i965: Avoid dependency hints on math opcodes

Putting NoDDClr and NoDDChk dependency control on instruction
sequences that include math opcodes can cause corruption of channels.
Treat math opcodes like send opcodes and suppress dependency hinting.

Signed-off-by: Mike Stroyan <mike@LunarG.com>
Tested-by: Tony Bertapelli <anthony.p.bertapelli@intel.com>
Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Matt Turner <mattst88@gmail.com>

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

@@ -849,6 +849,14 @@ vec4_visitor::opt_set_dependency_control()
             continue;
          }
 
+         /* Dependency control does not work well over math instructions.
+          */
+         if (inst->is_math()) {
+            memset(last_grf_write, 0, sizeof(last_grf_write));
+            memset(last_mrf_write, 0, sizeof(last_mrf_write));
+            continue;
+         }
+
          /* Now, see if we can do dependency control for this instruction
           * against a previous one writing to its destination.
           */