V = V->stripPointerCasts();
3948
3949 // If the value is a GEP instruction or constant expression, treat it as an
3950 // offset.
3951 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
3952 // The GEP operator should be based on a pointer to string constant, and is
3953 // indexing into the string constant.
3954 if (!isGEPBasedOnPointerToString(GEP, ElementSize))
3955 return false;
3956
3957 // If the second index isn't a ConstantInt, then this is a variable index
3958 // into the array. If this occurs, we can't say anything meaningful about
3959 // the string.
3960 uint64_t StartIdx = 0;
3961 if (const ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
3962 StartIdx = CI->getZExtValue();
3963 else
3964 return false;
3965 return getConstantDataArrayInfo(GEP->getOperand(0), Slice, ElementSize,
3966 StartIdx + Offset);
3967 }
3968
3969 // The GEP instruction, constant or instruction, must reference a global
3970 // variable that is a constant and is initialized. The referenced constant
3971 // initializer is the array that we'll use for optimization.
3972 const GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
3973 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer())
3974 return false;
3975
3976 const ConstantDataArray *Array;
3977 ArrayType *ArrayTy;
3978 if (GV->getInitializer()->isNullValue()) {
3979 Type *GVTy = GV->getValueType();
3980 if ( (ArrayTy = dyn_cast<ArrayType>(GVTy)) ) {
3981 // A zeroinitializer for the array; there is no ConstantDataArray.
3982 Array = nullptr;
3983 } else {
3984 const DataLayout &DL = GV->getParent()->getDataLayout();
3985 uint64_t SizeInBytes = DL.getTypeStoreSize(GVTy).getFixedSize();
3986 uint64_t Length = SizeInBytes / (ElementSize / 8);
3987 if (Length <= Offset)
3988 return false;
3989
3990 Slice.Array = nullptr;
3991 Slice.Offset = 0;
3992 Slice.Length = Length - Offset;
3993 return true;
3994 }
3995 } else {
3996 // This must be a ConstantDataArray.
3997 Array = dyn_cast<ConstantDataArray>(GV->getInitializer());
3998 if (!Array)
3999 return false;
4000 ArrayTy = Array->getType();
4001 }
4002 if (!ArrayTy->getElementType()->isIntegerTy(ElementSize))
4003 return false;
4004
4005 uint64_t NumElts = ArrayTy->getArrayNumElements();
4006 if (Offset > NumElts)
4007 return false;
4008
4009 Slice.Array = Array;
4010 Slice.Offset = Offset;
4011 Slice.Length = NumElts - Offset;
4012 return true;
4013}
4014
4015/// This function computes the length of a null-terminated C string pointed to
4016/// by V. If successful, it returns true and returns the string in Str.
4017/// If unsuccessful, it returns false.
4018bool llvm::getConstantStringInfo(const Value *V, StringRef &Str,
4019 uint64_t Offset, bool TrimAtNul) {
4020 ConstantDataArraySlice Slice;
4021 if (!getConstantDataArrayInfo(V, Slice, 8, Offset))
4022 return false;
4023
4024 if (Slice.Array == nullptr) {
4025 if (TrimAtNul) {
4026 Str = StringRef();
4027 return true;
4028 }
4029 if (Slice.Length == 1) {
4030 Str = StringRef("", 1);
4031 return true;
4032 }
4033 // We cannot instantiate a StringRef as we do not have an appropriate string
4034 // of 0s at hand.
4035 return false;
4036 }
4037
4038 // Start out with the entire array in the StringRef.
4039 Str = Slice.Array->getAsString();
4040 // Skip over 'offset' bytes.
4041 Str = Str.substr(Slice.Offset);
4042
4043 if (TrimAtNul) {
4044 // Trim off the \0 and anything after it. If the array is not nul
4045 // terminated, we just return the whole end of string. The client may know
4046 // some other way that the string is length-bound.
4047 Str = Str.substr(0, Str.find('\0'));
4048 }
4049 return true;
4050}
4051
4052// These next two are very similar to the above, but also look through PHI
4053// nodes.
4054// TODO: See if we can integrate these two together.
4055
4056/// If we can compute the length of the string pointed to by
4057/// the specified pointer, return 'len+1'. If we can't, return 0.
4058static uint64_t GetStringLengthH(const Value *V,
4059 SmallPtrSetImpl<const PHINode*> &PHIs,
4060 unsigned CharSize) {
4061 // Look through noop bitcast instructions.
4062 V = V->stripPointerCasts();
4063
4064 // If this is a PHI node, there are two cases: either we have already seen it
4065 // or we haven't.
4066 if (const PHINode *PN = dyn_cast<PHINode>(V)) {
4067 if (!PHIs.insert(PN).second)
4068 return ~0ULL; // already in the set.
4069
4070 // If it was new, see if all the input strings are the same length.
4071 uint64_t LenSoFar = ~0ULL;
4072 for (Value *IncValue : PN->incoming_values()) {
4073 uint64_t Len = GetStringLengthH(IncValue, PHIs, CharSize);
4074 if (Len == 0) return 0; // Unknown length -> unknown.
4075
4076 if (Len == ~0ULL) continue;
4077
4078 if (Len != LenSoFar && LenSoFar != ~0ULL)
4079 return 0; // Disagree -> unknown.
4080 LenSoFar = Len;
4081 }
4082
4083 // Success, all agree.
4084 return LenSoFar;
4085 }
4086
4087 // strlen(select(c,x,y)) -> strlen(x) ^ strlen(y)
4088 if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
4089 uint64_t Len1 = GetStringLengthH(SI->getTrueValue(), PHIs, CharSize);
4090 if (Len1 == 0) return 0;
4091 uint64_t Len2 = GetStringLengthH(SI->getFalseValue(), PHIs, CharSize);
4092 if (Len2 == 0) return 0;
4093 if (Len1 == ~0ULL) return Len2;
4094 if (Len2 == ~0ULL) return Len1;
4095 if (Len1 != Len2) return 0;
4096 return Len1;
4097 }
4098
4099 // Otherwise, see if we can read the string.
4100 ConstantDataArraySlice Slice;
4101 if (!getConstantDataArrayInfo(V, Slice, CharSize))
4102 return 0;
4103
4104 if (Slice.Array == nullptr)
4105 return 1;
4106
4107 // Search for nul characters
4108 unsigned NullIndex = 0;
4109 for (unsigned E = Slice.Length; NullIndex < E; ++NullIndex) {
4110 if (Slice.Array->getElementAsInteger(Slice.Offset + NullIndex) == 0)
4111 break;
4112 }
4113
4114 return NullIndex + 1;
4115}
4116
4117/// If we can compute the length of the string pointed to by
4118/// the specified pointer, return 'len+1'. If we can't, return 0.
4119uint64_t llvm::GetStringLength(const Value *V, unsigned CharSize) {
4120 if (!V->getType()->isPointerTy())
4121 return 0;
4122
4123 SmallPtrSet<const PHINode*, 32> PHIs;
4124 uint64_t Len = GetStringLengthH(V, PHIs, CharSize);
4125 // If Len is ~0ULL, we had an infinite phi cycle: this is dead code, so return
4126 // an empty string as a length.
4127 return Len == ~0ULL ? 1 : Len;
4128}
4129
4130const Value *
4131llvm::getArgumentAliasingToReturnedPointer(const CallBase *Call,
4132 bool MustPreserveNullness) {
4133 assert(Call &&((Call && "getArgumentAliasingToReturnedPointer only works on nonnull calls"
) ? static_cast<void> (0) : __assert_fail ("Call && \"getArgumentAliasingToReturnedPointer only works on nonnull calls\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 4134, __PRETTY_FUNCTION__))
4134 "getArgumentAliasingToReturnedPointer only works on nonnull calls")((Call && "getArgumentAliasingToReturnedPointer only works on nonnull calls"
) ? static_cast<void> (0) : __assert_fail ("Call && \"getArgumentAliasingToReturnedPointer only works on nonnull calls\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 4134, __PRETTY_FUNCTION__))
;
4135 if (const Value *RV = Call->getReturnedArgOperand())
4136 return RV;
4137 // This can be used only as a aliasing property.
4138 if (isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
4139 Call, MustPreserveNullness))
4140 return Call->getArgOperand(0);
4141 return nullptr;
4142}
4143
4144bool llvm::isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
4145 const CallBase *Call, bool MustPreserveNullness) {
4146 switch (Call->getIntrinsicID()) {
4147 case Intrinsic::launder_invariant_group:
4148 case Intrinsic::strip_invariant_group:
4149 case Intrinsic::aarch64_irg:
4150 case Intrinsic::aarch64_tagp:
4151 return true;
4152 case Intrinsic::ptrmask:
4153 return !MustPreserveNullness;
4154 default:
4155 return false;
4156 }
4157}
4158
4159/// \p PN defines a loop-variant pointer to an object. Check if the
4160/// previous iteration of the loop was referring to the same object as \p PN.
4161static bool isSameUnderlyingObjectInLoop(const PHINode *PN,
4162 const LoopInfo *LI) {
4163 // Find the loop-defined value.
4164 Loop *L = LI->getLoopFor(PN->getParent());
4165 if (PN->getNumIncomingValues() != 2)
4166 return true;
4167
4168 // Find the value from previous iteration.
4169 auto *PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(0));
4170 if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
4171 PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(1));
4172 if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
4173 return true;
4174
4175 // If a new pointer is loaded in the loop, the pointer references a different
4176 // object in every iteration. E.g.:
4177 // for (i)
4178 // int *p = a[i];
4179 // ...
4180 if (auto *Load = dyn_cast<LoadInst>(PrevValue))
4181 if (!L->isLoopInvariant(Load->getPointerOperand()))
4182 return false;
4183 return true;
4184}
4185
4186Value *llvm::getUnderlyingObject(Value *V, unsigned MaxLookup) {
4187 if (!V->getType()->isPointerTy())
4188 return V;
4189 for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
4190 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
4191 V = GEP->getPointerOperand();
4192 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
4193 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
4194 V = cast<Operator>(V)->getOperand(0);
4195 if (!V->getType()->isPointerTy())
4196 return V;
4197 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
4198 if (GA->isInterposable())
4199 return V;
4200 V = GA->getAliasee();
4201 } else {
4202 if (auto *PHI = dyn_cast<PHINode>(V)) {
4203 // Look through single-arg phi nodes created by LCSSA.
4204 if (PHI->getNumIncomingValues() == 1) {
4205 V = PHI->getIncomingValue(0);
4206 continue;
4207 }
4208 } else if (auto *Call = dyn_cast<CallBase>(V)) {
4209 // CaptureTracking can know about special capturing properties of some
4210 // intrinsics like launder.invariant.group, that can't be expressed with
4211 // the attributes, but have properties like returning aliasing pointer.
