1 //===- Inliner.cpp - Code common to all inliners --------------------------===//
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 implements the mechanics required to implement inlining without
11 // missing any calls and updating the call graph. The decisions of which calls
12 // are profitable to inline are implemented elsewhere.
14 //===----------------------------------------------------------------------===//
16 #include "llvm/Transforms/IPO/InlinerPass.h"
17 #include "llvm/ADT/SmallPtrSet.h"
18 #include "llvm/ADT/Statistic.h"
19 #include "llvm/Analysis/AliasAnalysis.h"
20 #include "llvm/Analysis/AssumptionCache.h"
21 #include "llvm/Analysis/CallGraph.h"
22 #include "llvm/Analysis/InlineCost.h"
23 #include "llvm/Analysis/TargetLibraryInfo.h"
24 #include "llvm/IR/CallSite.h"
25 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/DiagnosticInfo.h"
27 #include "llvm/IR/Instructions.h"
28 #include "llvm/IR/IntrinsicInst.h"
29 #include "llvm/IR/Module.h"
30 #include "llvm/Support/CommandLine.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/raw_ostream.h"
33 #include "llvm/Transforms/Utils/Cloning.h"
34 #include "llvm/Transforms/Utils/Local.h"
37 #define DEBUG_TYPE "inline"
39 STATISTIC(NumInlined, "Number of functions inlined");
40 STATISTIC(NumCallsDeleted, "Number of call sites deleted, not inlined");
41 STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
42 STATISTIC(NumMergedAllocas, "Number of allocas merged together");
44 // This weirdly named statistic tracks the number of times that, when attempting
45 // to inline a function A into B, we analyze the callers of B in order to see
46 // if those would be more profitable and blocked inline steps.
47 STATISTIC(NumCallerCallersAnalyzed, "Number of caller-callers analyzed");
50 InlineLimit("inline-threshold", cl::Hidden, cl::init(225), cl::ZeroOrMore,
51 cl::desc("Control the amount of inlining to perform (default = 225)"));
54 HintThreshold("inlinehint-threshold", cl::Hidden, cl::init(325),
55 cl::desc("Threshold for inlining functions with inline hint"));
57 // We instroduce this threshold to help performance of instrumentation based
58 // PGO before we actually hook up inliner with analysis passes such as BPI and
61 ColdThreshold("inlinecold-threshold", cl::Hidden, cl::init(225),
62 cl::desc("Threshold for inlining functions with cold attribute"));
64 // Threshold to use when optsize is specified (and there is no -inline-limit).
65 const int OptSizeThreshold = 75;
67 Inliner::Inliner(char &ID)
68 : CallGraphSCCPass(ID), InlineThreshold(InlineLimit), InsertLifetime(true) {}
70 Inliner::Inliner(char &ID, int Threshold, bool InsertLifetime)
71 : CallGraphSCCPass(ID), InlineThreshold(InlineLimit.getNumOccurrences() > 0 ?
72 InlineLimit : Threshold),
73 InsertLifetime(InsertLifetime) {}
75 /// For this class, we declare that we require and preserve the call graph.
76 /// If the derived class implements this method, it should
77 /// always explicitly call the implementation here.
78 void Inliner::getAnalysisUsage(AnalysisUsage &AU) const {
79 AU.addRequired<AliasAnalysis>();
80 AU.addRequired<AssumptionCacheTracker>();
81 CallGraphSCCPass::getAnalysisUsage(AU);
85 typedef DenseMap<ArrayType*, std::vector<AllocaInst*> >
86 InlinedArrayAllocasTy;
88 /// \brief If the inlined function had a higher stack protection level than the
89 /// calling function, then bump up the caller's stack protection level.
90 static void AdjustCallerSSPLevel(Function *Caller, Function *Callee) {
91 // If upgrading the SSP attribute, clear out the old SSP Attributes first.
