Merge pull request rust-lang#347 from tgross35/numeric-traits

Add float and integer traits from compiler-builtins

Author: tgross35

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;

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<Output = Self>
+    + ops::Sub<Output = Self>
+    + ops::Div<Output = Self>
+    + ops::Rem<Output = Self>
+{
+    /// A uint of the same width as the float
+    type Int: Int<OtherSign = Self::SignedInt, UnsignedInt = Self::Int>;
+
+    /// A int of the same width as the float
+    type SignedInt: Int + MinInt<OtherSign = Self::Int, UnsignedInt = Self::Int>;
+
+    /// 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);