src/ieee754/part_mul_add/multiply.py

   1 # SPDX-License-Identifier: LGPL-2.1-or-later
   2 # See Notices.txt for copyright information
   3 """Integer Multiplication."""
   4
   5 from nmigen import Signal, Module, Value, Elaboratable, Cat, C, Mux, Repl
   6 from nmigen.hdl.ast import Assign
   7 from abc import ABCMeta, abstractmethod
   8 from nmigen.cli import main
   9 from functools import reduce
  10 from operator import or_
  11
  12
  13 class PartitionPoints(dict):
  14     """Partition points and corresponding ``Value``s.
  15
  16     The points at where an ALU is partitioned along with ``Value``s that
  17     specify if the corresponding partition points are enabled.
  18
  19     For example: ``{1: True, 5: True, 10: True}`` with
  20     ``width == 16`` specifies that the ALU is split into 4 sections:
  21     * bits 0 <= ``i`` < 1
  22     * bits 1 <= ``i`` < 5
  23     * bits 5 <= ``i`` < 10
  24     * bits 10 <= ``i`` < 16
  25
  26     If the partition_points were instead ``{1: True, 5: a, 10: True}``
  27     where ``a`` is a 1-bit ``Signal``:
  28     * If ``a`` is asserted:
  29         * bits 0 <= ``i`` < 1
  30         * bits 1 <= ``i`` < 5
  31         * bits 5 <= ``i`` < 10
  32         * bits 10 <= ``i`` < 16
  33     * Otherwise
  34         * bits 0 <= ``i`` < 1
  35         * bits 1 <= ``i`` < 10
  36         * bits 10 <= ``i`` < 16
  37     """
  38
  39     def __init__(self, partition_points=None):
  40         """Create a new ``PartitionPoints``.
  41
  42         :param partition_points: the input partition points to values mapping.
  43         """
  44         super().__init__()
  45         if partition_points is not None:
  46             for point, enabled in partition_points.items():
  47                 if not isinstance(point, int):
  48                     raise TypeError("point must be a non-negative integer")
  49                 if point < 0:
  50                     raise ValueError("point must be a non-negative integer")
  51                 self[point] = Value.wrap(enabled)
  52
  53     def like(self, name=None, src_loc_at=0):
  54         """Create a new ``PartitionPoints`` with ``Signal``s for all values.
  55
  56         :param name: the base name for the new ``Signal``s.
  57         """
  58         if name is None:
  59             name = Signal(src_loc_at=1+src_loc_at).name  # get variable name
  60         retval = PartitionPoints()
  61         for point, enabled in self.items():
  62             retval[point] = Signal(enabled.shape(), name=f"{name}_{point}")
  63         return retval
  64
  65     def eq(self, rhs):
  66         """Assign ``PartitionPoints`` using ``Signal.eq``."""
  67         if set(self.keys()) != set(rhs.keys()):
  68             raise ValueError("incompatible point set")
  69         for point, enabled in self.items():
  70             yield enabled.eq(rhs[point])
  71
  72     def as_mask(self, width):
  73         """Create a bit-mask from `self`.
  74
  75         Each bit in the returned mask is clear only if the partition point at
  76         the same bit-index is enabled.
  77
  78         :param width: the bit width of the resulting mask
  79         """
  80         bits = []
  81         for i in range(width):
  82             if i in self:
  83                 bits.append(~self[i])
  84             else:
  85                 bits.append(True)
  86         return Cat(*bits)
  87
  88     def get_max_partition_count(self, width):
  89         """Get the maximum number of partitions.
  90
  91         Gets the number of partitions when all partition points are enabled.
  92         """
  93         retval = 1
  94         for point in self.keys():
  95             if point < width:
  96                 retval += 1
  97         return retval
  98
  99     def fits_in_width(self, width):
 100         """Check if all partition points are smaller than `width`."""
 101         for point in self.keys():
 102             if point >= width:
 103                 return False
 104         return True
 105
 106     def part_byte(self, index, mfactor=1): # mfactor used for "expanding"
 107         if index == -1 or index == 7:
 108             return C(True, 1)
 109         assert index >= 0 and index < 8
 110         return self[(index * 8 + 8)*mfactor]
 111
 112
 113 class FullAdder(Elaboratable):
 114     """Full Adder.
 115
 116     :attribute in0: the first input
 117     :attribute in1: the second input
 118     :attribute in2: the third input
 119     :attribute sum: the sum output
 120     :attribute carry: the carry output
 121
 122     Rather than do individual full adders (and have an array of them,
 123     which would be very slow to simulate), this module can specify the
 124     bit width of the inputs and outputs: in effect it performs multiple
 125     Full 3-2 Add operations "in parallel".
 126     """
 127
 128     def __init__(self, width):
 129         """Create a ``FullAdder``.
 130
 131         :param width: the bit width of the input and output
 132         """
 133         self.in0 = Signal(width)
 134         self.in1 = Signal(width)
 135         self.in2 = Signal(width)
 136         self.sum = Signal(width)
 137         self.carry = Signal(width)
 138
 139     def elaborate(self, platform):
 140         """Elaborate this module."""
 141         m = Module()
 142         m.d.comb += self.sum.eq(self.in0 ^ self.in1 ^ self.in2)
 143         m.d.comb += self.carry.eq((self.in0 & self.in1)
 144                                   | (self.in1 & self.in2)
 145                                   | (self.in2 & self.in0))
 146         return m
 147
 148
 149 class MaskedFullAdder(Elaboratable):
 150     """Masked Full Adder.
 151
 152     :attribute mask: the carry partition mask
 153     :attribute in0: the first input
 154     :attribute in1: the second input
 155     :attribute in2: the third input
 156     :attribute sum: the sum output
 157     :attribute mcarry: the masked carry output
 158
 159     FullAdders are always used with a "mask" on the output.  To keep
 160     the graphviz "clean", this class performs the masking here rather
 161     than inside a large for-loop.
