Optimizer: remove the -experimental-swift-based-closure-specialization option

Author: eeckstein

include/swift/AST/SILOptions.h

@@ -303,10 +303,6 @@ class SILOptions {
   /// Are we building in embedded Swift + -no-allocations?
   bool NoAllocations = false;
 
-  /// Should we use the experimental Swift based closure-specialization
-  /// optimization pass instead of the existing C++ one.
-  bool EnableExperimentalSwiftBasedClosureSpecialization = false;
-
   /// The name of the file to which the backend should save optimization
   /// records.
   std::string OptRecordFile;

include/swift/Option/FrontendOptions.td

@@ -393,10 +393,6 @@ def public_autolink_library :
 // HIDDEN FLAGS
 let Flags = [FrontendOption, NoDriverOption, HelpHidden] in {
 
-def enable_experimental_swift_based_closure_specialization :
-  Flag<["-"], "experimental-swift-based-closure-specialization">,
-  HelpText<"Use the experimental Swift based closure-specialization optimization pass instead of the existing C++ one">;
-
 def checked_async_objc_bridging : Joined<["-"], "checked-async-objc-bridging=">,
   HelpText<"Control whether checked continuations are used when bridging "
            "async calls from Swift to ObjC: 'on', 'off' ">;

lib/Frontend/CompilerInvocation.cpp

@@ -3226,9 +3226,6 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
 
   Opts.NoAllocations = Args.hasArg(OPT_no_allocations);
 
-  Opts.EnableExperimentalSwiftBasedClosureSpecialization =
-      Args.hasArg(OPT_enable_experimental_swift_based_closure_specialization);
-
   // If these optimizations are enabled never preserve functions for the
   // debugger.
   Opts.ShouldFunctionsBePreservedToDebugger =

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -789,12 +789,8 @@ static void addClosureSpecializePassPipeline(SILPassPipelinePlan &P) {
   // take advantage of static dispatch.
   P.addConstantCapturePropagation();
 
-  // Specialize closure.
-  if (P.getOptions().EnableExperimentalSwiftBasedClosureSpecialization) {
-    P.addExperimentalSwiftBasedClosureSpecialization();
-  } else {
-    P.addClosureSpecializer();
-  }
+  // TODO: replace this with the new ClosureSpecialization pass once we have OSSA at this point in the pipeline
+  P.addClosureSpecializer();
 
   // Do the second stack promotion on low-level SIL.
   P.addStackPromotion();