1 //===-- DeadArgumentElimination.cpp - Eliminate dead arguments ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass deletes dead arguments from internal functions. Dead argument
11 // elimination removes arguments which are directly dead, as well as arguments
12 // only passed into function calls as dead arguments of other functions. This
13 // pass also deletes dead arguments in a similar way.
15 // This pass is often useful as a cleanup pass to run after aggressive
16 // interprocedural passes, which add possibly-dead arguments.
18 //===----------------------------------------------------------------------===//
20 #define DEBUG_TYPE "deadargelim"
21 #include "llvm/Transforms/IPO.h"
22 #include "llvm/CallingConv.h"
23 #include "llvm/Constant.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/Instructions.h"
26 #include "llvm/IntrinsicInst.h"
27 #include "llvm/Module.h"
28 #include "llvm/Pass.h"
29 #include "llvm/Support/CallSite.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/ADT/Statistic.h"
36 Statistic NumArgumentsEliminated("deadargelim",
37 "Number of unread args removed");
38 Statistic NumRetValsEliminated("deadargelim",
39 "Number of unused return values removed");
41 /// DAE - The dead argument elimination pass.
43 class DAE : public ModulePass {
44 /// Liveness enum - During our initial pass over the program, we determine
45 /// that things are either definately alive, definately dead, or in need of
46 /// interprocedural analysis (MaybeLive).
48 enum Liveness { Live, MaybeLive, Dead };
50 /// LiveArguments, MaybeLiveArguments, DeadArguments - These sets contain
51 /// all of the arguments in the program. The Dead set contains arguments
52 /// which are completely dead (never used in the function). The MaybeLive
53 /// set contains arguments which are only passed into other function calls,
54 /// thus may be live and may be dead. The Live set contains arguments which
55 /// are known to be alive.
57 std::set<Argument*> DeadArguments, MaybeLiveArguments, LiveArguments;
59 /// DeadRetVal, MaybeLiveRetVal, LifeRetVal - These sets contain all of the
60 /// functions in the program. The Dead set contains functions whose return
61 /// value is known to be dead. The MaybeLive set contains functions whose
62 /// return values are only used by return instructions, and the Live set
63 /// contains functions whose return values are used, functions that are
64 /// external, and functions that already return void.
66 std::set<Function*> DeadRetVal, MaybeLiveRetVal, LiveRetVal;
68 /// InstructionsToInspect - As we mark arguments and return values
69 /// MaybeLive, we keep track of which instructions could make the values
70 /// live here. Once the entire program has had the return value and
71 /// arguments analyzed, this set is scanned to promote the MaybeLive objects
72 /// to be Live if they really are used.
73 std::vector<Instruction*> InstructionsToInspect;
75 /// CallSites - Keep track of the call sites of functions that have
76 /// MaybeLive arguments or return values.
77 std::multimap<Function*, CallSite> CallSites;
80 bool runOnModule(Module &M);
82 virtual bool ShouldHackArguments() const { return false; }
85 Liveness getArgumentLiveness(const Argument &A);
86 bool isMaybeLiveArgumentNowLive(Argument *Arg);
88 bool DeleteDeadVarargs(Function &Fn);
89 void SurveyFunction(Function &Fn);
91 void MarkArgumentLive(Argument *Arg);
92 void MarkRetValLive(Function *F);
93 void MarkReturnInstArgumentLive(ReturnInst *RI);
95 void RemoveDeadArgumentsFromFunction(Function *F);
97 RegisterPass<DAE> X("deadargelim", "Dead Argument Elimination");
99 /// DAH - DeadArgumentHacking pass - Same as dead argument elimination, but
100 /// deletes arguments to functions which are external. This is only for use
102 struct DAH : public DAE {
103 virtual bool ShouldHackArguments() const { return true; }
105 RegisterPass<DAH> Y("deadarghaX0r",
106 "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)");
109 /// createDeadArgEliminationPass - This pass removes arguments from functions
110 /// which are not used by the body of the function.
112 ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
113 ModulePass *llvm::createDeadArgHackingPass() { return new DAH(); }
115 /// DeleteDeadVarargs - If this is an function that takes a ... list, and if
116 /// llvm.vastart is never called, the varargs list is dead for the function.
