Add missing int_cst_rangeN checks to tree-vrp.c

Add missing int_cst_rangeN checks to tree-vrp.c

The BIT_AND_EXPR handling in extract_range_from_binary_expr_1
was using value_range_constant_singleton without first checking
whether the range was a constant.  The earlier handling was correctly
guarded:

	  /* If either input range contains only non-negative values
	     we can truncate the result range maximum to the respective
	     maximum of the input range.  */
	  if (int_cst_range0 && tree_int_cst_sgn (vr0.min) >= 0)
	    wmax = wi::min (wmax, vr0.max, TYPE_SIGN (expr_type));
	  if (int_cst_range1 && tree_int_cst_sgn (vr1.min) >= 0)
	    wmax = wi::min (wmax, vr1.max, TYPE_SIGN (expr_type));

so this patch uses the same guards again.

Existing tests showed the need for this once polynomial constants
are added.

2017-09-21  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* tree-vrp.c (extract_range_from_binary_expr_1): Check
	int_cst_rangeN before calling value_range_constant_singleton (&vrN).

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r253054