ScalarReplAggregates.cpp revision d2fa781169175b827e50953a1d0b7edc6b0c4801
1//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===// 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// 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/GlobalVariable.h" 28#include "llvm/Instructions.h" 29#include "llvm/IntrinsicInst.h" 30#include "llvm/Pass.h" 31#include "llvm/Analysis/Dominators.h" 32#include "llvm/Target/TargetData.h" 33#include "llvm/Transforms/Utils/PromoteMemToReg.h" 34#include "llvm/Support/Debug.h" 35#include "llvm/Support/GetElementPtrTypeIterator.h" 36#include "llvm/Support/MathExtras.h" 37#include "llvm/Support/Compiler.h" 38#include "llvm/ADT/SmallVector.h" 39#include "llvm/ADT/Statistic.h" 40#include "llvm/ADT/StringExtras.h" 41using namespace llvm; 42 43STATISTIC(NumReplaced, "Number of allocas broken up"); 44STATISTIC(NumPromoted, "Number of allocas promoted"); 45STATISTIC(NumConverted, "Number of aggregates converted to scalar"); 46STATISTIC(NumGlobals, "Number of allocas copied from constant global"); 47 48namespace { 49 struct VISIBILITY_HIDDEN SROA : public FunctionPass { 50 static char ID; // Pass identification, replacement for typeid 51 explicit SROA(signed T = -1) : FunctionPass(&ID) { 52 if (T == -1) 53 SRThreshold = 128; 54 else 55 SRThreshold = T; 56 } 57 58 bool runOnFunction(Function &F); 59 60 bool performScalarRepl(Function &F); 61 bool performPromotion(Function &F); 62 63 // getAnalysisUsage - This pass does not require any passes, but we know it 64 // will not alter the CFG, so say so. 65 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 66 AU.addRequired<DominatorTree>(); 67 AU.addRequired<DominanceFrontier>(); 68 AU.addRequired<TargetData>(); 69 AU.setPreservesCFG(); 70 } 71 72 private: 73 TargetData *TD; 74 75 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures 76 /// information about the uses. All these fields are initialized to false 77 /// and set to true when something is learned. 78 struct AllocaInfo { 79 /// isUnsafe - This is set to true if the alloca cannot be SROA'd. 80 bool isUnsafe : 1; 81 82 /// needsCanon - This is set to true if there is some use of the alloca 83 /// that requires canonicalization. 84 bool needsCanon : 1; 85 86 /// isMemCpySrc - This is true if this aggregate is memcpy'd from. 87 bool isMemCpySrc : 1; 88 89 /// isMemCpyDst - This is true if this aggregate is memcpy'd into. 90 bool isMemCpyDst : 1; 91 92 AllocaInfo() 93 : isUnsafe(false), needsCanon(false), 94 isMemCpySrc(false), isMemCpyDst(false) {} 95 }; 96 97 unsigned SRThreshold; 98 99 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; } 100 101 int isSafeAllocaToScalarRepl(AllocationInst *AI); 102 103 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, 104 AllocaInfo &Info); 105 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, 106 AllocaInfo &Info); 107 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, 108 unsigned OpNo, AllocaInfo &Info); 109 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI, 110 AllocaInfo &Info); 111 112 void DoScalarReplacement(AllocationInst *AI, 113 std::vector<AllocationInst*> &WorkList); 114 void CanonicalizeAllocaUsers(AllocationInst *AI); 115 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base); 116 117 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, 118 SmallVector<AllocaInst*, 32> &NewElts); 119 120 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, 121 AllocationInst *AI, 122 SmallVector<AllocaInst*, 32> &NewElts); 123 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI, 124 SmallVector<AllocaInst*, 32> &NewElts); 125 126 const Type *CanConvertToScalar(Value *V, bool &IsNotTrivial); 127 void ConvertToScalar(AllocationInst *AI, const Type *Ty); 128 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset); 129 Value *ConvertUsesOfLoadToScalar(LoadInst *LI, AllocaInst *NewAI, 130 unsigned Offset); 131 Value *ConvertUsesOfStoreToScalar(StoreInst *SI, AllocaInst *NewAI, 132 unsigned Offset); 133 static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI); 134 }; 135} 136 137char SROA::ID = 0; 138static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates"); 139 140// Public interface to the ScalarReplAggregates pass 141FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) { 142 return new SROA(Threshold); 143} 144 145 146bool SROA::runOnFunction(Function &F) { 147 TD = &getAnalysis<TargetData>(); 148 149 bool Changed = performPromotion(F); 150 while (1) { 151 bool LocalChange = performScalarRepl(F); 152 if (!LocalChange) break; // No need to repromote if no scalarrepl 153 Changed = true; 154 LocalChange = performPromotion(F); 155 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 156 } 157 158 return Changed; 159} 160 161 162bool SROA::performPromotion(Function &F) { 163 std::vector<AllocaInst*> Allocas; 164 DominatorTree &DT = getAnalysis<DominatorTree>(); 165 DominanceFrontier &DF = getAnalysis<DominanceFrontier>(); 166 167 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 168 169 bool Changed = false; 170 171 while (1) { 172 Allocas.clear(); 173 174 // Find allocas that are safe to promote, by looking at all instructions in 175 // the entry node 176 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 177 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 178 if (isAllocaPromotable(AI)) 179 Allocas.push_back(AI); 180 181 if (Allocas.empty()) break; 182 183 PromoteMemToReg(Allocas, DT, DF); 184 NumPromoted += Allocas.size(); 185 Changed = true; 186 } 187 188 return Changed; 189} 190 191/// getNumSAElements - Return the number of elements in the specific struct or 192/// array. 193static uint64_t getNumSAElements(const Type *T) { 194 if (const StructType *ST = dyn_cast<StructType>(T)) 195 return ST->getNumElements(); 196 return cast<ArrayType>(T)->getNumElements(); 197} 198 199// performScalarRepl - This algorithm is a simple worklist driven algorithm, 200// which runs on all of the malloc/alloca instructions in the function, removing 201// them if they are only used by getelementptr instructions. 202// 203bool SROA::performScalarRepl(Function &F) { 204 std::vector<AllocationInst*> WorkList; 205 206 // Scan the entry basic block, adding any alloca's and mallocs to the worklist 207 BasicBlock &BB = F.getEntryBlock(); 208 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 209 if (AllocationInst *A = dyn_cast<AllocationInst>(I)) 210 WorkList.push_back(A); 211 212 // Process the worklist 213 bool Changed = false; 214 while (!WorkList.empty()) { 215 AllocationInst *AI = WorkList.back(); 216 WorkList.pop_back(); 217 218 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 219 // with unused elements. 220 if (AI->use_empty()) { 221 AI->eraseFromParent(); 222 continue; 223 } 224 225 // If we can turn this aggregate value (potentially with casts) into a 226 // simple scalar value that can be mem2reg'd into a register value. 227 bool IsNotTrivial = false; 228 if (const Type *ActualType = CanConvertToScalar(AI, IsNotTrivial)) 229 if (IsNotTrivial && ActualType != Type::VoidTy) { 230 ConvertToScalar(AI, ActualType); 231 Changed = true; 232 continue; 233 } 234 235 // Check to see if we can perform the core SROA transformation. We cannot 236 // transform the allocation instruction if it is an array allocation 237 // (allocations OF arrays are ok though), and an allocation of a scalar 238 // value cannot be decomposed at all. 239 if (!AI->isArrayAllocation() && 240 (isa<StructType>(AI->getAllocatedType()) || 241 isa<ArrayType>(AI->getAllocatedType())) && 242 AI->getAllocatedType()->isSized() && 243 // Do not promote any struct whose size is larger than "128" bytes. 