ScalarReplAggregates.cpp revision ac9dcb94dde5f166ee29372385c0e3b695227ab4
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#define DEBUG_TYPE "scalarrepl" 23#include "llvm/Transforms/Scalar.h" 24#include "llvm/Constants.h" 25#include "llvm/DerivedTypes.h" 26#include "llvm/Function.h" 27#include "llvm/Pass.h" 28#include "llvm/Instructions.h" 29#include "llvm/Analysis/Dominators.h" 30#include "llvm/Target/TargetData.h" 31#include "llvm/Transforms/Utils/PromoteMemToReg.h" 32#include "llvm/Support/Debug.h" 33#include "llvm/Support/GetElementPtrTypeIterator.h" 34#include "llvm/Support/MathExtras.h" 35#include "llvm/Support/Compiler.h" 36#include "llvm/ADT/SmallVector.h" 37#include "llvm/ADT/Statistic.h" 38#include "llvm/ADT/StringExtras.h" 39using namespace llvm; 40 41STATISTIC(NumReplaced, "Number of allocas broken up"); 42STATISTIC(NumPromoted, "Number of allocas promoted"); 43STATISTIC(NumConverted, "Number of aggregates converted to scalar"); 44 45namespace { 46 struct VISIBILITY_HIDDEN SROA : public FunctionPass { 47 bool runOnFunction(Function &F); 48 49 bool performScalarRepl(Function &F); 50 bool performPromotion(Function &F); 51 52 // getAnalysisUsage - This pass does not require any passes, but we know it 53 // will not alter the CFG, so say so. 54 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 55 AU.addRequired<DominatorTree>(); 56 AU.addRequired<DominanceFrontier>(); 57 AU.addRequired<TargetData>(); 58 AU.setPreservesCFG(); 59 } 60 61 private: 62 int isSafeElementUse(Value *Ptr); 63 int isSafeUseOfAllocation(Instruction *User); 64 int isSafeAllocaToScalarRepl(AllocationInst *AI); 65 void CanonicalizeAllocaUsers(AllocationInst *AI); 66 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base); 67 68 const Type *CanConvertToScalar(Value *V, bool &IsNotTrivial); 69 void ConvertToScalar(AllocationInst *AI, const Type *Ty); 70 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset); 71 }; 72 73 RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates"); 74} 75 76// Public interface to the ScalarReplAggregates pass 77FunctionPass *llvm::createScalarReplAggregatesPass() { return new SROA(); } 78 79 80bool SROA::runOnFunction(Function &F) { 81 bool Changed = performPromotion(F); 82 while (1) { 83 bool LocalChange = performScalarRepl(F); 84 if (!LocalChange) break; // No need to repromote if no scalarrepl 85 Changed = true; 86 LocalChange = performPromotion(F); 87 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 88 } 89 90 return Changed; 91} 92 93 94bool SROA::performPromotion(Function &F) { 95 std::vector<AllocaInst*> Allocas; 96 const TargetData &TD = getAnalysis<TargetData>(); 97 DominatorTree &DT = getAnalysis<DominatorTree>(); 98 DominanceFrontier &DF = getAnalysis<DominanceFrontier>(); 99 100 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 101 102 bool Changed = false; 103 104 while (1) { 105 Allocas.clear(); 106 107 // Find allocas that are safe to promote, by looking at all instructions in 108 // the entry node 109 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 110 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 111 if (isAllocaPromotable(AI, TD)) 112 Allocas.push_back(AI); 113 114 if (Allocas.empty()) break; 115 116 PromoteMemToReg(Allocas, DT, DF, TD); 117 NumPromoted += Allocas.size(); 118 Changed = true; 119 } 120 121 return Changed; 122} 123 124// performScalarRepl - This algorithm is a simple worklist driven algorithm, 125// which runs on all of the malloc/alloca instructions in the function, removing 126// them if they are only used by getelementptr instructions. 