src/ieee754/fpcommon/roundz.py

   1 # IEEE Floating Point Adder (Single Precision)
   2 # Copyright (C) Jonathan P Dawson 2013
   3 # 2013-12-12
   4
   5 from nmigen import Module, Signal, Elaboratable
   6 from nmigen.cli import main, verilog
   7
   8 from ieee754.fpcommon.fpbase import FPNumBase, FPNumBaseRecord
   9 from ieee754.fpcommon.fpbase import FPState
  10 from .postnormalise import FPNorm1Data
  11
  12
  13 class FPRoundData:
  14
  15     def __init__(self, width, id_wid):
  16         self.z = FPNumBaseRecord(width, False)
  17         self.mid = Signal(id_wid, reset_less=True) # multiplex ID
  18         # pipeline bypass [data comes from specialcases]
  19         self.out_do_z = Signal(reset_less=True)
  20         self.oz = Signal(width, reset_less=True)
  21
  22     def eq(self, i):
  23         return [self.z.eq(i.z), self.out_do_z.eq(i.out_do_z), self.oz.eq(i.oz),
  24                 self.mid.eq(i.mid)]
  25
  26
  27 class FPRoundMod(Elaboratable):
  28
  29     def __init__(self, width, id_wid):
  30         self.width = width
  31         self.id_wid = id_wid
  32         self.i = self.ispec()
  33         self.out_z = self.ospec()
  34
  35     def ispec(self):
  36         return FPNorm1Data(self.width, self.id_wid)
  37
  38     def ospec(self):
  39         return FPRoundData(self.width, self.id_wid)
  40
  41     def process(self, i):
  42         return self.out_z
  43
  44     def setup(self, m, i):
  45         m.submodules.roundz = self
  46         m.d.comb += self.i.eq(i)
  47
  48     def elaborate(self, platform):
  49         m = Module()
  50         m.d.comb += self.out_z.eq(self.i) # copies mid, z, out_do_z
  51         with m.If(~self.i.out_do_z): # bypass wasn't enabled
  52             with m.If(self.i.roundz):
  53                 m.d.comb += self.out_z.z.m.eq(self.i.z.m + 1) # mantissa up
  54                 with m.If(self.i.z.m == self.i.z.m1s): # all 1s
  55                     m.d.comb += self.out_z.z.e.eq(self.i.z.e + 1) # exponent up
  56
  57         return m
  58
  59
  60 class FPRound(FPState):
  61
  62     def __init__(self, width, id_wid):
  63         FPState.__init__(self, "round")
  64         self.mod = FPRoundMod(width)
  65         self.out_z = self.ospec()
  66
  67     def ispec(self):
  68         return self.mod.ispec()
  69
  70     def ospec(self):
  71         return self.mod.ospec()
  72
  73     def setup(self, m, i):
  74         """ links module to inputs and outputs
  75         """
  76         self.mod.setup(m, i)
  77
  78         self.idsync(m)
  79         m.d.sync += self.out_z.eq(self.mod.out_z)
  80         m.d.sync += self.out_z.mid.eq(self.mod.o.mid)
  81
  82     def action(self, m):
  83         m.next = "corrections"