//===-- DeadArgumentElimination.cpp - Eliminate dead arguments ------------===//
//
+// 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 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.
+// only passed into function calls as dead arguments of other functions. This
+// 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.
//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "deadargelim"
#include "llvm/Transforms/IPO.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Constant.h"
-#include "llvm/iOther.h"
-#include "llvm/iTerminators.h"
+#include "llvm/Instructions.h"
#include "llvm/Support/CallSite.h"
-#include "Support/Debug.h"
-#include "Support/Statistic.h"
-#include "Support/iterator"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/iterator"
#include <set>
+using namespace llvm;
namespace {
- Statistic<> NumArgumentsEliminated("deadargelim", "Number of args removed");
-
- struct DAE : public Pass {
- DAE(bool DFEF = false) : DeleteFromExternalFunctions(DFEF) {}
- bool run(Module &M);
+ Statistic<> NumArgumentsEliminated("deadargelim",
+ "Number of unread args removed");
+ Statistic<> NumRetValsEliminated("deadargelim",
+ "Number of unused return values removed");
+
+ /// DAE - The dead argument elimination pass.
+ ///
+ class DAE : public ModulePass {
+ /// 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;
+
+ public:
+ bool runOnModule(Module &M);
+
+ virtual bool ShouldHackArguments() const { return false; }
private:
- bool DeleteFromExternalFunctions;
- bool FunctionArgumentsIntrinsicallyAlive(const Function &F);
- void RemoveDeadArgumentsFromFunction(Function *F,
- std::set<Argument*> &DeadArguments);
+ Liveness getArgumentLiveness(const Argument &A);
+ bool isMaybeLiveArgumentNowLive(Argument *Arg);
+
+ void SurveyFunction(Function &Fn);
+
+ void MarkArgumentLive(Argument *Arg);
+ void MarkRetValLive(Function *F);
+ void MarkReturnInstArgumentLive(ReturnInst *RI);
+
+ void RemoveDeadArgumentsFromFunction(Function *F);
};
RegisterOpt<DAE> X("deadargelim", "Dead Argument Elimination");
+
+ /// 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 {
+ virtual bool ShouldHackArguments() const { return true; }
+ };
+ RegisterPass<DAH> Y("deadarghaX0r",
+ "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)");
}
/// createDeadArgEliminationPass - This pass removes arguments from functions
-/// which are not used by the body of the function. If
-/// DeleteFromExternalFunctions is true, the pass will modify functions that
-/// have external linkage, which is not usually safe (this is used by bugpoint
-/// to reduce testcases).
+/// which are not used by the body of the function.
///
-Pass *createDeadArgEliminationPass(bool DeleteFromExternalFunctions) {
- return new DAE(DeleteFromExternalFunctions);
-}
-
-
-// FunctionArgumentsIntrinsicallyAlive - Return true if the arguments of the
-// specified function are intrinsically alive.
-//
-// We consider arguments of non-internal functions to be intrinsically alive as
-// well as arguments to functions which have their "address taken".
-//
-bool DAE::FunctionArgumentsIntrinsicallyAlive(const Function &F) {
- if (!F.hasInternalLinkage() && !DeleteFromExternalFunctions) return true;
-
- for (Value::use_const_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(const_cast<User*>(*I));
- if (!CS.getInstruction()) return true; // Not a valid call site?
-
- // 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) return true;
- }
+ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
+ModulePass *llvm::createDeadArgHackingPass() { return new DAH(); }
+
+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;
}
-namespace {
- enum ArgumentLiveness { Alive, MaybeLive, Dead };
-}
-
-// getArgumentLiveness - Inspect an argument, determining if is known Alive
+// 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).
-static ArgumentLiveness getArgumentLiveness(const Argument &A) {
+DAE::Liveness DAE::getArgumentLiveness(const Argument &A) {
if (A.use_empty()) return Dead; // First check, directly 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 Alive;
+ return Live;
}
// If it's an indirect call, mark it alive...
Function *Callee = CS.getCalledFunction();
- if (!Callee) return Alive;
+ if (!Callee) return Live;
// Check to see if it's passed through a va_arg area: if so, we cannot
// remove it.
- unsigned NumFixedArgs = Callee->getFunctionType()->getNumParams();
- for (CallSite::arg_iterator AI = CS.arg_begin()+NumFixedArgs;
- AI != CS.arg_end(); ++AI)
- if (AI->get() == &A) // If passed through va_arg area, we cannot remove it
- return Alive;
+ 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
}
-// isMaybeLiveArgumentNowAlive - 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. Check to see if the formal argument passed in is in the
-// LiveArguments set. If so, return true.
