ScalarReplAggregates.cpp revision 3da59db637a887474c1b1346c1f3ccf53b6c4663
1//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This transformation implements the well known scalar replacement of 11// aggregates transformation. This xform breaks up alloca instructions of 12// aggregate type (structure or array) into individual alloca instructions for 13// each member (if possible). Then, if possible, it transforms the individual 14// alloca instructions into nice clean scalar SSA form. 15// 16// This combines a simple SRoA algorithm with the Mem2Reg algorithm because 17// often interact, especially for C++ programs. As such, iterating between 18// SRoA, then Mem2Reg until we run out of things to promote works well. 19// 20//===----------------------------------------------------------------------===// 21 22#include "llvm/Transforms/Scalar.h" 23#include "llvm/Constants.h" 24#include "llvm/DerivedTypes.h" 25#include "llvm/Function.h" 26#include "llvm/Pass.h" 27#include "llvm/Instructions.h" 28#include "llvm/Analysis/Dominators.h" 29#include "llvm/Target/TargetData.h" 30#include "llvm/Transforms/Utils/PromoteMemToReg.h" 31#include "llvm/Support/Debug.h" 32#include "llvm/Support/GetElementPtrTypeIterator.h" 33#include "llvm/Support/MathExtras.h" 34#include "llvm/Support/Compiler.h" 35#include "llvm/ADT/Statistic.h" 36#include "llvm/ADT/StringExtras.h" 37using namespace llvm; 38 39namespace { 40 Statistic<> NumReplaced("scalarrepl", "Number of allocas broken up"); 41 Statistic<> NumPromoted("scalarrepl", "Number of allocas promoted"); 42 Statistic<> NumConverted("scalarrepl", 43 "Number of aggregates converted to scalar"); 44 45 struct VISIBILITY_HIDDEN SROA : public FunctionPass { 46 bool runOnFunction(Function &F); 47 48 bool performScalarRepl(Function &F); 49 bool performPromotion(Function &F); 50 51 // getAnalysisUsage - This pass does not require any passes, but we know it 52 // will not alter the CFG, so say so. 53 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 54 AU.addRequired<DominatorTree>(); 55 AU.addRequired<DominanceFrontier>(); 56 AU.addRequired<TargetData>(); 57 AU.setPreservesCFG(); 58 } 59 60 private: 61 int isSafeElementUse(Value *Ptr); 62 int isSafeUseOfAllocation(Instruction *User); 63 int isSafeAllocaToScalarRepl(AllocationInst *AI); 64 void CanonicalizeAllocaUsers(AllocationInst *AI); 65 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base); 66 67 const Type *CanConvertToScalar(Value *V, bool &IsNotTrivial); 68 void ConvertToScalar(AllocationInst *AI, const Type *Ty); 69 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset); 70 }; 71 72 RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates"); 73} 74 75// Public interface to the ScalarReplAggregates pass 76FunctionPass *llvm::createScalarReplAggregatesPass() { return new SROA(); } 77 78 79bool SROA::runOnFunction(Function &F) { 80 bool Changed = performPromotion(F); 81 while (1) { 82 bool LocalChange = performScalarRepl(F); 83 if (!LocalChange) break; // No need to repromote if no scalarrepl 84 Changed = true; 85 LocalChange = performPromotion(F); 86 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 87 } 88 89 return Changed; 90} 91 92 93bool SROA::performPromotion(Function &F) { 94 std::vector<AllocaInst*> Allocas; 95 const TargetData &TD = getAnalysis<TargetData>(); 96 DominatorTree &DT = getAnalysis<DominatorTree>(); 97 DominanceFrontier &DF = getAnalysis<DominanceFrontier>(); 98 99 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 100 101 bool Changed = false; 102 103 while (1) { 104 Allocas.clear(); 105 106 // Find allocas that are safe to promote, by looking at all instructions in 107 // the entry node 108 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 109 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 110 if (isAllocaPromotable(AI, TD)) 111 Allocas.push_back(AI); 112 113 if (Allocas.empty()) break; 114 115 PromoteMemToReg(Allocas, DT, DF, TD); 116 NumPromoted += Allocas.size(); 117 Changed = true; 118 } 119 120 return Changed; 121} 122 123// performScalarRepl - This algorithm is a simple worklist driven algorithm, 124// which runs on all of the malloc/alloca instructions in the function, removing 125// them if they are only used by getelementptr instructions. 