Hi,
as we discover targets of previously indirect calls in ipa-inline and
ipa-cp, we sometimes figure out that the targets are not a function.
One typical example is when NULL is passed as a function pointer
parameter, another is when C++ member-pointer points to a virtual
function and the overloaded field of the structure which can also hold
pointers to non-virtual methods contains odd integer constants.
I have gone through all the cases when this happens when LTO building
Mozilla Firefox and verified all of them were OK and legal. Because
no such call to a non-function can ever occur in a legal program, I
have decided to turn them into calls of builting_unreachable, which
then could help further optimizations.
Because calls to builtin_unreachable is not cgraph_maybe_hot_edge_p,
whereas an indirect call with an unknown destination is, this change
often triggered assertion tree-ipa-inline-transform.c:263. I have
discussed this with Honza and he has agreed to switch the check off
when there are newly discovered direct edges.
The patch has passed bootstrap and is undergoing testing now. OK for
trunk if it passes?
Thanks,
Martin
2013-05-09 Martin Jambor <mjam...@suse.cz>
* ipa-prop.c (ipa_make_edge_direct_to_target): Redirect calls to
non-functions to builtin_unreachable.
* ipa-inline-transform.c (inline_call): Do not assert estimates were
correct when new direct edges were discovered.
Index: src/gcc/ipa-prop.c
===================================================================
--- src.orig/gcc/ipa-prop.c
+++ src/gcc/ipa-prop.c
@@ -2200,6 +2200,7 @@ ipa_make_edge_direct_to_target (struct c
{
struct cgraph_node *callee;
struct inline_edge_summary *es = inline_edge_summary (ie);
+ bool unreachable = false;
if (TREE_CODE (target) == ADDR_EXPR)
target = TREE_OPERAND (target, 0);
@@ -2210,12 +2211,17 @@ ipa_make_edge_direct_to_target (struct c
{
if (dump_file)
fprintf (dump_file, "ipa-prop: Discovered direct call to
non-function"
- " in %s/%i.\n",
+ " in %s/%i, making it unreachable.\n",
cgraph_node_name (ie->caller), ie->caller->symbol.order);
- return NULL;
+ target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+ callee = cgraph_get_create_node (target);
+ unreachable = true;
}
+ else
+ callee = cgraph_get_node (target);
}
- callee = cgraph_get_node (target);
+ else
+ callee = cgraph_get_node (target);
/* Because may-edges are not explicitely represented and vtable may be
external,
we may create the first reference to the object in the unit. */
@@ -2252,7 +2258,7 @@ ipa_make_edge_direct_to_target (struct c
- eni_size_weights.call_cost);
es->call_stmt_time -= (eni_time_weights.indirect_call_cost
- eni_time_weights.call_cost);
- if (dump_file)
+ if (dump_file && !unreachable)
{
fprintf (dump_file, "ipa-prop: Discovered %s call to a known target "
"(%s/%i -> %s/%i), for stmt ",
Index: src/gcc/ipa-inline-transform.c
===================================================================
--- src.orig/gcc/ipa-inline-transform.c
+++ src/gcc/ipa-inline-transform.c
@@ -260,7 +260,7 @@ inline_call (struct cgraph_edge *e, bool
#ifdef ENABLE_CHECKING
/* Verify that estimated growth match real growth. Allow off-by-one
error due to INLINE_SIZE_SCALE roudoff errors. */
- gcc_assert (!update_overall_summary || !overall_size
+ gcc_assert (!update_overall_summary || !overall_size || new_edges_found
|| abs (estimated_growth - (new_size - old_size)) <= 1
/* FIXME: a hack. Edges with false predicate are accounted
wrong, we should remove them from callgraph. */
