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-rw-r--r--src/libcore/num/f32.rs74
-rw-r--r--src/libcore/num/f64.rs74
-rw-r--r--src/libstd/f32.rs143
-rw-r--r--src/libstd/f64.rs143
-rw-r--r--src/libstd/lib.rs1
5 files changed, 435 insertions, 0 deletions
diff --git a/src/libcore/num/f32.rs b/src/libcore/num/f32.rs
index 434569020d2..6313de31ce4 100644
--- a/src/libcore/num/f32.rs
+++ b/src/libcore/num/f32.rs
@@ -810,4 +810,78 @@ impl f32 {
     pub fn from_ne_bytes(bytes: [u8; 4]) -> Self {
         Self::from_bits(u32::from_ne_bytes(bytes))
     }
+
+    /// Returns an ordering between self and other values.
+    /// Unlike the standard partial comparison between floating point numbers,
+    /// this comparison always produces an ordering in accordance to
+    /// the totalOrder predicate as defined in IEEE 754 (2008 revision)
+    /// floating point standard. The values are ordered in following order:
+    /// - Negative quiet NaN
+    /// - Negative signaling NaN
+    /// - Negative infinity
+    /// - Negative numbers
+    /// - Negative subnormal numbers
+    /// - Negative zero
+    /// - Positive zero
+    /// - Positive subnormal numbers
+    /// - Positive numbers
+    /// - Positive infinity
+    /// - Positive signaling NaN
+    /// - Positive quiet NaN
+    ///
+    /// # Example
+    /// ```
+    /// #![feature(total_cmp)]
+    /// struct GoodBoy {
+    ///     name: String,
+    ///     weight: f32,
+    /// }
+    ///
+    /// let mut bois = vec![
+    ///     GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
+    ///     GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
+    ///     GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
+    ///     GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
+    ///     GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
+    ///     GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
+    /// ];
+    ///
+    /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
+    /// # assert!(bois.into_iter().map(|b| b.weight)
+    /// #     .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
+    /// #     .all(|(a, b)| a.to_bits() == b.to_bits()))
+    /// ```
+    #[unstable(feature = "total_cmp", issue = "72599")]
+    #[inline]
+    pub fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
+        let mut left = self.to_bits() as i32;
+        let mut right = other.to_bits() as i32;
+
+        // In case of negatives, flip all the bits except the sign
+        // to achieve a similar layout as two's complement integers
+        //
+        // Why does this work? IEEE 754 floats consist of three fields:
+        // Sign bit, exponent and mantissa. The set of exponent and mantissa
+        // fields as a whole have the property that their bitwise order is
+        // equal to the numeric magnitude where the magnitude is defined.
+        // The magnitude is not normally defined on NaN values, but
+        // IEEE 754 totalOrder defines the NaN values also to follow the
+        // bitwise order. This leads to order explained in the doc comment.
+        // However, the representation of magnitude is the same for negative
+        // and positive numbers – only the sign bit is different.
+        // To easily compare the floats as signed integers, we need to
+        // flip the exponent and mantissa bits in case of negative numbers.
+        // We effectively convert the numbers to "two's complement" form.
+        //
+        // To do the flipping, we construct a mask and XOR against it.
+        // We branchlessly calculate an "all-ones except for the sign bit"
+        // mask from negative-signed values: right shifting sign-extends
+        // the integer, so we "fill" the mask with sign bits, and then
+        // convert to unsigned to push one more zero bit.
+        // On positive values, the mask is all zeros, so it's a no-op.
+        left ^= (((left >> 31) as u32) >> 1) as i32;
+        right ^= (((right >> 31) as u32) >> 1) as i32;
+
+        left.cmp(&right)
+    }
 }
diff --git a/src/libcore/num/f64.rs b/src/libcore/num/f64.rs
index 6476ddb4541..d42e5392c58 100644
--- a/src/libcore/num/f64.rs
+++ b/src/libcore/num/f64.rs
@@ -824,4 +824,78 @@ impl f64 {
     pub fn from_ne_bytes(bytes: [u8; 8]) -> Self {
         Self::from_bits(u64::from_ne_bytes(bytes))
     }
+
+    /// Returns an ordering between self and other values.