126// 127bool SROA::performScalarRepl(Function &F) { 128 std::vector<AllocationInst*> WorkList; 129 130 // Scan the entry basic block, adding any alloca's and mallocs to the worklist 131 BasicBlock &BB = F.getEntryBlock(); 132 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 133 if (AllocationInst *A = dyn_cast<AllocationInst>(I)) 134 WorkList.push_back(A); 135 136 // Process the worklist 137 bool Changed = false; 138 while (!WorkList.empty()) { 139 AllocationInst *AI = WorkList.back(); 140 WorkList.pop_back(); 141 142 // If we can turn this aggregate value (potentially with casts) into a 143 // simple scalar value that can be mem2reg'd into a register value. 144 bool IsNotTrivial = false; 145 if (const Type *ActualType = CanConvertToScalar(AI, IsNotTrivial)) 146 if (IsNotTrivial && ActualType != Type::VoidTy) { 147 ConvertToScalar(AI, ActualType); 148 Changed = true; 149 continue; 150 } 151 152 // We cannot transform the allocation instruction if it is an array 153 // allocation (allocations OF arrays are ok though), and an allocation of a 154 // scalar value cannot be decomposed at all. 155 // 156 if (AI->isArrayAllocation() || 157 (!isa<StructType>(AI->getAllocatedType()) && 158 !isa<ArrayType>(AI->getAllocatedType()))) continue; 159 160 // Check that all of the users of the allocation are capable of being 161 // transformed. 162 switch (isSafeAllocaToScalarRepl(AI)) { 163 default: assert(0 && "Unexpected value!"); 164 case 0: // Not safe to scalar replace. 165 continue; 166 case 1: // Safe, but requires cleanup/canonicalizations first 167 CanonicalizeAllocaUsers(AI); 168 case 3: // Safe to scalar replace. 169 break; 170 } 171 172 DOUT << "Found inst to xform: " << *AI; 173 Changed = true; 174 175 std::vector<AllocaInst*> ElementAllocas; 176 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 177 ElementAllocas.reserve(ST->getNumContainedTypes()); 178 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 179 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 180 AI->getAlignment(), 181 AI->getName() + "." + utostr(i), AI); 182 ElementAllocas.push_back(NA); 183 WorkList.push_back(NA); // Add to worklist for recursive processing 184 } 185 } else { 186 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 187 ElementAllocas.reserve(AT->getNumElements()); 188 const Type *ElTy = AT->getElementType(); 189 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 190 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 191 AI->getName() + "." + utostr(i), AI); 192 ElementAllocas.push_back(NA); 193 WorkList.push_back(NA); // Add to worklist for recursive processing 194 } 195 } 196 197 // Now that we have created the alloca instructions that we want to use, 198 // expand the getelementptr instructions to use them. 199 // 200 while (!AI->use_empty()) { 201 Instruction *User = cast<Instruction>(AI->use_back()); 202 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User); 203 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst> 204 unsigned Idx = 205 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 206 207 assert(Idx < ElementAllocas.size() && "Index out of range?"); 208 AllocaInst *AllocaToUse = ElementAllocas[Idx]; 209 210 Value *RepValue; 211 if (GEPI->getNumOperands() == 3) { 212 // Do not insert a new getelementptr instruction with zero indices, only 213 // to have it optimized out later. 214 RepValue = AllocaToUse; 215 } else { 216 // We are indexing deeply into the structure, so we still need a 217 // getelement ptr instruction to finish the indexing. This may be 218 // expanded itself once the worklist is rerun. 