diff options
| -rw-r--r-- | library/core/src/num/f128.rs | 241 | ||||
| -rw-r--r-- | library/core/src/num/f16.rs | 283 | ||||
| -rw-r--r-- | library/std/src/f128/tests.rs | 66 | ||||
| -rw-r--r-- | library/std/src/f16/tests.rs | 66 |
4 files changed, 585 insertions, 71 deletions
diff --git a/library/core/src/num/f128.rs b/library/core/src/num/f128.rs index 58ed98c888c..002a41b5669 100644 --- a/library/core/src/num/f128.rs +++ b/library/core/src/num/f128.rs @@ -12,7 +12,10 @@ #![unstable(feature = "f128", issue = "116909")] use crate::convert::FloatToInt; +#[cfg(not(test))] +use crate::intrinsics; use crate::mem; +use crate::num::FpCategory; /// Basic mathematical constants. #[unstable(feature = "f128", issue = "116909")] @@ -251,6 +254,12 @@ impl f128 { #[cfg(not(bootstrap))] pub(crate) const SIGN_MASK: u128 = 0x8000_0000_0000_0000_0000_0000_0000_0000; + /// Exponent mask + pub(crate) const EXP_MASK: u128 = 0x7fff_0000_0000_0000_0000_0000_0000_0000; + + /// Mantissa mask + pub(crate) const MAN_MASK: u128 = 0x0000_ffff_ffff_ffff_ffff_ffff_ffff_ffff; + /// Minimum representable positive value (min subnormal) #[cfg(not(bootstrap))] const TINY_BITS: u128 = 0x1; @@ -354,6 +363,119 @@ impl f128 { self.abs_private() < Self::INFINITY } + /// Returns `true` if the number is [subnormal]. + /// + /// ``` + /// #![feature(f128)] + /// # // FIXME(f16_f128): remove when `eqtf2` is available + /// # #[cfg(all(target_arch = "x86_64", target_os = "linux"))] { + /// + /// let min = f128::MIN_POSITIVE; // 3.362103143e-4932f128 + /// let max = f128::MAX; + /// let lower_than_min = 1.0e-4960_f128; + /// let zero = 0.0_f128; + /// + /// assert!(!min.is_subnormal()); + /// assert!(!max.is_subnormal()); + /// + /// assert!(!zero.is_subnormal()); + /// assert!(!f128::NAN.is_subnormal()); + /// assert!(!f128::INFINITY.is_subnormal()); + /// // Values between `0` and `min` are Subnormal. + /// assert!(lower_than_min.is_subnormal()); + /// # } + /// ``` + /// + /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number + #[inline] + #[must_use] + #[cfg(not(bootstrap))] + #[unstable(feature = "f128", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + pub const fn is_subnormal(self) -> bool { + matches!(self.classify(), FpCategory::Subnormal) + } + + /// Returns `true` if the number is neither zero, infinite, [subnormal], or NaN. + /// + /// ``` + /// #![feature(f128)] + /// # // FIXME(f16_f128): remove when `eqtf2` is available + /// # #[cfg(all(target_arch = "x86_64", target_os = "linux"))] { + /// + /// let min = f128::MIN_POSITIVE; // 3.362103143e-4932f128 + /// let max = f128::MAX; + /// let lower_than_min = 1.0e-4960_f128; + /// let zero = 0.0_f128; + /// + /// assert!(min.is_normal()); + /// assert!(max.is_normal()); + /// + /// assert!(!zero.is_normal()); + /// assert!(!f128::NAN.is_normal()); + /// assert!(!f128::INFINITY.is_normal()); + /// // Values between `0` and `min` are Subnormal. + /// assert!(!lower_than_min.is_normal()); + /// # } + /// ``` + /// + /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number + #[inline] + #[must_use] + #[cfg(not(bootstrap))] + #[unstable(feature = "f128", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + pub const fn is_normal(self) -> bool { + matches!(self.classify(), FpCategory::Normal) + } + + /// Returns the floating point category of the number. If only one property + /// is going to be tested, it is generally faster to use the specific + /// predicate instead. + /// + /// ``` + /// #![feature(f128)] + /// # // FIXME(f16_f128): remove when `eqtf2` is available + /// # #[cfg(all(target_arch = "x86_64", target_os = "linux"))] { + /// + /// use std::num::FpCategory; + /// + /// let num = 12.4_f128; + /// let inf = f128::INFINITY; + /// + /// assert_eq!(num.classify(), FpCategory::Normal); + /// assert_eq!