SIL: Allow package decls to be serialized when appropriate.

swiftlang#70100 prohibited `package` declarations from
ever being serialized in order to solve a problem in which the declarations
were being serialized inappropriately. That's too heavy handed, though, because
an `@_alwaysEmitIntoClient` function with `package` access *must* be serialized
because it has public non-abi linkage.

Resolves rdar://104711625

Author: tshortli

lib/SIL/IR/SILDeclRef.cpp

@@ -844,7 +844,7 @@ IsSerialized_t SILDeclRef::isSerialized() const {
   }
 
   // Anything else that is not public is not serializable.
-  if (d->getEffectiveAccess() < AccessLevel::Public || d->hasPackageAccess())
+  if (d->getEffectiveAccess() < AccessLevel::Public)
     return IsNotSerialized;
 
   // Enum element constructors are serializable if the enum is

test/SILGen/always_emit_into_client_attribute.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-silgen -primary-file %s %S/Inputs/always_emit_into_client_other_file.swift | %FileCheck %s
+// RUN: %target-swift-emit-silgen -primary-file %s %S/Inputs/always_emit_into_client_other_file.swift -package-name Package | %FileCheck %s
 
 // CHECK-LABEL: sil non_abi [serialized] [ossa] @$s33always_emit_into_client_attribute0A22EmitIntoClientFunctionyyF : $@convention(thin) () -> ()
 @_alwaysEmitIntoClient public func alwaysEmitIntoClientFunction() {
@@ -12,6 +12,17 @@
   alwaysEmitIntoClientOtherFunction()
 }
 
+// CHECK-LABEL: sil non_abi [serialized] [ossa] @$s33always_emit_into_client_attribute35packageAlwaysEmitIntoClientFunctionyyF : $@convention(thin) () -> ()
+@_alwaysEmitIntoClient package func packageAlwaysEmitIntoClientFunction() {
+  alwaysEmitIntoClientOtherFunction()
+}
+
+// FIXME: @_alwaysEmitIntoClient should not be allowed on private decls
+// CHECK-LABEL: sil non_abi [serialized] [ossa] @$s33always_emit_into_client_attribute35privateAlwaysEmitIntoClientFunction33_5D0713A780245A446371C699E6F23C4FLLyyF : $@convention(thin) () -> ()
+@_alwaysEmitIntoClient private func privateAlwaysEmitIntoClientFunction() {
+  alwaysEmitIntoClientOtherFunction()
+}
+
 public struct S {
   // CHECK-LABEL: sil non_abi [serialized] [ossa] @$s33always_emit_into_client_attribute1SV8propertySivg : $@convention(method) (S) -> Int
   // CHECK-LABEL: sil non_abi [serialized] [ossa] @$s33always_emit_into_client_attribute1SV8propertySivs : $@convention(method) (Int, @inout S) -> ()