 162
 163     See the following discussion as to why this is no longer derived
 164     from FullAdder.  Each carry is shifted here *before* being ANDed
 165     with the mask, so that an AOI cell may be used (which is more
 166     gate-efficient)
 167     https://en.wikipedia.org/wiki/AND-OR-Invert
 168     https://groups.google.com/d/msg/comp.arch/fcq-GLQqvas/vTxmcA0QAgAJ
 169     """
 170
 171     def __init__(self, width):
 172         """Create a ``MaskedFullAdder``.
 173
 174         :param width: the bit width of the input and output
 175         """
 176         self.width = width
 177         self.mask = Signal(width, reset_less=True)
 178         self.mcarry = Signal(width, reset_less=True)
 179         self.in0 = Signal(width, reset_less=True)
 180         self.in1 = Signal(width, reset_less=True)
 181         self.in2 = Signal(width, reset_less=True)
 182         self.sum = Signal(width, reset_less=True)
 183
 184     def elaborate(self, platform):
 185         """Elaborate this module."""
 186         m = Module()
 187         s1 = Signal(self.width, reset_less=True)
 188         s2 = Signal(self.width, reset_less=True)
 189         s3 = Signal(self.width, reset_less=True)
 190         c1 = Signal(self.width, reset_less=True)
 191         c2 = Signal(self.width, reset_less=True)
 192         c3 = Signal(self.width, reset_less=True)
 193         m.d.comb += self.sum.eq(self.in0 ^ self.in1 ^ self.in2)
 194         m.d.comb += s1.eq(Cat(0, self.in0))
 195         m.d.comb += s2.eq(Cat(0, self.in1))
 196         m.d.comb += s3.eq(Cat(0, self.in2))
 197         m.d.comb += c1.eq(s1 & s2 & self.mask)
 198         m.d.comb += c2.eq(s2 & s3 & self.mask)
 199         m.d.comb += c3.eq(s3 & s1 & self.mask)
 200         m.d.comb += self.mcarry.eq(c1 | c2 | c3)
 201         return m
 202
 203
 204 class PartitionedAdder(Elaboratable):
 205     """Partitioned Adder.
 206
 207     Performs the final add.  The partition points are included in the
 208     actual add (in one of the operands only), which causes a carry over
 209     to the next bit.  Then the final output *removes* the extra bits from
 210     the result.
 211
 212     partition: .... P... P... P... P... (32 bits)
 213     a        : .... .... .... .... .... (32 bits)
 214     b        : .... .... .... .... .... (32 bits)
 215     exp-a    : ....P....P....P....P.... (32+4 bits, P=1 if no partition)
 216     exp-b    : ....0....0....0....0.... (32 bits plus 4 zeros)
 217     exp-o    : ....xN...xN...xN...xN... (32+4 bits - x to be discarded)
 218     o        : .... N... N... N... N... (32 bits - x ignored, N is carry-over)
 219
 220     :attribute width: the bit width of the input and output. Read-only.
 221     :attribute a: the first input to the adder
 222     :attribute b: the second input to the adder
 223     :attribute output: the sum output
 224     :attribute partition_points: the input partition points. Modification not
 225         supported, except for by ``Signal.eq``.
 226     """
 227
 228     def __init__(self, width, partition_points):
 229         """Create a ``PartitionedAdder``.
 230
 231         :param width: the bit width of the input and output
 232         :param partition_points: the input partition points
 233         """
 234         self.width = width
 235         self.a = Signal(width)
 236         self.b = Signal(width)
 237         self.output = Signal(width)
 238         self.partition_points = PartitionPoints(partition_points)
 239         if not self.partition_points.fits_in_width(width):
 240             raise ValueError("partition_points doesn't fit in width")
 241         expanded_width = 0
 242         for i in range(self.width):
 243             if i in self.partition_points:
 244                 expanded_width += 1
 245             expanded_width += 1
 246         self._expanded_width = expanded_width
 247         # XXX these have to remain here due to some horrible nmigen
 248         # simulation bugs involving sync.  it is *not* necessary to
 249         # have them here, they should (under normal circumstances)
 250         # be moved into elaborate, as they are entirely local
 251         self._expanded_a = Signal(expanded_width) # includes extra part-points
 252         self._expanded_b = Signal(expanded_width) # likewise.
 253         self._expanded_o = Signal(expanded_width) # likewise.
 254
 255     def elaborate(self, platform):
 256         """Elaborate this module."""
 257         m = Module()
 258         expanded_index = 0
 259         # store bits in a list, use Cat later.  graphviz is much cleaner
 260         al, bl, ol, ea, eb, eo = [],[],[],[],[],[]
 261
 262         # partition points are "breaks" (extra zeros or 1s) in what would
 263         # otherwise be a massive long add.  when the "break" points are 0,
 264         # whatever is in it (in the output) is discarded.  however when
 265         # there is a "1", it causes a roll-over carry to the *next* bit.
 266         # we still ignore the "break" bit in the [intermediate] output,
 267         # however by that time we've got the effect that we wanted: the
 268         # carry has been carried *over* the break point.
 269
 270         for i in range(self.width):
 271             if i in self.partition_points:
 272                 # add extra bit set to 0 + 0 for enabled partition points
 273                 # and 1 + 0 for disabled partition points
 274                 ea.append(self._expanded_a[expanded_index])
 275                 al.append(~self.partition_points[i]) # add extra bit in a
 276                 eb.append(self._expanded_b[expanded_index])
 277                 bl.append(C(0)) # yes, add a zero
 278                 expanded_index += 1 # skip the extra point.  NOT in the output
 279             ea.append(self._expanded_a[expanded_index])
 280             eb.append(self._expanded_b[expanded_index])
 281             eo.append(self._expanded_o[expanded_index])
 282             al.append(self.a[i])
 283             bl.append(self.b[i])
 284             ol.append(self.output[i])
 285             expanded_index += 1
 286
 287         # combine above using Cat
 288         m.d.comb += Cat(*ea).eq(Cat(*al))
 289         m.d.comb += Cat(*eb).eq(Cat(*bl))
 290         m.d.comb += Cat(*ol).eq(Cat(*eo))
 291
 292         # use only one addition to take advantage of look-ahead carry and
 293         # special hardware on FPGAs
 294         m.d.comb += self._expanded_o.eq(
 295             self._expanded_a + self._expanded_b)
 296         return m
 297
 298
 299 FULL_ADDER_INPUT_COUNT = 3
 300
 301
 302 class AddReduceSingle(Elaboratable):
 303     """Add list of numbers together.
