re PR middle-end/22141 (Missing optimization when storing structures)

	PR middle-end/22141
	* gimple-ssa-store-merging.c (merged_store_group::apply_stores): Fix
	arguments to clear_bit_region_be.

From-SVN: r254228

gcc/ChangeLog

+2017-10-30  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/22141
+	* gimple-ssa-store-merging.c (merged_store_group::apply_stores): Fix
+	arguments to clear_bit_region_be.
+
 2017-10-30  Jim Wilson  <wilson@tuliptree.org>
 
 	* gimplify.c: Include memmodel.h.

gcc/gimple-ssa-store-merging.c

@@ -701,7 +701,9 @@ merged_store_group::apply_stores ()
 	return false;
       unsigned char *m = mask + (pos_in_buffer / BITS_PER_UNIT);
       if (BYTES_BIG_ENDIAN)
-	clear_bit_region_be (m, pos_in_buffer % BITS_PER_UNIT, info->bitsize);
+	clear_bit_region_be (m, (BITS_PER_UNIT - 1
+				 - (pos_in_buffer % BITS_PER_UNIT)),
+			     info->bitsize);
       else
 	clear_bit_region (m, pos_in_buffer % BITS_PER_UNIT, info->bitsize);
     }