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 41 namespace llvm { 42 43 template <typename T, typename... TArgs> class AnalysisManager; 44 template <class T> class ArrayRef; 45 class AssumptionCache; 46 class BinaryOperator; 47 class CallBase; 48 class DataLayout; 49 class DominatorTree; 50 class Function; 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 { InstrInfoQueryInstrInfoQuery64 InstrInfoQuery(bool UMD) : UseInstrInfo(UMD) {} InstrInfoQueryInstrInfoQuery65 InstrInfoQuery() : UseInstrInfo(true) {} 66 bool UseInstrInfo = true; 67 getMetadataInstrInfoQuery68 MDNode *getMetadata(const Instruction *I, unsigned KindID) const { 69 if (UseInstrInfo) 70 return I->getMetadata(KindID); 71 return nullptr; 72 } 73 hasNoUnsignedWrapInstrInfoQuery74 template <class InstT> bool hasNoUnsignedWrap(const InstT *Op) const { 75 if (UseInstrInfo) 76 return Op->hasNoUnsignedWrap(); 77 return false; 78 } 79 hasNoSignedWrapInstrInfoQuery80 template <class InstT> bool hasNoSignedWrap(const InstT *Op) const { 81 if (UseInstrInfo) 82 return Op->hasNoSignedWrap(); 83 return false; 84 } 85 isExactInstrInfoQuery86 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) DLSimplifyQuery111 : 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) DLSimplifyQuery118 : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI), IIQ(UseInstrInfo), 119 CanUseUndef(CanUseUndef) {} getWithInstructionSimplifyQuery120 SimplifyQuery getWithInstruction(Instruction *I) const { 121 SimplifyQuery Copy(*this); 122 Copy.CxtI = I; 123 return Copy; 124 } getWithoutUndefSimplifyQuery125 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. isUndefValueSimplifyQuery133 bool isUndefValue(Value *V) const { 134 if (!CanUseUndef) 135 return false; 136 return isa<UndefValue>(V); 137 } 138 }; 139 140 // NOTE: the explicit multiple argument versions of these functions are 141 // deprecated. 142 // Please use the SimplifyQuery versions in new code. 143 144 /// Given operand for an FNeg, fold the result or return null. 145 Value *SimplifyFNegInst(Value *Op, FastMathFlags FMF, 146 const SimplifyQuery &Q); 147 148 /// Given operands for an Add, fold the result or return null. 149 Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW, 150 const SimplifyQuery &Q); 151 152 /// Given operands for a Sub, fold the result or return null. 153 Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW, 154 const SimplifyQuery &Q); 155 156 /// Given operands for an FAdd, fold the result or return null. 157 Value *SimplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF, 158 const SimplifyQuery &Q); 159 160 /// Given operands for an FSub, fold the result or return null. 161 Value *SimplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF, 162 const SimplifyQuery &Q); 163 164 /// Given operands for an FMul, fold the result or return null. 165 Value *SimplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF, 166 const SimplifyQuery &Q); 167 168 /// Given operands for the multiplication of a FMA, fold the result or return 169 /// null. In contrast to SimplifyFMulInst, this function will not perform 170 /// simplifications whose unrounded results differ when rounded to the argument 171 /// type. 172 Value *SimplifyFMAFMul(Value *LHS, Value *RHS, FastMathFlags FMF, 173 const SimplifyQuery &Q); 174 175 /// Given operands for a Mul, fold the result or return null. 176 Value *SimplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 177 178 /// Given operands for an SDiv, fold the result or return null. 179 Value *SimplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 180 181 /// Given operands for a UDiv, fold the result or return null. 182 Value *SimplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 183 184 /// Given operands for an FDiv, fold the result or return null. 185 Value *SimplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF, 186 const SimplifyQuery &Q); 187 188 /// Given operands for an SRem, fold the result or return null. 189 Value *SimplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 190 191 /// Given operands for a URem, fold the result or return null. 192 Value *SimplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 193 194 /// Given operands for an FRem, fold the result or return null. 195 Value *SimplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF, 196 const SimplifyQuery &Q); 197 198 /// Given operands for a Shl, fold the result or return null. 199 Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, 200 const SimplifyQuery &Q); 201 202 /// Given operands for a LShr, fold the result or return null. 203 Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact, 204 const SimplifyQuery &Q); 205 206 /// Given operands for a AShr, fold the result or return nulll. 