92 // Having multiple SSP attributes doesn't actually hurt, but it adds useless
95 B.addAttribute(Attribute::StackProtect)
96 .addAttribute(Attribute::StackProtectStrong);
97 AttributeSet OldSSPAttr = AttributeSet::get(Caller->getContext(),
98 AttributeSet::FunctionIndex,
101 if (Callee->hasFnAttribute(Attribute::StackProtectReq)) {
102 Caller->removeAttributes(AttributeSet::FunctionIndex, OldSSPAttr);
103 Caller->addFnAttr(Attribute::StackProtectReq);
104 } else if (Callee->hasFnAttribute(Attribute::StackProtectStrong) &&
105 !Caller->hasFnAttribute(Attribute::StackProtectReq)) {
106 Caller->removeAttributes(AttributeSet::FunctionIndex, OldSSPAttr);
107 Caller->addFnAttr(Attribute::StackProtectStrong);
108 } else if (Callee->hasFnAttribute(Attribute::StackProtect) &&
109 !Caller->hasFnAttribute(Attribute::StackProtectReq) &&
110 !Caller->hasFnAttribute(Attribute::StackProtectStrong))
111 Caller->addFnAttr(Attribute::StackProtect);
114 /// If it is possible to inline the specified call site,
115 /// do so and update the CallGraph for this operation.
117 /// This function also does some basic book-keeping to update the IR. The
118 /// InlinedArrayAllocas map keeps track of any allocas that are already
119 /// available from other functions inlined into the caller. If we are able to
120 /// inline this call site we attempt to reuse already available allocas or add
121 /// any new allocas to the set if not possible.
122 static bool InlineCallIfPossible(CallSite CS, InlineFunctionInfo &IFI,
123 InlinedArrayAllocasTy &InlinedArrayAllocas,
124 int InlineHistory, bool InsertLifetime) {
125 Function *Callee = CS.getCalledFunction();
126 Function *Caller = CS.getCaller();
128 // Try to inline the function. Get the list of static allocas that were
130 if (!InlineFunction(CS, IFI, InsertLifetime))
133 AdjustCallerSSPLevel(Caller, Callee);
135 // Look at all of the allocas that we inlined through this call site. If we
136 // have already inlined other allocas through other calls into this function,
137 // then we know that they have disjoint lifetimes and that we can merge them.
139 // There are many heuristics possible for merging these allocas, and the
140 // different options have different tradeoffs. One thing that we *really*
141 // don't want to hurt is SRoA: once inlining happens, often allocas are no
142 // longer address taken and so they can be promoted.
144 // Our "solution" for that is to only merge allocas whose outermost type is an
145 // array type. These are usually not promoted because someone is using a
146 // variable index into them. These are also often the most important ones to
149 // A better solution would be to have real memory lifetime markers in the IR
150 // and not have the inliner do any merging of allocas at all. This would
151 // allow the backend to do proper stack slot coloring of all allocas that
152 // *actually make it to the backend*, which is really what we want.
154 // Because we don't have this information, we do this simple and useful hack.
156 SmallPtrSet<AllocaInst*, 16> UsedAllocas;
158 // When processing our SCC, check to see if CS was inlined from some other
159 // call site. For example, if we're processing "A" in this code:
161 // B() { x = alloca ... C() }
162 // C() { y = alloca ... }
163 // Assume that C was not inlined into B initially, and so we're processing A
164 // and decide to inline B into A. Doing this makes an alloca available for
165 // reuse and makes a callsite (C) available for inlining. When we process
166 // the C call site we don't want to do any alloca merging between X and Y
167 // because their scopes are not disjoint. We could make this smarter by
168 // keeping track of the inline history for each alloca in the
169 // InlinedArrayAllocas but this isn't likely to be a significant win.
170 if (InlineHistory != -1) // Only do merging for top-level call sites in SCC.
173 // Loop over all the allocas we have so far and see if they can be merged with
174 // a previously inlined alloca. If not, remember that we had it.
