https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38534
--- Comment #46 from GCC 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:a307a26e8b392ba65edfdae15489556b7701db81 commit r14-9387-ga307a26e8b392ba65edfdae15489556b7701db81 Author: Jakub Jelinek <ja...@redhat.com> Date: Fri Mar 8 09:18:19 2024 +0100 i386: Guard noreturn no-callee-saved-registers optimization with -mnoreturn-no-callee-saved-registers [PR38534] The following patch hides the noreturn no_callee_saved_registers (except bp) optimization with a not enabled by default option. The reason is that most noreturn functions should be called just once in a program (unless they are recursive or invoke longjmp or similar, for exceptions we already punt), so it isn't that essential to save a few instructions in their prologue, but more importantly because it interferes with debugging. And unlike most other optimizations, doesn't actually make it harder to debug the given function, which can be solved by recompiling the given function if it is too hard to debug, but makes it harder to debug the callers of that noreturn function. Those can be from a different translation unit, different binary or even different package, so if e.g. glibc abort needs to use all of the callee saved registers (%rbx, %rbp, %r12, %r13, %r14, %r15), debugging any programs which abort will be harder because any DWARF expressions which use those registers will be optimized out, not just in the immediate caller, but in other callers as well until some frame restores a particular register from some stack slot. 2024-03-08 Jakub Jelinek <ja...@redhat.com> PR target/38534 * config/i386/i386.opt (mnoreturn-no-callee-saved-registers): New option. * config/i386/i386-options.cc (ix86_set_func_type): Don't use TYPE_NO_CALLEE_SAVED_REGISTERS_EXCEPT_BP unless ix86_noreturn_no_callee_saved_registers is enabled. * doc/invoke.texi (-mnoreturn-no-callee-saved-registers): Document. * gcc.target/i386/pr38534-1.c: Add -mnoreturn-no-callee-saved-registers to dg-options. * gcc.target/i386/pr38534-2.c: Likewise. * gcc.target/i386/pr38534-3.c: Likewise. * gcc.target/i386/pr38534-4.c: Likewise. * gcc.target/i386/pr38534-5.c: Likewise. * gcc.target/i386/pr38534-6.c: Likewise. * gcc.target/i386/pr114097-1.c: Likewise. * gcc.target/i386/stack-check-17.c: Likewise.
