[Bug tree-optimization/48714] New: gcc -O hangs gobbling memory, while gcc -O -fno-tree-fre finishes quickly

[Bug tree-optimization/48714] New: gcc -O hangs gobbling memory, while gcc -O -fno-tree-fre finishes quickly

[arthur.j.odwyer at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48714

           Summary: gcc -O hangs gobbling memory, while gcc -O
                    -fno-tree-fre finishes quickly
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: arthur.j.odwyer@gmail.com


Created attachment 24067
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24067
Output of "ajo-gcc -v -w -O -ftree-fre -c test105974-reduced.c"

This reproduces for me with svn revision 172796 (2011-04-20), but it doesn't
reproduce with gcc-4.4.  I'm on Ubuntu 10.10, x86-64.  Attached "gcc-v.txt".

cat >test105974.c <<EOF
extern volatile int g_4[1][4]; extern int g_7; void modify(int *);
void func_2() {
    int l_46 = 4;
    if (g_7) {
        modify(&l_46);
    } else {
        int i;
        for (i = 0; i != 5; i += 1) {
            volatile int *vp = &g_4[0][l_46]; *vp = 0;
        }
    }
}
EOF
gcc -w -O -c test105974.c
[hangs]
gcc -w -O -fno-tree-fre -c test105974.c
[passes]

This test case is reduced from the output of Csmith
(http://embed.cs.utah.edu/csmith/), using the following command line:
csmith --bitfields --packed-struct -s 105974 >test105974.c
gcc -w -I../csmith-2.0.0/runtime -O -c test105974.c

As I said, it reproduces for me only with a home-built bleeding-edge GCC, and
I'm still pretty unfamiliar with the GCC build process, so don't bite too hard
if this turns out to be user error on my end. ;)

[Bug tree-optimization/48714] gcc -O hangs gobbling memory, while gcc -O -fno-tree-fre finishes quickly

[arthur.j.odwyer at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48714

Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.4.5, 4.5.1
            Version|unknown                     |4.7.0

--- Comment #1 from Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> 2011-04-21 21:34:41 UTC ---
Here's another test case with exactly the same symptom. Again, it works with
gcc-4.4 but fails with my bleeding-edge gcc. The braces around the inner loop
are significant. Notice that the offending assignment to "gp" is actually dead
code.

cat >test106865.c <<EOF
extern volatile int g_89[5][9];
extern int g, *gp;
void func_64() {
    int i;
    for (i = 0; i < 1; ) {
        for (g = 0; g < 1; ) {
            return;
        }
        gp = &g_89[g][0];
    }
}
EOF
gcc -w -O1 -c test106865.c
[hangs]
gcc -w -O1 -fno-tree-pre -c test106865.c
[passes]

[Bug tree-optimization/48714] gcc -O hangs gobbling memory, while gcc -O -fno-tree-fre finishes quickly

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48714

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2011.04.22 09:21:41
         Depends on|                            |48694
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-04-22 09:21:41 UTC ---
Mine.  Indeed looks like 48694 - thanks for the small testcases.

[Bug tree-optimization/48714] gcc -O hangs gobbling memory, while gcc -O -fno-tree-fre finishes quickly

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48714

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

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

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-04-26 09:20:14 UTC ---
Dup.

*** This bug has been marked as a duplicate of bug 48694 ***