[PATCH] Bug fix in store_bit_field_1 for big endian targets (issue 51893)

[Aurelien Buhrig <aurelien.buhrig.gcc@gmail.com>]

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Hi,

This patch (for 4.6) fixes a wrong subword index computation in
store_bit_field_1 for big endian targets when value is at least 4 times
bigger than a word (DI REG value with HI words).

It fixes a regression on gcc.c-torture/execute/bitfld-3.c for my current
backend port.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51893

OK to commit?

Aurélien

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--- gcc-4.6.1.orig/gcc/expmed.c	2011-05-22 21:02:59.000000000 +0200
+++ src/gcc/expmed.c	2012-01-19 09:32:04.000000000 +0100
@@ -589,7 +589,10 @@
 	{
 	  /* 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,