ScalarReplAggregates.cpp revision 583dd6072eed7a446dad8f0e796fa34aec40aa12
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 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, 126 SmallVector<AllocaInst*, 32> &NewElts); 127 128 const Type *CanConvertToScalar(Value *V, bool &IsNotTrivial); 129 void ConvertToScalar(AllocationInst *AI, const Type *Ty); 130 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset); 131 Value *ConvertUsesOfLoadToScalar(LoadInst *LI, AllocaInst *NewAI, 132 unsigned Offset); 133 Value *ConvertUsesOfStoreToScalar(StoreInst *SI, AllocaInst *NewAI, 134 unsigned Offset); 135 static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI); 136 }; 137} 138 139char SROA::ID = 0; 140static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates"); 141 142// Public interface to the ScalarReplAggregates pass 143FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) { 144 return new SROA(Threshold); 145} 146 147 148bool SROA::runOnFunction(Function &F) { 149 TD = &getAnalysis<TargetData>(); 150 151 bool Changed = performPromotion(F); 152 while (1) { 153 bool LocalChange = performScalarRepl(F); 154 if (!LocalChange) break; // No need to repromote if no scalarrepl 155 Changed = true; 156 LocalChange = performPromotion(F); 157 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 158 } 159 160 return Changed; 161} 162 163 164bool SROA::performPromotion(Function &F) { 165 std::vector<AllocaInst*> Allocas; 166 DominatorTree &DT = getAnalysis<DominatorTree>(); 167 DominanceFrontier &DF = getAnalysis<DominanceFrontier>(); 168 169 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 170 171 bool Changed = false; 172 173 while (1) { 174 Allocas.clear(); 175 176 // Find allocas that are safe to promote, by looking at all instructions in 177 // the entry node 178 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 179 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 180 if (isAllocaPromotable(AI)) 181 Allocas.push_back(AI); 182 183 if (Allocas.empty()) break; 184 185 PromoteMemToReg(Allocas, DT, DF); 186 NumPromoted += Allocas.size(); 187 Changed = true; 188 } 189 190 return Changed; 191} 192 193/// getNumSAElements - Return the number of elements in the specific struct or 194/// array. 195static uint64_t getNumSAElements(const Type *T) { 196 if (const StructType *ST = dyn_cast<StructType>(T)) 197 return ST->getNumElements(); 198 return cast<ArrayType>(T)->getNumElements(); 199} 200 201// performScalarRepl - This algorithm is a simple worklist driven algorithm, 202// which runs on all of the malloc/alloca instructions in the function, removing 203// them if they are only used by getelementptr instructions. 204// 205bool SROA::performScalarRepl(Function &F) { 206 std::vector<AllocationInst*> WorkList; 207 208 // Scan the entry basic block, adding any alloca's and mallocs to the worklist 209 BasicBlock &BB = F.getEntryBlock(); 210 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 211 if (AllocationInst *A = dyn_cast<AllocationInst>(I)) 212 WorkList.push_back(A); 213 214 // Process the worklist 215 bool Changed = false; 216 while (!WorkList.empty()) { 217 AllocationInst *AI = WorkList.back(); 218 WorkList.pop_back(); 219 220 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 221 // with unused elements. 222 if (AI->use_empty()) { 223 AI->eraseFromParent(); 224 continue; 225 } 226 227 // If we can turn this aggregate value (potentially with casts) into a 228 // simple scalar value that can be mem2reg'd into a register value. 229 bool IsNotTrivial = false; 230 if (const Type *ActualType = CanConvertToScalar(AI, IsNotTrivial)) 231 if (IsNotTrivial && ActualType != Type::VoidTy) { 232 ConvertToScalar(AI, ActualType); 233 Changed = true; 234 continue; 235 } 236 237 // Check to see if we can perform the core SROA transformation. We cannot 238 // transform the allocation instruction if it is an array allocation 239 // (allocations OF arrays are ok though), and an allocation of a scalar 240 // value cannot be decomposed at all. 241 if (!AI->isArrayAllocation() && 242 (isa<StructType>(AI->getAllocatedType()) || 243 isa<ArrayType>(AI->getAllocatedType())) && 244 AI->getAllocatedType()->isSized() && 245 // Do not promote any struct whose size is larger than "128" bytes. 246 TD->getABITypeSize(AI->getAllocatedType()) < SRThreshold && 247 // Do not promote any struct into more than "32" separate vars. 248 getNumSAElements(AI->getAllocatedType()) < SRThreshold/4) { 249 // Check that all of the users of the allocation are capable of being 250 // transformed. 251 switch (isSafeAllocaToScalarRepl(AI)) { 252 default: assert(0 && "Unexpected value!"); 253 case 0: // Not safe to scalar replace. 254 break; 255 case 1: // Safe, but requires cleanup/canonicalizations first 256 CanonicalizeAllocaUsers(AI); 257 // FALL THROUGH. 258 case 3: // Safe to scalar replace. 259 DoScalarReplacement(AI, WorkList); 260 Changed = true; 261 continue; 262 } 263 } 264 265 // Check to see if this allocation is only modified by a memcpy/memmove from 266 // a constant global. If this is the case, we can change all users to use 267 // the constant global instead. This is commonly produced by the CFE by 268 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 269 // is only subsequently read. 270 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 271 DOUT << "Found alloca equal to global: " << *AI; 272 DOUT << " memcpy = " << *TheCopy; 273 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2)); 274 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 275 TheCopy->eraseFromParent(); // Don't mutate the global. 276 AI->eraseFromParent(); 277 ++NumGlobals; 278 Changed = true; 279 continue; 280 } 281 282 // Otherwise, couldn't process this. 283 } 284 285 return Changed; 286} 287 288/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 289/// predicate, do SROA now. 290void SROA::DoScalarReplacement(AllocationInst *AI, 291 std::vector<AllocationInst*> &WorkList) { 292 DOUT << "Found inst to SROA: " << *AI; 293 SmallVector<AllocaInst*, 32> ElementAllocas; 294 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 295 ElementAllocas.reserve(ST->getNumContainedTypes()); 296 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 297 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 298 AI->getAlignment(), 299 AI->getName() + "." + utostr(i), AI); 300 ElementAllocas.push_back(NA); 301 WorkList.push_back(NA); // Add to worklist for recursive processing 302 } 303 } else { 304 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 305 ElementAllocas.reserve(AT->getNumElements()); 306 const Type *ElTy = AT->getElementType(); 307 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 308 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 309 AI->getName() + "." + utostr(i), AI); 310 ElementAllocas.push_back(NA); 311 WorkList.push_back(NA); // Add to worklist for recursive processing 312 } 313 } 314 315 // Now that we have created the alloca instructions that we want to use, 316 // expand the getelementptr instructions to use them. 317 // 318 while (!AI->use_empty()) { 319 Instruction *User = cast<Instruction>(AI->use_back()); 320 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) { 321 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas); 322 BCInst->eraseFromParent(); 323 continue; 324 } 325 326 // Replace: 327 // %res = load { i32, i32 }* %alloc 328 // with: 329 // %load.0 = load i32* %alloc.0 330 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 331 // %load.1 = load i32* %alloc.1 332 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 333 // (Also works for arrays instead of structs) 334 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 335 Value *Insert = UndefValue::get(LI->getType()); 336 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { 337 Value *Load = new LoadInst(ElementAllocas[i], "load", LI); 338 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI); 339 } 340 LI->replaceAllUsesWith(Insert); 341 LI->eraseFromParent(); 342 continue; 343 } 344 345 // Replace: 346 // store { i32, i32 } %val, { i32, i32 }* %alloc 347 // with: 348 // %val.0 = extractvalue { i32, i32 } %val, 0 349 // store i32 %val.0, i32* %alloc.0 350 // %val.1 = extractvalue { i32, i32 } %val, 1 351 // store i32 %val.1, i32* %alloc.1 352 // (Also works for arrays instead of structs) 353 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 354 Value *Val = SI->getOperand(0); 355 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { 356 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI); 357 new StoreInst(Extract, ElementAllocas[i], SI); 358 } 359 SI->eraseFromParent(); 360 continue; 361 } 362 363 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User); 364 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst> 365 unsigned Idx = 366 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 367 368 assert(Idx < ElementAllocas.size() && "Index out of range?"); 369 AllocaInst *AllocaToUse = ElementAllocas[Idx]; 370 371 Value *RepValue; 372 if (GEPI->getNumOperands() == 3) { 373 // Do not insert a new getelementptr instruction with zero indices, only 374 // to have it optimized out later. 375 RepValue = AllocaToUse; 376 } else { 377 // We are indexing deeply into the structure, so we still need a 378 // getelement ptr instruction to finish the indexing. This may be 379 // expanded itself once the worklist is rerun. 380 // 381 SmallVector<Value*, 8> NewArgs; 382 NewArgs.push_back(Constant::getNullValue(Type::Int32Ty)); 383 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end()); 384 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(), 385 NewArgs.end(), "", GEPI); 386 RepValue->takeName(GEPI); 387 } 388 389 // If this GEP is to the start of the aggregate, check for memcpys. 390 if (Idx == 0 && GEPI->hasAllZeroIndices()) 391 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas); 392 393 // Move all of the users over to the new GEP. 394 GEPI->replaceAllUsesWith(RepValue); 395 // Delete the old GEP 396 GEPI->eraseFromParent(); 397 } 398 399 // Finally, delete the Alloca instruction 400 AI->eraseFromParent(); 401 NumReplaced++; 402} 403 404 405/// isSafeElementUse - Check to see if this use is an allowed use for a 406/// getelementptr instruction of an array aggregate allocation. isFirstElt 407/// indicates whether Ptr is known to the start of the aggregate. 408/// 409void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, 410 AllocaInfo &Info) { 411 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 412 I != E; ++I) { 413 Instruction *User = cast<Instruction>(*I); 414 switch (User->getOpcode()) { 415 case Instruction::Load: break; 416 case Instruction::Store: 417 // Store is ok if storing INTO the pointer, not storing the pointer 418 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info); 419 break; 420 case Instruction::GetElementPtr: { 421 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User); 422 bool AreAllZeroIndices = isFirstElt; 423 if (GEP->getNumOperands() > 1) { 424 if (!isa<ConstantInt>(GEP->getOperand(1)) || 425 !cast<ConstantInt>(GEP->getOperand(1))->isZero()) 426 // Using pointer arithmetic to navigate the array. 427 return MarkUnsafe(Info); 428 429 if (AreAllZeroIndices) 430 AreAllZeroIndices = GEP->hasAllZeroIndices(); 431 } 432 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info); 433 if (Info.isUnsafe) return; 434 break; 435 } 436 case Instruction::BitCast: 437 if (isFirstElt) { 438 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info); 439 if (Info.isUnsafe) return; 440 break; 441 } 442 DOUT << " Transformation preventing inst: " << *User; 443 return MarkUnsafe(Info); 444 case Instruction::Call: 445 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 446 if (isFirstElt) { 447 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info); 448 if (Info.isUnsafe) return; 449 break; 450 } 451 } 452 DOUT << " Transformation preventing inst: " << *User; 453 return MarkUnsafe(Info); 454 default: 455 DOUT << " Transformation preventing inst: " << *User; 456 return MarkUnsafe(Info); 457 } 458 } 459 return; // All users look ok :) 460} 461 462/// AllUsersAreLoads - Return true if all users of this value are loads. 463static bool AllUsersAreLoads(Value *Ptr) { 464 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 465 I != E; ++I) 466 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load) 467 return false; 468 return true; 469} 470 471/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an 472/// aggregate allocation. 473/// 474void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, 475 AllocaInfo &Info) { 476 if (BitCastInst *C = dyn_cast<BitCastInst>(User)) 477 return isSafeUseOfBitCastedAllocation(C, AI, Info); 478 479 if (isa<LoadInst>(User)) 480 return; // Loads (returning a first class aggregrate) are always rewritable 481 482 if (isa<StoreInst>(User) && User->getOperand(0) != AI) 483 return; // Store is ok if storing INTO the pointer, not storing the pointer 484 485 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User); 486 if (GEPI == 0) 487 return MarkUnsafe(Info); 488 489 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI); 490 491 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>". 492 if (I == E || 493 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) { 494 return MarkUnsafe(Info); 495 } 496 497 ++I; 498 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices?? 499 500 bool IsAllZeroIndices = true; 501 502 // If the first index is a non-constant index into an array, see if we can 503 // handle it as a special case. 504 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 505 if (!isa<ConstantInt>(I.getOperand())) { 506 IsAllZeroIndices = 0; 507 uint64_t NumElements = AT->getNumElements(); 508 509 // If this is an array index and the index is not constant, we cannot 510 // promote... that is unless the array has exactly one or two elements in 511 // it, in which case we CAN promote it, but we have to canonicalize this 512 // out if this is the only problem. 513 if ((NumElements == 1 || NumElements == 2) && 514 AllUsersAreLoads(GEPI)) { 515 Info.needsCanon = true; 516 return; // Canonicalization required! 517 } 518 return MarkUnsafe(Info); 519 } 520 } 521 522 // Walk through the GEP type indices, checking the types that this indexes 523 // into. 524 for (; I != E; ++I) { 525 // Ignore struct elements, no extra checking needed for these. 526 if (isa<StructType>(*I)) 527 continue; 528 529 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand()); 530 if (!IdxVal) return MarkUnsafe(Info); 531 532 // Are all indices still zero? 533 IsAllZeroIndices &= IdxVal->isZero(); 534 535 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 536 // This GEP indexes an array. Verify that this is an in-range constant 537 // integer. Specifically, consider A[0][i]. We cannot know that the user 538 // isn't doing invalid things like allowing i to index an out-of-range 539 // subscript that accesses A[1]. Because of this, we have to reject SROA 540 // of any accesses into structs where any of the components are variables. 