//===-- 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 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
//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "deadargelim"
#include "llvm/Transforms/IPO.h"
+#include "llvm/CallingConv.h"
+#include "llvm/Constant.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.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/Support/CallSite.h"
-#include "Support/Debug.h"
-#include "Support/Statistic.h"
-#include "Support/iterator"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Compiler.h"
+#include <map>
#include <set>
using namespace llvm;
-namespace {
- Statistic<> NumArgumentsEliminated("deadargelim",
- "Number of unread args removed");
- Statistic<> NumRetValsEliminated("deadargelim",
- "Number of unused return values removed");
+STATISTIC(NumArgumentsEliminated, "Number of unread args removed");
+STATISTIC(NumRetValsEliminated , "Number of unused return values removed");
+namespace {
/// DAE - The dead argument elimination pass.
///
- class DAE : public Pass {
+ class VISIBILITY_HIDDEN 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).
std::multimap<Function*, CallSite> CallSites;
public:
- bool run(Module &M);
+ static char ID; // Pass identification, replacement for typeid
+ DAE() : ModulePass((intptr_t)&ID) {}
+ bool runOnModule(Module &M);
virtual bool ShouldHackArguments() const { return false; }
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);
};
- RegisterOpt<DAE> X("deadargelim", "Dead Argument Elimination");
+ char DAE::ID = 0;
+ RegisterPass<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 {
+ static char ID;
virtual bool ShouldHackArguments() const { return true; }
};
+ char DAH::ID = 0;
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.
///
-Pass *llvm::createDeadArgEliminationPass() { return new DAE(); }
-Pass *llvm::createDeadArgHackingPass() { return new DAH(); }
+ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
+ModulePass *llvm::createDeadArgHackingPass() { return new DAH(); }
+
+/// DeleteDeadVarargs - If this is an function that takes a ... list, and if
+/// 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;
+
+ // 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;
+ }
+
+ // Okay, we know we can transform this function if safe. Scan its body
+ // looking for calls to llvm.vastart.
+ for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+ if (II->getIntrinsicID() == Intrinsic::vastart)
+ return false;
+ }
+ }
+ }
+
+ // If we get here, there are no calls to llvm.vastart in the function body,
+ // 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.
+ const FunctionType *FTy = Fn.getFunctionType();
+ std::vector<const Type*> Params(FTy->param_begin(), FTy->param_end());
+ 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 = Function::Create(NFTy, Fn.getLinkage());
+ NF->setCallingConv(Fn.getCallingConv());
+ NF->setParamAttrs(Fn.getParamAttrs());
+ if (Fn.hasCollector())
+ NF->setCollector(Fn.getCollector());
+ Fn.getParent()->getFunctionList().insert(&Fn, NF);
+ NF->takeName(&Fn);
+
+ // 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 (!Fn.use_empty()) {
+ CallSite CS = CallSite::get(Fn.use_back());
+ Instruction *Call = CS.getInstruction();
+
+ // Pass all the same arguments.
+ Args.assign(CS.arg_begin(), CS.arg_begin()+NumArgs);
+
+ // Drop any attributes that were on the vararg arguments.
+ PAListPtr PAL = CS.getParamAttrs();
+ if (!PAL.isEmpty() && PAL.getSlot(PAL.getNumSlots() - 1).Index > NumArgs) {
+ SmallVector<ParamAttrsWithIndex, 8> ParamAttrsVec;
+ for (unsigned i = 0; PAL.getSlot(i).Index <= NumArgs; ++i)
+ ParamAttrsVec.push_back(PAL.getSlot(i));
+ PAL = PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end());
+ }
+
+ Instruction *New;
+ if (InvokeInst *II = dyn_cast<InvokeInst>(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);
+ } else {
+ New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
+ cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
+ cast<CallInst>(New)->setParamAttrs(PAL);
+ if (cast<CallInst>(Call)->isTailCall())
+ cast<CallInst>(New)->setTailCall();
+ }
+ Args.clear();
+
+ if (!Call->use_empty())
+ Call->replaceAllUsesWith(New);
+
+ New->takeName(Call);
+
+ // Finally, remove the old call from the program, reducing the use-count of
+ // F.
