On Mon, Mar 25, 2013 at 2:40 PM, Brendan Eich <[email protected]> wrote: > Kenneth Russell wrote: >>> >>> > For interop, JS requires cross-browser (VM) NaN canonicalization to >>> > avoid >>> > observably different results on different browsers. >> >> >> As long as NaN values loaded from Float32Array and Float64Array obey >> ES6's semantics, such as returning true from isNaN(), then it should >> not matter whether the ES6 implementation happens to support multiple >> bit patterns for NaN. > > > That's at issue. By reading via an aliasing byte or wider integral-typed > array view, different results could be observed on two VMs for the exact > same code. > > >> NaNs are an error condition and corner case in >> floating-point algorithms, and it is important not to negatively >> impact the performance of the common case in order to achieve >> absolutely precise semantics for this error case. > > > I want "as close to the metal as safety and interop allow" performance. I'm > not sure we are actually in conflict here, given how aggressive JITs work. > > Have you measured the performance impact in any optimizing VM?
No. I won't have time to do so myself, but would be interested in working with anybody who does to measure the performance difference. -Ken > /be > _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
