[Bug tree-optimization/21559] [4.1 Regression] missed jump threading

[Bug tree-optimization/21559] [4.1 Regression] missed jump threading

[pinskia at gcc dot gnu dot org]

------- Comment #5 from pinskia at gcc dot gnu dot org  2005-10-27 00:12 -------
I should note that this is a true code gen regression and not just a missed one
at the tree level.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559

[Bug tree-optimization/21559] [4.1 Regression] missed jump threading

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2005-10-29 18:09 -------
Another one of these I filed this bug after looking at someone else's bug for
code gen regressions.


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.0                       |4.2.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559

[Bug tree-optimization/21559] [4.1 Regression] missed jump threading

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P2                          |P5
   Target Milestone|4.2.0                       |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559

[Bug tree-optimization/21559] [4.1/4.2 Regression] missed jump threading

[law at redhat dot com]

------- Comment #7 from law at redhat dot com  2006-02-07 20:03 -------
With today's changes we thread the "break" edge out of the loop.  We could
still do better.

Basically we need to realize that bytes can never have the value zero when we
hit the loop test "while (toread != 0)".  Once we realize that, then we'd know
that the test (if bytes == 0) has a known result on all paths reaching the
conditional.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559

[Bug tree-optimization/21559] [4.1/4.2 Regression] missed jump threading

[mmitchel at gcc dot gnu dot org]

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mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.0                       |4.1.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559

[Bug tree-optimization/21559] [4.1/4.2 Regression] missed jump threading

[mmitchel at gcc dot gnu dot org]

------- Comment #8 from mmitchel at gcc dot gnu dot org  2006-05-25 02:36 -------
Will not be fixed in 4.1.1; adjust target milestone to 4.1.2.


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mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.1                       |4.1.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559

[Bug tree-optimization/21559] [4.1/4.2/4.3 Regression] missed jump threading

[mmitchel at gcc dot gnu dot org]

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mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.2                       |4.1.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559

[Bug tree-optimization/21559] [4.2/4.3/4.4 Regression] missed jump threading

[jsm28 at gcc dot gnu dot org]

------- Comment #9 from jsm28 at gcc dot gnu dot org  2008-07-04 16:53 -------
Closing 4.1 branch.


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jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.1/4.2/4.3/4.4 Regression]|[4.2/4.3/4.4 Regression]
                   |missed jump threading       |missed jump threading
   Target Milestone|4.1.3                       |4.2.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559

[Bug tree-optimization/21559] [4.2/4.3/4.4 Regression] missed jump threading

[steven at gcc dot gnu dot org]

------- Comment #10 from steven at gcc dot gnu dot org  2008-11-22 11:36 -------
Trunk today generates the following code (this is the final_cleanup dump):

;; Function foo (foo)

foo ()
{
  static char eof_reached = 0;
  int bytes;
  int toread;

<bb 2>:
  toread = 4096;

<bb 3>:
  bytes = bar (toread);
  if (bytes <= 0)
    goto <bb 4>;
  else
    goto <bb 5>;

<bb 4>:
  if (bytes != 0)
    goto <bb 6>;
  else
    goto <bb 7>;

<bb 5>:
  toread = toread - bytes;

<bb 6>:
  if (toread != 0)
    goto <bb 3>;
  else
    goto <bb 8>;

<bb 7>:
  eof_reached = 1;

<bb 8>:
  return;

}


Looks like we can't do any better than that -- can we??


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559

[Bug tree-optimization/21559] [4.2/4.3 Regression] missed jump threading

[rguenth at gcc dot gnu dot org]

------- Comment #11 from rguenth at gcc dot gnu dot org  2008-11-22 15:47 -------
I don't see how.  Fixed thus, WONTFIX on the branches.


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
      Known to fail|4.3.0 4.2.0                 |4.3.2 4.2.4
         Resolution|                            |FIXED
   Target Milestone|4.2.5                       |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559