+/* Conditions for which we want to avoid setting the dependency control bits */
+bool
+vec4_visitor::is_dep_ctrl_unsafe(const vec4_instruction *inst)
+{
+#define IS_DWORD(reg) \
+ (reg.type == BRW_REGISTER_TYPE_UD || \
+ reg.type == BRW_REGISTER_TYPE_D)
+
+ /* From the destination hazard section of the spec:
+ * > Instructions other than send, may use this control as long as operations
+ * > that have different pipeline latencies are not mixed.
+ */
+ if (brw->gen >= 8) {
+ if (inst->opcode == BRW_OPCODE_MUL &&
+ IS_DWORD(inst->src[0]) &&
+ IS_DWORD(inst->src[1]))
+ return true;
+ }
+#undef IS_DWORD
+
+ /*
+ * mlen:
+ * In the presence of send messages, totally interrupt dependency
+ * control. They're long enough that the chance of dependency
+ * control around them just doesn't matter.
+ *
+ * predicate:
+ * From the Ivy Bridge PRM, volume 4 part 3.7, page 80:
+ * When a sequence of NoDDChk and NoDDClr are used, the last instruction that
+ * completes the scoreboard clear must have a non-zero execution mask. This
+ * means, if any kind of predication can change the execution mask or channel
+ * enable of the last instruction, the optimization must be avoided. This is
+ * to avoid instructions being shot down the pipeline when no writes are
+ * required.
+ *
+ * math:
+ * Dependency control does not work well over math instructions.
+ * NB: Discovered empirically
+ */
+ return (inst->mlen || inst->predicate || inst->is_math());
+}
+