#include "llvm/Support/raw_ostream.h"
#include <map>
#include <set>
+#include <tuple>
using namespace llvm;
#define DEBUG_TYPE "deadargelim"
}
std::string getDescription() const {
- return std::string((IsArg ? "Argument #" : "Return value #"))
- + utostr(Idx) + " of function " + F->getName().str();
+ return (Twine(IsArg ? "Argument #" : "Return value #") + utostr(Idx) +
+ " of function " + F->getName()).str();
}
};
// As the code generation for module is finished (and DIBuilder is
// finalized) we assume that subprogram descriptors won't be changed, and
// they are stored in map for short duration anyway.
- typedef DenseMap<Function*, DISubprogram> FunctionDIMap;
- FunctionDIMap FunctionDIs;
+ DenseMap<const Function *, DISubprogram *> FunctionDIs;
protected:
// DAH uses this to specify a different ID.
private:
Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses);
Liveness SurveyUse(const Use *U, UseVector &MaybeLiveUses,
- unsigned RetValNum = 0);
+ unsigned RetValNum = -1U);
Liveness SurveyUses(const Value *V, UseVector &MaybeLiveUses);
- void CollectFunctionDIs(Module &M);
void SurveyFunction(const Function &F);
void MarkValue(const RetOrArg &RA, Liveness L,
const UseVector &MaybeLiveUses);
ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
ModulePass *llvm::createDeadArgHackingPass() { return new DAH(); }
-/// CollectFunctionDIs - Map each function in the module to its debug info
-/// descriptor.
-void DAE::CollectFunctionDIs(Module &M) {
- FunctionDIs.clear();
-
- for (Module::named_metadata_iterator I = M.named_metadata_begin(),
- E = M.named_metadata_end(); I != E; ++I) {
- NamedMDNode &NMD = *I;
- for (unsigned MDIndex = 0, MDNum = NMD.getNumOperands();
- MDIndex < MDNum; ++MDIndex) {
- MDNode *Node = NMD.getOperand(MDIndex);
- if (!DIDescriptor(Node).isCompileUnit())
- continue;
- DICompileUnit CU(Node);
- const DIArray &SPs = CU.getSubprograms();
- for (unsigned SPIndex = 0, SPNum = SPs.getNumElements();
- SPIndex < SPNum; ++SPIndex) {
- DISubprogram SP(SPs.getElement(SPIndex));
- assert((!SP || SP.isSubprogram()) &&
- "A MDNode in subprograms of a CU should be null or a DISubprogram.");
- if (!SP)
- continue;
- if (Function *F = SP.getFunction())
- FunctionDIs[F] = SP;
- }
- }
- }
-}
-
/// DeleteDeadVarargs - If this is an function that takes a ... list, and if
/// llvm.vastart is never called, the varargs list is dead for the function.
bool DAE::DeleteDeadVarargs(Function &Fn) {
return false;
// Okay, we know we can transform this function if safe. Scan its body
- // looking for calls to llvm.vastart.
+ // looking for calls marked musttail or calls to llvm.vastart.
for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
- if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(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;
}
}
// Patch the pointer to LLVM function in debug info descriptor.
- FunctionDIMap::iterator DI = FunctionDIs.find(&Fn);
- if (DI != FunctionDIs.end())
- DI->second.replaceFunction(NF);
+ auto DI = FunctionDIs.find(&Fn);
+ if (DI != FunctionDIs.end()) {
+ DISubprogram *SP = DI->second;
+ SP->replaceFunction(NF);
+ // Ensure the map is updated so it can be reused on non-varargs argument
+ // eliminations of the same function.
+ FunctionDIs.erase(DI);
+ FunctionDIs[NF] = SP;
+ }
// Fix up any BlockAddresses that refer to the function.
Fn.replaceAllUsesWith(ConstantExpr::getBitCast(NF, Fn.getType()));
/// 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())
+ Type *RetTy = F->getReturnType();
+ if (RetTy->isVoidTy())
return 0;
- else if (StructType *STy = dyn_cast<StructType>(F->getReturnType()))
+ 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;
}
+/// Returns the sub-type a function will return at a given Idx. Should
+/// correspond to the result type of an ExtractValue instruction executed with
+/// just that one Idx (i.e. only top-level structure is considered).
+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;
+}
+
/// 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.
// 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
// original Use.
- RetOrArg Use = CreateRet(RI->getParent()->getParent(), RetValNum);
- // We might be live, depending on the liveness of Use.
- return MarkIfNotLive(Use, MaybeLiveUses);
+ const Function *F = RI->getParent()->getParent();
+ if (RetValNum != -1U) {
+ RetOrArg Use = CreateRet(F, RetValNum);
+ // We might be live, depending on the liveness of Use.
+ return MarkIfNotLive(Use, MaybeLiveUses);
+ } else {
+ DAE::Liveness Result = MaybeLive;
+ for (unsigned i = 0; i < NumRetVals(F); ++i) {
+ RetOrArg Use = CreateRet(F, i);
+ // We might be live, depending on the liveness of Use. If any
+ // sub-value is live, then the entire value is considered live. This
+ // is a conservative choice, and better tracking is possible.
+ 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()
return Result;
}
- if (ImmutableCallSite CS = V) {
+ if (auto CS = ImmutableCallSite(V)) {
const Function *F = CS.getCalledFunction();
if (F) {
// Used in a direct call.
