[LLVMdev] modify instructions

[xli3 at uiuc.edu]

Hi, I have a question about the modify of instruction:
Say I want to modify 
%a = getelementptr %struct %S, long 0, ubyte 1
into 
%a.f0 = getelementptr int* %S.f0, long 0

There are 3 ways I can think of to implement, but I'm not sure
what should I do.

1. I can use new GetElementPtr to create a new instruction and
use ReplaceInstWithInst() function to replace the old one.
 
2. I can use new GetElementPtr to create a new instruction and
then insert it into the code, then delete the old instruction,
but the problem is the program will automatically change the
name of the new instruction if you give it the same name with
the old one?

3. Just modify the operand 0 and delete the operand 2. But I
didn't see an command to delete an operand. 

Please let me know in LLVM, what's the best way to handle
this? Thanks,

xiaodong