+ Call->eraseFromParent();
+ }
+
+ // Since we have now created the new function, splice the body of the old
+ // function right into the new function, leaving the old rotting hulk of the
+ // function empty.
+ NF->getBasicBlockList().splice(NF->begin(), Fn.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.
+ //
+ for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(),
+ I2 = NF->arg_begin(); I != E; ++I, ++I2) {
+ // Move the name and users over to the new version.
+ I->replaceAllUsesWith(I2);
+ I2->takeName(I);
+ }
+
+ // Finally, nuke the old function.
+ Fn.eraseFromParent();
+ return true;
+}
+
static inline bool CallPassesValueThoughVararg(Instruction *Call,
const Value *Arg) {
// (used in a computation), MaybeLive (only passed as an argument to a call), or
// Dead (not used).
DAE::Liveness DAE::getArgumentLiveness(const Argument &A) {
- if (A.use_empty()) return Dead; // First check, directly dead?
+ 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) {
Liveness RetValLiveness = F.getReturnType() == Type::VoidTy ? Live : Dead;
if (!F.hasInternalLinkage() &&
- (!ShouldHackArguments() || F.getIntrinsicID()))
+ (!ShouldHackArguments() || F.isIntrinsic()))
FunctionIntrinsicallyLive = true;
- else
+ 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);
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 (FunctionIntrinsicallyLive) {
- DEBUG(std::cerr << " Intrinsically live fn: " << F.getName() << "\n");
- for (Function::aiterator AI = F.abegin(), E = F.aend(); AI != E; ++AI)
+ 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;
case Dead: DeadRetVal.insert(&F); break;
}
- DEBUG(std::cerr << " Inspecting args for fn: " << F.getName() << "\n");
+ 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
// if there are any arguments we assume that are dead.
//
bool AnyMaybeLiveArgs = false;
- for (Function::aiterator AI = F.abegin(), E = F.aend(); AI != E; ++AI)
+ 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");
+ DOUT << " Arg live by use: " << AI->getName() << "\n";
LiveArguments.insert(AI);
break;
case Dead:
- DEBUG(std::cerr << " Arg definitely dead: " <<AI->getName()<<"\n");
+ DOUT << " Arg definitely dead: " << AI->getName() <<"\n";
DeadArguments.insert(AI);
break;
case MaybeLive:
- DEBUG(std::cerr << " Arg only passed to calls: "
- << AI->getName() << "\n");
+ DOUT << " Arg only passed to calls: " << AI->getName() << "\n";
AnyMaybeLiveArgs = true;
MaybeLiveArguments.insert(AI);
break;
// 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))
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");
+
+ 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->abegin(), Function::aiterator(Arg));
+ 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) {
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");
+ DOUT << " MaybeLive retval now live: " << F->getName() << "\n";
MaybeLiveRetVal.erase(I);
LiveRetVal.insert(F); // It is now known to be live!
const FunctionType *FTy = F->getFunctionType();
std::vector<const Type*> Params;
- for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
- if (!DeadArguments.count(I))
- Params.push_back(I->getType());
+ // Set up to build a new list of parameter attributes
+ SmallVector<ParamAttrsWithIndex, 8> ParamAttrsVec;
+ const PAListPtr &PAL = F->getParamAttrs();
+ // The existing function return attributes.
+ ParameterAttributes RAttrs = PAL.getParamAttrs(0);
+
+ // 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::typeIncompatible(RetTy);
DeadRetVal.erase(F);
}
+ if (RAttrs)
+ ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, RAttrs));
+
+ // 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)) {
+ Params.push_back(I->getType());
+
+ if (ParameterAttributes Attrs = PAL.getParamAttrs(index))
+ ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), Attrs));
+ }
+
+ // Reconstruct the ParamAttrsList based on the vector we constructed.
