Re: Redundant logical operations left after early splitting

[hutchinsonandy at aim dot com]

Yes - the other approach is to lower at RTL expand.

Unfortunately there is no practical way to lower arithmetic and compare 
 operations. reload can add arithmetic which messes the "carry" 
handling attempts. So we end up with mixed higher level and lower level 
RTL.

This mixture then causes other miss optimisations - which historically 
have been very significant but grow less with time.

The splitting after combine allows existing optimisations to be kept 
largely intact.

The ports that benefit would be any that split operations - after 
expand (eg combine onwards). How much - who knows!

Unfortunately there is no way a target can hook into pass management to 
make this more specfic.

but I'm still thinking about it!

Andy


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