From 360d3ee184e821e9329a71a18361123aac8e2f8d Mon Sep 17 00:00:00 2001 From: Trevor Gross Date: Sat, 26 Oct 2024 00:42:02 -0500 Subject: [PATCH] Add float and integer traits from compiler-builtins In preparation of adding generic algorithms to `libm`, add the traits from `compiler-builtins`. Eventually we should be able to unify the two crates so we don't have duplicate implementations. --- .../compiler-builtins/libm/src/math/mod.rs | 2 + .../libm/src/math/support/float_traits.rs | 168 +++++++++ .../libm/src/math/support/int_traits.rs | 343 ++++++++++++++++++ .../libm/src/math/support/mod.rs | 5 + 4 files changed, 518 insertions(+) create mode 100644 library/compiler-builtins/libm/src/math/support/float_traits.rs create mode 100644 library/compiler-builtins/libm/src/math/support/int_traits.rs diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs index 393bc5150938..2cd77f1327b2 100644 --- a/library/compiler-builtins/libm/src/math/mod.rs +++ b/library/compiler-builtins/libm/src/math/mod.rs @@ -105,6 +105,8 @@ use self::k_tanf::k_tanf; use self::rem_pio2::rem_pio2; use self::rem_pio2_large::rem_pio2_large; use self::rem_pio2f::rem_pio2f; +#[allow(unused_imports)] +use self::support::{CastFrom, CastInto, DInt, Float, HInt, Int, MinInt}; // Public modules mod acos; diff --git a/library/compiler-builtins/libm/src/math/support/float_traits.rs b/library/compiler-builtins/libm/src/math/support/float_traits.rs new file mode 100644 index 000000000000..4cf5d7c61657 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/support/float_traits.rs @@ -0,0 +1,168 @@ +use core::ops; + +use super::int_traits::{Int, MinInt}; + +/// Trait for some basic operations on floats +#[allow(dead_code)] +pub trait Float: + Copy + + core::fmt::Debug + + PartialEq + + PartialOrd + + ops::AddAssign + + ops::MulAssign + + ops::Add + + ops::Sub + + ops::Div + + ops::Rem +{ + /// A uint of the same width as the float + type Int: Int; + + /// A int of the same width as the float + type SignedInt: Int + MinInt; + + /// An int capable of containing the exponent bits plus a sign bit. This is signed. + type ExpInt: Int; + + const ZERO: Self; + const ONE: Self; + + /// The bitwidth of the float type + const BITS: u32; + + /// The bitwidth of the significand + const SIGNIFICAND_BITS: u32; + + /// The bitwidth of the exponent + const EXPONENT_BITS: u32 = Self::BITS - Self::SIGNIFICAND_BITS - 1; + + /// The saturated value of the exponent (infinite representation), in the rightmost postiion. + const EXPONENT_MAX: u32 = (1 << Self::EXPONENT_BITS) - 1; + + /// The exponent bias value + const EXPONENT_BIAS: u32 = Self::EXPONENT_MAX >> 1; + + /// A mask for the sign bit + const SIGN_MASK: Self::Int; + + /// A mask for the significand + const SIGNIFICAND_MASK: Self::Int; + + /// The implicit bit of the float format + const IMPLICIT_BIT: Self::Int; + + /// A mask for the exponent + const EXPONENT_MASK: Self::Int; + + /// Returns `self` transmuted to `Self::Int` + fn to_bits(self) -> Self::Int; + + /// Returns `self` transmuted to `Self::SignedInt` + fn to_bits_signed(self) -> Self::SignedInt; + + /// Checks if two floats have the same bit representation. *Except* for NaNs! NaN can be + /// represented in multiple different ways. This method returns `true` if two NaNs are + /// compared. + fn eq_repr(self, rhs: Self) -> bool; + + /// Returns true if the sign is negative + fn is_sign_negative(self) -> bool; + + /// Returns the exponent, not adjusting for bias. + fn exp(self) -> Self::ExpInt; + + /// Returns the significand with no implicit bit (or the "fractional" part) + fn frac(self) -> Self::Int; + + /// Returns the significand with implicit bit + fn imp_frac(self) -> Self::Int; + + /// Returns a `Self::Int` transmuted back to `Self` + fn from_bits(a: Self::Int) -> Self; + + /// Constructs a `Self` from its parts. Inputs are