127// 128bool SROA::performScalarRepl(Function &F) { 129 std::vector<AllocationInst*> WorkList; 130 131 // Scan the entry basic block, adding any alloca's and mallocs to the worklist 132 BasicBlock &BB = F.getEntryBlock(); 133 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 134 if (AllocationInst *A = dyn_cast<AllocationInst>(I)) 135 WorkList.push_back(A); 136 137 // Process the worklist 138 bool Changed = false; 139 while (!WorkList.empty()) { 140 AllocationInst *AI = WorkList.back(); 141 WorkList.pop_back(); 142 143 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 144 // with unused elements. 145 if (AI->use_empty()) { 146 AI->eraseFromParent(); 147 continue; 148 } 149 150 // If we can turn this aggregate value (potentially with casts) into a 151 // simple scalar value that can be mem2reg'd into a register value. 152 bool IsNotTrivial = false; 153 if (const Type *ActualType = CanConvertToScalar(AI, IsNotTrivial)) 154 if (IsNotTrivial && ActualType != Type::VoidTy) { 155 ConvertToScalar(AI, ActualType); 156 Changed = true; 157 continue; 158 } 159 160 // We cannot transform the allocation instruction if it is an array 161 // allocation (allocations OF arrays are ok though), and an allocation of a 162 // scalar value cannot be decomposed at all. 163 // 164 if (AI->isArrayAllocation() || 165 (!isa<StructType>(AI->getAllocatedType()) && 166 !isa<ArrayType>(AI->getAllocatedType()))) continue; 167 168 // Check that all of the users of the allocation are capable of being 169 // transformed. 170 switch (isSafeAllocaToScalarRepl(AI)) { 171 default: assert(0 && "Unexpected value!"); 172 case 0: // Not safe to scalar replace. 173 continue; 174 case 1: // Safe, but requires cleanup/canonicalizations first 175 CanonicalizeAllocaUsers(AI); 176 case 3: // Safe to scalar replace. 177 break; 178 } 179 180 DOUT << "Found inst to xform: " << *AI; 181 Changed = true; 182 183 std::vector<AllocaInst*> ElementAllocas; 184 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 185 ElementAllocas.reserve(ST->getNumContainedTypes()); 186 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 187 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 188 AI->getAlignment(), 189 AI->getName() + "." + utostr(i), AI); 190 ElementAllocas.push_back(NA); 191 WorkList.push_back(NA); // Add to worklist for recursive processing 192 } 193 } else { 194 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 195 ElementAllocas.reserve(AT->getNumElements()); 196 const Type *ElTy = AT->getElementType(); 197 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 198 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 199 AI->getName() + "." + utostr(i), AI); 200 ElementAllocas.push_back(NA); 201 WorkList.push_back(NA); // Add to worklist for recursive processing 202 } 203 } 204 205 // Now that we have created the alloca instructions that we want to use, 206 // expand the getelementptr instructions to use them. 207 // 208 while (!AI->use_empty()) { 209 Instruction *User = cast<Instruction>(AI->use_back()); 210 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User); 211 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst> 212 unsigned Idx = 213 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 214 215 assert(Idx < ElementAllocas.size() && "Index out of range?"); 216 AllocaInst *AllocaToUse = ElementAllocas[Idx]; 217 218 Value *RepValue; 219 if (GEPI->getNumOperands() == 3) { 220 // Do not insert a new getelementptr instruction with zero indices, only 221 // to have it optimized out later. 222 RepValue = AllocaToUse; 223 } else { 224 // We are indexing deeply into the structure, so we still need a 225 // getelement ptr instruction to finish the indexing. This may be 226 // expanded itself once the worklist is rerun. 