CastOptimizer: handle isolated conformances

Check the isolation of conformances to avoid wrong folding of dynamic casts
rdar://147417762

Author: eeckstein

lib/SIL/Utils/DynamicCasts.cpp

@@ -115,8 +115,12 @@ classifyDynamicCastToProtocol(SILFunction *function, CanType source, CanType tar
 
   // If checkConformance() returns a valid conformance, then all conditional
   // requirements were satisfied.
-  if (checkConformance(source, TargetProtocol))
+  if (auto conformance = checkConformance(source, TargetProtocol)) {
+    if (!matchesActorIsolation(conformance, function))
+      return DynamicCastFeasibility::MaySucceed;
+
     return DynamicCastFeasibility::WillSucceed;
+  }
 
   auto *SourceNominalTy = source.getAnyNominal();
   if (!SourceNominalTy)

lib/SILOptimizer/Utils/CastOptimizer.cpp

@@ -1481,6 +1481,9 @@ static bool optimizeStaticallyKnownProtocolConformance(
     if (Conformance.isInvalid())
       return false;
 
+    if (!matchesActorIsolation(Conformance, Inst->getFunction()))
+      return false;
+
     auto layout = TargetType->getExistentialLayout();
     if (layout.getProtocols().size() != 1)
       return false;

test/SILOptimizer/constant_propagation_casts_ossa.sil

@@ -1,7 +1,14 @@
-// RUN: %target-sil-opt -enable-sil-verify-all %s -diagnostic-constant-propagation | %FileCheck %s
+// RUN: %target-sil-opt -enable-sil-verify-all %s -diagnostic-constant-propagation -enable-experimental-feature IsolatedConformances | %FileCheck %s
+
+// REQUIRES: swift_feature_IsolatedConformances
+// REQUIRES: concurrency
+
 sil_stage canonical
 
-//import Swift
+import Builtin
+import Swift
+import _Concurrency
+import SwiftShims
 
 class Klass {
 }
@@ -12,6 +19,15 @@ class SubKlass : Klass {
 class NoSubKlass {
 }
 
+protocol P {
+  func f() -> Int
+}
+
+struct X : @MainActor P {
+  func f() -> Int
+  init()
+}
+
 sil [noinline] @blackhole1 : $@convention(thin) (@guaranteed SubKlass) -> ()
 sil [noinline] @blackhole2 : $@convention(thin) (@guaranteed NoSubKlass) -> ()
 
@@ -94,3 +110,26 @@ bb3:
   return %r : $()
 }
 
+// CHECK-LABEL: sil [ossa] @isolated_conf_ucca :
+// CHECK:         unconditional_checked_cast_addr
+// CHECK-LABEL: } // end sil function 'isolated_conf_ucca'
+sil [ossa] @isolated_conf_ucca : $@convention(thin) (@in X) -> @out P {
+bb0(%0 : $*P, %1 : $*X):
+  unconditional_checked_cast_addr X in %1 to any P in %0
+  %2 = tuple ()
+  return %2
+}
+
+// CHECK-LABEL: sil [ossa] @isolated_conf_ccab :
+// CHECK:         checked_cast_addr_br
+// CHECK-LABEL: } // end sil function 'isolated_conf_ccab'
+sil [ossa] @isolated_conf_ccab : $@convention(thin) (@in X) -> @out P {
+bb0(%0 : $*P, %1 : $*X):
+  checked_cast_addr_br take_always X in %1 to any P in %0, bb1, bb2
+bb1:
+  %2 = tuple ()
+  return %2
+bb2:
+  unreachable
+}
+

test/SILOptimizer/isolated_conformances.swift

@@ -0,0 +1,59 @@
+// RUN: %empty-directory(%t) 
+// RUN: %target-build-swift -parse-as-library -O %s -enable-experimental-feature IsolatedConformances -o %t/a.out
+// RUN: %target-codesign %t/a.out
+// RUN: %target-run %t/a.out | %FileCheck %s --check-prefix=CHECK-OUTPUT
+
+// RUN: %target-build-swift -parse-as-library -O %s -enable-experimental-feature IsolatedConformances -Xllvm -sil-disable-pass=function-signature-opts -emit-sil | %FileCheck %s
+
+// REQUIRES: concurrency
+// REQUIRES: executable_test
+// REQUIRES: concurrency_runtime
+// REQUIRES: swift_feature_IsolatedConformances
+
+// UNSUPPORTED: back_deployment_runtime
+// UNSUPPORTED: back_deploy_concurrency
+
+protocol P {
+  func f() -> Int
+}
+
+struct X: @MainActor P {
+  func f() -> Int { 17 }
+}
+
+// CHECK-LABEL: sil hidden [noinline] @$s21isolated_conformances12castAnywhereySiSgAA1XVF :
+// CHECK:         checked_cast_addr_br take_always X in %{{[0-9]+}} to any P in %{{[0-9]+}}, bb1, bb2
+// CHECK:       } // end sil function '$s21isolated_conformances12castAnywhereySiSgAA1XVF'
+@inline(never)
+nonisolated func castAnywhere(_ value: X) -> Int? {
+  if let value = value as? P {
+    return value.f()
+  }
+  return nil
+}
+
+// CHECK-LABEL: sil hidden [noinline] @$s21isolated_conformances15castOnMainActorySiSgAA1XVF :
+// CHECK:         [[L:%.*]] = integer_literal {{.*}} 17
+// CHECK:         [[I:%.*]] = struct $Int ([[L]])
+// CHECK:         [[O:%.*]] = enum $Optional<Int>, #Optional.some!enumelt, [[I]]
+// CHECK:         return [[O]]
+// CHECK:       } // end sil function '$s21isolated_conformances15castOnMainActorySiSgAA1XVF'
+@MainActor
+@inline(never)
+func castOnMainActor(_ value: X) -> Int? {
+  if let value = value as? P {
+    return value.f()
+  }
+  return nil
+}
+
+
+@main
+struct Main {
+  static func main() async {
+    await Task.detached {
+      // CHECK-OUTPUT: nil
+      print(castAnywhere(X()))
+    }.value
+  }
+}