WIP: Fix MSVC

[davide]

LGTM to unbreak the bot. You should also add a comment saying we should drop this hack once we bump MSVC.

[davide]

looks fine, thanks.

[JDevlieghere]

Landed in rL323667

include/llvm/CodeGen/AccelTable.h

 private:
   /// The HeaderData describes the structure of the accelerator table through a
   /// list of Atoms.
   struct HeaderData {
     /// In the case of data that is referenced via DW_FORM_ref_* the offset
     /// base is used to describe the offset for all forms in the list of atoms.
     uint32_t DieOffsetBase;
 
-    SmallVector<Atom, 3> Atoms;
+    const SmallVector<Atom, 4> Atoms;
 
+#ifndef _MSC_VER
+    // See the `static constexpr` below why we need an alternative
+    // implementation for MSVC.
     HeaderData(ArrayRef<Atom> AtomList, uint32_t Offset = 0)
         : DieOffsetBase(Offset), Atoms(AtomList.begin(), AtomList.end()) {}
+#else
+    // FIXME: Erase this path once the minimum MSCV version has been bumped.
+    HeaderData(const SmallVectorImpl<Atom> &Atoms, uint32_t Offset = 0)
+        : DieOffsetBase(Offset), Atoms(Atoms.begin(), Atoms.end()) {}
+#endif
 
 #ifndef NDEBUG
     void print(raw_ostream &OS) const {
       OS << "DIE Offset Base: " << DieOffsetBase << "\n";
       for (auto Atom : Atoms)
         Atom.print(OS);
     }
 
     void dump() const { print(dbgs()); }
 #endif
   };
 
   Header Header;
   HeaderData HeaderData;
 
 public:
   /// The length of the header data is always going to be 4 + 4 + 4*NumAtoms.
+#ifndef _MSC_VER
+  // See the `static constexpr` below why we need an alternative implementation
+  // for MSVC.
   AppleAccelTableHeader(ArrayRef<AppleAccelTableHeader::Atom> Atoms)
       : Header(8 + (Atoms.size() * 4)), HeaderData(Atoms) {}
+#else
+  // FIXME: Erase this path once the minimum MSCV version has been bumped.
+  AppleAccelTableHeader(const SmallVectorImpl<Atom> &Atoms)
+      : Header(8 + (Atoms.size() * 4)), HeaderData(Atoms) {}
+#endif
 
   /// Update header with hash and bucket count.
   void setBucketAndHashCount(uint32_t HashCount);
 
   uint32_t getHashCount() const { return Header.HashCount; }
   uint32_t getBucketCount() const { return Header.BucketCount; }
 
   /// Emits the header via the AsmPrinter.
#endif
   StringEntries Entries;
 
   using HashList = std::vector<HashData *>;
   HashList Hashes;
 
   using BucketList = std::vector<HashList>;
   BucketList Buckets;
 
+#ifndef _MSC_VER
+  // See the `static constexpr` below why we need an alternative implementation
+  // for MSVC.
   AppleAccelTableBase(ArrayRef<AppleAccelTableHeader::Atom> Atoms)
       : Header(Atoms), Entries(Allocator) {}
+#else
+  // FIXME: Erase this path once the minimum MSCV version has been bumped.
+  AppleAccelTableBase(const SmallVectorImpl<AppleAccelTableHeader::Atom> &Atoms)
+      : Header(Atoms), Entries(Allocator) {}
+#endif
 
 private:
   /// Emits the header for the table via the AsmPrinter.
   void emitHeader(AsmPrinter *Asm);
 
   /// Helper function to compute the number of buckets needed based on the
   /// number of unique hashes.
   void computeBucketCount();

 /// Accelerator table data implementation for simple accelerator tables with
 /// just a DIE reference.
 class AppleAccelTableOffsetData : public AppleAccelTableData {
 public:
   AppleAccelTableOffsetData(const DIE *D) : Die(D) {}
 
   void emit(AsmPrinter *Asm) const override;
 
