1 //===- TailRecursionElimination.cpp - Eliminate Tail Calls ----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file transforms calls of the current function (self recursion) followed
11 // by a return instruction with a branch to the entry of the function, creating
12 // a loop. This pass also implements the following extensions to the basic
15 // 1. Trivial instructions between the call and return do not prevent the
16 // transformation from taking place, though currently the analysis cannot
17 // support moving any really useful instructions (only dead ones).
18 // 2. This pass transforms functions that are prevented from being tail
19 // recursive by an associative and commutative expression to use an
20 // accumulator variable, thus compiling the typical naive factorial or
21 // 'fib' implementation into efficient code.
22 // 3. TRE is performed if the function returns void, if the return
23 // returns the result returned by the call, or if the function returns a
24 // run-time constant on all exits from the function. It is possible, though
25 // unlikely, that the return returns something else (like constant 0), and
26 // can still be TRE'd. It can be TRE'd if ALL OTHER return instructions in
27 // the function return the exact same value.
28 // 4. If it can prove that callees do not access their caller stack frame,
29 // they are marked as eligible for tail call elimination (by the code
32 // There are several improvements that could be made:
34 // 1. If the function has any alloca instructions, these instructions will be
35 // moved out of the entry block of the function, causing them to be
36 // evaluated each time through the tail recursion. Safely keeping allocas
37 // in the entry block requires analysis to proves that the tail-called
38 // function does not read or write the stack object.
39 // 2. Tail recursion is only performed if the call immediately preceeds the
40 // return instruction. It's possible that there could be a jump between
41 // the call and the return.
42 // 3. There can be intervening operations between the call and the return that
43 // prevent the TRE from occurring. For example, there could be GEP's and
44 // stores to memory that will not be read or written by the call. This
45 // requires some substantial analysis (such as with DSA) to prove safe to
46 // move ahead of the call, but doing so could allow many more TREs to be
47 // performed, for example in TreeAdd/TreeAlloc from the treeadd benchmark.
48 // 4. The algorithm we use to detect if callees access their caller stack
49 // frames is very primitive.
51 //===----------------------------------------------------------------------===//
53 #define DEBUG_TYPE "tailcallelim"
54 #include "llvm/Transforms/Scalar.h"
55 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
56 #include "llvm/Transforms/Utils/Local.h"
57 #include "llvm/Constants.h"
58 #include "llvm/DerivedTypes.h"
59 #include "llvm/Function.h"
60 #include "llvm/Instructions.h"
61 #include "llvm/IntrinsicInst.h"
62 #include "llvm/Pass.h"
63 #include "llvm/Analysis/CaptureTracking.h"
64 #include "llvm/Analysis/InlineCost.h"
65 #include "llvm/Analysis/InstructionSimplify.h"
66 #include "llvm/Analysis/Loads.h"
67 #include "llvm/Support/CallSite.h"
68 #include "llvm/Support/CFG.h"
69 #include "llvm/Support/Debug.h"
70 #include "llvm/ADT/Statistic.h"
71 #include "llvm/ADT/STLExtras.h"
74 STATISTIC(NumEliminated, "Number of tail calls removed");
75 STATISTIC(NumAccumAdded, "Number of accumulators introduced");
78 struct TailCallElim : public FunctionPass {
79 static char ID; // Pass identification, replacement for typeid
80 TailCallElim() : FunctionPass(ID) {
81 initializeTailCallElimPass(*PassRegistry::getPassRegistry());
84 virtual bool runOnFunction(Function &F);
87 CallInst *FindTRECandidate(Instruction *I,
88 bool CannotTailCallElimCallsMarkedTail);
89 bool EliminateRecursiveTailCall(CallInst *CI, ReturnInst *Ret,
90 BasicBlock *&OldEntry,
91 bool &TailCallsAreMarkedTail,
92 SmallVector<PHINode*, 8> &ArgumentPHIs,
93 bool CannotTailCallElimCallsMarkedTail);
94 bool FoldReturnAndProcessPred(BasicBlock *BB,
95 ReturnInst *Ret, BasicBlock *&OldEntry,
96 bool &TailCallsAreMarkedTail,
97 SmallVector<PHINode*, 8> &ArgumentPHIs,
98 bool CannotTailCallElimCallsMarkedTail);
99 bool ProcessReturningBlock(ReturnInst *RI, BasicBlock *&OldEntry,
100 bool &TailCallsAreMarkedTail,
101 SmallVector<PHINode*, 8> &ArgumentPHIs,
102 bool CannotTailCallElimCallsMarkedTail);
103 bool CanMoveAboveCall(Instruction *I, CallInst *CI);
104 Value *CanTransformAccumulatorRecursion(Instruction *I, CallInst *CI);
108 char TailCallElim::ID = 0;
109 INITIALIZE_PASS(TailCallElim, "tailcallelim",
110 "Tail Call Elimination", false, false)
112 // Public interface to the TailCallElimination pass
113 FunctionPass *llvm::createTailCallEliminationPass() {
114 return new TailCallElim();
117 /// AllocaMightEscapeToCalls - Return true if this alloca may be accessed by
118 /// callees of this function. We only do very simple analysis right now, this
119 /// could be expanded in the future to use mod/ref information for particular
120 /// call sites if desired.
