PR c++/87481
* doc/invoke.texi (-fconstexpr-ops-limit=): Document.
* c.opt (-fconstexpr-ops-limit=): New option.
* constexpr.c (struct constexpr_ctx): Add constexpr_ops_count member.
(cxx_eval_constant_expression): When not skipping, not constant class
or location wrapper, increment *ctx->constexpr_ops_count and if it is
above constexpr_loop_nest_limit, diagnose failure.
(cxx_eval_outermost_constant_expr): Add constexpr_ops_count and
initialize ctx.constexpr_ops_count to its address.
(is_sub_constant_expr): Likewise.
* g++.dg/cpp1y/constexpr-87481.C: New test.
From-SVN: r269874