244 TD->getABITypeSize(AI->getAllocatedType()) < SRThreshold && 245 // Do not promote any struct into more than "32" separate vars. 246 getNumSAElements(AI->getAllocatedType()) < SRThreshold/4) { 247 // Check that all of the users of the allocation are capable of being 248 // transformed. 249 switch (isSafeAllocaToScalarRepl(AI)) { 250 default: assert(0 && "Unexpected value!"); 251 case 0: // Not safe to scalar replace. 252 break; 253 case 1: // Safe, but requires cleanup/canonicalizations first 254 CanonicalizeAllocaUsers(AI); 255 // FALL THROUGH. 256 case 3: // Safe to scalar replace. 257 DoScalarReplacement(AI, WorkList); 258 Changed = true; 259 continue; 260 } 261 } 262 263 // Check to see if this allocation is only modified by a memcpy/memmove from 264 // a constant global. If this is the case, we can change all users to use 265 // the constant global instead. This is commonly produced by the CFE by 266 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 267 // is only subsequently read. 268 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 269 DOUT << "Found alloca equal to global: " << *AI; 270 DOUT << " memcpy = " << *TheCopy; 271 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2)); 272 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 273 TheCopy->eraseFromParent(); // Don't mutate the global. 274 AI->eraseFromParent(); 275 ++NumGlobals; 276 Changed = true; 277 continue; 278 } 279 280 // Otherwise, couldn't process this. 281 } 282 283 return Changed; 284} 285 286/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 287/// predicate, do SROA now. 288void SROA::DoScalarReplacement(AllocationInst *AI, 289 std::vector<AllocationInst*> &WorkList) { 290 DOUT << "Found inst to SROA: " << *AI; 291 SmallVector<AllocaInst*, 32> ElementAllocas; 292 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 293 ElementAllocas.reserve(ST->getNumContainedTypes()); 294 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 295 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 296 AI->getAlignment(), 297 AI->getName() + "." + utostr(i), AI); 298 ElementAllocas.push_back(NA); 299 WorkList.push_back(NA); // Add to worklist for recursive processing 300 } 301 } else { 302 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 303 ElementAllocas.reserve(AT->getNumElements()); 304 const Type *ElTy = AT->getElementType(); 305 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 306 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 307 AI->getName() + "." + utostr(i), AI); 308 ElementAllocas.push_back(NA); 309 WorkList.push_back(NA); // Add to worklist for recursive processing 310 } 311 } 312 313 // Now that we have created the alloca instructions that we want to use, 314 // expand the getelementptr instructions to use them. 315 // 316 while (!AI->use_empty()) { 317 Instruction *User = cast<Instruction>(AI->use_back()); 318 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) { 319 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas); 320 BCInst->eraseFromParent(); 321 continue; 322 } 323 324 // Replace: 325 // %res = load { i32, i32 }* %alloc 326 // with: 327 // %load.0 = load i32* %alloc.0 328 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 329 // %load.1 = load i32* %alloc.1 330 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 331 // (Also works for arrays instead of structs) 332 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 333 Value *Insert = UndefValue::get(LI->getType()); 334 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { 335 Value *Load = new LoadInst(ElementAllocas[i], "load", LI); 336 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI); 337 } 338 LI->replaceAllUsesWith(Insert); 339 LI->eraseFromParent(); 340 continue; 341 } 342 343 // Replace: 344 // store { i32, i32 } %val, { i32, i32 }* %alloc 345 // with: 346 // %val.0 = extractvalue { i32, i32 } %val, 0 347 // store i32 %val.0, i32* %alloc.0 348 // %val.1 = extractvalue { i32, i32 } %val, 1 349 // store i32 %val.1, i32* %alloc.1 350 // (Also works for arrays instead of structs) 351 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 352 Value *Val = SI->getOperand(0); 353 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { 354 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI); 355 new StoreInst(Extract, ElementAllocas[i], SI); 356 } 357 SI->eraseFromParent(); 358 continue; 359 } 360 361 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User); 362 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst> 363 unsigned Idx = 364 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 365 366 assert(Idx < ElementAllocas.size() && "Index out of range?"); 367 AllocaInst *AllocaToUse = ElementAllocas[Idx]; 368 369 Value *RepValue; 370 if (GEPI->getNumOperands() == 3) { 371 // Do not insert a new getelementptr instruction with zero indices, only 372 // to have it optimized out later. 373 RepValue = AllocaToUse; 374 } else { 375 // We are indexing deeply into the structure, so we still need a 376 // getelement ptr instruction to finish the indexing. This may be 377 // expanded itself once the worklist is rerun. 378 // 379 SmallVector<Value*, 8> NewArgs; 380 NewArgs.push_back(Constant::getNullValue(Type::Int32Ty)); 381 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end()); 382 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(), 383 NewArgs.end(), "", GEPI); 384 RepValue->takeName(GEPI); 385 } 386 387 // If this GEP is to the start of the aggregate, check for memcpys. 388 if (Idx == 0 && GEPI->hasAllZeroIndices()) 389 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas); 390 391 // Move all of the users over to the new GEP. 392 GEPI->replaceAllUsesWith(RepValue); 393 // Delete the old GEP 394 GEPI->eraseFromParent(); 395 } 396 397 // Finally, delete the Alloca instruction 398 AI->eraseFromParent(); 399 NumReplaced++; 400} 401 402 403/// isSafeElementUse - Check to see if this use is an allowed use for a 404/// getelementptr instruction of an array aggregate allocation. isFirstElt 405/// indicates whether Ptr is known to the start of the aggregate. 406/// 407void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, 408 AllocaInfo &Info) { 409 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 410 I != E; ++I) { 411 Instruction *User = cast<Instruction>(*I); 412 switch (User->getOpcode()) { 413 case Instruction::Load: break; 414 case Instruction::Store: 415 // Store is ok if storing INTO the pointer, not storing the pointer 416 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info); 417 break; 418 case Instruction::GetElementPtr: { 419 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User); 420 bool AreAllZeroIndices = isFirstElt; 421 if (GEP->getNumOperands() > 1) { 422 if (!isa<ConstantInt>(GEP->getOperand(1)) || 423 !cast<ConstantInt>(GEP->getOperand(1))->isZero()) 424 // Using pointer arithmetic to navigate the array. 