On Wed, Aug 19, 2015 at 7:16 PM, Uday P. Khedker <u...@cse.iitb.ac.in> wrote:
>
> We are working on an analysis for identifying the class of an object flow
> sensitively for
> flow sensitive de-virtualization (i.e. replacing a virtual function call by
> a call to the
> function of a known class in the hierarchy). This is a regular ipa pass. It
> find outs the
> class of an object at point of creation and then propagates it.
Most of this is already in GCC 5 and above. Including the IPA pass.
Have you looked into that pass yet?
>
> In the examples we have seen so far, given a statement
>
> B beta ("str");
>
> It is is transformed by gcc-4.7.2 as shown below :
>
> __comp_ctor (&beta, "str");
>
> We use this information to identify the class.
>
> However, for case in the source of GNU package gperf-3.0.4, a statement
>
> Output_Enum style (" ");
>
> is transformed by gcc 4.7.2 as
>
> # DEBUG this => &style
> # DEBUG indent => ""
> # DEBUG D#62 => &style.D.4064
> # DEBUG this => D#62
> MEM[(struct Output_Constants *)&style]._vptr.Output_Constants =
> &MEM[(void *)&_ZTV16Output_Constants + 16B];
> style.D.4064._vptr.Output_Constants = &MEM[(void *)&_ZTV11Output_Enum
> + 16B];
> style._indentation = "";
>
> Why is this different? Why is __comp_ctor not invoked in each case?
This looks like the function has been inlined as it is short.
Thanks,
Andrew Pinski
>
> The class hierarchy in gperf is as given below :
>
> struct Output_Constants
> {
> virtual void output_start () = 0;
> virtual void output_item (const char *name, int value) = 0;
> virtual void output_end () = 0;
> Output_Constants () {}
> virtual ~Output_Constants () {}
> };
>
> struct Output_Enum : public Output_Constants
> {
> virtual void output_start ();
> virtual void output_item (const char *name, int value);
> virtual void output_end ();
> Output_Enum (const char *indent)
> : _indentation (indent) {}
> virtual ~Output_Enum () {}
> private:
> const char *_indentation;
> bool _pending_comma;
> };
>
> Thanks and regards,
>
> Uday Khedker.
>
>
