xref: /freebsd/contrib/llvm-project/llvm/lib/IR/ModuleSummaryIndex.cpp (revision ba3c1f5972d7b90feb6e6da47905ff2757e0fe57)
1 //===-- ModuleSummaryIndex.cpp - Module Summary Index ---------------------===//
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 module index and summary classes for the
10 // IR library.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/IR/ModuleSummaryIndex.h"
15 #include "llvm/ADT/SCCIterator.h"
16 #include "llvm/ADT/Statistic.h"
17 #include "llvm/Support/CommandLine.h"
18 #include "llvm/Support/Path.h"
19 #include "llvm/Support/raw_ostream.h"
20 using namespace llvm;
21 
22 #define DEBUG_TYPE "module-summary-index"
23 
24 STATISTIC(ReadOnlyLiveGVars,
25           "Number of live global variables marked read only");
26 STATISTIC(WriteOnlyLiveGVars,
27           "Number of live global variables marked write only");
28 
29 static cl::opt<bool> PropagateAttrs("propagate-attrs", cl::init(true),
30                                     cl::Hidden,
31                                     cl::desc("Propagate attributes in index"));
32 
33 static cl::opt<bool> ImportConstantsWithRefs(
34     "import-constants-with-refs", cl::init(true), cl::Hidden,
35     cl::desc("Import constant global variables with references"));
36 
37 constexpr uint32_t FunctionSummary::ParamAccess::RangeWidth;
38 
39 FunctionSummary FunctionSummary::ExternalNode =
40     FunctionSummary::makeDummyFunctionSummary({});
41 
42 GlobalValue::VisibilityTypes ValueInfo::getELFVisibility() const {
43   bool HasProtected = false;
44   for (const auto &S : make_pointee_range(getSummaryList())) {
45     if (S.getVisibility() == GlobalValue::HiddenVisibility)
46       return GlobalValue::HiddenVisibility;
47     if (S.getVisibility() == GlobalValue::ProtectedVisibility)
48       HasProtected = true;
49   }
50   return HasProtected ? GlobalValue::ProtectedVisibility
51                       : GlobalValue::DefaultVisibility;
52 }
53 
54 bool ValueInfo::isDSOLocal(bool WithDSOLocalPropagation) const {
55   // With DSOLocal propagation done, the flag in evey summary is the same.
56   // Check the first one is enough.
57   return WithDSOLocalPropagation
58              ? getSummaryList().size() && getSummaryList()[0]->isDSOLocal()
59              : getSummaryList().size() &&
60                    llvm::all_of(
61                        getSummaryList(),
62                        [](const std::unique_ptr<GlobalValueSummary> &Summary) {
63                          return Summary->isDSOLocal();
64                        });
65 }
66 
67 bool ValueInfo::canAutoHide() const {
68   // Can only auto hide if all copies are eligible to auto hide.
69   return getSummaryList().size() &&
70          llvm::all_of(getSummaryList(),
71                       [](const std::unique_ptr<GlobalValueSummary> &Summary) {
72                         return Summary->canAutoHide();
73                       });
74 }
75 
76 // Gets the number of readonly and writeonly refs in RefEdgeList
77 std::pair<unsigned, unsigned> FunctionSummary::specialRefCounts() const {
78   // Here we take advantage of having all readonly and writeonly references
79   // located in the end of the RefEdgeList.
80   auto Refs = refs();
81   unsigned RORefCnt = 0, WORefCnt = 0;
82   int I;
83   for (I = Refs.size() - 1; I >= 0 && Refs[I].isWriteOnly(); --I)
84     WORefCnt++;
85   for (; I >= 0 && Refs[I].isReadOnly(); --I)
86     RORefCnt++;
87   return {RORefCnt, WORefCnt};
88 }
89 
90 constexpr uint64_t ModuleSummaryIndex::BitcodeSummaryVersion;
91 
92 uint64_t ModuleSummaryIndex::getFlags() const {
93   uint64_t Flags = 0;
94   if (withGlobalValueDeadStripping())
95     Flags |= 0x1;
96   if (skipModuleByDistributedBackend())
97     Flags |= 0x2;
98   if (hasSyntheticEntryCounts())
99     Flags |= 0x4;
100   if (enableSplitLTOUnit())
101     Flags |= 0x8;
102   if (partiallySplitLTOUnits())
103     Flags |= 0x10;
104   if (withAttributePropagation())
105     Flags |= 0x20;
106   if (withDSOLocalPropagation())
107     Flags |= 0x40;
108   if (withWholeProgramVisibility())
109     Flags |= 0x80;
110   return Flags;
111 }
112 
113 void ModuleSummaryIndex::setFlags(uint64_t Flags) {
114   assert(Flags <= 0xff && "Unexpected bits in flag");
115   // 1 bit: WithGlobalValueDeadStripping flag.