117 bool DAE::DeleteDeadVarargs(Function &Fn) {
118 assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!");
119 if (Fn.isExternal() || !Fn.hasInternalLinkage()) return false;
121 // Ensure that the function is only directly called.
122 for (Value::use_iterator I = Fn.use_begin(), E = Fn.use_end(); I != E; ++I) {
123 // If this use is anything other than a call site, give up.
124 CallSite CS = CallSite::get(*I);
125 Instruction *TheCall = CS.getInstruction();
126 if (!TheCall) return false; // Not a direct call site?
128 // The addr of this function is passed to the call.
129 if (I.getOperandNo() != 0) return false;
132 // Okay, we know we can transform this function if safe. Scan its body
133 // looking for calls to llvm.vastart.
134 for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
135 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
136 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
137 if (II->getIntrinsicID() == Intrinsic::vastart)
143 // If we get here, there are no calls to llvm.vastart in the function body,
144 // remove the "..." and adjust all the calls.
146 // Start by computing a new prototype for the function, which is the same as
147 // the old function, but has fewer arguments.
148 const FunctionType *FTy = Fn.getFunctionType();
149 std::vector<const Type*> Params(FTy->param_begin(), FTy->param_end());
150 FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params, false);
151 unsigned NumArgs = Params.size();
153 // Create the new function body and insert it into the module...
154 Function *NF = new Function(NFTy, Fn.getLinkage(), Fn.getName());
155 NF->setCallingConv(Fn.getCallingConv());
156 Fn.getParent()->getFunctionList().insert(&Fn, NF);
158 // Loop over all of the callers of the function, transforming the call sites
159 // to pass in a smaller number of arguments into the new function.
161 std::vector<Value*> Args;
162 while (!Fn.use_empty()) {
163 CallSite CS = CallSite::get(Fn.use_back());
164 Instruction *Call = CS.getInstruction();
166 // Loop over the operands, dropping extraneous ones at the end of the list.
167 Args.assign(CS.arg_begin(), CS.arg_begin()+NumArgs);
170 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
171 New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
173 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
175 New = new CallInst(NF, Args, "", Call);
176 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
177 if (cast<CallInst>(Call)->isTailCall())
178 cast<CallInst>(New)->setTailCall();
182 if (!Call->use_empty())
183 Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
185 if (Call->hasName()) {
186 std::string Name = Call->getName();
191 // Finally, remove the old call from the program, reducing the use-count of
193 Call->getParent()->getInstList().erase(Call);
196 // Since we have now created the new function, splice the body of the old
197 // function right into the new function, leaving the old rotting hulk of the
199 NF->getBasicBlockList().splice(NF->begin(), Fn.getBasicBlockList());
201 // Loop over the argument list, transfering uses of the old arguments over to
202 // the new arguments, also transfering over the names as well. While we're at
203 // it, remove the dead arguments from the DeadArguments list.
205 for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(),
206 I2 = NF->arg_begin(); I != E; ++I, ++I2) {
207 // Move the name and users over to the new version.
208 I->replaceAllUsesWith(I2);
209 I2->setName(I->getName());
212 // Finally, nuke the old function.
213 Fn.eraseFromParent();
218 static inline bool CallPassesValueThoughVararg(Instruction *Call,
220 CallSite CS = CallSite::get(Call);
221 const Type *CalledValueTy = CS.getCalledValue()->getType();
222 const Type *FTy = cast<PointerType>(CalledValueTy)->getElementType();
223 unsigned NumFixedArgs = cast<FunctionType>(FTy)->getNumParams();
224 for (CallSite::arg_iterator AI = CS.arg_begin()+NumFixedArgs;
225 AI != CS.arg_end(); ++AI)
226 if (AI->get() == Arg)
231 // getArgumentLiveness - Inspect an argument, determining if is known Live
232 // (used in a computation), MaybeLive (only passed as an argument to a call), or
234 DAE::Liveness DAE::getArgumentLiveness(const Argument &A) {
235 // If this is the return value of a csret function, it's not really dead.
