ArgumentPromotion.cpp revision 1c8733e1fd69e634daaa7fefd0d1436b846a8eb3
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// 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! 23// 24// Note that this transformation could also be done for arguments that are only 25// stored to (returning the value instead), but does not currently. This case 26// would be best handled when and if LLVM begins supporting multiple return 27// values from functions. 28// 29//===----------------------------------------------------------------------===// 30 31#define DEBUG_TYPE "argpromotion" 32#include "llvm/Transforms/IPO.h" 33#include "llvm/Constants.h" 34#include "llvm/DerivedTypes.h" 35#include "llvm/Module.h" 36#include "llvm/CallGraphSCCPass.h" 37#include "llvm/Instructions.h" 38#include "llvm/Analysis/AliasAnalysis.h" 39#include "llvm/Analysis/CallGraph.h" 40#include "llvm/Target/TargetData.h" 41#include "llvm/Support/CallSite.h" 42#include "llvm/Support/CFG.h" 43#include "llvm/Support/Debug.h" 44#include "llvm/ADT/DepthFirstIterator.h" 45#include "llvm/ADT/Statistic.h" 46#include "llvm/ADT/StringExtras.h" 47#include "llvm/Support/Compiler.h" 48#include <set> 49using namespace llvm; 50 51STATISTIC(NumArgumentsPromoted , "Number of pointer arguments promoted"); 52STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted"); 53STATISTIC(NumByValArgsPromoted , "Number of byval arguments promoted"); 54STATISTIC(NumArgumentsDead , "Number of dead pointer args eliminated"); 55 56namespace { 57 /// ArgPromotion - The 'by reference' to 'by value' argument promotion pass. 58 /// 59 struct VISIBILITY_HIDDEN ArgPromotion : public CallGraphSCCPass { 60 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 61 AU.addRequired<AliasAnalysis>(); 62 AU.addRequired<TargetData>(); 63 CallGraphSCCPass::getAnalysisUsage(AU); 64 } 65 66 virtual bool runOnSCC(const std::vector<CallGraphNode *> &SCC); 67 static char ID; // Pass identification, replacement for typeid 68 ArgPromotion() : CallGraphSCCPass((intptr_t)&ID) {} 69 70 private: 71 bool PromoteArguments(CallGraphNode *CGN); 72 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const; 73 Function *DoPromotion(Function *F, 74 SmallPtrSet<Argument*, 8> &ArgsToPromote, 75 SmallPtrSet<Argument*, 8> &ByValArgsToTransform); 76 }; 77 78 char ArgPromotion::ID = 0; 79 RegisterPass<ArgPromotion> X("argpromotion", 80 "Promote 'by reference' arguments to scalars"); 81} 82 83Pass *llvm::createArgumentPromotionPass() { 84 return new ArgPromotion(); 85} 86 87bool ArgPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) { 88 bool Changed = false, LocalChange; 89 90 do { // Iterate until we stop promoting from this SCC. 91 LocalChange = false; 92 // Attempt to promote arguments from all functions in this SCC. 93 for (unsigned i = 0, e = SCC.size(); i != e; ++i) 94 LocalChange |= PromoteArguments(SCC[i]); 95 Changed |= LocalChange; // Remember that we changed something. 96 } while (LocalChange); 97 98 return Changed; 99} 100 101/// PromoteArguments - This method checks the specified function to see if there 102/// are any promotable arguments and if it is safe to promote the function (for 103/// example, all callers are direct). If safe to promote some arguments, it 104/// calls the DoPromotion method. 105/// 106bool ArgPromotion::PromoteArguments(CallGraphNode *CGN) { 107 Function *F = CGN->getFunction(); 108 109 // Make sure that it is local to this module. 110 if (!F || !F->hasInternalLinkage()) return false; 111 112 // First check: see if there are any pointer arguments! If not, quick exit. 113 SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs; 114 unsigned ArgNo = 0; 115 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); 116 I != E; ++I, ++ArgNo) 117 if (isa<PointerType>(I->getType())) 118 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo)); 119 if (PointerArgs.empty()) return false; 120 121 // Second check: make sure that all callers are direct callers. We can't 122 // transform functions that have indirect callers. 123 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); 124 UI != E; ++UI) { 125 CallSite CS = CallSite::get(*UI); 126 if (!CS.getInstruction()) // "Taking the address" of the function 127 return false; 128 129 // Ensure that this call site is CALLING the function, not passing it as 130 // an argument. 131 if (UI.getOperandNo() != 0) 132 return false; 133 } 134 135 // Check to see which arguments are promotable. If an argument is promotable, 136 // add it to ArgsToPromote. 