Handle C++14 constexpr flow control.

	* constexpr.c (cxx_eval_loop_expr, cxx_eval_switch_expr): New.
	(cxx_eval_statement_list): New.
	(cxx_eval_constant_expression): Handle LABEL_EXPR,
	CASE_LABEL_EXPR, GOTO_EXPR, LOOP_EXPR, SWITCH_EXPR.  Handle jump
	semantics of RETURN_EXPR.
	(many functions): Add jump_target parameter.
	(returns, breaks, continues, switches, label_matches): New.
	* cp-tree.h (LABEL_DECL_BREAK, LABEL_DECL_CONTINUE): New.
	* cp-gimplify.c (begin_bc_block): Set them.

From-SVN: r217670

gcc/cp/ChangeLog

 2014-11-17  Jason Merrill  <jason@redhat.com>
 
+	Handle C++14 constexpr flow control.
+	* constexpr.c (cxx_eval_loop_expr, cxx_eval_switch_expr): New.
+	(cxx_eval_statement_list): New.
+	(cxx_eval_constant_expression): Handle LABEL_EXPR,
+	CASE_LABEL_EXPR, GOTO_EXPR, LOOP_EXPR, SWITCH_EXPR.  Handle jump
+	semantics of RETURN_EXPR.
+	(many functions): Add jump_target parameter.
+	(returns, breaks, continues, switches, label_matches): New.
+	* cp-tree.h (LABEL_DECL_BREAK, LABEL_DECL_CONTINUE): New.
+	* cp-gimplify.c (begin_bc_block): Set them.
+
 	* cp-gimplify.c (genericize_cp_loop): Use LOOP_EXPR.
 	(genericize_for_stmt): Handle null statement-list.
 

gcc/cp/cp-gimplify.c

@@ -74,6 +74,10 @@ begin_bc_block (enum bc_t bc, location_t location)
   tree label = create_artificial_label (location);
   DECL_CHAIN (label) = bc_label[bc];
   bc_label[bc] = label;
+  if (bc == bc_break)
+    LABEL_DECL_BREAK (label) = true;
+  else
+    LABEL_DECL_CONTINUE (label) = true;
   return label;
 }
 

gcc/cp/cp-tree.h

@@ -148,12 +148,14 @@ c-common.h, not after.
       DECL_LOCAL_FUNCTION_P (in FUNCTION_DECL)
       DECL_MUTABLE_P (in FIELD_DECL)
       DECL_DEPENDENT_P (in USING_DECL)
+      LABEL_DECL_BREAK (in LABEL_DECL)
    1: C_TYPEDEF_EXPLICITLY_SIGNED (in TYPE_DECL).
       DECL_TEMPLATE_INSTANTIATED (in a VAR_DECL or a FUNCTION_DECL)
       DECL_MEMBER_TEMPLATE_P (in TEMPLATE_DECL)
       USING_DECL_TYPENAME_P (in USING_DECL)
       DECL_VLA_CAPTURE_P (in FIELD_DECL)
       DECL_ARRAY_PARAMETER_P (in PARM_DECL)
+      LABEL_DECL_CONTINUE (in LABEL_DECL)
    2: DECL_THIS_EXTERN (in VAR_DECL or FUNCTION_DECL).
       DECL_IMPLICIT_TYPEDEF_P (in a TYPE_DECL)
    3: DECL_IN_AGGR_P.
@@ -3243,6 +3245,14 @@ more_aggr_init_expr_args_p (const aggr_init_expr_arg_iterator *iter)
 #define DECL_LOCAL_FUNCTION_P(NODE) \
   DECL_LANG_FLAG_0 (FUNCTION_DECL_CHECK (NODE))
 
+/* Nonzero if NODE is the target for genericization of 'break' stmts.  */
+#define LABEL_DECL_BREAK(NODE) \
+  DECL_LANG_FLAG_0 (LABEL_DECL_CHECK (NODE))
+
+/* Nonzero if NODE is the target for genericization of 'continue' stmts.  */
+#define LABEL_DECL_CONTINUE(NODE) \
+  DECL_LANG_FLAG_1 (LABEL_DECL_CHECK (NODE))
+
 /* True if NODE was declared with auto in its return type, but it has
    started compilation and so the return type might have been changed by
    return type deduction; its declared return type should be found in

gcc/testsuite/g++.dg/cpp1y/constexpr-loop1.C

+// { dg-do compile { target c++14 } }
+
+constexpr int f (int i)
+{
+  int j = 0;
+  for (; i > 0; --i)
+    ++j;
+  return j;
+}
+
+constexpr int i = f(42);
+#define SA(X) static_assert((X),#X)
+SA(i==42);

gcc/testsuite/g++.dg/cpp1y/constexpr-return1.C

+// { dg-do compile { target c++14 } }
+
+constexpr int f (int i)
+{
+  return 24;
+  return 36;
+}
+
+constexpr int i = f(42);
+#define SA(X) static_assert((X),#X)
+SA(i==24);

gcc/testsuite/g++.dg/cpp1y/constexpr-return2.C

+// { dg-do compile { target c++14 } }
+
+constexpr int f (int i)
+{
+}
+
+constexpr int i = f(42);	// { dg-error "flows off the end" }

gcc/testsuite/g++.dg/cpp1y/constexpr-switch1.C

+// { dg-do compile { target c++14 } }
+
+constexpr int f (int i)
+{
+  switch (i)
+    {
+    case 1:
+      return 42;
+    default:
+      return 0;
+    }
+}
+
+constexpr int i = f(1);
+#define SA(X) static_assert((X),#X)
+SA(i==42);

gcc/testsuite/g++.dg/cpp1y/constexpr-switch2.C

+// { dg-do compile { target c++14 } }
+
+constexpr int f (int i)
+{
+  int j = 0;
+  switch (i)
+    {
+    case 1:
+      j = 42;
+      break;
+    default:
+      j = 24;
+      break;
+    }
+  return j;
+}
+
+constexpr int i = f(1);
+#define SA(X) static_assert((X),#X)
+SA(i==42);

gcc/testsuite/g++.dg/cpp1y/constexpr-switch3.C

+// { dg-do compile { target c++14 } }
+
+constexpr int f (int i)
+{
+  int j = 0;
+  switch (i)
+    {
+    case 1:
+      j = 42;
+      break;
+    default:
+      j = 24;
+      break;
+    }
+  return j;
+}
+
+constexpr int i = f(2);
+#define SA(X) static_assert((X),#X)
+SA(i==24);