//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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 arguments in a similar way.
+// pass also deletes dead return values in a similar way.
//
// This pass is often useful as a cleanup pass to run after aggressive
-// interprocedural passes, which add possibly-dead arguments.
+// interprocedural passes, which add possibly-dead arguments or return values.
//
//===----------------------------------------------------------------------===//
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
+#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
-#include "llvm/ParameterAttributes.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/Support/Compiler.h"
+#include "llvm/ADT/StringExtras.h"
+#include <map>
#include <set>
using namespace llvm;
namespace {
/// DAE - The dead argument elimination pass.
///
- class VISIBILITY_HIDDEN DAE : public ModulePass {
+ class DAE : public ModulePass {
+ public:
+
+ /// 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) {}
+ 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;
+ }
+
+ std::string getDescription() const {
+ return std::string((IsArg ? "Argument #" : "Return value #"))
+ + utostr(Idx) + " of function " + F->getNameStr();
+ }
+ };
+
/// 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 };
-
- /// 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;
-
- /// 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;
-
- /// 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;
+ /// 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);
+ }
+ /// Convenience wrapper
+ RetOrArg CreateArg(const Function *F, unsigned Idx) {
+ return RetOrArg(F, Idx, true);
+ }
+
+ typedef std::multimap<RetOrArg, RetOrArg> UseMap;
+ /// 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.
+ /// - 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;
+ typedef std::set<const Function*> LiveFuncSet;
+
+ /// This set contains all values that have been determined to be live.
+ LiveSet LiveValues;
+ /// This set contains all values that are cannot be changed in any way.
+ LiveFuncSet LiveFunctions;
+
+ typedef SmallVector<RetOrArg, 5> UseVector;
+
+ protected:
+ // DAH uses this to specify a different ID.
+ explicit DAE(void *ID) : ModulePass(ID) {}
public:
static char ID; // Pass identification, replacement for typeid
- DAE() : ModulePass((intptr_t)&ID) {}
+ DAE() : ModulePass(&ID) {}
+
bool runOnModule(Module &M);
virtual bool ShouldHackArguments() const { return false; }
private:
- Liveness getArgumentLiveness(const Argument &A);
- bool isMaybeLiveArgumentNowLive(Argument *Arg);
-
+ Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses);
+ Liveness SurveyUse(Value::const_use_iterator U, UseVector &MaybeLiveUses,
+ unsigned RetValNum = 0);
+ Liveness SurveyUses(const Value *V, UseVector &MaybeLiveUses);
+
+ void SurveyFunction(const Function &F);
+ void MarkValue(const RetOrArg &RA, Liveness L,
+ const UseVector &MaybeLiveUses);
+ void MarkLive(const RetOrArg &RA);
+ void MarkLive(const Function &F);
+ void PropagateLiveness(const RetOrArg &RA);
+ bool RemoveDeadStuffFromFunction(Function *F);
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;
- RegisterPass<DAE> X("deadargelim", "Dead Argument Elimination");
+char DAE::ID = 0;
+INITIALIZE_PASS(DAE, "deadargelim", "Dead Argument Elimination", false, false);
+namespace {
/// DAH - DeadArgumentHacking pass - Same as dead argument elimination, but
/// deletes arguments to functions which are external. This is only for use
/// by bugpoint.
struct DAH : public DAE {
static char ID;
+ DAH() : DAE(&ID) {}
+
virtual bool ShouldHackArguments() const { return true; }
};
- char DAH::ID = 0;
- RegisterPass<DAH> Y("deadarghaX0r",
- "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)");
}
+char DAH::ID = 0;
+INITIALIZE_PASS(DAH, "deadarghaX0r",
+ "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)",
+ false, false);
+
/// createDeadArgEliminationPass - This pass removes arguments from functions
/// which are not used by the body of the function.
///
/// llvm.vastart is never called, the varargs list is dead for the function.
bool DAE::DeleteDeadVarargs(Function &Fn) {
assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!");
- if (Fn.isDeclaration() || !Fn.hasInternalLinkage()) return false;
+ if (Fn.isDeclaration() || !Fn.hasLocalLinkage()) return false;
// Ensure that the function is only directly called.
- for (Value::use_iterator I = Fn.use_begin(), E = Fn.use_end(); I != E; ++I) {
- // If this use is anything other than a call site, give up.
- CallSite CS = CallSite::get(*I);
- Instruction *TheCall = CS.getInstruction();
- if (!TheCall) return false; // Not a direct call site?
