https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116922
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot
gnu.org
Keywords|needs-bisection |
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2024-10-01
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Deleting v_17 = PHI <{ 0.0, 0.0, 0.0, 0.0 }(4), v_19(6)>
static void
remove_unused_var (tree var)
{
gimple *stmt = SSA_NAME_DEF_STMT (var);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Deleting ");
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
}
gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
gsi_remove (&gsi, true);
release_defs (stmt);
}
That is wrong for phis.
It should have been something like:
if (gimple_code (t) == GIMPLE_PHI)
{
remove_phi_node (&gsi, true);
phiremoved++;
}
else
{
unlink_stmt_vdef (t);
gsi_remove (&gsi, true);
release_defs (t);
stmtremoved++;
}
remove_unused_var was added in GCC 6 though; r6-4109-g6a75d560c85508 .
Though backprop didn't start doing something for this testcase until GCC 10.
This should be easy to fix.
I am going to do 2 patches, one to fix remove_unused_var to use the correct way
of removing the phis. And then secondary change the code to use
simple_dce_from_worklist (if I get a chance).
