On Tue, Mar 18, 2014 at 11:19 PM, Paul Moore <p.f.mo...@gmail.com> wrote: > On 18 March 2014 19:46, Maciej Fijalkowski <fij...@gmail.com> wrote: >>> A question: how far away will this optimization apply? >>> >>> if x in d: >>> do_this() >>> do_that() >>> do_something_else() >>> spam = d[x] >> >> it depends what those functions do. JIT will inline them and if >> they're small, it should work (although a modification of a different >> dict is illegal, since aliasing is not proven), but at some point >> it'll give up (Note that it'll also give up with a call to C releasing >> GIL since some other thread can modify it). > > Surely in the presence of threads the optimisation is invalid anyway > as other threads can run in between each opcode (I don't know how > you'd phrase that in a way that wasn't language dependent other than > "everywhere" :-)) so > > if x in d: > # HERE > spam = d[x] > > d can be modified at HERE. (If d is a local variable, obviously the > chance that another thread has access to d is a lot lower, but do you > really do that level of alias tracking?) > > Paul
not in the case of JIT that *knows* where the GIL can be released. We precisely make it not possible every few bytecodes to avoid such situations. _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
