Please review writeup for fixing PR 78809 (inline strcmp for small constant strings)

[Qing Zhao]

> On Nov 17, 2017, at 7:39 PM, Jeff Law <law@redhat.com> wrote:
> 
>>> 
>> 
>> thanks for the info, Martin.
>> 
>> In my case, it’s the size of “100” cannot be collected in the
>> MINMAXLEN[1] for the string “s”. 
>> 
>> I need to make sure that the size of variable string s is larger than
>> the size of constant string “abc” to guarantee the safety of the
>> transformation.
>> 
>> currently, “get_range_strlen” cannot identify the simple VAR_DECL with
>> array_type to determine the maximum size of the string. 
> It sounds more like you want the object_size interfaces.  See
> tree-object-size.[ch]

As I mentioned in the other email, I tried the interface of object_size, i.e, “compute_builtin_object_size” to see whether it
can provide me good info on several simple examples, at that time, I didn’t see that it can provide good info for 
very simple cases, so I switched to use “get_range_strlen” and modified it to serve my purpose. 

I will double check on this.

Qing
> Jeff