Re: Is UBSan supposed to produce a finding for _mm_load_sd and _mm_store_sd

[Jeffrey Walton <noloader at gmail dot com>]

On Fri, Dec 8, 2017 at 12:28 PM, Marc Glisse <marc.glisse@inria.fr> wrote:
> On Fri, 8 Dec 2017, Jeffrey Walton wrote:
> ...
>> According to the Intel Intrinsics Guide (e.g., _mm_load_sd):
>>
>>    Load a double-precision (64-bit) floating-point element from memory
>>    into the lower of dst, and zero the upper element. mem_addr does
>>    not need to be aligned on any particular boundary.
>>
>> Should GCC be producing a finding in this case? Is there a way to work
>> around it without an extra memcpy?
>
> The way _mm_load_sd is currently implemented in gcc, yes, sanitizers are
> right to complain. Intel could have named the thing _mm_loadu_sd if that's
> what they meant. It would be simple to change if we decide to do so, please
> file a PR in bugzilla.
>
> Workaround: define a typedef for double with
> __attribute__((__aligned__(1))), and use _mm_set_sd(*(newtype*)p), that's
> how it will likely be done if we change emmintrin.h.

Thanks again Marc.

I opened an issue at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84508 .

Jeff