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
  17         # NOTE: difference between z and oz is that oz is created by
  18         # special-cases module(s) and will propagate, along with its
  19         # "bypass" signal out_do_z, through the pipeline, *disabling*
  20         # all processing of all subsequent stages.
  21         self.a = FPNumBaseRecord(width, m_extra)   # operand a
  22         self.b = FPNumBaseRecord(width, m_extra)   # operand b
  23         self.z = FPNumBaseRecord(width, False)     # denormed result
  24         self.oz = Signal(width, reset_less=True)   # "finished" (bypass) result
  25         self.out_do_z = Signal(reset_less=True)    # "bypass" enabled
  26         self.mid = Signal(id_wid, reset_less=True) # multiplexer ID
  27
  28     def __iter__(self):
  29         yield from self.a
  30         yield from self.b
  31         yield from self.z
  32         yield self.oz
  33         yield self.out_do_z
  34         yield self.mid
  35
  36     def eq(self, i):
  37         return [self.z.eq(i.z), self.out_do_z.eq(i.out_do_z), self.oz.eq(i.oz),
  38                 self.a.eq(i.a), self.b.eq(i.b), self.mid.eq(i.mid)]
  39
  40
  41 class FPAddDeNormMod(FPState, Elaboratable):
  42
  43     def __init__(self, width, id_wid, m_extra=True):
  44         self.width = width
  45         self.id_wid = id_wid
  46         self.m_extra = m_extra
  47         self.i = self.ispec()
  48         self.o = self.ospec()
  49
  50     def ispec(self):
  51         return FPSCData(self.width, self.id_wid, self.m_extra)
  52
  53     def ospec(self):
  54         return FPSCData(self.width, self.id_wid, self.m_extra)
  55
  56     def process(self, i):
  57         return self.o
  58
  59     def setup(self, m, i):
  60         """ links module to inputs and outputs
  61         """
  62         m.submodules.denormalise = self
  63         m.d.comb += self.i.eq(i)
  64
  65     def elaborate(self, platform):
  66         m = Module()
  67         m.submodules.denorm_in_a = in_a = FPNumBase(self.i.a)
  68         m.submodules.denorm_in_b = in_b = FPNumBase(self.i.b)
  69         #m.submodules.denorm_out_a = self.o.a
  70         #m.submodules.denorm_out_b = self.o.b
  71         #m.submodules.denorm_out_z = self.o.z
  72
  73         with m.If(~self.i.out_do_z):
  74             # XXX hmmm, don't like repeating identical code
  75             m.d.comb += self.o.a.eq(self.i.a)
  76             with m.If(in_a.exp_n127):
  77                 m.d.comb += self.o.a.e.eq(self.i.a.N126) # limit a exponent
  78             with m.Else():
  79                 m.d.comb += self.o.a.m[-1].eq(1) # set top mantissa bit
  80
  81             m.d.comb += self.o.b.eq(self.i.b)
  82             with m.If(in_b.exp_n127):
  83                 m.d.comb += self.o.b.e.eq(self.i.b.N126) # limit a exponent
  84             with m.Else():
  85                 m.d.comb += self.o.b.m[-1].eq(1) # set top mantissa bit
  86
  87         m.d.comb += self.o.mid.eq(self.i.mid)
  88         m.d.comb += self.o.z.eq(self.i.z)
  89         m.d.comb += self.o.out_do_z.eq(self.i.out_do_z)
  90         m.d.comb += self.o.oz.eq(self.i.oz)
  91
  92         return m
  93
  94
  95 class FPAddDeNorm(FPState):
  96
  97     def __init__(self, width, id_wid):
  98         FPState.__init__(self, "denormalise")
  99         self.mod = FPAddDeNormMod(width)
 100         self.out_a = FPNumBaseRecord(width)
 101         self.out_b = FPNumBaseRecord(width)
 102
 103     def setup(self, m, i):
 104         """ links module to inputs and outputs
 105         """
 106         self.mod.setup(m, i)
 107
 108         m.d.sync += self.out_a.eq(self.mod.out_a)
 109         m.d.sync += self.out_b.eq(self.mod.out_b)
 110
 111     def action(self, m):
 112         # Denormalised Number checks
 113         m.next = "align"
 114
 115