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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/65206] Vectorized version of loop is removed. Date: Wed, 25 Feb 2015 15:08:00 -0000 [thread overview] Message-ID: <bug-65206-4-aNY5ml4yda@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-65206-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65206 --- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- We apply versioning for aliasing but compute it as always aliasing in some way, thus the runtime check gets immediately folded and thus the vectorized loop removed: t.c:7:3: note: create runtime check for data references a1[i_16] and *_34 t.c:7:3: note: created 1 versioning for alias checks. t.c:7:3: note: loop versioned for vectorization because of possible aliasing ... but I see the alias runtime check nowhere. The DRs are (gdb) p debug_data_reference (dr_a.dr) #(Data Ref: # bb: 4 # stmt: _5 = a1[i_16]; # ref: a1[i_16]; # base_object: a1; # Access function 0: {0, +, 1}_1 #) $17 = void (gdb) p debug_data_reference (dr_b.dr) #(Data Ref: # bb: 4 # stmt: MASK_STORE (_34, 0B, _ifc__32, _9); # ref: *_34; # base_object: MEM[(float *)&a1]; # Access function 0: {0B, +, 4}_1 #) so maybe the code doing masked loads/stores updates the DRs in a way that will later confuse runtime alias checking. Or for some reason it doesn't update it enough to make data-dependence analysis handle it. Clearly this is a must-dependence (but with known distance), so sth that data dependence analysis should handle and sth that the runtime alias checking isn't handling.
next prev parent reply other threads:[~2015-02-25 14:55 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-02-25 14:50 [Bug tree-optimization/65206] New: " ysrumyan at gmail dot com 2015-02-25 14:55 ` [Bug tree-optimization/65206] " ysrumyan at gmail dot com 2015-02-25 15:08 ` rguenth at gcc dot gnu.org [this message] 2015-02-25 15:11 ` rguenth at gcc dot gnu.org 2015-02-25 15:30 ` rguenth at gcc dot gnu.org 2015-02-25 15:33 ` rguenth at gcc dot gnu.org 2015-02-26 12:15 ` rguenth at gcc dot gnu.org 2015-02-26 12:38 ` rguenth at gcc dot gnu.org 2021-09-08 11:08 ` rguenth at gcc dot gnu.org 2021-09-20 6:51 ` [Bug tree-optimization/65206] vectorized version of loop is removed, dependence analysis fails for *&a[i] vs a[j] cvs-commit at gcc dot gnu.org 2021-09-20 6:51 ` rguenth at gcc dot gnu.org 2022-03-29 12:57 ` rguenth at gcc dot gnu.org
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