4212 // Because some analysis may assume that nocaptured pointer is not
4213 // returned from some special intrinsic (because function would have to
4214 // be marked with returns attribute), it is crucial to use this function
4215 // because it should be in sync with CaptureTracking. Not using it may
4216 // cause weird miscompilations where 2 aliasing pointers are assumed to
4217 // noalias.
4218 if (auto *RP = getArgumentAliasingToReturnedPointer(Call, false)) {
4219 V = RP;
4220 continue;
4221 }
4222 }
4223
4224 return V;
4225 }
4226 assert(V->getType()->isPointerTy() && "Unexpected operand type!")((V->getType()->isPointerTy() && "Unexpected operand type!"
) ? static_cast<void> (0) : __assert_fail ("V->getType()->isPointerTy() && \"Unexpected operand type!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 4226, __PRETTY_FUNCTION__))
;
4227 }
4228 return V;
4229}
4230
4231void llvm::getUnderlyingObjects(const Value *V,
4232 SmallVectorImpl<const Value *> &Objects,
4233 LoopInfo *LI, unsigned MaxLookup) {
4234 SmallPtrSet<const Value *, 4> Visited;
4235 SmallVector<const Value *, 4> Worklist;
4236 Worklist.push_back(V);
4237 do {
4238 const Value *P = Worklist.pop_back_val();
4239 P = getUnderlyingObject(P, MaxLookup);
4240
4241 if (!Visited.insert(P).second)
4242 continue;
4243
4244 if (auto *SI = dyn_cast<SelectInst>(P)) {
4245 Worklist.push_back(SI->getTrueValue());
4246 Worklist.push_back(SI->getFalseValue());
4247 continue;
4248 }
4249
4250 if (auto *PN = dyn_cast<PHINode>(P)) {
4251 // If this PHI changes the underlying object in every iteration of the
4252 // loop, don't look through it. Consider:
4253 // int **A;
4254 // for (i) {
4255 // Prev = Curr; // Prev = PHI (Prev_0, Curr)
4256 // Curr = A[i];
4257 // *Prev, *Curr;
4258 //
4259 // Prev is tracking Curr one iteration behind so they refer to different
4260 // underlying objects.
4261 if (!LI || !LI->isLoopHeader(PN->getParent()) ||
4262 isSameUnderlyingObjectInLoop(PN, LI))
4263 append_range(Worklist, PN->incoming_values());
4264 continue;
4265 }
4266
4267 Objects.push_back(P);
4268 } while (!Worklist.empty());
4269}
4270
4271/// This is the function that does the work of looking through basic
4272/// ptrtoint+arithmetic+inttoptr sequences.
4273static const Value *getUnderlyingObjectFromInt(const Value *V) {
4274 do {
4275 if (const Operator *U = dyn_cast<Operator>(V)) {
4276 // If we find a ptrtoint, we can transfer control back to the
4277 // regular getUnderlyingObjectFromInt.
4278 if (U->getOpcode() == Instruction::PtrToInt)
4279 return U->getOperand(0);
4280 // If we find an add of a constant, a multiplied value, or a phi, it's
4281 // likely that the other operand will lead us to the base
4282 // object. We don't have to worry about the case where the
4283 // object address is somehow being computed by the multiply,
4284 // because our callers only care when the result is an
4285 // identifiable object.
4286 if (U->getOpcode() != Instruction::Add ||
4287 (!isa<ConstantInt>(U->getOperand(1)) &&
4288 Operator::getOpcode(U->getOperand(1)) != Instruction::Mul &&
4289 !isa<PHINode>(U->getOperand(1))))
4290 return V;
4291 V = U->getOperand(0);
4292 } else {
4293 return V;
4294 }
4295 assert(V->getType()->isIntegerTy() && "Unexpected operand type!")((V->getType()->isIntegerTy() && "Unexpected operand type!"
) ? static_cast<void> (0) : __assert_fail ("V->getType()->isIntegerTy() && \"Unexpected operand type!\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 4295, __PRETTY_FUNCTION__))
;
4296 } while (true);
4297}
4298
4299/// This is a wrapper around getUnderlyingObjects and adds support for basic
4300/// ptrtoint+arithmetic+inttoptr sequences.
4301/// It returns false if unidentified object is found in getUnderlyingObjects.
4302bool llvm::getUnderlyingObjectsForCodeGen(const Value *V,
4303 SmallVectorImpl<Value *> &Objects) {
4304 SmallPtrSet<const Value *, 16> Visited;
4305 SmallVector<const Value *, 4> Working(1, V);
4306 do {
4307 V = Working.pop_back_val();
4308
4309 SmallVector<const Value *, 4> Objs;
4310 getUnderlyingObjects(V, Objs);
4311
4312 for (const Value *V : Objs) {
4313 if (!Visited.insert(V).second)
4314 continue;
4315 if (Operator::getOpcode(V) == Instruction::IntToPtr) {
4316 const Value *O =
4317 getUnderlyingObjectFromInt(cast<User>(V)->getOperand(0));
4318 if (O->getType()->isPointerTy()) {
4319 Working.push_back(O);
4320 continue;
4321 }
4322 }
4323 // If getUnderlyingObjects fails to find an identifiable object,
4324 // getUnderlyingObjectsForCodeGen also fails for safety.
4325 if (!isIdentifiedObject(V)) {
4326 Objects.clear();
4327 return false;
4328 }
4329 Objects.push_back(const_cast<Value *>(V));
4330 }
4331 } while (!Working.empty());
4332 return true;
4333}
4334
4335AllocaInst *llvm::findAllocaForValue(Value *V, bool OffsetZero) {
4336 AllocaInst *Result = nullptr;
4337 SmallPtrSet<Value *, 4> Visited;
4338 SmallVector<Value *, 4> Worklist;
4339
4340 auto AddWork = [&](Value *V) {
4341 if (Visited.insert(V).second)
4342 Worklist.push_back(V);
4343 };
4344
4345 AddWork(V);
4346 do {
4347 V = Worklist.pop_back_val();
4348 assert(Visited.count(V))((Visited.count(V)) ? static_cast<void> (0) : __assert_fail
("Visited.count(V)", "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 4348, __PRETTY_FUNCTION__))
;
4349
4350 if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
4351 if (Result && Result != AI)
4352 return nullptr;
4353 Result = AI;
4354 } else if (CastInst *CI = dyn_cast<CastInst>(V)) {
4355 AddWork(CI->getOperand(0));
4356 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
4357 for (Value *IncValue : PN->incoming_values())
4358 AddWork(IncValue);
4359 } else if (auto *SI = dyn_cast<SelectInst>(V)) {
4360 AddWork(SI->getTrueValue());
4361 AddWork(SI->getFalseValue());
4362 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
4363 if (OffsetZero && !GEP->hasAllZeroIndices())
4364 return nullptr;
4365 AddWork(GEP->getPointerOperand());
4366 } else {
4367 return nullptr;
4368 }
4369 } while (!Worklist.empty());
4370
4371 return Result;
4372}
4373
4374static bool onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
4375 const Value *V, bool AllowLifetime, bool AllowDroppable) {
4376 for (const User *U : V->users()) {
4377 const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
4378 if (!II)
4379 return false;
4380
4381 if (AllowLifetime && II->isLifetimeStartOrEnd())
4382 continue;
4383
4384 if (AllowDroppable && II->isDroppable())
4385 continue;
4386
4387 return false;
4388 }
4389 return true;
4390}
4391
4392bool llvm::onlyUsedByLifetimeMarkers(const Value *V) {
4393 return onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
4394 V, /* AllowLifetime */ true, /* AllowDroppable */ false);
4395}
4396bool llvm::onlyUsedByLifetimeMarkersOrDroppableInsts(const Value *V) {
4397 return onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
4398 V, /* AllowLifetime */ true, /* AllowDroppable */ true);
4399}
4400
4401bool llvm::mustSuppressSpeculation(const LoadInst &LI) {
4402 if (!LI.isUnordered())
4403 return true;
4404 const Function &F = *LI.getFunction();
4405 // Speculative load may create a race that did not exist in the source.
4406 return F.hasFnAttribute(Attribute::SanitizeThread) ||
4407 // Speculative load may load data from dirty regions.
4408 F.hasFnAttribute(Attribute::SanitizeAddress) ||
4409 F.hasFnAttribute(Attribute::SanitizeHWAddress);
4410}
4411
4412
4413bool llvm::isSafeToSpeculativelyExecute(const Value *V,
4414 const Instruction *CtxI,
4415 const DominatorTree *DT) {
4416 const Operator *Inst = dyn_cast<Operator>(V);
4417 if (!Inst)
4418 return false;
4419
4420 for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
4421 if (Constant *C = dyn_cast<Constant>(Inst->getOperand(i)))
4422 if (C->canTrap())
4423 return false;
4424
4425 switch (Inst->getOpcode()) {
4426 default:
4427 return true;
4428 case Instruction::UDiv:
4429 case Instruction::URem: {
4430 // x / y is undefined if y == 0.
4431 const APInt *V;
4432 if (match(Inst->getOperand(1), m_APInt(V)))
4433 return *V != 0;
4434 return false;
4435 }
4436 case Instruction::SDiv:
4437 case Instruction::SRem: {
4438 // x / y is undefined if y == 0 or x == INT_MIN and y == -1
4439 const APInt *Numerator, *Denominator;
4440 if (!match(Inst->getOperand(1), m_APInt(Denominator)))
4441 return false;
4442 // We cannot hoist this division if the denominator is 0.
4443 if (*Denominator == 0)
4444 return false;
4445 // It's safe to hoist if the denominator is not 0 or -1.
4446 if (!Denominator->isAllOnesValue())
4447 return true;
4448 // At this point we know that the denominator is -1. It is safe to hoist as
4449 // long we know that the numerator is not INT_MIN.
4450 if (match(Inst->getOperand(0), m_APInt(Numerator)))
4451 return !Numerator->isMinSignedValue();
4452 // The numerator *might* be MinSignedValue.
4453 return false;
4454 }
4455 case Instruction::Load: {
4456 const LoadInst *LI = cast<LoadInst>(Inst);
4457 if (mustSuppressSpeculation(*LI))
4458 return false;
4459 const DataLayout &DL = LI->getModule()->getDataLayout();
4460 return isDereferenceableAndAlignedPointer(
4461 LI->getPointerOperand(), LI->getType(), MaybeAlign(LI->getAlignment()),
4462 DL, CtxI, DT);
4463 }
4464 case Instruction::Call: {
4465 auto *CI = cast<const CallInst>(Inst);
4466 const Function *Callee = CI->getCalledFunction();
4467
4468 // The called function could have undefined behavior or side-effects, even
4469 // if marked readnone nounwind.
