From d91b6c93f98cac71f5588d73191d08ad788e600c Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Fri, 9 Aug 2024 16:14:18 -0400 Subject: c++: ICE with NSDMIs and fn arguments [PR116015] The problem in this PR is that we ended up with {.rows=(&)->n, .outer_stride=(&)->rows} that is, two PLACEHOLDER_EXPRs for different types on the same level in one { }. That should not happen; we may, for instance, neglect to replace a PLACEHOLDER_EXPR due to CONSTRUCTOR_PLACEHOLDER_BOUNDARY on the constructor. The same problem happened in PR100252, which I fixed by introducing replace_placeholders_for_class_temp_r. That didn't work here, though, because r_p_for_c_t_r only works for non-eliding TARGET_EXPRs: replacing a PLACEHOLDER_EXPR with a temporary that is going to be elided will result in a crash in gimplify_var_or_parm_decl when it encounters such a loose decl. But leaving the PLACEHOLDER_EXPRs in is also bad because then we end up with this PR. TARGET_EXPRs for function arguments are elided in gimplify_arg. The argument will get a real temporary only in get_formal_tmp_var. One idea was to use the temporary that is going to be elided anyway, and then replace_decl it with the real object once we get it. But that didn't work out: one problem is that we elide the TARGET_EXPR for an argument before we create the real temporary for the argument, and when we get it, the context that this was a TARGET_EXPR for an argument has been lost. We're also in the middle end territory now, even though this is a C++-specific problem. A solution is to simply stop eliding TARGET_EXPRs whose initializer is a CONSTRUCTOR. Such copies can't be (at the moment) elided anyway. But not eliding all TARGET_EXPRs would be a pessimization. PR c++/116015 gcc/cp/ChangeLog: * call.cc (convert_for_arg_passing): Don't set_target_expr_eliding when the TARGET_EXPR initializer is a CONSTRUCTOR. gcc/ChangeLog: * gimplify.cc (gimplify_arg): Do not strip a TARGET_EXPR whose initializer is a CONSTRUCTOR. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/nsdmi-aggr23.C: New test. --- gcc/gimplify.cc | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'gcc/gimplify.cc') diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc index 71cc6c3..26a216e 100644 --- a/gcc/gimplify.cc +++ b/gcc/gimplify.cc @@ -3760,7 +3760,22 @@ gimplify_arg (tree *arg_p, gimple_seq *pre_p, location_t call_location, { tree init = TARGET_EXPR_INITIAL (*arg_p); if (init - && !VOID_TYPE_P (TREE_TYPE (init))) + && !VOID_TYPE_P (TREE_TYPE (init)) + /* Currently, due to c++/116015, it is not desirable to + strip a TARGET_EXPR whose initializer is a {}. The + problem is that if we do elide it, we also have to + replace all the occurrences of the slot temporary in the + initializer with the temporary created for the argument. + But we do not have that temporary yet so the replacement + would be quite awkward and it might be needed to resort + back to a PLACEHOLDER_EXPR. Note that stripping the + TARGET_EXPR wouldn't help anyway, as gimplify_expr would + just allocate a temporary to store the CONSTRUCTOR into. + (FIXME PR116375.) + + See convert_for_arg_passing for the C++ code that marks + the TARGET_EXPR as eliding or not. */ + && TREE_CODE (init) != CONSTRUCTOR) *arg_p = init; } } -- cgit v1.1