src/add/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, Cat, Mux, Array, Const
   6 from nmigen.lib.coding import PriorityEncoder
   7 from nmigen.cli import main, verilog
   8 from math import log
   9
  10 from fpbase import FPNumIn, FPNumOut, FPOp, Overflow, FPBase, FPNumBase
  11 from fpbase import MultiShiftRMerge, Trigger
  12 from singlepipe import (ControlBase, StageChain, UnbufferedPipeline,
  13                         PassThroughStage)
  14 from multipipe import CombMuxOutPipe
  15 from multipipe import PriorityCombMuxInPipe
  16
  17 from fpbase import FPState
  18 from fpcommon.getop import (FPGetOpMod, FPGetOp, FPNumBase2Ops, FPADDBaseData,                              FPGet2OpMod, FPGet2Op)
  19
  20
  21 class FPSCData:
  22
  23     def __init__(self, width, id_wid):
  24         self.a = FPNumBase(width, True)
  25         self.b = FPNumBase(width, True)
  26         self.z = FPNumOut(width, False)
  27         self.oz = Signal(width, reset_less=True)
  28         self.out_do_z = Signal(reset_less=True)
  29         self.mid = Signal(id_wid, reset_less=True)
  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):
  37
  38     def __init__(self, width, id_wid):
  39         self.width = width
  40         self.id_wid = id_wid
  41         self.i = self.ispec()
  42         self.o = self.ospec()
  43
  44     def ispec(self):
  45         return FPSCData(self.width, self.id_wid)
  46
  47     def ospec(self):
  48         return FPSCData(self.width, self.id_wid)
  49
  50     def process(self, i):
  51         return self.o
  52
  53     def setup(self, m, i):
  54         """ links module to inputs and outputs
  55         """
  56         m.submodules.denormalise = self
  57         m.d.comb += self.i.eq(i)
  58
  59     def elaborate(self, platform):
  60         m = Module()
  61         m.submodules.denorm_in_a = self.i.a
  62         m.submodules.denorm_in_b = self.i.b
  63         m.submodules.denorm_out_a = self.o.a
  64         m.submodules.denorm_out_b = self.o.b
  65
  66         with m.If(~self.i.out_do_z):
  67             # XXX hmmm, don't like repeating identical code
  68             m.d.comb += self.o.a.eq(self.i.a)
  69             with m.If(self.i.a.exp_n127):
  70                 m.d.comb += self.o.a.e.eq(self.i.a.N126) # limit a exponent
  71             with m.Else():
  72                 m.d.comb += self.o.a.m[-1].eq(1) # set top mantissa bit
  73
  74             m.d.comb += self.o.b.eq(self.i.b)
  75             with m.If(self.i.b.exp_n127):
  76                 m.d.comb += self.o.b.e.eq(self.i.b.N126) # limit a exponent
  77             with m.Else():
  78                 m.d.comb += self.o.b.m[-1].eq(1) # set top mantissa bit
  79
  80         m.d.comb += self.o.mid.eq(self.i.mid)
  81         m.d.comb += self.o.z.eq(self.i.z)
  82         m.d.comb += self.o.out_do_z.eq(self.i.out_do_z)
  83         m.d.comb += self.o.oz.eq(self.i.oz)
  84
  85         return m
  86
  87
  88 class FPAddDeNorm(FPState):
  89
  90     def __init__(self, width, id_wid):
  91         FPState.__init__(self, "denormalise")
  92         self.mod = FPAddDeNormMod(width)
  93         self.out_a = FPNumBase(width)
  94         self.out_b = FPNumBase(width)
  95
  96     def setup(self, m, i):
  97         """ links module to inputs and outputs
  98         """
  99         self.mod.setup(m, i)
 100
 101         m.d.sync += self.out_a.eq(self.mod.out_a)
 102         m.d.sync += self.out_b.eq(self.mod.out_b)
 103
 104     def action(self, m):
 105         # Denormalised Number checks
 106         m.next = "align"
 107
 108