[LLVMdev] Separate loop condition and loop body

[Benoit Boissinot]

On Mon, May 10, 2010 at 8:05 PM, Trevor Harmon <Trevor.W.Harmon at nasa.gov> wrote:
> On May 10, 2010, at 8:43 AM, Xinfinity wrote:
>
>> Is it possible to get the list of BasicBlocks building the condition
>> of a loop and the list of BasicBlocks that form the body?
>
> Based on my (limited) experience with Loop and LoopInfo, this isn't
> possible. (But don't take my word for it.)
>
>> My aim is to manipulate for loops, while and do-while loops unitary,
>> but I did not find an easy way to do this.
>
> I think the problem here is that LLVM's CFG is low-level enough such
> that the distinction between the loop header expression and the loop
> body is lost.
>
> Why exactly do you need to identify the blocks that form the loop
> header expression? I'm wondering if you could find some workaround
> that doesn't require this...
>
To me it looks like any basic block from the loop body with a
successor not in the loop body is a BB "building the condition" (an
"exit" block).
If you already have the loop body, it should be pretty easy to find
out about those nodes.

cheers,

Benoit