-
- // The addr of this function is passed to the call.
- if (I.getOperandNo() != 0) return false;
- }
+ if (Fn.hasAddressTaken())
+ return false;
// Okay, we know we can transform this function if safe. Scan its body
// looking for calls to llvm.vastart.
// 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 has fewer arguments.
+ // the old function, but doesn't have isVarArg set.
const FunctionType *FTy = Fn.getFunctionType();
+
std::vector<const Type*> Params(FTy->param_begin(), FTy->param_end());
- FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params, false);
+ FunctionType *NFTy = FunctionType::get(FTy->getReturnType(),
+ Params, false);
unsigned NumArgs = Params.size();
// Create the new function body and insert it into the module...
- Function *NF = new Function(NFTy, Fn.getLinkage());
- NF->setCallingConv(Fn.getCallingConv());
- NF->setParamAttrs(Fn.getParamAttrs());
+ Function *NF = Function::Create(NFTy, Fn.getLinkage());
+ NF->copyAttributesFrom(&Fn);
Fn.getParent()->getFunctionList().insert(&Fn, NF);
NF->takeName(&Fn);
// Pass all the same arguments.
Args.assign(CS.arg_begin(), CS.arg_begin()+NumArgs);
+ // Drop any attributes that were on the vararg arguments.
+ AttrListPtr PAL = CS.getAttributes();
+ if (!PAL.isEmpty() && PAL.getSlot(PAL.getNumSlots() - 1).Index > NumArgs) {
+ SmallVector<AttributeWithIndex, 8> AttributesVec;
+ for (unsigned i = 0; PAL.getSlot(i).Index <= NumArgs; ++i)
+ AttributesVec.push_back(PAL.getSlot(i));
+ if (Attributes FnAttrs = PAL.getFnAttributes())
+ AttributesVec.push_back(AttributeWithIndex::get(~0, FnAttrs));
+ PAL = AttrListPtr::get(AttributesVec.begin(), AttributesVec.end());
+ }
+
Instruction *New;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
- New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
- Args.begin(), Args.end(), "", Call);
+ New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
+ Args.begin(), Args.end(), "", Call);
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
- cast<InvokeInst>(New)->setParamAttrs(CS.getParamAttrs());
+ cast<InvokeInst>(New)->setAttributes(PAL);
} else {
- New = new CallInst(NF, Args.begin(), Args.end(), "", Call);
+ New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
- cast<CallInst>(New)->setParamAttrs(CS.getParamAttrs());
+ cast<CallInst>(New)->setAttributes(PAL);
if (cast<CallInst>(Call)->isTailCall())
cast<CallInst>(New)->setTailCall();
}
+ New->setDebugLoc(Call->getDebugLoc());
+
Args.clear();
if (!Call->use_empty())
return true;
}
-
-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;
+/// 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()->isVoidTy())
+ return 0;
+ else if (const StructType *STy = dyn_cast<StructType>(F->getReturnType()))
+ return STy->getNumElements();
+ else
+ return 1;
}
-// 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->isStructReturn() && &*(F->arg_begin()) == &A)
+/// 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 or its Function is already marked as live.
+ if (LiveFunctions.count(Use.F) || LiveValues.count(Use))
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;
+
+ // We're maybe live otherwise, but remember that we must become live if
+ // Use becomes live.
+ MaybeLiveUses.push_back(Use);
+ return MaybeLive;
+}
+
+
+/// SurveyUse - This looks at a single use of an argument or return value
+/// and determines if it should be alive or not. Adds this use to MaybeLiveUses
+/// if it causes the used value to become MaybeLive.
+///
+/// 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::const_use_iterator U,
+ UseVector &MaybeLiveUses, unsigned RetValNum) {
+ const User *V = *U;
+ if (const ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
+ // 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 MarkIfNotLive(Use, MaybeLiveUses);
+ }
+ if (const 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 = MaybeLive;
+ for (Value::const_use_iterator I = IV->use_begin(),
+ E = V->use_end(); I != E; ++I) {
+ Result = SurveyUse(I, MaybeLiveUses, RetValNum);
+ if (Result == Live)
+ break;
+ }
+ return Result;
}
- // 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
- }
- return MaybeLive; // It must be used, but only as argument to a function
+ if (ImmutableCallSite CS = V) {
+ const Function *F = CS.getCalledFunction();
+ if (F) {
+ // 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);
+
+ if (ArgNo >= F->getFunctionType()->getNumParams())
+ // The value is passed in through a vararg! Must be live.
