Some assembly language instructions seems to keep changing. Whats up?

Many instructions can be looked at in more that one way. "add x to x" is really the same as an "arithmetic left shift x". The assembly language nmemonics supported by mspgcc follow TI's original assembly language. There are alternative names for some instructions, to allow assembly language code to be written in a more expressive manner. You can write

add R15,R15
or
rla R15
and the same binary code will be produced. However, when you look at a listing from, say, the debugger or the C compiler the same source representation is always used for any particular binary instruction. This often confuses people, and results in a number of false bug reports. It is actually the expected behaviour.

There is more information about these alternative names for the instuctions in the mspgcc manual.