236 if (A.getParent()->getCallingConv() == CallingConv::CSRet &&
237 &*A.getParent()->arg_begin() == &A)
240 if (A.use_empty()) // First check, directly dead?
243 // Scan through all of the uses, looking for non-argument passing uses.
244 for (Value::use_const_iterator I = A.use_begin(), E = A.use_end(); I!=E;++I) {
245 // Return instructions do not immediately effect liveness.
246 if (isa<ReturnInst>(*I))
249 CallSite CS = CallSite::get(const_cast<User*>(*I));
250 if (!CS.getInstruction()) {
251 // If its used by something that is not a call or invoke, it's alive!
254 // If it's an indirect call, mark it alive...
255 Function *Callee = CS.getCalledFunction();
256 if (!Callee) return Live;
258 // Check to see if it's passed through a va_arg area: if so, we cannot
260 if (CallPassesValueThoughVararg(CS.getInstruction(), &A))
261 return Live; // If passed through va_arg area, we cannot remove it
264 return MaybeLive; // It must be used, but only as argument to a function
268 // SurveyFunction - This performs the initial survey of the specified function,
269 // checking out whether or not it uses any of its incoming arguments or whether
270 // any callers use the return value. This fills in the
271 // (Dead|MaybeLive|Live)(Arguments|RetVal) sets.
273 // We consider arguments of non-internal functions to be intrinsically alive as
274 // well as arguments to functions which have their "address taken".
276 void DAE::SurveyFunction(Function &F) {
277 bool FunctionIntrinsicallyLive = false;
278 Liveness RetValLiveness = F.getReturnType() == Type::VoidTy ? Live : Dead;
280 if (!F.hasInternalLinkage() &&
281 (!ShouldHackArguments() || F.getIntrinsicID()))
282 FunctionIntrinsicallyLive = true;
284 for (Value::use_iterator I = F.use_begin(), E = F.use_end(); I != E; ++I) {
285 // If this use is anything other than a call site, the function is alive.
286 CallSite CS = CallSite::get(*I);
287 Instruction *TheCall = CS.getInstruction();
288 if (!TheCall) { // Not a direct call site?
289 FunctionIntrinsicallyLive = true;
293 // Check to see if the return value is used...
294 if (RetValLiveness != Live)
295 for (Value::use_iterator I = TheCall->use_begin(),
296 E = TheCall->use_end(); I != E; ++I)
297 if (isa<ReturnInst>(cast<Instruction>(*I))) {
298 RetValLiveness = MaybeLive;
299 } else if (isa<CallInst>(cast<Instruction>(*I)) ||
300 isa<InvokeInst>(cast<Instruction>(*I))) {
301 if (CallPassesValueThoughVararg(cast<Instruction>(*I), TheCall) ||
302 !CallSite::get(cast<Instruction>(*I)).getCalledFunction()) {
303 RetValLiveness = Live;
306 RetValLiveness = MaybeLive;
309 RetValLiveness = Live;
313 // If the function is PASSED IN as an argument, its address has been taken
314 for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
316 if (AI->get() == &F) {
317 FunctionIntrinsicallyLive = true;
320 if (FunctionIntrinsicallyLive) break;
323 if (FunctionIntrinsicallyLive) {
324 DOUT << " Intrinsically live fn: " << F.getName() << "\n";
325 for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end();
327 LiveArguments.insert(AI);
328 LiveRetVal.insert(&F);
332 switch (RetValLiveness) {
333 case Live: LiveRetVal.insert(&F); break;
334 case MaybeLive: MaybeLiveRetVal.insert(&F); break;
335 case Dead: DeadRetVal.insert(&F); break;
338 DOUT << " Inspecting args for fn: " << F.getName() << "\n";
340 // If it is not intrinsically alive, we know that all users of the
341 // function are call sites. Mark all of the arguments live which are
342 // directly used, and keep track of all of the call sites of this function
343 // if there are any arguments we assume that are dead.
