[llvm-commits] [llvm] r52570 - in /llvm/trunk: lib/Transforms/IPO/DeadArgumentElimination.cpp test/Transforms/DeadArgElim/multdeadretval.ll
Evan Cheng
evan.cheng at apple.com
Fri Jun 20 17:31:44 PDT 2008
Author: evancheng
Date: Fri Jun 20 19:31:44 2008
New Revision: 52570
URL: http://llvm.org/viewvc/llvm-project?rev=52570&view=rev
Log:
Back out Matthijs' DAE patches. It's miscompiling gcc driver.
Modified:
llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp
llvm/trunk/test/Transforms/DeadArgElim/multdeadretval.ll
Modified: llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp?rev=52570&r1=52569&r2=52570&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp Fri Jun 20 19:31:44 2008
@@ -10,10 +10,10 @@
// This pass deletes dead arguments from internal functions. Dead argument
// elimination removes arguments which are directly dead, as well as arguments
// only passed into function calls as dead arguments of other functions. This
-// pass also deletes dead return values in a similar way.
+// pass also deletes dead arguments in a similar way.
//
// This pass is often useful as a cleanup pass to run after aggressive
-// interprocedural passes, which add possibly-dead arguments or return values.
+// interprocedural passes, which add possibly-dead arguments.
//
//===----------------------------------------------------------------------===//
@@ -42,71 +42,40 @@
/// DAE - The dead argument elimination pass.
///
class VISIBILITY_HIDDEN DAE : public ModulePass {
- public:
-
- /// Struct that represent either a (part of 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) {}
- const Function *F;
- unsigned Idx;
- bool IsArg;
-
- /// 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;
- else if (Idx != O.Idx)
- return Idx < O.Idx;
- else
- return IsArg < O.IsArg;
- }
-
- /// 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;
- }
- };
-
/// 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 };
- /// Convenience wrapper
- 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);
- }
-
- typedef std::multimap<RetOrArg, RetOrArg> UseMap;
- /// This map maps a return value or argument to all return values or
- /// arguments it uses.
- /// 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.
- /// - Uses[arg F] = ret G
- /// This means that some function calls G and passes its result as an
- /// argument to F.
- /// - Uses[ret F] = arg F
- /// This means that F returns one of its own arguments.
- /// - Uses[arg F] = arg G
- /// This means that G calls F and passes one of its own (G's) arguments
- /// directly to F.
- UseMap Uses;
-
- typedef std::set<RetOrArg> LiveSet;
+ /// LiveArguments, MaybeLiveArguments, DeadArguments - These sets contain
+ /// all of the arguments in the program. The Dead set contains arguments
+ /// which are completely dead (never used in the function). The MaybeLive
+ /// set contains arguments which are only passed into other function calls,
+ /// thus may be live and may be dead. The Live set contains arguments which
+ /// are known to be alive.
+ ///
+ std::set<Argument*> DeadArguments, MaybeLiveArguments, LiveArguments;
- /// This set contains all values that have been determined to be live
- LiveSet LiveValues;
+ /// DeadRetVal, MaybeLiveRetVal, LifeRetVal - These sets contain all of the
+ /// functions in the program. The Dead set contains functions whose return
+ /// value is known to be dead. The MaybeLive set contains functions whose
+ /// return values are only used by return instructions, and the Live set
+ /// contains functions whose return values are used, functions that are
+ /// external, and functions that already return void.
+ ///
+ std::set<Function*> DeadRetVal, MaybeLiveRetVal, LiveRetVal;
- typedef SmallVector<RetOrArg, 5> UseVector;
+ /// InstructionsToInspect - As we mark arguments and return values
+ /// MaybeLive, we keep track of which instructions could make the values
+ /// live here. Once the entire program has had the return value and
+ /// arguments analyzed, this set is scanned to promote the MaybeLive objects
+ /// to be Live if they really are used.
