Hi,
this patch fixes problem with partitioning WRT named labels. This problem
reproduces with linux kernel LTO and also on firefox with -fno-toplevel-reorder
at least.
Bootstrapped/regtested x86_64-linux and tested it fixes the problem on Firefx,
intend to commit it tomorrow after some more testing on chromium
The patch may need a bit more tweaking WRT nested functions contains nonlocal
adresses taken, but that is even more exotic than the problem I am trying
to solve so I think it can wait for next stage1. This patch should be
backportable
to earlier releases after reversing the C++ APi changes.
Honza
PR lto/50676
* symtab.c (symtab_node::get_partitioning_class): Local static
taking named label inherits partitioning property of the function
it belong to.
* lto-cgraph.c (lto_output_varpool_node, input_varpool_node): Stream
contains_named_label.
* tree.c (decl_address_ip_invariant_p): LABEL_DECL is not IP
invariant.
* cgraph.h (varpool_node): Add contains_named_label.
* cgraphbuild.c (record_reference): Record contains_named_label.
* lto-partition.c (add_references_to_partition,
add_symbol_to_partition_1): Local static var should stay in
same partition as its containing function when it reffer to
named label.
(add_sorted_nodes): Skip static var referring named label.
(lto_balanced_map): Likewise.
* varpool.c (varpool_node::dump): Dump contains_named_label.
* ipa.c (symbol_table::remove_unreachable_nodes): Variable
referring named label keeps its function alive.
* gcc.dg/lto/named-label.c: New testcase.
Index: symtab.c
===================================================================
--- symtab.c (revision 221757)
+++ symtab.c (working copy)
@@ -1682,6 +1682,11 @@ symtab_node::get_partitioning_class (voi
if (varpool_node *vnode = dyn_cast <varpool_node *> (this))
{
+ /* Static variables referring named label are always handled the same way
+ as the function they belong to. */
+ if (vnode->contains_named_label)
+ return cgraph_node::get (decl_function_context (decl))
+ ->get_partitioning_class ();
if (alias && definition && !ultimate_alias_target ()->definition)
return SYMBOL_EXTERNAL;
/* Constant pool references use local symbol names that can not
Index: lto-cgraph.c
===================================================================
--- lto-cgraph.c (revision 221757)
+++ lto-cgraph.c (working copy)
@@ -662,6 +663,7 @@ lto_output_varpool_node (struct lto_simp
bp_pack_value (&bp, node->tls_model, 3);
bp_pack_value (&bp, node->used_by_single_function, 1);
bp_pack_value (&bp, node->need_bounds_init, 1);
+ bp_pack_value (&bp, node->contains_named_label, 1);
streamer_write_bitpack (&bp);
group = node->get_comdat_group ();
@@ -1413,6 +1416,7 @@ input_varpool_node (struct lto_file_decl
node->tls_model = (enum tls_model)bp_unpack_value (&bp, 3);
node->used_by_single_function = (enum tls_model)bp_unpack_value (&bp, 1);
node->need_bounds_init = bp_unpack_value (&bp, 1);
+ node->contains_named_label = bp_unpack_value (&bp, 1);
group = read_identifier (ib);
if (group)
{
Index: tree.c
===================================================================
--- tree.c (revision 221757)
+++ tree.c (working copy)
@@ -3149,7 +3149,12 @@ decl_address_ip_invariant_p (const_tree
switch (TREE_CODE (op))
{
+ /* Theoretically label decls can be considered IP invariants, but until
+ we are able to handle them as regular symbols (i.e. output with
+ non-local visibility), we really want them to be contained in a function
+ they belong to. */
case LABEL_DECL:
+ return false;
case FUNCTION_DECL:
case STRING_CST:
return true;
Index: cgraph.h
===================================================================
--- cgraph.h (revision 221757)
+++ cgraph.h (working copy)
@@ -1778,6 +1780,9 @@ public:
if we did not do any inter-procedural code movement. */
unsigned used_by_single_function : 1;
+ /* Set if te variable is contains a named label. */
+ unsigned contains_named_label : 1;
+
private:
/* Assemble thunks and aliases associated to varpool node. */
void assemble_aliases (void);
Index: cgraphbuild.c
===================================================================
--- cgraphbuild.c (revision 221757)
+++ cgraphbuild.c (working copy)
@@ -112,6 +112,8 @@ record_reference (tree *tp, int *walk_su
varpool_node *vnode = varpool_node::get_create (decl);
ctx->varpool_node->create_reference (vnode, IPA_REF_ADDR);
}
+ if (TREE_CODE (decl) == LABEL_DECL)
+ ctx->varpool_node->contains_named_label = true;
*walk_subtrees = 0;
break;
Index: lto/lto-partition.c
===================================================================
--- lto/lto-partition.c (revision 221757)
+++ lto/lto-partition.c (working copy)
@@ -113,6 +113,14 @@ add_references_to_partition (ltrans_part
for (i = 0; node->iterate_reference (i, ref); i++)
if (ref->referred->get_partitioning_class () == SYMBOL_DUPLICATE)
add_symbol_to_partition (part, ref->referred);
+ /* A static variable referring to named labels must go to the same
+ partition as a function it belongs to. */
+ else if (is_a <varpool_node *> (ref->referred)
+ && (dyn_cast <varpool_node *> (ref->referred)
+ ->contains_named_label)
+ && node->decl == decl_function_context (ref->referred->decl)
+ && !lto_symtab_encoder_in_partition_p (part->encoder,
ref->referred))
+ add_symbol_to_partition (part, ref->referred);
/* References to a readonly variable may be constant foled into its value.
