RFR (M) 8059461: Refactor IndexSet for better performance (preliminary)

[John Rose]

On Nov 6, 2014, at 1:36 AM, Albert Noll <albert.noll at oracle.com> wrote:

> It would be good to have data from different applications / architectures.
> 
> Does anyone know more about the motivation for IndexSet, i.e., why it was introduced in the first place?

It is a bespoke type for the register allocator, originally called List16Set and written by Cliff Click in 1997 (or earlier, at Rice).  Original source file was chaitin.hpp.  In 1998 Todd Turnidge did a bunch of cleanups on the source base and factored it as IndexSet into its own header file.  Perhaps it was well tuned for the hardware of 1998.  :-)

— John