src/ieee754/fpcommon/denorm.py

   1 """IEEE754 Floating Point Library
   2
   3 Copyright (C) 2019 Luke Kenneth Casson Leighton <lkcl@lkcl.net>
   4
   5 """
   6
   7 from nmigen import Module, Mux
   8 from nmigen.cli import main, verilog
   9 from math import log
  10
  11 from nmutil.pipemodbase import PipeModBase
  12 from ieee754.fpcommon.fpbase import FPNumBase
  13 from ieee754.fpcommon.pscdata import FPSCData
  14
  15
  16 class FPAddDeNormMod(PipeModBase):
  17
  18     def __init__(self, pspec, m_extra):
  19         self.m_extra = m_extra
  20         super().__init__(pspec, "denormalise")
  21
  22     def ispec(self):
  23         return FPSCData(self.pspec, self.m_extra)
  24
  25     def ospec(self):
  26         return FPSCData(self.pspec, self.m_extra)
  27
  28     def elaborate(self, platform):
  29         m = Module()
  30         comb = m.d.comb
  31
  32         m.submodules.denorm_in_a = in_a = FPNumBase(self.i.a)
  33         m.submodules.denorm_in_b = in_b = FPNumBase(self.i.b)
  34
  35         # XXX hmmm, don't like repeating identical code
  36         comb += self.o.a.eq(self.i.a)
  37         ae = self.i.a.e
  38         am = self.i.a.m
  39         # either limit exponent, or set top mantissa bit
  40         comb += self.o.a.e.eq(Mux(in_a.exp_n127, self.i.a.N126, ae))
  41         comb += self.o.a.m[-1].eq(Mux(in_a.exp_n127, am[-1], 1))
  42
  43         # XXX code now repeated for b
  44         comb += self.o.b.eq(self.i.b)
  45         be = self.i.b.e
  46         bm = self.i.b.m
  47         # either limit exponent, or set top mantissa bit
  48         comb += self.o.b.e.eq(Mux(in_b.exp_n127, self.i.b.N126, be))
  49         comb += self.o.b.m[-1].eq(Mux(in_b.exp_n127, bm[-1], 1))
  50
  51         comb += self.o.ctx.eq(self.i.ctx)
  52         comb += self.o.z.eq(self.i.z)
  53         comb += self.o.out_do_z.eq(self.i.out_do_z)
  54         comb += self.o.oz.eq(self.i.oz)
  55
  56         return m