https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120424
--- Comment #13 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Alexandre Oliva <aol...@gcc.gnu.org>: https://gcc.gnu.org/g:be547188b632d8c1072341c431af339b7384c4a6 commit r16-1720-gbe547188b632d8c1072341c431af339b7384c4a6 Author: Alexandre Oliva <ol...@adacore.com> Date: Thu Jun 26 21:01:22 2025 -0300 [lra] recompute ranges upon disabling fp2sp elimination [PR120424] If the frame size grows to nonzero, arm_frame_pointer_required may flip to true under -fstack-clash-protection -fnon-call-exceptions, and that may disable the fp2sp elimination part-way through lra. If pseudos had got assigned to the frame pointer register before that, they have to be spilled, and that requires complete live range information. If !lra_reg_spill_p, lra_spill won't have live ranges for such pseudos, and they could end up sharing spill slots with other pseudos whose live ranges actually overlap. This affects at least Ada.Strings.Wide_Superbounded.Super_Insert and .Super_Replace_Slice in libgnat/a-stwisu.adb, when compiled with -O2 -fstack-clash-protection -march=armv7 (implied Thumb2), causing acats-4's cdd2a01 to fail. Recomputing live ranges including registers may renumber and compress points, so we have to recompute the aggregated live ranges for already-assigned spill slots as well. As a safety net, reject empty live ranges when computing slot sharing. for gcc/ChangeLog PR rtl-optimization/120424 * lra-eliminations.cc (lra_update_fp2sp_elimination): Compute complete live ranges and recompute slots' live ranges if needed. * lra-lives.cc (lra_reset_live_range_list): New. (lra_complete_live_ranges): New. * lra-spills.cc (assign_spill_hard_regs): Reject empty live ranges. (add_pseudo_to_slot): Likewise. (lra_recompute_slots_live_ranges): New. * lra-int.h (lra_reset_live_range_list): Declare. (lra_complete_live_ranges): Declare. (lra_recompute_slots_live_ranges): Declare.
