Created attachment 42980 [details]
getDOMNodeMap() (in V8DOMMap.cpp) is a surprisingly hot function in Dromaeo DOM benchmarks, enough so that I decided to optimize it somewhat. What I've done is inline together several of the calls that it makes — the function's not really doing much, so quite a lot of its time is just spent in function prolog/epilog boilerplate.
This took a bit more code-shuffling than it seems it ought to, because the code to be inlined wasn't all in the same source file; so I had to move some stuff from DOMData to MainThreadDOMData.
Result was that time spent in this function shrank by about half in my Shark profiles. Dromaeo scores improved 'a bit'; the test results on my machine are pretty noisy, but I saw consistently 1-2% better numbers. Which isn't a lot, but these things add up.
Comment on attachment 42980 [details]
Committed revision 50826.