 304
 305     :attribute inputs: input ``Signal``s to be summed. Modification not
 306         supported, except for by ``Signal.eq``.
 307     :attribute register_levels: List of nesting levels that should have
 308         pipeline registers.
 309     :attribute output: output sum.
 310     :attribute partition_points: the input partition points. Modification not
 311         supported, except for by ``Signal.eq``.
 312     """
 313
 314     def __init__(self, inputs, output_width, register_levels, partition_points,
 315                        part_ops):
 316         """Create an ``AddReduce``.
 317
 318         :param inputs: input ``Signal``s to be summed.
 319         :param output_width: bit-width of ``output``.
 320         :param register_levels: List of nesting levels that should have
 321             pipeline registers.
 322         :param partition_points: the input partition points.
 323         """
 324         self.part_ops = part_ops
 325         self.out_part_ops = [Signal(2, name=f"out_part_ops_{i}")
 326                           for i in range(len(part_ops))]
 327         self.inputs = list(inputs)
 328         self._resized_inputs = [
 329             Signal(output_width, name=f"resized_inputs[{i}]")
 330             for i in range(len(self.inputs))]
 331         self.register_levels = list(register_levels)
 332         self.output = Signal(output_width)
 333         self.partition_points = PartitionPoints(partition_points)
 334         if not self.partition_points.fits_in_width(output_width):
 335             raise ValueError("partition_points doesn't fit in output_width")
 336         self._reg_partition_points = self.partition_points.like()
 337
 338         max_level = AddReduceSingle.get_max_level(len(self.inputs))
 339         for level in self.register_levels:
 340             if level > max_level:
 341                 raise ValueError(
 342                     "not enough adder levels for specified register levels")
 343
 344         # this is annoying.  we have to create the modules (and terms)
 345         # because we need to know what they are (in order to set up the
 346         # interconnects back in AddReduce), but cannot do the m.d.comb +=
 347         # etc because this is not in elaboratable.
 348         self.groups = AddReduceSingle.full_adder_groups(len(self.inputs))
 349         self._intermediate_terms = []
 350         if len(self.groups) != 0:
 351             self.create_next_terms()
 352
 353     @staticmethod
 354     def get_max_level(input_count):
 355         """Get the maximum level.
 356
 357         All ``register_levels`` must be less than or equal to the maximum
 358         level.
 359         """
 360         retval = 0
 361         while True:
 362             groups = AddReduceSingle.full_adder_groups(input_count)
 363             if len(groups) == 0:
 364                 return retval
 365             input_count %= FULL_ADDER_INPUT_COUNT
 366             input_count += 2 * len(groups)
 367             retval += 1
 368
 369     @staticmethod
 370     def full_adder_groups(input_count):
 371         """Get ``inputs`` indices for which a full adder should be built."""
 372         return range(0,
 373                      input_count - FULL_ADDER_INPUT_COUNT + 1,
 374                      FULL_ADDER_INPUT_COUNT)
 375
 376     def elaborate(self, platform):
 377         """Elaborate this module."""
 378         m = Module()
 379
 380         # resize inputs to correct bit-width and optionally add in
 381         # pipeline registers
 382         resized_input_assignments = [self._resized_inputs[i].eq(self.inputs[i])
 383                                      for i in range(len(self.inputs))]
 384         copy_part_ops = [self.out_part_ops[i].eq(self.part_ops[i])
 385                                      for i in range(len(self.part_ops))]
 386         if 0 in self.register_levels:
 387             m.d.sync += copy_part_ops
 388             m.d.sync += resized_input_assignments
 389             m.d.sync += self._reg_partition_points.eq(self.partition_points)
 390         else:
 391             m.d.comb += copy_part_ops
 392             m.d.comb += resized_input_assignments
 393             m.d.comb += self._reg_partition_points.eq(self.partition_points)
 394
 395         for (value, term) in self._intermediate_terms:
 396             m.d.comb += term.eq(value)
 397
 398         # if there are no full adders to create, then we handle the base cases
 399         # and return, otherwise we go on to the recursive case
 400         if len(self.groups) == 0:
 401             if len(self.inputs) == 0:
 402                 # use 0 as the default output value
 403                 m.d.comb += self.output.eq(0)
 404             elif len(self.inputs) == 1:
 405                 # handle single input
 406                 m.d.comb += self.output.eq(self._resized_inputs[0])
 407             else:
 408                 # base case for adding 2 inputs
 409                 assert len(self.inputs) == 2
 410                 adder = PartitionedAdder(len(self.output),
 411                                          self._reg_partition_points)
 412                 m.submodules.final_adder = adder
 413                 m.d.comb += adder.a.eq(self._resized_inputs[0])
 414                 m.d.comb += adder.b.eq(self._resized_inputs[1])
 415                 m.d.comb += self.output.eq(adder.output)
 416             return m
 417
 418         mask = self._reg_partition_points.as_mask(len(self.output))
 419         m.d.comb += self.part_mask.eq(mask)
 420
 421         # add and link the intermediate term modules
 422         for i, (iidx, adder_i) in enumerate(self.adders):
 423             setattr(m.submodules, f"adder_{i}", adder_i)
 424
 425             m.d.comb += adder_i.in0.eq(self._resized_inputs[iidx])
 426             m.d.comb += adder_i.in1.eq(self._resized_inputs[iidx + 1])
 427             m.d.comb += adder_i.in2.eq(self._resized_inputs[iidx + 2])
 428             m.d.comb += adder_i.mask.eq(self.part_mask)
 429
 430         return m
 431
 432     def create_next_terms(self):
 433
 434         # go on to prepare recursive case
 435         intermediate_terms = []
 436         _intermediate_terms = []
 437
 438         def add_intermediate_term(value):
 439             intermediate_term = Signal(
 440                 len(self.output),
 441                 name=f"intermediate_terms[{len(intermediate_terms)}]")
 442             _intermediate_terms.append((value, intermediate_term))
 443             intermediate_terms.append(intermediate_term)
 444
 445         # store mask in intermediary (simplifies graph)
 446         self.part_mask = Signal(len(self.output), reset_less=True)
 447
 448         # create full adders for this recursive level.
