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Auto merge of rust-lang#85703 - clarfonthey:unchecked_shift, r=scottmcm
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Add inherent unchecked_shl, unchecked_shr to integers

Tracking issue: rust-lang#85122.

Adding more of these methods, since these are missing.
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@bors
bors committed May 29, 2021
2 parents 4664725 + 2a40f24 commit 6166929
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Showing 2 changed files with 154 additions and 12 deletions.
83 changes: 77 additions & 6 deletions library/core/src/num/int_macros.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -407,8 +407,15 @@ macro_rules! int_impl {
}

/// Unchecked integer addition. Computes `self + rhs`, assuming overflow
/// cannot occur. This results in undefined behavior when
#[doc = concat!("`self + rhs > ", stringify!($SelfT), "::MAX` or `self + rhs < ", stringify!($SelfT), "::MIN`.")]
/// cannot occur.
///
/// # Safety
///
/// This results in undefined behavior when
#[doc = concat!("`self + rhs > ", stringify!($SelfT), "::MAX` or `self + rhs < ", stringify!($SelfT), "::MIN`,")]
/// i.e. when [`checked_add`] would return `None`.
///
#[doc = concat!("[`checked_add`]: ", stringify!($SelfT), "::checked_add")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
Expand Down Expand Up @@ -446,8 +453,15 @@ macro_rules! int_impl {
}

/// Unchecked integer subtraction. Computes `self - rhs`, assuming overflow
/// cannot occur. This results in undefined behavior when
#[doc = concat!("`self - rhs > ", stringify!($SelfT), "::MAX` or `self - rhs < ", stringify!($SelfT), "::MIN`.")]
/// cannot occur.
///
/// # Safety
///
/// This results in undefined behavior when
#[doc = concat!("`self - rhs > ", stringify!($SelfT), "::MAX` or `self - rhs < ", stringify!($SelfT), "::MIN`,")]
/// i.e. when [`checked_sub`] would return `None`.
///
#[doc = concat!("[`checked_sub`]: ", stringify!($SelfT), "::checked_sub")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
Expand Down Expand Up @@ -485,8 +499,15 @@ macro_rules! int_impl {
}

/// Unchecked integer multiplication. Computes `self * rhs`, assuming overflow
/// cannot occur. This results in undefined behavior when
#[doc = concat!("`self * rhs > ", stringify!($SelfT), "::MAX` or `self * rhs < ", stringify!($SelfT), "::MIN`.")]
/// cannot occur.
///
/// # Safety
///
/// This results in undefined behavior when
#[doc = concat!("`self * rhs > ", stringify!($SelfT), "::MAX` or `self * rhs < ", stringify!($SelfT), "::MIN`,")]
/// i.e. when [`checked_mul`] would return `None`.
///
#[doc = concat!("[`checked_mul`]: ", stringify!($SelfT), "::checked_mul")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
Expand Down Expand Up @@ -645,6 +666,31 @@ macro_rules! int_impl {
if unlikely!(b) {None} else {Some(a)}
}

/// Unchecked shift left. Computes `self << rhs`, assuming that
/// `rhs` is less than the number of bits in `self`.
///
/// # Safety
///
/// This results in undefined behavior if `rhs` is larger than
/// or equal to the number of bits in `self`,
/// i.e. when [`checked_shl`] would return `None`.
///
#[doc = concat!("[`checked_shl`]: ", stringify!($SelfT), "::checked_shl")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
issue = "85122",
)]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
#[inline(always)]
pub const unsafe fn unchecked_shl(self, rhs: Self) -> Self {
// SAFETY: the caller must uphold the safety contract for
// `unchecked_shl`.
unsafe { intrinsics::unchecked_shl(self, rhs) }
}

/// Checked shift right. Computes `self >> rhs`, returning `None` if `rhs` is
/// larger than or equal to the number of bits in `self`.
///
Expand All @@ -666,6 +712,31 @@ macro_rules! int_impl {
if unlikely!(b) {None} else {Some(a)}
}

/// Unchecked shift right. Computes `self >> rhs`, assuming that
/// `rhs` is less than the number of bits in `self`.
///
/// # Safety
///
/// This results in undefined behavior if `rhs` is larger than
/// or equal to the number of bits in `self`,
/// i.e. when [`checked_shr`] would return `None`.
///
#[doc = concat!("[`checked_shr`]: ", stringify!($SelfT), "::checked_shr")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
issue = "85122",
)]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
#[inline(always)]
pub const unsafe fn unchecked_shr(self, rhs: Self) -> Self {
// SAFETY: the caller must uphold the safety contract for
// `unchecked_shr`.
unsafe { intrinsics::unchecked_shr(self, rhs) }
}