121 static bool AllocaMightEscapeToCalls(AllocaInst *AI) {
122 // FIXME: do simple 'address taken' analysis.
126 /// CheckForEscapingAllocas - Scan the specified basic block for alloca
127 /// instructions. If it contains any that might be accessed by calls, return
129 static bool CheckForEscapingAllocas(BasicBlock *BB,
130 bool &CannotTCETailMarkedCall) {
132 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
133 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
134 RetVal |= AllocaMightEscapeToCalls(AI);
136 // If this alloca is in the body of the function, or if it is a variable
137 // sized allocation, we cannot tail call eliminate calls marked 'tail'
138 // with this mechanism.
139 if (BB != &BB->getParent()->getEntryBlock() ||
140 !isa<ConstantInt>(AI->getArraySize()))
141 CannotTCETailMarkedCall = true;
146 bool TailCallElim::runOnFunction(Function &F) {
147 // If this function is a varargs function, we won't be able to PHI the args
148 // right, so don't even try to convert it...
149 if (F.getFunctionType()->isVarArg()) return false;
151 BasicBlock *OldEntry = 0;
152 bool TailCallsAreMarkedTail = false;
153 SmallVector<PHINode*, 8> ArgumentPHIs;
154 bool MadeChange = false;
155 bool FunctionContainsEscapingAllocas = false;
157 // CannotTCETailMarkedCall - If true, we cannot perform TCE on tail calls
158 // marked with the 'tail' attribute, because doing so would cause the stack
159 // size to increase (real TCE would deallocate variable sized allocas, TCE
161 bool CannotTCETailMarkedCall = false;
163 // Loop over the function, looking for any returning blocks, and keeping track
164 // of whether this function has any non-trivially used allocas.
165 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
166 if (FunctionContainsEscapingAllocas && CannotTCETailMarkedCall)
169 FunctionContainsEscapingAllocas |=
170 CheckForEscapingAllocas(BB, CannotTCETailMarkedCall);
173 /// FIXME: The code generator produces really bad code when an 'escaping
174 /// alloca' is changed from being a static alloca to being a dynamic alloca.
175 /// Until this is resolved, disable this transformation if that would ever
176 /// happen. This bug is PR962.
177 if (FunctionContainsEscapingAllocas)
180 // Second pass, change any tail calls to loops.
181 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
182 if (ReturnInst *Ret = dyn_cast<ReturnInst>(BB->getTerminator())) {
183 bool Change = ProcessReturningBlock(Ret, OldEntry, TailCallsAreMarkedTail,
184 ArgumentPHIs,CannotTCETailMarkedCall);
185 if (!Change && BB->getFirstNonPHIOrDbg() == Ret)
186 Change = FoldReturnAndProcessPred(BB, Ret, OldEntry,
187 TailCallsAreMarkedTail, ArgumentPHIs,
188 CannotTCETailMarkedCall);
189 MadeChange |= Change;
193 // If we eliminated any tail recursions, it's possible that we inserted some
194 // silly PHI nodes which just merge an initial value (the incoming operand)
195 // with themselves. Check to see if we did and clean up our mess if so. This
196 // occurs when a function passes an argument straight through to its tail
198 if (!ArgumentPHIs.empty()) {
199 for (unsigned i = 0, e = ArgumentPHIs.size(); i != e; ++i) {
200 PHINode *PN = ArgumentPHIs[i];
202 // If the PHI Node is a dynamic constant, replace it with the value it is.
