1 | //===-- InstructionSimplify.h - Fold instrs into simpler forms --*- C++ -*-===// |
---|---|

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 declares routines for folding instructions into simpler forms |

10 | // that do not require creating new instructions. This does constant folding |

11 | // ("add i32 1, 1" -> "2") but can also handle non-constant operands, either |

12 | // returning a constant ("and i32 %x, 0" -> "0") or an already existing value |

13 | // ("and i32 %x, %x" -> "%x"). If the simplification is also an instruction |

14 | // then it dominates the original instruction. |

15 | // |

16 | // These routines implicitly resolve undef uses. The easiest way to be safe when |

17 | // using these routines to obtain simplified values for existing instructions is |

18 | // to always replace all uses of the instructions with the resulting simplified |

19 | // values. This will prevent other code from seeing the same undef uses and |

20 | // resolving them to different values. |

21 | // |

22 | // These routines are designed to tolerate moderately incomplete IR, such as |

23 | // instructions that are not connected to basic blocks yet. However, they do |

24 | // require that all the IR that they encounter be valid. In particular, they |

25 | // require that all non-constant values be defined in the same function, and the |

26 | // same call context of that function (and not split between caller and callee |

27 | // contexts of a directly recursive call, for example). |

28 | // |

29 | // Additionally, these routines can't simplify to the instructions that are not |

30 | // def-reachable, meaning we can't just scan the basic block for instructions |

31 | // to simplify to. |

32 | // |

33 | //===----------------------------------------------------------------------===// |

34 | |

35 | #ifndef LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H |

36 | #define LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H |

37 | |

38 | #include "llvm/IR/PatternMatch.h" |

39 | |

40 | namespace llvm { |

41 | |

42 | template <typename T, typename... TArgs> class AnalysisManager; |

43 | template <class T> class ArrayRef; |

44 | class AssumptionCache; |

45 | class BinaryOperator; |

46 | class CallBase; |

47 | class DataLayout; |

48 | class DominatorTree; |

49 | class Function; |

50 | class Instruction; |

51 | struct LoopStandardAnalysisResults; |

52 | class MDNode; |

53 | class OptimizationRemarkEmitter; |

54 | class Pass; |

55 | template <class T, unsigned n> class SmallSetVector; |

56 | class TargetLibraryInfo; |

57 | class Type; |

58 | class Value; |

59 | |

60 | /// InstrInfoQuery provides an interface to query additional information for |

61 | /// instructions like metadata or keywords like nsw, which provides conservative |

62 | /// results if the users specified it is safe to use. |

63 | struct InstrInfoQuery { |

64 | InstrInfoQuery(bool UMD) : UseInstrInfo(UMD) {} |

65 | InstrInfoQuery() = default; |

66 | bool UseInstrInfo = true; |

67 | |

68 | MDNode *getMetadata(const Instruction *I, unsigned KindID) const { |

69 | if (UseInstrInfo) |

70 | return I->getMetadata(KindID); |

71 | return nullptr; |

72 | } |

73 | |

74 | template <class InstT> bool hasNoUnsignedWrap(const InstT *Op) const { |

75 | if (UseInstrInfo) |

76 | return Op->hasNoUnsignedWrap(); |

77 | return false; |

78 | } |

79 | |

80 | template <class InstT> bool hasNoSignedWrap(const InstT *Op) const { |

81 | if (UseInstrInfo) |

82 | return Op->hasNoSignedWrap(); |

83 | return false; |

84 | } |

85 | |

86 | bool isExact(const BinaryOperator *Op) const { |

87 | if (UseInstrInfo && isa<PossiblyExactOperator>(Op)) |

88 | return cast<PossiblyExactOperator>(Op)->isExact(); |

89 | return false; |

90 | } |

91 | }; |

92 | |

93 | struct SimplifyQuery { |

94 | const DataLayout &DL; |

95 | const TargetLibraryInfo *TLI = nullptr; |

96 | const DominatorTree *DT = nullptr; |

97 | AssumptionCache *AC = nullptr; |

98 | const Instruction *CxtI = nullptr; |

99 | |

100 | // Wrapper to query additional information for instructions like metadata or |