(inf.classify(), FpCategory::Infinite); + /// # } + /// ``` + #[inline] + #[cfg(not(bootstrap))] + #[unstable(feature = "f128", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + pub const fn classify(self) -> FpCategory { + // Other float types cannot use a bitwise classify because they may suffer a variety + // of errors if the backend chooses to cast to different float types (x87). `f128` cannot + // fit into any other float types so this is not a concern, and we rely on bit patterns. + + // SAFETY: POD bitcast, same as in `to_bits`. + let bits = unsafe { mem::transmute::<f128, u128>(self) }; + Self::classify_bits(bits) + } + + /// This operates on bits, and only bits, so it can ignore concerns about weird FPUs. + /// FIXME(jubilee): In a just world, this would be the entire impl for classify, + /// plus a transmute. We do not live in a just world, but we can make it more so. + #[inline] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + const fn classify_bits(b: u128) -> FpCategory { + match (b & Self::MAN_MASK, b & Self::EXP_MASK) { + (0, Self::EXP_MASK) => FpCategory::Infinite, + (_, Self::EXP_MASK) => FpCategory::Nan, + (0, 0) => FpCategory::Zero, + (_, 0) => FpCategory::Subnormal, + _ => FpCategory::Normal, + } + } + /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with /// positive sign bit and positive infinity. Note that IEEE 754 doesn't assign any /// meaning to the sign bit in case of a NaN, and as Rust doesn't guarantee that @@ -638,12 +760,52 @@ impl f128 { /// ``` #[inline] #[unstable(feature = "f128", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] #[must_use = "this returns the result of the operation, without modifying the original"] - pub fn to_bits(self) -> u128 { - // SAFETY: `u128` is a plain old datatype so we can always... uh... - // ...look, just pretend you forgot what you just read. - // Stability concerns. - unsafe { mem::transmute(self) } + pub const fn to_bits(self) -> u128 { + // SAFETY: `u128` is a plain old datatype so we can always transmute to it. + // ...sorta. + // + // It turns out that at runtime, it is possible for a floating point number + // to be subject to a floating point mode that alters nonzero subnormal numbers + // to zero on reads and writes, aka "denormals are zero" and "flush to zero". + // + // And, of course evaluating to a NaN value is fairly nondeterministic. + // More precisely: when NaN should be returned is knowable, but which NaN? + // So far that's defined by a combination of LLVM and the CPU, not Rust. + // This function, however, allows observing the bitstring of a NaN, + // thus introspection on CTFE. + // + // In order to preserve, at least for the moment, const-to-runtime equivalence, + // we reject any of these possible situations from happening. + #[inline] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + const fn ct_f128_to_u128(ct: f128) -> u128 { + // FIXME(f16_f128): we should use `.classify()` like `f32` and `f64`, but that + // is not available on all platforms (needs `netf2` and `unordtf2`). So classify + // the bits instead. + + // SAFETY: this is a POD transmutation + let bits = unsafe { mem::transmute::<f128, u128>(ct) }; + match f128::classify_bits(bits) { + FpCategory::Nan => { + panic!("const-eval error: cannot use f128::to_bits on a NaN") + } + FpCategory::Subnormal => { + panic!("const-eval error: cannot use f128::to_bits on a subnormal number") + } + FpCategory::Infinite | FpCategory::Normal | FpCategory::Zero => bits, + } + } + + #[inline(always)] // See https://github.com/rust-lang/compiler-builtins/issues/491 + fn rt_f128_to_u128(x: f128) -> u128 { + // SAFETY: `u128` is a plain old datatype so we can always... uh... + // ...look, just pretend you forgot what you just read. + // Stability concerns. + unsafe { mem::transmute(x) } + } + intrinsics::const_eval_select((self,), ct_f128_to_u128, rt_f128_to_u128) } /// Raw transmutation from `u128`. @@ -688,11 +850,52 @@ impl f128 { #[inline] #[must_use] #[unstable(feature = "f128", issue = "116909")] - pub fn from_bits(v: u128) -> Self { - // SAFETY: `u128 is a plain old datatype so we can always... uh... - // ...look, just pretend you forgot what you just read. - // Stability concerns. - unsafe { mem::transmute(v) } + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + pub const fn from_bits(v: u128) -> Self { + // It turns out the safety issues with sNaN were overblown! Hooray! + // SAFETY: `u128` is a plain old datatype