1//===- Inliner.cpp - Code common to all inliners --------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the mechanics required to implement inlining without
10// missing any calls and updating the call graph. The decisions of which calls
11// are profitable to inline are implemented elsewhere.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/Transforms/IPO/Inliner.h"
16#include "llvm/ADT/PriorityWorklist.h"
17#include "llvm/ADT/STLExtras.h"
18#include "llvm/ADT/ScopeExit.h"
19#include "llvm/ADT/SetVector.h"
20#include "llvm/ADT/SmallPtrSet.h"
21#include "llvm/ADT/SmallVector.h"
22#include "llvm/ADT/Statistic.h"
23#include "llvm/ADT/StringExtras.h"
24#include "llvm/ADT/StringRef.h"
25#include "llvm/Analysis/AssumptionCache.h"
26#include "llvm/Analysis/BasicAliasAnalysis.h"
27#include "llvm/Analysis/BlockFrequencyInfo.h"
28#include "llvm/Analysis/CGSCCPassManager.h"
29#include "llvm/Analysis/InlineAdvisor.h"
30#include "llvm/Analysis/InlineCost.h"
31#include "llvm/Analysis/LazyCallGraph.h"
32#include "llvm/Analysis/OptimizationRemarkEmitter.h"
33#include "llvm/Analysis/ProfileSummaryInfo.h"
34#include "llvm/Analysis/ReplayInlineAdvisor.h"
35#include "llvm/Analysis/TargetLibraryInfo.h"
36#include "llvm/Analysis/Utils/ImportedFunctionsInliningStatistics.h"
37#include "llvm/IR/Attributes.h"
38#include "llvm/IR/BasicBlock.h"
39#include "llvm/IR/DebugLoc.h"
40#include "llvm/IR/DerivedTypes.h"
41#include "llvm/IR/DiagnosticInfo.h"
42#include "llvm/IR/Function.h"
43#include "llvm/IR/InstIterator.h"
44#include "llvm/IR/Instruction.h"
45#include "llvm/IR/Instructions.h"
46#include "llvm/IR/IntrinsicInst.h"
47#include "llvm/IR/Metadata.h"
48#include "llvm/IR/Module.h"
49#include "llvm/IR/PassManager.h"
50#include "llvm/IR/User.h"
51#include "llvm/IR/Value.h"
52#include "llvm/Pass.h"
53#include "llvm/Support/Casting.h"
54#include "llvm/Support/CommandLine.h"
55#include "llvm/Support/Debug.h"
56#include "llvm/Support/raw_ostream.h"
57#include "llvm/Transforms/Utils/CallPromotionUtils.h"
58#include "llvm/Transforms/Utils/Cloning.h"
59#include "llvm/Transforms/Utils/Local.h"
60#include "llvm/Transforms/Utils/ModuleUtils.h"
61#include <algorithm>
62#include <cassert>
63#include <functional>
64#include <utility>
65
66using namespace llvm;
67
68#define DEBUG_TYPE "inline"
69
70STATISTIC(NumInlined, "Number of functions inlined");
71STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
72
73static cl::opt<int> IntraSCCCostMultiplier(
74 "intra-scc-cost-multiplier", cl::init(Val: 2), cl::Hidden,
75 cl::desc(
76 "Cost multiplier to multiply onto inlined call sites where the "
77 "new call was previously an intra-SCC call (not relevant when the "
78 "original call was already intra-SCC). This can accumulate over "
79 "multiple inlinings (e.g. if a call site already had a cost "
80 "multiplier and one of its inlined calls was also subject to "
81 "this, the inlined call would have the original multiplier "
82 "multiplied by intra-scc-cost-multiplier). This is to prevent tons of "
83 "inlining through a child SCC which can cause terrible compile times"));
84
85/// A flag for test, so we can print the content of the advisor when running it
86/// as part of the default (e.g. -O3) pipeline.
87static cl::opt<bool> KeepAdvisorForPrinting("keep-inline-advisor-for-printing",
88 cl::init(Val: false), cl::Hidden);
89
90/// Allows printing the contents of the advisor after each SCC inliner pass.