Recursively look into the initializers of the constant variable and add
references, too. */
@@ -193,6 +201,14 @@ add_symbol_to_partition_1 (ltrans_partit
add_symbol_to_partition_1 (part, cnode->instrumented_version);
}
+ /* Variables referring named labels must always go to the same section
+ as the function they belong to. */
+ if (is_a <varpool_node *> (node)
+ && dyn_cast <varpool_node *> (node)->contains_named_label)
+ add_symbol_to_partition_1 (part,
+ cgraph_node::get
+ (decl_function_context (node->decl)));
+
add_references_to_partition (part, node);
/* Add all aliases associated with the symbol. */
@@ -409,7 +425,12 @@ add_sorted_nodes (vec<symtab_node *> &ne
next_nodes.qsort (varpool_node_cmp);
FOR_EACH_VEC_ELT (next_nodes, i, node)
- if (!symbol_partitioned_p (node))
+ if (!symbol_partitioned_p (node)
+ /* Local statics containing named labels always go after their
+ functions. Do not partition on them and wait for them to be
+ dragged in, so we do not force reordering of the functions. */
+ && (!is_a <varpool_node *> (node)
+ || !dyn_cast <varpool_node *> (node)->contains_named_label))
add_symbol_to_partition (partition, node);
}
@@ -636,6 +657,7 @@ lto_balanced_map (int n_lto_partitions)
continue;
if (!symbol_partitioned_p (vnode) && flag_toplevel_reorder
&& !vnode->no_reorder
+ && !vnode->contains_named_label
&& vnode->get_partitioning_class () == SYMBOL_PARTITION)
add_symbol_to_partition (partition, vnode);
index = lto_symtab_encoder_lookup (partition->encoder,
@@ -674,6 +696,7 @@ lto_balanced_map (int n_lto_partitions)
if (!symbol_partitioned_p (vnode) && flag_toplevel_reorder
&& !vnode->no_reorder
&& !vnode->can_remove_if_no_refs_p ()
+ && !vnode->contains_named_label
&& vnode->get_partitioning_class () == SYMBOL_PARTITION)
add_symbol_to_partition (partition, vnode);
index = lto_symtab_encoder_lookup (partition->encoder,
Index: varpool.c
===================================================================
--- varpool.c (revision 221757)
+++ varpool.c (working copy)
@@ -256,6 +256,8 @@ varpool_node::dump (FILE *f)
fprintf (f, " const-value-known");
if (writeonly)
fprintf (f, " write-only");
+ if (contains_named_label)
+ fprintf (f, " contains-named-label");
if (tls_model)
fprintf (f, " tls-%s", tls_model_names [tls_model]);
fprintf (f, "\n");
Index: ipa.c
===================================================================
--- ipa.c (revision 221757)
+++ ipa.c (working copy)
@@ -406,6 +406,18 @@ symbol_table::remove_unreachable_nodes (
n->used_as_abstract_origin = true;
}
}
+
+ /* Static variables referring local label needs the containing
+ function to be output. */
+ if (is_a <varpool_node *> (node)
+ && dyn_cast <varpool_node *> (node)->contains_named_label)
+ {
+ cgraph_node *cn
+ = cgraph_node::get (decl_function_context (node->decl));
+ if (!reachable.add (cn))
+ enqueue_node (cn, &first, &reachable);
+ }
+
/* If any symbol in a comdat group is reachable, force
all externally visible symbols in the same comdat
group to be reachable as well. Comdat-local symbols
Index: testsuite/gcc.dg/lto/named-label.c
===================================================================
--- testsuite/gcc.dg/lto/named-label.c (revision 0)
+++ testsuite/gcc.dg/lto/named-label.c (revision 0)
@@ -0,0 +1,29 @@
+/* { dg-lto-do link } */
+/* { dg-lto-options { { -fPIC -flto -flto-partition=max } } } */
+void *p0,*p1;
+void test (void **p)
+{
+ if (p[0]==p[1])
+ __builtin_abort ();
+ p0=p[0];
+ p1=p[1];
+}
+void test2 (void **p)
+{
+ if (p[0]!=p0|| p[1] !=p1)
+ __builtin_abort ();
+}
+void ** t()
+{
+ static void * labelptr[2]={&&label, &&label2};
+label:
+ test (labelptr);
+label2:
+ return labelptr;
+}
+int
+main()
+{
+ void **labelptr = t();
+ test2 (labelptr);
+}
