ArgumentPromotion.cpp revision 089efffd7d1ca0d10522ace38d36e0a67f4fac2d
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), maxElements(maxElements) {} 70 71 private: 72 bool PromoteArguments(CallGraphNode *CGN); 73 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const; 74 Function *DoPromotion(Function *F, 75 SmallPtrSet<Argument*, 8> &ArgsToPromote, 76 SmallPtrSet<Argument*, 8> &ByValArgsToTransform); 77 /// The maximum number of elements to expand, or 0 for unlimited. 78 unsigned maxElements; 79 }; 80} 81 82char ArgPromotion::ID = 0; 83static RegisterPass<ArgPromotion> 84X("argpromotion", "Promote 'by reference' arguments to scalars"); 85 86Pass *llvm::createArgumentPromotionPass(unsigned maxElements) { 87 return new ArgPromotion(maxElements); 88} 89 90bool ArgPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) { 91 bool Changed = false, LocalChange; 92 93 do { // Iterate until we stop promoting from this SCC. 94 LocalChange = false; 95 // Attempt to promote arguments from all functions in this SCC. 96 for (unsigned i = 0, e = SCC.size(); i != e; ++i) 97 LocalChange |= PromoteArguments(SCC[i]); 98 Changed |= LocalChange; // Remember that we changed something. 99 } while (LocalChange); 100 101 return Changed; 102} 103 104/// PromoteArguments - This method checks the specified function to see if there 105/// are any promotable arguments and if it is safe to promote the function (for 106/// example, all callers are direct). If safe to promote some arguments, it 107/// calls the DoPromotion method. 108/// 109bool ArgPromotion::PromoteArguments(CallGraphNode *CGN) { 110 Function *F = CGN->getFunction(); 111 112 // Make sure that it is local to this module. 113 if (!F || !F->hasInternalLinkage()) return false; 114 115 // First check: see if there are any pointer arguments! If not, quick exit. 116 SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs; 117 unsigned ArgNo = 0; 118 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); 119 I != E; ++I, ++ArgNo) 120 if (isa<PointerType>(I->getType())) 121 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo)); 122 if (PointerArgs.empty()) return false; 123 124 // Second check: make sure that all callers are direct callers. We can't 125 // transform functions that have indirect callers. 126 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); 127 UI != E; ++UI) { 128 CallSite CS = CallSite::get(*UI); 129 if (!CS.getInstruction()) // "Taking the address" of the function 130 return false; 131 132 // Ensure that this call site is CALLING the function, not passing it as 133 // an argument. 134 if (UI.getOperandNo() != 0) 135 return false; 136 } 137 138 // Check to see which arguments are promotable. If an argument is promotable, 139 // add it to ArgsToPromote. 140 SmallPtrSet<Argument*, 8> ArgsToPromote; 141 SmallPtrSet<Argument*, 8> ByValArgsToTransform; 142 for (unsigned i = 0; i != PointerArgs.size(); ++i) { 143 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, ParamAttr::ByVal); 144 145 // If this is a byval argument, and if the aggregate type is small, just 146 // pass the elements, which is always safe. 147 Argument *PtrArg = PointerArgs[i].first; 148 if (isByVal) { 149 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType(); 150 if (const StructType *STy = dyn_cast<StructType>(AgTy)) 151 if (maxElements > 0 && STy->getNumElements() > maxElements) { 152 DOUT << "argpromotion disable promoting argument '" 153 << PtrArg->getName() << "' because it would require adding more " 154 << "than " << maxElements << " arguments to the function.\n"; 155 } else { 156 // If all the elements are first class types, we can promote it. 157 bool AllSimple = true; 158 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 159 if (!STy->getElementType(i)->isFirstClassType()) { 160 AllSimple = false; 161 break; 162 } 163 164 // Safe to transform, don't even bother trying to "promote" it. 165 // Passing the elements as a scalar will allow scalarrepl to hack on 166 // the new alloca we introduce. 167 if (AllSimple) { 168 ByValArgsToTransform.insert(PtrArg); 169 continue; 170 } 171 } 172 } 173 174 // Otherwise, see if we can promote the pointer to its value. 