91static cl::opt<bool>
92 EnablePostSCCAdvisorPrinting("enable-scc-inline-advisor-printing",
93 cl::init(Val: false), cl::Hidden);
94
95
96static cl::opt<std::string> CGSCCInlineReplayFile(
97 "cgscc-inline-replay", cl::init(Val: ""), cl::value_desc("filename"),
98 cl::desc(
99 "Optimization remarks file containing inline remarks to be replayed "
100 "by cgscc inlining."),
101 cl::Hidden);
102
103static cl::opt<ReplayInlinerSettings::Scope> CGSCCInlineReplayScope(
104 "cgscc-inline-replay-scope",
105 cl::init(Val: ReplayInlinerSettings::Scope::Function),
106 cl::values(clEnumValN(ReplayInlinerSettings::Scope::Function, "Function",
107 "Replay on functions that have remarks associated "
108 "with them (default)"),
109 clEnumValN(ReplayInlinerSettings::Scope::Module, "Module",
110 "Replay on the entire module")),
111 cl::desc("Whether inline replay should be applied to the entire "
112 "Module or just the Functions (default) that are present as "
113 "callers in remarks during cgscc inlining."),
114 cl::Hidden);
115
116static cl::opt<ReplayInlinerSettings::Fallback> CGSCCInlineReplayFallback(
117 "cgscc-inline-replay-fallback",
118 cl::init(Val: ReplayInlinerSettings::Fallback::Original),
119 cl::values(
120 clEnumValN(
121 ReplayInlinerSettings::Fallback::Original, "Original",
122 "All decisions not in replay send to original advisor (default)"),
123 clEnumValN(ReplayInlinerSettings::Fallback::AlwaysInline,
124 "AlwaysInline", "All decisions not in replay are inlined"),
125 clEnumValN(ReplayInlinerSettings::Fallback::NeverInline, "NeverInline",
126 "All decisions not in replay are not inlined")),
127 cl::desc(
128 "How cgscc inline replay treats sites that don't come from the replay. "
129 "Original: defers to original advisor, AlwaysInline: inline all sites "
130 "not in replay, NeverInline: inline no sites not in replay"),
131 cl::Hidden);
132
133static cl::opt<CallSiteFormat::Format> CGSCCInlineReplayFormat(
134 "cgscc-inline-replay-format",
135 cl::init(Val: CallSiteFormat::Format::LineColumnDiscriminator),
136 cl::values(
137 clEnumValN(CallSiteFormat::Format::Line, "Line", "<Line Number>"),
138 clEnumValN(CallSiteFormat::Format::LineColumn, "LineColumn",
139 "<Line Number>:<Column Number>"),
140 clEnumValN(CallSiteFormat::Format::LineDiscriminator,
141 "LineDiscriminator", "<Line Number>.<Discriminator>"),
142 clEnumValN(CallSiteFormat::Format::LineColumnDiscriminator,
143 "LineColumnDiscriminator",
144 "<Line Number>:<Column Number>.<Discriminator> (default)")),
145 cl::desc("How cgscc inline replay file is formatted"), cl::Hidden);
146
147/// Return true if the specified inline history ID
148/// indicates an inline history that includes the specified function.
149static bool inlineHistoryIncludes(
150 Function *F, int InlineHistoryID,
151 const SmallVectorImpl<std::pair<Function *, int>> &InlineHistory) {
152 while (InlineHistoryID != -1) {
153 assert(unsigned(InlineHistoryID) < InlineHistory.size() &&
154 "Invalid inline history ID");
155 if (InlineHistory[InlineHistoryID].first == F)
156 return true;
157 InlineHistoryID = InlineHistory[InlineHistoryID].second;
158 }
159 return false;
160}
161
162InlineAdvisor &
163InlinerPass::getAdvisor(const ModuleAnalysisManagerCGSCCProxy::Result &MAM,
164 FunctionAnalysisManager &FAM, Module &M) {
165 if (OwnedAdvisor)
166 return *OwnedAdvisor;
167
168 auto *IAA = MAM.getCachedResult<InlineAdvisorAnalysis>(IR&: M);
169 if (!IAA) {
170 // It should still be possible to run the inliner as a stand-alone SCC pass,
171 // for test scenarios. In that case, we default to the
172 // DefaultInlineAdvisor, which doesn't need to keep state between SCC pass
173 // runs. It also uses just the default InlineParams.
