static bool
dest_safe_for_nrv_p (tree dest)
{
switch (TREE_CODE (dest))
{
case VAR_DECL:
{
subvar_t subvar;
if (is_call_clobbered (dest))
return false;
for (subvar = get_subvars_for_var (dest);
subvar;
subvar = subvar->next)
if (is_call_clobbered (subvar->var))
return false;
return true;
}
case ARRAY_REF:
case COMPONENT_REF:
return dest_safe_for_nrv_p (TREE_OPERAND (dest, 0));
default:
return false;
}
}
static void
execute_return_slot_opt (void)
{
basic_block bb;
FOR_EACH_BB (bb)
{
block_stmt_iterator i;
for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
{
tree stmt = bsi_stmt (i);
tree call;
if (TREE_CODE (stmt) == MODIFY_EXPR
&& (call = TREE_OPERAND (stmt, 1),
TREE_CODE (call) == CALL_EXPR)
&& !CALL_EXPR_RETURN_SLOT_OPT (call)
&& aggregate_value_p (call, call))
{
def_operand_p def_p;
ssa_op_iter op_iter;
/* We determine whether or not the LHS address escapes by
asking whether it is call clobbered. When the LHS isn't a
simple decl, we need to check the VDEFs, so it's simplest
to just loop through all the DEFs. */
FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, op_iter, SSA_OP_ALL_DEFS)
{
tree def = DEF_FROM_PTR (def_p);
if (TREE_CODE (def) == SSA_NAME)
def = SSA_NAME_VAR (def);
if (is_call_clobbered (def))
goto unsafe;
}
/* No defs are call clobbered, so the optimization is safe. */
CALL_EXPR_RETURN_SLOT_OPT (call) = 1;
/* This is too late to mark the target addressable like we do
in gimplify_modify_expr_rhs, but that's OK; anything that
wasn't already addressable was handled there. */
unsafe:;
}
}
