object[key] access performance drop since 0.12

[yamsellem]

We've found a performance drop in our production code when migrating to node 0.12.
Here is a benchmark that reproduces it:

var Benchmark = require('benchmark');
var suite = new Benchmark.Suite;

var filter = function(obj) {
    obj['property'];
};

var filterOn = function(obj, value) {
    obj[value];
};

suite
.add('Filter#fixed', function() {
    filter({property: 2});
})
.add('Filter#on', function() {
    filterOn({property: 2}, 'property');
})
.on('cycle', function(event) {
    console.log(String(event.target));
})
.run({ 'async': true });

On node 0.10.24

Filter#fixed x 64,682,540 ops/sec ±1.70% (86 runs sampled)
Filter#on x 57,602,016 ops/sec ±2.02% (80 runs sampled)

On node 0.12.5

Filter#fixed x 95,081,906 ops/sec ±1.68% (94 runs sampled)
Filter#on x 38,661,204 ops/sec ±2.43% (80 runs sampled)

Whereas node 0.12 is way faster on a 'static' object's attribute access, is seems slower when using a variable to access an attribute value.

This may be nothing, and may be negligible regarding the overall performance.
This may be relative to the issue #25501

[a0viedo]

I would bet this is V8 credit. I run some tests in io.js V3 and the performance drop seems to improve. Could you re-run your suite in io.js latest?