345 bool AnyMaybeLiveArgs = false;
346 for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end();
348 switch (getArgumentLiveness(*AI)) {
350 DOUT << " Arg live by use: " << AI->getName() << "\n";
351 LiveArguments.insert(AI);
354 DOUT << " Arg definitely dead: " << AI->getName() <<"\n";
355 DeadArguments.insert(AI);
358 DOUT << " Arg only passed to calls: " << AI->getName() << "\n";
359 AnyMaybeLiveArgs = true;
360 MaybeLiveArguments.insert(AI);
364 // If there are any "MaybeLive" arguments, we need to check callees of
365 // this function when/if they become alive. Record which functions are
367 if (AnyMaybeLiveArgs || RetValLiveness == MaybeLive)
368 for (Value::use_iterator I = F.use_begin(), E = F.use_end();
370 if (AnyMaybeLiveArgs)
371 CallSites.insert(std::make_pair(&F, CallSite::get(*I)));
373 if (RetValLiveness == MaybeLive)
374 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
376 InstructionsToInspect.push_back(cast<Instruction>(*UI));
380 // isMaybeLiveArgumentNowLive - Check to see if Arg is alive. At this point, we
381 // know that the only uses of Arg are to be passed in as an argument to a
382 // function call or return. Check to see if the formal argument passed in is in
383 // the LiveArguments set. If so, return true.
385 bool DAE::isMaybeLiveArgumentNowLive(Argument *Arg) {
386 for (Value::use_iterator I = Arg->use_begin(), E = Arg->use_end(); I!=E; ++I){
387 if (isa<ReturnInst>(*I)) {
388 if (LiveRetVal.count(Arg->getParent())) return true;
392 CallSite CS = CallSite::get(*I);
394 // We know that this can only be used for direct calls...
395 Function *Callee = CS.getCalledFunction();
397 // Loop over all of the arguments (because Arg may be passed into the call
398 // multiple times) and check to see if any are now alive...
399 CallSite::arg_iterator CSAI = CS.arg_begin();
400 for (Function::arg_iterator AI = Callee->arg_begin(), E = Callee->arg_end();
401 AI != E; ++AI, ++CSAI)
402 // If this is the argument we are looking for, check to see if it's alive
403 if (*CSAI == Arg && LiveArguments.count(AI))
409 /// MarkArgumentLive - The MaybeLive argument 'Arg' is now known to be alive.
410 /// Mark it live in the specified sets and recursively mark arguments in callers
411 /// live that are needed to pass in a value.
413 void DAE::MarkArgumentLive(Argument *Arg) {
414 std::set<Argument*>::iterator It = MaybeLiveArguments.lower_bound(Arg);
415 if (It == MaybeLiveArguments.end() || *It != Arg) return;
417 DOUT << " MaybeLive argument now live: " << Arg->getName() <<"\n";
418 MaybeLiveArguments.erase(It);
419 LiveArguments.insert(Arg);
421 // Loop over all of the call sites of the function, making any arguments
422 // passed in to provide a value for this argument live as necessary.
424 Function *Fn = Arg->getParent();
425 unsigned ArgNo = std::distance(Fn->arg_begin(), Function::arg_iterator(Arg));
427 std::multimap<Function*, CallSite>::iterator I = CallSites.lower_bound(Fn);
428 for (; I != CallSites.end() && I->first == Fn; ++I) {
429 CallSite CS = I->second;
430 Value *ArgVal = *(CS.arg_begin()+ArgNo);
431 if (Argument *ActualArg = dyn_cast<Argument>(ArgVal)) {
432 MarkArgumentLive(ActualArg);
434 // If the value passed in at this call site is a return value computed by
435 // some other call site, make sure to mark the return value at the other
436 // call site as being needed.
437 CallSite ArgCS = CallSite::get(ArgVal);
438 if (ArgCS.getInstruction())
439 if (Function *Fn = ArgCS.getCalledFunction())
445 /// MarkArgumentLive - The MaybeLive return value for the specified function is
446 /// now known to be alive. Propagate this fact to the return instructions which
448 void DAE::MarkRetValLive(Function *F) {
449 assert(F && "Shame shame, we can't have null pointers here!");
451 // Check to see if we already knew it was live
452 std::set<Function*>::iterator I = MaybeLiveRetVal.lower_bound(F);
453 if (I == MaybeLiveRetVal.end() || *I != F) return; // It's already alive!
