llvm dev - Jan 2005 - [LLVMdev] the pred_begin and pred_end of BasicBlock

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.
Thanks.
Zhou Feng

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

-- 
http://nondot.org/sabre/
http://llvm.cs.uiuc.edu/

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
>