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 ieee754.fpcommon.getop import FPBaseData
  11 from .postnormalise import FPNorm1Data
  12
  13
  14 class FPRoundData:
  15
  16     def __init__(self, width, pspec):
  17         self.z = FPNumBaseRecord(width, False)
  18         self.ctx = FPBaseData(width, pspec)
  19         self.mid = self.ctx.mid
  20         # pipeline bypass [data comes from specialcases]
  21         self.out_do_z = Signal(reset_less=True)
  22         self.oz = Signal(width, reset_less=True)
  23
  24     def eq(self, i):
  25         ret = [self.z.eq(i.z), self.out_do_z.eq(i.out_do_z), self.oz.eq(i.oz),
  26                 self.ctx.eq(i.ctx)]
  27         return ret
  28
  29
  30 class FPRoundMod(Elaboratable):
  31
  32     def __init__(self, width, pspec):
  33         self.width = width
  34         self.pspec = pspec
  35         self.i = self.ispec()
  36         self.out_z = self.ospec()
  37
  38     def ispec(self):
  39         return FPNorm1Data(self.width, self.pspec)
  40
  41     def ospec(self):
  42         return FPRoundData(self.width, self.pspec)
  43
  44     def process(self, i):
  45         return self.out_z
  46
  47     def setup(self, m, i):
  48         m.submodules.roundz = self
  49         m.d.comb += self.i.eq(i)
  50
  51     def elaborate(self, platform):
  52         m = Module()
  53         m.d.comb += self.out_z.eq(self.i) # copies mid, z, out_do_z
  54         with m.If(~self.i.out_do_z): # bypass wasn't enabled
  55             with m.If(self.i.roundz):
  56                 m.d.comb += self.out_z.z.m.eq(self.i.z.m + 1) # mantissa up
  57                 with m.If(self.i.z.m == self.i.z.m1s): # all 1s
  58                     m.d.comb += self.out_z.z.e.eq(self.i.z.e + 1) # exponent up
  59
  60         return m
  61
  62
  63 class FPRound(FPState):
  64
  65     def __init__(self, width, id_wid):
  66         FPState.__init__(self, "round")
  67         self.mod = FPRoundMod(width)
  68         self.out_z = self.ospec()
  69
  70     def ispec(self):
  71         return self.mod.ispec()
  72
  73     def ospec(self):
  74         return self.mod.ospec()
  75
  76     def setup(self, m, i):
  77         """ links module to inputs and outputs
  78         """
  79         self.mod.setup(m, i)
  80
  81         self.idsync(m)
  82         m.d.sync += self.out_z.eq(self.mod.out_z)
  83         m.d.sync += self.out_z.ctx.eq(self.mod.o.ctx)
  84
  85     def action(self, m):
  86         m.next = "corrections"