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Make this pass substantially stronger by having it delete dead return values

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as well as arguments.  Now it can delete arguments and return values which are
only passed into other arguments or are returned, if they are dead.  This causes
it to delete several hundred extra args/retvals from the C++ hello world program,
shrinking it by about 2K.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@9398 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-10-23 03:48:17 +00:00
parent 3087550362
commit c3afd9bf4b
1 changed files with 353 additions and 126 deletions
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479
lib/Transforms/IPO/DeadArgumentElimination.cpp
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@ -9,7 +9,8 @@
//
// 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.
// only passed into function calls as dead arguments of other functions. This
// pass also deletes dead arguments in a similar way.
//
// This pass is often useful as a cleanup pass to run after aggressive
// interprocedural passes, which add possibly-dead arguments.
@ -30,17 +31,68 @@
#include <set>
namespace {
Statistic<> NumArgumentsEliminated("deadargelim", "Number of args removed");
Statistic<> NumArgumentsEliminated("deadargelim",
"Number of unread args removed");
Statistic<> NumRetValsEliminated("deadargelim",
"Number of unused return values removed");
struct DAE : public Pass {
/// DAE - The dead argument elimination pass.
///
class DAE : public Pass {
/// DeleteFromExternalFunctions - Bugpoint sets this flag to indicate that
/// it is safe to hack apart functions without internal linkage.
bool DeleteFromExternalFunctions;
/// 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;
public:
DAE(bool DFEF = false) : DeleteFromExternalFunctions(DFEF) {}
bool run(Module &M);
private:
bool DeleteFromExternalFunctions;
bool FunctionArgumentsIntrinsicallyAlive(const Function &F);
void RemoveDeadArgumentsFromFunction(Function *F,
std::set<Argument*> &DeadArguments);
Liveness getArgumentLiveness(const Argument &A);
bool isMaybeLiveArgumentNowLive(Argument *Arg);
void SurveyFunction(Function &Fn);
void MarkArgumentLive(Argument *Arg);
void MarkRetValLive(Function *F);
void MarkReturnInstArgumentLive(ReturnInst *RI);
void RemoveDeadArgumentsFromFunction(Function *F);
};
RegisterOpt<DAE> X("deadargelim", "Dead Argument Elimination");
}
@ -55,70 +107,172 @@ Pass *createDeadArgEliminationPass(bool DeleteFromExternalFunctions) {
return new DAE(DeleteFromExternalFunctions);
}
// FunctionArgumentsIntrinsicallyAlive - Return true if the arguments of the
// specified function are intrinsically alive.
//
// We consider arguments of non-internal functions to be intrinsically alive as
// well as arguments to functions which have their "address taken".
//
bool DAE::FunctionArgumentsIntrinsicallyAlive(const Function &F) {
if (!F.hasInternalLinkage() && !DeleteFromExternalFunctions) return true;
for (Value::use_const_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(const_cast<User*>(*I));
if (!CS.getInstruction()) return true; // Not a valid call site?
// 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) 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;
}
namespace {
enum ArgumentLiveness { Alive, MaybeLive, Dead };
}
// getArgumentLiveness - Inspect an argument, determining if is known Alive
// 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).
static ArgumentLiveness getArgumentLiveness(const Argument &A) {
DAE::Liveness DAE::getArgumentLiveness(const Argument &A) {
if (A.use_empty()) return Dead; // First check, directly 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 Alive;
return Live;
}
// If it's an indirect call, mark it alive...
Function *Callee = CS.getCalledFunction();
if (!Callee) return Alive;
if (!Callee) return Live;
// Check to see if it's passed through a va_arg area: if so, we cannot
// remove it.
unsigned NumFixedArgs = Callee->getFunctionType()->getNumParams();
for (CallSite::arg_iterator AI = CS.arg_begin()+NumFixedArgs;
AI != CS.arg_end(); ++AI)
if (AI->get() == &A) // If passed through va_arg area, we cannot remove it
return Alive;
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
}
// isMaybeLiveArgumentNowAlive - 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. Check to see if the formal argument passed in is in the
// LiveArguments set. If so, return true.
// 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.
