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Add core functions for f16 and f128 that require math routines

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`min`, `max`, and similar functions require external math routines. Add
these under the same gates as `std` math functions (`reliable_f16_math`
and `reliable_f128_math`).
This commit is contained in:
Trevor Gross 2024-07-17 16:17:09 -04:00
parent fc43c01417
commit e18036c769
4 changed files with 401 additions and 2 deletions
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176
library/core/src/num/f128.rs
View file

@ -686,6 +686,182 @@ impl f128 {
self * RADS_PER_DEG
}
/// Returns the maximum of the two numbers, ignoring NaN.
///
/// If one of the arguments is NaN, then the other argument is returned.
/// This follows the IEEE 754-2008 semantics for maxNum, except for handling of signaling NaNs;
/// this function handles all NaNs the same way and avoids maxNum's problems with associativity.
/// This also matches the behavior of libm’s fmax.
///
/// ```
/// #![feature(f128)]
/// # // Using aarch64 because `reliable_f128_math` is needed
/// # #[cfg(all(target_arch = "aarch64", target_os = "linux"))] {
///
/// let x = 1.0f128;
/// let y = 2.0f128;
///
/// assert_eq!(x.max(y), y);
/// # }
/// ```
#[inline]
#[unstable(feature = "f128", issue = "116909")]
#[must_use = "this returns the result of the comparison, without modifying either input"]
pub fn max(self, other: f128) -> f128 {
intrinsics::maxnumf128(self, other)
}
/// Returns the minimum of the two numbers, ignoring NaN.
///
/// If one of the arguments is NaN, then the other argument is returned.
/// This follows the IEEE 754-2008 semantics for minNum, except for handling of signaling NaNs;
/// this function handles all NaNs the same way and avoids minNum's problems with associativity.
/// This also matches the behavior of libm’s fmin.
///
/// ```
/// #![feature(f128)]
/// # // Using aarch64 because `reliable_f128_math` is needed
/// # #[cfg(all(target_arch = "aarch64", target_os = "linux"))] {
///
/// let x = 1.0f128;
/// let y = 2.0f128;
///
/// assert_eq!(x.min(y), x);
/// # }
/// ```
#[inline]
#[unstable(feature = "f128", issue = "116909")]
#[must_use = "this returns the result of the comparison, without modifying either input"]
pub fn min(self, other: f128) -> f128 {
intrinsics::minnumf128(self, other)
}
/// Returns the maximum of the two numbers, propagating NaN.
///
/// This returns NaN when *either* argument is NaN, as opposed to
/// [`f128::max`] which only returns NaN when *both* arguments are NaN.
///
/// ```
/// #![feature(f128)]
/// #![feature(float_minimum_maximum)]
/// # // Using aarch64 because `reliable_f128_math` is needed
/// # #[cfg(all(target_arch = "aarch64", target_os = "linux"))] {
///
/// let x = 1.0f128;
/// let y = 2.0f128;
///
/// assert_eq!(x.maximum(y), y);
/// assert!(x.maximum(f128::NAN).is_nan());
/// # }
/// ```
///
/// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the greater
/// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
/// Note that this follows the semantics specified in IEEE 754-2019.
///
/// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
/// operand is conserved; see [explanation of NaN as a special value](f128) for more info.
#[inline]
#[unstable(feature = "f128", issue = "116909")]
// #[unstable(feature = "float_minimum_maximum", issue = "91079")]
#[must_use = "this returns the result of the comparison, without modifying either input"]
pub fn maximum(self, other: f128) -> f128 {
if self > other {
self
} else if other > self {
other
} else if self == other {
if self.is_sign_positive() && other.is_sign_negative() { self } else { other }
} else {
self + other
}
}
/// Returns the minimum of the two numbers, propagating NaN.
///
/// This returns NaN when *either* argument is NaN, as opposed to
/// [`f128::min`] which only returns NaN when *both* arguments are NaN.
///
/// ```
/// #![feature(f128)]
/// #![feature(float_minimum_maximum)]
/// # // Using aarch64 because `reliable_f128_math` is needed
/// # #[cfg(all(target_arch = "aarch64", target_os = "linux"))] {
///
/// let x = 1.0f128;
/// let y = 2.0f128;
///
/// assert_eq!(x.minimum(y), x);
/// assert!(x.minimum(f128::NAN).is_nan());
/// # }
/// ```
///
/// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the lesser
/// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
/// Note that this follows the semantics specified in IEEE 754-2019.
///
/// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
/// operand is conserved; see [explanation of NaN as a special value](f128) for more info.
#[inline]
#[unstable(feature = "f128", issue = "116909")]
// #[unstable(feature = "float_minimum_maximum", issue = "91079")]
#[must_use = "this returns the result of the comparison, without modifying either input"]
pub fn minimum(self, other: f128) -> f128 {
if self < other {
self
} else if other < self {
other
} else if self == other {
if self.is_sign_negative() && other.is_sign_positive() { self } else { other }
} else {
// At least one input is NaN. Use `+` to perform NaN propagation and quieting.
self + other
}
}
/// Calculates the middle point of `self` and `rhs`.
///
/// This returns NaN when *either* argument is NaN or if a combination of
/// +inf and -inf is provided as arguments.
///
/// # Examples
///
/// ```
/// #![feature(f128)]
/// #![feature(num_midpoint)]
/// # // Using aarch64 because `reliable_f128_math` is needed
/// # #[cfg(all(target_arch = "aarch64", target_os = "linux"))] {
///
/// assert_eq!(1f128.midpoint(4.0), 2.5);
/// assert_eq!((-5.5f128).midpoint(8.0), 1.25);
/// # }
/// ```
#[inline]
#[unstable(feature = "f128", issue = "116909")]
// #[unstable(feature = "num_midpoint", issue = "110840")]
pub fn midpoint(self, other: f128) -> f128 {
const LO: f128 = f128::MIN_POSITIVE * 2.;
const HI: f128 = f128::MAX / 2.;
let (a, b) = (self, other);
let abs_a = a.abs_private();
let abs_b = b.abs_private();
if abs_a <= HI && abs_b <= HI {
// Overflow is impossible
(a + b) / 2.
} else if abs_a < LO {
// Not safe to halve a
a + (b / 2.)
} else if abs_b < LO {
// Not safe to halve b
(a / 2.) + b
} else {
// Not safe to halve a and b
(a / 2.) + (b / 2.)
}
}
/// Rounds toward zero and converts to any primitive integer type,
/// assuming that the value is finite and fits in that type.
///