174 // In this case, we need to use the provided FAM, which is valid for the
175 // duration of the inliner pass, and thus the lifetime of the owned advisor.
176 // The one we would get from the MAM can be invalidated as a result of the
177 // inliner's activity.
178 OwnedAdvisor = std::make_unique<DefaultInlineAdvisor>(
179 args&: M, args&: FAM, args: getInlineParams(),
180 args: InlineContext{.LTOPhase: LTOPhase, .Pass: InlinePass::CGSCCInliner});
181
182 if (!CGSCCInlineReplayFile.empty())
183 OwnedAdvisor = getReplayInlineAdvisor(
184 M, FAM, Context&: M.getContext(), OriginalAdvisor: std::move(OwnedAdvisor),
185 ReplaySettings: ReplayInlinerSettings{.ReplayFile: CGSCCInlineReplayFile,
186 .ReplayScope: CGSCCInlineReplayScope,
187 .ReplayFallback: CGSCCInlineReplayFallback,
188 .ReplayFormat: {.OutputFormat: CGSCCInlineReplayFormat}},
189 /*EmitRemarks=*/true,
190 IC: InlineContext{.LTOPhase: LTOPhase, .Pass: InlinePass::ReplayCGSCCInliner});
191
192 return *OwnedAdvisor;
193 }
194 assert(IAA->getAdvisor() &&
195 "Expected a present InlineAdvisorAnalysis also have an "
196 "InlineAdvisor initialized");
197 return *IAA->getAdvisor();
198}
199
200void makeFunctionBodyUnreachable(Function &F) {
201 F.dropAllReferences();
202 for (BasicBlock &BB : make_early_inc_range(Range&: F))
203 BB.eraseFromParent();
204 BasicBlock *BB = BasicBlock::Create(Context&: F.getContext(), Name: "", Parent: &F);
205 new UnreachableInst(F.getContext(), BB);
206}
207
208PreservedAnalyses InlinerPass::run(LazyCallGraph::SCC &InitialC,
209 CGSCCAnalysisManager &AM, LazyCallGraph &CG,
210 CGSCCUpdateResult &UR) {
211 const auto &MAMProxy =
212 AM.getResult<ModuleAnalysisManagerCGSCCProxy>(IR&: InitialC, ExtraArgs&: CG);
213 bool Changed = false;
214
215 assert(InitialC.size() > 0 && "Cannot handle an empty SCC!");
216 Module &M = *InitialC.begin()->getFunction().getParent();
217 ProfileSummaryInfo *PSI = MAMProxy.getCachedResult<ProfileSummaryAnalysis>(IR&: M);
218
219 FunctionAnalysisManager &FAM =
220 AM.getResult<FunctionAnalysisManagerCGSCCProxy>(IR&: InitialC, ExtraArgs&: CG)
221 .getManager();
222
223 InlineAdvisor &Advisor = getAdvisor(MAM: MAMProxy, FAM, M);
224 Advisor.onPassEntry(SCC: &InitialC);
225
226 // We use a single common worklist for calls across the entire SCC. We
227 // process these in-order and append new calls introduced during inlining to
228 // the end. The PriorityInlineOrder is optional here, in which the smaller
229 // callee would have a higher priority to inline.
230 //
231 // Note that this particular order of processing is actually critical to
232 // avoid very bad behaviors. Consider *highly connected* call graphs where
233 // each function contains a small amount of code and a couple of calls to
234 // other functions. Because the LLVM inliner is fundamentally a bottom-up
235 // inliner, it can handle gracefully the fact that these all appear to be
236 // reasonable inlining candidates as it will flatten things until they become
237 // too big to inline, and then move on and flatten another batch.