227 // 228 SmallVector<Value*, 8> NewArgs; 229 NewArgs.push_back(Constant::getNullValue(Type::Int32Ty)); 230 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end()); 231 RepValue = new GetElementPtrInst(AllocaToUse, &NewArgs[0], 232 NewArgs.size(), "", GEPI); 233 RepValue->takeName(GEPI); 234 } 235 236 // Move all of the users over to the new GEP. 237 GEPI->replaceAllUsesWith(RepValue); 238 // Delete the old GEP 239 GEPI->eraseFromParent(); 240 } 241 242 // Finally, delete the Alloca instruction 243 AI->eraseFromParent(); 244 NumReplaced++; 245 } 246 247 return Changed; 248} 249 250 251/// isSafeElementUse - Check to see if this use is an allowed use for a 252/// getelementptr instruction of an array aggregate allocation. 253/// 254int SROA::isSafeElementUse(Value *Ptr) { 255 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 256 I != E; ++I) { 257 Instruction *User = cast<Instruction>(*I); 258 switch (User->getOpcode()) { 259 case Instruction::Load: break; 260 case Instruction::Store: 261 // Store is ok if storing INTO the pointer, not storing the pointer 262 if (User->getOperand(0) == Ptr) return 0; 263 break; 264 case Instruction::GetElementPtr: { 265 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User); 266 if (GEP->getNumOperands() > 1) { 267 if (!isa<Constant>(GEP->getOperand(1)) || 268 !cast<Constant>(GEP->getOperand(1))->isNullValue()) 269 return 0; // Using pointer arithmetic to navigate the array... 270 } 271 if (!isSafeElementUse(GEP)) return 0; 272 break; 273 } 274 default: 275 DOUT << " Transformation preventing inst: " << *User; 276 return 0; 277 } 278 } 279 return 3; // All users look ok :) 280} 281 282/// AllUsersAreLoads - Return true if all users of this value are loads. 283static bool AllUsersAreLoads(Value *Ptr) { 284 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 285 I != E; ++I) 286 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load) 287 return false; 288 return true; 289} 290 291/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an 292/// aggregate allocation. 293/// 294int SROA::isSafeUseOfAllocation(Instruction *User) { 295 if (!isa<GetElementPtrInst>(User)) return 0; 296 297 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User); 298 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI); 299 300 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>". 301 if (I == E || 302 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) 303 return 0; 304 305 ++I; 306 if (I == E) return 0; // ran out of GEP indices?? 307 308 // If this is a use of an array allocation, do a bit more checking for sanity. 309 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 310 uint64_t NumElements = AT->getNumElements(); 311 312 if (isa<ConstantInt>(I.getOperand())) { 313 // Check to make sure that index falls within the array. If not, 314 // something funny is going on, so we won't do the optimization. 315 // 316 if (cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue() >= NumElements) 317 return 0; 318 319 // We cannot scalar repl this level of the array unless any array 320 // sub-indices are in-range constants. In particular, consider: 321 // A[0][i]. We cannot know that the user isn't doing invalid things like 322 // allowing i to index an out-of-range subscript that accesses A[1]. 323 // 324 // Scalar replacing *just* the outer index of the array is probably not 325 // going to be a win anyway, so just give up. 326 for (++I; I != E && (isa<ArrayType>(*I) || isa<VectorType>(*I)); ++I) { 327 uint64_t NumElements; 328 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*I)) 329 NumElements = SubArrayTy->getNumElements(); 330 else 331 NumElements = cast<VectorType>(*I)->getNumElements(); 332 333 if (!isa<ConstantInt>(I.getOperand())) return 0; 334 if (cast<ConstantInt>(I.getOperand())->getZExtValue() >= NumElements) 335 return 0; 336 } 337 338 } else { 339 // If this is an array index and the index is not constant, we cannot 340 // promote... that is unless the array has exactly one or two elements in 341 // it, in which case we CAN promote it, but we have to canonicalize this 342 // out if this is the only problem. 