On 01.08.2016 08:37, Vladimir Ivanov wrote:
And let's not forget:
- coroutine
- tail call
How do they relate to "Indy Support Group" (as recorded in JVMLS
agenda)? :-)
both of them most likely will need a special kind of method call. And
both could be implemented using a trampoline like base
For example if you had the ability to make a call and jump put of the
current stack frame at the same time you could implement tail calls to
some extend. A simple implementation I used in the past requires a
method that calls a tailcall enabled method to use a special call
instruction... something like this:
callcc foo(0)
def foo(i) {
returncc bar(i+1)
}
def bar(j) {
returncc foo(j+1)
}
returncc records the method call, but returns to callcc, which does the
actual execution of the call. Now imagine callcc and returncc being
invokedynamic functions, where returncc can return to the frame of
callcc and the callcc handle executes the handle produced by returncc.
My implementation I tried out in the past was actually using a special
return type and a loop in the implementation of callcc, which I found
questionable performance wise and too intrusive type-wise.
An idea for a coroutine would be to again have a similar "exit frame
with state", but this time instead of directly using that in the caller
code, to save the state in an object and to use that to get back and
continue with later on. The coroutine itself would have to be unrolled
to some extend, to allow jumping to a certain position in the bytecode
by restoring state from the coroutine object. Of course having your own
substack would be even better, but well...
But I guess such techniques are nothing new to anyone reading here ;)
Anyway... invokedynamic could help hiding implementation details here a
lot, and the ability to exit the current stack frame with user defined
state beyond a simple return would be really really interesting for
those implementations.
bye Jochen
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