425 return MarkUnsafe(Info); 426 427 if (AreAllZeroIndices) 428 AreAllZeroIndices = GEP->hasAllZeroIndices(); 429 } 430 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info); 431 if (Info.isUnsafe) return; 432 break; 433 } 434 case Instruction::BitCast: 435 if (isFirstElt) { 436 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info); 437 if (Info.isUnsafe) return; 438 break; 439 } 440 DOUT << " Transformation preventing inst: " << *User; 441 return MarkUnsafe(Info); 442 case Instruction::Call: 443 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 444 if (isFirstElt) { 445 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info); 446 if (Info.isUnsafe) return; 447 break; 448 } 449 } 450 DOUT << " Transformation preventing inst: " << *User; 451 return MarkUnsafe(Info); 452 default: 453 DOUT << " Transformation preventing inst: " << *User; 454 return MarkUnsafe(Info); 455 } 456 } 457 return; // All users look ok :) 458} 459 460/// AllUsersAreLoads - Return true if all users of this value are loads. 461static bool AllUsersAreLoads(Value *Ptr) { 462 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 463 I != E; ++I) 464 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load) 465 return false; 466 return true; 467} 468 469/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an 470/// aggregate allocation. 471/// 472void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, 473 AllocaInfo &Info) { 474 if (BitCastInst *C = dyn_cast<BitCastInst>(User)) 475 return isSafeUseOfBitCastedAllocation(C, AI, Info); 476 477 if (isa<LoadInst>(User)) 478 return; // Loads (returning a first class aggregrate) are always rewritable 479 480 if (isa<StoreInst>(User) && User->getOperand(0) != AI) 481 return; // Store is ok if storing INTO the pointer, not storing the pointer 482 483 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User); 484 if (GEPI == 0) 485 return MarkUnsafe(Info); 486 487 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI); 488 489 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>". 490 if (I == E || 491 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) { 492 return MarkUnsafe(Info); 493 } 494 495 ++I; 496 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices?? 497 498 bool IsAllZeroIndices = true; 499 500 // If the first index is a non-constant index into an array, see if we can 501 // handle it as a special case. 502 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 503 if (!isa<ConstantInt>(I.getOperand())) { 504 IsAllZeroIndices = 0; 505 uint64_t NumElements = AT->getNumElements(); 506 507 // If this is an array index and the index is not constant, we cannot 508 // promote... that is unless the array has exactly one or two elements in 509 // it, in which case we CAN promote it, but we have to canonicalize this 510 // out if this is the only problem. 511 if ((NumElements == 1 || NumElements == 2) && 512 AllUsersAreLoads(GEPI)) { 513 Info.needsCanon = true; 514 return; // Canonicalization required! 515 } 516 return MarkUnsafe(Info); 517 } 518 } 519 520 // Walk through the GEP type indices, checking the types that this indexes 521 // into. 522 for (; I != E; ++I) { 523 // Ignore struct elements, no extra checking needed for these. 524 if (isa<StructType>(*I)) 525 continue; 526 527 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand()); 528 if (!IdxVal) return MarkUnsafe(Info); 529 530 // Are all indices still zero? 531 IsAllZeroIndices &= IdxVal->isZero(); 532 533 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 534 // This GEP indexes an array. Verify that this is an in-range constant 535 // integer. Specifically, consider A[0][i]. We cannot know that the user 536 // isn't doing invalid things like allowing i to index an out-of-range 537 // subscript that accesses A[1]. Because of this, we have to reject SROA 538 // of any accesses into structs where any of the components are variables. 539 if (IdxVal->getZExtValue() >= AT->getNumElements()) 540 return MarkUnsafe(Info); 541 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) { 542 if (IdxVal->getZExtValue() >= VT->getNumElements()) 543 return MarkUnsafe(Info); 544 } 545 } 546 547 // If there are any non-simple uses of this getelementptr, make sure to reject 548 // them. 549 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info); 550} 551 552/// isSafeMemIntrinsicOnAllocation - Return true if the specified memory 553/// intrinsic can be promoted by SROA. At this point, we know that the operand 554/// of the memintrinsic is a pointer to the beginning of the allocation. 555void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, 556 unsigned OpNo, AllocaInfo &Info) { 557 // If not constant length, give up. 558 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 559 if (!Length) return MarkUnsafe(Info); 560 561 // If not the whole aggregate, give up. 562 if (Length->getZExtValue() != 563 TD->getABITypeSize(AI->getType()->getElementType())) 564 return MarkUnsafe(Info); 565 566 // We only know about memcpy/memset/memmove. 567 if (!isa<MemCpyInst>(MI) && !isa<MemSetInst>(MI) && !isa<MemMoveInst>(MI)) 568 return MarkUnsafe(Info); 569 570 // Otherwise, we can transform it. Determine whether this is a memcpy/set 571 // into or out of the aggregate. 572 if (OpNo == 1) 573 Info.isMemCpyDst = true; 574 else { 575 assert(OpNo == 2); 576 Info.isMemCpySrc = true; 577 } 578} 579 580/// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast 581/// are 582void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI, 583 AllocaInfo &Info) { 584 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end(); 585 UI != E; ++UI) { 586 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) { 587 isSafeUseOfBitCastedAllocation(BCU, AI, Info); 588 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) { 589 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info); 590 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 591 // If storing the entire alloca in one chunk through a bitcasted pointer 592 // to integer, we can transform it. This happens (for example) when you 593 // cast a {i32,i32}* to i64* and store through it. This is similar to the 594 // memcpy case and occurs in various "byval" cases and emulated memcpys. 595 if (isa<IntegerType>(SI->getOperand(0)->getType()) && 596 TD->getABITypeSize(SI->getOperand(0)->getType()) == 597 TD->getABITypeSize(AI->getType()->getElementType())) { 598 Info.isMemCpyDst = true; 599 continue; 600 } 601 return MarkUnsafe(Info); 602 } else { 603 return MarkUnsafe(Info); 604 } 605 if (Info.isUnsafe) return; 606 } 607} 608 609/// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes 610/// to its first element. Transform users of the cast to use the new values 611/// instead. 612void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, 613 SmallVector<AllocaInst*, 32> &NewElts) { 614 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end(); 615 while (UI != UE) { 616 Instruction *User = cast<Instruction>(*UI++); 617 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) { 618 RewriteBitCastUserOfAlloca(BCU, AI, NewElts); 619 if (BCU->use_empty()) BCU->eraseFromParent(); 620 continue; 621 } 622 623 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 624 // This must be memcpy/memmove/memset of the entire aggregate. 625 // Split into one per element. 626 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts); 627 continue; 628 } 629 630 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 631 // This must be a store of the entire alloca from an integer. 632 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 633 continue; 634 } 635 636 // Otherwise it must be some other user of a gep of the first pointer. Just 637 // leave these alone. 