DeadArgumentElimination.cpp revision 221345
1193323Sed//===-- DeadArgumentElimination.cpp - Eliminate dead arguments ------------===// 2193323Sed// 3193323Sed// The LLVM Compiler Infrastructure 4193323Sed// 5193323Sed// This file is distributed under the University of Illinois Open Source 6193323Sed// License. See LICENSE.TXT for details. 7193323Sed// 8193323Sed//===----------------------------------------------------------------------===// 9193323Sed// 10193323Sed// This pass deletes dead arguments from internal functions. Dead argument 11193323Sed// elimination removes arguments which are directly dead, as well as arguments 12193323Sed// only passed into function calls as dead arguments of other functions. This 13193323Sed// pass also deletes dead return values in a similar way. 14193323Sed// 15193323Sed// This pass is often useful as a cleanup pass to run after aggressive 16193323Sed// interprocedural passes, which add possibly-dead arguments or return values. 17193323Sed// 18193323Sed//===----------------------------------------------------------------------===// 19193323Sed 20193323Sed#define DEBUG_TYPE "deadargelim" 21193323Sed#include "llvm/Transforms/IPO.h" 22193323Sed#include "llvm/CallingConv.h" 23193323Sed#include "llvm/Constant.h" 24193323Sed#include "llvm/DerivedTypes.h" 25193323Sed#include "llvm/Instructions.h" 26193323Sed#include "llvm/IntrinsicInst.h" 27198090Srdivacky#include "llvm/LLVMContext.h" 28193323Sed#include "llvm/Module.h" 29193323Sed#include "llvm/Pass.h" 30193323Sed#include "llvm/Support/CallSite.h" 31193323Sed#include "llvm/Support/Debug.h" 32198090Srdivacky#include "llvm/Support/raw_ostream.h" 33193323Sed#include "llvm/ADT/SmallVector.h" 34193323Sed#include "llvm/ADT/Statistic.h" 35193323Sed#include "llvm/ADT/StringExtras.h" 36193323Sed#include <map> 37193323Sed#include <set> 38193323Sedusing namespace llvm; 39193323Sed 40193323SedSTATISTIC(NumArgumentsEliminated, "Number of unread args removed"); 41193323SedSTATISTIC(NumRetValsEliminated , "Number of unused return values removed"); 42218893SdimSTATISTIC(NumArgumentsReplacedWithUndef, 43218893Sdim "Number of unread args replaced with undef"); 44193323Sednamespace { 45193323Sed /// DAE - The dead argument elimination pass. 46193323Sed /// 47198892Srdivacky class DAE : public ModulePass { 48193323Sed public: 49193323Sed 50193323Sed /// Struct that represents (part of) either a return value or a function 51193323Sed /// argument. Used so that arguments and return values can be used 52221345Sdim /// interchangeably. 53193323Sed struct RetOrArg { 54206083Srdivacky RetOrArg(const Function *F, unsigned Idx, bool IsArg) : F(F), Idx(Idx), 55193323Sed IsArg(IsArg) {} 56193323Sed const Function *F; 57193323Sed unsigned Idx; 58193323Sed bool IsArg; 59193323Sed 60193323Sed /// Make RetOrArg comparable, so we can put it into a map. 61193323Sed bool operator<(const RetOrArg &O) const { 62193323Sed if (F != O.F) 63193323Sed return F < O.F; 64193323Sed else if (Idx != O.Idx) 65193323Sed return Idx < O.Idx; 66193323Sed else 67193323Sed return IsArg < O.IsArg; 68193323Sed } 69193323Sed 70193323Sed /// Make RetOrArg comparable, so we can easily iterate the multimap. 71193323Sed bool operator==(const RetOrArg &O) const { 72193323Sed return F == O.F && Idx == O.Idx && IsArg == O.IsArg; 73193323Sed } 74193323Sed 75193323Sed std::string getDescription() const { 76206083Srdivacky return std::string((IsArg ? "Argument #" : "Return value #")) 77198090Srdivacky + utostr(Idx) + " of function " + F->getNameStr(); 78193323Sed } 79193323Sed }; 80193323Sed 81193323Sed /// Liveness enum - During our initial pass over the program, we determine 82193323Sed /// that things are either alive or maybe alive. We don't mark anything 83193323Sed /// explicitly dead (even if we know they are), since anything not alive 84193323Sed /// with no registered uses (in Uses) will never be marked alive and will 85193323Sed /// thus become dead in the end. 86193323Sed enum Liveness { Live, MaybeLive }; 87193323Sed 88193323Sed /// Convenience wrapper 89193323Sed RetOrArg CreateRet(const Function *F, unsigned Idx) { 90193323Sed return RetOrArg(F, Idx, false); 91193323Sed } 92193323Sed /// Convenience wrapper 93193323Sed RetOrArg CreateArg(const Function *F, unsigned Idx) { 94193323Sed return RetOrArg(F, Idx, true); 95193323Sed } 96193323Sed 97193323Sed typedef std::multimap<RetOrArg, RetOrArg> UseMap; 98193323Sed /// This maps a return value or argument to any MaybeLive return values or 99193323Sed /// arguments it uses. This allows the MaybeLive values to be marked live 100193323Sed /// when any of its users is marked live. 101193323Sed /// For example (indices are left out for clarity): 102193323Sed /// - Uses[ret F] = ret G 103193323Sed /// This means that F calls G, and F returns the value returned by G. 104193323Sed /// - Uses[arg F] = ret G 105193323Sed /// This means that some function calls G and passes its result as an 106193323Sed /// argument to F. 107193323Sed /// - Uses[ret F] = arg F 108193323Sed /// This means that F returns one of its own arguments. 