//
static bool isMaybeLiveArgumentNowAlive(Argument *Arg,
const std::set<Argument*> &LiveArguments) {
// 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() && !DeleteFromExternalFunctions)
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;
}
// 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;
} else {
RetValLiveness = MaybeLive;
}
} else {
RetValLiveness = Live;
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;
}
if (FunctionIntrinsicallyLive) {
DEBUG(std::cerr << " Intrinsically live fn: " << F.getName() << "\n");
for (Function::aiterator AI = F.abegin(), E = F.aend(); 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;
}
DEBUG(std::cerr << " 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::aiterator AI = F.abegin(), E = F.aend(); AI != E; ++AI)
switch (getArgumentLiveness(*AI)) {
case Live:
DEBUG(std::cerr << " Arg live by use: " << AI->getName() << "\n");
LiveArguments.insert(AI);
break;
case Dead:
DEBUG(std::cerr << " Arg definitely dead: " <<AI->getName()<<"\n");
DeadArguments.insert(AI);
break;
case MaybeLive:
DEBUG(std::cerr << " 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...
@ -136,18 +290,16 @@ static bool isMaybeLiveArgumentNowAlive(Argument *Arg,
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.
//
static void MarkArgumentLive(Argument *Arg,
std::set<Argument*> &MaybeLiveArguments,
std::set<Argument*> &LiveArguments,
const std::multimap<Function*, CallSite> &CallSites) {
/// 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;
DEBUG(std::cerr << " MaybeLive argument now live: " << Arg->getName()<<"\n");
assert(MaybeLiveArguments.count(Arg) && !LiveArguments.count(Arg) &&
"Arg not MaybeLive?");
MaybeLiveArguments.erase(Arg);
MaybeLiveArguments.erase(It);
LiveArguments.insert(Arg);
// Loop over all of the call sites of the function, making any arguments
@ -156,14 +308,55 @@ static void MarkArgumentLive(Argument *Arg,
Function *Fn = Arg->getParent();
unsigned ArgNo = std::distance(Fn->abegin(), Function::aiterator(Arg));
std::multimap<Function*, CallSite>::const_iterator I =
CallSites.lower_bound(Fn);
std::multimap<Function*, CallSite>::iterator I = CallSites.lower_bound(Fn);
for (; I != CallSites.end() && I->first == Fn; ++I) {
const CallSite &CS = I->second;
if (Argument *ActualArg = dyn_cast<Argument>(*(CS.arg_begin()+ArgNo)))
if (MaybeLiveArguments.count(ActualArg))
MarkArgumentLive(ActualArg, MaybeLiveArguments, LiveArguments,
CallSites);
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);
}
}
}
/// 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!
DEBUG(std::cerr << " 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);
}
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);
}
}
@ -171,8 +364,7 @@ static void MarkArgumentLive(Argument *Arg,
// 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,
std::set<Argument*> &DeadArguments){
void DAE::RemoveDeadArgumentsFromFunction(Function *F) {
// Start by computing a new prototype for the function, which is the same as
// the old function, but has fewer arguments.
const FunctionType *FTy = F->getFunctionType();
@ -182,9 +374,14 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F,
if (!DeadArguments.count(I))
Params.push_back(I->getType());
FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params,
FTy->isVarArg());
const Type *RetTy = FTy->getReturnType();
if (DeadRetVal.count(F)) {
RetTy = Type::VoidTy;
DeadRetVal.erase(F);
}
FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
// Create the new function body and insert it into the module...
Function *NF = new Function(NFTy, F->getLinkage(), F->getName());
F->getParent()->getFunctionList().insert(F, NF);
@ -192,19 +389,40 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F,
// Loop over all of the callers of the function, transforming the call sites
// to pass in a smaller number of arguments into the new function.
//
std::vector<Value*> Args;
while (!F->use_empty()) {
CallSite CS = CallSite::get(F->use_back());
Instruction *Call = CS.getInstruction();
CS.setCalledFunction(NF); // Reduce the uses count of F
// Loop over the operands, deleting dead ones...