// 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;
- Type *STy = dyn_cast<StructType>(F.getReturnType());
// Loop all uses of the function.
for (const Use &U : F.uses()) {
// If the function is PASSED IN as an argument, its address has been
// 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 (const User *U : TheCall->users()) {
- const ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U);
- 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 {
- // 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 (NumLiveRetVals == RetCount)
+ continue;
+
+ // Check all uses of the return value.
+ for (const Use &U : TheCall->uses()) {
+ if (ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U.getUser())) {
+ // 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 {
- // Single return value
- RetValLiveness[0] = SurveyUses(TheCall, MaybeLiveRetUses[0]);
- if (RetValLiveness[0] == Live)
+ // Used by something else than extractvalue. Survey, but assume that the
+ // result applies to all sub-values.
+ 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());
+ }
+ }
}
}
}
if (RetTy->isVoidTy() || HasLiveReturnedArg) {
NRetTy = RetTy;
} else {
- 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;
- 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;
+ // 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(getRetComponentType(F, i));
+ NewRetIdxs[i] = RetTypes.size() - 1;
} else {
- DEBUG(dbgs() << "DAE - Removing return value from " << F->getName()
- << "\n");
++NumRetValsEliminated;
+ DEBUG(dbgs() << "DAE - Removing return value " << i << " from "
+ << F->getName() << "\n");
+ }
+ }
+ if (RetTypes.size() > 1) {
+ // More than one return type? Reduce it down to size.
+ if (StructType *STy = dyn_cast<StructType>(RetTy)) {
+ // Make the new struct packed if we used to return a packed struct
+ // already.
+ NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
+ } else {
+ assert(isa<ArrayType>(RetTy) && "unexpected multi-value return");
+ NRetTy = ArrayType::get(RetTypes[0], RetTypes.size());
}
- 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)
+ } 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();
// here. Currently, this should not be possible, but special handling might be
// required when new return value attributes are added.
if (NRetTy->isVoidTy())
- RAttrs =
- AttributeSet::get(NRetTy->getContext(), AttributeSet::ReturnIndex,
- AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
- removeAttributes(AttributeFuncs::
- typeIncompatible(NRetTy, AttributeSet::ReturnIndex),
- AttributeSet::ReturnIndex));
+ RAttrs = RAttrs.removeAttributes(NRetTy->getContext(),
+ AttributeSet::ReturnIndex,
+ AttributeFuncs::typeIncompatible(NRetTy));
else
assert(!AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
- hasAttributes(AttributeFuncs::
- typeIncompatible(NRetTy, AttributeSet::ReturnIndex),
- AttributeSet::ReturnIndex) &&
+ overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
"Return attributes no longer compatible?");
if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
AttributeSet RAttrs = CallPAL.getRetAttributes();
// Adjust in case the function was changed to return void.
- RAttrs =
- AttributeSet::get(NF->getContext(), AttributeSet::ReturnIndex,
- AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
- removeAttributes(AttributeFuncs::
- typeIncompatible(NF->getReturnType(),
- AttributeSet::ReturnIndex),
- AttributeSet::ReturnIndex));
+ RAttrs = RAttrs.removeAttributes(NRetTy->getContext(),
+ AttributeSet::ReturnIndex,
+ AttributeFuncs::typeIncompatible(NF->getReturnType()));
if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
AttributesVec.push_back(AttributeSet::get(NF->getContext(), RAttrs));
if (!Call->getType()->isX86_MMXTy())
Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
} else {
- assert(RetTy->isStructTy() &&
+ assert((RetTy->isStructTy() || RetTy->isArrayTy()) &&
"Return type changed, but not into a void. The old return type"
- " must have been a struct!");
+ " must have been a struct or an array!");
Instruction *InsertPt = Call;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
BasicBlock::iterator IP = II->getNormalDest()->begin();
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.
+ // We used to return a struct or array. Instead of doing smart stuff
+ // with all the uses, 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);
if (NFTy->getReturnType()->isVoidTy()) {
RetVal = nullptr;
} else {
- assert (RetTy->isStructTy());
- // The original return value was a struct, insert
+ assert(RetTy->isStructTy() || RetTy->isArrayTy());
+ // The original return value was a struct or array, 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
}
// Patch the pointer to LLVM function in debug info descriptor.
- FunctionDIMap::iterator DI = FunctionDIs.find(F);
+ auto DI = FunctionDIs.find(F);
if (DI != FunctionDIs.end())
- DI->second.replaceFunction(NF);
+ DI->second->replaceFunction(NF);
// Now that the old function is dead, delete it.
F->eraseFromParent();
bool Changed = false;
// Collect debug info descriptors for functions.
- CollectFunctionDIs(M);
+ FunctionDIs = makeSubprogramMap(M);
// 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
// determine that dead arguments passed into recursive functions are dead).
//
DEBUG(dbgs() << "DAE - Determining liveness\n");
- for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
- SurveyFunction(*I);
+ for (auto &F : M)
+ SurveyFunction(F);
// Now, remove all dead arguments and return values from each function in
// turn.
// Finally, look for any unused parameters in functions with non-local
// linkage and replace the passed in parameters with undef.
- for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
- Function& F = *I;
-
+ for (auto &F : M)
Changed |= RemoveDeadArgumentsFromCallers(F);
- }
return Changed;
}
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