541 if (IdxVal->getZExtValue() >= AT->getNumElements()) 542 return MarkUnsafe(Info); 543 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) { 544 if (IdxVal->getZExtValue() >= VT->getNumElements()) 545 return MarkUnsafe(Info); 546 } 547 } 548 549 // If there are any non-simple uses of this getelementptr, make sure to reject 550 // them. 551 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info); 552} 553 554/// isSafeMemIntrinsicOnAllocation - Return true if the specified memory 555/// intrinsic can be promoted by SROA. At this point, we know that the operand 556/// of the memintrinsic is a pointer to the beginning of the allocation. 557void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, 558 unsigned OpNo, AllocaInfo &Info) { 559 // If not constant length, give up. 560 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 561 if (!Length) return MarkUnsafe(Info); 562 563 // If not the whole aggregate, give up. 564 if (Length->getZExtValue() != 565 TD->getABITypeSize(AI->getType()->getElementType())) 566 return MarkUnsafe(Info); 567 568 // We only know about memcpy/memset/memmove. 569 if (!isa<MemCpyInst>(MI) && !isa<MemSetInst>(MI) && !isa<MemMoveInst>(MI)) 570 return MarkUnsafe(Info); 571 572 // Otherwise, we can transform it. Determine whether this is a memcpy/set 573 // into or out of the aggregate. 574 if (OpNo == 1) 575 Info.isMemCpyDst = true; 576 else { 577 assert(OpNo == 2); 578 Info.isMemCpySrc = true; 579 } 580} 581 582/// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast 583/// are 584void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI, 585 AllocaInfo &Info) { 586 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end(); 587 UI != E; ++UI) { 588 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) { 589 isSafeUseOfBitCastedAllocation(BCU, AI, Info); 590 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) { 591 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info); 592 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 593 // If storing the entire alloca in one chunk through a bitcasted pointer 594 // to integer, we can transform it. This happens (for example) when you 595 // cast a {i32,i32}* to i64* and store through it. This is similar to the 596 // memcpy case and occurs in various "byval" cases and emulated memcpys. 597 if (isa<IntegerType>(SI->getOperand(0)->getType()) && 598 TD->getABITypeSize(SI->getOperand(0)->getType()) == 599 TD->getABITypeSize(AI->getType()->getElementType())) { 600 Info.isMemCpyDst = true; 601 continue; 602 } 603 return MarkUnsafe(Info); 604 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) { 605 // If loading the entire alloca in one chunk through a bitcasted pointer 606 // to integer, we can transform it. This happens (for example) when you 607 // cast a {i32,i32}* to i64* and load through it. This is similar to the 608 // memcpy case and occurs in various "byval" cases and emulated memcpys. 609 if (isa<IntegerType>(LI->getType()) && 610 TD->getABITypeSize(LI->getType()) == 611 TD->getABITypeSize(AI->getType()->getElementType())) { 612 Info.isMemCpySrc = true; 613 continue; 614 } 615 return MarkUnsafe(Info); 616 } else { 617 return MarkUnsafe(Info); 618 } 619 if (Info.isUnsafe) return; 620 } 621} 622 623/// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes 624/// to its first element. Transform users of the cast to use the new values 625/// instead. 626void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, 627 SmallVector<AllocaInst*, 32> &NewElts) { 628 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end(); 629 while (UI != UE) { 630 Instruction *User = cast<Instruction>(*UI++); 631 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) { 632 RewriteBitCastUserOfAlloca(BCU, AI, NewElts); 633 if (BCU->use_empty()) BCU->eraseFromParent(); 634 continue; 635 } 636 637 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 638 // This must be memcpy/memmove/memset of the entire aggregate. 639 // Split into one per element. 640 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts); 641 continue; 642 } 643 644 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 645 // If this is a store of the entire alloca from an integer, rewrite it. 646 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 647 continue; 648 } 649 650 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 651 // If this is a load of the entire alloca to an integer, rewrite it. 652 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 653 continue; 654 } 655 656 // Otherwise it must be some other user of a gep of the first pointer. Just 657 // leave these alone. 658 continue; 659 } 660} 661 662/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 663/// Rewrite it to copy or set the elements of the scalarized memory. 664void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, 665 AllocationInst *AI, 666 SmallVector<AllocaInst*, 32> &NewElts) { 667 668 // If this is a memcpy/memmove, construct the other pointer as the 669 // appropriate type. 670 Value *OtherPtr = 0; 671 if (MemCpyInst *MCI = dyn_cast<MemCpyInst>(MI)) { 672 if (BCInst == MCI->getRawDest()) 673 OtherPtr = MCI->getRawSource(); 674 else { 675 assert(BCInst == MCI->getRawSource()); 676 OtherPtr = MCI->getRawDest(); 677 } 678 } else if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(MI)) { 679 if (BCInst == MMI->getRawDest()) 680 OtherPtr = MMI->getRawSource(); 681 else { 682 assert(BCInst == MMI->getRawSource()); 683 OtherPtr = MMI->getRawDest(); 684 } 685 } 686 687 // If there is an other pointer, we want to convert it to the same pointer 688 // type as AI has, so we can GEP through it safely. 689 if (OtherPtr) { 690 // It is likely that OtherPtr is a bitcast, if so, remove it. 691 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr)) 692 OtherPtr = BC->getOperand(0); 693 // All zero GEPs are effectively bitcasts. 694 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr)) 695 if (GEP->hasAllZeroIndices()) 696 OtherPtr = GEP->getOperand(0); 697 698 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr)) 699 if (BCE->getOpcode() == Instruction::BitCast) 700 OtherPtr = BCE->getOperand(0); 701 702 // If the pointer is not the right type, insert a bitcast to the right 703 // type. 704 if (OtherPtr->getType() != AI->getType()) 705 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(), 706 MI); 707 } 708 709 // Process each element of the aggregate. 710 Value *TheFn = MI->getOperand(0); 711 const Type *BytePtrTy = MI->getRawDest()->getType(); 712 bool SROADest = MI->getRawDest() == BCInst; 713 714 Constant *Zero = Constant::getNullValue(Type::Int32Ty); 715 716 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 717 // If this is a memcpy/memmove, emit a GEP of the other element address. 718 Value *OtherElt = 0; 719 if (OtherPtr) { 720 Value *Idx[2] = { Zero, ConstantInt::get(Type::Int32Ty, i) }; 721 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2, 722 OtherPtr->getNameStr()+"."+utostr(i), 723 MI); 724 } 725 726 Value *EltPtr = NewElts[i]; 727 const Type *EltTy =cast<PointerType>(EltPtr->getType())->getElementType(); 728 729 // If we got down to a scalar, insert a load or store as appropriate. 730 if (EltTy->isSingleValueType()) { 731 if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) { 732 Value *Elt = new LoadInst(SROADest ? OtherElt : EltPtr, "tmp", 733 MI); 734 new StoreInst(Elt, SROADest ? EltPtr : OtherElt, MI); 735 continue; 736 } 737 assert(isa<MemSetInst>(MI)); 738 739 // If the stored element is zero (common case), just store a null 740 // constant. 