+ ((nil)))))
+ (insert-step-instrumenting (callable-tn)
+ ;; Conditionally insert a conditional trap:
+ (when step-instrumenting
+ ;; Get the symbol-value of SB!IMPL::*STEPPING*
+ #!-sb-thread
+ (load-symbol-value stepping sb!impl::*stepping*)
+ #!+sb-thread
+ (loadw stepping thread-base-tn thread-stepping-slot)
+ (inst cmpw stepping null-tn)
+ ;; If it's not null, trap.
+ (inst beq step-done-label)
+ ;; CONTEXT-PC will be pointing here when the
+ ;; interrupt is handled, not after the UNIMP.
+ (note-this-location vop :step-before-vop)
+ ;; Construct a trap code with the low bits from
+ ;; SINGLE-STEP-AROUND-TRAP and the high bits from
+ ;; the register number of CALLABLE-TN.
+ (inst unimp (logior single-step-around-trap
+ (ash (reg-tn-encoding callable-tn)
+ 5)))
+ (emit-label step-done-label))))