-  static constexpr const AppleAccelTableHeader::Atom Atoms[] = {
+#ifndef _MSC_VER
+  // The line below is rejected by older versions (TBD) of MSVC.
+  static constexpr AppleAccelTableHeader::Atom Atoms[] = {
       AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_offset,
                                   dwarf::DW_FORM_data4)};
+#else
+  // FIXME: Erase this path once the minimum MSCV version has been bumped.
+  static const SmallVector<AppleAccelTableHeader::Atom, 4> Atoms;
+#endif
 
 #ifndef NDEBUG
   void print(raw_ostream &OS) const override {
     OS << "  Offset: " << Die->getOffset() << "\n";
   }
 
 #endif
 protected:
   uint64_t order() const override { return Die->getOffset(); }
 
   const DIE *Die;
 };
 
 /// Accelerator table data implementation for type accelerator tables.
 class AppleAccelTableTypeData : public AppleAccelTableOffsetData {
 public:
   AppleAccelTableTypeData(const DIE *D) : AppleAccelTableOffsetData(D) {}
 
   void emit(AsmPrinter *Asm) const override;
 
-  static constexpr const AppleAccelTableHeader::Atom Atoms[] = {
+#ifndef _MSC_VER
+  // The line below is rejected by older versions (TBD) of MSVC.
+  static constexpr AppleAccelTableHeader::Atom Atoms[] = {
       AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_offset,
                                   dwarf::DW_FORM_data4),
       AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_tag, dwarf::DW_FORM_data2),
       AppleAccelTableHeader::Atom(dwarf::DW_ATOM_type_flags,
                                   dwarf::DW_FORM_data1)};
+#else
+  // FIXME: Erase this path once the minimum MSCV version has been bumped.
+  static const SmallVector<AppleAccelTableHeader::Atom, 4> Atoms;
+#endif
 
 #ifndef NDEBUG
   void print(raw_ostream &OS) const override {
     OS << "  Offset: " << Die->getOffset() << "\n";
     OS << "  Tag: " << dwarf::TagString(Die->getTag()) << "\n";
   }
 #endif
 };
 
 /// Accelerator table data implementation for simple accelerator tables with
 /// a DIE offset but no actual DIE pointer.
 class AppleAccelTableStaticOffsetData : public AppleAccelTableData {
 public:
   AppleAccelTableStaticOffsetData(uint32_t Offset) : Offset(Offset) {}
 
   void emit(AsmPrinter *Asm) const override;
 
-  static constexpr const AppleAccelTableHeader::Atom Atoms[] = {
+#ifndef _MSC_VER
+  // The line below is rejected by older versions (TBD) of MSVC.
+  static constexpr AppleAccelTableHeader::Atom Atoms[] = {
       AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_offset,
                                   dwarf::DW_FORM_data4)};
+#else
+  // FIXME: Erase this path once the minimum MSCV version has been bumped.
+  static const SmallVector<AppleAccelTableHeader::Atom, 4> Atoms;
+#endif
 
 #ifndef NDEBUG
   void print(raw_ostream &OS) const override {
     OS << "  Static Offset: " << Offset << "\n";
   }
 
 #endif
 protected:
AppleAccelTableStaticTypeData(uint32_t Offset, uint16_t Tag,
                                 bool ObjCClassIsImplementation,
                                 uint32_t QualifiedNameHash)
       : AppleAccelTableStaticOffsetData(Offset),
         QualifiedNameHash(QualifiedNameHash), Tag(Tag),
         ObjCClassIsImplementation(ObjCClassIsImplementation) {}
 
   void emit(AsmPrinter *Asm) const override;
 
-  static constexpr const AppleAccelTableHeader::Atom Atoms[] = {
+#ifndef _MSC_VER
+  // The line below is rejected by older versions (TBD) of MSVC.
+  static constexpr AppleAccelTableHeader::Atom Atoms[] = {
       AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_offset,
                                   dwarf::DW_FORM_data4),
       AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_tag, dwarf::DW_FORM_data2),
       AppleAccelTableHeader::Atom(5, dwarf::DW_FORM_data1),
       AppleAccelTableHeader::Atom(6, dwarf::DW_FORM_data4)};
+#else
+  // FIXME: Erase this path once the minimum MSCV version has been bumped.
+  static const SmallVector<AppleAccelTableHeader::Atom, 4> Atoms;
+#endif
 