175 if (isSafeToPromoteArgument(PtrArg, isByVal)) 176 ArgsToPromote.insert(PtrArg); 177 } 178 179 // No promotable pointer arguments. 180 if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) return false; 181 182 Function *NewF = DoPromotion(F, ArgsToPromote, ByValArgsToTransform); 183 184 // Update the call graph to know that the function has been transformed. 185 getAnalysis<CallGraph>().changeFunction(F, NewF); 186 return true; 187} 188 189/// IsAlwaysValidPointer - Return true if the specified pointer is always legal 190/// to load. 191static bool IsAlwaysValidPointer(Value *V) { 192 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true; 193 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) 194 return IsAlwaysValidPointer(GEP->getOperand(0)); 195 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 196 if (CE->getOpcode() == Instruction::GetElementPtr) 197 return IsAlwaysValidPointer(CE->getOperand(0)); 198 199 return false; 200} 201 202/// AllCalleesPassInValidPointerForArgument - Return true if we can prove that 203/// all callees pass in a valid pointer for the specified function argument. 204static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) { 205 Function *Callee = Arg->getParent(); 206 207 unsigned ArgNo = std::distance(Callee->arg_begin(), 208 Function::arg_iterator(Arg)); 209 210 // Look at all call sites of the function. At this pointer we know we only 211 // have direct callees. 212 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end(); 213 UI != E; ++UI) { 214 CallSite CS = CallSite::get(*UI); 215 assert(CS.getInstruction() && "Should only have direct calls!"); 216 217 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo))) 218 return false; 219 } 220 return true; 221} 222 223 224/// isSafeToPromoteArgument - As you might guess from the name of this method, 225/// it checks to see if it is both safe and useful to promote the argument. 226/// This method limits promotion of aggregates to only promote up to three 227/// elements of the aggregate in order to avoid exploding the number of 228/// arguments passed in. 229bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const { 230 // We can only promote this argument if all of the uses are loads, or are GEP 231 // instructions (with constant indices) that are subsequently loaded. 232 233 // We can also only promote the load if we can guarantee that it will happen. 234 // Promoting a load causes the load to be unconditionally executed in the 235 // caller, so we can't turn a conditional load into an unconditional load in 236 // general. 237 bool SafeToUnconditionallyLoad = false; 238 if (isByVal) // ByVal arguments are always safe to load from. 239 SafeToUnconditionallyLoad = true; 240 241 BasicBlock *EntryBlock = Arg->getParent()->begin(); 242 SmallVector<LoadInst*, 16> Loads; 243 std::vector<SmallVector<ConstantInt*, 8> > GEPIndices; 244 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end(); 245 UI != E; ++UI) 246 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 247 if (LI->isVolatile()) return false; // Don't hack volatile loads 248 Loads.push_back(LI); 249 250 // If this load occurs in the entry block, then the pointer is 251 // unconditionally loaded. 252 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock; 253 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) { 254 if (GEP->use_empty()) { 255 // Dead GEP's cause trouble later. Just remove them if we run into 256 // them. 257 getAnalysis<AliasAnalysis>().deleteValue(GEP); 258 GEP->eraseFromParent(); 259 return isSafeToPromoteArgument(Arg, isByVal); 260 } 261 // Ensure that all of the indices are constants. 262 SmallVector<ConstantInt*, 8> Operands; 263 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i) 264 if (ConstantInt *C = dyn_cast<ConstantInt>(GEP->getOperand(i))) 265 Operands.push_back(C); 266 else 267 return false; // Not a constant operand GEP! 268 269 // Ensure that the only users of the GEP are load instructions. 270 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end(); 271 UI != E; ++UI) 272 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 273 if (LI->isVolatile()) return false; // Don't hack volatile loads 274 Loads.push_back(LI); 275 276 // If this load occurs in the entry block, then the pointer is 277 // unconditionally loaded. 