DeadArgumentElimination.cpp [plain text]
#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include <map>
#include <set>
#include <tuple>
using namespace llvm;
#define DEBUG_TYPE "deadargelim"
STATISTIC(NumArgumentsEliminated, "Number of unread args removed");
STATISTIC(NumRetValsEliminated , "Number of unused return values removed");
STATISTIC(NumArgumentsReplacedWithUndef,
"Number of unread args replaced with undef");
namespace {
class DAE : public ModulePass {
public:
struct RetOrArg {
RetOrArg(const Function *F, unsigned Idx, bool IsArg) : F(F), Idx(Idx),
IsArg(IsArg) {}
const Function *F;
unsigned Idx;
bool IsArg;
bool operator<(const RetOrArg &O) const {
return std::tie(F, Idx, IsArg) < std::tie(O.F, O.Idx, O.IsArg);
}
bool operator==(const RetOrArg &O) const {
return F == O.F && Idx == O.Idx && IsArg == O.IsArg;
}
std::string getDescription() const {
return (Twine(IsArg ? "Argument #" : "Return value #") + utostr(Idx) +
" of function " + F->getName()).str();
}
};
enum Liveness { Live, MaybeLive };
RetOrArg CreateRet(const Function *F, unsigned Idx) {
return RetOrArg(F, Idx, false);
}
RetOrArg CreateArg(const Function *F, unsigned Idx) {
return RetOrArg(F, Idx, true);
}
typedef std::multimap<RetOrArg, RetOrArg> UseMap;
UseMap Uses;
typedef std::set<RetOrArg> LiveSet;
typedef std::set<const Function*> LiveFuncSet;
LiveSet LiveValues;
LiveFuncSet LiveFunctions;
typedef SmallVector<RetOrArg, 5> UseVector;
protected:
explicit DAE(char &ID) : ModulePass(ID) {}
public:
static char ID; DAE() : ModulePass(ID) {
initializeDAEPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M) override;
virtual bool ShouldHackArguments() const { return false; }
private:
Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses);
Liveness SurveyUse(const Use *U, UseVector &MaybeLiveUses,
unsigned RetValNum = -1U);
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);
bool RemoveDeadArgumentsFromCallers(Function &Fn);
};
}
char DAE::ID = 0;
INITIALIZE_PASS(DAE, "deadargelim", "Dead Argument Elimination", false, false)
namespace {
struct DAH : public DAE {
static char ID;
DAH() : DAE(ID) {}
bool ShouldHackArguments() const override { return true; }
};
}
char DAH::ID = 0;
INITIALIZE_PASS(DAH, "deadarghaX0r",
"Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)",
false, false)
ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
ModulePass *llvm::createDeadArgHackingPass() { return new DAH(); }
bool DAE::DeleteDeadVarargs(Function &Fn) {
assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!");
if (Fn.isDeclaration() || !Fn.hasLocalLinkage()) return false;
if (Fn.hasAddressTaken())
return false;
if (Fn.hasFnAttribute(Attribute::Naked)) {
return false;
}
for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
CallInst *CI = dyn_cast<CallInst>(I);
if (!CI)
continue;
if (CI->isMustTailCall())
return false;
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
if (II->getIntrinsicID() == Intrinsic::vastart)
return false;
}
}
}
FunctionType *FTy = Fn.getFunctionType();
std::vector<Type*> Params(FTy->param_begin(), FTy->param_end());
FunctionType *NFTy = FunctionType::get(FTy->getReturnType(),
Params, false);
unsigned NumArgs = Params.size();
Function *NF = Function::Create(NFTy, Fn.getLinkage());
NF->copyAttributesFrom(&Fn);
Fn.getParent()->getFunctionList().insert(Fn.getIterator(), NF);
NF->takeName(&Fn);
std::vector<Value*> Args;
for (Value::user_iterator I = Fn.user_begin(), E = Fn.user_end(); I != E; ) {
CallSite CS(*I++);
if (!CS)
continue;
Instruction *Call = CS.getInstruction();
Args.assign(CS.arg_begin(), CS.arg_begin() + NumArgs);
AttributeSet PAL = CS.getAttributes();
if (!PAL.isEmpty() && PAL.getSlotIndex(PAL.getNumSlots() - 1) > NumArgs) {
