[fpc-devel] Maintainability

[J. Gareth Moreton]

Hi everyone,

This is a bit of a nebulous question, but when might something be 
considered unmaintainable and hence rejected? For example, with my 
x86_64 optimiser overhaul, I've tried to make the code as 
straightforward as possible, but there are a few questionable tricks 
because one of my design restrictions was that -O1 and -O2 must not 
perform any worse than before, which was a bit difficult because pass 1 
used to be executed twice no matter what (the one that stands out is how 
OptPass1MOV calls OptPass1XOR so it doesn't miss out on any 
optimisations with multiple concurrent MOV operations).  Might the 
restriction be waived if the resultant code became simpler?

There were other little ones like TransferUsedRegs - originally I had a 
version where you could choose to only transfer one set of registers 
(e.g. the integer registers) instead of all of them (which is a little 
costly), but there was concern that it might cause maintainability 
problems, possibly because of an optimisation playing with more than one 
type of register, for example.  Nevertheless, TransferUsedRegs also 
calls "Create" as a regular method, but I do my best to explain what's 
going on with comments.

Gareth aka. Kit


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