[Bug libstdc++/93584] std::string::find_first_not_of is about 9X slower than strspn

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93584

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2020-02-05
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=66414
     Ever confirmed|0                           |1

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The standard requires us to go through the char traits template parameter, but
for the std::string specialization we know how that behaves and so can replace
it with strspn or anything else that acts as if we used std::char_traits<char>.