1 //===- InstCombine.h - Main InstCombine pass definition ---------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef INSTCOMBINE_INSTCOMBINE_H 11 #define INSTCOMBINE_INSTCOMBINE_H 12 13 #include "InstCombineWorklist.h" 14 #include "llvm/Analysis/TargetFolder.h" 15 #include "llvm/Analysis/ValueTracking.h" 16 #include "llvm/IR/IRBuilder.h" 17 #include "llvm/IR/InstVisitor.h" 18 #include "llvm/IR/IntrinsicInst.h" 19 #include "llvm/IR/Operator.h" 20 #include "llvm/Pass.h" 21 #include "llvm/Transforms/Utils/SimplifyLibCalls.h" 22 23 #define DEBUG_TYPE "instcombine" 24 25 namespace llvm { 26 class CallSite; 27 class DataLayout; 28 class TargetLibraryInfo; 29 class DbgDeclareInst; 30 class MemIntrinsic; 31 class MemSetInst; 32 33 /// SelectPatternFlavor - We can match a variety of different patterns for 34 /// select operations. 35 enum SelectPatternFlavor { 36 SPF_UNKNOWN = 0, 37 SPF_SMIN, 38 SPF_UMIN, 39 SPF_SMAX, 40 SPF_UMAX, 41 SPF_ABS, 42 SPF_NABS 43 }; 44 45 /// getComplexity: Assign a complexity or rank value to LLVM Values... 46 /// 0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst 47 static inline unsigned getComplexity(Value *V) { 48 if (isa<Instruction>(V)) { 49 if (BinaryOperator::isNeg(V) || BinaryOperator::isFNeg(V) || 50 BinaryOperator::isNot(V)) 51 return 3; 52 return 4; 53 } 54 if (isa<Argument>(V)) 55 return 3; 56 return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2; 57 } 58 59 /// AddOne - Add one to a Constant 60 static inline Constant *AddOne(Constant *C) { 61 return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1)); 62 } 63 /// SubOne - Subtract one from a Constant 64 static inline Constant *SubOne(Constant *C) { 65 return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1)); 66 } 67 68 /// InstCombineIRInserter - This is an IRBuilder insertion helper that works 69 /// just like the normal insertion helper, but also adds any new instructions 70 /// to the instcombine worklist. 71 class LLVM_LIBRARY_VISIBILITY InstCombineIRInserter 72 : public IRBuilderDefaultInserter<true> { 73 InstCombineWorklist &Worklist; 74 75 public: 76 InstCombineIRInserter(InstCombineWorklist &WL) : Worklist(WL) {} 77 78 void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB, 79 BasicBlock::iterator InsertPt) const { 80 IRBuilderDefaultInserter<true>::InsertHelper(I, Name, BB, InsertPt); 81 Worklist.Add(I); 82 } 83 }; 84 85 /// InstCombiner - The -instcombine pass. 86 class LLVM_LIBRARY_VISIBILITY InstCombiner 87 : public FunctionPass, 88 public InstVisitor<InstCombiner, Instruction *> { 89 const DataLayout *DL; 90 TargetLibraryInfo *TLI; 91 bool MadeIRChange; 92 LibCallSimplifier *Simplifier; 93 bool MinimizeSize; 94 95 public: 96 /// Worklist - All of the instructions that need to be simplified. 97 InstCombineWorklist Worklist; 98 99 /// Builder - This is an IRBuilder that automatically inserts new 100 /// instructions into the worklist when they are created. 101 typedef IRBuilder<true, TargetFolder, InstCombineIRInserter> BuilderTy; 102 BuilderTy *Builder; 103 104 static char ID; // Pass identification, replacement for typeid 105 InstCombiner() : FunctionPass(ID), DL(nullptr), Builder(nullptr) { 106 MinimizeSize = false; 107 initializeInstCombinerPass(*PassRegistry::getPassRegistry()); 108 } 109 110 public: 111 bool runOnFunction(Function &F) override; 112 113 bool DoOneIteration(Function &F, unsigned ItNum); 114 115 void getAnalysisUsage(AnalysisUsage &AU) const override; 116 117 const DataLayout *getDataLayout() const { return DL; } 118 119 TargetLibraryInfo *getTargetLibraryInfo() const { return TLI; } 120 121 // Visitation implementation - Implement instruction combining for different 122 // instruction types. The semantics are as follows: 123 // Return Value: 124 // null - No change was made 125 // I - Change was made, I is still valid, I may be dead though 126 // otherwise - Change was made, replace I with returned instruction 127 // 128 Instruction *visitAdd(BinaryOperator &I); 129 Instruction *visitFAdd(BinaryOperator &I); 130 Value *OptimizePointerDifference(Value *LHS, Value *RHS, Type *Ty); 131 Instruction *visitSub(BinaryOperator &I); 132 