[Bug tree-optimization/49602] New: verify_ssa failed (definition does not dominate use) with "-O2 -g"

["arthur.j.odwyer at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49602

           Summary: verify_ssa failed (definition does not dominate use)
                    with "-O2 -g"
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: arthur.j.odwyer@gmail.com


Created attachment 24649
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24649
Output of "ajo-gcc -std=c99 -O2 -g -w -c test.c -v"

This failure reproduces for me with svn revision 175547
(2011-06-27). I've seen it twice in random testing, and never saw it back in
May, so it must be a fairly new regression. I'm on Ubuntu 10.10, x86-64.


cat >test.c <<EOF
static void use(int *p_29) { }
void func_25(int *p_29) {
    for (short p_26 = 0; p_26 == 1; ++p_26)
      p_29 = 0;
    use(p_29);
}
EOF
gcc -std=c99 -O2 -g -w -c test.c

test.c: In function ‘func_25’:
test.c:6:1: error: definition in block 3 does not dominate use in block 5
for SSA_NAME: p_29_3 in statement:
# DEBUG D#1 => p_29_3
test.c:6:1: internal compiler error: verify_ssa failed


Bug 40711 (from 2009) has the same symptom, but doesn't require "-g", so it
probably has a different root cause.

This test case is reduced from the output of Csmith 2.1.0 (git hash 01aa8b04,
https://github.com/Quuxplusone/csmith/), using the following command line:
csmith --no-paranoid --longlong --pointers --no-arrays --jumps --no-consts
--volatiles --checksum --no-divs --muls --no-bitfields --no-packed-struct -s
651222746