Pyrtl floating point library #475
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| from ._types import FloatingPointType, FPTypeProperties, PyrtlFloatConfig, RoundingMode | ||
| from .floatoperations import ( | ||
| BFloat16Operations, | ||
| Float16Operations, | ||
| Float32Operations, | ||
| Float64Operations, | ||
| FloatOperations, | ||
| ) | ||
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| __all__ = [ | ||
| "FloatingPointType", | ||
| "FPTypeProperties", | ||
| "PyrtlFloatConfig", | ||
| "RoundingMode", | ||
| "FloatOperations", | ||
| "BFloat16Operations", | ||
| "Float16Operations", | ||
| "Float32Operations", | ||
| "Float64Operations", | ||
| ] |
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| import pyrtl | ||
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| from ._float_utills import FloatUtils | ||
| from ._types import PyrtlFloatConfig, RoundingMode | ||
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| class AddSubHelper: | ||
| @staticmethod | ||
| def add( | ||
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| config: PyrtlFloatConfig, | ||
| operand_a: pyrtl.WireVector, | ||
| operand_b: pyrtl.WireVector, | ||
| ) -> pyrtl.WireVector: | ||
| fp_type_props = config.fp_type_properties | ||
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There was a problem hiding this comment. All user-facing methods/functions should check (somewhere, not necessarily here) that the operand bitwidths are consistent with |
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| rounding_mode = config.rounding_mode | ||
| num_exp_bits = fp_type_props.num_exponent_bits | ||
| num_mant_bits = fp_type_props.num_mantissa_bits | ||
| total_bits = num_exp_bits + num_mant_bits + 1 | ||
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| operand_a_daz = FloatUtils.make_denormals_zero(fp_type_props, operand_a) | ||
| operand_b_daz = FloatUtils.make_denormals_zero(fp_type_props, operand_b) | ||
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| # operand_smaller is the operand with the smaller absolute value and | ||
| # operand_larger is the operand with the larger absolute value | ||
| operand_smaller = pyrtl.WireVector(bitwidth=total_bits) | ||
| operand_larger = pyrtl.WireVector(bitwidth=total_bits) | ||
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| with pyrtl.conditional_assignment: | ||
| exponent_and_mantissa_len = num_mant_bits + num_exp_bits | ||
| with ( | ||
| operand_a_daz[:exponent_and_mantissa_len] | ||
| < operand_b_daz[:exponent_and_mantissa_len] | ||
| ): | ||
| operand_smaller |= operand_a_daz | ||
| operand_larger |= operand_b_daz | ||
| with pyrtl.otherwise: | ||
| operand_smaller |= operand_b_daz | ||
| operand_larger |= operand_a_daz | ||
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| smaller_operand_sign = FloatUtils.get_sign(fp_type_props, operand_smaller) | ||
| larger_operand_sign = FloatUtils.get_sign(fp_type_props, operand_larger) | ||
| smaller_operand_exponent = FloatUtils.get_exponent( | ||
| fp_type_props, operand_smaller | ||
| ) | ||
| larger_operand_exponent = FloatUtils.get_exponent(fp_type_props, operand_larger) | ||
| smaller_operand_mantissa = pyrtl.concat( | ||
| pyrtl.Const(1), FloatUtils.get_mantissa(fp_type_props, operand_smaller) | ||
| ) | ||
| larger_operand_mantissa = pyrtl.concat( | ||
| pyrtl.Const(1), FloatUtils.get_mantissa(fp_type_props, operand_larger) | ||
| ) | ||
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| exponent_diff = larger_operand_exponent - smaller_operand_exponent | ||
| smaller_mantissa_shifted = pyrtl.shift_right_logical( | ||
| smaller_operand_mantissa, exponent_diff | ||
| ) | ||
| grs = pyrtl.WireVector(bitwidth=3) # guard, round, sticky bits for rounding | ||
| with pyrtl.conditional_assignment: | ||
| with exponent_diff >= 2: | ||
| guard_and_round = pyrtl.shift_right_logical( | ||
| smaller_operand_mantissa, exponent_diff - 2 | ||
| )[:2] | ||
| mask = ( | ||
| pyrtl.shift_left_logical( | ||
