Add {f32,f64}::approx_unchecked_to<Int> unsafe methods

src/libcore/convert.rs → src/libcore/convert/mod.rs

@@ -40,6 +40,11 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
+mod num;
+
+#[unstable(feature = "convert_float_to_int", issue = "67057")]
+pub use num::FloatToInt;
+
 /// The identity function.
 ///
 /// Two things are important to note about this function:

src/libcore/convert/num.rs

@@ -0,0 +1,369 @@
+use super::{From, TryFrom};
+use crate::num::TryFromIntError;
+
+mod private {
+    /// This trait being unreachable from outside the crate
+    /// prevents other implementations of the `FloatToInt` trait,
+    /// which allows potentially adding more trait methods after the trait is `#[stable]`.
+    #[unstable(feature = "convert_float_to_int", issue = "67057")]
+    pub trait Sealed {}
+}
+
+/// Supporting trait for inherent methods of `f32` and `f64` such as `round_unchecked_to`.
+/// Typically doesn’t need to be used directly.
+#[unstable(feature = "convert_float_to_int", issue = "67057")]
+pub trait FloatToInt<Int>: private::Sealed + Sized {
+    #[cfg(not(bootstrap))]
+    #[unstable(feature = "float_approx_unchecked_to", issue = "67058")]
+    #[doc(hidden)]
+    unsafe fn approx_unchecked(self) -> Int;
+}
+
+macro_rules! impl_float_to_int {
+    ( $Float: ident => $( $Int: ident )+ ) => {
+        #[unstable(feature = "convert_float_to_int", issue = "67057")]
+        impl private::Sealed for $Float {}
+        $(
+            #[unstable(feature = "convert_float_to_int", issue = "67057")]
+            impl FloatToInt<$Int> for $Float {
+                #[cfg(not(bootstrap))]
+                #[doc(hidden)]
+                #[inline]
+                unsafe fn approx_unchecked(self) -> $Int {
+                    crate::intrinsics::float_to_int_approx_unchecked(self)
+                }
+            }
+        )+
+    }
+}
+
+impl_float_to_int!(f32 => u8 u16 u32 u64 u128 usize i8 i16 i32 i64 i128 isize);
+impl_float_to_int!(f64 => u8 u16 u32 u64 u128 usize i8 i16 i32 i64 i128 isize);
+
+// Conversion traits for primitive integer and float types
+// Conversions T -> T are covered by a blanket impl and therefore excluded
+// Some conversions from and to usize/isize are not implemented due to portability concerns
+macro_rules! impl_from {
+    ($Small: ty, $Large: ty, #[$attr:meta], $doc: expr) => {
+        #[$attr]
+        #[doc = $doc]
+        impl From<$Small> for $Large {
+            #[inline]
+            fn from(small: $Small) -> $Large {
+                small as $Large
+            }
+        }
+    };
+    ($Small: ty, $Large: ty, #[$attr:meta]) => {
+        impl_from!($Small,
+                   $Large,
+                   #[$attr],
+                   concat!("Converts `",
+                           stringify!($Small),
+                           "` to `",
+                           stringify!($Large),
+                           "` losslessly."));
+    }
+}
+
+macro_rules! impl_from_bool {
+    ($target: ty, #[$attr:meta]) => {
+        impl_from!(bool, $target, #[$attr], concat!("Converts a `bool` to a `",
+            stringify!($target), "`. The resulting value is `0` for `false` and `1` for `true`
+values.
+
+# Examples
+
+```
+assert_eq!(", stringify!($target), "::from(true), 1);
+assert_eq!(", stringify!($target), "::from(false), 0);
+```"));
+    };
+}
+
+// Bool -> Any
+impl_from_bool! { u8, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { u16, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { u32, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { u64, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { u128, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { usize, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { i8, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { i16, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { i32, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { i64, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { i128, #[stable(feature = "from_bool", since = "1.28.0")] }
