ins<15> instantiation - Use of uninitalised variable. about lc3-vm

[justinmeiners]

You have precisely the idea of how it is supposed to work. I think it is pretty nice as well, and is probably closer to how hardware like this might be built.

This is definitely a bug. From what I found it looked like OP_JSR was actually the problem.

lc3-alt.cpp: In function ‘void ins(uint16_t) [with unsigned int op = 4]’:
lc3-alt.cpp:282:23: warning: ‘r1’ may be used uninitialized in this function [-Wmaybe-uninitialized]
             reg[R_PC] = reg[r1];

JSR has two modes, and it looks like neither of our programs use the second mode which is why we didn't notice it.

I like the constexpr and will add it to opbit to emphasize what should be going on.
I won't add it to the conditional, as that requires C++17, and requires some other changes for clang.

#32