[Bug tree-optimization/50596] Problems in vectorization of condition expression

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50596

--- Comment #6 from rguenther at suse dot de <rguenther at suse dot de> 2011-10-04 11:26:51 UTC ---
On Tue, 4 Oct 2011, jakub at gcc dot gnu.org wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50596
> 
> --- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-10-04 11:13:58 UTC ---
> (In reply to comment #4)
> > I agree with the need to at least support vectorizing loads and stores of
> > 1-bit unsigned precision values.  We need to be careful with arithmetic
> > and conversions though (which is why we reject bools right now).
> 
> We could represent the arithmetic and conversions (or at least subset thereof)
> using *COND_EXPRs etc.  In any case, the bool representation is desirable for
> the scalar loop, so this isn't something we should be doing in ifcvt, it needs
> to be done in the vectorizer itself.

Sure.  Note that in GIMPLE

 bool = (bool) int;

isn't equivalent to bool = int != 0 but to a truncation to 1-bit
precision.  Thus for the truncation a BIT_AND is enough.  I'm just
worried about N-precision signed to mode-precision sign-extension
(for the 1-bit case we can use a COND_EXPR, but for more bits
it gets more difficult).

Richard.