[LLVMdev] LLVMdev Digest, Vol 76, Issue 43

[Török Edwin]

On Tue, 26 Oct 2010 10:00:32 +0200
Duncan Sands <baldrick at free.fr> wrote:

> Hi Kenneth,
> 
> > Well...strictly as LLVM IR I find externally visible incorrect
> > behavior unlikely, it's just a "different definition".  For C and
> > C++, I'd be looking at more complicated variations of
> >
> > int main()
> > {
> >      volatile int i = 1;
> >      return 0;
> > }
> >
> > It's clear that the LLVM IR representation of i cannot be simply
> > IR-volatile qualified, as that load gets optimized out while C and
> > C++ won't optimize it out.  I'd *hope* that DragonEgg and llvm-gcc
> > both leave the load of i in, when in --pedantic mode.  [That is, I
> > expect it to take something more intricate than this elementary
> > test case to trigger any bugs here.]
> 
> both dragonegg and llvm-gcc remove the volatile.  I don't see why they
> shouldn't, since the program behaves exactly the same (as far as
> anyone external can tell) as if it had been left there.

What if its address is taken, or it is a global variable?

--Edwin