[ThinLTO] Summarize vcall_visibility metadata

[tejohnson]

Summary

Second patch in series to support Safe Whole Program Devirtualization
Enablement, see RFC here:
http://lists.llvm.org/pipermail/llvm-dev/2019-December/137543.html

Summarize vcall_visibility metadata in ThinLTO global variable summary.

Depends on D71907.

[evgeny777]

llvm/include/llvm/IR/ModuleSummaryIndex.h

807

getVCallVisibility() ?

[tejohnson]

Implement suggested name change.

[tejohnson]

Attempt to fix patch to not include parent revision changes

[evgeny777]

I think this has to be rebased - I see multiple failures when trying to apply

[tejohnson]

In D71911#1823497, @evgeny777 wrote:

I think this has to be rebased - I see multiple failures when trying to apply

I'll rebase it today.

[tejohnson]

Rebase

[evgeny777]

llvm/include/llvm/IR/ModuleSummaryIndex.h

762

I think using default parameter is error prone here. Can you please get rid of it and update all places of usage respectively?

[tejohnson]

Address comment and rebase

[evgeny777]

LGTM

clang/test/CodeGenCXX/vcall-visibility-metadata.cpp

 // RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -emit-llvm -fvirtual-function-elimination -fwhole-program-vtables -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-VFE
 // RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -emit-llvm -fwhole-program-vtables -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-NOVFE
 
+// Check that in ThinLTO we also get vcall_visibility summary entries in the bitcode
+// RUN: %clang_cc1 -flto=thin -flto-unit -triple x86_64-unknown-linux -emit-llvm-bc -fwhole-program-vtables -o - %s | llvm-dis -o - | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-NOVFE --check-prefix=CHECK-SUMMARY
+
 
 // Anonymous namespace.
 namespace {
 // CHECK: @_ZTVN12_GLOBAL__N_11AE = {{.*}} !vcall_visibility [[VIS_TU:![0-9]+]]
 struct A {
   A() {}
   virtual int f() { return 1; }
 };

 void *construct_G() {
   return new G();
 }
 
 // CHECK-DAG: [[VIS_DSO]] = !{i64 1}
 // CHECK-DAG: [[VIS_TU]] = !{i64 2}
 // CHECK-VFE-DAG: !{i32 1, !"Virtual Function Elim", i32 1}
 // CHECK-NOVFE-DAG: !{i32 1, !"Virtual Function Elim", i32 0}
+
+// CHECK-SUMMARY-DAG: gv: (name: "_ZTV1B", {{.*}} vcall_visibility: 1
+// CHECK-SUMMARY-DAG: gv: (name: "_ZTVN12_GLOBAL__N_11FE", {{.*}} vcall_visibility: 0
+// CHECK-SUMMARY-DAG: gv: (name: "_ZTV1D", {{.*}} vcall_visibility: 0
+// CHECK-SUMMARY-DAG: gv: (name: "_ZTV1C", {{.*}} vcall_visibility: 0
+// CHECK-SUMMARY-DAG: gv: (name: "_ZTV1E", {{.*}} vcall_visibility: 0
+// CHECK-SUMMARY-DAG: gv: (name: "_ZTVN12_GLOBAL__N_11AE", {{.*}} vcall_visibility: 2
+// CHECK-SUMMARY-DAG: gv: (name: "_ZTVN12_GLOBAL__N_11GE", {{.*}} vcall_visibility: 1

llvm/include/llvm/IR/ModuleSummaryIndex.h

 class GlobalVarSummary : public GlobalValueSummary {
 private:
   /// For vtable definitions this holds the list of functions and
   /// their corresponding offsets within the initializer array.
   std::unique_ptr<VTableFuncList> VTableFuncs;
 
 public:
   struct GVarFlags {
-    GVarFlags(bool ReadOnly, bool WriteOnly, bool Constant)
+    GVarFlags(bool ReadOnly, bool WriteOnly, bool Constant,
+              GlobalObject::VCallVisibility Vis)
         : MaybeReadOnly(ReadOnly), MaybeWriteOnly(WriteOnly),
-          Constant(Constant) {}
+          Constant(Constant), VCallVisibility(Vis) {}
 