638 continue; 639 } 640} 641 642/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 643/// Rewrite it to copy or set the elements of the scalarized memory. 644void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, 645 AllocationInst *AI, 646 SmallVector<AllocaInst*, 32> &NewElts) { 647 648 // If this is a memcpy/memmove, construct the other pointer as the 649 // appropriate type. 650 Value *OtherPtr = 0; 651 if (MemCpyInst *MCI = dyn_cast<MemCpyInst>(MI)) { 652 if (BCInst == MCI->getRawDest()) 653 OtherPtr = MCI->getRawSource(); 654 else { 655 assert(BCInst == MCI->getRawSource()); 656 OtherPtr = MCI->getRawDest(); 657 } 658 } else if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(MI)) { 659 if (BCInst == MMI->getRawDest()) 660 OtherPtr = MMI->getRawSource(); 661 else { 662 assert(BCInst == MMI->getRawSource()); 663 OtherPtr = MMI->getRawDest(); 664 } 665 } 666 667 // If there is an other pointer, we want to convert it to the same pointer 668 // type as AI has, so we can GEP through it safely. 669 if (OtherPtr) { 670 // It is likely that OtherPtr is a bitcast, if so, remove it. 671 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr)) 672 OtherPtr = BC->getOperand(0); 673 // All zero GEPs are effectively bitcasts. 674 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr)) 675 if (GEP->hasAllZeroIndices()) 676 OtherPtr = GEP->getOperand(0); 677 678 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr)) 679 if (BCE->getOpcode() == Instruction::BitCast) 680 OtherPtr = BCE->getOperand(0); 681 682 // If the pointer is not the right type, insert a bitcast to the right 683 // type. 684 if (OtherPtr->getType() != AI->getType()) 685 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(), 686 MI); 687 } 688 689 // Process each element of the aggregate. 690 Value *TheFn = MI->getOperand(0); 691 const Type *BytePtrTy = MI->getRawDest()->getType(); 692 bool SROADest = MI->getRawDest() == BCInst; 693 694 Constant *Zero = Constant::getNullValue(Type::Int32Ty); 695 696 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 697 // If this is a memcpy/memmove, emit a GEP of the other element address. 698 Value *OtherElt = 0; 699 if (OtherPtr) { 700 Value *Idx[2] = { Zero, ConstantInt::get(Type::Int32Ty, i) }; 701 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2, 702 OtherPtr->getNameStr()+"."+utostr(i), 703 MI); 704 } 705 706 Value *EltPtr = NewElts[i]; 707 const Type *EltTy =cast<PointerType>(EltPtr->getType())->getElementType(); 708 709 // If we got down to a scalar, insert a load or store as appropriate. 710 if (EltTy->isSingleValueType()) { 711 if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) { 712 Value *Elt = new LoadInst(SROADest ? OtherElt : EltPtr, "tmp", 713 MI); 714 new StoreInst(Elt, SROADest ? EltPtr : OtherElt, MI); 715 continue; 716 } 717 assert(isa<MemSetInst>(MI)); 718 719 // If the stored element is zero (common case), just store a null 720 // constant. 721 Constant *StoreVal; 722 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) { 723 if (CI->isZero()) { 724 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 725 } else { 726 // If EltTy is a vector type, get the element type. 727 const Type *ValTy = EltTy; 728 if (const VectorType *VTy = dyn_cast<VectorType>(ValTy)) 729 ValTy = VTy->getElementType(); 730 731 // Construct an integer with the right value. 732 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 733 APInt OneVal(EltSize, CI->getZExtValue()); 734 APInt TotalVal(OneVal); 735 // Set each byte. 736 for (unsigned i = 0; 8*i < EltSize; ++i) { 737 TotalVal = TotalVal.shl(8); 738 TotalVal |= OneVal; 739 } 740 741 // Convert the integer value to the appropriate type. 742 StoreVal = ConstantInt::get(TotalVal); 743 if (isa<PointerType>(ValTy)) 744 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 745 else if (ValTy->isFloatingPoint()) 746 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 747 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 748 749 // If the requested value was a vector constant, create it. 750 if (EltTy != ValTy) { 751 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 752 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 753 StoreVal = ConstantVector::get(&Elts[0], NumElts); 754 } 755 } 756 new StoreInst(StoreVal, EltPtr, MI); 757 continue; 758 } 759 // Otherwise, if we're storing a byte variable, use a memset call for 760 // this element. 761 } 762 763 // Cast the element pointer to BytePtrTy. 764 if (EltPtr->getType() != BytePtrTy) 765 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI); 766 767 // Cast the other pointer (if we have one) to BytePtrTy. 768 if (OtherElt && OtherElt->getType() != BytePtrTy) 769 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(), 770 MI); 771 772 unsigned EltSize = TD->getABITypeSize(EltTy); 773 774 // Finally, insert the meminst for this element. 775 if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) { 776 Value *Ops[] = { 777 SROADest ? EltPtr : OtherElt, // Dest ptr 778 SROADest ? OtherElt : EltPtr, // Src ptr 779 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 780 Zero // Align 781 }; 782 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 783 } else { 784 assert(isa<MemSetInst>(MI)); 785 Value *Ops[] = { 786 EltPtr, MI->getOperand(2), // Dest, Value, 787 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 788 Zero // Align 789 }; 790 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 791 } 792 } 793 MI->eraseFromParent(); 794} 795 796/// RewriteStoreUserOfWholeAlloca - We found an store of an integer that 797/// overwrites the entire allocation. Extract out the pieces of the stored 798/// integer and store them individually. 799void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, 800 AllocationInst *AI, 801 SmallVector<AllocaInst*, 32> &NewElts){ 802 // Extract each element out of the integer according to its structure offset 803 // and store the element value to the individual alloca. 804 Value *SrcVal = SI->getOperand(0); 805 const Type *AllocaEltTy = AI->getType()->getElementType(); 806 uint64_t AllocaSizeBits = TD->getABITypeSizeInBits(AllocaEltTy); 807 808 // If this isn't a store of an integer to the whole alloca, it may be a store 809 // to the first element. Just ignore the store in this case and normal SROA 810 // will handle it. 811 if (!isa<IntegerType>(SrcVal->getType()) || 812 TD->getABITypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 813 return; 814 815 DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI; 816 817 // There are two forms here: AI could be an array or struct. Both cases 818 // have different ways to compute the element offset. 819 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 820 const StructLayout *Layout = TD->getStructLayout(EltSTy); 821 822 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 823 // Get the number of bits to shift SrcVal to get the value. 824 const Type *FieldTy = EltSTy->getElementType(i); 825 uint64_t Shift = Layout->getElementOffsetInBits(i); 826 827 if (TD->isBigEndian()) 828 Shift = AllocaSizeBits-Shift-TD->getABITypeSizeInBits(FieldTy); 829 830 Value *EltVal = SrcVal; 831 if (Shift) { 832 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 833 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 834 "sroa.store.elt", SI); 835 } 836 837 // Truncate down to an integer of the right size. 838 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 839 if (FieldSizeBits != AllocaSizeBits) 840 EltVal = new TruncInst(EltVal, IntegerType::get(FieldSizeBits), "", SI); 841 Value *DestField = NewElts[i]; 842 if (EltVal->getType() == FieldTy) { 843 // Storing to an integer field of this size, just do it. 844 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) { 845 // Bitcast to the right element type (for fp/vector values). 