X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FTransforms%2FIPO%2FDeadArgumentElimination.cpp;h=c06d688b3c4816555238a453b0252fc0062a7348;hp=8299dbc0d871643d6b09ae3d162dee9c7d7ba726;hb=d13db2c59cc94162d6cf0a04187d408bfef6d4a7;hpb=c9235d2e855c56e9aa157969f8132a05f9ba89d8 diff --git a/lib/Transforms/IPO/DeadArgumentElimination.cpp b/lib/Transforms/IPO/DeadArgumentElimination.cpp index 8299dbc0d87..c06d688b3c4 100644 --- a/lib/Transforms/IPO/DeadArgumentElimination.cpp +++ b/lib/Transforms/IPO/DeadArgumentElimination.cpp @@ -10,10 +10,10 @@ // This pass deletes dead arguments from internal functions. Dead argument // elimination removes arguments which are directly dead, as well as arguments // only passed into function calls as dead arguments of other functions. This -// pass also deletes dead arguments in a similar way. +// pass also deletes dead return values in a similar way. // // This pass is often useful as a cleanup pass to run after aggressive -// interprocedural passes, which add possibly-dead arguments. +// interprocedural passes, which add possibly-dead arguments or return values. // //===----------------------------------------------------------------------===// @@ -24,13 +24,15 @@ #include "llvm/DerivedTypes.h" #include "llvm/Instructions.h" #include "llvm/IntrinsicInst.h" +#include "llvm/LLVMContext.h" #include "llvm/Module.h" #include "llvm/Pass.h" #include "llvm/Support/CallSite.h" #include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/Statistic.h" -#include "llvm/Support/Compiler.h" +#include "llvm/ADT/StringExtras.h" #include #include using namespace llvm; @@ -41,77 +43,133 @@ STATISTIC(NumRetValsEliminated , "Number of unused return values removed"); namespace { /// DAE - The dead argument elimination pass. /// - class VISIBILITY_HIDDEN DAE : public ModulePass { + class DAE : public ModulePass { + public: + + /// Struct that represents (part of) either a return value or a function + /// argument. Used so that arguments and return values can be used + /// interchangably. + struct RetOrArg { + RetOrArg(const Function *F, unsigned Idx, bool IsArg) : F(F), Idx(Idx), + IsArg(IsArg) {} + const Function *F; + unsigned Idx; + bool IsArg; + + /// Make RetOrArg comparable, so we can put it into a map. + bool operator<(const RetOrArg &O) const { + if (F != O.F) + return F < O.F; + else if (Idx != O.Idx) + return Idx < O.Idx; + else + return IsArg < O.IsArg; + } + + /// Make RetOrArg comparable, so we can easily iterate the multimap. + bool operator==(const RetOrArg &O) const { + return F == O.F && Idx == O.Idx && IsArg == O.IsArg; + } + + std::string getDescription() const { + return std::string((IsArg ? "Argument #" : "Return value #")) + + utostr(Idx) + " of function " + F->getNameStr(); + } + }; + /// Liveness enum - During our initial pass over the program, we determine - /// that things are either definately alive, definately dead, or in need of - /// interprocedural analysis (MaybeLive). - /// - enum Liveness { Live, MaybeLive, Dead }; - - /// LiveArguments, MaybeLiveArguments, DeadArguments - These sets contain - /// all of the arguments in the program. The Dead set contains arguments - /// which are completely dead (never used in the function). The MaybeLive - /// set contains arguments which are only passed into other function calls, - /// thus may be live and may be dead. The Live set contains arguments which - /// are known to be alive. - /// - std::set DeadArguments, MaybeLiveArguments, LiveArguments; - - /// DeadRetVal, MaybeLiveRetVal, LifeRetVal - These sets contain all of the - /// functions in the program. The Dead set contains functions whose return - /// value is known to be dead. The MaybeLive set contains functions whose - /// return values are only used by return instructions, and the Live set - /// contains functions whose return values are used, functions that are - /// external, and functions that already return void. - /// - std::set DeadRetVal, MaybeLiveRetVal, LiveRetVal; - - /// InstructionsToInspect - As we mark arguments and return values - /// MaybeLive, we keep track of which instructions could make the values - /// live here. Once the entire program has had the return value and - /// arguments analyzed, this set is scanned to promote the MaybeLive objects - /// to be Live if they really are used. - std::vector InstructionsToInspect; - - /// CallSites - Keep track of the call sites of functions that have - /// MaybeLive arguments or return values. - std::multimap CallSites; + /// that things are either alive or maybe alive. We don't mark anything + /// explicitly dead (even if we know they are), since anything not alive + /// with no registered uses (in Uses) will never be marked alive and will + /// thus become dead in the end. + enum Liveness { Live, MaybeLive }; + + /// Convenience wrapper + RetOrArg CreateRet(const Function *F, unsigned Idx) { + return RetOrArg(F, Idx, false); + } + /// Convenience wrapper + RetOrArg CreateArg(const Function *F, unsigned Idx) { + return RetOrArg(F, Idx, true); + } + + typedef std::multimap UseMap; + /// This maps a return value or argument to any MaybeLive return values or + /// arguments it uses. This allows the MaybeLive values to be marked live + /// when any of its users is marked live. + /// For example (indices are left out for clarity): + /// - Uses[ret F] = ret G + /// This means that F calls G, and F returns the value returned by G. + /// - Uses[arg F] = ret G + /// This means that some function calls G and passes its result as an + /// argument to F. + /// - Uses[ret F] = arg F + /// This means that F returns one of its own arguments. + /// - Uses[arg F] = arg G + /// This means that G calls F and passes one of its own (G's) arguments + /// directly to F. + UseMap Uses; + + typedef std::set LiveSet; + typedef std::set LiveFuncSet; + + /// This set contains all values that have been determined to be live. + LiveSet LiveValues; + /// This set contains all values that are cannot be changed in any way. + LiveFuncSet LiveFunctions; + + typedef SmallVector UseVector; + + protected: + // DAH uses this to specify a different ID. + explicit DAE(void *ID) : ModulePass(ID) {} public: static char ID; // Pass identification, replacement for typeid - DAE() : ModulePass((intptr_t)&ID) {} + DAE() : ModulePass(&ID) {} + bool runOnModule(Module &M); virtual bool ShouldHackArguments() const { return false; } private: - Liveness getArgumentLiveness(const Argument &A); - bool isMaybeLiveArgumentNowLive(Argument *Arg); - + Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses); + Liveness SurveyUse(Value::const_use_iterator U, UseVector &MaybeLiveUses, + unsigned RetValNum = 0); + Liveness SurveyUses(const Value *V, UseVector &MaybeLiveUses); + + void SurveyFunction(const Function &F); + void MarkValue(const RetOrArg &RA, Liveness L, + const UseVector &MaybeLiveUses); + void MarkLive(const RetOrArg &RA); + void MarkLive(const Function &F); + void PropagateLiveness(const RetOrArg &RA); + bool RemoveDeadStuffFromFunction(Function *F); bool DeleteDeadVarargs(Function &Fn); - void SurveyFunction(Function &Fn); + }; +} - void MarkArgumentLive(Argument *Arg); - void MarkRetValLive(Function *F); - void MarkReturnInstArgumentLive(ReturnInst *RI); - void RemoveDeadArgumentsFromFunction(Function *F); - }; - char DAE::ID = 0; - RegisterPass X("deadargelim", "Dead Argument Elimination"); +char DAE::ID = 0; +INITIALIZE_PASS(DAE, "deadargelim", "Dead Argument Elimination", false, false); +namespace { /// DAH - DeadArgumentHacking pass - Same as dead argument elimination, but /// deletes arguments to functions which are external. This is only for use /// by bugpoint. struct DAH : public DAE { static char ID; + DAH() : DAE(&ID) {} + virtual bool ShouldHackArguments() const { return true; } }; - char DAH::ID = 0; - RegisterPass Y("deadarghaX0r", - "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)"); } +char DAH::ID = 0; +INITIALIZE_PASS(DAH, "deadarghaX0r", + "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)", + false, false); + /// createDeadArgEliminationPass - This pass removes arguments from functions /// which are not used by the body of the function. /// @@ -122,18 +180,11 @@ ModulePass *llvm::createDeadArgHackingPass() { return new DAH(); } /// llvm.vastart is never called, the varargs list is dead for the function. bool DAE::DeleteDeadVarargs(Function &Fn) { assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!"); - if (Fn.isDeclaration() || !Fn.hasInternalLinkage()) return false; + if (Fn.isDeclaration() || !Fn.hasLocalLinkage()) return false; // Ensure that the function is only directly called. - for (Value::use_iterator I = Fn.use_begin(), E = Fn.use_end(); I != E; ++I) { - // If this use is anything other than a call site, give up. - CallSite CS = CallSite::get(*I); - Instruction *TheCall = CS.getInstruction(); - if (!TheCall) return false; // Not a direct call site? - - // The addr of this function is passed to the call. - if (I.getOperandNo() != 0) return false; - } + if (Fn.hasAddressTaken()) + return false; // Okay, we know we can transform this function if safe. Scan its body // looking for calls to llvm.vastart. @@ -150,18 +201,17 @@ bool DAE::DeleteDeadVarargs(Function &Fn) { // remove the "..." and adjust all the calls. // Start by computing a new prototype for the function, which is the same as - // the old function, but has fewer arguments. + // the old function, but doesn't have isVarArg set. const FunctionType *FTy = Fn.getFunctionType(); + std::vector Params(FTy->param_begin(), FTy->param_end()); - FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params, false); + FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), + Params, false); unsigned NumArgs = Params.size(); // Create the new function body and insert it into the module... - Function *NF = new Function(NFTy, Fn.getLinkage()); - NF->setCallingConv(Fn.getCallingConv()); - NF->setParamAttrs(Fn.getParamAttrs()); - if (Fn.hasCollector()) - NF->setCollector(Fn.getCollector()); + Function *NF = Function::Create(NFTy, Fn.getLinkage()); + NF->copyAttributesFrom(&Fn); Fn.getParent()->getFunctionList().insert(&Fn, NF); NF->takeName(&Fn); @@ -177,27 +227,31 @@ bool DAE::DeleteDeadVarargs(Function &Fn) { Args.assign(CS.arg_begin(), CS.arg_begin()+NumArgs); // Drop any attributes that were on the vararg arguments. - PAListPtr PAL = CS.getParamAttrs(); + AttrListPtr PAL = CS.getAttributes(); if (!PAL.isEmpty() && PAL.getSlot(PAL.getNumSlots() - 1).Index > NumArgs) { - SmallVector ParamAttrsVec; + SmallVector AttributesVec; for (unsigned i = 0; PAL.getSlot(i).Index <= NumArgs; ++i) - ParamAttrsVec.push_back(PAL.getSlot(i)); - PAL = PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end()); + AttributesVec.push_back(PAL.getSlot(i)); + if (Attributes FnAttrs = PAL.getFnAttributes()) + AttributesVec.push_back(AttributeWithIndex::get(~0, FnAttrs)); + PAL = AttrListPtr::get(AttributesVec.begin(), AttributesVec.end()); } Instruction *New; if (InvokeInst *II = dyn_cast(Call)) { - New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(), - Args.begin(), Args.end(), "", Call); + New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(), + Args.begin(), Args.end(), "", Call); cast(New)->setCallingConv(CS.getCallingConv()); - cast(New)->setParamAttrs(PAL); + cast(New)->setAttributes(PAL); } else { - New = new CallInst(NF, Args.begin(), Args.end(), "", Call); + New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call); cast(New)->setCallingConv(CS.getCallingConv()); - cast(New)->setParamAttrs(PAL); + cast(New)->setAttributes(PAL); if (cast(Call)->isTailCall()) cast(New)->setTailCall(); } + New->setDebugLoc(Call->getDebugLoc()); + Args.clear(); if (!Call->use_empty()) @@ -231,330 +285,437 @@ bool DAE::DeleteDeadVarargs(Function &Fn) { return true; } - -static inline bool CallPassesValueThoughVararg(Instruction *Call, - const Value *Arg) { - CallSite CS = CallSite::get(Call); - const Type *CalledValueTy = CS.getCalledValue()->getType(); - const Type *FTy = cast(CalledValueTy)->getElementType(); - unsigned NumFixedArgs = cast(FTy)->getNumParams(); - for (CallSite::arg_iterator AI = CS.arg_begin()+NumFixedArgs; - AI != CS.arg_end(); ++AI) - if (AI->get() == Arg) - return true; - return false; +/// Convenience function that returns the number of return values. It returns 0 +/// for void functions and 1 for functions not returning a struct. It returns +/// the number of struct elements for functions returning a struct. +static unsigned NumRetVals(const Function *F) { + if (F->getReturnType()->isVoidTy()) + return 0; + else if (const StructType *STy = dyn_cast(F->getReturnType())) + return STy->getNumElements(); + else + return 1; } -// getArgumentLiveness - Inspect an argument, determining