455 DOUT << " MaybeLive retval now live: " << F->getName() << "\n";
457 MaybeLiveRetVal.erase(I);
458 LiveRetVal.insert(F); // It is now known to be live!
460 // Loop over all of the functions, noticing that the return value is now live.
461 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
462 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
463 MarkReturnInstArgumentLive(RI);
466 void DAE::MarkReturnInstArgumentLive(ReturnInst *RI) {
467 Value *Op = RI->getOperand(0);
468 if (Argument *A = dyn_cast<Argument>(Op)) {
470 } else if (CallInst *CI = dyn_cast<CallInst>(Op)) {
471 if (Function *F = CI->getCalledFunction())
473 } else if (InvokeInst *II = dyn_cast<InvokeInst>(Op)) {
474 if (Function *F = II->getCalledFunction())
479 // RemoveDeadArgumentsFromFunction - We know that F has dead arguments, as
480 // specified by the DeadArguments list. Transform the function and all of the
481 // callees of the function to not have these arguments.
483 void DAE::RemoveDeadArgumentsFromFunction(Function *F) {
484 // Start by computing a new prototype for the function, which is the same as
485 // the old function, but has fewer arguments.
486 const FunctionType *FTy = F->getFunctionType();
487 std::vector<const Type*> Params;
489 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I)
490 if (!DeadArguments.count(I))
491 Params.push_back(I->getType());
493 const Type *RetTy = FTy->getReturnType();
494 if (DeadRetVal.count(F)) {
495 RetTy = Type::VoidTy;
499 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
500 // have zero fixed arguments.
502 // FIXME: once this bug is fixed in the CWriter, this hack should be removed.
504 bool ExtraArgHack = false;
505 if (Params.empty() && FTy->isVarArg()) {
507 Params.push_back(Type::IntTy);
510 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
512 // Create the new function body and insert it into the module...
513 Function *NF = new Function(NFTy, F->getLinkage(), F->getName());
514 NF->setCallingConv(F->getCallingConv());
515 F->getParent()->getFunctionList().insert(F, NF);
517 // Loop over all of the callers of the function, transforming the call sites
518 // to pass in a smaller number of arguments into the new function.
520 std::vector<Value*> Args;
521 while (!F->use_empty()) {
522 CallSite CS = CallSite::get(F->use_back());
523 Instruction *Call = CS.getInstruction();
525 // Loop over the operands, deleting dead ones...
526 CallSite::arg_iterator AI = CS.arg_begin();
527 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
529 if (!DeadArguments.count(I)) // Remove operands for dead arguments
533 Args.push_back(Constant::getNullValue(Type::IntTy));
535 // Push any varargs arguments on the list
536 for (; AI != CS.arg_end(); ++AI)
540 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
541 New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
543 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
545 New = new CallInst(NF, Args, "", Call);
546 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
547 if (cast<CallInst>(Call)->isTailCall())
548 cast<CallInst>(New)->setTailCall();
552 if (!Call->use_empty()) {
553 if (New->getType() == Type::VoidTy)
554 Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
556 Call->replaceAllUsesWith(New);
557 std::string Name = Call->getName();
563 // Finally, remove the old call from the program, reducing the use-count of
565 Call->getParent()->getInstList().erase(Call);
568 // Since we have now created the new function, splice the body of the old
569 // function right into the new function, leaving the old rotting hulk of the
571 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
573 // Loop over the argument list, transfering uses of the old arguments over to
574 // the new arguments, also transfering over the names as well. While we're at
575 // it, remove the dead arguments from the DeadArguments list.
577 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
578 I2 = NF->arg_begin();
580 if (!DeadArguments.count(I)) {
581 // If this is a live argument, move the name and users over to the new
583 I->replaceAllUsesWith(I2);
584 I2->setName(I->getName());
587 // If this argument is dead, replace any uses of it with null constants
588 // (these are guaranteed to only be operands to call instructions which
589 // will later be simplified).
590 I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
591 DeadArguments.erase(I);
594 // If we change the return value of the function we must rewrite any return
595 // instructions. Check this now.
