[lectrick]

This is clever. However...

The problem as I see it with this sort of cleverness is that it's difficult to optimize to this. It leads to quite variable best-case and worst-case scenarios and general unpredictability. As, say, a C programmer and not a compiler designer, you might unintentionally pick lots of values that won't fit into the "immediate" scheme (worst-case). Or you might force your design to use numbers that DO fit into this scheme (best-case, but a bleed of lower-level design decisions affecting higher-level design decisions).

[fidotron]

These days if what you're writing is in C then you should really know the behaviour of the architecture underneath.

ARM really isn't that hard if you're already thinking like a low level programmer. Things like MIPS were (better) designed for being targeted from higher level languages, but the consequence is a much messier machine language. It's always struck me as amusing that the conventional view is MIPS is minimal, when ARM is really much more so, but it's from outside the Berkeley/Stanford RISC bubble so didn't really get on to their radars for some time.

[TorKlingberg]

There is lots of C code that is written to be portable, and trusts the compiler to generate optimized assembly. But those are probably ok with spending a couple of extra cycles for some immediate values.