Here it is again, without the DECL_COMDAT pieces; now that patch is in,
this becomes just an optimization to improve devirtualization.
As you said before, because of caching we might miss new overrides that
are introduced as a result of instantiating/synthesizing one of the
overrides on the first pass. This seems likely to be rare, so perhaps
it's not worth worrying about. What do you think?
Jason
commit 0271948001ca26f068935b04d13155a25c979af8
Author: Jason Merrill <ja...@redhat.com>
Date: Tue Jul 29 12:42:51 2014 -0400
gcc/
* ipa-devirt.c (possible_polymorphic_call_targets): Add overload
taking a single tree.
* ipa-utils.h: Declare it.
gcc/cp/
* call.c (build_over_call): Call note_fn_called_virtually.
* class.c (get_vtable_decl): Create a varpool node.
* cp-tree.h (FNDECL_CALLED_VIRTUALLY): New.
* decl2.c (fns_called_virtually, note_fn_called_virtually): New.
(mark_virtual_overrides): New.
(cp_write_global_declarations): Call it.
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 4d37c65..969e730 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -7364,6 +7364,8 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
ba_any, NULL, complain);
gcc_assert (binfo && binfo != error_mark_node);
+ note_fn_called_virtually (fn);
+
/* Warn about deprecated virtual functions now, since we're about
to throw away the decl. */
if (TREE_DEPRECATED (fn))
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 235c68a..1401069 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -817,6 +817,9 @@ get_vtable_decl (tree type, int complete)
decl = build_vtable (type, get_vtable_name (type), vtbl_type_node);
CLASSTYPE_VTABLES (type) = decl;
+ /* Make the vtable visible to build_type_inheritance_graph. */
+ varpool_node::get_create (decl);
+
if (complete)
{
DECL_EXTERNAL (decl) = 1;
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 0c0d804..c9f248a 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -109,6 +109,7 @@ c-common.h, not after.
BIND_EXPR_BODY_BLOCK (in BIND_EXPR)
DECL_NON_TRIVIALLY_INITIALIZED_P (in VAR_DECL)
CALL_EXPR_LIST_INIT_P (in CALL_EXPR, AGGR_INIT_EXPR)
+ FNDECL_CALLED_VIRTUALLY (in FUNCTION_DECL)
4: TREE_HAS_CONSTRUCTOR (in INDIRECT_REF, SAVE_EXPR, CONSTRUCTOR,
or FIELD_DECL).
IDENTIFIER_TYPENAME_P (in IDENTIFIER_NODE)
@@ -3222,6 +3223,11 @@ more_aggr_init_expr_args_p (const aggr_init_expr_arg_iterator *iter)
#define FNDECL_USED_AUTO(NODE) \
TREE_LANG_FLAG_2 (FUNCTION_DECL_CHECK (NODE))
+/* True if NODE was called through the vtable; used to avoid duplicates in
+ fns_called_virtually. */
+#define FNDECL_CALLED_VIRTUALLY(NODE) \
+ TREE_LANG_FLAG_3 (FUNCTION_DECL_CHECK (NODE))
+
/* Nonzero if NODE is a DECL which we know about but which has not
been explicitly declared, such as a built-in function or a friend
declared inside a class. In the latter case DECL_HIDDEN_FRIEND_P
@@ -5381,6 +5387,7 @@ extern tree get_tls_wrapper_fn (tree);
extern void mark_needed (tree);
extern bool decl_needed_p (tree);
extern void note_vague_linkage_fn (tree);
+extern void note_fn_called_virtually (tree);
extern tree build_artificial_parm (tree, tree);
extern bool possibly_inlined_p (tree);
extern int parm_index (tree);
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index eafdce5..dbb669a 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -47,6 +47,8 @@ along with GCC; see the file COPYING3. If not see
#include "c-family/c-common.h"
#include "c-family/c-objc.h"
#include "cgraph.h"
+/* For build_type_inheritance_graph and possible_polymorphic_call_targets. */
+#include "ipa-utils.h"
#include "tree-inline.h"
#include "c-family/c-pragma.h"
#include "dumpfile.h"
@@ -103,6 +105,10 @@ static GTY(()) vec<tree, va_gc> *deferred_fns;
sure are defined. */
static GTY(()) vec<tree, va_gc> *no_linkage_decls;
+/* A list of functions called through the vtable, so we can mark their
+ overriders as used. */
+static GTY(()) vec<tree, va_gc> *fns_called_virtually;
+
/* Nonzero if we're done parsing and into end-of-file activities. */
int at_eof;
@@ -786,6 +792,19 @@ note_vague_linkage_fn (tree decl)
vec_safe_push (deferred_fns, decl);
}
+/* DECL is a function being called through the vtable. Remember it so that
+ at the end of the translation unit we can mark as used any functions
+ that override it, for devirtualization. */
+
+void
+note_fn_called_virtually (tree decl)
+{
+ if (FNDECL_CALLED_VIRTUALLY (decl))
+ return;
+ FNDECL_CALLED_VIRTUALLY (decl) = true;
+ vec_safe_push (fns_called_virtually, decl);
+}
+
/* We have just processed the DECL, which is a static data member.
