Merge pull request #34626 from nkcsgexi/opt-out-forwarding

driver: add an option to avoid forwarding to the new driver

Author: nkcsgexi

include/swift/Option/Options.td

@@ -177,6 +177,10 @@ def verify_incremental_dependencies :
   Flags<[FrontendOption, HelpHidden]>,
   HelpText<"Enable the dependency verifier for each frontend job">;
 
+def disallow_forwarding_driver :
+  Flag<["-"], "disallow-use-new-driver">, Flags<[]>,
+  HelpText<"Disable using new swift-driver">;
+
 def driver_emit_fine_grained_dependency_dot_file_after_every_import :
 Flag<["-"], "driver-emit-fine-grained-dependency-dot-file-after-every-import">,
 InternalDebugOpt,

tools/driver/driver.cpp

@@ -164,10 +164,12 @@ static int run_driver(StringRef ExecName,
   if (auto driverNameOp = llvm::sys::Process::GetEnv("SWIFT_USE_NEW_DRIVER")) {
     newDriverName = driverNameOp.getValue();
   }
-
+  auto disallowForwarding = llvm::find_if(argv, [](const char* arg) {
+    return StringRef(arg) == "-disallow-use-new-driver";
+  }) != argv.end();
   // Forwarding calls to the swift driver if the C++ driver is invoked as `swift`
   // or `swiftc`, and an environment variable SWIFT_USE_NEW_DRIVER is defined.
-  if (!newDriverName.empty() &&
+  if (!newDriverName.empty() && !disallowForwarding &&
       (ExecName == "swift" || ExecName == "swiftc")) {
     SmallString<256> NewDriverPath(llvm::sys::path::parent_path(Path));
     llvm::sys::path::append(NewDriverPath, newDriverName);