SIL: Consider Builtin.FixedArray and @_rawLayout types to be structurally addressable-for-dependencies.

A primary purpose of these features is to enable persistent references into their storage, so it's
reasonable to assume this property for these types and types containing them.

Author: jckarter

lib/SIL/IR/TypeLowering.cpp

@@ -389,6 +389,11 @@ namespace {
 
       props = mergeIsTypeExpansionSensitive(isSensitive, props);
 
+      // Fixed array regions are implied to be addressable-for-dependencies,
+      // since the developer probably wants to be able to form Spans etc.
+      // over them.
+      props.setAddressableForDependencies();
+      
       // If the size isn't a known literal, then the layout is also dependent,
       // so make it address-only. If the size is massive, also treat it as
       // address-only since there's little practical benefit to passing around
@@ -2540,6 +2545,7 @@ namespace {
       // If the type has raw storage, it is move-only and address-only.
       if (D->getAttrs().hasAttribute<RawLayoutAttr>()) {
         properties.setAddressOnly();
+        properties.setAddressableForDependencies();
         properties.setNonTrivial();
         properties.setLexical(IsLexical);
         return handleMoveOnlyAddressOnly(structType, properties);

test/SILOptimizer/addressable_dependencies.swift

@@ -1,8 +1,9 @@
-// RUN: %target-swift-frontend -emit-sil -enable-experimental-feature BuiltinModule -enable-experimental-feature LifetimeDependence -enable-experimental-feature AddressableTypes %s | %FileCheck %s
+// RUN: %target-swift-frontend -emit-sil -enable-experimental-feature BuiltinModule -enable-experimental-feature LifetimeDependence -enable-experimental-feature AddressableTypes -enable-experimental-feature ValueGenerics %s | %FileCheck %s
 
 // REQUIRES: swift_feature_BuiltinModule
 // REQUIRES: swift_feature_AddressableTypes
 // REQUIRES: swift_feature_LifetimeDependence
+// REQUIRES: swift_feature_ValueGenerics
 
 import Builtin
 
@@ -58,3 +59,22 @@ struct AllocatedNode: ~Copyable {
     }
 }
 
+struct Schmector {
+    // structurally addressable-for-dependencies by virtue of containing a
+    // Builtin.FixedArray
+    private var elements: Builtin.FixedArray<10, Int>
+
+    var storage: Spam {
+        // CHECK-LABEL: sil {{.*}}@${{.*}}9SchmectorV7storage{{.*}}Vvg :
+        // CHECK-SAME:    (@in_guaranteed Schmector) ->
+        @lifetime(borrow self)
+        borrowing get {
+            return Spam(base: UnsafePointer(Builtin.addressOfBorrow(self)), count: 10)
+        }
+    }
+}
+
+struct Spam: ~Escapable {
+    @_unsafeNonescapableResult
+    init(base: UnsafePointer<Int>, count: Int) {}
+}