ArgumentPromotion.cpp revision 5e46321d665d6b1f445aff70d8eabb4870a6cf0e
1//===-- ArgumentPromotion.cpp - Promote by-reference arguments ------------===// 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 pass promotes "by reference" arguments to be "by value" arguments. In 11// practice, this means looking for internal functions that have pointer 12// arguments. If it can prove, through the use of alias analysis, that an 13// argument is *only* loaded, then it can pass the value into the function 14// instead of the address of the value. This can cause recursive simplification 15// of code and lead to the elimination of allocas (especially in C++ template 16// code like the STL). 17// 18// This pass also handles aggregate arguments that are passed into a function, 19// scalarizing them if the elements of the aggregate are only loaded. Note that 20// by default it refuses to scalarize aggregates which would require passing in more than 21// three operands to the function, because passing thousands of operands for a 22// large array or structure is unprofitable! This limit is can be configured or 23// disabled, however. 24// 25// Note that this transformation could also be done for arguments that are only 26// stored to (returning the value instead), but does not currently. This case 27// would be best handled when and if LLVM begins supporting multiple return 28// values from functions. 29// 30//===----------------------------------------------------------------------===// 31 32#define DEBUG_TYPE "argpromotion" 33#include "llvm/Transforms/IPO.h" 34#include "llvm/Constants.h" 35#include "llvm/DerivedTypes.h" 36#include "llvm/Module.h" 37#include "llvm/CallGraphSCCPass.h" 38#include "llvm/Instructions.h" 39#include "llvm/Analysis/AliasAnalysis.h" 40#include "llvm/Analysis/CallGraph.h" 41#include "llvm/Target/TargetData.h" 42#include "llvm/Support/CallSite.h" 43#include "llvm/Support/CFG.h" 44#include "llvm/Support/Debug.h" 45#include "llvm/ADT/DepthFirstIterator.h" 46#include "llvm/ADT/Statistic.h" 47#include "llvm/ADT/StringExtras.h" 48#include "llvm/Support/Compiler.h" 49#include <set> 50using namespace llvm; 51 52STATISTIC(NumArgumentsPromoted , "Number of pointer arguments promoted"); 53STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted"); 54STATISTIC(NumByValArgsPromoted , "Number of byval arguments promoted"); 55STATISTIC(NumArgumentsDead , "Number of dead pointer args eliminated"); 56 57namespace { 58 /// ArgPromotion - The 'by reference' to 'by value' argument promotion pass. 59 /// 60 struct VISIBILITY_HIDDEN ArgPromotion : public CallGraphSCCPass { 61 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 62 AU.addRequired<AliasAnalysis>(); 63 AU.addRequired<TargetData>(); 64 CallGraphSCCPass::getAnalysisUsage(AU); 65 } 66 67 virtual bool runOnSCC(const std::vector<CallGraphNode *> &SCC); 68 static char ID; // Pass identification, replacement for typeid 69 ArgPromotion(unsigned maxElements = 3) : CallGraphSCCPass((intptr_t)&ID), 70 maxElements(maxElements) {} 71 72 private: 73 bool PromoteArguments(CallGraphNode *CGN); 74 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const; 75 Function *DoPromotion(Function *F, 76 SmallPtrSet<Argument*, 8> &ArgsToPromote, 77 SmallPtrSet<Argument*, 8> &ByValArgsToTransform); 78 /// The maximum number of elements to expand, or 0 for unlimited. 79 unsigned maxElements; 80 }; 81} 82 83char ArgPromotion::ID = 0; 84static RegisterPass<ArgPromotion> 85X("argpromotion", "Promote 'by reference' arguments to scalars"); 86 87Pass *llvm::createArgumentPromotionPass(unsigned maxElements) { 88 return new ArgPromotion(maxElements); 89} 90 91bool ArgPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) { 92 bool Changed = false, LocalChange; 93 94 do { // Iterate until we stop promoting from this SCC. 95 LocalChange = false; 96 // Attempt to promote arguments from all functions in this SCC. 97 for (unsigned i = 0, e = SCC.size(); i != e; ++i) 98 LocalChange |= PromoteArguments(SCC[i]); 99 Changed |= LocalChange; // Remember that we changed something. 