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/Instruction.h" 39 #include "llvm/IR/Operator.h" 40 #include "llvm/IR/PatternMatch.h" 41 42 namespace llvm { 43 44 template <typename T, typename... TArgs> class AnalysisManager; 45 template <class T> class ArrayRef; 46 class AssumptionCache; 47 class BinaryOperator; 48 class CallBase; 49 class DataLayout; 50 class DominatorTree; 51 class Function; 52 struct LoopStandardAnalysisResults; 53 class MDNode; 54 class OptimizationRemarkEmitter; 55 class Pass; 56 template <class T, unsigned n> class SmallSetVector; 57 class TargetLibraryInfo; 58 class Type; 59 class Value; 60 61 /// InstrInfoQuery provides an interface to query additional information for 62 /// instructions like metadata or keywords like nsw, which provides conservative 63 /// results if the users specified it is safe to use. 64 struct InstrInfoQuery { InstrInfoQueryInstrInfoQuery65 InstrInfoQuery(bool UMD) : UseInstrInfo(UMD) {} InstrInfoQueryInstrInfoQuery66 InstrInfoQuery() : UseInstrInfo(true) {} 67 bool UseInstrInfo = true; 68 getMetadataInstrInfoQuery69 MDNode *getMetadata(const Instruction *I, unsigned KindID) const { 70 if (UseInstrInfo) 71 return I->getMetadata(KindID); 72 return nullptr; 73 } 74 hasNoUnsignedWrapInstrInfoQuery75 template <class InstT> bool hasNoUnsignedWrap(const InstT *Op) const { 76 if (UseInstrInfo) 77 return Op->hasNoUnsignedWrap(); 78 return false; 79 } 80 hasNoSignedWrapInstrInfoQuery81 template <class InstT> bool hasNoSignedWrap(const InstT *Op) const { 82 if (UseInstrInfo) 83 return Op->hasNoSignedWrap(); 84 return false; 85 } 86 isExactInstrInfoQuery87 bool isExact(const BinaryOperator *Op) const { 88 if (UseInstrInfo && isa<PossiblyExactOperator>(Op)) 89 return cast<PossiblyExactOperator>(Op)->isExact(); 90 return false; 91 } 92 }; 93 94 struct SimplifyQuery { 95 const DataLayout &DL; 96 const TargetLibraryInfo *TLI = nullptr; 97 const DominatorTree *DT = nullptr; 98 AssumptionCache *AC = nullptr; 99 const Instruction *CxtI = nullptr; 100 101 // Wrapper to query additional information for instructions like metadata or 102 // keywords like nsw, which provides conservative results if those cannot 103 // be safely used. 104 const InstrInfoQuery IIQ; 105 106 /// Controls whether simplifications are allowed to constrain the range of 107 /// possible values for uses of undef. If it is false, simplifications are not 108 /// allowed to assume a particular value for a use of undef for example. 109 bool CanUseUndef = true; 110 111 SimplifyQuery(const DataLayout &DL, const Instruction *CXTI = nullptr) DLSimplifyQuery112 : DL(DL), CxtI(CXTI) {} 113 114 SimplifyQuery(const DataLayout &DL, const TargetLibraryInfo *TLI, 115 const DominatorTree *DT = nullptr, 116 AssumptionCache *AC = nullptr, 117 const Instruction *CXTI = nullptr, bool UseInstrInfo = true, 118 bool CanUseUndef = true) DLSimplifyQuery119 : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI), IIQ(UseInstrInfo), 120 CanUseUndef(CanUseUndef) {} getWithInstructionSimplifyQuery121 SimplifyQuery getWithInstruction(Instruction *I) const { 122 SimplifyQuery Copy(*this); 123 Copy.CxtI = I; 124 return Copy; 125 } getWithoutUndefSimplifyQuery126 SimplifyQuery getWithoutUndef() const { 127 SimplifyQuery Copy(*this); 128 Copy.CanUseUndef = false; 129 return Copy; 130 } 131 132 /// If CanUseUndef is true, returns whether \p V is undef. 133 /// Otherwise always return false. isUndefValueSimplifyQuery134 bool isUndefValue(Value *V) const { 135 if (!CanUseUndef) 136 return false; 137 138 using namespace PatternMatch; 139 return match(V, m_Undef()); 140 } 141 }; 142 143 // NOTE: the explicit multiple argument versions of these functions are 144 // deprecated. 145 // Please use the SimplifyQuery versions in new code. 146 147 /// Given operand for an FNeg, fold the result or return null. 148 Value *SimplifyFNegInst(Value *Op, FastMathFlags FMF, const SimplifyQuery &Q); 149 150 /// Given operands for an Add, fold the result or return null. 151 Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW, 152 const SimplifyQuery &Q); 153 154 /// Given operands for a Sub, fold the result or return null. 155 Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW, 156 const SimplifyQuery &Q); 157 158 /// Given operands for an FAdd, fold the result or return null. 159 Value * 160 SimplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF, 161 