Finding Voters After Symbiflow Renames Primitives

[jacobdbrown4]

Symbiflow renames some primitives during symbiflow_synth. For example, an FDRE is renamed to be FDRE_ZINI. This causes spydrnet's function to find voter insertion points to come up empty.

For now I've just been finding voter insertion points manually (with a few lines of code).

[wirthlin]

Do you know if the tool is creating a wrapper around the FDRE or is it indeed a leaf cell? Dr. Nelson thinks there is a wrapper. @nelsobe

[nelsobe]

ZINI appears all through Symbiflow. Symbiflow usually uses ZINI to refer to initialization. So, it might be wrapper for a flip flop that is initialized to a 1 or to a 0 or something like that. I would do some digging into that.

Also, one of the issues I have with Symbiflow is they rename lots of things which makes it hard to inter-operate with Vivado. For example - they name some BEL properties differently than Vivado names them... It sounds ike this is another case of that maybe?

[jacobdbrown4]

In the netlist it shows up as a leaf cell.

It probably is another case of renaming something to possibly carry information.

In ~/opt/symbiflow/xc7/install/share/symbiflow/techmaps there are files with verilog modules. It looks like they are imported into yosys during synthesis. Here is one for FDRE:

module FDRE (output reg Q, input C, CE, D, R);

parameter [0:0] INIT = 1'b0;

wire CE_SIG;
wire SR_SIG;

CESR_MUX cesr_mux(
    .CE(CE),
    .SR(R),
    .CE_OUT(CE_SIG),
    .SR_OUT(SR_SIG)
);

FDRE_ZINI #(.ZINI(!|INIT), .IS_C_INVERTED(|0))
  _TECHMAP_REPLACE_ (.D(D), .Q(Q), .C(C), .CE(CE_SIG), .R(SR_SIG));

endmodule

FDRE_ZINI shows up at the bottom.

[jacobdbrown4]

A lot of things are renamed. For example: OBUF --> OBUFT_VPR IBUF --> IBUF_VPR INV --> T_INV

[jacobdbrown4]

This page may be helpful to us: Technology mapping for VPR