741 Constant *StoreVal; 742 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) { 743 if (CI->isZero()) { 744 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 745 } else { 746 // If EltTy is a vector type, get the element type. 747 const Type *ValTy = EltTy; 748 if (const VectorType *VTy = dyn_cast<VectorType>(ValTy)) 749 ValTy = VTy->getElementType(); 750 751 // Construct an integer with the right value. 752 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 753 APInt OneVal(EltSize, CI->getZExtValue()); 754 APInt TotalVal(OneVal); 755 // Set each byte. 756 for (unsigned i = 0; 8*i < EltSize; ++i) { 757 TotalVal = TotalVal.shl(8); 758 TotalVal |= OneVal; 759 } 760 761 // Convert the integer value to the appropriate type. 762 StoreVal = ConstantInt::get(TotalVal); 763 if (isa<PointerType>(ValTy)) 764 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 765 else if (ValTy->isFloatingPoint()) 766 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 767 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 768 769 // If the requested value was a vector constant, create it. 770 if (EltTy != ValTy) { 771 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 772 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 773 StoreVal = ConstantVector::get(&Elts[0], NumElts); 774 } 775 } 776 new StoreInst(StoreVal, EltPtr, MI); 777 continue; 778 } 779 // Otherwise, if we're storing a byte variable, use a memset call for 780 // this element. 781 } 782 783 // Cast the element pointer to BytePtrTy. 784 if (EltPtr->getType() != BytePtrTy) 785 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI); 786 787 // Cast the other pointer (if we have one) to BytePtrTy. 788 if (OtherElt && OtherElt->getType() != BytePtrTy) 789 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(), 790 MI); 791 792 unsigned EltSize = TD->getABITypeSize(EltTy); 793 794 // Finally, insert the meminst for this element. 795 if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) { 796 Value *Ops[] = { 797 SROADest ? EltPtr : OtherElt, // Dest ptr 798 SROADest ? OtherElt : EltPtr, // Src ptr 799 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 800 Zero // Align 801 }; 802 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 803 } else { 804 assert(isa<MemSetInst>(MI)); 805 Value *Ops[] = { 806 EltPtr, MI->getOperand(2), // Dest, Value, 807 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 808 Zero // Align 809 }; 810 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 811 } 812 } 813 MI->eraseFromParent(); 814} 815 816/// RewriteStoreUserOfWholeAlloca - We found an store of an integer that 817/// overwrites the entire allocation. Extract out the pieces of the stored 818/// integer and store them individually. 819void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, 820 AllocationInst *AI, 821 SmallVector<AllocaInst*, 32> &NewElts){ 822 // Extract each element out of the integer according to its structure offset 823 // and store the element value to the individual alloca. 824 Value *SrcVal = SI->getOperand(0); 825 const Type *AllocaEltTy = AI->getType()->getElementType(); 826 uint64_t AllocaSizeBits = TD->getABITypeSizeInBits(AllocaEltTy); 827 828 // If this isn't a store of an integer to the whole alloca, it may be a store 829 // to the first element. Just ignore the store in this case and normal SROA 830 // will handle it. 831 if (!isa<IntegerType>(SrcVal->getType()) || 832 TD->getABITypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 833 return; 834 835 DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI; 836 837 // There are two forms here: AI could be an array or struct. Both cases 838 // have different ways to compute the element offset. 839 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 840 const StructLayout *Layout = TD->getStructLayout(EltSTy); 841 842 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 843 // Get the number of bits to shift SrcVal to get the value. 844 const Type *FieldTy = EltSTy->getElementType(i); 845 uint64_t Shift = Layout->getElementOffsetInBits(i); 846 847 if (TD->isBigEndian()) 848 Shift = AllocaSizeBits-Shift-TD->getABITypeSizeInBits(FieldTy); 849 850 Value *EltVal = SrcVal; 851 if (Shift) { 852 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 853 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 854 "sroa.store.elt", SI); 855 } 856 857 // Truncate down to an integer of the right size. 858 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 859 860 // Ignore zero sized fields like {}, they obviously contain no data. 861 if (FieldSizeBits == 0) continue; 862 863 if (FieldSizeBits != AllocaSizeBits) 864 EltVal = new TruncInst(EltVal, IntegerType::get(FieldSizeBits), "", SI); 865 Value *DestField = NewElts[i]; 866 if (EltVal->getType() == FieldTy) { 867 // Storing to an integer field of this size, just do it. 868 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) { 869 // Bitcast to the right element type (for fp/vector values). 870 EltVal = new BitCastInst(EltVal, FieldTy, "", SI); 871 } else { 872 // Otherwise, bitcast the dest pointer (for aggregates). 873 DestField = new BitCastInst(DestField, 874 PointerType::getUnqual(EltVal->getType()), 875 "", SI); 876 } 877 new StoreInst(EltVal, DestField, SI); 878 } 879 880 } else { 881 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 882 const Type *ArrayEltTy = ATy->getElementType(); 883 uint64_t ElementOffset = TD->getABITypeSizeInBits(ArrayEltTy); 884 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 885 886 uint64_t Shift; 887 888 if (TD->isBigEndian()) 889 Shift = AllocaSizeBits-ElementOffset; 890 else 891 Shift = 0; 892 893 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 894 // Ignore zero sized fields like {}, they obviously contain no data. 895 if (ElementSizeBits == 0) continue; 896 897 Value *EltVal = SrcVal; 898 if (Shift) { 899 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 900 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 901 "sroa.store.elt", SI); 902 } 903 904 // Truncate down to an integer of the right size. 905 if (ElementSizeBits != AllocaSizeBits) 906 EltVal = new TruncInst(EltVal, IntegerType::get(ElementSizeBits),"",SI); 907 Value *DestField = NewElts[i]; 908 if (EltVal->getType() == ArrayEltTy) { 909 // Storing to an integer field of this size, just do it. 910 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) { 911 // Bitcast to the right element type (for fp/vector values). 912 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI); 913 } else { 914 // Otherwise, bitcast the dest pointer (for aggregates). 915 DestField = new BitCastInst(DestField, 916 PointerType::getUnqual(EltVal->getType()), 917 "", SI); 918 } 919 new StoreInst(EltVal, DestField, SI); 920 921 if (TD->isBigEndian()) 922 Shift -= ElementOffset; 923 else 924 Shift += ElementOffset; 925 } 926 } 927 928 SI->eraseFromParent(); 929} 930 931/// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to 932/// an integer. Load the individual pieces to form the aggregate value. 933void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, 934 SmallVector<AllocaInst*, 32> &NewElts) { 935 // Extract each element out of the NewElts according to its structure offset 936 // and form the result value. 937 const Type *AllocaEltTy = AI->getType()->getElementType(); 938 uint64_t AllocaSizeBits = TD->getABITypeSizeInBits(AllocaEltTy); 939 940 // If this isn't a load of the whole alloca to an integer, it may be a load 941 // of the first element. Just ignore the load in this case and normal SROA 942 // will handle it. 943 if (!isa<IntegerType>(LI->getType()) || 944 TD->getABITypeSizeInBits(LI->getType()) != AllocaSizeBits) 945 return; 946 947 DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI; 948 949 // There are two forms here: AI could be an array or struct. Both cases 950 // have different ways to compute the element offset. 