const SimplifyQuery &Q, 162 fp::ExceptionBehavior ExBehavior = fp::ebIgnore, 163 RoundingMode Rounding = RoundingMode::NearestTiesToEven); 164 165 /// Given operands for an FSub, fold the result or return null. 166 Value * 167 SimplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF, 168 const SimplifyQuery &Q, 169 fp::ExceptionBehavior ExBehavior = fp::ebIgnore, 170 RoundingMode Rounding = RoundingMode::NearestTiesToEven); 171 172 /// Given operands for an FMul, fold the result or return null. 173 Value * 174 SimplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF, 175 const SimplifyQuery &Q, 176 fp::ExceptionBehavior ExBehavior = fp::ebIgnore, 177 RoundingMode Rounding = RoundingMode::NearestTiesToEven); 178 179 /// Given operands for the multiplication of a FMA, fold the result or return 180 /// null. In contrast to SimplifyFMulInst, this function will not perform 181 /// simplifications whose unrounded results differ when rounded to the argument 182 /// type. 183 Value *SimplifyFMAFMul(Value *LHS, Value *RHS, FastMathFlags FMF, 184 const SimplifyQuery &Q, 185 fp::ExceptionBehavior ExBehavior = fp::ebIgnore, 186 RoundingMode Rounding = RoundingMode::NearestTiesToEven); 187 188 /// Given operands for a Mul, fold the result or return null. 189 Value *SimplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 190 191 /// Given operands for an SDiv, fold the result or return null. 192 Value *SimplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 193 194 /// Given operands for a UDiv, fold the result or return null. 195 Value *SimplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 196 197 /// Given operands for an FDiv, fold the result or return null. 198 Value * 199 SimplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF, 200 const SimplifyQuery &Q, 201 fp::ExceptionBehavior ExBehavior = fp::ebIgnore, 202 RoundingMode Rounding = RoundingMode::NearestTiesToEven); 203 204 /// Given operands for an SRem, fold the result or return null. 205 Value *SimplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 206 207 /// Given operands for a URem, fold the result or return null. 208 Value *SimplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 209 210 /// Given operands for an FRem, fold the result or return null. 211 Value * 212 SimplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF, 213 const SimplifyQuery &Q, 214 fp::ExceptionBehavior ExBehavior = fp::ebIgnore, 215 RoundingMode Rounding = RoundingMode::NearestTiesToEven); 216 217 /// Given operands for a Shl, fold the result or return null. 218 Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 219 const SimplifyQuery &Q); 220 221 /// Given operands for a LShr, fold the result or return null. 222 Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact, 223 const SimplifyQuery &Q); 224 225 /// Given operands for a AShr, fold the result or return nulll. 226 Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact, 227 const SimplifyQuery &Q); 228 229 /// Given operands for an And, fold the result or return null. 230 Value *SimplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 231 232 /// Given operands for an Or, fold the result or return null. 233 Value *SimplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 234 235 /// Given operands for an Xor, fold the result or return null. 236 Value *SimplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 237 238 /// Given operands for an ICmpInst, fold the result or return null. 239 Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 240 const SimplifyQuery &Q); 241 242 /// Given operands for an FCmpInst, fold the result or return null. 243 Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 244 FastMathFlags FMF, const SimplifyQuery &Q); 245 246 /// Given operands for a SelectInst, fold the result or return null. 247 Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal, 248 const SimplifyQuery &Q); 249 250 /// Given operands for a GetElementPtrInst, fold the result or return null. 251 Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops, bool InBounds, 252 const SimplifyQuery &Q); 253 254 /// Given operands for an InsertValueInst, fold the result or return null. 255 Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs, 256 const SimplifyQuery &Q); 257 258 /// Given operands for an InsertElement, fold the result or return null. 259 Value *SimplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx, 