| pyrtl.Const(1, bitwidth=num_mant_bits), exponent_diff - 2 | ||
| ) | ||
| - 1 | ||
| ) | ||
| sticky = (smaller_operand_mantissa & mask) != 0 | ||
| grs |= pyrtl.concat(guard_and_round, sticky) | ||
| with exponent_diff == 1: | ||
| grs |= pyrtl.concat( | ||
| smaller_operand_mantissa[0], pyrtl.Const(0, bitwidth=2) | ||
| ) | ||
| with pyrtl.otherwise: | ||
| grs |= 0 | ||
| smaller_mantissa_shifted_grs = pyrtl.concat(smaller_mantissa_shifted, grs) | ||
| larger_mantissa_extended = pyrtl.concat( | ||
| larger_operand_mantissa, pyrtl.Const(0, bitwidth=3) | ||
| ) | ||
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| sum_exponent, sum_mantissa, sum_grs, sum_carry = AddSubHelper._add_operands( | ||
| larger_operand_exponent, | ||
| smaller_mantissa_shifted_grs, | ||
| larger_mantissa_extended, | ||
| ) | ||
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| sub_exponent, sub_mantissa, sub_grs, num_leading_zeros = ( | ||
| AddSubHelper._sub_operands( | ||
| num_mant_bits, | ||
| larger_operand_exponent, | ||
| smaller_mantissa_shifted_grs, | ||
| larger_mantissa_extended, | ||
| ) | ||
| ) | ||
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| # WireVectors for the raw addition or subtraction result, before handling | ||
| # special cases | ||
| raw_result_exponent = pyrtl.WireVector(bitwidth=num_exp_bits) | ||
| raw_result_mantissa = pyrtl.WireVector(bitwidth=num_mant_bits) | ||
| if rounding_mode == RoundingMode.RNE: | ||
| raw_result_grs = pyrtl.WireVector(bitwidth=3) | ||
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| with pyrtl.conditional_assignment: | ||
| with smaller_operand_sign == larger_operand_sign: # add | ||
| raw_result_exponent |= sum_exponent | ||
| raw_result_mantissa |= sum_mantissa | ||
| if rounding_mode == RoundingMode.RNE: | ||
| raw_result_grs |= sum_grs | ||
| with pyrtl.otherwise: # sub | ||
| raw_result_exponent |= sub_exponent | ||
| raw_result_mantissa |= sub_mantissa | ||
| if rounding_mode == RoundingMode.RNE: | ||
| raw_result_grs |= sub_grs | ||
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| if rounding_mode == RoundingMode.RNE: | ||
| ( | ||
| raw_result_rounded_exponent, | ||
| raw_result_rounded_mantissa, | ||
| rounding_exponent_incremented, | ||
| ) = AddSubHelper._round( | ||
| num_mant_bits, | ||
| num_exp_bits, | ||
| raw_result_exponent, | ||
| raw_result_mantissa, | ||
| raw_result_grs, | ||
| ) | ||
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| smaller_operand_nan = FloatUtils.is_NaN(fp_type_props, operand_smaller) | ||
| larger_operand_nan = FloatUtils.is_NaN(fp_type_props, operand_larger) | ||
| smaller_operand_inf = FloatUtils.is_inf(fp_type_props, operand_smaller) | ||
| larger_operand_inf = FloatUtils.is_inf(fp_type_props, operand_larger) | ||
| smaller_operand_zero = FloatUtils.is_zero(fp_type_props, operand_smaller) | ||
| larger_operand_zero = FloatUtils.is_zero(fp_type_props, operand_larger) | ||
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| # WireVectors for the final result after handling special cases | ||
| final_result_sign = pyrtl.WireVector(bitwidth=1) | ||
| final_result_mantissa = pyrtl.WireVector(bitwidth=num_mant_bits) | ||
| final_result_exponent = pyrtl.WireVector(bitwidth=num_exp_bits) | ||
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| # handle special cases | ||
| with pyrtl.conditional_assignment: | ||
| # if either operand is NaN or both operands are infinity of opposite signs, | ||
| # the result is NaN | ||
| with ( | ||
| smaller_operand_nan | ||
| | larger_operand_nan | ||
| | ( | ||
| smaller_operand_inf | ||
| & larger_operand_inf | ||
| & (larger_operand_sign != smaller_operand_sign) | ||
| ) | ||
| ): | ||
| final_result_sign |= larger_operand_sign | ||
| FloatUtils.make_output_NaN( | ||
| fp_type_props, final_result_exponent, final_result_mantissa | ||
| ) | ||
| # infinities | ||
| with smaller_operand_inf: | ||
| final_result_sign |= larger_operand_sign | ||