if is known Live -// (used in a computation), MaybeLive (only passed as an argument to a call), or -// Dead (not used). -DAE::Liveness DAE::getArgumentLiveness(const Argument &A) { - const Function *F = A.getParent(); - - // If this is the return value of a struct function, it's not really dead. - if (F->hasStructRetAttr() && &*(F->arg_begin()) == &A) +/// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not +/// live, it adds Use to the MaybeLiveUses argument. Returns the determined +/// liveness of Use. +DAE::Liveness DAE::MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses) { + // We're live if our use or its Function is already marked as live. + if (LiveFunctions.count(Use.F) || LiveValues.count(Use)) return Live; - - if (A.use_empty()) // First check, directly dead? - return Dead; - - // Scan through all of the uses, looking for non-argument passing uses. - for (Value::use_const_iterator I = A.use_begin(), E = A.use_end(); I!=E;++I) { - // Return instructions do not immediately effect liveness. - if (isa(*I)) - continue; - - CallSite CS = CallSite::get(const_cast(*I)); - if (!CS.getInstruction()) { - // If its used by something that is not a call or invoke, it's alive! - return Live; + + // We're maybe live otherwise, but remember that we must become live if + // Use becomes live. + MaybeLiveUses.push_back(Use); + return MaybeLive; +} + + +/// SurveyUse - This looks at a single use of an argument or return value +/// and determines if it should be alive or not. Adds this use to MaybeLiveUses +/// if it causes the used value to become MaybeLive. +/// +/// RetValNum is the return value number to use when this use is used in a +/// return instruction. This is used in the recursion, you should always leave +/// it at 0. +DAE::Liveness DAE::SurveyUse(Value::const_use_iterator U, + UseVector &MaybeLiveUses, unsigned RetValNum) { + const User *V = *U; + if (const ReturnInst *RI = dyn_cast(V)) { + // The value is returned from a function. It's only live when the + // function's return value is live. We use RetValNum here, for the case + // that U is really a use of an insertvalue instruction that uses the + // orginal Use. + RetOrArg Use = CreateRet(RI->getParent()->getParent(), RetValNum); + // We might be live, depending on the liveness of Use. + return MarkIfNotLive(Use, MaybeLiveUses); + } + if (const InsertValueInst *IV = dyn_cast(V)) { + if (U.getOperandNo() != InsertValueInst::getAggregateOperandIndex() + && IV->hasIndices()) + // The use we are examining is inserted into an aggregate. Our liveness + // depends on all uses of that aggregate, but if it is used as a return + // value, only index at which we were inserted counts. + RetValNum = *IV->idx_begin(); + + // Note that if we are used as the aggregate operand to the insertvalue, + // we don't change RetValNum, but do survey all our uses. + + Liveness Result = MaybeLive; + for (Value::const_use_iterator I = IV->use_begin(), + E = V->use_end(); I != E; ++I) { + Result = SurveyUse(I, MaybeLiveUses, RetValNum); + if (Result == Live) + break; + } + return Result; } - // If it's an indirect call, mark it alive... - Function *Callee = CS.getCalledFunction(); - if (!Callee) return Live; - - // Check to see if it's passed through a va_arg area: if so, we cannot - // remove it. - if (CallPassesValueThoughVararg(CS.getInstruction(), &A)) - return Live; // If passed through va_arg area, we cannot remove it - } - return MaybeLive; // It must be used, but only as argument to a function + if (ImmutableCallSite CS = V) { + const Function *F = CS.getCalledFunction(); + if (F) { + // Used in a direct call. + + // Find the argument number. We know for sure that this use is an + // argument, since if it was the function argument this would be an + // indirect call and the we know can't be looking at a value of the + // label type (for the invoke instruction). + unsigned ArgNo = CS.getArgumentNo(U); + + if (ArgNo >= F->getFunctionType()->getNumParams()) + // The value is passed in through a vararg! Must be live. + return Live; + + assert(CS.getArgument(ArgNo) + == CS->getOperand(U.getOperandNo()) + && "Argument is not where we expected it"); + + // Value passed to a normal call. It's only live when the corresponding + // argument to the called function turns out live. + RetOrArg Use = CreateArg(F, ArgNo); + return MarkIfNotLive(Use, MaybeLiveUses); + } + } + // Used in any other way? Value must be live. + return Live; } +/// SurveyUses - This looks at all the uses of the given value +/// Returns the Liveness deduced from the uses of this value. +/// +/// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. If +/// the result is Live, MaybeLiveUses might be modified but its content should +/// be ignored (since it might not be complete). +DAE::Liveness DAE::SurveyUses(const Value *V, UseVector &MaybeLiveUses) { + // Assume it's dead (which will only hold if there are no uses at all..). + Liveness Result = MaybeLive; + // Check each use. + for (Value::const_use_iterator I = V->use_begin(), + E = V->use_end(); I != E; ++I) { + Result = SurveyUse(I, MaybeLiveUses); + if (Result == Live) + break; + } + return Result; +} // SurveyFunction - This performs the initial survey of the specified function, // checking out whether or not it uses any of its incoming arguments or whether -// any callers use the return value. This fills in the -// (Dead|MaybeLive|Live)(Arguments|RetVal) sets. +// any callers use the return value. This fills in the LiveValues set and Uses +// map. // // We consider arguments of non-internal functions to be intrinsically alive as // well as arguments to functions which have their "address taken". // -void DAE::SurveyFunction(Function &F) { - bool FunctionIntrinsicallyLive = false; - Liveness RetValLiveness = F.getReturnType() == Type::VoidTy ? Live : Dead; - - if (!F.hasInternalLinkage() && - (!ShouldHackArguments() || F.isIntrinsic())) - FunctionIntrinsicallyLive = true; - else - for (Value::use_iterator I = F.use_begin(), E = F.use_end(); I != E; ++I) { - // If this use is anything other than a call site, the function is alive. - CallSite CS = CallSite::get(*I); - Instruction *TheCall = CS.getInstruction(); - if (!TheCall) { // Not a direct call site? - FunctionIntrinsicallyLive = true; - break; +void DAE::SurveyFunction(const Function &F) { + unsigned RetCount = NumRetVals(&F); + // Assume