diff options
Diffstat (limited to 'library/core/src/num/int_macros.rs')
| -rw-r--r-- | library/core/src/num/int_macros.rs | 63 |
1 files changed, 39 insertions, 24 deletions
diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs index 914dca61b..57096f439 100644 --- a/library/core/src/num/int_macros.rs +++ b/library/core/src/num/int_macros.rs @@ -107,6 +107,9 @@ macro_rules! int_impl { /// Returns the number of leading zeros in the binary representation of `self`. /// + /// Depending on what you're doing with the value, you might also be interested in the + /// [`ilog2`] function which returns a consistent number, even if the type widens. + /// /// # Examples /// /// Basic usage: @@ -116,6 +119,7 @@ macro_rules! int_impl { /// /// assert_eq!(n.leading_zeros(), 0); /// ``` + #[doc = concat!("[`ilog2`]: ", stringify!($SelfT), "::ilog2")] #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_int_methods", since = "1.32.0")] #[must_use = "this returns the result of the operation, \ @@ -757,10 +761,11 @@ macro_rules! int_impl { #[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")] #[inline(always)] #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces - pub const unsafe fn unchecked_shl(self, rhs: Self) -> Self { + pub const unsafe fn unchecked_shl(self, rhs: u32) -> Self { // SAFETY: the caller must uphold the safety contract for // `unchecked_shl`. - unsafe { intrinsics::unchecked_shl(self, rhs) } + // Any legal shift amount is losslessly representable in the self type. + unsafe { intrinsics::unchecked_shl(self, rhs.try_into().ok().unwrap_unchecked()) } } /// Checked shift right. Computes `self >> rhs`, returning `None` if `rhs` is @@ -804,10 +809,11 @@ macro_rules! int_impl { #[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")] #[inline(always)] #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces - pub const unsafe fn unchecked_shr(self, rhs: Self) -> Self { + pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self { // SAFETY: the caller must uphold the safety contract for // `unchecked_shr`. - unsafe { intrinsics::unchecked_shr(self, rhs) } + // Any legal shift amount is losslessly representable in the self type. + unsafe { intrinsics::unchecked_shr(self, rhs.try_into().ok().unwrap_unchecked()) } } /// Checked absolute value. Computes `self.abs()`, returning `None` if @@ -1354,11 +1360,12 @@ macro_rules! int_impl { #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline(always)] + #[rustc_allow_const_fn_unstable(const_inherent_unchecked_arith)] pub const fn wrapping_shl(self, rhs: u32) -> Self { // SAFETY: the masking by the bitsize of the type ensures that we do not shift // out of bounds unsafe { - intrinsics::unchecked_shl(self, (rhs & ($BITS - 1)) as $SelfT) + self.unchecked_shl(rhs & ($BITS - 1)) } } @@ -1383,11 +1390,12 @@ macro_rules! int_impl { #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline(always)] + #[rustc_allow_const_fn_unstable(const_inherent_unchecked_arith)] pub const fn wrapping_shr(self, rhs: u32) -> Self { // SAFETY: the masking by the bitsize of the type ensures that we do not shift // out of bounds unsafe { - intrinsics::unchecked_shr(self, (rhs & ($BITS - 1)) as $SelfT) + self.unchecked_shr(rhs & ($BITS - 1)) } } @@ -2068,11 +2076,15 @@ macro_rules! int_impl { pub const fn rem_euclid(self, rhs: Self) -> Self { let r = self % rhs; if r < 0 { - if rhs < 0 { - r - rhs - } else { - r + rhs - } + // Semantically equivalent to `if rhs < 0 { r - rhs } else { r + rhs }`. + // If `rhs` is not `Self::MIN`, then `r + abs(rhs)` will not overflow + // and is clearly equivalent, because `r` is negative. + // Otherwise, `rhs` is `Self::MIN`, then we have + // `r.wrapping_add(Self::MIN.wrapping_abs())`, which evaluates + // to `r.wrapping_add(Self::MIN)`, which is equivalent to + // `r - Self::MIN`, which is what we wanted (and will not overflow + // for negative `r`). + r.wrapping_add(rhs.wrapping_abs()) } else { r } @@ -2271,15 +2283,16 @@ macro_rules! int_impl { /// # Panics /// /// This function will panic if `self` is less than or equal to zero, - /// or if `base` is less then 2. + /// or if `base` is less than 2. /// /// # Examples /// /// ``` - /// #![feature(int_log)] #[doc = concat!("assert_eq!(5", stringify!($SelfT), ".ilog(5), 1);")] /// ``` - #[unstable(feature = "int_log", issue = "70887")] + #[stable(feature = "int_log", since = "1.67.0")] + #[rustc_const_stable(feature = "int_log", since = "1.67.0")] + #[rustc_allow_const_fn_unstable(const_option)] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] @@ -2298,10 +2311,11 @@ macro_rules! int_impl { /// # Examples /// /// ``` - /// #![feature(int_log)] #[doc = concat!("assert_eq!(2", stringify!($SelfT), ".ilog2(), 1);")] /// ``` - #[unstable(feature = "int_log", issue = "70887")] + #[stable(feature = "int_log", since = "1.67.0")] + #[rustc_const_stable(feature = "int_log", since = "1.67.0")] + #[rustc_allow_const_fn_unstable(const_option)] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] @@ -2319,10 +2333,11 @@ macro_rules! int_impl { /// # Example /// /// ``` - /// #![feature(int_log)] #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".ilog10(), 1);")] /// ``` - #[unstable(feature = "int_log", issue = "70887")] + #[stable(feature = "int_log", since = "1.67.0")] + #[rustc_const_stable(feature = "int_log", since = "1.67.0")] + #[rustc_allow_const_fn_unstable(const_option)] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] @@ -2343,10 +2358,10 @@ macro_rules! int_impl { /// # Examples /// /// ``` - /// #![feature(int_log)] #[doc = concat!("assert_eq!(5", stringify!($SelfT), ".checked_ilog(5), Some(1));")] /// ``` - #[unstable(feature = "int_log", issue = "70887")] + #[stable(feature = "int_log", since = "1.67.0")] + #[rustc_const_stable(feature = "int_log", since = "1.67.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] @@ -2379,10 +2394,10 @@ macro_rules! int_impl { /// # Examples /// /// ``` - /// #![feature(int_log)] #[doc = concat!("assert_eq!(2", stringify!($SelfT), ".checked_ilog2(), Some(1));")] /// ``` - #[unstable(feature = "int_log", issue = "70887")] + #[stable(feature = "int_log", since = "1.67.0")] + #[rustc_const_stable(feature = "int_log", since = "1.67.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] @@ -2403,10 +2418,10 @@ macro_rules! int_impl { /// # Example /// /// ``` - /// #![feature(int_log)] #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".checked_ilog10(), Some(1));")] /// ``` - #[unstable(feature = "int_log", issue = "70887")] + #[stable(feature = "int_log", since = "1.67.0")] + #[rustc_const_stable(feature = "int_log", since = "1.67.0")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] |