846 EltVal = new BitCastInst(EltVal, FieldTy, "", SI); 847 } else { 848 // Otherwise, bitcast the dest pointer (for aggregates). 849 DestField = new BitCastInst(DestField, 850 PointerType::getUnqual(EltVal->getType()), 851 "", SI); 852 } 853 new StoreInst(EltVal, DestField, SI); 854 } 855 856 } else { 857 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 858 const Type *ArrayEltTy = ATy->getElementType(); 859 uint64_t ElementOffset = TD->getABITypeSizeInBits(ArrayEltTy); 860 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 861 862 uint64_t Shift; 863 864 if (TD->isBigEndian()) 865 Shift = AllocaSizeBits-ElementOffset; 866 else 867 Shift = 0; 868 869 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 870 871 Value *EltVal = SrcVal; 872 if (Shift) { 873 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 874 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 875 "sroa.store.elt", SI); 876 } 877 878 // Truncate down to an integer of the right size. 879 if (ElementSizeBits != AllocaSizeBits) 880 EltVal = new TruncInst(EltVal, IntegerType::get(ElementSizeBits),"",SI); 881 Value *DestField = NewElts[i]; 882 if (EltVal->getType() == ArrayEltTy) { 883 // Storing to an integer field of this size, just do it. 884 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) { 885 // Bitcast to the right element type (for fp/vector values). 886 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI); 887 } else { 888 // Otherwise, bitcast the dest pointer (for aggregates). 889 DestField = new BitCastInst(DestField, 890 PointerType::getUnqual(EltVal->getType()), 891 "", SI); 892 } 893 new StoreInst(EltVal, DestField, SI); 894 895 if (TD->isBigEndian()) 896 Shift -= ElementOffset; 897 else 898 Shift += ElementOffset; 899 } 900 } 901 902 SI->eraseFromParent(); 903} 904 905 906/// HasPadding - Return true if the specified type has any structure or 907/// alignment padding, false otherwise. 908static bool HasPadding(const Type *Ty, const TargetData &TD) { 909 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 910 const StructLayout *SL = TD.getStructLayout(STy); 911 unsigned PrevFieldBitOffset = 0; 912 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 913 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 914 915 // Padding in sub-elements? 916 if (HasPadding(STy->getElementType(i), TD)) 917 return true; 918 919 // Check to see if there is any padding between this element and the 920 // previous one. 921 if (i) { 922 unsigned PrevFieldEnd = 923 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 924 if (PrevFieldEnd < FieldBitOffset) 925 return true; 926 } 927 928 PrevFieldBitOffset = FieldBitOffset; 929 } 930 931 // Check for tail padding. 932 if (unsigned EltCount = STy->getNumElements()) { 933 unsigned PrevFieldEnd = PrevFieldBitOffset + 934 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 935 if (PrevFieldEnd < SL->getSizeInBits()) 936 return true; 937 } 938 939 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 940 return HasPadding(ATy->getElementType(), TD); 941 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) { 942 return HasPadding(VTy->getElementType(), TD); 943 } 944 return TD.getTypeSizeInBits(Ty) != TD.getABITypeSizeInBits(Ty); 945} 946 947/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 948/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 949/// or 1 if safe after canonicalization has been performed. 950/// 951int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) { 952 // Loop over the use list of the alloca. We can only transform it if all of 953 // the users are safe to transform. 954 AllocaInfo Info; 955 956 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); 957 I != E; ++I) { 958 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info); 959 if (Info.isUnsafe) { 960 DOUT << "Cannot transform: " << *AI << " due to user: " << **I; 961 return 0; 962 } 963 } 964 965 // Okay, we know all the users are promotable. If the aggregate is a memcpy 966 // source and destination, we have to be careful. In particular, the memcpy 967 // could be moving around elements that live in structure padding of the LLVM 968 // types, but may actually be used. In these cases, we refuse to promote the 969 // struct. 970 if (Info.isMemCpySrc && Info.isMemCpyDst && 971 HasPadding(AI->getType()->getElementType(), *TD)) 972 return 0; 973 974 // If we require cleanup, return 1, otherwise return 3. 975 return Info.needsCanon ? 1 : 3; 976} 977 978/// CanonicalizeAllocaUsers - If SROA reported that it can promote the specified 979/// allocation, but only if cleaned up, perform the cleanups required. 980void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) { 981 // At this point, we know that the end result will be SROA'd and promoted, so 982 // we can insert ugly code if required so long as sroa+mem2reg will clean it 983 // up. 984 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 985 UI != E; ) { 986 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI++); 987 if (!GEPI) continue; 988 gep_type_iterator I = gep_type_begin(GEPI); 989 ++I; 990 991 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 992 uint64_t NumElements = AT->getNumElements(); 993 994 if (!isa<ConstantInt>(I.getOperand())) { 995 if (NumElements == 1) { 996 GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty)); 997 } else { 998 assert(NumElements == 2 && "Unhandled case!"); 999 // All users of the GEP must be loads. At each use of the GEP, insert 1000 // two loads of the appropriate indexed GEP and select between them. 1001 Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(), 1002 Constant::getNullValue(I.getOperand()->getType()), 1003 "isone", GEPI); 1004 // Insert the new GEP instructions, which are properly indexed. 1005 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end()); 1006 Indices[1] = Constant::getNullValue(Type::Int32Ty); 1007 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1008 Indices.begin(), 1009 Indices.end(), 1010 GEPI->getName()+".0", GEPI); 1011 Indices[1] = ConstantInt::get(Type::Int32Ty, 1); 1012 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1013 Indices.begin(), 1014 Indices.end(), 1015 GEPI->getName()+".1", GEPI); 1016 // Replace all loads of the variable index GEP with loads from both 1017 // indexes and a select. 1018 while (!GEPI->use_empty()) { 1019 LoadInst *LI = cast<LoadInst>(GEPI->use_back()); 1020 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI); 1021 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI); 1022 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI); 1023 LI->replaceAllUsesWith(R); 1024 LI->eraseFromParent(); 1025 } 1026 GEPI->eraseFromParent(); 1027 } 1028 } 1029 } 1030 } 1031} 1032 1033/// MergeInType - Add the 'In' type to the accumulated type so far. If the 1034/// types are incompatible, return true, otherwise update Accum and return 1035/// false. 1036/// 1037/// There are three cases we handle here: 1038/// 1) An effectively-integer union, where the pieces are stored into as 1039/// smaller integers (common with byte swap and other idioms). 1040/// 2) A union of vector types of the same size and potentially its elements. 