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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/46970] [4.3/4.4/4.5/4.6 Regression] wrong code with -Os -ftree-loop-linear Date: Fri, 17 Dec 2010 16:17:00 -0000 [thread overview] Message-ID: <bug-46970-4-U9ERqbHTr5@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-46970-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46970 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jakub at gcc dot gnu.org --- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2010-12-17 16:17:39 UTC --- I think the bug is in that gcc_loop_to_lambda_loop doesn't record whether the SSA_NAME compared in the exit condition was the induction var or incremented induction var. E.g. on ltrans-3.c testcase we have <bb 5>: # j_25 = PHI <j_15(4), 0(9)> ... j_15 = j_25 + 1; if (N.2_3 > j_15) goto <bb 4>; else goto <bb 6>; and thus the exit condition tests the incremented iv (gcc_loop_to_lambda_loop btw. doesn't bother to check whether the def stmt of the rhs of exit condition here actually increments by step, and doesn't bother to check that step fits into int (so I guess step like 0x100000001ULL would cause trouble). It just records lower bound 0, upper bound N.2_3 - 1 here and step 1. But with -Os -ftree-loop-linear on this testcase we have before ltrans: j_12 = j_2 + 1; <bb 4>: # j_2 = PHI <0(7), j_12(3)> if (j_2 < n_5(D)) goto <bb 3>; else goto <bb 5>; Here similarly it records lower bound 0, upper bound n_5 - 1 and step 1. But there is an important difference in between the two. In the former case we correctly use gimple_cond_set_condition (exitcond, testtype, newupperbound, ivvarinced); but we use it in the second case too, which is wrong.
next prev parent reply other threads:[~2010-12-17 16:17 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2010-12-15 20:11 [Bug tree-optimization/46970] New: " zsojka at seznam dot cz 2010-12-16 0:46 ` [Bug tree-optimization/46970] " hjl.tools at gmail dot com 2010-12-16 0:49 ` hjl.tools at gmail dot com 2010-12-16 0:51 ` hjl.tools at gmail dot com 2010-12-16 14:55 ` rguenth at gcc dot gnu.org 2010-12-17 16:17 ` jakub at gcc dot gnu.org [this message] 2010-12-17 17:14 ` jakub at gcc dot gnu.org 2011-01-03 21:01 ` rguenth at gcc dot gnu.org 2011-01-18 20:58 ` spop at gcc dot gnu.org 2011-01-18 20:59 ` spop at gcc dot gnu.org 2011-01-25 21:27 ` spop at gcc dot gnu.org 2011-01-25 21:54 ` spop at gcc dot gnu.org 2011-02-02 17:54 ` dnovillo at gcc dot gnu.org
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