175 for (unsigned AllocaNo = 0, e = IFI.StaticAllocas.size();
176 AllocaNo != e; ++AllocaNo) {
177 AllocaInst *AI = IFI.StaticAllocas[AllocaNo];
179 // Don't bother trying to merge array allocations (they will usually be
180 // canonicalized to be an allocation *of* an array), or allocations whose
181 // type is not itself an array (because we're afraid of pessimizing SRoA).
182 ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
183 if (!ATy || AI->isArrayAllocation())
186 // Get the list of all available allocas for this array type.
187 std::vector<AllocaInst*> &AllocasForType = InlinedArrayAllocas[ATy];
189 // Loop over the allocas in AllocasForType to see if we can reuse one. Note
190 // that we have to be careful not to reuse the same "available" alloca for
191 // multiple different allocas that we just inlined, we use the 'UsedAllocas'
192 // set to keep track of which "available" allocas are being used by this
193 // function. Also, AllocasForType can be empty of course!
194 bool MergedAwayAlloca = false;
195 for (unsigned i = 0, e = AllocasForType.size(); i != e; ++i) {
196 AllocaInst *AvailableAlloca = AllocasForType[i];
198 unsigned Align1 = AI->getAlignment(),
199 Align2 = AvailableAlloca->getAlignment();
201 // The available alloca has to be in the right function, not in some other
202 // function in this SCC.
203 if (AvailableAlloca->getParent() != AI->getParent())
206 // If the inlined function already uses this alloca then we can't reuse
208 if (!UsedAllocas.insert(AvailableAlloca).second)
211 // Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
213 DEBUG(dbgs() << " ***MERGED ALLOCA: " << *AI << "\n\t\tINTO: "
214 << *AvailableAlloca << '\n');
216 AI->replaceAllUsesWith(AvailableAlloca);
218 if (Align1 != Align2) {
219 if (!Align1 || !Align2) {
220 const DataLayout &DL = Caller->getParent()->getDataLayout();
221 unsigned TypeAlign = DL.getABITypeAlignment(AI->getAllocatedType());
223 Align1 = Align1 ? Align1 : TypeAlign;
224 Align2 = Align2 ? Align2 : TypeAlign;
228 AvailableAlloca->setAlignment(AI->getAlignment());
231 AI->eraseFromParent();
232 MergedAwayAlloca = true;
234 IFI.StaticAllocas[AllocaNo] = nullptr;
238 // If we already nuked the alloca, we're done with it.
239 if (MergedAwayAlloca)
242 // If we were unable to merge away the alloca either because there are no
243 // allocas of the right type available or because we reused them all
244 // already, remember that this alloca came from an inlined function and mark
245 // it used so we don't reuse it for other allocas from this inline
247 AllocasForType.push_back(AI);
248 UsedAllocas.insert(AI);
254 unsigned Inliner::getInlineThreshold(CallSite CS) const {
255 int thres = InlineThreshold; // -inline-threshold or else selected by
258 // If -inline-threshold is not given, listen to the optsize attribute when it
259 // would decrease the threshold.
260 Function *Caller = CS.getCaller();
261 bool OptSize = Caller && !Caller->isDeclaration() &&
262 Caller->hasFnAttribute(Attribute::OptimizeForSize);
263 if (!(InlineLimit.getNumOccurrences() > 0) && OptSize &&
264 OptSizeThreshold < thres)
265 thres = OptSizeThreshold;
267 // Listen to the inlinehint attribute when it would increase the threshold
268 // and the caller does not need to minimize its size.
269 Function *Callee = CS.getCalledFunction();
270 bool InlineHint = Callee && !Callee->isDeclaration() &&
271 Callee->hasFnAttribute(Attribute::InlineHint);
272 if (InlineHint && HintThreshold > thres &&
273 !Caller->hasFnAttribute(Attribute::MinSize))
274 thres = HintThreshold;
276 // Listen to the cold attribute when it would decrease the threshold.