 #ifndef NDEBUG
   void print(raw_ostream &OS) const override {
     OS << "  Static Offset: " << Offset << "\n";
     OS << "  QualifiedNameHash: " << format("%x\n", QualifiedNameHash) << "\n";
     OS << "  Tag: " << dwarf::TagString(Tag) << "\n";
     OS << "  ObjCClassIsImplementation: "
        << (ObjCClassIsImplementation ? "true" : "false");

lib/CodeGen/AsmPrinter/AccelTable.cpp

void AppleAccelTableHeader::setBucketAndHashCount(uint32_t HashCount) {
   else if (HashCount > 16)
     Header.BucketCount = HashCount / 2;
   else
     Header.BucketCount = HashCount > 0 ? HashCount : 1;
 
   Header.HashCount = HashCount;
 }
 
-constexpr const AppleAccelTableHeader::Atom AppleAccelTableTypeData::Atoms[];
-constexpr const AppleAccelTableHeader::Atom AppleAccelTableOffsetData::Atoms[];
-constexpr const AppleAccelTableHeader::Atom AppleAccelTableStaticOffsetData::Atoms[];
-constexpr const AppleAccelTableHeader::Atom AppleAccelTableStaticTypeData::Atoms[];
-
 void AppleAccelTableBase::emitHeader(AsmPrinter *Asm) { Header.emit(Asm); }
 
 void AppleAccelTableBase::emitBuckets(AsmPrinter *Asm) {
   unsigned index = 0;
   for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
     Asm->OutStreamer->AddComment("Bucket " + Twine(i));
     if (!Buckets[i].empty())
       Asm->EmitInt32(index);

 
 void AppleAccelTableStaticTypeData::emit(AsmPrinter *Asm) const {
   Asm->EmitInt32(Offset);
   Asm->EmitInt16(Tag);
   Asm->EmitInt8(ObjCClassIsImplementation ? dwarf::DW_FLAG_type_implementation
                                           : 0);
   Asm->EmitInt32(QualifiedNameHash);
 }
+
+#ifndef _MSC_VER
+// The lines below are rejected by older versions (TBD) of MSVC.
+constexpr AppleAccelTableHeader::Atom AppleAccelTableTypeData::Atoms[];
+constexpr AppleAccelTableHeader::Atom AppleAccelTableOffsetData::Atoms[];
+constexpr AppleAccelTableHeader::Atom AppleAccelTableStaticOffsetData::Atoms[];
+constexpr AppleAccelTableHeader::Atom AppleAccelTableStaticTypeData::Atoms[];
+#else
+// FIXME: Erase this path once the minimum MSCV version has been bumped.
+const SmallVector<AppleAccelTableHeader::Atom, 4>
+    AppleAccelTableOffsetData::Atoms = {AppleAccelTableHeader::Atom(
+        dwarf::DW_ATOM_die_offset, dwarf::DW_FORM_data4)};
+const SmallVector<AppleAccelTableHeader::Atom, 4>
+    AppleAccelTableTypeData::Atoms = {
+        AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_offset,
+                                    dwarf::DW_FORM_data4),
+        AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_tag,
+                                    dwarf::DW_FORM_data2),
+        AppleAccelTableHeader::Atom(dwarf::DW_ATOM_type_flags,
+                                    dwarf::DW_FORM_data1)};
+const SmallVector<AppleAccelTableHeader::Atom, 4>
+    AppleAccelTableStaticOffsetData::Atoms = {AppleAccelTableHeader::Atom(
+        dwarf::DW_ATOM_die_offset, dwarf::DW_FORM_data4)};
+const SmallVector<AppleAccelTableHeader::Atom, 4>
+    AppleAccelTableStaticTypeData::Atoms = {
+        AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_offset,
+                                    dwarf::DW_FORM_data4),
+        AppleAccelTableHeader::Atom(dwarf::DW_ATOM_die_tag,
+                                    dwarf::DW_FORM_data2),
+        AppleAccelTableHeader::Atom(5, dwarf::DW_FORM_data1),
+        AppleAccelTableHeader::Atom(6, dwarf::DW_FORM_data4)};
+#endif