We're out of tree codes; now what?

Nicholas Nethercote njn@csse.unimelb.edu.au
Mon Mar 19 21:12:00 GMT 2007


On Mon, 19 Mar 2007, Doug Gregor wrote:

>> > It's going to have a big performance impact. To extract a 9-bit value,
>> > the compiler will need to do a lot of masking every time it accesses
>> > the TREE_CODE.
>> 
> So, about 16% slower with --enable-checking, 5% slower with 
> --disable-checking.
>
> Subcodes might still be the way to go, but I'm feeling less bad about
> the 9-bit tree code option.

As an interested outsider:  GCC's compile-time speed has been gradually 
decreasing for a while now.  It seems to be acknowledged as an undesirable 
thing, but not much has happened to change it.  AIUI, this is largely 
because it's very difficult.  Nonetheless, seeing a 5% slow-down caused by 
fixing a data structure design bogon is disappointing.

Nick



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