Fix getAddressFromInstr so that it copies displacements of global variable
I don't have a test case yet, since I have only encountered this issue while developing a pass that I have not yet open-sourced. However, I'll look for where else this routine is used and I'll see if I can generate a test based on that.
I'm not familiar with all of the different types of memory operands, but I'm concerned that additional types may not be handled properly here given this issue with handling global address operands. Just to pick one more example, perhaps external symbol operands need special handling, but I'm not sure. Maybe I should revise my comment to "FIXME: Special handling may be required for additional types of operands below."