109193323Sed /// - Uses[arg F] = arg G 110193323Sed /// This means that G calls F and passes one of its own (G's) arguments 111193323Sed /// directly to F. 112193323Sed UseMap Uses; 113193323Sed 114193323Sed typedef std::set<RetOrArg> LiveSet; 115193323Sed typedef std::set<const Function*> LiveFuncSet; 116193323Sed 117193323Sed /// This set contains all values that have been determined to be live. 118193323Sed LiveSet LiveValues; 119193323Sed /// This set contains all values that are cannot be changed in any way. 120193323Sed LiveFuncSet LiveFunctions; 121193323Sed 122193323Sed typedef SmallVector<RetOrArg, 5> UseVector; 123193323Sed 124210299Sed protected: 125210299Sed // DAH uses this to specify a different ID. 126212904Sdim explicit DAE(char &ID) : ModulePass(ID) {} 127210299Sed 128193323Sed public: 129193323Sed static char ID; // Pass identification, replacement for typeid 130218893Sdim DAE() : ModulePass(ID) { 131218893Sdim initializeDAEPass(*PassRegistry::getPassRegistry()); 132218893Sdim } 133210299Sed 134193323Sed bool runOnModule(Module &M); 135193323Sed 136193323Sed virtual bool ShouldHackArguments() const { return false; } 137193323Sed 138193323Sed private: 139193323Sed Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses); 140206083Srdivacky Liveness SurveyUse(Value::const_use_iterator U, UseVector &MaybeLiveUses, 141193323Sed unsigned RetValNum = 0); 142206083Srdivacky Liveness SurveyUses(const Value *V, UseVector &MaybeLiveUses); 143193323Sed 144206083Srdivacky void SurveyFunction(const Function &F); 145193323Sed void MarkValue(const RetOrArg &RA, Liveness L, 146193323Sed const UseVector &MaybeLiveUses); 147193323Sed void MarkLive(const RetOrArg &RA); 148193323Sed void MarkLive(const Function &F); 149193323Sed void PropagateLiveness(const RetOrArg &RA); 150193323Sed bool RemoveDeadStuffFromFunction(Function *F); 151193323Sed bool DeleteDeadVarargs(Function &Fn); 152218893Sdim bool RemoveDeadArgumentsFromCallers(Function &Fn); 153193323Sed }; 154193323Sed} 155193323Sed 156193323Sed 157193323Sedchar DAE::ID = 0; 158218893SdimINITIALIZE_PASS(DAE, "deadargelim", "Dead Argument Elimination", false, false) 159193323Sed 160193323Sednamespace { 161193323Sed /// DAH - DeadArgumentHacking pass - Same as dead argument elimination, but 162193323Sed /// deletes arguments to functions which are external. This is only for use 163193323Sed /// by bugpoint. 164193323Sed struct DAH : public DAE { 165193323Sed static char ID; 166212904Sdim DAH() : DAE(ID) {} 167210299Sed 168193323Sed virtual bool ShouldHackArguments() const { return true; } 169193323Sed }; 170193323Sed} 171193323Sed 172193323Sedchar DAH::ID = 0; 173212904SdimINITIALIZE_PASS(DAH, "deadarghaX0r", 174212904Sdim "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)", 175218893Sdim false, false) 176193323Sed 177193323Sed/// createDeadArgEliminationPass - This pass removes arguments from functions 178193323Sed/// which are not used by the body of the function. 179193323Sed/// 180193323SedModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); } 181193323SedModulePass *llvm::createDeadArgHackingPass() { return new DAH(); } 182193323Sed 183193323Sed/// DeleteDeadVarargs - If this is an function that takes a ... list, and if 184193323Sed/// llvm.vastart is never called, the varargs list is dead for the function. 185193323Sedbool DAE::DeleteDeadVarargs(Function &Fn) { 186193323Sed assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!"); 187193323Sed if (Fn.isDeclaration() || !Fn.hasLocalLinkage()) return false; 188193323Sed 189193323Sed // Ensure that the function is only directly called. 190194178Sed if (Fn.hasAddressTaken()) 191194178Sed return false; 192193323Sed 193193323Sed // Okay, we know we can transform this function if safe. Scan its body 194193323Sed // looking for calls to llvm.vastart. 195193323Sed for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) { 196193323Sed for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 197193323Sed if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { 198193323Sed if (II->getIntrinsicID() == Intrinsic::vastart) 199193323Sed return false; 200193323Sed } 201193323Sed } 202193323Sed } 203193323Sed 204193323Sed // If we get here, there are no calls to llvm.vastart in the function body, 205193323Sed // remove the "..." and adjust all the calls. 206193323Sed 207193323Sed // Start by computing a new prototype for the function, which is the same as 208193323Sed // the old function, but doesn't have isVarArg set. 209193323Sed const FunctionType *FTy = Fn.getFunctionType(); 210206083Srdivacky 211193323Sed std::vector<const Type*> Params(FTy->param_begin(), FTy->param_end()); 212198090Srdivacky FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), 213198090Srdivacky Params, false); 214193323Sed unsigned NumArgs = Params.size(); 215193323Sed 216193323Sed // Create the new function body and insert it into the module... 217193323Sed Function *NF = Function::Create(NFTy, Fn.getLinkage()); 218193323Sed NF->copyAttributesFrom(&Fn); 219193323Sed Fn.getParent()->getFunctionList().insert(&Fn, NF); 220193323Sed NF->takeName(&Fn); 221193323Sed 222193323Sed // Loop over all of the callers of the function, transforming the call sites 223193323Sed // to pass in a smaller number of arguments into the new function. 224193323Sed // 225193323Sed std::vector<Value*> Args; 226193323Sed while (!Fn.use_empty()) { 227212904Sdim CallSite CS(Fn.use_back()); 228193323Sed Instruction *Call = CS.getInstruction(); 229193323Sed 230193323Sed // Pass all the same arguments. 231212904Sdim Args.assign(CS.arg_begin(), CS.arg_begin() + NumArgs); 232193323Sed 233193323Sed // Drop any attributes that were on the vararg arguments. 234193323Sed AttrListPtr PAL = CS.getAttributes(); 235193323Sed if (!PAL.isEmpty() && PAL.getSlot(PAL.getNumSlots() - 1).Index > NumArgs) { 236193323Sed SmallVector<AttributeWithIndex, 8> AttributesVec; 237193323Sed for (unsigned i = 0; PAL.getSlot(i).Index <= NumArgs; ++i) 238193323Sed AttributesVec.push_back(PAL.getSlot(i)); 239206083Srdivacky if (Attributes FnAttrs = PAL.getFnAttributes()) 240193323Sed AttributesVec.push_back(AttributeWithIndex::get(~0, FnAttrs)); 241193323Sed PAL = AttrListPtr::get(AttributesVec.begin(), AttributesVec.end()); 242193323Sed } 243193323Sed 244193323Sed Instruction *New; 245193323Sed if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) { 246193323Sed New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(), 247193323Sed Args.begin(), Args.end(), "", Call); 248193323Sed cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv()); 249193323Sed cast<InvokeInst>(New)->setAttributes(PAL); 250193323Sed } else { 251193323Sed New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call); 252193323Sed cast<CallInst>(New)->setCallingConv(CS.getCallingConv()); 253193323Sed cast<CallInst>(New)->setAttributes(PAL); 254193323Sed if (cast<CallInst>(Call)->isTailCall()) 255193323Sed cast<CallInst>(New)->setTailCall(); 256193323Sed } 257212904Sdim New->setDebugLoc(Call->getDebugLoc()); 258207618Srdivacky 259193323Sed Args.clear(); 260193323Sed 261193323Sed if (!Call->use_empty()) 262193323Sed Call->replaceAllUsesWith(New); 263193323Sed 264193323Sed New->takeName(Call); 265193323Sed 266193323Sed // Finally, remove the old call from the program, reducing the use-count of 267193323Sed // F. 268193323Sed Call->eraseFromParent(); 269193323Sed } 270193323Sed 271193323Sed // Since we have now created the new function, splice the body of the old 272193323Sed // function right into the new function, leaving the old rotting hulk of the 273193323Sed // function empty. 