343 if ((NumElements == 1 || NumElements == 2) && 344 AllUsersAreLoads(GEPI)) 345 return 1; // Canonicalization required! 346 return 0; 347 } 348 } 349 350 // If there are any non-simple uses of this getelementptr, make sure to reject 351 // them. 352 return isSafeElementUse(GEPI); 353} 354 355/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 356/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 357/// or 1 if safe after canonicalization has been performed. 358/// 359int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) { 360 // Loop over the use list of the alloca. We can only transform it if all of 361 // the users are safe to transform. 362 // 363 int isSafe = 3; 364 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); 365 I != E; ++I) { 366 isSafe &= isSafeUseOfAllocation(cast<Instruction>(*I)); 367 if (isSafe == 0) { 368 DOUT << "Cannot transform: " << *AI << " due to user: " << **I; 369 return 0; 370 } 371 } 372 // If we require cleanup, isSafe is now 1, otherwise it is 3. 373 return isSafe; 374} 375 376/// CanonicalizeAllocaUsers - If SROA reported that it can promote the specified 377/// allocation, but only if cleaned up, perform the cleanups required. 378void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) { 379 // At this point, we know that the end result will be SROA'd and promoted, so 380 // we can insert ugly code if required so long as sroa+mem2reg will clean it 381 // up. 382 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 383 UI != E; ) { 384 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(*UI++); 385 gep_type_iterator I = gep_type_begin(GEPI); 386 ++I; 387 388 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 389 uint64_t NumElements = AT->getNumElements(); 390 391 if (!isa<ConstantInt>(I.getOperand())) { 392 if (NumElements == 1) { 393 GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty)); 394 } else { 395 assert(NumElements == 2 && "Unhandled case!"); 396 // All users of the GEP must be loads. At each use of the GEP, insert 397 // two loads of the appropriate indexed GEP and select between them. 398 Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(), 399 Constant::getNullValue(I.getOperand()->getType()), 400 "isone", GEPI); 401 // Insert the new GEP instructions, which are properly indexed. 402 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end()); 403 Indices[1] = Constant::getNullValue(Type::Int32Ty); 404 Value *ZeroIdx = new GetElementPtrInst(GEPI->getOperand(0), 405 &Indices[0], Indices.size(), 406 GEPI->getName()+".0", GEPI); 407 Indices[1] = ConstantInt::get(Type::Int32Ty, 1); 408 Value *OneIdx = new GetElementPtrInst(GEPI->getOperand(0), 409 &Indices[0], Indices.size(), 410 GEPI->getName()+".1", GEPI); 411 // Replace all loads of the variable index GEP with loads from both 412 // indexes and a select. 413 while (!GEPI->use_empty()) { 414 LoadInst *LI = cast<LoadInst>(GEPI->use_back()); 415 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI); 416 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI); 417 Value *R = new SelectInst(IsOne, One, Zero, LI->getName(), LI); 418 LI->replaceAllUsesWith(R); 419 LI->eraseFromParent(); 420 } 421 GEPI->eraseFromParent(); 422 } 423 } 424 } 425 } 426} 427 428/// MergeInType - Add the 'In' type to the accumulated type so far. If the 429/// types are incompatible, return true, otherwise update Accum and return 430/// false. 431/// 432/// There are three cases we handle here: 433/// 1) An effectively-integer union, where the pieces are stored into as 434/// smaller integers (common with byte swap and other idioms). 435/// 2) A union of vector types of the same size and potentially its elements. 436/// Here we turn element accesses into insert/extract element operations. 