Changing pointer addresses in Transform pass


I have the following code and I want to update the pointers via LLVM
during the transformation pass. Assume I work on FunctionPass level
and need to append logic on runOnFunction(). Assume I also know the
pointers that needs to be changed, before hand (in this example namely
A and B)

Can anyone give me pointers on how to go about achieving this ?

Original code logic:

char A[100];
char B[100];

func () {

A[1] = 1;
A[99] = 99;

A needs to be updated to B after transformation pass.

Modified Code logic:

func () {
B[1] = 1;
B[99] 99;