c++: Fix ICE due to folding a call to constructor on cdtor_returns_this arches (aka...

When targetm.cxx.cdtor_returns_this () (aka on arm32 TARGET_AAPCS_BASED)
constructor is supposed to return this pointer, but when we cp_fold such
a call, we don't take that into account and just INIT_EXPR the object,
so we can later ICE during gimplification, because the expression doesn't
have the right type.

2024-02-23  Jakub Jelinek  <jakub@redhat.com>

	PR c++/113083
	* cp-gimplify.cc (cp_fold): For targetm.cxx.cdtor_returns_this ()
	wrap r into a COMPOUND_EXPR and return folded CALL_EXPR_ARG (x, 0).

	* g++.dg/cpp0x/constexpr-113083.C: New test.

diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index 30e94797f9fd04fa8f13cb18460d05003e199a6f..f3baae6ade7527a1c99626cc7eff268fca9deba5 100644 (file)
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -3412,9 +3412,15 @@ cp_fold (tree x, fold_flags_t flags)
            if (DECL_CONSTRUCTOR_P (callee))
              {
                loc = EXPR_LOCATION (x);
-               tree s = build_fold_indirect_ref_loc (loc,
-                                                     CALL_EXPR_ARG (x, 0));
+               tree a = CALL_EXPR_ARG (x, 0);
+               bool return_this = targetm.cxx.cdtor_returns_this ();
+               if (return_this)
+                 a = cp_save_expr (a);
+               tree s = build_fold_indirect_ref_loc (loc, a);
                r = cp_build_init_expr (s, r);
+               if (return_this)
+                 r = build2_loc (loc, COMPOUND_EXPR, TREE_TYPE (x), r,
+                                 fold_convert_loc (loc, TREE_TYPE (x), a));
              }
            x = r;
            break;

diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-113083.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-113083.C
new file mode 100644 (file)
index 0000000..3829ac5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-113083.C
@@ -0,0 +1,16 @@
+// PR c++/113083
+// { dg-do compile { target c++11 } }
+// { dg-options "-Os" }
+
+struct A { constexpr A (); };
+
+void
+foo ()
+{
+  A b;
+}
+
+constexpr
+A::A ()
+{
+}