171
library/core/src/num/f16.rs
View file

@ -720,6 +720,177 @@ impl f16 {
self * RADS_PER_DEG
}
/// Returns the maximum of the two numbers, ignoring NaN.
///
/// If one of the arguments is NaN, then the other argument is returned.
/// This follows the IEEE 754-2008 semantics for maxNum, except for handling of signaling NaNs;
/// this function handles all NaNs the same way and avoids maxNum's problems with associativity.
/// This also matches the behavior of libm’s fmax.
///
/// ```
/// #![feature(f16)]
/// # #[cfg(target_arch = "aarch64")] { // FIXME(f16_F128): rust-lang/rust#123885
///
/// let x = 1.0f16;
/// let y = 2.0f16;
///
/// assert_eq!(x.max(y), y);
/// # }
/// ```
#[inline]
#[unstable(feature = "f16", issue = "116909")]
#[must_use = "this returns the result of the comparison, without modifying either input"]
pub fn max(self, other: f16) -> f16 {
intrinsics::maxnumf16(self, other)
}
/// Returns the minimum of the two numbers, ignoring NaN.
///
/// If one of the arguments is NaN, then the other argument is returned.
/// This follows the IEEE 754-2008 semantics for minNum, except for handling of signaling NaNs;
/// this function handles all NaNs the same way and avoids minNum's problems with associativity.
/// This also matches the behavior of libm’s fmin.
///
/// ```
/// #![feature(f16)]
/// # #[cfg(target_arch = "aarch64")] { // FIXME(f16_F128): rust-lang/rust#123885
///
/// let x = 1.0f16;
/// let y = 2.0f16;
///
/// assert_eq!(x.min(y), x);
/// # }
/// ```
#[inline]
#[unstable(feature = "f16", issue = "116909")]
#[must_use = "this returns the result of the comparison, without modifying either input"]
pub fn min(self, other: f16) -> f16 {
intrinsics::minnumf16(self, other)
}
/// Returns the maximum of the two numbers, propagating NaN.
///
/// This returns NaN when *either* argument is NaN, as opposed to
/// [`f16::max`] which only returns NaN when *both* arguments are NaN.
///
/// ```
/// #![feature(f16)]
/// #![feature(float_minimum_maximum)]
/// # #[cfg(target_arch = "aarch64")] { // FIXME(f16_F128): rust-lang/rust#123885
///
/// let x = 1.0f16;
/// let y = 2.0f16;
///
/// assert_eq!(x.maximum(y), y);
/// assert!(x.maximum(f16::NAN).is_nan());
/// # }
/// ```
///
/// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the greater
/// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
/// Note that this follows the semantics specified in IEEE 754-2019.
///
/// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
/// operand is conserved; see [explanation of NaN as a special value](f16) for more info.
#[inline]
#[unstable(feature = "f16", issue = "116909")]
// #[unstable(feature = "float_minimum_maximum", issue = "91079")]
#[must_use = "this returns the result of the comparison, without modifying either input"]
pub fn maximum(self, other: f16) -> f16 {
if self > other {
self
} else if other > self {
other
} else if self == other {
if self.is_sign_positive() && other.is_sign_negative() { self } else { other }
} else {
self + other
}
}
/// Returns the minimum of the two numbers, propagating NaN.
///
/// This returns NaN when *either* argument is NaN, as opposed to
/// [`f16::min`] which only returns NaN when *both* arguments are NaN.
///
/// ```
/// #![feature(f16)]
/// #![feature(float_minimum_maximum)]
/// # #[cfg(target_arch = "aarch64")] { // FIXME(f16_F128): rust-lang/rust#123885
///
/// let x = 1.0f16;
/// let y = 2.0f16;
///
/// assert_eq!(x.minimum(y), x);
/// assert!(x.minimum(f16::NAN).is_nan());
/// # }
/// ```
///
/// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the lesser
/// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
/// Note that this follows the semantics specified in IEEE 754-2019.
///
/// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
/// operand is conserved; see [explanation of NaN as a special value](f16) for more info.
#[inline]
#[unstable(feature = "f16", issue = "116909")]
// #[unstable(feature = "float_minimum_maximum", issue = "91079")]
#[must_use = "this returns the result of the comparison, without modifying either input"]
pub fn minimum(self, other: f16) -> f16 {
if self < other {
self
} else if other < self {
other
} else if self == other {
if self.is_sign_negative() && other.is_sign_positive() { self } else { other }
} else {
// At least one input is NaN. Use `+` to perform NaN propagation and quieting.
self + other
}
}
/// Calculates the middle point of `self` and `rhs`.
///
/// This returns NaN when *either* argument is NaN or if a combination of
/// +inf and -inf is provided as arguments.
///
/// # Examples
///
/// ```
/// #![feature(f16)]
/// #![feature(num_midpoint)]
/// # #[cfg(target_arch = "aarch64")] { // FIXME(f16_F128): rust-lang/rust#123885
///
/// assert_eq!(1f16.midpoint(4.0), 2.5);
/// assert_eq!((-5.5f16).midpoint(8.0), 1.25);
/// # }
/// ```
#[inline]
#[unstable(feature = "f16", issue = "116909")]
// #[unstable(feature = "num_midpoint", issue = "110840")]
pub fn midpoint(self, other: f16) -> f16 {
const LO: f16 = f16::MIN_POSITIVE * 2.;
const HI: f16 = f16::MAX / 2.;
let (a, b) = (self, other);
let abs_a = a.abs_private();
let abs_b = b.abs_private();
if abs_a <= HI && abs_b <= HI {
// Overflow is impossible
(a + b) / 2.
} else if abs_a < LO {
// Not safe to halve a
a + (b / 2.)
} else if abs_b < LO {
// Not safe to halve b
(a / 2.) + b
} else {
// Not safe to halve a and b
(a / 2.) + (b / 2.)
}
}
/// Rounds toward zero and converts to any primitive integer type,
/// assuming that the value is finite and fits in that type.
///