+    /// Unlike the standard partial comparison between floating point numbers,
+    /// this comparison always produces an ordering in accordance to
+    /// the totalOrder predicate as defined in IEEE 754 (2008 revision)
+    /// floating point standard. The values are ordered in following order:
+    /// - Negative quiet NaN
+    /// - Negative signaling NaN
+    /// - Negative infinity
+    /// - Negative numbers
+    /// - Negative subnormal numbers
+    /// - Negative zero
+    /// - Positive zero
+    /// - Positive subnormal numbers
+    /// - Positive numbers
+    /// - Positive infinity
+    /// - Positive signaling NaN
+    /// - Positive quiet NaN
+    ///
+    /// # Example
+    /// ```
+    /// #![feature(total_cmp)]
+    /// struct GoodBoy {
+    ///     name: String,
+    ///     weight: f64,
+    /// }
+    ///
+    /// let mut bois = vec![
+    ///     GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
+    ///     GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
+    ///     GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
+    ///     GoodBoy { name: "Chonk".to_owned(), weight: f64::INFINITY },
+    ///     GoodBoy { name: "Abs. Unit".to_owned(), weight: f64::NAN },
+    ///     GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
+    /// ];
+    ///
+    /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
+    /// # assert!(bois.into_iter().map(|b| b.weight)
+    /// #     .zip([-5.0, 0.1, 10.0, 99.0, f64::INFINITY, f64::NAN].iter())
+    /// #     .all(|(a, b)| a.to_bits() == b.to_bits()))
+    /// ```
+    #[unstable(feature = "total_cmp", issue = "72599")]
+    #[inline]
+    pub fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
+        let mut left = self.to_bits() as i64;
+        let mut right = other.to_bits() as i64;
+
+        // In case of negatives, flip all the bits except the sign
+        // to achieve a similar layout as two's complement integers
+        //
+        // Why does this work? IEEE 754 floats consist of three fields:
+        // Sign bit, exponent and mantissa. The set of exponent and mantissa
+        // fields as a whole have the property that their bitwise order is
+        // equal to the numeric magnitude where the magnitude is defined.
+        // The magnitude is not normally defined on NaN values, but
+        // IEEE 754 totalOrder defines the NaN values also to follow the
+        // bitwise order. This leads to order explained in the doc comment.
+        // However, the representation of magnitude is the same for negative
+        // and positive numbers – only the sign bit is different.
+        // To easily compare the floats as signed integers, we need to
+        // flip the exponent and mantissa bits in case of negative numbers.
+        // We effectively convert the numbers to "two's complement" form.
+        //
+        // To do the flipping, we construct a mask and XOR against it.
+        // We branchlessly calculate an "all-ones except for the sign bit"
+        // mask from negative-signed values: right shifting sign-extends
+        // the integer, so we "fill" the mask with sign bits, and then
+        // convert to unsigned to push one more zero bit.
+        // On positive values, the mask is all zeros, so it's a no-op.
+        left ^= (((left >> 63) as u64) >> 1) as i64;
+        right ^= (((right >> 63) as u64) >> 1) as i64;
+
+        left.cmp(&right)
+    }
 }
diff --git a/src/libstd/f32.rs b/src/libstd/f32.rs
index deb9eb5b4b0..8ff19557a30 100644
--- a/src/libstd/f32.rs
+++ b/src/libstd/f32.rs
@@ -1531,4 +1531,147 @@ mod tests {
     fn test_clamp_max_is_nan() {
         let _ = 1.0f32.clamp(3.0, NAN);
     }
+
+    #[test]
+    fn test_total_cmp() {
+        use core::cmp::Ordering;
+
+        fn quiet_bit_mask() -> u32 {
+            1 << (f32::MANTISSA_DIGITS - 2)
+        }
+
+        fn min_subnorm() -> f32 {
+            f32::MIN_POSITIVE / f32::powf(2.0, f32::MANTISSA_DIGITS as f32 - 1.0)
+        }
+
+        fn max_subnorm() -> f32 {
+            f32::MIN_POSITIVE - min_subnorm()
+        }
+
+        fn q_nan() -> f32 {
+            f32::from_bits(f32::NAN.to_bits() | quiet_bit_mask())
+        }
+
+        fn s_nan() -> f32 {
+            f32::from_bits((f32::NAN.to_bits() & !quiet_bit_mask()) + 42)
+        }
+
+        assert_eq!(Ordering::Equal, (-q_nan()).total_cmp(&-q_nan()));
+        assert_eq!(Ordering::Equal, (-s_nan()).total_cmp(&-s_nan()));
+        assert_eq!(Ordering::Equal, (-f32::INFINITY).total_cmp(&-f32::INFINITY));
+        assert_eq!(Ordering::Equal, (-f32::MAX).total_cmp(&-f32::MAX));
+        assert_eq!(Ordering::Equal, (-2.5_f32).total_cmp(&-2.5));
+        assert_eq!(Ordering::Equal, (-1.0_f32).total_cmp(&-1.0));
+        assert_eq!(Ordering::Equal, (-1.5_f32).total_cmp(&-1.5));
+        assert_eq!(Ordering::Equal, (-0.5_f32).total_cmp(&-0.5));