274193323Sed NF->getBasicBlockList().splice(NF->begin(), Fn.getBasicBlockList()); 275193323Sed 276221345Sdim // Loop over the argument list, transferring uses of the old arguments over to 277221345Sdim // the new arguments, also transferring over the names as well. While we're at 278193323Sed // it, remove the dead arguments from the DeadArguments list. 279193323Sed // 280193323Sed for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(), 281193323Sed I2 = NF->arg_begin(); I != E; ++I, ++I2) { 282193323Sed // Move the name and users over to the new version. 283193323Sed I->replaceAllUsesWith(I2); 284193323Sed I2->takeName(I); 285193323Sed } 286193323Sed 287193323Sed // Finally, nuke the old function. 288193323Sed Fn.eraseFromParent(); 289193323Sed return true; 290193323Sed} 291193323Sed 292218893Sdim/// RemoveDeadArgumentsFromCallers - Checks if the given function has any 293218893Sdim/// arguments that are unused, and changes the caller parameters to be undefined 294218893Sdim/// instead. 295218893Sdimbool DAE::RemoveDeadArgumentsFromCallers(Function &Fn) 296218893Sdim{ 297221345Sdim if (Fn.isDeclaration() || Fn.mayBeOverridden()) 298218893Sdim return false; 299218893Sdim 300218893Sdim // Functions with local linkage should already have been handled. 301218893Sdim if (Fn.hasLocalLinkage()) 302218893Sdim return false; 303218893Sdim 304218893Sdim if (Fn.use_empty()) 305218893Sdim return false; 306218893Sdim 307218893Sdim llvm::SmallVector<unsigned, 8> UnusedArgs; 308218893Sdim for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(); 309218893Sdim I != E; ++I) { 310218893Sdim Argument *Arg = I; 311218893Sdim 312218893Sdim if (Arg->use_empty() && !Arg->hasByValAttr()) 313218893Sdim UnusedArgs.push_back(Arg->getArgNo()); 314218893Sdim } 315218893Sdim 316218893Sdim if (UnusedArgs.empty()) 317218893Sdim return false; 318218893Sdim 319218893Sdim bool Changed = false; 320218893Sdim 321218893Sdim for (Function::use_iterator I = Fn.use_begin(), E = Fn.use_end(); 322218893Sdim I != E; ++I) { 323218893Sdim CallSite CS(*I); 324218893Sdim if (!CS || !CS.isCallee(I)) 325218893Sdim continue; 326218893Sdim 327218893Sdim // Now go through all unused args and replace them with "undef". 328218893Sdim for (unsigned I = 0, E = UnusedArgs.size(); I != E; ++I) { 329218893Sdim unsigned ArgNo = UnusedArgs[I]; 330218893Sdim 331218893Sdim Value *Arg = CS.getArgument(ArgNo); 332218893Sdim CS.setArgument(ArgNo, UndefValue::get(Arg->getType())); 333218893Sdim ++NumArgumentsReplacedWithUndef; 334218893Sdim Changed = true; 335218893Sdim } 336218893Sdim } 337218893Sdim 338218893Sdim return Changed; 339218893Sdim} 340218893Sdim 341193323Sed/// Convenience function that returns the number of return values. It returns 0 342193323Sed/// for void functions and 1 for functions not returning a struct. It returns 343193323Sed/// the number of struct elements for functions returning a struct. 344193323Sedstatic unsigned NumRetVals(const Function *F) { 345206083Srdivacky if (F->getReturnType()->isVoidTy()) 346193323Sed return 0; 347193323Sed else if (const StructType *STy = dyn_cast<StructType>(F->getReturnType())) 348193323Sed return STy->getNumElements(); 349193323Sed else 350193323Sed return 1; 351193323Sed} 352193323Sed 353193323Sed/// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not 354193323Sed/// live, it adds Use to the MaybeLiveUses argument. Returns the determined 355193323Sed/// liveness of Use. 356193323SedDAE::Liveness DAE::MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses) { 357193323Sed // We're live if our use or its Function is already marked as live. 358193323Sed if (LiveFunctions.count(Use.F) || LiveValues.count(Use)) 359193323Sed return Live; 360193323Sed 361193323Sed // We're maybe live otherwise, but remember that we must become live if 362193323Sed // Use becomes live. 363193323Sed MaybeLiveUses.push_back(Use); 364193323Sed return MaybeLive; 365193323Sed} 366193323Sed 367193323Sed 368193323Sed/// SurveyUse - This looks at a single use of an argument or return value 369193323Sed/// and determines if it should be alive or not. Adds this use to MaybeLiveUses 370206083Srdivacky/// if it causes the used value to become MaybeLive. 371193323Sed/// 372193323Sed/// RetValNum is the return value number to use when this use is used in a 373193323Sed/// return instruction. This is used in the recursion, you should always leave 374193323Sed/// it at 0. 375206083SrdivackyDAE::Liveness DAE::SurveyUse(Value::const_use_iterator U, 376206083Srdivacky UseVector &MaybeLiveUses, unsigned RetValNum) { 377206083Srdivacky const User *V = *U; 378206083Srdivacky if (const ReturnInst *RI = dyn_cast<ReturnInst>(V)) { 379193323Sed // The value is returned from a function. It's only live when the 380193323Sed // function's return value is live. We use RetValNum here, for the case 381193323Sed // that U is really a use of an insertvalue instruction that uses the 382221345Sdim // original Use. 383193323Sed RetOrArg Use = CreateRet(RI->getParent()->getParent(), RetValNum); 384193323Sed // We might be live, depending on the liveness of Use. 385193323Sed return MarkIfNotLive(Use, MaybeLiveUses); 386193323Sed } 387206083Srdivacky if (const InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) { 388193323Sed if (U.getOperandNo() != InsertValueInst::getAggregateOperandIndex() 389193323Sed && IV->hasIndices()) 390193323Sed // The use we are examining is inserted into an aggregate. Our liveness 391193323Sed // depends on all uses of that aggregate, but if it is used as a return 392193323Sed // value, only index at which we were inserted counts. 