277 bool ColdCallee = Callee && !Callee->isDeclaration() &&
278 Callee->hasFnAttribute(Attribute::Cold);
279 // Command line argument for InlineLimit will override the default
280 // ColdThreshold. If we have -inline-threshold but no -inlinecold-threshold,
281 // do not use the default cold threshold even if it is smaller.
282 if ((InlineLimit.getNumOccurrences() == 0 ||
283 ColdThreshold.getNumOccurrences() > 0) && ColdCallee &&
284 ColdThreshold < thres)
285 thres = ColdThreshold;
290 static void emitAnalysis(CallSite CS, const Twine &Msg) {
291 Function *Caller = CS.getCaller();
292 LLVMContext &Ctx = Caller->getContext();
293 DebugLoc DLoc = CS.getInstruction()->getDebugLoc();
294 emitOptimizationRemarkAnalysis(Ctx, DEBUG_TYPE, *Caller, DLoc, Msg);
297 /// Return true if the inliner should attempt to inline at the given CallSite.
298 bool Inliner::shouldInline(CallSite CS) {
299 InlineCost IC = getInlineCost(CS);
302 DEBUG(dbgs() << " Inlining: cost=always"
303 << ", Call: " << *CS.getInstruction() << "\n");
304 emitAnalysis(CS, Twine(CS.getCalledFunction()->getName()) +
305 " should always be inlined (cost=always)");
310 DEBUG(dbgs() << " NOT Inlining: cost=never"
311 << ", Call: " << *CS.getInstruction() << "\n");
312 emitAnalysis(CS, Twine(CS.getCalledFunction()->getName() +
313 " should never be inlined (cost=never)"));
317 Function *Caller = CS.getCaller();
319 DEBUG(dbgs() << " NOT Inlining: cost=" << IC.getCost()
320 << ", thres=" << (IC.getCostDelta() + IC.getCost())
321 << ", Call: " << *CS.getInstruction() << "\n");
322 emitAnalysis(CS, Twine(CS.getCalledFunction()->getName() +
323 " too costly to inline (cost=") +
324 Twine(IC.getCost()) + ", threshold=" +
325 Twine(IC.getCostDelta() + IC.getCost()) + ")");
329 // Try to detect the case where the current inlining candidate caller (call
330 // it B) is a static or linkonce-ODR function and is an inlining candidate
331 // elsewhere, and the current candidate callee (call it C) is large enough
332 // that inlining it into B would make B too big to inline later. In these
333 // circumstances it may be best not to inline C into B, but to inline B into
336 // This only applies to static and linkonce-ODR functions because those are
337 // expected to be available for inlining in the translation units where they
338 // are used. Thus we will always have the opportunity to make local inlining
339 // decisions. Importantly the linkonce-ODR linkage covers inline functions
340 // and templates in C++.
342 // FIXME: All of this logic should be sunk into getInlineCost. It relies on
343 // the internal implementation of the inline cost metrics rather than
344 // treating them as truly abstract units etc.
345 if (Caller->hasLocalLinkage() || Caller->hasLinkOnceODRLinkage()) {
346 int TotalSecondaryCost = 0;
347 // The candidate cost to be imposed upon the current function.
348 int CandidateCost = IC.getCost() - (InlineConstants::CallPenalty + 1);
349 // This bool tracks what happens if we do NOT inline C into B.
350 bool callerWillBeRemoved = Caller->hasLocalLinkage();
351 // This bool tracks what happens if we DO inline C into B.
352 bool inliningPreventsSomeOuterInline = false;
353 for (User *U : Caller->users()) {
356 // If this isn't a call to Caller (it could be some other sort
357 // of reference) skip it. Such references will prevent the caller
358 // from being removed.
359 if (!CS2 || CS2.getCalledFunction() != Caller) {
360 callerWillBeRemoved = false;
364 InlineCost IC2 = getInlineCost(CS2);
365 ++NumCallerCallersAnalyzed;
367 callerWillBeRemoved = false;
373 // See if inlining or original callsite would erase the cost delta of
374 // this callsite. We subtract off the penalty for the call instruction,
375 // which we would be deleting.
