Repro:

(describe #'COMMUTE-RZ-AFTER-CPHASE)

Output:

#<COMPILER COMMUTE-RZ-AFTER-CPHASE {10149CF36B}>
  [funcallable-instance]


Lambda-list: (X Y &KEY CONTEXT)
Derived type: (FUNCTION (T T &KEY (:CONTEXT T)) (VALUES T &OPTIONAL))
Documentation:
  T
Source file: quilc/src/compressor/rewriting-rules.lisp

Slots with :INSTANCE allocation:
  NAME                           

It looks like the upcoming sbcl 2.0.1 release includes changes to move certain symbols out of cl:*features* and into sb-impl:+internal-features+ [[1]]. IIUC, any "non-public" features will continue to work (for now), but issue a warning [[2]].

I haven't tested it, but it looks like we use at least one such soon-to-be-deprecated feature, namely avx2. We should figure out what to do about