203 if (Value *PNV = SimplifyInstruction(PN)) {
204 PN->replaceAllUsesWith(PNV);
205 PN->eraseFromParent();
210 // Finally, if this function contains no non-escaping allocas, mark all calls
211 // in the function as eligible for tail calls (there is no stack memory for
213 if (!FunctionContainsEscapingAllocas)
214 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
215 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
216 if (CallInst *CI = dyn_cast<CallInst>(I)) {
225 /// CanMoveAboveCall - Return true if it is safe to move the specified
226 /// instruction from after the call to before the call, assuming that all
227 /// instructions between the call and this instruction are movable.
229 bool TailCallElim::CanMoveAboveCall(Instruction *I, CallInst *CI) {
230 // FIXME: We can move load/store/call/free instructions above the call if the
231 // call does not mod/ref the memory location being processed.
232 if (I->mayHaveSideEffects()) // This also handles volatile loads.
235 if (LoadInst *L = dyn_cast<LoadInst>(I)) {
236 // Loads may always be moved above calls without side effects.
237 if (CI->mayHaveSideEffects()) {
238 // Non-volatile loads may be moved above a call with side effects if it
239 // does not write to memory and the load provably won't trap.
240 // FIXME: Writes to memory only matter if they may alias the pointer
241 // being loaded from.
242 if (CI->mayWriteToMemory() ||
243 !isSafeToLoadUnconditionally(L->getPointerOperand(), L,
249 // Otherwise, if this is a side-effect free instruction, check to make sure
250 // that it does not use the return value of the call. If it doesn't use the
251 // return value of the call, it must only use things that are defined before
252 // the call, or movable instructions between the call and the instruction
254 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
255 if (I->getOperand(i) == CI)
260 // isDynamicConstant - Return true if the specified value is the same when the
261 // return would exit as it was when the initial iteration of the recursive
262 // function was executed.
264 // We currently handle static constants and arguments that are not modified as
265 // part of the recursion.
267 static bool isDynamicConstant(Value *V, CallInst *CI, ReturnInst *RI) {
268 if (isa<Constant>(V)) return true; // Static constants are always dyn consts
270 // Check to see if this is an immutable argument, if so, the value
271 // will be available to initialize the accumulator.
272 if (Argument *Arg = dyn_cast<Argument>(V)) {
273 // Figure out which argument number this is...
275 Function *F = CI->getParent()->getParent();
276 for (Function::arg_iterator AI = F->arg_begin(); &*AI != Arg; ++AI)
279 // If we are passing this argument into call as the corresponding
280 // argument operand, then the argument is dynamically constant.
281 // Otherwise, we cannot transform this function safely.
282 if (CI->getArgOperand(ArgNo) == Arg)
286 // Switch cases are always constant integers. If the value is being switched
287 // on and the return is only reachable from one of its cases, it's
288 // effectively constant.
289 if (BasicBlock *UniquePred = RI->getParent()->getUniquePredecessor())
290 if (SwitchInst *SI = dyn_cast<SwitchInst>(UniquePred->getTerminator()))
291 if (SI->getCondition() == V)
292 return SI->getDefaultDest() != RI->getParent();
294 // Not a constant or immutable argument, we can't safely transform.
298 // getCommonReturnValue - Check to see if the function containing the specified
299 // tail call consistently returns the same runtime-constant value at all exit
300 // points except for IgnoreRI. If so, return the returned value.
302 static Value *getCommonReturnValue(ReturnInst *IgnoreRI, CallInst *CI) {
303 Function *F = CI->getParent()->getParent();
304 Value *ReturnedValue = 0;
306 for (Function::iterator BBI = F->begin(), E = F->end(); BBI != E; ++BBI) {
307 ReturnInst *RI = dyn_cast<ReturnInst>(BBI->getTerminator());
308 if (RI == 0 || RI == IgnoreRI) continue;
310 // We can only perform this transformation if the value returned is
311 // evaluatable at the start of the initial invocation of the function,
312 // instead of at the end of the evaluation.
314 Value *RetOp = RI->getOperand(0);
315 if (!isDynamicConstant(RetOp, CI, RI))
318 if (ReturnedValue && RetOp != ReturnedValue)
319 return 0; // Cannot transform if differing values are returned.
