Designated initializers with anonymous unions don't work in MSVC or
GCC < 4.6. With a couple of constructor methods, we don't need them any
more and the code is actually cleaner.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88467
Reviewed-by: Connor Abbot <cwabbott0@gmail.com>
As it was, we weren't ever using load_const in a non-SSA way. This allows
us to substantially simplify the load_const instruction. If we ever need a
non-SSA constant load, we can do a load_const and an imov.
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