278 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock; 279 } else { 280 return false; 281 } 282 283 // See if there is already a GEP with these indices. If not, check to 284 // make sure that we aren't promoting too many elements. If so, nothing 285 // to do. 286 if (std::find(GEPIndices.begin(), GEPIndices.end(), Operands) == 287 GEPIndices.end()) { 288 if (maxElements > 0 && GEPIndices.size() == maxElements) { 289 DOUT << "argpromotion disable promoting argument '" 290 << Arg->getName() << "' because it would require adding more " 291 << "than " << maxElements << " arguments to the function.\n"; 292 // We limit aggregate promotion to only promoting up to a fixed number 293 // of elements of the aggregate. 294 return false; 295 } 296 GEPIndices.push_back(Operands); 297 } 298 } else { 299 return false; // Not a load or a GEP. 300 } 301 302 if (Loads.empty()) return true; // No users, this is a dead argument. 303 304 // If we decide that we want to promote this argument, the value is going to 305 // be unconditionally loaded in all callees. This is only safe to do if the 306 // pointer was going to be unconditionally loaded anyway (i.e. there is a load 307 // of the pointer in the entry block of the function) or if we can prove that 308 // all pointers passed in are always to legal locations (for example, no null 309 // pointers are passed in, no pointers to free'd memory, etc). 310 if (!SafeToUnconditionallyLoad && 311 !AllCalleesPassInValidPointerForArgument(Arg)) 312 return false; // Cannot prove that this is safe!! 313 314 // Okay, now we know that the argument is only used by load instructions and 315 // it is safe to unconditionally load the pointer. Use alias analysis to 316 // check to see if the pointer is guaranteed to not be modified from entry of 317 // the function to each of the load instructions. 318 319 // Because there could be several/many load instructions, remember which 320 // blocks we know to be transparent to the load. 321 SmallPtrSet<BasicBlock*, 16> TranspBlocks; 322 323 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 324 TargetData &TD = getAnalysis<TargetData>(); 325 326 for (unsigned i = 0, e = Loads.size(); i != e; ++i) { 327 // Check to see if the load is invalidated from the start of the block to 328 // the load itself. 329 LoadInst *Load = Loads[i]; 330 BasicBlock *BB = Load->getParent(); 331 332 const PointerType *LoadTy = 333 cast<PointerType>(Load->getOperand(0)->getType()); 334 unsigned LoadSize = (unsigned)TD.getTypeStoreSize(LoadTy->getElementType()); 335 336 if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize)) 337 return false; // Pointer is invalidated! 338 339 // Now check every path from the entry block to the load for transparency. 340 // To do this, we perform a depth first search on the inverse CFG from the 341 // loading block. 342 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 343 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> > 344 I = idf_ext_begin(*PI, TranspBlocks), 345 E = idf_ext_end(*PI, TranspBlocks); I != E; ++I) 346 if (AA.canBasicBlockModify(**I, Arg, LoadSize)) 347 return false; 348 } 349 350 // If the path from the entry of the function to each load is free of 351 // instructions that potentially invalidate the load, we can make the 352 // transformation! 353 return true; 354} 355 356namespace { 357 /// GEPIdxComparator - Provide a strong ordering for GEP indices. All Value* 358 /// elements are instances of ConstantInt. 359 /// 360 struct GEPIdxComparator { 361 bool operator()(const std::vector<Value*> &LHS, 362 const std::vector<Value*> &RHS) const { 363 unsigned idx = 0; 364 for (; idx < LHS.size() && idx < RHS.size(); ++idx) { 365 if (LHS[idx] != RHS[idx]) { 366 return cast<ConstantInt>(LHS[idx])->getZExtValue() < 367 cast<ConstantInt>(RHS[idx])->getZExtValue(); 368 } 369 } 370 371 // Return less than if we ran out of stuff in LHS and we didn't run out of 372 // stuff in RHS. 373 return idx == LHS.size() && idx != RHS.size(); 374 } 375 }; 376} 377 378 379/// DoPromotion - This method actually performs the promotion of the specified 380/// arguments, and returns the new function. At this point, we know that it's 381/// safe to do so. 382Function *ArgPromotion::DoPromotion(Function *F, 383 SmallPtrSet<Argument*, 8> &ArgsToPromote, 384 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) { 385 386 // Start by computing a new prototype for the function, which is the same as 387 // the old function, but has modified arguments. 