[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" <gcc-bugzilla at gcc dot gnu dot org>]

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. ;)