larith.asm

gcc-you can use this code to learn something about gcc, and inquire further into linux,

	bne	Loop
Return:
	rts
Return_zero:
	clrb
	rts
#endif

#ifdef L_divmodhi4
#ifndef mc68hc12
/* 68HC12 signed divisions are generated inline (idivs).  */

	declare_near __divmodhi4

;
;; D = numerator
;; X = denominator
;;
;; Result:	D = D / X
;;		X = D % X
;; 
	tsta
	bpl	Numerator_pos
	comb			; D = -D <=> D = (~D) + 1
	coma
	xgdx
	inx
	tsta
	bpl	Numerator_neg_denominator_pos
Numerator_neg_denominator_neg:
	comb			; X = -X
	coma
	addd	#1
	xgdx
	idiv
	coma
	comb
	xgdx			; Remainder <= 0 and result >= 0
	inx
	rts

Numerator_pos_denominator_pos:
	xgdx
	idiv
	xgdx			; Both values are >= 0
	rts
	
Numerator_pos:
	xgdx
	tsta
	bpl	Numerator_pos_denominator_pos
Numerator_pos_denominator_neg:
	coma			; X = -X
	comb
	xgdx
	inx
	idiv
	xgdx			; Remainder >= 0 but result <= 0
	coma
	comb
	addd	#1
	rts
	
Numerator_neg_denominator_pos:
	xgdx
	idiv
	coma			; One value is > 0 and the other < 0
	comb			; Change the sign of result and remainder
	xgdx
	inx
	coma
	comb
	addd	#1
	rts
#endif /* !mc68hc12 */
#endif

#ifdef L_mulqi3
	declare_near ___mulqi3

;
; short __mulqi3(signed char a, signed char b);
;
;	signed char a	-> register A
;	signed char b	-> register B
;
; returns the signed result of A * B in register D.
;
	tsta
	bmi	A_neg
	tstb
	bmi	B_neg
	mul
	rts
B_neg:
	negb
	bra	A_or_B_neg
A_neg:
	nega
	tstb
	bmi	AB_neg
A_or_B_neg:
	mul
	coma
	comb
	addd	#1
	rts
AB_neg:
	negb
	mul
	rts
#endif
	
#ifdef L_mulhi3
	declare_near ___mulhi3

;
;
;  unsigned short ___mulhi3(unsigned short a, unsigned short b)
;
;	a = register D
;	b = register X
;
#ifdef mc68hc12
	pshx			; Preserve X
	exg	x,y
	emul
	exg	x,y
	pulx
	rts
#else
#ifdef NO_TMP
	;
	; 16 bit multiplication without temp memory location.
	; (smaller but slower)
	;
	pshx			; (4)
	ins			; (3)
	pshb			; (3)
	psha			; (3)
	pshx			; (4)
	pula			; (4)
	pulx			; (5)
	mul			; (10) B.high * A.low
	xgdx			; (3)
	mul			; (10) B.low * A.high
	abx			; (3)
	pula			; (4)
	pulb			; (4)
	mul			; (10) B.low * A.low
	pshx			; (4) 
	tsx			; (3)
	adda	1,x		; (4)
	pulx			; (5)
	rts			; (5) 20 bytes
				; ---
				; 91 cycles
#else
	stx	*_.tmp		; (4)
	pshb			; (3)
	ldab	*_.tmp+1	; (3)
	mul			; (10) A.high * B.low
	ldaa	*_.tmp		; (3)
	stab	*_.tmp		; (3)
	pulb			; (4)
	pshb			; (4)
	mul			; (10) A.low * B.high
	addb	*_.tmp		; (4)
	stab	*_.tmp		; (3)
	ldaa	*_.tmp+1	; (3)
	pulb			; (4)
	mul			; (10) A.low * B.low
	adda	*_.tmp		; (4)
	rts			; (5) 24/32 bytes
				; 77/85 cycles
#endif
#endif
#endif

