[gstreamer-bugs] [Bug 615696] Shaders using GLSL 1.20 without #version.

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=615696
  GStreamer | gst-plugins-gl | git

--- Comment #2 from Eric Anholt <eric at anholt.net> 2010-04-14 21:15:39 UTC ---
I don't know how to test performance using gst-launch, but I suspect there was
a big impact from making these changes.  The 965+ takes about a 30% speed hit
if there is conditional execution.  The current Mesa compiler doesn't turn your
conditionals into unconditional execution with conditional moves to avoid that,
and pre-965 we can't do conditional execution at all.  The loops are getting
unrolled, though, and the arrays turned into scalars (loops are so painful to
hardware that Mesa will unroll just about anything you hand it.  The one piece
of real world code I've seen that doesn't get unrolled also doesn't execute
correctly!)

Texture fetches do call out to the shared texture fetch unit, but given the
locality of access, the latency of it should be pretty decent.  Probably
comparable with the cost of doing the divide I optimized out.

Do you expect the convolution kernels to change over time?  If not, then you
could bake the constants in your shader sources at compile time instead of
using uniforms, which would give the compiler the chance to do all the
optimizations I was doing by hand.

-- 
Configure bugmail: https://bugzilla.gnome.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the QA contact for the bug.
You are the assignee for the bug.