[lldb] Add setting to disable PCM validation (from Swift)

lldb/include/lldb/Target/Target.h

@@ -188,6 +188,8 @@ class TargetProperties : public Properties {
 
   bool GetSwiftAllowExplicitModules() const;
 
+  bool GetSwiftDisablePCMValidation() const;
+
   Args GetSwiftPluginServerForPath() const;
 
   bool GetSwiftAutoImportFrameworks() const;

lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp

@@ -57,7 +57,9 @@
 #include "clang/Basic/TargetOptions.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Frontend/CompilerInstance.h"
+#include "clang/Lex/Preprocessor.h"
 
+#include "clang/Lex/PreprocessorOptions.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
@@ -3748,6 +3750,12 @@ ThreadSafeASTContext SwiftASTContext::GetASTContext() {
   // 4. Install the clang importer.
   if (clang_importer_ap) {
     m_clangimporter = (swift::ClangImporter *)clang_importer_ap.get();
+    TargetSP target_sp = GetTargetWP().lock();
+    if (target_sp && target_sp->GetSwiftDisablePCMValidation())
+      m_clangimporter->getClangPreprocessor()
+          .getPreprocessorOpts()
+          .DisablePCHOrModuleValidation =
+          clang::DisableValidationForModuleKind::Module;
     m_ast_context_ap->addModuleLoader(std::move(clang_importer_ap),
                                       /*isClang=*/true);
     m_clangimporter_typesystem = std::make_shared<TypeSystemClang>(

lldb/source/Target/Target.cpp

@@ -4927,6 +4927,19 @@ bool TargetProperties::GetSwiftAllowExplicitModules() const {
   return true;
 }
 
+bool TargetProperties::GetSwiftDisablePCMValidation() const {
+  const Property *exp_property =
+      m_collection_sp->GetPropertyAtIndex(ePropertyExperimental);
+  OptionValueProperties *exp_values =
+      exp_property->GetValue()->GetAsProperties();
+  if (exp_values)
+    return exp_values
+        ->GetPropertyAtIndexAs<bool>(ePropertySwiftDisablePCMValidation)
+        .value_or(true);
+
+  return true;
+}
+
 Args TargetProperties::GetSwiftPluginServerForPath() const {
   const uint32_t idx = ePropertySwiftPluginServerForPath;
 

lldb/source/Target/TargetProperties.td

@@ -26,6 +26,9 @@ let Definition = "target_experimental" in {
   def SwiftAllowExplicitModules: Property<"swift-allow-explicit-modules", "Boolean">,
     DefaultTrue,
     Desc<"Allows explicit module flags to be passed through to ClangImporter.">;
+  def SwiftDisablePCMValidation: Property<"swift-disable-pcm-validation", "Boolean">,
+    DefaultFalse,
+    Desc<"Disable validation when loading Clang PCM files (-fno-validate-pch).">;
 }
 
 let Definition = "target" in {