diff options
Diffstat (limited to 'lib/Transforms/IPO')
| -rw-r--r-- | lib/Transforms/IPO/DeadArgumentElimination.cpp | 838 |
1 files changed, 469 insertions, 369 deletions
diff --git a/lib/Transforms/IPO/DeadArgumentElimination.cpp b/lib/Transforms/IPO/DeadArgumentElimination.cpp index 604a1483c4..331152aeaf 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. // //===----------------------------------------------------------------------===// @@ -42,40 +42,66 @@ namespace { /// DAE - The dead argument elimination pass. /// class VISIBILITY_HIDDEN DAE : public ModulePass { + public: + + /// Struct that represent either a (part of 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; + } + }; + /// 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<Argument*> 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<Function*> 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<Instruction*> InstructionsToInspect; - - /// CallSites - Keep track of the call sites of functions that have - /// MaybeLive arguments or return values. - std::multimap<Function*, CallSite> CallSites; + /// 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<RetOrArg, RetOrArg> UseMap; + /// This map maps a return value or argument to all return values or + /// arguments it uses. + /// 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<RetOrArg> LiveSet; + + /// This set contains all values that have been determined to be live + LiveSet LiveValues; + + typedef SmallVector<RetOrArg, 5> UseVector; + + /// This is the set of functions that have been inspected. Since LiveValues + /// keeps a list of live values for inspected functions only, this way we + /// can prevent uninspected functions becoming completely dead. + std::set<Function*> InspectedFunctions; public: static char ID; // Pass identification, replacement for typeid @@ -85,20 +111,19 @@ namespace { virtual bool ShouldHackArguments() const { return false; } private: - Liveness getArgumentLiveness(const Argument &A); - bool isMaybeLiveArgumentNowLive(Argument *Arg); - + Liveness IsMaybeLive(RetOrArg Use, UseVector &MaybeLiveUses); + Liveness SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses, unsigned RetValNum = 0); + Liveness SurveyUses(Value *V, UseVector &MaybeLiveUses); + + void SurveyFunction(Function &F); + void MarkValue(const RetOrArg &RA, Liveness L, const UseVector &MaybeLiveUses); + void MarkLive(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; static RegisterPass<DAE> X("deadargelim", "Dead Argument Elimination"); @@ -155,7 +180,7 @@ 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<const Type*> Params(FTy->param_begin(), FTy->param_end()); FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params, false); @@ -233,57 +258,110 @@ 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<PointerType>(CalledValueTy)->getElementType(); - unsigned NumFixedArgs = cast<FunctionType>(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() == Type::VoidTy) + return 0; + else if (const StructType *STy = dyn_cast<StructType>(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) +/// IsMaybeAlive - This checks Use for liveness. If Use is live, returns Live, +/// else returns MaybeLive. Also, adds Use to MaybeLiveUses in the latter case. +DAE::Liveness DAE::IsMaybeLive(RetOrArg Use, UseVector &MaybeLiveUses) { + // We're live if our use is already marked as live + if (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<ReturnInst>(*I)) - continue; - - CallSite CS = CallSite::get(const_cast<User*>(*I)); - if (!CS.getInstruction()) { - // If its used by something that is not a call or invoke, it's alive! - return Live; - } - // 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 + // 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 MaybeAlive. +/// +/// 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::use_iterator U, UseVector &MaybeLiveUses, unsigned RetValNum) { + Value *V = *U; + if (ReturnInst *RI = dyn_cast<ReturnInst>(V)) { + // The value is returned from another function. It's only live when the + // caller's return value is live + RetOrArg Use = CreateRet(RI->getParent()->getParent(), RetValNum); + // We might be live, depending on the liveness of Use + return IsMaybeLive(Use, MaybeLiveUses); + } + if (InsertValueInst *IV = dyn_cast<InsertValueInst>(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 = Dead; + for (Value::use_iterator I = IV->use_begin(), + E = V->use_end(); I != E; ++I) { + Result = SurveyUse(I, MaybeLiveUses, RetValNum); + if (Result == Live) + break; + } + return Result; + } + CallSite CS = CallSite::get(V); + if (CS.getInstruction()) { + Function *F = CS.getCalledFunction(); + if (F) { + // Used in a direct call + + // Check for vararg. Do - 1 to skip the first operand to call (the + // function itself). + if (U.getOperandNo() - 1 >= F->getFunctionType()->getNumParams()) + // The value is passed in through a vararg! Must be live. + return Live; + + // Value passed to a normal call. It's only live when the corresponding + // argument (operand number - 1 to skip the function pointer operand) to + // the called function turns out live + RetOrArg Use = CreateArg(F, U.getOperandNo() - 1); + return IsMaybeLive(Use, MaybeLiveUses); + } else { + // Used in any other way? Value must be live. + return Live; + } + } + // Used in any other way? Value must be live. + return Live; } +/// SurveyUses - This looks at all the uses of the given return value +/// (possibly a partial return value from a function returning a struct). +/// Returns the Liveness deduced from the uses of this value. +/// +/// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. +DAE::Liveness DAE::SurveyUses(Value *V, UseVector &MaybeLiveUses) { + // Assume it's dead (which will only hold if there are no uses at all..) + Liveness Result = Dead; + // Check each use + for (Value::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 @@ -294,13 +372,36 @@ DAE::Liveness DAE::getArgumentLiveness(const Argument &A) { // well as arguments to functions which have their "address taken". // void DAE::SurveyFunction(Function &F) { + InspectedFunctions.insert(&F); bool FunctionIntrinsicallyLive = false; - Liveness RetValLiveness = F.getReturnType() == Type::VoidTy ? Live : Dead; - - if (!F.hasInternalLinkage() && - (!ShouldHackArguments() || F.isIntrinsic())) + unsigned RetCount = NumRetVals(&F); + // Assume all return values are dead + typedef SmallVector<Liveness, 5> RetVals; + RetVals RetValLiveness(RetCount, Dead); + + // These vectors maps each return value to the uses that make it MaybeLive, so + // we can add those to the MaybeLiveRetVals list if the return value + // really turns out to be MaybeLive. Initializes to RetCount empty vectors + typedef SmallVector<UseVector, 5> RetUses; + // Intialized to a list of RetCount empty lists + RetUses MaybeLiveRetUses(RetCount); + + for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) + if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) + if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType() != F.getFunctionType()->getReturnType()) { + // We don't support old style multiple return values + FunctionIntrinsicallyLive = true; + break; + } + if (!F.hasInternalLinkage() && (!ShouldHackArguments() || F.isIntrinsic())) FunctionIntrinsicallyLive = true; - else + if (!FunctionIntrinsicallyLive) { + DOUT << "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<StructType>(F.getReturnType()); + // Loop all uses of the function for (Value::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 if (I.getOperandNo() != 0) { @@ -315,191 +416,138 @@ void DAE::SurveyFunction(Function &F) { FunctionIntrinsicallyLive = true; break; } - - // 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<ReturnInst>(cast<Instruction>(*I))) { - RetValLiveness = MaybeLive; - } else if (isa<CallInst>(cast<Instruction>(*I)) || - isa<InvokeInst>(cast<Instruction>(*I))) { - if (CallPassesValueThoughVararg(cast<Instruction>(*I), TheCall) || - !CallSite::get(cast<Instruction>(*I)).getCalledFunction()) { - RetValLiveness = Live; - break; + + // 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::use_iterator I = TheCall->use_begin(), + E = TheCall->use_end(); I != E; ++I) { + ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(*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 = MaybeLive; + // 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; } - } else { - RetValLiveness = Live; - 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"; + DOUT << "DAE - Intrinsically live fn: " << F.getName() << "\n"; + // Mark all arguments as live + unsigned i = 0; for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); - AI != E; ++AI) - LiveArguments.insert(AI); - LiveRetVal.insert(&F); + AI != E; ++AI, ++i) + MarkLive(CreateArg(&F, i)); + // Mark all return values as live + i = 0; + for (unsigned i = 0, e = RetValLiveness.size(); i != e; ++i) + MarkLive(CreateRet(&F, i)); 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, e = RetValLiveness.size(); i != e; ++i) { + RetOrArg Ret = CreateRet(&F, i); + // Mark the result down + MarkValue(Ret, RetValLiveness[i], MaybeLiveRetUses[i]); } - - 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; - case MaybeLive: - DOUT << " Arg only passed to calls: " << AI->getName() << "\n"; - AnyMaybeLiveArgs = true; - MaybeLiveArguments.insert(AI); - 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<Instruction>(*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<ReturnInst>(*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; + DOUT << "DAE - Inspecting args for fn: " << F.getName() << "\n"; + + // Now, check all of our arguments + unsigned i = 0; + UseVector