Re: Avoid generating useless range info

[Aldy Hernandez <aldyh at redhat dot com>]

On Fri, Jun 23, 2017 at 6:24 AM, Richard Biener
<richard.guenther@gmail.com> wrote:
> On Fri, Jun 23, 2017 at 10:59 AM, Aldy Hernandez <aldyh@redhat.com> wrote:
>>
>>
>> On Fri, Jun 16, 2017 at 4:00 AM, Richard Biener <richard.guenther@gmail.com>
>> wrote:
>>>
>>> On Wed, Jun 14, 2017 at 6:41 PM, Aldy Hernandez <aldyh@redhat.com> wrote:
>>> > Hi!
>>> >
>>> > As discovered in my range class work, we seem to generate a significant
>>> > amount of useless range info out of VRP.
>>> >
>>> > Is there any reason why we can't avoid generating any range info that
>>> > spans
>>> > the entire domain, and yet contains nothing in the non-zero bitmask?
>>> >
>>> > The attached patch passes bootstrap, and the one regression it causes is
>>> > because now the -Walloca-larger-than= pass is better able to determine
>>> > that
>>> > there is no range information at all, and the testcase is unbounded.
>>> > So...win, win.
>>> >
>>> > OK for trunk?
>>>
>>> Can you please do this in set_range_info itself?  Thus, if min ==
>>> wi::min_value && max == wi::max_value
>>> simply return?  (do not use TYPE_MIN?MAX_VALUE please)
>>
>>
>> The reason I did it in vrp_finalize is because if you do it in
>> set_range_info, you break set_nonzero_bits when setting bits on an SSA that
>> currently has no range info:
>>
>> void
>> set_nonzero_bits (tree name, const wide_int_ref &mask)
>> {
>>   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
>>   if (SSA_NAME_RANGE_INFO (name) == NULL)
>>     set_range_info (name, VR_RANGE,
>>    TYPE_MIN_VALUE (TREE_TYPE (name)),
>>    TYPE_MAX_VALUE (TREE_TYPE (name)));
>>   range_info_def *ri = SSA_NAME_RANGE_INFO (name);
>>   ri->set_nonzero_bits (mask);
>> }
>>
>> Let me know how you'd like me to proceed.
>
> Just factor out a set_range_info_raw and call that then from here.

How about this?

Aldy

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