+ return Live;
+
+ assert(CS.getArgument(ArgNo)
+ == CS->getOperand(U.getOperandNo())
+ && "Argument is not where we expected it");
+
+ // Value passed to a normal call. It's only live when the corresponding
+ // 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 value
+/// Returns the Liveness deduced from the uses of this value.
+///
+/// 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(const Value *V, UseVector &MaybeLiveUses) {
+ // Assume it's dead (which will only hold if there are no uses at all..).
+ Liveness Result = MaybeLive;
+ // Check each use.
+ for (Value::const_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
-// (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;
- Liveness RetValLiveness = F.getReturnType() == Type::VoidTy ? Live : Dead;
-
- if (!F.hasInternalLinkage() &&
- (!ShouldHackArguments() || F.isIntrinsic()))
- FunctionIntrinsicallyLive = true;
- else
- for (Value::use_iterator I = F.use_begin(), E = F.use_end(); I != E; ++I) {
- // 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;
+void DAE::SurveyFunction(const Function &F) {
+ unsigned RetCount = NumRetVals(&F);
+ // Assume all return values are dead
+ typedef SmallVector<Liveness, 5> RetVals;
+ RetVals RetValLiveness(RetCount, MaybeLive);
+
+ typedef SmallVector<UseVector, 5> RetUses;
+ // These vectors map each return value to the uses that make it MaybeLive, so
+ // we can add those to the Uses map if the return value really turns out to be
+ // MaybeLive. Initialized to a list of RetCount empty lists.
+ RetUses MaybeLiveRetUses(RetCount);
+
+ for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+ if (const 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.
+ MarkLive(F);
+ return;
}
- // 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;
+ if (!F.hasLocalLinkage() && (!ShouldHackArguments() || F.isIntrinsic())) {
+ MarkLive(F);
+ return;
+ }
+
+ DEBUG(dbgs() << "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::const_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.
+ ImmutableCallSite CS(*I);
+ if (!CS || !CS.isCallee(I)) {
+ MarkLive(F);
+ return;
+ }
+
+ // If this use is anything other than a call site, the function is alive.
+ const 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::const_use_iterator I = TheCall->use_begin(),
+ E = TheCall->use_end(); I != E; ++I) {
+ const 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 {
- RetValLiveness = 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;
break;
}
-
- // If the function is PASSED IN as an argument, its address has been taken
- for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
- AI != E; ++AI)
- if (AI->get() == &F) {
- FunctionIntrinsicallyLive = true;
- break;
}
- if (FunctionIntrinsicallyLive) break;
+ } else {
+ // Single return value
+ RetValLiveness[0] = SurveyUses(TheCall, MaybeLiveRetUses[0]);
+ if (RetValLiveness[0] == Live)
+ NumLiveRetVals = RetCount;
+ }
}
-
- if (FunctionIntrinsicallyLive) {
- DOUT << " Intrinsically live fn: " << F.getName() << "\n";
- for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end();
- AI != E; ++AI)
- LiveArguments.insert(AI);
- LiveRetVal.insert(&F);
- return;
}
- switch (RetValLiveness) {
- case Live: LiveRetVal.insert(&F); break;
- case MaybeLive: MaybeLiveRetVal.insert(&F); break;
- case Dead: DeadRetVal.insert(&F); break;
+ // Now we've inspected all callers, record the liveness of our return values.
+ for (unsigned i = 0; i != RetCount; ++i)
+ MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
+
+ DEBUG(dbgs() << "DAE - Inspecting args for fn: " << F.getName() << "\n");
+
+ // Now, check all of our arguments.
+ unsigned i = 0;
+ UseVector MaybeLiveArgUses;
+ for (Function::const_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);
+ // Mark the result.
+ MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
+ // Clear the vector again for the next iteration.
+ MaybeLiveArgUses.clear();
}
+}
- 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;
+/// MarkValue - This function marks the liveness of RA depending on L. If L is
+/// 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:
- DOUT << " Arg only passed to calls: " << AI->getName() << "\n";
- AnyMaybeLiveArgs = true;
- MaybeLiveArguments.insert(AI);
+ {
+ // Note any uses of this value, so this return value can be
+ // marked live whenever one of the uses becomes live.
