https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119491
--- Comment #6 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:8ea537988f718f026d94b558e09479c3b5fe088a commit r15-9154-g8ea537988f718f026d94b558e09479c3b5fe088a Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Apr 2 20:02:34 2025 +0200 tailc: Deal with trivially useless EH cleanups [PR119491] The following testcases FAIL, because EH cleanup is performed only before IPA and then right before musttail pass. At -O2 etc. (except for -O0/-Og) we handle musttail calls in the tailc pass though, and we can fail at that point because the calls might appear to throw internal exceptions which just don't do anything interesting (perhaps have debug statements or clobber statements in them) before they continue with resume of the exception (i.e. throw it externally). As Richi said in the PR (and I agree) that moving passes is risky at this point, the following patch instead teaches the tail{r,c} and musttail passes to deal with such extra EDGE_EH edges. It is fairly simple thing, if we see an EDGE_EH edge from the call we just look up where it lands and if there are no non-debug/non-clobber/non-label statements before resx which throws externally, such edge can be ignored for tail call optimization or tail recursion. At other spots I just need to avoid using single_succ/single_succ_edge because the bb might have another edge - EDGE_EH. To make this less risky, this is done solely for the musttail calls for now. 2025-04-02 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/119491 * tree-tailcall.cc (single_non_eh_succ_edge): New function. (independent_of_stmt_p): Use single_non_eh_succ_edge (bb)->dest instead of single_succ (bb). (empty_eh_cleanup): New function. (find_tail_calls): Diagnose throwing of exceptions which do not propagate only if there are no EDGE_EH successor edges. If there are and the call is musttail, use empty_eh_cleanup to find if the cleanup is not empty. If not or the call is not musttail, use different diagnostics. Set is_noreturn even if there are successor edges. Use single_non_eh_succ_edge (abb) instead of single_succ_edge (abb). Punt on internal noreturn calls. (decrease_profile): Don't assert 0 or 1 successor edges. (eliminate_tail_call): Use single_non_eh_succ_edge (gsi_bb (t->call_gsi)) instead of single_succ_edge (gsi_bb (t->call_gsi)). (tree_optimize_tail_calls_1): Also look into basic blocks with single succ edge which is EDGE_EH for noreturn musttail calls. * g++.dg/opt/musttail3.C: New test. * g++.dg/opt/musttail4.C: New test. * g++.dg/opt/musttail5.C: New test.