all return values are dead + typedef SmallVector RetVals; + RetVals RetValLiveness(RetCount, MaybeLive); + + typedef SmallVector RetUses; + // These vectors map each return value to the uses that make it MaybeLive, so + // we can add those to the Uses map if the return value really turns out to be + // MaybeLive. Initialized to a list of RetCount empty lists. + RetUses MaybeLiveRetUses(RetCount); + + for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB) + if (const ReturnInst *RI = dyn_cast(BB->getTerminator())) + if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType() + != F.getFunctionType()->getReturnType()) { + // We don't support old style multiple return values. + MarkLive(F); + return; } - // Check to see if the return value is used... - if (RetValLiveness != Live) - for (Value::use_iterator I = TheCall->use_begin(), - E = TheCall->use_end(); I != E; ++I) - if (isa(cast(*I))) { - RetValLiveness = MaybeLive; - } else if (isa(cast(*I)) || - isa(cast(*I))) { - if (CallPassesValueThoughVararg(cast(*I), TheCall) || - !CallSite::get(cast(*I)).getCalledFunction()) { - RetValLiveness = Live; - break; - } else { - RetValLiveness = MaybeLive; + if (!F.hasLocalLinkage() && (!ShouldHackArguments() || F.isIntrinsic())) { + MarkLive(F); + return; + } + + DEBUG(dbgs() << "DAE - Inspecting callers for fn: " << F.getName() << "\n"); + // Keep track of the number of live retvals, so we can skip checks once all + // of them turn out to be live. + unsigned NumLiveRetVals = 0; + const Type *STy = dyn_cast(F.getReturnType()); + // Loop all uses of the function. + for (Value::const_use_iterator I = F.use_begin(), E = F.use_end(); + I != E; ++I) { + // If the function is PASSED IN as an argument, its address has been + // taken. + ImmutableCallSite CS(*I); + if (!CS || !CS.isCallee(I)) { + MarkLive(F); + return; + } + + // If this use is anything other than a call site, the function is alive. + const Instruction *TheCall = CS.getInstruction(); + if (!TheCall) { // Not a direct call site? + MarkLive(F); + return; + } + + // If we end up here, we are looking at a direct call to our function. + + // Now, check how our return value(s) is/are used in this caller. Don't + // bother checking return values if all of them are live already. + if (NumLiveRetVals != RetCount) { + if (STy) { + // Check all uses of the return value. + for (Value::const_use_iterator I = TheCall->use_begin(), + E = TheCall->use_end(); I != E; ++I) { + const ExtractValueInst *Ext = dyn_cast(*I); + if (Ext && Ext->hasIndices()) { + // This use uses a part of our return value, survey the uses of + // that part and store the results for this index only. + unsigned Idx = *Ext->idx_begin(); + if (RetValLiveness[Idx] != Live) { + RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]); + if (RetValLiveness[Idx] == Live) + NumLiveRetVals++; } } else { - RetValLiveness = Live; + // Used by something else than extractvalue. Mark all return + // values as live. + for (unsigned i = 0; i != RetCount; ++i ) + RetValLiveness[i] = Live; + NumLiveRetVals = RetCount; break; } - - // If the function is PASSED IN as an argument, its address has been taken - for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end(); - AI != E; ++AI) - if (AI->get() == &F) { - FunctionIntrinsicallyLive = true; - break; } - if (FunctionIntrinsicallyLive) break; + } else { + // Single return value + RetValLiveness[0] = SurveyUses(TheCall, MaybeLiveRetUses[0]); + if (RetValLiveness[0] == Live) + NumLiveRetVals = RetCount; + } } - - if (FunctionIntrinsicallyLive) { - DOUT << " Intrinsically live fn: " << F.getName() << "\n"; - for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); - AI != E; ++AI) - LiveArguments.insert(AI); - LiveRetVal.insert(&F); - return; } - switch (RetValLiveness) { - case Live: LiveRetVal.insert(&F); break; - case MaybeLive: MaybeLiveRetVal.insert(&F); break; - case Dead: DeadRetVal.insert(&F); break; + // Now we've inspected all callers, record the liveness of our return values. + for (unsigned i = 0; i != RetCount; ++i) + MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]); + + DEBUG(dbgs() << "DAE - Inspecting args for fn: " << F.getName() << "\n"); + + // Now, check all of our arguments. + unsigned i = 0; + UseVector MaybeLiveArgUses; + for (Function::const_arg_iterator AI = F.arg_begin(), + E = F.arg_end(); AI != E; ++AI, ++i) { + // See what the effect of this use is (recording any uses that cause + // MaybeLive in MaybeLiveArgUses). + Liveness Result = SurveyUses(AI, MaybeLiveArgUses); + // Mark the result. + MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses); + // Clear the vector again for the next iteration. + MaybeLiveArgUses.clear(); } +} - DOUT << " Inspecting args for fn: " << F.getName() << "\n"; - - // If it is not intrinsically alive, we know that all users of the - // function are call sites. Mark all of the arguments live which are - // directly used, and keep track of all of the call sites of this function - // if there are any arguments we assume that are dead. - // - bool AnyMaybeLiveArgs = false; - for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); - AI != E; ++AI) - switch (getArgumentLiveness(*AI)) { - case Live: - DOUT << " Arg live by use: " << AI->getName() << "\n"; - LiveArguments.insert(AI); - break; - case Dead: - DOUT << " Arg definitely dead: " << AI->getName() <<"\n"; - DeadArguments.insert(AI); - break; +/// MarkValue - This function marks the liveness of RA depending on L. If L is +/// MaybeLive, it also takes all uses in MaybeLiveUses and records them in Uses, +/// such that RA will be marked live if any use in MaybeLiveUses gets marked +/// live later on. +void DAE::MarkValue(const RetOrArg &RA, Liveness L, + const UseVector &MaybeLiveUses) { + switch (L) { + case Live: MarkLive(RA); break; case MaybeLive: - DOUT << " Arg only passed to calls: " << AI->getName() << "\n"; - AnyMaybeLiveArgs = true; - MaybeLiveArguments.insert(AI); + { + // Note any uses of this value, so this return value can be + // marked live whenever one of the uses becomes live. + for (UseVector::const_iterator UI = MaybeLiveUses.begin(), + UE = MaybeLiveUses.end(); UI != UE; ++UI) + Uses.insert(std::make_pair(*UI, RA)); break; } - - // If there are any "MaybeLive" arguments, we need to check callees of - // this function when/if they become alive. Record which functions are - // callees... - if (AnyMaybeLiveArgs || RetValLiveness == MaybeLive) - for (Value::use_iterator I = F.use_begin(), E = F.use_end(); - I != E; ++I) { - if (AnyMaybeLiveArgs) - CallSites.insert(std::make_pair(&F, CallSite::get(*I))); - - if (RetValLiveness == MaybeLive) - for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); - UI != E; ++UI) - InstructionsToInspect.push_back(cast(*UI)); - } -} - -// isMaybeLiveArgumentNowLive - Check to see if Arg is alive. At this point, we -// know that the only uses of Arg are to be passed in as an argument to a -// function call or return. Check to see if the formal argument passed in is in -// the LiveArguments set. If so, return true. -// -bool DAE::isMaybeLiveArgumentNowLive(Argument *Arg) { - for (Value::use_iterator I = Arg->use_begin(), E = Arg->use_end(); I!