[PUSHED 6/8] Use irange API in test_for_singularity.

Aldy Hernandez aldyh@redhat.com
Tue Aug 4 09:55:55 GMT 2020



On 8/4/20 8:58 AM, Richard Biener wrote:
> On Tue, Aug 4, 2020 at 8:40 AM Aldy Hernandez via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>>
>> gcc/ChangeLog:
>>
>>          * vr-values.c (test_for_singularity): Use irange API.
>>          (simplify_using_ranges::simplify_cond_using_ranges_1): Do not
>>          special case VR_RANGE.
>> ---
>>   gcc/vr-values.c | 13 ++++++++-----
>>   1 file changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/gcc/vr-values.c b/gcc/vr-values.c
>> index 90ba8fca246..e78b25596b0 100644
>> --- a/gcc/vr-values.c
>> +++ b/gcc/vr-values.c
>> @@ -3480,10 +3480,13 @@ test_for_singularity (enum tree_code cond_code, tree op0,
>>        value range information we have for op0.  */
>>     if (min && max)
>>       {
>> -      if (compare_values (vr->min (), min) == 1)
>> -       min = vr->min ();
>> -      if (compare_values (vr->max (), max) == -1)
>> -       max = vr->max ();
>> +      tree type = TREE_TYPE (op0);
>> +      tree tmin = wide_int_to_tree (type, vr->lower_bound ());
>> +      tree tmax = wide_int_to_tree (type, vr->upper_bound ());
> 
> I guess with symbolic ranges this just doesn't work anymore
> (or rather will give a pessimistinc upper/lower bound)?

Yes, though we do slightly better than VARYING.  The symbolic 
normalizing code will rewrite [SYM, 5] as [-INF, 5], etc.

When I implemented this originally in the ranger branch, I 
pessimistically downgraded all symbolics to [MIN,MAX] to see if there 
was any difference in the generated code.  There wasn't.

I think most of vr-values.c does no better without symbolics, with the 
exception of compare_value* and the corresponding code that handles 
comparisons and equivalences.

Aldy



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