Instruction *visitFSub(BinaryOperator &I); 133 Instruction *visitMul(BinaryOperator &I); 134 Value *foldFMulConst(Instruction *FMulOrDiv, Constant *C, 135 Instruction *InsertBefore); 136 Instruction *visitFMul(BinaryOperator &I); 137 Instruction *visitURem(BinaryOperator &I); 138 Instruction *visitSRem(BinaryOperator &I); 139 Instruction *visitFRem(BinaryOperator &I); 140 bool SimplifyDivRemOfSelect(BinaryOperator &I); 141 Instruction *commonRemTransforms(BinaryOperator &I); 142 Instruction *commonIRemTransforms(BinaryOperator &I); 143 Instruction *commonDivTransforms(BinaryOperator &I); 144 Instruction *commonIDivTransforms(BinaryOperator &I); 145 Instruction *visitUDiv(BinaryOperator &I); 146 Instruction *visitSDiv(BinaryOperator &I); 147 Instruction *visitFDiv(BinaryOperator &I); 148 Value *FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS); 149 Value *FoldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS); 150 Instruction *visitAnd(BinaryOperator &I); 151 Value *FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS); 152 Value *FoldOrOfFCmps(FCmpInst *LHS, FCmpInst *RHS); 153 Instruction *FoldOrWithConstants(BinaryOperator &I, Value *Op, Value *A, 154 Value *B, Value *C); 155 Instruction *visitOr(BinaryOperator &I); 156 Instruction *visitXor(BinaryOperator &I); 157 Instruction *visitShl(BinaryOperator &I); 158 Instruction *visitAShr(BinaryOperator &I); 159 Instruction *visitLShr(BinaryOperator &I); 160 Instruction *commonShiftTransforms(BinaryOperator &I); 161 Instruction *FoldFCmp_IntToFP_Cst(FCmpInst &I, Instruction *LHSI, 162 Constant *RHSC); 163 Instruction *FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, 164 GlobalVariable *GV, CmpInst &ICI, 165 ConstantInt *AndCst = nullptr); 166 Instruction *visitFCmpInst(FCmpInst &I); 167 Instruction *visitICmpInst(ICmpInst &I); 168 Instruction *visitICmpInstWithCastAndCast(ICmpInst &ICI); 169 Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI, Instruction *LHS, 170 ConstantInt *RHS); 171 Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI, 172 ConstantInt *DivRHS); 173 Instruction *FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *DivI, 174 ConstantInt *DivRHS); 175 Instruction *FoldICmpAddOpCst(Instruction &ICI, Value *X, ConstantInt *CI, 176 ICmpInst::Predicate Pred); 177 Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS, 178 ICmpInst::Predicate Cond, Instruction &I); 179 Instruction *FoldShiftByConstant(Value *Op0, Constant *Op1, 180 BinaryOperator &I); 181 Instruction *commonCastTransforms(CastInst &CI); 182 Instruction *commonPointerCastTransforms(CastInst &CI); 183 Instruction *visitTrunc(TruncInst &CI); 184 Instruction *visitZExt(ZExtInst &CI); 185 Instruction *visitSExt(SExtInst &CI); 186 Instruction *visitFPTrunc(FPTruncInst &CI); 187 Instruction *visitFPExt(CastInst &CI); 188 Instruction *visitFPToUI(FPToUIInst &FI); 189 Instruction *visitFPToSI(FPToSIInst &FI); 190 Instruction *visitUIToFP(CastInst &CI); 191 Instruction *visitSIToFP(CastInst &CI); 192 Instruction *visitPtrToInt(PtrToIntInst &CI); 193 Instruction *visitIntToPtr(IntToPtrInst &CI); 194 Instruction *visitBitCast(BitCastInst &CI); 195 Instruction *visitAddrSpaceCast(AddrSpaceCastInst &CI); 196 Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI, Instruction *FI); 197 Instruction *FoldSelectIntoOp(SelectInst &SI, Value *, Value *); 198 Instruction *FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1, 199 Value *A, Value *B, Instruction &Outer, 200 SelectPatternFlavor SPF2, Value *C); 201 Instruction *visitSelectInst(SelectInst &SI); 202 Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI); 203 Instruction *visitCallInst(CallInst &CI); 204 Instruction *visitInvokeInst(InvokeInst &II); 205 206 Instruction *SliceUpIllegalIntegerPHI(PHINode &PN); 207 Instruction *visitPHINode(PHINode &PN); 208 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP); 209 Instruction *visitAllocaInst(AllocaInst &AI); 210 Instruction *visitAllocSite(Instruction &FI); 211 Instruction *visitFree(CallInst &FI); 212 Instruction *visitLoadInst(LoadInst &LI); 213 Instruction *visitStoreInst(StoreInst &SI); 214 Instruction *visitBranchInst(BranchInst &BI); 215 Instruction *visitSwitchInst(SwitchInst &SI); 216 Instruction *visitInsertValueInst(InsertValueInst &IV); 217 Instruction *visitInsertElementInst(InsertElementInst &IE); 218 Instruction *visitExtractElementInst(ExtractElementInst &EI); 219 Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI); 220 Instruction *visitExtractValueInst(ExtractValueInst &EV); 221 Instruction *visitLandingPadInst(LandingPadInst &LI); 222 223 // visitInstruction - Specify what to return for unhandled instructions... 