[LLVMdev] Manipulating basic blocks with the C bindings

[Evan Shaw]

On Thu, May 27, 2010 at 6:38 PM, Kenneth Uildriks <kennethuil at gmail.com> wrote:
> On Thu, May 27, 2010 at 5:47 PM, Evan Shaw <chickencha at gmail.com> wrote:
>> I'm writing a frontend with the LLVM C bindings for a language that
>> has a goto statement, similar to C's. I'm having some trouble figuring
>> out what to do for the case where the label is declared after the
>> goto, like this:
>>
>> goto label;
>> ...
>> label:
>> ...
>>
>> When I generate the code for the goto, I'd like to create a basic
>> block that's not inserted anywhere in particular and then put it in
>> the right place when I hit the label (or error out appropriately if I
>> never find it). It looks like the C++ API allows one to do what I'm
>> describing, but I don't see a way to do it with the C bindings.\
>
> When you hit the "goto", create an empty basic block with
> LLVMAppendBasicBlockInContext and put in an unconditional branch to
> it.  Later, when you hit the label, put another unconditional branch
> to that same block, then call LLVMPositionBuilderAtEnd(labelBlock) and
> continue on your way.
That would work. It just seems like there ought to be a better way. Thanks.

- Evan