+        assert_eq!(Ordering::Equal, (-f32::MIN_POSITIVE).total_cmp(&-f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Equal, (-max_subnorm()).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Equal, (-min_subnorm()).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Equal, (-0.0_f32).total_cmp(&-0.0));
+        assert_eq!(Ordering::Equal, 0.0_f32.total_cmp(&0.0));
+        assert_eq!(Ordering::Equal, min_subnorm().total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Equal, max_subnorm().total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Equal, f32::MIN_POSITIVE.total_cmp(&f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Equal, 0.5_f32.total_cmp(&0.5));
+        assert_eq!(Ordering::Equal, 1.0_f32.total_cmp(&1.0));
+        assert_eq!(Ordering::Equal, 1.5_f32.total_cmp(&1.5));
+        assert_eq!(Ordering::Equal, 2.5_f32.total_cmp(&2.5));
+        assert_eq!(Ordering::Equal, f32::MAX.total_cmp(&f32::MAX));
+        assert_eq!(Ordering::Equal, f32::INFINITY.total_cmp(&f32::INFINITY));
+        assert_eq!(Ordering::Equal, s_nan().total_cmp(&s_nan()));
+        assert_eq!(Ordering::Equal, q_nan().total_cmp(&q_nan()));
+
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-s_nan()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-f32::INFINITY));
+        assert_eq!(Ordering::Less, (-f32::INFINITY).total_cmp(&-f32::MAX));
+        assert_eq!(Ordering::Less, (-f32::MAX).total_cmp(&-2.5));
+        assert_eq!(Ordering::Less, (-2.5_f32).total_cmp(&-1.5));
+        assert_eq!(Ordering::Less, (-1.5_f32).total_cmp(&-1.0));
+        assert_eq!(Ordering::Less, (-1.0_f32).total_cmp(&-0.5));
+        assert_eq!(Ordering::Less, (-0.5_f32).total_cmp(&-f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-f32::MIN_POSITIVE).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Less, (-max_subnorm()).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Less, (-min_subnorm()).total_cmp(&-0.0));
+        assert_eq!(Ordering::Less, (-0.0_f32).total_cmp(&0.0));
+        assert_eq!(Ordering::Less, 0.0_f32.total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Less, min_subnorm().total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Less, max_subnorm().total_cmp(&f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, f32::MIN_POSITIVE.total_cmp(&0.5));
+        assert_eq!(Ordering::Less, 0.5_f32.total_cmp(&1.0));
+        assert_eq!(Ordering::Less, 1.0_f32.total_cmp(&1.5));
+        assert_eq!(Ordering::Less, 1.5_f32.total_cmp(&2.5));
+        assert_eq!(Ordering::Less, 2.5_f32.total_cmp(&f32::MAX));
+        assert_eq!(Ordering::Less, f32::MAX.total_cmp(&f32::INFINITY));
+        assert_eq!(Ordering::Less, f32::INFINITY.total_cmp(&s_nan()));
+        assert_eq!(Ordering::Less, s_nan().total_cmp(&q_nan()));
+
+        assert_eq!(Ordering::Greater, (-s_nan()).total_cmp(&-q_nan()));
+        assert_eq!(Ordering::Greater, (-f32::INFINITY).total_cmp(&-s_nan()));
+        assert_eq!(Ordering::Greater, (-f32::MAX).total_cmp(&-f32::INFINITY));
+        assert_eq!(Ordering::Greater, (-2.5_f32).total_cmp(&-f32::MAX));
+        assert_eq!(Ordering::Greater, (-1.5_f32).total_cmp(&-2.5));
+        assert_eq!(Ordering::Greater, (-1.0_f32).total_cmp(&-1.5));
+        assert_eq!(Ordering::Greater, (-0.5_f32).total_cmp(&-1.0));
+        assert_eq!(Ordering::Greater, (-f32::MIN_POSITIVE).total_cmp(&-0.5));
+        assert_eq!(Ordering::Greater, (-max_subnorm()).total_cmp(&-f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Greater, (-min_subnorm()).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Greater, (-0.0_f32).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Greater, 0.0_f32.total_cmp(&-0.0));
+        assert_eq!(Ordering::Greater, min_subnorm().total_cmp(&0.0));
+        assert_eq!(Ordering::Greater, max_subnorm().total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Greater, f32::MIN_POSITIVE.total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Greater, 0.5_f32.total_cmp(&f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Greater, 1.0_f32.total_cmp(&0.5));
+        assert_eq!(Ordering::Greater, 1.5_f32.total_cmp(&1.0));
+        assert_eq!(Ordering::Greater, 2.5_f32.total_cmp(&1.5));
+        assert_eq!(Ordering::Greater, f32::MAX.total_cmp(&2.5));
+        assert_eq!(Ordering::Greater, f32::INFINITY.total_cmp(&f32::MAX));
+        assert_eq!(Ordering::Greater, s_nan().total_cmp(&f32::INFINITY));
+        assert_eq!(Ordering::Greater, q_nan().total_cmp(&s_nan()));
+
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-s_nan()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-f32::INFINITY));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-f32::MAX));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-2.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-1.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-1.0));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-0.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-0.0));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&0.0));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&0.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&1.0));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&1.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&2.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&f32::MAX));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&f32::INFINITY));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&s_nan()));