 449         # this shrinks N terms to 2 * (N // 3) plus the remainder
 450         self.adders = []
 451         for i in self.groups:
 452             adder_i = MaskedFullAdder(len(self.output))
 453             self.adders.append((i, adder_i))
 454             # add both the sum and the masked-carry to the next level.
 455             # 3 inputs have now been reduced to 2...
 456             add_intermediate_term(adder_i.sum)
 457             add_intermediate_term(adder_i.mcarry)
 458         # handle the remaining inputs.
 459         if len(self.inputs) % FULL_ADDER_INPUT_COUNT == 1:
 460             add_intermediate_term(self._resized_inputs[-1])
 461         elif len(self.inputs) % FULL_ADDER_INPUT_COUNT == 2:
 462             # Just pass the terms to the next layer, since we wouldn't gain
 463             # anything by using a half adder since there would still be 2 terms
 464             # and just passing the terms to the next layer saves gates.
 465             add_intermediate_term(self._resized_inputs[-2])
 466             add_intermediate_term(self._resized_inputs[-1])
 467         else:
 468             assert len(self.inputs) % FULL_ADDER_INPUT_COUNT == 0
 469
 470         self.intermediate_terms = intermediate_terms
 471         self._intermediate_terms = _intermediate_terms
 472
 473
 474 class AddReduce(Elaboratable):
 475     """Recursively Add list of numbers together.
 476
 477     :attribute inputs: input ``Signal``s to be summed. Modification not
 478         supported, except for by ``Signal.eq``.
 479     :attribute register_levels: List of nesting levels that should have
 480         pipeline registers.
 481     :attribute output: output sum.
 482     :attribute partition_points: the input partition points. Modification not
 483         supported, except for by ``Signal.eq``.
 484     """
 485
 486     def __init__(self, inputs, output_width, register_levels, partition_points,
 487                        part_ops):
 488         """Create an ``AddReduce``.
 489
 490         :param inputs: input ``Signal``s to be summed.
 491         :param output_width: bit-width of ``output``.
 492         :param register_levels: List of nesting levels that should have
 493             pipeline registers.
 494         :param partition_points: the input partition points.
 495         """
 496         self.inputs = inputs
 497         self.part_ops = part_ops
 498         self.out_part_ops = [Signal(2, name=f"out_part_ops_{i}")
 499                           for i in range(len(part_ops))]
 500         self.output = Signal(output_width)
 501         self.output_width = output_width
 502         self.register_levels = register_levels
 503         self.partition_points = partition_points
 504
 505         self.create_levels()
 506
 507     @staticmethod
 508     def get_max_level(input_count):
 509         return AddReduceSingle.get_max_level(input_count)
 510
 511     @staticmethod
 512     def next_register_levels(register_levels):
 513         """``Iterable`` of ``register_levels`` for next recursive level."""
 514         for level in register_levels:
 515             if level > 0:
 516                 yield level - 1
 517
 518     def create_levels(self):
 519         """creates reduction levels"""
 520
 521         mods = []
 522         next_levels = self.register_levels
 523         partition_points = self.partition_points
 524         inputs = self.inputs
 525         part_ops = self.part_ops
 526         while True:
 527             next_level = AddReduceSingle(inputs, self.output_width, next_levels,
 528                                          partition_points, part_ops)
 529             mods.append(next_level)
 530             if len(next_level.groups) == 0:
 531                 break
 532             next_levels = list(AddReduce.next_register_levels(next_levels))
 533             partition_points = next_level._reg_partition_points
 534             inputs = next_level.intermediate_terms
 535             part_ops = next_level.out_part_ops
 536
 537         self.levels = mods
 538
 539     def elaborate(self, platform):
 540         """Elaborate this module."""
 541         m = Module()
 542
 543         for i, next_level in enumerate(self.levels):
 544             setattr(m.submodules, "next_level%d" % i, next_level)
 545
 546         # output comes from last module
 547         m.d.comb += self.output.eq(next_level.output)
 548         copy_part_ops = [self.out_part_ops[i].eq(next_level.out_part_ops[i])
 549                                      for i in range(len(self.part_ops))]
 550         m.d.comb += copy_part_ops
 551
 552         return m
 553
 554
 555 OP_MUL_LOW = 0
 556 OP_MUL_SIGNED_HIGH = 1
 557 OP_MUL_SIGNED_UNSIGNED_HIGH = 2  # a is signed, b is unsigned
 558 OP_MUL_UNSIGNED_HIGH = 3
 559
 560
 561 def get_term(value, shift=0, enabled=None):
 562     if enabled is not None:
 563         value = Mux(enabled, value, 0)
 564     if shift > 0:
 565         value = Cat(Repl(C(0, 1), shift), value)
 566     else:
 567         assert shift == 0
 568     return value
 569
 570
 571 class ProductTerm(Elaboratable):
 572     """ this class creates a single product term (a[..]*b[..]).
 573         it has a design flaw in that is the *output* that is selected,
 574         where the multiplication(s) are combinatorially generated
 575         all the time.