+
+// 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.
+//
+// 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.getIntrinsicID()))
+ 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;
+ }
+
+ // 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;
+ }
+
+ // 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;
+ }
+
+ if (FunctionIntrinsicallyLive) {
+ DEBUG(std::cerr << " 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;
+ }
+
+ DEBUG(std::cerr << " 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:
+ DEBUG(std::cerr << " Arg live by use: " << AI->getName() << "\n");
+ LiveArguments.insert(AI);
+ break;
+ case Dead:
+ DEBUG(std::cerr << " Arg definitely dead: " <<AI->getName()<<"\n");
+ DeadArguments.insert(AI);
+ break;
+ case MaybeLive:
+ DEBUG(std::cerr << " Arg only passed to calls: "
+ << AI->getName() << "\n");
+ AnyMaybeLiveArgs = true;
+ MaybeLiveArguments.insert(AI);
+ 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.
//
-static bool isMaybeLiveArgumentNowAlive(Argument *Arg,
- const std::set<Argument*> &LiveArguments) {
+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 = cast<Function>(CS.getCalledValue());
+ 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::aiterator AI = Callee->abegin(), E = Callee->aend();
+ 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 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.
-//
-static void MarkArgumentLive(Argument *Arg,
- std::set<Argument*> &MaybeLiveArguments,
- std::set<Argument*> &LiveArguments,
- const std::multimap<Function*, CallSite> &CallSites) {
+/// 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;
+
DEBUG(std::cerr << " MaybeLive argument now live: " << Arg->getName()<<"\n");
- assert(MaybeLiveArguments.count(Arg) && !LiveArguments.count(Arg) &&
- "Arg not MaybeLive?");
- MaybeLiveArguments.erase(Arg);
+ 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->abegin(), Function::aiterator(Arg));
+ unsigned ArgNo = std::distance(Fn->arg_begin(), Function::arg_iterator(Arg));
- std::multimap<Function*, CallSite>::const_iterator I =
- CallSites.lower_bound(Fn);
+ std::multimap<Function*, CallSite>::iterator I = CallSites.lower_bound(Fn);
for (; I != CallSites.end() && I->first == Fn; ++I) {
- const CallSite &CS = I->second;
- if (Argument *ActualArg = dyn_cast<Argument>(*(CS.arg_begin()+ArgNo)))
- if (MaybeLiveArguments.count(ActualArg))
- MarkArgumentLive(ActualArg, MaybeLiveArguments, LiveArguments,
- CallSites);
+ 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);
+ }
+ }
+}
+
+/// 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!
+
+ DEBUG(std::cerr << " 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);
+}
+
+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);
}
}
// specified by the DeadArguments list. Transform the function and all of the
// callees of the function to not have these arguments.
//
-void DAE::RemoveDeadArgumentsFromFunction(Function *F,
- std::set<Argument*> &DeadArguments){
+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.
const FunctionType *FTy = F->getFunctionType();
std::vector<const Type*> Params;
- for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
+ for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I)
if (!DeadArguments.count(I))
Params.push_back(I->getType());
- FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params,
- FTy->isVarArg());
-
+ const Type *RetTy = FTy->getReturnType();
+ if (DeadRetVal.count(F)) {
+ RetTy = Type::VoidTy;
+ DeadRetVal.erase(F);
+ }
+
+ // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
+ // have zero fixed arguments.
+ //
+ // FIXME: once this bug is fixed in the CWriter, this hack should be removed.
+ //
+ bool ExtraArgHack = false;
+ if (Params.empty() && FTy->isVarArg()) {
+ ExtraArgHack = true;
+ Params.push_back(Type::IntTy);
+ }
+
+ FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
+
// Create the new function body and insert it into the module...
Function *NF = new Function(NFTy, F->getLinkage(), F->getName());
+ NF->setCallingConv(F->getCallingConv());
F->getParent()->getFunctionList().insert(F, NF);
// Loop over all of the callers of the function, transforming the call sites
// to pass in a smaller number of arguments into the new function.
//
+ std::vector<Value*> Args;
while (!F->use_empty()) {
CallSite CS = CallSite::get(F->use_back());
Instruction *Call = CS.getInstruction();
- CS.setCalledFunction(NF); // Reduce the uses count of F
-
+
// Loop over the operands, deleting dead ones...
CallSite::arg_iterator AI = CS.arg_begin();
- for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
- if (DeadArguments.count(I)) { // Remove operands for dead arguments
- AI = Call->op_erase(AI);
- } else {
- ++AI; // Leave live operands alone...
