emit-rtl.c (change_address, [...]): Return early when there is nothing to change.

	* emit-rtl.c (change_address, adjust_address_1, offset_address,
	widen_memory_access):  Return early when there is nothing to change.

From-SVN: r76512

gcc/ChangeLog

+2004-01-24  Jan Hubicka  <jh@suse.cz>
+
+	* emit-rtl.c (change_address, adjust_address_1, offset_address,
+	widen_memory_access):  Return early when there is nothing to change.
+
 2004-01-24  Jakub Jelinek  <jakub@redhat.com>
 
 	* simplify-rtx.c (simplify_relational_operation): Don't

gcc/emit-rtl.c

@@ -1872,6 +1872,10 @@ change_address (rtx memref, enum machine_mode mode, rtx addr)
   rtx new = change_address_1 (memref, mode, addr, 1);
   enum machine_mode mmode = GET_MODE (new);
 
+  /* If there are no changes, just return the original memory reference.  */
+  if (new == memref)
+    return new;
+
   MEM_ATTRS (new)
     = get_mem_attrs (MEM_ALIAS_SET (memref), 0, 0,
 		     mmode == BLKmode ? 0 : GEN_INT (GET_MODE_SIZE (mmode)),
@@ -1898,6 +1902,11 @@ adjust_address_1 (rtx memref, enum machine_mode mode, HOST_WIDE_INT offset,
   rtx size = 0;
   unsigned int memalign = MEM_ALIGN (memref);
 
+  /* If there are no changes, just return the original memory reference.  */
+  if (mode == GET_MODE (memref) && !offset
+      && (!validate || memory_address_p (mode, addr)))
+    return memref;
+
   /* ??? Prefer to create garbage instead of creating shared rtl.
      This may happen even if offset is nonzero -- consider
      (plus (plus reg reg) const_int) -- so do this always.  */
@@ -1988,6 +1997,10 @@ offset_address (rtx memref, rtx offset, unsigned HOST_WIDE_INT pow2)
   update_temp_slot_address (XEXP (memref, 0), new);
   new = change_address_1 (memref, VOIDmode, new, 1);
 
+  /* If there are no changes, just return the original memory reference.  */
+  if (new == memref)
+    return new;
+
   /* Update the alignment to reflect the offset.  Reset the offset, which
      we don't know.  */
   MEM_ATTRS (new)
@@ -2032,6 +2045,10 @@ widen_memory_access (rtx memref, enum machine_mode mode, HOST_WIDE_INT offset)
   rtx memoffset = MEM_OFFSET (new);
   unsigned int size = GET_MODE_SIZE (mode);
 
+  /* If there are no changes, just return the original memory reference.  */
+  if (new == memref)
+    return new;
+
   /* If we don't know what offset we were at within the expression, then
      we can't know if we've overstepped the bounds.  */
   if (! memoffset)