+ std::vector<Instruction*> InstructionsToInspect;
+
+ /// CallSites - Keep track of the call sites of functions that have
+ /// MaybeLive arguments or return values.
+ std::multimap<Function*, CallSite> CallSites;
public:
static char ID; // Pass identification, replacement for typeid
@@ -116,21 +85,20 @@
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 SurveyUses(Value *V, UseVector &MaybeLiveUses);
-
- void SurveyFunction(Function &F);
- void MarkValue(const RetOrArg &RA, Liveness L,
- const UseVector &MaybeLiveUses);
- void MarkLive(RetOrArg RA);
- bool RemoveDeadStuffFromFunction(Function *F);
+ Liveness getArgumentLiveness(const Argument &A);
+ bool isMaybeLiveArgumentNowLive(Argument *Arg);
+
bool DeleteDeadVarargs(Function &Fn);
+ void SurveyFunction(Function &Fn);
+
+ void MarkArgumentLive(Argument *Arg);
+ void MarkRetValLive(Function *F);
+ void MarkReturnInstArgumentLive(ReturnInst *RI);
+
+ void RemoveDeadArgumentsFromFunction(Function *F);
};
}
-
char DAE::ID = 0;
static RegisterPass<DAE>
X("deadargelim", "Dead Argument Elimination");
@@ -187,7 +155,7 @@
// remove the "..." and adjust all the calls.
// Start by computing a new prototype for the function, which is the same as
- // the old function, but doesn't have isVarArg set.
+ // the old function, but has fewer arguments.
const FunctionType *FTy = Fn.getFunctionType();
std::vector<const Type*> Params(FTy->param_begin(), FTy->param_end());
FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params, false);
@@ -265,113 +233,58 @@
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;
-}
-/// 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
- if (LiveValues.count(Use))
+static inline bool CallPassesValueThoughVararg(Instruction *Call,
+ const Value *Arg) {
+ CallSite CS = CallSite::get(Call);
+ const Type *CalledValueTy = CS.getCalledValue()->getType();
+ const Type *FTy = cast<PointerType>(CalledValueTy)->getElementType();
+ unsigned NumFixedArgs = cast<FunctionType>(FTy)->getNumParams();
+ for (CallSite::arg_iterator AI = CS.arg_begin()+NumFixedArgs;
+ AI != CS.arg_end(); ++AI)
+ if (AI->get() == Arg)
+ return true;
+ return false;
+}
+
+// getArgumentLiveness - Inspect an argument, determining if is known Live
+// (used in a computation), MaybeLive (only passed as an argument to a call), or
+// Dead (not used).
+DAE::Liveness DAE::getArgumentLiveness(const Argument &A) {
+ const Function *F = A.getParent();
+
+ // If this is the return value of a struct function, it's not really dead.
+ if (F->hasStructRetAttr() && &*(F->arg_begin()) == &A)
return Live;
+
+ if (A.use_empty()) // First check, directly dead?
+ return Dead;
+
+ // Scan through all of the uses, looking for non-argument passing uses.
+ for (Value::use_const_iterator I = A.use_begin(), E = A.use_end(); I!=E;++I) {
+ // Return instructions do not immediately effect liveness.
+ if (isa<ReturnInst>(*I))
+ continue;
+
+ CallSite CS = CallSite::get(const_cast<User*>(*I));
+ if (!CS.getInstruction()) {
+ // If its used by something that is not a call or invoke, it's alive!
+ return Live;
+ }
+ // If it's an indirect call, mark it alive...
+ Function *Callee = CS.getCalledFunction();
+ if (!Callee) return Live;
+
+ // Check to see if it's passed through a va_arg area: if so, we cannot
+ // remove it.
+ if (CallPassesValueThoughVararg(CS.getInstruction(), &A))
+ return Live; // If passed through va_arg area, we cannot remove it
+ }
- // We're maybe live otherwise, but remember that we must become live if
- // Use becomes live.
