[fpc-devel] Progress on pure functions

[Sven Barth]

Am 14.12.2022 um 12:15 schrieb J. Gareth Moreton via fpc-devel:
>
> To better explain how purity analysis currently works (I'm sure 
> there's a better name than "purity analysis"), it takes a copy of the 
> unoptimised node tree (this is the same as the tree used for inline, 
> and for a space saving, they share the same field), adds explicit 
> definitions for the formal parameters so they equal the constants 
> passed in, and then tries to collapse the node tree down to a single 
> assignment to the result.  This is done by running the following 
> operations in this order:
>

What do you mean with “share the same field”? A pure function might 
still be called and inlined like a normal function and for that you 
shouldn't transform the node tree needlessly as that might influence the 
debugging experience. So you should have two different copies, one for 
inlining and one for pure related transformations.

Regards,
Sven