I am testing the following to fix PR81053. Bootstrap and regtest running on x86_64-unknown-linux-gnu.
Richard. 2017-06-12 Richard Biener <rguent...@suse.de> PR tree-optimization/81053 * tree-vect-loop.c (vect_is_simple_reduction): Handle PHI with backedge value not defined in loop. Simplify def stmt compute. * gcc.dg/torture/pr81053.c: New testcase. Index: gcc/tree-vect-loop.c =================================================================== --- gcc/tree-vect-loop.c (revision 249112) +++ gcc/tree-vect-loop.c (working copy) @@ -2790,15 +2790,17 @@ vect_is_simple_reduction (loop_vec_info } def_stmt = SSA_NAME_DEF_STMT (loop_arg); - if (gimple_nop_p (def_stmt)) + if (is_gimple_assign (def_stmt)) { - if (dump_enabled_p ()) - dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location, - "reduction: no def_stmt\n"); - return NULL; + name = gimple_assign_lhs (def_stmt); + phi_def = false; } - - if (!is_gimple_assign (def_stmt) && gimple_code (def_stmt) != GIMPLE_PHI) + else if (gimple_code (def_stmt) == GIMPLE_PHI) + { + name = PHI_RESULT (def_stmt); + phi_def = true; + } + else { if (dump_enabled_p ()) { @@ -2809,37 +2811,27 @@ vect_is_simple_reduction (loop_vec_info return NULL; } - if (is_gimple_assign (def_stmt)) - { - name = gimple_assign_lhs (def_stmt); - phi_def = false; - } - else - { - name = PHI_RESULT (def_stmt); - phi_def = true; - } - nloop_uses = 0; auto_vec<gphi *, 3> lcphis; - FOR_EACH_IMM_USE_FAST (use_p, imm_iter, name) - { - gimple *use_stmt = USE_STMT (use_p); - if (is_gimple_debug (use_stmt)) - continue; - if (flow_bb_inside_loop_p (loop, gimple_bb (use_stmt))) - nloop_uses++; - else - /* We can have more than one loop-closed PHI. */ - lcphis.safe_push (as_a <gphi *> (use_stmt)); - if (nloop_uses > 1) - { - if (dump_enabled_p ()) - dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location, - "reduction used in loop.\n"); - return NULL; - } - } + if (flow_bb_inside_loop_p (loop, gimple_bb (def_stmt))) + FOR_EACH_IMM_USE_FAST (use_p, imm_iter, name) + { + gimple *use_stmt = USE_STMT (use_p); + if (is_gimple_debug (use_stmt)) + continue; + if (flow_bb_inside_loop_p (loop, gimple_bb (use_stmt))) + nloop_uses++; + else + /* We can have more than one loop-closed PHI. */ + lcphis.safe_push (as_a <gphi *> (use_stmt)); + if (nloop_uses > 1) + { + if (dump_enabled_p ()) + dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location, + "reduction used in loop.\n"); + return NULL; + } + } /* If DEF_STMT is a phi node itself, we expect it to have a single argument defined in the inner loop. */ Index: gcc/testsuite/gcc.dg/torture/pr81053.c =================================================================== --- gcc/testsuite/gcc.dg/torture/pr81053.c (revision 0) +++ gcc/testsuite/gcc.dg/torture/pr81053.c (working copy) @@ -0,0 +1,12 @@ +/* { dg-do compile } */ + +int a, b[2], c, d; + +void fn1 () +{ + for (; d < 2; d++) + { + b[d] = a; + a = c; + } +}