[Bug middle-end/70526] [5/6 Regression] GCC 6 miscompiles Firefox JIT compiler

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70526

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
          Component|rtl-optimization            |middle-end
         Resolution|---                         |FIXED

--- Comment #22 from Richard Biener <rguenth at gcc dot gnu.org> ---
C++14 3.10/10 (that's basically the same as the C standard says).  The question
remains on whether

  ConstantOrRegister cr = ToConstantOrRegister(&lir, 0, MIRType_Object);

(the aggregate copy performed by the init expression) applies to

"If a program attempts to access the stored value of an object through a
grvalue
of other than one of the following types..."

Where "the stored value" in this case is of type Register and the type of
the grvalue is TypedOrValueRegister (which does not include 'Register' as
member).

To fix your case I'd simply use

class TypedOrValueRegister
{
    MIRType type_;
    union {
       Register reg_;
       ... whatever other type you need ...
    };
...
};


Fixed (what I fixed with the commit) and INVALID for the rest.