 576     """
 577
 578     def __init__(self, width, twidth, pbwid, a_index, b_index):
 579         self.a_index = a_index
 580         self.b_index = b_index
 581         shift = 8 * (self.a_index + self.b_index)
 582         self.pwidth = width
 583         self.twidth = twidth
 584         self.width = width*2
 585         self.shift = shift
 586
 587         self.ti = Signal(self.width, reset_less=True)
 588         self.term = Signal(twidth, reset_less=True)
 589         self.a = Signal(twidth//2, reset_less=True)
 590         self.b = Signal(twidth//2, reset_less=True)
 591         self.pb_en = Signal(pbwid, reset_less=True)
 592
 593         self.tl = tl = []
 594         min_index = min(self.a_index, self.b_index)
 595         max_index = max(self.a_index, self.b_index)
 596         for i in range(min_index, max_index):
 597             tl.append(self.pb_en[i])
 598         name = "te_%d_%d" % (self.a_index, self.b_index)
 599         if len(tl) > 0:
 600             term_enabled = Signal(name=name, reset_less=True)
 601         else:
 602             term_enabled = None
 603         self.enabled = term_enabled
 604         self.term.name = "term_%d_%d" % (a_index, b_index) # rename
 605
 606     def elaborate(self, platform):
 607
 608         m = Module()
 609         if self.enabled is not None:
 610             m.d.comb += self.enabled.eq(~(Cat(*self.tl).bool()))
 611
 612         bsa = Signal(self.width, reset_less=True)
 613         bsb = Signal(self.width, reset_less=True)
 614         a_index, b_index = self.a_index, self.b_index
 615         pwidth = self.pwidth
 616         m.d.comb += bsa.eq(self.a.part(a_index * pwidth, pwidth))
 617         m.d.comb += bsb.eq(self.b.part(b_index * pwidth, pwidth))
 618         m.d.comb += self.ti.eq(bsa * bsb)
 619         m.d.comb += self.term.eq(get_term(self.ti, self.shift, self.enabled))
 620         """
 621         #TODO: sort out width issues, get inputs a/b switched on/off.
 622         #data going into Muxes is 1/2 the required width
 623
 624         pwidth = self.pwidth
 625         width = self.width
 626         bsa = Signal(self.twidth//2, reset_less=True)
 627         bsb = Signal(self.twidth//2, reset_less=True)
 628         asel = Signal(width, reset_less=True)
 629         bsel = Signal(width, reset_less=True)
 630         a_index, b_index = self.a_index, self.b_index
 631         m.d.comb += asel.eq(self.a.part(a_index * pwidth, pwidth))
 632         m.d.comb += bsel.eq(self.b.part(b_index * pwidth, pwidth))
 633         m.d.comb += bsa.eq(get_term(asel, self.shift, self.enabled))
 634         m.d.comb += bsb.eq(get_term(bsel, self.shift, self.enabled))
 635         m.d.comb += self.ti.eq(bsa * bsb)
 636         m.d.comb += self.term.eq(self.ti)
 637         """
 638
 639         return m
 640
 641
 642 class ProductTerms(Elaboratable):
 643     """ creates a bank of product terms.  also performs the actual bit-selection
 644         this class is to be wrapped with a for-loop on the "a" operand.
 645         it creates a second-level for-loop on the "b" operand.
 646     """
 647     def __init__(self, width, twidth, pbwid, a_index, blen):
 648         self.a_index = a_index
 649         self.blen = blen
 650         self.pwidth = width
 651         self.twidth = twidth
 652         self.pbwid = pbwid
 653         self.a = Signal(twidth//2, reset_less=True)
 654         self.b = Signal(twidth//2, reset_less=True)
 655         self.pb_en = Signal(pbwid, reset_less=True)
 656         self.terms = [Signal(twidth, name="term%d"%i, reset_less=True) \
 657                             for i in range(blen)]
 658
 659     def elaborate(self, platform):
 660
 661         m = Module()
 662
 663         for b_index in range(self.blen):
 664             t = ProductTerm(self.pwidth, self.twidth, self.pbwid,
 665                             self.a_index, b_index)
 666             setattr(m.submodules, "term_%d" % b_index, t)
 667
 668             m.d.comb += t.a.eq(self.a)
 669             m.d.comb += t.b.eq(self.b)
 670             m.d.comb += t.pb_en.eq(self.pb_en)
 671
 672             m.d.comb += self.terms[b_index].eq(t.term)
 673
 674         return m
 675
 676
 677 class LSBNegTerm(Elaboratable):
 678
 679     def __init__(self, bit_width):
 680         self.bit_width = bit_width
 681         self.part = Signal(reset_less=True)
 682         self.signed = Signal(reset_less=True)
 683         self.op = Signal(bit_width, reset_less=True)
 684         self.msb = Signal(reset_less=True)
 685         self.nt = Signal(bit_width*2, reset_less=True)
 686         self.nl = Signal(bit_width*2, reset_less=True)
 687
 688     def elaborate(self, platform):
 689         m = Module()
 690         comb = m.d.comb
 691         bit_wid = self.bit_width
 692         ext = Repl(0, bit_wid) # extend output to HI part
 693
 694         # determine sign of each incoming number *in this partition*
 695         enabled = Signal(reset_less=True)
 696         m.d.comb += enabled.eq(self.part & self.msb & self.signed)
 697
 698         # for 8-bit values: form a * 0xFF00 by using -a * 0x100, the
 699         # negation operation is split into a bitwise not and a +1.
 700         # likewise for 16, 32, and 64-bit values.
 701
 702         # width-extended 1s complement if a is signed, otherwise zero
 703         comb += self.nt.eq(Mux(enabled, Cat(ext, ~self.op), 0))
 704
 705         # add 1 if signed, otherwise add zero
 706         comb += self.nl.eq(Cat(ext, enabled, Repl(0, bit_wid-1)))
 707
 708         return m
 709
 710
 711 class Part(Elaboratable):
 712     """ a key class which, depending on the partitioning, will determine
 713         what action to take when parts of the output are signed or unsigned.
 714
 715         this requires 2 pieces of data *per operand, per partition*:
 716         whether the MSB is HI/LO (per partition!), and whether a signed
 717         or unsigned operation has been *requested*.
 718
 719         once that is determined, signed is basically carried out
 720         by splitting 2's complement into 1's complement plus one.