224 Instruction *visitInstruction(Instruction &I) { return nullptr; } 225 226 private: 227 bool ShouldChangeType(Type *From, Type *To) const; 228 Value *dyn_castNegVal(Value *V) const; 229 Value *dyn_castFNegVal(Value *V, bool NoSignedZero = false) const; 230 Type *FindElementAtOffset(Type *PtrTy, int64_t Offset, 231 SmallVectorImpl<Value *> &NewIndices); 232 Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI); 233 234 /// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually 235 /// results in any code being generated and is interesting to optimize out. If 236 /// the cast can be eliminated by some other simple transformation, we prefer 237 /// to do the simplification first. 238 bool ShouldOptimizeCast(Instruction::CastOps opcode, const Value *V, 239 Type *Ty); 240 241 Instruction *visitCallSite(CallSite CS); 242 Instruction *tryOptimizeCall(CallInst *CI, const DataLayout *DL); 243 bool transformConstExprCastCall(CallSite CS); 244 Instruction *transformCallThroughTrampoline(CallSite CS, 245 IntrinsicInst *Tramp); 246 Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI, 247 bool DoXform = true); 248 Instruction *transformSExtICmp(ICmpInst *ICI, Instruction &CI); 249 bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS); 250 bool WillNotOverflowUnsignedAdd(Value *LHS, Value *RHS); 251 Value *EmitGEPOffset(User *GEP); 252 Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN); 253 Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask); 254 255 public: 256 // InsertNewInstBefore - insert an instruction New before instruction Old 257 // in the program. Add the new instruction to the worklist. 258 // 259 Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) { 260 assert(New && !New->getParent() && 261 "New instruction already inserted into a basic block!"); 262 BasicBlock *BB = Old.getParent(); 263 BB->getInstList().insert(&Old, New); // Insert inst 264 Worklist.Add(New); 265 return New; 266 } 267 268 // InsertNewInstWith - same as InsertNewInstBefore, but also sets the 269 // debug loc. 270 // 271 Instruction *InsertNewInstWith(Instruction *New, Instruction &Old) { 272 New->setDebugLoc(Old.getDebugLoc()); 273 return InsertNewInstBefore(New, Old); 274 } 275 276 // ReplaceInstUsesWith - This method is to be used when an instruction is 277 // found to be dead, replacable with another preexisting expression. Here 278 // we add all uses of I to the worklist, replace all uses of I with the new 279 // value, then return I, so that the inst combiner will know that I was 280 // modified. 281 // 282 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) { 283 Worklist.AddUsersToWorkList(I); // Add all modified instrs to worklist. 284 285 // If we are replacing the instruction with itself, this must be in a 286 // segment of unreachable code, so just clobber the instruction. 287 if (&I == V) 288 V = UndefValue::get(I.getType()); 289 290 DEBUG(dbgs() << "IC: Replacing " << I << "\n" 291 " with " << *V << '\n'); 292 293 I.replaceAllUsesWith(V); 294 return &I; 295 } 296 297 // EraseInstFromFunction - When dealing with an instruction that has side 298 // effects or produces a void value, we can't rely on DCE to delete the 299 // instruction. Instead, visit methods should return the value returned by 300 // this function. 301 Instruction *EraseInstFromFunction(Instruction &I) { 302 DEBUG(dbgs() << "IC: ERASE " << I << '\n'); 303 304 assert(I.use_empty() && "Cannot erase instruction that is used!"); 305 // Make sure that we reprocess all operands now that we reduced their 306 // use counts. 