[Bug tree-optimization/23622] Dom jump threading at -O1 confuses branch prediction

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23622

Jeffrey A. Law  changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 CC||law at redhat dot com
 Resolution|--- |FIXED

--- Comment #5 from Jeffrey A. Law  ---
AFAICT this works fine in the 4.9 trunk.

[Bug tree-optimization/23622] Dom jump threading at -O1 confuses branch prediction

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-15 
19:28 ---
Confirmed.

-- 
   What|Removed |Added

 Status|UNCONFIRMED |NEW
 Ever Confirmed||1
   Last reconfirmed|-00-00 00:00:00 |2005-09-15 19:28:17
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23622

[Bug tree-optimization/23622] Dom jump threading at -O1 confuses branch prediction

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-29 
12:57 ---
Hmm, in dom1 we get:
:
  goto  ();

  # i_4 = PHI ;
:;
  something ();
  i_3 = i_4 + 1;

  # i_1 = PHI ;
:;
  if (i_1 <= 99) goto ; else goto ;

:;
  return;

  # i_2 = PHI <0(0)>;
:;
  goto  ();

In PHI-OPT we get:
  # i_4 = PHI ;
:;
  something ();
  i_3 = i_4 + 1;
  if (i_3 <= 99) goto ; else goto ;

Becuase we run a cfg cleanup.  I don't see anything wrong here now.

This is the same for -O2 also.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23622

[Bug tree-optimization/23622] Dom jump threading at -O1 confuses branch prediction

[rakdver at gcc dot gnu dot org]

--- Additional Comments From rakdver at gcc dot gnu dot org  2005-08-29 
13:18 ---
Sorry, I have simplified the testcase and only looked at the dom1 dump.  You
need the following testcase to reproduce the problem (for the second loop):

void foo (void)
{
  int i;

  for (i = 0; i < 100; i++)
something ();
  for (i = 0; i < 100; i++)
something ();
}

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23622

[Bug tree-optimization/23622] Dom jump threading at -O1 confuses branch prediction

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-29 
16:20 ---
If we run CCP right after DOM and do a DCE, we get a cleaned up loops.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23622