Correctly handle switches on values in a high register

When dx generates a switch on a value in a high register, it prepends a move
instruction, to move the value to a low register. However, this causes the
switch data pseudo-instruction to use address of the move instruction as the
base address of the switch targets, rather than the address of the switch
instruction

Change-Id: I0708d35ec3059c30221cd0a64f426244411d31ea
7 files changed