#ifdef L_mulhi32

;
;
;  unsigned long __mulhi32(unsigned short a, unsigned short b)
;
;	a = register D
;	b = value on stack
;
;	+---------------+
;       |  B low	| <- 7,x
;	+---------------+
;       |  B high	| <- 6,x
;	+---------------+
;       |  PC low	|  
;	+---------------+
;       |  PC high	|  
;	+---------------+
;	|  Tmp low	|
;	+---------------+
;	|  Tmp high     |
;	+---------------+
;	|  A low	|
;	+---------------+
;	|  A high	|
;	+---------------+  <- 0,x
;
;
;      <B-low>    5,x
;      <B-high>   4,x
;      <ret>      2,x
;      <A-low>    1,x
;      <A-high>   0,x
;
	declare_near	__mulhi32

#ifdef mc68hc12
	ldy	2,sp
	emul
	exg	x,y
	rts
#else
	pshx			; Room for temp value
	pshb
	psha
	tsx
	ldab	6,x
	mul
	xgdy			; A.high * B.high
	ldab	7,x
	pula
	mul			; A.high * B.low
	std	2,x
	ldaa	1,x
	ldab	6,x
	mul			; A.low * B.high
	addd	2,x
	stab	2,x
	tab
	aby
	bcc	N
	ldab	#0xff
	aby
	iny
N:
	ldab	7,x
	pula
	mul			; A.low * B.low
	adda	2,x
	pulx			; Drop temp location
	pshy			; Put high part in X
	pulx
	bcc	Ret
	inx
Ret:
	rts
#endif	
#endif

#ifdef L_mulsi3

;
;      <B-low>    8,y
;      <B-high>   6,y
;      <ret>      4,y
;	<tmp>	  2,y
;      <A-low>    0,y
;
; D,X   -> A
; Stack -> B
;
; The result is:
;
;	(((A.low * B.high) + (A.high * B.low)) << 16) + (A.low * B.low)
;
;
;

	declare	__mulsi3

#ifdef mc68hc12
	pshd				; Save A.low
	ldy	ARG(4),sp
	emul				; A.low * B.high
	ldy	ARG(6),sp
	exg	x,d
	emul				; A.high * B.low
	leax	d,x
	ldy	ARG(6),sp
	puld
	emul				; A.low * B.low
	exg	d,y
	leax	d,x
	exg	d,y
	ret
#else
B_low	=	ARG(8)
B_high	=	ARG(6)
A_low	=	0
A_high	=	2
	pshx
	pshb
	psha
	tsy
;
; If B.low is 0, optimize into: (A.low * B.high) << 16
;
	ldd	B_low,y
	beq	B_low_zero
;
; If A.high is 0, optimize into: (A.low * B.high) << 16 + (A.low * B.low)
;
	cpx	#0
	beq	A_high_zero
	bsr	___mulhi3		; A.high * B.low
;
; If A.low is 0, optimize into: (A.high * B.low) << 16
;
	ldx	A_low,y
	beq	A_low_zero		; X = 0, D = A.high * B.low
	std	2,y
;
; If B.high is 0, we can avoid the (A.low * B.high) << 16 term.
;
	ldd	B_high,y
	beq	B_high_zero
	bsr	___mulhi3		; A.low * B.high
	addd	2,y
	std	2,y
;
; Here, we know that A.low and B.low are not 0.
;
B_high_zero:
	ldd	B_low,y			; A.low is on the stack
	bsr	__mulhi32		; A.low * B.low
	xgdx
	tsy				; Y was clobbered, get it back
	addd	2,y
A_low_zero:				; See A_low_zero_non_optimized below
	xgdx
Return:
	ins
	ins
	ins
	ins
	ret
;
; 
; A_low_zero_non_optimized:
;
; At this step, X = 0 and D = (A.high * B.low)
; Optimize into: (A.high * B.low) << 16
;
;	xgdx
;	clra			; Since X was 0, clearing D is superfuous.
;	clrb
;	bra	Return
; ----------------
; B.low == 0, the result is:	(A.low * B.high) << 16
;
; At this step:
;   D = B.low				= 0 
;   X = A.high				?
;       A.low is at A_low,y		?
;       B.low is at B_low,y		?
;
B_low_zero:
	ldd	A_low,y
	beq	Zero1
	ldx	B_high,y
	beq	Zero2
	bsr	___mulhi3
Zero1:
	xgdx
Zero2:
	clra
	clrb
	bra	Return
; ----------------
; A.high is 0, optimize into: (A.low * B.high) << 16 + (A.low * B.low)
;
; At this step:
;   D = B.low				!= 0 
;   X = A.high				= 0
;       A.low is at A_low,y		?
;       B.low is at B_low,y		?
;
A_high_zero:
	ldd	A_low,y		; A.low
	beq	Zero1
	ldx	B_high,y	; B.high
	beq	A_low_B_low
	bsr	___mulhi3
	std	2,y
	bra	B_high_zero	; Do the (A.low * B.low) and the add.

