Exactly. And even if we want to optimize access for those architectures, there surely must be ways to do that. Maybe compilers already do that if you use alignas(int32_t) on the byte array at the call site and ensure that read_int32() function of mine gets inlined?

No they won’t, if not in very basic cases that can’t be generalized as a rule of thumb solution. Your suggestion bargains correctness with performance.

If you know you are reading aligned memory and you need to do it with a single word memory access, then you need to use intNN_t* and use htonl or similar functions to byteswap. There’s no way around it.

The compiler can generate a test for alignment, and then a branch between two pieces of code. However, if the test and branch branch causes pipeline stalls due to bad prediction, it could be worse than just running the byte-banging code unconditionally.

I.e. "if that means doing what the programmer literally expressed, so be it."