     // If true indicates that this global variable might be accessed
     // purely by non-volatile load instructions. This in turn means
     // it can be internalized in source and destination modules during
     // thin LTO import because it neither modified nor its address
     // is taken.
     unsigned MaybeReadOnly : 1;
     // If true indicates that variable is possibly only written to, so
     // its value isn't loaded and its address isn't taken anywhere.
     // False, when 'Constant' attribute is set.
     unsigned MaybeWriteOnly : 1;
     // Indicates that value is a compile-time constant. Global variable
     // can be 'Constant' while not being 'ReadOnly' on several occasions:
     // - it is volatile, (e.g mapped device address)
     // - its address is taken, meaning that unlike 'ReadOnly' vars we can't
     //   internalize it.
     // Constant variables are always imported thus giving compiler an
     // opportunity to make some extra optimizations. Readonly constants
     // are also internalized.
     unsigned Constant : 1;
+    // Set from metadata on vtable definitions during the module summary
+    // analysis.
+    unsigned VCallVisibility : 2;
   } VarFlags;
 
   GlobalVarSummary(GVFlags Flags, GVarFlags VarFlags,
                    std::vector<ValueInfo> Refs)
       : GlobalValueSummary(GlobalVarKind, Flags, std::move(Refs)),
         VarFlags(VarFlags) {}
 
   /// Check if this is a global variable summary.
   static bool classof(const GlobalValueSummary *GVS) {
     return GVS->getSummaryKind() == GlobalVarKind;
   }
 
   GVarFlags varflags() const { return VarFlags; }
   void setReadOnly(bool RO) { VarFlags.MaybeReadOnly = RO; }
   void setWriteOnly(bool WO) { VarFlags.MaybeWriteOnly = WO; }
   bool maybeReadOnly() const { return VarFlags.MaybeReadOnly; }
   bool maybeWriteOnly() const { return VarFlags.MaybeWriteOnly; }
   bool isConstant() const { return VarFlags.Constant; }
+  void setVCallVisibility(GlobalObject::VCallVisibility Vis) {
+    VarFlags.VCallVisibility = Vis;
+  }
+  GlobalObject::VCallVisibility getVCallVisibility() const {
+    return (GlobalObject::VCallVisibility)VarFlags.VCallVisibility;
+  }
 
   void setVTableFuncs(VTableFuncList Funcs) {
     assert(!VTableFuncs);
     VTableFuncs = std::make_unique<VTableFuncList>(std::move(Funcs));
   }
 
   ArrayRef<VirtFuncOffset> vTableFuncs() const {
     if (VTableFuncs)

llvm/lib/Analysis/ModuleSummaryAnalysis.cpp

if (!Index.enableSplitLTOUnit()) {
     }
   }
 
   // Don't mark variables we won't be able to internalize as read/write-only.
   bool CanBeInternalized =
       !V.hasComdat() && !V.hasAppendingLinkage() && !V.isInterposable() &&
       !V.hasAvailableExternallyLinkage() && !V.hasDLLExportStorageClass();
   bool Constant = V.isConstant();
-  GlobalVarSummary::GVarFlags VarFlags(
-      CanBeInternalized, Constant ? false : CanBeInternalized, Constant);
+  GlobalVarSummary::GVarFlags VarFlags(CanBeInternalized,
+                                       Constant ? false : CanBeInternalized,
+                                       Constant, V.getVCallVisibility());
   auto GVarSummary = std::make_unique<GlobalVarSummary>(Flags, VarFlags,
                                                          RefEdges.takeVector());
   if (NonRenamableLocal)
     CantBePromoted.insert(V.getGUID());
   if (HasBlockAddress)
     GVarSummary->setNotEligibleToImport();
   if (!VTableFuncs.empty())
     GVarSummary->setVTableFuncs(VTableFuncs);
ModuleSymbolTable::CollectAsmSymbols(
                     ArrayRef<FunctionSummary::ConstVCall>{},
                     ArrayRef<FunctionSummary::ConstVCall>{});
             Index.addGlobalValueSummary(*GV, std::move(Summary));
           } else {
             std::unique_ptr<GlobalVarSummary> Summary =
                 std::make_unique<GlobalVarSummary>(
                     GVFlags,
                     GlobalVarSummary::GVarFlags(
-                        false, false, cast<GlobalVariable>(GV)->isConstant()),
+                        false, false, cast<GlobalVariable>(GV)->isConstant(),
+                        GlobalObject::VCallVisibilityPublic),
                     ArrayRef<ValueInfo>{});
             Index.addGlobalValueSummary(*GV, std::move(Summary));
           }
         });
   }
 
