src/ieee754/cordic/fp_pipe_init_stages.py

   1 from nmigen import (Module, Signal, Cat, Const, Mux, Repl, signed,
   2                     unsigned)
   3 from nmigen.cli import main, verilog
   4
   5 from ieee754.fpcommon.fpbase import FPNumDecode, FPNumBaseRecord
   6
   7 from nmutil.pipemodbase import PipeModBase
   8 from ieee754.fpcommon.basedata import FPBaseData
   9 from ieee754.fpcommon.denorm import FPSCData
  10 from ieee754.cordic.fp_pipe_data import CordicInitialData
  11
  12
  13 class FPCordicInitStage(PipeModBase):
  14     def __init__(self, pspec):
  15         super().__init__(pspec, "specialcases")
  16
  17     def ispec(self):
  18         return FPBaseData(self.pspec)
  19
  20     def ospec(self):
  21         return FPSCData(self.pspec, False)
  22
  23     def elaborate(self, platform):
  24         m = Module()
  25         comb = m.d.comb
  26
  27         # decode a/b
  28         width = self.pspec.width
  29         a1 = FPNumBaseRecord(width, False)
  30         m.submodules.sc_decode_a = a1 = FPNumDecode(None, a1)
  31         comb += [a1.v.eq(self.i.a),
  32                  self.o.a.eq(a1)
  33         ]
  34
  35         #  pass through context
  36         comb += self.o.ctx.eq(self.i.ctx)
  37
  38         return m
  39
  40
  41 class FPCordicConvertFixed(PipeModBase):
  42     def __init__(self, pspec):
  43         super().__init__(pspec, "tofixed")
  44
  45     def ispec(self):
  46         return FPSCData(self.pspec, False)
  47
  48     def ospec(self):
  49         return CordicInitialData(self.pspec)
  50
  51     def elaborate(self, platform):
  52         m = Module()
  53         comb = m.d.comb
  54
  55         shifter = Signal(self.i.a.e.width)
  56         comb += shifter.eq(-self.i.a.e)
  57
  58         z_intermed = Signal(unsigned(self.o.z0.width))
  59         z_shifted = Signal(signed(self.o.z0.width))
  60         comb += z_intermed.eq(Cat(Repl(0, self.pspec.fracbits -
  61                                        self.i.a.rmw),
  62                                   self.i.a.m))
  63         comb += z_shifted.eq(z_intermed >> shifter)
  64         comb += self.o.z0.eq(Mux(self.i.a.s,
  65                                  ~z_shifted + 1,
  66                                  z_shifted))
  67
  68         return m
  69