diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 30f18bedf66..6113012ef7d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2000-12-22  Michael Hayes  <m.hayes@elec.canterbury.ac.nz>
+
+	* resource.c (mark_set_resources): Use MARK_SRC_DEST for
+	PRE_MODIFY and POST_MODIFY cases.
+
+	* rtlanal.c (side_effects_p): Handle PRE_MODIFY and POST_MODIFY.
+
 2000-12-22  Michael Hayes  <m.hayes@elec.canterbury.ac.nz>
 
 	* md.texi (Looping Patterns): New node.
diff --git a/gcc/resource.c b/gcc/resource.c
index 4faaedf9a81..979de4d5cc9 100644
--- a/gcc/resource.c
+++ b/gcc/resource.c
@@ -723,9 +723,9 @@ mark_set_resources (x, res, in_dest, mark_type)
 
     case PRE_MODIFY:
     case POST_MODIFY:
-      mark_set_resources (XEXP (x, 0), res, 1, 0);
-      mark_set_resources (XEXP (XEXP (x, 1), 0), res, 0, 0);
-      mark_set_resources (XEXP (XEXP (x, 1), 1), res, 0, 0);
+      mark_set_resources (XEXP (x, 0), res, 1, MARK_SRC_DEST);
+      mark_set_resources (XEXP (XEXP (x, 1), 0), res, 0, MARK_SRC_DEST);
+      mark_set_resources (XEXP (XEXP (x, 1), 1), res, 0, MARK_SRC_DEST);
       return;
 
     case SIGN_EXTRACT:
diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c
index 00aebf47558..a19ebeff81e 100644
--- a/gcc/rtlanal.c
+++ b/gcc/rtlanal.c
@@ -1849,6 +1849,8 @@ side_effects_p (x)
     case PRE_DEC:
     case POST_INC:
     case POST_DEC:
+    case PRE_MODIFY:
+    case POST_MODIFY:
     case CALL:
     case UNSPEC_VOLATILE:
  /* case TRAP_IF: This isn't clear yet.  */