+ for (UseVector::const_iterator UI = MaybeLiveUses.begin(),
+ UE = MaybeLiveUses.end(); UI != UE; ++UI)
+ Uses.insert(std::make_pair(*UI, RA));
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 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) {
+ DEBUG(dbgs() << "DAE - Intrinsically live fn: " << F.getName() << "\n");
+ // Mark the function as live.
+ LiveFunctions.insert(&F);
+ // Mark all arguments as live.
+ for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
+ PropagateLiveness(CreateArg(&F, i));
+ // Mark all return values as live.
+ for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
+ PropagateLiveness(CreateRet(&F, i));
}
-/// 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!");
-
- // 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";
+/// 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(const RetOrArg &RA) {
+ if (LiveFunctions.count(RA.F))
+ return; // Function was already marked Live.
- MaybeLiveRetVal.erase(I);
- LiveRetVal.insert(F); // It is now known to be live!
+ if (!LiveValues.insert(RA).second)
+ return; // We were already marked 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);
+ DEBUG(dbgs() << "DAE - Marking " << RA.getDescription() << " live\n");
+ PropagateLiveness(RA);
}
-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);
- }
+/// PropagateLiveness - Given that RA is a live value, propagate it's liveness
+/// to any other values it uses (according to Uses).
+void DAE::PropagateLiveness(const RetOrArg &RA) {
+ // We don't use upper_bound (or equal_range) here, because our recursive call
+ // 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();
+ 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);
}
-// 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.
+// RemoveDeadStuffFromFunction - Remove any arguments and return values from F
+// that are not in LiveValues. Transform the function and all of the callees of
+// the function to not have these arguments and return values.
//
-void DAE::RemoveDeadArgumentsFromFunction(Function *F) {
+bool DAE::RemoveDeadStuffFromFunction(Function *F) {
+ // Don't modify fully live functions
+ if (LiveFunctions.count(F))
+ return false;
+
// Start by computing a new prototype for the function, which is the same as
- // the old function, but has fewer arguments.
+ // the old function, but has fewer arguments and a different return type.
const FunctionType *FTy = F->getFunctionType();
std::vector<const Type*> Params;
- // Set up to build a new list of parameter attributes
- ParamAttrsVector ParamAttrsVec;
- const ParamAttrsList *PAL = F->getParamAttrs();
+ // Set up to build a new list of parameter attributes.
+ SmallVector<AttributeWithIndex, 8> AttributesVec;
+ const AttrListPtr &PAL = F->getAttributes();
// The existing function return attributes.
- uint16_t RAttrs = PAL ? PAL->getParamAttrs(0) : 0;
+ Attributes RAttrs = PAL.getRetAttributes();
+ Attributes FnAttrs = PAL.getFnAttributes();
+
+ // Find out the new return value.
- // Make the function return void if the return value is dead.
const Type *RetTy = FTy->getReturnType();
- if (DeadRetVal.count(F)) {
- RetTy = Type::VoidTy;
- RAttrs &= ~ParamAttr::VoidTypeIncompatible;
- DeadRetVal.erase(F);
+ const Type *NRetTy = NULL;
+ unsigned RetCount = NumRetVals(F);
+
+ // -1 means unused, other numbers are the new index
+ SmallVector<int, 5> NewRetIdxs(RetCount, -1);
+ std::vector<const Type*> RetTypes;
+ if (RetTy->isVoidTy()) {
+ NRetTy = RetTy;
+ } else {
+ 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;
+ DEBUG(dbgs() << "DAE - Removing return value " << i << " from "
+ << F->getName() << "\n");
+ }
+ }
+ else
+ // We used to return a single value.
+ if (LiveValues.erase(CreateRet(F, 0))) {
+ RetTypes.push_back(RetTy);
+ NewRetIdxs[0] = 0;
+ } else {
+ DEBUG(dbgs() << "DAE - Removing return value from " << F->getName()
+ << "\n");
+ ++NumRetValsEliminated;
+ }
+ if (RetTypes.size() > 1)
+ // More than one return type? Return a struct with them. Also, if we used
+ // to return a struct and didn't change the number of return values,
+ // return a struct again. This prevents changing {something} into
+ // something and {} into void.
+ // Make the new struct packed if we used to return a packed struct
+ // already.
+ NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
+ else if (RetTypes.size() == 1)
+ // 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::getVoidTy(F->getContext());
}
+ 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->isVoidTy())
+ RAttrs &= ~Attribute::typeIncompatible(NRetTy);
+ else
+ assert((RAttrs & Attribute::typeIncompatible(NRetTy)) == 0
+ && "Return attributes no longer compatible?");
+
if (RAttrs)
- ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, RAttrs));
+ AttributesVec.push_back(AttributeWithIndex::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.
