On Aug 28, 12:41 pm, Tal Liron <tal.li...@gmail.com> wrote: > > If you look at the links in my previous e-mail (specifically this one > >https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/C...). > > The reflection is done in the compiler only when there is a tag (i.e. a type > > hint). Otherwise the compiler just emits an invoke instruction to call the > > Reflector at runtime. That invoke could be replaced with an invokedynamic > > instruction. > > Yes, that's exactly where one of us is mistaken. :) My understanding is that > this constructor is only called once during the analysis mode. Then, one of > the emit() methods is called, and from then on we are only executing the > compiled code.
Well, the statement you just made is true, but nonetheless you are the one who is mistaken. The emit() method is called, but if not enough information was present at compile time to resolve to a real method call (that is, if `method = null` was executed), then the emit() code emits a call to clojure.lang.Reflector/invokeMatchingMethod, which does runtime reflection. See https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/Compiler.java#L1426 where the "fast path" code is only emitted if `method != null`, and https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/Compiler.java#L1446 where the slow code is emitted instead. Most of what I know about invokedynamic is from watching this thread, but here seems to definitely be an area where you could avoid some runtime reflection, which is quite slow. You have to be careful, though, because the Method resolved the first time may not be right the second time. Consider (. some-obj (size)). If it is called on a j.u.Collection, we can do the reflection and create a MethodHandle for faster dispatch later. but if someone later passes in a j.u.Map (which is not a Collection), you have to reflect again and come up with another MethodHandle. I assume there's some way to do this, but it's harder than just shoving all runtime reflection into MethodHandles. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
