On 2017-11-11 12:41:40 -0500, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > That's using SSE, which requires 16byte alignment IIRC. I think we need
> > a function that properly allocate int128 vars with the right alignment -
> > don't think we want to go for full 16byte alignment for everything.
>
> Yeah, changing MAXALIGN is out of the question. I'm thinking about
> another flag bit for MemoryContextAllocExtended. Do we need to think
> about other use-cases besides int128? Should we just force 16-byte
> alignment on all architectures, or does it need to be platform-specific?
I'm not sure we want to
a) Rely on one alignment being enough for everybody.
b) Additionally burden already hot code paths with a growing number of alignment flag tests, and the necessary math.
How about a MemoryContextAllocAligned(context, size, alignto, flags)
that passes on most flags but adds the necessary overhead to size, and
padds the result appropriately?
Greetings,
Andres Freund
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