[DRAFT][SYCL RTC] Implement --auto-pch support

clang/include/clang/Driver/Options.h

@@ -41,6 +41,7 @@ enum ClangVisibility {
   FlangOption = (1 << 4),
   FC1Option = (1 << 5),
   DXCOption = (1 << 6),
+  SYCLRTCOnlyOption = (1 << 7),
 };
 
 enum ID {

clang/include/clang/Driver/Options.td

@@ -107,6 +107,8 @@ def FC1Option : OptionVisibility;
 // are made available when the driver is running in DXC compatibility mode.
 def DXCOption : OptionVisibility;
 
+def SYCLRTCOnlyOption : OptionVisibility;
+
 /////////
 // Docs
 
@@ -195,6 +197,11 @@ def sycl_Group : OptionGroup<"<SYCL group>">, Group<f_Group>,
                  DocName<"SYCL options">,
                  Visibility<[ClangOption, CLOption]>;
 
+def sycl_rtc_only_Group : OptionGroup<"<SYCL RTC only group">,
+                          Group<f_Group>,
+                          DocName<"SYCL RTC specific options">,
+                          Visibility<[SYCLRTCOnlyOption]>;
+
 def cuda_Group : OptionGroup<"<CUDA group>">, Group<f_Group>,
                    DocName<"CUDA options">,
                    Visibility<[ClangOption, CLOption]>;
@@ -7460,6 +7467,13 @@ def fsyclbin : Flag<["-"], "fsyclbin">, Alias<fsyclbin_EQ>,
   AliasArgs<["executable"]>;
 } // let Group = sycl_Group
 
+let Visibility = [SYCLRTCOnlyOption] in {
+  let Group = sycl_rtc_only_Group in {
+    def auto_pch : Flag<["--"], "auto-pch">,
+                   HelpText<"Enable Auto-PCH for SYCL RTC Compilation">;
+  } // let Group = sycl_rtc_only_Group
+} // let Visibility = [SYCLRTCOnlyOption]
+
 // FIXME: -fsycl-explicit-simd is deprecated. remove it when support is dropped.
 def : Flag<["-"], "fsycl-explicit-simd">, Flags<[Deprecated]>,
   Group<clang_ignored_legacy_options_Group>,

clang/include/clang/Frontend/PrecompiledPreamble.h

@@ -87,8 +87,8 @@ class PrecompiledPreamble {
         DiagnosticsEngine &Diagnostics,
         IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
         std::shared_ptr<PCHContainerOperations> PCHContainerOps,
-        bool StoreInMemory, StringRef StoragePath,
-        PreambleCallbacks &Callbacks);
+        bool StoreInMemory, StringRef StoragePath, PreambleCallbacks &Callbacks,
+        bool AllowASTWithErrors = true);
 
   PrecompiledPreamble(PrecompiledPreamble &&);
   PrecompiledPreamble &operator=(PrecompiledPreamble &&);

clang/lib/Frontend/PrecompiledPreamble.cpp

@@ -249,9 +249,10 @@ class TempPCHFile {
 class PrecompilePreambleAction : public ASTFrontendAction {
 public:
   PrecompilePreambleAction(std::shared_ptr<PCHBuffer> Buffer, bool WritePCHFile,
-                           PreambleCallbacks &Callbacks)
+                           PreambleCallbacks &Callbacks,
+                           bool AllowASTWithErrors = true)
       : Buffer(std::move(Buffer)), WritePCHFile(WritePCHFile),
-        Callbacks(Callbacks) {}
+        Callbacks(Callbacks), AllowASTWithErrors(AllowASTWithErrors) {}
 
   std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                  StringRef InFile) override;
@@ -287,16 +288,18 @@ class PrecompilePreambleAction : public ASTFrontendAction {
   bool WritePCHFile; // otherwise the PCH is written into the PCHBuffer only.
   std::unique_ptr<llvm::raw_pwrite_stream> FileOS; // null if in-memory
   PreambleCallbacks &Callbacks;
+  bool AllowASTWithErrors;
 };
 