- MaybeLiveUses.push_back(Use);
- return MaybeLive;
+ return MaybeLive; // It must be used, but only as argument to a function
}
-/// 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 0.
-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
- RetOrArg Use = CreateRet(RI->getParent()->getParent(), RetValNum);
- // We might be live, depending on the liveness of Use
- return IsMaybeLive(Use, MaybeLiveUses);
- }
- if (InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
- 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.
- RetValNum = *IV->idx_begin();
-
- // 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;
- for (Value::use_iterator I = IV->use_begin(),
- E = V->use_end(); I != E; ++I) {
- Result = SurveyUse(I, MaybeLiveUses, RetValNum);
- if (Result == Live)
- break;
- }
- return Result;
- }
- CallSite CS = CallSite::get(V);
- 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())
- // The value is passed in through a vararg! Must be live.
- return Live;
-
- // 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;
- }
- }
- // 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).
-/// Returns the Liveness deduced from the uses of this value.
-///
-/// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses.
-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
- for (Value::use_iterator I = V->use_begin(),
- E = V->use_end(); I != E; ++I) {
- Result = SurveyUse(I, MaybeLiveUses);
- if (Result == Live)
- break;
- }
- return Result;
-}
-
// 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
@@ -382,37 +295,12 @@
//
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);
-
- // 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
- RetUses MaybeLiveRetUses(RetCount);
+ Liveness RetValLiveness = F.getReturnType() == Type::VoidTy ? Live : Dead;
- 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 (!F.hasInternalLinkage() && (!ShouldHackArguments() || F.isIntrinsic()))
+ 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
+ else
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) {
@@ -428,143 +316,190 @@
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;
+ // Check to see if the return value is used...
+ if (RetValLiveness != Live)
+ for (Value::use_iterator I = TheCall->use_begin(),
+ E = TheCall->use_end(); I != E; ++I)
+ if (isa<ReturnInst>(cast<Instruction>(*I))) {
+ RetValLiveness = MaybeLive;
+ } else if (isa<CallInst>(cast<Instruction>(*I)) ||
+ isa<InvokeInst>(cast<Instruction>(*I))) {
+ if (CallPassesValueThoughVararg(cast<Instruction>(*I), TheCall) ||
+ !CallSite::get(cast<Instruction>(*I)).getCalledFunction()) {
+ RetValLiveness = Live;
break;
+ } else {
+ RetValLiveness = MaybeLive;
}
+ } else {
+ RetValLiveness = Live;
+ 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;
+ DOUT << " Intrinsically live fn: " << F.getName() << "\n";
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));
+ AI != E; ++AI)
+ LiveArguments.insert(AI);
+ LiveRetVal.insert(&F);
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]);
- }
- DOUT << "DAE - Inspecting args for fn: " << F.getName() << "\n";
-
- // 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)
- 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
- MaybeLiveArgUses.clear();
+ switch (RetValLiveness) {
+ case Live: LiveRetVal.insert(&F); break;
+ case MaybeLive: MaybeLiveRetVal.insert(&F); break;
+ case Dead: DeadRetVal.insert(&F); break;
}
-}
-/// 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) {
- switch (L) {
- case Live: MarkLive(RA); break;
+ DOUT << " Inspecting args for fn: " << F.getName() << "\n";
+
+ // If it is not intrinsically alive, we know that all users of the
+ // function are call sites. Mark all of the arguments live which are
+ // directly used, and keep track of all of the call sites of this function
+ // if there are any arguments we assume that are dead.
