I have compared two very short versions of the same code in C and Rust and found that Rust emits useless code around the stack.
C: https://godbolt.org/g/pc2u4J (gcc) https://godbolt.org/g/fiZM2h (clang)
Rust: https://godbolt.org/g/sTkQtU
Why rust always emit this?
push rbp mov rbp, rsp
and this
pop rbp
For such an easy case?
I believe this is because of an extra compiler flag godbolt includes by default (see https://stackoverflow.com/a/45562380 and https://github.com/rust-lang/rust/issues/11906), which you can turn off by explicitly adding “-C debuginfo=0”. When I do that, these superfluous instructions go away and the Rust and C outputs are identical.
Awesome thanks! I thought how it can be possible that both clang and rust use libllvm and have different code… So I was wrong, Thanks! Though, I don’t understand why the godbolt adds any flags which are not visible.
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