Missed optimization in if with constant branches

I assume the following two functions behave identically, and therefore should result in the same codegen. https://godbolt.org/z/vj9ornqbG

#[no_mangle]
pub fn cast(x: bool) -> f32 {
    x as u8 as f32
}

#[no_mangle]
pub fn ifelse(x: bool) -> f32 {
    if x { 1. } else { 0. }
}

However, ifelse fails to be optimised to a cast.

cast:
        cvtsi2ss        xmm0, edi
        ret

.LCPI1_0:
        .long   0x3f800000
ifelse:
        test    edi, edi
        jne     .LBB1_1
        xorps   xmm0, xmm0
        ret
.LBB1_1:
        movss   xmm0, dword ptr [rip + .LCPI1_0]
        ret

Start by reproducing the Rust example from the issue in the linked Compiler Explorer output and compare the generated assembly for cast and ifelse. Trace the compiler optimization path handling the constant branches, then add coverage showing that equivalent functions produce the expected optimized codegen.