 721         1's complement is just a bit-inversion.
 722
 723         the extra terms - as separate terms - are then thrown at the
 724         AddReduce alongside the multiplication part-results.
 725     """
 726     def __init__(self, width, n_parts, n_levels, pbwid):
 727
 728         # inputs
 729         self.a = Signal(64)
 730         self.b = Signal(64)
 731         self.a_signed = [Signal(name=f"a_signed_{i}") for i in range(8)]
 732         self.b_signed = [Signal(name=f"_b_signed_{i}") for i in range(8)]
 733         self.pbs = Signal(pbwid, reset_less=True)
 734
 735         # outputs
 736         self.parts = [Signal(name=f"part_{i}") for i in range(n_parts)]
 737         self.delayed_parts = [
 738             [Signal(name=f"delayed_part_{delay}_{i}")
 739              for i in range(n_parts)]
 740                 for delay in range(n_levels)]
 741         # XXX REALLY WEIRD BUG - have to take a copy of the last delayed_parts
 742         self.dplast = [Signal(name=f"dplast_{i}")
 743                          for i in range(n_parts)]
 744
 745         self.not_a_term = Signal(width)
 746         self.neg_lsb_a_term = Signal(width)
 747         self.not_b_term = Signal(width)
 748         self.neg_lsb_b_term = Signal(width)
 749
 750     def elaborate(self, platform):
 751         m = Module()
 752
 753         pbs, parts, delayed_parts = self.pbs, self.parts, self.delayed_parts
 754         # negated-temporary copy of partition bits
 755         npbs = Signal.like(pbs, reset_less=True)
 756         m.d.comb += npbs.eq(~pbs)
 757         byte_count = 8 // len(parts)
 758         for i in range(len(parts)):
 759             pbl = []
 760             pbl.append(npbs[i * byte_count - 1])
 761             for j in range(i * byte_count, (i + 1) * byte_count - 1):
 762                 pbl.append(pbs[j])
 763             pbl.append(npbs[(i + 1) * byte_count - 1])
 764             value = Signal(len(pbl), name="value_%di" % i, reset_less=True)
 765             m.d.comb += value.eq(Cat(*pbl))
 766             m.d.comb += parts[i].eq(~(value).bool())
 767             m.d.comb += delayed_parts[0][i].eq(parts[i])
 768             m.d.sync += [delayed_parts[j + 1][i].eq(delayed_parts[j][i])
 769                          for j in range(len(delayed_parts)-1)]
 770             m.d.comb += self.dplast[i].eq(delayed_parts[-1][i])
 771
 772         not_a_term, neg_lsb_a_term, not_b_term, neg_lsb_b_term = \
 773                 self.not_a_term, self.neg_lsb_a_term, \
 774                 self.not_b_term, self.neg_lsb_b_term
 775
 776         byte_width = 8 // len(parts) # byte width
 777         bit_wid = 8 * byte_width     # bit width
 778         nat, nbt, nla, nlb = [], [], [], []
 779         for i in range(len(parts)):
 780             # work out bit-inverted and +1 term for a.
 781             pa = LSBNegTerm(bit_wid)
 782             setattr(m.submodules, "lnt_%d_a_%d" % (bit_wid, i), pa)
 783             m.d.comb += pa.part.eq(parts[i])
 784             m.d.comb += pa.op.eq(self.a.part(bit_wid * i, bit_wid))
 785             m.d.comb += pa.signed.eq(self.b_signed[i * byte_width]) # yes b
 786             m.d.comb += pa.msb.eq(self.b[(i + 1) * bit_wid - 1]) # really, b
 787             nat.append(pa.nt)
 788             nla.append(pa.nl)
 789
 790             # work out bit-inverted and +1 term for b
 791             pb = LSBNegTerm(bit_wid)
 792             setattr(m.submodules, "lnt_%d_b_%d" % (bit_wid, i), pb)
 793             m.d.comb += pb.part.eq(parts[i])
 794             m.d.comb += pb.op.eq(self.b.part(bit_wid * i, bit_wid))
 795             m.d.comb += pb.signed.eq(self.a_signed[i * byte_width]) # yes a
 796             m.d.comb += pb.msb.eq(self.a[(i + 1) * bit_wid - 1]) # really, a
 797             nbt.append(pb.nt)
 798             nlb.append(pb.nl)
 799
 800         # concatenate together and return all 4 results.
 801         m.d.comb += [not_a_term.eq(Cat(*nat)),
 802                      not_b_term.eq(Cat(*nbt)),
 803                      neg_lsb_a_term.eq(Cat(*nla)),
 804                      neg_lsb_b_term.eq(Cat(*nlb)),
 805                     ]
 806
 807         return m
 808
 809
 810 class IntermediateOut(Elaboratable):
 811     """ selects the HI/LO part of the multiplication, for a given bit-width
 812         the output is also reconstructed in its SIMD (partition) lanes.
 813     """
 814     def __init__(self, width, out_wid, n_parts):
 815         self.width = width
 816         self.n_parts = n_parts
 817         self.part_ops = [Signal(2, name="dpop%d" % i, reset_less=True)
 818                                      for i in range(8)]
 819         self.intermed = Signal(out_wid, reset_less=True)
 820         self.output = Signal(out_wid//2, reset_less=True)
 821
 822     def elaborate(self, platform):
 823         m = Module()
 824
 825         ol = []
 826         w = self.width
 827         sel = w // 8
 828         for i in range(self.n_parts):
 829             op = Signal(w, reset_less=True, name="op%d_%d" % (w, i))
 830             m.d.comb += op.eq(
 831                 Mux(self.part_ops[sel * i] == OP_MUL_LOW,
 832                     self.intermed.part(i * w*2, w),
 833                     self.intermed.part(i * w*2 + w, w)))
 834             ol.append(op)
 835         m.d.comb += self.output.eq(Cat(*ol))
 836
 837         return m
 838
 839
 840 class FinalOut(Elaboratable):
 841     """ selects the final output based on the partitioning.
