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From: "bernd.edlinger at hotmail dot de" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/57904] [4.9 Regression] Bogus(?) "invokes undefined behavior" warning with Fortran's finalization wrapper (gfortran.dg/class_48.f90) Date: Fri, 20 Dec 2013 09:54:00 -0000 [thread overview] Message-ID: <bug-57904-4-2QDaB0IrLk@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-57904-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57904 --- Comment #13 from Bernd Edlinger <bernd.edlinger at hotmail dot de> --- (In reply to Jakub Jelinek from comment #12) > But you can always create testcases (in C/C++ etc.) that will hit this > warning, so while the FE change is possible, we need to do something either > about the optimization passes in between IPA and cunrolli (copyprop change > Jeff talks about, perhaps only done for that single pass instance and not > others, or all?, guess depending on how expensive it is) or scheduling there > another instance of some other cleanup pass, or deferring the warning > reporting until some cleanup. > Could someone please provide a C test case that generates this warning? maybe something like: int dovar = from; if (dovar <= to) for (;;) { ... if (dovar == to) break; dovar += step; } > For the FE change, I guess most important are benchmark results, doesn't it > slow down important benchmarks? I think the change in the simple DO-loops really makes sense, independent of this warning. It generates the IL code just a bit more like it is done in C: for (dovar=from; dovar <= to; dovar+=step) { ... } => dovar = from; if (dovar <= to) { loop: ... dovar+=step; if (dovar <= to) goto loop; } Therefore the IL is easier to analyze and chances are good that the optimizer performs better. I can't do these benchmarks however. Who could do that for us?
next prev parent reply other threads:[~2013-12-20 9:54 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-07-16 9:05 [Bug fortran/57904] New: " burnus at gcc dot gnu.org 2013-07-23 19:53 ` [Bug fortran/57904] " jamborm at gcc dot gnu.org 2013-08-09 12:53 ` ro at gcc dot gnu.org 2013-08-19 23:03 ` [Bug fortran/57904] [4.9 Regression] " hp at gcc dot gnu.org 2013-08-20 17:40 ` bernd.edlinger at hotmail dot de 2013-10-30 13:13 ` [Bug middle-end/57904] " rguenth at gcc dot gnu.org 2013-11-27 15:55 ` jakub at gcc dot gnu.org 2013-11-27 15:59 ` Joost.VandeVondele at mat dot ethz.ch 2013-12-19 21:32 ` law at redhat dot com 2013-12-20 5:51 ` bernd.edlinger at hotmail dot de 2013-12-20 6:26 ` law at redhat dot com 2013-12-20 7:21 ` dominiq at lps dot ens.fr 2013-12-20 8:36 ` jakub at gcc dot gnu.org 2013-12-20 9:54 ` bernd.edlinger at hotmail dot de [this message] 2013-12-20 19:22 ` law at redhat dot com 2013-12-20 21:56 ` dominiq at lps dot ens.fr 2013-12-20 21:58 ` dominiq at lps dot ens.fr 2013-12-20 22:27 ` law at redhat dot com 2013-12-20 22:28 ` law at redhat dot com 2014-01-17 17:50 ` law at gcc dot gnu.org 2014-01-17 17:51 ` law at redhat dot com
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