1041/// Here we turn element accesses into insert/extract element operations. 1042/// 3) A union of scalar types, such as int/float or int/pointer. Here we 1043/// merge together into integers, allowing the xform to work with #1 as 1044/// well. 1045static bool MergeInType(const Type *In, const Type *&Accum, 1046 const TargetData &TD) { 1047 // If this is our first type, just use it. 1048 const VectorType *PTy; 1049 if (Accum == Type::VoidTy || In == Accum) { 1050 Accum = In; 1051 } else if (In == Type::VoidTy) { 1052 // Noop. 1053 } else if (In->isInteger() && Accum->isInteger()) { // integer union. 1054 // Otherwise pick whichever type is larger. 1055 if (cast<IntegerType>(In)->getBitWidth() > 1056 cast<IntegerType>(Accum)->getBitWidth()) 1057 Accum = In; 1058 } else if (isa<PointerType>(In) && isa<PointerType>(Accum)) { 1059 // Pointer unions just stay as one of the pointers. 1060 } else if (isa<VectorType>(In) || isa<VectorType>(Accum)) { 1061 if ((PTy = dyn_cast<VectorType>(Accum)) && 1062 PTy->getElementType() == In) { 1063 // Accum is a vector, and we are accessing an element: ok. 1064 } else if ((PTy = dyn_cast<VectorType>(In)) && 1065 PTy->getElementType() == Accum) { 1066 // In is a vector, and accum is an element: ok, remember In. 1067 Accum = In; 1068 } else if ((PTy = dyn_cast<VectorType>(In)) && isa<VectorType>(Accum) && 1069 PTy->getBitWidth() == cast<VectorType>(Accum)->getBitWidth()) { 1070 // Two vectors of the same size: keep Accum. 1071 } else { 1072 // Cannot insert an short into a <4 x int> or handle 1073 // <2 x int> -> <4 x int> 1074 return true; 1075 } 1076 } else { 1077 // Pointer/FP/Integer unions merge together as integers. 1078 switch (Accum->getTypeID()) { 1079 case Type::PointerTyID: Accum = TD.getIntPtrType(); break; 1080 case Type::FloatTyID: Accum = Type::Int32Ty; break; 1081 case Type::DoubleTyID: Accum = Type::Int64Ty; break; 1082 case Type::X86_FP80TyID: return true; 1083 case Type::FP128TyID: return true; 1084 case Type::PPC_FP128TyID: return true; 1085 default: 1086 assert(Accum->isInteger() && "Unknown FP type!"); 1087 break; 1088 } 1089 1090 switch (In->getTypeID()) { 1091 case Type::PointerTyID: In = TD.getIntPtrType(); break; 1092 case Type::FloatTyID: In = Type::Int32Ty; break; 1093 case Type::DoubleTyID: In = Type::Int64Ty; break; 1094 case Type::X86_FP80TyID: return true; 1095 case Type::FP128TyID: return true; 1096 case Type::PPC_FP128TyID: return true; 1097 default: 1098 assert(In->isInteger() && "Unknown FP type!"); 1099 break; 1100 } 1101 return MergeInType(In, Accum, TD); 1102 } 1103 return false; 1104} 1105 1106/// getIntAtLeastAsBigAs - Return an integer type that is at least as big as the 1107/// specified type. If there is no suitable type, this returns null. 1108const Type *getIntAtLeastAsBigAs(unsigned NumBits) { 1109 if (NumBits > 64) return 0; 1110 if (NumBits > 32) return Type::Int64Ty; 1111 if (NumBits > 16) return Type::Int32Ty; 1112 if (NumBits > 8) return Type::Int16Ty; 1113 return Type::Int8Ty; 1114} 1115 1116/// CanConvertToScalar - V is a pointer. If we can convert the pointee to a 1117/// single scalar integer type, return that type. Further, if the use is not 1118/// a completely trivial use that mem2reg could promote, set IsNotTrivial. If 1119/// there are no uses of this pointer, return Type::VoidTy to differentiate from 1120/// failure. 1121/// 1122const Type *SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial) { 1123 const Type *UsedType = Type::VoidTy; // No uses, no forced type. 1124 const PointerType *PTy = cast<PointerType>(V->getType()); 1125 1126 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1127 Instruction *User = cast<Instruction>(*UI); 1128 1129 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1130 // FIXME: Loads of a first class aggregrate value could be converted to a 1131 // series of loads and insertvalues 1132 if (!LI->getType()->isSingleValueType()) 1133 return 0; 1134 1135 if (MergeInType(LI->getType(), UsedType, *TD)) 1136 return 0; 1137 continue; 1138 } 1139 1140 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1141 // Storing the pointer, not into the value? 1142 if (SI->getOperand(0) == V) return 0; 1143 1144 // FIXME: Stores of a first class aggregrate value could be converted to a 1145 // series of extractvalues and stores 1146 if (!SI->getOperand(0)->getType()->isSingleValueType()) 1147 return 0; 1148 1149 // NOTE: We could handle storing of FP imms into integers here! 1150 1151 if (MergeInType(SI->getOperand(0)->getType(), UsedType, *TD)) 1152 return 0; 1153 continue; 1154 } 1155 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 1156 IsNotTrivial = true; 1157 const Type *SubTy = CanConvertToScalar(CI, IsNotTrivial); 1158 if (!SubTy || MergeInType(SubTy, UsedType, *TD)) return 0; 1159 continue; 1160 } 1161 1162 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1163 // Check to see if this is stepping over an element: GEP Ptr, int C 1164 if (GEP->getNumOperands() == 2 && isa<ConstantInt>(GEP->getOperand(1))) { 1165 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue(); 1166 unsigned ElSize = TD->getABITypeSize(PTy->getElementType()); 1167 unsigned BitOffset = Idx*ElSize*8; 1168 if (BitOffset > 64 || !isPowerOf2_32(ElSize)) return 0; 1169 1170 IsNotTrivial = true; 1171 const Type *SubElt = CanConvertToScalar(GEP, IsNotTrivial); 1172 if (SubElt == 0) return 0; 1173 if (SubElt != Type::VoidTy && SubElt->isInteger()) { 1174 const Type *NewTy = 1175 getIntAtLeastAsBigAs(TD->getABITypeSizeInBits(SubElt)+BitOffset); 1176 if (NewTy == 0 || MergeInType(NewTy, UsedType, *TD)) return 0; 1177 continue; 1178 } 1179 // Cannot handle this! 1180 return 0; 1181 } 1182 1183 if (GEP->getNumOperands() == 3 && 1184 isa<ConstantInt>(GEP->getOperand(1)) && 1185 isa<ConstantInt>(GEP->getOperand(2)) && 1186 cast<ConstantInt>(GEP->getOperand(1))->isZero()) { 1187 // We are stepping into an element, e.g. a structure or an array: 1188 // GEP Ptr, i32 0, i32 Cst 1189 const Type *AggTy = PTy->getElementType(); 1190 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 1191 1192 if (const ArrayType *ATy = dyn_cast<ArrayType>(AggTy)) { 1193 if (Idx >= ATy->getNumElements()) return 0; // Out of range. 1194 } else if (const VectorType *VectorTy = dyn_cast<VectorType>(AggTy)) { 1195 // Getting an element of the vector. 1196 if (Idx >= VectorTy->getNumElements()) return 0; // Out of range. 1197 1198 // Merge in the vector type. 1199 if (MergeInType(VectorTy, UsedType, *TD)) return 0; 1200 1201 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); 1202 if (SubTy == 0) return 0; 1203 1204 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, *TD)) 1205 return 0; 1206 1207 // We'll need to change this to an insert/extract element operation. 1208 IsNotTrivial = true; 1209 continue; // Everything looks ok 1210 1211 } else if (isa<StructType>(AggTy)) { 1212 // Structs are always ok. 1213 } else { 1214 return 0; 1215 } 1216 const Type *NTy = getIntAtLeastAsBigAs(TD->getABITypeSizeInBits(AggTy)); 1217 if (NTy == 0 || MergeInType(NTy, UsedType, *TD)) return 0; 1218 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); 1219 if (SubTy == 0) return 0; 1220 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, *TD)) 1221 return 0; 1222 continue; // Everything looks ok 1223 } 1224 return 0; 1225 } 1226 1227 // Cannot handle this! 1228 return 0; 1229 } 1230 1231 return UsedType; 1232} 1233 1234/// ConvertToScalar - The specified alloca passes the CanConvertToScalar 1235/// predicate and is non-trivial. Convert it to something that can be trivially 1236/// promoted into a register by mem2reg. 1237void SROA::ConvertToScalar(AllocationInst *AI, const Type *ActualTy) { 1238 DOUT << "CONVERT TO SCALAR: " << *AI << " TYPE = " 1239 << *ActualTy << "\n"; 1240 ++NumConverted; 1241 1242 BasicBlock *EntryBlock = AI->getParent(); 1243 assert(EntryBlock == &EntryBlock->getParent()->getEntryBlock() && 1244 "Not in the entry block!"); 1245 EntryBlock->getInstList().remove(AI); // Take the alloca out of the program. 