Tail Call Optimization

[Cristian Esquivias]

Thanks for the help Stefan & Christian. I switched over to passing
CallTarget objects and following the SimpleLanguage example for an inline
cache of direct dispatch node. No more opt failures.

https://github.com/cesquivias/mumbler/commit/ba4986d33d983b17eaa19892e4a37fb3d42a212c

Unfortunately, even though the direct dispatch node is called, performance
has taken a big hit. The median time on my microbenchmark increased over
50% (360ms to 550ms). Is throwing a flow exception out of function frames
not very fast?

Microbenchmark:
https://github.com/cesquivias/mumbler/commit/616fcdea94d50ec8a121ac4da2eb3eef9d5092be

On Tue, Jan 13, 2015 at 4:31 PM, Christian Humer <christian.humer at gmail.com>
wrote:

> Hi Christian,
>
> You should not pass nodes around like values (like you do with the
> DirectCallNode). Instead let the TailCallException carry a CallTarget.
>
> As Stefan pointed out, in the catch block of the TailCallException you are
> going to need another inline cache similar to the one in
> SLDirectDispatchNode. To try it out quickly you can also use an
> IndirectCallNode instead, but don't expect perfect performance from this.
>
> - Christian Humer
>
>
>
> On Wed Jan 14 2015 at 00:18:13 Cristian Esquivias <
> cristian.esquivias at gmail.com> wrote:
>
>> Hi Stefan,
>>
>> Thanks for taking a look. So I would create a linked list of dispatch
>> nodes
>> like in Simple Language?
>>
>> http://hg.openjdk.java.net/graal/graal/file/3a59e1411192/gra
>> al/com.oracle.truffle.sl/src/com/oracle/truffle/sl/nodes/call/
>> SLDirectDispatchNode.java
>>
>> Since the function object and the call target don't change, how should I
>> test for equality between one dispatch node and another? That is, how do I
>> know to use one dispatch node versus another?
>>
>> Thanks again,
>> Cristian
>>
>> On Tue, Jan 13, 2015 at 3:06 PM, Stefan Marr <java at stefan-marr.de> wrote:
>>
>> > Hi Cristian:
>> >
>> > > On 13 Jan 2015, at 23:25, Cristian Esquivias <
>> > cristian.esquivias at gmail.com> wrote:
>> > >
>> > > I'm trying to add tail call optimization to my test language and have
>> a
>> > > functional version (no stackoverflows).
>> > >
>> > >
>> > https://github.com/cesquivias/mumbler/commit/3b61f7ccdad7429
>> d2feac6068b0f57edce6a4151
>> >
>> > Looking at the diff/code, I think the issue is the call node that you
>> pass
>> > back in the exception.
>> > At the point where you handle the exception, you’ll probably need to
>> make
>> > that node a constant as part of the AST, by using a dispatch node
>> chain/an
>> > inline cache.
>> >
>> > Best regards
>> > Stefan
>> >
>> >
>> > --
>> > Stefan Marr
>> > INRIA Lille - Nord Europe
>> > http://stefan-marr.de/research/
>> >
>> >
>> >
>> >
>>
>