437/// 3) A union of scalar types, such as int/float or int/pointer. Here we 438/// merge together into integers, allowing the xform to work with #1 as 439/// well. 440static bool MergeInType(const Type *In, const Type *&Accum, 441 const TargetData &TD) { 442 // If this is our first type, just use it. 443 const VectorType *PTy; 444 if (Accum == Type::VoidTy || In == Accum) { 445 Accum = In; 446 } else if (In == Type::VoidTy) { 447 // Noop. 448 } else if (In->isInteger() && Accum->isInteger()) { // integer union. 449 // Otherwise pick whichever type is larger. 450 if (cast<IntegerType>(In)->getBitWidth() > 451 cast<IntegerType>(Accum)->getBitWidth()) 452 Accum = In; 453 } else if (isa<PointerType>(In) && isa<PointerType>(Accum)) { 454 // Pointer unions just stay as one of the pointers. 455 } else if (isa<VectorType>(In) || isa<VectorType>(Accum)) { 456 if ((PTy = dyn_cast<VectorType>(Accum)) && 457 PTy->getElementType() == In) { 458 // Accum is a vector, and we are accessing an element: ok. 459 } else if ((PTy = dyn_cast<VectorType>(In)) && 460 PTy->getElementType() == Accum) { 461 // In is a vector, and accum is an element: ok, remember In. 462 Accum = In; 463 } else if ((PTy = dyn_cast<VectorType>(In)) && isa<VectorType>(Accum) && 464 PTy->getBitWidth() == cast<VectorType>(Accum)->getBitWidth()) { 465 // Two vectors of the same size: keep Accum. 466 } else { 467 // Cannot insert an short into a <4 x int> or handle 468 // <2 x int> -> <4 x int> 469 return true; 470 } 471 } else { 472 // Pointer/FP/Integer unions merge together as integers. 473 switch (Accum->getTypeID()) { 474 case Type::PointerTyID: Accum = TD.getIntPtrType(); break; 475 case Type::FloatTyID: Accum = Type::Int32Ty; break; 476 case Type::DoubleTyID: Accum = Type::Int64Ty; break; 477 default: 478 assert(Accum->isInteger() && "Unknown FP type!"); 479 break; 480 } 481 482 switch (In->getTypeID()) { 483 case Type::PointerTyID: In = TD.getIntPtrType(); break; 484 case Type::FloatTyID: In = Type::Int32Ty; break; 485 case Type::DoubleTyID: In = Type::Int64Ty; break; 486 default: 487 assert(In->isInteger() && "Unknown FP type!"); 488 break; 489 } 490 return MergeInType(In, Accum, TD); 491 } 492 return false; 493} 494 495/// getUIntAtLeastAsBitAs - Return an unsigned integer type that is at least 496/// as big as the specified type. If there is no suitable type, this returns 497/// null. 498const Type *getUIntAtLeastAsBitAs(unsigned NumBits) { 499 if (NumBits > 64) return 0; 500 if (NumBits > 32) return Type::Int64Ty; 501 if (NumBits > 16) return Type::Int32Ty; 502 if (NumBits > 8) return Type::Int16Ty; 503 return Type::Int8Ty; 504} 505 506/// CanConvertToScalar - V is a pointer. If we can convert the pointee to a 507/// single scalar integer type, return that type. Further, if the use is not 508/// a completely trivial use that mem2reg could promote, set IsNotTrivial. If 509/// there are no uses of this pointer, return Type::VoidTy to differentiate from 510/// failure. 511/// 512const Type *SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial) { 513 const Type *UsedType = Type::VoidTy; // No uses, no forced type. 514 const TargetData &TD = getAnalysis<TargetData>(); 515 const PointerType *PTy = cast<PointerType>(V->getType()); 516 517 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 518 Instruction *User = cast<Instruction>(*UI); 519 520 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 521 if (MergeInType(LI->getType(), UsedType, TD)) 522 return 0; 523 524 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 525 // Storing the pointer, not into the value? 