393193323Sed RetValNum = *IV->idx_begin(); 394193323Sed 395193323Sed // Note that if we are used as the aggregate operand to the insertvalue, 396193323Sed // we don't change RetValNum, but do survey all our uses. 397193323Sed 398193323Sed Liveness Result = MaybeLive; 399206083Srdivacky for (Value::const_use_iterator I = IV->use_begin(), 400193323Sed E = V->use_end(); I != E; ++I) { 401193323Sed Result = SurveyUse(I, MaybeLiveUses, RetValNum); 402193323Sed if (Result == Live) 403193323Sed break; 404193323Sed } 405193323Sed return Result; 406193323Sed } 407206083Srdivacky 408206083Srdivacky if (ImmutableCallSite CS = V) { 409206083Srdivacky const Function *F = CS.getCalledFunction(); 410193323Sed if (F) { 411193323Sed // Used in a direct call. 412206083Srdivacky 413193323Sed // Find the argument number. We know for sure that this use is an 414193323Sed // argument, since if it was the function argument this would be an 415193323Sed // indirect call and the we know can't be looking at a value of the 416193323Sed // label type (for the invoke instruction). 417206083Srdivacky unsigned ArgNo = CS.getArgumentNo(U); 418193323Sed 419193323Sed if (ArgNo >= F->getFunctionType()->getNumParams()) 420193323Sed // The value is passed in through a vararg! Must be live. 421193323Sed return Live; 422193323Sed 423206083Srdivacky assert(CS.getArgument(ArgNo) 424206083Srdivacky == CS->getOperand(U.getOperandNo()) 425193323Sed && "Argument is not where we expected it"); 426193323Sed 427193323Sed // Value passed to a normal call. It's only live when the corresponding 428193323Sed // argument to the called function turns out live. 429193323Sed RetOrArg Use = CreateArg(F, ArgNo); 430193323Sed return MarkIfNotLive(Use, MaybeLiveUses); 431193323Sed } 432193323Sed } 433193323Sed // Used in any other way? Value must be live. 434193323Sed return Live; 435193323Sed} 436193323Sed 437193323Sed/// SurveyUses - This looks at all the uses of the given value 438193323Sed/// Returns the Liveness deduced from the uses of this value. 439193323Sed/// 440193323Sed/// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. If 441193323Sed/// the result is Live, MaybeLiveUses might be modified but its content should 442193323Sed/// be ignored (since it might not be complete). 443206083SrdivackyDAE::Liveness DAE::SurveyUses(const Value *V, UseVector &MaybeLiveUses) { 444193323Sed // Assume it's dead (which will only hold if there are no uses at all..). 445193323Sed Liveness Result = MaybeLive; 446193323Sed // Check each use. 447206083Srdivacky for (Value::const_use_iterator I = V->use_begin(), 448193323Sed E = V->use_end(); I != E; ++I) { 449193323Sed Result = SurveyUse(I, MaybeLiveUses); 450193323Sed if (Result == Live) 451193323Sed break; 452193323Sed } 453193323Sed return Result; 454193323Sed} 455193323Sed 456193323Sed// SurveyFunction - This performs the initial survey of the specified function, 457193323Sed// checking out whether or not it uses any of its incoming arguments or whether 458193323Sed// any callers use the return value. This fills in the LiveValues set and Uses 459193323Sed// map. 460193323Sed// 461193323Sed// We consider arguments of non-internal functions to be intrinsically alive as 462193323Sed// well as arguments to functions which have their "address taken". 463193323Sed// 464206083Srdivackyvoid DAE::SurveyFunction(const Function &F) { 465193323Sed unsigned RetCount = NumRetVals(&F); 466193323Sed // Assume all return values are dead 467193323Sed typedef SmallVector<Liveness, 5> RetVals; 468193323Sed RetVals RetValLiveness(RetCount, MaybeLive); 469193323Sed 470193323Sed typedef SmallVector<UseVector, 5> RetUses; 471193323Sed // These vectors map each return value to the uses that make it MaybeLive, so 472193323Sed // we can add those to the Uses map if the return value really turns out to be 473193323Sed // MaybeLive. Initialized to a list of RetCount empty lists. 474193323Sed RetUses MaybeLiveRetUses(RetCount); 475193323Sed 476206083Srdivacky for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB) 477206083Srdivacky if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) 478193323Sed if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType() 479193323Sed != F.getFunctionType()->getReturnType()) { 480193323Sed // We don't support old style multiple return values. 481193323Sed MarkLive(F); 482193323Sed return; 483193323Sed } 484193323Sed 485193323Sed if (!F.hasLocalLinkage() && (!ShouldHackArguments() || F.isIntrinsic())) { 486193323Sed MarkLive(F); 487193323Sed return; 488193323Sed } 489193323Sed 490202375Srdivacky DEBUG(dbgs() << "DAE - Inspecting callers for fn: " << F.getName() << "\n"); 491193323Sed // Keep track of the number of live retvals, so we can skip checks once all 492193323Sed // of them turn out to be live. 493193323Sed unsigned NumLiveRetVals = 0; 494193323Sed const Type *STy = dyn_cast<StructType>(F.getReturnType()); 495193323Sed // Loop all uses of the function. 496206083Srdivacky for (Value::const_use_iterator I = F.use_begin(), E = F.use_end(); 497206083Srdivacky I != E; ++I) { 498193323Sed // If the function is PASSED IN as an argument, its address has been 499193323Sed // taken. 500206083Srdivacky ImmutableCallSite CS(*I); 501206083Srdivacky if (!CS || !CS.isCallee(I)) { 502193323Sed MarkLive(F); 503193323Sed return; 504193323Sed } 505193323Sed 506193323Sed // If this use is anything other than a call site, the function is alive. 