NFC: throws prediction frontend flag

Author: kavon

include/swift/AST/SILOptions.h

@@ -118,6 +118,10 @@ class SILOptions {
   /// Controls whether to run async demotion pass.
   bool EnableAsyncDemotion = false;
 
+  /// Controls whether to always assume that functions rarely throw an Error
+  /// within the optimizer. This influences static branch prediction.
+  bool EnableThrowsPrediction = false;
+
   /// Should we run any SIL performance optimizations
   ///
   /// Useful when you want to enable -O LLVM opts but not -O SIL opts.

include/swift/Option/FrontendOptions.td

@@ -540,6 +540,11 @@ def enable_spec_devirt : Flag<["-"], "enable-spec-devirt">,
 def enable_async_demotion : Flag<["-"], "enable-experimental-async-demotion">,
   HelpText<"Enables an optimization pass to demote async functions.">;
 
+def enable_throws_prediction : Flag<["-"], "enable-throws-prediction">,
+  HelpText<"Enables optimization assumption that functions rarely throw errors.">;
+def disable_throws_prediction : Flag<["-"], "disable-throws-prediction">,
+  HelpText<"Disables optimization assumption that functions rarely throw errors.">;
+
 def disable_access_control : Flag<["-"], "disable-access-control">,
   HelpText<"Don't respect access control restrictions">;
 def enable_access_control : Flag<["-"], "enable-access-control">,

lib/DriverTool/sil_opt_main.cpp

@@ -289,6 +289,10 @@ struct SILOptOptions {
   EnableAsyncDemotion = llvm::cl::opt<bool>("enable-async-demotion",
                     llvm::cl::desc("Enables an optimization pass to demote async functions."));
 
+  llvm::cl::opt<bool>
+  EnableThrowsPrediction = llvm::cl::opt<bool>("enable-throws-prediction",
+                     llvm::cl::desc("Enables optimization assumption that functions rarely throw errors."));
+
   llvm::cl::opt<bool>
   EnableMoveInoutStackProtection = llvm::cl::opt<bool>("enable-move-inout-stack-protector",
                     llvm::cl::desc("Enable the stack protector by moving values to temporaries."));
@@ -847,6 +851,7 @@ int sil_opt_main(ArrayRef<const char *> argv, void *MainAddr) {
 
   SILOpts.EnableSpeculativeDevirtualization = options.EnableSpeculativeDevirtualization;
   SILOpts.EnableAsyncDemotion = options.EnableAsyncDemotion;
+  SILOpts.EnableThrowsPrediction = options.EnableThrowsPrediction;
   SILOpts.IgnoreAlwaysInline = options.IgnoreAlwaysInline;
   SILOpts.EnableOSSAModules = options.EnableOSSAModules;
   SILOpts.EnableSILOpaqueValues = options.EnableSILOpaqueValues;

lib/Frontend/CompilerInvocation.cpp

@@ -2597,6 +2597,9 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
       OPT_enable_sil_opaque_values, OPT_disable_sil_opaque_values, false);
   Opts.EnableSpeculativeDevirtualization |= Args.hasArg(OPT_enable_spec_devirt);
   Opts.EnableAsyncDemotion |= Args.hasArg(OPT_enable_async_demotion);
+  Opts.EnableThrowsPrediction = Args.hasFlag(
+      OPT_enable_throws_prediction, OPT_disable_throws_prediction,
+      Opts.EnableThrowsPrediction);
   Opts.EnableActorDataRaceChecks |= Args.hasFlag(
       OPT_enable_actor_data_race_checks,
       OPT_disable_actor_data_race_checks, /*default=*/false);