Add sfe_to_memcpy

compiler/mono/src/layout.rs

@@ -78,6 +78,22 @@ impl<'a> Layout<'a> {
         }
     }
 
+    pub fn safe_to_memcpy(&self) -> bool {
+        use Layout::*;
+
+        match self {
+            Builtin(builtin) => builtin.safe_to_memcpy(),
+            Struct(fields) => fields
+                .iter()
+                .all(|(_, field_layout)| field_layout.safe_to_memcpy()),
+            Tag(tags) => tags.iter().all(|tag_layout| tag_layout.safe_to_memcpy()),
+            FunctionPointer(_, _) => {
+                // Function pointers are immutable and can always be safely copied
+                true
+            }
+        }
+    }
+
     pub fn stack_size(&self, pointer_size: u32) -> u32 {
         use Layout::*;
 
@@ -138,6 +154,17 @@ impl<'a> Builtin<'a> {
             List(_) | EmptyList => Builtin::LIST_WORDS * pointer_size,
         }
     }
+
+    pub fn safe_to_memcpy(&self) -> bool {
+        use Builtin::*;
+
+        match self {
+            Int64 | Float64 | Bool(_, _) | Byte(_) | EmptyStr | EmptyMap | EmptyList | EmptySet => {
+                true
+            }
+            Str | Map(_, _) | Set(_) | List(_) => false,
+        }
+    }
 }
 
 #[allow(clippy::cognitive_complexity)]