951 const StructLayout *Layout = 0; 952 uint64_t ArrayEltBitOffset = 0; 953 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 954 Layout = TD->getStructLayout(EltSTy); 955 } else { 956 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 957 ArrayEltBitOffset = TD->getABITypeSizeInBits(ArrayEltTy); 958 } 959 960 Value *ResultVal = Constant::getNullValue(LI->getType()); 961 962 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 963 // Load the value from the alloca. If the NewElt is an aggregate, cast 964 // the pointer to an integer of the same size before doing the load. 965 Value *SrcField = NewElts[i]; 966 const Type *FieldTy = 967 cast<PointerType>(SrcField->getType())->getElementType(); 968 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 969 970 // Ignore zero sized fields like {}, they obviously contain no data. 971 if (FieldSizeBits == 0) continue; 972 973 const IntegerType *FieldIntTy = IntegerType::get(FieldSizeBits); 974 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() && 975 !isa<VectorType>(FieldTy)) 976 SrcField = new BitCastInst(SrcField, PointerType::getUnqual(FieldIntTy), 977 "", LI); 978 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 979 980 // If SrcField is a fp or vector of the right size but that isn't an 981 // integer type, bitcast to an integer so we can shift it. 982 if (SrcField->getType() != FieldIntTy) 983 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 984 985 // Zero extend the field to be the same size as the final alloca so that 986 // we can shift and insert it. 987 if (SrcField->getType() != ResultVal->getType()) 988 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 989 990 // Determine the number of bits to shift SrcField. 991 uint64_t Shift; 992 if (Layout) // Struct case. 993 Shift = Layout->getElementOffsetInBits(i); 994 else // Array case. 995 Shift = i*ArrayEltBitOffset; 996 997 if (TD->isBigEndian()) 998 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 999 1000 if (Shift) { 1001 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); 1002 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 1003 } 1004 1005 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 1006 } 1007 1008 LI->replaceAllUsesWith(ResultVal); 1009 LI->eraseFromParent(); 1010} 1011 1012 1013/// HasPadding - Return true if the specified type has any structure or 1014/// alignment padding, false otherwise. 1015static bool HasPadding(const Type *Ty, const TargetData &TD) { 1016 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 1017 const StructLayout *SL = TD.getStructLayout(STy); 1018 unsigned PrevFieldBitOffset = 0; 1019 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 1020 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 1021 1022 // Padding in sub-elements? 1023 if (HasPadding(STy->getElementType(i), TD)) 1024 return true; 1025 1026 // Check to see if there is any padding between this element and the 1027 // previous one. 1028 if (i) { 1029 unsigned PrevFieldEnd = 1030 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 1031 if (PrevFieldEnd < FieldBitOffset) 1032 return true; 1033 } 1034 1035 PrevFieldBitOffset = FieldBitOffset; 1036 } 1037 1038 // Check for tail padding. 1039 if (unsigned EltCount = STy->getNumElements()) { 1040 unsigned PrevFieldEnd = PrevFieldBitOffset + 1041 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 1042 if (PrevFieldEnd < SL->getSizeInBits()) 1043 return true; 1044 } 1045 1046 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1047 return HasPadding(ATy->getElementType(), TD); 1048 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) { 1049 return HasPadding(VTy->getElementType(), TD); 1050 } 1051 return TD.getTypeSizeInBits(Ty) != TD.getABITypeSizeInBits(Ty); 1052} 1053 1054/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 1055/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 1056/// or 1 if safe after canonicalization has been performed. 1057/// 1058int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) { 1059 // Loop over the use list of the alloca. We can only transform it if all of 1060 // the users are safe to transform. 1061 AllocaInfo Info; 1062 1063 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); 1064 I != E; ++I) { 1065 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info); 1066 if (Info.isUnsafe) { 1067 DOUT << "Cannot transform: " << *AI << " due to user: " << **I; 1068 return 0; 1069 } 1070 } 1071 1072 // Okay, we know all the users are promotable. If the aggregate is a memcpy 1073 // source and destination, we have to be careful. In particular, the memcpy 1074 // could be moving around elements that live in structure padding of the LLVM 1075 // types, but may actually be used. In these cases, we refuse to promote the 1076 // struct. 1077 if (Info.isMemCpySrc && Info.isMemCpyDst && 1078 HasPadding(AI->getType()->getElementType(), *TD)) 1079 return 0; 1080 1081 // If we require cleanup, return 1, otherwise return 3. 1082 return Info.needsCanon ? 1 : 3; 1083} 1084 1085/// CanonicalizeAllocaUsers - If SROA reported that it can promote the specified 1086/// allocation, but only if cleaned up, perform the cleanups required. 1087void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) { 1088 // At this point, we know that the end result will be SROA'd and promoted, so 1089 // we can insert ugly code if required so long as sroa+mem2reg will clean it 1090 // up. 1091 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 1092 UI != E; ) { 1093 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI++); 1094 if (!GEPI) continue; 1095 gep_type_iterator I = gep_type_begin(GEPI); 1096 ++I; 1097 1098 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 1099 uint64_t NumElements = AT->getNumElements(); 1100 1101 if (!isa<ConstantInt>(I.getOperand())) { 1102 if (NumElements == 1) { 1103 GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty)); 1104 } else { 1105 assert(NumElements == 2 && "Unhandled case!"); 1106 // All users of the GEP must be loads. At each use of the GEP, insert 1107 // two loads of the appropriate indexed GEP and select between them. 1108 Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(), 1109 Constant::getNullValue(I.getOperand()->getType()), 1110 "isone", GEPI); 1111 // Insert the new GEP instructions, which are properly indexed. 1112 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end()); 1113 Indices[1] = Constant::getNullValue(Type::Int32Ty); 1114 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1115 Indices.begin(), 1116 Indices.end(), 1117 GEPI->getName()+".0", GEPI); 1118 Indices[1] = ConstantInt::get(Type::Int32Ty, 1); 1119 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1120 Indices.begin(), 1121 Indices.end(), 1122 GEPI->getName()+".1", GEPI); 1123 // Replace all loads of the variable index GEP with loads from both 1124 // indexes and a select. 1125 while (!GEPI->use_empty()) { 1126 LoadInst *LI = cast<LoadInst>(GEPI->use_back()); 1127 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI); 1128 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI); 1129 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI); 1130 LI->replaceAllUsesWith(R); 1131 LI->eraseFromParent(); 1132 } 1133 GEPI->eraseFromParent(); 1134 } 1135 } 1136 } 1137 } 1138} 1139 1140/// MergeInType - Add the 'In' type to the accumulated type so far. If the 1141/// types are incompatible, return true, otherwise update Accum and return 1142/// false. 