507206083Srdivacky const Instruction *TheCall = CS.getInstruction(); 508193323Sed if (!TheCall) { // Not a direct call site? 509193323Sed MarkLive(F); 510193323Sed return; 511193323Sed } 512193323Sed 513193323Sed // If we end up here, we are looking at a direct call to our function. 514193323Sed 515193323Sed // Now, check how our return value(s) is/are used in this caller. Don't 516193323Sed // bother checking return values if all of them are live already. 517193323Sed if (NumLiveRetVals != RetCount) { 518193323Sed if (STy) { 519193323Sed // Check all uses of the return value. 520206083Srdivacky for (Value::const_use_iterator I = TheCall->use_begin(), 521193323Sed E = TheCall->use_end(); I != E; ++I) { 522206083Srdivacky const ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(*I); 523193323Sed if (Ext && Ext->hasIndices()) { 524193323Sed // This use uses a part of our return value, survey the uses of 525193323Sed // that part and store the results for this index only. 526193323Sed unsigned Idx = *Ext->idx_begin(); 527193323Sed if (RetValLiveness[Idx] != Live) { 528193323Sed RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]); 529193323Sed if (RetValLiveness[Idx] == Live) 530193323Sed NumLiveRetVals++; 531193323Sed } 532193323Sed } else { 533193323Sed // Used by something else than extractvalue. Mark all return 534193323Sed // values as live. 535193323Sed for (unsigned i = 0; i != RetCount; ++i ) 536193323Sed RetValLiveness[i] = Live; 537193323Sed NumLiveRetVals = RetCount; 538193323Sed break; 539193323Sed } 540193323Sed } 541193323Sed } else { 542193323Sed // Single return value 543193323Sed RetValLiveness[0] = SurveyUses(TheCall, MaybeLiveRetUses[0]); 544193323Sed if (RetValLiveness[0] == Live) 545193323Sed NumLiveRetVals = RetCount; 546193323Sed } 547193323Sed } 548193323Sed } 549193323Sed 550193323Sed // Now we've inspected all callers, record the liveness of our return values. 551193323Sed for (unsigned i = 0; i != RetCount; ++i) 552193323Sed MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]); 553193323Sed 554202375Srdivacky DEBUG(dbgs() << "DAE - Inspecting args for fn: " << F.getName() << "\n"); 555193323Sed 556193323Sed // Now, check all of our arguments. 557193323Sed unsigned i = 0; 558193323Sed UseVector MaybeLiveArgUses; 559206083Srdivacky for (Function::const_arg_iterator AI = F.arg_begin(), 560193323Sed E = F.arg_end(); AI != E; ++AI, ++i) { 561193323Sed // See what the effect of this use is (recording any uses that cause 562193323Sed // MaybeLive in MaybeLiveArgUses). 563193323Sed Liveness Result = SurveyUses(AI, MaybeLiveArgUses); 564193323Sed // Mark the result. 565193323Sed MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses); 566193323Sed // Clear the vector again for the next iteration. 567193323Sed MaybeLiveArgUses.clear(); 568193323Sed } 569193323Sed} 570193323Sed 571193323Sed/// MarkValue - This function marks the liveness of RA depending on L. If L is 572193323Sed/// MaybeLive, it also takes all uses in MaybeLiveUses and records them in Uses, 573193323Sed/// such that RA will be marked live if any use in MaybeLiveUses gets marked 574193323Sed/// live later on. 575193323Sedvoid DAE::MarkValue(const RetOrArg &RA, Liveness L, 576193323Sed const UseVector &MaybeLiveUses) { 577193323Sed switch (L) { 578193323Sed case Live: MarkLive(RA); break; 579193323Sed case MaybeLive: 580193323Sed { 581193323Sed // Note any uses of this value, so this return value can be 582193323Sed // marked live whenever one of the uses becomes live. 583193323Sed for (UseVector::const_iterator UI = MaybeLiveUses.begin(), 584193323Sed UE = MaybeLiveUses.end(); UI != UE; ++UI) 585193323Sed Uses.insert(std::make_pair(*UI, RA)); 586193323Sed break; 587193323Sed } 588193323Sed } 589193323Sed} 590193323Sed 591193323Sed/// MarkLive - Mark the given Function as alive, meaning that it cannot be 592193323Sed/// changed in any way. Additionally, 593193323Sed/// mark any values that are used as this function's parameters or by its return 594193323Sed/// values (according to Uses) live as well. 595193323Sedvoid DAE::MarkLive(const Function &F) { 596202375Srdivacky DEBUG(dbgs() << "DAE - Intrinsically live fn: " << F.getName() << "\n"); 597208599Srdivacky // Mark the function as live. 598208599Srdivacky LiveFunctions.insert(&F); 599208599Srdivacky // Mark all arguments as live. 600208599Srdivacky for (unsigned i = 0, e = F.arg_size(); i != e; ++i) 601208599Srdivacky PropagateLiveness(CreateArg(&F, i)); 602208599Srdivacky // Mark all return values as live. 603208599Srdivacky for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i) 604208599Srdivacky PropagateLiveness(CreateRet(&F, i)); 605193323Sed} 606193323Sed 607193323Sed/// MarkLive - Mark the given return value or argument as live. Additionally, 608193323Sed/// mark any values that are used by this value (according to Uses) live as 609193323Sed/// well. 610193323Sedvoid DAE::MarkLive(const RetOrArg &RA) { 611193323Sed if (LiveFunctions.count(RA.F)) 612193323Sed return; // Function was already marked Live. 613193323Sed 614193323Sed if (!LiveValues.insert(RA).second) 615193323Sed return; // We were already marked Live. 616193323Sed 617202375Srdivacky DEBUG(dbgs() << "DAE - Marking " << RA.getDescription() << " live\n"); 618193323Sed PropagateLiveness(RA); 619193323Sed} 620193323Sed 621193323Sed/// PropagateLiveness - Given that RA is a live value, propagate it's liveness 622193323Sed/// to any other values it uses (according to Uses). 623193323Sedvoid DAE::PropagateLiveness(const RetOrArg &RA) { 624193323Sed // We don't use upper_bound (or equal_range) here, because our recursive call 625193323Sed // to ourselves is likely to cause the upper_bound (which is the first value 626193323Sed // not belonging to RA) to become erased and the iterator invalidated. 627193323Sed UseMap::iterator Begin = Uses.lower_bound(RA); 628193323Sed UseMap::iterator E = Uses.end(); 629193323Sed UseMap::iterator I; 630193323Sed for (I = Begin; I != E && I->first == RA; ++I) 631193323Sed MarkLive(I->second); 632193323Sed 633193323Sed // Erase RA from the Uses map (from the lower bound to wherever we ended up 634193323Sed // after the loop). 