+ //
+ bool AnyMaybeLiveArgs = false;
+ for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end();
+ AI != E; ++AI)
+ switch (getArgumentLiveness(*AI)) {
+ case Live:
+ DOUT << " Arg live by use: " << AI->getName() << "\n";
+ LiveArguments.insert(AI);
+ break;
+ case Dead:
+ DOUT << " Arg definitely dead: " << AI->getName() <<"\n";
+ DeadArguments.insert(AI);
+ 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(),
- UE = MaybeLiveUses.end(); UI != UE; ++UI)
- Where = Uses.insert(Where, UseMap::value_type(*UI, RA));
+ DOUT << " Arg only passed to calls: " << AI->getName() << "\n";
+ AnyMaybeLiveArgs = true;
+ MaybeLiveArguments.insert(AI);
break;
}
- case Dead: break;
+
+ // If there are any "MaybeLive" arguments, we need to check callees of
+ // this function when/if they become alive. Record which functions are
+ // callees...
+ if (AnyMaybeLiveArgs || RetValLiveness == MaybeLive)
+ for (Value::use_iterator I = F.use_begin(), E = F.use_end();
+ I != E; ++I) {
+ if (AnyMaybeLiveArgs)
+ CallSites.insert(std::make_pair(&F, CallSite::get(*I)));
+
+ if (RetValLiveness == MaybeLive)
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+ UI != E; ++UI)
+ InstructionsToInspect.push_back(cast<Instruction>(*UI));
+ }
+}
+
+// isMaybeLiveArgumentNowLive - Check to see if Arg is alive. At this point, we
+// know that the only uses of Arg are to be passed in as an argument to a
+// function call or return. Check to see if the formal argument passed in is in
+// the LiveArguments set. If so, return true.
+//
+bool DAE::isMaybeLiveArgumentNowLive(Argument *Arg) {
+ for (Value::use_iterator I = Arg->use_begin(), E = Arg->use_end(); I!=E; ++I){
+ if (isa<ReturnInst>(*I)) {
+ if (LiveRetVal.count(Arg->getParent())) return true;
+ continue;
+ }
+
+ CallSite CS = CallSite::get(*I);
+
+ // We know that this can only be used for direct calls...
+ Function *Callee = CS.getCalledFunction();
+
+ // Loop over all of the arguments (because Arg may be passed into the call
+ // multiple times) and check to see if any are now alive...
+ CallSite::arg_iterator CSAI = CS.arg_begin();
+ for (Function::arg_iterator AI = Callee->arg_begin(), E = Callee->arg_end();
+ AI != E; ++AI, ++CSAI)
+ // If this is the argument we are looking for, check to see if it's alive
+ if (*CSAI == Arg && LiveArguments.count(AI))
+ return true;
+ }
+ return false;
+}
+
+/// MarkArgumentLive - The MaybeLive argument 'Arg' is now known to be alive.
+/// Mark it live in the specified sets and recursively mark arguments in callers
+/// live that are needed to pass in a value.
+///
+void DAE::MarkArgumentLive(Argument *Arg) {
+ std::set<Argument*>::iterator It = MaybeLiveArguments.lower_bound(Arg);
+ if (It == MaybeLiveArguments.end() || *It != Arg) return;
+
+ DOUT << " MaybeLive argument now live: " << Arg->getName() <<"\n";
+ MaybeLiveArguments.erase(It);
+ LiveArguments.insert(Arg);
+
+ // Loop over all of the call sites of the function, making any arguments
+ // passed in to provide a value for this argument live as necessary.
+ //
+ Function *Fn = Arg->getParent();
+ unsigned ArgNo = std::distance(Fn->arg_begin(), Function::arg_iterator(Arg));
+
+ std::multimap<Function*, CallSite>::iterator I = CallSites.lower_bound(Fn);
+ for (; I != CallSites.end() && I->first == Fn; ++I) {
+ CallSite CS = I->second;
+ Value *ArgVal = *(CS.arg_begin()+ArgNo);
+ if (Argument *ActualArg = dyn_cast<Argument>(ArgVal)) {
+ MarkArgumentLive(ActualArg);
+ } else {
+ // If the value passed in at this call site is a return value computed by
+ // some other call site, make sure to mark the return value at the other
+ // call site as being needed.
