#include "llvm/Support/Debug.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Compiler.h"
#include <map>
#include <set>
class VISIBILITY_HIDDEN DAE : public ModulePass {
public:
- /// Struct that represent either a (part of a) return value or a function
+ /// Struct that represents (part of) either 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) {}
+ 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
+
+ /// 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;
return IsArg < O.IsArg;
}
- /// Make RetOrArg comparable, so we can easily iterate the multimap
+ /// Make RetOrArg comparable, so we can easily iterate the multimap.
bool operator==(const RetOrArg &O) const {
return F == O.F && Idx == O.Idx && IsArg == O.IsArg;
}
+
+ std::string getDescription() {
+ return std::string((IsArg ? "Argument #" : "Return value #"))
+ + utostr(Idx) + " of function " + F->getName();
+ }
};
-
+
/// 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 };
+ /// that things are either alive or maybe alive. We don't mark anything
+ /// explicitly dead (even if we know they are), since anything not alive
+ /// with no registered uses (in Uses) will never be marked alive and will
+ /// thus become dead in the end.
+ enum Liveness { Live, MaybeLive };
/// Convenience wrapper
- RetOrArg CreateRet(const Function *F, unsigned Idx) { return RetOrArg(F, Idx, false); }
+ 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); }
+ 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.
+ /// This maps a return value or argument to any MaybeLive return values or
+ /// arguments it uses. This allows the MaybeLive values to be marked live
+ /// when any of its users is marked live.
/// 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.
typedef std::set<RetOrArg> LiveSet;
- /// This set contains all values that have been determined to be live
+ /// This set contains all values that have been determined to be live.
LiveSet LiveValues;
-
+
typedef SmallVector<RetOrArg, 5> UseVector;
public:
virtual bool ShouldHackArguments() const { return false; }
private:
- Liveness IsMaybeLive(RetOrArg Use, UseVector &MaybeLiveUses);
- Liveness SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses, unsigned RetValNum = 0);
+ Liveness MarkIfNotLive(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 MarkValue(const RetOrArg &RA, Liveness L,
+ const UseVector &MaybeLiveUses);
void MarkLive(RetOrArg RA);
+ void MarkLive(const Function &F);
bool RemoveDeadStuffFromFunction(Function *F);
bool DeleteDeadVarargs(Function &Fn);
};
return 1;
}
-/// 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
+/// 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.
+DAE::Liveness DAE::MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses) {
+ // We're live if our use is already marked as live.
if (LiveValues.count(Use))
return Live;
/// 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) {
+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
+ // The value is returned from a function. It's only live when the
+ // 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
+ // orginal Use.
RetOrArg Use = CreateRet(RI->getParent()->getParent(), RetValNum);
- // We might be live, depending on the liveness of Use
- return IsMaybeLive(Use, MaybeLiveUses);
- }
+ // We might be live, depending on the liveness of Use.
+ return MarkIfNotLive(Use, MaybeLiveUses);
+ }
if (InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
- if (U.getOperandNo() != InsertValueInst::getAggregateOperandIndex() && IV->hasIndices())
+ 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.
// 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;
+
+ Liveness Result = MaybeLive;
for (Value::use_iterator I = IV->use_begin(),
E = V->use_end(); I != E; ++I) {
Result = SurveyUse(I, MaybeLiveUses, RetValNum);
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())
+ // Used in a direct call.
+
+ // Find the argument number. We know for sure that this use is an
+ // argument, since if it was the function argument this would be an
+ // indirect call and the we know can't be looking at a value of the
+ // label type (for the invoke instruction).
+ unsigned ArgNo = CS.getArgumentNo(U.getOperandNo());
+
+ if (ArgNo >= F->getFunctionType()->getNumParams())
// The value is passed in through a vararg! Must be live.
return Live;
+ assert(CS.getArgument(ArgNo)
+ == CS.getInstruction()->getOperand(U.getOperandNo())
+ && "Argument is not where we expected it");
+
// 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;
+ // argument to the called function turns out live.
+ RetOrArg Use = CreateArg(F, ArgNo);
+ return MarkIfNotLive(Use, MaybeLiveUses);
}
}
// 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).
+/// SurveyUses - This looks at all the uses of the given value
/// Returns the Liveness deduced from the uses of this value.
///
-/// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses.
+/// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. If
+/// the result is Live, MaybeLiveUses might be modified but its content should
+/// be ignored (since it might not be complete).
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
+ // Assume it's dead (which will only hold if there are no uses at all..).
+ Liveness Result = MaybeLive;
+ // Check each use.
for (Value::use_iterator I = V->use_begin(),
E = V->use_end(); I != E; ++I) {
Result = SurveyUse(I, MaybeLiveUses);
// 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.
+// any callers use the return value. This fills in the LiveValues set and Uses
+// map.
//
// 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;
unsigned RetCount = NumRetVals(&F);
// Assume all return values are dead
typedef SmallVector<Liveness, 5> RetVals;
- RetVals RetValLiveness(RetCount, Dead);
+ RetVals RetValLiveness(RetCount, MaybeLive);
- // 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
+ // 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. 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()))
- if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType() != F.getFunctionType()->getReturnType()) {
- // We don't support old style multiple return values
- FunctionIntrinsicallyLive = true;
- break;
+ if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
+ != F.getFunctionType()->getReturnType()) {
+ // We don't support old style multiple return values.
