https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104558
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:e6e6e0a97340068c90fe091482efbaacd6474754 commit r12-7458-ge6e6e0a97340068c90fe091482efbaacd6474754 Author: Jakub Jelinek <ja...@redhat.com> Date: Thu Mar 3 09:11:09 2022 +0100 calls: When bypassing emit_push_insn for 0 sized arg, emit at least anti_adjust_stack for alignment pad if needed [PR104558] The following testcase ICEs on x86_64 when asked to use the pre-GCC 8 ABI where zero sized arguments weren't ignored. In GCC 7 the emit_push_insn calls in store_one_arg were unconditional, it is true that they didn't actually push anything because it had zero size, but because arg->locate.alignment_pad is 8 in this case, emit_push_insn at the end performs if (alignment_pad && args_addr == 0) anti_adjust_stack (alignment_pad); and an assert larger on is upset if we don't do it. The following patch keeps the emit_push_insn conditional but calls the anti_adjust_stack when needed by hand for the zero sized arguments. For the new x86_64 ABI where zero sized arguments are ignored arg->locate.alignment_pad is 0 in this case, so nothing changes - we in that case really do ignore it. There is another emit_push_insn call earlier in store_one_arg, also made conditional on non-zero size by Marek in GCC 8, but that one is for arguments with non-BLKmode and the only way those can be zero size is if they are TYPE_EMPTY_P aka when they are completely ignored. But I believe arg->locate.alignment_pad should be 0 in that case, so IMHO there is no need to do anything in the second spot. 2022-03-03 Jakub Jelinek <ja...@redhat.com> PR middle-end/104558 * calls.cc (store_one_arg): When not calling emit_push_insn because size_rtx is const0_rtx, call at least anti_adjust_stack on arg->locate.alignment_pad if !argblock and the alignment might be non-zero. * gcc.dg/pr104558.c: New test.
