No. I have yet to propose the patches formally. The SBCL maintainers are reviewing the high-level proposal (on my blog) first. You can try the implementation, however. There's a pointer to the repo/branch on my blog. I need to build a proper benchmarking framework and publish some real numbers that people can reproduce before I am confident enough to submit the patches for review.
Let me know if you try it out. I would love some feedback (via github)
it came up in the SBCL mailing list as well, and its author has been commenting there as well. seems like it has some legs! would be a very nice feature to have.