; ----------------
; A.high and B.high are 0 optimize into: (A.low * B.low)
;
; At this step:
;   D = B.high				= 0 
;   X = A.low				!= 0
;       A.low is at A_low,y		!= 0
;       B.high is at B_high,y		= 0
;
A_low_B_low:
	ldd	B_low,y			; A.low is on the stack
	bsr	__mulhi32
	bra	Return
#endif
#endif

#ifdef L_map_data

	.sect	.install2,"ax",@progbits
	.globl	__map_data_section
	.globl __data_image
#ifdef mc68hc12
	.globl __data_section_size
#endif
__map_data_section:
#ifdef mc68hc12
	ldx	#__data_image
	ldy	#__data_section_start
	ldd	#__data_section_size
	beq	Done
Loop:
	movb	1,x+,1,y+
	dbne	d,Loop
#else
	ldx	#__data_image
	ldy	#__data_section_start
	bra	Start_map
Loop:
	ldaa	0,x
	staa	0,y
	inx
	iny
Start_map:
	cpx	#__data_image_end
	blo	Loop
#endif
Done:

#endif

#ifdef L_init_bss

	.sect	.install2,"ax",@progbits
	.globl	__init_bss_section

__init_bss_section:
	ldd	#__bss_size
	beq	Done
	ldx	#__bss_start
Loop:
#ifdef mc68hc12
	clr	1,x+
	dbne	d,Loop
#else
	clr	0,x
	inx
	subd	#1
	bne	Loop
#endif
Done:

#endif

#ifdef L_ctor

; End of constructor table
	.sect	.install3,"ax",@progbits
	.globl	__do_global_ctors

__do_global_ctors:
	; Start from the end - sizeof(void*)
	ldx	#__CTOR_END__-2
ctors_loop:
	cpx	#__CTOR_LIST__
	blo	ctors_done
	pshx
	ldx	0,x
	jsr	0,x
	pulx
	dex
	dex
	bra	ctors_loop
ctors_done:

#endif

#ifdef L_dtor

	.sect	.fini3,"ax",@progbits
	.globl	__do_global_dtors

;;
;; This piece of code is inserted in the _exit() code by the linker.
;;
__do_global_dtors:
	pshb	; Save exit code
	psha
	ldx	#__DTOR_LIST__
dtors_loop:
	cpx	#__DTOR_END__
	bhs	dtors_done
	pshx
	ldx	0,x
	jsr	0,x
	pulx
	inx
	inx
	bra	dtors_loop
dtors_done:
	pula	; Restore exit code
	pulb

#endif

#ifdef L_far_tramp
#ifdef mc68hc12
	.sect	.tramp,"ax",@progbits
	.globl	__far_trampoline