+ for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
+ I != E; ++I, ++AI)
+ if (!DeadArguments.count(I)) // Remove operands for dead arguments
+ Args.push_back(*AI);
+
+ if (ExtraArgHack)
+ Args.push_back(Constant::getNullValue(Type::IntTy));
+
+ // Push any varargs arguments on the list
+ for (; AI != CS.arg_end(); ++AI)
+ Args.push_back(*AI);
+
+ Instruction *New;
+ if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
+ New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
+ Args, "", Call);
+ cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
+ } else {
+ New = new CallInst(NF, Args, "", Call);
+ cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
+ if (cast<CallInst>(Call)->isTailCall())
+ cast<CallInst>(New)->setTailCall();
+ }
+ Args.clear();
+
+ if (!Call->use_empty()) {
+ if (New->getType() == Type::VoidTy)
+ Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
+ else {
+ Call->replaceAllUsesWith(New);
+ std::string Name = Call->getName();
+ Call->setName("");
+ New->setName(Name);
}
+ }
+
+ // Finally, remove the old call from the program, reducing the use-count of
+ // F.
+ Call->getParent()->getInstList().erase(Call);
}
// Since we have now created the new function, splice the body of the old
// 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::aiterator I = F->abegin(), E = F->aend(), I2 = NF->abegin();
+ for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
+ 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
DeadArguments.erase(I);
}
+ // If we change the return value of the function we must rewrite any return
+ // instructions. Check this now.
+ 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);
+ BB->getInstList().erase(RI);
+ }
+
// Now that the old function is dead, delete it.
F->getParent()->getFunctionList().erase(F);
}
-bool DAE::run(Module &M) {
+bool DAE::runOnModule(Module &M) {
// First phase: loop through the module, determining which arguments are live.
// We assume all arguments are dead unless proven otherwise (allowing us to
- // determing that dead arguments passed into recursive functions are dead).
+ // determine that dead arguments passed into recursive functions are dead).
//
- std::set<Argument*> LiveArguments, MaybeLiveArguments, DeadArguments;
- std::multimap<Function*, CallSite> CallSites;
-
DEBUG(std::cerr << "DAE - Determining liveness\n");
- for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
- Function &Fn = *I;
- // If the function is intrinsically alive, just mark the arguments alive.
- if (FunctionArgumentsIntrinsicallyAlive(Fn)) {
- for (Function::aiterator AI = Fn.abegin(), E = Fn.aend(); AI != E; ++AI)
- LiveArguments.insert(AI);
- DEBUG(std::cerr << " Args intrinsically live for fn: " << Fn.getName()
- << "\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 {
- DEBUG(std::cerr << " Inspecting args for fn: " << Fn.getName() << "\n");
+ CallSite CS = CallSite::get(I);
+ assert(CS.getInstruction() && "Unknown instruction for the I2I list!");
- // 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::aiterator AI = Fn.abegin(), E = Fn.aend(); AI != E; ++AI)
- switch (getArgumentLiveness(*AI)) {
- case Alive:
- DEBUG(std::cerr << " Arg live by use: " << AI->getName() << "\n");
- LiveArguments.insert(AI);
- break;
- case Dead:
- DEBUG(std::cerr << " Arg definitely dead: " <<AI->getName()<<"\n");
- DeadArguments.insert(AI);
- break;
- case MaybeLive:
- DEBUG(std::cerr << " Arg only passed to calls: "
- << AI->getName() << "\n");
- AnyMaybeLiveArgs = true;
- MaybeLiveArguments.insert(AI);
- break;
- }
+ Function *Callee = CS.getCalledFunction();
- // 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)
- for (Value::use_iterator I = Fn.use_begin(), E = Fn.use_end();
- I != E; ++I)
- CallSites.insert(std::make_pair(&Fn, CallSite::get(*I)));
+ // 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);
+ }
}
}
// 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 list, copy it
- // to a temporary vector.
+ // 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) &&
- isMaybeLiveArgumentNowAlive(MLA, LiveArguments)) {
- MarkArgumentLive(MLA, MaybeLiveArguments, LiveArguments, CallSites);
- }
+ isMaybeLiveArgumentNowLive(MLA))
+ MarkArgumentLive(MLA);
}
// Recover memory early...
// 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())
+ if (MaybeLiveArguments.empty() && DeadArguments.empty() &&
+ MaybeLiveRetVal.empty() && DeadRetVal.empty())
return false;
-
+
// 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(),
- DeadArguments);
+ RemoveDeadArgumentsFromFunction((*DeadArguments.begin())->getParent());
+
+ while (!DeadRetVal.empty())
+ RemoveDeadArgumentsFromFunction(*DeadRetVal.begin());
return true;
}
projects / oota-llvm.git / blobdiff