src/ieee754/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, Elaboratable
   6 from nmigen.cli import main, verilog
   7 from math import log
   8
   9 from ieee754.fpcommon.fpbase import FPNumIn, FPNumOut, FPNumBaseRecord
  10 from ieee754.fpcommon.fpbase import FPState, FPNumBase
  11
  12
  13 class FPSCData:
  14
  15     def __init__(self, width, id_wid, m_extra=True):
  16         self.a = FPNumBase(width, m_extra)
  17         self.b = FPNumBase(width, m_extra)
  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, Elaboratable):
  37
  38     def __init__(self, width, id_wid, m_extra=True):
  39         self.width = width
  40         self.id_wid = id_wid
  41         self.m_extra = m_extra
  42         self.i = self.ispec()
  43         self.o = self.ospec()
  44
  45     def ispec(self):
  46         return FPSCData(self.width, self.id_wid, self.m_extra)
  47
  48     def ospec(self):
  49         return FPSCData(self.width, self.id_wid, self.m_extra)
  50
  51     def process(self, i):
  52         return self.o
  53
  54     def setup(self, m, i):
  55         """ links module to inputs and outputs
  56         """
  57         m.submodules.denormalise = self
  58         m.d.comb += self.i.eq(i)
  59
  60     def elaborate(self, platform):
  61         m = Module()
  62         m.submodules.denorm_in_a = self.i.a
  63         m.submodules.denorm_in_b = self.i.b
  64         m.submodules.denorm_in_z = self.i.z
  65         m.submodules.denorm_out_a = self.o.a
  66         m.submodules.denorm_out_b = self.o.b
  67         m.submodules.denorm_out_z = self.o.z
  68
  69         with m.If(~self.i.out_do_z):
  70             # XXX hmmm, don't like repeating identical code
  71             m.d.comb += self.o.a.eq(self.i.a)
  72             with m.If(self.i.a.exp_n127):
  73                 m.d.comb += self.o.a.e.eq(self.i.a.N126) # limit a exponent
  74             with m.Else():
  75                 m.d.comb += self.o.a.m[-1].eq(1) # set top mantissa bit
  76
  77             m.d.comb += self.o.b.eq(self.i.b)
  78             with m.If(self.i.b.exp_n127):
  79                 m.d.comb += self.o.b.e.eq(self.i.b.N126) # limit a exponent
  80             with m.Else():
  81                 m.d.comb += self.o.b.m[-1].eq(1) # set top mantissa bit
  82
  83         m.d.comb += self.o.mid.eq(self.i.mid)
  84         m.d.comb += self.o.z.eq(self.i.z)
  85         m.d.comb += self.o.out_do_z.eq(self.i.out_do_z)
  86         m.d.comb += self.o.oz.eq(self.i.oz)
  87
  88         return m
  89
  90
  91 class FPAddDeNorm(FPState):
  92
  93     def __init__(self, width, id_wid):
  94         FPState.__init__(self, "denormalise")
  95         self.mod = FPAddDeNormMod(width)
  96         self.out_a = FPNumBase(width)
  97         self.out_b = FPNumBase(width)
  98
  99     def setup(self, m, i):
 100         """ links module to inputs and outputs
 101         """
 102         self.mod.setup(m, i)
 103
 104         m.d.sync += self.out_a.eq(self.mod.out_a)
 105         m.d.sync += self.out_b.eq(self.mod.out_b)
 106
 107     def action(self, m):
 108         # Denormalised Number checks
 109         m.next = "align"
 110
 111