1143/// 1144/// There are three cases we handle here: 1145/// 1) An effectively-integer union, where the pieces are stored into as 1146/// smaller integers (common with byte swap and other idioms). 1147/// 2) A union of vector types of the same size and potentially its elements. 1148/// Here we turn element accesses into insert/extract element operations. 1149/// 3) A union of scalar types, such as int/float or int/pointer. Here we 1150/// merge together into integers, allowing the xform to work with #1 as 1151/// well. 1152static bool MergeInType(const Type *In, const Type *&Accum, 1153 const TargetData &TD) { 1154 // If this is our first type, just use it. 1155 const VectorType *PTy; 1156 if (Accum == Type::VoidTy || In == Accum) { 1157 Accum = In; 1158 } else if (In == Type::VoidTy) { 1159 // Noop. 1160 } else if (In->isInteger() && Accum->isInteger()) { // integer union. 1161 // Otherwise pick whichever type is larger. 1162 if (cast<IntegerType>(In)->getBitWidth() > 1163 cast<IntegerType>(Accum)->getBitWidth()) 1164 Accum = In; 1165 } else if (isa<PointerType>(In) && isa<PointerType>(Accum)) { 1166 // Pointer unions just stay as one of the pointers. 1167 } else if (isa<VectorType>(In) || isa<VectorType>(Accum)) { 1168 if ((PTy = dyn_cast<VectorType>(Accum)) && 1169 PTy->getElementType() == In) { 1170 // Accum is a vector, and we are accessing an element: ok. 1171 } else if ((PTy = dyn_cast<VectorType>(In)) && 1172 PTy->getElementType() == Accum) { 1173 // In is a vector, and accum is an element: ok, remember In. 1174 Accum = In; 1175 } else if ((PTy = dyn_cast<VectorType>(In)) && isa<VectorType>(Accum) && 1176 PTy->getBitWidth() == cast<VectorType>(Accum)->getBitWidth()) { 1177 // Two vectors of the same size: keep Accum. 1178 } else { 1179 // Cannot insert an short into a <4 x int> or handle 1180 // <2 x int> -> <4 x int> 1181 return true; 1182 } 1183 } else { 1184 // Pointer/FP/Integer unions merge together as integers. 1185 switch (Accum->getTypeID()) { 1186 case Type::PointerTyID: Accum = TD.getIntPtrType(); break; 1187 case Type::FloatTyID: Accum = Type::Int32Ty; break; 1188 case Type::DoubleTyID: Accum = Type::Int64Ty; break; 1189 case Type::X86_FP80TyID: return true; 1190 case Type::FP128TyID: return true; 1191 case Type::PPC_FP128TyID: return true; 1192 default: 1193 assert(Accum->isInteger() && "Unknown FP type!"); 1194 break; 1195 } 1196 1197 switch (In->getTypeID()) { 1198 case Type::PointerTyID: In = TD.getIntPtrType(); break; 1199 case Type::FloatTyID: In = Type::Int32Ty; break; 1200 case Type::DoubleTyID: In = Type::Int64Ty; break; 1201 case Type::X86_FP80TyID: return true; 1202 case Type::FP128TyID: return true; 1203 case Type::PPC_FP128TyID: return true; 1204 default: 1205 assert(In->isInteger() && "Unknown FP type!"); 1206 break; 1207 } 1208 return MergeInType(In, Accum, TD); 1209 } 1210 return false; 1211} 1212 1213/// getIntAtLeastAsBigAs - Return an integer type that is at least as big as the 1214/// specified type. If there is no suitable type, this returns null. 1215const Type *getIntAtLeastAsBigAs(unsigned NumBits) { 1216 if (NumBits > 64) return 0; 1217 if (NumBits > 32) return Type::Int64Ty; 1218 if (NumBits > 16) return Type::Int32Ty; 1219 if (NumBits > 8) return Type::Int16Ty; 1220 return Type::Int8Ty; 1221} 1222 1223/// CanConvertToScalar - V is a pointer. If we can convert the pointee to a 1224/// single scalar integer type, return that type. Further, if the use is not 1225/// a completely trivial use that mem2reg could promote, set IsNotTrivial. If 1226/// there are no uses of this pointer, return Type::VoidTy to differentiate from 1227/// failure. 1228/// 1229const Type *SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial) { 1230 const Type *UsedType = Type::VoidTy; // No uses, no forced type. 1231 const PointerType *PTy = cast<PointerType>(V->getType()); 1232 1233 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1234 Instruction *User = cast<Instruction>(*UI); 1235 1236 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1237 // FIXME: Loads of a first class aggregrate value could be converted to a 1238 // series of loads and insertvalues 1239 if (!LI->getType()->isSingleValueType()) 1240 return 0; 1241 1242 if (MergeInType(LI->getType(), UsedType, *TD)) 1243 return 0; 1244 continue; 1245 } 1246 1247 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1248 // Storing the pointer, not into the value? 1249 if (SI->getOperand(0) == V) return 0; 1250 1251 // FIXME: Stores of a first class aggregrate value could be converted to a 1252 // series of extractvalues and stores 1253 if (!SI->getOperand(0)->getType()->isSingleValueType()) 1254 return 0; 1255 1256 // NOTE: We could handle storing of FP imms into integers here! 1257 1258 if (MergeInType(SI->getOperand(0)->getType(), UsedType, *TD)) 1259 return 0; 1260 continue; 1261 } 1262 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 1263 IsNotTrivial = true; 1264 const Type *SubTy = CanConvertToScalar(CI, IsNotTrivial); 1265 if (!SubTy || MergeInType(SubTy, UsedType, *TD)) return 0; 1266 continue; 1267 } 1268 1269 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1270 // Check to see if this is stepping over an element: GEP Ptr, int C 1271 if (GEP->getNumOperands() == 2 && isa<ConstantInt>(GEP->getOperand(1))) { 1272 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue(); 1273 unsigned ElSize = TD->getABITypeSize(PTy->getElementType()); 1274 unsigned BitOffset = Idx*ElSize*8; 1275 if (BitOffset > 64 || !isPowerOf2_32(ElSize)) return 0; 1276 1277 IsNotTrivial = true; 1278 const Type *SubElt = CanConvertToScalar(GEP, IsNotTrivial); 1279 if (SubElt == 0) return 0; 1280 if (SubElt != Type::VoidTy && SubElt->isInteger()) { 1281 const Type *NewTy = 1282 getIntAtLeastAsBigAs(TD->getABITypeSizeInBits(SubElt)+BitOffset); 1283 if (NewTy == 0 || MergeInType(NewTy, UsedType, *TD)) return 0; 1284 continue; 1285 } 1286 // Cannot handle this! 1287 return 0; 1288 } 1289 1290 if (GEP->getNumOperands() == 3 && 1291 isa<ConstantInt>(GEP->getOperand(1)) && 1292 isa<ConstantInt>(GEP->getOperand(2)) && 1293 cast<ConstantInt>(GEP->getOperand(1))->isZero()) { 1294 // We are stepping into an element, e.g. a structure or an array: 1295 // GEP Ptr, i32 0, i32 Cst 1296 const Type *AggTy = PTy->getElementType(); 1297 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 1298 1299 if (const ArrayType *ATy = dyn_cast<ArrayType>(AggTy)) { 1300 if (Idx >= ATy->getNumElements()) return 0; // Out of range. 1301 } else if (const VectorType *VectorTy = dyn_cast<VectorType>(AggTy)) { 1302 // Getting an element of the vector. 1303 if (Idx >= VectorTy->getNumElements()) return 0; // Out of range. 1304 1305 // Merge in the vector type. 1306 if (MergeInType(VectorTy, UsedType, *TD)) return 0; 1307 1308 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); 1309 if (SubTy == 0) return 0; 1310 1311 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, *TD)) 1312 return 0; 1313 1314 // We'll need to change this to an insert/extract element operation. 