320 ReturnedValue = RetOp;
322 return ReturnedValue;
325 /// CanTransformAccumulatorRecursion - If the specified instruction can be
326 /// transformed using accumulator recursion elimination, return the constant
327 /// which is the start of the accumulator value. Otherwise return null.
329 Value *TailCallElim::CanTransformAccumulatorRecursion(Instruction *I,
331 if (!I->isAssociative() || !I->isCommutative()) return 0;
332 assert(I->getNumOperands() == 2 &&
333 "Associative/commutative operations should have 2 args!");
335 // Exactly one operand should be the result of the call instruction.
336 if ((I->getOperand(0) == CI && I->getOperand(1) == CI) ||
337 (I->getOperand(0) != CI && I->getOperand(1) != CI))
340 // The only user of this instruction we allow is a single return instruction.
341 if (!I->hasOneUse() || !isa<ReturnInst>(I->use_back()))
344 // Ok, now we have to check all of the other return instructions in this
345 // function. If they return non-constants or differing values, then we cannot
346 // transform the function safely.
347 return getCommonReturnValue(cast<ReturnInst>(I->use_back()), CI);
350 static Instruction *FirstNonDbg(BasicBlock::iterator I) {
351 while (isa<DbgInfoIntrinsic>(I))
357 TailCallElim::FindTRECandidate(Instruction *TI,
358 bool CannotTailCallElimCallsMarkedTail) {
359 BasicBlock *BB = TI->getParent();
360 Function *F = BB->getParent();
362 if (&BB->front() == TI) // Make sure there is something before the terminator.
365 // Scan backwards from the return, checking to see if there is a tail call in
366 // this block. If so, set CI to it.
368 BasicBlock::iterator BBI = TI;
370 CI = dyn_cast<CallInst>(BBI);
371 if (CI && CI->getCalledFunction() == F)
374 if (BBI == BB->begin())
375 return 0; // Didn't find a potential tail call.
379 // If this call is marked as a tail call, and if there are dynamic allocas in
380 // the function, we cannot perform this optimization.
381 if (CI->isTailCall() && CannotTailCallElimCallsMarkedTail)
384 // As a special case, detect code like this:
385 // double fabs(double f) { return __builtin_fabs(f); } // a 'fabs' call
386 // and disable this xform in this case, because the code generator will
387 // lower the call to fabs into inline code.
388 if (BB == &F->getEntryBlock() &&
389 FirstNonDbg(BB->front()) == CI &&
390 FirstNonDbg(llvm::next(BB->begin())) == TI &&
392 // A single-block function with just a call and a return. Check that
393 // the arguments match.
394 CallSite::arg_iterator I = CallSite(CI).arg_begin(),
395 E = CallSite(CI).arg_end();
396 Function::arg_iterator FI = F->arg_begin(),
398 for (; I != E && FI != FE; ++I, ++FI)
399 if (*I != &*FI) break;
400 if (I == E && FI == FE)
407 bool TailCallElim::EliminateRecursiveTailCall(CallInst *CI, ReturnInst *Ret,
408 BasicBlock *&OldEntry,
409 bool &TailCallsAreMarkedTail,
410 SmallVector<PHINode*, 8> &ArgumentPHIs,
411 bool CannotTailCallElimCallsMarkedTail) {
412 // If we are introducing accumulator recursion to eliminate operations after
413 // the call instruction that are both associative and commutative, the initial
414 // value for the accumulator is placed in this variable. If this value is set
415 // then we actually perform accumulator recursion elimination instead of
416 // simple tail recursion elimination. If the operation is an LLVM instruction
417 // (eg: "add") then it is recorded in AccumulatorRecursionInstr. If not, then
418 // we are handling the case when the return instruction returns a constant C
419 // which is different to the constant returned by other return instructions
420 // (which is recorded in AccumulatorRecursionEliminationInitVal). This is a
421 // special case of accumulator recursion, the operation being "return C".
422 Value *AccumulatorRecursionEliminationInitVal = 0;
423 Instruction *AccumulatorRecursionInstr = 0;
425 // Ok, we found a potential tail call. We can currently only transform the
426 // tail call if all of the instructions between the call and the return are
427 // movable to above the call itself, leaving the call next to the return.
428 // Check that this is the case now.
