Re: [Committed] Tweak fold_builtin_unordered_cmp API

[Kazu Hirata <kazu at cs dot umass dot edu>]

Hi Rogerm

> My belief/expectation is that the there shouldn't be a difference and
> the few places that use TREE_TYPE (exp) can safely be replaced with
> TREE_TYPE (TREE_TYPE (fndecl)).  We could probably add an assert to
> fold_builtin to confirm this, but I'd be more concerned that using
> pointer equality to test for equal types would trigger false positives.
> As Mark puts it, using pointer equality to compare types is almost
> always wrong.
> 
> At the moment, builtins.c randomly mixes these types on the assumption
> they're the same.  Being different should indicate a latent bug elsewhere.

Thanks!  I'll start with easy ones that allow mechanical replacements
like fold_builtin_logarithm.

I was just going to say that I would probably go through bootstrap and
regtesting to verify that those two types are indeed identical, but
then how would I compare two types if pointer comparison is likely to
give false positives?  Is ther a convenient function?  (I grepped
certain keywords in GCC, but I didn't find anything that's close to
our purpose.)

Kazu Hirata