238 //
239 // However, when processing call edges *within* an SCC we cannot rely on this
240 // bottom-up behavior. As a consequence, with heavily connected *SCCs* of
241 // functions we can end up incrementally inlining N calls into each of
242 // N functions because each incremental inlining decision looks good and we
243 // don't have a topological ordering to prevent explosions.
244 //
245 // To compensate for this, we don't process transitive edges made immediate
246 // by inlining until we've done one pass of inlining across the entire SCC.
247 // Large, highly connected SCCs still lead to some amount of code bloat in
248 // this model, but it is uniformly spread across all the functions in the SCC
249 // and eventually they all become too large to inline, rather than
250 // incrementally maknig a single function grow in a super linear fashion.
251 SmallVector<std::pair<CallBase *, int>, 16> Calls;
252
253 // Populate the initial list of calls in this SCC.
254 for (auto &N : InitialC) {
255 auto &ORE =
256 FAM.getResult<OptimizationRemarkEmitterAnalysis>(IR&: N.getFunction());
257 // We want to generally process call sites top-down in order for
258 // simplifications stemming from replacing the call with the returned value
259 // after inlining to be visible to subsequent inlining decisions.
260 // FIXME: Using instructions sequence is a really bad way to do this.
261 // Instead we should do an actual RPO walk of the function body.
262 for (Instruction &I : instructions(F&: N.getFunction()))
263 if (auto *CB = dyn_cast<CallBase>(Val: &I))
264 if (Function *Callee = CB->getCalledFunction()) {
265 if (!Callee->isDeclaration())
266 Calls.push_back(Elt: {CB, -1});
267 else if (!isa<IntrinsicInst>(Val: I)) {
268 using namespace ore;
269 setInlineRemark(CB&: *CB, Message: "unavailable definition");
270 ORE.emit(RemarkBuilder: [&]() {
271 return OptimizationRemarkMissed(DEBUG_TYPE, "NoDefinition", &I)
272 << NV("Callee", Callee) << " will not be inlined into "
273 << NV("Caller", CB->getCaller())
274 << " because its definition is unavailable"
275 << setIsVerbose();
276 });
277 }
278 }
279 }
280
281 // Capture updatable variable for the current SCC.
282 auto *C = &InitialC;
283
284 auto AdvisorOnExit = make_scope_exit(F: [&] { Advisor.onPassExit(SCC: C); });
285
286 if (Calls.empty())
287 return PreservedAnalyses::all();
288
289 // When inlining a callee produces new call sites, we want to keep track of
290 // the fact that they were inlined from the callee. This allows us to avoid
291 // infinite inlining in some obscure cases. To represent this, we use an
292 // index into the InlineHistory vector.
293 SmallVector<std::pair<Function *, int>, 16> InlineHistory;
294
295 // Track a set vector of inlined callees so that we can augment the caller
296 // with all of their edges in the call graph before pruning out the ones that
297 // got simplified away.
298 SmallSetVector<Function *, 4> InlinedCallees;
299
300 // Track the dead functions to delete once finished with inlining calls. We
301 // defer deleting these to make it easier to handle the call graph updates.
302 SmallVector<Function *, 4> DeadFunctions;
303
304 // Track potentially dead non-local functions with comdats to see if they can
305 // be deleted as a batch after inlining.
306 SmallVector<Function *, 4> DeadFunctionsInComdats;
307
308 // Loop forward over all of the calls. Note that we cannot cache the size as
309 // inlining can introduce new calls that need to be processed.
310 for (int I = 0; I < (int)Calls.size(); ++I) {
311 // We expect the calls to typically be batched with sequences of calls that
312 // have the same caller, so we first set up some shared infrastructure for
313 // this caller. We also do any pruning we can at this layer on the caller
314 // alone.
315 Function &F = *Calls[I].first->getCaller();
316 LazyCallGraph::Node &N = *CG.lookup(F);
317 if (CG.lookupSCC(N) != C)
318 continue;
319
320 LLVM_DEBUG(dbgs() << "Inlining calls in: " << F.getName() << "\n"
321 << " Function size: " << F.getInstructionCount()
322 << "\n");
323
324 auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
325 return FAM.getResult<AssumptionAnalysis>(IR&: F);
326 };
327
328 // Now process as many calls as we have within this caller in the sequence.