116   // Set on combined index only.
117   if (Flags & 0x1)
118     setWithGlobalValueDeadStripping();
119   // 1 bit: SkipModuleByDistributedBackend flag.
120   // Set on combined index only.
121   if (Flags & 0x2)
122     setSkipModuleByDistributedBackend();
123   // 1 bit: HasSyntheticEntryCounts flag.
124   // Set on combined index only.
125   if (Flags & 0x4)
126     setHasSyntheticEntryCounts();
127   // 1 bit: DisableSplitLTOUnit flag.
128   // Set on per module indexes. It is up to the client to validate
129   // the consistency of this flag across modules being linked.
130   if (Flags & 0x8)
131     setEnableSplitLTOUnit();
132   // 1 bit: PartiallySplitLTOUnits flag.
133   // Set on combined index only.
134   if (Flags & 0x10)
135     setPartiallySplitLTOUnits();
136   // 1 bit: WithAttributePropagation flag.
137   // Set on combined index only.
138   if (Flags & 0x20)
139     setWithAttributePropagation();
140   // 1 bit: WithDSOLocalPropagation flag.
141   // Set on combined index only.
142   if (Flags & 0x40)
143     setWithDSOLocalPropagation();
144   // 1 bit: WithWholeProgramVisibility flag.
145   // Set on combined index only.
146   if (Flags & 0x80)
147     setWithWholeProgramVisibility();
148 }
149 
150 // Collect for the given module the list of function it defines
151 // (GUID -> Summary).
152 void ModuleSummaryIndex::collectDefinedFunctionsForModule(
153     StringRef ModulePath, GVSummaryMapTy &GVSummaryMap) const {
154   for (auto &GlobalList : *this) {
155     auto GUID = GlobalList.first;
156     for (auto &GlobSummary : GlobalList.second.SummaryList) {
157       auto *Summary = dyn_cast_or_null<FunctionSummary>(GlobSummary.get());
158       if (!Summary)
159         // Ignore global variable, focus on functions
160         continue;
161       // Ignore summaries from other modules.
162       if (Summary->modulePath() != ModulePath)
163         continue;
164       GVSummaryMap[GUID] = Summary;
165     }
166   }
167 }
168 
169 GlobalValueSummary *
170 ModuleSummaryIndex::getGlobalValueSummary(uint64_t ValueGUID,
171                                           bool PerModuleIndex) const {
172   auto VI = getValueInfo(ValueGUID);
173   assert(VI && "GlobalValue not found in index");
174   assert((!PerModuleIndex || VI.getSummaryList().size() == 1) &&
175          "Expected a single entry per global value in per-module index");
176   auto &Summary = VI.getSummaryList()[0];
177   return Summary.get();
178 }
179 
180 bool ModuleSummaryIndex::isGUIDLive(GlobalValue::GUID GUID) const {
181   auto VI = getValueInfo(GUID);
182   if (!VI)
183     return true;
184   const auto &SummaryList = VI.getSummaryList();
185   if (SummaryList.empty())
186     return true;
187   for (auto &I : SummaryList)
188     if (isGlobalValueLive(I.get()))
189       return true;
190   return false;
191 }
192 
193 static void
194 propagateAttributesToRefs(GlobalValueSummary *S,
195                           DenseSet<ValueInfo> &MarkedNonReadWriteOnly) {
196   // If reference is not readonly or writeonly then referenced summary is not
197   // read/writeonly either. Note that:
198   // - All references from GlobalVarSummary are conservatively considered as
199   //   not readonly or writeonly. Tracking them properly requires more complex
200   //   analysis then we have now.