100 } while (LocalChange); 101 102 return Changed; 103} 104 105/// PromoteArguments - This method checks the specified function to see if there 106/// are any promotable arguments and if it is safe to promote the function (for 107/// example, all callers are direct). If safe to promote some arguments, it 108/// calls the DoPromotion method. 109/// 110bool ArgPromotion::PromoteArguments(CallGraphNode *CGN) { 111 Function *F = CGN->getFunction(); 112 113 // Make sure that it is local to this module. 114 if (!F || !F->hasInternalLinkage()) return false; 115 116 // First check: see if there are any pointer arguments! If not, quick exit. 117 SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs; 118 unsigned ArgNo = 0; 119 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); 120 I != E; ++I, ++ArgNo) 121 if (isa<PointerType>(I->getType())) 122 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo)); 123 if (PointerArgs.empty()) return false; 124 125 // Second check: make sure that all callers are direct callers. We can't 126 // transform functions that have indirect callers. 127 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); 128 UI != E; ++UI) { 129 CallSite CS = CallSite::get(*UI); 130 if (!CS.getInstruction()) // "Taking the address" of the function 131 return false; 132 133 // Ensure that this call site is CALLING the function, not passing it as 134 // an argument. 135 if (UI.getOperandNo() != 0) 136 return false; 137 } 138 139 // Check to see which arguments are promotable. If an argument is promotable, 140 // add it to ArgsToPromote. 141 SmallPtrSet<Argument*, 8> ArgsToPromote; 142 SmallPtrSet<Argument*, 8> ByValArgsToTransform; 143 for (unsigned i = 0; i != PointerArgs.size(); ++i) { 144 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, ParamAttr::ByVal); 145 146 // If this is a byval argument, and if the aggregate type is small, just 147 // pass the elements, which is always safe. 148 Argument *PtrArg = PointerArgs[i].first; 149 if (isByVal) { 150 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType(); 151 if (const StructType *STy = dyn_cast<StructType>(AgTy)) { 152 if (maxElements > 0 && STy->getNumElements() > maxElements) { 153 DOUT << "argpromotion disable promoting argument '" 154 << PtrArg->getName() << "' because it would require adding more " 155 << "than " << maxElements << " arguments to the function.\n"; 156 } else { 157 // If all the elements are single-value types, we can promote it. 158 bool AllSimple = true; 159 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 160 if (!STy->getElementType(i)->isSingleValueType()) { 161 AllSimple = false; 162 break; 163 } 164 165 // Safe to transform, don't even bother trying to "promote" it. 166 // Passing the elements as a scalar will allow scalarrepl to hack on 167 // the new alloca we introduce. 168 if (AllSimple) { 169 ByValArgsToTransform.insert(PtrArg); 170 continue; 171 } 172 } 173 } 174 } 175 176 // Otherwise, see if we can promote the pointer to its value. 177 if (isSafeToPromoteArgument(PtrArg, isByVal)) 178 ArgsToPromote.insert(PtrArg); 179 } 180 181 // No promotable pointer arguments. 182 if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) return false; 183 184 Function *NewF = DoPromotion(F, ArgsToPromote, ByValArgsToTransform); 185 186 // Update the call graph to know that the function has been transformed. 187 getAnalysis<CallGraph>().changeFunction(F, NewF); 188 return true; 189} 190 191/// IsAlwaysValidPointer - Return true if the specified pointer is always legal 192/// to load. 193static bool IsAlwaysValidPointer(Value *V) { 194 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true; 195 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) 196 return IsAlwaysValidPointer(GEP->getOperand(0)); 197 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 198 if (CE->getOpcode() == Instruction::GetElementPtr) 199 return IsAlwaysValidPointer(CE->getOperand(0)); 200 201 return false; 202} 203 204/// AllCalleesPassInValidPointerForArgument - Return true if we can prove that 205/// all callees pass in a valid pointer for the specified function argument. 