I actually already did put it as a fixed register using the FIXED_REGISTER macro. However, I have not yet tested the EPILOGUE_USES because it said that : "The stack and frame pointer are already assumed to be used as needed".
My current port defines a different FRAME_POINTER_REGNUM from the HARD_FRAME_POINTER_REGNUM. I have this because before register allocation it is not possible to know the offset as it is said in the Internals. Basically, my code looks like this: move stack pointer down conditional trap on stack pointer store on stack the return address store on stack the frame pointer HARD_FRAME_POINTER_REGNUM (it's the old one so that we know where it started) mov HARD_FRAME_POINTER_REGNUM, stack_pointer ... Function code ... restore return address restore HARD_FRAME_POINTER_REGNUM mov stack_pointer, HARD_FRAME_POINTER_REGNUM This seemed like the simplest solution but it seems to be that, because I restore it in the epilogue, it considers the move as being useless since it doesn't realize it is needed by subsequent function calls in the function code. Thanks for any input, Jc On Mon, Nov 9, 2009 at 10:40 AM, Ian Lance Taylor <i...@google.com> wrote: > Jean Christophe Beyler <jean.christophe.bey...@gmail.com> writes: > >> How can I force the prologue to keep this instruction. It is useless >> only in the case that there is no function call or no alloca. But I >> have a case where there is a function call and it is still removed. > > Make the hard frame pointer register a fixed register, or add it to > EPILOGUE_USES. > > Ian >
