Implement {get,set}_range_info() variants that work with value_range's

[Jeff Law]

On 11/8/18 7:44 AM, Aldy Hernandez wrote:
> 
> 
> On 11/8/18 9:41 AM, Richard Biener wrote:
>> On Thu, Nov 8, 2018 at 3:05 PM Aldy Hernandez <aldyh@redhat.com> wrote:
>>>
>>>
>>>
>>> On 11/8/18 8:59 AM, Richard Biener wrote:
>>>> On Thu, Nov 8, 2018 at 12:52 PM Aldy Hernandez <aldyh@redhat.com>
>>>> wrote:
>>>>>
>>>>> get/set_range_info() currently returns the extremes of a range.  I
>>>>> have
>>>>> implemented overloaded variants that return a proper range.  In the
>>>>> future we should use actual ranges throughout, and not depend on range
>>>>> extremes, as depending on this behavior could causes us to lose
>>>>> precision.
>>>>>
>>>>> I am also including changes to size_must_be_zero_p() to show how we
>>>>> should be using the range API, as opposed to performing error prone
>>>>> ad-hoc calculations on ranges and anti-ranges.
>>>>
>>>> Yeah, I've been talking this all along but not being heard...
>>>
>>> My girlfriend says I don't listen.  It could be related.
>>>
>>>>> Martin, I'm not saying your code is wrong.  There are numerous other
>>>>> places in the compiler where we manipulate ranges/anti-ranges
>>>>> directly,
>>>>> all of which should be adapted in the future.  Everywhere there is a
>>>>> mention of VR_RANGE/VR_ANTI_RANGE in the compiler is suspect.  We
>>>>> should
>>>>> ideally be using intersect/union/may_contain_p/null_p, etc.
>>>>
>>>> null_p is a bad name btw, I just confused it with empty_p ... (which
>>>> we have
>>>> as undefined_p).  contains_only_zero_p would be less confusing.
>>>
>>> Yes, a horrible name.  I noticed so as I debugged precisely this bit.
>>> How about zero_p?
>>
>> Probably the same ambiguous connotation?  But yes, way better than
>> null_p.
> 
> Well...for starters I started with the nomenclature already in VRP which
> was range_is_null.
Probably due to using it for NULL pointer test elimination.  But yea, in
retrospect it's an awful name.

> 
> Also, how is zero_p() ambiguous?  We want to know if the range is [0,
> 0].  That reads pretty obvious to me.
Seems reasonable to me.  THe question is will we push that name into all
the other places that use "null" when discussing ranges like ~[0,0] or
ranges that ultimately include [0,0].  Not all of these are in [E]VRP IIRC.

jeff