+
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-f32::INFINITY));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-f32::MAX));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-2.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-1.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-1.0));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-0.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-0.0));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&0.0));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&f32::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&0.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&1.0));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&1.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&2.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&f32::MAX));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&f32::INFINITY));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&s_nan()));
+    }
 }
diff --git a/src/libstd/f64.rs b/src/libstd/f64.rs
index b79e550ed26..d7845fd2c4d 100644
--- a/src/libstd/f64.rs
+++ b/src/libstd/f64.rs
@@ -1554,4 +1554,147 @@ mod tests {
     fn test_clamp_max_is_nan() {
         let _ = 1.0f64.clamp(3.0, NAN);
     }
+
+    #[test]
+    fn test_total_cmp() {
+        use core::cmp::Ordering;
+
+        fn quiet_bit_mask() -> u64 {
+            1 << (f64::MANTISSA_DIGITS - 2)
+        }
+
+        fn min_subnorm() -> f64 {
+            f64::MIN_POSITIVE / f64::powf(2.0, f64::MANTISSA_DIGITS as f64 - 1.0)
+        }
+
+        fn max_subnorm() -> f64 {
+            f64::MIN_POSITIVE - min_subnorm()
+        }
+
+        fn q_nan() -> f64 {
+            f64::from_bits(f64::NAN.to_bits() | quiet_bit_mask())
+        }
+
+        fn s_nan() -> f64 {
+            f64::from_bits((f64::NAN.to_bits() & !quiet_bit_mask()) + 42)
+        }
+
+        assert_eq!(Ordering::Equal, (-q_nan()).total_cmp(&-q_nan()));
+        assert_eq!(Ordering::Equal, (-s_nan()).total_cmp(&-s_nan()));
+        assert_eq!(Ordering::Equal, (-f64::INFINITY).total_cmp(&-f64::INFINITY));
+        assert_eq!(Ordering::Equal, (-f64::MAX).total_cmp(&-f64::MAX));
+        assert_eq!(Ordering::Equal, (-2.5_f64).total_cmp(&-2.5));
+        assert_eq!(Ordering::Equal, (-1.0_f64).total_cmp(&-1.0));
+        assert_eq!(Ordering::Equal, (-1.5_f64).total_cmp(&-1.5));
+        assert_eq!(Ordering::Equal, (-0.5_f64).total_cmp(&-0.5));
+        assert_eq!(Ordering::Equal, (-f64::MIN_POSITIVE).total_cmp(&-f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Equal, (-max_subnorm()).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Equal, (-min_subnorm()).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Equal, (-0.0_f64).total_cmp(&-0.0));
+        assert_eq!(Ordering::Equal, 0.0_f64.total_cmp(&0.0));
+        assert_eq!(Ordering::Equal, min_subnorm().total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Equal, max_subnorm().total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Equal, f64::MIN_POSITIVE.total_cmp(&f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Equal, 0.5_f64.total_cmp(&0.5));
+        assert_eq!(Ordering::Equal, 1.0_f64.total_cmp(&1.0));
+        assert_eq!(Ordering::Equal, 1.5_f64.total_cmp(&1.5));
+        assert_eq!(Ordering::Equal, 2.5_f64.total_cmp(&2.5));
+        assert_eq!(Ordering::Equal, f64::MAX.total_cmp(&f64::MAX));
+        assert_eq!(Ordering::Equal, f64::INFINITY.total_cmp(&f64::INFINITY));
+        assert_eq!(Ordering::Equal, s_nan().total_cmp(&s_nan()));
+        assert_eq!(Ordering::Equal, q_nan().total_cmp(&q_nan()));
+
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-s_nan()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-f64::INFINITY));
+        assert_eq!(Ordering::Less, (-f64::INFINITY).total_cmp(&-f64::MAX));
+        assert_eq!(Ordering::Less, (-f64::MAX).total_cmp(&-2.5));
+        assert_eq!(Ordering::Less, (-2.5_f64).total_cmp(&-1.5));
+        assert_eq!(Ordering::Less, (-1.5_f64).total_cmp(&-1.0));
+        assert_eq!(Ordering::Less, (-1.0_f64).total_cmp(&-0.5));
+        assert_eq!(Ordering::Less, (-0.5_f64).total_cmp(&-f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-f64::MIN_POSITIVE).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Less, (-max_subnorm()).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Less, (-min_subnorm()).total_cmp(&-0.0));
+        assert_eq!(Ordering::Less, (-0.0_f64).total_cmp(&0.0));