137 SmallPtrSet<Argument*, 8> ArgsToPromote; 138 SmallPtrSet<Argument*, 8> ByValArgsToTransform; 139 for (unsigned i = 0; i != PointerArgs.size(); ++i) { 140 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, ParamAttr::ByVal); 141 142 // If this is a byval argument, and if the aggregate type is small, just 143 // pass the elements, which is always safe. 144 Argument *PtrArg = PointerArgs[i].first; 145 if (isByVal) { 146 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType(); 147 if (const StructType *STy = dyn_cast<StructType>(AgTy)) 148 if (STy->getNumElements() <= 3) { 149 // If all the elements are first class types, we can promote it. 150 bool AllSimple = true; 151 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 152 if (!STy->getElementType(i)->isFirstClassType()) { 153 AllSimple = false; 154 break; 155 } 156 157 // Safe to transform, don't even bother trying to "promote" it. 158 // Passing the elements as a scalar will allow scalarrepl to hack on 159 // the new alloca we introduce. 160 if (AllSimple) { 161 ByValArgsToTransform.insert(PtrArg); 162 continue; 163 } 164 } 165 } 166 167 // Otherwise, see if we can promote the pointer to its value. 168 if (isSafeToPromoteArgument(PtrArg, isByVal)) 169 ArgsToPromote.insert(PtrArg); 170 } 171 172 // No promotable pointer arguments. 173 if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) return false; 174 175 Function *NewF = DoPromotion(F, ArgsToPromote, ByValArgsToTransform); 176 177 // Update the call graph to know that the function has been transformed. 178 getAnalysis<CallGraph>().changeFunction(F, NewF); 179 return true; 180} 181 182/// IsAlwaysValidPointer - Return true if the specified pointer is always legal 183/// to load. 184static bool IsAlwaysValidPointer(Value *V) { 185 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true; 186 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) 187 return IsAlwaysValidPointer(GEP->getOperand(0)); 188 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 189 if (CE->getOpcode() == Instruction::GetElementPtr) 190 return IsAlwaysValidPointer(CE->getOperand(0)); 191 192 return false; 193} 194 195/// AllCalleesPassInValidPointerForArgument - Return true if we can prove that 196/// all callees pass in a valid pointer for the specified function argument. 197static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) { 198 Function *Callee = Arg->getParent(); 199 200 unsigned ArgNo = std::distance(Callee->arg_begin(), 201 Function::arg_iterator(Arg)); 202 203 // Look at all call sites of the function. At this pointer we know we only 204 // have direct callees. 205 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end(); 206 UI != E; ++UI) { 207 CallSite CS = CallSite::get(*UI); 208 assert(CS.getInstruction() && "Should only have direct calls!"); 209 210 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo))) 211 return false; 212 } 213 return true; 214} 215 216 217/// isSafeToPromoteArgument - As you might guess from the name of this method, 218/// it checks to see if it is both safe and useful to promote the argument. 219/// This method limits promotion of aggregates to only promote up to three 220/// elements of the aggregate in order to avoid exploding the number of 221/// arguments passed in. 222bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const { 223 // We can only promote this argument if all of the uses are loads, or are GEP 224 // instructions (with constant indices) that are subsequently loaded. 225 226 // We can also only promote the load if we can guarantee that it will happen. 227 // Promoting a load causes the load to be unconditionally executed in the 228 // caller, so we can't turn a conditional load into an unconditional load in 229 // general. 230 bool SafeToUnconditionallyLoad = false; 231 if (isByVal) // ByVal arguments are always safe to load from. 232 SafeToUnconditionallyLoad = true; 233 234 BasicBlock *EntryBlock = Arg->getParent()->begin(); 235 SmallVector<LoadInst*, 16> Loads; 236 std::vector<SmallVector<ConstantInt*, 8> > GEPIndices; 237 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end(); 238 UI != E; ++UI) 239 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 240 if (LI->isVolatile()) return false; // Don't hack volatile loads 241 Loads.push_back(LI); 242 243 // If this load occurs in the entry block, then the pointer is 244 // unconditionally loaded. 