4470 return Callee && Callee->isSpeculatable();
4471 }
4472 case Instruction::VAArg:
4473 case Instruction::Alloca:
4474 case Instruction::Invoke:
4475 case Instruction::CallBr:
4476 case Instruction::PHI:
4477 case Instruction::Store:
4478 case Instruction::Ret:
4479 case Instruction::Br:
4480 case Instruction::IndirectBr:
4481 case Instruction::Switch:
4482 case Instruction::Unreachable:
4483 case Instruction::Fence:
4484 case Instruction::AtomicRMW:
4485 case Instruction::AtomicCmpXchg:
4486 case Instruction::LandingPad:
4487 case Instruction::Resume:
4488 case Instruction::CatchSwitch:
4489 case Instruction::CatchPad:
4490 case Instruction::CatchRet:
4491 case Instruction::CleanupPad:
4492 case Instruction::CleanupRet:
4493 return false; // Misc instructions which have effects
4494 }
4495}
4496
4497bool llvm::mayBeMemoryDependent(const Instruction &I) {
4498 return I.mayReadOrWriteMemory() || !isSafeToSpeculativelyExecute(&I);
4499}
4500
4501/// Convert ConstantRange OverflowResult into ValueTracking OverflowResult.
4502static OverflowResult mapOverflowResult(ConstantRange::OverflowResult OR) {
4503 switch (OR) {
4504 case ConstantRange::OverflowResult::MayOverflow:
4505 return OverflowResult::MayOverflow;
4506 case ConstantRange::OverflowResult::AlwaysOverflowsLow:
4507 return OverflowResult::AlwaysOverflowsLow;
4508 case ConstantRange::OverflowResult::AlwaysOverflowsHigh:
4509 return OverflowResult::AlwaysOverflowsHigh;
4510 case ConstantRange::OverflowResult::NeverOverflows:
4511 return OverflowResult::NeverOverflows;
4512 }
4513 llvm_unreachable("Unknown OverflowResult")::llvm::llvm_unreachable_internal("Unknown OverflowResult", "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 4513)
;
4514}
4515
4516/// Combine constant ranges from computeConstantRange() and computeKnownBits().
4517static ConstantRange computeConstantRangeIncludingKnownBits(
4518 const Value *V, bool ForSigned, const DataLayout &DL, unsigned Depth,
4519 AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
4520 OptimizationRemarkEmitter *ORE = nullptr, bool UseInstrInfo = true) {
4521 KnownBits Known = computeKnownBits(
4522 V, DL, Depth, AC, CxtI, DT, ORE, UseInstrInfo);
4523 ConstantRange CR1 = ConstantRange::fromKnownBits(Known, ForSigned);
4524 ConstantRange CR2 = computeConstantRange(V, UseInstrInfo);
4525 ConstantRange::PreferredRangeType RangeType =
4526 ForSigned ? ConstantRange::Signed : ConstantRange::Unsigned;
4527 return CR1.intersectWith(CR2, RangeType);
4528}
4529
4530OverflowResult llvm::computeOverflowForUnsignedMul(
4531 const Value *LHS, const Value *RHS, const DataLayout &DL,
4532 AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
4533 bool UseInstrInfo) {
4534 KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT,
4535 nullptr, UseInstrInfo);
4536 KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT,
4537 nullptr, UseInstrInfo);
4538 ConstantRange LHSRange = ConstantRange::fromKnownBits(LHSKnown, false);
4539 ConstantRange RHSRange = ConstantRange::fromKnownBits(RHSKnown, false);
4540 return mapOverflowResult(LHSRange.unsignedMulMayOverflow(RHSRange));
4541}
4542
4543OverflowResult
4544llvm::computeOverflowForSignedMul(const Value *LHS, const Value *RHS,
4545 const DataLayout &DL, AssumptionCache *AC,
4546 const Instruction *CxtI,
4547 const DominatorTree *DT, bool UseInstrInfo) {
4548 // Multiplying n * m significant bits yields a result of n + m significant
4549 // bits. If the total number of significant bits does not exceed the
4550 // result bit width (minus 1), there is no overflow.
4551 // This means if we have enough leading sign bits in the operands
4552 // we can guarantee that the result does not overflow.
4553 // Ref: "Hacker's Delight" by Henry Warren
4554 unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
4555
4556 // Note that underestimating the number of sign bits gives a more
4557 // conservative answer.
4558 unsigned SignBits = ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) +
4559 ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT);
4560
4561 // First handle the easy case: if we have enough sign bits there's
4562 // definitely no overflow.
4563 if (SignBits > BitWidth + 1)
4564 return OverflowResult::NeverOverflows;
4565
4566 // There are two ambiguous cases where there can be no overflow:
4567 // SignBits == BitWidth + 1 and
4568 // SignBits == BitWidth
4569 // The second case is difficult to check, therefore we only handle the
4570 // first case.
4571 if (SignBits == BitWidth + 1) {
4572 // It overflows only when both arguments are negative and the true
4573 // product is exactly the minimum negative number.
4574 // E.g. mul i16 with 17 sign bits: 0xff00 * 0xff80 = 0x8000
4575 // For simplicity we just check if at least one side is not negative.
4576 KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT,
4577 nullptr, UseInstrInfo);
4578 KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT,
4579 nullptr, UseInstrInfo);
4580 if (LHSKnown.isNonNegative() || RHSKnown.isNonNegative())
4581 return OverflowResult::NeverOverflows;
4582 }
4583 return OverflowResult::MayOverflow;
4584}
4585
4586OverflowResult llvm::computeOverflowForUnsignedAdd(
4587 const Value *LHS, const Value *RHS, const DataLayout &DL,
4588 AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
4589 bool UseInstrInfo) {
4590 ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
4591 LHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT,
4592 nullptr, UseInstrInfo);
4593 ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
4594 RHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT,
4595 nullptr, UseInstrInfo);
4596 return mapOverflowResult(LHSRange.unsignedAddMayOverflow(RHSRange));
4597}
4598
4599static OverflowResult computeOverflowForSignedAdd(const Value *LHS,
4600 const Value *RHS,
4601 const AddOperator *Add,
4602 const DataLayout &DL,
4603 AssumptionCache *AC,
4604 const Instruction *CxtI,
4605 const DominatorTree *DT) {
4606 if (Add && Add->hasNoSignedWrap()) {
4607 return OverflowResult::NeverOverflows;
4608 }
4609
4610 // If LHS and RHS each have at least two sign bits, the addition will look
4611 // like
4612 //
4613 // XX..... +
4614 // YY.....
4615 //
4616 // If the carry into the most significant position is 0, X and Y can't both
4617 // be 1 and therefore the carry out of the addition is also 0.
4618 //
4619 // If the carry into the most significant position is 1, X and Y can't both
4620 // be 0 and therefore the carry out of the addition is also 1.
4621 //
4622 // Since the carry into the most significant position is always equal to
4623 // the carry out of the addition, there is no signed overflow.
4624 if (ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) > 1 &&
4625 ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT) > 1)
4626 return OverflowResult::NeverOverflows;
4627
4628 ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
4629 LHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
4630 ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
4631 RHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
4632 OverflowResult OR =
4633 mapOverflowResult(LHSRange.signedAddMayOverflow(RHSRange));
4634 if (OR != OverflowResult::MayOverflow)
4635 return OR;
4636
4637 // The remaining code needs Add to be available. Early returns if not so.
4638 if (!Add)
4639 return OverflowResult::MayOverflow;
4640
4641 // If the sign of Add is the same as at least one of the operands, this add
4642 // CANNOT overflow. If this can be determined from the known bits of the
4643 // operands the above signedAddMayOverflow() check will have already done so.
4644 // The only other way to improve on the known bits is from an assumption, so
4645 // call computeKnownBitsFromAssume() directly.
4646 bool LHSOrRHSKnownNonNegative =
4647 (LHSRange.isAllNonNegative() || RHSRange.isAllNonNegative());
4648 bool LHSOrRHSKnownNegative =
4649 (LHSRange.isAllNegative() || RHSRange.isAllNegative());
4650 if (LHSOrRHSKnownNonNegative || LHSOrRHSKnownNegative) {
4651 KnownBits AddKnown(LHSRange.getBitWidth());
4652 computeKnownBitsFromAssume(
4653 Add, AddKnown, /*Depth=*/0, Query(DL, AC, CxtI, DT, true));
4654 if ((AddKnown.isNonNegative() && LHSOrRHSKnownNonNegative) ||
4655 (AddKnown.isNegative() && LHSOrRHSKnownNegative))
4656 return OverflowResult::NeverOverflows;
4657 }
4658
4659 return OverflowResult::MayOverflow;
4660}
4661
4662OverflowResult llvm::computeOverflowForUnsignedSub(const Value *LHS,
4663 const Value *RHS,
4664 const DataLayout &DL,
4665 AssumptionCache *AC,
4666 const Instruction *CxtI,
4667 const DominatorTree *DT) {
4668 // Checking for conditions implied by dominating conditions may be expensive.
4669 // Limit it to usub_with_overflow calls for now.
4670 if (match(CxtI,
4671 m_Intrinsic<Intrinsic::usub_with_overflow>(m_Value(), m_Value())))
4672 if (auto C =
4673 isImpliedByDomCondition(CmpInst::ICMP_UGE, LHS, RHS, CxtI, DL)) {
4674 if (*C)
4675 return OverflowResult::NeverOverflows;
4676 return OverflowResult::AlwaysOverflowsLow;
4677 }
4678 ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
4679 LHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT);
4680 ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
4681 RHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT);
4682 return mapOverflowResult(LHSRange.unsignedSubMayOverflow(RHSRange));
4683}
4684
4685OverflowResult llvm::computeOverflowForSignedSub(const Value *LHS,
4686 const Value *RHS,
4687 const DataLayout &DL,
4688 AssumptionCache *AC,
4689 const Instruction *CxtI,
4690 const DominatorTree *DT) {
4691 // If LHS and RHS each have at least two sign bits, the subtraction
4692 // cannot overflow.
4693 if (ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) > 1 &&
4694 ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT) > 1)
4695 return OverflowResult::NeverOverflows;
4696
4697 ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
4698 LHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
4699 ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
4700 RHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
4701 return mapOverflowResult(LHSRange.signedSubMayOverflow(RHSRange));
4702}
4703
4704bool llvm::isOverflowIntrinsicNoWrap(const WithOverflowInst *WO,
4705 const DominatorTree &DT) {
4706 SmallVector<const BranchInst *, 2> GuardingBranches;
4707 SmallVector<const ExtractValueInst *, 2> Results;
4708
4709 for (const User *U : WO->users()) {
4710 if (const auto *EVI = dyn_cast<ExtractValueInst>(U)) {
4711 assert(EVI->getNumIndices() == 1 && "Obvious from CI's type")((EVI->getNumIndices() == 1 && "Obvious from CI's type"
) ? static_cast<void> (0) : __assert_fail ("EVI->getNumIndices() == 1 && \"Obvious from CI's type\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 4711, __PRETTY_FUNCTION__))
;
4712
4713 if (EVI->getIndices()[0] == 0)
4714 Results.push_back(EVI);
4715 else {
4716 assert(EVI->getIndices()[0] == 1 && "Obvious from CI's type")((EVI->getIndices()[0] == 1 && "Obvious from CI's type"
) ? static_cast<void> (0) : __assert_fail ("EVI->getIndices()[0] == 1 && \"Obvious from CI's type\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 4716, __PRETTY_FUNCTION__))
;
4717
4718 for (const auto *U : EVI->users())
4719 if (const auto *B = dyn_cast<BranchInst>(U)) {
4720 assert(B->isConditional() && "How else is it using an i1?")((B->isConditional() && "How else is it using an i1?"