201   //
202   // - AliasSummary objects have no refs at all so this function is a no-op
203   //   for them.
204   for (auto &VI : S->refs()) {
205     assert(VI.getAccessSpecifier() == 0 || isa<FunctionSummary>(S));
206     if (!VI.getAccessSpecifier()) {
207       if (!MarkedNonReadWriteOnly.insert(VI).second)
208         continue;
209     } else if (MarkedNonReadWriteOnly.contains(VI))
210       continue;
211     for (auto &Ref : VI.getSummaryList())
212       // If references to alias is not read/writeonly then aliasee
213       // is not read/writeonly
214       if (auto *GVS = dyn_cast<GlobalVarSummary>(Ref->getBaseObject())) {
215         if (!VI.isReadOnly())
216           GVS->setReadOnly(false);
217         if (!VI.isWriteOnly())
218           GVS->setWriteOnly(false);
219       }
220   }
221 }
222 
223 // Do the access attribute and DSOLocal propagation in combined index.
224 // The goal of attribute propagation is internalization of readonly (RO)
225 // or writeonly (WO) variables. To determine which variables are RO or WO
226 // and which are not we take following steps:
227 // - During analysis we speculatively assign readonly and writeonly
228 //   attribute to all variables which can be internalized. When computing
229 //   function summary we also assign readonly or writeonly attribute to a
230 //   reference if function doesn't modify referenced variable (readonly)
231 //   or doesn't read it (writeonly).
232 //
233 // - After computing dead symbols in combined index we do the attribute
234 //   and DSOLocal propagation. During this step we:
235 //   a. clear RO and WO attributes from variables which are preserved or
236 //      can't be imported
237 //   b. clear RO and WO attributes from variables referenced by any global
238 //      variable initializer
239 //   c. clear RO attribute from variable referenced by a function when
240 //      reference is not readonly
241 //   d. clear WO attribute from variable referenced by a function when
242 //      reference is not writeonly
243 //   e. clear IsDSOLocal flag in every summary if any of them is false.
244 //
245 //   Because of (c, d) we don't internalize variables read by function A
246 //   and modified by function B.
247 //
248 // Internalization itself happens in the backend after import is finished
249 // See internalizeGVsAfterImport.
250 void ModuleSummaryIndex::propagateAttributes(
251     const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) {
252   if (!PropagateAttrs)
253     return;
254   DenseSet<ValueInfo> MarkedNonReadWriteOnly;
255   for (auto &P : *this) {
256     bool IsDSOLocal = true;
257     for (auto &S : P.second.SummaryList) {
258       if (!isGlobalValueLive(S.get())) {
259         // computeDeadSymbolsAndUpdateIndirectCalls should have marked all
260         // copies live. Note that it is possible that there is a GUID collision
261         // between internal symbols with the same name in different files of the
262         // same name but not enough distinguishing path. Because
263         // computeDeadSymbolsAndUpdateIndirectCalls should conservatively mark
264         // all copies live we can assert here that all are dead if any copy is
265         // dead.
266         assert(llvm::none_of(
267             P.second.SummaryList,
268             [&](const std::unique_ptr<GlobalValueSummary> &Summary) {
269               return isGlobalValueLive(Summary.get());
270             }));
271         // We don't examine references from dead objects
272         break;
273       }
274 
275       // Global variable can't be marked read/writeonly if it is not eligible
276       // to import since we need to ensure that all external references get
277       // a local (imported) copy. It also can't be marked read/writeonly if
278       // it or any alias (since alias points to the same memory) are preserved
279       // or notEligibleToImport, since either of those means there could be
280       // writes (or reads in case of writeonly) that are not visible (because
281       // preserved means it could have external to DSO writes or reads, and
282       // notEligibleToImport means it could have writes or reads via inline
283       // assembly leading it to be in the @llvm.*used).
284       if (auto *GVS = dyn_cast<GlobalVarSummary>(S->getBaseObject()))
285         // Here we intentionally pass S.get() not GVS, because S could be
286         // an alias. We don't analyze references here, because we have to
287         // know exactly if GV is readonly to do so.