so we can always transmute from it + // ...sorta. + // + // It turns out that at runtime, it is possible for a floating point number + // to be subject to floating point modes that alter nonzero subnormal numbers + // to zero on reads and writes, aka "denormals are zero" and "flush to zero". + // This is not a problem usually, but at least one tier2 platform for Rust + // actually exhibits this behavior by default: thumbv7neon + // aka "the Neon FPU in AArch32 state" + // + // And, of course evaluating to a NaN value is fairly nondeterministic. + // More precisely: when NaN should be returned is knowable, but which NaN? + // So far that's defined by a combination of LLVM and the CPU, not Rust. + // This function, however, allows observing the bitstring of a NaN, + // thus introspection on CTFE. + // + // In order to preserve, at least for the moment, const-to-runtime equivalence, + // reject any of these possible situations from happening. + #[inline] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + const fn ct_u128_to_f128(ct: u128) -> f128 { + match f128::classify_bits(ct) { + FpCategory::Subnormal => { + panic!("const-eval error: cannot use f128::from_bits on a subnormal number") + } + FpCategory::Nan => { + panic!("const-eval error: cannot use f128::from_bits on NaN") + } + FpCategory::Infinite | FpCategory::Normal | FpCategory::Zero => { + // SAFETY: It's not a frumious number + unsafe { mem::transmute::<u128, f128>(ct) } + } + } + } + + #[inline(always)] // See https://github.com/rust-lang/compiler-builtins/issues/491 + fn rt_u128_to_f128(x: u128) -> f128 { + // SAFETY: `u128` is a plain old datatype so we can always... uh... + // ...look, just pretend you forgot what you just read. + // Stability concerns. + unsafe { mem::transmute(x) } + } + intrinsics::const_eval_select((v,), ct_u128_to_f128, rt_u128_to_f128) } /// Return the memory representation of this floating point number as a byte array in @@ -715,8 +918,9 @@ impl f128 { /// ``` #[inline] #[unstable(feature = "f128", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] #[must_use = "this returns the result of the operation, without modifying the original"] - pub fn to_be_bytes(self) -> [u8; 16] { + pub const fn to_be_bytes(self) -> [u8; 16] { self.to_bits().to_be_bytes() } @@ -740,8 +944,9 @@ impl f128 { /// ``` #[inline] #[unstable(feature = "f128", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] #[must_use = "this returns the result of the operation, without modifying the original"] - pub fn to_le_bytes(self) -> [u8; 16] { + pub const fn to_le_bytes(self) -> [u8; 16] { self.to_bits().to_le_bytes() } @@ -776,8 +981,9 @@ impl f128 { /// ``` #[inline] #[unstable(feature = "f128", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] #[must_use = "this returns the result of the operation, without modifying the original"] - pub fn to_ne_bytes(self) -> [u8; 16] { + pub const fn to_ne_bytes(self) -> [u8; 16] { self.to_bits().to_ne_bytes() } @@ -803,7 +1009,8 @@ impl f128 { #[inline] #[must_use] #[unstable(feature = "f128", issue = "116909")] - pub fn from_be_bytes(bytes: [u8; 16]) -> Self { + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + pub const fn from_be_bytes(bytes: [u8; 16]) -> Self { Self::from_bits(u128::from_be_bytes(bytes)) } @@ -829,7 +1036,8 @@ impl f128 { #[inline] #[must_use] #[unstable(feature = "f128", issue = "116909")] - pub fn from_le_bytes(bytes: [u8; 16]) -> Self { + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + pub const fn from_le_bytes(bytes: [u8; 16]) -> Self { Self::from_bits(u128::from_le_bytes(bytes)) } @@ -865,7 +1073,8 @@ impl f128 { #[inline] #[must_use] #[unstable(feature = "f128", issue = "116909")] - pub fn from_ne_bytes(bytes: [u8; 16]) -> Self { + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + pub const fn from_ne_bytes(bytes: [u8; 16]) -> Self { Self::from_bits(u128::from_ne_bytes(bytes)) } diff --git a/library/core/src/num/f16.rs b/library/core/src/num/f16.rs index 0e54d78231d..2a8ede93838 100644 --- a/library/core/src/num/f16.rs +++ b/library/core/src/num/f16.rs @@ -12,7 +12,10 @@ #![unstable(feature = "f16", issue = "116909")] use crate::convert::FloatToInt; +#[cfg(not(test))] +use crate::intrinsics; use crate::mem; +use crate::num::FpCategory; /// Basic mathematical constants. #[unstable(feature = "f16", issue = "116909")] @@ -244,7 +247,13 @@ impl f16 { /// Sign bit #[cfg(not(bootstrap))] - const SIGN_MASK: u16 = 0x8000; + pub(crate) const SIGN_MASK: u16 = 0x8000; + + /// Exponent mask + pub(crate) const EXP_MASK: u16 = 0x7c00; + + /// Mantissa mask + pub(crate) const MAN_MASK: u16 = 0x03ff; /// Minimum representable positive value (min subnormal) #[cfg(not(bootstrap))] @@ -344,6 +353,159 @@ impl f16 { self.abs_private() < Self::INFINITY } + /// Returns `true` if the number is [subnormal]. + /// + /// ``` + /// #![feature(f16)] + /// # #[cfg(target_arch = "aarch64")] { // FIXME(f16_F128): rust-lang/rust#123885 + /// + /// let min = f16::MIN_POSITIVE; // 6.1035e-5 + /// let max = f16::MAX; + /// let lower_than_min = 1.0e-7_f16; + /// let zero = 0.0_f16; + /// + /// assert!(!min.is_subnormal()); + /// assert!(!max.is_subnormal()); + /// + /// assert!(!zero.is_subnormal()); + /// assert!(!f16::NAN.is_subnormal()); + /// assert!(!f16::INFINITY.is_subnormal()); + /// // Values between `0` and `min` are Subnormal. + /// assert!(lower_than_min.is_subnormal()); + /// # } + /// ``` + /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number + #[inline] + #[must_use] + #[cfg(not(bootstrap))] + #[unstable(feature = "f16", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + pub const fn is_subnormal(self) -> bool { + matches!(self.classify(), FpCategory::Subnormal) + } + + /// Returns `true` if the number is neither zero, infinite, [subnormal], or NaN. + /// + /// ``` + /// #![feature(f16)] + /// # #[cfg(target_arch = "aarch64")] { // FIXME(f16_F128): rust-lang/rust#123885 + /// + /// let min = f16::MIN_POSITIVE; // 6.1035e-5 + /// let max = f16::MAX; + /// let lower_than_min = 1.0e-7_f16; + /// let zero = 0.0_f16; + /// + /// assert!(min.is_normal()); + /// assert!(max.is_normal()); + /// + /// assert!(!zero.is_normal()); + /// assert!(!f16::NAN.is_normal()); + /// assert!(!f16::INFINITY.is_normal()); + /// // Values between `0` and `min` are Subnormal. + /// assert!(!lower_than_min.is_normal()); + /// # } + /// ``` + /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number + #[inline] + #[must_use] + #[cfg(not(bootstrap))] + #[unstable(feature = "f16", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + pub const fn is_normal(self) -> bool { + matches!(self.classify(), FpCategory::Normal) + } + + /// Returns the floating point category of the number. If only one property + /// is going to be tested, it is generally faster to use the specific + /// predicate instead. + /// + /// ``` + /// #![feature(f16)] + /// # #[cfg(target_arch = "aarch64")] { // FIXME(f16_F128): rust-lang/rust#123885 + /// + /// use std::num::FpCategory; + /// + /// let num = 12.4_f16; + /// let inf = f16::INFINITY; + /// + /// assert_eq!(num.classify(), FpCategory::Normal); + /// assert_eq!(inf.classify(), FpCategory::Infinite); + /// # } + /// ``` + #[inline] + #[cfg(not(bootstrap))] + #[unstable(feature = "f16", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + pub const fn classify(self) -> FpCategory { + // A previous implementation for f32/f64 tried to only use bitmask-based checks, + // using `to_bits` to transmute the float to its bit repr and match on that. + // Unfortunately, floating point numbers can be much worse than that. + // This also needs to not result in recursive evaluations of `to_bits`. + // + + // Platforms without native support generally convert to `f32` to perform operations, + // and most of these platforms correctly round back to `f16` after each operation. + // However, some platforms have bugs where they keep the excess `f32` precision (e.g. + // WASM, see llvm/llvm-project#96437). This implementation makes a best-effort attempt + // to account for that excess precision. + if self.is_infinite() { + // Thus, a value may compare unequal to infinity, despite having a "full" exponent mask. + FpCategory::Infinite + } else if self.is_nan() { + // And it may not be NaN, as