[Bug target/92658] x86 lacks vector extend / truncate

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92658

--- Comment #11 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 14 May 2020, ubizjak at gmail dot com wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92658
> 
> --- Comment #10 from Uroš Bizjak <ubizjak at gmail dot com> ---
> The patch is ready to be pushed, it is waiting for a decision what to do with
> failed cases.
> 
> Richi, should this patch move forward (eventually XFAILing failed cases), or do
> you plan to look at the fails from the generic vectorizer POV?

I think we should go forward with the patch, either XFAILing the testcases
or splitting out the testcase (and backend patterns that do not get
exercised due to the issue).

I've already said in comment#8 that the issue here is optabs working
with modes and not vector types, so it's a bit hard to use the
same mechanism to deal with the currently failing cases.  One
possible route would be to add V4QImode similar to how we now
do V2SFmode with SSE but of course where do we stop ...

As said we can try to tackle this incrementally.  Maybe Richard also
has input here?