245 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock; 246 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) { 247 if (GEP->use_empty()) { 248 // Dead GEP's cause trouble later. Just remove them if we run into 249 // them. 250 getAnalysis<AliasAnalysis>().deleteValue(GEP); 251 GEP->eraseFromParent(); 252 return isSafeToPromoteArgument(Arg, isByVal); 253 } 254 // Ensure that all of the indices are constants. 255 SmallVector<ConstantInt*, 8> Operands; 256 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i) 257 if (ConstantInt *C = dyn_cast<ConstantInt>(GEP->getOperand(i))) 258 Operands.push_back(C); 259 else 260 return false; // Not a constant operand GEP! 261 262 // Ensure that the only users of the GEP are load instructions. 263 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end(); 264 UI != E; ++UI) 265 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 266 if (LI->isVolatile()) return false; // Don't hack volatile loads 267 Loads.push_back(LI); 268 269 // If this load occurs in the entry block, then the pointer is 270 // unconditionally loaded. 271 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock; 272 } else { 273 return false; 274 } 275 276 // See if there is already a GEP with these indices. If not, check to 277 // make sure that we aren't promoting too many elements. If so, nothing 278 // to do. 279 if (std::find(GEPIndices.begin(), GEPIndices.end(), Operands) == 280 GEPIndices.end()) { 281 if (GEPIndices.size() == 3) { 282 DOUT << "argpromotion disable promoting argument '" 283 << Arg->getName() << "' because it would require adding more " 284 << "than 3 arguments to the function.\n"; 285 // We limit aggregate promotion to only promoting up to three elements 286 // of the aggregate. 287 return false; 288 } 289 GEPIndices.push_back(Operands); 290 } 291 } else { 292 return false; // Not a load or a GEP. 293 } 294 295 if (Loads.empty()) return true; // No users, this is a dead argument. 296 297 // If we decide that we want to promote this argument, the value is going to 298 // be unconditionally loaded in all callees. This is only safe to do if the 299 // pointer was going to be unconditionally loaded anyway (i.e. there is a load 300 // of the pointer in the entry block of the function) or if we can prove that 301 // all pointers passed in are always to legal locations (for example, no null 302 // pointers are passed in, no pointers to free'd memory, etc). 303 if (!SafeToUnconditionallyLoad && 304 !AllCalleesPassInValidPointerForArgument(Arg)) 305 return false; // Cannot prove that this is safe!! 306 307 // Okay, now we know that the argument is only used by load instructions and 308 // it is safe to unconditionally load the pointer. Use alias analysis to 309 // check to see if the pointer is guaranteed to not be modified from entry of 310 // the function to each of the load instructions. 311 312 // Because there could be several/many load instructions, remember which 313 // blocks we know to be transparent to the load. 314 SmallPtrSet<BasicBlock*, 16> TranspBlocks; 315 316 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 317 TargetData &TD = getAnalysis<TargetData>(); 318 319 for (unsigned i = 0, e = Loads.size(); i != e; ++i) { 320 // Check to see if the load is invalidated from the start of the block to 321 // the load itself. 322 LoadInst *Load = Loads[i]; 323 BasicBlock *BB = Load->getParent(); 324 325 const PointerType *LoadTy = 326 cast<PointerType>(Load->getOperand(0)->getType()); 327 unsigned LoadSize = (unsigned)TD.getTypeStoreSize(LoadTy->getElementType()); 328 329 if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize)) 330 return false; // Pointer is invalidated! 331 332 // Now check every path from the entry block to the load for transparency. 333 // To do this, we perform a depth first search on the inverse CFG from the 334 // loading block. 335 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) 336 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> > 337 I = idf_ext_begin(*PI, TranspBlocks), 338 E = idf_ext_end(*PI, TranspBlocks); I != E; ++I) 339 if (AA.canBasicBlockModify(**I, Arg, LoadSize)) 340 return false; 341 } 342 343 // If the path from the entry of the function to each load is free of 344 // instructions that potentially invalidate the load, we can make the 345 // transformation! 