GC for pure functions -- implementation ideas

[Fawzi Mohamed]

On 17-apr-11, at 21:44, Don wrote:

> [...]
> Basically, my contribution is this: the compiler can easily work  
> out, for each function, whenever it has entered and exited a non- 
> leaky pure function. It can make a call into the GC whenever this  
> happens. This gives the GC many more potential strategies.

yes more info is always better, I didn't want to diminish your work,  
but to point toward a general improvement in the GC
My fear is that the overhead of this approach will make it worth only  
for big allocations (getting rid of eventual false pointers), and thus  
only under the programmer control.

Classifying the "allocation potential" of a function might help make  
better automatic decisions.
That is difficult in general  (one can flag alloc in loop with unknown  
length or more than 4 elements as large for example, something that  
would miss recursive allocations), but it would be useful, because for  
those that allocate little could do nothing, or use a fixed stack like  
heap, whereas those that allocate a lot could checkpoint the heap  
(assuming a separate pool for each thread) or use a new pool.

Fawzi