1246 1247 // Create and insert the alloca. 1248 AllocaInst *NewAI = new AllocaInst(ActualTy, 0, AI->getName(), 1249 EntryBlock->begin()); 1250 ConvertUsesToScalar(AI, NewAI, 0); 1251 delete AI; 1252} 1253 1254 1255/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 1256/// directly. This happens when we are converting an "integer union" to a 1257/// single integer scalar, or when we are converting a "vector union" to a 1258/// vector with insert/extractelement instructions. 1259/// 1260/// Offset is an offset from the original alloca, in bits that need to be 1261/// shifted to the right. By the end of this, there should be no uses of Ptr. 1262void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset) { 1263 while (!Ptr->use_empty()) { 1264 Instruction *User = cast<Instruction>(Ptr->use_back()); 1265 1266 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1267 Value *NV = ConvertUsesOfLoadToScalar(LI, NewAI, Offset); 1268 LI->replaceAllUsesWith(NV); 1269 LI->eraseFromParent(); 1270 continue; 1271 } 1272 1273 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1274 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 1275 1276 Value *SV = ConvertUsesOfStoreToScalar(SI, NewAI, Offset); 1277 new StoreInst(SV, NewAI, SI); 1278 SI->eraseFromParent(); 1279 continue; 1280 } 1281 1282 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 1283 ConvertUsesToScalar(CI, NewAI, Offset); 1284 CI->eraseFromParent(); 1285 continue; 1286 } 1287 1288 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1289 const PointerType *AggPtrTy = 1290 cast<PointerType>(GEP->getOperand(0)->getType()); 1291 unsigned AggSizeInBits = 1292 TD->getABITypeSizeInBits(AggPtrTy->getElementType()); 1293 1294 // Check to see if this is stepping over an element: GEP Ptr, int C 1295 unsigned NewOffset = Offset; 1296 if (GEP->getNumOperands() == 2) { 1297 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue(); 1298 unsigned BitOffset = Idx*AggSizeInBits; 1299 1300 NewOffset += BitOffset; 1301 ConvertUsesToScalar(GEP, NewAI, NewOffset); 1302 GEP->eraseFromParent(); 1303 continue; 1304 } 1305 1306 assert(GEP->getNumOperands() == 3 && "Unsupported operation"); 1307 1308 // We know that operand #2 is zero. 1309 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 1310 const Type *AggTy = AggPtrTy->getElementType(); 1311 if (const SequentialType *SeqTy = dyn_cast<SequentialType>(AggTy)) { 1312 unsigned ElSizeBits = 1313 TD->getABITypeSizeInBits(SeqTy->getElementType()); 1314 1315 NewOffset += ElSizeBits*Idx; 1316 } else { 1317 const StructType *STy = cast<StructType>(AggTy); 1318 unsigned EltBitOffset = 1319 TD->getStructLayout(STy)->getElementOffsetInBits(Idx); 1320 1321 NewOffset += EltBitOffset; 1322 } 1323 ConvertUsesToScalar(GEP, NewAI, NewOffset); 1324 GEP->eraseFromParent(); 1325 continue; 1326 } 1327 1328 assert(0 && "Unsupported operation!"); 1329 abort(); 1330 } 1331} 1332 1333/// ConvertUsesOfLoadToScalar - Convert all of the users the specified load to 1334/// use the new alloca directly, returning the value that should replace the 1335/// load. This happens when we are converting an "integer union" to a 1336/// single integer scalar, or when we are converting a "vector union" to a 1337/// vector with insert/extractelement instructions. 1338/// 1339/// Offset is an offset from the original alloca, in bits that need to be 1340/// shifted to the right. By the end of this, there should be no uses of Ptr. 1341Value *SROA::ConvertUsesOfLoadToScalar(LoadInst *LI, AllocaInst *NewAI, 1342 unsigned Offset) { 1343 // The load is a bit extract from NewAI shifted right by Offset bits. 1344 Value *NV = new LoadInst(NewAI, LI->getName(), LI); 1345 1346 if (NV->getType() == LI->getType() && Offset == 0) { 1347 // We win, no conversion needed. 1348 return NV; 1349 } 1350 1351 // If the result type of the 'union' is a pointer, then this must be ptr->ptr 1352 // cast. Anything else would result in NV being an integer. 1353 if (isa<PointerType>(NV->getType())) { 1354 assert(isa<PointerType>(LI->getType())); 1355 return new BitCastInst(NV, LI->getType(), LI->getName(), LI); 1356 } 1357 1358 if (const VectorType *VTy = dyn_cast<VectorType>(NV->getType())) { 1359 // If the result alloca is a vector type, this is either an element 1360 // access or a bitcast to another vector type. 1361 if (isa<VectorType>(LI->getType())) 1362 return new BitCastInst(NV, LI->getType(), LI->getName(), LI); 1363 1364 // Otherwise it must be an element access. 1365 unsigned Elt = 0; 1366 if (Offset) { 1367 unsigned EltSize = TD->getABITypeSizeInBits(VTy->getElementType()); 1368 Elt = Offset/EltSize; 1369 Offset -= EltSize*Elt; 1370 } 1371 NV = new ExtractElementInst(NV, ConstantInt::get(Type::Int32Ty, Elt), 1372 "tmp", LI); 1373 1374 // If we're done, return this element. 1375 if (NV->getType() == LI->getType() && Offset == 0) 1376 return NV; 1377 } 1378 1379 const IntegerType *NTy = cast<IntegerType>(NV->getType()); 1380 1381 // If this is a big-endian system and the load is narrower than the 1382 // full alloca type, we need to do a shift to get the right bits. 1383 int ShAmt = 0; 1384 if (TD->isBigEndian()) { 1385 // On big-endian machines, the lowest bit is stored at the bit offset 1386 // from the pointer given by getTypeStoreSizeInBits. This matters for 1387 // integers with a bitwidth that is not a multiple of 8. 1388 ShAmt = TD->getTypeStoreSizeInBits(NTy) - 1389 TD->getTypeStoreSizeInBits(LI->getType()) - Offset; 1390 } else { 1391 ShAmt = Offset; 1392 } 1393 1394 // Note: we support negative bitwidths (with shl) which are not defined. 1395 // We do this to support (f.e.) loads off the end of a structure where 1396 // only some bits are used. 1397 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 1398 NV = BinaryOperator::CreateLShr(NV, 1399 ConstantInt::get(NV->getType(),ShAmt), 1400 LI->getName(), LI); 1401 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 1402 NV = BinaryOperator::CreateShl(NV, 1403 ConstantInt::get(NV->getType(),-ShAmt), 1404 LI->getName(), LI); 1405 1406 // Finally, unconditionally truncate the integer to the right width. 1407 unsigned LIBitWidth = TD->getTypeSizeInBits(LI->getType()); 1408 if (LIBitWidth < NTy->getBitWidth()) 1409 NV = new TruncInst(NV, IntegerType::get(LIBitWidth), 1410 LI->getName(), LI); 1411 1412 // If the result is an integer, this is a trunc or bitcast. 1413 if (isa<IntegerType>(LI->getType())) { 1414 // Should be done. 1415 } else if (LI->getType()->isFloatingPoint()) { 1416 // Just do a bitcast, we know the sizes match up. 1417 NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI); 1418 } else { 1419 // Otherwise must be a pointer. 