288         if (!canImportGlobalVar(S.get(), /* AnalyzeRefs */ false) ||
289             GUIDPreservedSymbols.count(P.first)) {
290           GVS->setReadOnly(false);
291           GVS->setWriteOnly(false);
292         }
293       propagateAttributesToRefs(S.get(), MarkedNonReadWriteOnly);
294 
295       // If the flag from any summary is false, the GV is not DSOLocal.
296       IsDSOLocal &= S->isDSOLocal();
297     }
298     if (!IsDSOLocal)
299       // Mark the flag in all summaries false so that we can do quick check
300       // without going through the whole list.
301       for (const std::unique_ptr<GlobalValueSummary> &Summary :
302            P.second.SummaryList)
303         Summary->setDSOLocal(false);
304   }
305   setWithAttributePropagation();
306   setWithDSOLocalPropagation();
307   if (llvm::AreStatisticsEnabled())
308     for (auto &P : *this)
309       if (P.second.SummaryList.size())
310         if (auto *GVS = dyn_cast<GlobalVarSummary>(
311                 P.second.SummaryList[0]->getBaseObject()))
312           if (isGlobalValueLive(GVS)) {
313             if (GVS->maybeReadOnly())
314               ReadOnlyLiveGVars++;
315             if (GVS->maybeWriteOnly())
316               WriteOnlyLiveGVars++;
317           }
318 }
319 
320 bool ModuleSummaryIndex::canImportGlobalVar(GlobalValueSummary *S,
321                                             bool AnalyzeRefs) const {
322   auto HasRefsPreventingImport = [this](const GlobalVarSummary *GVS) {
323     // We don't analyze GV references during attribute propagation, so
324     // GV with non-trivial initializer can be marked either read or
325     // write-only.
326     // Importing definiton of readonly GV with non-trivial initializer
327     // allows us doing some extra optimizations (like converting indirect
328     // calls to direct).
329     // Definition of writeonly GV with non-trivial initializer should also
330     // be imported. Not doing so will result in:
331     // a) GV internalization in source module (because it's writeonly)
332     // b) Importing of GV declaration to destination module as a result
333     //    of promotion.
334     // c) Link error (external declaration with internal definition).
335     // However we do not promote objects referenced by writeonly GV
336     // initializer by means of converting it to 'zeroinitializer'
337     return !(ImportConstantsWithRefs && GVS->isConstant()) &&
338            !isReadOnly(GVS) && !isWriteOnly(GVS) && GVS->refs().size();
339   };
340   auto *GVS = cast<GlobalVarSummary>(S->getBaseObject());
341 
342   // Global variable with non-trivial initializer can be imported
343   // if it's readonly. This gives us extra opportunities for constant
344   // folding and converting indirect calls to direct calls. We don't
345   // analyze GV references during attribute propagation, because we
346   // don't know yet if it is readonly or not.
347   return !GlobalValue::isInterposableLinkage(S->linkage()) &&
348          !S->notEligibleToImport() &&
349          (!AnalyzeRefs || !HasRefsPreventingImport(GVS));
350 }
351 
352 // TODO: write a graphviz dumper for SCCs (see ModuleSummaryIndex::exportToDot)
353 // then delete this function and update its tests
354 LLVM_DUMP_METHOD
355 void ModuleSummaryIndex::dumpSCCs(raw_ostream &O) {
356   for (scc_iterator<ModuleSummaryIndex *> I =
357            scc_begin<ModuleSummaryIndex *>(this);
358        !I.isAtEnd(); ++I) {
359     O << "SCC (" << utostr(I->size()) << " node" << (I->size() == 1 ? "" : "s")
360       << ") {\n";
361     for (const ValueInfo &V : *I) {
362       FunctionSummary *F = nullptr;
363       if (V.getSummaryList().size())
364         F = cast<FunctionSummary>(V.getSummaryList().front().get());
365       O << " " << (F == nullptr ? "External" : "") << " " << utostr(V.getGUID())
366         << (I.hasCycle() ? " (has cycle)" : "") << "\n";
367     }
368     O << "}\n";
369   }
370 }
371 
372 namespace {
373 struct Attributes {
374   void add(const Twine &Name, const Twine &Value,
