Commen=
t # 12
on bug 98664<=
/a>
from Ilia Mirkin
(In reply to Nicolai H=C3=A4hnle from comment #10)
> The geometry shader is incorrect. I guess it wor=
ks on i965 because the NIR
> path skips some optimizations that are allowed by the GLSL spec, which=
has
> this to say about EmitVertex():
>=20
> "Emits the current values of output variables to the current
> output primitive. On return from this call, the values of
> output variables are undefined."
>=20
> In other words, you need to store outMinEdge / outMaxEdge in temporary
> variables.
FWIW I've noticed that NVIDIA blob tends to go exactly counter to this, and
explicitly "latches" the values. (While i965 hardware behaves thi=
s way by
default, NVIDIA hw does not - it takes extra effort to make it do that, and=
the
NVIDIA blob does it. We've resorted to doing it for gl_Layer/gl_ViewportInd=
ex
in nouveau, but not other varyings.)
Note that it's not necessary to re-emit flat varyings for every vertex, just
the provoking vertex. This tends to be the last vertex by default, I believ=
e.
(And I don't know if that's prior to strip decomposition or not.)