) ? static_cast<void> (0) : __assert_fail ("B->isConditional() && \"How else is it using an i1?\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 4720, __PRETTY_FUNCTION__))
;
4721 GuardingBranches.push_back(B);
4722 }
4723 }
4724 } else {
4725 // We are using the aggregate directly in a way we don't want to analyze
4726 // here (storing it to a global, say).
4727 return false;
4728 }
4729 }
4730
4731 auto AllUsesGuardedByBranch = [&](const BranchInst *BI) {
4732 BasicBlockEdge NoWrapEdge(BI->getParent(), BI->getSuccessor(1));
4733 if (!NoWrapEdge.isSingleEdge())
4734 return false;
4735
4736 // Check if all users of the add are provably no-wrap.
4737 for (const auto *Result : Results) {
4738 // If the extractvalue itself is not executed on overflow, the we don't
4739 // need to check each use separately, since domination is transitive.
4740 if (DT.dominates(NoWrapEdge, Result->getParent()))
4741 continue;
4742
4743 for (auto &RU : Result->uses())
4744 if (!DT.dominates(NoWrapEdge, RU))
4745 return false;
4746 }
4747
4748 return true;
4749 };
4750
4751 return llvm::any_of(GuardingBranches, AllUsesGuardedByBranch);
4752}
4753
4754static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly) {
4755 // See whether I has flags that may create poison
4756 if (const auto *OvOp = dyn_cast<OverflowingBinaryOperator>(Op)) {
4757 if (OvOp->hasNoSignedWrap() || OvOp->hasNoUnsignedWrap())
4758 return true;
4759 }
4760 if (const auto *ExactOp = dyn_cast<PossiblyExactOperator>(Op))
4761 if (ExactOp->isExact())
4762 return true;
4763 if (const auto *FP = dyn_cast<FPMathOperator>(Op)) {
4764 auto FMF = FP->getFastMathFlags();
4765 if (FMF.noNaNs() || FMF.noInfs())
4766 return true;
4767 }
4768
4769 unsigned Opcode = Op->getOpcode();
4770
4771 // Check whether opcode is a poison/undef-generating operation
4772 switch (Opcode) {
4773 case Instruction::Shl:
4774 case Instruction::AShr:
4775 case Instruction::LShr: {
4776 // Shifts return poison if shiftwidth is larger than the bitwidth.
4777 if (auto *C = dyn_cast<Constant>(Op->getOperand(1))) {
4778 SmallVector<Constant *, 4> ShiftAmounts;
4779 if (auto *FVTy = dyn_cast<FixedVectorType>(C->getType())) {
4780 unsigned NumElts = FVTy->getNumElements();
4781 for (unsigned i = 0; i < NumElts; ++i)
4782 ShiftAmounts.push_back(C->getAggregateElement(i));
4783 } else if (isa<ScalableVectorType>(C->getType()))
4784 return true; // Can't tell, just return true to be safe
4785 else
4786 ShiftAmounts.push_back(C);
4787
4788 bool Safe = llvm::all_of(ShiftAmounts, [](Constant *C) {
4789 auto *CI = dyn_cast_or_null<ConstantInt>(C);
4790 return CI && CI->getValue().ult(C->getType()->getIntegerBitWidth());
4791 });
4792 return !Safe;
4793 }
4794 return true;
4795 }
4796 case Instruction::FPToSI:
4797 case Instruction::FPToUI:
4798 // fptosi/ui yields poison if the resulting value does not fit in the
4799 // destination type.
4800 return true;
4801 case Instruction::Call:
4802 case Instruction::CallBr:
4803 case Instruction::Invoke: {
4804 const auto *CB = cast<CallBase>(Op);
4805 return !CB->hasRetAttr(Attribute::NoUndef);
4806 }
4807 case Instruction::InsertElement:
4808 case Instruction::ExtractElement: {
4809 // If index exceeds the length of the vector, it returns poison
4810 auto *VTy = cast<VectorType>(Op->getOperand(0)->getType());
4811 unsigned IdxOp = Op->getOpcode() == Instruction::InsertElement ? 2 : 1;
4812 auto *Idx = dyn_cast<ConstantInt>(Op->getOperand(IdxOp));
4813 if (!Idx || Idx->getValue().uge(VTy->getElementCount().getKnownMinValue()))
4814 return true;
4815 return false;
4816 }
4817 case Instruction::ShuffleVector: {
4818 // shufflevector may return undef.
4819 if (PoisonOnly)
4820 return false;
4821 ArrayRef<int> Mask = isa<ConstantExpr>(Op)
4822 ? cast<ConstantExpr>(Op)->getShuffleMask()
4823 : cast<ShuffleVectorInst>(Op)->getShuffleMask();
4824 return is_contained(Mask, UndefMaskElem);
4825 }
4826 case Instruction::FNeg:
4827 case Instruction::PHI:
4828 case Instruction::Select:
4829 case Instruction::URem:
4830 case Instruction::SRem:
4831 case Instruction::ExtractValue:
4832 case Instruction::InsertValue:
4833 case Instruction::Freeze:
4834 case Instruction::ICmp:
4835 case Instruction::FCmp:
4836 return false;
4837 case Instruction::GetElementPtr: {
4838 const auto *GEP = cast<GEPOperator>(Op);
4839 return GEP->isInBounds();
4840 }
4841 default: {
4842 const auto *CE = dyn_cast<ConstantExpr>(Op);
4843 if (isa<CastInst>(Op) || (CE && CE->isCast()))
4844 return false;
4845 else if (Instruction::isBinaryOp(Opcode))
4846 return false;
4847 // Be conservative and return true.
4848 return true;
4849 }
4850 }
4851}
4852
4853bool llvm::canCreateUndefOrPoison(const Operator *Op) {
4854 return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/false);
4855}
4856
4857bool llvm::canCreatePoison(const Operator *Op) {
4858 return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/true);
4859}
4860
4861static bool directlyImpliesPoison(const Value *ValAssumedPoison,
4862 const Value *V, unsigned Depth) {
4863 if (ValAssumedPoison == V)
4864 return true;
4865
4866 const unsigned MaxDepth = 2;
4867 if (Depth >= MaxDepth)
4868 return false;
4869
4870 if (const auto *I = dyn_cast<Instruction>(V)) {
4871 if (propagatesPoison(cast<Operator>(I)))
4872 return any_of(I->operands(), [=](const Value *Op) {
4873 return directlyImpliesPoison(ValAssumedPoison, Op, Depth + 1);
4874 });
4875
4876 // V = extractvalue V0, idx
4877 // V2 = extractvalue V0, idx2
4878 // V0's elements are all poison or not. (e.g., add_with_overflow)
4879 const WithOverflowInst *II;
4880 if (match(I, m_ExtractValue(m_WithOverflowInst(II))) &&
4881 match(ValAssumedPoison, m_ExtractValue(m_Specific(II))))
4882 return true;
4883 }
4884 return false;
4885}
4886
4887static bool impliesPoison(const Value *ValAssumedPoison, const Value *V,
4888 unsigned Depth) {
4889 if (isGuaranteedNotToBeUndefOrPoison(ValAssumedPoison))
4890 return true;
4891
4892 if (directlyImpliesPoison(ValAssumedPoison, V, /* Depth */ 0))
4893 return true;
4894
4895 const unsigned MaxDepth = 2;
4896 if (Depth >= MaxDepth)
4897 return false;
4898
4899 const auto *I = dyn_cast<Instruction>(ValAssumedPoison);
4900 if (I && !canCreatePoison(cast<Operator>(I))) {
4901 return all_of(I->operands(), [=](const Value *Op) {
4902 return impliesPoison(Op, V, Depth + 1);
4903 });
4904 }
4905 return false;
4906}
4907
4908bool llvm::impliesPoison(const Value *ValAssumedPoison, const Value *V) {
4909 return ::impliesPoison(ValAssumedPoison, V, /* Depth */ 0);
4910}
4911
4912static bool programUndefinedIfUndefOrPoison(const Value *V,
4913 bool PoisonOnly);
4914
4915static bool isGuaranteedNotToBeUndefOrPoison(const Value *V,
4916 AssumptionCache *AC,
4917 const Instruction *CtxI,
4918 const DominatorTree *DT,
4919 unsigned Depth, bool PoisonOnly) {
4920 if (Depth >= MaxAnalysisRecursionDepth)
4921 return false;
4922
4923 if (isa<MetadataAsValue>(V))
4924 return false;
4925
4926 if (const auto *A = dyn_cast<Argument>(V)) {
4927 if (A->hasAttribute(Attribute::NoUndef))
4928 return true;
4929 }
4930
4931 if (auto *C = dyn_cast<Constant>(V)) {
4932 if (isa<UndefValue>(C))
4933 return PoisonOnly && !isa<PoisonValue>(C);
4934
4935 if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(V) ||
4936 isa<ConstantPointerNull>(C) || isa<Function>(C))
4937 return true;
4938
4939 if (C->getType()->isVectorTy() && !isa<ConstantExpr>(C))
4940 return (PoisonOnly ? !C->containsPoisonElement()
4941 : !C->containsUndefOrPoisonElement()) &&
4942 !C->containsConstantExpression();
4943 }
4944
4945 // Strip cast operations from a pointer value.
4946 // Note that stripPointerCastsSameRepresentation can strip off getelementptr
4947 // inbounds with zero offset. To guarantee that the result isn't poison, the
4948 // stripped pointer is checked as it has to be pointing into an allocated
4949 // object or be null `null` to ensure `inbounds` getelement pointers with a
4950 // zero offset could not produce poison.
4951 // It can strip off addrspacecast that do not change bit representation as
4952 // well. We believe that such addrspacecast is equivalent to no-op.
4953 auto *StrippedV = V->stripPointerCastsSameRepresentation();
4954 if (isa<AllocaInst>(StrippedV) || isa<GlobalVariable>(StrippedV) ||
4955 isa<Function>(StrippedV) || isa<ConstantPointerNull>(StrippedV))
4956 return true;
4957
4958 auto OpCheck = [&](const Value *V) {
4959 return isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth + 1,
4960 PoisonOnly);
4961 };
4962
4963 if (auto *Opr = dyn_cast<Operator>(V)) {
4964 // If the value is a freeze instruction, then it can never
4965 // be undef or poison.