429 BasicBlock::iterator BBI = CI;
430 for (++BBI; &*BBI != Ret; ++BBI) {
431 if (CanMoveAboveCall(BBI, CI)) continue;
433 // If we can't move the instruction above the call, it might be because it
434 // is an associative and commutative operation that could be tranformed
435 // using accumulator recursion elimination. Check to see if this is the
436 // case, and if so, remember the initial accumulator value for later.
437 if ((AccumulatorRecursionEliminationInitVal =
438 CanTransformAccumulatorRecursion(BBI, CI))) {
439 // Yes, this is accumulator recursion. Remember which instruction
441 AccumulatorRecursionInstr = BBI;
443 return false; // Otherwise, we cannot eliminate the tail recursion!
447 // We can only transform call/return pairs that either ignore the return value
448 // of the call and return void, ignore the value of the call and return a
449 // constant, return the value returned by the tail call, or that are being
450 // accumulator recursion variable eliminated.
451 if (Ret->getNumOperands() == 1 && Ret->getReturnValue() != CI &&
452 !isa<UndefValue>(Ret->getReturnValue()) &&
453 AccumulatorRecursionEliminationInitVal == 0 &&
454 !getCommonReturnValue(0, CI)) {
455 // One case remains that we are able to handle: the current return
456 // instruction returns a constant, and all other return instructions
457 // return a different constant.
458 if (!isDynamicConstant(Ret->getReturnValue(), CI, Ret))
459 return false; // Current return instruction does not return a constant.
460 // Check that all other return instructions return a common constant. If
461 // so, record it in AccumulatorRecursionEliminationInitVal.
462 AccumulatorRecursionEliminationInitVal = getCommonReturnValue(Ret, CI);
463 if (!AccumulatorRecursionEliminationInitVal)
467 BasicBlock *BB = Ret->getParent();
468 Function *F = BB->getParent();
470 // OK! We can transform this tail call. If this is the first one found,
471 // create the new entry block, allowing us to branch back to the old entry.
473 OldEntry = &F->getEntryBlock();
474 BasicBlock *NewEntry = BasicBlock::Create(F->getContext(), "", F, OldEntry);
475 NewEntry->takeName(OldEntry);
476 OldEntry->setName("tailrecurse");
477 BranchInst::Create(OldEntry, NewEntry);
479 // If this tail call is marked 'tail' and if there are any allocas in the
480 // entry block, move them up to the new entry block.
481 TailCallsAreMarkedTail = CI->isTailCall();
482 if (TailCallsAreMarkedTail)
483 // Move all fixed sized allocas from OldEntry to NewEntry.
484 for (BasicBlock::iterator OEBI = OldEntry->begin(), E = OldEntry->end(),
485 NEBI = NewEntry->begin(); OEBI != E; )
486 if (AllocaInst *AI = dyn_cast<AllocaInst>(OEBI++))
487 if (isa<ConstantInt>(AI->getArraySize()))
488 AI->moveBefore(NEBI);
490 // Now that we have created a new block, which jumps to the entry
491 // block, insert a PHI node for each argument of the function.
492 // For now, we initialize each PHI to only have the real arguments
493 // which are passed in.
494 Instruction *InsertPos = OldEntry->begin();
495 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
497 PHINode *PN = PHINode::Create(I->getType(),
498 I->getName() + ".tr", InsertPos);
499 I->replaceAllUsesWith(PN); // Everyone use the PHI node now!
500 PN->addIncoming(I, NewEntry);
501 ArgumentPHIs.push_back(PN);
505 // If this function has self recursive calls in the tail position where some
506 // are marked tail and some are not, only transform one flavor or another. We
507 // have to choose whether we move allocas in the entry block to the new entry
508 // block or not, so we can't make a good choice for both. NOTE: We could do
509 // slightly better here in the case that the function has no entry block
511 if (TailCallsAreMarkedTail && !CI->isTailCall())
514 // Ok, now that we know we have a pseudo-entry block WITH all of the
515 // required PHI nodes, add entries into the PHI node for the actual
516 // parameters passed into the tail-recursive call.
517 for (unsigned i = 0, e = CI->getNumArgOperands(); i != e; ++i)
518 ArgumentPHIs[i]->addIncoming(CI->getArgOperand(i), BB);
520 // If we are introducing an accumulator variable to eliminate the recursion,
521 // do so now. Note that we _know_ that no subsequent tail recursion
522 // eliminations will happen on this function because of the way the
523 // accumulator recursion predicate is set up.
