diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index da613e789fba..34abb3be7efa 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2007-02-07  Ian Lance Taylor  <iant@google.com>
+
+	* lower-subreg.c (simple_move): Reject PARTIAL_INT modes.
+
 2007-02-07  Roger Sayle  <roger@eyesopen.com>
 
 	* config/rs6000/rs6000.md (ctz<mode>2, ffs<mode>2, popcount<mode>2,
diff --git a/gcc/lower-subreg.c b/gcc/lower-subreg.c
index 8d04390da936..fbb506c572e6 100644
--- a/gcc/lower-subreg.c
+++ b/gcc/lower-subreg.c
@@ -136,6 +136,11 @@ simple_move (rtx insn)
 	  == BLKmode))
     return NULL_RTX;
 
+  /* Reject PARTIAL_INT modes.  They are used for processor specific
+     purposes and it's probably best not to tamper with them.  */
+  if (GET_MODE_CLASS (mode) == MODE_PARTIAL_INT)
+    return NULL_RTX;
+
   return set;
 }