635193323Sed Uses.erase(Begin, I); 636193323Sed} 637193323Sed 638193323Sed// RemoveDeadStuffFromFunction - Remove any arguments and return values from F 639193323Sed// that are not in LiveValues. Transform the function and all of the callees of 640193323Sed// the function to not have these arguments and return values. 641193323Sed// 642193323Sedbool DAE::RemoveDeadStuffFromFunction(Function *F) { 643193323Sed // Don't modify fully live functions 644193323Sed if (LiveFunctions.count(F)) 645193323Sed return false; 646193323Sed 647193323Sed // Start by computing a new prototype for the function, which is the same as 648193323Sed // the old function, but has fewer arguments and a different return type. 649193323Sed const FunctionType *FTy = F->getFunctionType(); 650193323Sed std::vector<const Type*> Params; 651193323Sed 652193323Sed // Set up to build a new list of parameter attributes. 653193323Sed SmallVector<AttributeWithIndex, 8> AttributesVec; 654193323Sed const AttrListPtr &PAL = F->getAttributes(); 655193323Sed 656193323Sed // The existing function return attributes. 657193323Sed Attributes RAttrs = PAL.getRetAttributes(); 658193323Sed Attributes FnAttrs = PAL.getFnAttributes(); 659193323Sed 660193323Sed // Find out the new return value. 661193323Sed 662193323Sed const Type *RetTy = FTy->getReturnType(); 663193323Sed const Type *NRetTy = NULL; 664193323Sed unsigned RetCount = NumRetVals(F); 665206083Srdivacky 666193323Sed // -1 means unused, other numbers are the new index 667193323Sed SmallVector<int, 5> NewRetIdxs(RetCount, -1); 668193323Sed std::vector<const Type*> RetTypes; 669206083Srdivacky if (RetTy->isVoidTy()) { 670206083Srdivacky NRetTy = RetTy; 671193323Sed } else { 672193323Sed const StructType *STy = dyn_cast<StructType>(RetTy); 673193323Sed if (STy) 674193323Sed // Look at each of the original return values individually. 675193323Sed for (unsigned i = 0; i != RetCount; ++i) { 676193323Sed RetOrArg Ret = CreateRet(F, i); 677193323Sed if (LiveValues.erase(Ret)) { 678193323Sed RetTypes.push_back(STy->getElementType(i)); 679193323Sed NewRetIdxs[i] = RetTypes.size() - 1; 680193323Sed } else { 681193323Sed ++NumRetValsEliminated; 682202375Srdivacky DEBUG(dbgs() << "DAE - Removing return value " << i << " from " 683198090Srdivacky << F->getName() << "\n"); 684193323Sed } 685193323Sed } 686193323Sed else 687193323Sed // We used to return a single value. 688193323Sed if (LiveValues.erase(CreateRet(F, 0))) { 689193323Sed RetTypes.push_back(RetTy); 690193323Sed NewRetIdxs[0] = 0; 691193323Sed } else { 692202375Srdivacky DEBUG(dbgs() << "DAE - Removing return value from " << F->getName() 693198090Srdivacky << "\n"); 694193323Sed ++NumRetValsEliminated; 695193323Sed } 696193323Sed if (RetTypes.size() > 1) 697193323Sed // More than one return type? Return a struct with them. Also, if we used 698193323Sed // to return a struct and didn't change the number of return values, 699193323Sed // return a struct again. This prevents changing {something} into 700193323Sed // something and {} into void. 701193323Sed // Make the new struct packed if we used to return a packed struct 702193323Sed // already. 703198090Srdivacky NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked()); 704193323Sed else if (RetTypes.size() == 1) 705193323Sed // One return type? Just a simple value then, but only if we didn't use to 706193323Sed // return a struct with that simple value before. 707193323Sed NRetTy = RetTypes.front(); 708193323Sed else if (RetTypes.size() == 0) 709193323Sed // No return types? Make it void, but only if we didn't use to return {}. 710198090Srdivacky NRetTy = Type::getVoidTy(F->getContext()); 711193323Sed } 712193323Sed 713193323Sed assert(NRetTy && "No new return type found?"); 714193323Sed 715193323Sed // Remove any incompatible attributes, but only if we removed all return 716193323Sed // values. Otherwise, ensure that we don't have any conflicting attributes 717193323Sed // here. Currently, this should not be possible, but special handling might be 718193323Sed // required when new return value attributes are added. 719206083Srdivacky if (NRetTy->isVoidTy()) 720193323Sed RAttrs &= ~Attribute::typeIncompatible(NRetTy); 721193323Sed else 722206083Srdivacky assert((RAttrs & Attribute::typeIncompatible(NRetTy)) == 0 723193323Sed && "Return attributes no longer compatible?"); 724193323Sed 725193323Sed if (RAttrs) 726193323Sed AttributesVec.push_back(AttributeWithIndex::get(0, RAttrs)); 727193323Sed 728193323Sed // Remember which arguments are still alive. 729193323Sed SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false); 730193323Sed // Construct the new parameter list from non-dead arguments. Also construct 731193323Sed // a new set of parameter attributes to correspond. Skip the first parameter 732193323Sed // attribute, since that belongs to the return value. 733193323Sed unsigned i = 0; 734193323Sed for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); 735193323Sed I != E; ++I, ++i) { 736193323Sed RetOrArg Arg = CreateArg(F, i); 737193323Sed if (LiveValues.erase(Arg)) { 738193323Sed Params.push_back(I->getType()); 739193323Sed ArgAlive[i] = true; 740193323Sed 741193323Sed // Get the original parameter attributes (skipping the first one, that is 742193323Sed // for the return value. 743193323Sed if (Attributes Attrs = PAL.getParamAttributes(i + 1)) 744193323Sed AttributesVec.push_back(AttributeWithIndex::get(Params.size(), Attrs)); 745193323Sed } else { 746193323Sed ++NumArgumentsEliminated; 747202375Srdivacky DEBUG(dbgs() << "DAE - Removing argument " << i << " (" << I->getName() 748198090Srdivacky << ") from " << F->getName() << "\n"); 749193323Sed } 750193323Sed } 751193323Sed 752206083Srdivacky if (FnAttrs != Attribute::None) 753193323Sed AttributesVec.push_back(AttributeWithIndex::get(~0, FnAttrs)); 754193323Sed 755193323Sed // Reconstruct the AttributesList based on the vector we constructed. 