SmallVector<AttributeSet, 8> AttributesVec;
for (unsigned i = 0; PAL.getSlotIndex(i) <= NumArgs; ++i)
AttributesVec.push_back(PAL.getSlotAttributes(i));
if (PAL.hasAttributes(AttributeSet::FunctionIndex))
AttributesVec.push_back(AttributeSet::get(Fn.getContext(),
PAL.getFnAttributes()));
PAL = AttributeSet::get(Fn.getContext(), AttributesVec);
}
Instruction *New;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
Args, "", Call);
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
cast<InvokeInst>(New)->setAttributes(PAL);
} else {
New = CallInst::Create(NF, Args, "", Call);
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
cast<CallInst>(New)->setAttributes(PAL);
if (cast<CallInst>(Call)->isTailCall())
cast<CallInst>(New)->setTailCall();
}
New->setDebugLoc(Call->getDebugLoc());
Args.clear();
if (!Call->use_empty())
Call->replaceAllUsesWith(New);
New->takeName(Call);
Call->eraseFromParent();
}
NF->getBasicBlockList().splice(NF->begin(), Fn.getBasicBlockList());
for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(),
I2 = NF->arg_begin(); I != E; ++I, ++I2) {
I->replaceAllUsesWith(&*I2);
I2->takeName(&*I);
}
NF->setSubprogram(Fn.getSubprogram());
Fn.replaceAllUsesWith(ConstantExpr::getBitCast(NF, Fn.getType()));
NF->removeDeadConstantUsers();
Fn.eraseFromParent();
return true;
}
bool DAE::RemoveDeadArgumentsFromCallers(Function &Fn)
{
if (!Fn.isStrongDefinitionForLinker())
return false;
if (Fn.hasLocalLinkage() && !Fn.getFunctionType()->isVarArg())
return false;
if (Fn.hasFnAttribute(Attribute::Naked))
return false;
if (Fn.use_empty())
return false;
SmallVector<unsigned, 8> UnusedArgs;
for (Argument &Arg : Fn.args()) {
if (Arg.use_empty() && !Arg.hasByValOrInAllocaAttr())
UnusedArgs.push_back(Arg.getArgNo());
}
if (UnusedArgs.empty())
return false;
bool Changed = false;
for (Use &U : Fn.uses()) {
CallSite CS(U.getUser());
if (!CS || !CS.isCallee(&U))
continue;
for (unsigned I = 0, E = UnusedArgs.size(); I != E; ++I) {
unsigned ArgNo = UnusedArgs[I];
Value *Arg = CS.getArgument(ArgNo);
CS.setArgument(ArgNo, UndefValue::get(Arg->getType()));
++NumArgumentsReplacedWithUndef;
Changed = true;
}
}
return Changed;
}
static unsigned NumRetVals(const Function *F) {
Type *RetTy = F->getReturnType();
if (RetTy->isVoidTy())
return 0;
else if (StructType *STy = dyn_cast<StructType>(RetTy))
return STy->getNumElements();
else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
return ATy->getNumElements();
else
return 1;
}
static Type *getRetComponentType(const Function *F, unsigned Idx) {
Type *RetTy = F->getReturnType();
assert(!RetTy->isVoidTy() && "void type has no subtype");
if (StructType *STy = dyn_cast<StructType>(RetTy))
return STy->getElementType(Idx);
else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
return ATy->getElementType();
else
return RetTy;
}
DAE::Liveness DAE::MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses) {
if (LiveFunctions.count(Use.F) || LiveValues.count(Use))
return Live;
MaybeLiveUses.push_back(Use);
return MaybeLive;
}
DAE::Liveness DAE::SurveyUse(const Use *U,
UseVector &MaybeLiveUses, unsigned RetValNum) {
const User *V = U->getUser();
if (const ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
const Function *F = RI->getParent()->getParent();
if (RetValNum != -1U) {
RetOrArg Use = CreateRet(F, RetValNum);
return MarkIfNotLive(Use, MaybeLiveUses);
} else {
DAE::Liveness Result = MaybeLive;
for (unsigned i = 0; i < NumRetVals(F); ++i) {
RetOrArg Use = CreateRet(F, i);
DAE::Liveness SubResult = MarkIfNotLive(Use, MaybeLiveUses);
if (Result != Live)
Result = SubResult;
}
return Result;
}
}
if (const InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
