u64 has an alignment of 8 bytes on i686-pc-windows-msvc instead of 4 as implied in the reference

The rust reference states:

Most primitives are generally aligned to their size, although this is platform-specific behavior. In particular, on x86 u64 and f64 are only aligned to 32 bits.

-- https://doc.rust-lang.org/reference/type-layout.html

This is true for i686-unknown-linux-gnu:

> cat foo.rs
fn main() {
    println!("{}", std::mem::align_of::<u64>());
}
> rustc --target i686-unknown-linux-gnu foo.rs && ./foo
4

However, currently on i686-pc-windows-msvc the alignment of u64 is 8 bytes:

> rustc --target i686-pc-windows-msvc foo.rs
> foo.exe
8

The C++ compiler on that platform (at least the one UE uses) aligns u64 inside classes and structs to 4 bytes. I had expected repr(C) in rust do to the same (especially having read the part above from the reference) and was surprised it didn't. As I assume that some code somewhere relies on u64 being aligned to 8 bytes on that target, should the documentation in the reference be changed to reflect this difference?

Start with the Rust Reference type-layout page cited in the issue and verify the reported u64 alignment on i686-pc-windows-msvc against i686-unknown-linux-gnu and the platform's C++ behavior. Done means the reference accurately explains the target-specific alignment, or the issue is redirected if the implementation behavior needs correction first.