307 if (I.getNumOperands() < 8) { 308 for (User::op_iterator i = I.op_begin(), e = I.op_end(); i != e; ++i) 309 if (Instruction *Op = dyn_cast<Instruction>(*i)) 310 Worklist.Add(Op); 311 } 312 Worklist.Remove(&I); 313 I.eraseFromParent(); 314 MadeIRChange = true; 315 return nullptr; // Don't do anything with FI 316 } 317 318 void computeKnownBits(Value *V, APInt &KnownZero, APInt &KnownOne, 319 unsigned Depth = 0) const { 320 return llvm::computeKnownBits(V, KnownZero, KnownOne, DL, Depth); 321 } 322 323 bool MaskedValueIsZero(Value *V, const APInt &Mask, 324 unsigned Depth = 0) const { 325 return llvm::MaskedValueIsZero(V, Mask, DL, Depth); 326 } 327 unsigned ComputeNumSignBits(Value *Op, unsigned Depth = 0) const { 328 return llvm::ComputeNumSignBits(Op, DL, Depth); 329 } 330 331 private: 332 /// SimplifyAssociativeOrCommutative - This performs a few simplifications for 333 /// operators which are associative or commutative. 334 bool SimplifyAssociativeOrCommutative(BinaryOperator &I); 335 336 /// SimplifyUsingDistributiveLaws - This tries to simplify binary operations 337 /// which some other binary operation distributes over either by factorizing 338 /// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this 339 /// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is 340 /// a win). Returns the simplified value, or null if it didn't simplify. 341 Value *SimplifyUsingDistributiveLaws(BinaryOperator &I); 342 343 /// SimplifyDemandedUseBits - Attempts to replace V with a simpler value 344 /// based on the demanded bits. 345 Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask, APInt &KnownZero, 346 APInt &KnownOne, unsigned Depth); 347 bool SimplifyDemandedBits(Use &U, APInt DemandedMask, APInt &KnownZero, 348 APInt &KnownOne, unsigned Depth = 0); 349 /// Helper routine of SimplifyDemandedUseBits. It tries to simplify demanded 350 /// bit for "r1 = shr x, c1; r2 = shl r1, c2" instruction sequence. 351 Value *SimplifyShrShlDemandedBits(Instruction *Lsr, Instruction *Sftl, 352 APInt DemandedMask, APInt &KnownZero, 353 APInt &KnownOne); 354 355 /// SimplifyDemandedInstructionBits - Inst is an integer instruction that 356 /// SimplifyDemandedBits knows about. See if the instruction has any 357 /// properties that allow us to simplify its operands. 358 bool SimplifyDemandedInstructionBits(Instruction &Inst); 359 360 Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts, 361 APInt &UndefElts, unsigned Depth = 0); 362 363 Value *SimplifyVectorOp(BinaryOperator &Inst); 364 365 // FoldOpIntoPhi - Given a binary operator, cast instruction, or select 366 // which has a PHI node as operand #0, see if we can fold the instruction 367 // into the PHI (which is only possible if all operands to the PHI are 368 // constants). 369 // 370 Instruction *FoldOpIntoPhi(Instruction &I); 371 372 // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary" 373 // operator and they all are only used by the PHI, PHI together their 374 // inputs, and do the operation once, to the result of the PHI. 375 Instruction *FoldPHIArgOpIntoPHI(PHINode &PN); 376 Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN); 377 Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN); 378 Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN); 379 380 Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS, 381 ConstantInt *AndRHS, BinaryOperator &TheAnd); 382 383 Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask, 384 bool isSub, Instruction &I); 385 Value *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi, bool isSigned, 386 bool Inside); 387 Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI); 388 Instruction *MatchBSwap(BinaryOperator &I); 389 bool SimplifyStoreAtEndOfBlock(StoreInst &SI); 390 Instruction *SimplifyMemTransfer(MemIntrinsic *MI); 391 Instruction *SimplifyMemSet(MemSetInst *MI); 392 393 Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned); 394 395 /// Descale - Return a value X such that Val = X * Scale, or null if none. If 396 /// the multiplication is known not to overflow then NoSignedWrap is set. 397 Value *Descale(Value *Val, APInt Scale, bool &NoSignedWrap); 398 }; 399 400 } // end namespace llvm. 401 402 #undef DEBUG_TYPE 403 404 #endif 405