526 if (SI->getOperand(0) == V) return 0; 527 528 // NOTE: We could handle storing of FP imms into integers here! 529 530 if (MergeInType(SI->getOperand(0)->getType(), UsedType, TD)) 531 return 0; 532 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 533 IsNotTrivial = true; 534 const Type *SubTy = CanConvertToScalar(CI, IsNotTrivial); 535 if (!SubTy || MergeInType(SubTy, UsedType, TD)) return 0; 536 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 537 // Check to see if this is stepping over an element: GEP Ptr, int C 538 if (GEP->getNumOperands() == 2 && isa<ConstantInt>(GEP->getOperand(1))) { 539 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue(); 540 unsigned ElSize = TD.getTypeSize(PTy->getElementType()); 541 unsigned BitOffset = Idx*ElSize*8; 542 if (BitOffset > 64 || !isPowerOf2_32(ElSize)) return 0; 543 544 IsNotTrivial = true; 545 const Type *SubElt = CanConvertToScalar(GEP, IsNotTrivial); 546 if (SubElt == 0) return 0; 547 if (SubElt != Type::VoidTy && SubElt->isInteger()) { 548 const Type *NewTy = 549 getUIntAtLeastAsBitAs(TD.getTypeSize(SubElt)*8+BitOffset); 550 if (NewTy == 0 || MergeInType(NewTy, UsedType, TD)) return 0; 551 continue; 552 } 553 } else if (GEP->getNumOperands() == 3 && 554 isa<ConstantInt>(GEP->getOperand(1)) && 555 isa<ConstantInt>(GEP->getOperand(2)) && 556 cast<Constant>(GEP->getOperand(1))->isNullValue()) { 557 // We are stepping into an element, e.g. a structure or an array: 558 // GEP Ptr, int 0, uint C 559 const Type *AggTy = PTy->getElementType(); 560 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 561 562 if (const ArrayType *ATy = dyn_cast<ArrayType>(AggTy)) { 563 if (Idx >= ATy->getNumElements()) return 0; // Out of range. 564 } else if (const VectorType *VectorTy = dyn_cast<VectorType>(AggTy)) { 565 // Getting an element of the packed vector. 566 if (Idx >= VectorTy->getNumElements()) return 0; // Out of range. 567 568 // Merge in the vector type. 569 if (MergeInType(VectorTy, UsedType, TD)) return 0; 570 571 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); 572 if (SubTy == 0) return 0; 573 574 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD)) 575 return 0; 576 577 // We'll need to change this to an insert/extract element operation. 578 IsNotTrivial = true; 579 continue; // Everything looks ok 580 581 } else if (isa<StructType>(AggTy)) { 582 // Structs are always ok. 583 } else { 584 return 0; 585 } 586 const Type *NTy = getUIntAtLeastAsBitAs(TD.getTypeSize(AggTy)*8); 587 if (NTy == 0 || MergeInType(NTy, UsedType, TD)) return 0; 588 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); 589 if (SubTy == 0) return 0; 590 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD)) 591 return 0; 592 continue; // Everything looks ok 593 } 594 return 0; 595 } else { 596 // Cannot handle this! 597 return 0; 598 } 599 } 600 601 return UsedType; 602} 603 604/// ConvertToScalar - The specified alloca passes the CanConvertToScalar 605/// predicate and is non-trivial. Convert it to something that can be trivially 606/// promoted into a register by mem2reg. 607void SROA::ConvertToScalar(AllocationInst *AI, const Type *ActualTy) { 608 DOUT << "CONVERT TO SCALAR: " << *AI << " TYPE = " 609 << *ActualTy << "\n"; 610 ++NumConverted; 611 612 BasicBlock *EntryBlock = AI->getParent(); 613 assert(EntryBlock == &EntryBlock->getParent()->front() && 614 "Not in the entry block!"); 615 EntryBlock->getInstList().remove(AI); // Take the alloca out of the program. 616 617 // Create and insert the alloca. 618 AllocaInst *NewAI = new AllocaInst(ActualTy, 0, AI->getName(), 619 EntryBlock->begin()); 620 ConvertUsesToScalar(AI, NewAI, 0); 621 delete AI; 622} 623 624 625/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 626/// directly. This happens when we are converting an "integer union" to a 627/// single integer scalar, or when we are converting a "vector union" to a 628/// vector with insert/extractelement instructions. 