   bool IsThinLTO = true;
   if (auto *MD =

llvm/lib/AsmParser/LLLexer.cpp

#define KEYWORD(STR)                                                           \
   KEYWORD(inline);
   KEYWORD(single);
   KEYWORD(allOnes);
   KEYWORD(sizeM1BitWidth);
   KEYWORD(alignLog2);
   KEYWORD(sizeM1);
   KEYWORD(bitMask);
   KEYWORD(inlineBits);
+  KEYWORD(vcall_visibility);
   KEYWORD(wpdResolutions);
   KEYWORD(wpdRes);
   KEYWORD(indir);
   KEYWORD(singleImpl);
   KEYWORD(branchFunnel);
   KEYWORD(singleImplName);
   KEYWORD(resByArg);
   KEYWORD(byArg);

llvm/lib/AsmParser/LLParser.cpp

bool LLParser::ParseVariableSummary(std::string Name, GlobalValue::GUID GUID,
   Lex.Lex();
 
   StringRef ModulePath;
   GlobalValueSummary::GVFlags GVFlags = GlobalValueSummary::GVFlags(
       /*Linkage=*/GlobalValue::ExternalLinkage, /*NotEligibleToImport=*/false,
       /*Live=*/false, /*IsLocal=*/false, /*CanAutoHide=*/false);
   GlobalVarSummary::GVarFlags GVarFlags(/*ReadOnly*/ false,
                                         /* WriteOnly */ false,
-                                        /* Constant */ false);
+                                        /* Constant */ false,
+                                        GlobalObject::VCallVisibilityPublic);
   std::vector<ValueInfo> Refs;
   VTableFuncList VTableFuncs;
   if (ParseToken(lltok::colon, "expected ':' here") ||
       ParseToken(lltok::lparen, "expected '(' here") ||
       ParseModuleReference(ModulePath) ||
       ParseToken(lltok::comma, "expected ',' here") || ParseGVFlags(GVFlags) ||
       ParseToken(lltok::comma, "expected ',' here") ||
       ParseGVarFlags(GVarFlags))
case lltok::kw_writeonly:
         return true;
       GVarFlags.MaybeWriteOnly = Flag;
       break;
     case lltok::kw_constant:
       if (ParseRest(Flag))
         return true;
       GVarFlags.Constant = Flag;
       break;
+    case lltok::kw_vcall_visibility:
+      if (ParseRest(Flag))
+        return true;
+      GVarFlags.VCallVisibility = Flag;
+      break;
     default:
       return Error(Lex.getLoc(), "expected gvar flag type");
     }
   } while (EatIfPresent(lltok::comma));
   return ParseToken(lltok::rparen, "expected ')' here");
 }
 
 /// ModuleReference

llvm/lib/AsmParser/LLToken.h

enum Kind {
   kw_inline,
   kw_single,
   kw_allOnes,
   kw_sizeM1BitWidth,
   kw_alignLog2,
   kw_sizeM1,
   kw_bitMask,
   kw_inlineBits,
+  kw_vcall_visibility,
   kw_wpdResolutions,
   kw_wpdRes,
   kw_indir,
   kw_singleImpl,
   kw_branchFunnel,
   kw_singleImplName,
   kw_resByArg,
   kw_byArg,

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

static GlobalValueSummary::GVFlags getDecodedGVSummaryFlags(uint64_t RawFlags,
   bool Local = (RawFlags & 0x4);
   bool AutoHide = (RawFlags & 0x8);
 
   return GlobalValueSummary::GVFlags(Linkage, NotEligibleToImport, Live, Local, AutoHide);
 }
 
 // Decode the flags for GlobalVariable in the summary
 static GlobalVarSummary::GVarFlags getDecodedGVarFlags(uint64_t RawFlags) {
-  return GlobalVarSummary::GVarFlags((RawFlags & 0x1) ? true : false,
-                                     (RawFlags & 0x2) ? true : false,
-                                     (RawFlags & 0x4) ? true : false);
+  return GlobalVarSummary::GVarFlags(
+      (RawFlags & 0x1) ? true : false, (RawFlags & 0x2) ? true : false,
+      (RawFlags & 0x4) ? true : false,
+      (GlobalObject::VCallVisibility)(RawFlags >> 3));
 }
 
 static GlobalValue::VisibilityTypes getDecodedVisibility(unsigned Val) {
   switch (Val) {
   default: // Map unknown visibilities to default.
   case 0: return GlobalValue::DefaultVisibility;
   case 1: return GlobalValue::HiddenVisibility;
   case 2: return GlobalValue::ProtectedVisibility;
while (true) {
     }
     // FS_PERMODULE_GLOBALVAR_INIT_REFS: [valueid, flags, varflags, n x valueid]
     case bitc::FS_PERMODULE_GLOBALVAR_INIT_REFS: {
       unsigned ValueID = Record[0];
       uint64_t RawFlags = Record[1];
       unsigned RefArrayStart = 2;
       GlobalVarSummary::GVarFlags GVF(/* ReadOnly */ false,
                                       /* WriteOnly */ false,
-                                      /* Constant */ false);
+                                      /* Constant */ false,
+                                      GlobalObject::VCallVisibilityPublic);
       auto Flags = getDecodedGVSummaryFlags(RawFlags, Version);
       if (Version >= 5) {
         GVF = getDecodedGVarFlags(Record[2]);
         RefArrayStart = 3;
       }
       std::vector<ValueInfo> Refs =
           makeRefList(ArrayRef<uint64_t>(Record).slice(RefArrayStart));
       auto FS =
while (true) {
     // FS_COMBINED_GLOBALVAR_INIT_REFS: [valueid, modid, flags, n x valueid]
     case bitc::FS_COMBINED_GLOBALVAR_INIT_REFS: {
       unsigned ValueID = Record[0];
       uint64_t ModuleId = Record[1];
       uint64_t RawFlags = Record[2];
       unsigned RefArrayStart = 3;
       GlobalVarSummary::GVarFlags GVF(/* ReadOnly */ false,
                                       /* WriteOnly */ false,
-                                      /* Constant */ false);
+                                      /* Constant */ false,
+                                      GlobalObject::VCallVisibilityPublic);
       auto Flags = getDecodedGVSummaryFlags(RawFlags, Version);
       if (Version >= 5) {
         GVF = getDecodedGVarFlags(Record[3]);
         RefArrayStart = 4;
       }
       std::vector<ValueInfo> Refs =
           makeRefList(ArrayRef<uint64_t>(Record).slice(RefArrayStart));
       auto FS =

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags) {
   // change to the getEncodedLinkage() function will need to be taken into
   // account here as well.
   RawFlags = (RawFlags << 4) | Flags.Linkage; // 4 bits
 
   return RawFlags;
 }
 
 static uint64_t getEncodedGVarFlags(GlobalVarSummary::GVarFlags Flags) {
-  uint64_t RawFlags =
-      Flags.MaybeReadOnly | (Flags.MaybeWriteOnly << 1) | (Flags.Constant << 2);
+  uint64_t RawFlags = Flags.MaybeReadOnly | (Flags.MaybeWriteOnly << 1) |
+                      (Flags.Constant << 2) | Flags.VCallVisibility << 3;
   return RawFlags;
 }
 
 static unsigned getEncodedVisibility(const GlobalValue &GV) {
   switch (GV.getVisibility()) {
   case GlobalValue::DefaultVisibility:   return 0;
   case GlobalValue::HiddenVisibility:    return 1;
   case GlobalValue::ProtectedVisibility: return 2;

