https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108352
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Richard Biener <rgue...@gcc.gnu.org>: https://gcc.gnu.org/g:7c9f20fcfdc2d8453df88ceb7e693debfcd678c0 commit r13-5103-g7c9f20fcfdc2d8453df88ceb7e693debfcd678c0 Author: Richard Biener <rguent...@suse.de> Date: Wed Jan 11 12:07:16 2023 +0100 tree-optimization/108352 - FSM threads creating irreducible loops The following relaxes a heuristic that prevents creating irreducible loops from FSM threads not covering multi-way branches. Instead of allowing threads that adhere to && (n_insns * (unsigned) param_fsm_scale_path_stmts > (m_path.length () * (unsigned) param_fsm_scale_path_blocks)) with reasoning "We also consider it worth creating an irreducible inner loop if the number of copied statement is low relative to the length of the path -- in that case there's little the traditional loop optimizer would have done anyway, so an irreducible loop is not so bad." that I cannot make much sense of the following patch changes that to only allow those after loop optimization and when they are (scaled) short: && (!(cfun->curr_properties & PROP_loop_opts_done) || (m_n_insns * param_fsm_scale_path_stmts >= param_max_jump_thread_duplication_stmts))) This allows us to get rid of --param fsm-scale-path-blocks which previous to the bisected revision allowed an enlarged path covering the original allowance (but we do not consider that enlarged path now because enlarging it doesn't add any information). PR tree-optimization/108352 * tree-ssa-threadbackward.cc (back_threader_profitability::profitable_path_p): Adjust heuristic that allows non-multi-way branch threads creating irreducible loops. * doc/invoke.texi (--param fsm-scale-path-blocks): Remove. (--param fsm-scale-path-stmts): Adjust. * params.opt (--param=fsm-scale-path-blocks=): Remove. (-param=fsm-scale-path-stmts=): Adjust description. * gcc.dg/tree-ssa/ssa-thread-21.c: New testcase. * gcc.dg/tree-ssa/vrp46.c: Remove --param fsm-scale-path-blocks=1.