219 // 220 std::string OldName = GEPI->getName(); // Steal the old name. 221 std::vector<Value*> NewArgs; 222 NewArgs.push_back(Constant::getNullValue(Type::IntTy)); 223 NewArgs.insert(NewArgs.end(), GEPI->op_begin()+3, GEPI->op_end()); 224 GEPI->setName(""); 225 RepValue = new GetElementPtrInst(AllocaToUse, NewArgs, OldName, GEPI); 226 } 227 228 // Move all of the users over to the new GEP. 229 GEPI->replaceAllUsesWith(RepValue); 230 // Delete the old GEP 231 GEPI->eraseFromParent(); 232 } 233 234 // Finally, delete the Alloca instruction 235 AI->getParent()->getInstList().erase(AI); 236 NumReplaced++; 237 } 238 239 return Changed; 240} 241 242 243/// isSafeElementUse - Check to see if this use is an allowed use for a 244/// getelementptr instruction of an array aggregate allocation. 245/// 246int SROA::isSafeElementUse(Value *Ptr) { 247 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 248 I != E; ++I) { 249 Instruction *User = cast<Instruction>(*I); 250 switch (User->getOpcode()) { 251 case Instruction::Load: break; 252 case Instruction::Store: 253 // Store is ok if storing INTO the pointer, not storing the pointer 254 if (User->getOperand(0) == Ptr) return 0; 255 break; 256 case Instruction::GetElementPtr: { 257 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User); 258 if (GEP->getNumOperands() > 1) { 259 if (!isa<Constant>(GEP->getOperand(1)) || 260 !cast<Constant>(GEP->getOperand(1))->isNullValue()) 261 return 0; // Using pointer arithmetic to navigate the array... 262 } 263 if (!isSafeElementUse(GEP)) return 0; 264 break; 265 } 266 default: 267 DOUT << " Transformation preventing inst: " << *User; 268 return 0; 269 } 270 } 271 return 3; // All users look ok :) 272} 273 274/// AllUsersAreLoads - Return true if all users of this value are loads. 275static bool AllUsersAreLoads(Value *Ptr) { 276 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 277 I != E; ++I) 278 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load) 279 return false; 280 return true; 281} 282 283/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an 284/// aggregate allocation. 285/// 286int SROA::isSafeUseOfAllocation(Instruction *User) { 287 if (!isa<GetElementPtrInst>(User)) return 0; 288 289 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User); 290 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI); 291 292 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>". 293 if (I == E || 294 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) 295 return 0; 296 297 ++I; 298 if (I == E) return 0; // ran out of GEP indices?? 299 300 // If this is a use of an array allocation, do a bit more checking for sanity. 301 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 302 uint64_t NumElements = AT->getNumElements(); 303 304 if (isa<ConstantInt>(I.getOperand())) { 305 // Check to make sure that index falls within the array. If not, 306 // something funny is going on, so we won't do the optimization. 307 // 308 if (cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue() >= NumElements) 309 return 0; 310 311 // We cannot scalar repl this level of the array unless any array 312 // sub-indices are in-range constants. In particular, consider: 313 // A[0][i]. We cannot know that the user isn't doing invalid things like 314 // allowing i to index an out-of-range subscript that accesses A[1]. 315 // 316 // Scalar replacing *just* the outer index of the array is probably not 317 // going to be a win anyway, so just give up. 318 for (++I; I != E && (isa<ArrayType>(*I) || isa<PackedType>(*I)); ++I) { 319 uint64_t NumElements; 320 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*I)) 321 NumElements = SubArrayTy->getNumElements(); 322 else 323 NumElements = cast<PackedType>(*I)->getNumElements(); 324 325 if (!isa<ConstantInt>(I.getOperand())) return 0; 326 if (cast<ConstantInt>(I.getOperand())->getZExtValue() >= NumElements) 327 return 0; 328 } 329 330 } else { 331 // If this is an array index and the index is not constant, we cannot 332 // promote... that is unless the array has exactly one or two elements in 333 // it, in which case we CAN promote it, but we have to canonicalize this 334 // out if this is the only problem. 335 if ((NumElements == 1 || NumElements == 2) && 336 AllUsersAreLoads(GEPI)) 337 return 1; // Canonicalization required! 