207 Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact, 208 const SimplifyQuery &Q); 209 210 /// Given operands for an And, fold the result or return null. 211 Value *SimplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 212 213 /// Given operands for an Or, fold the result or return null. 214 Value *SimplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 215 216 /// Given operands for an Xor, fold the result or return null. 217 Value *SimplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q); 218 219 /// Given operands for an ICmpInst, fold the result or return null. 220 Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 221 const SimplifyQuery &Q); 222 223 /// Given operands for an FCmpInst, fold the result or return null. 224 Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 225 FastMathFlags FMF, const SimplifyQuery &Q); 226 227 /// Given operands for a SelectInst, fold the result or return null. 228 Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal, 229 const SimplifyQuery &Q); 230 231 /// Given operands for a GetElementPtrInst, fold the result or return null. 232 Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops, 233 const SimplifyQuery &Q); 234 235 /// Given operands for an InsertValueInst, fold the result or return null. 236 Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs, 237 const SimplifyQuery &Q); 238 239 /// Given operands for an InsertElement, fold the result or return null. 240 Value *SimplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx, 241 const SimplifyQuery &Q); 242 243 /// Given operands for an ExtractValueInst, fold the result or return null. 244 Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs, 245 const SimplifyQuery &Q); 246 247 /// Given operands for an ExtractElementInst, fold the result or return null. 248 Value *SimplifyExtractElementInst(Value *Vec, Value *Idx, 249 const SimplifyQuery &Q); 250 251 /// Given operands for a CastInst, fold the result or return null. 252 Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty, 253 const SimplifyQuery &Q); 254 255 /// Given operands for a ShuffleVectorInst, fold the result or return null. 256 /// See class ShuffleVectorInst for a description of the mask representation. 257 Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, ArrayRef<int> Mask, 258 Type *RetTy, const SimplifyQuery &Q); 259 260 //=== Helper functions for higher up the class hierarchy. 261 262 /// Given operands for a CmpInst, fold the result or return null. 263 Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, 264 const SimplifyQuery &Q); 265 266 /// Given operand for a UnaryOperator, fold the result or return null. 267 Value *SimplifyUnOp(unsigned Opcode, Value *Op, const SimplifyQuery &Q); 268 269 /// Given operand for a UnaryOperator, fold the result or return null. 270 /// Try to use FastMathFlags when folding the result. 271 Value *SimplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF, 272 const SimplifyQuery &Q); 273 274 /// Given operands for a BinaryOperator, fold the result or return null. 275 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 276 const SimplifyQuery &Q); 277 278 /// Given operands for a BinaryOperator, fold the result or return null. 279 /// Try to use FastMathFlags when folding the result. 280 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, 281 FastMathFlags FMF, const SimplifyQuery &Q); 282 283 /// Given a callsite, fold the result or return null. 284 Value *SimplifyCall(CallBase *Call, const SimplifyQuery &Q); 285 286 /// Given an operand for a Freeze, see if we can fold the result. 287 /// If not, this returns null. 288 Value *SimplifyFreezeInst(Value *Op, const SimplifyQuery &Q); 289 290 /// See if we can compute a simplified version of this instruction. If not, 291 /// return null. 292 Value *SimplifyInstruction(Instruction *I, const SimplifyQuery &Q, 293 OptimizationRemarkEmitter *ORE = nullptr); 294 295 /// See if V simplifies when its operand Op is replaced with RepOp. If not, 296 /// return null. 297 /// AllowRefinement specifies whether the simplification can be a refinement, 298 /// or whether it needs to be strictly identical. 299 Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp, 300 const SimplifyQuery &Q, bool AllowRefinement); 301 302 /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively. 303 /// 304 /// This first performs a normal RAUW of I with SimpleV. It then recursively 305 /// attempts to simplify those users updated by the operation. The 'I' 306 /// instruction must not be equal to the simplified value 'SimpleV'. 307 /// If UnsimplifiedUsers is provided, instructions that could not be simplified 308 /// are added to it. 309 /// 310 /// The function returns true if any simplifications were performed. 311 bool replaceAndRecursivelySimplify( 312 Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr, 313 const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr, 314 SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr); 315 316 /// Recursively attempt to simplify an instruction. 317 /// 318 /// This routine uses SimplifyInstruction to simplify 'I', and if successful 319 /// replaces uses of 'I' with the simplified value. It then recurses on each 320 /// of the users impacted. It returns true if any simplifications were 321 /// performed. 322 bool recursivelySimplifyInstruction(Instruction *I, 323 const TargetLibraryInfo *TLI = nullptr, 324 const DominatorTree *DT = nullptr, 325 AssumptionCache *AC = nullptr); 326 327 // These helper functions return a SimplifyQuery structure that contains as 328 // many of the optional analysis we use as are currently valid. This is the 329 // strongly preferred way of constructing SimplifyQuery in passes. 330 const SimplifyQuery getBestSimplifyQuery(Pass &, Function &); 331 template <class T, class... TArgs> 332 const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &, 333 Function &); 334 const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &, 335 const DataLayout &); 336 } // end namespace llvm 337 338 #endif 339 340