Re: [mdt-ocl.dev] Partial IA code generated evaluation

[Axel Uhl <eclipse@xxxxxxxxxxxxxxxxxx>]

Another challenge in porting the IA to Pivot will be the semantics of 
OperationCallExp in the presence of redefinitions in subclasses. In OCL 
Ecore the somewhat bizarre, yet easy to handle for IA, semantics are 
that calling an OCL-defined operation from Java through the Ecore APIs 
will behave polymorphically, while evaluating an OperationCallExp will 
evaluate the expression in the statically-bound referredOperation.

For porting to IA, the traceback for an OperationCallExp would need to 
compute and join all traceback paths of all possible redefinitions.

How about redefinition of derived properties in subclasses? Is this 
possible with Pivot?

Best,
-- Axel

On 12/23/2011 10:25 PM, Ed Willink wrote:
> Hi Axel
>
> On 23/12/2011 20:23, Axel Uhl wrote:
> > It would be very difficult to change the partial evaluation required
> > by the IA to partially evaluate compiled expressions. It would require
> > a capability to inject variable values into the evaluation context,
> > and it depends on a specific exception to be thrown when a VariableExp
> > is evaluated without the respective variable being in the context.
> > This kind of support would probably require some careful and tricky
> > preparation for the compilation.
> The code generator currently does Static Single Assignment with almost
> no evaluation context as such. Everything is on the stack, sometimes as
> final variables to support visibility to nested iterator bodies.
>
> A a = ... ;
> B b = ... ;
> C c = ... ;
>
> Presumably for partial evaluation this needs to be changed to
>
> if (cache.a == null) cache.a = ... ;
> if (cache.b == null) cache.b = ... ;
> if (cache.c == null) cache.c = ... ;
>
> with cache an instance of an auto-generated class passed into the
> evaluation routine.
>
> class Cache {
> A a = null;
> B b = null;
> C c = null;
> ...
> }
>
> potentially with nested caches for nested iterations.
>
> If necessary variable reads can be differently coded.
>
> Regards
>
> Ed
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