338 return 0; 339 } 340 } 341 342 // If there are any non-simple uses of this getelementptr, make sure to reject 343 // them. 344 return isSafeElementUse(GEPI); 345} 346 347/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 348/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 349/// or 1 if safe after canonicalization has been performed. 350/// 351int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) { 352 // Loop over the use list of the alloca. We can only transform it if all of 353 // the users are safe to transform. 354 // 355 int isSafe = 3; 356 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); 357 I != E; ++I) { 358 isSafe &= isSafeUseOfAllocation(cast<Instruction>(*I)); 359 if (isSafe == 0) { 360 DOUT << "Cannot transform: " << *AI << " due to user: " << **I; 361 return 0; 362 } 363 } 364 // If we require cleanup, isSafe is now 1, otherwise it is 3. 365 return isSafe; 366} 367 368/// CanonicalizeAllocaUsers - If SROA reported that it can promote the specified 369/// allocation, but only if cleaned up, perform the cleanups required. 370void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) { 371 // At this point, we know that the end result will be SROA'd and promoted, so 372 // we can insert ugly code if required so long as sroa+mem2reg will clean it 373 // up. 374 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 375 UI != E; ) { 376 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(*UI++); 377 gep_type_iterator I = gep_type_begin(GEPI); 378 ++I; 379 380 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 381 uint64_t NumElements = AT->getNumElements(); 382 383 if (!isa<ConstantInt>(I.getOperand())) { 384 if (NumElements == 1) { 385 GEPI->setOperand(2, Constant::getNullValue(Type::IntTy)); 386 } else { 387 assert(NumElements == 2 && "Unhandled case!"); 388 // All users of the GEP must be loads. At each use of the GEP, insert 389 // two loads of the appropriate indexed GEP and select between them. 390 Value *IsOne = BinaryOperator::createSetNE(I.getOperand(), 391 Constant::getNullValue(I.getOperand()->getType()), 392 "isone", GEPI); 393 // Insert the new GEP instructions, which are properly indexed. 394 std::vector<Value*> Indices(GEPI->op_begin()+1, GEPI->op_end()); 395 Indices[1] = Constant::getNullValue(Type::IntTy); 396 Value *ZeroIdx = new GetElementPtrInst(GEPI->getOperand(0), Indices, 397 GEPI->getName()+".0", GEPI); 398 Indices[1] = ConstantInt::get(Type::IntTy, 1); 399 Value *OneIdx = new GetElementPtrInst(GEPI->getOperand(0), Indices, 400 GEPI->getName()+".1", GEPI); 401 // Replace all loads of the variable index GEP with loads from both 402 // indexes and a select. 403 while (!GEPI->use_empty()) { 404 LoadInst *LI = cast<LoadInst>(GEPI->use_back()); 405 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI); 406 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI); 407 Value *R = new SelectInst(IsOne, One, Zero, LI->getName(), LI); 408 LI->replaceAllUsesWith(R); 409 LI->eraseFromParent(); 410 } 411 GEPI->eraseFromParent(); 412 } 413 } 414 } 415 } 416} 417 418/// MergeInType - Add the 'In' type to the accumulated type so far. If the 419/// types are incompatible, return true, otherwise update Accum and return 420/// false. 421/// 422/// There are two cases we handle here: 423/// 1) An effectively integer union, where the pieces are stored into as 424/// smaller integers (common with byte swap and other idioms). 425/// 2) A union of a vector and its elements. Here we turn element accesses 426/// into insert/extract element operations. 427static bool MergeInType(const Type *In, const Type *&Accum, 428 const TargetData &TD) { 429 // If this is our first type, just use it. 430 const PackedType *PTy; 431 if (Accum == Type::VoidTy || In == Accum) { 432 Accum = In; 433 } else if (In->isIntegral() && Accum->isIntegral()) { // integer union. 434 // Otherwise pick whichever type is larger. 435 if (In->getTypeID() > Accum->getTypeID()) 436 Accum = In; 437 } else if (isa<PointerType>(In) && isa<PointerType>(Accum)) { 438 // Pointer unions just stay as one of the pointers. 