+ CallSite ArgCS = CallSite::get(ArgVal);
+ if (ArgCS.getInstruction())
+ if (Function *Fn = ArgCS.getCalledFunction())
+ MarkRetValLive(Fn);
+ }
}
}
-/// 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
+/// MarkArgumentLive - The MaybeLive return value for the specified function is
+/// now known to be alive. Propagate this fact to the return instructions which
+/// produce it.
+void DAE::MarkRetValLive(Function *F) {
+ assert(F && "Shame shame, we can't have null pointers here!");
- if (RA.IsArg)
- 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";
+ // Check to see if we already knew it was live
+ std::set<Function*>::iterator I = MaybeLiveRetVal.lower_bound(F);
+ if (I == MaybeLiveRetVal.end() || *I != F) return; // It's already alive!
+
+ DOUT << " MaybeLive retval now live: " << F->getName() << "\n";
+
+ MaybeLiveRetVal.erase(I);
+ LiveRetVal.insert(F); // It is now known to be live!
+
+ // Loop over all of the functions, noticing that the return value is now live.
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
+ if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
+ MarkReturnInstArgumentLive(RI);
+}
- // 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
- // not belonging to RA) to become erased and the iterator invalidated.
- 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);
-
- // Erase RA from the Uses map (from the lower bound to wherever we ended up
- // after the loop).
- Uses.erase(Begin, I);
-}
-
-// 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.
+void DAE::MarkReturnInstArgumentLive(ReturnInst *RI) {
+ Value *Op = RI->getOperand(0);
+ if (Argument *A = dyn_cast<Argument>(Op)) {
+ MarkArgumentLive(A);
+ } else if (CallInst *CI = dyn_cast<CallInst>(Op)) {
+ if (Function *F = CI->getCalledFunction())
+ MarkRetValLive(F);
+ } else if (InvokeInst *II = dyn_cast<InvokeInst>(Op)) {
+ if (Function *F = II->getCalledFunction())
+ MarkRetValLive(F);
+ }
+}
+
+// RemoveDeadArgumentsFromFunction - We know that F has dead arguments, as
// specified by the DeadArguments list. Transform the function and all of the
// callees of the function to not have these arguments.
//
-bool DAE::RemoveDeadStuffFromFunction(Function *F) {
- // Quick exit path for external functions
- if (!F->hasInternalLinkage() && (!ShouldHackArguments() || F->isIntrinsic()))
- return false;
-
+void DAE::RemoveDeadArgumentsFromFunction(Function *F) {
// Start by computing a new prototype for the function, which is the same as
- // the old function, but has fewer arguments and a different return type.
+ // the old function, but has fewer arguments.
const FunctionType *FTy = F->getFunctionType();
std::vector<const Type*> Params;
@@ -575,92 +510,28 @@
// The existing function return attributes.
ParameterAttributes RAttrs = PAL.getParamAttrs(0);
-
- // Find out the new return value
-
+ // Make the function return void if the return value is dead.
const Type *RetTy = FTy->getReturnType();
- const Type *NRetTy;
- unsigned RetCount = NumRetVals(F);
- // Explicitely 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) {
- 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));
- NewRetIdxs[i] = RetTypes.size() - 1;
- } else {
- ++NumRetValsEliminated;
- DOUT << "DAE - Removing return value " << i << " from "
- << F->getNameStart() << "\n";
- Changed = true;
- }
- }
- 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 chaning {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, but only if we didn't use to
- // return a struct with that simple value before.
- NRetTy = RetTypes.front();
- 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;
+ if (DeadRetVal.count(F)) {
+ RetTy = Type::VoidTy;
+ RAttrs &= ~ParamAttr::typeIncompatible(RetTy);
+ DeadRetVal.erase(F);
}
- // Remove any incompatible attributes
- RAttrs &= ~ParamAttr::typeIncompatible(NRetTy);
if (RAttrs)
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, RAttrs));
- // 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
- // attribute, since that belongs to the return value.