+ MarkLive(F);
+ return;
}
- if (!F.hasInternalLinkage() && (!ShouldHackArguments() || F.isIntrinsic()))
- FunctionIntrinsicallyLive = true;
-
- 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) {
- FunctionIntrinsicallyLive = true;
- break;
- }
+ if (!F.hasInternalLinkage() && (!ShouldHackArguments() || F.isIntrinsic())) {
+ MarkLive(F);
+ return;
+ }
- // 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;
- }
-
- // 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 {
- // 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;
+ 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) {
+ MarkLive(F);
+ return;
+ }
+
+ // 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?
+ MarkLive(F);
+ return;
+ }
+
+ // 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 {
- // Single return value
- RetValLiveness[0] = SurveyUses(TheCall, MaybeLiveRetUses[0]);
- if (RetValLiveness[0] == Live)
+ } 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;
}
}
}
- if (FunctionIntrinsicallyLive) {
- 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, ++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;
- }
-
+
// 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]);
- }
+ for (unsigned i = 0; i != RetCount; ++i)
+ MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
+
DOUT << "DAE - Inspecting args for fn: " << F.getName() << "\n";
- // Now, check all of our arguments
+ // Now, check all of our arguments.
unsigned i = 0;
UseVector MaybeLiveArgUses;
- for (Function::arg_iterator AI = F.arg_begin(),
+ 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)
+ // 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
+ // Mark the result.
+ MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
+ // Clear the vector again for the next iteration.
MaybeLiveArgUses.clear();
}
}
/// 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) {
+/// MaybeLive, it also takes all uses in MaybeLiveUses and records them in Uses,
+/// 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(),
+ for (UseVector::const_iterator UI = MaybeLiveUses.begin(),
UE = MaybeLiveUses.end(); UI != UE; ++UI)
- Where = Uses.insert(Where, UseMap::value_type(*UI, RA));
+ Uses.insert(std::make_pair(*UI, RA));
break;
}
- case Dead: break;
}
}
+/// MarkLive - Mark the given Function as alive, meaning that it cannot be
+/// changed in any way. Additionally,
+/// mark any values that are used as this function's parameters or by its return
+/// values (according to Uses) live as well.
+void DAE::MarkLive(const Function &F) {
+ DOUT << "DAE - Intrinsically live fn: " << F.getName() << "\n";
+ // Mark all arguments as live.
+ for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
+ MarkLive(CreateArg(&F, i));
+ // Mark all return values as live.
+ for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
+ MarkLive(CreateRet(&F, i));
+}
+
/// 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
+ return; // We were already marked Live.
if (RA.IsArg)
- DOUT << "DAE - Marking argument " << RA.Idx << " to function " << RA.F->getNameStart() << " live\n";
+ 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";
+ DOUT << "DAE - Marking return value " << RA.Idx << " of function "
+ << RA.F->getNameStart() << " live\n";
// We don't use upper_bound (or equal_range) here, because our recursive call
- // to ourselves is likely to mark the upper_bound (which is the first value
+ // to ourselves is likely to cause the upper_bound (which is the first value
// not belonging to RA) to become erased and the iterator invalidated.
UseMap::iterator Begin = Uses.lower_bound(RA);
UseMap::iterator E = Uses.end();
}
// 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.
+// that are not in LiveValues. Transform the function and all of the callees of
+// the function to not have these arguments and return values.
//
bool DAE::RemoveDeadStuffFromFunction(Function *F) {
// Quick exit path for external functions
const FunctionType *FTy = F->getFunctionType();
std::vector<const Type*> Params;
- // Set up to build a new list of parameter attributes
+ // Set up to build a new list of parameter attributes.
SmallVector<ParamAttrsWithIndex, 8> ParamAttrsVec;
const PAListPtr &PAL = F->getParamAttrs();
// The existing function return attributes.
ParameterAttributes RAttrs = PAL.getParamAttrs(0);
-
- // Find out the new return value
-
+
+ // Find out the new return value.
+
const Type *RetTy = FTy->getReturnType();
- const Type *NRetTy;
+ const Type *NRetTy = NULL;
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 (RetTy != Type::VoidTy) {
+ if (RetTy == Type::VoidTy) {
+ NRetTy = Type::VoidTy;
+ } else {
const StructType *STy = dyn_cast<StructType>(RetTy);
if (STy)
- // Look at each of the original return values individually
+ // 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)) {
NewRetIdxs[i] = RetTypes.size() - 1;
} else {
++NumRetValsEliminated;
- DOUT << "DAE - Removing return value " << i << " from " << F->getNameStart() << "\n";
+ DOUT << "DAE - Removing return value " << i << " from "
+ << F->getNameStart() << "\n";
+ Changed = true;
}
}
else
- // We used to return a single value
+ // 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";
+ DOUT << "DAE - Removing return value from " << F->getNameStart()
+ << "\n";
++NumRetValsEliminated;
- }
- if (RetTypes.size() == 0)
- // No return types? Make it void
- NRetTy = Type::VoidTy;
+ 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());
else if (RetTypes.size() == 1)
- // One return type? Just a simple value then
+ // 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();
- else
- // More return types? Return a struct with them
- NRetTy = StructType::get(RetTypes);
- } else {
- NRetTy = Type::VoidTy;
+ else if (RetTypes.size() == 0)
+ // No return types? Make it void, but only if we didn't use to return {}.
