[LLVMdev] Propagate clang attribute to IR

Rinaldini Julien julien.rinaldini at heig-vd.ch
Tue Mar 24 07:40:05 PDT 2015

> On 24 Mar 2015, at 14:55, Aaron Ballman <aaron at aaronballman.com> wrote:
> On Tue, Mar 24, 2015 at 9:48 AM, Rinaldini Julien
> <julien.rinaldini at heig-vd.ch> wrote:
>> Hi,
>> I want to *tag* some functions with some *flags*. I was using annotate((“myFlag”)) and everything was working fine until I tried on ObjC method. It seems that clang just ignore it.
>> So, to be able to *flag* my functions I’m trying to add a *real* attribute to clang.
>> I’ve added a new attribute to clang in tools/clang/include/clang/Basic/Attr.td:
>> def NoFLA : Attr {
>>  let Spellings = [GNU<"nofla">, CXX11<"gnu", "nofla">];
>> }
>> In tools/clang/lib/Sema/SemaDeclAttr.cpp I added my new attribute to the switch that handle it and created my own handler function.
>> I’m trying to simply pass my attribute to the IR attribute list, but, sadly, I have absolutely no idea how to do that. I looked at others handler but none seems to do that. I also tried to use handleSimpleAttribute, but it doesn’t work either.
>> Any idea how to do that (or enable annotate on ObjC method)?
> handleSimpleAttribute takes the parsed attribute (AttributeList entry)
> and turns it into a semantic attribute (Attr subclass). You have to
> manually handle the semantic attribute in whatever way makes sense for
> your attribute. Check out CodeGenModule::ConstructAttributeList for an
> example of how function semantic attributes translate into IR
> attributes to be passed along to LLVM.
> HTH!
> ~Aaron


Thx for your answer...

I tried that without any luck:

  static void handleOBF(Sema &S, Decl *D, const AttributeList &Attr) {
    D->addAttr(::new (S.Context)NoFLAAttr(Attr.getRange(), S.Context, Attr.getAttributeSpellingListIndex()));

    // ???????????                  
    llvm::AttrBuilder FuncAttrs;  

In CodeGenModule::ConstructAttributeList it uses a AttrBuilder, I tried there to add a random attribute and it works.
But I’m not understanding how to do that in SemaDeclAttr.cpp.


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