329 // We bail out as soon as the caller has to change so we can update the
330 // call graph and prepare the context of that new caller.
331 bool DidInline = false;
332 for (; I < (int)Calls.size() && Calls[I].first->getCaller() == &F; ++I) {
333 auto &P = Calls[I];
334 CallBase *CB = P.first;
335 const int InlineHistoryID = P.second;
336 Function &Callee = *CB->getCalledFunction();
337
338 if (InlineHistoryID != -1 &&
339 inlineHistoryIncludes(F: &Callee, InlineHistoryID, InlineHistory)) {
340 LLVM_DEBUG(dbgs() << "Skipping inlining due to history: " << F.getName()
341 << " -> " << Callee.getName() << "\n");
342 setInlineRemark(CB&: *CB, Message: "recursive");
343 // Set noinline so that we don't forget this decision across CGSCC
344 // iterations.
345 CB->setIsNoInline();
346 continue;
347 }
348
349 // Check if this inlining may repeat breaking an SCC apart that has
350 // already been split once before. In that case, inlining here may
351 // trigger infinite inlining, much like is prevented within the inliner
352 // itself by the InlineHistory above, but spread across CGSCC iterations
353 // and thus hidden from the full inline history.
354 LazyCallGraph::SCC *CalleeSCC = CG.lookupSCC(N&: *CG.lookup(F: Callee));
355 if (CalleeSCC == C && UR.InlinedInternalEdges.count(V: {&N, C})) {
356 LLVM_DEBUG(dbgs() << "Skipping inlining internal SCC edge from a node "
357 "previously split out of this SCC by inlining: "
358 << F.getName() << " -> " << Callee.getName() << "\n");
359 setInlineRemark(CB&: *CB, Message: "recursive SCC split");
360 continue;
361 }
362
363 std::unique_ptr<InlineAdvice> Advice =
364 Advisor.getAdvice(CB&: *CB, MandatoryOnly: OnlyMandatory);
365
366 // Check whether we want to inline this callsite.
367 if (!Advice)
368 continue;
369
370 if (!Advice->isInliningRecommended()) {
371 Advice->recordUnattemptedInlining();
372 continue;
373 }
374
375 int CBCostMult =
376 getStringFnAttrAsInt(
377 CB&: *CB, AttrKind: InlineConstants::FunctionInlineCostMultiplierAttributeName)
378 .value_or(u: 1);
379
380 // Setup the data structure used to plumb customization into the
381 // `InlineFunction` routine.
382 InlineFunctionInfo IFI(
383 GetAssumptionCache, PSI,
384 &FAM.getResult<BlockFrequencyAnalysis>(IR&: *(CB->getCaller())),
385 &FAM.getResult<BlockFrequencyAnalysis>(IR&: Callee));
386
387 InlineResult IR =
388 InlineFunction(CB&: *CB, IFI, /*MergeAttributes=*/true,
389 CalleeAAR: &FAM.getResult<AAManager>(IR&: *CB->getCaller()));
390 if (!IR.isSuccess()) {
391 Advice->recordUnsuccessfulInlining(Result: IR);
392 continue;
393 }
394
395 DidInline = true;
396 InlinedCallees.insert(X: &Callee);
397 ++NumInlined;
398
399 LLVM_DEBUG(dbgs() << " Size after inlining: "
400 << F.getInstructionCount() << "\n");
401
402 // Add any new callsites to defined functions to the worklist.
403 if (!IFI.InlinedCallSites.empty()) {
404 int NewHistoryID = InlineHistory.size();
405 InlineHistory.push_back(Elt: {&Callee, InlineHistoryID});
406
407 for (CallBase *ICB : reverse(C&: IFI.InlinedCallSites)) {
408 Function *NewCallee = ICB->getCalledFunction();
409 assert(!(NewCallee && NewCallee->isIntrinsic()) &&
410 "Intrinsic calls should not be tracked.");
411 if (!NewCallee) {
412 // Try to promote an indirect (virtual) call without waiting for
413 // the post-inline cleanup and the next DevirtSCCRepeatedPass
414 // iteration because the next iteration may not happen and we may
415 // miss inlining it.