101 | // keywords like nsw, which provides conservative results if those cannot |

102 | // be safely used. |

103 | const InstrInfoQuery IIQ; |

104 | |

105 | /// Controls whether simplifications are allowed to constrain the range of |

106 | /// possible values for uses of undef. If it is false, simplifications are not |

107 | /// allowed to assume a particular value for a use of undef for example. |

108 | bool CanUseUndef = true; |

109 | |

110 | SimplifyQuery(const DataLayout &DL, const Instruction *CXTI = nullptr) |

111 | : DL(DL), CxtI(CXTI) {} |

112 | |

113 | SimplifyQuery(const DataLayout &DL, const TargetLibraryInfo *TLI, |

114 | const DominatorTree *DT = nullptr, |

115 | AssumptionCache *AC = nullptr, |

116 | const Instruction *CXTI = nullptr, bool UseInstrInfo = true, |

117 | bool CanUseUndef = true) |

118 | : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI), IIQ(UseInstrInfo), |

119 | CanUseUndef(CanUseUndef) {} |

120 | SimplifyQuery getWithInstruction(Instruction *I) const { |

121 | SimplifyQuery Copy(*this); |

122 | Copy.CxtI = I; |

123 | return Copy; |

124 | } |

125 | SimplifyQuery getWithoutUndef() const { |

126 | SimplifyQuery Copy(*this); |

127 | Copy.CanUseUndef = false; |

128 | return Copy; |

129 | } |

130 | |

131 | /// If CanUseUndef is true, returns whether \p V is undef. |

132 | /// Otherwise always return false. |

133 | bool isUndefValue(Value *V) const { |

134 | if (!CanUseUndef) |

135 | return false; |

136 | |

137 | using namespace PatternMatch; |

138 | return match(V, m_Undef()); |

139 | } |

140 | }; |

141 | |

142 | // NOTE: the explicit multiple argument versions of these functions are |

143 | // deprecated. |

144 | // Please use the SimplifyQuery versions in new code. |

145 | |

146 | /// Given operand for an FNeg, fold the result or return null. |

147 | Value *simplifyFNegInst(Value *Op, FastMathFlags FMF, const SimplifyQuery &Q); |

148 | |

149 | /// Given operands for an Add, fold the result or return null. |

150 | Value *simplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW, |

151 | const SimplifyQuery &Q); |

152 | |

153 | /// Given operands for a Sub, fold the result or return null. |

154 | Value *simplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW, |

155 | const SimplifyQuery &Q); |

156 | |

157 | /// Given operands for an FAdd, fold the result or return null. |

158 | Value * |

159 | simplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF, |

160 | const SimplifyQuery &Q, |

161 | fp::ExceptionBehavior ExBehavior = fp::ebIgnore, |

162 | RoundingMode Rounding = RoundingMode::NearestTiesToEven); |

163 | |

164 | /// Given operands for an FSub, fold the result or return null. |

165 | Value * |

166 | simplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF, |

167 | const SimplifyQuery &Q, |

168 | fp::ExceptionBehavior ExBehavior = fp::ebIgnore, |

169 | RoundingMode Rounding = RoundingMode::NearestTiesToEven); |

170 | |

171 | /// Given operands for an FMul, fold the result or return null. |

172 | Value * |

173 | simplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF, |

174 | const SimplifyQuery &Q, |

175 | fp::ExceptionBehavior ExBehavior = fp::ebIgnore, |

176 | RoundingMode Rounding = RoundingMode::NearestTiesToEven); |

177 | |

178 | /// Given operands for the multiplication of a FMA, fold the result or return |

179 | /// null. In contrast to simplifyFMulInst, this function will not perform |

180 | /// simplifications whose unrounded results differ when rounded to the argument |

