src/ieee754/part_cmp/equal.py

   1 # SPDX-License-Identifier: LGPL-2.1-or-later
   2 # See Notices.txt for copyright information
   3
   4 """
   5 Copyright (C) 2020 Luke Kenneth Casson Leighton <lkcl@lkcl.net>
   6
   7 dynamically-partitionable "comparison" class, directly equivalent
   8 to Signal.__eq__ except SIMD-partitionable
   9 """
  10
  11 from nmigen import Signal, Module, Elaboratable, Cat, C, Mux, Repl
  12 from nmigen.cli import main
  13
  14 from ieee754.part_mul_add.partpoints import PartitionPoints
  15
  16 class PartitionedEq(Elaboratable):
  17
  18     def __init__(self, width, partition_points):
  19         """Create a ``PartitionedEq`` operator
  20         """
  21         self.width = width
  22         self.a = Signal(width, reset_less=True)
  23         self.b = Signal(width, reset_less=True)
  24         self.partition_points = PartitionPoints(partition_points)
  25         self.mwidth = len(self.partition_points)+1
  26         self.output = Signal(self.mwidth, reset_less=True)
  27         if not self.partition_points.fits_in_width(width):
  28             raise ValueError("partition_points doesn't fit in width")
  29
  30     def elaborate(self, platform):
  31         m = Module()
  32
  33         # make a series of "eqs", splitting a and b into partition chunks
  34         eqs = Signal(self.mwidth, reset_less=True)
  35         eql = []
  36         keys = list(self.partition_points.keys()) + [self.width]
  37         start = 0
  38         for i in range(len(keys)):
  39             end = keys[i]
  40             eql.append(self.a[start:end] == self.b[start:end])
  41             start = end # for next time round loop
  42         m.d.comb += eqs.eq(Cat(*eql))
  43
  44         # now, based on the partition points, create the (multi-)boolean result
  45         eqsigs = []
  46         for i in range(self.mwidth):
  47             eqsig = Signal(self.mwidth, name="eqsig%d"%i, reset_less=True)
  48             if i == 0:
  49                 m.d.comb += eqsig.eq(eqs[i])
  50             else:
  51                 ppt = self.partition_points[keys[i-1]]
  52                 m.d.comb += eqsig.eq(eqs[i] & ppt & eqsigs[i-1])
  53             eqsigs.append(eqsig)
  54         print ("eqsigs", eqsigs, self.output.shape())
  55         # XXX moo?? something going on here
  56         for i in range(self.mwidth):
  57             m.d.comb += self.output[i].eq(eqsigs[i])
  58
  59         return m