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


On 7/3/19 3:35 AM, Aldy Hernandez wrote:
> 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.
Ah.  Cool.  Thanks for enlightening me ;-)

jeff


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