c++: constexpr, trivial, and non-alias target [PR111075]

On Darwin and other targets with !can_alias_cdtor, we instead go to
maybe_thunk_ctor, which builds a thunk function that calls the general
constructor.  And then cp_fold tries to constant-evaluate that call, and we
ICE because we don't expect to ever be asked to constant-evaluate a call to
a trivial function.

No new test because this fixes g++.dg/torture/tail-padding1.C on affected
targets.

	PR c++/111075

gcc/cp/ChangeLog:

	* constexpr.cc (cxx_eval_call_expression): Allow trivial
	call from a thunk.

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index dc59f59aa3f34759f800ee8f1683310a60b4cb73..4346b29abc685e0102e4624d42dbef4c2f1cb6f7 100644 (file)
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -3103,6 +3103,9 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
      we can only get a trivial function here with -fno-elide-constructors.  */
   gcc_checking_assert (!trivial_fn_p (fun)
                       || !flag_elide_constructors
+                      /* Or it's a call from maybe_thunk_body (111075).  */
+                      || (TREE_CODE (t) == CALL_EXPR ? CALL_FROM_THUNK_P (t)
+                          : AGGR_INIT_FROM_THUNK_P (t))
                       /* We don't elide constructors when processing
                          a noexcept-expression.  */
                       || cp_noexcept_operand);