+impl_from_bool! { isize, #[stable(feature = "from_bool", since = "1.28.0")] }
+
+// Unsigned -> Unsigned
+impl_from! { u8, u16, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u8, u32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u8, u64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u8, u128, #[stable(feature = "i128", since = "1.26.0")] }
+impl_from! { u8, usize, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u16, u32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u16, u64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u16, u128, #[stable(feature = "i128", since = "1.26.0")] }
+impl_from! { u32, u64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u32, u128, #[stable(feature = "i128", since = "1.26.0")] }
+impl_from! { u64, u128, #[stable(feature = "i128", since = "1.26.0")] }
+
+// Signed -> Signed
+impl_from! { i8, i16, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { i8, i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { i8, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { i8, i128, #[stable(feature = "i128", since = "1.26.0")] }
+impl_from! { i8, isize, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { i16, i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { i16, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { i16, i128, #[stable(feature = "i128", since = "1.26.0")] }
+impl_from! { i32, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { i32, i128, #[stable(feature = "i128", since = "1.26.0")] }
+impl_from! { i64, i128, #[stable(feature = "i128", since = "1.26.0")] }
+
+// Unsigned -> Signed
+impl_from! { u8, i16, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u8, i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u8, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u8, i128, #[stable(feature = "i128", since = "1.26.0")] }
+impl_from! { u16, i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u16, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u16, i128, #[stable(feature = "i128", since = "1.26.0")] }
+impl_from! { u32, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
+impl_from! { u32, i128, #[stable(feature = "i128", since = "1.26.0")] }
+impl_from! { u64, i128, #[stable(feature = "i128", since = "1.26.0")] }
+
+// The C99 standard defines bounds on INTPTR_MIN, INTPTR_MAX, and UINTPTR_MAX
+// which imply that pointer-sized integers must be at least 16 bits:
+// https://port70.net/~nsz/c/c99/n1256.html#7.18.2.4
+impl_from! { u16, usize, #[stable(feature = "lossless_iusize_conv", since = "1.26.0")] }
+impl_from! { u8, isize, #[stable(feature = "lossless_iusize_conv", since = "1.26.0")] }
+impl_from! { i16, isize, #[stable(feature = "lossless_iusize_conv", since = "1.26.0")] }
+
+// RISC-V defines the possibility of a 128-bit address space (RV128).
+
+// CHERI proposes 256-bit “capabilities”. Unclear if this would be relevant to usize/isize.
+// https://www.cl.cam.ac.uk/research/security/ctsrd/pdfs/20171017a-cheri-poster.pdf
+// http://www.csl.sri.com/users/neumann/2012resolve-cheri.pdf
+
+
+// Note: integers can only be represented with full precision in a float if
+// they fit in the significand, which is 24 bits in f32 and 53 bits in f64.
+// Lossy float conversions are not implemented at this time.
+
+// Signed -> Float
+impl_from! { i8, f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+impl_from! { i8, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+impl_from! { i16, f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+impl_from! { i16, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+impl_from! { i32, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+
+// Unsigned -> Float
