On 06/19/2014 01:39 AM, Tom de Vries wrote:
> On 19-06-14 05:53, Richard Henderson wrote:
>> Do we in fact make sure this isn't an ifunc resolver? I don't immediately
>> see
>> how those get wired up in the cgraph...
>
> Richard,
>
> using the patch below I changed the
> gcc/testsuite/gcc.target/i386/fuse-caller-save.c testcase to use an ifunc
> resolver, and observed that the fuse-caller-save optimization didn't work.
>
> The reason the optimization doesn't work in this case is that
> default_binds_local_p_1 checks the ifunc attribute:
> ...
> /* Weakrefs may not bind locally, even though the weakref itself is always
> static and therefore local. Similarly, the resolver for ifunc functions
> might resolve to a non-local function.
> FIXME: We can resolve the weakref case more curefuly by looking at the
> weakref alias. */
> else if (lookup_attribute ("weakref", DECL_ATTRIBUTES (exp))
> || (TREE_CODE (exp) == FUNCTION_DECL
> && lookup_attribute ("ifunc", DECL_ATTRIBUTES (exp))))
> local_p = false;
> ...
>
> The default_binds_local_p_1 function is used via this path in the
> optimization:
> get_call_reg_set_usage -> get_call_cgraph_rtl_info ->
> decl_binds_to_current_def_p -> default_binds_local_p ->
> default_binds_local_p_1 .
Excellent. Thanks for doing the digging I was too lazy to finish last night.
r~
