On Thu, Mar 12, 2020 at 5:31 PM Erick Ochoa
<erick.oc...@theobroma-systems.com> wrote:
>
> Hello,
>
> I am trying to find out the arguments of functions which are undefined
> during LTO.
>
> Basically:
>
> gcc_assert(in_lto_p && !cnode->definition)
> // Do we have arguments?
> gcc_assert(DECL_ARGUMENTS(cnode->decl)) // fails
> // No, we don't.
>
> As I understand it, functions which are not defined are ones which have
> have been declared external.
>
> I believe that, when building an application with -flto, the only
> functions which are not visible during LTO **and** are declared external
> are functions defined in libraries which have not been compiled with
> -flto. An example of this is glibc.
>
> Indeed, I have implemented an analysis pass in gcc which prints out
> undefined functions, and it prints out the following:
>
> undefined function __gcov_merge_add
> undefined function fopen
> undefined function printf
> undefined function __builtin_putchar
> undefined function calloc
> undefined function __gcov_merge_topn
> undefined function strtol
> undefined function free
> ... and more
>
> Now, I am not interested in the bodies of these. I am only interested in
> determining the type of the arguments passed to these functions.
> However, when I call the following function:
>
> ```
> void
> print_parameters_undefined_functions(const cgraph_node *cnode)
> {
> gcc_assert(cnode);
> gcc_assert(in_lto_p);
> gcc_assert(!cnode->definition);
>
> tree function = cnode->decl;
> gcc_assert(function);
> enum tree_code code = TREE_CODE (function);
> bool is_function_decl = FUNCTION_DECL == code;
> gcc_assert (is_function_decl);
>
> log("about to print decl_arguments(%s)\n", cnode->name());
> for (tree parm = DECL_ARGUMENTS (function); parm; parm =
> DECL_CHAIN(parm))
> {
> log("hello world\n");
> }
> ```
>
> I never see "hello world" but I do see "about to print...".
> Does anyone have any idea on how to obtain the arguments to undefined
> functions?
The argument types or the actual arguments to all calls? "hello world" sounds
like you want actual arguments. For those you need to look at the callgraph
edges to the cgraph node of the external functions (node->callers) and there
at the call stmts - which will not be available in WPA mode.
>
> The only way I see to do this, is to walk through the gimple
> instructions, find GIMPLE_CALL statements and look at the argument list
> at that moment. But I was wondering if there's a more efficient way to
> do it.
>
> Thanks!