- unsigned index = 1;
- for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
- ++I, ++index)
- if (!DeadArguments.count(I)) {
+ // 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)) {
Params.push_back(I->getType());
- uint16_t Attrs = PAL ? PAL->getParamAttrs(index) : 0;
- if (Attrs)
- ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), Attrs));
+ ArgAlive[i] = true;
+
+ // Get the original parameter attributes (skipping the first one, that is
+ // for the return value.
+ if (Attributes Attrs = PAL.getParamAttributes(i + 1))
+ AttributesVec.push_back(AttributeWithIndex::get(Params.size(), Attrs));
+ } else {
+ ++NumArgumentsEliminated;
+ DEBUG(dbgs() << "DAE - Removing argument " << i << " (" << I->getName()
+ << ") from " << F->getName() << "\n");
}
+ }
- // Reconstruct the ParamAttrsList based on the vector we constructed.
- PAL = ParamAttrsList::get(ParamAttrsVec);
+ if (FnAttrs != Attribute::None)
+ AttributesVec.push_back(AttributeWithIndex::get(~0, FnAttrs));
- // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
- // have zero fixed arguments.
- //
- bool ExtraArgHack = false;
- if (Params.empty() && FTy->isVarArg()) {
- ExtraArgHack = true;
- Params.push_back(Type::Int32Ty);
- }
+ // Reconstruct the AttributesList based on the vector we constructed.
+ AttrListPtr NewPAL = AttrListPtr::get(AttributesVec.begin(),
+ AttributesVec.end());
// Create the new function type based on the recomputed parameters.
- FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
+ FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
+
+ // No change?
+ if (NFTy == FTy)
+ return false;
// Create the new function body and insert it into the module...
- Function *NF = new Function(NFTy, F->getLinkage());
- NF->setCallingConv(F->getCallingConv());
- NF->setParamAttrs(PAL);
+ Function *NF = Function::Create(NFTy, F->getLinkage());
+ NF->copyAttributesFrom(F);
+ NF->setAttributes(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);
while (!F->use_empty()) {
CallSite CS = CallSite::get(F->use_back());
Instruction *Call = CS.getInstruction();
- ParamAttrsVec.clear();
- PAL = CS.getParamAttrs();
+
+ AttributesVec.clear();
+ const AttrListPtr &CallPAL = CS.getAttributes();
// The call return attributes.
- uint16_t RAttrs = PAL ? PAL->getParamAttrs(0) : 0;
+ Attributes RAttrs = CallPAL.getRetAttributes();
+ Attributes FnAttrs = CallPAL.getFnAttributes();
// Adjust in case the function was changed to return void.
- if (NF->getReturnType() == Type::VoidTy)
- RAttrs &= ~ParamAttr::VoidTypeIncompatible;
+ RAttrs &= ~Attribute::typeIncompatible(NF->getReturnType());
if (RAttrs)
- ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, RAttrs));
-
- // 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);
- uint16_t Attrs = PAL ? PAL->getParamAttrs(index) : 0;
- if (Attrs)
- ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
+ AttributesVec.push_back(AttributeWithIndex::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 (Attributes Attrs = CallPAL.getParamAttributes(i + 1))
+ AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
}
- // Reconstruct the ParamAttrsList based on the vector we constructed.
- PAL = ParamAttrsList::get(ParamAttrsVec);
+ // 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 (Attributes Attrs = CallPAL.getParamAttributes(i + 1))
+ AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
+ }
- if (ExtraArgHack)
- Args.push_back(UndefValue::get(Type::Int32Ty));
+ if (FnAttrs != Attribute::None)
+ AttributesVec.push_back(AttributeWithIndex::get(~0, FnAttrs));
- // Push any varargs arguments on the list
- for (; AI != CS.arg_end(); ++AI)
- Args.push_back(*AI);
+ // Reconstruct the AttributesList based on the vector we constructed.