181 | /// type. |

182 | Value *simplifyFMAFMul(Value *LHS, Value *RHS, FastMathFlags FMF, |

183 | const SimplifyQuery &Q, |

184 | fp::ExceptionBehavior ExBehavior = fp::ebIgnore, |

185 | RoundingMode Rounding = RoundingMode::NearestTiesToEven); |

186 | |

187 | /// Given operands for a Mul, fold the result or return null. |

188 | Value *simplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); |

189 | |

190 | /// Given operands for an SDiv, fold the result or return null. |

191 | Value *simplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); |

192 | |

193 | /// Given operands for a UDiv, fold the result or return null. |

194 | Value *simplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); |

195 | |

196 | /// Given operands for an FDiv, fold the result or return null. |

197 | Value * |

198 | simplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF, |

199 | const SimplifyQuery &Q, |

200 | fp::ExceptionBehavior ExBehavior = fp::ebIgnore, |

201 | RoundingMode Rounding = RoundingMode::NearestTiesToEven); |

202 | |

203 | /// Given operands for an SRem, fold the result or return null. |

204 | Value *simplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); |

205 | |

206 | /// Given operands for a URem, fold the result or return null. |

207 | Value *simplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); |

208 | |

209 | /// Given operands for an FRem, fold the result or return null. |

210 | Value * |

211 | simplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF, |

212 | const SimplifyQuery &Q, |

213 | fp::ExceptionBehavior ExBehavior = fp::ebIgnore, |

214 | RoundingMode Rounding = RoundingMode::NearestTiesToEven); |

215 | |

216 | /// Given operands for a Shl, fold the result or return null. |

217 | Value *simplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, |

218 | const SimplifyQuery &Q); |

219 | |

220 | /// Given operands for a LShr, fold the result or return null. |

221 | Value *simplifyLShrInst(Value *Op0, Value *Op1, bool isExact, |

222 | const SimplifyQuery &Q); |

223 | |

224 | /// Given operands for a AShr, fold the result or return nulll. |

225 | Value *simplifyAShrInst(Value *Op0, Value *Op1, bool isExact, |

226 | const SimplifyQuery &Q); |

227 | |

228 | /// Given operands for an And, fold the result or return null. |

229 | Value *simplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); |

230 | |

231 | /// Given operands for an Or, fold the result or return null. |

232 | Value *simplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); |

233 | |

234 | /// Given operands for an Xor, fold the result or return null. |

235 | Value *simplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); |

236 | |

237 | /// Given operands for an ICmpInst, fold the result or return null. |

238 | Value *simplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, |

239 | const SimplifyQuery &Q); |

240 | |

241 | /// Given operands for an FCmpInst, fold the result or return null. |

242 | Value *simplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, |

243 | FastMathFlags FMF, const SimplifyQuery &Q); |

244 | |

245 | /// Given operands for a SelectInst, fold the result or return null. |

246 | Value *simplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal, |

247 | const SimplifyQuery &Q); |

248 | |

249 | /// Given operands for a GetElementPtrInst, fold the result or return null. |

250 | Value *simplifyGEPInst(Type *SrcTy, Value *Ptr, ArrayRef<Value *> Indices, |

251 | bool InBounds, const SimplifyQuery &Q); |

252 | |

253 | /// Given operands for an InsertValueInst, fold the result or return null. |

254 | Value *simplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs, |

255 | const SimplifyQuery &Q); |

256 | |

257 | /// Given operands for an InsertElement, fold the result or return null. |

258 | Value *simplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx, |

259 | const SimplifyQuery &Q); |

260 | |

261 | /// Given operands for an ExtractValueInst, fold the result or return null. |

262 | Value *simplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs, |

263 | const SimplifyQuery &Q); |

264 | |

265 | /// Given operands for an ExtractElementInst, fold the result or return null. |

266 | Value *simplifyExtractElementInst(Value *Vec, Value *Idx, |

267 | const SimplifyQuery &Q); |

268 | |

269 | /// Given operands for a CastInst, fold the result or return null. |

270 | Value *simplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty, |

271 | const SimplifyQuery &Q); |

272 | |

273 | /// Given operands for a ShuffleVectorInst, fold the result or return null. |

274 | /// See class ShuffleVectorInst for a description of the mask representation. |

275 | Value *simplifyShuffleVectorInst(Value *Op0, Value *Op1, ArrayRef<int> Mask, |

