Fix handling of enum tags that aren't literals (#926)

An `enum` case currently lowers to the IR as the value of its tag expression, so if we have:

```hlsl
enum E
{
    X = 99,
}
```

then `X` will lower as IR for the expression `99` which is just a literal.
If instead we have:

```hlsl
enum E
{
    X = 99u,
}
```

then after type checking the expression is `int(99u)`, which will get emitted to the global (module) scope as a cast/conversion instruction, that then gets referenced at the use sites of `E.X`.

The emit logic wasn't set up to handle the case of referencing something directly from the global scope, so this change makes it so that side-effect-free global instructions are treated just like literal constants. This simple handling is fine for now since it will only apply to `enum` tag values (true global constants declared with `static const` have different handling).

0 files changed, 0 insertions, 0 deletions