I've been looking for a list of the opcodes used in ARM Cortex M3/M4/M4F, without luck.
There are plenty of [online] references to the 32-bit format of ARM instructions.
References to Thumb-2 instructions are scarce, but available.
The version used in -M variants, however, I cannot find!
The ARM Technical Reference Manual has a "programmers Model" section which lists instructions, cycles per instruction... but no actual codes.
I found a "Definitive Guide" which has the same problem.
The information must be out there somewhere- you need it to write a compiler.
Where should I be looking?
The ARM Technical Reference Manual [...]
Wrong manual. You need the ARM ARM, or ARM Architecture manual for armv7-m. I cannot link to it here because ARM allows downloads of the ARM ARM only for registered users.