if (U->getOperandNo() != InsertValueInst::getAggregateOperandIndex()
&& IV->hasIndices())
RetValNum = *IV->idx_begin();
Liveness Result = MaybeLive;
for (const Use &UU : IV->uses()) {
Result = SurveyUse(&UU, MaybeLiveUses, RetValNum);
if (Result == Live)
break;
}
return Result;
}
if (auto CS = ImmutableCallSite(V)) {
const Function *F = CS.getCalledFunction();
if (F) {
unsigned ArgNo = CS.getArgumentNo(U);
if (ArgNo >= F->getFunctionType()->getNumParams())
return Live;
assert(CS.getArgument(ArgNo)
== CS->getOperand(U->getOperandNo())
&& "Argument is not where we expected it");
RetOrArg Use = CreateArg(F, ArgNo);
return MarkIfNotLive(Use, MaybeLiveUses);
}
}
return Live;
}
DAE::Liveness DAE::SurveyUses(const Value *V, UseVector &MaybeLiveUses) {
Liveness Result = MaybeLive;
for (const Use &U : V->uses()) {
Result = SurveyUse(&U, MaybeLiveUses);
if (Result == Live)
break;
}
return Result;
}
void DAE::SurveyFunction(const Function &F) {
if (F.getAttributes().hasAttrSomewhere(Attribute::InAlloca)) {
MarkLive(F);
return;
}
if (F.hasFnAttribute(Attribute::Naked)) {
MarkLive(F);
return;
}
unsigned RetCount = NumRetVals(&F);
typedef SmallVector<Liveness, 5> RetVals;
RetVals RetValLiveness(RetCount, MaybeLive);
typedef SmallVector<UseVector, 5> RetUses;
RetUses MaybeLiveRetUses(RetCount);
for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
!= F.getFunctionType()->getReturnType()) {
MarkLive(F);
return;
}
if (!F.hasLocalLinkage() && (!ShouldHackArguments() || F.isIntrinsic())) {
MarkLive(F);
return;
}
DEBUG(dbgs() << "DAE - Inspecting callers for fn: " << F.getName() << "\n");
unsigned NumLiveRetVals = 0;
for (const Use &U : F.uses()) {
ImmutableCallSite CS(U.getUser());
if (!CS || !CS.isCallee(&U)) {
MarkLive(F);
return;
}
const Instruction *TheCall = CS.getInstruction();
if (!TheCall) { MarkLive(F);
return;
}
if (NumLiveRetVals == RetCount)
continue;
for (const Use &U : TheCall->uses()) {
if (ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U.getUser())) {
unsigned Idx = *Ext->idx_begin();
if (RetValLiveness[Idx] != Live) {
RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
if (RetValLiveness[Idx] == Live)
NumLiveRetVals++;
}
} else {
UseVector MaybeLiveAggregateUses;
if (SurveyUse(&U, MaybeLiveAggregateUses) == Live) {
NumLiveRetVals = RetCount;
RetValLiveness.assign(RetCount, Live);
break;
} else {
for (unsigned i = 0; i != RetCount; ++i) {
if (RetValLiveness[i] != Live)
MaybeLiveRetUses[i].append(MaybeLiveAggregateUses.begin(),
MaybeLiveAggregateUses.end());
}
}
}
}
}
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");
unsigned i = 0;
UseVector MaybeLiveArgUses;
for (Function::const_arg_iterator AI = F.arg_begin(),
E = F.arg_end(); AI != E; ++AI, ++i) {
Liveness Result;
if (F.getFunctionType()->isVarArg()) {
Result = Live;
} else {
Result = SurveyUses(&*AI, MaybeLiveArgUses);
}
MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
MaybeLiveArgUses.clear();
}
}
void DAE::MarkValue(const RetOrArg &RA, Liveness L,
const UseVector &MaybeLiveUses) {
switch (L) {
case Live: MarkLive(RA); break;
case MaybeLive:
{
for (UseVector::const_iterator UI = MaybeLiveUses.begin(),
UE = MaybeLiveUses.end(); UI != UE; ++UI)
Uses.insert(std::make_pair(*UI, RA));
break;
}
}
}
void DAE::MarkLive(const Function &F) {
DEBUG(dbgs() << "DAE - Intrinsically live fn: " << F.getName() << "\n");
LiveFunctions.insert(&F);
for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
PropagateLiveness(CreateArg(&F, i));
for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
PropagateLiveness(CreateRet(&F, i));
}
void DAE::MarkLive(const RetOrArg &RA) {
if (LiveFunctions.count(RA.F))
return;
if (!LiveValues.insert(RA).second)
return;
DEBUG(dbgs() << "DAE - Marking " << RA.getDescription() << " live\n");