4966 if (isa<FreezeInst>(V))
4967 return true;
4968
4969 if (const auto *CB = dyn_cast<CallBase>(V)) {
4970 if (CB->hasRetAttr(Attribute::NoUndef))
4971 return true;
4972 }
4973
4974 if (const auto *PN = dyn_cast<PHINode>(V)) {
4975 unsigned Num = PN->getNumIncomingValues();
4976 bool IsWellDefined = true;
4977 for (unsigned i = 0; i < Num; ++i) {
4978 auto *TI = PN->getIncomingBlock(i)->getTerminator();
4979 if (!isGuaranteedNotToBeUndefOrPoison(PN->getIncomingValue(i), AC, TI,
4980 DT, Depth + 1, PoisonOnly)) {
4981 IsWellDefined = false;
4982 break;
4983 }
4984 }
4985 if (IsWellDefined)
4986 return true;
4987 } else if (!canCreateUndefOrPoison(Opr) && all_of(Opr->operands(), OpCheck))
4988 return true;
4989 }
4990
4991 if (auto *I = dyn_cast<LoadInst>(V))
4992 if (I->getMetadata(LLVMContext::MD_noundef))
4993 return true;
4994
4995 if (programUndefinedIfUndefOrPoison(V, PoisonOnly))
4996 return true;
4997
4998 // CxtI may be null or a cloned instruction.
4999 if (!CtxI || !CtxI->getParent() || !DT)
5000 return false;
5001
5002 auto *DNode = DT->getNode(CtxI->getParent());
5003 if (!DNode)
5004 // Unreachable block
5005 return false;
5006
5007 // If V is used as a branch condition before reaching CtxI, V cannot be
5008 // undef or poison.
5009 // br V, BB1, BB2
5010 // BB1:
5011 // CtxI ; V cannot be undef or poison here
5012 auto *Dominator = DNode->getIDom();
5013 while (Dominator) {
5014 auto *TI = Dominator->getBlock()->getTerminator();
5015
5016 Value *Cond = nullptr;
5017 if (auto BI = dyn_cast<BranchInst>(TI)) {
5018 if (BI->isConditional())
5019 Cond = BI->getCondition();
5020 } else if (auto SI = dyn_cast<SwitchInst>(TI)) {
5021 Cond = SI->getCondition();
5022 }
5023
5024 if (Cond) {
5025 if (Cond == V)
5026 return true;
5027 else if (PoisonOnly && isa<Operator>(Cond)) {
5028 // For poison, we can analyze further
5029 auto *Opr = cast<Operator>(Cond);
5030 if (propagatesPoison(Opr) && is_contained(Opr->operand_values(), V))
5031 return true;
5032 }
5033 }
5034
5035 Dominator = Dominator->getIDom();
5036 }
5037
5038 SmallVector<Attribute::AttrKind, 2> AttrKinds{Attribute::NoUndef};
5039 if (getKnowledgeValidInContext(V, AttrKinds, CtxI, DT, AC))
5040 return true;
5041
5042 return false;
5043}
5044
5045bool llvm::isGuaranteedNotToBeUndefOrPoison(const Value *V, AssumptionCache *AC,
5046 const Instruction *CtxI,
5047 const DominatorTree *DT,
5048 unsigned Depth) {
5049 return ::isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth, false);
5050}
5051
5052bool llvm::isGuaranteedNotToBePoison(const Value *V, AssumptionCache *AC,
5053 const Instruction *CtxI,
5054 const DominatorTree *DT, unsigned Depth) {
5055 return ::isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth, true);
5056}
5057
5058OverflowResult llvm::computeOverflowForSignedAdd(const AddOperator *Add,
5059 const DataLayout &DL,
5060 AssumptionCache *AC,
5061 const Instruction *CxtI,
5062 const DominatorTree *DT) {
5063 return ::computeOverflowForSignedAdd(Add->getOperand(0), Add->getOperand(1),
5064 Add, DL, AC, CxtI, DT);
5065}
5066
5067OverflowResult llvm::computeOverflowForSignedAdd(const Value *LHS,
5068 const Value *RHS,
5069 const DataLayout &DL,
5070 AssumptionCache *AC,
5071 const Instruction *CxtI,
5072 const DominatorTree *DT) {
5073 return ::computeOverflowForSignedAdd(LHS, RHS, nullptr, DL, AC, CxtI, DT);
5074}
5075
5076bool llvm::isGuaranteedToTransferExecutionToSuccessor(const Instruction *I) {
5077 // Note: An atomic operation isn't guaranteed to return in a reasonable amount
5078 // of time because it's possible for another thread to interfere with it for an
5079 // arbitrary length of time, but programs aren't allowed to rely on that.
5080
5081 // If there is no successor, then execution can't transfer to it.
5082 if (isa<ReturnInst>(I))
5083 return false;
5084 if (isa<UnreachableInst>(I))
5085 return false;
5086
5087 // An instruction that returns without throwing must transfer control flow
5088 // to a successor.
5089 return !I->mayThrow() && I->willReturn();
5090}
5091
5092bool llvm::isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB) {
5093 // TODO: This is slightly conservative for invoke instruction since exiting
5094 // via an exception *is* normal control for them.
5095 for (const Instruction &I : *BB)
5096 if (!isGuaranteedToTransferExecutionToSuccessor(&I))
5097 return false;
5098 return true;
5099}
5100
5101bool llvm::isGuaranteedToExecuteForEveryIteration(const Instruction *I,
5102 const Loop *L) {
5103 // The loop header is guaranteed to be executed for every iteration.
5104 //
5105 // FIXME: Relax this constraint to cover all basic blocks that are
5106 // guaranteed to be executed at every iteration.
5107 if (I->getParent() != L->getHeader()) return false;
5108
5109 for (const Instruction &LI : *L->getHeader()) {
5110 if (&LI == I) return true;
5111 if (!isGuaranteedToTransferExecutionToSuccessor(&LI)) return false;
5112 }
5113 llvm_unreachable("Instruction not contained in its own parent basic block.")::llvm::llvm_unreachable_internal("Instruction not contained in its own parent basic block."
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 5113)
;
5114}
5115
5116bool llvm::propagatesPoison(const Operator *I) {
5117 switch (I->getOpcode()) {
5118 case Instruction::Freeze:
5119 case Instruction::Select:
5120 case Instruction::PHI:
5121 case Instruction::Call:
5122 case Instruction::Invoke:
5123 return false;
5124 case Instruction::ICmp:
5125 case Instruction::FCmp:
5126 case Instruction::GetElementPtr:
5127 return true;
5128 default:
5129 if (isa<BinaryOperator>(I) || isa<UnaryOperator>(I) || isa<CastInst>(I))
5130 return true;
5131
5132 // Be conservative and return false.
5133 return false;
5134 }
5135}
5136
5137void llvm::getGuaranteedWellDefinedOps(
5138 const Instruction *I, SmallPtrSetImpl<const Value *> &Operands) {
5139 switch (I->getOpcode()) {
5140 case Instruction::Store:
5141 Operands.insert(cast<StoreInst>(I)->getPointerOperand());
5142 break;
5143
5144 case Instruction::Load:
5145 Operands.insert(cast<LoadInst>(I)->getPointerOperand());
5146 break;
5147
5148 // Since dereferenceable attribute imply noundef, atomic operations
5149 // also implicitly have noundef pointers too
5150 case Instruction::AtomicCmpXchg:
5151 Operands.insert(cast<AtomicCmpXchgInst>(I)->getPointerOperand());
5152 break;
5153
5154 case Instruction::AtomicRMW:
5155 Operands.insert(cast<AtomicRMWInst>(I)->getPointerOperand());
5156 break;
5157
5158 case Instruction::Call:
5159 case Instruction::Invoke: {
5160 const CallBase *CB = cast<CallBase>(I);
5161 if (CB->isIndirectCall())
5162 Operands.insert(CB->getCalledOperand());
5163 for (unsigned i = 0; i < CB->arg_size(); ++i) {
5164 if (CB->paramHasAttr(i, Attribute::NoUndef) ||
5165 CB->paramHasAttr(i, Attribute::Dereferenceable))
5166 Operands.insert(CB->getArgOperand(i));
5167 }
5168 break;
5169 }
5170
5171 default:
5172 break;
5173 }
5174}
5175
5176void llvm::getGuaranteedNonPoisonOps(const Instruction *I,
5177 SmallPtrSetImpl<const Value *> &Operands) {
5178 getGuaranteedWellDefinedOps(I, Operands);
5179 switch (I->getOpcode()) {
5180 // Divisors of these operations are allowed to be partially undef.
5181 case Instruction::UDiv:
5182 case Instruction::SDiv:
5183 case Instruction::URem:
5184 case Instruction::SRem:
5185 Operands.insert(I->getOperand(1));
5186 break;
5187
5188 default:
5189 break;
5190 }
5191}
5192
5193bool llvm::mustTriggerUB(const Instruction *I,
5194 const SmallSet<const Value *, 16>& KnownPoison) {
5195 SmallPtrSet<const Value *, 4> NonPoisonOps;
5196 getGuaranteedNonPoisonOps(I, NonPoisonOps);
5197
5198 for (const auto *V : NonPoisonOps)
5199 if (KnownPoison.count(V))
5200 return true;
5201
5202 return false;
5203}
5204
5205static bool programUndefinedIfUndefOrPoison(const Value *V,
5206 bool PoisonOnly) {
5207 // We currently only look for uses of values within the same basic
5208 // block, as that makes it easier to guarantee that the uses will be
5209 // executed given that Inst is executed.
5210 //
5211 // FIXME: Expand this to consider uses beyond the same basic block. To do
5212 // this, look out for the distinction between post-dominance and strong
5213 // post-dominance.
5214 const BasicBlock *BB = nullptr;
5215 BasicBlock::const_iterator Begin;
5216 if (const auto *Inst = dyn_cast<Instruction>(V)) {
5217 BB = Inst->getParent();
5218 Begin = Inst->getIterator();
5219 Begin++;
5220 } else if (const auto *Arg = dyn_cast<Argument>(V)) {
5221 BB = &Arg->getParent()->getEntryBlock();
5222 Begin = BB->begin();
5223 } else {
5224 return false;
5225 }
5226
5227 BasicBlock::const_iterator End = BB->end();
5228
5229 if (!PoisonOnly) {
5230 // Since undef does not propagate eagerly, be conservative & just check
5231 // whether a value is directly passed to an instruction that must take
5232 // well-defined operands.
