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 from ieee754.fpcommon.getop import FPPipeContext
  12
  13
  14 class FPSCData:
  15
  16     def __init__(self, pspec, m_extra):
  17         width = pspec['width']
  18         # NOTE: difference between z and oz is that oz is created by
  19         # special-cases module(s) and will propagate, along with its
  20         # "bypass" signal out_do_z, through the pipeline, *disabling*
  21         # all processing of all subsequent stages.
  22         self.a = FPNumBaseRecord(width, m_extra)   # operand a
  23         self.b = FPNumBaseRecord(width, m_extra)   # operand b
  24         self.z = FPNumBaseRecord(width, False)     # denormed result
  25         self.oz = Signal(width, reset_less=True)   # "finished" (bypass) result
  26         self.out_do_z = Signal(reset_less=True)    # "bypass" enabled
  27         self.ctx = FPPipeContext(pspec)
  28         self.muxid = self.ctx.muxid
  29
  30     def __iter__(self):
  31         yield from self.a
  32         yield from self.b
  33         yield from self.z
  34         yield self.oz
  35         yield self.out_do_z
  36         yield from self.ctx
  37
  38     def eq(self, i):
  39         ret = [self.z.eq(i.z), self.out_do_z.eq(i.out_do_z), self.oz.eq(i.oz),
  40                 self.a.eq(i.a), self.b.eq(i.b), self.ctx.eq(i.ctx)]
  41         return ret
  42
  43
  44 class FPAddDeNormMod(FPState, Elaboratable):
  45
  46     def __init__(self, pspec, m_extra):
  47         self.pspec = pspec
  48         self.m_extra = m_extra
  49         self.i = self.ispec()
  50         self.o = self.ospec()
  51
  52     def ispec(self):
  53         return FPSCData(self.pspec, self.m_extra)
  54
  55     def ospec(self):
  56         return FPSCData(self.pspec, self.m_extra)
  57
  58     def process(self, i):
  59         return self.o
  60
  61     def setup(self, m, i):
  62         """ links module to inputs and outputs
  63         """
  64         m.submodules.denormalise = self
  65         m.d.comb += self.i.eq(i)
  66
  67     def elaborate(self, platform):
  68         m = Module()
  69         m.submodules.denorm_in_a = in_a = FPNumBase(self.i.a)
  70         m.submodules.denorm_in_b = in_b = FPNumBase(self.i.b)
  71         #m.submodules.denorm_out_a = self.o.a
  72         #m.submodules.denorm_out_b = self.o.b
  73         #m.submodules.denorm_out_z = self.o.z
  74
  75         with m.If(~self.i.out_do_z):
  76             # XXX hmmm, don't like repeating identical code
  77             m.d.comb += self.o.a.eq(self.i.a)
  78             with m.If(in_a.exp_n127):
  79                 m.d.comb += self.o.a.e.eq(self.i.a.N126) # limit a exponent
  80             with m.Else():
  81                 m.d.comb += self.o.a.m[-1].eq(1) # set top mantissa bit
  82
  83             m.d.comb += self.o.b.eq(self.i.b)
  84             with m.If(in_b.exp_n127):
  85                 m.d.comb += self.o.b.e.eq(self.i.b.N126) # limit a exponent
  86             with m.Else():
  87                 m.d.comb += self.o.b.m[-1].eq(1) # set top mantissa bit
  88
  89         m.d.comb += self.o.ctx.eq(self.i.ctx)
  90         m.d.comb += self.o.z.eq(self.i.z)
  91         m.d.comb += self.o.out_do_z.eq(self.i.out_do_z)
  92         m.d.comb += self.o.oz.eq(self.i.oz)
  93
  94         return m
  95
  96
  97 class FPAddDeNorm(FPState):
  98
  99     def __init__(self, width, id_wid):
 100         FPState.__init__(self, "denormalise")
 101         self.mod = FPAddDeNormMod(width)
 102         self.out_a = FPNumBaseRecord(width)
 103         self.out_b = FPNumBaseRecord(width)
 104
 105     def setup(self, m, i):
 106         """ links module to inputs and outputs
 107         """
 108         self.mod.setup(m, i)
 109
 110         m.d.sync += self.out_a.eq(self.mod.out_a)
 111         m.d.sync += self.out_b.eq(self.mod.out_b)
 112
 113     def action(self, m):
 114         # Denormalised Number checks
 115         m.next = "align"
 116
 117