439 } else if ((PTy = dyn_cast<PackedType>(Accum)) && 440 PTy->getElementType() == In) { 441 // Accum is a vector, and we are accessing an element: ok. 442 } else if ((PTy = dyn_cast<PackedType>(In)) && 443 PTy->getElementType() == Accum) { 444 // In is a vector, and accum is an element: ok, remember In. 445 Accum = In; 446 } else if (isa<PointerType>(In) && Accum->isIntegral()) { 447 // Pointer/Integer unions merge together as integers. 448 return MergeInType(TD.getIntPtrType(), Accum, TD); 449 } else if (isa<PointerType>(Accum) && In->isIntegral()) { 450 // Pointer/Integer unions merge together as integers. 451 Accum = TD.getIntPtrType(); 452 return MergeInType(In, Accum, TD); 453 } else { 454 return true; 455 } 456 return false; 457} 458 459/// getUIntAtLeastAsBitAs - Return an unsigned integer type that is at least 460/// as big as the specified type. If there is no suitable type, this returns 461/// null. 462const Type *getUIntAtLeastAsBitAs(unsigned NumBits) { 463 if (NumBits > 64) return 0; 464 if (NumBits > 32) return Type::ULongTy; 465 if (NumBits > 16) return Type::UIntTy; 466 if (NumBits > 8) return Type::UShortTy; 467 return Type::UByteTy; 468} 469 470/// CanConvertToScalar - V is a pointer. If we can convert the pointee to a 471/// single scalar integer type, return that type. Further, if the use is not 472/// a completely trivial use that mem2reg could promote, set IsNotTrivial. If 473/// there are no uses of this pointer, return Type::VoidTy to differentiate from 474/// failure. 475/// 476const Type *SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial) { 477 const Type *UsedType = Type::VoidTy; // No uses, no forced type. 478 const TargetData &TD = getAnalysis<TargetData>(); 479 const PointerType *PTy = cast<PointerType>(V->getType()); 480 481 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 482 Instruction *User = cast<Instruction>(*UI); 483 484 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 485 if (MergeInType(LI->getType(), UsedType, TD)) 486 return 0; 487 488 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 489 // Storing the pointer, not the into the value? 490 if (SI->getOperand(0) == V) return 0; 491 492 // NOTE: We could handle storing of FP imms into integers here! 493 494 if (MergeInType(SI->getOperand(0)->getType(), UsedType, TD)) 495 return 0; 496 } else if (CastInst *CI = dyn_cast<CastInst>(User)) { 497 if (!isa<PointerType>(CI->getType())) return 0; 498 IsNotTrivial = true; 499 const Type *SubTy = CanConvertToScalar(CI, IsNotTrivial); 500 if (!SubTy || MergeInType(SubTy, UsedType, TD)) return 0; 501 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 502 // Check to see if this is stepping over an element: GEP Ptr, int C 503 if (GEP->getNumOperands() == 2 && isa<ConstantInt>(GEP->getOperand(1))) { 504 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue(); 505 unsigned ElSize = TD.getTypeSize(PTy->getElementType()); 506 unsigned BitOffset = Idx*ElSize*8; 507 if (BitOffset > 64 || !isPowerOf2_32(ElSize)) return 0; 508 509 IsNotTrivial = true; 510 const Type *SubElt = CanConvertToScalar(GEP, IsNotTrivial); 511 if (SubElt == 0) return 0; 512 if (SubElt != Type::VoidTy && SubElt->isInteger()) { 513 const Type *NewTy = 514 getUIntAtLeastAsBitAs(TD.getTypeSize(SubElt)*8+BitOffset); 515 if (NewTy == 0 || MergeInType(NewTy, UsedType, TD)) return 0; 516 continue; 517 } 518 } else if (GEP->getNumOperands() == 3 && 519 isa<ConstantInt>(GEP->getOperand(1)) && 520 isa<ConstantInt>(GEP->getOperand(2)) && 521 cast<Constant>(GEP->getOperand(1))->isNullValue()) { 522 // We are stepping into an element, e.g. a structure or an array: 523 // GEP Ptr, int 0, uint C 524 const Type *AggTy = PTy->getElementType(); 525 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 526 527 if (const ArrayType *ATy = dyn_cast<ArrayType>(AggTy)) { 528 if (Idx >= ATy->getNumElements()) return 0; // Out of range. 529 } else if (const PackedType *PackedTy = dyn_cast<PackedType>(AggTy)) { 530 // Getting an element of the packed vector. 