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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/66917] [4.9/5/6 regression] ARM: NEON: memcpy compiles to vst1 with incorrect alignment due to SRA
Date: Thu, 30 Jul 2015 14:39:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66917

--- Comment #14 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 30 Jul 2015, rearnsha at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66917
> 
> Richard Earnshaw <rearnsha at gcc dot gnu.org> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>           Component|target                      |tree-optimization
> 
> --- Comment #12 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
> > but the arm hook seems to say "yes, I can vectorize with V2DImode
> > for a vector with element type unsigned long long __attribute__((aligned(1)))"
> > which it obviously cannot.
> 
> It can vectorize for this case, but the loads must not be marked as aligned
> loads.  That is, the mid-end must use the misaligned code hooks.
> 
> So I don't think this is a target bug.

Hmm, indeed.  It's a vectorizer bug that always communicates at least
element alignment (thus doesn't properly code-gen for the packed_p
case)