expmed.c (store_fixed_bit_field): Don't use a mode bigger than the mode of the memory location.

2001-07-03  Andrew Haley  <aph@redhat.com>

        * expmed.c (store_fixed_bit_field): Don't use a mode bigger than
        the mode of the memory location.

From-SVN: r43864

gcc/ChangeLog

+2001-07-03  Andrew Haley  <aph@redhat.com>
+
+	* expmed.c (store_fixed_bit_field): Don't use a mode bigger than
+	the mode of the memory location.
+
 2001-07-09  Bo Thorsen  <bo@suse.co.uk>
 
 	* config/i386/unix.h (ASM_OUTPUT_MI_THUNK): Fix x86-64 vtable support.

gcc/expmed.c

@@ -673,10 +673,15 @@ store_fixed_bit_field (op0, offset, bitsize, bitpos, value, struct_align)
     {
       /* Get the proper mode to use for this field.  We want a mode that
 	 includes the entire field.  If such a mode would be larger than
-	 a word, we won't be doing the extraction the normal way.  */
+	 a word, we won't be doing the extraction the normal way.  
+	 We don't want a mode bigger than the destination.  */
 
+      mode = GET_MODE (op0);
+      if (GET_MODE_BITSIZE (mode) == 0
+          || GET_MODE_BITSIZE (mode) > GET_MODE_BITSIZE (word_mode))
+        mode = word_mode;
       mode = get_best_mode (bitsize, bitpos + offset * BITS_PER_UNIT,
-			    struct_align, word_mode,
+			    struct_align, mode,
 			    GET_CODE (op0) == MEM && MEM_VOLATILE_P (op0));
 
       if (mode == VOIDmode)