https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94468
--- Comment #6 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:bab8d9625f4cdeaf9bb45e28ab62abe47c3827f9 commit r10-7551-gbab8d9625f4cdeaf9bb45e28ab62abe47c3827f9 Author: Jakub Jelinek <ja...@redhat.com> Date: Sat Apr 4 10:32:41 2020 +0200 cselib: Don't consider SP_DERIVED_VALUE_P values as useless [PR94468] The following testcase ICEs, because at one point we see the SP_DERIVED_VALUE_P VALUE as useless (not PRESERVED_VALUE_P and no locs) and so expect it to be discarded as useless. But, later on we are adding some new VALUE that is equivalent to it, and when adding the equivalency that that new VALUE is equal to this SP_DERIVED_VALUE_P, new_elt_loc_list has code for VALUE canonicalization and reverses addition if uid is smaller, and at that point a new loc is added to the SP_DERIVED_VALUE_P VALUE and it isn't discarded as useless anymore. Now, I think we don't want to discard the SP_DERIVED_VALUE_P values even if they have no locs, because they still have the special behaviour that they then force other new VALUEs to be canonicalized against them, which is what this patch implements. I've not set PRESERVED_VALUE_P on the SP_DERIVED_VALUE_P at the creation time, because whether a VALUE is preserved or not is something that affects var-tracking decisions quite a lot and we shouldn't set it blindly on other VALUEs. Or, to avoid the repetitive code, should I introduce static bool cselib_useless_value_p (cselib_val *v) { return (v->locs == 0 && !PRESERVED_VALUE_P (v->val_rtx) && !SP_DERIVED_VALUE_P (v->val_rtx))); } predicate and use it in those 6 spots? 2020-04-04 Jakub Jelinek <ja...@redhat.com> PR rtl-optimization/94468 * cselib.c (references_value_p): Formatting fix. (cselib_useless_value_p): New function. (discard_useless_locs, discard_useless_values, cselib_invalidate_regno_val, cselib_invalidate_mem, cselib_record_set): Use it instead of v->locs == 0 && !PRESERVED_VALUE_P (v->val_rtx). * g++.dg/opt/pr94468.C: New test.
