Re: A question about java/lang.c:java_get_callee_fndecl.

[Andrew Haley <aph at redhat dot com>]

Kazu Hirata writes:
 > Hi,
 > 
 > I see that the implementation of LANG_HOOKS_GET_CALLEE_FNDECL in Java
 > always returns NULL (at least for the time being).
 > 
 > static tree
 > java_get_callee_fndecl (tree call_expr)
 > {
 >   tree method, table, element, atable_methods;
 > 
 >   HOST_WIDE_INT index;
 > 
 >   /* FIXME: This is disabled because we end up passing calls through
 >      the PLT, and we do NOT want to do that.  */
 >   return NULL;
 > 
 >   :
 >   :
 > 
 > Is anybody planning to fix this?

Yes.

The problem is that I want to expose opportunities for inlining but I
do not want calls to global functions to go through the PLT as
required by C semantics.  To do that causes endless problems.  

We now generate local aliases for all global functions, so my
intention is to call those aliases, rather than the global functions
themselves.  But I do need to give inlining a chance to work, and for
that to happen the middle end needs to see the _real_ function decl.

 > If not, I'm thinking about removing this language hook.  The reason
 > is not just clean up.  Rather it is because I need to change the
 > prototype of get_callee_fndecl and
 > LANG_HOOKS_GET_CALLEE_FNDECL..  Currently, fold_ternary has the
 > following call tree.
 > 
 >   fold_ternary
 >     get_callee_fndecl
 >       java_get_callee_fndecl
 > 
 > If I change fold_ternary to take components of CALL_EXPR like the
 > address expression of CALL_EXPR and the argument list, instead of
 > CALL_EXPR itself, I would have to change java_get_callee_fndecl to
 > take the first operand of a CALL_EXPR, instead of a CALL_EXPR.

So do that.

 > It's not that the change is so involved, but it doesn't make much
 > sense to keep something dead up to date.

It's not dead, it's resting.

 > In other words, when I posted the following patch
 > 
 >   http://gcc.gnu.org/ml/gcc-patches/2005-03/msg02038.html
 > 
 > Roger Sayle requested to keep the call to get_callee_fndecl so that we
 > can "fold" the first operand of a CALL_EXPR to a FUNCTION_DECL.

That's a good thing to do.

 > FYI, the above FIXME comes from
 > 
 >   http://gcc.gnu.org/ml/java-patches/2004-q2/msg00083.html

Andrew.