- 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)) {
+ // a new set of parameter attributes to correspond.
+ unsigned index = 1;
+ for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
+ ++I, ++index)
+ if (!DeadArguments.count(I)) {
Params.push_back(I->getType());
- ArgAlive[i] = true;
-
- // Get the original parameter attributes (skipping the first one, that is
- // for the return value
- if (ParameterAttributes Attrs = PAL.getParamAttrs(i + 1))
+
+ if (ParameterAttributes Attrs = PAL.getParamAttrs(index))
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), Attrs));
- } else {
- ++NumArgumentsEliminated;
- DOUT << "DAE - Removing argument " << i << " (" << I->getNameStart()
- << ") from " << F->getNameStart() << "\n";
- Changed = true;
}
- }
// Reconstruct the ParamAttrsList based on the vector we constructed.
PAListPtr NewPAL = PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end());
@@ -668,33 +539,19 @@
// 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
- // arguments anymore, but did have them before (so don't bother fixing
- // functions that were already broken wrt CWriter).
bool ExtraArgHack = false;
- if (Params.empty() && FTy->isVarArg() && FTy->getNumParams() != 0) {
+ if (Params.empty() && FTy->isVarArg()) {
ExtraArgHack = true;
Params.push_back(Type::Int32Ty);
}
// 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 retrurn values"
- "were removed!");
+ FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
// 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
F->getParent()->getFunctionList().insert(F, NF);
NF->takeName(F);
@@ -705,7 +562,6 @@
while (!F->use_empty()) {
CallSite CS = CallSite::get(F->use_back());
Instruction *Call = CS.getInstruction();
-
ParamAttrsVec.clear();
const PAListPtr &CallPAL = CS.getParamAttrs();
@@ -716,17 +572,14 @@
if (RAttrs)
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
- CallSite::arg_iterator I = CS.arg_begin();
- 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
- if (ParameterAttributes Attrs = CallPAL.getParamAttrs(i + 1))
+ // Loop over the operands, deleting dead ones...
+ CallSite::arg_iterator AI = CS.arg_begin();
+ index = 1;
+ for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
+ I != E; ++I, ++AI, ++index)
+ if (!DeadArguments.count(I)) { // Remove operands for dead arguments
+ Args.push_back(*AI);
+ if (ParameterAttributes Attrs = CallPAL.getParamAttrs(index))
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
}
@@ -734,9 +587,9 @@
Args.push_back(UndefValue::get(Type::Int32Ty));
// Push any varargs arguments on the list. Don't forget their attributes.
- for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
- Args.push_back(*I);
- if (ParameterAttributes Attrs = CallPAL.getParamAttrs(i + 1))
+ for (; AI != CS.arg_end(); ++AI) {
+ Args.push_back(*AI);
+ if (ParameterAttributes Attrs = CallPAL.getParamAttrs(index++))
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
}
@@ -760,54 +613,10 @@
Args.clear();
if (!Call->use_empty()) {
- 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.
+ if (New->getType() == Type::VoidTy)
Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
- } 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?");
- 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?");
- unsigned Idx = *EV->idx_begin();
- if (NewRetIdxs[Idx] != -1) {
- if (RetTypes.size() > 1) {
- // We're still returning a struct, create a new extractvalue
- // 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);
- EV->replaceAllUsesWith(NEV);
- EV->eraseFromParent();
- } else {
- // We are now only returning a simple value, remove the
- // extractvalue
- EV->replaceAllUsesWith(New);
- EV->eraseFromParent();
- }
- } else {
- // Value unused, replace uses by null for now, they will get removed
- // later on
- EV->replaceAllUsesWith(Constant::getNullValue(EV->getType()));
- EV->eraseFromParent();
- }
- }
+ else {
+ Call->replaceAllUsesWith(New);
New->takeName(Call);
}
}
@@ -823,11 +632,13 @@
NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
// Loop over the argument list, transfering uses of the old arguments over to
- // the new arguments, also transfering over the names as well.