PropagateLiveness(RA);
}
void DAE::PropagateLiveness(const RetOrArg &RA) {
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);
Uses.erase(Begin, I);
}
bool DAE::RemoveDeadStuffFromFunction(Function *F) {
if (LiveFunctions.count(F))
return false;
FunctionType *FTy = F->getFunctionType();
std::vector<Type*> Params;
bool HasLiveReturnedArg = false;
SmallVector<AttributeSet, 8> AttributesVec;
const AttributeSet &PAL = F->getAttributes();
SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
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 (PAL.hasAttributes(i + 1)) {
AttrBuilder B(PAL, i + 1);
if (B.contains(Attribute::Returned))
HasLiveReturnedArg = true;
AttributesVec.
push_back(AttributeSet::get(F->getContext(), Params.size(), B));
}
} else {
++NumArgumentsEliminated;
DEBUG(dbgs() << "DAE - Removing argument " << i << " (" << I->getName()
<< ") from " << F->getName() << "\n");
}
}
Type *RetTy = FTy->getReturnType();
Type *NRetTy = nullptr;
unsigned RetCount = NumRetVals(F);
SmallVector<int, 5> NewRetIdxs(RetCount, -1);
std::vector<Type*> RetTypes;
if (RetTy->isVoidTy() || HasLiveReturnedArg) {
NRetTy = RetTy;
} else {
for (unsigned i = 0; i != RetCount; ++i) {
RetOrArg Ret = CreateRet(F, i);
if (LiveValues.erase(Ret)) {
RetTypes.push_back(getRetComponentType(F, i));
NewRetIdxs[i] = RetTypes.size() - 1;
} else {
++NumRetValsEliminated;
DEBUG(dbgs() << "DAE - Removing return value " << i << " from "
<< F->getName() << "\n");
}
}
if (RetTypes.size() > 1) {
if (StructType *STy = dyn_cast<StructType>(RetTy)) {
NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
} else {
assert(isa<ArrayType>(RetTy) && "unexpected multi-value return");
NRetTy = ArrayType::get(RetTypes[0], RetTypes.size());
}
} else if (RetTypes.size() == 1)
NRetTy = RetTypes.front();
else if (RetTypes.size() == 0)
NRetTy = Type::getVoidTy(F->getContext());
}
assert(NRetTy && "No new return type found?");
AttributeSet RAttrs = PAL.getRetAttributes();
if (NRetTy->isVoidTy())
RAttrs = RAttrs.removeAttributes(NRetTy->getContext(),
AttributeSet::ReturnIndex,
AttributeFuncs::typeIncompatible(NRetTy));
else
assert(!AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
"Return attributes no longer compatible?");
if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
AttributesVec.push_back(AttributeSet::get(NRetTy->getContext(), RAttrs));
if (PAL.hasAttributes(AttributeSet::FunctionIndex))
AttributesVec.push_back(AttributeSet::get(F->getContext(),
PAL.getFnAttributes()));
AttributeSet NewPAL = AttributeSet::get(F->getContext(), AttributesVec);
FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
if (NFTy == FTy)
return false;
Function *NF = Function::Create(NFTy, F->getLinkage());
NF->copyAttributesFrom(F);
NF->setAttributes(NewPAL);
F->getParent()->getFunctionList().insert(F->getIterator(), NF);
NF->takeName(F);
std::vector<Value*> Args;
while (!F->use_empty()) {
CallSite CS(F->user_back());
Instruction *Call = CS.getInstruction();
AttributesVec.clear();
const AttributeSet &CallPAL = CS.getAttributes();
AttributeSet RAttrs = CallPAL.getRetAttributes();
RAttrs = RAttrs.removeAttributes(NRetTy->getContext(),
AttributeSet::ReturnIndex,
AttributeFuncs::typeIncompatible(NF->getReturnType()));
if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
AttributesVec.push_back(AttributeSet::get(NF->getContext(), RAttrs));
CallSite::arg_iterator I = CS.arg_begin();
unsigned i = 0;
for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
if (ArgAlive[i]) {
Args.push_back(*I);
if (CallPAL.hasAttributes(i + 1)) {
AttrBuilder B(CallPAL, i + 1);
if (NRetTy != RetTy && B.contains(Attribute::Returned))
B.removeAttribute(Attribute::Returned);
AttributesVec.
