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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/49419] [4.6/4.7 regression] gcc -O2 miscompiles gp2c
Date: Wed, 15 Jun 2011 12:19:00 -0000	[thread overview]
Message-ID: <bug-49419-4-EpSsOVh12N@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-49419-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49419

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-06-15 12:19:00 UTC ---
So, i_47 which is the i value on entry of the second loop is determined to be
[0, +INF(OVF)] and something goes wrong afterwards.  The bug will be there, but
I should note that VRP should easily prove that i never overflows.
Simpler testcases for that:
void bar (void);

void foo (int x, int y)
{
  if (x < y)
    {
      if (x == __INT_MAX__)
        bar ();
    }
}

void baz (int x, int y, int z)
{
  if (x < y || x < z)
    {
      if (x == __INT_MAX__)
        bar ();
    }
}

Here IMNSHO vrp should optimize the call to bar away, as when x is smaller than
some variable of the same type, it can't be the maximum of that type, because
even if the other number is __INT_MAX__, x must be smaller than that.


  parent reply	other threads:[~2011-06-15 12:19 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-15 11:11 [Bug target/49419] New: " doko at ubuntu dot com
2011-06-15 11:41 ` [Bug target/49419] " rguenth at gcc dot gnu.org
2011-06-15 11:55 ` mikpe at it dot uu.se
2011-06-15 11:56 ` jakub at gcc dot gnu.org
2011-06-15 12:19 ` jakub at gcc dot gnu.org [this message]
2011-06-15 12:30 ` jakub at gcc dot gnu.org
2011-06-15 15:00 ` jakub at gcc dot gnu.org
2011-06-15 16:04 ` [Bug tree-optimization/49419] " jakub at gcc dot gnu.org
2011-06-16  7:46 ` jakub at gcc dot gnu.org
2011-06-16  7:55 ` jakub at gcc dot gnu.org
2011-06-16  8:19 ` jakub at gcc dot gnu.org
2011-06-16 18:19 ` jakub at gcc dot gnu.org

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