376 if (IC2.getCostDelta() <= CandidateCost) {
377 inliningPreventsSomeOuterInline = true;
378 TotalSecondaryCost += IC2.getCost();
381 // If all outer calls to Caller would get inlined, the cost for the last
382 // one is set very low by getInlineCost, in anticipation that Caller will
383 // be removed entirely. We did not account for this above unless there
384 // is only one caller of Caller.
385 if (callerWillBeRemoved && !Caller->use_empty())
386 TotalSecondaryCost += InlineConstants::LastCallToStaticBonus;
388 if (inliningPreventsSomeOuterInline && TotalSecondaryCost < IC.getCost()) {
389 DEBUG(dbgs() << " NOT Inlining: " << *CS.getInstruction() <<
390 " Cost = " << IC.getCost() <<
391 ", outer Cost = " << TotalSecondaryCost << '\n');
393 CS, Twine("Not inlining. Cost of inlining " +
394 CS.getCalledFunction()->getName() +
395 " increases the cost of inlining " +
396 CS.getCaller()->getName() + " in other contexts"));
401 DEBUG(dbgs() << " Inlining: cost=" << IC.getCost()
402 << ", thres=" << (IC.getCostDelta() + IC.getCost())
403 << ", Call: " << *CS.getInstruction() << '\n');
405 CS, CS.getCalledFunction()->getName() + Twine(" can be inlined into ") +
406 CS.getCaller()->getName() + " with cost=" + Twine(IC.getCost()) +
407 " (threshold=" + Twine(IC.getCostDelta() + IC.getCost()) + ")");
411 /// Return true if the specified inline history ID
412 /// indicates an inline history that includes the specified function.
413 static bool InlineHistoryIncludes(Function *F, int InlineHistoryID,
414 const SmallVectorImpl<std::pair<Function*, int> > &InlineHistory) {
415 while (InlineHistoryID != -1) {
416 assert(unsigned(InlineHistoryID) < InlineHistory.size() &&
417 "Invalid inline history ID");
418 if (InlineHistory[InlineHistoryID].first == F)
420 InlineHistoryID = InlineHistory[InlineHistoryID].second;
425 bool Inliner::runOnSCC(CallGraphSCC &SCC) {
426 CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
427 AssumptionCacheTracker *ACT = &getAnalysis<AssumptionCacheTracker>();
428 auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
429 const TargetLibraryInfo *TLI = TLIP ? &TLIP->getTLI() : nullptr;
430 AliasAnalysis *AA = &getAnalysis<AliasAnalysis>();
432 SmallPtrSet<Function*, 8> SCCFunctions;
433 DEBUG(dbgs() << "Inliner visiting SCC:");
434 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
435 Function *F = (*I)->getFunction();
436 if (F) SCCFunctions.insert(F);
437 DEBUG(dbgs() << " " << (F ? F->getName() : "INDIRECTNODE"));
440 // Scan through and identify all call sites ahead of time so that we only
441 // inline call sites in the original functions, not call sites that result
442 // from inlining other functions.
443 SmallVector<std::pair<CallSite, int>, 16> CallSites;
445 // When inlining a callee produces new call sites, we want to keep track of
446 // the fact that they were inlined from the callee. This allows us to avoid
447 // infinite inlining in some obscure cases. To represent this, we use an
448 // index into the InlineHistory vector.
449 SmallVector<std::pair<Function*, int>, 8> InlineHistory;
451 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
452 Function *F = (*I)->getFunction();
455 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
456 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
457 CallSite CS(cast<Value>(I));
458 // If this isn't a call, or it is a call to an intrinsic, it can
460 if (!CS || isa<IntrinsicInst>(I))
463 // If this is a direct call to an external function, we can never inline
464 // it. If it is an indirect call, inlining may resolve it to be a
465 // direct call, so we keep it.
