Re: PATCH: [4.1 Regression]: java compiler generates wrong code on ia64

["H. J. Lu" <hjl at lucon dot org>]

On Mon, Apr 18, 2005 at 12:34:04PM -0700, H. J. Lu wrote:
> On Mon, Apr 18, 2005 at 12:16:10PM -0700, H. J. Lu wrote:
> > On Mon, Apr 18, 2005 at 03:03:02PM -0400, Bryce McKinlay wrote:
> > > H. J. Lu wrote:
> > > 
> > > >>The function pointers in the GCJ method metadata (_Jv_Method) are always 
> > > >>local, except in the case of CNI functions. But, even local function 
> > > >>references in a .so will point at PLT entries if the function is also 
> > > >>referenced from the main binary.
> > > >>   
> > > >>
> > > >
> > > >Whan you said "local function", did you mean
> > > >
> > > >1. A local data variable with function type. Or
> > > >2. A function symbol which isn't visible to the outside. Or
> > > >3. A global data variable with function type pointing to a local
> > > >function.
> > > >
> > > >I ran into a very tricky issue. But I don't have a testcase. This
> > > >problem may be related.
> > > > 
> > > >
> > > I mean "a reference to a function which is public (visible to the 
> > > outside) and defined within the same compilation unit"
> > 
> > That makes senses now. For me, "local function" means a different
> > thing :-). If you want to know if a function will be bound locally
> > at the run time, you should use targetm.binds_local_p. I think this
> > patch is correct.
> > 
> > 
> > H.J.
> > ---
> > 2005-04-18  H.J. Lu  <hongjiu.lu@intel.com>
> > 
> > 	PR java/21070
> > 	* class.c (make_local_function_alias): Use targetm.binds_local_p
> > 	to check if a function is bound locally.
> > 
> 
> Second thought. Since you can only create an aliase for a symbol
> defined within the same file, targetm.binds_local_p alone may not be
> suitable for this purpose.
> 

I am not familiar with Java semantics. targetm.binds_local_p will
tell you if a function may be discarded at the link time or overriden
by something else at the run time. If a function is public and defined
within the same compilation unit, it can be discarded at the link time
due to linkonce/comdat and can be overriden by dynamic linker. If it is
discarded or overriden, does a local alias make any more senses for
Java? It seems that

  if (DECL_EXTERNAL (method) || !targetm.binds_local_p (method))
    return method;

will make sure that an aliase will only be created when the function
is defined within the compilation unit and won't be discarded or
overriden.


H.J.