[LLVMdev] Inconsistent label syntax in LLVM assembly

[Duncan Sands]

Hi Nikolaos,

On 20/01/13 12:00, nkavv at physics.auth.gr wrote:
> Hi all,
>
> i'm writing a TXL (http://www.txl.ca) grammar and a revamp of bison/flex grammar
> for LLVM.
>
> I've noticed an inconsistency regarding label naming conventions.
>
> For instance, the following is a segment of legit LLVM assembly (human-readable)
> IR:
>
>    br i1 %38, label %17, label %39
> ; <label>:39                                      ; preds = %._crit_edge
>    ret void
>
> However, ";" is a comment-line character. How is this interpreted, as a
> meta-comment? (a semantically important comment)?

it's just a comment and has no semantic comment.  You can delete it, it won't
make any difference.

Ciao, Duncan.

>
> Other branches appear using regular conventions:
>
>    br i1 %exitcond, label %._crit_edge, label %.lr.ph
> ._crit_edge:             ; preds = %.lr.ph, %.preheader
>
> So, naturally I have some questions:
>
> 1) What is the differences among the branch labels? Differences in the formation
> (e.g. emitted by different passes?)
>
> 2) How to normalize the appearance of branch labels? I.e. is it possible to not
> emit the strange ; <label>:39 like ones?
>
> 3) Why <label>:39 and not 39: ?
>
> 4) Why not prefixing all labels with <label>?
>
> Best regards
> Nikolaos Kavvadias
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev