Why align all pinned array payloads on 16 bytes?

[Alexander Kjeldaas]

The SSE types require 16-byte alignment.  Most of the original SSE
instructions have versions that accept non-aligned data though.

Alexander

On Tue, Oct 16, 2018 at 11:18 PM Simon Marlow <marlowsd at gmail.com> wrote:

> I vaguely recall that this was because 16 byte alignment is the minimum
> you need for certain foreign types, and it's what malloc() does.  Perhaps
> check the FFI spec and the guarantees that mallocForeignPtrBytes and
> friends provide?
>
> Cheers
> Simon
>
> On Thu, 11 Oct 2018 at 18:44, Ömer Sinan Ağacan <omeragacan at gmail.com>
> wrote:
>
>> Hi,
>>
>> I just found out we currently align all pinned array payloads to 16 bytes
>> and
>> I'm wondering why. I don't see any comments/notes on this, and it's also
>> not
>> part of the primop documentation. We also have another primop for aligned
>> allocation: newAlignedPinnedByteArray#. Given that alignment behavior of
>> newPinnedByteArray# is not documented and we have another one for aligned
>> allocation, perhaps we can remove alignment in newPinnedByteArray#.
>>
>> Does anyone remember what was the motivation for always aligning pinned
>> arrays?
>>
>> Thanks
>>
>> Ömer
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