I have never had the need to write assembly on any embedded device. There are C (or other high language) compilers for just about any architecture. For very specific instructions (i.e. interrupt jumps) there is usually available as a compiler alias/feature.

If you want to turn an AVR/AtMega32 into a spectrum analyzer, you need to massage the x, y and z registers that support implicit incement/decrement adressing. C fails hard for such code.