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From: "bmei at broadcom dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/59651] Vectorizer failing to spot dependence causes incorrect code generation. Date: Tue, 31 Dec 2013 16:53:00 -0000 [thread overview] Message-ID: <bug-59651-4-MVZdjlHTzG@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-59651-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59651 --- Comment #1 from Bingfeng Mei <bmei at broadcom dot com> --- That is interesting. On x86-64, GCC does say it cannot determine dist vector between a[3] & a[b] and needs run-time aliasing test. In the end it gives up due to too few iterations. note: === vect_analyze_data_ref_dependences === (compute_affine_dependence stmt_a: _5 = a[3]; stmt_b: a[b.0_16] = _7; (analyze_overlapping_iterations (chrec_a = 3) (chrec_b = {3, +, -1}_1) (analyze_siv_subscript ) (overlap_iterations_a = [0]) (overlap_iterations_b = [0])) (Dependence relation cannot be represented by distance vector.) ) (compute_affine_dependence stmt_a: _5 = a[3]; stmt_b: _5 = a[3]; (analyze_overlapping_iterations (chrec_a = 3) (chrec_b = 3) (overlap_iterations_a = [0]) (overlap_iterations_b = [0])) ) (compute_affine_dependence stmt_a: a[b.0_16] = _7; stmt_b: a[b.0_16] = _7; (analyze_overlapping_iterations (chrec_a = {3, +, -1}_1) (chrec_b = {3, +, -1}_1) (overlap_iterations_a = [0]) (overlap_iterations_b = [0])) ) /projects/firepath_tools1_scratch/bmei/trunk/gcc/testsuite/gcc.dg/torture/pr52943.c:13:7: note: versioning for alias required: bad dist vector for a[3] and a[b.0_16] /projects/firepath_tools1_scratch/bmei/trunk/gcc/testsuite/gcc.dg/torture/pr52943.c:13:7: note: mark for run-time aliasing test between a[3] and a[b.0_16]
next prev parent reply other threads:[~2013-12-31 16:53 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-12-31 16:28 [Bug tree-optimization/59651] New: " belagod at gcc dot gnu.org 2013-12-31 16:53 ` bmei at broadcom dot com [this message] 2013-12-31 17:12 ` [Bug tree-optimization/59651] " belagod at gcc dot gnu.org 2013-12-31 21:07 ` [Bug tree-optimization/59651] [4.9 Regression] " pinskia at gcc dot gnu.org 2013-12-31 22:42 ` bmei at broadcom dot com 2014-01-01 18:31 ` belagod at gcc dot gnu.org 2014-01-02 11:04 ` bmei at broadcom dot com 2014-01-02 11:37 ` belagod at gcc dot gnu.org 2014-01-03 10:53 ` belagod at gcc dot gnu.org 2014-01-03 15:41 ` meibf at gcc dot gnu.org 2014-01-04 12:04 ` jakub at gcc dot gnu.org 2014-01-21 14:16 ` mshawcroft at gcc dot gnu.org
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