416 if (tryPromoteCall(CB&: *ICB))
417 NewCallee = ICB->getCalledFunction();
418 }
419 if (NewCallee) {
420 if (!NewCallee->isDeclaration()) {
421 Calls.push_back(Elt: {ICB, NewHistoryID});
422 // Continually inlining through an SCC can result in huge compile
423 // times and bloated code since we arbitrarily stop at some point
424 // when the inliner decides it's not profitable to inline anymore.
425 // We attempt to mitigate this by making these calls exponentially
426 // more expensive.
427 // This doesn't apply to calls in the same SCC since if we do
428 // inline through the SCC the function will end up being
429 // self-recursive which the inliner bails out on, and inlining
430 // within an SCC is necessary for performance.
431 if (CalleeSCC != C &&
432 CalleeSCC == CG.lookupSCC(N&: CG.get(F&: *NewCallee))) {
433 Attribute NewCBCostMult = Attribute::get(
434 Context&: M.getContext(),
435 Kind: InlineConstants::FunctionInlineCostMultiplierAttributeName,
436 Val: itostr(X: CBCostMult * IntraSCCCostMultiplier));
437 ICB->addFnAttr(Attr: NewCBCostMult);
438 }
439 }
440 }
441 }
442 }
443
444 // For local functions or discardable functions without comdats, check
445 // whether this makes the callee trivially dead. In that case, we can drop
446 // the body of the function eagerly which may reduce the number of callers
447 // of other functions to one, changing inline cost thresholds. Non-local
448 // discardable functions with comdats are checked later on.
449 bool CalleeWasDeleted = false;
450 if (Callee.isDiscardableIfUnused() && Callee.hasZeroLiveUses() &&
451 !CG.isLibFunction(F&: Callee)) {
452 if (Callee.hasLocalLinkage() || !Callee.hasComdat()) {
453 Calls.erase(
454 CS: std::remove_if(first: Calls.begin() + I + 1, last: Calls.end(),
455 pred: [&](const std::pair<CallBase *, int> &Call) {
456 return Call.first->getCaller() == &Callee;
457 }),
458 CE: Calls.end());
459
460 // Clear the body and queue the function itself for call graph
461 // updating when we finish inlining.
462 makeFunctionBodyUnreachable(F&: Callee);
463 assert(!is_contained(DeadFunctions, &Callee) &&
464 "Cannot put cause a function to become dead twice!");
465 DeadFunctions.push_back(Elt: &Callee);
466 CalleeWasDeleted = true;
467 } else {
468 DeadFunctionsInComdats.push_back(Elt: &Callee);
469 }
470 }
471 if (CalleeWasDeleted)
472 Advice->recordInliningWithCalleeDeleted();
473 else
474 Advice->recordInlining();
475 }
476
477 // Back the call index up by one to put us in a good position to go around
478 // the outer loop.
479 --I;
480
481 if (!DidInline)
482 continue;
483 Changed = true;
484
485 // At this point, since we have made changes we have at least removed
486 // a call instruction. However, in the process we do some incremental
487 // simplification of the surrounding code. This simplification can
488 // essentially do all of the same things as a function pass and we can
489 // re-use the exact same logic for updating the call graph to reflect the
490 // change.
491
492 // Inside the update, we also update the FunctionAnalysisManager in the
493 // proxy for this particular SCC. We do this as the SCC may have changed and
494 // as we're going to mutate this particular function we want to make sure
495 // the proxy is in place to forward any invalidation events.
