src/add/pipeline.py

   1 """ Example 5: Making use of PyRTL and Introspection. """
   2
   3 from nmigen import Signal
   4 from nmigen.hdl.rec import Record
   5 from nmigen import tracer
   6 from nmigen.compat.fhdl.bitcontainer import value_bits_sign
   7
   8 from singlepipe import eq
   9
  10
  11 # The following example shows how pyrtl can be used to make some interesting
  12 # hardware structures using python introspection.  In particular, this example
  13 # makes a N-stage pipeline structure.  Any specific pipeline is then a derived
  14 # class of SimplePipeline where methods with names starting with "stage" are
  15 # stages, and new members with names not starting with "_" are to be registered
  16 # for the next stage.
  17
  18
  19 class ObjectProxy:
  20     def __init__(self, pipe, name=None):
  21         self._pipe = pipe
  22         if name is None:
  23             name = tracer.get_var_name(default=None)
  24         self.name = name
  25
  26     @classmethod
  27     def like(cls, pipe, value, name=None, src_loc_at=0, **kwargs):
  28         name = name or tracer.get_var_name(depth=2 + src_loc_at,
  29                                             default="$like")
  30
  31         src_loc_at_1 = 1 + src_loc_at
  32         r = ObjectProxy(pipe, value.name)
  33         for a in value.ports():
  34             aname = a.name
  35             setattr(r, aname, a)
  36         return r
  37
  38     def eq(self, i):
  39         res = []
  40         for a in self.ports():
  41             aname = a.name
  42             ai = getattr(i, aname)
  43             res.append(a.eq(ai))
  44         return res
  45
  46     def ports(self):
  47         res = []
  48         for aname in dir(self):
  49             a = getattr(self, aname)
  50             if isinstance(a, Signal) or isinstance(a, ObjectProxy) or \
  51                isinstance(a, Record):
  52                 res.append(a)
  53         return res
  54
  55     def __setattr__(self, name, value):
  56         if name.startswith('_') or name == 'name':
  57             # do not do anything tricky with variables starting with '_'
  58             object.__setattr__(self, name, value)
  59             return
  60         #rname = "%s_%s" % (self.name, name)
  61         rname = name
  62         if isinstance(value, ObjectProxy):
  63             new_pipereg = ObjectProxy.like(self._pipe, value,
  64                                            name=rname, reset_less=True)
  65         else:
  66             new_pipereg = Signal.like(value, name=rname, reset_less=True)
  67
  68         object.__setattr__(self, name, new_pipereg)
  69         self._pipe.sync += eq(new_pipereg, value)
  70
  71
  72 class SimplePipeline(object):
  73     """ Pipeline builder with auto generation of pipeline registers.
  74     """
  75
  76     def __init__(self, pipe):
  77         self._pipe = pipe
  78         self._pipeline_register_map = {}
  79         self._current_stage_num = 0
  80
  81     def _setup(self):
  82         stage_list = []
  83         for method in dir(self):
  84             if method.startswith('stage'):
  85                 stage_list.append(method)
  86         for stage in sorted(stage_list):
  87             stage_method = getattr(self, stage)
  88             stage_method()
  89             self._current_stage_num += 1
  90
  91     def __getattr__(self, name):
  92         try:
  93             return self._pipeline_register_map[self._current_stage_num][name]
  94         except KeyError:
  95             raise AttributeError(
  96                 'error, no pipeline register "%s" defined for stage %d'
  97                 % (name, self._current_stage_num))
  98
  99     def __setattr__(self, name, value):
 100         if name.startswith('_'):
 101             # do not do anything tricky with variables starting with '_'
 102             object.__setattr__(self, name, value)
 103             return
 104         next_stage = self._current_stage_num + 1
 105         pipereg_id = str(self._current_stage_num) + 'to' + str(next_stage)
 106         rname = 'pipereg_' + pipereg_id + '_' + name
 107         #new_pipereg = Signal(value_bits_sign(value), name=rname,
 108         #                     reset_less=True)
 109         if isinstance(value, ObjectProxy):
 110             new_pipereg = ObjectProxy.like(self._pipe, value,
 111                                            name=rname, reset_less = True)
 112         else:
 113             new_pipereg = Signal.like(value, name=rname, reset_less = True)
 114         if next_stage not in self._pipeline_register_map:
 115             self._pipeline_register_map[next_stage] = {}
 116         self._pipeline_register_map[next_stage][name] = new_pipereg
 117         self._pipe.sync += eq(new_pipereg, value)
 118