Sounds like "procvar = @myproc" would be -O4 at best due to the side-effects, otherwise I would wonder if it's possible to track such references, especially with units that are pre-compiled.

Gareth aka. Kit

On 16/10/2021 15:32, Jonas Maebe via fpc-devel wrote:
On 13/10/2021 19:33, J. Gareth Moreton via fpc-devel wrote:
I figure this would be a whole-program optimization though due to inter-unit calls and comparisons and the like.

Usually this is an optimisation that is performed at link-time because you don't need any compiler-level information for it. And then it can also consider code from statically linked libraries etc. Most standard linkers don't have support for it, but link-time optimisation frameworks generally do.

One thing you have to be mindful of is that if the address of a routine gets taken in any way then you cannot merge it anymore, because there might be a comparison somewhere in the program such as

if procvar = @myproc then
  ..
end;

and if myproc gets merged with other routines, then this will return true in more cases.


Jonas
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