#Is `null` passed to an optional argument considered comptime-known?

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naive crystal
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I’m trying to understand whether passing null as a value to an optional argument of a function is considered comptime by the compiler, and if it can optimize away paths that follow in case of null. Here’s a trivial example:
https://godbolt.org/z/51zqf6Tso
I barely know assembly but I noticed that the loop in the example disappeared.

Compiler Explorer - Zig (zig 0.13.0)

fn incUntil100(num: usize, until: ?usize) usize {
var n = num;
while (if (until) |u| num != u else true) {
n += 1;
if (n == 100) return n;
break;
}
return n;
}

export fn testWithNull(num: usize) usize {
return incUntil100(num, null);
}

export fn testWithoutNull(num: usize) usize {
return incUntil...

#

In my real code, I'd like to use null as a comptime mark to change/remove loop condition (in the same way it is shown at line 3).

still glade
#

arguments to (non-inline) fns, which aren't of comptime-only types, nor marked comptime, are considered runtime known.
LLVM is smart enough to do its own optimisations, but they're beyond Zig's semantics