346 return true; 347} 348 349namespace { 350 /// GEPIdxComparator - Provide a strong ordering for GEP indices. All Value* 351 /// elements are instances of ConstantInt. 352 /// 353 struct GEPIdxComparator { 354 bool operator()(const std::vector<Value*> &LHS, 355 const std::vector<Value*> &RHS) const { 356 unsigned idx = 0; 357 for (; idx < LHS.size() && idx < RHS.size(); ++idx) { 358 if (LHS[idx] != RHS[idx]) { 359 return cast<ConstantInt>(LHS[idx])->getZExtValue() < 360 cast<ConstantInt>(RHS[idx])->getZExtValue(); 361 } 362 } 363 364 // Return less than if we ran out of stuff in LHS and we didn't run out of 365 // stuff in RHS. 366 return idx == LHS.size() && idx != RHS.size(); 367 } 368 }; 369} 370 371 372/// DoPromotion - This method actually performs the promotion of the specified 373/// arguments, and returns the new function. At this point, we know that it's 374/// safe to do so. 375Function *ArgPromotion::DoPromotion(Function *F, 376 SmallPtrSet<Argument*, 8> &ArgsToPromote, 377 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) { 378 379 // Start by computing a new prototype for the function, which is the same as 380 // the old function, but has modified arguments. 381 const FunctionType *FTy = F->getFunctionType(); 382 std::vector<const Type*> Params; 383 384 typedef std::set<std::vector<Value*>, GEPIdxComparator> ScalarizeTable; 385 386 // ScalarizedElements - If we are promoting a pointer that has elements 387 // accessed out of it, keep track of which elements are accessed so that we 388 // can add one argument for each. 389 // 390 // Arguments that are directly loaded will have a zero element value here, to 391 // handle cases where there are both a direct load and GEP accesses. 392 // 393 std::map<Argument*, ScalarizeTable> ScalarizedElements; 394 395 // OriginalLoads - Keep track of a representative load instruction from the 396 // original function so that we can tell the alias analysis implementation 397 // what the new GEP/Load instructions we are inserting look like. 398 std::map<std::vector<Value*>, LoadInst*> OriginalLoads; 399 400 // ParamAttrs - Keep track of the parameter attributes for the arguments 401 // that we are *not* promoting. For the ones that we do promote, the parameter 402 // attributes are lost 403 SmallVector<ParamAttrsWithIndex, 8> ParamAttrsVec; 404 const PAListPtr &PAL = F->getParamAttrs(); 405 406 // Add any return attributes. 407 if (ParameterAttributes attrs = PAL.getParamAttrs(0)) 408 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs)); 409 410 unsigned ArgIndex = 1; 411 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; 412 ++I, ++ArgIndex) { 413 if (ByValArgsToTransform.count(I)) { 414 // Just add all the struct element types. 415 const Type *AgTy = cast<PointerType>(I->getType())->getElementType(); 416 const StructType *STy = cast<StructType>(AgTy); 417 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 418 Params.push_back(STy->getElementType(i)); 419 ++NumByValArgsPromoted; 420 } else if (!ArgsToPromote.count(I)) { 421 Params.push_back(I->getType()); 422 if (ParameterAttributes attrs = PAL.getParamAttrs(ArgIndex)) 423 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), attrs)); 424 } else if (I->use_empty()) { 425 ++NumArgumentsDead; 426 } else { 427 // Okay, this is being promoted. Check to see if there are any GEP uses 428 // of the argument. 429 ScalarizeTable &ArgIndices = ScalarizedElements[I]; 430 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; 431 ++UI) { 432 Instruction *User = cast<Instruction>(*UI); 433 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User)); 434 std::vector<Value*> Indices(User->op_begin()+1, User->op_end()); 435 ArgIndices.insert(Indices); 436 LoadInst *OrigLoad; 437 if (LoadInst *L = dyn_cast<LoadInst>(User)) 438 OrigLoad = L; 439 else 440 OrigLoad = cast<LoadInst>(User->use_back()); 441 OriginalLoads[Indices] = OrigLoad; 442 } 443 444 // Add a parameter to the function for each element passed in. 445 for (ScalarizeTable::iterator SI = ArgIndices.begin(), 446 E = ArgIndices.end(); SI != E; ++SI) 447 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(), 448 SI->begin(), 449 SI->end())); 450 451 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty()) 452 ++NumArgumentsPromoted; 453 else 454 ++NumAggregatesPromoted; 455 } 456 } 457 458 const Type *RetTy = FTy->getReturnType(); 459 460 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which 461 // have zero fixed arguments. 