MaybeLiveArgUses; + for (Function::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); + RetOrArg Arg = CreateArg(&F, i); + // Mark the result down + MarkValue(Arg, Result, MaybeLiveArgUses); + // Clear the vector again for the next iteration + MaybeLiveArgUses.clear(); } - 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<Argument*>::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<Function*, CallSite>::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<Argument>(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); +/// MarkValue - This function marks the liveness of RA depending on L. If L is +/// MaybeLive, it also records any uses in MaybeLiveUses 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: + { + // Note any uses of this value, so this return value can be + // marked live whenever one of the uses becomes live. + UseMap::iterator Where = Uses.begin(); + for (UseVector::const_iterator UI = MaybeLiveUses.begin(), + UE = MaybeLiveUses.end(); UI != UE; ++UI) + Where = Uses.insert(Where, UseMap::value_type(*UI, RA)); + break; } + case Dead: break; } } -/// 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<Function*>::iterator I = MaybeLiveRetVal.lower_bound(F); - if (I == MaybeLiveRetVal.end() || *I != F) return; // It's already alive! - - DOUT << " MaybeLive retval now live: " << F->getName() << "\n"; - - 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<ReturnInst>(BB->getTerminator())) - MarkReturnInstArgumentLive(RI); -} +/// 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(RetOrArg RA) { + if (!LiveValues.insert(RA).second) + return; // We were already marked Live -void DAE::MarkReturnInstArgumentLive(ReturnInst *RI) { - Value *Op = RI->getOperand(0); - if (Argument *A = dyn_cast<Argument>(Op)) { - MarkArgumentLive(A); - } else if (CallInst *CI = dyn_cast<CallInst>(Op)) { - if (Function *F = CI->getCalledFunction()) - MarkRetValLive(F); - } else if (InvokeInst *II = dyn_cast<InvokeInst>(Op)) { - if (Function *F = II->getCalledFunction()) - MarkRetValLive(F); - } + if (RA.IsArg) + DOUT << "DAE - Marking argument " << RA.Idx << " to function " << RA.F->getNameStart() << " live\n"; + else + DOUT << "DAE - Marking return value " << RA.Idx << " of function " << RA.F->getNameStart() << " live\n"; + + std::pair<UseMap::iterator, UseMap::iterator> Range = Uses.equal_range(RA); + UseMap::iterator E = Range.second; + UseMap::iterator I = Range.first; + for (; I != E; ++I) + MarkLive(I->second); + // Erase RA from the Uses map (from the lower bound to wherever we ended up + // after the loop). + Uses.erase(Range.first, Range.second); } -// RemoveDeadArgumentsFromFunction - We know that F has dead arguments, as +// RemoveDeadStuffFromFunction - Remove any arguments and return values from F +// that are not in LiveValues. This function is a noop for any Function created +// by this function before, or any function that was not inspected for liveness. // specified by the DeadArguments list. Transform the function and all of the // callees of the function to not have these arguments. // -void DAE::RemoveDeadArgumentsFromFunction(Function *F) { +bool DAE::RemoveDeadStuffFromFunction(Function *F) { + // Don't process functions we didn't inspect (such as external functions, or + // functions that we've newly created). + if (!InspectedFunctions.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<const Type*> Params; @@ -510,28 +558,78 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) { // The existing function return attributes. ParameterAttributes RAttrs = PAL.getParamAttrs(0); - // Make the function return void if the return value is dead. + + // Find out the new return value + const Type *RetTy = FTy->getReturnType(); - if (DeadRetVal.count(F)) { - RetTy = Type::VoidTy; - RAttrs &= ~ParamAttr::typeIncompatible(RetTy); - DeadRetVal.erase(F); + const Type *NRetTy; + unsigned RetCount = NumRetVals(F); + // -1 means unused, other numbers are the new index + SmallVector<int, 5> NewRetIdxs(RetCount, -1); + std::vector<const Type*> RetTypes; + if (RetTy != Type::VoidTy) { + const StructType *STy = dyn_cast<StructType>(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; + DOUT << "DAE - Removing return value " << i << " from " << F->getNameStart() << "\n"; + } + } + else + // We used to return a single value + if (LiveValues.erase(CreateRet(F, 0))) { + RetTypes.push_back(RetTy); + NewRetIdxs[0] = 0; + } else { + DOUT << "DAE - Removing return value from " << F->getNameStart() << "\n"; + ++NumRetValsEliminated; + } + if (RetTypes.size() == 0) + // No return types? Make it void + NRetTy = Type::VoidTy; + else if (RetTypes.size() == 1) + // One return type? Just a simple value then + NRetTy = RetTypes.front(); + else + // More return types? Return a struct with them + NRetTy = StructType::get(RetTypes); + } else { + NRetTy = Type::VoidTy; } - + + // Remove any incompatible attributes + RAttrs &= ~ParamAttr::typeIncompatible(NRetTy); if (RAttrs) ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, RAttrs)); - + + // Remember which arguments are still alive + SmallVector<bool, 10> 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()); + ArgAlive[i] = true; - if (ParameterAttributes Attrs = PAL.getParamAttrs(index)) + // Get the original parameter attributes (skipping the first one, that is + // for the return value + if (ParameterAttributes Attrs = PAL.getParamAttrs(i + 1)) ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), Attrs)); + } else { + ++NumArgumentsEliminated; + DOUT << "DAE - Removing argument " << i << " (" << I->getNameStart() << ") from " << F->getNameStart() << "\n"; } + } // Reconstruct the ParamAttrsList based on the vector we constructed. PAListPtr NewPAL = PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end()); @@ -546,7 +644,11 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) { } // 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 = Function::Create(NFTy, F->getLinkage()); @@ -572,14 +674,17 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) { 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)) + // 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 (ParameterAttributes Attrs = CallPAL.getParamAttrs(i + 1)) ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); } @@ -587,9 +692,9 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) { 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++)) + for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) { + Args.push_back(*I); + if (ParameterAttributes Attrs = CallPAL.getParamAttrs(i + 1)) ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs)); } @@ -614,8 +719,45 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F) { if (!Call->use_empty()) { if (New->getType() == Type::VoidTy) + // Our return value was unused, replace by null for now, uses will get + // removed later on Call->replaceAllUsesWith(Constant::getNullValue(Call->getType())); - else { + else if (isa<StructType>(RetTy)) { + // The original return value was a struct, update all uses (which are + // all extractvalue instructions). + for (Value::use_iterator I = Call->use_begin(), E = Call->use_end(); + I != E;) { + assert(isa<ExtractValueInst>(*I) && "Return value not only used by extractvalue?"); + ExtractValueInst *EV = cast<ExtractValueInst>(*I); + // Increment now, since we're about to throw away this use. + ++I; + assert(EV->hasIndices() && "Return value used by extractvalue without indices?"); + unsigned Idx = *EV->idx_begin(); + if (NewRetIdxs[Idx] != -1) { + if (RetTypes.size() > 1) { + // We're still returning a struct, create a new extractvalue + // instruction with the first index updated + std::vector<unsigned> NewIdxs(EV->idx_begin(), EV->idx_end()); + NewIdxs[0] = NewRetIdxs[Idx]; + Value *NEV = ExtractValueInst::Create(New, NewIdxs.begin(), NewIdxs.end(), "retval", EV); + EV->replaceAllUsesWith(NEV); + EV->eraseFromParent(); + } else { + // We are now only returning a simple value, remove the + // extractvalue + EV->replaceAllUsesWith(New); + EV->eraseFromParent(); + } + } else { + // Value unused, replace uses by null for now, they will get removed + // later on + EV->replaceAllUsesWith(Constant::getNullValue(EV->getType())); + EV->eraseFromParent(); + } + } + New->takeName(Call); + } else { + // The original function had a single return value Call->replaceAllUsesWith(New); New->takeName(Call); } @@ -632,13 +774,11 @@ 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); @@ -646,10 +786,8 @@ 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 @@ -657,12 +795,45 @@ 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<ReturnInst>(BB->getTerminator())) { - ReturnInst::Create(0, RI); + Value *RetVal; + + if (NFTy->getReturnType() == Type::VoidTy) { + RetVal = 0; + } else { + assert (isa<StructType>(RetTy)); + // 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 = llvm::UndefValue::get(NRetTy); + for (unsigned i = 0; i != RetCount; ++i) + if (NewRetIdxs[i] != -1) { + ExtractValueInst *EV = ExtractValueInst::Create(OldRet, i, "newret", 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], "oldret"); + } 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(RetVal, RI); BB->getInstList().erase(RI); } // Now that the old function is dead, delete it. F->eraseFromParent(); + + return true; } bool DAE::runOnModule(Module &M) { @@ -677,7 +848,7 @@ bool DAE::runOnModule(Module &M) { 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). @@ -686,85 +857,14 @@ bool DAE::runOnModule(Module &M) { 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<ReturnInst>(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<Argument*> 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; } |