[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, 8 insertions, 8 deletions

diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
index 8c75e1a..d14d091 100644
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -685,21 +685,21 @@ namespace {
       return false;
     }
 
-    bool ReadDiagnosticOptions(IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts,
+    bool ReadDiagnosticOptions(DiagnosticOptions &DiagOpts,
                                StringRef ModuleFilename,
                                bool Complain) override {
       Out.indent(2) << "Diagnostic options:\n";
-#define DIAGOPT(Name, Bits, Default) DUMP_BOOLEAN(DiagOpts->Name, #Name);
-#define ENUM_DIAGOPT(Name, Type, Bits, Default) \
-      Out.indent(4) << #Name << ": " << DiagOpts->get##Name() << "\n";
-#define VALUE_DIAGOPT(Name, Bits, Default) \
-      Out.indent(4) << #Name << ": " << DiagOpts->Name << "\n";
+#define DIAGOPT(Name, Bits, Default) DUMP_BOOLEAN(DiagOpts.Name, #Name);
+#define ENUM_DIAGOPT(Name, Type, Bits, Default)                              \
+    Out.indent(4) << #Name << ": " << DiagOpts.get##Name() << "\n";
+#define VALUE_DIAGOPT(Name, Bits, Default)                                   \
+    Out.indent(4) << #Name << ": " << DiagOpts.Name << "\n";
 #include "clang/Basic/DiagnosticOptions.def"
 
       Out.indent(4) << "Diagnostic flags:\n";
-      for (const std::string &Warning : DiagOpts->Warnings)
+      for (const std::string &Warning : DiagOpts.Warnings)
         Out.indent(6) << "-W" << Warning << "\n";
-      for (const std::string &Remark : DiagOpts->Remarks)
+      for (const std::string &Remark : DiagOpts.Remarks)
         Out.indent(6) << "-R" << Remark << "\n";
 
       return false;