re PR c++/88449 (__builtin_is_constant_evaluated misbehaves due to constexpr call...

re PR c++/88449 (__builtin_is_constant_evaluated misbehaves due to constexpr call caching)

	PR c++/88449
	* constexpr.c (struct constexpr_call): Add pretend_const_required
	member.
	(constexpr_call_hasher::equal): Return false if pretend_const_required
	members differ.
	(cxx_eval_call_expression): Adjust new_call initialization.  Hash in
	ctx->pretend_const_required.

	* g++.dg/cpp2a/is-constant-evaluated1.C: Change from dg-do compile
	to dg-do run.
	(e): Adjust comment with correct expected value.
	(main): Expect e == 1.
	* g++.dg/cpp2a/is-constant-evaluated2.C: New test.

From-SVN: r267044