Messages in this thread |  | | | Subject | Re: Article: IBM wants to "clean up the license" of Linux | | From | David Wragg <> | | Date | 26 Dec 1998 02:05:58 +0000 |
| |
C S Hendrix <shendrix@escape.widomaker.com> writes: > In message <3682cf95.1309356@mail.cloud9.net>, John Alvord writes: > > I suspect gcc will have a much improved register allocation scheme in > > 2003 for the same reason. > > If someone were to go ahead and write the code now, I'd use it. > > Has anyone ever asked for permission to use that patent?
It would be silly to implement the original Chaitin colouring allocator in gcc today. It is by now thoroughly outdated. While the gcc allocator is not brilliant, it is certainly better than a straight implementation of the original Chaitin allocator.
Chaitin's contribution is not what appears in that patent, but that it gives a nice abstract description of the register allocation problem as it was conceived in the late 70's. However, it completely omits issues which are now understood to be significant for performance of generated code on modern load/store architectures. Even ignoring this, the algorithm presented in the patent can be significantly improved with some simple changes (which are themselves the subject of a patent by Rice University).
If someone was seeking to completely reimplement the gcc/egcs register allocator, they should look at register allocation papers published more recently; of course, they should bear patent encumberment in mind as they do so.
This just goes to show that 17 years is too long for a software patent in an active research field. By the time it expires, its value is purely historical, thus the patent system has achieved nothing.
Dave Wragg
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
|  |