[Bug middle-end/19652] New: should always optimize constant second argument to strspn & Co. at compile time

[Bug middle-end/19652] New: should always optimize constant second argument to strspn & Co. at compile time

[melkov at comptek dot ru]

strspn, strcspn, strpbrk functions make a bitmap out of their second argument 
and then process their first argument using that bitmap.
If the second argument is a constant string, that bitmap should be built at the 
compile time, and strspn call be replaced with some intrinsic function that can 
use that bitmap.

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           Summary: should always optimize constant second argument to
                    strspn & Co. at compile time
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: melkov at comptek dot ru
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19652

[Bug middle-end/19652] should always optimize constant second argument to strspn & Co. at compile time

[falk at debian dot org]

------- Additional Comments From falk at debian dot org  2005-01-27 09:02 -------
(In reply to comment #0)
> strspn, strcspn, strpbrk functions make a bitmap out of their second argument 
> and then process their first argument using that bitmap.
> If the second argument is a constant string, that bitmap should be built at the 
> compile time, and strspn call be replaced with some intrinsic function that can 
> use that bitmap.

Well, with that we'd be wandering off far into libc land. While this kind of
optimization is nice, I wouldn't really want to have strspn code for 40
platforms in gcc to maintain (and if you're that desperate for speed, you
want platform-specific code). Alternatively, you could try to convince your
libc providers to include such functions in their libc, and then we might
implement calling them.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19652

[Bug middle-end/19652] should always optimize constant second argument to strspn & Co. at compile time

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-01-27 13:31 -------
I am going to agree with Falk here, this is a hard problem to solve inside gcc. Again talk with you libc 
provider.

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           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19652