diff --git a/base/common/DecomposedFloat.h b/base/common/DecomposedFloat.h index 078ba823c15..0b283f1ef6f 100644 --- a/base/common/DecomposedFloat.h +++ b/base/common/DecomposedFloat.h @@ -91,10 +91,12 @@ struct DecomposedFloat /// Compare float with integer of arbitrary width (both signed and unsigned are supported). Assuming two's complement arithmetic. + /// This function is generic, big integers (128, 256 bit) are supported as well. /// Infinities are compared correctly. NaNs are treat similarly to infinities, so they can be less than all numbers. /// (note that we need total order) + /// Returns -1, 0 or 1. template - int compare(Int rhs) + int compare(Int rhs) const { if (rhs == 0) return sign(); @@ -137,10 +139,11 @@ struct DecomposedFloat if (normalized_exponent() >= static_cast(8 * sizeof(Int) - is_signed_v)) return is_negative() ? -1 : 1; - using UInt = make_unsigned_t; + using UInt = std::conditional_t<(sizeof(Int) > sizeof(typename Traits::UInt)), make_unsigned_t, typename Traits::UInt>; UInt uint_rhs = rhs < 0 ? -rhs : rhs; /// Smaller octave: abs(rhs) < abs(float) + /// FYI, TIL: octave is also called "binade", https://en.wikipedia.org/wiki/Binade if (uint_rhs < (static_cast(1) << normalized_exponent())) return is_negative() ? -1 : 1; @@ -154,11 +157,11 @@ struct DecomposedFloat bool large_and_always_integer = normalized_exponent() >= static_cast(Traits::mantissa_bits); - typename Traits::UInt a = large_and_always_integer - ? mantissa() << (normalized_exponent() - Traits::mantissa_bits) - : mantissa() >> (Traits::mantissa_bits - normalized_exponent()); + UInt a = large_and_always_integer + ? static_cast(mantissa()) << (normalized_exponent() - Traits::mantissa_bits) + : static_cast(mantissa()) >> (Traits::mantissa_bits - normalized_exponent()); - typename Traits::UInt b = uint_rhs - (static_cast(1) << normalized_exponent()); + UInt b = uint_rhs - (static_cast(1) << normalized_exponent()); if (a < b) return is_negative() ? 1 : -1; @@ -175,40 +178,73 @@ struct DecomposedFloat template - bool equals(Int rhs) + bool equals(Int rhs) const { return compare(rhs) == 0; } template - bool notEquals(Int rhs) + bool notEquals(Int rhs) const { return compare(rhs) != 0; } template - bool less(Int rhs) + bool less(Int rhs) const { return compare(rhs) < 0; } template - bool greater(Int rhs) + bool greater(Int rhs) const { return compare(rhs) > 0; } template - bool lessOrEquals(Int rhs) + bool lessOrEquals(Int rhs) const { return compare(rhs) <= 0; } template - bool greaterOrEquals(Int rhs) + bool greaterOrEquals(Int rhs) const { return compare(rhs) >= 0; } + + + template + Int toInt() const + { + /// sign * (2 ^ normalized_exponent + mantissa * 2 ^ (normalized_exponent - mantissa_bits)) + + /// Too large exponent, implementation specific behaviour. Includes infs and NaNs. + if (normalized_exponent() >= sizeof(Int) * 8) + return is_negative() ? std::numeric_limits::lowest() : std::numeric_limits::max(); + + if (normalized_exponent() < 0) + return 0; + + Int res{1}; + res <<= normalized_exponent(); + + if (normalized_exponent() >= static_cast(Traits::mantissa_bits)) + { + res += static_cast(mantissa()) << (normalized_exponent() - Traits::mantissa_bits); + } + else + { + /// NOTE rounding towards zero, it can be different to current CPU rounding mode. + res += static_cast(mantissa()) >> (Traits::mantissa_bits - normalized_exponent()); + } + + /// Avoid UB on negation of the most negative numbers. Also implementation specific behaviour for unsigned integers. + if (is_negative() && res != std::numeric_limits::lowest()) + res = -res; + + return res; + } };