On 12/04/2012 03:57 PM, Brendan Eich wrote: > Allen Wirfs-Brock wrote: >> The timing of copying is only an issue if the function actually assigns to a >> formal parameter. Such assignments should be pretty easy to >> (conservatively) statically check for. > > I'm telling you what engines do. Not what they might do. I did assignment > analysis in SpiderMonkey for Firefox 3.6, it was helpful in its day. I think > a bunch has been ripped out because modern JITs don't need it. > > [...]the point I made, cited above: " engines don't do it currently and feel > little pressure to do so. Chicken and egg."
SpiderMonkey's implementation of the arguments object functions exactly as described here for functions with strict mode code -- actually for all functions, I think. Regarding the strict mode semantics specifically, it was fairly easy to make those optimizations when I was implementing the various strict mode arguments semantics, so I did them. There hasn't been a time where SpiderMonkey's had strict mode arguments semantics, without these optimizations. Jeff _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
