rtl.h (mem_attrs): Spell out more clearly the roles of ALIGN, SIZE, EXPR and OFFSET.

	* rtl.h (mem_attrs): Spell out more clearly the roles of ALIGN,
	SIZE, EXPR and OFFSET.

From-SVN: r55753

gcc/ChangeLog

+Thu Jul 25 18:57:50 2002  J"orn Rennecke <joern.rennecke@superh.com>
+
+	* rtl.h (mem_attrs): Spell out more clearly the roles of ALIGN,
+	SIZE, EXPR and OFFSET.
+
 2002-07-25  Richard Henderson  <rth@redhat.com>
 
 	* emit-rtl.c (set_mem_attributes): Fix size and alignment thinkos

gcc/rtl.h

@@ -89,6 +89,9 @@ typedef struct
    so MEMs that the same attributes share a data structure.  This means
    they cannot be modified in place.  If any element is nonzero, it means
    the value of the corresponding attribute is unknown.  */
+/* ALIGN and SIZE are the alignment and size of the MEM itself,
+   while EXPR can describe a larger underlying object, which might have a
+   stricter alignment; OFFSET is the offset of the MEM within that object.  */
 typedef struct mem_attrs GTY(())
 {
   HOST_WIDE_INT alias;		/* Memory alias set.  */