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From: "law at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/102608] New: [12 regression] Recent change to VN causes bogus Wuninitialized warnings & kernel build failures
Date: Tue, 05 Oct 2021 14:51:33 +0000	[thread overview]
Message-ID: <bug-102608-4@http.gcc.gnu.org/bugzilla/> (raw)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102608

            Bug ID: 102608
           Summary: [12 regression] Recent change to VN causes bogus
                    Wuninitialized warnings & kernel build failures
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: law at gcc dot gnu.org
  Target Milestone: ---

Created attachment 51555
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51555&action=edit
Testcase

This change:
55a3be2f5255d69e740d61b2c5aaba1ccbc643b8 is the first bad commit
commit 55a3be2f5255d69e740d61b2c5aaba1ccbc643b8
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Oct 4 10:57:45 2021 +0200

    tree-optimization/102570 - teach VN about internal functions

    We're now using internal functions for a lot of stuff but there's
    still missing VN support out of laziness.  The following instantiates
    support and adds testcases for FRE and PRE (hoisting).

Is causing mips64-linux-gnu and mips64el-linux-gnu kernel build failures due to
a bogus uninitialized warning with the attached file when compiled with -O2
-ftrivial-auto-var-init=zero:

../arch/mips/kernel/cmpxchg.c: In function '__xchg_small':
../arch/mips/kernel/cmpxchg.c:44:36: warning: 'old32' is used uninitialized
[-Wuninitialized]
../arch/mips/kernel/cmpxchg.c:12:6: note: 'old32' was declared here
 __cmpxchg_small
../arch/mips/kernel/cmpxchg.c: In function '__cmpxchg_small':
../arch/mips/kernel/cmpxchg.c:100:36: warning: 'mask' may be used uninitialized
[-Wmaybe-uninitialized]
../arch/mips/kernel/cmpxchg.c:53:6: note: 'mask' was declared here


I haven't tracked this down any further.

             reply	other threads:[~2021-10-05 14:51 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-05 14:51 law at gcc dot gnu.org [this message]
2021-10-05 15:37 ` [Bug tree-optimization/102608] " pinskia at gcc dot gnu.org
2021-10-05 15:38 ` pinskia at gcc dot gnu.org
2021-10-06  8:39 ` rguenth at gcc dot gnu.org
2021-10-07 12:28 ` cvs-commit at gcc dot gnu.org
2021-10-07 12:29 ` rguenth at gcc dot gnu.org

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