src/ieee754/pipeline.py

   1 # SPDX-License-Identifier: LGPL-2.1-or-later
   2 # See Notices.txt for copyright information
   3
   4 from abc import ABCMeta
   5 from nmigen import Elaboratable
   6
   7 from nmutil.singlepipe import SimpleHandshake
   8 import threading
   9
  10
  11 class PipelineSpec:
  12     """ Pipeline Specification base class.
  13
  14     :attribute width: the IEEE754 FP bitwidth
  15     :attribute id_wid: the Reservation Station muxid bitwidth
  16     :attribute op_wid: an "operand bitwidth" passed down all stages
  17     :attribute opkls: an optional class that is instantiated as the "operand"
  18
  19     See ieee754/fpcommon/getop FPPipeContext for how (where) PipelineSpec
  20     is used.  FPPipeContext is passed down *every* stage of a pipeline
  21     and contains the Reservation Station multiplexer ID as well as
  22     an optional "operand".  This "operand" may be used to *change*
  23     the behaviour of the pipeline.  In RISC-V terminology it would
  24     typically be set to e.g. funct7 or parts thereof.
  25
  26     """
  27
  28     def __init__(self, width, id_width, op_wid=0, opkls=None, pipekls=None):
  29         """ Create a PipelineSpec. """
  30         self.width = width
  31         self.id_wid = id_width
  32         self.op_wid = op_wid
  33         self.opkls = opkls
  34         self.pipekls = pipekls or SimpleHandshakeRedir
  35         self.core_config = None
  36         self.fpformat = None
  37         self.n_comb_stages = None
  38
  39 # with many thanks to jsbueno on stackexchange for this one
  40 # https://stackoverflow.com/questions/57273070/
  41 # list post:
  42 # http://lists.libre-riscv.org/pipermail/libre-riscv-dev/2019-July/002259.html
  43
  44 class Meta(ABCMeta):
  45     registry = {}
  46     recursing = threading.local()
  47     recursing.check = False
  48     mlock = threading.Lock()
  49
  50     def __call__(cls, *args, **kw):
  51         mcls = cls.__class__
  52         if mcls.recursing.check:
  53             return super().__call__(*args, **kw)
  54         spec = args[0]
  55         base = spec.pipekls # pick up the dynamic class from PipelineSpec, HERE
  56
  57         if (cls, base) not in mcls.registry:
  58             print ("__call__", args, kw, cls, base, base.__bases__, cls.__bases__)
  59             mcls.registry[cls, base] = type(
  60                 cls.__name__,
  61                 (cls, base) + cls.__bases__[1:],
  62                 {}
  63             )
  64         real_cls = mcls.registry[cls, base]
  65
  66         with mcls.mlock:
  67             mcls.recursing.check = True
  68             instance = real_cls.__class__.__call__(real_cls, *args, **kw)
  69             mcls.recursing.check = False
  70         return instance
  71
  72
  73 # Inherit from this class instead of SimpleHandshake (or other ControlBase
  74 # derivative), and the metaclass will instead *replace* DynamicPipe -
  75 # *at runtime* - with the class that is specified *as a parameter*
  76 # in PipelineSpec.
  77 #
  78 # as explained in the list posting and in the stackexchange post, this is
  79 # needed to avoid a MASSIVE suite of duplicated multiple-inheritance classes
  80 # that "Mix in" SimpleHandshake (or other).
  81 #
  82 # unfortunately, composition does not work in this instance
  83 # (make an *instance* of SimpleHandshake or other class and pass it in)
  84 # due to the multiple level inheritance, and in several places
  85 # the inheriting class needs to do some setup that the deriving class
  86 # needs in order to function correctly.
  87
  88 class DynamicPipe(metaclass=Meta):
  89     def __init__(self, *args):
  90         print ("DynamicPipe init", super(), args)
  91         super().__init__(self, *args)
  92
  93
  94 # bad hack: the DynamicPipe metaclass ends up creating an __init__ signature
  95 # for the dynamically-derived class.  luckily, SimpleHandshake only needs
  96 # "self" as the 1st argument (it is its own "Stage").  anything else
  97 # could hypothetically be passed through the pspec.
  98 class SimpleHandshakeRedir(SimpleHandshake):
  99     def __init__(self, pspec, *args):
 100         print ("redir", pspec, args)
 101         SimpleHandshake.__init__(self, self)
 102