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: # TODO - this is for FPDivStage0Mod
  37             # REQUIRED.  do NOT change.
  38             return FPSCData(self.width, self.pspec, False) # from denorm
  39
  40         if self.end: # TODO - this is for FPDivStage2Mod
  41             # XXX TODO: replace with "intermediary" (DivPipeCoreInterstageData?)
  42             return FPDivStage0Data(self.width, self.pspec) # DIV ispec (loop)
  43
  44         # TODO - this is for FPDivStage1Mod
  45         # XXX TODO: replace with "intermediary" (DivPipeCoreInterstageData)
  46         return FPDivStage0Data(self.width, self.pspec) # DIV ispec (loop)
  47
  48     def ospec(self):
  49         if self.begin: # TODO - this is for FPDivStage0Mod
  50             # XXX TODO: replace with "intermediary" (DivPipeCoreInterstageData)
  51             return FPDivStage0Data(self.width, self.pspec) # DIV ospec (loop)
  52
  53         if self.end: # TODO - this is for FPDivStage2Mod
  54             # REQUIRED.  do NOT change.
  55             return FPAddStage1Data(self.width, self.pspec) # to post-norm
  56
  57         # TODO - this is for FPDivStage1Mod
  58         # XXX TODO: replace with "intermediary" (DivPipeCoreInterstageData)
  59         return FPDivStage0Data(self.width, self.pspec) # DIV ospec (loop)
  60
  61     def setup(self, m, i):
  62         """ links module to inputs and outputs
  63         """
  64
  65         # start mode accepts data from the FP normalisation stage
  66         # and does a bit of munging of the data.  it will be chained
  67         # into the first DIV combinatorial block,
  68
  69         # end mode takes the DIV pipeline/chain data and munges it
  70         # into the format that the normalisation can accept.
  71
  72         # neither start nor end mode simply takes the exact same
  73         # data in as out, this is where the Q/Rem comes in and Q/Rem goes out
  74
  75         divstages = []
  76
  77         if self.begin: # XXX check this
  78             divstages.append(FPDivStage0Mod(self.width, self.pspec))
  79             # XXX if FPDivStage0Mod is to be used to convert from
  80             # FPSCData into DivPipeCoreInputData, rather than
  81             # DivPipeCoreSetupStage conforming *to* FPSCData format,
  82             # then DivPipeCoreSetupStage needs to be added here:
  83             # vvvvvvv
  84             # FIXME divstages.append(DivPipeCoreSetupStage(something))
  85             # ^^^^^^^
  86
  87         for count in range(self.n_stages): # number of combinatorial stages
  88             divstages.append(FPDivStage1Mod(self.width, self.pspec))
  89
  90         if self.end: # XXX check this
  91             divstages.append(FPDivStage2Mod(self.width, self.pspec))
  92
  93         chain = StageChain(divstages)
  94         chain.setup(m, i)
  95
  96         # output is from the last pipe stage
  97         self.o = divstages[-1].o
  98
  99     def process(self, i):
 100         return self.o
 101
 102     def action(self, m):
 103         m.d.sync += self.m1o.eq(self.process(None))
 104         m.next = "normalise_1"
 105
 106