531 if (Idx >= PackedTy->getNumElements()) return 0; // Out of range. 532 533 // Merge in the packed type. 534 if (MergeInType(PackedTy, UsedType, TD)) return 0; 535 536 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); 537 if (SubTy == 0) return 0; 538 539 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD)) 540 return 0; 541 542 // We'll need to change this to an insert/extract element operation. 543 IsNotTrivial = true; 544 continue; // Everything looks ok 545 546 } else if (isa<StructType>(AggTy)) { 547 // Structs are always ok. 548 } else { 549 return 0; 550 } 551 const Type *NTy = getUIntAtLeastAsBitAs(TD.getTypeSize(AggTy)*8); 552 if (NTy == 0 || MergeInType(NTy, UsedType, TD)) return 0; 553 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); 554 if (SubTy == 0) return 0; 555 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD)) 556 return 0; 557 continue; // Everything looks ok 558 } 559 return 0; 560 } else { 561 // Cannot handle this! 562 return 0; 563 } 564 } 565 566 return UsedType; 567} 568 569/// ConvertToScalar - The specified alloca passes the CanConvertToScalar 570/// predicate and is non-trivial. Convert it to something that can be trivially 571/// promoted into a register by mem2reg. 572void SROA::ConvertToScalar(AllocationInst *AI, const Type *ActualTy) { 573 DOUT << "CONVERT TO SCALAR: " << *AI << " TYPE = " 574 << *ActualTy << "\n"; 575 ++NumConverted; 576 577 BasicBlock *EntryBlock = AI->getParent(); 578 assert(EntryBlock == &EntryBlock->getParent()->front() && 579 "Not in the entry block!"); 580 EntryBlock->getInstList().remove(AI); // Take the alloca out of the program. 581 582 if (ActualTy->isInteger()) 583 ActualTy = ActualTy->getUnsignedVersion(); 584 585 // Create and insert the alloca. 586 AllocaInst *NewAI = new AllocaInst(ActualTy, 0, AI->getName(), 587 EntryBlock->begin()); 588 ConvertUsesToScalar(AI, NewAI, 0); 589 delete AI; 590} 591 592 593/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 594/// directly. This happens when we are converting an "integer union" to a 595/// single integer scalar, or when we are converting a "vector union" to a 596/// vector with insert/extractelement instructions. 597/// 598/// Offset is an offset from the original alloca, in bits that need to be 599/// shifted to the right. By the end of this, there should be no uses of Ptr. 600void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset) { 601 bool isVectorInsert = isa<PackedType>(NewAI->getType()->getElementType()); 602 const TargetData &TD = getAnalysis<TargetData>(); 603 while (!Ptr->use_empty()) { 604 Instruction *User = cast<Instruction>(Ptr->use_back()); 605 606 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 607 // The load is a bit extract from NewAI shifted right by Offset bits. 608 Value *NV = new LoadInst(NewAI, LI->getName(), LI); 609 if (NV->getType() != LI->getType()) { 610 if (const PackedType *PTy = dyn_cast<PackedType>(NV->getType())) { 611 // Must be an element access. 612 unsigned Elt = Offset/(TD.getTypeSize(PTy->getElementType())*8); 613 NV = new ExtractElementInst(NV, ConstantInt::get(Type::UIntTy, Elt), 614 "tmp", LI); 615 } else { 616 if (Offset) { 617 assert(NV->getType()->isInteger() && "Unknown promotion!"); 618 if (Offset < TD.getTypeSize(NV->getType())*8) { 619 NV = new ShiftInst(Instruction::LShr, NV, 620 ConstantInt::get(Type::UByteTy, Offset), 621 LI->getName(), LI); 622 } 623 } else { 624 assert((NV->getType()->isInteger() || 625 isa<PointerType>(NV->getType())) && "Unknown promotion!"); 626 } 627 NV = CastInst::createInferredCast(NV, LI->getType(), LI->getName(), 628 LI); 629 } 630 } 631 LI->replaceAllUsesWith(NV); 632 LI->eraseFromParent(); 633 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 634 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 635 636 // Convert the stored type to the actual type, shift it left to insert 637 // then 'or' into place. 