James Cook <falsifian@falsifian.org> writes:

> On Mon, Apr 22, 2024 at 11:21:36AM GMT, Greg Steuck wrote:

>> James, if you'd like to play with this on -current, please remove both
>> patch-libraries_text_simdutf_simdutf_h and
>> patch-libraries_text_cbits_measure_off_c
>> 
>> This should make the offending check disappear and the pre-existing
>> checks should correctly report the OS doesn't support these instructions
>> on your machine. We can then confirm that avx-512 is working for people
>> who previously had problems.
>
> It works. I upgraded to -current and built ghc (now version 9.6.5)
> after deleting patches/patch-libraries_text_cbits_measure_off_c and
> patches/patch-libraries_text_simdutf_simdutf_h. All three examples
> now work (i.e. no SIGILL):

Excellent, thanks James! Antoine, would you be willing to repeat this on
an avx512 machine so that we can fix this in -current?

>
> - T.take 1 $ T.pack "aa" in ghci
> - pandoc </dev/null
> - cabal-bundler
>
> This is on the old AMD Phenom machine.
>
> If you're interested in fixing it on 7.5 (I don't know how much
> effort patching -stable ports is) please let me know if there's any
> more testing that would be helpful for the patch I sent earlier
> that makes has_avx512_vl_bw unconditionally return false. I can
> still boot this machine to 7.5 with a USB stick.

I'd be hesitant to do more work on this as you are already unblocked.  I
suspect the number of people who use ghc-built packages on such CPUs is
low enough in our user base that the effort is not likely to be well
spent.

Thanks
Greg