| FloatUtils.make_output_inf( | ||
| fp_type_props, final_result_exponent, final_result_mantissa | ||
| ) | ||
| with larger_operand_inf: | ||
| final_result_sign |= larger_operand_sign | ||
| FloatUtils.make_output_inf( | ||
| fp_type_props, final_result_exponent, final_result_mantissa | ||
| ) | ||
| # +num + -num = +0 | ||
| with ( | ||
| (smaller_operand_mantissa == larger_operand_mantissa) | ||
| & (smaller_operand_exponent == larger_operand_exponent) | ||
| & (larger_operand_sign != smaller_operand_sign) | ||
| ): | ||
| final_result_sign |= 0 | ||
| FloatUtils.make_output_zero( | ||
| final_result_exponent, final_result_mantissa | ||
| ) | ||
| with smaller_operand_zero: | ||
| final_result_sign |= larger_operand_sign | ||
| final_result_mantissa |= larger_operand_mantissa | ||
| final_result_exponent |= larger_operand_exponent | ||
| with larger_operand_zero: | ||
| final_result_sign |= smaller_operand_sign | ||
| final_result_mantissa |= smaller_operand_mantissa | ||
| final_result_exponent |= smaller_operand_exponent | ||
| # overflow and underflow | ||
| initial_larger_exponent_max_value = pyrtl.Const(2**num_exp_bits - 2) | ||
| if rounding_mode == RoundingMode.RNE: | ||
| larger_exponent_max_value = ( | ||
| initial_larger_exponent_max_value | ||
| - sum_carry | ||
| - rounding_exponent_incremented | ||
| ) | ||
| else: | ||
| larger_exponent_max_value = ( | ||
| initial_larger_exponent_max_value - sum_carry | ||
| ) | ||
| initial_larger_exponent_min_value = pyrtl.Const(1) | ||
| if rounding_mode == RoundingMode.RNE: | ||
| larger_exponent_min_value = ( | ||
| initial_larger_exponent_min_value | ||
| + num_leading_zeros | ||
| - rounding_exponent_incremented | ||
| ) | ||
| else: | ||
| larger_exponent_min_value = ( | ||
| initial_larger_exponent_min_value + num_leading_zeros | ||
| ) | ||
| with (smaller_operand_sign == larger_operand_sign) & ( | ||
| larger_operand_exponent > larger_exponent_max_value | ||
| ): # detect overflow on addition | ||
| final_result_sign |= larger_operand_sign | ||
| if rounding_mode == RoundingMode.RNE: | ||
| FloatUtils.make_output_inf( | ||
| fp_type_props, final_result_exponent, final_result_mantissa | ||
| ) | ||
| else: | ||
| FloatUtils.make_output_largest_finite_number( | ||
| fp_type_props, final_result_exponent, final_result_mantissa | ||
| ) | ||
| with (smaller_operand_sign != larger_operand_sign) & ( | ||
| larger_operand_exponent < larger_exponent_min_value | ||
| ): # detect underflow on subtraction | ||
| final_result_sign |= larger_operand_sign | ||
| FloatUtils.make_output_zero( | ||
| final_result_exponent, final_result_mantissa | ||
| ) | ||
| with pyrtl.otherwise: | ||
| final_result_sign |= larger_operand_sign | ||
| if rounding_mode == RoundingMode.RNE: | ||
| final_result_exponent |= raw_result_rounded_exponent | ||
| final_result_mantissa |= raw_result_rounded_mantissa | ||
| else: | ||
| final_result_exponent |= raw_result_exponent | ||
| final_result_mantissa |= raw_result_mantissa | ||
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| return pyrtl.concat( | ||
| final_result_sign, final_result_exponent, final_result_mantissa | ||
| ) | ||
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| @staticmethod | ||
| def sub( | ||
| config: PyrtlFloatConfig, | ||
| operand_a: pyrtl.WireVector, | ||
| operand_b: pyrtl.WireVector, | ||
| ) -> pyrtl.WireVector: | ||
| num_exp_bits = config.fp_type_properties.num_exponent_bits | ||
| num_mant_bits = config.fp_type_properties.num_mantissa_bits | ||
| operand_b_negated = operand_b ^ pyrtl.concat( | ||
| pyrtl.Const(1, bitwidth=1), | ||
| pyrtl.Const(0, bitwidth=num_exp_bits + num_mant_bits), | ||
| ) | ||
| return AddSubHelper.add(config, operand_a, operand_b_negated) | ||
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| @staticmethod | ||
| def _add_operands( | ||
| larger_operand_exponent: pyrtl.WireVector, | ||
| smaller_mantissa_shifted_grs: pyrtl.WireVector, | ||
| larger_mantissa_extended: pyrtl.WireVector, | ||
