[LLVMdev] Dynamic Creation of a simple program

[xavier]

Hi,

Given these C instructions:

==============================
struct stru { struct stru  *Next; }; 

struct list  *NewStru = malloc ( sizeof ( struct stru ) );
struct list  *tmp.3;
...
tmp.3 = NewStru->Next;
==============================

LLVM generates something like this:

%tmp.0 = malloc %struct.stru		; <%struct.stru*>
%tmp.3 = getelementptr %struct.stru* %tmp.0, int 0, uint 1		; <%struct.stru**>

I have been trying to re create that code with the GetElementPtrInst class, but I always get
segmentation faults. I could not find any example of how to use GetElementPtrInst for that kind of
situations

How can I do that?

Thanks



--- Chris Lattner <sabre at nondot.org> wrote:

> On Tue, 15 Mar 2005, xavier wrote:
> > Thanks for the information
> > I am trying to use one of your examples for recursive data structures:
> >
> > =========================
> > PATypeHolder StructTy = OpaqueType::get();
> > std::vector<const Type*> Elts;
> > Elts.push_back(PointerType::get(StructTy));
> > Elts.push_back(PointerType::get(Type::SByteTy));
> > StructType *NewSTy = StructType::get(Elts);
> >
> > // At this point, NewSTy = "{ opaque*, sbyte* }", tell VMCore that
> > // the struct and the opaque type are actually the same.
> > cast<OpaqueType>(StructTy.get())->refineAbstractTypeTo(NewSTy);
> >
> > // NewSTy is potentially invalidated, but StructTy (a PATypeHolder) is
> > // kept up-to-date.
> > NewSTy = StructTy.get();
> > =========================
> >
> > It gives this error in the last line:
> >
> >         invalid conversion from `llvm::Type*' to `llvm::StructType*'
> > How can I create such a recursive DS?
> 
> Replace the last line with:
> 
>    NewSTy = cast<StructType>(StructTy.get());
> 
> -Chris
> 
> > --- Chris Lattner <sabre at nondot.org> wrote:
> >> On Mon, 14 Mar 2005, xavier wrote:
> >>
> >>> Could please somebody give some guidelines? Maybe I can compile a
> >>> program with the LLVM and then load the bytecode in memory and finally
> >>> dump some kind of text/XML representation which I will use to understand
> >>> the set of classes needed to dynamically create the sample program
> >>
> >> Check out these directories:
> >>
> >> examples/ModuleMaker/ : Builds a module from scratch
> >>
> >> examples/Fibonacci/
> >> examples/HowToUseJIT/ : Examples building a module and JIT'ing them.
> >>
> >> -Chris
> >>
> >> --
> >> http://nondot.org/sabre/
> >> http://llvm.cs.uiuc.edu/
> >>
> >> _______________________________________________
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> >>
> >
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> 
> -Chris
> 
> -- 
> http://nondot.org/sabre/
> http://llvm.cs.uiuc.edu/
> 
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