466 if (CS.getCalledFunction() && CS.getCalledFunction()->isDeclaration())
469 CallSites.push_back(std::make_pair(CS, -1));
473 DEBUG(dbgs() << ": " << CallSites.size() << " call sites.\n");
475 // If there are no calls in this function, exit early.
476 if (CallSites.empty())
479 // Now that we have all of the call sites, move the ones to functions in the
480 // current SCC to the end of the list.
481 unsigned FirstCallInSCC = CallSites.size();
482 for (unsigned i = 0; i < FirstCallInSCC; ++i)
483 if (Function *F = CallSites[i].first.getCalledFunction())
484 if (SCCFunctions.count(F))
485 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
488 InlinedArrayAllocasTy InlinedArrayAllocas;
489 InlineFunctionInfo InlineInfo(&CG, AA, ACT);
491 // Now that we have all of the call sites, loop over them and inline them if
492 // it looks profitable to do so.
493 bool Changed = false;
497 // Iterate over the outer loop because inlining functions can cause indirect
498 // calls to become direct calls.
499 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi) {
500 CallSite CS = CallSites[CSi].first;
502 Function *Caller = CS.getCaller();
503 Function *Callee = CS.getCalledFunction();
505 // If this call site is dead and it is to a readonly function, we should
506 // just delete the call instead of trying to inline it, regardless of
507 // size. This happens because IPSCCP propagates the result out of the
508 // call and then we're left with the dead call.
509 if (isInstructionTriviallyDead(CS.getInstruction(), TLI)) {
510 DEBUG(dbgs() << " -> Deleting dead call: "
511 << *CS.getInstruction() << "\n");
512 // Update the call graph by deleting the edge from Callee to Caller.
513 CG[Caller]->removeCallEdgeFor(CS);
514 CS.getInstruction()->eraseFromParent();
517 // We can only inline direct calls to non-declarations.
518 if (!Callee || Callee->isDeclaration()) continue;
520 // If this call site was obtained by inlining another function, verify
521 // that the include path for the function did not include the callee
522 // itself. If so, we'd be recursively inlining the same function,
523 // which would provide the same callsites, which would cause us to
524 // infinitely inline.
525 int InlineHistoryID = CallSites[CSi].second;
526 if (InlineHistoryID != -1 &&
527 InlineHistoryIncludes(Callee, InlineHistoryID, InlineHistory))
530 LLVMContext &CallerCtx = Caller->getContext();
532 // Get DebugLoc to report. CS will be invalid after Inliner.
533 DebugLoc DLoc = CS.getInstruction()->getDebugLoc();
535 // If the policy determines that we should inline this function,
537 if (!shouldInline(CS)) {
538 emitOptimizationRemarkMissed(CallerCtx, DEBUG_TYPE, *Caller, DLoc,
539 Twine(Callee->getName() +
540 " will not be inlined into " +
545 // Attempt to inline the function.
546 if (!InlineCallIfPossible(CS, InlineInfo, InlinedArrayAllocas,
547 InlineHistoryID, InsertLifetime)) {
548 emitOptimizationRemarkMissed(CallerCtx, DEBUG_TYPE, *Caller, DLoc,
549 Twine(Callee->getName() +
550 " will not be inlined into " +
556 // Report the inline decision.
557 emitOptimizationRemark(
558 CallerCtx, DEBUG_TYPE, *Caller, DLoc,
559 Twine(Callee->getName() + " inlined into " + Caller->getName()));
561 // If inlining this function gave us any new call sites, throw them
562 // onto our worklist to process. They are useful inline candidates.
563 if (!InlineInfo.InlinedCalls.empty()) {
564 // Create a new inline history entry for this, so that we remember
565 // that these new callsites came about due to inlining Callee.
566 int NewHistoryID = InlineHistory.size();
567 InlineHistory.push_back(std::make_pair(Callee, InlineHistoryID));
569 for (unsigned i = 0, e = InlineInfo.InlinedCalls.size();
571 Value *Ptr = InlineInfo.InlinedCalls[i];
572 CallSites.push_back(std::make_pair(CallSite(Ptr), NewHistoryID));
577 // If we inlined or deleted the last possible call site to the function,
578 // delete the function body now.
