Is there a place where compiler directive syntax is documented?

Using Swift
1

Hello, I'm trying to find a document that describes what are the exact capabilities of Swift compiler directives. As of now, I know about the support for &&, ||, ! operators, is there something else?
And is it correct to call #if syntax a compiler directive?

2

Here is the grammar description in the The Swift Programming Language Book:

Scroll down to "Grammar of a conditional compilation block"

And here in the language reference chapter: