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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/110052] useless local variable not optimized away Date: Wed, 31 May 2023 08:51:35 +0000 [thread overview] Message-ID: <bug-110052-4-pUfqR2PC5M@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-110052-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110052 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |WAITING Last reconfirmed| |2023-05-31 Ever confirmed|0 |1 --- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- /* This is the original code, the local variable is superfluous */ int size = foo->size; if (!m) m = myrealloc(m, 256, &size); foo->size = size; I'm not sure we are allowed to change the &size argument to &foo->size since it's observable whether the argument is equal to &foo->size or not since 'foo' is global and myrealloc could have access to it and also clobber it. Consider myrealloc(..., int *size) { *size = 4; foo->size = 0; } if 'foo' were global. Can you make the testcase avoid these considerations? I think we have no pass doing this kind of transform. Maybe sth along int size1, size2; foo (&size1); size2 = size1; bar (&size2); of course since size1 escapes to foo() bar() might do the same as myrealloc above and it would break passing &size1 to bar().
next prev parent reply other threads:[~2023-05-31 8:51 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-31 8:06 [Bug middle-end/110052] New: " aldot at gcc dot gnu.org 2023-05-31 8:31 ` [Bug middle-end/110052] " amonakov at gcc dot gnu.org 2023-05-31 8:51 ` rguenth at gcc dot gnu.org [this message] 2023-05-31 18:12 ` aldot at gcc dot gnu.org 2023-05-31 18:24 ` aldot at gcc dot gnu.org 2023-06-01 12:48 ` amonakov at gcc dot gnu.org
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