diff --git a/gcc/combine.cc b/gcc/combine.cc
index 22bf8e1ec89..c41d8a09b3b 100644
--- a/gcc/combine.cc
+++ b/gcc/combine.cc
@@ -10055,9 +10055,10 @@ simplify_and_const_int_1 (scalar_int_mode mode, rtx varop,
 
   /* See what bits may be nonzero in VAROP.  Unlike the general case of
      a call to nonzero_bits, here we don't care about bits outside
-     MODE.  */
+     MODE unless WORD_REGISTER_OPERATIONS is true.  */
 
-  nonzero = nonzero_bits (varop, mode) & GET_MODE_MASK (mode);
+  enum machine_mode tmode = WORD_REGISTER_OPERATIONS ? word_mode : mode;
+  nonzero = nonzero_bits (varop, tmode) & GET_MODE_MASK (tmode);
 
   /* Turn off all bits in the constant that are known to already be zero.
      Thus, if the AND isn't needed at all, we will have CONSTOP == NONZERO_BITS
diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index 3b33afa2461..5f6f70491d8 100644
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -3752,7 +3752,10 @@ simplify_context::simplify_binary_operation_1 (rtx_code code,
 	return op0;
       if (HWI_COMPUTABLE_MODE_P (mode))
 	{
-	  HOST_WIDE_INT nzop0 = nonzero_bits (trueop0, mode);
+	  /* When WORD_REGISTER_OPERATIONS is true, we need to know the
+	     nonzero bits in WORD_MODE rather than MODE.  */
+	  HOST_WIDE_INT nzop0
+	    = nonzero_bits (trueop0, WORD_REGISTER_OPERATIONS ? word_mode : mode);
 	  HOST_WIDE_INT nzop1;
 	  if (CONST_INT_P (trueop1))
 	    {