[LLVMdev] Address of label

[Reid Spencer]

This question needs an FAQ. This is the fourth time I've seen this 
question asked on llvm-dev. Could someone in-the-know write a succinct 
FAQ on this topic and add it to the documentation (similarly to the one 
I did for GEP)? I think that would help answer these kinds of questions 
in the future.

Mikael: sorry, I don't have the answer, but I'm sure someone will 
(again!) answer this question :)

Reid.

Peltier, Mikael wrote:

> Hello,
>
> I search information in order to access address (i.e. value) of label 
> directly in llvm assembler file.
>
> This can be useful to realize jump table from address, etc.
>
> I generate the file /branch.ll/ from a C file.
>
> In this file, we saw that branches are realized by affecting virtually 
> an id to each label and use a switch in order to find the right target.
>
> I want to know if there is another way to do this, for instance, by 
> accessing the address of label and to branch directly to it?
>
> In order to optimize the program (to decrease the cost of branch 
> dispatch), I use the following command line:
>
> /llvmc –O5 –o branch_opt branch.bc/
>
> /llc –march=arm –mcpu=arm1136j-s –mattr=+v6 –f –o branch_opt.s 
> branch_opt.bc/
>
> In the optimized program (/branch_opt.arm/), I saw that all branches 
> are not suppressed.
>
> I want to know, if it is possible to suppress the remaining useless 
> branches? if yes, how ?
>
> Thanks in advance.
>
> Mikaël.
>
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