/// Struct that represents (part of) either a return value or a function
/// argument. Used so that arguments and return values can be used
- /// interchangably. Idx == -1 means the entire return value, while other
- /// indices mean the corresponding element in the struct return type (if
- /// any).
+ /// interchangably.
struct RetOrArg {
- RetOrArg(const Function* F, signed Idx, bool IsArg) : F(F), Idx(Idx),
+ RetOrArg(const Function* F, unsigned Idx, bool IsArg) : F(F), Idx(Idx),
IsArg(IsArg) {}
const Function *F;
- signed Idx;
+ unsigned Idx;
bool IsArg;
/// Make RetOrArg comparable, so we can put it into a map.
}
std::string getDescription() const {
- return std::string((!IsArg && Idx != -1 ? "partial " : ""))
- + (IsArg ? "argument #" : "return value")
- + (!IsArg && Idx == -1 ? "" : " #" + utostr(Idx))
- + " of function " + F->getName();
+ return std::string((IsArg ? "Argument #" : "Return value #"))
+ + utostr(Idx) + " of function " + F->getName();
}
};
enum Liveness { Live, MaybeLive };
/// Convenience wrapper
- RetOrArg CreateRet(const Function *F, signed Idx) {
+ RetOrArg CreateRet(const Function *F, unsigned Idx) {
return RetOrArg(F, Idx, false);
}
/// Convenience wrapper
- RetOrArg CreateArg(const Function *F, signed Idx) {
+ RetOrArg CreateArg(const Function *F, unsigned Idx) {
return RetOrArg(F, Idx, true);
}
private:
Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses);
Liveness SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses,
- signed RetValNum = -1);
+ unsigned RetValNum = 0);
Liveness SurveyUses(Value *V, UseVector &MaybeLiveUses);
void SurveyFunction(Function &F);
return true;
}
+/// 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;
+}
+
/// 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.
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 -1.
+/// it at 0.
DAE::Liveness DAE::SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses,
- signed RetValNum) {
+ unsigned RetValNum) {
Value *V = *U;
if (ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
// The value is returned from a function. It's only live when the
// well as arguments to functions which have their "address taken".
//
void DAE::SurveyFunction(Function &F) {
- const StructType *STy = dyn_cast<StructType>(F.getFunctionType()->getReturnType());
- // Store the number of partial return values, which we only have if the return
- // type is a struct.
- unsigned PartialRetVals = (STy ? STy->getNumElements() : 0);
+ unsigned RetCount = NumRetVals(&F);
// Assume all return values are dead
typedef SmallVector<Liveness, 5> RetVals;
- // Allocate one slot for the entire return value (index 0) and one for each
- // partial return value.
- RetVals RetValLiveness(PartialRetVals + 1, MaybeLive);
+ RetVals RetValLiveness(RetCount, MaybeLive);
typedef SmallVector<UseVector, 5> RetUses;
// These vectors map each return value to the uses that make it MaybeLive, so
// we can add those to the Uses map if the return value really turns out to be
- // MaybeLive.
- // Allocate one slot for the entire return value (index 0) and one for each
- // partial return value.
- RetUses MaybeLiveRetUses(PartialRetVals + 1);
+ // MaybeLive. Initialized 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()))
}
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
// 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 the entire value is live already.
- if (RetValLiveness[0] != Live) {
- // 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();
- // + 1 to skip the "entire retval" index (0)
- Liveness &IsLive = RetValLiveness[Idx + 1];
- if (IsLive != Live) {
- // Don't bother checking if this retval was already live
- // Survey all uses of the extractvalue
- // + 1 to skip the "entire retval" index (0)
- IsLive = SurveyUses(Ext, MaybeLiveRetUses[Idx + 1]);
- }
- } else {
- // Survey this use
- RetValLiveness[0] = SurveyUse(I, MaybeLiveRetUses[0]);
- if (RetValLiveness[0] == Live)
+ // 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 {
+ // 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 {
+ // Single return value
+ RetValLiveness[0] = SurveyUses(TheCall, MaybeLiveRetUses[0]);
+ if (RetValLiveness[0] == Live)
+ NumLiveRetVals = RetCount;
}
}
}
// Now we've inspected all callers, record the liveness of our return values.
- MarkValue(CreateRet(&F, -1), RetValLiveness[0], MaybeLiveRetUses[0]);
- if (RetValLiveness[0] != Live)
- // If the entire retval (0) is Live, MarkValue will have marked all other retvals live
- // as well, so we can skip this.
- for (unsigned i = 0; i != PartialRetVals; ++i)
- // + 1 to skip the "entire retval" index (0)
- MarkValue(CreateRet(&F, i), RetValLiveness[i + 1], MaybeLiveRetUses[i + 1]);
+ for (unsigned i = 0; i != RetCount; ++i)
+ MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
DOUT << "DAE - Inspecting args for fn: " << F.getName() << "\n";
for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
PropagateLiveness(CreateArg(&F, i));
// Mark all return values as live.
- const Type *RTy = F.getFunctionType()->getReturnType();
- if (const StructType *STy = dyn_cast<StructType>(RTy))
- for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
- PropagateLiveness(CreateRet(&F, i));
- PropagateLiveness(CreateRet(&F, -1));
+ for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
+ PropagateLiveness(CreateRet(&F, i));
}
/// MarkLive - Mark the given return value or argument as live. Additionally,
DOUT << "DAE - Marking " << RA.getDescription() << " live\n";
PropagateLiveness(RA);
-
- if (!RA.IsArg && RA.Idx == -1) {
- // Entire return value live?
- const Type *RTy = RA.F->getFunctionType()->getReturnType();
- if (const StructType *STy = dyn_cast<StructType>(RTy))
- // And the function returns a struct?
- for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
- // Mark all partial return values live as well then
- MarkLive(CreateRet(RA.F, i));
- }
}
/// PropagateLiveness - Given that RA is a live value, propagate it's liveness
// Find out the new return value.
const Type *RetTy = FTy->getReturnType();
- const StructType *STy = dyn_cast<StructType>(RetTy);
- const unsigned PartialRetVals = (STy ? STy->getNumElements() : 0);
const Type *NRetTy = NULL;
- // -1 means unused, other numbers are the new index. Initialized to -1 for
- // every partial return value we have.
- SmallVector<int, 5> NewRetIdxs(PartialRetVals, -1);
+ unsigned RetCount = NumRetVals(F);
+ // Explicitly track if anything changed, for debugging.
+ bool Changed = false;
+ // -1 means unused, other numbers are the new index
+ SmallVector<int, 5> NewRetIdxs(RetCount, -1);
std::vector<const Type*> RetTypes;
- if (LiveValues.count(CreateRet(F, -1))) {
- // If the entire return value is live, leave it unchanged.
- NRetTy = RetTy;
+ if (RetTy == Type::VoidTy) {
+ NRetTy = Type::VoidTy;
} else {
- if (STy) {
- // Look at each of the partial return values individually.
- for (unsigned i = 0; i != PartialRetVals; ++i) {
+ 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));
++NumRetValsEliminated;
DOUT << "DAE - Removing return value " << i << " from "
<< F->getNameStart() << "\n";
- // We remove the value by not adding anything to RetTypes.
+ Changed = true;
}
}
- } else if (RetTy != Type::VoidTy) {
- // We used to return a single value, which is now dead (already checked in
- // the if above)
- DOUT << "DAE - Removing return value from " << F->getNameStart()
- << "\n";
- ++NumRetValsEliminated;
- // We remove the value by not adding anything to RetTypes.
- }
-
- if (RetTypes.size() > 1)
- // More than one return type? Return a struct with them.
+ 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;
+ Changed = true;
+ }
+ if (RetTypes.size() > 1 || (STy && STy->getNumElements()==RetTypes.size()))
+ // 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(RetTypes, STy->isPacked());
// return a struct with that simple value before.
NRetTy = RetTypes.front();
else if (RetTypes.size() == 0)
- // No return types? Make it void.
+ // No return types? Make it void, but only if we didn't use to return {}.
NRetTy = Type::VoidTy;
}
++NumArgumentsEliminated;
DOUT << "DAE - Removing argument " << i << " (" << I->getNameStart()
<< ") from " << F->getNameStart() << "\n";
+ Changed = true;
}
}
if (NFTy == FTy)
return false;
+ // The function type is only allowed to be different if we actually left out
+ // an argument or return value.
+ assert(Changed && "Function type changed while no arguments or return values"
+ "were removed!");
+
// Create the new function body and insert it into the module...
Function *NF = Function::Create(NFTy, F->getLinkage());
NF->copyAttributesFrom(F);
// Replace by null for now.
Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
} else {
- assert(STy && "Return type changed, but not into a void. The old "
- "return type must have been a struct!");
+ assert(isa<StructType>(RetTy) && "Return type changed, but not into a"
+ "void. The old return type must have"
+ "been a struct!");
// We used to return a struct. Instead of doing smart stuff with all the
// uses of this struct, we will just rebuild it using
// extract/insertvalue chaining and let instcombine clean that up.
//
// Start out building up our return value from undef
Value *RetVal = llvm::UndefValue::get(RetTy);
- for (unsigned i = 0; i != PartialRetVals; ++i)
+ for (unsigned i = 0; i != RetCount; ++i)
if (NewRetIdxs[i] != -1) {
Value *V;
if (RetTypes.size() > 1)
Value *OldRet = RI->getOperand(0);
// Start out building up our return value from undef
RetVal = llvm::UndefValue::get(NRetTy);
- for (unsigned i = 0; i != PartialRetVals; ++i)
+ for (unsigned i = 0; i != RetCount; ++i)
if (NewRetIdxs[i] != -1) {
ExtractValueInst *EV = ExtractValueInst::Create(OldRet, i,
"oldret", RI);
projects / oota-llvm.git / commitdiff