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Re: Avoid generating useless range info


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.

Richard.

> Aldy
>
>>
>> Thanks,
>> Richard.
>>
>> > Aldy
>
>


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