From: Luke Kenneth Casson Leighton Date: Wed, 21 Aug 2019 09:20:00 +0000 (+0100) Subject: move final adder to separate module X-Git-Tag: ls180-24jan2020~447 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=66657754c88fbd4c684fb9f6eb1fba2c14aeb652;p=ieee754fpu.git move final adder to separate module --- diff --git a/src/ieee754/part_mul_add/multiply.py b/src/ieee754/part_mul_add/multiply.py index a9e9c70d..6950a6d9 100644 --- a/src/ieee754/part_mul_add/multiply.py +++ b/src/ieee754/part_mul_add/multiply.py @@ -317,6 +317,63 @@ class AddReduceData: for i in range(len(self.part_ops))] +class FinalAdd(Elaboratable): + """ Final stage of add reduce + """ + + def __init__(self, inputs, output_width, register_levels, partition_points, + part_ops): + self.part_ops = part_ops + self.out_part_ops = [Signal(2, name=f"out_part_ops_{i}") + for i in range(len(part_ops))] + self.inputs = list(inputs) + self._resized_inputs = [ + Signal(output_width, name=f"resized_inputs[{i}]") + for i in range(len(self.inputs))] + self.register_levels = list(register_levels) + self.output = Signal(output_width) + self.partition_points = PartitionPoints(partition_points) + if not self.partition_points.fits_in_width(output_width): + raise ValueError("partition_points doesn't fit in output_width") + self._reg_partition_points = self.partition_points.like() + + def elaborate(self, platform): + """Elaborate this module.""" + m = Module() + + # resize inputs to correct bit-width and optionally add in + # pipeline registers + resized_input_assignments = [self._resized_inputs[i].eq(self.inputs[i]) + for i in range(len(self.inputs))] + copy_part_ops = [self.out_part_ops[i].eq(self.part_ops[i]) + for i in range(len(self.part_ops))] + if 0 in self.register_levels: + m.d.sync += copy_part_ops + m.d.sync += resized_input_assignments + m.d.sync += self._reg_partition_points.eq(self.partition_points) + else: + m.d.comb += copy_part_ops + m.d.comb += resized_input_assignments + m.d.comb += self._reg_partition_points.eq(self.partition_points) + + if len(self.inputs) == 0: + # use 0 as the default output value + m.d.comb += self.output.eq(0) + elif len(self.inputs) == 1: + # handle single input + m.d.comb += self.output.eq(self._resized_inputs[0]) + else: + # base case for adding 2 inputs + assert len(self.inputs) == 2 + adder = PartitionedAdder(len(self.output), + self._reg_partition_points) + m.submodules.final_adder = adder + m.d.comb += adder.a.eq(self._resized_inputs[0]) + m.d.comb += adder.b.eq(self._resized_inputs[1]) + m.d.comb += self.output.eq(adder.output) + return m + + class AddReduceSingle(Elaboratable): """Add list of numbers together. @@ -339,6 +396,7 @@ class AddReduceSingle(Elaboratable): pipeline registers. :param partition_points: the input partition points. """ + self.output_width = output_width self.part_ops = part_ops self.out_part_ops = [Signal(2, name=f"out_part_ops_{i}") for i in range(len(part_ops))] @@ -347,7 +405,6 @@ class AddReduceSingle(Elaboratable): Signal(output_width, name=f"resized_inputs[{i}]") for i in range(len(self.inputs))] self.register_levels = list(register_levels) - self.output = Signal(output_width) self.partition_points = PartitionPoints(partition_points) if not self.partition_points.fits_in_width(output_width): raise ValueError("partition_points doesn't fit in output_width") @@ -413,27 +470,7 @@ class AddReduceSingle(Elaboratable): for (value, term) in self._intermediate_terms: m.d.comb += term.eq(value) - # if there are no full adders to create, then we handle the base cases - # and return, otherwise we go on to the recursive case - if len(self.groups) == 0: - if len(self.inputs) == 0: - # use 0 as the default output value - m.d.comb += self.output.eq(0) - elif len(self.inputs) == 1: - # handle single input - m.d.comb += self.output.eq(self._resized_inputs[0]) - else: - # base case for adding 2 inputs - assert len(self.inputs) == 2 - adder = PartitionedAdder(len(self.output), - self._reg_partition_points) - m.submodules.final_adder = adder - m.d.comb += adder.a.eq(self._resized_inputs[0]) - m.d.comb += adder.b.eq(self._resized_inputs[1]) - m.d.comb += self.output.eq(adder.output) - return m - - mask = self._reg_partition_points.as_mask(len(self.output)) + mask = self._reg_partition_points.as_mask(self.output_width) m.d.comb += self.part_mask.eq(mask) # add and link the intermediate term modules @@ -455,19 +492,19 @@ class AddReduceSingle(Elaboratable): def add_intermediate_term(value): intermediate_term = Signal( - len(self.output), + self.output_width, name=f"intermediate_terms[{len(intermediate_terms)}]") _intermediate_terms.append((value, intermediate_term)) intermediate_terms.append(intermediate_term) # store mask in intermediary (simplifies graph) - self.part_mask = Signal(len(self.output), reset_less=True) + self.part_mask = Signal(self.output_width, reset_less=True) # create full adders for this recursive level. # this shrinks N terms to 2 * (N // 3) plus the remainder self.adders = [] for i in self.groups: - adder_i = MaskedFullAdder(len(self.output)) + adder_i = MaskedFullAdder(self.output_width) self.adders.append((i, adder_i)) # add both the sum and the masked-carry to the next level. # 3 inputs have now been reduced to 2... @@ -545,12 +582,17 @@ class AddReduce(Elaboratable): next_level = AddReduceSingle(inputs, self.output_width, next_levels, partition_points, part_ops) mods.append(next_level) - if len(next_level.groups) == 0: - break next_levels = list(AddReduce.next_register_levels(next_levels)) partition_points = next_level._reg_partition_points inputs = next_level.intermediate_terms part_ops = next_level.out_part_ops + groups = AddReduceSingle.full_adder_groups(len(inputs)) + if len(groups) == 0: + break + + next_level = FinalAdd(inputs, self.output_width, next_levels, + partition_points, part_ops) + mods.append(next_level) self.levels = mods