375            const Twine &Comment = Twine());
376   void addComment(const Twine &Comment);
377   std::string getAsString() const;
378 
379   std::vector<std::string> Attrs;
380   std::string Comments;
381 };
382 
383 struct Edge {
384   uint64_t SrcMod;
385   int Hotness;
386   GlobalValue::GUID Src;
387   GlobalValue::GUID Dst;
388 };
389 }
390 
391 void Attributes::add(const Twine &Name, const Twine &Value,
392                      const Twine &Comment) {
393   std::string A = Name.str();
394   A += "=\"";
395   A += Value.str();
396   A += "\"";
397   Attrs.push_back(A);
398   addComment(Comment);
399 }
400 
401 void Attributes::addComment(const Twine &Comment) {
402   if (!Comment.isTriviallyEmpty()) {
403     if (Comments.empty())
404       Comments = " // ";
405     else
406       Comments += ", ";
407     Comments += Comment.str();
408   }
409 }
410 
411 std::string Attributes::getAsString() const {
412   if (Attrs.empty())
413     return "";
414 
415   std::string Ret = "[";
416   for (auto &A : Attrs)
417     Ret += A + ",";
418   Ret.pop_back();
419   Ret += "];";
420   Ret += Comments;
421   return Ret;
422 }
423 
424 static std::string linkageToString(GlobalValue::LinkageTypes LT) {
425   switch (LT) {
426   case GlobalValue::ExternalLinkage:
427     return "extern";
428   case GlobalValue::AvailableExternallyLinkage:
429     return "av_ext";
430   case GlobalValue::LinkOnceAnyLinkage:
431     return "linkonce";
432   case GlobalValue::LinkOnceODRLinkage:
433     return "linkonce_odr";
434   case GlobalValue::WeakAnyLinkage:
435     return "weak";
436   case GlobalValue::WeakODRLinkage:
437     return "weak_odr";
438   case GlobalValue::AppendingLinkage:
439     return "appending";
440   case GlobalValue::InternalLinkage:
441     return "internal";
442   case GlobalValue::PrivateLinkage:
443     return "private";
444   case GlobalValue::ExternalWeakLinkage:
445     return "extern_weak";
446   case GlobalValue::CommonLinkage:
447     return "common";
448   }
449 
450   return "<unknown>";
451 }
452 
453 static std::string fflagsToString(FunctionSummary::FFlags F) {
454   auto FlagValue = [](unsigned V) { return V ? '1' : '0'; };
455   char FlagRep[] = {FlagValue(F.ReadNone),
456                     FlagValue(F.ReadOnly),
457                     FlagValue(F.NoRecurse),
458                     FlagValue(F.ReturnDoesNotAlias),
459                     FlagValue(F.NoInline),
460                     FlagValue(F.AlwaysInline),
461                     FlagValue(F.NoUnwind),
462                     FlagValue(F.MayThrow),
463                     FlagValue(F.HasUnknownCall),
464                     FlagValue(F.MustBeUnreachable),
465                     0};
466 
467   return FlagRep;
468 }
469 
470 // Get string representation of function instruction count and flags.
471 static std::string getSummaryAttributes(GlobalValueSummary* GVS) {
472   auto *FS = dyn_cast_or_null<FunctionSummary>(GVS);
473   if (!FS)
474     return "";
475 
476   return std::string("inst: ") + std::to_string(FS->instCount()) +
477          ", ffl: " + fflagsToString(FS->fflags());
478 }
479 
480 static std::string getNodeVisualName(GlobalValue::GUID Id) {
481   return std::string("@") + std::to_string(Id);
482 }
483 
484 static std::string getNodeVisualName(const ValueInfo &VI) {
485   return VI.name().empty() ? getNodeVisualName(VI.getGUID()) : VI.name().str();
486 }
487 
488 static std::string getNodeLabel(const ValueInfo &VI, GlobalValueSummary *GVS) {
489   if (isa<AliasSummary>(GVS))
490     return getNodeVisualName(VI);
491 
492   std::string Attrs = getSummaryAttributes(GVS);
493   std::string Label =
494       getNodeVisualName(VI) + "|" + linkageToString(GVS->linkage());
495   if (!Attrs.empty())
496     Label += std::string(" (") + Attrs + ")";
497   Label += "}";
498 
499   return Label;
500 }
501 
502 // Write definition of external node, which doesn't have any
503 // specific module associated with it. Typically this is function
504 // or variable defined in native object or library.