CallSite::arg_iterator AI = CS.arg_begin();
for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
if (DeadArguments.count(I)) { // Remove operands for dead arguments
AI = Call->op_erase(AI);
} else {
++AI; // Leave live operands alone...
for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I, ++AI)
if (!DeadArguments.count(I)) // Remove operands for dead arguments
Args.push_back(*AI);
Instruction *New;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
New = new InvokeInst(NF, II->getNormalDest(), II->getExceptionalDest(),
Args, "", Call);
} else {
New = new CallInst(NF, Args, "", Call);
}
Args.clear();
if (!Call->use_empty()) {
if (New->getType() == Type::VoidTy)
Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
else {
Call->replaceAllUsesWith(New);
std::string Name = Call->getName();
Call->setName("");
New->setName(Name);
}
}
// Finally, remove the old call from the program, reducing the use-count of
// F.
Call->getParent()->getInstList().erase(Call);
}
// Since we have now created the new function, splice the body of the old
@ -232,6 +450,15 @@ void DAE::RemoveDeadArgumentsFromFunction(Function *F,
DeadArguments.erase(I);
}
// If we change the return value of the function we must rewrite any return
// instructions. Check this now.
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())) {
new ReturnInst(0, RI);
BB->getInstList().erase(RI);
}
// Now that the old function is dead, delete it.
F->getParent()->getFunctionList().erase(F);
}
@ -241,52 +468,44 @@ bool DAE::run(Module &M) {
// We assume all arguments are dead unless proven otherwise (allowing us to
// determine that dead arguments passed into recursive functions are dead).
//
std::set<Argument*> LiveArguments, MaybeLiveArguments, DeadArguments;
std::multimap<Function*, CallSite> CallSites;
DEBUG(std::cerr << "DAE - Determining liveness\n");
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
Function &Fn = *I;
// If the function is intrinsically alive, just mark the arguments alive.
if (FunctionArgumentsIntrinsicallyAlive(Fn)) {
for (Function::aiterator AI = Fn.abegin(), E = Fn.aend(); AI != E; ++AI)
LiveArguments.insert(AI);
DEBUG(std::cerr << " Args intrinsically live for fn: " << Fn.getName()
<< "\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<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 {
DEBUG(std::cerr << " Inspecting args for fn: " << Fn.getName() << "\n");
CallSite CS = CallSite::get(I);
assert(CS.getInstruction() && "Unknown instruction for the I2I list!");
// 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.
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.
//
bool AnyMaybeLiveArgs = false;
for (Function::aiterator AI = Fn.abegin(), E = Fn.aend(); AI != E; ++AI)
switch (getArgumentLiveness(*AI)) {
case Alive:
DEBUG(std::cerr << " Arg live by use: " << AI->getName() << "\n");
LiveArguments.insert(AI);
break;
case Dead:
DEBUG(std::cerr << " Arg definitely dead: " <<AI->getName()<<"\n");
DeadArguments.insert(AI);
break;
case MaybeLive:
DEBUG(std::cerr << " 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)
for (Value::use_iterator I = Fn.use_begin(), E = Fn.use_end();
I != E; ++I)
CallSites.insert(std::make_pair(&Fn, CallSite::get(*I)));
CallSite::arg_iterator AI = CS.arg_begin(); // ActualIterator
for (Function::aiterator FI = Callee->abegin(), E = Callee->aend();
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);
}
}
}
@ -295,17 +514,16 @@ bool DAE::run(Module &M) {
// 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 list, copy it
// to a temporary vector.
// 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) &&
isMaybeLiveArgumentNowAlive(MLA, LiveArguments)) {
MarkArgumentLive(MLA, MaybeLiveArguments, LiveArguments, CallSites);
}
isMaybeLiveArgumentNowLive(MLA))
MarkArgumentLive(MLA);
}
// Recover memory early...
@ -314,17 +532,26 @@ bool DAE::run(Module &M) {
// 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())
if (MaybeLiveArguments.empty() && DeadArguments.empty() &&
MaybeLiveRetVal.empty() && DeadRetVal.empty())
return false;
// 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(),
DeadArguments);
RemoveDeadArgumentsFromFunction((*DeadArguments.begin())->getParent());
while (!DeadRetVal.empty())
RemoveDeadArgumentsFromFunction(*DeadRetVal.begin());
return true;
}