Re: We're out of tree codes; now what?

[Mark Mitchell <mark at codesourcery dot com>]

Steven Bosscher wrote:

> Let's be fair here: A 3% hit is small compared to the cumulative
> slowdown we already have in GCC 4.3 since the start of stage 1, and
> negligible compared to the total slowdown we've accumulated over the
> years. I know this is not really an argument, but let's face it: Much
> larger patches and branch merges have unintentionally increased
> compile time by more than 3%, and we didn't have a large discussion
> about it.

Yes, that's true.  Here, however, we have two paths in front of us:
9-bit tree codes, or some language-dependent subcodes.  The benefit of
9-bit tree codes is that they're easy to understand; the benefit of
subcodes is that they might be faster, but, then again, they might use
more memory.  I'd be interested in understanding the tradeoff.

> Subcodes require a bigger 'tree' data structure so there will be a
> memory usage hit, I don't think there's disagreement about that.

I thought the plan was to this in TYPE_LANG_SPECIFIC, etc., so that it's
not a generic effect on all trees?

Thanks,

-- 
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713