Cristian Orost <orost@xxxxxxxxx> writes: > I am quite new to gcc but I already have a specific question. It is > possible to modify the gcc backend in such a way that the set of > target instructions is somehow limited? Can this be configured in > some way, or would it be necessary to hack in the source code? You can certainly modify a backend to adjust the generated instructions. You can do this in such a way that a command line option controls whether your change is used in a particular compilation. You would have to hack in the source code to actually implement this. > For example, it should be possible (for IA32) to remove the "JG" > (jump when greater) instruction. It should be possible to use "JLE" > or similar instead, without limiting the set of compilable > programs. Similarly, a SUB could be replaced by forming a 2's > complement and an ADD instruction, etc. I assume gcc must have this > capability, since a RISC instruction is also limited in this way. Yes, gcc is able to do this sort of thing if you change the backend to make it happen. Ian