629/// 630/// Offset is an offset from the original alloca, in bits that need to be 631/// shifted to the right. By the end of this, there should be no uses of Ptr. 632void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset) { 633 bool isVectorInsert = isa<VectorType>(NewAI->getType()->getElementType()); 634 const TargetData &TD = getAnalysis<TargetData>(); 635 while (!Ptr->use_empty()) { 636 Instruction *User = cast<Instruction>(Ptr->use_back()); 637 638 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 639 // The load is a bit extract from NewAI shifted right by Offset bits. 640 Value *NV = new LoadInst(NewAI, LI->getName(), LI); 641 if (NV->getType() != LI->getType()) { 642 if (const VectorType *PTy = dyn_cast<VectorType>(NV->getType())) { 643 // If the result alloca is a vector type, this is either an element 644 // access or a bitcast to another vector type. 645 if (isa<VectorType>(LI->getType())) { 646 NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI); 647 } else { 648 // Must be an element access. 649 unsigned Elt = Offset/(TD.getTypeSize(PTy->getElementType())*8); 650 NV = new ExtractElementInst( 651 NV, ConstantInt::get(Type::Int32Ty, Elt), "tmp", LI); 652 } 653 } else if (isa<PointerType>(NV->getType())) { 654 assert(isa<PointerType>(LI->getType())); 655 // Must be ptr->ptr cast. Anything else would result in NV being 656 // an integer. 657 NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI); 658 } else { 659 assert(NV->getType()->isInteger() && "Unknown promotion!"); 660 if (Offset && Offset < TD.getTypeSize(NV->getType())*8) { 661 NV = BinaryOperator::createLShr(NV, 662 ConstantInt::get(NV->getType(), Offset), 663 LI->getName(), LI); 664 } 665 666 // If the result is an integer, this is a trunc or bitcast. 667 if (LI->getType()->isInteger()) { 668 NV = CastInst::createTruncOrBitCast(NV, LI->getType(), 669 LI->getName(), LI); 670 } else if (LI->getType()->isFloatingPoint()) { 671 // If needed, truncate the integer to the appropriate size. 672 if (NV->getType()->getPrimitiveSizeInBits() > 673 LI->getType()->getPrimitiveSizeInBits()) { 674 switch (LI->getType()->getTypeID()) { 675 default: assert(0 && "Unknown FP type!"); 676 case Type::FloatTyID: 677 NV = new TruncInst(NV, Type::Int32Ty, LI->getName(), LI); 678 break; 679 case Type::DoubleTyID: 680 NV = new TruncInst(NV, Type::Int64Ty, LI->getName(), LI); 681 break; 682 } 683 } 684 685 // Then do a bitcast. 686 NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI); 687 } else { 688 // Otherwise must be a pointer. 689 NV = new IntToPtrInst(NV, LI->getType(), LI->getName(), LI); 690 } 691 } 692 } 693 LI->replaceAllUsesWith(NV); 694 LI->eraseFromParent(); 695 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 696 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 697 698 // Convert the stored type to the actual type, shift it left to insert 699 // then 'or' into place. 700 Value *SV = SI->getOperand(0); 701 const Type *AllocaType = NewAI->getType()->getElementType(); 702 if (SV->getType() != AllocaType) { 703 Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI); 704 705 if (const VectorType *PTy = dyn_cast<VectorType>(AllocaType)) { 706 // If the result alloca is a vector type, this is either an element 707 // access or a bitcast to another vector type. 708 if (isa<VectorType>(SV->getType())) { 709 SV = new BitCastInst(SV, AllocaType, SV->getName(), SI); 710 } else { 711 // Must be an element insertion. 712 unsigned Elt = Offset/(TD.getTypeSize(PTy->getElementType())*8); 713 SV = new InsertElementInst(Old, SV, 714 ConstantInt::get(Type::Int32Ty, Elt), 715 "tmp", SI); 716 } 717 } else { 718 // If SV is a float, convert it to the appropriate integer type. 719 // If it is a pointer, do the same, and also handle ptr->ptr casts 720 // here. 721 switch (SV->getType()->getTypeID()) { 722 default: 723 assert(!SV->getType()->isFloatingPoint() && "Unknown FP type!"); 724 break; 725 case Type::FloatTyID: 726 SV = new BitCastInst(SV, Type::Int32Ty, SV->getName(), SI); 727 break; 728 case Type::DoubleTyID: 729 SV = new BitCastInst(SV, Type::Int64Ty, SV->getName(), SI); 730 break; 731 case Type::PointerTyID: 732 if (isa<PointerType>(AllocaType)) 733 SV = new BitCastInst(SV, AllocaType, SV->getName(), SI); 734 else 735 SV = new PtrToIntInst(SV, TD.getIntPtrType(), SV->getName(), SI); 736 break; 737 } 738 739 unsigned SrcSize = TD.getTypeSize(SV->getType())*8; 740 741 // Always zero extend the value if needed. 