Retrieving argument value from __attribute__

[naga raj <gnuuser dot raj at gmail dot com>]

Hi All,

   I am working on Microblaze port. I have a requirement in which user
will declare a handler number in the function prototype as below
   ex: void matrix_const(int ) __attribute__((svc_handler(777)));

   So my requirement is whenever the matrix_const function is called
then the compiler has to store the attribute value (777) in to a
temporary register(R18) after which user will have his own
implementation of jump tables using r18 register.

  To support this I have added it to attribute_spec with req_handler
as "svc_handler_attribute"


static tree
svc_handler_attribute (tree *node ATTRIBUTE_UNUSED,
                                tree name,
                                tree args,
                                int flags ATTRIBUTE_UNUSED,
                                bool *no_add_attrs)
{
  tree value = TREE_VALUE (args);
   HOST_WIDE_INT value1 = TREE_INT_CST_LOW (TREE_VALUE (args));
    if (TREE_CODE (value) != INTEGER_CST)
    {
      warning (OPT_Wattributes,
               "argument of %qE attribute is not a string constant",
               name);
      *no_add_attrs = true;
    }

  return NULL_TREE;
}


With the above handler I am able to extract 777 to value1 variable,
but I think this function will only be called when parsing the
function prototype.

My requirement is to store 777 when matrix_const function is called,
but  I was able to find only the type of  __attribute__ i.e
svc_handler with below function.

static int
microblaze_svc_handler_function_p (tree func)
{
  tree a;

  if (TREE_CODE (func) != FUNCTION_DECL)
    return 0;
  warning (OPT_Wattributes,"argument of %d attribute is not a string
constant", value1->name);

  a = lookup_attribute ("svc_handler", DECL_ATTRIBUTES (func));
  return a != NULL_TREE;
}

I am calling this function in   "compute_frame_size (HOST_WIDE_INT size)"....

My question is how to find the argument value(777) using
"microblaze_svc_handler_function_p" ?? Do we have any ATTRIBUTE
related function to do this.
 Please suggest a solution/document by which we can extract the
argument value...


Thanks in Advance,
Nagaraju