kazuyukitanimura commented on code in PR #6551:
URL: https://github.com/apache/arrow-rs/pull/6551#discussion_r1802569870
##########
arrow-buffer/src/util/bit_mask.rs:
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@@ -127,16 +127,16 @@ unsafe fn set_upto_64bits(
}
/// # Safety
-/// The caller must ensure all arguments are within the valid range.
+/// The caller must ensure `data` has `offset..(offset + 8)` range, and `count
<= 8`.
#[inline]
unsafe fn read_bytes_to_u64(data: &[u8], offset: usize, count: usize) -> u64 {
debug_assert!(count <= 8);
- let mut tmp = std::mem::MaybeUninit::<u64>::new(0);
+ let mut tmp: u64 = 0;
Review Comment:
> MaybeUninit(0) and 0 should have no difference in performance.
Understood, but I wanted that to be confirmed experimentally
> For this to be an optimization, this ought to have used
MaybeUninit::uninit()
I initially did that but Miri did not allow to leave uninitialized bytes
even those are unused. So I quickly switched to `new(0)` and checked the
performance implications of the change. Perhaps I should have experimented `0`
at the time.
Anyway, I just wanted to make sure the change would not cause any unexpected
performance results.
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