462 bool ExtraArgHack = false; 463 if (Params.empty() && FTy->isVarArg()) { 464 ExtraArgHack = true; 465 Params.push_back(Type::Int32Ty); 466 } 467 468 // Construct the new function type using the new arguments. 469 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg()); 470 471 // Create the new function body and insert it into the module... 472 Function *NF = new Function(NFTy, F->getLinkage(), F->getName()); 473 NF->setCallingConv(F->getCallingConv()); 474 475 // Recompute the parameter attributes list based on the new arguments for 476 // the function. 477 NF->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end())); 478 ParamAttrsVec.clear(); 479 480 if (F->hasCollector()) 481 NF->setCollector(F->getCollector()); 482 F->getParent()->getFunctionList().insert(F, NF); 483 484 // Get the alias analysis information that we need to update to reflect our 485 // changes. 486 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 487 488 // Loop over all of the callers of the function, transforming the call sites 489 // to pass in the loaded pointers. 490 // 491 SmallVector<Value*, 16> Args; 492 while (!F->use_empty()) { 493 CallSite CS = CallSite::get(F->use_back()); 494 Instruction *Call = CS.getInstruction(); 495 const PAListPtr &CallPAL = CS.getParamAttrs(); 496 497 // Add any return attributes. 498 if (ParameterAttributes attrs = CallPAL.getParamAttrs(0)) 499 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs)); 500 501 // Loop over the operands, inserting GEP and loads in the caller as 502 // appropriate. 503 CallSite::arg_iterator AI = CS.arg_begin(); 504 ArgIndex = 1; 505 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); 506 I != E; ++I, ++AI, ++ArgIndex) 507 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) { 508 Args.push_back(*AI); // Unmodified argument 509 510 if (ParameterAttributes Attrs = CallPAL.getParamAttrs(ArgIndex)) 511 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); 512 513 } else if (ByValArgsToTransform.count(I)) { 514 // Emit a GEP and load for each element of the struct. 515 const Type *AgTy = cast<PointerType>(I->getType())->getElementType(); 516 const StructType *STy = cast<StructType>(AgTy); 517 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 }; 518 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 519 Idxs[1] = ConstantInt::get(Type::Int32Ty, i); 520 Value *Idx = new GetElementPtrInst(*AI, Idxs, Idxs+2, 521 (*AI)->getName()+"."+utostr(i), 522 Call); 523 // TODO: Tell AA about the new values? 524 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call)); 525 } 526 } else if (!I->use_empty()) { 527 // Non-dead argument: insert GEPs and loads as appropriate. 528 ScalarizeTable &ArgIndices = ScalarizedElements[I]; 529 for (ScalarizeTable::iterator SI = ArgIndices.begin(), 530 E = ArgIndices.end(); SI != E; ++SI) { 531 Value *V = *AI; 532 LoadInst *OrigLoad = OriginalLoads[*SI]; 533 if (!SI->empty()) { 534 V = new GetElementPtrInst(V, SI->begin(), SI->end(), 535 V->getName()+".idx", Call); 536 AA.copyValue(OrigLoad->getOperand(0), V); 537 } 538 Args.push_back(new LoadInst(V, V->getName()+".val", Call)); 539 AA.copyValue(OrigLoad, Args.back()); 540 } 541 } 542 543 if (ExtraArgHack) 544 Args.push_back(Constant::getNullValue(Type::Int32Ty)); 545 546 // Push any varargs arguments on the list 547 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) { 548 Args.push_back(*AI); 549 if (ParameterAttributes Attrs = CallPAL.getParamAttrs(ArgIndex)) 550 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); 551 } 552 553 Instruction *New; 554 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) { 555 New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(), 556 Args.begin(), Args.end(), "", Call); 557 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv()); 558 cast<InvokeInst>(New)->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), 559 ParamAttrsVec.end())); 560 } else { 561 New = new CallInst(NF, Args.begin(), Args.end(), "", Call); 562 cast<CallInst>(New)->setCallingConv(CS.getCallingConv()); 563 cast<CallInst>(New)->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), 564 ParamAttrsVec.end())); 565 if (cast<CallInst>(Call)->isTailCall()) 566 cast<CallInst>(New)->setTailCall(); 567 } 568 Args.clear(); 569 ParamAttrsVec.clear(); 570 571 // Update the alias analysis implementation to know that we are replacing 572 // the old call with a new one. 573 AA.replaceWithNewValue(Call, New); 574 575 if (!Call->use_empty()) { 576 Call->replaceAllUsesWith(New); 577 New->takeName(Call); 578 } 579 580 // Finally, remove the old call from the program, reducing the use-count of 581 // F. 582 Call->eraseFromParent(); 583 } 584 585 // Since we have now created the new function, splice the body of the old 586 // function right into the new function, leaving the old rotting hulk of the 587 // function empty. 