A simple empty class copy is still simple when wrapped in a TARGET_EXPR, so
we need to strip that as well. This change also exposed some unnecessary
copies in return statements, which when returning by invisible reference led
to <RETURN_EXPR <MEM_REF <RESULT_DECL>>>, which gimplify_return_expr didn't
like. So we also need to strip the _REF when we eliminate the INIT_EXPR.
gcc/cp/ChangeLog
2020-03-19 Jason Merrill <jason@redhat.com>
PR c++/94175
* cp-gimplify.c (simple_empty_class_p): Look through
SIMPLE_TARGET_EXPR_P.
(cp_gimplify_expr) [MODIFY_EXPR]: Likewise.
[RETURN_EXPR]: Avoid producing 'return *retval;'.
* call.c (build_call_a): Strip TARGET_EXPR from empty class arg.
* cp-tree.h (SIMPLE_TARGET_EXPR_P): Check that TARGET_EXPR_INITIAL
is non-null.
