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From: Richard Biener <rguenth@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-3406] Avoid PHI - PHI recurrence in vectorization Date: Thu, 20 Oct 2022 10:50:03 +0000 (GMT) [thread overview] Message-ID: <20221020105003.862353851171@sourceware.org> (raw) https://gcc.gnu.org/g:5362b5cc8dba9de70904613fff1d5391a9c087ce commit r13-3406-g5362b5cc8dba9de70904613fff1d5391a9c087ce Author: Richard Biener <rguenther@suse.de> Date: Thu Oct 20 11:04:21 2022 +0200 Avoid PHI - PHI recurrence in vectorization The reported regression of libgomp loop-14.C shows that there isn't generally a good reliable place to insert the permute upfront so the following simply restricts recurrence vectorization to the cases where the latch value isn't defined by a PHI. * tree-vect-loop.cc (vect_phi_first_order_recurrence_p): Disallow latch PHI defs. (vectorizable_recurr): Revert previous change. Diff: --- gcc/tree-vect-loop.cc | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc index 92790bd8095..d5c2bff80be 100644 --- a/gcc/tree-vect-loop.cc +++ b/gcc/tree-vect-loop.cc @@ -543,6 +543,7 @@ vect_phi_first_order_recurrence_p (loop_vec_info loop_vinfo, class loop *loop, tree ldef = PHI_ARG_DEF_FROM_EDGE (phi, latch); if (TREE_CODE (ldef) != SSA_NAME || SSA_NAME_IS_DEFAULT_DEF (ldef) + || is_a <gphi *> (SSA_NAME_DEF_STMT (ldef)) || !flow_bb_inside_loop_p (loop, gimple_bb (SSA_NAME_DEF_STMT (ldef)))) return false; @@ -8486,14 +8487,8 @@ vectorizable_recurr (loop_vec_info loop_vinfo, stmt_vec_info stmt_info, vectorized the latch definition. */ edge le = loop_latch_edge (LOOP_VINFO_LOOP (loop_vinfo)); gimple *latch_def = SSA_NAME_DEF_STMT (PHI_ARG_DEF_FROM_EDGE (phi, le)); - gimple_stmt_iterator gsi2; - if (is_a <gphi *> (latch_def)) - gsi2 = gsi_after_labels (gimple_bb (latch_def)); - else - { - gsi2 = gsi_for_stmt (latch_def); - gsi_next (&gsi2); - } + gimple_stmt_iterator gsi2 = gsi_for_stmt (latch_def); + gsi_next (&gsi2); for (unsigned i = 0; i < ncopies; ++i) {
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