[Bug optimization/15357] New: [tree-ssa] combing if statements

[Bug optimization/15357] New: [tree-ssa] combing if statements

[pinskia at gcc dot gnu dot org]

The following two functions should give the same asm (If the branch cost is high 
enough):
int g(void);
int h(int a, int b, int c, int d)
{
  if (a==b)
   if (c==d)
     return g();
  return 0;
}
int h1(int a, int b, int c, int d)
{
  if (a==b && c==d)
    return g();
  return 0;
}

And these two:
int j(int a, int b, int c, int d)
{
  if (a==b)
   goto a;
  if (c==d)
   goto a;
  else
   goto b;
a:
  return g();
b:
  return 0;
}
int j1(int a, int b, int c, int d)
{
  if (a==b || c==d)
    return g();
  return 0;
}

-- 
           Summary: [tree-ssa] combing if statements
           Product: gcc
           Version: tree-ssa
            Status: UNCONFIRMED
          Keywords: pessimizes-code, memory-hog, compile-time-hog
          Severity: enhancement
          Priority: P2
         Component: optimization
        AssignedTo: pinskia at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
OtherBugsDependingO 15241,15348,15352
             nThis:


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15357

[Bug optimization/15357] [tree-ssa] combing if statements

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-09 22:20 -------
Mine I am working on this, then we should be able to removed this optimization in fold 
which causes this to happen in the one statement one.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-05-09 22:20:20
               date|                            |
   Target Milestone|---                         |tree-ssa


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15357

[Bug tree-optimization/15357] [tree-ssa] combing if statements

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.5.0                       |---


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15357

[Bug tree-optimization/15357] [tree-ssa] combing if statements

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-08 18:17 -------
I lost the code which I was using to do this so I am no longer working on this.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|pinskia at gcc dot gnu dot  |unassigned at gcc dot gnu
                   |org                         |dot org
             Status|ASSIGNED                    |NEW


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15357

[Bug tree-optimization/15357] [tree-ssa] combing if statements

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2007-01-26 13:44 -------
Another thing we should be able to do is combine bit-tests like

 if (a & (1 << b))
   if (a & (1 << c))
     ...

to a single test

 if (a & ((1 << b) | (1 << c)) == ((1 << b) | (1 << c)))
   ...


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15357

[Bug tree-optimization/15357] [tree-ssa] combing if statements

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2007-06-12 12:10 -------
The new if-combining pass can be told to make the transformation suggested in
the description.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15357

[Bug tree-optimization/15357] [tree-ssa] combing if statements

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15357

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |pinskia at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-01-21 22:02:24 UTC ---
I have a patch which implements this.  I will be posting it for 4.8.

[Bug tree-optimization/15357] [tree-ssa] combing if statements

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15357

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |4.9.0

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed by:
2013-10-29  Andrew Pinski <apinski@cavium.com>

        * tree-ssa-ifcombine.c: Include rtl.h and tm_p.h.
        (ifcombine_ifandif): Handle cases where maybe_fold_and_comparisons
        fails, combining the branches anyways.
        (tree_ssa_ifcombine): Inverse the order of the basic block walk,
        increases the number of combinings.
        * gimple.h (gsi_start_nondebug_after_labels_bb): New function.