496 LazyCallGraph::SCC *OldC = C;
497 C = &updateCGAndAnalysisManagerForCGSCCPass(G&: CG, C&: *C, N, AM, UR, FAM);
498 LLVM_DEBUG(dbgs() << "Updated inlining SCC: " << *C << "\n");
499
500 // If this causes an SCC to split apart into multiple smaller SCCs, there
501 // is a subtle risk we need to prepare for. Other transformations may
502 // expose an "infinite inlining" opportunity later, and because of the SCC
503 // mutation, we will revisit this function and potentially re-inline. If we
504 // do, and that re-inlining also has the potentially to mutate the SCC
505 // structure, the infinite inlining problem can manifest through infinite
506 // SCC splits and merges. To avoid this, we capture the originating caller
507 // node and the SCC containing the call edge. This is a slight over
508 // approximation of the possible inlining decisions that must be avoided,
509 // but is relatively efficient to store. We use C != OldC to know when
510 // a new SCC is generated and the original SCC may be generated via merge
511 // in later iterations.
512 //
513 // It is also possible that even if no new SCC is generated
514 // (i.e., C == OldC), the original SCC could be split and then merged
515 // into the same one as itself. and the original SCC will be added into
516 // UR.CWorklist again, we want to catch such cases too.
517 //
518 // FIXME: This seems like a very heavyweight way of retaining the inline
519 // history, we should look for a more efficient way of tracking it.
520 if ((C != OldC || UR.CWorklist.count(key: OldC)) &&
521 llvm::any_of(Range&: InlinedCallees, P: [&](Function *Callee) {
522 return CG.lookupSCC(N&: *CG.lookup(F: *Callee)) == OldC;
523 })) {
524 LLVM_DEBUG(dbgs() << "Inlined an internal call edge and split an SCC, "
525 "retaining this to avoid infinite inlining.\n");
526 UR.InlinedInternalEdges.insert(V: {&N, OldC});
527 }
528 InlinedCallees.clear();
529
530 // Invalidate analyses for this function now so that we don't have to
531 // invalidate analyses for all functions in this SCC later.
532 FAM.invalidate(IR&: F, PA: PreservedAnalyses::none());
533 }
534
535 // We must ensure that we only delete functions with comdats if every function
536 // in the comdat is going to be deleted.
537 if (!DeadFunctionsInComdats.empty()) {
538 filterDeadComdatFunctions(DeadComdatFunctions&: DeadFunctionsInComdats);
539 for (auto *Callee : DeadFunctionsInComdats)
540 makeFunctionBodyUnreachable(F&: *Callee);
541 DeadFunctions.append(RHS: DeadFunctionsInComdats);
542 }
543
544 // Now that we've finished inlining all of the calls across this SCC, delete
545 // all of the trivially dead functions, updating the call graph and the CGSCC
546 // pass manager in the process.
547 //
548 // Note that this walks a pointer set which has non-deterministic order but
549 // that is OK as all we do is delete things and add pointers to unordered
550 // sets.
551 for (Function *DeadF : DeadFunctions) {
552 CG.markDeadFunction(F&: *DeadF);
553 // Get the necessary information out of the call graph and nuke the
554 // function there. Also, clear out any cached analyses.
555 auto &DeadC = *CG.lookupSCC(N&: *CG.lookup(F: *DeadF));
556 FAM.clear(IR&: *DeadF, Name: DeadF->getName());
557 AM.clear(IR&: DeadC, Name: DeadC.getName());
558
559 // Mark the relevant parts of the call graph as invalid so we don't visit
560 // them.
561 UR.InvalidatedSCCs.insert(Ptr: &DeadC);
562
563 UR.DeadFunctions.push_back(Elt: DeadF);
564
565 ++NumDeleted;
566 }
567
568 if (!Changed)
569 return PreservedAnalyses::all();
570
571 PreservedAnalyses PA;
572 // Even if we change the IR, we update the core CGSCC data structures and so
573 // can preserve the proxy to the function analysis manager.
574 PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
575 // We have already invalidated all analyses on modified functions.
