re PR c++/92343 ([[likely]]/[[unlikely]] prevent method from being a constant expression)

	PR c++/92343
	* constexpr.c (potential_constant_expression_1): Return true rather
	than false for PREDICT_EXPR.

	* g++.dg/cpp2a/attr-likely6.C: New test.

From-SVN: r277819

gcc/cp/ChangeLog

 2019-11-05  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/92343
+	* constexpr.c (potential_constant_expression_1): Return true rather
+	than false for PREDICT_EXPR.
+
 	* decl.c (omp_declare_variant_finalize_one): Call
 	declare_simd_adjust_this not just on the context, but also on the
 	variant-id expression for methods.  Don't call

gcc/cp/constexpr.c

@@ -6493,6 +6493,7 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
     case LABEL_DECL:
     case LABEL_EXPR:
     case CASE_LABEL_EXPR:
+    case PREDICT_EXPR:
     case CONST_DECL:
     case SIZEOF_EXPR:
     case ALIGNOF_EXPR:
@@ -7354,7 +7355,6 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
       return true;
 
     case EMPTY_CLASS_EXPR:
-    case PREDICT_EXPR:
       return false;
 
     case GOTO_EXPR:

gcc/testsuite/ChangeLog

+2019-11-05  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/92343
+	* g++.dg/cpp2a/attr-likely6.C: New test.
+
 2019-11-05  Martin Liska  <mliska@suse.cz>
 
 	PR c++/92339

gcc/testsuite/g++.dg/cpp2a/attr-likely6.C

+// PR c++/92343
+// { dg-do compile { target c++14 } }
+
+constexpr bool
+foo (bool x)
+{
+  if (x)
+    [[unlikely]] return true;
+  else
+    [[likely]] return false;
+}
+
+static_assert (foo (true), "");
+static_assert (!foo (false), "");