[Mesa-dev] [PATCH 2/5] i965/fs: Lower 32x32 bit multiplication on BXT.

[Matt Turner]

On Mon, Aug 10, 2015 at 12:01 PM, Neil Roberts <neil at linux.intel.com> wrote:
> Are you sure this patch is necessary? The documentation for the multiply
> instruction on BDW+ says:
>
> SourceType :    *D
> DestinationType :       *D
> Project :       EXCLUDE(CHV)
>
> This to me implies that it should work on BXT because it doesn't say
> EXCLUDE(BXT).

Unclear since EXCLUDE(CHV) didn't exist until recently either. :)

I tried checking the BXT bug database, but the search is now broken...

> I made a little test case and ran it on my BXT and it seems to work even
> without this patch. I looked at the assembler source and it is
> definitely doing a MUL instruction with D types for the dst and two
> sources.
>
> https://github.com/bpeel/piglit/blob/test-integer-multiply/tests/general/mult32.c

That seems like pretty good evidence. Reverting the patch and running
piglit on BXT is probably the only way to know for sure.