;; This is a trampoline used by the linker to invoke a function
;; using rtc to return and being called with jsr/bsr.
;; The trampoline generated is:
;;
;;	foo_tramp:
;;		ldy	#foo
;;		call	__far_trampoline,page(foo)
;;
;; The linker transforms:
;;
;;		jsr	foo
;;
;; into
;;		jsr	foo_tramp
;;
;; The linker generated trampoline and _far_trampoline must be in 
;; non-banked memory.
;;
__far_trampoline:
	movb	0,sp, 2,sp	; Copy page register below the caller's return
	leas	2,sp		; address.
	jmp	0,y		; We have a 'call/rtc' stack layout now
				; and can jump to the far handler
				; (whose memory bank is mapped due to the
				; call to the trampoline).
#endif

#ifdef mc68hc11
	.sect	.tramp,"ax",@progbits
	.globl __far_trampoline

;; Trampoline generated by gcc for 68HC11:
;;
;;	pshb
;;	ldab	#%page(func)
;;	ldy	#%addr(func)
;;	jmp	__far_trampoline
;;
__far_trampoline:
	psha				; (2) Save function parameter (high)
	;; <Read current page in A>
	psha				; (2)
	;; <Set currenge page from B>
	pshx				; (4)
	tsx				; (3)
	ldab	4,x			; (4) Restore function parameter (low)
	ldaa	2,x			; (4) Get saved page number
	staa	4,x			; (4) Save it below return PC
	pulx				; (5)
	pula				; (3)
	pula				; (3) Restore function parameter (high)
	jmp	0,y			; (4)
#endif
#endif

#ifdef L_call_far
#ifdef mc68hc11
	.sect	.tramp,"ax",@progbits
	.globl __call_a16
	.globl __call_a32
;;
;; The call methods are used for 68HC11 to support memory bank switching.
;; Every far call is redirected to these call methods.  Its purpose is to:
;;
;;  1/ Save the current page on the stack (1 byte to follow 68HC12 call frame)
;;  2/ Install the new page
;;  3/ Jump to the real function
;;
;; The page switching (get/save) is board dependent.  The default provided
;; here does nothing (just create the appropriate call frame).
;;
;; Call sequence (10 bytes, 13 cycles):
;;
;;	ldx #page			; (3)
;;	ldy #func			; (4)
;;	jsr __call_a16			; (6)
;;
;; Call trampoline (11 bytes, 19 cycles):
;;
__call_a16:
	;; xgdx				; (3)
	;; <Read current page in A>	; (3) ldaa _current_page
	psha				; (2)
	;; <Set current page from B>	; (4) staa _current_page
	;; xgdx				; (3)
	jmp 0,y				; (4)

;;
;; Call sequence (10 bytes, 14 cycles):
;;
;;	pshb				; (2)
;;	ldab #page			; (2)
;;	ldy  #func			; (4)
;;	jsr __call_a32			; (6)
;;
;; Call trampoline (87 bytes, 57 cycles):
;;
__call_a32:
	pshx				; (4)
	psha				; (2)
	;; <Read current page in A>	; (3) ldaa _current_page
	psha				; (2)
	;; <Set current page from B>	; (4) staa _current_page
	tsx				; (3)
	ldab	6,x			; (4) Restore function parameter
	ldaa	5,x			; (4) Move PC return at good place
	staa	6,x			; (4)
	ldaa	4,x			; (4)
	staa	5,x			; (4)
	pula				; (3)
	staa	4,x			; (4)
	pula				; (3)
	pulx				; (5)
	jmp	0,y			; (4)
#endif
#endif

#ifdef L_return_far
#ifdef mc68hc11
	.sect	.tramp,"ax",@progbits
       .globl __return_void
       .globl __return_16
       .globl __return_32

__return_void:
	;; pulb
	;; <Set current page from B> (Board specific)
	;; rts
__return_16:
	;; xgdx
	;; pulb
	;; <Set current page from B> (Board specific)
	;; xgdx
	;; rts
__return_32:
	;; xgdy
	;; pulb
	;; <Set current page from B> (Board specific)
	;; xgdy
	;; rts
	ins
	rts
#endif
#endif
.Lend:
;-----------------------------------------
; end required gcclib code
;-----------------------------------------