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From: "guojiufu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/102131] [12 Regression] wrong code at -O1 and above on x86_64-linux-gnu Date: Thu, 02 Sep 2021 07:14:56 +0000 [thread overview] Message-ID: <bug-102131-4-oqnbFDwYpT@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-102131-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102131 --- Comment #6 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> --- Drafted a patch as below. With this patch, those cases can pass. diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c index 7af92d1c893..a400c42919b 100644 --- a/gcc/tree-ssa-loop-niter.c +++ b/gcc/tree-ssa-loop-niter.c @@ -1866,6 +1866,24 @@ number_of_iterations_cond (class loop *loop, || !iv0->no_overflow || !iv1->no_overflow)) return false; + /* GT/GE has been transformed to LT/LE already. + cmp_code could be LT, LE or NE + + For LE/LT transform + {iv0.base, iv0.step} LT/LE {iv1.base, iv1.step} + to + {iv0.base, iv0.step - iv1.step} LT/LE {iv1.base, 0} + Negative iv0.step - iv1.step means decreasing until wrap, + then the transform is not accurate. + + For example: + {1, +, 1} <= {4, +, 3} + is not same with + {1, +, -2} <= {4, +, 0} + */ + if ((code == LE_EXPR || code == LT_EXPR) && tree_int_cst_sign_bit (step)) + return false; + iv0->step = step; if (!POINTER_TYPE_P (type)) iv0->no_overflow = false;
next prev parent reply other threads:[~2021-09-02 7:14 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-30 17:12 [Bug tree-optimization/102131] New: " zhendong.su at inf dot ethz.ch 2021-08-30 18:13 ` [Bug tree-optimization/102131] [12 Regression] " jakub at gcc dot gnu.org 2021-08-31 6:34 ` guojiufu at gcc dot gnu.org 2021-08-31 9:51 ` guojiufu at gcc dot gnu.org 2021-08-31 10:34 ` amker at gcc dot gnu.org 2021-09-01 9:23 ` guojiufu at gcc dot gnu.org 2021-09-02 7:14 ` guojiufu at gcc dot gnu.org [this message] 2021-11-15 17:04 ` [Bug tree-optimization/102131] [12 Regression] wrong code at -O1 and above on x86_64-linux-gnu since r12-3136 jakub at gcc dot gnu.org 2021-11-16 2:01 ` guojiufu at gcc dot gnu.org 2021-12-15 10:18 ` zhendong.su at inf dot ethz.ch 2022-01-24 10:43 ` rguenth at gcc dot gnu.org 2022-01-24 12:15 ` cvs-commit at gcc dot gnu.org 2022-01-24 12:48 ` rguenth at gcc dot gnu.org 2022-01-25 1:28 ` crazylht at gmail dot com
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