[clang] [clang] Introduce copy-on-write `CompilerInvocation` (PR #65412)

[Ben Langmuir via cfe-commits]

================
@@ -123,49 +123,101 @@ static Expected<std::optional<uint32_t>> parseToleranceOption(StringRef Arg) {
 }
 
 //===----------------------------------------------------------------------===//
-// Initialization.
+// Storage details.
 //===----------------------------------------------------------------------===//
 
-CompilerInvocationRefBase::CompilerInvocationRefBase()
-    : LangOpts(new LangOptions()), TargetOpts(new TargetOptions()),
-      DiagnosticOpts(new DiagnosticOptions()),
-      HeaderSearchOpts(new HeaderSearchOptions()),
-      PreprocessorOpts(new PreprocessorOptions()),
-      AnalyzerOpts(new AnalyzerOptions()) {}
-
-CompilerInvocationRefBase::CompilerInvocationRefBase(
-    const CompilerInvocationRefBase &X)
-    : LangOpts(new LangOptions(X.getLangOpts())),
-      TargetOpts(new TargetOptions(X.getTargetOpts())),
-      DiagnosticOpts(new DiagnosticOptions(X.getDiagnosticOpts())),
-      HeaderSearchOpts(new HeaderSearchOptions(X.getHeaderSearchOpts())),
-      PreprocessorOpts(new PreprocessorOptions(X.getPreprocessorOpts())),
-      AnalyzerOpts(new AnalyzerOptions(X.getAnalyzerOpts())) {}
-
-CompilerInvocationRefBase::CompilerInvocationRefBase(
-    CompilerInvocationRefBase &&X) = default;
-
-CompilerInvocationRefBase &
-CompilerInvocationRefBase::operator=(CompilerInvocationRefBase X) {
-  LangOpts.swap(X.LangOpts);
-  TargetOpts.swap(X.TargetOpts);
-  DiagnosticOpts.swap(X.DiagnosticOpts);
-  HeaderSearchOpts.swap(X.HeaderSearchOpts);
-  PreprocessorOpts.swap(X.PreprocessorOpts);
-  AnalyzerOpts.swap(X.AnalyzerOpts);
+namespace clang::CompilerInvocationDetail {
+namespace {
+template <class T> std::shared_ptr<T> make_shared(const T &X) {
+  return std::make_shared<T>(X);
+}
+
+template <class T> llvm::IntrusiveRefCntPtr<T> makeIntrusiveRefCnt(const T &X) {
+  return llvm::makeIntrusiveRefCnt<T>(X);
+}
+} // namespace
+
+RefBase::RefBase()
+    : LangOpts(std::make_shared<LangOptions>()),
+      TargetOpts(std::make_shared<TargetOptions>()),
+      DiagnosticOpts(llvm::makeIntrusiveRefCnt<DiagnosticOptions>()),
+      HeaderSearchOpts(std::make_shared<HeaderSearchOptions>()),
+      PreprocessorOpts(std::make_shared<PreprocessorOptions>()),
+      AnalyzerOpts(llvm::makeIntrusiveRefCnt<AnalyzerOptions>()) {}
+
+RefBase::RefBase(const RefBase &X, DeepCopy)
----------------
benlangmuir wrote:

Would it make sense to implement these constructors using `assign`?

https://github.com/llvm/llvm-project/pull/65412