- i = 0;
+ // the new arguments, also transfering over the names as well. While we're at
+ // it, remove the dead arguments from the DeadArguments list.
+ //
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
- I2 = NF->arg_begin(); I != E; ++I, ++i)
- if (ArgAlive[i]) {
+ I2 = NF->arg_begin();
+ I != E; ++I)
+ if (!DeadArguments.count(I)) {
// If this is a live argument, move the name and users over to the new
// version.
I->replaceAllUsesWith(I2);
@@ -835,8 +646,10 @@
++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 only be operands to call instructions which
+ // will later be simplified).
I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
+ DeadArguments.erase(I);
}
// If we change the return value of the function we must rewrite any return
@@ -844,47 +657,12 @@
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() == Type::VoidTy) {
- RetVal = 0;
- } else {
- assert (isa<StructType>(RetTy));
- // The original return value was a struct, 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
- // 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);
- 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");
- } else {
- // We are now only returning a simple value, so just return the
- // 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);
+ ReturnInst::Create(0, RI);
BB->getInstList().erase(RI);
}
// Now that the old function is dead, delete it.
F->eraseFromParent();
-
- return true;
}
bool DAE::runOnModule(Module &M) {
@@ -899,7 +677,7 @@
if (F.getFunctionType()->isVarArg())
Changed |= DeleteDeadVarargs(F);
}
-
+
// Second phase:loop through the module, determining which arguments are live.
// We assume all arguments are dead unless proven otherwise (allowing us to
// determine that dead arguments passed into recursive functions are dead).
@@ -908,14 +686,85 @@
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)
- Function *F = I++;
- Changed |= RemoveDeadStuffFromFunction(F);
+ // Loop over the instructions to inspect, propagating liveness among arguments
+ // and return values which are MaybeLive.
+ while (!InstructionsToInspect.empty()) {
+ Instruction *I = InstructionsToInspect.back();
+ InstructionsToInspect.pop_back();
+
+ if (ReturnInst *RI = dyn_cast<ReturnInst>(I)) {
+ // For return instructions, we just have to check to see if the return
+ // value for the current function is known now to be alive. If so, any
+ // arguments used by it are now alive, and any call instruction return
+ // value is alive as well.
+ if (LiveRetVal.count(RI->getParent()->getParent()))
+ MarkReturnInstArgumentLive(RI);
+
+ } else {
+ CallSite CS = CallSite::get(I);
+ assert(CS.getInstruction() && "Unknown instruction for the I2I list!");
+
+ Function *Callee = CS.getCalledFunction();
+
+ // If we found a call or invoke instruction on this list, that means that
+ // an argument of the function is a call instruction. If the argument is
+ // live, then the return value of the called instruction is now live.
+ //
+ CallSite::arg_iterator AI = CS.arg_begin(); // ActualIterator
+ for (Function::arg_iterator FI = Callee->arg_begin(),
+ E = Callee->arg_end(); FI != E; ++AI, ++FI) {
+ // If this argument is another call...
+ CallSite ArgCS = CallSite::get(*AI);
+ if (ArgCS.getInstruction() && LiveArguments.count(FI))
+ if (Function *Callee = ArgCS.getCalledFunction())
+ MarkRetValLive(Callee);
+ }
+ }
}
- return Changed;
+ // Now we loop over all of the MaybeLive arguments, promoting them to be live
+ // arguments if one of the calls that uses the arguments to the calls they are
+ // passed into requires them to be live. Of course this could make other
+ // arguments live, so process callers recursively.
+ //
+ // Because elements can be removed from the MaybeLiveArguments set, copy it to
+ // a temporary vector.