260 const SimplifyQuery &Q); 261 262 /// Given operands for an ExtractValueInst, fold the result or return null. 263 Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs, 264 const SimplifyQuery &Q); 265 266 /// Given operands for an ExtractElementInst, fold the result or return null. 267 Value *SimplifyExtractElementInst(Value *Vec, Value *Idx, 268 const SimplifyQuery &Q); 269 270 /// Given operands for a CastInst, fold the result or return null. 271 Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty, 272 const SimplifyQuery &Q); 273 274 /// Given operands for a ShuffleVectorInst, fold the result or return null. 275 /// See class ShuffleVectorInst for a description of the mask representation. 276 Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, ArrayRef<int> Mask, 277 Type *RetTy, const SimplifyQuery &Q); 278 279 //=== Helper functions for higher up the class hierarchy. 280 281 /// Given operands for a CmpInst, fold the result or return null. 282 Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 283 const SimplifyQuery &Q); 284 285 /// Given operand for a UnaryOperator, fold the result or return null. 286 Value *SimplifyUnOp(unsigned Opcode, Value *Op, const SimplifyQuery &Q); 287 288 /// Given operand for a UnaryOperator, fold the result or return null. 289 /// Try to use FastMathFlags when folding the result. 290 Value *SimplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF, 291 const SimplifyQuery &Q); 292 293 /// Given operands for a BinaryOperator, fold the result or return null. 294 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 295 const SimplifyQuery &Q); 296 297 /// Given operands for a BinaryOperator, fold the result or return null. 298 /// Try to use FastMathFlags when folding the result. 299 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, FastMathFlags FMF, 300 const SimplifyQuery &Q); 301 302 /// Given a callsite, fold the result or return null. 303 Value *SimplifyCall(CallBase *Call, const SimplifyQuery &Q); 304 305 /// Given an operand for a Freeze, see if we can fold the result. 306 /// If not, this returns null. 307 Value *SimplifyFreezeInst(Value *Op, const SimplifyQuery &Q); 308 309 /// See if we can compute a simplified version of this instruction. If not, 310 /// return null. 311 Value *SimplifyInstruction(Instruction *I, const SimplifyQuery &Q, 312 OptimizationRemarkEmitter *ORE = nullptr); 313 314 /// Like \p SimplifyInstruction but the operands of \p I are replaced with 315 /// \p NewOps. Returns a simplified value, or null if none was found. 316 Value * 317 SimplifyInstructionWithOperands(Instruction *I, ArrayRef<Value *> NewOps, 318 const SimplifyQuery &Q, 319 OptimizationRemarkEmitter *ORE = nullptr); 320 321 /// See if V simplifies when its operand Op is replaced with RepOp. If not, 322 /// return null. 323 /// AllowRefinement specifies whether the simplification can be a refinement 324 /// (e.g. 0 instead of poison), or whether it needs to be strictly identical. 325 Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp, 326 const SimplifyQuery &Q, bool AllowRefinement); 327 328 /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively. 329 /// 330 /// This first performs a normal RAUW of I with SimpleV. It then recursively 331 /// attempts to simplify those users updated by the operation. The 'I' 332 /// instruction must not be equal to the simplified value 'SimpleV'. 333 /// If UnsimplifiedUsers is provided, instructions that could not be simplified 334 /// are added to it. 335 /// 336 /// The function returns true if any simplifications were performed. 337 bool replaceAndRecursivelySimplify( 338 Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr, 339 const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr, 340 SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr); 341 342 // These helper functions return a SimplifyQuery structure that contains as 343 // many of the optional analysis we use as are currently valid. This is the 344 // strongly preferred way of constructing SimplifyQuery in passes. 345 const SimplifyQuery getBestSimplifyQuery(Pass &, Function &); 346 template <class T, class... TArgs> 347 const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &, 348 Function &); 349 const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &, 350 const DataLayout &); 351 } // end namespace llvm 352 353 #endif 354