[backport from gcc-4.7.1 r185909 <mikpe@it.uu.se>]

gcc/

2012-03-28  Aurelien Buhrig  <aurelien.buhrig.gcc@gmail.com>

	PR middle-end/51893
	* expmed.c (store_bit_field_1): Fix wordnum value for big-endian
	targets.

--- gcc-4.6.3/gcc/expmed.c.~1~	2011-05-22 21:02:59.000000000 +0200
+++ gcc-4.6.3/gcc/expmed.c	2012-06-10 14:44:45.000000000 +0200
@@ -589,7 +589,10 @@ store_bit_field_1 (rtx str_rtx, unsigned
 	{
 	  /* If I is 0, use the low-order word in both field and target;
 	     if I is 1, use the next to lowest word; and so on.  */
-	  unsigned int wordnum = (backwards ? nwords - i - 1 : i);
+	  unsigned int wordnum = (backwards
+				  ? GET_MODE_SIZE (fieldmode) / UNITS_PER_WORD
+				  - i - 1
+				  : i);
 	  unsigned int bit_offset = (backwards
 				     ? MAX ((int) bitsize - ((int) i + 1)
 					    * BITS_PER_WORD,