it can simply be an "overextended" finite value. + FpCategory::Nan + } else { + // However, std can't simply compare to zero to check for zero, either, + // as correctness requires avoiding equality tests that may be Subnormal == -0.0 + // because it may be wrong under "denormals are zero" and "flush to zero" modes. + // Most of std's targets don't use those, but they are used for thumbv7neon. + // So, this does use bitpattern matching for the rest. + + // SAFETY: f16 to u16 is fine. Usually. + // If classify has gotten this far, the value is definitely in one of these categories. + unsafe { f16::partial_classify(self) } + } + } + + /// This doesn't actually return a right answer for NaN on purpose, + /// seeing as how it cannot correctly discern between a floating point NaN, + /// and some normal floating point numbers truncated from an x87 FPU. + /// + /// # Safety + /// + /// This requires making sure you call this function for values it answers correctly on, + /// otherwise it returns a wrong answer. This is not important for memory safety per se, + /// but getting floats correct is important for not accidentally leaking const eval + /// runtime-deviating logic which may or may not be acceptable. + #[inline] + #[cfg(not(bootstrap))] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + const unsafe fn partial_classify(self) -> FpCategory { + // SAFETY: The caller is not asking questions for which this will tell lies. + let b = unsafe { mem::transmute::<f16, u16>(self) }; + match (b & Self::MAN_MASK, b & Self::EXP_MASK) { + (0, Self::EXP_MASK) => FpCategory::Infinite, + (0, 0) => FpCategory::Zero, + (_, 0) => FpCategory::Subnormal, + _ => FpCategory::Normal, + } + } + + /// This operates on bits, and only bits, so it can ignore concerns about weird FPUs. + /// FIXME(jubilee): In a just world, this would be the entire impl for classify, + /// plus a transmute. We do not live in a just world, but we can make it more so. + #[inline] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + const fn classify_bits(b: u16) -> FpCategory { + match (b & Self::MAN_MASK, b & Self::EXP_MASK) { + (0, Self::EXP_MASK) => FpCategory::Infinite, + (_, Self::EXP_MASK) => FpCategory::Nan, + (0, 0) => FpCategory::Zero, + (_, 0) => FpCategory::Subnormal, + _ => FpCategory::Normal, + } + } + /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with /// positive sign bit and positive infinity. Note that IEEE 754 doesn't assign any /// meaning to the sign bit in case of a NaN, and as Rust doesn't guarantee that @@ -634,12 +796,52 @@ impl f16 { /// ``` #[inline] #[unstable(feature = "f16", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] #[must_use = "this returns the result of the operation, without modifying the original"] - pub fn to_bits(self) -> u16 { - // SAFETY: `u16` is a plain old datatype so we can always... uh... - // ...look, just pretend you forgot what you just read. - // Stability concerns. - unsafe { mem::transmute(self) } + pub const fn to_bits(self) -> u16 { + // SAFETY: `u16` is a plain old datatype so we can always transmute to it. + // ...sorta. + // + // It turns out that at runtime, it is possible for a floating point number + // to be subject to a floating point mode that alters nonzero subnormal numbers + // to zero on reads and writes, aka "denormals are zero" and "flush to zero". + // + // And, of course evaluating to a NaN value is fairly nondeterministic. + // More precisely: when NaN should be returned is knowable, but which NaN? + // So far that's defined by a combination of LLVM and the CPU, not Rust. + // This function, however, allows observing the bitstring of a NaN, + // thus introspection on CTFE. + // + // In order to preserve, at least for the moment, const-to-runtime equivalence, + // we reject any of these possible situations from happening. + #[inline] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + const fn ct_f16_to_u16(ct: f16) -> u16 { + // FIXME(f16_f128): we should use `.classify()` like `f32` and `f64`, but we don't yet + // want to rely on that on all platforms because it is nondeterministic (e.g. x86 has + // convention discrepancies calling intrinsics). So just classify the bits instead. + + // SAFETY: this is a POD transmutation + let bits = unsafe { mem::transmute::<f16, u16>(ct) }; + match f16::classify_bits(bits) { + FpCategory::Nan => { + panic!