Re: [range-ops] patch 02/04: enforce canonicalization in value_range

[Aldy Hernandez <aldyh@redhat.com>]

On 7/2/19 5:36 PM, Jeff Law wrote:

> I don't see anything inherently concerning here.  I do wonder if there's
> any value in having a debugging function in the class that would iterate
> over the ranges and check them for proper canonicalization, verify that
> VR_{VARYING,UNDEFINED} objects do not have equivalences, etc.  Thoughts?

In patch 01 we have:

> diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
> index 594ee9adc17..97046c22ed1 100644
> --- a/gcc/tree-vrp.c
> +++ b/gcc/tree-vrp.c
> @@ -86,6 +86,8 @@ value_range_base::set (enum value_range_kind kind, tree min, t
> ree max)
>  void
>  value_range::set_equiv (bitmap equiv)
>  {
> +  if (undefined_p () || varying_p ())
> +    equiv = NULL;

So it shouldn't be possible to attach an equivalence to a VARYING / 
UNDEFINED range.  Plus, we already have a sanity checker:

> void
> value_range::check ()
> {
>   value_range_base::check ();
>   switch (m_kind)
>     {
>     case VR_UNDEFINED:
>     case VR_VARYING:
>       gcc_assert (!m_equiv || bitmap_empty_p (m_equiv));
>     default:;
>     }
> }

We have no methods for altering a range, except for changing 
equivalences.  So it shouldn't be possible to create a non-canonicalized 
range.

Aldy