 class PrecompilePreambleConsumer : public PCHGenerator {
 public:
   PrecompilePreambleConsumer(PrecompilePreambleAction &Action, Preprocessor &PP,
                              ModuleCache &ModCache, StringRef isysroot,
-                             std::shared_ptr<PCHBuffer> Buffer)
+                             std::shared_ptr<PCHBuffer> Buffer,
+                             bool AllowASTWithErrors = true)
       : PCHGenerator(PP, ModCache, "", isysroot, std::move(Buffer),
                      ArrayRef<std::shared_ptr<ModuleFileExtension>>(),
-                     /*AllowASTWithErrors=*/true),
+                     AllowASTWithErrors),
         Action(Action) {}
 
   bool HandleTopLevelDecl(DeclGroupRef DG) override {
@@ -337,7 +340,8 @@ PrecompilePreambleAction::CreateASTConsumer(CompilerInstance &CI,
     Sysroot.clear();
 
   return std::make_unique<PrecompilePreambleConsumer>(
-      *this, CI.getPreprocessor(), CI.getModuleCache(), Sysroot, Buffer);
+      *this, CI.getPreprocessor(), CI.getModuleCache(), Sysroot, Buffer,
+      AllowASTWithErrors);
 }
 
 template <class T> bool moveOnNoError(llvm::ErrorOr<T> Val, T &Output) {
@@ -415,7 +419,8 @@ llvm::ErrorOr<PrecompiledPreamble> PrecompiledPreamble::Build(
     DiagnosticsEngine &Diagnostics,
     IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
     std::shared_ptr<PCHContainerOperations> PCHContainerOps, bool StoreInMemory,
-    StringRef StoragePath, PreambleCallbacks &Callbacks) {
+    StringRef StoragePath, PreambleCallbacks &Callbacks,
+    bool AllowASTWithErrors) {
   assert(VFS && "VFS is null");
 
   auto PreambleInvocation = std::make_shared<CompilerInvocation>(Invocation);
@@ -511,7 +516,7 @@ llvm::ErrorOr<PrecompiledPreamble> PrecompiledPreamble::Build(
   auto Act = std::make_unique<PrecompilePreambleAction>(
       std::move(Buffer),
       /*WritePCHFile=*/Storage->getKind() == PCHStorage::Kind::TempFile,
-      Callbacks);
+      Callbacks, AllowASTWithErrors);
   if (!Act->BeginSourceFile(*Clang, Clang->getFrontendOpts().Inputs[0]))
     return BuildPreambleError::BeginSourceFileFailed;
 

clang/test/Driver/sycl-unsupported.cpp

@@ -64,6 +64,15 @@
 // UNSUPPORTED_OPT-NOT: clang{{.*}} "-fsycl-is-device"{{.*}} "[[OPT_CC1]]{{.*}}"
 // UNSUPPORTED_OPT: clang{{.*}} "-fsycl-is-host"{{.*}} "[[OPT_CC1]]{{.*}}"
 
+// "--auto-pch" should only be enabled for SYCL RTC compilations, regular driver
+// shouldn't know about it:
+//
+// RUN: not %clangxx                    -### %s --auto-pch 2>&1 | FileCheck %s --check-prefix AUTO_PCH
+// RUN: not %clangxx -fsycl-device-only -### %s --auto-pch 2>&1 | FileCheck %s --check-prefix AUTO_PCH
+// RUN: not %clangxx -fsycl             -### %s --auto-pch 2>&1 | FileCheck %s --check-prefix AUTO_PCH
+//
+// AUTO_PCH: error: unknown argument: '--auto-pch'
+
 // FPGA support has been removed, usage of any FPGA specific options and any
 // options that have FPGA specific arguments should emit a specific error
 // diagnostic.