[webkit-dev] jit, unordered compare

Geoffrey Garen ggaren at apple.com
Fri Oct 16 09:23:25 PDT 2009

> Hi
> fortunately, no, I don't need double branch here. "cmpvs reg0, reg0"  
> is a
> conditional instruction, which only executes if the v flag is set.
> My proposal would be to add a new DoubleCondition called  
> DoubleEqualOrNAN,
> or something similar to clarify what we expect from the conditional
> branch. Since I feel (and by IEEE as you mentioned) a comparison to  
> NaN
> should be false, not true as x86 actually does.

Yes, I think this is a great approach.

I would slightly prefer "DoubleEqualOrUnordered" to "NaN", since  
"unordered" matches the terminology of assembly languages.

I haven't thought this through fully, but you'll probably need  
DoubleNotEqualAndNotUnordered as well.


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