+ //
+ std::vector<Argument*> TmpArgList(MaybeLiveArguments.begin(),
+ MaybeLiveArguments.end());
+ for (unsigned i = 0, e = TmpArgList.size(); i != e; ++i) {
+ Argument *MLA = TmpArgList[i];
+ if (MaybeLiveArguments.count(MLA) &&
+ isMaybeLiveArgumentNowLive(MLA))
+ MarkArgumentLive(MLA);
+ }
+
+ // Recover memory early...
+ CallSites.clear();
+
+ // At this point, we know that all arguments in DeadArguments and
+ // MaybeLiveArguments are dead. If the two sets are empty, there is nothing
+ // to do.
+ if (MaybeLiveArguments.empty() && DeadArguments.empty() &&
+ MaybeLiveRetVal.empty() && DeadRetVal.empty())
+ return Changed;
+
+ // Otherwise, compact into one set, and start eliminating the arguments from
+ // the functions.
+ DeadArguments.insert(MaybeLiveArguments.begin(), MaybeLiveArguments.end());
+ MaybeLiveArguments.clear();
+ DeadRetVal.insert(MaybeLiveRetVal.begin(), MaybeLiveRetVal.end());
+ MaybeLiveRetVal.clear();
+
+ LiveArguments.clear();
+ LiveRetVal.clear();
+
+ NumArgumentsEliminated += DeadArguments.size();
+ NumRetValsEliminated += DeadRetVal.size();
+ while (!DeadArguments.empty())
+ RemoveDeadArgumentsFromFunction((*DeadArguments.begin())->getParent());
+
+ while (!DeadRetVal.empty())
+ RemoveDeadArgumentsFromFunction(*DeadRetVal.begin());
+ return true;
}
Modified: llvm/trunk/test/Transforms/DeadArgElim/multdeadretval.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/DeadArgElim/multdeadretval.ll?rev=52570&r1=52569&r2=52570&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/DeadArgElim/multdeadretval.ll (original)
+++ llvm/trunk/test/Transforms/DeadArgElim/multdeadretval.ll Fri Jun 20 19:31:44 2008
@@ -1,39 +0,0 @@
-; This test sees if return values (and arguments) are properly removed when they
-; are unused. All unused values are typed i16, so we can easily check. We also
-; run instcombine to fold insert/extractvalue chains and we run dce to clean up
-; any remaining dead stuff.
-; RUN: llvm-as < %s | opt -deadargelim -instcombine -dce | llvm-dis | not grep i16
-
-define internal {i16, i32} @test(i16 %DEADARG) {
- %A = insertvalue {i16,i32} undef, i16 1, 0
- %B = insertvalue {i16,i32} %A, i32 1001, 1
- ret {i16,i32} %B
-}
-
-define internal {i32, i16} @test2() {
- %DEAD = call i16 @test4()
- %A = insertvalue {i32,i16} undef, i32 1, 0
- %B = insertvalue {i32,i16} %A, i16 %DEAD, 1
- ret {i32,i16} %B
-}
-
-define internal i32 @test3(i16 %A) {
- %ret = call {i16, i32} @test( i16 %A ) ; <i32> [#uses=0]
- %DEAD = extractvalue {i16, i32} %ret, 0
- %LIVE = extractvalue {i16, i32} %ret, 1
- ret i32 %LIVE
-}
-
-define internal i16 @test4() {
- ret i16 0
-}
-
-define i32 @main() {
- %ret = call {i32, i16} @test2() ; <i32> [#uses=1]
- %LIVE = extractvalue {i32, i16} %ret, 0
- %DEAD = extractvalue {i32, i16} %ret, 1
- %Y = add i32 %LIVE, -123 ; <i32> [#uses=1]
- %LIVE2 = call i32 @test3(i16 %DEAD) ; <i32> [#uses=1]
- %Z = add i32 %LIVE2, %Y ; <i32> [#uses=1]
- ret i32 %Z
-}
More information about the llvm-commits
mailing list