src/soc/fu/shift_rot/input_stage.py

   1 # This stage is intended to adjust the input data before sending it to
   2 # the acutal ALU. Things like handling inverting the input, carry_in
   3 # generation for subtraction, and handling of immediates should happen
   4 # here
   5 from soc.fu.common_input_stage import CommonInputStage
   6 from soc.fu.shift_rot.pipe_data import ShiftRotInputData
   7
   8
   9 class ShiftRotInputStage(CommonInputStage):
  10     def __init__(self, pspec):
  11         super().__init__(pspec, "input")
  12
  13     def ispec(self):
  14         return ShiftRotInputData(self.pspec)
  15
  16     def ospec(self):
  17         return ShiftRotInputData(self.pspec)
  18
  19     def elaborate(self, platform):
  20         m = super().elaborate(platform) # handles A, carry and sticky overflow
  21         comb = m.d.comb
  22
  23         # operand rs
  24         comb += self.o.rs.eq(self.i.rs)
  25
  26         return m