(extract_muldiv): When constructing a multiplier/divisor...

(extract_muldiv): When constructing a multiplier/divisor, do not expect
const_binop to correctly determine if overflow has occured, so check explicitly.

From-SVN: r34135

gcc/ChangeLog

+2000-05-24  Nick Clifton  <nickc@cygnus.com>
+
+	* fold-const.c (extract_muldiv): When constructing a
+	multiplier/divisor, do not expect const_binop to correctly
+	determine if overflow has occured, so check explicitly.
+
 2000-05-24  Alexandre Oliva  <aoliva@cygnus.com>
 
 	* c-decl.c (build_enumerator): Don't modify the value's type,

gcc/fold-const.c

@@ -4451,6 +4451,10 @@ extract_muldiv (t, c, code, wide_type)
 	 or floor division, by a power of two, so we can treat it that
 	 way unless the multiplier or divisor overflows.  */
       if (TREE_CODE (op1) == INTEGER_CST
+	  /* const_binop may not detect overflow correctly,
+	     so check for it explicitly here.  */
+	  && TYPE_PRECISION (TREE_TYPE (size_one_node)) > TREE_INT_CST_LOW (op1)
+	  && TREE_INT_CST_HIGH (op1) == 0
 	  && 0 != (t1 = convert (ctype,
 				 const_binop (LSHIFT_EXPR, size_one_node,
 					      op1, 0)))