ihalt.ppcs

;;; -*- Mode: LISP; Syntax: Common-Lisp; Package: ALPHA-AXP-INTERNALS; Base: 10; Lowercase: T -*-

(comment "This file implements the out-of-line parts of the instruction dispatch loop.")

;(include "alphamac")	; load the alpha macros
;(include "intrpmac")   ; load the interpreter macros.

;(include-header "aihead.s")
;(include-header "aistat.s")

(passthru ".globl SUSPENDMACHINE")
(passthru ".globl ILLEGALINSTRUCTION")
(passthru ".globl HALTMACHINE")

(define-procedure |iOutOfLine| ()

    ;; The following must not clobber T2, or ARG3 if it takes the
    ;; branch back to CONTINUECURRENTINSTRUCTION
  (label traporsuspendmachine "Here when someone wants the emulator to trap or stop.")
    ;; We use a conditional store to clear the suspend/interrupt
    ;; register.  We don't care if our store fails, that simply means
    ;; another thread ran and posted an interrupt; in which case we
    ;; won't have clobbered it and will deal with it next cycle.  If the
    ;; clear succeeds, we also clear stop_interpreter, since we know
    ;; that there are no new interrupts and we will handle the current
    ;; ones in priority order.  There is no sense leaving
    ;; stop_interpreter set to penalize every branch or go in the
    ;; interrupt handler.  It also gets reset if there are other pending
    ;; interrupts or preempts on the next function return (which is the
    ;; soonest possible time you could deal with them anyways).
    (get-control-register t4)
    (STD iSP PROCESSORSTATE_RESTARTSP (ivory) "Be sure this is up-to-date")
    (li t5 PROCESSORSTATE_PLEASE_STOP)
    (LDARX R0 t5 ivory "Has the spy asked us to stop or trap?")
    (clr t6)
    (STDCX-DOT t6 t5 ivory)
    (bc 4 2 collision)
;   #+ignore ;;I think this is the culprit in RGETF hang -- Kalman
    (stzd PROCESSORSTATE_STOP_INTERPRETER (ivory))
  (unlikely-label collision)
    (rotldi R0 R0 32 "Put PLEASE_STOP in lower half, PLEASE_TRAP in upper half")
    (CMPLI 0 1 R0 |HaltReasonIllInstn| "EQ if we've been asked to stop")
    (BC 12 2 suspendmachine)

    (comment "Here when someone wants the emulator to trap.")
    (srdi R0 R0 32 "Extract PROCESSORSTATE_PLEASE_TRAP (ivory)")
    (srdi t4 t4 30 "Isolate current trap mode")
    (basic-dispatch R0 t3
      (|TrapReasonHighPrioritySequenceBreak|
        (CMPLI 0 1 t4 |TrapModeExtraStack| "Only interrupts EXTRA-STACK and EMULATOR")
	(bclong 12 1 continuecurrentinstruction)
	(external-branch highprioritysequencebreak))
      ;; --- This wouldn't work if we needed it, since high-pri can
      ;; clobber low-pri; Luckily, we don't use low-pri!
      (|TrapReasonLowPrioritySequenceBreak|
	;; (CMPLI 0 1 t4 |TrapModeEmulator| "Only interrupts EMULATOR")
	;; (bclong 12 1 continuecurrentinstruction)
	(long-branch-if-nonzero t4 continuecurrentinstruction "Only interrupts EMULATOR")
	(external-branch lowprioritysequencebreak))
      (:else
	(comment "Check for preempt-request trap")
	(LWA t5 PROCESSORSTATE_INTERRUPTREG (ivory) "Get the preempt-pending bit")
	;; (CMPLI 0 1 t4 |TrapModeEmulator| "Only interrupts EMULATOR")
	;; (BC 4 1 dopreemptrequest)
	(long-branch-if-nonzero t4 continuecurrentinstruction "Don't take preempt trap unless in emulator mode")
	(ANDI-DOT R31 t5 1 "BLBC")
	(bclong 12 2 continuecurrentinstruction "Jump if preempt request not pending")
	(external-branch preemptrequesttrap)))

  (label suspendmachine "Here when someone wants to stop the emulator.")
    (clrldi t1 R0 32 "Get the reason")
    (B stopinterp)

  (label illegalinstruction "Here if we detect an illegal instruction.")
    (li t1 |HaltReasonIllInstn|)
    (B stopinterp)

  (label haltmachine "Here to halt machine")
    (li t1 |HaltReasonHalted|)
    (B stopinterp)

  (label fatalstackoverflow "Here if we detected a fatal stack overflow")
    (li t1 |HaltReasonFatalStackOverflow|)
    (B stopinterp)

  (label illegaltrapvector "Here if we detected a non-PC in a trap vector")
    (li t1 |HaltReasonIllegalTrapVector|)
    (B stopinterp)

  (label stopinterp)
    ;; cleanup and leave! here +++ save interpreter state!
    (mov arg1 t1 "Return the halt reason")
    (stzw PROCESSORSTATE_PLEASE_STOP (ivory) "Clear the request flag")
    (decache-ivory-state)
    (STD R31 PROCESSORSTATE_RUNNINGP (ivory) "Stop the (emulated) chip")
    (LD SP PROCESSORSTATE_IINTERPRET_SP (ivory) "Pop back to iInterpret's stack frame")
    (elf-epilogue)
)

;;; End of ihalt