[Mesa-dev] [Mesa-stable] [PATCH] i965/fs: Don't emit SEL instructions for type-converting MOVs.

[Matt Turner]

On Fri, Mar 24, 2017 at 12:06 AM, Francisco Jerez <currojerez at riseup.net> wrote:
> Samuel Iglesias Gonsálvez <siglesias at igalia.com> writes:
>
>> On Thu, 2017-03-23 at 13:50 -0700, Matt Turner wrote:
>>> SEL can only convert between a few integer types, which we basically
>>> never do.
>>>
>>> Fixes fs/vs-double-uniform-array-direct-indirect-non-uniform-control-
>>> flow
>>> Cc: mesa-stable at lists.freedesktop.org
>>
>> I sent a similar but wrong patch (taking only into account the type
>> size) some time ago, but after discussing it with Curro, the solution
>> was to fix it inside d2x pass. This is what this patch "i965/fs:
>> generalize the legalization d2x pass" does.
>>
>> I am still working on improving that patch but I expect to have
>> something soon. If you prefer to land this now, please add my R-b but
>> you probably want to discuss it with Curro before:
>>
>> Reviewed-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
>>
>
> Samuel's d2x patch has the advantage that it will allow the SEL peephole
> to replace control flow with SEL instructions even where there is a type
> conversion.  That said this patch shouldn't hurt in mesa-stable in the
> meantime if we remember to revert it in master when Samuel's patch
> lands.  Patch is:
>
> Acked-by: Francisco Jerez <currojerez at riseup.net>

Oh, I didn't realize that pass was going to handle instructions not
operating on DF types. That's surprising given its name.

To confirm: with that pass in place it should be save to do a
type-converting SEL (on, say, integer sources and a float destination)
in the IR?

If that's the case, I'll delay committing this patch until lower_d2x
is committed, so that we don't have to remember to revert my patch,
and there's no chance of bugs being fixed on the stable branch but not
in master.