=E; ++I){ - if (isa(*I)) { - if (LiveRetVal.count(Arg->getParent())) return true; - continue; - } - - CallSite CS = CallSite::get(*I); - - // We know that this can only be used for direct calls... - Function *Callee = CS.getCalledFunction(); - - // Loop over all of the arguments (because Arg may be passed into the call - // multiple times) and check to see if any are now alive... - CallSite::arg_iterator CSAI = CS.arg_begin(); - for (Function::arg_iterator AI = Callee->arg_begin(), E = Callee->arg_end(); - AI != E; ++AI, ++CSAI) - // If this is the argument we are looking for, check to see if it's alive - if (*CSAI == Arg && LiveArguments.count(AI)) - return true; } - return false; } -/// MarkArgumentLive - The MaybeLive argument 'Arg' is now known to be alive. -/// Mark it live in the specified sets and recursively mark arguments in callers -/// live that are needed to pass in a value. -/// -void DAE::MarkArgumentLive(Argument *Arg) { - std::set::iterator It = MaybeLiveArguments.lower_bound(Arg); - if (It == MaybeLiveArguments.end() || *It != Arg) return; - - DOUT << " MaybeLive argument now live: " << Arg->getName() <<"\n"; - MaybeLiveArguments.erase(It); - LiveArguments.insert(Arg); - - // Loop over all of the call sites of the function, making any arguments - // passed in to provide a value for this argument live as necessary. - // - Function *Fn = Arg->getParent(); - unsigned ArgNo = std::distance(Fn->arg_begin(), Function::arg_iterator(Arg)); - - std::multimap::iterator I = CallSites.lower_bound(Fn); - for (; I != CallSites.end() && I->first == Fn; ++I) { - CallSite CS = I->second; - Value *ArgVal = *(CS.arg_begin()+ArgNo); - if (Argument *ActualArg = dyn_cast(ArgVal)) { - MarkArgumentLive(ActualArg); - } else { - // If the value passed in at this call site is a return value computed by - // some other call site, make sure to mark the return value at the other - // call site as being needed. - CallSite ArgCS = CallSite::get(ArgVal); - if (ArgCS.getInstruction()) - if (Function *Fn = ArgCS.getCalledFunction()) - MarkRetValLive(Fn); - } - } +/// MarkLive - Mark the given Function as alive, meaning that it cannot be +/// changed in any way. Additionally, +/// mark any values that are used as this function's parameters or by its return +/// values (according to Uses) live as well. +void DAE::MarkLive(const Function &F) { + DEBUG(dbgs() << "DAE - Intrinsically live fn: " << F.getName() << "\n"); + // Mark the function as live. + LiveFunctions.insert(&F); + // Mark all arguments as live. + for (unsigned i = 0, e = F.arg_size(); i != e; ++i) + PropagateLiveness(CreateArg(&F, i)); + // Mark all return values as live. + for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i) + PropagateLiveness(CreateRet(&F, i)); } -/// MarkArgumentLive - The MaybeLive return value for the specified function is -/// now known to be alive. Propagate this fact to the return instructions which -/// produce it. -void DAE::MarkRetValLive(Function *F) { - assert(F && "Shame shame, we can't have null pointers here!"); - - // Check to see if we already knew it was live - std::set::iterator I = MaybeLiveRetVal.lower_bound(F); - if (I == MaybeLiveRetVal.end() || *I != F) return; // It's already alive! +/// MarkLive - Mark the given return value or argument as live. Additionally, +/// mark any values that are used by this value (according to Uses) live as +/// well. +void DAE::MarkLive(const RetOrArg &RA) { + if (LiveFunctions.count(RA.F)) + return; // Function was already marked Live. - DOUT << " MaybeLive retval now live: " << F->getName() << "\n"; + if (!LiveValues.insert(RA).second) + return; // We were already marked Live. - MaybeLiveRetVal.erase(I); - LiveRetVal.insert(F); // It is now known to be live! - - // Loop over all of the functions, noticing that the return value is now live. - for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) - if (ReturnInst *RI = dyn_cast(BB->getTerminator())) - MarkReturnInstArgumentLive(RI); + DEBUG(dbgs() << "DAE - Marking " << RA.getDescription() << " live\n"); + PropagateLiveness(RA); } -void DAE::MarkReturnInstArgumentLive(ReturnInst *RI) { - Value *Op = RI->getOperand(0); - if (Argument *A = dyn_cast(Op)) { - MarkArgumentLive(A); - } else if (CallInst *CI = dyn_cast(Op)) { - if (Function *F = CI->getCalledFunction()) - MarkRetValLive(F); - } else if (InvokeInst *II = dyn_cast(Op)) { - if (Function *F = II->getCalledFunction()) - MarkRetValLive(F); - } +/// PropagateLiveness - Given that RA is a live value, propagate it's liveness +/// to any other values it uses (according to Uses). +void DAE::PropagateLiveness(const RetOrArg &RA) { + // We don't use upper_bound (or equal_range) here, because our recursive call + // to ourselves is likely to cause the upper_bound (which is the first value + // not belonging to RA) to become erased and the iterator invalidated. + UseMap::iterator Begin = Uses.lower_bound(RA); + UseMap::iterator E = Uses.end(); + UseMap::iterator I; + for (I = Begin; I != E && I->first == RA; ++I) + MarkLive(I->second); + + // Erase RA from the Uses map (from the lower bound to wherever we ended up + // after the loop). + Uses.erase(Begin, I); } -// RemoveDeadArgumentsFromFunction - We know that F has dead arguments, as -// specified by the DeadArguments list. Transform the function and all of the -// callees of the function to not have these arguments. +// RemoveDeadStuffFromFunction - Remove any arguments and return values from F +// that are not in LiveValues. Transform the function and all of the callees of +// the function to not have