The new force_nonfallthru was modelled on redirect_edge_and_branch_force, but this means that it is doing superfluous work when the edge can be turned into a non-fallthru edge without creating a new basic block.
Fixed thusly, bootstrapped/regested on x86_64-suse-linux, applied. 2011-04-11 Eric Botcazou <ebotca...@adacore.com> * cfghooks.c (redirect_edge_and_branch_force): Localize variable. (force_nonfallthru): Do not alter the loop nest if no basic block was created. -- Eric Botcazou
Index: cfghooks.c =================================================================== --- cfghooks.c (revision 172247) +++ cfghooks.c (working copy) @@ -388,7 +388,6 @@ basic_block redirect_edge_and_branch_force (edge e, basic_block dest) { basic_block ret, src = e->src; - struct loop *loop; if (!cfg_hooks->redirect_edge_and_branch_force) internal_error ("%s does not support redirect_edge_and_branch_force", @@ -398,6 +397,7 @@ redirect_edge_and_branch_force (edge e, rescan_loop_exit (e, false, true); ret = cfg_hooks->redirect_edge_and_branch_force (e, dest); + if (ret != NULL && dom_info_available_p (CDI_DOMINATORS)) set_immediate_dominator (CDI_DOMINATORS, ret, src); @@ -405,8 +405,9 @@ redirect_edge_and_branch_force (edge e, { if (ret != NULL) { - loop = find_common_loop (single_pred (ret)->loop_father, - single_succ (ret)->loop_father); + struct loop *loop + = find_common_loop (single_pred (ret)->loop_father, + single_succ (ret)->loop_father); add_bb_to_loop (ret, loop); } else if (find_edge (src, dest) == e) @@ -882,30 +883,26 @@ tidy_fallthru_edges (void) basic_block force_nonfallthru (edge e) { - basic_block ret, src = e->src, dest = e->dest; - struct loop *loop; + basic_block ret, src = e->src; if (!cfg_hooks->force_nonfallthru) internal_error ("%s does not support force_nonfallthru", cfg_hooks->name); - if (current_loops != NULL) - rescan_loop_exit (e, false, true); - ret = cfg_hooks->force_nonfallthru (e); - if (ret != NULL && dom_info_available_p (CDI_DOMINATORS)) - set_immediate_dominator (CDI_DOMINATORS, ret, src); - - if (current_loops != NULL) + if (ret != NULL) { - if (ret != NULL) + if (dom_info_available_p (CDI_DOMINATORS)) + set_immediate_dominator (CDI_DOMINATORS, ret, src); + + if (current_loops != NULL) { - loop = find_common_loop (single_pred (ret)->loop_father, - single_succ (ret)->loop_father); + struct loop *loop + = find_common_loop (single_pred (ret)->loop_father, + single_succ (ret)->loop_father); + rescan_loop_exit (e, false, true); add_bb_to_loop (ret, loop); } - else if (find_edge (src, dest) == e) - rescan_loop_exit (e, true, false); } return ret;