https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116015
--- Comment #9 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:d91b6c93f98cac71f5588d73191d08ad788e600c commit r15-2920-gd91b6c93f98cac71f5588d73191d08ad788e600c Author: Marek Polacek <pola...@redhat.com> Date: Fri Aug 9 16:14:18 2024 -0400 c++: ICE with NSDMIs and fn arguments [PR116015] The problem in this PR is that we ended up with {.rows=(&<PLACEHOLDER_EXPR struct Widget>)->n, .outer_stride=(&<PLACEHOLDER_EXPR struct MatrixLayout>)->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.
