[clang] [clangd] Fix C++20 modules crash (PR #81919)

[via cfe-commits]

https://github.com/CLRN created https://github.com/llvm/llvm-project/pull/81919

This fix partially reverts https://github.com/llvm/llvm-project/commit/a0b6747804e46665ecfd00295b60432bfe1775b6.

The serialization part is restored to the state prior to the mentioned commit as it causing issue with reading back Decl.
ODR checks logic is kept in place.

Close https://github.com/llvm/llvm-project/issues/80570.

>From dae725e0c48837a18aa9b90945de0b86a33890ff Mon Sep 17 00:00:00 2001
From: clrn <clrnmail at gmail.com>
Date: Thu, 15 Feb 2024 20:41:34 +0000
Subject: [PATCH] [clangd] Fix C++20 modules crash

This fix partially reverts https://github.com/llvm/llvm-project/commit/a0b6747804e46665ecfd00295b60432bfe1775b6.

The serialization part is restored to the state prior to the mentioned commit as it causing issue with reading back Decl.
ODR checks logic is kept in place.

Close https://github.com/llvm/llvm-project/issues/80570.
---
 clang/lib/Serialization/ASTReaderDecl.cpp | 21 +++++++--------------
 clang/lib/Serialization/ASTWriter.cpp     |  9 +++------
 clang/lib/Serialization/ASTWriterDecl.cpp |  8 ++------
 3 files changed, 12 insertions(+), 26 deletions(-)

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index ffba04f28782ea..4e58301a6b8eef 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -804,10 +804,8 @@ void ASTDeclReader::VisitEnumDecl(EnumDecl *ED) {
   ED->setScopedUsingClassTag(EnumDeclBits.getNextBit());
   ED->setFixed(EnumDeclBits.getNextBit());
 
-  if (!shouldSkipCheckingODR(ED)) {
-    ED->setHasODRHash(true);
-    ED->ODRHash = Record.readInt();
-  }
+  ED->setHasODRHash(true);
+  ED->ODRHash = Record.readInt();
 
   // If this is a definition subject to the ODR, and we already have a
   // definition, merge this one into it.
@@ -1102,10 +1100,8 @@ void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
   if (FD->isExplicitlyDefaulted())
     FD->setDefaultLoc(readSourceLocation());
 
-  if (!shouldSkipCheckingODR(FD)) {
-    FD->ODRHash = Record.readInt();
-    FD->setHasODRHash(true);
-  }
+  FD->ODRHash = Record.readInt();
+  FD->setHasODRHash(true);
 
   if (FD->isDefaulted()) {
     if (unsigned NumLookups = Record.readInt()) {
@@ -1981,12 +1977,9 @@ void ASTDeclReader::ReadCXXDefinitionData(
 #include "clang/AST/CXXRecordDeclDefinitionBits.def"
 #undef FIELD
 
-  // We only perform ODR checks for decls not in GMF.
-  if (!shouldSkipCheckingODR(D)) {
-    // Note: the caller has deserialized the IsLambda bit already.
-    Data.ODRHash = Record.readInt();
-    Data.HasODRHash = true;
-  }
+  // Note: the caller has deserialized the IsLambda bit already.
+  Data.ODRHash = Record.readInt();
+  Data.HasODRHash = true;
 
   if (Record.readInt()) {
     Reader.DefinitionSource[D] =
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 740bec586a5e33..31789cfb289154 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6068,12 +6068,9 @@ void ASTRecordWriter::AddCXXDefinitionData(const CXXRecordDecl *D) {
 
   Record->push_back(DefinitionBits);
 
-  // We only perform ODR checks for decls not in GMF.
-  if (!shouldSkipCheckingODR(D)) {
-    // getODRHash will compute the ODRHash if it has not been previously
-    // computed.
-    Record->push_back(D->getODRHash());
-  }
+  // getODRHash will compute the ODRHash if it has not been previously
+  // computed.
+  Record->push_back(D->getODRHash());
 
   bool ModulesDebugInfo =
       Writer->Context->getLangOpts().ModulesDebugInfo && !D->isDependentType();
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index f224075643e998..496c0fdbe0ebf6 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -493,9 +493,7 @@ void ASTDeclWriter::VisitEnumDecl(EnumDecl *D) {
   EnumDeclBits.addBit(D->isFixed());
   Record.push_back(EnumDeclBits);
 
-  // We only perform ODR checks for decls not in GMF.
-  if (!shouldSkipCheckingODR(D))
-    Record.push_back(D->getODRHash());
+  Record.push_back(D->getODRHash());
 
   if (MemberSpecializationInfo *MemberInfo = D->getMemberSpecializationInfo()) {
     Record.AddDeclRef(MemberInfo->getInstantiatedFrom());
@@ -703,9 +701,7 @@ void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
   if (D->isExplicitlyDefaulted())
     Record.AddSourceLocation(D->getDefaultLoc());
 
-  // We only perform ODR checks for decls not in GMF.
-  if (!shouldSkipCheckingODR(D))
-    Record.push_back(D->getODRHash());
+  Record.push_back(D->getODRHash());
 
   if (D->isDefaulted()) {
     if (auto *FDI = D->getDefaultedFunctionInfo()) {