On 03/21/2012 06:36 AM, Brian Paul wrote:
On 03/21/2012 05:42 AM, Jose Fonseca wrote:
The increase sounds good to me.
But 64 seems small. SM3 allows loops up to 255 iterations, and
Microsoft HLSL compiler will unroll loops that big.
I'm happy to raise the limit higher. If there's no objections let's go
with 255.
Although I wonder why we don't simply unroll everything until we hit
PIPE_SHADER_CAP_MAX_INSTRUCTIONS too, when options->EmitNoLoops is false.
Luca Barbieri wrote this code in commit
b37459388b22fb6a831d45bc08e51cdb7b9c610c.
I'd be happy to set the MaxUnrollIterations unconditionally, without
regard to EmitNoLoops. I was just trying to make the least invasive
change to fix the problem at hand (and I think I'd still prefer to do
that for the time being).
We have to be careful with # of instructions vs. # of iterations. Most
loops have at least two instructions so
PIPE_SHADER_CAP_MAX_INSTRUCTIONS/2 would seem to be a better choice.
Though even that's probably unneccesarily large.
I guess the key question is do we want smaller shaders with loops or
larger shaders without loops?
Unfortunately, the answer to that question depends entirely on the
hardware and on the size of the loop body (usually). We're still in
want of a better loop unroller.
The other issue, that has been noted by at least one piglit test, is
that allowing huge amounts of unrolling can cause compile times to
explode to unacceptable levels.
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/mesa-dev
