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Compiler cant hoist following branch out of loop #544
Description
Objectives
Why can't the compiler hoist branch out of the loop in the following code?
use std::hint::black_box;
use hashbrown::HashMap;
pub fn main() {
let mut map: HashMap<u32, u32> = hashbrown::HashMap::default();
map.insert(0, 0);
for i in 0..10000 {
if let Some(_) = map.get(&0) {
continue;
} else {
black_box(i);
}
}
}online assembly https://rust.godbolt.org/z/vr3WGsfhP
Activity
Amanieu commentedon Aug 21, 2024
This happens because
hashbrown::raw::RawTable<T,A>::findis not inlined and therefore LLVM doesn't know that it is a pure function.re0312 commentedon Aug 21, 2024
Thanks for your reply. but I checked the code and it seems that
RawTable::findhas been marked as inline, and there are no extra call in the assembly