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From: "torvalds@linux-foundation.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/100363] gcc generating wider load/store than
 warranted at -O3
Date: Sat, 01 May 2021 23:09:45 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100363

--- Comment #8 from Linus Torvalds <torvalds@linux-foundation.org> ---
(In reply to Alexander Monakov from comment #7)
>=20
> Most likely the issue is that sout/sfrom are misaligned at runtime, while
> the vectorized code somewhere relies on them being sufficiently aligned f=
or
> a 'short'.

They absolutely are.

And we build the kernel with -Wno-strict-aliasing exactly to make sure the
compiler doesn't think that "oh, I can make aliasing decisions based on type
information".

Because we have those kinds of issues all over, and we know which architect=
ures
support unaligned loads etc, and all the tricks with "memcpy()" and unions =
make
for entirely unreadable code.

So please fix the aliasing logic to not be type-based when people explicitly
tell you not to do that.

Linus=