llvm/lib/IR/AsmWriter.cpp

void AssemblyWriter::printAliasSummary(const AliasSummary *AS) {
   // that case by just emitting "null" as the aliasee.
   if (AS->hasAliasee())
     Out << "^" << Machine.getGUIDSlot(SummaryToGUIDMap[&AS->getAliasee()]);
   else
     Out << "null";
 }
 
 void AssemblyWriter::printGlobalVarSummary(const GlobalVarSummary *GS) {
+  auto VTableFuncs = GS->vTableFuncs();
   Out << ", varFlags: (readonly: " << GS->VarFlags.MaybeReadOnly << ", "
       << "writeonly: " << GS->VarFlags.MaybeWriteOnly << ", "
-      << "constant: " << GS->VarFlags.Constant << ")";
+      << "constant: " << GS->VarFlags.Constant;
+  if (!VTableFuncs.empty())
+    Out << ", "
+        << "vcall_visibility: " << GS->VarFlags.VCallVisibility;
+  Out << ")";
 
-  auto VTableFuncs = GS->vTableFuncs();
   if (!VTableFuncs.empty()) {
     Out << ", vTableFuncs: (";
     FieldSeparator FS;
     for (auto &P : VTableFuncs) {
       Out << FS;
       Out << "(virtFunc: ^" << Machine.getGUIDSlot(P.FuncVI.getGUID())
           << ", offset: " << P.VTableOffset;
       Out << ")";

llvm/test/Assembler/thinlto-vtable-summary.ll

 declare i32 @_ZN1C1fEi(%struct.C*, i32)
 
 !0 = !{i64 16, !"_ZTS1A"}
 !1 = !{i64 16, !"_ZTS1B"}
 !2 = !{i64 16, !"_ZTS1C"}
 
 ^0 = module: (path: "<stdin>", hash: (0, 0, 0, 0, 0))
 ^1 = gv: (name: "_ZN1A1nEi") ; guid = 1621563287929432257
-^2 = gv: (name: "_ZTV1B", summaries: (variable: (module: ^0, flags: (linkage: external, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0), varFlags: (readonly: 0, writeonly: 0, constant: 0), vTableFuncs: ((virtFunc: ^3, offset: 16), (virtFunc: ^1, offset: 24)), refs: (^3, ^1)))) ; guid = 5283576821522790367
+^2 = gv: (name: "_ZTV1B", summaries: (variable: (module: ^0, flags: (linkage: external, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0), varFlags: (readonly: 0, writeonly: 0, constant: 0, vcall_visibility: 0), vTableFuncs: ((virtFunc: ^3, offset: 16), (virtFunc: ^1, offset: 24)), refs: (^3, ^1)))) ; guid = 5283576821522790367
 ^3 = gv: (name: "_ZN1B1fEi") ; guid = 7162046368816414394
-^4 = gv: (name: "_ZTV1C", summaries: (variable: (module: ^0, flags: (linkage: external, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0), varFlags: (readonly: 0, writeonly: 0, constant: 0), vTableFuncs: ((virtFunc: ^5, offset: 16), (virtFunc: ^1, offset: 24)), refs: (^1, ^5)))) ; guid = 13624023785555846296
+^4 = gv: (name: "_ZTV1C", summaries: (variable: (module: ^0, flags: (linkage: external, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0), varFlags: (readonly: 0, writeonly: 0, constant: 0, vcall_visibility: 0), vTableFuncs: ((virtFunc: ^5, offset: 16), (virtFunc: ^1, offset: 24)), refs: (^1, ^5)))) ; guid = 13624023785555846296
 ^5 = gv: (name: "_ZN1C1fEi") ; guid = 14876272565662207556
 ^6 = typeidCompatibleVTable: (name: "_ZTS1A", summary: ((offset: 16, ^2), (offset: 16, ^4))) ; guid = 7004155349499253778
 ^7 = typeidCompatibleVTable: (name: "_ZTS1B", summary: ((offset: 16, ^2))) ; guid = 6203814149063363976
 ^8 = typeidCompatibleVTable: (name: "_ZTS1C", summary: ((offset: 16, ^4))) ; guid = 1884921850105019584