Optimise style comparison when computing damage

style/properties/properties.mako.rs

@@ -3004,11 +3004,22 @@ const_assert!(std::mem::size_of::<longhands::${longhand.ident}::SpecifiedValue>(
 % for effect_name in ["repaint", "recalculate_overflow", "rebuild_stacking_context", "rebuild_box"]:
 pub(crate) fn restyle_damage_${effect_name} (old: &ComputedValues, new: &ComputedValues) -> bool {
     % for style_struct in data.active_style_structs():
-        % for longhand in style_struct.longhands:
+        <% longhands_affected = [effect_name in longhand.servo_restyle_damage.split() for longhand in style_struct.longhands if not longhand.logical] %>
+        % if any(longhands_affected):
+        let old_${style_struct.name_lower} = old.get_${style_struct.name_lower}();
+        let new_${style_struct.name_lower} = new.get_${style_struct.name_lower}();
+        if !std::ptr::eq(old_${style_struct.name_lower}, new_${style_struct.name_lower}) {
+            if 
+            % for longhand in style_struct.longhands:
             % if effect_name in longhand.servo_restyle_damage.split() and not longhand.logical:
-                old.get_${style_struct.name_lower}().${longhand.ident} != new.get_${style_struct.name_lower}().${longhand.ident} ||
+                old_${style_struct.name_lower}.${longhand.ident} != new_${style_struct.name_lower}.${longhand.ident} ||
             % endif
-        % endfor
+            % endfor
+            false {
+                return true;
+            }
+        }
+        % endif
     % endfor
     false
 }

style/servo/restyle_damage.rs

@@ -59,7 +59,12 @@ impl ServoRestyleDamage {
         old: &ComputedValues,
         new: &ComputedValues,
     ) -> StyleDifference {
-        let mut damage = compute_damage(old, new);
+        let mut damage = if std::ptr::eq(old, new) {
+            ServoRestyleDamage::empty()
+        } else {
+            compute_damage(old, new)
+        };
+
         if damage.is_empty() {
             return StyleDifference {
                 damage,