("const-eval error: cannot use f16::to_bits on a NaN") + } + FpCategory::Subnormal => { + panic!("const-eval error: cannot use f16::to_bits on a subnormal number") + } + FpCategory::Infinite | FpCategory::Normal | FpCategory::Zero => bits, + } + } + + #[inline(always)] // See https://github.com/rust-lang/compiler-builtins/issues/491 + fn rt_f16_to_u16(x: f16) -> u16 { + // SAFETY: `u16` is a plain old datatype so we can always... uh... + // ...look, just pretend you forgot what you just read. + // Stability concerns. + unsafe { mem::transmute(x) } + } + intrinsics::const_eval_select((self,), ct_f16_to_u16, rt_f16_to_u16) } /// Raw transmutation from `u16`. @@ -683,11 +885,52 @@ impl f16 { #[inline] #[must_use] #[unstable(feature = "f16", issue = "116909")] - pub fn from_bits(v: u16) -> Self { - // SAFETY: `u16` is a plain old datatype so we can always... uh... - // ...look, just pretend you forgot what you just read. - // Stability concerns. - unsafe { mem::transmute(v) } + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + pub const fn from_bits(v: u16) -> Self { + // It turns out the safety issues with sNaN were overblown! Hooray! + // SAFETY: `u16` is a plain old datatype so we can always transmute from it + // ...sorta. + // + // It turns out that at runtime, it is possible for a floating point number + // to be subject to floating point modes that alter nonzero subnormal numbers + // to zero on reads and writes, aka "denormals are zero" and "flush to zero". + // This is not a problem usually, but at least one tier2 platform for Rust + // actually exhibits this behavior by default: thumbv7neon + // aka "the Neon FPU in AArch32 state" + // + // And, of course evaluating to a NaN value is fairly nondeterministic. + // More precisely: when NaN should be returned is knowable, but which NaN? + // So far that's defined by a combination of LLVM and the CPU, not Rust. + // This function, however, allows observing the bitstring of a NaN, + // thus introspection on CTFE. + // + // In order to preserve, at least for the moment, const-to-runtime equivalence, + // reject any of these possible situations from happening. + #[inline] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + const fn ct_u16_to_f16(ct: u16) -> f16 { + match f16::classify_bits(ct) { + FpCategory::Subnormal => { + panic!("const-eval error: cannot use f16::from_bits on a subnormal number") + } + FpCategory::Nan => { + panic!("const-eval error: cannot use f16::from_bits on NaN") + } + FpCategory::Infinite | FpCategory::Normal | FpCategory::Zero => { + // SAFETY: It's not a frumious number + unsafe { mem::transmute::<u16, f16>(ct) } + } + } + } + + #[inline(always)] // See https://github.com/rust-lang/compiler-builtins/issues/491 + fn rt_u16_to_f16(x: u16) -> f16 { + // SAFETY: `u16` is a plain old datatype so we can always... uh... + // ...look, just pretend you forgot what you just read. + // Stability concerns. + unsafe { mem::transmute(x) } + } + intrinsics::const_eval_select((v,), ct_u16_to_f16, rt_u16_to_f16) } /// Return the memory representation of this floating point number as a byte array in @@ -709,8 +952,9 @@ impl f16 { /// ``` #[inline] #[unstable(feature = "f16", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] #[must_use = "this returns the result of the operation, without modifying the original"] - pub fn to_be_bytes(self) -> [u8; 2] { + pub const fn to_be_bytes(self) -> [u8; 2] { self.to_bits().to_be_bytes() } @@ -733,8 +977,9 @@ impl f16 { /// ``` #[inline] #[unstable(feature = "f16", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] #[must_use = "this returns the result of the operation, without modifying the original"] - pub fn to_le_bytes(self) -> [u8; 2] { + pub const fn to_le_bytes(self) -> [u8; 2] { self.to_bits().to_le_bytes() } @@ -770,8 +1015,9 @@ impl f16 { /// ``` #[inline] #[unstable(feature = "f16", issue = "116909")] + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] #[must_use = "this returns the result of the operation, without modifying the original"] - pub fn to_ne_bytes(self) -> [u8; 2] { + pub const fn to_ne_bytes(self) -> [u8; 2] { self.to_bits().to_ne_bytes() } @@ -793,7 +1039,8 @@ impl f16 { #[inline] #[must_use] #[unstable(feature = "f16", issue = "116909")] - pub fn from_be_bytes(bytes: [u8; 2]) -> Self { + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + pub const fn from_be_bytes(bytes: [u8; 2]) -> Self { Self::from_bits(u16::from_be_bytes(bytes)) } @@ -815,7 +1062,8 @@ impl f16 { #[inline] #[must_use] #[unstable(feature = "f16", issue = "116909")] - pub fn from_le_bytes(bytes: [u8; 2]) -> Self { + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + pub const fn from_le_bytes(bytes: [u8; 2]) -> Self { Self::from_bits(u16::from_le_bytes(bytes)) } @@ -848,7 +1096,8 @@ impl f16 { #[inline] #[must_use] #[unstable(feature = "f16", issue = "116909")] - pub fn from_ne_bytes(bytes: [u8; 2]) -> Self { + #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] + pub const fn from_ne_bytes(bytes: [u8; 2]) -> Self { Self::from_bits(u16::from_ne_bytes(bytes)) } diff --git a/library/std/src/f128/tests.rs b/library/std/src/f128/tests.rs index bd7a921c502..0b3e485b0e7 100644 --- a/library/std/src/f128/tests.rs +++ b/library/std/src/f128/tests.rs @@ -3,6 +3,7 @@ #![cfg(reliable_f128)] use crate::f128::consts; +use crate::num::FpCategory as Fp; use crate::num::*; /// Smallest number @@ -52,9 +53,8 @@ fn test_nan() { assert!(!nan.is_finite()); assert!(nan.is_sign_positive()); assert!(!nan.is_sign_negative()); - // FIXME(f16_f128): classify - // assert!(!nan.is_normal()); - // assert_eq!(Fp::Nan, nan.classify()); + assert!(!nan.is_normal()); + assert_eq!(Fp::Nan, nan.classify()); } #[test] @@ -65,9 +65,8 @@ fn test_infinity() { assert!(inf.is_sign_positive()); assert!(!inf.is_sign_negative()); assert!(!inf.is_nan()); - // FIXME(f16_f128): classify - // assert!(!inf.is_normal()); - // assert_eq!(Fp::Infinite, inf.classify()); + assert!(!inf.is_normal()); + assert_eq!(Fp::Infinite, inf.classify()); } #[test] @@ -78,9 +77,8 @@ fn test_neg_infinity() { assert!(!neg_inf.is_sign_positive()); assert!(neg_inf.is_sign_negative()); assert!(!neg_inf.is_nan()); - // FIXME(f16_f128): classify - // assert!(!neg_inf.is_normal()); - // assert_eq!(Fp::Infinite, neg_inf.classify()); + assert!(!neg_inf.is_normal()); + assert_eq!(Fp::Infinite, neg_inf.classify()); } #[test] @@ -92,9 +90,8 @@ fn test_zero() { assert!(zero.is_sign_positive()); assert!(!zero.is_sign_negative()); assert!(!zero.is_nan()); - // FIXME(f16_f128): classify - // assert!(!zero.is_normal()); - // assert_eq!(Fp::Zero, zero.classify()); + assert!(!zero.is_normal()); + assert_eq!(Fp::Zero, zero.classify()); } #[test] @@ -106,9 +103,8 @@ fn test_neg_zero() { assert!(!neg_zero.is_sign_positive()); assert!(neg_zero.is_sign_negative()); assert!(!neg_zero.is_nan()); - // FIXME(f16_f128): classify - // assert!(!neg_zero.is_normal()); - // assert_eq!(Fp::Zero, neg_zero.classify()); + assert!(!neg_zero.is_normal()); + assert_eq!(Fp::Zero, neg_zero.classify()); } #[test] @@ -120,9 +116,8 @@ fn test_one() { assert!(one.is_sign_positive()); assert!(!one.is_sign_negative()); assert!(!one.is_nan()); - // FIXME(f16_f128): classify - // assert!(one.is_normal()); - // assert_eq!(Fp::Normal, one.classify()); + assert!(one.is_normal()); + assert_eq!(Fp::Normal, one.classify()); } #[test] @@ -164,7 +159,40 @@ fn test_is_finite() { assert!((-109.2f128).is_finite()); } -// FIXME(f16_f128): add `test_is_normal` and `test_classify` when classify is working +#[test] +fn test_is_normal() { + let nan: f128 = f128::NAN; + let inf: f128 = f128::INFINITY; + let neg_inf: f128 = f128::NEG_INFINITY; + let zero: f128 = 0.0f128; + let neg_zero: f128 = -0.0; + assert!(!nan.is_normal()); + assert!(!inf.is_normal()); + assert!(!neg_inf.is_normal()); + assert!(!zero.is_normal()); + assert!(!neg_zero.is_normal()); + assert!(1f128.is_normal()); + assert!(1e-4931f128.is_normal()); + assert!