FEEDBACK wires need a default assignment in code

[JulianKemmerer]

without then tool mistakenly reads from feedback signal like a register and is just wire connected to self connected to nothing...

uint8_t reg_wr_data;
#pragma FEEDBACK reg_wr_data

if(thing)
  reg_wr_data = 1;
else
  reg_wr_data = 0;

Will get synthesis warning about net with no driver

feedback_vars.reg_wr_data <= feedback_vars.reg_wr_data; will appear in VHDL

Change to

reg_wr_data = 0;
if(thing)
  reg_wr_data = 1;

to have explicit default driver of feedback variable