diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 587c95053395..b6723ea9039b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+Fri Sep 24 17:10:56 1999  Nick Clifton  <nickc@cygnus.com>
+
+	* combine.c (simplify_comparison): Cope with downshifting a 32 bit
+	constant on a 64 bit host.  Patch supplied by Geoffrey Keating
+	<geoffk@cygnus.com>.
+
 Fri Sep 24 10:48:10 1999  Bernd Schmidt  <bernds@cygnus.co.uk>
 
 	* builtins.c (expand_builtin): Use MD_EXPAND_BUILTIN if defined.
diff --git a/gcc/combine.c b/gcc/combine.c
index 0e556db4ab9b..61d55d0c893e 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -10364,10 +10364,10 @@ simplify_comparison (code, pop0, pop1)
 	    {
 	      /* We must perform a logical shift, not an arithmetic one,
 		 as we want the top N bits of C to be zero.  */
-	      unsigned HOST_WIDE_INT temp = const_op;
+	      unsigned HOST_WIDE_INT temp = const_op & GET_MODE_MASK (mode);
 	      
 	      temp >>= INTVAL (XEXP (op0, 1));
-	      op1 = GEN_INT (temp);
+	      op1 = GEN_INT (trunc_int_for_mode (temp, mode));
 	      op0 = XEXP (op0, 0);
 	      continue;
 	    }