these arguments and return values. // -void DAE::RemoveDeadArgumentsFromFunction(Function *F) { +bool DAE::RemoveDeadStuffFromFunction(Function *F) { + // Don't modify fully live functions + if (LiveFunctions.count(F)) + return false; + // Start by computing a new prototype for the function, which is the same as - // the old function, but has fewer arguments. + // the old function, but has fewer arguments and a different return type. const FunctionType *FTy = F->getFunctionType(); std::vector Params; - // Set up to build a new list of parameter attributes - SmallVector ParamAttrsVec; - const PAListPtr &PAL = F->getParamAttrs(); + // Set up to build a new list of parameter attributes. + SmallVector AttributesVec; + const AttrListPtr &PAL = F->getAttributes(); // The existing function return attributes. - ParameterAttributes RAttrs = PAL.getParamAttrs(0); + Attributes RAttrs = PAL.getRetAttributes(); + Attributes FnAttrs = PAL.getFnAttributes(); + + // Find out the new return value. - // Make the function return void if the return value is dead. const Type *RetTy = FTy->getReturnType(); - if (DeadRetVal.count(F)) { - RetTy = Type::VoidTy; - RAttrs &= ~ParamAttr::typeIncompatible(RetTy); - DeadRetVal.erase(F); + const Type *NRetTy = NULL; + unsigned RetCount = NumRetVals(F); + + // -1 means unused, other numbers are the new index + SmallVector NewRetIdxs(RetCount, -1); + std::vector RetTypes; + if (RetTy->isVoidTy()) { + NRetTy = RetTy; + } else { + const StructType *STy = dyn_cast(RetTy); + if (STy) + // Look at each of the original return values individually. + for (unsigned i = 0; i != RetCount; ++i) { + RetOrArg Ret = CreateRet(F, i); + if (LiveValues.erase(Ret)) { + RetTypes.push_back(STy->getElementType(i)); + NewRetIdxs[i] = RetTypes.size() - 1; + } else { + ++NumRetValsEliminated; + DEBUG(dbgs() << "DAE - Removing return value " << i << " from " + << F->getName() << "\n"); + } + } + else + // We used to return a single value. + if (LiveValues.erase(CreateRet(F, 0))) { + RetTypes.push_back(RetTy); + NewRetIdxs[0] = 0; + } else { + DEBUG(dbgs() << "DAE - Removing return value from " << F->getName() + << "\n"); + ++NumRetValsEliminated; + } + if (RetTypes.size() > 1) + // More than one return type? Return a struct with them. Also, if we used + // to return a struct and didn't change the number of return values, + // return a struct again. This prevents changing {something} into + // something and {} into void. + // Make the new struct packed if we used to return a packed struct + // already. + NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked()); + else if (RetTypes.size() == 1) + // One return type? Just a simple value then, but only if we didn't use to + // return a struct with that simple value before. + NRetTy = RetTypes.front(); + else if (RetTypes.size() == 0) + // No return types? Make it void, but only if we didn't use to return {}. + NRetTy = Type::getVoidTy(F->getContext()); } + assert(NRetTy && "No new return type found?"); + + // Remove any incompatible attributes, but only if we removed all return + // values. Otherwise, ensure that we don't have any conflicting attributes + // here. Currently, this should not be possible, but special handling might be + // required when new return value attributes are added. + if (NRetTy->isVoidTy()) + RAttrs &= ~Attribute::typeIncompatible(NRetTy); + else + assert((RAttrs & Attribute::typeIncompatible(NRetTy)) == 0 + && "Return attributes no longer compatible?"); + if (RAttrs) - ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, RAttrs)); + AttributesVec.push_back(AttributeWithIndex::get(0, RAttrs)); + // Remember which arguments are still alive. + SmallVector ArgAlive(FTy->getNumParams(), false); // Construct the new parameter list from non-dead arguments. Also construct - // a new set of parameter attributes to correspond. - unsigned index = 1; - for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; - ++I, ++index) - if (!DeadArguments.count(I)) { + // a new set of parameter attributes to correspond. Skip the first parameter + // attribute, since that belongs to the return value. + unsigned i = 0; + for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); + I != E; ++I, ++i) { + RetOrArg Arg = CreateArg(F, i); + if (LiveValues.erase(Arg)) { Params.push_back(I->getType()); - - if (ParameterAttributes Attrs = PAL.getParamAttrs(index)) - ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), Attrs)); + ArgAlive[i] = true; + + // Get the original parameter attributes (skipping the first one, that is + // for the return value. + if (Attributes Attrs = PAL.getParamAttributes(i + 1)) + AttributesVec.push_back(AttributeWithIndex::get(Params.size(), Attrs)); + } else { + ++NumArgumentsEliminated; + DEBUG(dbgs() << "DAE - Removing argument " << i << " (" << I->getName() + << ") from " << F->getName() << "\n"); } + } - // Reconstruct the ParamAttrsList based on the vector we constructed. - PAListPtr NewPAL = PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end()); + if (FnAttrs != Attribute::None) + AttributesVec.push_back(AttributeWithIndex::get(~0, FnAttrs)); - // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which - // have zero fixed arguments. - // - bool ExtraArgHack = false; - if (Params.empty() && FTy->isVarArg()) { - ExtraArgHack = true; - Params.push_back(Type::Int32Ty); - } + // Reconstruct the AttributesList based on the vector we constructed. + AttrListPtr NewPAL = AttrListPtr::get(AttributesVec.begin(), + AttributesVec.end()); // Create the new function type based on the recomputed parameters. - FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg()); + FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg()); + + // No change? + if (NFTy == FTy) + return false; // Create the new function body and insert it into the module... - Function *NF = new Function(NFTy, F->getLinkage()); - NF->setCallingConv(F->getCallingConv()); - NF->setParamAttrs(NewPAL); - if (F->hasCollector()) - NF->setCollector(F->getCollector()); + Function *NF = Function::Create(NFTy, F->getLinkage()); + NF->copyAttributesFrom(F); + NF->setAttributes(NewPAL); + // Insert the new function before the old function, so we won't be processing + // it again. F->getParent()->getFunctionList().insert(F, NF); NF->takeName(F); @@ -565,68 +726,113 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) { while (!F->use_empty()) { CallSite CS = CallSite::get(F->use_back()); Instruction *Call = CS.getInstruction(); - ParamAttrsVec.clear(); - const PAListPtr &CallPAL = CS.getParamAttrs(); + + AttributesVec.clear(); + const AttrListPtr &CallPAL = CS.getAttributes(); // The call return attributes. - ParameterAttributes RAttrs = CallPAL.getParamAttrs(0); + Attributes RAttrs = CallPAL.getRetAttributes(); + Attributes FnAttrs = CallPAL.getFnAttributes(); // Adjust in case the function was changed to return void. - RAttrs &= ~ParamAttr::typeIncompatible(NF->getReturnType()); + RAttrs &= ~Attribute::typeIncompatible(NF->getReturnType()); if (RAttrs) - ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, RAttrs)); - - // Loop over the operands, deleting dead ones... - CallSite::arg_iterator AI = CS.arg_begin(); - index = 1; - for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); - I != E; ++I, ++AI, ++index) - if (!DeadArguments.count(I)) { // Remove operands for dead arguments - Args.push_back(*AI); - if (ParameterAttributes Attrs = CallPAL.getParamAttrs(index)) - ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); + AttributesVec.push_back(AttributeWithIndex::get(0, RAttrs)); + + // Declare these outside of the loops, so we can reuse them for the second + // loop, which loops the varargs. + CallSite::arg_iterator I = CS.arg_begin(); + unsigned i = 0; + // Loop over those operands, corresponding to the normal arguments to the + // original function, and add those that are still alive. + for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i) + if (ArgAlive[i]) { + Args.push_back(*I); + // Get original parameter attributes, but skip return attributes. + if (Attributes Attrs = CallPAL.getParamAttributes(i + 1)) + AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs)); } - if (ExtraArgHack) - Args.push_back(UndefValue::get(Type::Int32Ty)); - // Push any varargs arguments on the list. Don't forget their attributes. - for (; AI != CS.arg_end(); ++AI) { - Args.push_back(*AI); - if (ParameterAttributes Attrs = CallPAL.getParamAttrs(index++)) - ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); + for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) { + Args.push_back(*I); + if (Attributes Attrs = CallPAL.getParamAttributes(i + 1)) + AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs)); } - // Reconstruct the ParamAttrsList based on the vector we constructed. - PAListPtr NewCallPAL = PAListPtr::get(ParamAttrsVec.begin(), - ParamAttrsVec.end()); + if (FnAttrs != Attribute::None) + AttributesVec.push_back(AttributeWithIndex::get(~0, FnAttrs)); + + // Reconstruct the AttributesList based on the vector we constructed. + AttrListPtr NewCallPAL = AttrListPtr::get(AttributesVec.begin(), + AttributesVec.end()); Instruction *New; if (InvokeInst *II = dyn_cast(Call)) { - New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(), - Args.begin(), Args.end(), "", Call); + New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(), + Args.begin(), Args.end(), "", Call); cast(New)->setCallingConv(CS.getCallingConv()); - cast(New)->setParamAttrs(NewCallPAL); + cast(New)->setAttributes(NewCallPAL); } else { - New = new CallInst(NF, Args.begin(), Args.end(), "", Call); + New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call); cast(New)->setCallingConv(CS.getCallingConv()); - cast(New)->setParamAttrs(NewCallPAL); + cast(New)->setAttributes(NewCallPAL); if (cast(Call)->isTailCall()) cast(New)->setTailCall(); } + New->setDebugLoc(Call->getDebugLoc()); + Args.clear(); if (!Call->use_empty()) { - if (New->getType() == Type::VoidTy) - Call->replaceAllUsesWith(Constant::getNullValue(Call->getType())); - else { + if (New->getType() == Call->getType()) { + // Return type not changed? Just replace users then. Call->replaceAllUsesWith(New); New->takeName(Call); + } else if (New->getType()->isVoidTy()) { + // Our return value has uses, but they will get removed later on. + // Replace by null for now. + Call->replaceAllUsesWith(Constant::getNullValue(Call->getType())); + } else { + assert(RetTy->isStructTy() && + "Return type changed, but not into a void. The old return type" + " must have been a struct!"); + Instruction *InsertPt = Call; + if (InvokeInst *II = dyn_cast(Call)) { + BasicBlock::iterator IP = II->getNormalDest()->begin(); + while (isa(IP)) ++IP; + InsertPt = IP; + } + + // We used to return a struct. Instead of doing smart stuff with all the + // uses of this struct, we will just rebuild it using + // extract/insertvalue chaining and let instcombine clean that up. + // + // Start out building up our return value from undef + Value *RetVal = UndefValue::get(RetTy); + for (unsigned i = 0; i != RetCount; ++i) + if (NewRetIdxs[i] != -1) { + Value *V; + if (RetTypes.size() > 1) + // We are still returning a struct, so extract the value from our + // return value + V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret", + InsertPt); + else + // We are now returning a single element, so just insert that + V = New; + // Insert the value at the old position + RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt); + } + // Now, replace all uses of the old call instruction with the return + // struct we built + Call->replaceAllUsesWith(RetVal); + New->takeName(Call); } } // Finally, remove the old call from the program, reducing the use-count of // F. - Call->getParent()->getInstList().erase(Call); + Call->eraseFromParent(); } // Since we have now created the new function, splice the body of the old @@ -635,13 +841,11 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) { NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList()); // Loop over the argument list, transfering uses of the old arguments over to - // the new arguments, also transfering over the names as well. While we're at - // it, remove the dead arguments from the DeadArguments list. - // + // the new arguments, also transfering over the names as well. + i = 0; for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(), - I2 = NF->arg_begin(); - I != E; ++I) - if (!DeadArguments.count(I)) { + I2 = NF->arg_begin(); I != E; ++I, ++i) + if (ArgAlive[i]) { // If this is a live argument, move the name and users over to the new // version. I->replaceAllUsesWith(I2); @@ -649,10 +853,8 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) { ++I2; } else { // If this argument is dead, replace any uses of it with null