Example for polymorphic inline caching

equivalent-object-type-specification.js

function foo(o) {
  //Two call sites in the code below where inline caches would be created, 
  //one each to access property `a` and `b` 
  return o.a + o.b;
}

// Initial call creates inline cache for Type {a,b}
foo({a: 1, b: 2});
// Hurray! Faster property access because inline cache for Type {a,b} exists
foo({a: 3, b: 4});
// Despite being a different type, with Equivalent Object Type Specialization,
// the call sites in the function foo will treat the following object
// equivalent with the above two, as a and b are at the same relative slot 
// locations in the object layout. The call will execute faster than the speedup 
// provided by polymorphic caches.
foo({a: 5, b: 6, c: 7});