[SILGen] Put actor data-race checking behind a flag.

Introduce flags `-enable-actor-data-race-checks` and
`-disable-actor-data-race-checks` to enable/disable emission of code
that checks that we are on the correct actor. Default to `false` for
now but make it easy to enable in the future.

Author: DougGregor

include/swift/AST/SILOptions.h

@@ -65,6 +65,9 @@ class SILOptions {
   /// It is turned off by default.
   bool EnableSpeculativeDevirtualization = false;
 
+  /// Controls whether to emit actor data-race checks.
+  bool EnableActorDataRaceChecks = 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/Options.td

@@ -607,6 +607,16 @@ def warn_swift3_objc_inference_minimal :
   Flags<[FrontendOption, DoesNotAffectIncrementalBuild]>,
   HelpText<"Warn about deprecated @objc inference in Swift 3 based on direct uses of the Objective-C entrypoint">;
 
+def enable_actor_data_race_checks :
+  Flag<["-"], "enable-actor-data-race-checks">,
+  Flags<[FrontendOption, DoesNotAffectIncrementalBuild]>,
+  HelpText<"Emit runtime checks for actor data races">;
+
+def disable_actor_data_race_checks :
+  Flag<["-"], "disable-actor-data-race-checks">,
+  Flags<[FrontendOption, DoesNotAffectIncrementalBuild]>,
+  HelpText<"Disable runtime checks for actor data races">;
+
 def warn_implicit_overrides :
   Flag<["-"], "warn-implicit-overrides">,
   Flags<[FrontendOption, DoesNotAffectIncrementalBuild]>,

lib/Driver/ToolChains.cpp

@@ -218,6 +218,9 @@ void ToolChain::addCommonFrontendArgs(const OutputInfo &OI,
   inputArgs.AddLastArg(arguments,
                        options::OPT_warn_swift3_objc_inference_minimal,
                        options::OPT_warn_swift3_objc_inference_complete);
+  inputArgs.AddLastArg(arguments,
+                       options::OPT_enable_actor_data_race_checks,
+                       options::OPT_disable_actor_data_race_checks);
   inputArgs.AddLastArg(arguments, options::OPT_warn_concurrency);
   inputArgs.AddLastArg(arguments, options::OPT_warn_implicit_overrides);
   inputArgs.AddLastArg(arguments, options::OPT_typo_correction_limit);

lib/Frontend/CompilerInvocation.cpp

@@ -1222,6 +1222,9 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
   Opts.EnableOSSAModules |= Args.hasArg(OPT_enable_ossa_modules);
   Opts.EnableOSSAOptimizations &= !Args.hasArg(OPT_disable_ossa_opts);
   Opts.EnableSpeculativeDevirtualization |= Args.hasArg(OPT_enable_spec_devirt);
+  Opts.EnableActorDataRaceChecks |= Args.hasFlag(
+      OPT_enable_actor_data_race_checks,
+      OPT_disable_actor_data_race_checks, /*default=*/false);
   Opts.DisableSILPerfOptimizations |= Args.hasArg(OPT_disable_sil_perf_optzns);
   Opts.CrossModuleOptimization |= Args.hasArg(OPT_CrossModuleOptimization);
   Opts.VerifyAll |= Args.hasArg(OPT_sil_verify_all);

lib/SILGen/SILGenProlog.cpp

@@ -492,6 +492,10 @@ void SILGenFunction::emitProlog(CaptureInfo captureInfo,
 
   // Initialize ExpectedExecutor if the function is an actor-isolated
   // function or closure.
+  bool wantDataRaceChecks = getOptions().EnableActorDataRaceChecks &&
+      !F.isAsync() &&
+      !isInActorDestructor(FunctionDC);
+
   if (auto *funcDecl =
         dyn_cast_or_null<AbstractFunctionDecl>(FunctionDC->getAsDecl())) {
     auto actorIsolation = getActorIsolation(funcDecl);
@@ -508,7 +512,7 @@ void SILGenFunction::emitProlog(CaptureInfo captureInfo,
       // are prone to dynamic data races in code that does not enforce Sendable
       // completely.
       if (F.isAsync() ||
-          (funcDecl->isLocalCapture() && !isInActorDestructor(funcDecl))) {
+          (wantDataRaceChecks && funcDecl->isLocalCapture())) {
         auto loc = RegularLocation::getAutoGeneratedLocation(F.getLocation());
         ManagedValue selfArg = ManagedValue::forUnmanaged(F.getSelfArgument());
         ExpectedExecutor = emitLoadActorExecutor(loc, selfArg);
@@ -517,15 +521,15 @@ void SILGenFunction::emitProlog(CaptureInfo captureInfo,
     }
 
     case ActorIsolation::GlobalActor:
-      if (F.isAsync() || !isInActorDestructor(funcDecl)) {
+      if (F.isAsync() || wantDataRaceChecks) {
         ExpectedExecutor =
           emitLoadGlobalActorExecutor(actorIsolation.getGlobalActor());
       }
       break;
     }
   } else if (auto *closureExpr = dyn_cast<AbstractClosureExpr>(FunctionDC)) {
     bool wantExecutor = F.isAsync() ||
-      (!isInActorDestructor(closureExpr) &&
+      (wantDataRaceChecks &&
        !(isa<ClosureExpr>(closureExpr) &&
          cast<ClosureExpr>(closureExpr)->isUnsafeMainActor()));
     auto actorIsolation = closureExpr->getActorIsolation();

test/Concurrency/Runtime/data_race_detection.swift

@@ -1,4 +1,4 @@
-// RUN: %target-run-simple-swift(-Xfrontend -enable-experimental-concurrency  %import-libdispatch -parse-as-library) > %t.log 2>&1
+// RUN: %target-run-simple-swift(-Xfrontend -enable-experimental-concurrency  -enable-actor-data-race-checks %import-libdispatch -parse-as-library) > %t.log 2>&1
 // RUN: %FileCheck %s < %t.log
 
 // REQUIRES: executable_test

test/SILGen/check_executor.swift

@@ -1,5 +1,5 @@
-// RUN: %target-swift-frontend -emit-silgen %s -module-name test -swift-version 5 -enable-experimental-concurrency | %FileCheck --enable-var-scope %s --check-prefix=CHECK-RAW
-// RUN: %target-swift-frontend -emit-silgen %s -module-name test -swift-version 5 -enable-experimental-concurrency > %t.sil
+// RUN: %target-swift-frontend -emit-silgen %s -module-name test -swift-version 5 -enable-experimental-concurrency -enable-actor-data-race-checks | %FileCheck --enable-var-scope %s --check-prefix=CHECK-RAW
+// RUN: %target-swift-frontend -emit-silgen %s -module-name test -swift-version 5 -enable-experimental-concurrency -enable-actor-data-race-checks > %t.sil
 // RUN: %target-sil-opt -enable-sil-verify-all %t.sil -lower-hop-to-actor -enable-experimental-concurrency | %FileCheck --enable-var-scope %s --check-prefix=CHECK-CANONICAL
 // REQUIRES: concurrency