756206083Srdivacky AttrListPtr NewPAL = AttrListPtr::get(AttributesVec.begin(), 757206083Srdivacky AttributesVec.end()); 758193323Sed 759193323Sed // Create the new function type based on the recomputed parameters. 760206083Srdivacky FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg()); 761193323Sed 762193323Sed // No change? 763193323Sed if (NFTy == FTy) 764193323Sed return false; 765193323Sed 766193323Sed // Create the new function body and insert it into the module... 767193323Sed Function *NF = Function::Create(NFTy, F->getLinkage()); 768193323Sed NF->copyAttributesFrom(F); 769193323Sed NF->setAttributes(NewPAL); 770193323Sed // Insert the new function before the old function, so we won't be processing 771193323Sed // it again. 772193323Sed F->getParent()->getFunctionList().insert(F, NF); 773193323Sed NF->takeName(F); 774193323Sed 775193323Sed // Loop over all of the callers of the function, transforming the call sites 776193323Sed // to pass in a smaller number of arguments into the new function. 777193323Sed // 778193323Sed std::vector<Value*> Args; 779193323Sed while (!F->use_empty()) { 780212904Sdim CallSite CS(F->use_back()); 781193323Sed Instruction *Call = CS.getInstruction(); 782193323Sed 783193323Sed AttributesVec.clear(); 784193323Sed const AttrListPtr &CallPAL = CS.getAttributes(); 785193323Sed 786193323Sed // The call return attributes. 787193323Sed Attributes RAttrs = CallPAL.getRetAttributes(); 788193323Sed Attributes FnAttrs = CallPAL.getFnAttributes(); 789193323Sed // Adjust in case the function was changed to return void. 790193323Sed RAttrs &= ~Attribute::typeIncompatible(NF->getReturnType()); 791193323Sed if (RAttrs) 792193323Sed AttributesVec.push_back(AttributeWithIndex::get(0, RAttrs)); 793193323Sed 794193323Sed // Declare these outside of the loops, so we can reuse them for the second 795193323Sed // loop, which loops the varargs. 796193323Sed CallSite::arg_iterator I = CS.arg_begin(); 797193323Sed unsigned i = 0; 798193323Sed // Loop over those operands, corresponding to the normal arguments to the 799193323Sed // original function, and add those that are still alive. 800193323Sed for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i) 801193323Sed if (ArgAlive[i]) { 802193323Sed Args.push_back(*I); 803193323Sed // Get original parameter attributes, but skip return attributes. 804193323Sed if (Attributes Attrs = CallPAL.getParamAttributes(i + 1)) 805193323Sed AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs)); 806193323Sed } 807193323Sed 808193323Sed // Push any varargs arguments on the list. Don't forget their attributes. 809193323Sed for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) { 810193323Sed Args.push_back(*I); 811193323Sed if (Attributes Attrs = CallPAL.getParamAttributes(i + 1)) 812193323Sed AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs)); 813193323Sed } 814193323Sed 815193323Sed if (FnAttrs != Attribute::None) 816193323Sed AttributesVec.push_back(AttributeWithIndex::get(~0, FnAttrs)); 817193323Sed 818193323Sed // Reconstruct the AttributesList based on the vector we constructed. 819193323Sed AttrListPtr NewCallPAL = AttrListPtr::get(AttributesVec.begin(), 820193323Sed AttributesVec.end()); 821193323Sed 822193323Sed Instruction *New; 823193323Sed if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) { 824193323Sed New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(), 825193323Sed Args.begin(), Args.end(), "", Call); 826193323Sed cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv()); 827193323Sed cast<InvokeInst>(New)->setAttributes(NewCallPAL); 828193323Sed } else { 829193323Sed New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call); 830193323Sed cast<CallInst>(New)->setCallingConv(CS.getCallingConv()); 831193323Sed cast<CallInst>(New)->setAttributes(NewCallPAL); 832193323Sed if (cast<CallInst>(Call)->isTailCall()) 833193323Sed cast<CallInst>(New)->setTailCall(); 834193323Sed } 835212904Sdim New->setDebugLoc(Call->getDebugLoc()); 836207618Srdivacky 837193323Sed Args.clear(); 838193323Sed 839193323Sed if (!Call->use_empty()) { 840193323Sed if (New->getType() == Call->getType()) { 841193323Sed // Return type not changed? Just replace users then. 842193323Sed Call->replaceAllUsesWith(New); 843193323Sed New->takeName(Call); 844206083Srdivacky } else if (New->getType()->isVoidTy()) { 845193323Sed // Our return value has uses, but they will get removed later on. 846193323Sed // Replace by null for now. 847218893Sdim if (!Call->getType()->isX86_MMXTy()) 848218893Sdim Call->replaceAllUsesWith(Constant::getNullValue(Call->getType())); 849193323Sed } else { 850204642Srdivacky assert(RetTy->isStructTy() && 851193323Sed "Return type changed, but not into a void. The old return type" 852193323Sed " must have been a struct!"); 853193323Sed Instruction *InsertPt = Call; 854193323Sed if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) { 855193323Sed BasicBlock::iterator IP = II->getNormalDest()->begin(); 856193323Sed while (isa<PHINode>(IP)) ++IP; 857193323Sed InsertPt = IP; 858193323Sed } 859206083Srdivacky 860193323Sed // We used to return a struct. Instead of doing smart stuff with all the 861193323Sed // uses of this struct, we will just rebuild it using 862193323Sed // extract/insertvalue chaining and let instcombine clean that up. 863193323Sed // 864193323Sed // Start out building up our return value from undef 865198090Srdivacky Value *RetVal = UndefValue::get(RetTy); 866193323Sed for (unsigned i = 0; i != RetCount; ++i) 867193323Sed if (NewRetIdxs[i] != -1) { 868193323Sed Value *V; 869193323Sed if (RetTypes.size() > 1) 870193323Sed // We are still returning a struct, so extract the value from our 871193323Sed // return value 872193323Sed V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret", 873193323Sed InsertPt); 874193323Sed else 875193323Sed // We are now returning a single element, so just insert that 876193323Sed V = New; 877193323Sed // Insert the value at the old position 878193323Sed RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt); 879193323Sed } 880193323Sed // Now, replace all uses of the old call instruction with the return 881193323Sed // struct we built 882193323Sed Call->replaceAllUsesWith(RetVal); 883193323Sed New->takeName(Call); 884193323Sed } 885193323Sed } 886193323Sed 887193323Sed // Finally, remove the old call from the program, reducing the use-count of 888193323Sed // F. 889193323Sed Call->eraseFromParent(); 890193323Sed } 891193323Sed 892193323Sed // Since we have now created the new function, splice the body of the old 893193323Sed // function right into the new function, leaving the old rotting hulk of the 894193323Sed // function empty. 