+ PAListPtr NewPAL = PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end());
+
// 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);
+ Params.push_back(Type::Int32Ty);
}
+ // Create the new function type based on the recomputed parameters.
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());
+ Function *NF = Function::Create(NFTy, F->getLinkage());
+ NF->setCallingConv(F->getCallingConv());
+ NF->setParamAttrs(NewPAL);
+ if (F->hasCollector())
+ NF->setCollector(F->getCollector());
F->getParent()->getFunctionList().insert(F, NF);
+ NF->takeName(F);
// 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.
while (!F->use_empty()) {
CallSite CS = CallSite::get(F->use_back());
Instruction *Call = CS.getInstruction();
+ ParamAttrsVec.clear();
+ const PAListPtr &CallPAL = CS.getParamAttrs();
+
+ // The call return attributes.
+ ParameterAttributes RAttrs = CallPAL.getParamAttrs(0);
+ // Adjust in case the function was changed to return void.
+ RAttrs &= ~ParamAttr::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();
- for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I, ++AI)
- if (!DeadArguments.count(I)) // Remove operands for dead arguments
+ 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));
+ }
if (ExtraArgHack)
- Args.push_back(Constant::getNullValue(Type::IntTy));
+ Args.push_back(UndefValue::get(Type::Int32Ty));
- // Push any varargs arguments on the list
- for (; AI != CS.arg_end(); ++AI)
+ // Push any varargs arguments on the list. Don't forget their attributes.
+ for (; AI != CS.arg_end(); ++AI) {
Args.push_back(*AI);
+ if (ParameterAttributes Attrs = CallPAL.getParamAttrs(index++))
+ ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
+ }
+
+ // Reconstruct the ParamAttrsList based on the vector we constructed.
+ PAListPtr NewCallPAL = PAListPtr::get(ParamAttrsVec.begin(),
+ ParamAttrsVec.end());
Instruction *New;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
- New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
- Args, "", Call);
+ New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
+ Args.begin(), Args.end(), "", Call);
+ cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
+ cast<InvokeInst>(New)->setParamAttrs(NewCallPAL);
} else {
- New = new CallInst(NF, Args, "", Call);
+ New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
+ cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
+ cast<CallInst>(New)->setParamAttrs(NewCallPAL);
+ if (cast<CallInst>(Call)->isTailCall())
+ cast<CallInst>(New)->setTailCall();
}
Args.clear();
Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
else {
Call->replaceAllUsesWith(New);
- std::string Name = Call->getName();
- Call->setName("");
- New->setName(Name);
+ New->takeName(Call);
}
}
-
+
// Finally, remove the old call from the program, reducing the use-count of
// F.
Call->getParent()->getInstList().erase(Call);
// 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
// version.
I->replaceAllUsesWith(I2);
- I2->setName(I->getName());
+ I2->takeName(I);
++I2;
} else {
// If this argument is dead, replace any uses of it with null constants
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);
+ ReturnInst::Create(0, RI);
BB->getInstList().erase(RI);
}
F->getParent()->getFunctionList().erase(F);
}
-bool DAE::run(Module &M) {
- // First phase: loop through the module, determining which arguments are live.
+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";
+ 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).
//
- DEBUG(std::cerr << "DAE - Determining liveness\n");
+ DOUT << "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
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::aiterator FI = Callee->abegin(), E = Callee->aend();
- FI != E; ++AI, ++FI) {
+ 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))
// to do.
if (MaybeLiveArguments.empty() && DeadArguments.empty() &&
MaybeLiveRetVal.empty() && DeadRetVal.empty())
- return false;
-
+ return Changed;
+
// Otherwise, compact into one set, and start eliminating the arguments from
// the functions.
DeadArguments.insert(MaybeLiveArguments.begin(), MaybeLiveArguments.end());
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