 842
 843         each byte is selectable independently, i.e. it is possible
 844         that some partitions requested 8-bit computation whilst others
 845         requested 16 or 32 bit.
 846     """
 847     def __init__(self, out_wid):
 848         # inputs
 849         self.d8 = [Signal(name=f"d8_{i}", reset_less=True) for i in range(8)]
 850         self.d16 = [Signal(name=f"d16_{i}", reset_less=True) for i in range(4)]
 851         self.d32 = [Signal(name=f"d32_{i}", reset_less=True) for i in range(2)]
 852
 853         self.i8 = Signal(out_wid, reset_less=True)
 854         self.i16 = Signal(out_wid, reset_less=True)
 855         self.i32 = Signal(out_wid, reset_less=True)
 856         self.i64 = Signal(out_wid, reset_less=True)
 857
 858         # output
 859         self.out = Signal(out_wid, reset_less=True)
 860
 861     def elaborate(self, platform):
 862         m = Module()
 863         ol = []
 864         for i in range(8):
 865             # select one of the outputs: d8 selects i8, d16 selects i16
 866             # d32 selects i32, and the default is i64.
 867             # d8 and d16 are ORed together in the first Mux
 868             # then the 2nd selects either i8 or i16.
 869             # if neither d8 nor d16 are set, d32 selects either i32 or i64.
 870             op = Signal(8, reset_less=True, name="op_%d" % i)
 871             m.d.comb += op.eq(
 872                 Mux(self.d8[i] | self.d16[i // 2],
 873                     Mux(self.d8[i], self.i8.part(i * 8, 8),
 874                                      self.i16.part(i * 8, 8)),
 875                     Mux(self.d32[i // 4], self.i32.part(i * 8, 8),
 876                                           self.i64.part(i * 8, 8))))
 877             ol.append(op)
 878         m.d.comb += self.out.eq(Cat(*ol))
 879         return m
 880
 881
 882 class OrMod(Elaboratable):
 883     """ ORs four values together in a hierarchical tree
 884     """
 885     def __init__(self, wid):
 886         self.wid = wid
 887         self.orin = [Signal(wid, name="orin%d" % i, reset_less=True)
 888                      for i in range(4)]
 889         self.orout = Signal(wid, reset_less=True)
 890
 891     def elaborate(self, platform):
 892         m = Module()
 893         or1 = Signal(self.wid, reset_less=True)
 894         or2 = Signal(self.wid, reset_less=True)
 895         m.d.comb += or1.eq(self.orin[0] | self.orin[1])
 896         m.d.comb += or2.eq(self.orin[2] | self.orin[3])
 897         m.d.comb += self.orout.eq(or1 | or2)
 898
 899         return m
 900
 901
 902 class Signs(Elaboratable):
 903     """ determines whether a or b are signed numbers
 904         based on the required operation type (OP_MUL_*)
 905     """
 906
 907     def __init__(self):
 908         self.part_ops = Signal(2, reset_less=True)
 909         self.a_signed = Signal(reset_less=True)
 910         self.b_signed = Signal(reset_less=True)
 911
 912     def elaborate(self, platform):
 913
 914         m = Module()
 915
 916         asig = self.part_ops != OP_MUL_UNSIGNED_HIGH
 917         bsig = (self.part_ops == OP_MUL_LOW) \
 918                     | (self.part_ops == OP_MUL_SIGNED_HIGH)
 919         m.d.comb += self.a_signed.eq(asig)
 920         m.d.comb += self.b_signed.eq(bsig)
 921
 922         return m
 923
 924
 925 class Mul8_16_32_64(Elaboratable):
 926     """Signed/Unsigned 8/16/32/64-bit partitioned integer multiplier.
 927
 928     Supports partitioning into any combination of 8, 16, 32, and 64-bit
 929     partitions on naturally-aligned boundaries. Supports the operation being
 930     set for each partition independently.
 931
 932     :attribute part_pts: the input partition points. Has a partition point at
 933         multiples of 8 in 0 < i < 64. Each partition point's associated
 934         ``Value`` is a ``Signal``. Modification not supported, except for by
 935         ``Signal.eq``.
 936     :attribute part_ops: the operation for each byte. The operation for a
 937         particular partition is selected by assigning the selected operation
 938         code to each byte in the partition. The allowed operation codes are:
 939
 940         :attribute OP_MUL_LOW: the LSB half of the product. Equivalent to
 941             RISC-V's `mul` instruction.
 942         :attribute OP_MUL_SIGNED_HIGH: the MSB half of the product where both
 943             ``a`` and ``b`` are signed. Equivalent to RISC-V's `mulh`
 944             instruction.
 945         :attribute OP_MUL_SIGNED_UNSIGNED_HIGH: the MSB half of the product
 946             where ``a`` is signed and ``b`` is unsigned. Equivalent to RISC-V's
 947             `mulhsu` instruction.
 948         :attribute OP_MUL_UNSIGNED_HIGH: the MSB half of the product where both
 949             ``a`` and ``b`` are unsigned. Equivalent to RISC-V's `mulhu`
 950             instruction.
 951     """
 952
 953     def __init__(self, register_levels=()):
 954         """ register_levels: specifies the points in the cascade at which
 955             flip-flops are to be inserted.
