irange: Compare nonzero bits in irange with widest_int [PR108639]

irange: Compare nonzero bits in irange with widest_int [PR108639]

The problem here is we are trying to compare two ranges with different
precisions and the == operator in wide_int is complaining.

Interestingly, the problem is not the nonzero bits, but the fact that
the entire ranges have different precisions.  The reason we don't ICE
when comparing the sub-ranges, is because the code in
irange::operator== works on trees, and tree_int_cst_equal is
promoting the comparison to a widest int:

  if (TREE_CODE (t1) == INTEGER_CST
      && TREE_CODE (t2) == INTEGER_CST
      && wi::to_widest (t1) == wi::to_widest (t2))
    return 1;

This is why we don't see the ICE until the nonzero bits comparison is
done on wide ints.  I think we should maintain the current equality
behavior, and follow suit in the nonzero bit comparison.

I have also fixed the legacy equality code, even though technically
nonzero bits shouldn't appear in legacy.  But better safe than sorry.

	PR tree-optimization/108639

gcc/ChangeLog:

	* value-range.cc (irange::legacy_equal_p): Compare nonzero bits as
	widest_int.
	(irange::operator==): Same.