[fpc-devel] Merging identical procedure proposals

Jonas Maebe jonas at freepascal.org
Sat Oct 16 16:32:40 CEST 2021

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

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


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