895193323Sed NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList()); 896193323Sed 897221345Sdim // Loop over the argument list, transferring uses of the old arguments over to 898221345Sdim // the new arguments, also transferring over the names as well. 899193323Sed i = 0; 900193323Sed for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(), 901193323Sed I2 = NF->arg_begin(); I != E; ++I, ++i) 902193323Sed if (ArgAlive[i]) { 903193323Sed // If this is a live argument, move the name and users over to the new 904193323Sed // version. 905193323Sed I->replaceAllUsesWith(I2); 906193323Sed I2->takeName(I); 907193323Sed ++I2; 908193323Sed } else { 909193323Sed // If this argument is dead, replace any uses of it with null constants 910193323Sed // (these are guaranteed to become unused later on). 911218893Sdim if (!I->getType()->isX86_MMXTy()) 912218893Sdim I->replaceAllUsesWith(Constant::getNullValue(I->getType())); 913193323Sed } 914193323Sed 915193323Sed // If we change the return value of the function we must rewrite any return 916193323Sed // instructions. Check this now. 917193323Sed if (F->getReturnType() != NF->getReturnType()) 918193323Sed for (Function::iterator BB = NF->begin(), E = NF->end(); BB != E; ++BB) 919193323Sed if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) { 920193323Sed Value *RetVal; 921193323Sed 922208599Srdivacky if (NFTy->getReturnType()->isVoidTy()) { 923193323Sed RetVal = 0; 924193323Sed } else { 925204642Srdivacky assert (RetTy->isStructTy()); 926193323Sed // The original return value was a struct, insert 927193323Sed // extractvalue/insertvalue chains to extract only the values we need 928193323Sed // to return and insert them into our new result. 929193323Sed // This does generate messy code, but we'll let it to instcombine to 930193323Sed // clean that up. 931193323Sed Value *OldRet = RI->getOperand(0); 932193323Sed // Start out building up our return value from undef 933198090Srdivacky RetVal = UndefValue::get(NRetTy); 934193323Sed for (unsigned i = 0; i != RetCount; ++i) 935193323Sed if (NewRetIdxs[i] != -1) { 936193323Sed ExtractValueInst *EV = ExtractValueInst::Create(OldRet, i, 937193323Sed "oldret", RI); 938193323Sed if (RetTypes.size() > 1) { 939193323Sed // We're still returning a struct, so reinsert the value into 940193323Sed // our new return value at the new index 941193323Sed 942193323Sed RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i], 943193323Sed "newret", RI); 944193323Sed } else { 945193323Sed // We are now only returning a simple value, so just return the 946193323Sed // extracted value. 947193323Sed RetVal = EV; 948193323Sed } 949193323Sed } 950193323Sed } 951193323Sed // Replace the return instruction with one returning the new return 952193323Sed // value (possibly 0 if we became void). 953198090Srdivacky ReturnInst::Create(F->getContext(), RetVal, RI); 954193323Sed BB->getInstList().erase(RI); 955193323Sed } 956193323Sed 957193323Sed // Now that the old function is dead, delete it. 958193323Sed F->eraseFromParent(); 959193323Sed 960193323Sed return true; 961193323Sed} 962193323Sed 963193323Sedbool DAE::runOnModule(Module &M) { 964193323Sed bool Changed = false; 965193323Sed 966193323Sed // First pass: Do a simple check to see if any functions can have their "..." 967193323Sed // removed. We can do this if they never call va_start. This loop cannot be 968193323Sed // fused with the next loop, because deleting a function invalidates 969193323Sed // information computed while surveying other functions. 970202375Srdivacky DEBUG(dbgs() << "DAE - Deleting dead varargs\n"); 971193323Sed for (Module::iterator I = M.begin(), E = M.end(); I != E; ) { 972193323Sed Function &F = *I++; 973193323Sed if (F.getFunctionType()->isVarArg()) 974193323Sed Changed |= DeleteDeadVarargs(F); 975193323Sed } 976193323Sed 977193323Sed // Second phase:loop through the module, determining which arguments are live. 978193323Sed // We assume all arguments are dead unless proven otherwise (allowing us to 979193323Sed // determine that dead arguments passed into recursive functions are dead). 980193323Sed // 981202375Srdivacky DEBUG(dbgs() << "DAE - Determining liveness\n"); 982193323Sed for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 983193323Sed SurveyFunction(*I); 984206083Srdivacky 985193323Sed // Now, remove all dead arguments and return values from each function in 986206083Srdivacky // turn. 987193323Sed for (Module::iterator I = M.begin(), E = M.end(); I != E; ) { 988206083Srdivacky // Increment now, because the function will probably get removed (ie. 989193323Sed // replaced by a new one). 990193323Sed Function *F = I++; 991193323Sed Changed |= RemoveDeadStuffFromFunction(F); 992193323Sed } 993218893Sdim 994218893Sdim // Finally, look for any unused parameters in functions with non-local 995218893Sdim // linkage and replace the passed in parameters with undef. 996218893Sdim for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) { 997218893Sdim Function& F = *I; 998218893Sdim 999218893Sdim Changed |= RemoveDeadArgumentsFromCallers(F); 1000218893Sdim } 1001218893Sdim 1002193323Sed return Changed; 1003193323Sed} 1004