Using deftransform/defknown in SBCL internals to get the compiler to transform user authored functions

Question

At the end of section 6.5 in the current SBCL manual, we have the following quote:

If your system\'s performance is suffering because of some construc

Answer 1

You achieve what you want in portable Common Lisp using define-compiler-macro

AFAIK reading the SBCL sources is the only way to learn how deftransform works. But before diving into SBCL sources checkout Paul Khuong's Starting to Hack on SBCL or at the very least The Python Compiler for CMU Common Lisp it links to to have an overview of how SBCL works.