Introduce apple_objc representation in MCCAS

MCCAS has an ability to have different block types for different data,
this patch introduces AppleObjCRef and AppleObjCSectionRef to represent
the apple_objc section in DWARF4.

Author: rastogishubham

llvm/include/llvm/MCCAS/MCCASObjectV1.def

@@ -27,6 +27,7 @@ CASV1_SIMPLE_DATA_REF(DebugNamesRef, mc:debug_names)
 CASV1_SIMPLE_DATA_REF(AppleNamesRef, mc:apple_names)
 CASV1_SIMPLE_DATA_REF(AppleTypesRef, mc:apple_types)
 CASV1_SIMPLE_DATA_REF(AppleNamespaceRef, mc:apple_namespac)
+CASV1_SIMPLE_DATA_REF(AppleObjCRef, mc:apple_objc)
 CASV1_SIMPLE_DATA_REF(DebugLineRef, mc:debug_line)
 CASV1_SIMPLE_DATA_REF(DebugLineUnoptRef, mc:debug_line_unopt)
 CASV1_SIMPLE_DATA_REF(DebugLineStrRef, mc:debug_line_str)
@@ -60,6 +61,7 @@ CASV1_SIMPLE_GROUP_REF(DebugNamesSectionRef, mc:debug_names_section)
 CASV1_SIMPLE_GROUP_REF(AppleNamesSectionRef, mc:apple_names_section)
 CASV1_SIMPLE_GROUP_REF(AppleTypesSectionRef, mc:apple_types_section)
 CASV1_SIMPLE_GROUP_REF(AppleNamespaceSectionRef, mc:apple_namepsac_section)
+CASV1_SIMPLE_GROUP_REF(AppleObjCSectionRef, mc:apple_objc_section)
 CASV1_SIMPLE_GROUP_REF(DIEAbbrevSetRef, mc:debug_DIE_abbrev_set)
 CASV1_SIMPLE_GROUP_REF(DIETopLevelRef, mc:debug_DIE_top_level)
 CASV1_SIMPLE_GROUP_REF(DIEDedupeTopLevelRef, mc:debug_DIE_Dedupe_top_level)

llvm/include/llvm/MCCAS/MCCASObjectV1.h

@@ -489,6 +489,7 @@ struct DwarfSectionsCache {
   MCSection *AppleNames;
   MCSection *AppleTypes;
   MCSection *AppleNamespace;
+  MCSection *AppleObjC;
 };
 
 /// Queries `Asm` for all dwarf sections and returns an object with (possibly
@@ -648,6 +649,10 @@ class MCCASBuilder {
   // object for the section.
   Error createAppleNamespaceSection();
 
+  // If a DWARF Apple Objc section exists, create a AppleObjcRef CAS
+  // object for the section.
+  Error createAppleObjCSection();
+
   /// If there is any padding between one section and the next, create a
   /// PaddingRef CAS object to represent the bytes of Padding between the two
   /// sections.

llvm/lib/MCCAS/MCCASObjectV1.cpp

@@ -905,6 +905,20 @@ AppleNamespaceSectionRef::create(MCCASBuilder &MB,
   return get(B->build());
 }
 
+Expected<AppleObjCSectionRef>
+AppleObjCSectionRef::create(MCCASBuilder &MB,
+                                 ArrayRef<cas::ObjectRef> Fragments) {
+  Expected<Builder> B = Builder::startNode(MB.Schema, KindString);
+  if (!B)
+    return B.takeError();
+
+  if (auto E = createGenericDebugSection<AppleObjCSectionRef>(MB, Fragments,
+                                                              B->Data, B->Refs))
+    return E;
+
+  return get(B->build());
+}
+
 Expected<uint64_t> SectionRef::materialize(MCCASReader &Reader,
                                            raw_ostream *Stream) const {
   // Start a new section for relocations.
@@ -1437,6 +1451,13 @@ AppleNamespaceSectionRef::materialize(MCCASReader &Reader,
       Reader, Remaining, *this);
 }
 
