[LLVMdev] question about the 3th and 4th arguments in the registration function

[Hui Zhang]

Is there anyone who can clear my confusion ?

thanks !

On Mon, Feb 2, 2015 at 11:32 AM, Hui Zhang <wayne.huizhang at gmail.com> wrote:

> Hello,
>
> I'm a little confused about the 3th and 4th arguments in the registration
> function, explained here:
> http://llvm.org/releases/3.3/docs/WritingAnLLVMPass.html
>
> e.g
>
> static RegisterPass<Hello> X("hello", "Hello World Pass",
>                              false /* Only looks at CFG */,
>                              false /* Analysis Pass */);
>
>
> "Lastly, we *register our class*
> <http://llvm.org/releases/3.3/docs/WritingAnLLVMPass.html#writing-an-llvm-pass-registration>
> Hello, giving it a command line argument “hello”, and a name “Hello World
> Pass”. The last two arguments describe its behavior: if a pass walks CFG
> without modifying it then the third argument is set to true; if a pass is
> an analysis pass, for example dominator tree pass, then true is supplied
> as the fourth argument."
>
> In this simple "Hello" pass, it only look at all the functions and print
> out their name. So what's the difference between 3th and 4th argument here
> ??
>
> And since Hello pass didn't modify the module but analized it(as I
> understand), shouldn't both of them be true instead of false in the example
> ??
>
> thanks
>
> --
> Best regards
>
>
> Hui Zhang
>



-- 
Best regards


Hui Zhang
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