Re: Not-terribly-safe checks for CRC intrinsic support

On Sat, Mar 15, 2025 at 6:04 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> In short, I think we ought to apply and perhaps back-patch something
> like the attached.

Seems like reasonable defensive coding and consistency.

- /* return computed value, to prevent the above being optimized away */
+ /* else this function could get optimized away altogether: */

- /* return computed value, to prevent the above being optimized away */
+ /* return computed value, just to be extra sure this isn't
optimized away */

I'd be okay with keeping the original comment, though, since it seems
to be explaining the choice well enough.

> BTW, it looks to me like PGAC_AVX512_POPCNT_INTRINSICS is at similar
> hazard, but I'm not entirely sure how to fix that one.

"buf" is the variable there that we're loading from, so that would be
the one to make global.

--
John Naylor
Amazon Web Services