constants - // (these are guaranteed to only be operands to call instructions which - // will later be simplified). + // (these are guaranteed to become unused later on). I->replaceAllUsesWith(Constant::getNullValue(I->getType())); - DeadArguments.erase(I); } // If we change the return value of the function we must rewrite any return @@ -660,114 +862,78 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) { if (F->getReturnType() != NF->getReturnType()) for (Function::iterator BB = NF->begin(), E = NF->end(); BB != E; ++BB) if (ReturnInst *RI = dyn_cast(BB->getTerminator())) { - new ReturnInst(0, RI); + Value *RetVal; + + if (NFTy->getReturnType()->isVoidTy()) { + RetVal = 0; + } else { + assert (RetTy->isStructTy()); + // The original return value was a struct, insert + // extractvalue/insertvalue chains to extract only the values we need + // to return and insert them into our new result. + // This does generate messy code, but we'll let it to instcombine to + // clean that up. + Value *OldRet = RI->getOperand(0); + // Start out building up our return value from undef + RetVal = UndefValue::get(NRetTy); + for (unsigned i = 0; i != RetCount; ++i) + if (NewRetIdxs[i] != -1) { + ExtractValueInst *EV = ExtractValueInst::Create(OldRet, i, + "oldret", RI); + if (RetTypes.size() > 1) { + // We're still returning a struct, so reinsert the value into + // our new return value at the new index + + RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i], + "newret", RI); + } else { + // We are now only returning a simple value, so just return the + // extracted value. + RetVal = EV; + } + } + } + // Replace the return instruction with one returning the new return + // value (possibly 0 if we became void). + ReturnInst::Create(F->getContext(), RetVal, RI); BB->getInstList().erase(RI); } // Now that the old function is dead, delete it. - F->getParent()->getFunctionList().erase(F); + F->eraseFromParent(); + + return true; } bool DAE::runOnModule(Module &M) { bool Changed = false; + // First pass: Do a simple check to see if any functions can have their "..." // removed. We can do this if they never call va_start. This loop cannot be // fused with the next loop, because deleting a function invalidates // information computed while surveying other functions. - DOUT << "DAE - Deleting dead varargs\n"; + DEBUG(dbgs() << "DAE - Deleting dead varargs\n"); for (Module::iterator I = M.begin(), E = M.end(); I != E; ) { Function &F = *I++; if (F.getFunctionType()->isVarArg()) Changed |= DeleteDeadVarargs(F); } - + // Second phase:loop through the module, determining which arguments are live. // We assume all arguments are dead unless proven otherwise (allowing us to // determine that dead arguments passed into recursive functions are dead). // - DOUT << "DAE - Determining liveness\n"; + DEBUG(dbgs() << "DAE - Determining liveness\n"); for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) SurveyFunction(*I); - // Loop over the instructions to inspect, propagating liveness among arguments - // and return values which are MaybeLive. - while (!InstructionsToInspect.empty()) { - Instruction *I = InstructionsToInspect.back(); - InstructionsToInspect.pop_back(); - - if (ReturnInst *RI = dyn_cast(I)) { - // For return instructions, we just have to check to see if the return - // value for the current function is known now to be alive. If so, any - // arguments used by it are now alive, and any call instruction return - // value is alive as well. - if (LiveRetVal.count(RI->getParent()->getParent())) - MarkReturnInstArgumentLive(RI); - - } else { - CallSite CS = CallSite::get(I); - assert(CS.getInstruction() && "Unknown instruction for the I2I list!"); - - Function *Callee = CS.getCalledFunction(); - - // If we found a call or invoke instruction on this list, that means that - // an argument of the function is a call instruction. If the argument is - // live, then the return value of the called instruction is now live. - // - CallSite::arg_iterator AI = CS.arg_begin(); // ActualIterator - for (Function::arg_iterator FI = Callee->arg_begin(), - E = Callee->arg_end(); FI != E; ++AI, ++FI) { - // If this argument is another call... - CallSite ArgCS = CallSite::get(*AI); - if (ArgCS.getInstruction() && LiveArguments.count(FI)) - if (Function *Callee = ArgCS.getCalledFunction()) - MarkRetValLive(Callee); - } - } - } - - // Now we loop over all of the MaybeLive arguments, promoting them to be live - // arguments if one of the calls that uses the arguments to the calls they are - // passed into requires them to be live. Of course this could make other - // arguments live, so process callers recursively. - // - // Because elements can be removed from the MaybeLiveArguments set, copy it to - // a temporary vector. - // - std::vector TmpArgList(MaybeLiveArguments.begin(), - MaybeLiveArguments.end()); - for (unsigned i = 0, e = TmpArgList.size(); i != e; ++i) { - Argument *MLA = TmpArgList[i]; - if (MaybeLiveArguments.count(MLA) && - isMaybeLiveArgumentNowLive(MLA)) - MarkArgumentLive(MLA); + // Now, remove all dead arguments and return values from each function in + // turn. + for (Module::iterator I = M.begin(), E = M.end(); I != E; ) { + // Increment now, because the function will probably get removed (ie. + // replaced by a new one). + Function *F = I++; + Changed |= RemoveDeadStuffFromFunction(F); } - - // Recover memory early... - CallSites.clear(); - - // At this point, we know that all arguments in DeadArguments and - // MaybeLiveArguments are dead. If the two sets are empty, there is nothing - // to do. - if (MaybeLiveArguments.empty() && DeadArguments.empty() && - MaybeLiveRetVal.empty() && DeadRetVal.empty()) - return Changed; - - // Otherwise, compact into one set, and start eliminating the arguments from - // the functions. - DeadArguments.insert(MaybeLiveArguments.begin(), MaybeLiveArguments.end()); - MaybeLiveArguments.clear(); - DeadRetVal.insert(MaybeLiveRetVal.begin(), MaybeLiveRetVal.end()); - MaybeLiveRetVal.clear(); - - LiveArguments.clear(); - LiveRetVal.clear(); - - NumArgumentsEliminated += DeadArguments.size(); - NumRetValsEliminated += DeadRetVal.size(); - while (!DeadArguments.empty()) - RemoveDeadArgumentsFromFunction((*DeadArguments.begin())->getParent()); - - while (!DeadRetVal.empty()) - RemoveDeadArgumentsFromFunction(*DeadRetVal.begin()); - return true; + return Changed; }