579 if (Callee && Callee->use_empty() && Callee->hasLocalLinkage() &&
580 // TODO: Can remove if in SCC now.
581 !SCCFunctions.count(Callee) &&
583 // The function may be apparently dead, but if there are indirect
584 // callgraph references to the node, we cannot delete it yet, this
585 // could invalidate the CGSCC iterator.
586 CG[Callee]->getNumReferences() == 0) {
587 DEBUG(dbgs() << " -> Deleting dead function: "
588 << Callee->getName() << "\n");
589 CallGraphNode *CalleeNode = CG[Callee];
591 // Remove any call graph edges from the callee to its callees.
592 CalleeNode->removeAllCalledFunctions();
594 // Removing the node for callee from the call graph and delete it.
595 delete CG.removeFunctionFromModule(CalleeNode);
599 // Remove this call site from the list. If possible, use
600 // swap/pop_back for efficiency, but do not use it if doing so would
601 // move a call site to a function in this SCC before the
602 // 'FirstCallInSCC' barrier.
603 if (SCC.isSingular()) {
604 CallSites[CSi] = CallSites.back();
605 CallSites.pop_back();
607 CallSites.erase(CallSites.begin()+CSi);
614 } while (LocalChange);
619 /// Remove now-dead linkonce functions at the end of
620 /// processing to avoid breaking the SCC traversal.
621 bool Inliner::doFinalization(CallGraph &CG) {
622 return removeDeadFunctions(CG);
625 /// Remove dead functions that are not included in DNR (Do Not Remove) list.
626 bool Inliner::removeDeadFunctions(CallGraph &CG, bool AlwaysInlineOnly) {
627 SmallVector<CallGraphNode*, 16> FunctionsToRemove;
629 // Scan for all of the functions, looking for ones that should now be removed
630 // from the program. Insert the dead ones in the FunctionsToRemove set.
631 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
632 CallGraphNode *CGN = I->second;
633 Function *F = CGN->getFunction();
634 if (!F || F->isDeclaration())
637 // Handle the case when this function is called and we only want to care
638 // about always-inline functions. This is a bit of a hack to share code
639 // between here and the InlineAlways pass.
640 if (AlwaysInlineOnly && !F->hasFnAttribute(Attribute::AlwaysInline))
643 // If the only remaining users of the function are dead constants, remove
645 F->removeDeadConstantUsers();
647 if (!F->isDefTriviallyDead())
650 // It is unsafe to drop a function with discardable linkage from a COMDAT
651 // without also dropping the other members of the COMDAT.
652 // The inliner doesn't visit non-function entities which are in COMDAT
653 // groups so it is unsafe to do so *unless* the linkage is local.
654 if (!F->hasLocalLinkage() && F->hasComdat())
657 // Remove any call graph edges from the function to its callees.
658 CGN->removeAllCalledFunctions();
660 // Remove any edges from the external node to the function's call graph
661 // node. These edges might have been made irrelegant due to
662 // optimization of the program.
663 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
665 // Removing the node for callee from the call graph and delete it.
666 FunctionsToRemove.push_back(CGN);
668 if (FunctionsToRemove.empty())
671 // Now that we know which functions to delete, do so. We didn't want to do
672 // this inline, because that would invalidate our CallGraph::iterator
675 // Note that it doesn't matter that we are iterating over a non-stable order
676 // here to do this, it doesn't matter which order the functions are deleted
678 array_pod_sort(FunctionsToRemove.begin(), FunctionsToRemove.end());
679 FunctionsToRemove.erase(std::unique(FunctionsToRemove.begin(),
680 FunctionsToRemove.end()),
681 FunctionsToRemove.end());
682 for (SmallVectorImpl<CallGraphNode *>::iterator I = FunctionsToRemove.begin(),
683 E = FunctionsToRemove.end();
685 delete CG.removeFunctionFromModule(*I);