Commen=
t # 16
on bug 98664<=
/a>
from Roland Scheidegger
(In reply to Nicolai H=C3=A4hnle from comment #14)
> I suspect the reason that the blob drivers do it=
this way is that if you
> don't, you're likely to hit a subtle bug with emit inside control flow=
. And
> making the effort to exploit the undefined-ness probably pays off very
> rarely, so...
Also, you can do this with dx10, so app developers porting things are somew=
hat
likely to get it wrong (I suppose that's similar to other such subtle issues
like discard killing your derivatives if you have per-pixel control flow wi=
th
gl, but not with dx10).
At least I think so from the description of emit:
https://msdn.microsoft.com/en-us/library/windows/desktop=
/hh447053(v=3Dvs.85).aspx
"emit causes all declared o# registers to be read out of the Geometry =
Shader to
generate a vertex." Doesn't say explicitly the registers are still val=
id
afterwards, but since reading a register usually doesn't nuke the value, the
reg getting undefined would be a side-effect which should have been
mentioned...