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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/59193] Unused postfix operator temporaries Date: Wed, 19 Feb 2014 09:58:00 -0000 [thread overview] Message-ID: <bug-59193-4-aemWNHhYDG@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-59193-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59193 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|REOPENED |RESOLVED Resolution|--- |INVALID --- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Take: int f(int a) { a++; return a; } int g(int a) { ++a; return a; } ------------------- CUT ------------------- The gimplifier produces the exact same IR for both cases: f (int a) { int D.1790; a = a + 1; D.1790 = a; return D.1790; } g (int a) { int D.1792; a = a + 1; D.1792 = a; return D.1792; } ------------------- CUT ------------------- So the compiler is already smart enough to remove the "temporary storage" even at -O0. With: int f(int a) { int b = a++; return a; } It does not remove it but that is because the result of a++ is not unused. So it is the gimplifier knows if the result is unused and will not use them otherwise. This is the same issue as memcpy and its return value.
next prev parent reply other threads:[~2014-02-19 9:58 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <bug-59193-4@http.gcc.gnu.org/bugzilla/> 2013-11-19 16:41 ` joseph at codesourcery dot com 2013-11-20 0:59 ` pinskia at gcc dot gnu.org 2014-02-05 9:07 ` mpolacek at gcc dot gnu.org 2014-02-12 19:22 ` mtewoodbury at gmail dot com 2014-02-12 19:30 ` pinskia at gcc dot gnu.org 2014-02-19 6:15 ` mtewoodbury at gmail dot com 2014-02-19 9:58 ` pinskia at gcc dot gnu.org [this message] 2014-02-19 10:18 ` jakub at gcc dot gnu.org 2014-02-20 2:48 ` mtewoodbury at gmail dot com 2014-02-20 6:15 ` pinskia at gcc dot gnu.org 2014-02-22 2:03 ` mtewoodbury at gmail dot com 2014-02-22 4:19 ` pinskia at gcc dot gnu.org 2014-02-22 11:10 ` mtewoodbury at gmail dot com 2014-06-25 11:27 ` mpolacek at gcc dot gnu.org
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