 956         """
 957
 958         # parameter(s)
 959         self.register_levels = list(register_levels)
 960
 961         # inputs
 962         self.part_pts = PartitionPoints()
 963         for i in range(8, 64, 8):
 964             self.part_pts[i] = Signal(name=f"part_pts_{i}")
 965         self.part_ops = [Signal(2, name=f"part_ops_{i}") for i in range(8)]
 966         self.a = Signal(64)
 967         self.b = Signal(64)
 968
 969         # intermediates (needed for unit tests)
 970         self._intermediate_output = Signal(128)
 971
 972         # output
 973         self.output = Signal(64)
 974
 975     def elaborate(self, platform):
 976         m = Module()
 977
 978         # collect part-bytes
 979         pbs = Signal(8, reset_less=True)
 980         tl = []
 981         for i in range(8):
 982             pb = Signal(name="pb%d" % i, reset_less=True)
 983             m.d.comb += pb.eq(self.part_pts.part_byte(i))
 984             tl.append(pb)
 985         m.d.comb += pbs.eq(Cat(*tl))
 986
 987         # create (doubled) PartitionPoints (output is double input width)
 988         expanded_part_pts = PartitionPoints()
 989         for i, v in self.part_pts.items():
 990             ep = Signal(name=f"expanded_part_pts_{i*2}", reset_less=True)
 991             expanded_part_pts[i * 2] = ep
 992             m.d.comb += ep.eq(v)
 993
 994         # local variables
 995         signs = []
 996         for i in range(8):
 997             s = Signs()
 998             signs.append(s)
 999             setattr(m.submodules, "signs%d" % i, s)
1000             m.d.comb += s.part_ops.eq(self.part_ops[i])
1001
1002         n_levels = len(self.register_levels)+1
1003         m.submodules.part_8 = part_8 = Part(128, 8, n_levels, 8)
1004         m.submodules.part_16 = part_16 = Part(128, 4, n_levels, 8)
1005         m.submodules.part_32 = part_32 = Part(128, 2, n_levels, 8)
1006         m.submodules.part_64 = part_64 = Part(128, 1, n_levels, 8)
1007         nat_l, nbt_l, nla_l, nlb_l = [], [], [], []
1008         for mod in [part_8, part_16, part_32, part_64]:
1009             m.d.comb += mod.a.eq(self.a)
1010             m.d.comb += mod.b.eq(self.b)
1011             for i in range(len(signs)):
1012                 m.d.comb += mod.a_signed[i].eq(signs[i].a_signed)
1013                 m.d.comb += mod.b_signed[i].eq(signs[i].b_signed)
1014             m.d.comb += mod.pbs.eq(pbs)
1015             nat_l.append(mod.not_a_term)
1016             nbt_l.append(mod.not_b_term)
1017             nla_l.append(mod.neg_lsb_a_term)
1018             nlb_l.append(mod.neg_lsb_b_term)
1019
1020         terms = []
1021
1022         for a_index in range(8):
1023             t = ProductTerms(8, 128, 8, a_index, 8)
1024             setattr(m.submodules, "terms_%d" % a_index, t)
1025
1026             m.d.comb += t.a.eq(self.a)
1027             m.d.comb += t.b.eq(self.b)
1028             m.d.comb += t.pb_en.eq(pbs)
1029
1030             for term in t.terms:
1031                 terms.append(term)
1032
1033         # it's fine to bitwise-or data together since they are never enabled
1034         # at the same time
1035         m.submodules.nat_or = nat_or = OrMod(128)
1036         m.submodules.nbt_or = nbt_or = OrMod(128)
1037         m.submodules.nla_or = nla_or = OrMod(128)
1038         m.submodules.nlb_or = nlb_or = OrMod(128)
1039         for l, mod in [(nat_l, nat_or),
1040                              (nbt_l, nbt_or),
1041                              (nla_l, nla_or),
1042                              (nlb_l, nlb_or)]:
1043             for i in range(len(l)):
1044                 m.d.comb += mod.orin[i].eq(l[i])
1045             terms.append(mod.orout)
1046
1047         add_reduce = AddReduce(terms,
1048                                128,
1049                                self.register_levels,
1050                                expanded_part_pts,
1051                                self.part_ops)
1052
1053         out_part_ops = add_reduce.levels[-1].out_part_ops
1054
1055         m.submodules.add_reduce = add_reduce
1056         m.d.comb += self._intermediate_output.eq(add_reduce.output)
1057         # create _output_64
1058         m.submodules.io64 = io64 = IntermediateOut(64, 128, 1)
1059         m.d.comb += io64.intermed.eq(self._intermediate_output)
1060         for i in range(8):
1061             m.d.comb += io64.part_ops[i].eq(out_part_ops[i])
1062
1063         # create _output_32
1064         m.submodules.io32 = io32 = IntermediateOut(32, 128, 2)
1065         m.d.comb += io32.intermed.eq(self._intermediate_output)
1066         for i in range(8):
1067             m.d.comb += io32.part_ops[i].eq(out_part_ops[i])
1068
1069         # create _output_16
1070         m.submodules.io16 = io16 = IntermediateOut(16, 128, 4)
1071         m.d.comb += io16.intermed.eq(self._intermediate_output)
1072         for i in range(8):
1073             m.d.comb += io16.part_ops[i].eq(out_part_ops[i])
1074
1075         # create _output_8
1076         m.submodules.io8 = io8 = IntermediateOut(8, 128, 8)
1077         m.d.comb += io8.intermed.eq(self._intermediate_output)
1078         for i in range(8):
1079             m.d.comb += io8.part_ops[i].eq(out_part_ops[i])
1080
1081         # final output
1082         m.submodules.finalout = finalout = FinalOut(64)
1083         for i in range(len(part_8.delayed_parts[-1])):
1084             m.d.comb += finalout.d8[i].eq(part_8.dplast[i])
1085         for i in range(len(part_16.delayed_parts[-1])):
1086             m.d.comb += finalout.d16[i].eq(part_16.dplast[i])
1087         for i in range(len(part_32.delayed_parts[-1])):
1088             m.d.comb += finalout.d32[i].eq(part_32.dplast[i])
1089         m.d.comb += finalout.i8.eq(io8.output)
1090         m.d.comb += finalout.i16.eq(io16.output)
1091         m.d.comb += finalout.i32.eq(io32.output)
1092         m.d.comb += finalout.i64.eq(io64.output)
1093         m.d.comb += self.output.eq(finalout.out)
1094
1095         return m
1096
1097
1098 if __name__ == "__main__":
1099     m = Mul8_16_32_64()
1100     main(m, ports=[m.a,
1101                    m.b,
1102                    m._intermediate_output,
1103                    m.output,
1104                    *m.part_ops,
1105                    *m.part_pts.values()])