[backport gcc-4.9/trunk r200926 <mikpe@it.uu.se>]

gcc/

2013-07-12  Michael Matz  <matz@suse.de>

	PR middle-end/55771
	* convert.c (convert_to_real): Reject non-float inner types.

gcc/testsuite/

2013-07-12  Michael Matz  <matz@suse.de>

	PR middle-end/55771
	* c-c++-common/pr55771.c: New test.

--- gcc-4.7.3/gcc/convert.c.~1~	2012-04-27 12:51:58.000000000 +0200
+++ gcc-4.7.3/gcc/convert.c	2013-07-13 09:06:12.994308969 +0200
@@ -261,11 +261,12 @@ convert_to_real (tree type, tree expr)
     switch (TREE_CODE (expr))
       {
 	/* Convert (float)-x into -(float)x.  This is safe for
-	   round-to-nearest rounding mode.  */
+	   round-to-nearest rounding mode when the inner type is float.  */
 	case ABS_EXPR:
 	case NEGATE_EXPR:
 	  if (!flag_rounding_math
-	      && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (expr)))
+	      && FLOAT_TYPE_P (itype)
+	      && TYPE_PRECISION (type) < TYPE_PRECISION (itype))
 	    return build1 (TREE_CODE (expr), type,
 			   fold (convert_to_real (type,
 						  TREE_OPERAND (expr, 0))));
--- gcc-4.7.3/gcc/testsuite/c-c++-common/pr55771.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.7.3/gcc/testsuite/c-c++-common/pr55771.c	2013-07-13 09:06:12.994308969 +0200
@@ -0,0 +1,12 @@
+/* { dg-do run } */
+
+float global;
+int main()
+{
+  unsigned long z = 1;
+  float x = -z;
+  global = x;
+  if (global < 0)
+    __builtin_abort ();
+  return 0;
+}