[runtime] Store constructor function index on primitive maps.

src/arm64/builtins-arm64.cc

Index: src/arm64/builtins-arm64.cc
diff --git a/src/arm64/builtins-arm64.cc b/src/arm64/builtins-arm64.cc
index c147a196c6d1da6eb6dfee09878b501a649c94b2..59b55a9f9f612a25232f712a1f50f29799d516a6 100644
--- a/src/arm64/builtins-arm64.cc
+++ b/src/arm64/builtins-arm64.cc
@@ -436,8 +436,10 @@ static void Generate_JSConstructStubHelper(MacroAssembler* masm,
               Map::kUnusedPropertyFieldsByte * kBitsPerByte, kBitsPerByte);
       __ Ldr(inst_sizes_or_attrs,
              FieldMemOperand(init_map, Map::kInstanceSizesOffset));
-      __ Ubfx(inobject_props, inst_sizes_or_attrs,
-              Map::kInObjectPropertiesByte * kBitsPerByte, kBitsPerByte);
+      __ Ubfx(
+          inobject_props, inst_sizes_or_attrs,
+          Map::kInObjectPropertiesOrConstructorFunctionIndexByte * kBitsPerByte,
+          kBitsPerByte);
       __ Sub(prealloc_fields, inobject_props, unused_props);
 
       // Calculate number of property fields in the object.