+Expected<uint64_t> AppleObjCSectionRef::materialize(MCCASReader &Reader,
+                                                    raw_ostream *Stream) const {
+  StringRef Remaining = getData();
+  return materializeGenericDebugSection<AppleObjCSectionRef>(Reader, Remaining,
+                                                             *this);
+}
+
 Expected<AtomRef> AtomRef::create(MCCASBuilder &MB,
                                   ArrayRef<cas::ObjectRef> Fragments) {
   Expected<Builder> B = Builder::startNode(MB.Schema, KindString);
@@ -1775,7 +1796,8 @@ DwarfSectionsCache mccasformats::v1::getDwarfSections(MCAssembler &Asm) {
       Asm.getContext().getObjectFileInfo()->getDwarfDebugNamesSection(),
       Asm.getContext().getObjectFileInfo()->getDwarfAccelNamesSection(),
       Asm.getContext().getObjectFileInfo()->getDwarfAccelTypesSection(),
-      Asm.getContext().getObjectFileInfo()->getDwarfAccelNamespaceSection()};
+      Asm.getContext().getObjectFileInfo()->getDwarfAccelNamespaceSection(),
+      Asm.getContext().getObjectFileInfo()->getDwarfAccelObjCSection()};
 }
 
 Error MCCASBuilder::prepare() {
@@ -2770,6 +2792,23 @@ Error MCCASBuilder::createAppleNamespaceSection() {
   return finalizeSection<AppleNamespaceSectionRef>();
 }
 
+Error MCCASBuilder::createAppleObjCSection() {
+
+  auto MaybeAppleObjCRef =
+      createGenericDebugRef<AppleObjCRef>(DwarfSections.AppleObjC);
+  if (!MaybeAppleObjCRef)
+    return Error::success();
+
+  if (!*MaybeAppleObjCRef)
+    return MaybeAppleObjCRef->takeError();
+
+  startSection(DwarfSections.AppleObjC);
+  addNode(**MaybeAppleObjCRef);
+  if (auto E = createPaddingRef(DwarfSections.AppleObjC))
+    return E;
+  return finalizeSection<AppleObjCSectionRef>();
+}
+
 static ArrayRef<char> getFragmentContents(const MCFragment &Fragment) {
   switch (Fragment.getKind()) {
 #define MCFRAGMENT_NODE_REF(MCFragmentName, MCEnumName, MCEnumIdentifier)      \
@@ -2971,6 +3010,13 @@ Error MCCASBuilder::buildFragments() {
       continue;
     }
 
+    // Handle Debug AppleObjC sections separately.
+    if (&Sec == DwarfSections.AppleObjC) {
+      if (auto E = createAppleObjCSection())
+        return E;
+      continue;
+    }
+
     // Start Subsection for one section.
     startSection(&Sec);
 
@@ -3135,7 +3181,7 @@ void MCCASBuilder::startSection(const MCSection *Sec) {
           Sec != DwarfSections.Rangelists && Sec != DwarfSections.LineStr &&
           Sec != DwarfSections.Names && Sec != DwarfSections.AppleNames &&
           Sec != DwarfSections.AppleTypes &&
-          Sec != DwarfSections.AppleNamespace)
+          Sec != DwarfSections.AppleNamespace && Sec != DwarfSections.AppleObjC)
         RelMap[R.F].push_back(R.MRE);
       else
         // If the fragment is nullptr, it should a section with only relocation
@@ -3358,6 +3404,8 @@ Expected<uint64_t> MCCASReader::materializeGroup(cas::ObjectRef ID) {
     return F->materialize(*this);
   if (auto F = AppleNamespaceSectionRef::Cast(*Node))
     return F->materialize(*this);
+  if (auto F = AppleObjCSectionRef::Cast(*Node))
+    return F->materialize(*this);
   if (auto F = CStringRef::Cast(*Node)) {
     auto Size = F->materialize(OS);
     if (!Size)
@@ -3442,6 +3490,8 @@ Expected<uint64_t> MCCASReader::materializeSection(cas::ObjectRef ID,
     return F->materialize(*Stream);
   if (auto F = AppleNamespaceRef::Cast(*Node))
     return F->materialize(*Stream);
+  if (auto F = AppleObjCRef::Cast(*Node))
+    return F->materialize(*Stream);
   if (auto F = AddendsRef::Cast(*Node))
     // AddendsRef is already handled when materializing Atoms, skip.
     return 0;