Brief explanation about the control signal fields

CtrlType(optType, isCurOptPredicateBased, [registersUsedForComputation], [portsWithDataToBeRouted], [predicatesForFutureComputation])

• optType can be found in lib/opt_type.py, there are currently more or less 40 operation/computation types supported, which represented in 6 bits.
• isCurOptPredicateBased indicates whether this operation is predicate-based. Specifically, if set as false, this operation will be executed. If true, the execution of this operation depends on the predicate bit embedded in the data message. Normally, the predicate in the data message is calculated by the phi operation (to enable control-flow). Just set this field as b1(0) if no control-flow is involved.
• [registersUsedForComputation] is a list contains num_fu_in (i.e., 4 in this case) items. It indicates the register ID that will be used for computation. There are 4 possible inputs in this tile configuration, so the length of the list is 4. Note that maybe less than 4 operations are used for computations. For example, NOT requires one, Add requires two, MAC requires three, and the complex FU that contains two parallel adders require four. In addition, the register ID starts from 1 as 0 is reserved to indicate invalid. For example, if data a is located in the second register while data b is located in the first register, to perform a - b, [registersUsedForComputation] should be set as [2,1,0,0].
• [portsWithDataToBeRouted] indicates how the data will be routed on the xbar. It contains num_xbar_outports items, which means each outport picks one inport for data delivery. In this case, we can see there are 8 items. The first 4 are the tile's outports (i.e., North, South, West, East). The second 4 are the 4 registers used for computation (i.e., [registersUsedForComputation]). Each item can choose the value ranging from 0 to 6. 0 is reserved indicating invalid, 1-4 indicate the inport N, S, W, and E. And 5-6 indicate the two outports of the functional unit.
• [predicatesForFutureComputation] is used to indicate that the predicate bit in the result message will be calculated based on the data coming from this port. Ignore this field if no control-flow is involved.