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From: "law at redhat dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/61409] [4.9/5 regression] -Wmaybe-uninitialized false-positive with -O2
Date: Fri, 13 Feb 2015 03:34:00 -0000	[thread overview]
Message-ID: <bug-61409-4-5d9odSwFDJ@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-61409-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61409

--- Comment #13 from Jeffrey A. Law <law at redhat dot com> ---
So we don't thread this case because of the limits we place on the number of
statements in the duplicated block.

If --param max-jump-thread-duplication-stmts=16 is added to the command line,
jump threading will kick in creating the pseudo-code I posted in c#11.  For
reference, the default value of that param is 15.

What I don't understand from c#4 is uninit can't simplify this condition:

if (_35 == 4611686018595160064 (.AND.)  (.NOT.) _31 != 5) is false

While we may not know the full condition, does realizing that the (*.NOT.) _31
!= 5 is totally pointless help?


  parent reply	other threads:[~2015-02-13  3:34 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-04  7:40 [Bug c/61409] New: [4.9 " eggert at gnu dot org
2014-06-04  9:29 ` [Bug c/61409] " manu at gcc dot gnu.org
2014-06-04  9:59 ` manu at gcc dot gnu.org
2014-06-04 10:31 ` [Bug middle-end/61409] [4.9/4.10 " rguenth at gcc dot gnu.org
2014-06-04 15:28 ` eggert at gnu dot org
2014-06-04 15:57 ` manu at gcc dot gnu.org
2014-06-25 13:26 ` jakub at gcc dot gnu.org
2014-06-25 13:30 ` jakub at gcc dot gnu.org
2014-06-26 12:45 ` rguenth at gcc dot gnu.org
2014-07-16 13:31 ` jakub at gcc dot gnu.org
2014-10-30 10:43 ` [Bug middle-end/61409] [4.9/5 " jakub at gcc dot gnu.org
2015-02-12 23:04 ` law at redhat dot com
2015-02-12 23:54 ` law at redhat dot com
2015-02-13  2:39 ` law at redhat dot com
2015-02-13  3:34 ` law at redhat dot com [this message]
2015-03-02 19:25 ` manu at gcc dot gnu.org
2015-06-26 20:09 ` [Bug middle-end/61409] [4.9/5/6 " jakub at gcc dot gnu.org
2015-06-26 20:35 ` jakub at gcc dot gnu.org

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