Actor-isolated top-level global variables test

Adding a test to verify that actor-isolated variables in top-level code
jump to the correct actor.

Also ensure that raw globals are not hopping to actors.

Author: etcwilde

test/SILGen/toplevel_globalactorvars.swift

@@ -0,0 +1,76 @@
+// RUN: %target-swift-emit-silgen -disable-availability-checking -Xllvm -sil-full-demangle -enable-experimental-async-top-level %s | %FileCheck %s
+
+// a
+// CHECK-LABEL: sil_global hidden @$s24toplevel_globalactorvars1aSivp : $Int
+// b
+// CHECK-LABEL: sil_global hidden @$s24toplevel_globalactorvars1bSivp : $Int
+
+// CHECK-LABEL: sil hidden [ossa] @async_Main
+// CHECK: bb0:
+// CHECK-NEXT: alloc_global @$s24toplevel_globalactorvars1aSivp
+// CHECK-NEXT: [[AREF:%[0-9]+]] = global_addr @$s24toplevel_globalactorvars1aSivp : $*Int
+
+actor MyActorImpl {}
+
+@globalActor
+struct MyActor {
+    static let shared = MyActorImpl()
+}
+
+@MyActor
+var a = 10
+
+@MyActor
+func incrementA() {
+    a += 1
+}
+
+await print(a)
+
+// CHECK: [[ACTORREF:%[0-9]+]] = begin_borrow {{%[0-9]+}} : $MyActorImpl
+// CHECK: [[OLDACTOR:%[0-9]+]] = builtin "getCurrentExecutor"() : $Optional<Builtin.Executor>
+// CHECK: hop_to_executor [[ACTORREF]] : $MyActorImpl
+// CHECK: [[AACCESS:%[0-9]+]] = begin_access [read] [dynamic] [[AREF]] : $*Int
+// CHECK: [[AGLOBAL:%[0-9]+]] = load [trivial] [[AACCESS]] : $*Int
+// CHECK: end_access [[AACCESS]]
+// CHECK: hop_to_executor [[OLDACTOR]]
+// CHECK: end_borrow [[ACTORREF]]
+
+await incrementA()
+
+// CHECK: [[INCREMENTA:%[0-9]+]] = function_ref @$s24toplevel_globalactorvars10incrementAyyF
+// CHECK: [[ACTORREF:%[0-9]+]] = begin_borrow {{%[0-9]+}} : $MyActorImpl
+// CHECK: [[OLDACTOR:%[0-9]+]] = builtin "getCurrentExecutor"() : $Optional<Builtin.Executor>
+// CHECK: hop_to_executor [[ACTORREF]] : $MyActorImpl
+// CHECK: {{%[0-9]+}} = apply [[INCREMENTA]]()
+// CHECK: hop_to_executor [[OLDACTOR]]
+// CHECK: end_borrow [[ACTORREF]]
+
+await print(a)
+
+// CHECK: [[ACTORREF:%[0-9]+]] = begin_borrow {{%[0-9]+}} : $MyActorImpl
+// CHECK: [[OLDACTOR:%[0-9]+]] = builtin "getCurrentExecutor"() : $Optional<Builtin.Executor>
+// CHECK: hop_to_executor [[ACTORREF]] : $MyActorImpl
+// CHECK: [[AACCESS:%[0-9]+]] = begin_access [read] [dynamic] [[AREF]] : $*Int
+// CHECK: [[AGLOBAL:%[0-9]+]] = load [trivial] [[AACCESS]] : $*Int
+// CHECK: end_access [[AACCESS]]
+// CHECK: hop_to_executor [[OLDACTOR]]
+// CHECK: end_borrow [[ACTORREF]]
+
+var b = 11
+
+// CHECK: alloc_global @$s24toplevel_globalactorvars1bSivp
+// CHECK: [[BGLOBAL_ADDR:%[0-9]+]] = global_addr @$s24toplevel_globalactorvars1bSivp
+// Int.init(_builtinIntegerLiteral:)
+// CHECK: [[INT_INIT_FUNC:%[0-9]+]] = function_ref @$sSi22_builtinIntegerLiteralSiBI_tcfC
+// CHECK: [[INITD_INT:%[0-9]+]] = apply [[INT_INIT_FUNC]]({{%[0-9]+}}, {{%[0-9]+}})
+// CHECK: store [[INITD_INT]] to [trivial] [[BGLOBAL_ADDR]]
+
+b += 1
+
+// CHECK-NOT: hop_to_executor
+// CHECK: [[BACCESS:%[0-9]+]] = begin_access [modify] [dynamic] [[BGLOBAL_ADDR]]
+// static Int.+= infix(_:_:)
+// CHECK: [[PE_INT_FUNC:%[0-9]+]] = function_ref @$sSi2peoiyySiz_SitFZ
+// CHECK: [[INCREMENTED:%[0-9]+]] = apply [[PE_INT_FUNC]]([[BACCESS]], {{%[0-9]+}}, {{%[0-9]+}})
+// CHECK: end_access [[BACCESS]]