388 const FunctionType *FTy = F->getFunctionType(); 389 std::vector<const Type*> Params; 390 391 typedef std::set<std::vector<Value*>, GEPIdxComparator> ScalarizeTable; 392 393 // ScalarizedElements - If we are promoting a pointer that has elements 394 // accessed out of it, keep track of which elements are accessed so that we 395 // can add one argument for each. 396 // 397 // Arguments that are directly loaded will have a zero element value here, to 398 // handle cases where there are both a direct load and GEP accesses. 399 // 400 std::map<Argument*, ScalarizeTable> ScalarizedElements; 401 402 // OriginalLoads - Keep track of a representative load instruction from the 403 // original function so that we can tell the alias analysis implementation 404 // what the new GEP/Load instructions we are inserting look like. 405 std::map<std::vector<Value*>, LoadInst*> OriginalLoads; 406 407 // ParamAttrs - Keep track of the parameter attributes for the arguments 408 // that we are *not* promoting. For the ones that we do promote, the parameter 409 // attributes are lost 410 SmallVector<ParamAttrsWithIndex, 8> ParamAttrsVec; 411 const PAListPtr &PAL = F->getParamAttrs(); 412 413 // Add any return attributes. 414 if (ParameterAttributes attrs = PAL.getParamAttrs(0)) 415 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs)); 416 417 unsigned ArgIndex = 1; 418 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; 419 ++I, ++ArgIndex) { 420 if (ByValArgsToTransform.count(I)) { 421 // Just add all the struct element types. 422 const Type *AgTy = cast<PointerType>(I->getType())->getElementType(); 423 const StructType *STy = cast<StructType>(AgTy); 424 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 425 Params.push_back(STy->getElementType(i)); 426 ++NumByValArgsPromoted; 427 } else if (!ArgsToPromote.count(I)) { 428 Params.push_back(I->getType()); 429 if (ParameterAttributes attrs = PAL.getParamAttrs(ArgIndex)) 430 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), attrs)); 431 } else if (I->use_empty()) { 432 ++NumArgumentsDead; 433 } else { 434 // Okay, this is being promoted. Check to see if there are any GEP uses 435 // of the argument. 436 ScalarizeTable &ArgIndices = ScalarizedElements[I]; 437 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; 438 ++UI) { 439 Instruction *User = cast<Instruction>(*UI); 440 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User)); 441 std::vector<Value*> Indices(User->op_begin()+1, User->op_end()); 442 ArgIndices.insert(Indices); 443 LoadInst *OrigLoad; 444 if (LoadInst *L = dyn_cast<LoadInst>(User)) 445 OrigLoad = L; 446 else 447 OrigLoad = cast<LoadInst>(User->use_back()); 448 OriginalLoads[Indices] = OrigLoad; 449 } 450 451 // Add a parameter to the function for each element passed in. 452 for (ScalarizeTable::iterator SI = ArgIndices.begin(), 453 E = ArgIndices.end(); SI != E; ++SI) 454 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(), 455 SI->begin(), 456 SI->end())); 457 458 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty()) 459 ++NumArgumentsPromoted; 460 else 461 ++NumAggregatesPromoted; 462 } 463 } 464 465 const Type *RetTy = FTy->getReturnType(); 466 467 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which 468 // have zero fixed arguments. 469 bool ExtraArgHack = false; 470 if (Params.empty() && FTy->isVarArg()) { 471 ExtraArgHack = true; 472 Params.push_back(Type::Int32Ty); 473 } 474 475 // Construct the new function type using the new arguments. 476 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg()); 477 478 // Create the new function body and insert it into the module... 479 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName()); 480 NF->setCallingConv(F->getCallingConv()); 481 482 // Recompute the parameter attributes list based on the new arguments for 483 // the function. 