I recommend taking a look at the Programmer's Manual - it has a pretty decent coverage of the basics.
In particular, there's a section about creating and inserting new instructions. The simplest way is just to provide an existing instruction as the last argument for the new instruction's constructor, which will then insert that instruction immediately before the existing one.
Alternatively, you can pass the enclosing basic block if you just want to add to its end (but remember you need to take care of the terminator!). Finally, you can just call getInstList()
on the enclosing basic block, then insert
or push_back
to insert new instructions there.
As an aside, you don't have to iterate over all blocks and then over all instructions in each, you can just iterate over the instructions directly; see the section about the instruction iterator in the programmer's manual.