28
library/std/src/f128/tests.rs
View file

@ -56,7 +56,33 @@ fn test_num_f128() {
test_num(10f128, 2f128);
}
// FIXME(f16_f128): add min and max tests when available
#[test]
#[cfg(reliable_f128_math)]
fn test_min_nan() {
assert_eq!(f128::NAN.min(2.0), 2.0);
assert_eq!(2.0f128.min(f128::NAN), 2.0);
}
#[test]
#[cfg(reliable_f128_math)]
fn test_max_nan() {
assert_eq!(f128::NAN.max(2.0), 2.0);
assert_eq!(2.0f128.max(f128::NAN), 2.0);
}
#[test]
#[cfg(reliable_f128_math)]
fn test_minimum() {
assert!(f128::NAN.minimum(2.0).is_nan());
assert!(2.0f128.minimum(f128::NAN).is_nan());
}
#[test]
#[cfg(reliable_f128_math)]
fn test_maximum() {
assert!(f128::NAN.maximum(2.0).is_nan());
assert!(2.0f128.maximum(f128::NAN).is_nan());
}
#[test]
fn test_nan() {

28
library/std/src/f16/tests.rs
View file

@ -57,7 +57,33 @@ fn test_num_f16() {
test_num(10f16, 2f16);
}
// FIXME(f16_f128): add min and max tests when available
#[test]
#[cfg(reliable_f16_math)]
fn test_min_nan() {
assert_eq!(f16::NAN.min(2.0), 2.0);
assert_eq!(2.0f16.min(f16::NAN), 2.0);
}
#[test]
#[cfg(reliable_f16_math)]
fn test_max_nan() {
assert_eq!(f16::NAN.max(2.0), 2.0);
assert_eq!(2.0f16.max(f16::NAN), 2.0);
}
#[test]
#[cfg(reliable_f16_math)]
fn test_minimum() {
assert!(f16::NAN.minimum(2.0).is_nan());
assert!(2.0f16.minimum(f16::NAN).is_nan());
}
#[test]
#[cfg(reliable_f16_math)]
fn test_maximum() {
assert!(f16::NAN.maximum(2.0).is_nan());
assert!(2.0f16.maximum(f16::NAN).is_nan());
}
#[test]
fn test_nan() {