[Bug c++/53364] New: [4.7/4.8 Regression] Wrong code generation

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53364

             Bug #: 53364
           Summary: [4.7/4.8 Regression] Wrong code generation
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: foom@fuhm.net


On the following code, minimized from a much larger program:

test.cpp
=====================
#include <algorithm>

struct A
{
    int m_x;

    explicit A(int x) : m_x(x) {}
    operator int() const { return m_x; }
};

struct B : public A
{
 public:
    explicit B(int x)
    : A(x) {}
};

int data = 1;

int main() {
    B b = B(10);
    b = std::min(b, B(data));
    return int(b);
}
=================

Running: g++ -O2 -c test.cpp
With gcc version: g++ (Debian 4.7.0-8) 4.7.0
(which says it's built from r187339 on the gcc 4.7 branch).
On architecture: x86-64

The program ought to return 1, but instead, it returns randomness. Running
valgrind confirms that this program is using uninitialized values.

Testing with the debian gcc-snapshot package (trunk rev 187013) shows the same
bug.
Testing with the debian gcc 4.6.3 package does not show the bug.
Using -O1 does not show the bug.
Using -O1 -fstrict-aliasing shows the bug.