i965/vec4: Call opt_algebraic after opt_cse.

The next patch adds an algebraic optimization for the pattern

   sqrt a, b
   rcp  c, a

and turns it into

   sqrt a, b
   rsq  c, b

but many vertex shaders do

   a = sqrt(b);
   var1 /= a;
   var2 /= a;

which generates

   sqrt a, b
   rcp  c, a
   rcp  d, a

If we apply the algebraic optimization before CSE, we'll end up with

   sqrt a, b
   rsq  c, b
   rcp  d, a

Applying CSE combines the RCP instructions, preventing this from
happening.

No shader-db changes.

Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/mesa/drivers/dri/i965/brw_vec4.cpp

@@ -1790,8 +1790,8 @@ vec4_visitor::run()
       OPT(dead_code_eliminate);
       OPT(dead_control_flow_eliminate, this);
       OPT(opt_copy_propagation);
-      OPT(opt_algebraic);
       OPT(opt_cse);
+      OPT(opt_algebraic);
       OPT(opt_register_coalesce);
    } while (progress);