[Bug tree-optimization/48739] New: ICE in check_loop_closed_ssa_use() with "-ftree-parallelize-loops=2 -fno-tree-dominator-opts"

[arthur.j.odwyer at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48739

           Summary: ICE in check_loop_closed_ssa_use() with
                    "-ftree-parallelize-loops=2 -fno-tree-dominator-opts"
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: arthur.j.odw...@gmail.com


Created attachment 24077
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24077
Output of "ajo-gcc -w -O1 -ftree-parallelize-loops=2 -fno-tree-dominator-opts
-c test1942241936.c -v"

This reproduces for me with svn revision 172796 (2011-04-20), but it doesn't
reproduce with gcc-4.5.  I'm on Ubuntu 10.10, x86-64.  Attached "gcc-v.txt".

cat >test1942241936.c <<EOF
extern int g;
extern void func_48(void);
int func_70(int p) {
    int a, b, *ptr = &g;
    for (a = 0; a < 10; ++a) {
        func_48();
        for (b = 0; b < 5; ++b) {
            for (g = 0; g < 1; ++g) {
                p = 0;
                ptr = &p;
            }
        }
    }
    *ptr = p;
    for (p = 0; p != 10; p += 3u) { }
    return g;
}
EOF
gcc -w -O1 -ftree-parallelize-loops=2 -fno-tree-dominator-opts -c
test1942241936.c

test1942241936.c: In function ‘func_70’:
test1942241936.c:3:5: internal compiler error: in check_loop_closed_ssa_use, at
tree-ssa-loop-manip.c:422


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 1942241936 >test1942241936.c

Notice that the final for-loop has undefined behavior due to signed integer
overflow, which might be putting the compiler in an unfamiliar state... but
surely it shouldn't *crash* the compiler! -fwrapv doesn't make the crash go
away, either.