5233
5234 for (auto &I : make_range(Begin, End)) {
5235 SmallPtrSet<const Value *, 4> WellDefinedOps;
5236 getGuaranteedWellDefinedOps(&I, WellDefinedOps);
5237 for (auto *Op : WellDefinedOps) {
5238 if (Op == V)
5239 return true;
5240 }
5241 if (!isGuaranteedToTransferExecutionToSuccessor(&I))
5242 break;
5243 }
5244 return false;
5245 }
5246
5247 // Set of instructions that we have proved will yield poison if Inst
5248 // does.
5249 SmallSet<const Value *, 16> YieldsPoison;
5250 SmallSet<const BasicBlock *, 4> Visited;
5251
5252 YieldsPoison.insert(V);
5253 auto Propagate = [&](const User *User) {
5254 if (propagatesPoison(cast<Operator>(User)))
5255 YieldsPoison.insert(User);
5256 };
5257 for_each(V->users(), Propagate);
5258 Visited.insert(BB);
5259
5260 unsigned Iter = 0;
5261 while (Iter++ < MaxAnalysisRecursionDepth) {
5262 for (auto &I : make_range(Begin, End)) {
5263 if (mustTriggerUB(&I, YieldsPoison))
5264 return true;
5265 if (!isGuaranteedToTransferExecutionToSuccessor(&I))
5266 return false;
5267
5268 // Mark poison that propagates from I through uses of I.
5269 if (YieldsPoison.count(&I))
5270 for_each(I.users(), Propagate);
5271 }
5272
5273 if (auto *NextBB = BB->getSingleSuccessor()) {
5274 if (Visited.insert(NextBB).second) {
5275 BB = NextBB;
5276 Begin = BB->getFirstNonPHI()->getIterator();
5277 End = BB->end();
5278 continue;
5279 }
5280 }
5281
5282 break;
5283 }
5284 return false;
5285}
5286
5287bool llvm::programUndefinedIfUndefOrPoison(const Instruction *Inst) {
5288 return ::programUndefinedIfUndefOrPoison(Inst, false);
5289}
5290
5291bool llvm::programUndefinedIfPoison(const Instruction *Inst) {
5292 return ::programUndefinedIfUndefOrPoison(Inst, true);
5293}
5294
5295static bool isKnownNonNaN(const Value *V, FastMathFlags FMF) {
5296 if (FMF.noNaNs())
5297 return true;
5298
5299 if (auto *C = dyn_cast<ConstantFP>(V))
5300 return !C->isNaN();
5301
5302 if (auto *C = dyn_cast<ConstantDataVector>(V)) {
5303 if (!C->getElementType()->isFloatingPointTy())
5304 return false;
5305 for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
5306 if (C->getElementAsAPFloat(I).isNaN())
5307 return false;
5308 }
5309 return true;
5310 }
5311
5312 if (isa<ConstantAggregateZero>(V))
5313 return true;
5314
5315 return false;
5316}
5317
5318static bool isKnownNonZero(const Value *V) {
5319 if (auto *C = dyn_cast<ConstantFP>(V))
5320 return !C->isZero();
5321
5322 if (auto *C = dyn_cast<ConstantDataVector>(V)) {
5323 if (!C->getElementType()->isFloatingPointTy())
5324 return false;
5325 for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
5326 if (C->getElementAsAPFloat(I).isZero())
5327 return false;
5328 }
5329 return true;
5330 }
5331
5332 return false;
5333}
5334
5335/// Match clamp pattern for float types without care about NaNs or signed zeros.
5336/// Given non-min/max outer cmp/select from the clamp pattern this
5337/// function recognizes if it can be substitued by a "canonical" min/max
5338/// pattern.
5339static SelectPatternResult matchFastFloatClamp(CmpInst::Predicate Pred,
5340 Value *CmpLHS, Value *CmpRHS,
5341 Value *TrueVal, Value *FalseVal,
5342 Value *&LHS, Value *&RHS) {
5343 // Try to match
5344 // X < C1 ? C1 : Min(X, C2) --> Max(C1, Min(X, C2))
5345 // X > C1 ? C1 : Max(X, C2) --> Min(C1, Max(X, C2))
5346 // and return description of the outer Max/Min.
5347
5348 // First, check if select has inverse order:
5349 if (CmpRHS == FalseVal) {
5350 std::swap(TrueVal, FalseVal);
5351 Pred = CmpInst::getInversePredicate(Pred);
5352 }
5353
5354 // Assume success now. If there's no match, callers should not use these anyway.
5355 LHS = TrueVal;
5356 RHS = FalseVal;
5357
5358 const APFloat *FC1;
5359 if (CmpRHS != TrueVal || !match(CmpRHS, m_APFloat(FC1)) || !FC1->isFinite())
5360 return {SPF_UNKNOWN, SPNB_NA, false};
5361
5362 const APFloat *FC2;
5363 switch (Pred) {
5364 case CmpInst::FCMP_OLT:
5365 case CmpInst::FCMP_OLE:
5366 case CmpInst::FCMP_ULT:
5367 case CmpInst::FCMP_ULE:
5368 if (match(FalseVal,
5369 m_CombineOr(m_OrdFMin(m_Specific(CmpLHS), m_APFloat(FC2)),
5370 m_UnordFMin(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
5371 *FC1 < *FC2)
5372 return {SPF_FMAXNUM, SPNB_RETURNS_ANY, false};
5373 break;
5374 case CmpInst::FCMP_OGT:
5375 case CmpInst::FCMP_OGE:
5376 case CmpInst::FCMP_UGT:
5377 case CmpInst::FCMP_UGE:
5378 if (match(FalseVal,
5379 m_CombineOr(m_OrdFMax(m_Specific(CmpLHS), m_APFloat(FC2)),
5380 m_UnordFMax(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
5381 *FC1 > *FC2)
5382 return {SPF_FMINNUM, SPNB_RETURNS_ANY, false};
5383 break;
5384 default:
5385 break;
5386 }
5387
5388 return {SPF_UNKNOWN, SPNB_NA, false};
5389}
5390
5391/// Recognize variations of:
5392/// CLAMP(v,l,h) ==> ((v) < (l) ? (l) : ((v) > (h) ? (h) : (v)))
5393static SelectPatternResult matchClamp(CmpInst::Predicate Pred,
5394 Value *CmpLHS, Value *CmpRHS,
5395 Value *TrueVal, Value *FalseVal) {
5396 // Swap the select operands and predicate to match the patterns below.
5397 if (CmpRHS != TrueVal) {
5398 Pred = ICmpInst::getSwappedPredicate(Pred);
5399 std::swap(TrueVal, FalseVal);
5400 }
5401 const APInt *C1;
5402 if (CmpRHS == TrueVal && match(CmpRHS, m_APInt(C1))) {
5403 const APInt *C2;
5404 // (X <s C1) ? C1 : SMIN(X, C2) ==> SMAX(SMIN(X, C2), C1)
5405 if (match(FalseVal, m_SMin(m_Specific(CmpLHS), m_APInt(C2))) &&
5406 C1->slt(*C2) && Pred == CmpInst::ICMP_SLT)
5407 return {SPF_SMAX, SPNB_NA, false};
5408
5409 // (X >s C1) ? C1 : SMAX(X, C2) ==> SMIN(SMAX(X, C2), C1)
5410 if (match(FalseVal, m_SMax(m_Specific(CmpLHS), m_APInt(C2))) &&
5411 C1->sgt(*C2) && Pred == CmpInst::ICMP_SGT)
5412 return {SPF_SMIN, SPNB_NA, false};
5413
5414 // (X <u C1) ? C1 : UMIN(X, C2) ==> UMAX(UMIN(X, C2), C1)
5415 if (match(FalseVal, m_UMin(m_Specific(CmpLHS), m_APInt(C2))) &&
5416 C1->ult(*C2) && Pred == CmpInst::ICMP_ULT)
5417 return {SPF_UMAX, SPNB_NA, false};
5418
5419 // (X >u C1) ? C1 : UMAX(X, C2) ==> UMIN(UMAX(X, C2), C1)
5420 if (match(FalseVal, m_UMax(m_Specific(CmpLHS), m_APInt(C2))) &&
5421 C1->ugt(*C2) && Pred == CmpInst::ICMP_UGT)
5422 return {SPF_UMIN, SPNB_NA, false};
5423 }
5424 return {SPF_UNKNOWN, SPNB_NA, false};
5425}
5426
5427/// Recognize variations of:
5428/// a < c ? min(a,b) : min(b,c) ==> min(min(a,b),min(b,c))
5429static SelectPatternResult matchMinMaxOfMinMax(CmpInst::Predicate Pred,
5430 Value *CmpLHS, Value *CmpRHS,
5431 Value *TVal, Value *FVal,
5432 unsigned Depth) {
5433 // TODO: Allow FP min/max with nnan/nsz.
5434 assert(CmpInst::isIntPredicate(Pred) && "Expected integer comparison")((CmpInst::isIntPredicate(Pred) && "Expected integer comparison"
) ? static_cast<void> (0) : __assert_fail ("CmpInst::isIntPredicate(Pred) && \"Expected integer comparison\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 5434, __PRETTY_FUNCTION__))
;
5435
5436 Value *A = nullptr, *B = nullptr;
5437 SelectPatternResult L = matchSelectPattern(TVal, A, B, nullptr, Depth + 1);
5438 if (!SelectPatternResult::isMinOrMax(L.Flavor))
5439 return {SPF_UNKNOWN, SPNB_NA, false};
5440
5441 Value *C = nullptr, *D = nullptr;
5442 SelectPatternResult R = matchSelectPattern(FVal, C, D, nullptr, Depth + 1);
5443 if (L.Flavor != R.Flavor)
5444 return {SPF_UNKNOWN, SPNB_NA, false};
5445
5446 // We have something like: x Pred y ? min(a, b) : min(c, d).
5447 // Try to match the compare to the min/max operations of the select operands.
5448 // First, make sure we have the right compare predicate.
5449 switch (L.Flavor) {
5450 case SPF_SMIN:
5451 if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE) {
5452 Pred = ICmpInst::getSwappedPredicate(Pred);
5453 std::swap(CmpLHS, CmpRHS);
5454 }
5455 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
5456 break;
5457 return {SPF_UNKNOWN, SPNB_NA, false};
5458 case SPF_SMAX:
5459 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) {
5460 Pred = ICmpInst::getSwappedPredicate(Pred);
5461 std::swap(CmpLHS, CmpRHS);
5462 }
5463 if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
5464 break;
5465 return {SPF_UNKNOWN, SPNB_NA, false};
5466 case SPF_UMIN:
5467 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) {
5468 Pred = ICmpInst::getSwappedPredicate(Pred);
5469 std::swap(CmpLHS, CmpRHS);
5470 }
5471 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE)
5472 break;
5473 return {SPF_UNKNOWN, SPNB_NA, false};
5474 case SPF_UMAX:
5475 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
5476 Pred = ICmpInst::getSwappedPredicate(Pred);
5477 std::swap(CmpLHS, CmpRHS);
5478 }
5479 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
5480 break;
5481 return {SPF_UNKNOWN, SPNB_NA, false};
5482 default:
5483 return {SPF_UNKNOWN, SPNB_NA, false};
5484 }
5485
5486 // If there is a common operand in the already matched min/max and the other
5487 // min/max operands match the compare operands (either directly or inverted),
5488 // then this is min/max of the same flavor.
