[Bug optimization/15347] New: [tree-ssa] fold if ("<12ers" + 1 == 0).

[Bug optimization/15347] New: [tree-ssa] fold if ("<12ers" + 1 == 0).

[kazu at cs dot umass dot edu]

void bar ();

int
foo (void)
{
  if ("<12ers" + 1 == 0)
    bar ();
}

which is reduced from from

extern const char tree_code_type[];

extern char *strchr (__const char *__s, int __c) __attribute__ ((__pure__));

extern void abort (void) __attribute__ ((__noreturn__));

int
foo (int a)
{
  if (tree_code_type[a] == '1')
    if (strchr ("<12ers", tree_code_type[a]) == 0)
      abort ();
}

which is in turn reduced from find_base_decl() in alias.c.

-- 
           Summary: [tree-ssa] fold if ("<12ers" + 1 == 0).
           Product: gcc
           Version: tree-ssa
            Status: UNCONFIRMED
          Keywords: pessimizes-code
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        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=15347

[Bug optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-09 19:41 -------
I think the two test cases are not related at all, the second one only needs to fold strchr ("<12ers", '1' ) 
to 1 (which it does when expanding to RTL).  There are two problems with the first testcase, first 
"<12ers" + 1 == 0 is "folded" to "<12ers" == -1 by fold, and but if you add a tempary variable then "< 
12ers" + 1 == 0 is not folded to false.  Confirmed otherwise, the orginal testcase is not done on the 
RTL level but the other two are.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |TREE
   Last reconfirmed|0000-00-00 00:00:00         |2004-05-09 19:41:05
               date|                            |
   Target Milestone|---                         |tree-ssa


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

[Bug optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2004-05-09 20:15 -------
Andrew, I forgot to say that the first testcase can be obtained more or less
if you use Steven's strchr optimization patch.
IIRC, His strchr optimization happens in CCP, so
fold does not get to fold "<12ers" + 1 == 0 into false.

In any case, all the stupidity in this area should go away.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

[Bug optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2004-05-09 20:22 -------
See also PR 14819.
If strchr() is folded to NULL, we don't have to worry about anything.
Otherwise, resolution of this PR is important.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[pinskia at gcc dot gnu dot org]

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2004-06-01 06:45 -------
Now that Steven's strchr patch is in, let me reiterate the problem.

void bar (void);

void
foo (void)
{
  int c = '1';

  if (strchr ("<12ers", c) == 0)
    bar ();
}

void
baz (void)
{
  int c = '1';

  if ("<12ers" + 1 == 0)
    bar ();
}

The last tree-ssa form looks like:

;; Function foo (foo)

foo ()
{
  int c;
  char * T.0;

<bb 0>:
  T.0_2 = "<12ers" + 1B;
  if (T.0_2 == 0B) goto <L0>; else goto <L1>;

<L0>:;
  bar () [tail call];

<L1>:;
  return;

}



;; Function baz (baz)

baz ()
{
  int c;

<bb 0>:
  if ("<12ers" == -1B) goto <L0>; else goto <L1>;

<L0>:;
  bar () [tail call];

<L1>:;
  return;

}

In either case, we miss the folding opportunity.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2004-06-01 06:47 -------
"int c = '1';" in baz() in comment #4 is an unintended garbage.
Please ignore it.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-06-03 23:22 -------
I should note that "12ers" == 0 is folded to false by:
      /* If this is an equality comparison of the address of a non-weak
         object against zero, then we know the result.  */

So improving that part will help.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347
Bug 15347 depends on bug 15459, which changed state.

Bug 15459 Summary: [meta-bug] there should be a tree combiner like the rtl one
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=15459

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

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

--- Comment #11 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-04-28 09:55:46 UTC ---
Author: rguenth
Date: Thu Apr 28 09:55:41 2011
New Revision: 173064

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=173064
Log:
2011-04-28  Richard Guenther  <rguenther@suse.de>

    PR tree-optimization/40052
    PR tree-optimization/15347
    * gcc.dg/tree-ssa/vrp57.c: New testcase.
    * gcc.dg/pr15347.c: Likewise.

Added:
    trunk/gcc/testsuite/gcc.dg/pr15347.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/vrp57.c
Modified:
    trunk/gcc/testsuite/ChangeLog

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.6.0

--- Comment #12 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-04-28 09:56:52 UTC ---
Fixed.  Thanks for noticing.

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

Richard Guenther <rguenth at gcc dot gnu.org> changed:

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

--- Comment #13 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-04-28 09:57:05 UTC ---
Fi-xed.

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

--- Comment #10 from H.J. Lu <hjl.tools at gmail dot com> 2011-04-27 18:32:34 UTC ---
(In reply to comment #9)
> This appears to be fixed in 4.6.0. Mark as resolved?

Need to add a few testcases first.

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[matt at use dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

Matt Hargett <matt at use dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matt at use dot net

--- Comment #9 from Matt Hargett <matt at use dot net> 2011-04-27 17:52:06 UTC ---
This appears to be fixed in 4.6.0. Mark as resolved?

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[pinskia at gcc dot gnu dot org]

------- Comment #8 from pinskia at gcc dot gnu dot org  2006-09-17 08:44 -------
Just to clarify what testcase is still broken, here it is:
void baz (void)
{
  if ("<12ers" + 1 == 0)
    bar ();
}

------
The reason why strchr testcase is fixed is because we turn the strchr call into
&"<12ers"[1].


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
   Last reconfirmed|2006-03-01 02:45:29         |2006-09-17 08:44:52
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347

[Bug tree-optimization/15347] [tree-ssa] fold if ("<12ers" + 1 == 0).

[pinskia at gcc dot gnu dot org]

------- Comment #7 from pinskia at gcc dot gnu dot org  2005-12-07 03:23 -------
I should note that the first testcase in comment #0 in the bug is fixed but not
the second, non reduced one.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2005-09-07 18:50:42         |2005-12-07 03:23:13
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15347