Weird behavior when comparing function pointers

[VictorKoenders]

As per the discussion on twitter

This piece of code in release mode has weird behavior when comparing 2 pointers twice. This behavior happens only in release mode and does appear on stable.

It looks like a LLVM optimization to me, @eddyb thinks it "might be an accidental optimization"

fn foo(_: i32) -> i32 {
    1
}
fn bar(_: i32) -> i32 {
    1
}

fn main() {
    let x: fn(i32) -> i32 = foo;
    let y: fn(i32) -> i32 = bar;
    
    if x == y {
        println!("true")
    } else {
        println!("false {:?}", x);
    }

    if x == y {
        println!("true")
    } else {
        println!("false {:?}", x);
    }
}

false 0x55eabbd342f0
true

play.rust-lang.org link

[sfackler]

Duplicate of #54685.