[PATCH][ARM64] Fix "Cannot select" for vector ctpop

[Quentin Colombet]

Hi Adam,

LGTM.

Thanks,
-Quentin

On Apr 16, 2014, at 3:27 PM, Adam Nemet <anemet at apple.com> wrote:

> The commit of r205855:
> 
> Author: Arnold Schwaighofer <aschwaighofer at apple.com>
> Date:   Wed Apr 9 14:20:47 2014 +0000
> 
>    SLPVectorizer: Only vectorize intrinsics whose operands are widened equally
> 
>    The vectorizer only knows how to vectorize intrinics by widening all operands by
>    the same factor.
> 
>    Patch by Tyler Nowicki!
> 
> exposed a backend bug causing a regression (Cannot select ctpop).
> 
> The commit msg is a bit confusing because the patch actually changes the
> behavior for the loop-vectorizer as well.  As things got refactored into a
> helper ctpop got snuck in to the trivially-vectorizable helper which is now
> used by both vectorizers.  In other words, we started seeing vector-ctpops in
> the backend.
> 
> This change makes ctpop LegalizeAction::Expand for the types not supported by
> the byte-only CNT instruction.  We may be able to custom-lower these later to
> a single CNT but this is to fix the compiler crash first.
> 
> Fixes <rdar://problem/16578951>
> 
> Adam
> 
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