[Bug tree-optimization/21031] New: Another missed forward propagation opportunity

[Bug tree-optimization/21031] New: Another missed forward propagation opportunity

[kazu at cs dot umass dot edu]

Consider:

int
foo (int a)
{
  int b = a != 0;
  unsigned char c = b;
  if (c)
    return 1;
  else
    return 0;
}

We end up with code like this:

  b_3 = a_2 != 0;
  c_4 = (unsigned char) b_3;
  if (c_4 != 0) goto <L0>; else goto <L2>;

We want to forward-propagate the preceding two statements into the COND_EXPR
and get

  if (a_2 != 0) goto <L0>; else goto <L2>;

Unlike forward propagation opportunities noted in PR 14754 or PR15558,
this kind of opportunity occurs often in practice.

-- 
           Summary: Another missed forward propagation opportunity
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: kazu at cs dot umass dot edu
        ReportedBy: kazu at cs dot umass dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21031

[Bug tree-optimization/21031] Another missed forward propagation opportunity

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-04-14 20:50 -------
Confirmed, I thought I saw a bug like before.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-04-14 20:50:59
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21031

[Bug tree-optimization/21031] Another missed forward propagation opportunity

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2005-04-15 15:30 -------
Patch posted:
http://gcc.gnu.org/ml/gcc-patches/2005-04/msg01726.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21031

[Bug tree-optimization/21031] Another missed forward propagation opportunity

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-04-15 18:42 -------
Subject: Bug 21031

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	kazu@gcc.gnu.org	2005-04-15 18:42:38

Modified files:
	gcc            : ChangeLog tree-ssa-forwprop.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/gcc.dg/tree-ssa: pr21031.c 

Log message:
	gcc/
	PR tree-optimization/21031
	* tree-ssa-forwprop.c (ssa_name_defined_by_comparison_p): New.
	(forward_propagate_into_cond_1): Call it.  Forward propagate
	integer-integer casts into COND_EXPRs.
	
	testsuite/
	PR tree-optimization/21031
	* gcc.dg/tree-ssa/pr21031.c: New.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.8313&r2=2.8314
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-ssa-forwprop.c.diff?cvsroot=gcc&r1=2.13&r2=2.14
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.5354&r2=1.5355
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/tree-ssa/pr21031.c.diff?cvsroot=gcc&r1=NONE&r2=1.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21031

[Bug tree-optimization/21031] Another missed forward propagation opportunity

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2005-04-15 18:44 -------
Just checked in a patch.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21031

[Bug tree-optimization/21031] Another missed forward propagation opportunity

[pinskia at gcc dot gnu dot org]

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21031