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Optimize core::ptr::align_offset

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- Stopping condition inside mod_inv can be >= instead of >
- Remove intrinsics::unchecked_rem, we are working modulu powers-of-2 so
we can simply mask
This commit is contained in:
Amos Onn 2020-01-30 20:04:24 +01:00
parent f43c34a134
commit e835d0d761
1 changed files with 2 additions and 2 deletions
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4
src/libcore/ptr/mod.rs
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@ -1083,7 +1083,7 @@ pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
// anyway.
inverse = inverse.wrapping_mul(2usize.wrapping_sub(x.wrapping_mul(inverse)))
& (going_mod - 1);
if going_mod > m {
if going_mod >= m {
return inverse & (m - 1);
}
going_mod = going_mod.wrapping_mul(going_mod);
@ -1134,7 +1134,7 @@ pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
// to take the result $o mod lcm(s, a)$. We can replace $lcm(s, a)$ with just a $a / g$.
let j = a.wrapping_sub(pmoda) >> gcdpow;
let k = smoda >> gcdpow;
return intrinsics::unchecked_rem(j.wrapping_mul(mod_inv(k, a)), a >> gcdpow);
return (j.wrapping_mul(mod_inv(k, a))) & ((a >> gcdpow).wrapping_sub(1));
}
// Cannot be aligned at all.