505 static void defineExternalNode(raw_ostream &OS, const char *Pfx,
506                                const ValueInfo &VI, GlobalValue::GUID Id) {
507   auto StrId = std::to_string(Id);
508   OS << "  " << StrId << " [label=\"";
509 
510   if (VI) {
511     OS << getNodeVisualName(VI);
512   } else {
513     OS << getNodeVisualName(Id);
514   }
515   OS << "\"]; // defined externally\n";
516 }
517 
518 static bool hasReadOnlyFlag(const GlobalValueSummary *S) {
519   if (auto *GVS = dyn_cast<GlobalVarSummary>(S))
520     return GVS->maybeReadOnly();
521   return false;
522 }
523 
524 static bool hasWriteOnlyFlag(const GlobalValueSummary *S) {
525   if (auto *GVS = dyn_cast<GlobalVarSummary>(S))
526     return GVS->maybeWriteOnly();
527   return false;
528 }
529 
530 static bool hasConstantFlag(const GlobalValueSummary *S) {
531   if (auto *GVS = dyn_cast<GlobalVarSummary>(S))
532     return GVS->isConstant();
533   return false;
534 }
535 
536 void ModuleSummaryIndex::exportToDot(
537     raw_ostream &OS,
538     const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) const {
539   std::vector<Edge> CrossModuleEdges;
540   DenseMap<GlobalValue::GUID, std::vector<uint64_t>> NodeMap;
541   using GVSOrderedMapTy = std::map<GlobalValue::GUID, GlobalValueSummary *>;
542   std::map<StringRef, GVSOrderedMapTy> ModuleToDefinedGVS;
543   collectDefinedGVSummariesPerModule(ModuleToDefinedGVS);
544 
545   // Get node identifier in form MXXX_<GUID>. The MXXX prefix is required,
546   // because we may have multiple linkonce functions summaries.
547   auto NodeId = [](uint64_t ModId, GlobalValue::GUID Id) {
548     return ModId == (uint64_t)-1 ? std::to_string(Id)
549                                  : std::string("M") + std::to_string(ModId) +
550                                        "_" + std::to_string(Id);
551   };
552 
553   auto DrawEdge = [&](const char *Pfx, uint64_t SrcMod, GlobalValue::GUID SrcId,
554                       uint64_t DstMod, GlobalValue::GUID DstId,
555                       int TypeOrHotness) {
556     // 0 - alias
557     // 1 - reference
558     // 2 - constant reference
559     // 3 - writeonly reference
560     // Other value: (hotness - 4).
561     TypeOrHotness += 4;
562     static const char *EdgeAttrs[] = {
563         " [style=dotted]; // alias",
564         " [style=dashed]; // ref",
565         " [style=dashed,color=forestgreen]; // const-ref",
566         " [style=dashed,color=violetred]; // writeOnly-ref",
567         " // call (hotness : Unknown)",
568         " [color=blue]; // call (hotness : Cold)",
569         " // call (hotness : None)",
570         " [color=brown]; // call (hotness : Hot)",
571         " [style=bold,color=red]; // call (hotness : Critical)"};
572 
573     assert(static_cast<size_t>(TypeOrHotness) < std::size(EdgeAttrs));
574     OS << Pfx << NodeId(SrcMod, SrcId) << " -> " << NodeId(DstMod, DstId)
575        << EdgeAttrs[TypeOrHotness] << "\n";
576   };
577 
578   OS << "digraph Summary {\n";
579   for (auto &ModIt : ModuleToDefinedGVS) {
580     auto ModId = getModuleId(ModIt.first);
581     OS << "  // Module: " << ModIt.first << "\n";
582     OS << "  subgraph cluster_" << std::to_string(ModId) << " {\n";
583     OS << "    style = filled;\n";
584     OS << "    color = lightgrey;\n";
585     OS << "    label = \"" << sys::path::filename(ModIt.first) << "\";\n";
586     OS << "    node [style=filled,fillcolor=lightblue];\n";
587 
588     auto &GVSMap = ModIt.second;