276 | Type *RetTy, const SimplifyQuery &Q); |

277 | |

278 | //=== Helper functions for higher up the class hierarchy. |

279 | |

280 | /// Given operands for a CmpInst, fold the result or return null. |

281 | Value *simplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, |

282 | const SimplifyQuery &Q); |

283 | |

284 | /// Given operand for a UnaryOperator, fold the result or return null. |

285 | Value *simplifyUnOp(unsigned Opcode, Value *Op, const SimplifyQuery &Q); |

286 | |

287 | /// Given operand for a UnaryOperator, fold the result or return null. |

288 | /// Try to use FastMathFlags when folding the result. |

289 | Value *simplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF, |

290 | const SimplifyQuery &Q); |

291 | |

292 | /// Given operands for a BinaryOperator, fold the result or return null. |

293 | Value *simplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, |

294 | const SimplifyQuery &Q); |

295 | |

296 | /// Given operands for a BinaryOperator, fold the result or return null. |

297 | /// Try to use FastMathFlags when folding the result. |

298 | Value *simplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, FastMathFlags FMF, |

299 | const SimplifyQuery &Q); |

300 | |

301 | /// Given a callsite, fold the result or return null. |

302 | Value *simplifyCall(CallBase *Call, const SimplifyQuery &Q); |

303 | |

304 | /// Given a constrained FP intrinsic call, tries to compute its simplified |

305 | /// version. Returns a simplified result or null. |

306 | /// |

307 | /// This function provides an additional contract: it guarantees that if |

308 | /// simplification succeeds that the intrinsic is side effect free. As a result, |

309 | /// successful simplification can be used to delete the intrinsic not just |

310 | /// replace its result. |

311 | Value *simplifyConstrainedFPCall(CallBase *Call, const SimplifyQuery &Q); |

312 | |

313 | /// Given an operand for a Freeze, see if we can fold the result. |

314 | /// If not, this returns null. |

315 | Value *simplifyFreezeInst(Value *Op, const SimplifyQuery &Q); |

316 | |

317 | /// See if we can compute a simplified version of this instruction. If not, |

318 | /// return null. |

319 | Value *simplifyInstruction(Instruction *I, const SimplifyQuery &Q, |

320 | OptimizationRemarkEmitter *ORE = nullptr); |

321 | |

322 | /// Like \p simplifyInstruction but the operands of \p I are replaced with |

323 | /// \p NewOps. Returns a simplified value, or null if none was found. |

324 | Value * |

325 | simplifyInstructionWithOperands(Instruction *I, ArrayRef<Value *> NewOps, |

326 | const SimplifyQuery &Q, |

327 | OptimizationRemarkEmitter *ORE = nullptr); |

328 | |

329 | /// See if V simplifies when its operand Op is replaced with RepOp. If not, |

330 | /// return null. |

331 | /// AllowRefinement specifies whether the simplification can be a refinement |

332 | /// (e.g. 0 instead of poison), or whether it needs to be strictly identical. |

333 | Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp, |

334 | const SimplifyQuery &Q, bool AllowRefinement); |

335 | |

336 | /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively. |

337 | /// |

338 | /// This first performs a normal RAUW of I with SimpleV. It then recursively |

339 | /// attempts to simplify those users updated by the operation. The 'I' |

340 | /// instruction must not be equal to the simplified value 'SimpleV'. |

341 | /// If UnsimplifiedUsers is provided, instructions that could not be simplified |

342 | /// are added to it. |

343 | /// |

344 | /// The function returns true if any simplifications were performed. |

345 | bool replaceAndRecursivelySimplify( |

346 | Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr, |

347 | const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr, |

348 | SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr); |

349 | |

350 | // These helper functions return a SimplifyQuery structure that contains as |

351 | // many of the optional analysis we use as are currently valid. This is the |

352 | // strongly preferred way of constructing SimplifyQuery in passes. |

353 | const SimplifyQuery getBestSimplifyQuery(Pass &, Function &); |

354 | template <class T, class... TArgs> |

355 | const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &, |

356 | Function &); |

357 | const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &, |

358 | const DataLayout &); |

359 | } // end namespace llvm |

360 | |

361 | #endif |

362 |