src/ieee754/fpcommon/roundz.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
   8 from ieee754.fpcommon.fpbase import FPNumBase, FPNumBaseRecord
   9 from ieee754.fpcommon.fpbase import FPState
  10 from ieee754.fpcommon.getop import FPPipeContext
  11 from .postnormalise import FPNorm1Data
  12
  13
  14 class FPRoundData:
  15
  16     def __init__(self, pspec):
  17         width = pspec.width
  18         self.z = FPNumBaseRecord(width, False, name="z")
  19         self.ctx = FPPipeContext(pspec)
  20         self.muxid = self.ctx.muxid
  21         # pipeline bypass [data comes from specialcases]
  22         self.out_do_z = Signal(reset_less=True)
  23         self.oz = Signal(width, reset_less=True)
  24
  25     def eq(self, i):
  26         ret = [self.z.eq(i.z), self.out_do_z.eq(i.out_do_z), self.oz.eq(i.oz),
  27                self.ctx.eq(i.ctx)]
  28         return ret
  29
  30
  31 class FPRoundMod(Elaboratable):
  32
  33     def __init__(self, pspec):
  34         self.pspec = pspec
  35         self.i = self.ispec()
  36         self.out_z = self.ospec()
  37
  38     def ispec(self):
  39         return FPNorm1Data(self.pspec)
  40
  41     def ospec(self):
  42         return FPRoundData(self.pspec)
  43
  44     def process(self, i):
  45         return self.out_z
  46
  47     def setup(self, m, i):
  48         m.submodules.roundz = self
  49         m.d.comb += self.i.eq(i)
  50
  51     def elaborate(self, platform):
  52         m = Module()
  53         m.d.comb += self.out_z.eq(self.i)  # copies muxid, z, out_do_z
  54         with m.If(~self.i.out_do_z):  # bypass wasn't enabled
  55             with m.If(self.i.roundz):
  56                 m.d.comb += self.out_z.z.m.eq(self.i.z.m + 1)  # mantissa up
  57                 with m.If(self.i.z.m == self.i.z.m1s):  # all 1s
  58                     # exponent up
  59                     m.d.comb += self.out_z.z.e.eq(self.i.z.e + 1)
  60
  61         return m
  62
  63
  64 class FPRound(FPState):
  65
  66     def __init__(self, width, id_wid):
  67         FPState.__init__(self, "round")
  68         self.mod = FPRoundMod(width)
  69         self.out_z = self.ospec()
  70
  71     def ispec(self):
  72         return self.mod.ispec()
  73
  74     def ospec(self):
  75         return self.mod.ospec()
  76
  77     def setup(self, m, i):
  78         """ links module to inputs and outputs
  79         """
  80         self.mod.setup(m, i)
  81
  82         self.idsync(m)
  83         m.d.sync += self.out_z.eq(self.mod.out_z)
  84         m.d.sync += self.out_z.ctx.eq(self.mod.o.ctx)
  85
  86     def action(self, m):
  87         m.next = "corrections"