206static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) { 207 Function *Callee = Arg->getParent(); 208 209 unsigned ArgNo = std::distance(Callee->arg_begin(), 210 Function::arg_iterator(Arg)); 211 212 // Look at all call sites of the function. At this pointer we know we only 213 // have direct callees. 214 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end(); 215 UI != E; ++UI) { 216 CallSite CS = CallSite::get(*UI); 217 assert(CS.getInstruction() && "Should only have direct calls!"); 218 219 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo))) 220 return false; 221 } 222 return true; 223} 224 225 226/// isSafeToPromoteArgument - As you might guess from the name of this method, 227/// it checks to see if it is both safe and useful to promote the argument. 228/// This method limits promotion of aggregates to only promote up to three 229/// elements of the aggregate in order to avoid exploding the number of 230/// arguments passed in. 231bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const { 232 // We can only promote this argument if all of the uses are loads, or are GEP 233 // instructions (with constant indices) that are subsequently loaded. 234 235 // We can also only promote the load if we can guarantee that it will happen. 236 // Promoting a load causes the load to be unconditionally executed in the 237 // caller, so we can't turn a conditional load into an unconditional load in 238 // general. 239 bool SafeToUnconditionallyLoad = false; 240 if (isByVal) // ByVal arguments are always safe to load from. 241 SafeToUnconditionallyLoad = true; 242 243 BasicBlock *EntryBlock = Arg->getParent()->begin(); 244 SmallVector<LoadInst*, 16> Loads; 245 std::vector<SmallVector<ConstantInt*, 8> > GEPIndices; 246 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end(); 247 UI != E; ++UI) 248 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 249 if (LI->isVolatile()) return false; // Don't hack volatile loads 250 Loads.push_back(LI); 251 252 // If this load occurs in the entry block, then the pointer is 253 // unconditionally loaded. 254 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock; 255 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) { 256 if (GEP->use_empty()) { 257 // Dead GEP's cause trouble later. Just remove them if we run into 258 // them. 259 getAnalysis<AliasAnalysis>().deleteValue(GEP); 260 GEP->eraseFromParent(); 261 return isSafeToPromoteArgument(Arg, isByVal); 262 } 263 // Ensure that all of the indices are constants. 264 SmallVector<ConstantInt*, 8> Operands; 265 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); 266 i != e; ++i) 267 if (ConstantInt *C = dyn_cast<ConstantInt>(*i)) 268 Operands.push_back(C); 269 else 270 return false; // Not a constant operand GEP! 271 272 // Ensure that the only users of the GEP are load instructions. 273 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end(); 274 UI != E; ++UI) 275 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 276 if (LI->isVolatile()) return false; // Don't hack volatile loads 277 Loads.push_back(LI); 278 279 // If this load occurs in the entry block, then the pointer is 280 // unconditionally loaded. 281 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock; 282 } else { 283 return false; 284 } 285 286 // See if there is already a GEP with these indices. If not, check to 287 // make sure that we aren't promoting too many elements. If so, nothing 288 // to do. 289 if (std::find(GEPIndices.begin(), GEPIndices.end(), Operands) == 290 GEPIndices.end()) { 291 if (maxElements > 0 && GEPIndices.size() == maxElements) { 292 DOUT << "argpromotion disable promoting argument '" 293 << Arg->getName() << "' because it would require adding more " 294 << "than " << maxElements << " arguments to the function.