https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118939
--- Comment #19 from Richard Earnshaw <rearnsha at gcc dot gnu.org> --- (In reply to Eric Botcazou from comment #18) > > So the real question is why has the size of the frame changed once it's too > > late to change the frame layout? > > The frame size has not changed, rather the value returned by get_frame_size > has because of the way it is implemented: If the value returned is different from earlier, then it has changed. Using different methods for calculating the size during different passes would a recipe for endless bugs, especially if crufted into the back-ends. > But the more fundamental problem is that, if <target>_frame_pointer_required > does not return the same answer at the beginning of IRA and during LRA, then > LRA will materialize the frame pointer very late in the game, after the > frame is laid out, and I guess that most targets will break like in the case > at hand. The mid-end code has to cope with that. There may be circumstances where we initially think the frame-pointer can be eliminated, but later find we can't. It won't flip-flop randomly, but it might have to change based on additional knowledge that is aquired as the frame layout process is done.
