3 files changed, 41 insertions, 0 deletions
diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 0a6aaa5..50c4ea1 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,8 @@
+2010-09-06  Mark Mitchell  <mark@codesourcery.com>
+
+	* c-common.h (do_warn_double_promotion): Declare.
+	* c-common.c (do_warn_double_promotion): Define.
+
 2010-09-05  Mark Mitchell  <mark@codesourcery.com>
 
 	* c.opt (Wdouble-promotion): New.
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 6b9a967..48c67b4 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -9128,6 +9128,40 @@ warn_for_sign_compare (location_t location,
     }
 }
 
+/* RESULT_TYPE is the result of converting TYPE1 and TYPE2 to a common
+   type via c_common_type.  If -Wdouble-promotion is in use, and the
+   conditions for warning have been met, issue a warning.  GMSGID is
+   the warning message.  It must have two %T specifiers for the type
+   that was converted (generally "float") and the type to which it was
+   converted (generally "double), respectively.  LOC is the location
+   to which the awrning should refer.  */
+
+void
+do_warn_double_promotion (tree result_type, tree type1, tree type2,
+			 const char *gmsgid, location_t loc)
+{
+  tree source_type;
+
+  if (!warn_double_promotion)
+    return;
+  /* If the conversion will not occur at run-time, there is no need to
+     warn about it.  */
+  if (c_inhibit_evaluation_warnings)
+    return;
+  if (TYPE_MAIN_VARIANT (result_type) != double_type_node
+      && TYPE_MAIN_VARIANT (result_type) != complex_double_type_node)
+    return;
+  if (TYPE_MAIN_VARIANT (type1) == float_type_node
+      || TYPE_MAIN_VARIANT (type1) == complex_float_type_node)
+    source_type = type1;
+  else if (TYPE_MAIN_VARIANT (type2) == float_type_node
+	   || TYPE_MAIN_VARIANT (type2) == complex_float_type_node)
+    source_type = type2;
+  else
+    return;
+  warning_at (loc, OPT_Wdouble_promotion, gmsgid, source_type, result_type);
+}
+
 /* Setup a TYPE_DECL node as a typedef representation.
 
    X is a TYPE_DECL for a typedef statement.  Create a brand new
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 3f22485..6118f51 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -900,6 +900,8 @@ extern void warn_for_sign_compare (location_t,
 				   tree op0, tree op1,
 				   tree result_type,
 				   enum tree_code resultcode);
+extern void do_warn_double_promotion (tree, tree, tree, const char *, 
+				      location_t);
 extern void set_underlying_type (tree x);
 extern VEC(tree,gc) *make_tree_vector (void);
 extern void release_tree_vector (VEC(tree,gc) *);