treated as bits and shifted into position. + fn from_parts(negative: bool, exponent: Self::Int, significand: Self::Int) -> Self; + + fn abs(self) -> Self { + let abs_mask = !Self::SIGN_MASK; + Self::from_bits(self.to_bits() & abs_mask) + } + + /// Returns (normalized exponent, normalized significand) + fn normalize(significand: Self::Int) -> (i32, Self::Int); + + /// Returns if `self` is subnormal + fn is_subnormal(self) -> bool; +} + +macro_rules! float_impl { + ($ty:ident, $ity:ident, $sity:ident, $expty:ident, $bits:expr, $significand_bits:expr) => { + impl Float for $ty { + type Int = $ity; + type SignedInt = $sity; + type ExpInt = $expty; + + const ZERO: Self = 0.0; + const ONE: Self = 1.0; + + const BITS: u32 = $bits; + const SIGNIFICAND_BITS: u32 = $significand_bits; + + const SIGN_MASK: Self::Int = 1 << (Self::BITS - 1); + const SIGNIFICAND_MASK: Self::Int = (1 << Self::SIGNIFICAND_BITS) - 1; + const IMPLICIT_BIT: Self::Int = 1 << Self::SIGNIFICAND_BITS; + const EXPONENT_MASK: Self::Int = !(Self::SIGN_MASK | Self::SIGNIFICAND_MASK); + + fn to_bits(self) -> Self::Int { + self.to_bits() + } + fn to_bits_signed(self) -> Self::SignedInt { + self.to_bits() as Self::SignedInt + } + fn eq_repr(self, rhs: Self) -> bool { + fn is_nan(x: $ty) -> bool { + // When using mangled-names, the "real" compiler-builtins might not have the + // necessary builtin (__unordtf2) to test whether `f128` is NaN. + // FIXME(f16_f128): Remove once the nightly toolchain has the __unordtf2 builtin + // x is NaN if all the bits of the exponent are set and the significand is non-0 + x.to_bits() & $ty::EXPONENT_MASK == $ty::EXPONENT_MASK + && x.to_bits() & $ty::SIGNIFICAND_MASK != 0 + } + if is_nan(self) && is_nan(rhs) { true } else { self.to_bits() == rhs.to_bits() } + } + fn is_sign_negative(self) -> bool { + self.is_sign_negative() + } + fn exp(self) -> Self::ExpInt { + ((self.to_bits() & Self::EXPONENT_MASK) >> Self::SIGNIFICAND_BITS) as Self::ExpInt + } + fn frac(self) -> Self::Int { + self.to_bits() & Self::SIGNIFICAND_MASK + } + fn imp_frac(self) -> Self::Int { + self.frac() | Self::IMPLICIT_BIT + } + fn from_bits(a: Self::Int) -> Self { + Self::from_bits(a) + } + fn from_parts(negative: bool, exponent: Self::Int, significand: Self::Int) -> Self { + Self::from_bits( + ((negative as Self::Int) << (Self::BITS - 1)) + | ((exponent << Self::SIGNIFICAND_BITS) & Self::EXPONENT_MASK) + | (significand & Self::SIGNIFICAND_MASK), + ) + } + fn normalize(significand: Self::Int) -> (i32, Self::Int) { + let shift = significand.leading_zeros().wrapping_sub(Self::EXPONENT_BITS); + (1i32.wrapping_sub(shift as i32), significand << shift as Self::Int) + } + fn is_subnormal(self) -> bool { + (self.to_bits() & Self::EXPONENT_MASK) == Self::Int::ZERO + } + } + }; +} + +float_impl!(f32, u32, i32, i16, 32, 23); +float_impl!(f64, u64, i64, i16, 64, 52); diff --git a/library/compiler-builtins/libm/src/math/support/int_traits.rs b/library/compiler-builtins/libm/src/math/support/int_traits.rs new file mode 100644 index 000000000000..bdf3afd48cef --- /dev/null +++ b/library/compiler-builtins/libm/src/math/support/int_traits.rs @@ -0,0 +1,343 @@ +use core::{fmt, ops}; + +/// Minimal integer implementations needed on all integer types, including wide integers. +#[allow(dead_code)] +pub trait MinInt: + Copy + + fmt::Debug + + ops::BitOr + + ops::Not + + ops::Shl +{ + /// Type with the same width but other signedness + type OtherSign: MinInt; + /// Unsigned version of Self + type UnsignedInt: MinInt; + + /// If `Self` is a signed integer + const SIGNED: bool; + + /// The bitwidth of the int type + const BITS: u32; + + const ZERO: Self; + const ONE: Self; + const MIN: Self; + const MAX: Self; +} + +/// Trait for some basic operations on integers +#[allow(dead_code)] +pub trait Int: + MinInt + + PartialEq + + PartialOrd + + ops::AddAssign + + ops::SubAssign + + ops::BitAndAssign + + ops::BitOrAssign + + ops::BitXorAssign + + ops::ShlAssign + + ops::ShrAssign + + ops::Add + + ops::Sub + + ops::Mul + + ops::Div + + ops::Shr + + ops::BitXor + + ops::BitAnd +{ + fn unsigned(self) -> Self::UnsignedInt; + fn from_unsigned(unsigned: Self::UnsignedInt) -> Self; + + fn from_bool(b: bool) -> Self; + + /// Prevents the need for excessive conversions between signed and unsigned + fn logical_shr(self, other: u32) -> Self; + + /// Absolute difference between two integers. + fn abs_diff(self, other: Self) -> Self::UnsignedInt; + + // copied from primitive integers, but put in a trait + fn is_zero(self) -> bool; + fn wrapping_neg(self) -> Self; + fn wrapping_add(self, other: Self) -> Self; + fn wrapping_mul(self, other: Self) -> Self; + fn wrapping_sub(self, other: Self) -> Self; + fn wrapping_shl(self, other: u32) -> Self; + fn wrapping_shr(self, other: u32) -> Self; + fn rotate_left(self, other: u32) -> Self; + fn overflowing_add(self, other: Self) -> (Self, bool); + fn leading_zeros(self) -> u32; + fn ilog2(self) -> u32; +} + +macro_rules! int_impl_common { + ($ty:ty) => { + fn from_bool(b: bool) -> Self { + b as $ty + } + + fn logical_shr(self, other: u32) -> Self { + Self::from_unsigned(self.unsigned().wrapping_shr(other)) + } + + fn is_zero(self) -> bool { + self == Self::ZERO + } + + fn wrapping_neg(self) -> Self { + ::wrapping_neg(self) + } + + fn wrapping_add(self, other: Self) -> Self { + ::wrapping_add(self, other) + } + + fn wrapping_mul(self, other: Self) -> Self { + ::wrapping_mul(self, other) + } + + fn wrapping_sub(self, other: Self) -> Self { + ::wrapping_sub(self, other) + } + + fn wrapping_shl(self, other: u32) -> Self { + ::wrapping_shl(self, other) + } + + fn wrapping_shr(self, other: u32) -> Self { + ::wrapping_shr(self, other) + } + + fn rotate_left(self, other: u32) -> Self { + ::rotate_left(self, other) + } + + fn overflowing_add(self, other: Self) -> (Self, bool) { + ::overflowing_add(self, other) + } + + fn leading_zeros(self) -> u32 { + ::leading_zeros(self) + } + + fn ilog2(self) -> u32 { + ::ilog2(self) + } + }; +} + +macro_rules! int_impl { + ($ity:ty, $uty:ty) => { + impl MinInt for $uty { + type OtherSign = $ity; + type UnsignedInt = $uty; + + const BITS: u32 = ::ZERO.count_zeros(); + const SIGNED: bool = Self::MIN != Self::ZERO; + + const ZERO: Self = 0; + const ONE: Self = 1; + const MIN: Self = ::MIN; + const MAX: Self = ::MAX; + } + + impl Int for $uty { + fn unsigned(self) -> $uty { + self + } + + // It makes writing macros easier if this is implemented for both signed and unsigned + #[allow(clippy::wrong_self_convention)] + fn from_unsigned(me: $uty) -> Self { + me + } + + fn abs_diff(self, other: Self) -> Self { + if self < other { other.wrapping_sub(self) } else { self.wrapping_sub(other) } + } + + int_impl_common!($uty); + } + + impl MinInt for $ity { + type OtherSign = $uty; + type UnsignedInt = $uty; + + const BITS: u32 = ::ZERO.count_zeros(); + const SIGNED: bool = Self::MIN != Self::ZERO; + + const ZERO: Self = 0; + const ONE: Self = 1; + const MIN: Self = ::MIN; + const MAX: Self = ::MAX; + } + + impl Int for $ity { + fn unsigned(self) -> $uty { + self as $uty + } + + fn from_unsigned(me: $uty) -> Self { + me as $ity + } + + fn abs_diff(self, other: Self) -> $uty { + self.wrapping_sub(other).wrapping_abs() as $uty + } + + int_impl_common!($ity); + } + }; +} + +int_impl!(isize, usize); +int_impl!(i8, u8); +int_impl!(i16, u16); +int_impl!(i32, u32); +int_impl!(i64, u64); +int_impl!