\n"; 295 // We limit aggregate promotion to only promoting up to a fixed number 296 // of elements of the aggregate. 297 return false; 298 } 299 GEPIndices.push_back(Operands); 300 } 301 } else { 302 return false; // Not a load or a GEP. 303 } 304 305 if (Loads.empty()) return true; // No users, this is a dead argument. 306 307 // If we decide that we want to promote this argument, the value is going to 308 // be unconditionally loaded in all callees. This is only safe to do if the 309 // pointer was going to be unconditionally loaded anyway (i.e. there is a load 310 // of the pointer in the entry block of the function) or if we can prove that 311 // all pointers passed in are always to legal locations (for example, no null 312 // pointers are passed in, no pointers to free'd memory, etc). 313 if (!SafeToUnconditionallyLoad && 314 !AllCalleesPassInValidPointerForArgument(Arg)) 315 return false; // Cannot prove that this is safe!! 316 317 // Okay, now we know that the argument is only used by load instructions and 318 // it is safe to unconditionally load the pointer. Use alias analysis to 319 // check to see if the pointer is guaranteed to not be modified from entry of 320 // the function to each of the load instructions. 321 322 // Because there could be several/many load instructions, remember which 323 // blocks we know to be transparent to the load. 324 SmallPtrSet<BasicBlock*, 16> TranspBlocks; 325 326 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 327 TargetData &TD = getAnalysis<TargetData>(); 328 329 for (unsigned i = 0, e = Loads.size(); i != e; ++i) { 330 // Check to see if the load is invalidated from the start of the block to 331 // the load itself. 332 LoadInst *Load = Loads[i]; 333 BasicBlock *BB = Load->getParent(); 334 335 const PointerType *LoadTy = 336 cast<PointerType>(Load->getOperand(0)->getType()); 337 unsigned LoadSize = (unsigned)TD.getTypeStoreSize(LoadTy->getElementType()); 338 339 if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize)) 340 return false; // Pointer is invalidated! 341 342 // Now check every path from the entry block to the load for transparency. 343 // To do this, we perform a depth first search on the inverse CFG from the 344 // loading block. 345 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 346 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> > 347 I = idf_ext_begin(*PI, TranspBlocks), 348 E = idf_ext_end(*PI, TranspBlocks); I != E; ++I) 349 if (AA.canBasicBlockModify(**I, Arg, LoadSize)) 350 return false; 351 } 352 353 // If the path from the entry of the function to each load is free of 354 // instructions that potentially invalidate the load, we can make the 355 // transformation! 356 return true; 357} 358 359namespace { 360 /// GEPIdxComparator - Provide a strong ordering for GEP indices. All Value* 361 /// elements are instances of ConstantInt. 362 /// 363 struct GEPIdxComparator { 364 bool operator()(const std::vector<Value*> &LHS, 365 const std::vector<Value*> &RHS) const { 366 unsigned idx = 0; 367 for (; idx < LHS.size() && idx < RHS.size(); ++idx) { 368 if (LHS[idx] != RHS[idx]) { 369 return cast<ConstantInt>(LHS[idx])->getZExtValue() < 370 cast<ConstantInt>(RHS[idx])->getZExtValue(); 371 } 372 } 373 374 // Return less than if we ran out of stuff in LHS and we didn't run out of 375 // stuff in RHS. 376 return idx == LHS.size() && idx != RHS.size(); 377 } 378 }; 379} 380 381 382/// DoPromotion - This method actually performs the promotion of the specified 383/// arguments, and returns the new function. At this point, we know that it's 384/// safe to do so. 385Function *ArgPromotion::DoPromotion(Function *F, 386 SmallPtrSet<Argument*, 8> &ArgsToPromote, 387 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) { 388 389 // Start by computing a new prototype for the function, which is the same as 390 // the old function, but has modified arguments. 