[clang] [WIP][Modules] Delay deserialization of preferred_name attribute at r… (PR #122726)

[Ilya Biryukov via cfe-commits]

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@@ -4424,6 +4454,51 @@ void ASTReader::loadPendingDeclChain(Decl *FirstLocal, uint64_t LocalOffset) {
   ASTDeclReader::attachLatestDecl(CanonDecl, MostRecent);
 }
 
+void ASTReader::loadPreferredNameAttribute(
+    const PendingPreferredNameAttribute &PreferredNameAttribute) {
+  Decl *D = PreferredNameAttribute.D;
+  ModuleFile *M = getOwningModuleFile(D);
+
+  unsigned LocalDeclIndex = D->getGlobalID().getLocalDeclIndex();
+  const DeclOffset &DOffs = M->DeclOffsets[LocalDeclIndex];
+  RecordLocation Loc(M, DOffs.getBitOffset(M->DeclsBlockStartOffset));
+
+  llvm::BitstreamCursor &Cursor = Loc.F->DeclsCursor;
+  SavedStreamPosition SavedPosition(Cursor);
+  if (llvm::Error Err = Cursor.JumpToBit(Loc.Offset)) {
+    Error(std::move(Err));
+  }
+
+  Expected<unsigned> MaybeCode = Cursor.ReadCode();
+  if (!MaybeCode) {
+    llvm::report_fatal_error(
+        Twine("ASTReader::loadPreferredNameAttribute failed reading code: ") +
+        toString(MaybeCode.takeError()));
+  }
+  unsigned Code = MaybeCode.get();
+
+  ASTRecordReader Record(*this, *Loc.F);
+  Expected<unsigned> MaybeRecCode = Record.readRecord(Cursor, Code);
+  if (!MaybeRecCode) {
+    llvm::report_fatal_error(
+        Twine(
+            "ASTReader::loadPreferredNameAttribute failed reading rec code: ") +
+        toString(MaybeCode.takeError()));
+  }
+  unsigned RecCode = MaybeRecCode.get();
+  if (RecCode != DECL_CXX_RECORD) {
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ilya-biryukov wrote:

Any reason to limit this to this particular `Decl`?
I think having a generic mechanism that works for any decls is fine here, just in case we need to defer more attributes.

https://github.com/llvm/llvm-project/pull/122726