Checks that are always true _in some context_ are entirely normal and by design if the code can be used in a different context. If your code is reused in a way that let's the optimizer re-optimize the code per-context, then you'll benefit from the compiler's ability to remove dead code or even merely to choose less expensive special case ops. Macros, templates and inlining are some common ways that happens, but platform-specific builds and perhaps others exist too.

For example, imagine you have some SIM wide value, and you want to do something to each word or byte that the SIMD value contains. In today's C, you can just write a bunch of ifs: is width < 2? then... is width < 4? then... etc. The compiler with completely elide those ifs and leave behind only the reachable code - if it can specialize that re-used code for the given context.

Furthermore, today those checks might be implicit via the use of UB. That's perhaps not a great solution looking at the entire ecosystem, but it is the situation we're in. Changing that might be quite a lot of work.