[clang] Remove intrusive reference count from `DiagnosticOptions` (#139584)

The `DiagnosticOptions` class is currently intrusively
reference-counted, which makes reasoning about its lifetime very
difficult in some cases. For example, `CompilerInvocation` owns the
`DiagnosticOptions` instance (wrapped in `llvm::IntrusiveRefCntPtr`) and
only exposes an accessor returning `DiagnosticOptions &`. One would
think this gives `CompilerInvocation` exclusive ownership of the object,
but that's not the case:

```c++
void shareOwnership(CompilerInvocation &CI) {
  llvm::IntrusiveRefCntPtr<DiagnosticOptions> CoOwner = &CI.getDiagnosticOptions();
  // ...
}
```

This is a perfectly valid pattern that is being actually used in the
codebase.

I would like to ensure the ownership of `DiagnosticOptions` by
`CompilerInvocation` is guaranteed to be exclusive. This can be
leveraged for a copy-on-write optimization later on. This PR changes
usages of `DiagnosticOptions` across `clang`, `clang-tools-extra` and
`lldb` to not be intrusively reference-counted.

1 files changed, 12 insertions, 2 deletions

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 5a79fe0..457043c 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -803,7 +803,8 @@ void ASTUnit::ConfigureDiags(IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
 
 std::unique_ptr<ASTUnit> ASTUnit::LoadFromASTFile(
     StringRef Filename, const PCHContainerReader &PCHContainerRdr,
-    WhatToLoad ToLoad, IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+    WhatToLoad ToLoad, std::shared_ptr<DiagnosticOptions> DiagOpts,
+    IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
     const FileSystemOptions &FileSystemOpts, const HeaderSearchOptions &HSOpts,
     const LangOptions *LangOpts, bool OnlyLocalDecls,
     CaptureDiagsKind CaptureDiagnostics, bool AllowASTWithCompilerErrors,
@@ -823,6 +824,7 @@ std::unique_ptr<ASTUnit> ASTUnit::LoadFromASTFile(
                            : std::make_unique<LangOptions>();
   AST->OnlyLocalDecls = OnlyLocalDecls;
   AST->CaptureDiagnostics = CaptureDiagnostics;
+  AST->DiagOpts = DiagOpts;
   AST->Diagnostics = Diags;
   AST->FileMgr = new FileManager(FileSystemOpts, VFS);
   AST->UserFilesAreVolatile = UserFilesAreVolatile;
@@ -1534,6 +1536,7 @@ StringRef ASTUnit::getASTFileName() const {
 
 std::unique_ptr<ASTUnit>
 ASTUnit::create(std::shared_ptr<CompilerInvocation> CI,
+                std::shared_ptr<DiagnosticOptions> DiagOpts,
                 IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
                 CaptureDiagsKind CaptureDiagnostics,
                 bool UserFilesAreVolatile) {
@@ -1541,6 +1544,7 @@ ASTUnit::create(std::shared_ptr<CompilerInvocation> CI,
   ConfigureDiags(Diags, *AST, CaptureDiagnostics);
   IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS =
       createVFSFromCompilerInvocation(*CI, *Diags);
+  AST->DiagOpts = DiagOpts;
   AST->Diagnostics = Diags;
   AST->FileSystemOpts = CI->getFileSystemOpts();
   AST->Invocation = std::move(CI);
@@ -1556,6 +1560,7 @@ ASTUnit::create(std::shared_ptr<CompilerInvocation> CI,
 ASTUnit *ASTUnit::LoadFromCompilerInvocationAction(
     std::shared_ptr<CompilerInvocation> CI,
     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+    std::shared_ptr<DiagnosticOptions> DiagOpts,
     IntrusiveRefCntPtr<DiagnosticsEngine> Diags, FrontendAction *Action,
     ASTUnit *Unit, bool Persistent, StringRef ResourceFilesPath,
     bool OnlyLocalDecls, CaptureDiagsKind CaptureDiagnostics,
@@ -1567,7 +1572,8 @@ ASTUnit *ASTUnit::LoadFromCompilerInvocationAction(
   ASTUnit *AST = Unit;
   if (!AST) {
     // Create the AST unit.
-    OwnAST = create(CI, Diags, CaptureDiagnostics, UserFilesAreVolatile);
+    OwnAST =
+        create(CI, DiagOpts, Diags, CaptureDiagnostics, UserFilesAreVolatile);
     AST = OwnAST.get();
     if (!AST)
       return nullptr;
@@ -1729,6 +1735,7 @@ bool ASTUnit::LoadFromCompilerInvocation(
 std::unique_ptr<ASTUnit> ASTUnit::LoadFromCompilerInvocation(
     std::shared_ptr<CompilerInvocation> CI,
     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+    std::shared_ptr<DiagnosticOptions> DiagOpts,
     IntrusiveRefCntPtr<DiagnosticsEngine> Diags, FileManager *FileMgr,
     bool OnlyLocalDecls, CaptureDiagsKind CaptureDiagnostics,
     unsigned PrecompilePreambleAfterNParses, TranslationUnitKind TUKind,
@@ -1737,6 +1744,7 @@ std::unique_ptr<ASTUnit> ASTUnit::LoadFromCompilerInvocation(
   // Create the AST unit.
   std::unique_ptr<ASTUnit> AST(new ASTUnit(false));
   ConfigureDiags(Diags, *AST, CaptureDiagnostics);
+  AST->DiagOpts = DiagOpts;
   AST->Diagnostics = Diags;
   AST->OnlyLocalDecls = OnlyLocalDecls;
   AST->CaptureDiagnostics = CaptureDiagnostics;
@@ -1766,6 +1774,7 @@ std::unique_ptr<ASTUnit> ASTUnit::LoadFromCompilerInvocation(
 std::unique_ptr<ASTUnit> ASTUnit::LoadFromCommandLine(
     const char **ArgBegin, const char **ArgEnd,
     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+    std::shared_ptr<DiagnosticOptions> DiagOpts,
     IntrusiveRefCntPtr<DiagnosticsEngine> Diags, StringRef ResourceFilesPath,
     bool StorePreamblesInMemory, StringRef PreambleStoragePath,
     bool OnlyLocalDecls, CaptureDiagsKind CaptureDiagnostics,
@@ -1828,6 +1837,7 @@ std::unique_ptr<ASTUnit> ASTUnit::LoadFromCommandLine(
   AST->NumStoredDiagnosticsFromDriver = StoredDiagnostics.size();
   AST->StoredDiagnostics.swap(StoredDiagnostics);
   ConfigureDiags(Diags, *AST, CaptureDiagnostics);
+  AST->DiagOpts = DiagOpts;
   AST->Diagnostics = Diags;
   AST->FileSystemOpts = CI->getFileSystemOpts();
   VFS = createVFSFromCompilerInvocation(*CI, *Diags, VFS);