742 if (SV->getType() != AllocaType) 743 SV = CastInst::createZExtOrBitCast(SV, AllocaType, 744 SV->getName(), SI); 745 if (Offset && Offset < AllocaType->getPrimitiveSizeInBits()) 746 SV = BinaryOperator::createShl(SV, 747 ConstantInt::get(SV->getType(), Offset), 748 SV->getName()+".adj", SI); 749 // Mask out the bits we are about to insert from the old value. 750 unsigned TotalBits = TD.getTypeSize(SV->getType())*8; 751 if (TotalBits != SrcSize) { 752 assert(TotalBits > SrcSize); 753 uint64_t Mask = ~(((1ULL << SrcSize)-1) << Offset); 754 Mask = Mask & cast<IntegerType>(SV->getType())->getBitMask(); 755 Old = BinaryOperator::createAnd(Old, 756 ConstantInt::get(Old->getType(), Mask), 757 Old->getName()+".mask", SI); 758 SV = BinaryOperator::createOr(Old, SV, SV->getName()+".ins", SI); 759 } 760 } 761 } 762 new StoreInst(SV, NewAI, SI); 763 SI->eraseFromParent(); 764 765 } else if (CastInst *CI = dyn_cast<CastInst>(User)) { 766 unsigned NewOff = Offset; 767 const TargetData &TD = getAnalysis<TargetData>(); 768 if (TD.isBigEndian() && !isVectorInsert) { 769 // Adjust the pointer. For example, storing 16-bits into a 32-bit 770 // alloca with just a cast makes it modify the top 16-bits. 771 const Type *SrcTy = cast<PointerType>(Ptr->getType())->getElementType(); 772 const Type *DstTy = cast<PointerType>(CI->getType())->getElementType(); 773 int PtrDiffBits = TD.getTypeSize(SrcTy)*8-TD.getTypeSize(DstTy)*8; 774 NewOff += PtrDiffBits; 775 } 776 ConvertUsesToScalar(CI, NewAI, NewOff); 777 CI->eraseFromParent(); 778 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 779 const PointerType *AggPtrTy = 780 cast<PointerType>(GEP->getOperand(0)->getType()); 781 const TargetData &TD = getAnalysis<TargetData>(); 782 unsigned AggSizeInBits = TD.getTypeSize(AggPtrTy->getElementType())*8; 783 784 // Check to see if this is stepping over an element: GEP Ptr, int C 785 unsigned NewOffset = Offset; 786 if (GEP->getNumOperands() == 2) { 787 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue(); 788 unsigned BitOffset = Idx*AggSizeInBits; 789 790 if (TD.isLittleEndian() || isVectorInsert) 791 NewOffset += BitOffset; 792 else 793 NewOffset -= BitOffset; 794 795 } else if (GEP->getNumOperands() == 3) { 796 // We know that operand #2 is zero. 797 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 798 const Type *AggTy = AggPtrTy->getElementType(); 799 if (const SequentialType *SeqTy = dyn_cast<SequentialType>(AggTy)) { 800 unsigned ElSizeBits = TD.getTypeSize(SeqTy->getElementType())*8; 801 802 if (TD.isLittleEndian() || isVectorInsert) 803 NewOffset += ElSizeBits*Idx; 804 else 805 NewOffset += AggSizeInBits-ElSizeBits*(Idx+1); 806 } else if (const StructType *STy = dyn_cast<StructType>(AggTy)) { 807 unsigned EltBitOffset = 808 TD.getStructLayout(STy)->getElementOffset(Idx)*8; 809 810 if (TD.isLittleEndian() || isVectorInsert) 811 NewOffset += EltBitOffset; 812 else { 813 const PointerType *ElPtrTy = cast<PointerType>(GEP->getType()); 814 unsigned ElSizeBits = TD.getTypeSize(ElPtrTy->getElementType())*8; 815 NewOffset += AggSizeInBits-(EltBitOffset+ElSizeBits); 816 } 817 818 } else { 819 assert(0 && "Unsupported operation!"); 820 abort(); 821 } 822 } else { 823 assert(0 && "Unsupported operation!"); 824 abort(); 825 } 826 ConvertUsesToScalar(GEP, NewAI, NewOffset); 827 GEP->eraseFromParent(); 828 } else { 829 assert(0 && "Unsupported operation!"); 830 abort(); 831 } 832 } 833} 834