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ptr::copy_nonoverlapping slower then manual bytewise copy #97022
Description
The following code:
#[inline]
unsafe fn copy_bytes(src: *const u8, dst: *mut u8, count: usize){
for i in 0..count{
*dst.add(i) = *src.add(i);
}
}is significantly FASTER then ptr::copy_nonoverlapping, for small counts, and cases where count is not known at compile time. (2-3 times for 8 byte copy).
People suggest that this happens, because compiler does not inline copy_nonoverlapping code:
https://users.rust-lang.org/t/ptr-copy-nonoverlapping-slower-then-manual-per-byte-copy/75588/2?u=tower120
I'm not sure if this is actually a bug though...
Activity
saethlin commentedon May 14, 2022
Similar to #92993
mati865 commentedon May 29, 2022
Related to #83785
zeroflaw commentedon Sep 7, 2023
fyi, this now compiles down to the same assembly as copy_nonoverlapping.