Some Cava optimization

• Optimize Cava's CPU schedule.
• Add fork-fusion pass for fusing unrelated but adjacent fork-joins.
• Add intrinsic functions to math expressions.
• Add print pass for debugging schedules.
• Avoid some edges in dot output to help little xdot out.
• TODO: need more relaxed bounds for forkify to parallelize demosaic.

juno_samples/cava/src/cava.jn

@@ -153,7 +153,7 @@ fn gamut<row : usize, col : usize, num_ctrl_pts : usize>(
         l2_dist[cp] = sqrt!::<f32>(v);
       }
 
-      for chan = 0 to CHAN {
+      @channel_loop for chan = 0 to CHAN {
         let chan_val : f32 = 0.0;
         for cp = 0 to num_ctrl_pts {
           chan_val += l2_dist[cp] * weights[cp, chan];