src/ieee754/add/fpcommon/denorm.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
   6 from nmigen.cli import main, verilog
   7 from math import log
   8
   9 from fpbase import FPNumIn, FPNumOut, FPNumBase
  10 from fpbase import FPState
  11
  12
  13 class FPSCData:
  14
  15     def __init__(self, width, id_wid):
  16         self.a = FPNumBase(width, True)
  17         self.b = FPNumBase(width, True)
  18         self.z = FPNumOut(width, False)
  19         self.oz = Signal(width, reset_less=True)
  20         self.out_do_z = Signal(reset_less=True)
  21         self.mid = Signal(id_wid, reset_less=True)
  22
  23     def __iter__(self):
  24         yield from self.a
  25         yield from self.b
  26         yield from self.z
  27         yield self.oz
  28         yield self.out_do_z
  29         yield self.mid
  30
  31     def eq(self, i):
  32         return [self.z.eq(i.z), self.out_do_z.eq(i.out_do_z), self.oz.eq(i.oz),
  33                 self.a.eq(i.a), self.b.eq(i.b), self.mid.eq(i.mid)]
  34
  35
  36 class FPAddDeNormMod(FPState):
  37
  38     def __init__(self, width, id_wid):
  39         self.width = width
  40         self.id_wid = id_wid
  41         self.i = self.ispec()
  42         self.o = self.ospec()
  43
  44     def ispec(self):
  45         return FPSCData(self.width, self.id_wid)
  46
  47     def ospec(self):
  48         return FPSCData(self.width, self.id_wid)
  49
  50     def process(self, i):
  51         return self.o
  52
  53     def setup(self, m, i):
  54         """ links module to inputs and outputs
  55         """
  56         m.submodules.denormalise = self
  57         m.d.comb += self.i.eq(i)
  58
  59     def elaborate(self, platform):
  60         m = Module()
  61         m.submodules.denorm_in_a = self.i.a
  62         m.submodules.denorm_in_b = self.i.b
  63         m.submodules.denorm_out_a = self.o.a
  64         m.submodules.denorm_out_b = self.o.b
  65
  66         with m.If(~self.i.out_do_z):
  67             # XXX hmmm, don't like repeating identical code
  68             m.d.comb += self.o.a.eq(self.i.a)
  69             with m.If(self.i.a.exp_n127):
  70                 m.d.comb += self.o.a.e.eq(self.i.a.N126) # limit a exponent
  71             with m.Else():
  72                 m.d.comb += self.o.a.m[-1].eq(1) # set top mantissa bit
  73
  74             m.d.comb += self.o.b.eq(self.i.b)
  75             with m.If(self.i.b.exp_n127):
  76                 m.d.comb += self.o.b.e.eq(self.i.b.N126) # limit a exponent
  77             with m.Else():
  78                 m.d.comb += self.o.b.m[-1].eq(1) # set top mantissa bit
  79
  80         m.d.comb += self.o.mid.eq(self.i.mid)
  81         m.d.comb += self.o.z.eq(self.i.z)
  82         m.d.comb += self.o.out_do_z.eq(self.i.out_do_z)
  83         m.d.comb += self.o.oz.eq(self.i.oz)
  84
  85         return m
  86
  87
  88 class FPAddDeNorm(FPState):
  89
  90     def __init__(self, width, id_wid):
  91         FPState.__init__(self, "denormalise")
  92         self.mod = FPAddDeNormMod(width)
  93         self.out_a = FPNumBase(width)
  94         self.out_b = FPNumBase(width)
  95
  96     def setup(self, m, i):
  97         """ links module to inputs and outputs
  98         """
  99         self.mod.setup(m, i)
 100
 101         m.d.sync += self.out_a.eq(self.mod.out_a)
 102         m.d.sync += self.out_b.eq(self.mod.out_b)
 103
 104     def action(self, m):
 105         # Denormalised Number checks
 106         m.next = "align"
 107
 108