# Bachelor thesis logbook

Camil Staps

### 2016-09-18
ARM/Thumb-2 mode switches are expensive, and since a Clean program continuously
switches between the RTS and the program itself, it is not viable to have the
RTS run in ARM mode and the code generator generate Thumb-2 code. Hence, I
started to rewrite the RTS for Thumb-2. Mostly minor, trivial changes:

 - Invisible registers for some instructions (auxiliary register needed)

Started to make changes to the code generator:

 - Added `.thumb`, `.syntax unified` to the top of each generated file
 - Added `.thumb_func` before each code label
 - Fix for the `str pc,[sp,#-4]!` and similar instructions, since `pc` cannot
   be the `Rd` operand in a `str` instruction: copy to scratch register first.