1315 IsNotTrivial = true; 1316 continue; // Everything looks ok 1317 1318 } else if (isa<StructType>(AggTy)) { 1319 // Structs are always ok. 1320 } else { 1321 return 0; 1322 } 1323 const Type *NTy = getIntAtLeastAsBigAs(TD->getABITypeSizeInBits(AggTy)); 1324 if (NTy == 0 || MergeInType(NTy, UsedType, *TD)) return 0; 1325 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); 1326 if (SubTy == 0) return 0; 1327 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, *TD)) 1328 return 0; 1329 continue; // Everything looks ok 1330 } 1331 return 0; 1332 } 1333 1334 // Cannot handle this! 1335 return 0; 1336 } 1337 1338 return UsedType; 1339} 1340 1341/// ConvertToScalar - The specified alloca passes the CanConvertToScalar 1342/// predicate and is non-trivial. Convert it to something that can be trivially 1343/// promoted into a register by mem2reg. 1344void SROA::ConvertToScalar(AllocationInst *AI, const Type *ActualTy) { 1345 DOUT << "CONVERT TO SCALAR: " << *AI << " TYPE = " 1346 << *ActualTy << "\n"; 1347 ++NumConverted; 1348 1349 BasicBlock *EntryBlock = AI->getParent(); 1350 assert(EntryBlock == &EntryBlock->getParent()->getEntryBlock() && 1351 "Not in the entry block!"); 1352 EntryBlock->getInstList().remove(AI); // Take the alloca out of the program. 1353 1354 // Create and insert the alloca. 1355 AllocaInst *NewAI = new AllocaInst(ActualTy, 0, AI->getName(), 1356 EntryBlock->begin()); 1357 ConvertUsesToScalar(AI, NewAI, 0); 1358 delete AI; 1359} 1360 1361 1362/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 1363/// directly. This happens when we are converting an "integer union" to a 1364/// single integer scalar, or when we are converting a "vector union" to a 1365/// vector with insert/extractelement instructions. 1366/// 1367/// Offset is an offset from the original alloca, in bits that need to be 1368/// shifted to the right. By the end of this, there should be no uses of Ptr. 1369void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset) { 1370 while (!Ptr->use_empty()) { 1371 Instruction *User = cast<Instruction>(Ptr->use_back()); 1372 1373 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1374 Value *NV = ConvertUsesOfLoadToScalar(LI, NewAI, Offset); 1375 LI->replaceAllUsesWith(NV); 1376 LI->eraseFromParent(); 1377 continue; 1378 } 1379 1380 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1381 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 1382 1383 Value *SV = ConvertUsesOfStoreToScalar(SI, NewAI, Offset); 1384 new StoreInst(SV, NewAI, SI); 1385 SI->eraseFromParent(); 1386 continue; 1387 } 1388 1389 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 1390 ConvertUsesToScalar(CI, NewAI, Offset); 1391 CI->eraseFromParent(); 1392 continue; 1393 } 1394 1395 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1396 const PointerType *AggPtrTy = 1397 cast<PointerType>(GEP->getOperand(0)->getType()); 1398 unsigned AggSizeInBits = 1399 TD->getABITypeSizeInBits(AggPtrTy->getElementType()); 1400 1401 // Check to see if this is stepping over an element: GEP Ptr, int C 1402 unsigned NewOffset = Offset; 1403 if (GEP->getNumOperands() == 2) { 1404 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue(); 1405 unsigned BitOffset = Idx*AggSizeInBits; 1406 1407 NewOffset += BitOffset; 1408 ConvertUsesToScalar(GEP, NewAI, NewOffset); 1409 GEP->eraseFromParent(); 1410 continue; 1411 } 1412 1413 assert(GEP->getNumOperands() == 3 && "Unsupported operation"); 1414 1415 // We know that operand #2 is zero. 1416 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 1417 const Type *AggTy = AggPtrTy->getElementType(); 1418 if (const SequentialType *SeqTy = dyn_cast<SequentialType>(AggTy)) { 1419 unsigned ElSizeBits = 1420 TD->getABITypeSizeInBits(SeqTy->getElementType()); 1421 1422 NewOffset += ElSizeBits*Idx; 1423 } else { 1424 const StructType *STy = cast<StructType>(AggTy); 1425 unsigned EltBitOffset = 1426 TD->getStructLayout(STy)->getElementOffsetInBits(Idx); 1427 1428 NewOffset += EltBitOffset; 1429 } 1430 ConvertUsesToScalar(GEP, NewAI, NewOffset); 1431 GEP->eraseFromParent(); 1432 continue; 1433 } 1434 1435 assert(0 && "Unsupported operation!"); 1436 abort(); 1437 } 1438} 1439 1440/// ConvertUsesOfLoadToScalar - Convert all of the users the specified load to 1441/// use the new alloca directly, returning the value that should replace the 1442/// load. This happens when we are converting an "integer union" to a 1443/// single integer scalar, or when we are converting a "vector union" to a 1444/// vector with insert/extractelement instructions. 1445/// 1446/// Offset is an offset from the original alloca, in bits that need to be 1447/// shifted to the right. By the end of this, there should be no uses of Ptr. 1448Value *SROA::ConvertUsesOfLoadToScalar(LoadInst *LI, AllocaInst *NewAI, 1449 unsigned Offset) { 1450 // The load is a bit extract from NewAI shifted right by Offset bits. 1451 Value *NV = new LoadInst(NewAI, LI->getName(), LI); 1452 1453 if (NV->getType() == LI->getType() && Offset == 0) { 1454 // We win, no conversion needed. 1455 return NV; 1456 } 1457 1458 // If the result type of the 'union' is a pointer, then this must be ptr->ptr 1459 // cast. Anything else would result in NV being an integer. 1460 if (isa<PointerType>(NV->getType())) { 1461 assert(isa<PointerType>(LI->getType())); 1462 return new BitCastInst(NV, LI->getType(), LI->getName(), LI); 1463 } 1464 1465 if (const VectorType *VTy = dyn_cast<VectorType>(NV->getType())) { 1466 // If the result alloca is a vector type, this is either an element 1467 // access or a bitcast to another vector type. 1468 if (isa<VectorType>(LI->getType())) 1469 return new BitCastInst(NV, LI->getType(), LI->getName(), LI); 1470 1471 // Otherwise it must be an element access. 1472 unsigned Elt = 0; 1473 if (Offset) { 1474 unsigned EltSize = TD->getABITypeSizeInBits(VTy->getElementType()); 1475 Elt = Offset/EltSize; 1476 Offset -= EltSize*Elt; 1477 } 1478 NV = new ExtractElementInst(NV, ConstantInt::get(Type::Int32Ty, Elt), 1479 "tmp", LI); 1480 1481 // If we're done, return this element. 1482 if (NV->getType() == LI->getType() && Offset == 0) 1483 return NV; 1484 } 1485 1486 const IntegerType *NTy = cast<IntegerType>(NV->getType()); 1487 1488 // If this is a big-endian system and the load is narrower than the 1489 // full alloca type, we need to do a shift to get the right bits. 1490 int ShAmt = 0; 1491 if (TD->isBigEndian()) { 1492 // On big-endian machines, the lowest bit is stored at the bit offset 1493 // from the pointer given by getTypeStoreSizeInBits. This matters for 1494 // integers with a bitwidth that is not a multiple of 8. 1495 ShAmt = TD->getTypeStoreSizeInBits(NTy) - 1496 TD->getTypeStoreSizeInBits(LI->getType()) - Offset; 1497 } else { 1498 ShAmt = Offset; 1499 } 1500 1501 // Note: we support negative bitwidths (with shl) which are not defined. 1502 // We do this to support (f.e.) loads off the end of a structure where 1503 // only some bits are used. 1504 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 1505 NV = BinaryOperator::CreateLShr(NV, 1506 ConstantInt::get(NV->getType(),ShAmt), 1507 LI->getName(), LI); 1508 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 1509 NV = BinaryOperator::CreateShl(NV, 1510 ConstantInt::get(NV->getType(),-ShAmt), 1511 LI->getName(), LI); 1512 1513 // Finally, unconditionally truncate the integer to the right width. 1514 unsigned LIBitWidth = TD->getTypeSizeInBits(LI->getType()); 1515 if (LIBitWidth < NTy->getBitWidth()) 1516 NV = new TruncInst(NV, IntegerType::get(LIBitWidth), 1517 LI->getName(), LI); 1518 1519 // If the result is an integer, this is a trunc or bitcast. 1520 if (isa<IntegerType>(LI->getType())) { 1521 // Should be done. 1522 } else if (LI->getType()->isFloatingPoint()) { 1523 // Just do a bitcast, we know the sizes match up. 1524 NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI); 1525 } else { 1526 // Otherwise must be a pointer. 