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From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug regression/40886] [4.3/4.4/4.5 Regression] No loop counter reversal for simple loops anymore Date: Tue, 28 Jul 2009 11:09:00 -0000 [thread overview] Message-ID: <20090728110927.27900.qmail@sourceware.org> (raw) In-Reply-To: <bug-40886-7834@http.gcc.gnu.org/bugzilla/> ------- Comment #1 from rguenth at gcc dot gnu dot org 2009-07-28 11:09 ------- The tree optimizers canonicalize the loop to <bb 3>: # i_5 = PHI <i_3(4), 0(2)> # ivtmp.23_1 = PHI <ivtmp.23_4(4), 10(2)> f2 (); i_3 = i_5 + 1; ivtmp.23_4 = ivtmp.23_1 - 1; if (ivtmp.23_4 != 0) goto <bb 4>; else goto <bb 5>; <bb 4>: goto <bb 3>; But then IVOPTs chooses i as the induction variable again. Maybe a DCE pass before IVOPTs magically would solve the regression - or simply do not consider candidates without uses? -- rguenth at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |rakdver at gcc dot gnu dot | |org Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Keywords| |missed-optimization Known to fail| |4.0.0 Known to work| |3.4.6 Last reconfirmed|0000-00-00 00:00:00 |2009-07-28 11:09:27 date| | Summary|No loop counter reversal for|[4.3/4.4/4.5 Regression] No |simple loops anymore |loop counter reversal for | |simple loops anymore Target Milestone|--- |4.3.4 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40886
next prev parent reply other threads:[~2009-07-28 11:09 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-07-27 21:40 [Bug regression/40886] New: " andi-gcc at firstfloor dot org 2009-07-28 11:09 ` rguenth at gcc dot gnu dot org [this message] 2009-08-04 12:49 ` [Bug regression/40886] [4.3/4.4/4.5 Regression] " rguenth at gcc dot gnu dot org 2009-08-07 8:44 ` rakdver at gcc dot gnu dot org 2009-08-07 8:50 ` andi-gcc at firstfloor dot org 2009-08-07 8:54 ` rakdver at kam dot mff dot cuni dot cz 2009-08-07 9:39 ` andi-gcc at firstfloor dot org 2009-08-07 9:47 ` steven at gcc dot gnu dot org 2009-08-07 9:52 ` andi-gcc at firstfloor dot org 2009-08-16 21:42 ` rguenth at gcc dot gnu dot org 2010-02-09 4:57 ` spop at gcc dot gnu dot org 2010-02-09 6:00 ` spop at gcc dot gnu dot org 2010-02-09 8:30 ` rakdver at kam dot mff dot cuni dot cz 2010-02-09 17:17 ` spop at gcc dot gnu dot org 2010-02-11 15:46 ` spop at gcc dot gnu dot org 2010-02-11 15:47 ` [Bug regression/40886] [4.3/4.4 " spop at gcc dot gnu dot org 2010-05-22 18:33 ` rguenth at gcc dot gnu dot org 2010-06-09 11:21 ` andi-gcc at firstfloor dot org 2010-06-09 11:57 ` rguenth at gcc dot gnu dot org
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