push_back(AttributeSet::get(F->getContext(), Args.size(), B));
}
}
for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
Args.push_back(*I);
if (CallPAL.hasAttributes(i + 1)) {
AttrBuilder B(CallPAL, i + 1);
AttributesVec.
push_back(AttributeSet::get(F->getContext(), Args.size(), B));
}
}
if (CallPAL.hasAttributes(AttributeSet::FunctionIndex))
AttributesVec.push_back(AttributeSet::get(Call->getContext(),
CallPAL.getFnAttributes()));
AttributeSet NewCallPAL = AttributeSet::get(F->getContext(), AttributesVec);
Instruction *New;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
Args, "", Call->getParent());
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
cast<InvokeInst>(New)->setAttributes(NewCallPAL);
} else {
New = CallInst::Create(NF, Args, "", Call);
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
cast<CallInst>(New)->setAttributes(NewCallPAL);
if (cast<CallInst>(Call)->isTailCall())
cast<CallInst>(New)->setTailCall();
}
New->setDebugLoc(Call->getDebugLoc());
Args.clear();
if (!Call->use_empty()) {
if (New->getType() == Call->getType()) {
Call->replaceAllUsesWith(New);
New->takeName(Call);
} else if (New->getType()->isVoidTy()) {
if (!Call->getType()->isX86_MMXTy())
Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
} else {
assert((RetTy->isStructTy() || RetTy->isArrayTy()) &&
"Return type changed, but not into a void. The old return type"
" must have been a struct or an array!");
Instruction *InsertPt = Call;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
BasicBlock *NewEdge = SplitEdge(New->getParent(), II->getNormalDest());
InsertPt = &*NewEdge->getFirstInsertionPt();
}
Value *RetVal = UndefValue::get(RetTy);
for (unsigned i = 0; i != RetCount; ++i)
if (NewRetIdxs[i] != -1) {
Value *V;
if (RetTypes.size() > 1)
V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
InsertPt);
else
V = New;
RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
}
Call->replaceAllUsesWith(RetVal);
New->takeName(Call);
}
}
Call->eraseFromParent();
}
NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
i = 0;
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
I2 = NF->arg_begin(); I != E; ++I, ++i)
if (ArgAlive[i]) {
I->replaceAllUsesWith(&*I2);
I2->takeName(&*I);
++I2;
} else {
if (!I->getType()->isX86_MMXTy())
I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
}
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())) {
Value *RetVal;
if (NFTy->getReturnType()->isVoidTy()) {
RetVal = nullptr;
} else {
assert(RetTy->isStructTy() || RetTy->isArrayTy());
Value *OldRet = RI->getOperand(0);
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) {
RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
"newret", RI);
} else {
RetVal = EV;
}
}
}
ReturnInst::Create(F->getContext(), RetVal, RI);
BB->getInstList().erase(RI);
}
NF->setSubprogram(F->getSubprogram());
F->eraseFromParent();
return true;
}
bool DAE::runOnModule(Module &M) {
bool Changed = false;
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);
}
DEBUG(dbgs() << "DAE - Determining liveness\n");
for (auto &F : M)
SurveyFunction(F);
for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
Function *F = &*I++;
Changed |= RemoveDeadStuffFromFunction(F);
}
for (auto &F : M)
Changed |= RemoveDeadArgumentsFromCallers(F);
return Changed;
}