This reduces GC walk recursion depth in two ways.
First by re-ordering tree_type_common members to move 'name' last
and 'canonical' before 'next_variant'. That makes us
first recurse downward (type, pointer_to/reference_to), then
on the same level (canonical, next_variant, main_variant)
and finally upward (context, name->decl_context).
For TS_TYPE_NON_COMMON we still walk down afterwards via values,
on the same level via minval/maxval and upwards via binfo, so
that the patch helps is maybe too much handwaving? (but it
helps a reduced testcase without doing the 2nd part)
Second by choosing sth different for chain_next for types
than TREE_CHAIN (which is TYPE_STUB_DECL, no chain at all).
That makes the unreduced testcase work and apart from the issue
below should be obvious enough (though there usually shouldn't
be so many type variants - still if for every type we save
two or three recursions that still helps).
Martin verified this fixes PR60553.
I've changed chain_next only for the LTO frontend as
while (ggc_test_and_set_mark (xlimit))
xlimit = (CODE_CONTAINS_STRUCT (TREE_CODE (&(*xlimit).generic),
TS_TYPE_COMMON) ? ((union lang_tree_node *)
(*xlimit).generic.type_common.next_variant) : CODE_CONTAINS_STRUCT
(TREE_CODE (&(*xlimit).generic), TS_COMMON) ? ((union lang_tree_node *)
(*xlimit).generic.common.chain) : NULL);
likely doesn't create great code ... (note duplicate tree checks
with checking here for other frontends, fixed LTO with the patch
below).
LTO bootstrap running on x86_64-unknown-linux-gnu.
Ok for trunk?
Thanks,
Richard.
2014-03-19 Richard Biener <rguent...@suse.de>
PR middle-end/60553
* tree-core.h (tree_type_common): Re-order pointer members
to reduce recursion depth during GC walks.
lto/
* lto-tree.h (lang_tree_node): For types use TYPE_NEXT_VARIANT
instead of TREE_CHAIN as chain_next.
Index: gcc/tree-core.h
===================================================================
--- gcc/tree-core.h (revision 208642)
+++ gcc/tree-core.h (working copy)
@@ -1265,11 +1265,11 @@ struct GTY(()) tree_type_common {
const char * GTY ((tag ("TYPE_SYMTAB_IS_POINTER"))) pointer;
struct die_struct * GTY ((tag ("TYPE_SYMTAB_IS_DIE"))) die;
} GTY ((desc ("debug_hooks->tree_type_symtab_field"))) symtab;
- tree name;
+ tree canonical;
tree next_variant;
tree main_variant;
tree context;
- tree canonical;
+ tree name;
};
struct GTY(()) tree_type_with_lang_specific {
Index: gcc/lto/lto-tree.h
===================================================================
--- gcc/lto/lto-tree.h (revision 208642)
+++ gcc/lto/lto-tree.h (working copy)
@@ -48,7 +48,7 @@ enum lto_tree_node_structure_enum {
};
union GTY((desc ("lto_tree_node_structure (&%h)"),
- chain_next ("CODE_CONTAINS_STRUCT (TREE_CODE (&%h.generic),
TS_COMMON) ? ((union lang_tree_node *) TREE_CHAIN (&%h.generic)) : NULL")))
+ chain_next ("CODE_CONTAINS_STRUCT (TREE_CODE (&%h.generic),
TS_TYPE_COMMON) ? ((union lang_tree_node *)
%h.generic.type_common.next_variant) : CODE_CONTAINS_STRUCT (TREE_CODE
(&%h.generic), TS_COMMON) ? ((union lang_tree_node *) %h.generic.common.chain)
: NULL")))
lang_tree_node
{
union tree_node GTY ((tag ("TS_LTO_GENERIC"),