391 const FunctionType *FTy = F->getFunctionType(); 392 std::vector<const Type*> Params; 393 394 typedef std::set<std::vector<Value*>, GEPIdxComparator> ScalarizeTable; 395 396 // ScalarizedElements - If we are promoting a pointer that has elements 397 // accessed out of it, keep track of which elements are accessed so that we 398 // can add one argument for each. 399 // 400 // Arguments that are directly loaded will have a zero element value here, to 401 // handle cases where there are both a direct load and GEP accesses. 402 // 403 std::map<Argument*, ScalarizeTable> ScalarizedElements; 404 405 // OriginalLoads - Keep track of a representative load instruction from the 406 // original function so that we can tell the alias analysis implementation 407 // what the new GEP/Load instructions we are inserting look like. 408 std::map<std::vector<Value*>, LoadInst*> OriginalLoads; 409 410 // ParamAttrs - Keep track of the parameter attributes for the arguments 411 // that we are *not* promoting. For the ones that we do promote, the parameter 412 // attributes are lost 413 SmallVector<ParamAttrsWithIndex, 8> ParamAttrsVec; 414 const PAListPtr &PAL = F->getParamAttrs(); 415 416 // Add any return attributes. 417 if (ParameterAttributes attrs = PAL.getParamAttrs(0)) 418 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs)); 419 420 unsigned ArgIndex = 1; 421 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; 422 ++I, ++ArgIndex) { 423 if (ByValArgsToTransform.count(I)) { 424 // Just add all the struct element types. 425 const Type *AgTy = cast<PointerType>(I->getType())->getElementType(); 426 const StructType *STy = cast<StructType>(AgTy); 427 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 428 Params.push_back(STy->getElementType(i)); 429 ++NumByValArgsPromoted; 430 } else if (!ArgsToPromote.count(I)) { 431 Params.push_back(I->getType()); 432 if (ParameterAttributes attrs = PAL.getParamAttrs(ArgIndex)) 433 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), attrs)); 434 } else if (I->use_empty()) { 435 ++NumArgumentsDead; 436 } else { 437 // Okay, this is being promoted. Check to see if there are any GEP uses 438 // of the argument. 439 ScalarizeTable &ArgIndices = ScalarizedElements[I]; 440 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; 441 ++UI) { 442 Instruction *User = cast<Instruction>(*UI); 443 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User)); 444 std::vector<Value*> Indices(User->op_begin()+1, User->op_end()); 445 ArgIndices.insert(Indices); 446 LoadInst *OrigLoad; 447 if (LoadInst *L = dyn_cast<LoadInst>(User)) 448 OrigLoad = L; 449 else 450 OrigLoad = cast<LoadInst>(User->use_back()); 451 OriginalLoads[Indices] = OrigLoad; 452 } 453 454 // Add a parameter to the function for each element passed in. 455 for (ScalarizeTable::iterator SI = ArgIndices.begin(), 456 E = ArgIndices.end(); SI != E; ++SI) 457 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(), 458 SI->begin(), 459 SI->end())); 460 461 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty()) 462 ++NumArgumentsPromoted; 463 else 464 ++NumAggregatesPromoted; 465 } 466 } 467 468 const Type *RetTy = FTy->getReturnType(); 469 470 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which 471 // have zero fixed arguments. 472 bool ExtraArgHack = false; 473 if (Params.empty() && FTy->isVarArg()) { 474 ExtraArgHack = true; 475 Params.push_back(Type::Int32Ty); 476 } 477 478 // Construct the new function type using the new arguments. 479 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg()); 480 481 // Create the new function body and insert it into the module... 482 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName()); 483 NF->copyAttributesFrom(F); 484 485 // Recompute the parameter attributes list based on the new arguments for 486 // the function. 487 NF->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end())); 488 ParamAttrsVec.clear(); 489 490 F->getParent()->getFunctionList().insert(F, NF); 491 NF->takeName(F); 492 493 // Get the alias analysis information that we need to update to reflect our 494 // changes. 