src/ieee754/fpdiv/divstages.py

   1 """IEEE754 Floating Point pipelined Divider
   2
   3 Relevant bugreport: http://bugs.libre-riscv.org/show_bug.cgi?id=99
   4
   5 """
   6
   7 from nmigen import Module
   8 from nmigen.cli import main, verilog
   9
  10 from nmutil.singlepipe import (StageChain, SimpleHandshake)
  11
  12 from ieee754.fpcommon.fpbase import FPState
  13 from ieee754.fpcommon.denorm import FPSCData
  14 from ieee754.fpcommon.postcalc import FPAddStage1Data
  15
  16 # TODO: write these
  17 from .div0 import FPDivStage0Mod
  18 from .div1 import FPDivStage1Mod
  19 from .div2 import FPDivStage2Mod
  20 from .div0 import FPDivStage0Data
  21
  22
  23 class FPDivStages(FPState, SimpleHandshake):
  24
  25     def __init__(self, width, pspec, n_stages, begin, end):
  26         FPState.__init__(self, "align")
  27         self.width = width
  28         self.pspec = pspec
  29         self.n_stages = n_stages # number of combinatorial stages
  30         self.begin = begin # "begin" mode
  31         self.end = end # "end" mode
  32         SimpleHandshake.__init__(self, self) # pipeline is its own stage
  33         self.m1o = self.ospec()
  34
  35     def ispec(self):
  36         if self.begin:
  37             return FPSCData(self.width, self.pspec, False) # from denorm
  38         return FPDivStage0Data(self.width, self.pspec) # DIV ispec (loop)
  39
  40     def ospec(self):
  41         if self.end: # TODO
  42             return FPAddStage1Data(self.width, self.pspec) # to post-norm
  43         return FPDivStage0Data(self.width, self.pspec) # DIV ospec (loop)
  44
  45     def setup(self, m, i):
  46         """ links module to inputs and outputs
  47         """
  48
  49         # start mode accepts data from the FP normalisation stage
  50         # and does a bit of munging of the data.  it will be chained
  51         # into the first DIV combinatorial block,
  52
  53         # end mode takes the DIV pipeline/chain data and munges it
  54         # into the format that the normalisation can accept.
  55
  56         # neither start nor end mode simply takes the exact same
  57         # data in as out, this is where the Q/Rem comes in and Q/Rem goes out
  58
  59         divstages = []
  60
  61         if self.begin: # XXX check this
  62             divstages.append(FPDivStage0Mod(self.width, self.pspec))
  63
  64         for count in range(self.n_stages): # number of combinatorial stages
  65             divstages.append(FPDivStage1Mod(self.width, self.pspec))
  66
  67         if self.end: # XXX check this
  68             divstages.append(FPDivStage2Mod(self.width, self.pspec))
  69
  70         chain = StageChain(divstages)
  71         chain.setup(m, i)
  72
  73         # output is from the last pipe stage
  74         self.o = divstages[-1].o
  75
  76     def process(self, i):
  77         return self.o
  78
  79     def action(self, m):
  80         m.d.sync += self.m1o.eq(self.process(None))
  81         m.next = "normalise_1"
  82
  83