588 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList()); 589 590 // Loop over the argument list, transfering uses of the old arguments over to 591 // the new arguments, also transfering over the names as well. 592 // 593 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(), 594 I2 = NF->arg_begin(); I != E; ++I) { 595 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) { 596 // If this is an unmodified argument, move the name and users over to the 597 // new version. 598 I->replaceAllUsesWith(I2); 599 I2->takeName(I); 600 AA.replaceWithNewValue(I, I2); 601 ++I2; 602 continue; 603 } 604 605 if (ByValArgsToTransform.count(I)) { 606 // In the callee, we create an alloca, and store each of the new incoming 607 // arguments into the alloca. 608 Instruction *InsertPt = NF->begin()->begin(); 609 610 // Just add all the struct element types. 611 const Type *AgTy = cast<PointerType>(I->getType())->getElementType(); 612 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt); 613 const StructType *STy = cast<StructType>(AgTy); 614 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 }; 615 616 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 617 Idxs[1] = ConstantInt::get(Type::Int32Ty, i); 618 Value *Idx = new GetElementPtrInst(TheAlloca, Idxs, Idxs+2, 619 TheAlloca->getName()+"."+utostr(i), 620 InsertPt); 621 I2->setName(I->getName()+"."+utostr(i)); 622 new StoreInst(I2++, Idx, InsertPt); 623 } 624 625 // Anything that used the arg should now use the alloca. 626 I->replaceAllUsesWith(TheAlloca); 627 TheAlloca->takeName(I); 628 AA.replaceWithNewValue(I, TheAlloca); 629 continue; 630 } 631 632 if (I->use_empty()) { 633 AA.deleteValue(I); 634 continue; 635 } 636 637 // Otherwise, if we promoted this argument, then all users are load 638 // instructions, and all loads should be using the new argument that we 639 // added. 640 ScalarizeTable &ArgIndices = ScalarizedElements[I]; 641 642 while (!I->use_empty()) { 643 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) { 644 assert(ArgIndices.begin()->empty() && 645 "Load element should sort to front!"); 646 I2->setName(I->getName()+".val"); 647 LI->replaceAllUsesWith(I2); 648 AA.replaceWithNewValue(LI, I2); 649 LI->eraseFromParent(); 650 DOUT << "*** Promoted load of argument '" << I->getName() 651 << "' in function '" << F->getName() << "'\n"; 652 } else { 653 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back()); 654 std::vector<Value*> Operands(GEP->op_begin()+1, GEP->op_end()); 655 656 Function::arg_iterator TheArg = I2; 657 for (ScalarizeTable::iterator It = ArgIndices.begin(); 658 *It != Operands; ++It, ++TheArg) { 659 assert(It != ArgIndices.end() && "GEP not handled??"); 660 } 661 662 std::string NewName = I->getName(); 663 for (unsigned i = 0, e = Operands.size(); i != e; ++i) 664 if (ConstantInt *CI = dyn_cast<ConstantInt>(Operands[i])) 665 NewName += "." + CI->getValue().toStringUnsigned(10); 666 else 667 NewName += ".x"; 668 TheArg->setName(NewName+".val"); 669 670 DOUT << "*** Promoted agg argument '" << TheArg->getName() 671 << "' of function '" << F->getName() << "'\n"; 672 673 // All of the uses must be load instructions. Replace them all with 674 // the argument specified by ArgNo. 675 while (!GEP->use_empty()) { 676 LoadInst *L = cast<LoadInst>(GEP->use_back()); 677 L->replaceAllUsesWith(TheArg); 678 AA.replaceWithNewValue(L, TheArg); 679 L->eraseFromParent(); 680 } 681 AA.deleteValue(GEP); 682 GEP->eraseFromParent(); 683 } 684 } 685 686 // Increment I2 past all of the arguments added for this promoted pointer. 687 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i) 688 ++I2; 689 } 690 691 // Notify the alias analysis implementation that we inserted a new argument. 692 if (ExtraArgHack) 693 AA.copyValue(Constant::getNullValue(Type::Int32Ty), NF->arg_begin()); 694 695 696 // Tell the alias analysis that the old function is about to disappear. 697 AA.replaceWithNewValue(F, NF); 698 699 // Now that the old function is dead, delete it. 700 F->eraseFromParent(); 701 return NF; 702} 703