On 3/21/07, Mark Mitchell <[EMAIL PROTECTED]> wrote:
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?
I think this makes sense. All subcoded types would have their primary
TREE_CODE be LANG_TYPE. The subcode itself would live in
TYPE_LANG_SPECIFIC, along with any additional information we need for
that specific type node.
I suspect we would see a small increase in memory usage, because
subcoded types would have to allocate some memory for
TYPE_LANG_SPECIFIC to point at (it'll be only 4 bytes in most cases).
That said, the tree_type struct desperately needs refactoring, because
there are a lot of fields in there that I suspect aren't used by the
majority of types in the C++ front end, especially those that only
exist in templates (like TYPENAME_TYPE). Something akin to the DECL
hierarchy refactoring is needed.
I'll take a shot at an updated subcode implementation, since I already
have part of it working.
Cheers,
Doug