+impl_from! { u8, f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+impl_from! { u8, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+impl_from! { u16, f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+impl_from! { u16, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+impl_from! { u32, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+
+// Float -> Float
+impl_from! { f32, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
+
+// no possible bounds violation
+macro_rules! try_from_unbounded {
+    ($source:ty, $($target:ty),*) => {$(
+        #[stable(feature = "try_from", since = "1.34.0")]
+        impl TryFrom<$source> for $target {
+            type Error = TryFromIntError;
+
+            /// Try to create the target number type from a source
+            /// number type. This returns an error if the source value
+            /// is outside of the range of the target type.
+            #[inline]
+            fn try_from(value: $source) -> Result<Self, Self::Error> {
+                Ok(value as $target)
+            }
+        }
+    )*}
+}
+
+// only negative bounds
+macro_rules! try_from_lower_bounded {
+    ($source:ty, $($target:ty),*) => {$(
+        #[stable(feature = "try_from", since = "1.34.0")]
+        impl TryFrom<$source> for $target {
+            type Error = TryFromIntError;
+
+            /// Try to create the target number type from a source
+            /// number type. This returns an error if the source value
+            /// is outside of the range of the target type.
+            #[inline]
+            fn try_from(u: $source) -> Result<$target, TryFromIntError> {
+                if u >= 0 {
+                    Ok(u as $target)
+                } else {
+                    Err(TryFromIntError(()))
+                }
+            }
+        }
+    )*}
+}
+
+// unsigned to signed (only positive bound)
+macro_rules! try_from_upper_bounded {
+    ($source:ty, $($target:ty),*) => {$(
+        #[stable(feature = "try_from", since = "1.34.0")]
+        impl TryFrom<$source> for $target {
+            type Error = TryFromIntError;
+
+            /// Try to create the target number type from a source
+            /// number type. This returns an error if the source value
+            /// is outside of the range of the target type.
+            #[inline]
+            fn try_from(u: $source) -> Result<$target, TryFromIntError> {
+                if u > (<$target>::max_value() as $source) {
+                    Err(TryFromIntError(()))
+                } else {
+                    Ok(u as $target)
+                }
+            }
+        }
+    )*}
+}
+
+// all other cases
+macro_rules! try_from_both_bounded {
+    ($source:ty, $($target:ty),*) => {$(
+        #[stable(feature = "try_from", since = "1.34.0")]
+        impl TryFrom<$source> for $target {
+            type Error = TryFromIntError;
+
+            /// Try to create the target number type from a source
+            /// number type. This returns an error if the source value
+            /// is outside of the range of the target type.
+            #[inline]
+            fn try_from(u: $source) -> Result<$target, TryFromIntError> {
+                let min = <$target>::min_value() as $source;
+                let max = <$target>::max_value() as $source;
+                if u < min || u > max {
+                    Err(TryFromIntError(()))
+                } else {
+                    Ok(u as $target)
+                }
+            }
+        }
+    )*}
+}
+
+macro_rules! rev {
+    ($mac:ident, $source:ty, $($target:ty),*) => {$(
+        $mac!($target, $source);
+    )*}
+}
+
+// intra-sign conversions
+try_from_upper_bounded!(u16, u8);
+try_from_upper_bounded!(u32, u16, u8);
+try_from_upper_bounded!(u64, u32, u16, u8);
+try_from_upper_bounded!(u128, u64, u32, u16, u8);
+
+try_from_both_bounded!(i16, i8);
+try_from_both_bounded!(i32, i16, i8);
+try_from_both_bounded!(i64, i32, i16, i8);
+try_from_both_bounded!(i128, i64, i32, i16, i8);
+
+// unsigned-to-signed