1420 NV = new IntToPtrInst(NV, LI->getType(), LI->getName(), LI); 1421 } 1422 assert(NV->getType() == LI->getType() && "Didn't convert right?"); 1423 return NV; 1424} 1425 1426 1427/// ConvertUsesOfStoreToScalar - Convert the specified store to a load+store 1428/// pair of the new alloca directly, returning the value that should be stored 1429/// to the alloca. This happens when we are converting an "integer union" to a 1430/// single integer scalar, or when we are converting a "vector union" to a 1431/// vector with insert/extractelement instructions. 1432/// 1433/// Offset is an offset from the original alloca, in bits that need to be 1434/// shifted to the right. By the end of this, there should be no uses of Ptr. 1435Value *SROA::ConvertUsesOfStoreToScalar(StoreInst *SI, AllocaInst *NewAI, 1436 unsigned Offset) { 1437 1438 // Convert the stored type to the actual type, shift it left to insert 1439 // then 'or' into place. 1440 Value *SV = SI->getOperand(0); 1441 const Type *AllocaType = NewAI->getType()->getElementType(); 1442 if (SV->getType() == AllocaType && Offset == 0) { 1443 // All is well. 1444 } else if (const VectorType *PTy = dyn_cast<VectorType>(AllocaType)) { 1445 Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI); 1446 1447 // If the result alloca is a vector type, this is either an element 1448 // access or a bitcast to another vector type. 1449 if (isa<VectorType>(SV->getType())) { 1450 SV = new BitCastInst(SV, AllocaType, SV->getName(), SI); 1451 } else { 1452 // Must be an element insertion. 1453 unsigned Elt = Offset/TD->getABITypeSizeInBits(PTy->getElementType()); 1454 SV = InsertElementInst::Create(Old, SV, 1455 ConstantInt::get(Type::Int32Ty, Elt), 1456 "tmp", SI); 1457 } 1458 } else if (isa<PointerType>(AllocaType)) { 1459 // If the alloca type is a pointer, then all the elements must be 1460 // pointers. 1461 if (SV->getType() != AllocaType) 1462 SV = new BitCastInst(SV, AllocaType, SV->getName(), SI); 1463 } else { 1464 Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI); 1465 1466 // If SV is a float, convert it to the appropriate integer type. 1467 // If it is a pointer, do the same, and also handle ptr->ptr casts 1468 // here. 1469 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType()); 1470 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType); 1471 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType()); 1472 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType); 1473 if (SV->getType()->isFloatingPoint()) 1474 SV = new BitCastInst(SV, IntegerType::get(SrcWidth), 1475 SV->getName(), SI); 1476 else if (isa<PointerType>(SV->getType())) 1477 SV = new PtrToIntInst(SV, TD->getIntPtrType(), SV->getName(), SI); 1478 1479 // Always zero extend the value if needed. 1480 if (SV->getType() != AllocaType) 1481 SV = new ZExtInst(SV, AllocaType, SV->getName(), SI); 1482 1483 // If this is a big-endian system and the store is narrower than the 1484 // full alloca type, we need to do a shift to get the right bits. 1485 int ShAmt = 0; 1486 if (TD->isBigEndian()) { 1487 // On big-endian machines, the lowest bit is stored at the bit offset 1488 // from the pointer given by getTypeStoreSizeInBits. This matters for 1489 // integers with a bitwidth that is not a multiple of 8. 1490 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 1491 } else { 1492 ShAmt = Offset; 1493 } 1494 1495 // Note: we support negative bitwidths (with shr) which are not defined. 1496 // We do this to support (f.e.) stores off the end of a structure where 1497 // only some bits in the structure are set. 1498 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 1499 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 1500 SV = BinaryOperator::CreateShl(SV, 1501 ConstantInt::get(SV->getType(), ShAmt), 1502 SV->getName(), SI); 1503 Mask <<= ShAmt; 1504 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 1505 SV = BinaryOperator::CreateLShr(SV, 1506 ConstantInt::get(SV->getType(),-ShAmt), 1507 SV->getName(), SI); 1508 Mask = Mask.lshr(ShAmt); 1509 } 1510 1511 // Mask out the bits we are about to insert from the old value, and or 1512 // in the new bits. 1513 if (SrcWidth != DestWidth) { 1514 assert(DestWidth > SrcWidth); 1515 Old = BinaryOperator::CreateAnd(Old, ConstantInt::get(~Mask), 1516 Old->getName()+".mask", SI); 1517 SV = BinaryOperator::CreateOr(Old, SV, SV->getName()+".ins", SI); 1518 } 1519 } 1520 return SV; 1521} 1522 1523 1524 1525/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 1526/// some part of a constant global variable. This intentionally only accepts 1527/// constant expressions because we don't can't rewrite arbitrary instructions. 1528static bool PointsToConstantGlobal(Value *V) { 1529 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 1530 return GV->isConstant(); 1531 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 1532 if (CE->getOpcode() == Instruction::BitCast || 1533 CE->getOpcode() == Instruction::GetElementPtr) 1534 return PointsToConstantGlobal(CE->getOperand(0)); 1535 return false; 1536} 1537 1538/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 1539/// pointer to an alloca. Ignore any reads of the pointer, return false if we 1540/// see any stores or other unknown uses. If we see pointer arithmetic, keep 1541/// track of whether it moves the pointer (with isOffset) but otherwise traverse 1542/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 1543/// the alloca, and if the source pointer is a pointer to a constant global, we 1544/// can optimize this. 1545static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy, 1546 bool isOffset) { 1547 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1548 if (isa<LoadInst>(*UI)) { 1549 // Ignore loads, they are always ok. 1550 continue; 1551 } 1552 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) { 1553 // If uses of the bitcast are ok, we are ok. 1554 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 1555 return false; 1556 continue; 1557 } 1558 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) { 1559 // If the GEP has all zero indices, it doesn't offset the pointer. If it 1560 // doesn't, it does. 1561 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 1562 isOffset || !GEP->hasAllZeroIndices())) 1563 return false; 1564 continue; 1565 } 1566 1567 // If this is isn't our memcpy/memmove, reject it as something we can't 1568 // handle. 1569 if (!isa<MemCpyInst>(*UI) && !isa<MemMoveInst>(*UI)) 1570 return false; 1571 1572 // If we already have seen a copy, reject the second one. 1573 if (TheCopy) return false; 1574 1575 // If the pointer has been offset from the start of the alloca, we can't 1576 // safely handle this. 1577 if (isOffset) return false; 1578 1579 // If the memintrinsic isn't using the alloca as the dest, reject it. 1580 if (UI.getOperandNo() != 1) return false; 1581 1582 MemIntrinsic *MI = cast<MemIntrinsic>(*UI); 1583 1584 // If the source of the memcpy/move is not a constant global, reject it. 1585 if (!PointsToConstantGlobal(MI->getOperand(2))) 1586 return false; 1587 1588 // Otherwise, the transform is safe. Remember the copy instruction. 1589 TheCopy = MI; 1590 } 1591 return true; 1592} 1593 1594/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 1595/// modified by a copy from a constant global. If we can prove this, we can 1596/// replace any uses of the alloca with uses of the global directly. 1597Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) { 1598 Instruction *TheCopy = 0; 1599 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 1600 return TheCopy; 1601 return 0; 1602} 1603