[Webkit-unassigned] [Bug 68320] DFG JIT does not speculate aggressively enough on GetById

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=68320


Filip Pizlo <fpizlo at apple.com> changed:

           What    |Removed                     |Added
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 Attachment #107786|0                           |1
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--- Comment #3 from Filip Pizlo <fpizlo at apple.com>  2011-09-18 12:54:54 PST ---
Created an attachment (id=107791)
 --> (https://bugs.webkit.org/attachment.cgi?id=107791&action=review)
work in progress

Still testing this, but it's looking pretty good - 76% speed-up on property accesses.  Consider this simple program:

function foo(o, n) {
    var result = 0;
    while(n-->0) {
        result += o.a + o.b + o.c;
    }
    return result;
}

var object = {a:1, b:2, c:3};
var before = preciseTime();
var result = foo(object, 10000000);
var after = preciseTime();
print("Result: "+result+"  Time: "+((after-before)*1000));

Here's the before/after:

BEFORE: 
Result: 60000000  Time: 57.630062103271484

AFTER:
Result: 60000000  Time: 32.59611129760742

I still need to test this on real programs.

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