525 if (AccumulatorRecursionEliminationInitVal) {
526 Instruction *AccRecInstr = AccumulatorRecursionInstr;
527 // Start by inserting a new PHI node for the accumulator.
529 PHINode::Create(AccumulatorRecursionEliminationInitVal->getType(),
530 "accumulator.tr", OldEntry->begin());
532 // Loop over all of the predecessors of the tail recursion block. For the
533 // real entry into the function we seed the PHI with the initial value,
534 // computed earlier. For any other existing branches to this block (due to
535 // other tail recursions eliminated) the accumulator is not modified.
536 // Because we haven't added the branch in the current block to OldEntry yet,
537 // it will not show up as a predecessor.
538 for (pred_iterator PI = pred_begin(OldEntry), PE = pred_end(OldEntry);
541 if (P == &F->getEntryBlock())
542 AccPN->addIncoming(AccumulatorRecursionEliminationInitVal, P);
544 AccPN->addIncoming(AccPN, P);
548 // Add an incoming argument for the current block, which is computed by
549 // our associative and commutative accumulator instruction.
550 AccPN->addIncoming(AccRecInstr, BB);
552 // Next, rewrite the accumulator recursion instruction so that it does not
553 // use the result of the call anymore, instead, use the PHI node we just
555 AccRecInstr->setOperand(AccRecInstr->getOperand(0) != CI, AccPN);
557 // Add an incoming argument for the current block, which is just the
558 // constant returned by the current return instruction.
559 AccPN->addIncoming(Ret->getReturnValue(), BB);
562 // Finally, rewrite any return instructions in the program to return the PHI
563 // node instead of the "initval" that they do currently. This loop will
564 // actually rewrite the return value we are destroying, but that's ok.
565 for (Function::iterator BBI = F->begin(), E = F->end(); BBI != E; ++BBI)
566 if (ReturnInst *RI = dyn_cast<ReturnInst>(BBI->getTerminator()))
567 RI->setOperand(0, AccPN);
571 // Now that all of the PHI nodes are in place, remove the call and
572 // ret instructions, replacing them with an unconditional branch.
573 BranchInst::Create(OldEntry, Ret);
574 BB->getInstList().erase(Ret); // Remove return.
575 BB->getInstList().erase(CI); // Remove call.
580 bool TailCallElim::FoldReturnAndProcessPred(BasicBlock *BB,
581 ReturnInst *Ret, BasicBlock *&OldEntry,
582 bool &TailCallsAreMarkedTail,
583 SmallVector<PHINode*, 8> &ArgumentPHIs,
584 bool CannotTailCallElimCallsMarkedTail) {
587 // If the return block contains nothing but the return and PHI's,
588 // there might be an opportunity to duplicate the return in its
589 // predecessors and perform TRC there. Look for predecessors that end
590 // in unconditional branch and recursive call(s).
591 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB);
593 BasicBlock *Pred = *PI;
594 TerminatorInst *PTI = Pred->getTerminator();
595 if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) {
597 if (BI->isUnconditional() &&
598 (CI = FindTRECandidate(BI, CannotTailCallElimCallsMarkedTail))) {
599 DEBUG(dbgs() << "FOLDING: " << *BB
600 << "INTO UNCOND BRANCH PRED: " << *Pred);
601 EliminateRecursiveTailCall(CI,
602 FoldReturnIntoUncondBranch(Ret, BB, Pred),
603 OldEntry, TailCallsAreMarkedTail, ArgumentPHIs,
604 CannotTailCallElimCallsMarkedTail);
613 bool TailCallElim::ProcessReturningBlock(ReturnInst *Ret, BasicBlock *&OldEntry,
614 bool &TailCallsAreMarkedTail,
615 SmallVector<PHINode*, 8> &ArgumentPHIs,
616 bool CannotTailCallElimCallsMarkedTail) {
617 CallInst *CI = FindTRECandidate(Ret, CannotTailCallElimCallsMarkedTail);
621 return EliminateRecursiveTailCall(CI, Ret, OldEntry, TailCallsAreMarkedTail,
623 CannotTailCallElimCallsMarkedTail);