495 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 496 497 // Loop over all of the callers of the function, transforming the call sites 498 // to pass in the loaded pointers. 499 // 500 SmallVector<Value*, 16> Args; 501 while (!F->use_empty()) { 502 CallSite CS = CallSite::get(F->use_back()); 503 Instruction *Call = CS.getInstruction(); 504 const PAListPtr &CallPAL = CS.getParamAttrs(); 505 506 // Add any return attributes. 507 if (ParameterAttributes attrs = CallPAL.getParamAttrs(0)) 508 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs)); 509 510 // Loop over the operands, inserting GEP and loads in the caller as 511 // appropriate. 512 CallSite::arg_iterator AI = CS.arg_begin(); 513 ArgIndex = 1; 514 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); 515 I != E; ++I, ++AI, ++ArgIndex) 516 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) { 517 Args.push_back(*AI); // Unmodified argument 518 519 if (ParameterAttributes Attrs = CallPAL.getParamAttrs(ArgIndex)) 520 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); 521 522 } else if (ByValArgsToTransform.count(I)) { 523 // Emit a GEP and load for each element of the struct. 524 const Type *AgTy = cast<PointerType>(I->getType())->getElementType(); 525 const StructType *STy = cast<StructType>(AgTy); 526 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 }; 527 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 528 Idxs[1] = ConstantInt::get(Type::Int32Ty, i); 529 Value *Idx = GetElementPtrInst::Create(*AI, Idxs, Idxs+2, 530 (*AI)->getName()+"."+utostr(i), 531 Call); 532 // TODO: Tell AA about the new values? 533 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call)); 534 } 535 } else if (!I->use_empty()) { 536 // Non-dead argument: insert GEPs and loads as appropriate. 537 ScalarizeTable &ArgIndices = ScalarizedElements[I]; 538 for (ScalarizeTable::iterator SI = ArgIndices.begin(), 539 E = ArgIndices.end(); SI != E; ++SI) { 540 Value *V = *AI; 541 LoadInst *OrigLoad = OriginalLoads[*SI]; 542 if (!SI->empty()) { 543 V = GetElementPtrInst::Create(V, SI->begin(), SI->end(), 544 V->getName()+".idx", Call); 545 AA.copyValue(OrigLoad->getOperand(0), V); 546 } 547 Args.push_back(new LoadInst(V, V->getName()+".val", Call)); 548 AA.copyValue(OrigLoad, Args.back()); 549 } 550 } 551 552 if (ExtraArgHack) 553 Args.push_back(Constant::getNullValue(Type::Int32Ty)); 554 555 // Push any varargs arguments on the list 556 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) { 557 Args.push_back(*AI); 558 if (ParameterAttributes Attrs = CallPAL.getParamAttrs(ArgIndex)) 559 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); 560 } 561 562 Instruction *New; 563 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) { 564 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(), 565 Args.begin(), Args.end(), "", Call); 566 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv()); 567 cast<InvokeInst>(New)->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), 568 ParamAttrsVec.end())); 569 } else { 570 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call); 571 cast<CallInst>(New)->setCallingConv(CS.getCallingConv()); 572 cast<CallInst>(New)->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), 573 ParamAttrsVec.end())); 574 if (cast<CallInst>(Call)->isTailCall()) 575 cast<CallInst>(New)->setTailCall(); 576 } 577 Args.clear(); 578 ParamAttrsVec.clear(); 579 580 // Update the alias analysis implementation to know that we are replacing 581 // the old call with a new one. 582 AA.replaceWithNewValue(Call, New); 583 584 if (!Call->use_empty()) { 585 Call->replaceAllUsesWith(New); 586 New->takeName(Call); 587 } 588 589 // Finally, remove the old call from the program, reducing the use-count of 590 // F. 591 Call->eraseFromParent(); 592 } 593 594 // Since we have now created the new function, splice the body of the old 595 // function right into the new function, leaving the old rotting hulk of the 596 // function empty. 