596 if (F->getReturnType() != NF->getReturnType())
597 for (Function::iterator BB = NF->begin(), E = NF->end(); BB != E; ++BB)
598 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
599 new ReturnInst(0, RI);
600 BB->getInstList().erase(RI);
603 // Now that the old function is dead, delete it.
604 F->getParent()->getFunctionList().erase(F);
607 bool DAE::runOnModule(Module &M) {
608 // First phase: loop through the module, determining which arguments are live.
609 // We assume all arguments are dead unless proven otherwise (allowing us to
610 // determine that dead arguments passed into recursive functions are dead).
612 DOUT << "DAE - Determining liveness\n";
613 for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
615 if (F.getFunctionType()->isVarArg())
616 if (DeleteDeadVarargs(F))
622 // Loop over the instructions to inspect, propagating liveness among arguments
623 // and return values which are MaybeLive.
625 while (!InstructionsToInspect.empty()) {
626 Instruction *I = InstructionsToInspect.back();
627 InstructionsToInspect.pop_back();
629 if (ReturnInst *RI = dyn_cast<ReturnInst>(I)) {
630 // For return instructions, we just have to check to see if the return
631 // value for the current function is known now to be alive. If so, any
632 // arguments used by it are now alive, and any call instruction return
633 // value is alive as well.
634 if (LiveRetVal.count(RI->getParent()->getParent()))
635 MarkReturnInstArgumentLive(RI);
638 CallSite CS = CallSite::get(I);
639 assert(CS.getInstruction() && "Unknown instruction for the I2I list!");
641 Function *Callee = CS.getCalledFunction();
643 // If we found a call or invoke instruction on this list, that means that
644 // an argument of the function is a call instruction. If the argument is
645 // live, then the return value of the called instruction is now live.
647 CallSite::arg_iterator AI = CS.arg_begin(); // ActualIterator
648 for (Function::arg_iterator FI = Callee->arg_begin(),
649 E = Callee->arg_end(); FI != E; ++AI, ++FI) {
650 // If this argument is another call...
651 CallSite ArgCS = CallSite::get(*AI);
652 if (ArgCS.getInstruction() && LiveArguments.count(FI))
653 if (Function *Callee = ArgCS.getCalledFunction())
654 MarkRetValLive(Callee);
659 // Now we loop over all of the MaybeLive arguments, promoting them to be live
660 // arguments if one of the calls that uses the arguments to the calls they are
661 // passed into requires them to be live. Of course this could make other
662 // arguments live, so process callers recursively.
664 // Because elements can be removed from the MaybeLiveArguments set, copy it to
665 // a temporary vector.
667 std::vector<Argument*> TmpArgList(MaybeLiveArguments.begin(),
668 MaybeLiveArguments.end());
669 for (unsigned i = 0, e = TmpArgList.size(); i != e; ++i) {
670 Argument *MLA = TmpArgList[i];
671 if (MaybeLiveArguments.count(MLA) &&
672 isMaybeLiveArgumentNowLive(MLA))
673 MarkArgumentLive(MLA);
676 // Recover memory early...
679 // At this point, we know that all arguments in DeadArguments and
680 // MaybeLiveArguments are dead. If the two sets are empty, there is nothing
682 if (MaybeLiveArguments.empty() && DeadArguments.empty() &&
683 MaybeLiveRetVal.empty() && DeadRetVal.empty())
686 // Otherwise, compact into one set, and start eliminating the arguments from
688 DeadArguments.insert(MaybeLiveArguments.begin(), MaybeLiveArguments.end());
689 MaybeLiveArguments.clear();
690 DeadRetVal.insert(MaybeLiveRetVal.begin(), MaybeLiveRetVal.end());
691 MaybeLiveRetVal.clear();
693 LiveArguments.clear();
696 NumArgumentsEliminated += DeadArguments.size();
697 NumRetValsEliminated += DeadRetVal.size();
698 while (!DeadArguments.empty())
699 RemoveDeadArgumentsFromFunction((*DeadArguments.begin())->getParent());
701 while (!DeadRetVal.empty())
702 RemoveDeadArgumentsFromFunction(*DeadRetVal.begin());