484 NF->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end())); 485 ParamAttrsVec.clear(); 486 487 if (F->hasCollector()) 488 NF->setCollector(F->getCollector()); 489 F->getParent()->getFunctionList().insert(F, NF); 490 NF->takeName(F); 491 492 // Get the alias analysis information that we need to update to reflect our 493 // changes. 494 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 495 496 // Loop over all of the callers of the function, transforming the call sites 497 // to pass in the loaded pointers. 498 // 499 SmallVector<Value*, 16> Args; 500 while (!F->use_empty()) { 501 CallSite CS = CallSite::get(F->use_back()); 502 Instruction *Call = CS.getInstruction(); 503 const PAListPtr &CallPAL = CS.getParamAttrs(); 504 505 // Add any return attributes. 506 if (ParameterAttributes attrs = CallPAL.getParamAttrs(0)) 507 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs)); 508 509 // Loop over the operands, inserting GEP and loads in the caller as 510 // appropriate. 511 CallSite::arg_iterator AI = CS.arg_begin(); 512 ArgIndex = 1; 513 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); 514 I != E; ++I, ++AI, ++ArgIndex) 515 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) { 516 Args.push_back(*AI); // Unmodified argument 517 518 if (ParameterAttributes Attrs = CallPAL.getParamAttrs(ArgIndex)) 519 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); 520 521 } else if (ByValArgsToTransform.count(I)) { 522 // Emit a GEP and load for each element of the struct. 523 const Type *AgTy = cast<PointerType>(I->getType())->getElementType(); 524 const StructType *STy = cast<StructType>(AgTy); 525 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 }; 526 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 527 Idxs[1] = ConstantInt::get(Type::Int32Ty, i); 528 Value *Idx = GetElementPtrInst::Create(*AI, Idxs, Idxs+2, 529 (*AI)->getName()+"."+utostr(i), 530 Call); 531 // TODO: Tell AA about the new values? 532 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call)); 533 } 534 } else if (!I->use_empty()) { 535 // Non-dead argument: insert GEPs and loads as appropriate. 536 ScalarizeTable &ArgIndices = ScalarizedElements[I]; 537 for (ScalarizeTable::iterator SI = ArgIndices.begin(), 538 E = ArgIndices.end(); SI != E; ++SI) { 539 Value *V = *AI; 540 LoadInst *OrigLoad = OriginalLoads[*SI]; 541 if (!SI->empty()) { 542 V = GetElementPtrInst::Create(V, SI->begin(), SI->end(), 543 V->getName()+".idx", Call); 544 AA.copyValue(OrigLoad->getOperand(0), V); 545 } 546 Args.push_back(new LoadInst(V, V->getName()+".val", Call)); 547 AA.copyValue(OrigLoad, Args.back()); 548 } 549 } 550 551 if (ExtraArgHack) 552 Args.push_back(Constant::getNullValue(Type::Int32Ty)); 553 554 // Push any varargs arguments on the list 555 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) { 556 Args.push_back(*AI); 557 if (ParameterAttributes Attrs = CallPAL.getParamAttrs(ArgIndex)) 558 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); 559 } 560 561 Instruction *New; 562 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) { 563 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(), 564 Args.begin(), Args.end(), "", Call); 565 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv()); 566 cast<InvokeInst>(New)->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), 567 ParamAttrsVec.end())); 568 } else { 569 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call); 570 cast<CallInst>(New)->setCallingConv(CS.getCallingConv()); 571 cast<CallInst>(New)->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), 572 ParamAttrsVec.end())); 573 if (cast<CallInst>(Call)->isTailCall()) 574 cast<CallInst>(New)->setTailCall(); 575 } 576 Args.clear(); 577 ParamAttrsVec.clear(); 578 579 // Update the alias analysis implementation to know that we are replacing 580 // the old call with a new one. 581 AA.replaceWithNewValue(Call, New); 582 583 if (!Call->use_empty()) { 584 Call->replaceAllUsesWith(New); 585 New->takeName(Call); 586 } 587 588 // Finally, remove the old call from the program, reducing the use-count of 589 // F. 590 Call->eraseFromParent(); 591 } 592 593 // Since we have now created the new function, splice the body of the old 594 // function right into the new function, leaving the old rotting hulk of the 595 // function empty. 