Tighten tree-ssa-ccp.c:get_value_for_expr condition

Tighten tree-ssa-ccp.c:get_value_for_expr condition

bit_value_unop and bit_value_binop require constant values
to be INTEGER_CSTs:

  gcc_assert ((rval.lattice_val == CONSTANT
               && TREE_CODE (rval.value) == INTEGER_CST)
              || wi::sext (rval.mask, TYPE_PRECISION (TREE_TYPE (rhs))) == -1);

However, when deciding whether to record a constant value,
the for_bits_p handling in get_value_for_expr used a negative
test for ADDR_EXPR:

  else if (is_gimple_min_invariant (expr)
           && (!for_bits_p || TREE_CODE (expr) != ADDR_EXPR))

This patch uses a positive test for INTEGER_CST instead.

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-ssa-ccp.c (get_value_for_expr): Use a positive test for
	INTEGER_CST rather than a negative test for ADDR_EXPR.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@253056 138bc75d-0d04-0410-961f-82ee72b054a4