https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99951
Bug ID: 99951
Summary: Dead return value after modify_call() is not released
Product: gcc
Version: tree-ssa
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ipa
Assignee: unassigned at gcc dot gnu.org
Reporter: fxue at os dot amperecomputing.com
CC: marxin at gcc dot gnu.org
Target Milestone: ---
By ipa_param_adjustments::modify_call(), a call statement with return value
might be replaced to a new void-return call. But the original return value SSA
is not released, which would give us garbage SSA when traversing
FOR_EACH_SSA_NAME.
In the following code, all uses of stmt's lhs are redirected to a new one, and
it becomes unused, but is never released from SSA name table.
if (tree lhs = gimple_call_lhs (stmt))
{
if (!m_skip_return)
gimple_call_set_lhs (new_stmt, lhs);
else if (TREE_CODE (lhs) == SSA_NAME)
{
/* LHS should now by a default-def SSA. Unfortunately default-def
SSA_NAMEs need a backing variable (or at least some code examining
SSAs assumes it is non-NULL). So we either have to re-use the
decl we have at hand or introdice a new one. */
tree repl = create_tmp_var (TREE_TYPE (lhs), "removed_return");
repl = get_or_create_ssa_default_def (cfun, repl);
SSA_NAME_IS_DEFAULT_DEF (repl) = true;
imm_use_iterator ui;
use_operand_p use_p;
gimple *using_stmt;
FOR_EACH_IMM_USE_STMT (using_stmt, ui, lhs)
{
FOR_EACH_IMM_USE_ON_STMT (use_p, ui)
{
SET_USE (use_p, repl);
}
update_stmt (using_stmt);
}
}
}
