[backport from gcc-4.7/trunk <mikpe@it.uu.se>]

gcc/cp/

2011-03-16  Jason Merrill  <jason@redhat.com>

	PR c++/47570
	* semantics.c (cxx_eval_constant_expression) [COMPOUND_EXPR]: Don't
	use the generic binary expression handling.

gcc/testsuite/

2011-03-16  Jason Merrill  <jason@redhat.com>

	* g++.dg/cpp0x/constexpr-47570.C: New.

--- gcc-4.6-20110318/gcc/cp/semantics.c.~1~	2011-03-08 06:28:13.000000000 +0100
+++ gcc-4.6-20110318/gcc/cp/semantics.c	2011-03-21 15:42:05.000000000 +0100
@@ -6896,7 +6896,13 @@ cxx_eval_constant_expression (const cons
 	  r = cxx_eval_constant_expression (call, op0, allow_non_constant,
 					    addr, non_constant_p);
 	else
-	  goto binary;
+	  {
+	    /* Check that the LHS is constant and then discard it.  */
+	    cxx_eval_constant_expression (call, op0, allow_non_constant,
+					  false, non_constant_p);
+	    r = cxx_eval_constant_expression (call, op1, allow_non_constant,
+					      addr, non_constant_p);
+	  }
       }
       break;
 
@@ -6938,7 +6944,6 @@ cxx_eval_constant_expression (const cons
     case UNEQ_EXPR:
     case RANGE_EXPR:
     case COMPLEX_EXPR:
-    binary:
       r = cxx_eval_binary_expression (call, t, allow_non_constant, addr,
 				      non_constant_p);
       break;
--- gcc-4.6-20110318/gcc/testsuite/g++.dg/cpp0x/constexpr-47570.C.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6-20110318/gcc/testsuite/g++.dg/cpp0x/constexpr-47570.C	2011-03-21 15:42:05.000000000 +0100
@@ -0,0 +1,25 @@
+// PR c++/47570
+// { dg-options -std=c++0x }
+
+unsigned int constexpr one()
+{ return 1; }
+
+int constexpr one_B()
+{ return 1; }
+
+int main()
+{
+  // FAIL TO COMPILE:
+  static bool constexpr SC_huh1 = ((unsigned int)one()) >= ((unsigned int)0);
+  static bool constexpr SC_huh2 = one() >= ((unsigned int)0);
+  static bool constexpr SC_huh3 = one() >= 0;
+
+  // COMPILE OK:
+  static bool constexpr SC_huh4 = ((one() == 0) || (one() > 0));
+  static bool constexpr SC_huh5 = one() == 0;
+  static bool constexpr SC_huh6 = one() > 0;
+  static bool constexpr SC_huh7 = one_B() >= 0;
+  static bool constexpr SC_huh8 = one() >= 1;
+
+  return SC_huh3;
+}