#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 {
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
}
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;
virtual bool ShouldHackArguments() const { return false; }
private:
- Liveness IsMaybeLive(RetOrArg Use, UseVector &MaybeLiveUses);
+ Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses);
Liveness SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses,
unsigned RetValNum = 0);
Liveness SurveyUses(Value *V, 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;
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()
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..)
+ // Assume it's dead (which will only hold if there are no uses at all..).
Liveness Result = MaybeLive;
- // Check each use
+ // 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
-// LiveValues set and Uses map.
+// 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, 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;
+ // We don't support old style multiple return values.
+ MarkLive(F);
+ return;
}
- if (!F.hasInternalLinkage() && (!ShouldHackArguments() || F.isIntrinsic()))
- FunctionIntrinsicallyLive = true;
+ if (!F.hasInternalLinkage() && (!ShouldHackArguments() || F.isIntrinsic())) {
+ MarkLive(F);
+ return;
+ }
- 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
+ // 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 the function is PASSED IN as an argument, its address has been
+ // taken.
if (I.getOperandNo() != 0) {
- FunctionIntrinsicallyLive = true;
- break;
+ 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;
+ 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
+ // bother checking return values if all of them are live already.
if (NumLiveRetVals != RetCount) {
if (STy) {
- // Check all uses of the return value
+ // 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);
NumLiveRetVals++;
}
} else {
- // Used by something else than extractvalue. Mark all
- // return values as live.
+ // Used by something else than extractvalue. Mark all return
+ // values as live.
for (unsigned i = 0; i != RetCount; ++i )
RetValLiveness[i] = 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(),
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.
+/// 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) {
{
// 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(),
UE = MaybeLiveUses.end(); UI != UE; ++UI)
- Where = Uses.insert(Where, UseMap::value_type(*UI, RA));
+ Uses.insert(std::make_pair(*UI, RA));
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";
// 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();
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 = NULL;
unsigned RetCount = NumRetVals(F);
- // Explicitely track if anything changed, for debugging
+ // 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)) {
}
}
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;
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.
+ // 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() == 0)
// No return types? Make it void, but only if we didn't use to return {}.
NRetTy = Type::VoidTy;
- } else {
- NRetTy = Type::VoidTy;
}
assert(NRetTy && "No new return type found?");
- // Remove any incompatible attributes
- RAttrs &= ~ParamAttr::typeIncompatible(NRetTy);
+ // 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
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 {
// 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;
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;
// Loop over those operands, corresponding to the normal arguments to the
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));
}
if (!Call->use_empty()) {
if (New->getType() == Call->getType()) {
- // Return type not changed? Just replace users then
+ // Return type not changed? Just replace users then.
Call->replaceAllUsesWith(New);
New->takeName(Call);
} else if (New->getType() == Type::VoidTy) {
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();
}
++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);
+ "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");
+ "newret", RI);
} else {
// We are now only returning a simple value, so just return the
- // extracted value
+ // extracted value.
RetVal = EV;
}
}
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;
}
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