[LLVMdev] the pred_begin and pred_end of BasicBlock

Zhou Feng
Thu, 13 Jan 2005 06:41:43 -0000

Sorry, still a bit confused. Say we have two basic blocks: A and B. B
has a label. There is no branch/control flow instructions explicit uses
B. like this:
A: code sequence does not contain br/other control flow instruction
B:
 lable_of_b:
    code sequence
Is A still a predecessor of B?
Thanks.

Chris Lattner wrote:

> On Thu, 13 Jan 2005, Zhou Feng wrote:
>
>> hi,
>> I'm a bit confused by the pred_begin/end of BasicBlock in CFG.h. I
>> cann't understand what is a **use** of a BasicBlock. Also, I have
no
>> idea of when CFG would be constructed in LLVM.
>
>
> The CFG is always implicit in LLVM.  The two things that "use"
> BasicBlocks are branch/control flow instructions and PHI nodes.
>
> -Chris
>