576 PA.preserveSet<AllAnalysesOn<Function>>();
577 return PA;
578}
579
580ModuleInlinerWrapperPass::ModuleInlinerWrapperPass(InlineParams Params,
581 bool MandatoryFirst,
582 InlineContext IC,
583 InliningAdvisorMode Mode,
584 unsigned MaxDevirtIterations)
585 : Params(Params), IC(IC), Mode(Mode),
586 MaxDevirtIterations(MaxDevirtIterations) {
587 // Run the inliner first. The theory is that we are walking bottom-up and so
588 // the callees have already been fully optimized, and we want to inline them
589 // into the callers so that our optimizations can reflect that.
590 // For PreLinkThinLTO pass, we disable hot-caller heuristic for sample PGO
591 // because it makes profile annotation in the backend inaccurate.
592 if (MandatoryFirst) {
593 PM.addPass(Pass: InlinerPass(/*OnlyMandatory*/ true));
594 if (EnablePostSCCAdvisorPrinting)
595 PM.addPass(Pass: InlineAdvisorAnalysisPrinterPass(dbgs()));
596 }
597 PM.addPass(Pass: InlinerPass());
598 if (EnablePostSCCAdvisorPrinting)
599 PM.addPass(Pass: InlineAdvisorAnalysisPrinterPass(dbgs()));
600}
601
602PreservedAnalyses ModuleInlinerWrapperPass::run(Module &M,
603 ModuleAnalysisManager &MAM) {
604 auto &IAA = MAM.getResult<InlineAdvisorAnalysis>(IR&: M);
605 if (!IAA.tryCreate(Params, Mode,
606 ReplaySettings: {.ReplayFile: CGSCCInlineReplayFile,
607 .ReplayScope: CGSCCInlineReplayScope,
608 .ReplayFallback: CGSCCInlineReplayFallback,
609 .ReplayFormat: {.OutputFormat: CGSCCInlineReplayFormat}},
610 IC)) {
611 M.getContext().emitError(
612 ErrorStr: "Could not setup Inlining Advisor for the requested "
613 "mode and/or options");
614 return PreservedAnalyses::all();
615 }
616
617 // We wrap the CGSCC pipeline in a devirtualization repeater. This will try
618 // to detect when we devirtualize indirect calls and iterate the SCC passes
619 // in that case to try and catch knock-on inlining or function attrs
620 // opportunities. Then we add it to the module pipeline by walking the SCCs
621 // in postorder (or bottom-up).
622 // If MaxDevirtIterations is 0, we just don't use the devirtualization
623 // wrapper.
624 if (MaxDevirtIterations == 0)
625 MPM.addPass(Pass: createModuleToPostOrderCGSCCPassAdaptor(Pass: std::move(PM)));
626 else
627 MPM.addPass(Pass: createModuleToPostOrderCGSCCPassAdaptor(
628 Pass: createDevirtSCCRepeatedPass(Pass: std::move(PM), MaxIterations: MaxDevirtIterations)));
629
630 MPM.addPass(Pass: std::move(AfterCGMPM));
631 MPM.run(IR&: M, AM&: MAM);
632
633 // Discard the InlineAdvisor, a subsequent inlining session should construct
634 // its own.
635 auto PA = PreservedAnalyses::all();
636 if (!KeepAdvisorForPrinting)
637 PA.abandon<InlineAdvisorAnalysis>();
638 return PA;
639}
640
641void InlinerPass::printPipeline(
642 raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
643 static_cast<PassInfoMixin<InlinerPass> *>(this)->printPipeline(
644 OS, MapClassName2PassName);
645 if (OnlyMandatory)
646 OS << "<only-mandatory>";
647}
648
649void ModuleInlinerWrapperPass::printPipeline(
650 raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
651 // Print some info about passes added to the wrapper. This is however
652 // incomplete as InlineAdvisorAnalysis part isn't included (which also depends
653 // on Params and Mode).
654 if (!MPM.isEmpty()) {
655 MPM.printPipeline(OS, MapClassName2PassName);
656 OS << ',';
657 }
658 OS << "cgscc(";
659 if (MaxDevirtIterations != 0)
660 OS << "devirt<" << MaxDevirtIterations << ">(";
661 PM.printPipeline(OS, MapClassName2PassName);
662 if (MaxDevirtIterations != 0)
663 OS << ')';
664 OS << ')';
665}
666