+ AttrListPtr NewCallPAL = AttrListPtr::get(AttributesVec.begin(),
+ AttributesVec.end());
Instruction *New;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
- New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
- Args.begin(), Args.end(), "", Call);
+ New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
+ Args.begin(), Args.end(), "", Call);
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
- cast<InvokeInst>(New)->setParamAttrs(PAL);
+ cast<InvokeInst>(New)->setAttributes(NewCallPAL);
} else {
- New = new CallInst(NF, Args.begin(), Args.end(), "", Call);
+ New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
- cast<CallInst>(New)->setParamAttrs(PAL);
+ cast<CallInst>(New)->setAttributes(NewCallPAL);
if (cast<CallInst>(Call)->isTailCall())
cast<CallInst>(New)->setTailCall();
}
+ New->setDebugLoc(Call->getDebugLoc());
+
Args.clear();
if (!Call->use_empty()) {
- if (New->getType() == Type::VoidTy)
- Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
- else {
+ if (New->getType() == Call->getType()) {
+ // Return type not changed? Just replace users then.
Call->replaceAllUsesWith(New);
New->takeName(Call);
+ } else if (New->getType()->isVoidTy()) {
+ // Our return value has uses, but they will get removed later on.
+ // Replace by null for now.
+ Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
+ } else {
+ assert(RetTy->isStructTy() &&
+ "Return type changed, but not into a void. The old return type"
+ " must have been a struct!");
+ Instruction *InsertPt = Call;
+ if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
+ BasicBlock::iterator IP = II->getNormalDest()->begin();
+ while (isa<PHINode>(IP)) ++IP;
+ InsertPt = IP;
+ }
+
+ // We used to return a struct. Instead of doing smart stuff with all the
+ // uses of this struct, we will just rebuild it using
+ // extract/insertvalue chaining and let instcombine clean that up.
+ //
+ // Start out building up our return value from undef
+ Value *RetVal = UndefValue::get(RetTy);
+ for (unsigned i = 0; i != RetCount; ++i)
+ if (NewRetIdxs[i] != -1) {
+ Value *V;
+ if (RetTypes.size() > 1)
+ // We are still returning a struct, so extract the value from our
+ // return value
+ V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
+ InsertPt);
+ else
+ // We are now returning a single element, so just insert that
+ V = New;
+ // Insert the value at the old position
+ RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
+ }
+ // Now, replace all uses of the old call instruction with the return
+ // struct we built
+ Call->replaceAllUsesWith(RetVal);
+ New->takeName(Call);
}
}
// Finally, remove the old call from the program, reducing the use-count of
// F.
- Call->getParent()->getInstList().erase(Call);
+ Call->eraseFromParent();
}
// Since we have now created the new function, splice the body of the old
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. While we're at
- // it, remove the dead arguments from the DeadArguments list.
- //
+ // the new arguments, also transfering over the names as well.
+ i = 0;
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
- I2 = NF->arg_begin();
- I != E; ++I)
- if (!DeadArguments.count(I)) {
+ I2 = NF->arg_begin(); I != E; ++I, ++i)
+ if (ArgAlive[i]) {
// If this is a live argument, move the name and users over to the new
// version.
I->replaceAllUsesWith(I2);
++I2;
} else {
// If this argument is dead, replace any uses of it with null constants
- // (these are guaranteed to only be operands to call instructions which
- // will later be simplified).
+ // (these are guaranteed to become unused later on).
I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
- DeadArguments.erase(I);
}
// If we change the return value of the function we must rewrite any return
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())) {
- new ReturnInst(0, RI);
+ Value *RetVal;
+
+ if (NFTy->getReturnType()->isVoidTy()) {
+ RetVal = 0;
+ } else {
+ assert (RetTy->isStructTy());
+ // 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 = UndefValue::get(NRetTy);
+ for (unsigned i = 0; i != RetCount; ++i)
+ if (NewRetIdxs[i] != -1) {
+ 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],
+ "newret", RI);
+ } 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(F->getContext(), RetVal, RI);
BB->getInstList().erase(RI);
}
// Now that the old function is dead, delete it.
- F->getParent()->getFunctionList().erase(F);
+ F->eraseFromParent();
+
+ return true;
}
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
// information computed while surveying other functions.
- DOUT << "DAE - Deleting dead varargs\n";
+ DEBUG(dbgs() << "DAE - Deleting dead varargs\n");
for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
Function &F = *I++;
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).
//
- DOUT << "DAE - Determining liveness\n";
+ DEBUG(dbgs() << "DAE - Determining liveness\n");
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
SurveyFunction(*I);
- // 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);
- }
- }
- }
-
- // 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);
+ // 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);
}
-
- // 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;
+ return Changed;
}
projects / oota-llvm.git / blobdiff