| ) -> tuple[pyrtl.WireVector, pyrtl.WireVector, pyrtl.WireVector, pyrtl.WireVector]: | ||
| sum_mantissa_grs = pyrtl.WireVector() | ||
| sum_mantissa_grs <<= larger_mantissa_extended + smaller_mantissa_shifted_grs | ||
| sum_carry = sum_mantissa_grs[-1] | ||
| sum_mantissa = pyrtl.select( | ||
| sum_carry, sum_mantissa_grs[4:], sum_mantissa_grs[3:-1] | ||
| ) | ||
| sum_grs = pyrtl.select( | ||
| sum_carry, | ||
| pyrtl.concat(sum_mantissa_grs[2:4], sum_mantissa_grs[:2] != 0), | ||
| sum_mantissa_grs[:3], | ||
| ) | ||
| sum_exponent = pyrtl.select( | ||
| sum_carry, larger_operand_exponent + 1, larger_operand_exponent | ||
| ) | ||
| return sum_exponent, sum_mantissa, sum_grs, sum_carry | ||
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| @staticmethod | ||
| def _sub_operands( | ||
| num_mant_bits: int, | ||
| larger_operand_exponent: pyrtl.WireVector, | ||
| smaller_mantissa_shifted_grs: pyrtl.WireVector, | ||
| larger_mantissa_extended: pyrtl.WireVector, | ||
| ) -> tuple[pyrtl.WireVector, pyrtl.WireVector, pyrtl.WireVector, pyrtl.WireVector]: | ||
| def leading_zero_priority_encoder(wire: pyrtl.WireVector, length: int): | ||
| out = pyrtl.WireVector( | ||
| bitwidth=pyrtl.infer_val_and_bitwidth(length - 1).bitwidth | ||
| ) | ||
| with pyrtl.conditional_assignment: | ||
| for i in range(wire.bitwidth - 1, wire.bitwidth - length - 1, -1): | ||
| with wire[i]: | ||
| out |= wire.bitwidth - i - 1 | ||
| return out | ||
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| sub_mantissa_grs = pyrtl.WireVector(bitwidth=num_mant_bits + 4) | ||
| sub_mantissa_grs <<= larger_mantissa_extended - smaller_mantissa_shifted_grs | ||
| num_leading_zeros = leading_zero_priority_encoder( | ||
| sub_mantissa_grs, num_mant_bits + 1 | ||
| ) | ||
| sub_mantissa_grs_shifted = pyrtl.shift_left_logical( | ||
| sub_mantissa_grs, num_leading_zeros | ||
| ) | ||
| sub_mantissa = sub_mantissa_grs_shifted[3:] | ||
| sub_grs = sub_mantissa_grs_shifted[:3] | ||
| sub_exponent = larger_operand_exponent - num_leading_zeros | ||
| return sub_exponent, sub_mantissa, sub_grs, num_leading_zeros | ||
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| @staticmethod | ||
| def _round( | ||
| num_mant_bits: int, | ||
| num_exp_bits: int, | ||
| raw_result_exponent: pyrtl.WireVector, | ||
| raw_result_mantissa: pyrtl.WireVector, | ||
| raw_result_grs: pyrtl.WireVector, | ||
| ) -> tuple[pyrtl.WireVector, pyrtl.WireVector]: | ||
| last = raw_result_mantissa[0] | ||
| guard = raw_result_grs[2] | ||
|
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| round = raw_result_grs[1] | ||
| sticky = raw_result_grs[0] | ||
| round_up = guard & (last | round | sticky) | ||
| raw_result_rounded_mantissa = pyrtl.WireVector(bitwidth=num_mant_bits) | ||
| raw_result_rounded_exponent = pyrtl.WireVector(bitwidth=num_exp_bits) | ||
| rounding_exponent_incremented = pyrtl.WireVector(bitwidth=1) | ||
| with pyrtl.conditional_assignment: | ||
| with round_up: | ||
| with raw_result_mantissa == (1 << num_mant_bits) - 1: | ||
| raw_result_rounded_mantissa |= 0 | ||
| raw_result_rounded_exponent |= raw_result_exponent + 1 | ||
| rounding_exponent_incremented |= 1 | ||
| with pyrtl.otherwise: | ||
| raw_result_rounded_mantissa |= raw_result_mantissa + 1 | ||
| raw_result_rounded_exponent |= raw_result_exponent | ||
| rounding_exponent_incremented |= 0 | ||
| with pyrtl.otherwise: | ||
| raw_result_rounded_mantissa |= raw_result_mantissa | ||
| raw_result_rounded_exponent |= raw_result_exponent | ||
| rounding_exponent_incremented |= 0 | ||
| return ( | ||
| raw_result_rounded_exponent, | ||
| raw_result_rounded_mantissa, | ||
| rounding_exponent_incremented, | ||
| ) | ||
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Generally, classes with only
@staticmethods probably shouldn't be classes :) It looks like this class can be removed, and all the static methods can be ordinary functions? Same comment forFloatUtilsandMultiplicationHelper