597 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList()); 598 599 // Loop over the argument list, transfering uses of the old arguments over to 600 // the new arguments, also transfering over the names as well. 601 // 602 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(), 603 I2 = NF->arg_begin(); I != E; ++I) { 604 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) { 605 // If this is an unmodified argument, move the name and users over to the 606 // new version. 607 I->replaceAllUsesWith(I2); 608 I2->takeName(I); 609 AA.replaceWithNewValue(I, I2); 610 ++I2; 611 continue; 612 } 613 614 if (ByValArgsToTransform.count(I)) { 615 // In the callee, we create an alloca, and store each of the new incoming 616 // arguments into the alloca. 617 Instruction *InsertPt = NF->begin()->begin(); 618 619 // Just add all the struct element types. 620 const Type *AgTy = cast<PointerType>(I->getType())->getElementType(); 621 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt); 622 const StructType *STy = cast<StructType>(AgTy); 623 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 }; 624 625 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 626 Idxs[1] = ConstantInt::get(Type::Int32Ty, i); 627 Value *Idx = GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2, 628 TheAlloca->getName()+"."+utostr(i), 629 InsertPt); 630 I2->setName(I->getName()+"."+utostr(i)); 631 new StoreInst(I2++, Idx, InsertPt); 632 } 633 634 // Anything that used the arg should now use the alloca. 635 I->replaceAllUsesWith(TheAlloca); 636 TheAlloca->takeName(I); 637 AA.replaceWithNewValue(I, TheAlloca); 638 continue; 639 } 640 641 if (I->use_empty()) { 642 AA.deleteValue(I); 643 continue; 644 } 645 646 // Otherwise, if we promoted this argument, then all users are load 647 // instructions, and all loads should be using the new argument that we 648 // added. 649 ScalarizeTable &ArgIndices = ScalarizedElements[I]; 650 651 while (!I->use_empty()) { 652 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) { 653 assert(ArgIndices.begin()->empty() && 654 "Load element should sort to front!"); 655 I2->setName(I->getName()+".val"); 656 LI->replaceAllUsesWith(I2); 657 AA.replaceWithNewValue(LI, I2); 658 LI->eraseFromParent(); 659 DOUT << "*** Promoted load of argument '" << I->getName() 660 << "' in function '" << F->getName() << "'\n"; 661 } else { 662 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back()); 663 std::vector<Value*> Operands(GEP->op_begin()+1, GEP->op_end()); 664 665 Function::arg_iterator TheArg = I2; 666 for (ScalarizeTable::iterator It = ArgIndices.begin(); 667 *It != Operands; ++It, ++TheArg) { 668 assert(It != ArgIndices.end() && "GEP not handled??"); 669 } 670 671 std::string NewName = I->getName(); 672 for (unsigned i = 0, e = Operands.size(); i != e; ++i) 673 if (ConstantInt *CI = dyn_cast<ConstantInt>(Operands[i])) 674 NewName += "." + CI->getValue().toStringUnsigned(10); 675 else 676 NewName += ".x"; 677 TheArg->setName(NewName+".val"); 678 679 DOUT << "*** Promoted agg argument '" << TheArg->getName() 680 << "' of function '" << F->getName() << "'\n"; 681 682 // All of the uses must be load instructions. Replace them all with 683 // the argument specified by ArgNo. 684 while (!GEP->use_empty()) { 685 LoadInst *L = cast<LoadInst>(GEP->use_back()); 686 L->replaceAllUsesWith(TheArg); 687 AA.replaceWithNewValue(L, TheArg); 688 L->eraseFromParent(); 689 } 690 AA.deleteValue(GEP); 691 GEP->eraseFromParent(); 692 } 693 } 694 695 // Increment I2 past all of the arguments added for this promoted pointer. 696 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i) 697 ++I2; 698 } 699 700 // Notify the alias analysis implementation that we inserted a new argument. 701 if (ExtraArgHack) 702 AA.copyValue(Constant::getNullValue(Type::Int32Ty), NF->arg_begin()); 703 704 705 // Tell the alias analysis that the old function is about to disappear. 706 AA.replaceWithNewValue(F, NF); 707 708 // Now that the old function is dead, delete it. 709 F->eraseFromParent(); 710 return NF; 711} 712