On Aug 1, 2013, at 8:09 AM, Jan Hubicka <hubi...@ucw.cz> wrote:
> Now when we have abstract origins tracked, this patch makes DECL_ARGUMENTS and
> DECL_RESULT to be removed from FUNCTION_DECLs that are never passed to symbol
> table. This reduces LTO streaming effort (by about 1/3rd of PARM_DECls)
So, I was tracking down an lto failure in the C++ test suite,
g++.dg/ipa/pr46984.C, and it appears to be caused by
4df870fdeec85907db3dcabf1992cf8b63e1d562 aka
svn+ssh://gcc.gnu.org/svn/gcc/trunk@201468. I was trying to find the
gcc-patches email for this work, but could not. :-( Anyway, the above is the
closest work to that, that I can find.
The problem is that DECL_ARGUMENTS of the thunk (aka _ZThn528_N1D3fooEv) is
used during thunk code-generation, and thunk code-generation happens during the
output of D::foo.
My port is a targetm.asm_out.can_output_mi_thunk false port.
RESULT_DECL is synthesized on the fly like this:
/* Build the return declaration for the function. */
restype = TREE_TYPE (TREE_TYPE (thunk_fndecl));
if (DECL_RESULT (thunk_fndecl) == NULL_TREE)
{
resdecl = build_decl (input_location, RESULT_DECL, 0, restype);
DECL_ARTIFICIAL (resdecl) = 1;
DECL_IGNORED_P (resdecl) = 1;
DECL_RESULT (thunk_fndecl) = resdecl;
}
else
resdecl = DECL_RESULT (thunk_fndecl);
in expand_thunk, but DECL_ARGUMENTS is not. Either it needs to be, or it has
to be saved and restored in some fashion.
input_function is never called for the thunk. If it had been, then it would
have worked I think. I think this translates into output_function not being
called on the thunk.
Anyway, the core dump looks like:
In member function 'non-virtual thunk to D::foo()':
lto1: internal compiler error: Segmentation fault
0x995d3f crash_signal
../../gcc/gcc/toplev.c:335
0x6a5828 contains_struct_check
../../gcc/gcc/tree.h:3804
0x6a5828 fold_build_pointer_plus_hwi_loc
../../gcc/gcc/tree.h:5871
0x6a5828 thunk_adjust
../../gcc/gcc/cgraphunit.c:1240
0x6a6ffd expand_thunk(cgraph_node*)
../../gcc/gcc/cgraphunit.c:1440
0x6a799d assemble_thunks_and_aliases
../../gcc/gcc/cgraphunit.c:1549
0x6a7a32 assemble_thunks_and_aliases
../../gcc/gcc/cgraphunit.c:1565
0x6a7bce expand_function
../../gcc/gcc/cgraphunit.c:1675
0x6a983c expand_all_functions
../../gcc/gcc/cgraphunit.c:1717
0x6a983c compile()
../../gcc/gcc/cgraphunit.c:2054
0x62ccd7 lto_main()
../../gcc/gcc/lto/lto.c:3843
It appears that
>
> Bootstrapped/regtested ppc64-linux, will commit it after further testing on
> x86_64-linux.
>
> Honza
>
> * cgraph.h (release_function_body): Declare.
> * tree.c (free_lang_data_in_decl): Free, parameters and return values
> of unused delcarations.
> Index: cgraph.h
> ===================================================================
> --- cgraph.h (revision 201408)
> +++ cgraph.h (working copy)
> @@ -606,6 +606,7 @@ void debug_cgraph_node (struct cgraph_no
> void cgraph_remove_edge (struct cgraph_edge *);
> void cgraph_remove_node (struct cgraph_node *);
> void cgraph_release_function_body (struct cgraph_node *);
> +void release_function_body (tree);
> void cgraph_node_remove_callees (struct cgraph_node *node);
> struct cgraph_edge *cgraph_create_edge (struct cgraph_node *,
> struct cgraph_node *,
> Index: tree.c
> ===================================================================
> --- tree.c (revision 201367)
> +++ tree.c (working copy)
> @@ -4886,6 +4886,20 @@ free_lang_data_in_decl (tree decl)
>
> if (TREE_CODE (decl) == FUNCTION_DECL)
> {
> + struct cgraph_node *node;
> + if (!(node = cgraph_get_node (decl))
> + || (!node->symbol.definition && !node->clones))
> + {
> + if (node)
> + cgraph_release_function_body (node);
> + else
> + {
> + release_function_body (decl);
> + DECL_ARGUMENTS (decl) = NULL;
> + DECL_RESULT (decl) = NULL;
> + DECL_INITIAL (decl) = error_mark_node;
> + }
> + }
> if (gimple_has_body_p (decl))
> {
> tree t;