The other parameters are as for cp_finish_decl. */
@@ -4263,6 +4282,39 @@ dump_tu (void)
}
}
+/* Now that we've seen all the types in the translation unit, go back over
+ the list of functions called through the vtable and mark any overriders
+ as used so they're available for devirtualization. */
+
+static bool
+mark_virtual_overrides (void)
+{
+ if (!fns_called_virtually)
+ return false;
+
+ build_type_inheritance_graph ();
+
+ bool reconsider = false;
+ size_t i; tree fn;
+ FOR_EACH_VEC_SAFE_ELT (fns_called_virtually, i, fn)
+ {
+ vec<cgraph_node*> targets
+ = possible_polymorphic_call_targets (fn);
+
+ size_t j; cgraph_node *n;
+ FOR_EACH_VEC_ELT (targets, j, n)
+ {
+ if (!DECL_ODR_USED (n->decl))
+ reconsider = true;
+ mark_used (n->decl);
+ }
+ }
+
+ release_tree_vector (fns_called_virtually);
+ fns_called_virtually = NULL;
+ return reconsider;
+}
+
/* This routine is called at the end of compilation.
Its job is to create all the code needed to initialize and
destroy the global aggregates. We do the destruction
@@ -4376,6 +4428,11 @@ cp_write_global_declarations (void)
}
}
+ /* If we've seen virtual function calls, mark any overriders of those
+ functions as used so they get instantiated or synthesized. */
+ if (mark_virtual_overrides ())
+ reconsider = true;
+
/* Write out needed type info variables. We have to be careful
looping through unemitted decls, because emit_tinfo_decl may
cause other variables to be needed. New elements will be
diff --git a/gcc/ipa-devirt.c b/gcc/ipa-devirt.c
index 1c6d19d..bc79a7c 100644
--- a/gcc/ipa-devirt.c
+++ b/gcc/ipa-devirt.c
@@ -2804,6 +2804,17 @@ possible_polymorphic_call_targets (tree otr_type,
return nodes;
}
+/* Return vector containing possible targets of polymorphic call to
+ function FN. */
+
+vec <cgraph_node *>
+possible_polymorphic_call_targets (tree fn)
+{
+ return possible_polymorphic_call_targets
+ (DECL_CONTEXT (fn), tree_to_uhwi (DECL_VINDEX (fn)),
+ ipa_dummy_polymorphic_call_context);
+}
+
/* Dump all possible targets of a polymorphic call. */
void
diff --git a/gcc/ipa-utils.h b/gcc/ipa-utils.h
index 1254304..807fbd5 100644
--- a/gcc/ipa-utils.h
+++ b/gcc/ipa-utils.h
@@ -84,6 +84,7 @@ possible_polymorphic_call_targets (tree, HOST_WIDE_INT,
bool *final = NULL,
void **cache_token = NULL,
int *nonconstruction_targets = NULL);
+vec <cgraph_node *> possible_polymorphic_call_targets (tree fn);
odr_type get_odr_type (tree, bool insert = false);
void dump_possible_polymorphic_call_targets (FILE *, tree, HOST_WIDE_INT,
const ipa_polymorphic_call_context &);
