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From: "juzhe.zhong at rivai dot ai" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/109088] GCC does not always vectorize conditional reduction Date: Tue, 26 Sep 2023 12:14:10 +0000 [thread overview] Message-ID: <bug-109088-4-SHc7LaFBS2@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-109088-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109088 --- Comment #6 from JuzheZhong <juzhe.zhong at rivai dot ai> --- After investigations: GCC failed to vectorize reduction with multiple conditional operations: ifcvt dump: # result_20 = PHI <result_9(8), 0(18)> ... _11 = result_20 + 10; result_17 = _4 + _11; _23 = _4 > _7; result_9 = _23 ? result_17 : result_20; It's odd that GCC failed to vectorize it since they are not complicate statements. In LLVM, it will vectorize them into: vector_ssa_2 = <vector_ssa_result, 0> ... vector_ssa_1 = vector_ssa_2 + 10; vector_ssa_3 = vector_ssa_1 + 10; mask_ssa_1 = vector_ssa_4 > vector_ssa_5; vector_ssa_result = select <mask_ssa_1, vector_ssa_3, vector_ssa_2> I think GCC should be able to vectorize it like LLVM: vector_ssa_2 = <vector_ssa_result, 0> ... vector_ssa_1 = vector_ssa_2 + 10; vector_ssa_3 = vector_ssa_1 + 10; mask_ssa_1 = vector_ssa_4 > vector_ssa_5; vector_ssa_result = VCOND_MASK <mask_ssa_1, vector_ssa_3, vector_ssa_2> I saw this code disable the vectorization: else if (!bbs.is_empty () && bb->loop_father->header == bb && bb->loop_father->dont_vectorize) { if (dump_enabled_p ()) dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location, "splitting region at dont-vectorize loop %d " "entry at bb%d\n", bb->loop_father->num, bb->index); split = true; } I am not familiar with these codes, any ideas ? Thanks.
next prev parent reply other threads:[~2023-09-26 12:14 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-03-10 9:24 [Bug c/109088] New: GCC fail auto-vectorization juzhe.zhong at rivai dot ai 2023-03-10 10:39 ` [Bug c/109088] " ubizjak at gmail dot com 2023-03-10 12:39 ` [Bug tree-optimization/109088] " rguenth at gcc dot gnu.org 2023-03-10 13:16 ` juzhe.zhong at rivai dot ai 2023-03-10 14:04 ` pinskia at gcc dot gnu.org 2023-03-10 14:09 ` [Bug tree-optimization/109088] GCC does not always vectorize conditional reduction pinskia at gcc dot gnu.org 2023-09-26 12:14 ` juzhe.zhong at rivai dot ai [this message] 2023-09-27 2:45 ` juzhe.zhong at rivai dot ai 2023-09-27 2:58 ` juzhe.zhong at rivai dot ai 2023-09-27 7:15 ` rguenth at gcc dot gnu.org 2023-09-27 7:34 ` juzhe.zhong at rivai dot ai 2023-09-27 9:06 ` rguenth at gcc dot gnu.org 2023-09-27 9:27 ` juzhe.zhong at rivai dot ai 2023-09-27 14:11 ` juzhe.zhong at rivai dot ai 2023-10-06 9:44 ` rguenth at gcc dot gnu.org 2023-11-10 12:02 ` juzhe.zhong at rivai dot ai 2023-11-10 13:10 ` rguenth at gcc dot gnu.org 2023-11-10 13:42 ` juzhe.zhong at rivai dot ai 2023-11-15 14:09 ` rguenth at gcc dot gnu.org 2023-11-15 14:38 ` juzhe.zhong at rivai dot ai 2023-11-15 14:42 ` rguenther at suse dot de 2023-11-16 1:06 ` juzhe.zhong at rivai dot ai 2023-11-16 6:50 ` rguenther at suse dot de
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