On Tue, Aug 04, 2015 at 10:28:00AM -0700, H.J. Lu wrote: > >> Any comments on my middle-end patch? > > > > So, if the answer is the same as frame_address (0), why not have the > > fallback just expand to that? Then, one can use this builtin everywhere > > that frame address is used today. People that want a faster, tighter port > > can then implement the hook and achieve higher performance. > > The motivation of __builtin_stack_top is that frame_address requires a > frame pointer register, which isn't desirable for x86. __builtin_stack_top > doesn't require a frame pointer register.
If the target just returns frame_pointer_rtx from INITIAL_FRAME_ADDRESS_RTX, you don't get crtl->accesses_prior_frames set either, and as far as I can see everything works fine? For __builtin_frame_address(0). You might have a reason why you want the entry stack address instead of the frame address, but you didn't really explain I think? Or I missed it. Segher