/// Checked absolute value. Computes `self.abs()`, returning `None` if
/// `self == MIN`.
///
Expand Down
83 changes: 77 additions & 6 deletions library/core/src/num/uint_macros.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -417,8 +417,15 @@ macro_rules! uint_impl {
}

/// Unchecked integer addition. Computes `self + rhs`, assuming overflow
/// cannot occur. This results in undefined behavior when
#[doc = concat!("`self + rhs > ", stringify!($SelfT), "::MAX` or `self + rhs < ", stringify!($SelfT), "::MIN`.")]
/// cannot occur.
///
/// # Safety
///
/// This results in undefined behavior when
#[doc = concat!("`self + rhs > ", stringify!($SelfT), "::MAX` or `self + rhs < ", stringify!($SelfT), "::MIN`,")]
/// i.e. when [`checked_add`] would return `None`.
///
#[doc = concat!("[`checked_add`]: ", stringify!($SelfT), "::checked_add")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
Expand Down Expand Up @@ -456,8 +463,15 @@ macro_rules! uint_impl {
}

/// Unchecked integer subtraction. Computes `self - rhs`, assuming overflow
/// cannot occur. This results in undefined behavior when
#[doc = concat!("`self - rhs > ", stringify!($SelfT), "::MAX` or `self - rhs < ", stringify!($SelfT), "::MIN`.")]
/// cannot occur.
///
/// # Safety
///
/// This results in undefined behavior when
#[doc = concat!("`self - rhs > ", stringify!($SelfT), "::MAX` or `self - rhs < ", stringify!($SelfT), "::MIN`,")]
/// i.e. when [`checked_sub`] would return `None`.
///
#[doc = concat!("[`checked_sub`]: ", stringify!($SelfT), "::checked_sub")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
Expand Down Expand Up @@ -495,8 +509,15 @@ macro_rules! uint_impl {
}

/// Unchecked integer multiplication. Computes `self * rhs`, assuming overflow
/// cannot occur. This results in undefined behavior when
#[doc = concat!("`self * rhs > ", stringify!($SelfT), "::MAX` or `self * rhs < ", stringify!($SelfT), "::MIN`.")]
/// cannot occur.
///
/// # Safety
///
/// This results in undefined behavior when
#[doc = concat!("`self * rhs > ", stringify!($SelfT), "::MAX` or `self * rhs < ", stringify!($SelfT), "::MIN`,")]
/// i.e. when [`checked_mul`] would return `None`.
///
#[doc = concat!("[`checked_mul`]: ", stringify!($SelfT), "::checked_mul")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
Expand Down Expand Up @@ -655,6 +676,31 @@ macro_rules! uint_impl {
if unlikely!(b) {None} else {Some(a)}
}

/// Unchecked shift left. Computes `self << rhs`, assuming that
/// `rhs` is less than the number of bits in `self`.
///
/// # Safety
///
/// This results in undefined behavior if `rhs` is larger than
/// or equal to the number of bits in `self`,
/// i.e. when [`checked_shl`] would return `None`.
///
#[doc = concat!("[`checked_shl`]: ", stringify!($SelfT), "::checked_shl")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
issue = "85122",
)]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
#[inline(always)]
pub const unsafe fn unchecked_shl(self, rhs: Self) -> Self {
// SAFETY: the caller must uphold the safety contract for
// `unchecked_shl`.
unsafe { intrinsics::unchecked_shl(self, rhs) }
}

/// Checked shift right. Computes `self >> rhs`, returning `None`
/// if `rhs` is larger than or equal to the number of bits in `self`.
///
Expand All @@ -676,6 +722,31 @@ macro_rules! uint_impl {
if unlikely!(b) {None} else {Some(a)}
}

/// Unchecked shift right. Computes `self >> rhs`, assuming that
/// `rhs` is less than the number of bits in `self`.
///
/// # Safety
///
/// This results in undefined behavior if `rhs` is larger than
/// or equal to the number of bits in `self`,
/// i.e. when [`checked_shr`] would return `None`.
///
#[doc = concat!("[`checked_shr`]: ", stringify!($SelfT), "::checked_shr")]
#[unstable(
feature = "unchecked_math",
reason = "niche optimization path",
issue = "85122",
)]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
#[inline(always)]
pub const unsafe fn unchecked_shr(self, rhs: Self) -> Self {
// SAFETY: the caller must uphold the safety contract for
// `unchecked_shr`.
unsafe { intrinsics::unchecked_shr(self, rhs) }
}

/// Checked exponentiation. Computes `self.pow(exp)`, returning `None` if
/// overflow occurred.
///
Expand Down

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