[Bug c++/77656] New: 64-bit integral template parameter gets incorrectly sized as 32-bits

[matt at matthewfagan dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77656

            Bug ID: 77656
           Summary: 64-bit integral template parameter gets incorrectly
                    sized as 32-bits
           Product: gcc
           Version: 6.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: matt at matthewfagan dot com
  Target Milestone: ---

GCC incorrectly sizes 64-bit integer template parameters, resulting in spurious
warnings (and perhaps incorrect code generation - unable to test this part).
The following sample code demonstrates the error: (Compiled for Target:
x86_64-pc-linux-gnu)

#include <stdint.h>

template<
        uint64_t _Val,
        int _Val2 = (_Val >> 32)
> class Test {
};

template<uint32_t _X>
class Test2 : Test<_X> {};

template<uint32_t _X>
class Test3 : Test<(uint64_t) _X> {};

Upon compilation, Test2 produces a spurious warning, but Test3 does not.