[tree-ssa] vectorizer related issues

[S. Bosscher]

Dorit Naishlos asked:
> Q6.3: Should we add new TREE_CODES (and corresponding optabs?) for the
> new types of operations we want to express?
> Or instead, Q6.4: should the vectorizer generate calls to target
> specific builtins?

I would prefer tree codes for generic operations and operations that can be
expressed as a sequence of simpler operations, but please note that we risk
running out of tree codes RSN. Obj-C++ can only barely fit in the existing
maximum of 256 tree codes :-/
Also perhaps target builtins are better because this is obviously all target
specific anyway...

Gr.
Steven