(!1e-4932f128.is_normal()); +} + +#[test] +fn test_classify() { + let nan: f128 = f128::NAN; + let inf: f128 = f128::INFINITY; + let neg_inf: f128 = f128::NEG_INFINITY; + let zero: f128 = 0.0f128; + let neg_zero: f128 = -0.0; + assert_eq!(nan.classify(), Fp::Nan); + assert_eq!(inf.classify(), Fp::Infinite); + assert_eq!(neg_inf.classify(), Fp::Infinite); + assert_eq!(zero.classify(), Fp::Zero); + assert_eq!(neg_zero.classify(), Fp::Zero); + assert_eq!(1f128.classify(), Fp::Normal); + assert_eq!(1e-4931f128.classify(), Fp::Normal); + assert_eq!(1e-4932f128.classify(), Fp::Subnormal); +} + // FIXME(f16_f128): add missing math functions when available #[test] diff --git a/library/std/src/f16/tests.rs b/library/std/src/f16/tests.rs index bb6a811529e..26658a0be87 100644 --- a/library/std/src/f16/tests.rs +++ b/library/std/src/f16/tests.rs @@ -3,6 +3,7 @@ #![cfg(reliable_f16)] use crate::f16::consts; +use crate::num::FpCategory as Fp; use crate::num::*; // We run out of precision pretty quickly with f16 @@ -58,9 +59,8 @@ fn test_nan() { assert!(!nan.is_finite()); assert!(nan.is_sign_positive()); assert!(!nan.is_sign_negative()); - // FIXME(f16_f128): classify - // assert!(!nan.is_normal()); - // assert_eq!(Fp::Nan, nan.classify()); + assert!(!nan.is_normal()); + assert_eq!(Fp::Nan, nan.classify()); } #[test] @@ -71,9 +71,8 @@ fn test_infinity() { assert!(inf.is_sign_positive()); assert!(!inf.is_sign_negative()); assert!(!inf.is_nan()); - // FIXME(f16_f128): classify - // assert!(!inf.is_normal()); - // assert_eq!(Fp::Infinite, inf.classify()); + assert!(!inf.is_normal()); + assert_eq!(Fp::Infinite, inf.classify()); } #[test] @@ -84,9 +83,8 @@ fn test_neg_infinity() { assert!(!neg_inf.is_sign_positive()); assert!(neg_inf.is_sign_negative()); assert!(!neg_inf.is_nan()); - // FIXME(f16_f128): classify - // assert!(!neg_inf.is_normal()); - // assert_eq!(Fp::Infinite, neg_inf.classify()); + assert!(!neg_inf.is_normal()); + assert_eq!(Fp::Infinite, neg_inf.classify()); } #[test] @@ -98,9 +96,8 @@ fn test_zero() { assert!(zero.is_sign_positive()); assert!(!zero.is_sign_negative()); assert!(!zero.is_nan()); - // FIXME(f16_f128): classify - // assert!(!zero.is_normal()); - // assert_eq!(Fp::Zero, zero.classify()); + assert!(!zero.is_normal()); + assert_eq!(Fp::Zero, zero.classify()); } #[test] @@ -112,9 +109,8 @@ fn test_neg_zero() { assert!(!neg_zero.is_sign_positive()); assert!(neg_zero.is_sign_negative()); assert!(!neg_zero.is_nan()); - // FIXME(f16_f128): classify - // assert!(!neg_zero.is_normal()); - // assert_eq!(Fp::Zero, neg_zero.classify()); + assert!(!neg_zero.is_normal()); + assert_eq!(Fp::Zero, neg_zero.classify()); } #[test] @@ -126,9 +122,8 @@ fn test_one() { assert!(one.is_sign_positive()); assert!(!one.is_sign_negative()); assert!(!one.is_nan()); - // FIXME(f16_f128): classify - // assert!(one.is_normal()); - // assert_eq!(Fp::Normal, one.classify()); + assert!(one.is_normal()); + assert_eq!(Fp::Normal, one.classify()); } #[test] @@ -170,7 +165,40 @@ fn test_is_finite() { assert!((-109.2f16).is_finite()); } -// FIXME(f16_f128): add `test_is_normal` and `test_classify` when classify is working +#[test] +fn test_is_normal() { + let nan: f16 = f16::NAN; + let inf: f16 = f16::INFINITY; + let neg_inf: f16 = f16::NEG_INFINITY; + let zero: f16 = 0.0f16; + let neg_zero: f16 = -0.0; + assert!(!nan.is_normal()); + assert!(!inf.is_normal()); + assert!(!neg_inf.is_normal()); + assert!(!zero.is_normal()); + assert!(!neg_zero.is_normal()); + assert!(1f16.is_normal()); + assert!(1e-4f16.is_normal()); + assert!(!1e-5f16.is_normal()); +} + +#[test] +fn test_classify() { + let nan: f16 = f16::NAN; + let inf: f16 = f16::INFINITY; + let neg_inf: f16 = f16::NEG_INFINITY; + let zero: f16 = 0.0f16; + let neg_zero: f16 = -0.0; + assert_eq!(nan.classify(), Fp::Nan); + assert_eq!(inf.classify(), Fp::Infinite); + assert_eq!(neg_inf.classify(), Fp::Infinite); + assert_eq!(zero.classify(), Fp::Zero); + assert_eq!(neg_zero.classify(), Fp::Zero); + assert_eq!(1f16.classify(), Fp::Normal); + assert_eq!(1e-4f16.classify(), Fp::Normal); + assert_eq!(1e-5f16.classify(), Fp::Subnormal); +} + // FIXME(f16_f128): add missing math functions when available #[test] |