2007-06-01  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/32139
	* c-typeck.c (common_pointer_type): Set TYPE_READONLY
	and TYPE_VOLATILE on the merged pointed to FUNCTION_TYPE
	only if both pointed_to_1 and pointed_to_2 are TYPE_READONLY
	resp. TYPE_VOLATILE.

	* gcc.c-torture/compile/20070531-1.c: New test.

--- gcc/c-typeck.c.jj	2007-04-25 10:13:52.000000000 +0200
+++ gcc/c-typeck.c	2007-06-01 10:51:53.000000000 +0200
@@ -499,6 +499,7 @@ common_pointer_type (tree t1, tree t2)
   tree pointed_to_1, mv1;
   tree pointed_to_2, mv2;
   tree target;
+  int type_quals;
 
   /* Save time if the two types are the same.  */
 
@@ -526,10 +527,19 @@ common_pointer_type (tree t1, tree t2)
   if (TREE_CODE (mv2) != ARRAY_TYPE)
     mv2 = TYPE_MAIN_VARIANT (pointed_to_2);
   target = composite_type (mv1, mv2);
-  t1 = build_pointer_type (c_build_qualified_type
-			   (target,
-			    TYPE_QUALS (pointed_to_1) |
-			    TYPE_QUALS (pointed_to_2)));
+  type_quals = TYPE_QUALS (pointed_to_1) | TYPE_QUALS (pointed_to_2);
+  if (TREE_CODE (pointed_to_1) == FUNCTION_TYPE)
+    {
+      /* TYPE_READONLY and TYPE_VOLATILE on FUNCTION_TYPE should be
+	 logically ANDed, not ORed, as if one function is
+	 __attribute__((const)) and the other is not, the common type
+	 must be conservatively not __attribute__((const))
+	 and similarly for __attribute__((noreturn)).  */
+      type_quals &= ~(TYPE_QUAL_CONST | TYPE_QUAL_VOLATILE);
+      type_quals |= (TYPE_QUALS (pointed_to_1) & TYPE_QUALS (pointed_to_2))
+		    & (TYPE_QUAL_CONST | TYPE_QUAL_VOLATILE);
+    }
+  t1 = build_pointer_type (c_build_qualified_type (target, type_quals));
   return build_type_attribute_variant (t1, attributes);
 }
 
--- gcc/testsuite/gcc.c-torture/compile/20070531-1.c.jj	2007-05-31 13:47:22.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/compile/20070531-1.c	2007-06-01 10:57:15.000000000 +0200
@@ -0,0 +1,11 @@
+/* PR tree-optimization/32139 */
+int foo (void);
+int bar (void) __attribute__ ((const));
+
+int
+test (int x)
+{
+  int a = (x == 10000 ? foo : bar) ();
+  int b = (x == 10000 ? foo : bar) ();
+  return a + b;
+}