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From: "noloader at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/84508] Load of misaligned address using _mm_load_sd
Date: Wed, 29 May 2024 19:01:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D84508

--- Comment #23 from Jeffrey Walton <noloader at gmail dot com> ---
(In reply to Peter Cordes from comment #22)
> [...]
> That instruction is useless and should never be used in asm except for
> code-alignment reasons (1 byte longer than MOVLPS, same length as MOVSD, =
all
> three doing the same thing for the memory-destination form).  But easy to
> imagine some code using that intrinsic to store an unaligned double into a
> byte buffer.

Reading from and writing to a [unaligned] byte stream in 4 or 8 byte chunks=
 is
our use case. Eventually, we need to perform traditional SIMD processing. B=
ut
the loads and stores have to occur using these old instrinsics due to the w=
ord
types, data stream format and supported ISA's.

I believe the other option is to memcpy the byte stream into a properly ali=
gned
intermediate buffer. But that could incur a performance hit if the optimizer
misses the opportunity (and fails to elide the memcpy).=