[LLVMdev] insertion points for newly created instructions

[Nuno Lopes]

Thanks for your reply!


> On Wed, Mar 24, 2010 at 4:16 PM, Nuno Lopes <nunoplopes at sapo.pt> wrote:
>> Hi,
>>
>> I've been scratching my head with a little problem: how to determine the
>> insertion point for a newly created instruction?
>> The operands of these instructions can be defined in different BBs, and 
>> they
>> may have several users. Thereby determining where to put those 
>> instructions
>> is not obvious. In my case, these instructions don't have side-effects, 
>> and
>> so they could be placed anywhere after the definition of the
>> "more-recently-defined" operand, but before the last dominator of all the
>> users.
>>
>> Does LLVM already has any function that will do this (i.e., magically 
>> insert
>> an instruction in a valid point)?
>
> There is no magical utility function available to do this.

That's what I was afraid of :)


>> If not, is there any way I can implement
>> this without transversing all the instructions in the enclosing function?
>
> Find a user that dominates all other users and then insert this
> instruction just before the dominating users.

The problem is if none of the users dominates the other ones. That's why I 
wanted to somewhat insert the new instruction after the last definition of 
the operands. I guess that's a tricky business..

Nuno