Using mem_attrs to get the tree of a function being called?

[Alexandre Courbot <Alexandre dot Courbot at lifl dot fr>]

Hello everybody,

When outputting a function call, I need to know the exact structure of the 
function being called (name, arguments types, etc.). The best way to get all 
these informations being the tree representation. Since in a call insn the 
function to be called is a mem expression, I assumed that I could get the 
decl of the function thanks to the mem_attrs. So my output pattern for 
call_value contains the following code to check I can do so (operands[1] 
being the function):

        tree mexpr = MEM_EXPR(operands[1]);
        if (mexpr) printf("Expr is valid!\n");
        else printf("Expr is NULL\n");

Unfortunately, mexpr is always NULL, while I expected it to point to the 
function_decl corresponding to the function being called. Even the MEM_ATTRS 
macro returns NULL. Are mem_attrs not used when dealing with functions? If 
so, is there any good reason why this is so or shall I go ahead and try to 
implement it? Or am I missing something else?

Any hint welcome,
Thanks,
Alex.