http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49775
--- Comment #8 from Praveen Kaushik <praveen.r.kaushik at gmail dot com> 2012-09-21 10:36:20 UTC --- This bug seems to be duplicate of this : http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26504 The assertion, gcc_assert ((SUPPORTS_STACK_ALIGNMENT && (elim == hard_frame_pointer_rtx || elim == stack_pointer_rtx)) || elim == (frame_pointer_needed ? hard_frame_pointer_rtx : stack_pointer_rtx)); instead of being checked in 'compute_frame_pointer_to_fb_displacement ()' is now assigned to 'frame_pointer_fb_offset_valid' and the assertion is moved to 'based_loc_descr()' (where it actually fails). http://gcc.gnu.org/viewcvs/trunk/gcc/dwarf2out.c?r1=174715&r2=175018&diff_format=h PR26504 was resolved by defining 'FRAME_POINTER_CFA_OFFSET' macro in avr.h. This macro was removed later in Revision 171295, so that ARG_POINTER_CFA_OFFSET can be defined. These changes were done in order to fix PR48459. http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48459 snip from dwarf2out.c ---- #ifdef FRAME_POINTER_CFA_OFFSET reg = frame_pointer_rtx; offset += FRAME_POINTER_CFA_OFFSET (current_function_decl); #else reg = arg_pointer_rtx; offset += ARG_POINTER_CFA_OFFSET (current_function_decl); #endif elim = eliminate_regs (reg, VOIDmode, NULL_RTX); ---- Here `reg' is initialized with `arg_pointer_rtx' since FRAME_POINTER_CFA_OFFSET is not defined. ---- frame_pointer_fb_offset_valid = ((SUPPORTS_STACK_ALIGNMENT && (elim == hard_frame_pointer_rtx || elim == stack_pointer_rtx)) || elim == (frame_pointer_needed ? hard_frame_pointer_rtx : stack_pointer_rtx)); ---- In this, `elim' is expected to be equal to `stack_pointer_rtx' (as frame_pointer_needed is false) in order to have 'frame_pointer_fb_offset_valid' value TRUE. But AVR does not have any elimination to reduce `arg_pointer_rtx' to `stack_pointer_rtx', so this assertion ought to fail in this case. So IMO, to fix this issue either FRAME_POINTER_CFA_OFFSET should be defined or an elimination should be defined which reduces `arg_pointer_rtx' to `stack_pointer_rtx'.