638 Value *SV = SI->getOperand(0); 639 const Type *AllocaType = NewAI->getType()->getElementType(); 640 if (SV->getType() != AllocaType) { 641 Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI); 642 643 if (const PackedType *PTy = dyn_cast<PackedType>(AllocaType)) { 644 // Must be an element insertion. 645 unsigned Elt = Offset/(TD.getTypeSize(PTy->getElementType())*8); 646 SV = new InsertElementInst(Old, SV, 647 ConstantInt::get(Type::UIntTy, Elt), 648 "tmp", SI); 649 } else { 650 // Always zero extend the value. 651 if (SV->getType()->isSigned()) 652 SV = CastInst::createInferredCast(SV, 653 SV->getType()->getUnsignedVersion(), SV->getName(), SI); 654 SV = CastInst::createInferredCast(SV, Old->getType(), SV->getName(), 655 SI); 656 if (Offset && Offset < TD.getTypeSize(SV->getType())*8) 657 SV = new ShiftInst(Instruction::Shl, SV, 658 ConstantInt::get(Type::UByteTy, Offset), 659 SV->getName()+".adj", SI); 660 // Mask out the bits we are about to insert from the old value. 661 unsigned TotalBits = TD.getTypeSize(SV->getType())*8; 662 unsigned InsertBits = TD.getTypeSize(SI->getOperand(0)->getType())*8; 663 if (TotalBits != InsertBits) { 664 assert(TotalBits > InsertBits); 665 uint64_t Mask = ~(((1ULL << InsertBits)-1) << Offset); 666 if (TotalBits != 64) 667 Mask = Mask & ((1ULL << TotalBits)-1); 668 Old = BinaryOperator::createAnd(Old, 669 ConstantInt::get(Old->getType(), Mask), 670 Old->getName()+".mask", SI); 671 SV = BinaryOperator::createOr(Old, SV, SV->getName()+".ins", SI); 672 } 673 } 674 } 675 new StoreInst(SV, NewAI, SI); 676 SI->eraseFromParent(); 677 678 } else if (CastInst *CI = dyn_cast<CastInst>(User)) { 679 unsigned NewOff = Offset; 680 const TargetData &TD = getAnalysis<TargetData>(); 681 if (TD.isBigEndian() && !isVectorInsert) { 682 // Adjust the pointer. For example, storing 16-bits into a 32-bit 683 // alloca with just a cast makes it modify the top 16-bits. 684 const Type *SrcTy = cast<PointerType>(Ptr->getType())->getElementType(); 685 const Type *DstTy = cast<PointerType>(CI->getType())->getElementType(); 686 int PtrDiffBits = TD.getTypeSize(SrcTy)*8-TD.getTypeSize(DstTy)*8; 687 NewOff += PtrDiffBits; 688 } 689 ConvertUsesToScalar(CI, NewAI, NewOff); 690 CI->eraseFromParent(); 691 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 692 const PointerType *AggPtrTy = 693 cast<PointerType>(GEP->getOperand(0)->getType()); 694 const TargetData &TD = getAnalysis<TargetData>(); 695 unsigned AggSizeInBits = TD.getTypeSize(AggPtrTy->getElementType())*8; 696 697 // Check to see if this is stepping over an element: GEP Ptr, int C 698 unsigned NewOffset = Offset; 699 if (GEP->getNumOperands() == 2) { 700 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue(); 701 unsigned BitOffset = Idx*AggSizeInBits; 702 703 if (TD.isLittleEndian() || isVectorInsert) 704 NewOffset += BitOffset; 705 else 706 NewOffset -= BitOffset; 707 708 } else if (GEP->getNumOperands() == 3) { 709 // We know that operand #2 is zero. 710 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 711 const Type *AggTy = AggPtrTy->getElementType(); 712 if (const SequentialType *SeqTy = dyn_cast<SequentialType>(AggTy)) { 713 unsigned ElSizeBits = TD.getTypeSize(SeqTy->getElementType())*8; 714 715 if (TD.isLittleEndian() || isVectorInsert) 716 NewOffset += ElSizeBits*Idx; 717 else 718 NewOffset += AggSizeInBits-ElSizeBits*(Idx+1); 719 } else if (const StructType *STy = dyn_cast<StructType>(AggTy)) { 720 unsigned EltBitOffset = TD.getStructLayout(STy)->MemberOffsets[Idx]*8; 721 722 if (TD.isLittleEndian() || isVectorInsert) 723 NewOffset += EltBitOffset; 724 else { 725 const PointerType *ElPtrTy = cast<PointerType>(GEP->getType()); 726 unsigned ElSizeBits = TD.getTypeSize(ElPtrTy->getElementType())*8; 727 NewOffset += AggSizeInBits-(EltBitOffset+ElSizeBits); 728 } 729 730 } else { 731 assert(0 && "Unsupported operation!"); 732 abort(); 733 } 734 } else { 735 assert(0 && "Unsupported operation!"); 736 abort(); 737 } 738 ConvertUsesToScalar(GEP, NewAI, NewOffset); 739 GEP->eraseFromParent(); 740 } else { 741 assert(0 && "Unsupported operation!"); 742 abort(); 743 } 744 } 745} 746