Sema: Add -disable-optimized-restrictions flag

Author: slavapestov

include/swift/Basic/LangOptions.h

@@ -926,6 +926,9 @@ namespace swift {
 
     /// Disable the component splitter phase of the expression type checker.
     bool SolverDisableSplitter = false;
+
+    /// Disable some experimental optimizations.
+    bool DisableOptimizedRestrictions = false;
   };
 
   /// Options for controlling the behavior of the Clang importer.

include/swift/Option/FrontendOptions.td

@@ -849,6 +849,9 @@ def solver_disable_splitter : Flag<["-"], "solver-disable-splitter">,
 def disable_constraint_solver_performance_hacks : Flag<["-"], "disable-constraint-solver-performance-hacks">,
   HelpText<"Disable all the hacks in the constraint solver">;
 
+def disable_optimized_restrictions : Flag<["-"], "disable-optimized-restrictions">,
+  HelpText<"Disable an experimental constraint solver optimization">;
+
 def enable_operator_designated_types :
   Flag<["-"], "enable-operator-designated-types">,
   HelpText<"Enable operator designated types">;

lib/Frontend/CompilerInvocation.cpp

@@ -1865,6 +1865,9 @@ static bool ParseTypeCheckerArgs(TypeCheckerOptions &Opts, ArgList &Args,
   if (Args.getLastArg(OPT_solver_disable_splitter))
     Opts.SolverDisableSplitter = true;
 
+  if (Args.getLastArg(OPT_disable_optimized_restrictions))
+    Opts.DisableOptimizedRestrictions = true;
+
   if (FrontendOpts.RequestedAction == FrontendOptions::ActionType::Immediate)
     Opts.DeferToRuntime = true;