https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120146
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Component|tree-optimization |ipa
CC| |hubicka at gcc dot gnu.org
Ever confirmed|0 |1
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
Last reconfirmed| |2025-05-07
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
I'd guess openacc creates a global but does not create a varpool node for it
and thus
varpool_node *vnode = varpool_node::get (decl);
/* For escaped variables initialize them from nonlocal. */
if (!vnode->all_refs_explicit_p ())
make_copy_constraint (vi, nonlocal_id);
gets a NULL vnode.
Hmm, the decl is
$1 = <var_decl 0x7ffff6fe8390 _ZTV14basic_ifstreamIcE>
<var_decl 0x7ffff6fe8390 _ZTV14basic_ifstreamIcE
...
readonly addressable used public static tree_1 tree_2 ignored external read
virtual decl_5 decl_8 BLK t.c:5:28 size <integer_cst 0x7ffff6e20708 192>
unit-size <integer_cst 0x7ffff6e206d8 24>
which is referenced from the CONSTRUCTOR
{&MEM <int (*) ()> [(void *)&_ZTV14basic_ifstreamIcE + 24B], &MEM <int (*) ()>
[(void *)&_ZTC14basic_ifstreamIcE0_13basic_istream + 24B]}
of
$5 = <varpool_node * 0x7ffff6e26880 "_ZTT14basic_ifstreamIcE"/16>
and -fopenacc simply enables early IPA PTA it seems:
PUSH_INSERT_PASSES_WITHIN (pass_ipa_oacc)
NEXT_PASS (pass_ipa_pta);
/* Pass group that runs when the function is an offloaded function
containing oacc kernels loops. */
NEXT_PASS (pass_ipa_oacc_kernels);
...
Likely caused by my fix for PR119973. I'm not sure why the variables
referenced in the global var initializer are not finalized? I see
_ZTT14basic_ifstreamIcE/17 (constexpr const void*
basic_ifstream<char>::_ZTT14basic_ifstreamIcE [2])
Type: variable definition analyzed
Visibility: semantic_interposition external public virtual artificial
Aux: @0x4f8c200
References: _ZTV14basic_ifstreamIcE/8 (addr)
_ZTC14basic_ifstreamIcE0_13basic_istream/20 (addr)
But at the time IPA PTA runs the symbol is elided, but the reference through
the CTOR is still there? That is, DECL_INITIAL isn't pruned? At the
IPA PTA point the variable refering to the elided node is
_ZTT14basic_ifstreamIcE/17 (constexpr const void*
basic_ifstream<char>::_ZTT14basic_ifstreamIcE [2])
Type: variable
Body removed by symtab_remove_unreachable_nodes
Visibility: externally_visible semantic_interposition external public virtual
artificial
References:
Referring: _Z18CompareFiles_path2v/7 (read)
Availability: not_available
Varpool flags: initialized read-only const-value-known
so it's const-value-known, but it no longer has references (from said
initializer) and it's not_available, whatever that means.
IPA PTA in it's walk over globals still does the following, not sure
if it should skip some variables. The one in question has !var->analyzed
for example, for whatever reason.
/* Create constraints for global variables and their initializers. */
FOR_EACH_VARIABLE (var)
{
if (var->alias && var->analyzed)
continue;
varinfo_t vi = get_vi_for_tree (var->decl);
/* For the purpose of IPA PTA unit-local globals are not
escape points. */
bool nonlocal_p = (DECL_EXTERNAL (var->decl)
|| TREE_PUBLIC (var->decl)
|| var->used_from_other_partition
|| var->force_output);
var->call_for_symbol_and_aliases (refered_from_nonlocal_var,
&nonlocal_p, true);
if (nonlocal_p)
vi->is_ipa_escape_point = true;
}
Not processing globals with !var->analyzed does not help since we still
refer to those from the IL (CompareFiles_path2):
# VUSE <.MEM_2>
_4 = MEM[(const void * *)&_ZTT14basic_ifstreamIcE + 8B];
so why was the varpool node "elided"? Or why is it not analyzed/available?
I'm confused.
I can paper over the ICE by simply "dealing" with a NULL varpool node
but I think this is just playing whack-a-mole without understanding
what IPA does here :/
"Fix:"
diff --git a/gcc/tree-ssa-structalias.cc b/gcc/tree-ssa-structalias.cc
index 3ad0c69930c..1a6522593ba 100644
--- a/gcc/tree-ssa-structalias.cc
+++ b/gcc/tree-ssa-structalias.cc
@@ -6562,7 +6562,7 @@ create_variable_info_for (tree decl, const char *name,
bool add_id)
varpool_node *vnode = varpool_node::get (decl);
/* For escaped variables initialize them from nonlocal. */
- if (!vnode->all_refs_explicit_p ())
+ if (!vnode || !vnode->all_refs_explicit_p ())
make_copy_constraint (vi, nonlocal_id);
/* While we can in theory walk references for the varpool
@@ -6581,7 +6581,7 @@ create_variable_info_for (tree decl, const char *name,
bool add_id)
process_constraint (new_constraint (lhs, *rhsp));
/* If this is a variable that escapes from the unit
the initializer escapes as well. */
- if (!vnode->all_refs_explicit_p ())
+ if (!vnode || !vnode->all_refs_explicit_p ())
{
lhs.var = escaped_id;
lhs.offset = 0;
