v8/test/mjsunit/regress/regress-2595.js

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//
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// Flags: --allow-natives-syntax

var p = {
  f: function() {
    return 'p';
  }
};
var o = Object.create(p);
o.x = true;
delete o.x;  // slow case object

var u = {
  x: 0,
  f: function() {
    return 'u';
  }
};  // object with some other map

function F(x) {
  return x.f();
}

// First make CALL IC in F go MEGAMORPHIC and ensure that we put the stub
// that calls p.f (guarded by a negative dictionary lookup on the receiver)
// into the stub cache
;
%PrepareFunctionForOptimization(F);
assertEquals('p', F(o));
assertEquals('p', F(o));
assertEquals("u", F(u));
assertEquals("p", F(o));
assertEquals("u", F(u));

// Optimize F. We will inline p.f into F guarded by map checked against
// receiver which does not work for slow case objects.
%OptimizeFunctionOnNextCall(F);
assertEquals("p", F(o));

// Add f to o. o's map will *not* change.
o.f = function() {
  return 'o';
};
assertEquals("o", F(o));