(in-package :sb-vm)

(defknown fast-mpsc-queue:atomic-swap-car (cons t)

t (always-translatable)

:overwrite-fndb-silently t)

(define-vop (fast-mpsc-queue:atomic-swap-car)

(:translate fast-mpsc-queue:atomic-swap-car)

(:policy :fast-safe)

(:args (cons :scs (descriptor-reg))

(val :scs (descriptor-reg any-reg) :target r))

(:temporary (:sc descriptor-reg) tmp)

(:results (r :scs (descriptor-reg any-reg)))

(:vop-var vop)

(:generator

5

(emit-gengc-barrier cons nil tmp (vop-nth-arg 1 vop) val)

(move r val)

(inst xchg (ea (- list-pointer-lowtag) cons) r)))