+ NRetTy = Type::VoidTy;
}
-
- // Remove any incompatible attributes
- RAttrs &= ~ParamAttr::typeIncompatible(NRetTy);
+
+ assert(NRetTy && "No new return type found?");
+
+ // Remove any incompatible attributes, but only if we removed all return
+ // values. Otherwise, ensure that we don't have any conflicting attributes
+ // here. Currently, this should not be possible, but special handling might be
+ // required when new return value attributes are added.
+ if (NRetTy == Type::VoidTy)
+ RAttrs &= ~ParamAttr::typeIncompatible(NRetTy);
+ else
+ assert((RAttrs & ParamAttr::typeIncompatible(NRetTy)) == 0
+ && "Return attributes no longer compatible?");
+
if (RAttrs)
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, RAttrs));
-
- // Remember which arguments are still alive
+
+ // 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. Skip the first parameter
if (LiveValues.erase(Arg)) {
Params.push_back(I->getType());
ArgAlive[i] = true;
-
+
// Get the original parameter attributes (skipping the first one, that is
- // for the return value
+ // 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";
+ DOUT << "DAE - Removing argument " << i << " (" << I->getNameStart()
+ << ") from " << F->getNameStart() << "\n";
+ Changed = true;
}
}
// Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
// have zero fixed arguments.
//
- // Not that we apply this hack for a vararg fuction that does not have any
+ // Note that we apply this hack for a vararg fuction that does not have any
// arguments anymore, but did have them before (so don't bother fixing
// functions that were already broken wrt CWriter).
bool ExtraArgHack = false;
// Create the new function type based on the recomputed parameters.
FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
-
+
// No change?
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);
NF->setParamAttrs(NewPAL);
// Insert the new function before the old function, so we won't be processing
- // it again
+ // it again.
F->getParent()->getFunctionList().insert(F, NF);
NF->takeName(F);
while (!F->use_empty()) {
CallSite CS = CallSite::get(F->use_back());
Instruction *Call = CS.getInstruction();
- if (!Call) {
- DOUT << "Old: " << *FTy << "\n";
- DOUT << "New: " << *NFTy << "\n";
- }
ParamAttrsVec.clear();
const PAListPtr &CallPAL = CS.getParamAttrs();
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, RAttrs));
// Declare these outside of the loops, so we can reuse them for the second
- // loop, which loops the varargs
+ // loop, which loops the varargs.
CallSite::arg_iterator I = CS.arg_begin();
- unsigned i = 0;
+ 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
+ // Get original parameter attributes, but skip return attributes.
if (ParameterAttributes Attrs = CallPAL.getParamAttrs(i + 1))
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
}
Args.clear();
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
+ if (New->getType() == Call->getType()) {
+ // Return type not changed? Just replace users then.
+ Call->replaceAllUsesWith(New);
+ New->takeName(Call);
+ } else if (New->getType() == Type::VoidTy) {
+ // Our return value has uses, but they will get removed later on.
+ // Replace by null for now.
Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
- else if (isa<StructType>(RetTy)) {
+ } else {
+ assert(isa<StructType>(RetTy) && "Return type changed, but not into a"
+ "void. The old return type must have"
+ "been a struct!");
// 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?");
+ 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?");
+ assert(EV->hasIndices() && "Return value used by extractvalue without"
+ "indices?");
unsigned Idx = *EV->idx_begin();
if (NewRetIdxs[Idx] != -1) {
if (RetTypes.size() > 1) {
// 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);
+ 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
+ // extractvalue.
EV->replaceAllUsesWith(New);
EV->eraseFromParent();
}
} else {
// Value unused, replace uses by null for now, they will get removed
- // later on
+ // 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);
}
}
++I2;
} else {
// If this argument is dead, replace any uses of it with null constants
- // (these are guaranteed to become unused later on)
+ // (these are guaranteed to become unused later on).
I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
}
// 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
+ // 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);
+ ExtractValueInst *EV = ExtractValueInst::Create(OldRet, i,
+ "oldret", 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");
+ RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
+ "newret", RI);
} else {
// We are now only returning a simple value, so just return the
- // extracted value
+ // 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);
bool DAE::runOnModule(Module &M) {
bool Changed = false;
+
// 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
// fused with the next loop, because deleting a function invalidates
DOUT << "DAE - Determining liveness\n";
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
SurveyFunction(*I);
-
+
// 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)
+ // replaced by a new one).
Function *F = I++;
Changed |= RemoveDeadStuffFromFunction(F);
}
-
return Changed;
}
projects / oota-llvm.git / blobdiff