;; Lab 13
;;
;; Team Member A:
;; Team Member B:
;;
;;;;  Don't modify anything before the SYR function
;;;;  It starts at the very end of the file

	.orig	x3000
	lea	R6, stack
	lea	R0, prptmes
	puts
	and	R3, R3, #0	; R3 <- 0
	add	R2, R3, #4	; R2 <- 4
	ld	R4, cm48

inplop	getc			; input loop
	out
	add	R0, R0, R4
	add	R1, R0, #-10
	brn	nothex
	add	R0, R0, #-7
	and	R0, R0, #15
nothex	and	R1, R1, #0
	add	R1, R1, #4
shflop1	add	R3, R3, R3	; left shift four loop
	add	R1, R1, #-1
	brp	shflop1			; end left shift loop
	add	R3, R3, R0
	add	R2, R2, #-1
	brp	inplop			; end input loop
	and	R0, R0, #0
	add	R0, R0, #10
	out

;; User number has been input to R3

syrlop	lea	R0, syrmes	; Syracuse loop
	puts
	add	r1, r3, #0
	and	r2, r2, #0
	add	r2, r2, #4
outlop	and	r0, r0, #0	; output loop
	add	r4, r0, #4
shflop2	add	r0, r0, r0	; left shift loop
	add	r1, r1, #0
	brzp	noadd
	add	r0, r0, #1
noadd	add	r1, r1, r1
	add	r4, r4, #-1
	brp	shflop2			; end left shift loop
	add	r4, r0, #-10
	brzp	itshex
	ld	r4, c48
	jmp	prdig
itshex	ld	r4, c55
prdig	add	r0, r0, r4
	out
	add	r2, r2, #-1
	brp	outlop			; end output loop
	and	r0, r0, #0
	add	r0, r0, #10
	out

;;	if R3 == 1, halt
	add	r1, r3, #-1
	brnp	callsyr
	halt

;;  It's time to call the Syrcuse function SYR
;;  Argument is stored in R3

;;  Build a stack frame for the call -- pretend old stack frame is of size 4
callsyr	str	r6, r6, #6	; store dynamic link
	str	r3, r6, #7	; store the single argument
	add	r6, r6, #4
	jsr	SYR		; call SYR
	ldr	r3, r6, #4	; load return value back into R3
;;  End of call sequence -- return value is in R3

	jmp	syrlop		; end of syracuse loop

prptmes	.stringz  "Enter a four hexadecimal-digit number: "
syrmes	.stringz  "  Syracuse output: "
c48	.fill	#48
c55	.fill	#55
cm48	.fill	#-48
stack	.blkw	100

;; The divide by 2 function
;; activation record
;;    0 -- return value		X/2
;;    1 -- return address
;;    2 -- dynamic link
;;    3 -- argument		X
DIV2	str	r7, r6, #1	; store the return address
	ldr	r0, r6, #3	; R0 <- X
	and	r1, r1, #0	; R1 <- 0
	add	r2, r1, #14	; R2 <- 14
	add	r0, r0, #0
	brzp	dv2lp
	add	r1, r1, #1	; R1 <- 1, if high bit of R0 set
dv2lp	add	r1, r1, r1
	add	r0, r0, r0
	brzp	dvnost
	add	r1, r1, #1
dvnost	add	r2, r2, #-1
	brp	dv2lp
	str	r1, r6, #0	; store return value
	ldr	r7, r6, #1	; load return address
	ldr	r6, r6, #2	; restore dynamic link
	ret	

;;;; This is the SYR function -- start your modifications here
SYR	
	ldr	r6, r6, #2
	ret

	.end