src/soc/minerva/units/compare.py

   1 from nmigen import Elaboratable, Module, Signal
   2
   3 from ..isa import Funct3
   4
   5
   6 __all__ = ["CompareUnit"]
   7
   8
   9 class CompareUnit(Elaboratable):
  10     def __init__(self):
  11         self.op = Signal(3)
  12         self.zero = Signal()
  13         self.negative = Signal()
  14         self.overflow = Signal()
  15         self.carry = Signal()
  16
  17         self.condition_met = Signal()
  18
  19     def elaborate(self, platform):
  20         m = Module()
  21
  22         with m.Switch(self.op):
  23             with m.Case(Funct3.BEQ):
  24                 m.d.comb += self.condition_met.eq(self.zero)
  25             with m.Case(Funct3.BNE):
  26                 m.d.comb += self.condition_met.eq(~self.zero)
  27             with m.Case(Funct3.BLT):
  28                 m.d.comb += self.condition_met.eq(~self.zero & (self.negative != self.overflow))
  29             with m.Case(Funct3.BGE):
  30                 m.d.comb += self.condition_met.eq(self.negative == self.overflow)
  31             with m.Case(Funct3.BLTU):
  32                 m.d.comb += self.condition_met.eq(~self.zero & self.carry)
  33             with m.Case(Funct3.BGEU):
  34                 m.d.comb += self.condition_met.eq(~self.carry)
  35
  36         return m