1527 NV = new IntToPtrInst(NV, LI->getType(), LI->getName(), LI); 1528 } 1529 assert(NV->getType() == LI->getType() && "Didn't convert right?"); 1530 return NV; 1531} 1532 1533 1534/// ConvertUsesOfStoreToScalar - Convert the specified store to a load+store 1535/// pair of the new alloca directly, returning the value that should be stored 1536/// to the alloca. This happens when we are converting an "integer union" to a 1537/// single integer scalar, or when we are converting a "vector union" to a 1538/// vector with insert/extractelement instructions. 1539/// 1540/// Offset is an offset from the original alloca, in bits that need to be 1541/// shifted to the right. By the end of this, there should be no uses of Ptr. 1542Value *SROA::ConvertUsesOfStoreToScalar(StoreInst *SI, AllocaInst *NewAI, 1543 unsigned Offset) { 1544 1545 // Convert the stored type to the actual type, shift it left to insert 1546 // then 'or' into place. 1547 Value *SV = SI->getOperand(0); 1548 const Type *AllocaType = NewAI->getType()->getElementType(); 1549 if (SV->getType() == AllocaType && Offset == 0) { 1550 // All is well. 1551 } else if (const VectorType *PTy = dyn_cast<VectorType>(AllocaType)) { 1552 Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI); 1553 1554 // If the result alloca is a vector type, this is either an element 1555 // access or a bitcast to another vector type. 1556 if (isa<VectorType>(SV->getType())) { 1557 SV = new BitCastInst(SV, AllocaType, SV->getName(), SI); 1558 } else { 1559 // Must be an element insertion. 1560 unsigned Elt = Offset/TD->getABITypeSizeInBits(PTy->getElementType()); 1561 SV = InsertElementInst::Create(Old, SV, 1562 ConstantInt::get(Type::Int32Ty, Elt), 1563 "tmp", SI); 1564 } 1565 } else if (isa<PointerType>(AllocaType)) { 1566 // If the alloca type is a pointer, then all the elements must be 1567 // pointers. 1568 if (SV->getType() != AllocaType) 1569 SV = new BitCastInst(SV, AllocaType, SV->getName(), SI); 1570 } else { 1571 Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI); 1572 1573 // If SV is a float, convert it to the appropriate integer type. 1574 // If it is a pointer, do the same, and also handle ptr->ptr casts 1575 // here. 1576 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType()); 1577 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType); 1578 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType()); 1579 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType); 1580 if (SV->getType()->isFloatingPoint()) 1581 SV = new BitCastInst(SV, IntegerType::get(SrcWidth), 1582 SV->getName(), SI); 1583 else if (isa<PointerType>(SV->getType())) 1584 SV = new PtrToIntInst(SV, TD->getIntPtrType(), SV->getName(), SI); 1585 1586 // Always zero extend the value if needed. 1587 if (SV->getType() != AllocaType) 1588 SV = new ZExtInst(SV, AllocaType, SV->getName(), SI); 1589 1590 // If this is a big-endian system and the store is narrower than the 1591 // full alloca type, we need to do a shift to get the right bits. 1592 int ShAmt = 0; 1593 if (TD->isBigEndian()) { 1594 // On big-endian machines, the lowest bit is stored at the bit offset 1595 // from the pointer given by getTypeStoreSizeInBits. This matters for 1596 // integers with a bitwidth that is not a multiple of 8. 1597 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 1598 } else { 1599 ShAmt = Offset; 1600 } 1601 1602 // Note: we support negative bitwidths (with shr) which are not defined. 1603 // We do this to support (f.e.) stores off the end of a structure where 1604 // only some bits in the structure are set. 1605 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 1606 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 1607 SV = BinaryOperator::CreateShl(SV, 1608 ConstantInt::get(SV->getType(), ShAmt), 1609 SV->getName(), SI); 1610 Mask <<= ShAmt; 1611 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 1612 SV = BinaryOperator::CreateLShr(SV, 1613 ConstantInt::get(SV->getType(),-ShAmt), 1614 SV->getName(), SI); 1615 Mask = Mask.lshr(ShAmt); 1616 } 1617 1618 // Mask out the bits we are about to insert from the old value, and or 1619 // in the new bits. 1620 if (SrcWidth != DestWidth) { 1621 assert(DestWidth > SrcWidth); 1622 Old = BinaryOperator::CreateAnd(Old, ConstantInt::get(~Mask), 1623 Old->getName()+".mask", SI); 1624 SV = BinaryOperator::CreateOr(Old, SV, SV->getName()+".ins", SI); 1625 } 1626 } 1627 return SV; 1628} 1629 1630 1631 1632/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 1633/// some part of a constant global variable. This intentionally only accepts 1634/// constant expressions because we don't can't rewrite arbitrary instructions. 1635static bool PointsToConstantGlobal(Value *V) { 1636 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 1637 return GV->isConstant(); 1638 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 1639 if (CE->getOpcode() == Instruction::BitCast || 1640 CE->getOpcode() == Instruction::GetElementPtr) 1641 return PointsToConstantGlobal(CE->getOperand(0)); 1642 return false; 1643} 1644 1645/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 1646/// pointer to an alloca. Ignore any reads of the pointer, return false if we 1647/// see any stores or other unknown uses. If we see pointer arithmetic, keep 1648/// track of whether it moves the pointer (with isOffset) but otherwise traverse 1649/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 1650/// the alloca, and if the source pointer is a pointer to a constant global, we 1651/// can optimize this. 1652static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy, 1653 bool isOffset) { 1654 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1655 if (isa<LoadInst>(*UI)) { 1656 // Ignore loads, they are always ok. 1657 continue; 1658 } 1659 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) { 1660 // If uses of the bitcast are ok, we are ok. 1661 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 1662 return false; 1663 continue; 1664 } 1665 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) { 1666 // If the GEP has all zero indices, it doesn't offset the pointer. If it 1667 // doesn't, it does. 1668 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 1669 isOffset || !GEP->hasAllZeroIndices())) 1670 return false; 1671 continue; 1672 } 1673 1674 // If this is isn't our memcpy/memmove, reject it as something we can't 1675 // handle. 1676 if (!isa<MemCpyInst>(*UI) && !isa<MemMoveInst>(*UI)) 1677 return false; 1678 1679 // If we already have seen a copy, reject the second one. 1680 if (TheCopy) return false; 1681 1682 // If the pointer has been offset from the start of the alloca, we can't 1683 // safely handle this. 1684 if (isOffset) return false; 1685 1686 // If the memintrinsic isn't using the alloca as the dest, reject it. 1687 if (UI.getOperandNo() != 1) return false; 1688 1689 MemIntrinsic *MI = cast<MemIntrinsic>(*UI); 1690 1691 // If the source of the memcpy/move is not a constant global, reject it. 1692 if (!PointsToConstantGlobal(MI->getOperand(2))) 1693 return false; 1694 1695 // Otherwise, the transform is safe. Remember the copy instruction. 1696 TheCopy = MI; 1697 } 1698 return true; 1699} 1700 1701/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 1702/// modified by a copy from a constant global. If we can prove this, we can 1703/// replace any uses of the alloca with uses of the global directly. 1704Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) { 1705 Instruction *TheCopy = 0; 1706 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 1707 return TheCopy; 1708 return 0; 1709} 1710