589     auto Draw = [&](GlobalValue::GUID IdFrom, GlobalValue::GUID IdTo, int Hotness) {
590       if (!GVSMap.count(IdTo)) {
591         CrossModuleEdges.push_back({ModId, Hotness, IdFrom, IdTo});
592         return;
593       }
594       DrawEdge("    ", ModId, IdFrom, ModId, IdTo, Hotness);
595     };
596 
597     for (auto &SummaryIt : GVSMap) {
598       NodeMap[SummaryIt.first].push_back(ModId);
599       auto Flags = SummaryIt.second->flags();
600       Attributes A;
601       if (isa<FunctionSummary>(SummaryIt.second)) {
602         A.add("shape", "record", "function");
603       } else if (isa<AliasSummary>(SummaryIt.second)) {
604         A.add("style", "dotted,filled", "alias");
605         A.add("shape", "box");
606       } else {
607         A.add("shape", "Mrecord", "variable");
608         if (Flags.Live && hasReadOnlyFlag(SummaryIt.second))
609           A.addComment("immutable");
610         if (Flags.Live && hasWriteOnlyFlag(SummaryIt.second))
611           A.addComment("writeOnly");
612         if (Flags.Live && hasConstantFlag(SummaryIt.second))
613           A.addComment("constant");
614       }
615       if (Flags.Visibility)
616         A.addComment("visibility");
617       if (Flags.DSOLocal)
618         A.addComment("dsoLocal");
619       if (Flags.CanAutoHide)
620         A.addComment("canAutoHide");
621       if (GUIDPreservedSymbols.count(SummaryIt.first))
622         A.addComment("preserved");
623 
624       auto VI = getValueInfo(SummaryIt.first);
625       A.add("label", getNodeLabel(VI, SummaryIt.second));
626       if (!Flags.Live)
627         A.add("fillcolor", "red", "dead");
628       else if (Flags.NotEligibleToImport)
629         A.add("fillcolor", "yellow", "not eligible to import");
630 
631       OS << "    " << NodeId(ModId, SummaryIt.first) << " " << A.getAsString()
632          << "\n";
633     }
634     OS << "    // Edges:\n";
635 
636     for (auto &SummaryIt : GVSMap) {
637       auto *GVS = SummaryIt.second;
638       for (auto &R : GVS->refs())
639         Draw(SummaryIt.first, R.getGUID(),
640              R.isWriteOnly() ? -1 : (R.isReadOnly() ? -2 : -3));
641 
642       if (auto *AS = dyn_cast_or_null<AliasSummary>(SummaryIt.second)) {
643         Draw(SummaryIt.first, AS->getAliaseeGUID(), -4);
644         continue;
645       }
646 
647       if (auto *FS = dyn_cast_or_null<FunctionSummary>(SummaryIt.second))
648         for (auto &CGEdge : FS->calls())
649           Draw(SummaryIt.first, CGEdge.first.getGUID(),
650                static_cast<int>(CGEdge.second.Hotness));
651     }
652     OS << "  }\n";
653   }
654 
655   OS << "  // Cross-module edges:\n";
656   for (auto &E : CrossModuleEdges) {
657     auto &ModList = NodeMap[E.Dst];
658     if (ModList.empty()) {
659       defineExternalNode(OS, "  ", getValueInfo(E.Dst), E.Dst);
660       // Add fake module to the list to draw an edge to an external node
661       // in the loop below.
662       ModList.push_back(-1);
663     }
664     for (auto DstMod : ModList)
665       // The edge representing call or ref is drawn to every module where target
666       // symbol is defined. When target is a linkonce symbol there can be
667       // multiple edges representing a single call or ref, both intra-module and
668       // cross-module. As we've already drawn all intra-module edges before we
669       // skip it here.
670       if (DstMod != E.SrcMod)
671         DrawEdge("  ", E.SrcMod, E.Src, DstMod, E.Dst, E.Hotness);
672   }
673 
674   OS << "}";
675 }
676