Rust builder pattern performance

builder_pattern.rs

pub struct X {
    a: i32,
    b: i32,
    c: i32,
    d: i32,
}

impl X {
    pub fn set_a_mut(&mut self, a: i32) {
        self.a = a;
    }

    pub fn set_a_move(mut self, a: i32) -> Self {
        self.a = a;
        self
    }
}

builder_pattern.s

// https://rust.godbolt.org/
// rustc 1.29.0
// -C opt-level=3 -C lto=thin -C codegen-units=1

example::X::set_a_mut:
        mov     dword ptr [rdi], esi
        ret

example::X::set_a_move:
        mov     dword ptr [rsi], edx
        mov     eax, dword ptr [rsi]
        mov     dword ptr [rdi], eax
        mov     rax, qword ptr [rsi + 4]
        mov     qword ptr [rdi + 4], rax
        mov     eax, dword ptr [rsi + 12]
        mov     dword ptr [rdi + 12], eax
        mov     rax, rdi
        ret