+        assert_eq!(Ordering::Less, 0.0_f64.total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Less, min_subnorm().total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Less, max_subnorm().total_cmp(&f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, f64::MIN_POSITIVE.total_cmp(&0.5));
+        assert_eq!(Ordering::Less, 0.5_f64.total_cmp(&1.0));
+        assert_eq!(Ordering::Less, 1.0_f64.total_cmp(&1.5));
+        assert_eq!(Ordering::Less, 1.5_f64.total_cmp(&2.5));
+        assert_eq!(Ordering::Less, 2.5_f64.total_cmp(&f64::MAX));
+        assert_eq!(Ordering::Less, f64::MAX.total_cmp(&f64::INFINITY));
+        assert_eq!(Ordering::Less, f64::INFINITY.total_cmp(&s_nan()));
+        assert_eq!(Ordering::Less, s_nan().total_cmp(&q_nan()));
+
+        assert_eq!(Ordering::Greater, (-s_nan()).total_cmp(&-q_nan()));
+        assert_eq!(Ordering::Greater, (-f64::INFINITY).total_cmp(&-s_nan()));
+        assert_eq!(Ordering::Greater, (-f64::MAX).total_cmp(&-f64::INFINITY));
+        assert_eq!(Ordering::Greater, (-2.5_f64).total_cmp(&-f64::MAX));
+        assert_eq!(Ordering::Greater, (-1.5_f64).total_cmp(&-2.5));
+        assert_eq!(Ordering::Greater, (-1.0_f64).total_cmp(&-1.5));
+        assert_eq!(Ordering::Greater, (-0.5_f64).total_cmp(&-1.0));
+        assert_eq!(Ordering::Greater, (-f64::MIN_POSITIVE).total_cmp(&-0.5));
+        assert_eq!(Ordering::Greater, (-max_subnorm()).total_cmp(&-f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Greater, (-min_subnorm()).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Greater, (-0.0_f64).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Greater, 0.0_f64.total_cmp(&-0.0));
+        assert_eq!(Ordering::Greater, min_subnorm().total_cmp(&0.0));
+        assert_eq!(Ordering::Greater, max_subnorm().total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Greater, f64::MIN_POSITIVE.total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Greater, 0.5_f64.total_cmp(&f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Greater, 1.0_f64.total_cmp(&0.5));
+        assert_eq!(Ordering::Greater, 1.5_f64.total_cmp(&1.0));
+        assert_eq!(Ordering::Greater, 2.5_f64.total_cmp(&1.5));
+        assert_eq!(Ordering::Greater, f64::MAX.total_cmp(&2.5));
+        assert_eq!(Ordering::Greater, f64::INFINITY.total_cmp(&f64::MAX));
+        assert_eq!(Ordering::Greater, s_nan().total_cmp(&f64::INFINITY));
+        assert_eq!(Ordering::Greater, q_nan().total_cmp(&s_nan()));
+
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-s_nan()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-f64::INFINITY));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-f64::MAX));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-2.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-1.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-1.0));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-0.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&-0.0));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&0.0));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&0.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&1.0));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&1.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&2.5));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&f64::MAX));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&f64::INFINITY));
+        assert_eq!(Ordering::Less, (-q_nan()).total_cmp(&s_nan()));
+
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-f64::INFINITY));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-f64::MAX));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-2.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-1.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-1.0));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-0.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-max_subnorm()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-min_subnorm()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&-0.0));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&0.0));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&min_subnorm()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&max_subnorm()));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&f64::MIN_POSITIVE));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&0.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&1.0));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&1.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&2.5));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&f64::MAX));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&f64::INFINITY));
+        assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&s_nan()));
+    }
 }
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index cc3e613fa3d..72dfe2937f4 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -311,6 +311,7 @@
 #![feature(test)]
 #![feature(thread_local)]
 #![feature(toowned_clone_into)]
+#![feature(total_cmp)]
 #![feature(trace_macros)]
 #![feature(track_caller)]
 #![feature(try_reserve)]