[jvm-l] JSR 292 Goodness: Almost static final field

[Szymon Jachim]

Hi,
  This is cool but made me think again about some things I have already
asked on this group some time ago.

Does it mean that now with 7u2 the chain
  invokeExact() -> dynamicInvoker -> MutableCallSite -> SwitchPoint ->
constant(x)
will be optimistically inlined (until deoptimized for some reason)?

Other thing... Is there any real, technical reason why SwitchPoint left
branch is called fast and right - slow?
If SwitchPoint stays invalidated for a long time will it also get inlined?
In other words can I treat use them the other way?
First handle for computing the value (slow), second - to MutableCallSite's
dynamicInvoker, which in turn points to a now constant value.

I'm again thinking about possible optimizations for LambdaVM's thunks [1].

Great thing about jsr292 is that a seasoned hacker of languages
runtimes can just cross his fingers and wait until things work better... ;-)

Thanks,

Szymon

[1] http://wiki.brianweb.net/LambdaVM/Implementation


On Sat, Dec 17, 2011 at 7:33 PM, Rémi Forax <forax at univ-mlv.fr> wrote:

> I've written a blog entry about how to write a static volatile final
> variable, i.e. a variable which is considered as constant
> by the compiler (the JIT) and if the variable changes, the JITed code is
> deoptimized and
> jump back in interpreter mode to eventually optimize it again later.
>
> http://weblogs.java.net/blog/**forax/archive/2011/12/17/jsr-**
> 292-goodness-almost-static-**final-field<http://weblogs.java.net/blog/forax/archive/2011/12/17/jsr-292-goodness-almost-static-final-field>
>
> The code is a little bit more convoluted than it should because there is
> no invokedynamic
> in Java but you can emulate it.
>
> Rémi
>
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