SH4 is relatively compact (16-bit instructions) but it isn't really compressed in the same way Thumb is. They shaved some corners to make things fit; e.g. there's only room for a 4 bit displacement in a load [R + disp] -> R type instruction. If you want to use an 8 bit displacement you have to use R0. This naturally leads to a lot of two-instruction sequences to calculate an offset into the stack, etc. which ends up practically more like classic MIPS in density.