+ ((nil)))))
+ (insert-step-instrumenting (callable-tn)
+ ;; Conditionally insert a conditional trap:
+ (when step-instrumenting
+ ;; Get the symbol-value of SB!IMPL::*STEPPING*
+ (loadw stepping
+ null-tn
+ (+ symbol-value-slot
+ (truncate (static-symbol-offset 'sb!impl::*stepping*)
+ n-word-bytes))
+ other-pointer-lowtag)
+ (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))))