596 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList()); 597 598 // Loop over the argument list, transfering uses of the old arguments over to 599 // the new arguments, also transfering over the names as well. 600 // 601 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(), 602 I2 = NF->arg_begin(); I != E; ++I) { 603 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) { 604 // If this is an unmodified argument, move the name and users over to the 605 // new version. 606 I->replaceAllUsesWith(I2); 607 I2->takeName(I); 608 AA.replaceWithNewValue(I, I2); 609 ++I2; 610 continue; 611 } 612 613 if (ByValArgsToTransform.count(I)) { 614 // In the callee, we create an alloca, and store each of the new incoming 615 // arguments into the alloca. 616 Instruction *InsertPt = NF->begin()->begin(); 617 618 // Just add all the struct element types. 619 const Type *AgTy = cast<PointerType>(I->getType())->getElementType(); 620 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt); 621 const StructType *STy = cast<StructType>(AgTy); 622 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 }; 623 624 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 625 Idxs[1] = ConstantInt::get(Type::Int32Ty, i); 626 Value *Idx = GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2, 627 TheAlloca->getName()+"."+utostr(i), 628 InsertPt); 629 I2->setName(I->getName()+"."+utostr(i)); 630 new StoreInst(I2++, Idx, InsertPt); 631 } 632 633 // Anything that used the arg should now use the alloca. 634 I->replaceAllUsesWith(TheAlloca); 635 TheAlloca->takeName(I); 636 AA.replaceWithNewValue(I, TheAlloca); 637 continue; 638 } 639 640 if (I->use_empty()) { 641 AA.deleteValue(I); 642 continue; 643 } 644 645 // Otherwise, if we promoted this argument, then all users are load 646 // instructions, and all loads should be using the new argument that we 647 // added. 648 ScalarizeTable &ArgIndices = ScalarizedElements[I]; 649 650 while (!I->use_empty()) { 651 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) { 652 assert(ArgIndices.begin()->empty() && 653 "Load element should sort to front!"); 654 I2->setName(I->getName()+".val"); 655 LI->replaceAllUsesWith(I2); 656 AA.replaceWithNewValue(LI, I2); 657 LI->eraseFromParent(); 658 DOUT << "*** Promoted load of argument '" << I->getName() 659 << "' in function '" << F->getName() << "'\n"; 660 } else { 661 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back()); 662 std::vector<Value*> Operands(GEP->op_begin()+1, GEP->op_end()); 663 664 Function::arg_iterator TheArg = I2; 665 for (ScalarizeTable::iterator It = ArgIndices.begin(); 666 *It != Operands; ++It, ++TheArg) { 667 assert(It != ArgIndices.end() && "GEP not handled??"); 668 } 669 670 std::string NewName = I->getName(); 671 for (unsigned i = 0, e = Operands.size(); i != e; ++i) 672 if (ConstantInt *CI = dyn_cast<ConstantInt>(Operands[i])) 673 NewName += "." + CI->getValue().toStringUnsigned(10); 674 else 675 NewName += ".x"; 676 TheArg->setName(NewName+".val"); 677 678 DOUT << "*** Promoted agg argument '" << TheArg->getName() 679 << "' of function '" << F->getName() << "'\n"; 680 681 // All of the uses must be load instructions. Replace them all with 682 // the argument specified by ArgNo. 683 while (!GEP->use_empty()) { 684 LoadInst *L = cast<LoadInst>(GEP->use_back()); 685 L->replaceAllUsesWith(TheArg); 686 AA.replaceWithNewValue(L, TheArg); 687 L->eraseFromParent(); 688 } 689 AA.deleteValue(GEP); 690 GEP->eraseFromParent(); 691 } 692 } 693 694 // Increment I2 past all of the arguments added for this promoted pointer. 695 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i) 696 ++I2; 697 } 698 699 // Notify the alias analysis implementation that we inserted a new argument. 700 if (ExtraArgHack) 701 AA.copyValue(Constant::getNullValue(Type::Int32Ty), NF->arg_begin()); 702 703 704 // Tell the alias analysis that the old function is about to disappear. 705 AA.replaceWithNewValue(F, NF); 706 707 // Now that the old function is dead, delete it. 708 F->eraseFromParent(); 709 return NF; 710} 711