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ctutils: import core::hint::black_box in primitives module #1574

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Merged
tarcieri merged 1 commit into from
Oct 23, 2026
Merged

ctutils: import core::hint::black_box in primitives module #1574

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10 changes: 6 additions & 4 deletions ctutils/src/primitives.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,9 @@
//! be checked for the target and compiler in use.
//!
//! Native zero counts are used when supported and advertised by the target configuration.

use crate::Choice;
use core::hint::black_box;

/// Bitwise less-than-or equal: returns `1` if `x <= y`, and otherwise returns `0`.
///
Expand Down Expand Up @@ -52,7 +54,7 @@ macro_rules! comparison_primitives {
pub(crate) const fn $le(lhs: $ty, rhs: $ty) -> Choice {
let bit = bitle!(lhs, rhs, <$ty>::BITS);
#[cfg(all(target_arch = "arm", not(target_has_atomic = "ptr")))]
let bit = core::hint::black_box(bit);
let bit = black_box(bit);
Choice::$from_lsb(bit)
}

Expand All @@ -67,15 +69,15 @@ macro_rules! comparison_primitives {
pub(crate) const fn $lt(lhs: $ty, rhs: $ty) -> Choice {
let bit = bitlt!(lhs, rhs, <$ty>::BITS);
#[cfg(all(target_arch = "arm", not(target_has_atomic = "ptr")))]
let bit = core::hint::black_box(bit);
let bit = black_box(bit);
Choice::$from_lsb(bit)
}

#[inline(always)]
pub(crate) const fn $nz(value: $ty) -> Choice {
let bit = bitnz!(value, <$ty>::BITS);
#[cfg(all(target_arch = "arm", not(target_has_atomic = "ptr")))]
let bit = core::hint::black_box(bit);
let bit = black_box(bit);
Choice::$from_lsb(bit)
}
};
Expand All @@ -98,7 +100,7 @@ macro_rules! borrowing_sub_primitives {
// optimization on older compilers: https://github.com/rust-lang/rust/issues/149522
// Keep the full-width bit opaque before narrowing it to Choice, so a caller's
// masked add-back cannot be folded into a secret-dependent branch.
let borrow = core::hint::black_box(bitborrow!(lhs, rhs, difference, <$ty>::BITS));
let borrow = black_box(bitborrow!(lhs, rhs, difference, <$ty>::BITS));
(difference, Choice::$from_lsb(borrow))
}
};
Expand Down
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