5489
5490 // a pred c ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
5491 // ~c pred ~a ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
5492 if (D == B) {
5493 if ((CmpLHS == A && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
5494 match(A, m_Not(m_Specific(CmpRHS)))))
5495 return {L.Flavor, SPNB_NA, false};
5496 }
5497 // a pred d ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
5498 // ~d pred ~a ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
5499 if (C == B) {
5500 if ((CmpLHS == A && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
5501 match(A, m_Not(m_Specific(CmpRHS)))))
5502 return {L.Flavor, SPNB_NA, false};
5503 }
5504 // b pred c ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
5505 // ~c pred ~b ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
5506 if (D == A) {
5507 if ((CmpLHS == B && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
5508 match(B, m_Not(m_Specific(CmpRHS)))))
5509 return {L.Flavor, SPNB_NA, false};
5510 }
5511 // b pred d ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
5512 // ~d pred ~b ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
5513 if (C == A) {
5514 if ((CmpLHS == B && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
5515 match(B, m_Not(m_Specific(CmpRHS)))))
5516 return {L.Flavor, SPNB_NA, false};
5517 }
5518
5519 return {SPF_UNKNOWN, SPNB_NA, false};
5520}
5521
5522/// If the input value is the result of a 'not' op, constant integer, or vector
5523/// splat of a constant integer, return the bitwise-not source value.
5524/// TODO: This could be extended to handle non-splat vector integer constants.
5525static Value *getNotValue(Value *V) {
5526 Value *NotV;
5527 if (match(V, m_Not(m_Value(NotV))))
5528 return NotV;
5529
5530 const APInt *C;
5531 if (match(V, m_APInt(C)))
5532 return ConstantInt::get(V->getType(), ~(*C));
5533
5534 return nullptr;
5535}
5536
5537/// Match non-obvious integer minimum and maximum sequences.
5538static SelectPatternResult matchMinMax(CmpInst::Predicate Pred,
5539 Value *CmpLHS, Value *CmpRHS,
5540 Value *TrueVal, Value *FalseVal,
5541 Value *&LHS, Value *&RHS,
5542 unsigned Depth) {
5543 // Assume success. If there's no match, callers should not use these anyway.
5544 LHS = TrueVal;
5545 RHS = FalseVal;
5546
5547 SelectPatternResult SPR = matchClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal);
5548 if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
5549 return SPR;
5550
5551 SPR = matchMinMaxOfMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, Depth);
5552 if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
5553 return SPR;
5554
5555 // Look through 'not' ops to find disguised min/max.
5556 // (X > Y) ? ~X : ~Y ==> (~X < ~Y) ? ~X : ~Y ==> MIN(~X, ~Y)
5557 // (X < Y) ? ~X : ~Y ==> (~X > ~Y) ? ~X : ~Y ==> MAX(~X, ~Y)
5558 if (CmpLHS == getNotValue(TrueVal) && CmpRHS == getNotValue(FalseVal)) {
5559 switch (Pred) {
5560 case CmpInst::ICMP_SGT: return {SPF_SMIN, SPNB_NA, false};
5561 case CmpInst::ICMP_SLT: return {SPF_SMAX, SPNB_NA, false};
5562 case CmpInst::ICMP_UGT: return {SPF_UMIN, SPNB_NA, false};
5563 case CmpInst::ICMP_ULT: return {SPF_UMAX, SPNB_NA, false};
5564 default: break;
5565 }
5566 }
5567
5568 // (X > Y) ? ~Y : ~X ==> (~X < ~Y) ? ~Y : ~X ==> MAX(~Y, ~X)
5569 // (X < Y) ? ~Y : ~X ==> (~X > ~Y) ? ~Y : ~X ==> MIN(~Y, ~X)
5570 if (CmpLHS == getNotValue(FalseVal) && CmpRHS == getNotValue(TrueVal)) {
5571 switch (Pred) {
5572 case CmpInst::ICMP_SGT: return {SPF_SMAX, SPNB_NA, false};
5573 case CmpInst::ICMP_SLT: return {SPF_SMIN, SPNB_NA, false};
5574 case CmpInst::ICMP_UGT: return {SPF_UMAX, SPNB_NA, false};
5575 case CmpInst::ICMP_ULT: return {SPF_UMIN, SPNB_NA, false};
5576 default: break;
5577 }
5578 }
5579
5580 if (Pred != CmpInst::ICMP_SGT && Pred != CmpInst::ICMP_SLT)
5581 return {SPF_UNKNOWN, SPNB_NA, false};
5582
5583 // Z = X -nsw Y
5584 // (X >s Y) ? 0 : Z ==> (Z >s 0) ? 0 : Z ==> SMIN(Z, 0)
5585 // (X <s Y) ? 0 : Z ==> (Z <s 0) ? 0 : Z ==> SMAX(Z, 0)
5586 if (match(TrueVal, m_Zero()) &&
5587 match(FalseVal, m_NSWSub(m_Specific(CmpLHS), m_Specific(CmpRHS))))
5588 return {Pred == CmpInst::ICMP_SGT ? SPF_SMIN : SPF_SMAX, SPNB_NA, false};
5589
5590 // Z = X -nsw Y
5591 // (X >s Y) ? Z : 0 ==> (Z >s 0) ? Z : 0 ==> SMAX(Z, 0)
5592 // (X <s Y) ? Z : 0 ==> (Z <s 0) ? Z : 0 ==> SMIN(Z, 0)
5593 if (match(FalseVal, m_Zero()) &&
5594 match(TrueVal, m_NSWSub(m_Specific(CmpLHS), m_Specific(CmpRHS))))
5595 return {Pred == CmpInst::ICMP_SGT ? SPF_SMAX : SPF_SMIN, SPNB_NA, false};
5596
5597 const APInt *C1;
5598 if (!match(CmpRHS, m_APInt(C1)))
5599 return {SPF_UNKNOWN, SPNB_NA, false};
5600
5601 // An unsigned min/max can be written with a signed compare.
5602 const APInt *C2;
5603 if ((CmpLHS == TrueVal && match(FalseVal, m_APInt(C2))) ||
5604 (CmpLHS == FalseVal && match(TrueVal, m_APInt(C2)))) {
5605 // Is the sign bit set?
5606 // (X <s 0) ? X : MAXVAL ==> (X >u MAXVAL) ? X : MAXVAL ==> UMAX
5607 // (X <s 0) ? MAXVAL : X ==> (X >u MAXVAL) ? MAXVAL : X ==> UMIN
5608 if (Pred == CmpInst::ICMP_SLT && C1->isNullValue() &&
5609 C2->isMaxSignedValue())
5610 return {CmpLHS == TrueVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
5611
5612 // Is the sign bit clear?
5613 // (X >s -1) ? MINVAL : X ==> (X <u MINVAL) ? MINVAL : X ==> UMAX
5614 // (X >s -1) ? X : MINVAL ==> (X <u MINVAL) ? X : MINVAL ==> UMIN
5615 if (Pred == CmpInst::ICMP_SGT && C1->isAllOnesValue() &&
5616 C2->isMinSignedValue())
5617 return {CmpLHS == FalseVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
5618 }
5619
5620 return {SPF_UNKNOWN, SPNB_NA, false};
5621}
5622
5623bool llvm::isKnownNegation(const Value *X, const Value *Y, bool NeedNSW) {
5624 assert(X && Y && "Invalid operand")((X && Y && "Invalid operand") ? static_cast<
void> (0) : __assert_fail ("X && Y && \"Invalid operand\""
, "/build/llvm-toolchain-snapshot-13~++20210223111116+16ede0956cb1/llvm/lib/Analysis/ValueTracking.cpp"
, 5624, __PRETTY_FUNCTION__))
;
5625
5626 // X = sub (0, Y) || X = sub nsw (0, Y)
5627 if ((!NeedNSW && match(X, m_Sub(m_ZeroInt(), m_Specific(Y)))) ||
5628 (NeedNSW && match(X, m_NSWSub(m_ZeroInt(), m_Specific(Y)))))
5629 return true;
5630
5631 // Y = sub (0, X) || Y = sub nsw (0, X)
5632 if ((!NeedNSW && match(Y, m_Sub(m_ZeroInt(), m_Specific(X)))) ||
5633 (NeedNSW && match(Y, m_NSWSub(m_ZeroInt(), m_Specific(X)))))
5634 return true;
5635
5636 // X = sub (A, B), Y = sub (B, A) || X = sub nsw (A, B), Y = sub nsw (B, A)
5637 Value *A, *B;
5638 return (!NeedNSW && (match(X, m_Sub(m_Value(A), m_Value(B))) &&
5639 match(Y, m_Sub(m_Specific(B), m_Specific(A))))) ||
5640 (NeedNSW && (match(X, m_NSWSub(m_Value(A), m_Value(B))) &&
5641 match(Y, m_NSWSub(m_Specific(B), m_Specific(A)))));
5642}
5643
5644static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
5645 FastMathFlags FMF,
5646 Value *CmpLHS, Value *CmpRHS,
5647 Value *TrueVal, Value *FalseVal,
5648 Value *&LHS, Value *&RHS,
5649 unsigned Depth) {
5650 if (CmpInst::isFPPredicate(Pred)) {
5651 // IEEE-754 ignores the sign of 0.0 in comparisons. So if the select has one
5652 // 0.0 operand, set the compare's 0.0 operands to that same value for the
5653 // purpose of identifying min/max. Disregard vector constants with undefined
5654 // elements because those can not be back-propagated for analysis.
5655 Value *OutputZeroVal = nullptr;
5656 if (match(TrueVal, m_AnyZeroFP()) && !match(FalseVal, m_AnyZeroFP()) &&
5657 !cast<Constant>(TrueVal)->containsUndefOrPoisonElement())
5658 OutputZeroVal = TrueVal;
5659 else if (match(FalseVal, m_AnyZeroFP()) && !match(TrueVal, m_AnyZeroFP()) &&
5660 !cast<Constant>(FalseVal)->containsUndefOrPoisonElement())
5661 OutputZeroVal = FalseVal;
5662
5663 if (OutputZeroVal) {
5664 if (match(CmpLHS, m_AnyZeroFP()))
5665 CmpLHS = OutputZeroVal;
5666 if (match(CmpRHS, m_AnyZeroFP()))
5667 CmpRHS = OutputZeroVal;
5668 }
5669 }
5670
5671 LHS = CmpLHS;
5672 RHS = CmpRHS;
5673
5674 // Signed zero may return inconsistent results between implementations.