(i128, u128); + +/// Trait for integers twice the bit width of another integer. This is implemented for all +/// primitives except for `u8`, because there is not a smaller primitive. +#[allow(unused)] +pub trait DInt: MinInt { + /// Integer that is half the bit width of the integer this trait is implemented for + type H: HInt; + + /// Returns the low half of `self` + fn lo(self) -> Self::H; + /// Returns the high half of `self` + fn hi(self) -> Self::H; + /// Returns the low and high halves of `self` as a tuple + fn lo_hi(self) -> (Self::H, Self::H) { + (self.lo(), self.hi()) + } + /// Constructs an integer using lower and higher half parts + fn from_lo_hi(lo: Self::H, hi: Self::H) -> Self { + lo.zero_widen() | hi.widen_hi() + } +} + +/// Trait for integers half the bit width of another integer. This is implemented for all +/// primitives except for `u128`, because it there is not a larger primitive. +#[allow(unused)] +pub trait HInt: Int { + /// Integer that is double the bit width of the integer this trait is implemented for + type D: DInt + MinInt; + + // NB: some of the below methods could have default implementations (e.g. `widen_hi`), but for + // unknown reasons this can cause infinite recursion when optimizations are disabled. See + // for context. + + /// Widens (using default extension) the integer to have double bit width + fn widen(self) -> Self::D; + /// Widens (zero extension only) the integer to have double bit width. This is needed to get + /// around problems with associated type bounds (such as `Int`) being unstable + fn zero_widen(self) -> Self::D; + /// Widens the integer to have double bit width and shifts the integer into the higher bits + fn widen_hi(self) -> Self::D; + /// Widening multiplication with zero widening. This cannot overflow. + fn zero_widen_mul(self, rhs: Self) -> Self::D; + /// Widening multiplication. This cannot overflow. + fn widen_mul(self, rhs: Self) -> Self::D; +} + +macro_rules! impl_d_int { + ($($X:ident $D:ident),*) => { + $( + impl DInt for $D { + type H = $X; + + fn lo(self) -> Self::H { + self as $X + } + fn hi(self) -> Self::H { + (self >> <$X as MinInt>::BITS) as $X + } + } + )* + }; +} + +macro_rules! impl_h_int { + ($($H:ident $uH:ident $X:ident),*) => { + $( + impl HInt for $H { + type D = $X; + + fn widen(self) -> Self::D { + self as $X + } + fn zero_widen(self) -> Self::D { + (self as $uH) as $X + } + fn zero_widen_mul(self, rhs: Self) -> Self::D { + self.zero_widen().wrapping_mul(rhs.zero_widen()) + } + fn widen_mul(self, rhs: Self) -> Self::D { + self.widen().wrapping_mul(rhs.widen()) + } + fn widen_hi(self) -> Self::D { + (self as $X) << ::BITS + } + } + )* + }; +} + +impl_d_int!(u8 u16, u16 u32, u32 u64, u64 u128, i8 i16, i16 i32, i32 i64, i64 i128); +impl_h_int!( + u8 u8 u16, + u16 u16 u32, + u32 u32 u64, + u64 u64 u128, + i8 u8 i16, + i16 u16 i32, + i32 u32 i64, + i64 u64 i128 +); + +/// Trait to express (possibly lossy) casting of integers +#[allow(unused)] +pub trait CastInto: Copy { + fn cast(self) -> T; +} + +#[allow(unused)] +pub trait CastFrom: Copy { + fn cast_from(value: T) -> Self; +} + +impl + Copy> CastFrom for T { + fn cast_from(value: U) -> Self { + value.cast() + } +} + +macro_rules! cast_into { + ($ty:ty) => { + cast_into!($ty; usize, isize, u8, i8, u16, i16, u32, i32, u64, i64, u128, i128); + }; + ($ty:ty; $($into:ty),*) => {$( + impl CastInto<$into> for $ty { + fn cast(self) -> $into { + self as $into + } + } + )*}; +} + +cast_into!(usize); +cast_into!(isize); +cast_into!(u8); +cast_into!(i8); +cast_into!(u16); +cast_into!(i16); +cast_into!(u32); +cast_into!(i32); +cast_into!(u64); +cast_into!(i64); +cast_into!(u128); +cast_into!(i128); diff --git a/library/compiler-builtins/libm/src/math/support/mod.rs b/library/compiler-builtins/libm/src/math/support/mod.rs index 10532f0d115a..f054df6cdf31 100644 --- a/library/compiler-builtins/libm/src/math/support/mod.rs +++ b/library/compiler-builtins/libm/src/math/support/mod.rs @@ -1,2 +1,7 @@ #[macro_use] pub mod macros; +mod float_traits; +mod int_traits; + +pub use float_traits::Float; +pub use int_traits::{CastFrom, CastInto, DInt, HInt, Int, MinInt};