+try_from_upper_bounded!(u8, i8);
+try_from_upper_bounded!(u16, i8, i16);
+try_from_upper_bounded!(u32, i8, i16, i32);
+try_from_upper_bounded!(u64, i8, i16, i32, i64);
+try_from_upper_bounded!(u128, i8, i16, i32, i64, i128);
+
+// signed-to-unsigned
+try_from_lower_bounded!(i8, u8, u16, u32, u64, u128);
+try_from_lower_bounded!(i16, u16, u32, u64, u128);
+try_from_lower_bounded!(i32, u32, u64, u128);
+try_from_lower_bounded!(i64, u64, u128);
+try_from_lower_bounded!(i128, u128);
+try_from_both_bounded!(i16, u8);
+try_from_both_bounded!(i32, u16, u8);
+try_from_both_bounded!(i64, u32, u16, u8);
+try_from_both_bounded!(i128, u64, u32, u16, u8);
+
+// usize/isize
+try_from_upper_bounded!(usize, isize);
+try_from_lower_bounded!(isize, usize);
+
+#[cfg(target_pointer_width = "16")]
+mod ptr_try_from_impls {
+    use super::TryFromIntError;
+    use crate::convert::TryFrom;
+
+    try_from_upper_bounded!(usize, u8);
+    try_from_unbounded!(usize, u16, u32, u64, u128);
+    try_from_upper_bounded!(usize, i8, i16);
+    try_from_unbounded!(usize, i32, i64, i128);
+
+    try_from_both_bounded!(isize, u8);
+    try_from_lower_bounded!(isize, u16, u32, u64, u128);
+    try_from_both_bounded!(isize, i8);
+    try_from_unbounded!(isize, i16, i32, i64, i128);
+
+    rev!(try_from_upper_bounded, usize, u32, u64, u128);
+    rev!(try_from_lower_bounded, usize, i8, i16);
+    rev!(try_from_both_bounded, usize, i32, i64, i128);
+
+    rev!(try_from_upper_bounded, isize, u16, u32, u64, u128);
+    rev!(try_from_both_bounded, isize, i32, i64, i128);
+}
+
+#[cfg(target_pointer_width = "32")]
+mod ptr_try_from_impls {
+    use super::TryFromIntError;
+    use crate::convert::TryFrom;
+
+    try_from_upper_bounded!(usize, u8, u16);
+    try_from_unbounded!(usize, u32, u64, u128);
+    try_from_upper_bounded!(usize, i8, i16, i32);
+    try_from_unbounded!(usize, i64, i128);
+
+    try_from_both_bounded!(isize, u8, u16);
+    try_from_lower_bounded!(isize, u32, u64, u128);
+    try_from_both_bounded!(isize, i8, i16);
+    try_from_unbounded!(isize, i32, i64, i128);
+
+    rev!(try_from_unbounded, usize, u32);
+    rev!(try_from_upper_bounded, usize, u64, u128);
+    rev!(try_from_lower_bounded, usize, i8, i16, i32);
+    rev!(try_from_both_bounded, usize, i64, i128);
+
+    rev!(try_from_unbounded, isize, u16);
+    rev!(try_from_upper_bounded, isize, u32, u64, u128);
+    rev!(try_from_unbounded, isize, i32);
+    rev!(try_from_both_bounded, isize, i64, i128);
+}
+
+#[cfg(target_pointer_width = "64")]
+mod ptr_try_from_impls {
+    use super::TryFromIntError;
+    use crate::convert::TryFrom;
+
+    try_from_upper_bounded!(usize, u8, u16, u32);
+    try_from_unbounded!(usize, u64, u128);
+    try_from_upper_bounded!(usize, i8, i16, i32, i64);
+    try_from_unbounded!(usize, i128);
+
+    try_from_both_bounded!(isize, u8, u16, u32);
+    try_from_lower_bounded!(isize, u64, u128);
+    try_from_both_bounded!(isize, i8, i16, i32);
+    try_from_unbounded!(isize, i64, i128);
+
+    rev!(try_from_unbounded, usize, u32, u64);
+    rev!(try_from_upper_bounded, usize, u128);
+    rev!(try_from_lower_bounded, usize, i8, i16, i32, i64);
+    rev!(try_from_both_bounded, usize, i128);
+
+    rev!(try_from_unbounded, isize, u16, u32);
+    rev!(try_from_upper_bounded, isize, u64, u128);
+    rev!(try_from_unbounded, isize, i32, i64);
+    rev!(try_from_both_bounded, isize, i128);
+}

src/libcore/intrinsics.rs

@@ -1144,6 +1144,11 @@ extern "rust-intrinsic" {
     /// May assume inputs are finite.
     pub fn frem_fast<T>(a: T, b: T) -> T;
 
+    /// Convert with LLVM’s fptoui/fptosi, which may return undef for values out of range
+    /// https://github.com/rust-lang/rust/issues/10184
+    #[cfg(not(bootstrap))]
+    pub fn float_to_int_approx_unchecked<Float, Int>(value: Float) -> Int;
+
 
     /// Returns the number of bits set in an integer type `T`
     pub fn ctpop<T>(x: T) -> T;