5675 // (0.0 <= -0.0) ? 0.0 : -0.0 // Returns 0.0
5676 // minNum(0.0, -0.0) // May return -0.0 or 0.0 (IEEE 754-2008 5.3.1)
5677 // Therefore, we behave conservatively and only proceed if at least one of the
5678 // operands is known to not be zero or if we don't care about signed zero.
5679 switch (Pred) {
5680 default: break;
5681 // FIXME: Include OGT/OLT/UGT/ULT.
5682 case CmpInst::FCMP_OGE: case CmpInst::FCMP_OLE:
5683 case CmpInst::FCMP_UGE: case CmpInst::FCMP_ULE:
5684 if (!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
5685 !isKnownNonZero(CmpRHS))
5686 return {SPF_UNKNOWN, SPNB_NA, false};
5687 }
5688
5689 SelectPatternNaNBehavior NaNBehavior = SPNB_NA;
5690 bool Ordered = false;
5691
5692 // When given one NaN and one non-NaN input:
5693 // - maxnum/minnum (C99 fmaxf()/fminf()) return the non-NaN input.
5694 // - A simple C99 (a < b ? a : b) construction will return 'b' (as the
5695 // ordered comparison fails), which could be NaN or non-NaN.
5696 // so here we discover exactly what NaN behavior is required/accepted.
5697 if (CmpInst::isFPPredicate(Pred)) {
5698 bool LHSSafe = isKnownNonNaN(CmpLHS, FMF);
5699 bool RHSSafe = isKnownNonNaN(CmpRHS, FMF);
5700
5701 if (LHSSafe && RHSSafe) {
5702 // Both operands are known non-NaN.
5703 NaNBehavior = SPNB_RETURNS_ANY;
5704 } else if (CmpInst::isOrdered(Pred)) {
5705 // An ordered comparison will return false when given a NaN, so it
5706 // returns the RHS.
5707 Ordered = true;
5708 if (LHSSafe)
5709 // LHS is non-NaN, so if RHS is NaN then NaN will be returned.
5710 NaNBehavior = SPNB_RETURNS_NAN;
5711 else if (RHSSafe)
5712 NaNBehavior = SPNB_RETURNS_OTHER;
5713 else
5714 // Completely unsafe.
5715 return {SPF_UNKNOWN, SPNB_NA, false};
5716 } else {
5717 Ordered = false;
5718 // An unordered comparison will return true when given a NaN, so it
5719 // returns the LHS.
5720 if (LHSSafe)
5721 // LHS is non-NaN, so if RHS is NaN then non-NaN will be returned.
5722 NaNBehavior = SPNB_RETURNS_OTHER;
5723 else if (RHSSafe)
5724 NaNBehavior = SPNB_RETURNS_NAN;
5725 else
5726 // Completely unsafe.
5727 return {SPF_UNKNOWN, SPNB_NA, false};
5728 }
5729 }
5730
5731 if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
5732 std::swap(CmpLHS, CmpRHS);
5733 Pred = CmpInst::getSwappedPredicate(Pred);
5734 if (NaNBehavior == SPNB_RETURNS_NAN)
5735 NaNBehavior = SPNB_RETURNS_OTHER;
5736 else if (NaNBehavior == SPNB_RETURNS_OTHER)
5737 NaNBehavior = SPNB_RETURNS_NAN;
5738 Ordered = !Ordered;
5739 }
5740
5741 // ([if]cmp X, Y) ? X : Y
5742 if (TrueVal == CmpLHS && FalseVal == CmpRHS) {
5743 switch (Pred) {
5744 default: return {SPF_UNKNOWN, SPNB_NA, false}; // Equality.
5745 case ICmpInst::ICMP_UGT:
5746 case ICmpInst::ICMP_UGE: return {SPF_UMAX, SPNB_NA, false};
5747 case ICmpInst::ICMP_SGT:
5748 case ICmpInst::ICMP_SGE: return {SPF_SMAX, SPNB_NA, false};
5749 case ICmpInst::ICMP_ULT:
5750 case ICmpInst::ICMP_ULE: return {SPF_UMIN, SPNB_NA, false};
5751 case ICmpInst::ICMP_SLT:
5752 case ICmpInst::ICMP_SLE: return {SPF_SMIN, SPNB_NA, false};
5753 case FCmpInst::FCMP_UGT:
5754 case FCmpInst::FCMP_UGE:
5755 case FCmpInst::FCMP_OGT:
5756 case FCmpInst::FCMP_OGE: return {SPF_FMAXNUM, NaNBehavior, Ordered};
5757 case FCmpInst::FCMP_ULT:
5758 case FCmpInst::FCMP_ULE:
5759 case FCmpInst::FCMP_OLT:
5760 case FCmpInst::FCMP_OLE: return {SPF_FMINNUM, NaNBehavior, Ordered};
5761 }
5762 }
5763
5764 if (isKnownNegation(TrueVal, FalseVal)) {
5765 // Sign-extending LHS does not change its sign, so TrueVal/FalseVal can
5766 // match against either LHS or sext(LHS).
5767 auto MaybeSExtCmpLHS =
5768 m_CombineOr(m_Specific(CmpLHS), m_SExt(m_Specific(CmpLHS)));
5769 auto ZeroOrAllOnes = m_CombineOr(m_ZeroInt(), m_AllOnes());
5770 auto ZeroOrOne = m_CombineOr(m_ZeroInt(), m_One());
5771 if (match(TrueVal, MaybeSExtCmpLHS)) {
5772 // Set the return values. If the compare uses the negated value (-X >s 0),
5773 // swap the return values because the negated value is always 'RHS'.
5774 LHS = TrueVal;
5775 RHS = FalseVal;
5776 if (match(CmpLHS, m_Neg(m_Specific(FalseVal))))
5777 std::swap(LHS, RHS);
5778
5779 // (X >s 0) ? X : -X or (X >s -1) ? X : -X --> ABS(X)
5780 // (-X >s 0) ? -X : X or (-X >s -1) ? -X : X --> ABS(X)
5781 if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
5782 return {SPF_ABS, SPNB_NA, false};
5783
5784 // (X >=s 0) ? X : -X or (X >=s 1) ? X : -X --> ABS(X)
5785 if (Pred == ICmpInst::ICMP_SGE && match(CmpRHS, ZeroOrOne))
5786 return {SPF_ABS, SPNB_NA, false};
5787
5788 // (X <s 0) ? X : -X or (X <s 1) ? X : -X --> NABS(X)
5789 // (-X <s 0) ? -X : X or (-X <s 1) ? -X : X --> NABS(X)
5790 if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
5791 return {SPF_NABS, SPNB_NA, false};
5792 }
5793 else if (match(FalseVal, MaybeSExtCmpLHS)) {
5794 // Set the return values. If the compare uses the negated value (-X >s 0),
5795 // swap the return values because the negated value is always 'RHS'.
5796 LHS = FalseVal;
5797 RHS = TrueVal;
5798 if (match(CmpLHS, m_Neg(m_Specific(TrueVal))))
5799 std::swap(LHS, RHS);
5800
5801 // (X >s 0) ? -X : X or (X >s -1) ? -X : X --> NABS(X)
5802 // (-X >s 0) ? X : -X or (-X >s -1) ? X : -X --> NABS(X)
5803 if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
5804 return {SPF_NABS, SPNB_NA, false};
5805
5806 // (X <s 0) ? -X : X or (X <s 1) ? -X : X --> ABS(X)
5807 // (-X <s 0) ? X : -X or (-X <s 1) ? X : -X --> ABS(X)
5808 if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
5809 return {SPF_ABS, SPNB_NA, false};
5810 }
5811 }
5812
5813 if (CmpInst::isIntPredicate(Pred))
5814 return matchMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS, Depth);
5815
5816 // According to (IEEE 754-2008 5.3.1), minNum(0.0, -0.0) and similar
5817 // may return either -0.0 or 0.0, so fcmp/select pair has stricter
5818 // semantics than minNum. Be conservative in such case.
5819 if (NaNBehavior != SPNB_RETURNS_ANY ||
5820 (!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
5821 !isKnownNonZero(CmpRHS)))
5822 return {SPF_UNKNOWN, SPNB_NA, false};
5823
5824 return matchFastFloatClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS);
5825}
5826
5827/// Helps to match a select pattern in case of a type mismatch.
5828///
5829/// The function processes the case when type of true and false values of a
5830/// select instruction differs from type of the cmp instruction operands because
5831/// of a cast instruction. The function checks if it is legal to move the cast
5832/// operation after "select". If yes, it returns the new second value of
5833/// "select" (with the assumption that cast is moved):
5834/// 1. As operand of cast instruction when both values of "select" are same cast
5835/// instructions.
5836/// 2. As restored constant (by applying reverse cast operation) when the first
5837/// value of the "select" is a cast operation and the second value is a
5838/// constant.
5839/// NOTE: We return only the new second value because the first value could be
5840/// accessed as operand of cast instruction.
5841static Value *lookThroughCast(CmpInst *CmpI, Value *V1, Value *V2,
5842 Instruction::CastOps *CastOp) {
5843 auto *Cast1 = dyn_cast<CastInst>(V1);
5844 if (!Cast1)
5845 return nullptr;
5846
5847 *CastOp = Cast1->getOpcode();
5848 Type *SrcTy = Cast1->getSrcTy();
5849 if (auto *Cast2 = dyn_cast<CastInst>(V2)) {
5850 // If V1 and V2 are both the same cast from the same type, look through V1.
5851 if (*CastOp == Cast2->getOpcode() && SrcTy == Cast2->getSrcTy())
5852 return Cast2->getOperand(0);
5853 return nullptr;
5854 }
5855
5856 auto *C = dyn_cast<Constant>(V2);
5857 if (!C)
5858 return nullptr;
5859
5860 Constant *CastedTo = nullptr;
5861 switch (*CastOp) {
5862 case Instruction::ZExt:
5863 if (CmpI->isUnsigned())
5864 CastedTo = ConstantExpr::getTrunc(C, SrcTy);
5865 break;
5866 case Instruction::SExt:
5867 if (CmpI->isSigned())
5868 CastedTo = ConstantExpr::getTrunc(C, SrcTy, true);
5869 break;
5870 case Instruction::Trunc:
5871 Constant *CmpConst;
5872 if (match(CmpI->getOperand(1), m_Constant(CmpConst)) &&
5873 CmpConst->getType() == SrcTy) {
5874 // Here we have the following case:
5875 //
5876 // %cond = cmp iN %x, CmpConst
5877 // %tr = trunc iN %x to iK
5878 // %narrowsel = select i1 %cond, iK %t, iK C
5879 //
5880 // We can always move trunc after select operation:
5881 //
5882