On Fri, 30 Mar 2012, Richard Guenther wrote:
> On Thu, 29 Mar 2012, Jan Hubicka wrote:
>
> > With Mozilla folks I used the dumps from first WPA unreachable function
> > removal pass
> > with some degree of success. This gets a lot of non-trivial cases of dead
> > code,
> > but also there are a lot of funny false positives wrt comdats etc.
> > > + for (caller = node->callers; caller; caller = caller->next_caller)
> > > + {
> > > + if (!caller_tu)
> > > + caller_tu = DECL_CONTEXT (caller->caller->decl);
> > > + else if (caller_tu
> > > + && DECL_CONTEXT (caller->caller->decl) != caller_tu)
> > > + found = false;
> > > + }
> > Extending to IPA-REF should be straighforward.
> > > + if (found && caller_tu)
> > > + {
> > > + expanded_location loc1 = expand_location (DECL_SOURCE_LOCATION
> > > (node->decl));
> > > + expanded_location loc2 = expand_location (DECL_SOURCE_LOCATION
> > > (node->callers->caller->decl));
> > > +
> > > + if (DECL_CONTEXT (node->decl) == caller_tu)
> > > + fprintf (f, "%s:%s can be made static\n",
> > > + loc1.file, IDENTIFIER_POINTER (DECL_NAME
> > > (node->decl)));
> > Indeed, this is also useful. Any plans to turn this into general
> > -W<something>,
> > or you will also stay just with an internal hack like I did? :)
>
> ;) The result has way too many false positives (LTO bootstrap produces
> quite some dead functions due to early inlining). So yes, this will
> stay internal ;)
Btw, the following is the last incarnation of the patch - I've stopped
here for now. If you LTO bootstrap with it you can find *.callers
files in the build tree (remember to use -O0 for added precision).
Richard.
Index: gcc/lto/lto.c
===================================================================
--- gcc/lto/lto.c (revision 186007)
+++ gcc/lto/lto.c (working copy)
@@ -2721,6 +2721,70 @@ read_cgraph_and_symbols (unsigned nfiles
lto_symtab_merge_cgraph_nodes ();
ggc_collect ();
+ if (flag_wpa)
+ {
+ struct cgraph_node *node;
+ FILE *f = fopen (concat (dump_base_name, ".callers", NULL), "w");
+ for (node = cgraph_nodes; node; node = node->next)
+ {
+ tree caller_tu = NULL_TREE;
+ struct cgraph_edge *caller;
+ bool found = true;
+
+ if (!TREE_PUBLIC (node->decl)
+ || !TREE_STATIC (node->decl)
+ || DECL_PRESERVE_P (node->decl)
+ || resolution_used_from_other_file_p (node->resolution))
+ continue;
+
+ /* For now, until we walk references. */
+ if (node->address_taken)
+ continue;
+
+ if (!node->callers)
+ {
+ expanded_location loc = expand_location (DECL_SOURCE_LOCATION
(node->decl));
+ fprintf (f, "%s:%s no calls\n",
+ loc.file, IDENTIFIER_POINTER (DECL_NAME (node->decl)));
+ }
+ for (caller = node->callers; caller; caller = caller->next_caller)
+ {
+ if (!caller_tu)
+ caller_tu = DECL_CONTEXT (caller->caller->decl);
+ else if (caller_tu
+ && DECL_CONTEXT (caller->caller->decl) != caller_tu)
+ found = false;
+ }
+ if (found && caller_tu)
+ {
+ expanded_location loc1 = expand_location (DECL_SOURCE_LOCATION
(node->decl));
+ expanded_location loc2 = expand_location (DECL_SOURCE_LOCATION
(node->callers->caller->decl));
+
+ if (DECL_CONTEXT (node->decl) == caller_tu)
+ fprintf (f, "%s:%s can be made static\n",
+ loc1.file, IDENTIFIER_POINTER (DECL_NAME
(node->decl)));
+ else
+ {
+ struct cgraph_edge *callee;
+ bool calls_nonpublic_static_fn = false;
+ /* Check if we can move node to the caller TU without
+ moving anything else. */
+ for (callee = node->callees; callee; callee =
callee->next_callee)
+ {
+ if (!TREE_PUBLIC (callee->callee->decl)
+ && TREE_STATIC (callee->callee->decl))
+ calls_nonpublic_static_fn = true;
+ }
+ if (!calls_nonpublic_static_fn)
+ fprintf (f, "%s:%s called only from %s\n",
+ loc1.file, IDENTIFIER_POINTER (DECL_NAME
(node->decl)),
+ loc2.file);
+ }
+ }
+ }
+ fclose (f);
+ }
+
if (flag_ltrans)
for (node = cgraph_nodes; node; node = node->next)
{
