#asm

* C include file -- run-time support for Small-C 



*   SmallC Cross Compiler Run-Time Support.  
*   Target 68HC11.
 
*	L. Konneker Feb. 7, 1987 
*	Retarget for 6811 and different assembler.



******************************************************
*	Run-time start off 
*
*   for MC68HC11 EVB board
*

* 	Initialize stack
* 	For EVB, put stack in high user ram, HEX DFFF downward
	ldx	#57343  	hex DFFF
	txs
	
* 	Some would clear all of memory, not necessary on EVB.

*	Clear certain things so that start conditions are always same.
*	This is defensive programming but may hide bugs.
	clra
	clrb
	jmp	_main
*	note main must not return

*	Run time routines are not listed in assembler output.
	OPT	nol
	
******************************************************
*	Small C v1 comparison support 
*	All are dyadic except for lneg. 

*   Reg x used as a temp  



cceq:	
	tsx
	cpd 2,x 
	beq cctrue 
	bra ccfals 


ccne:	
	tsx
	cpd 2,x  
	bne cctrue 
	bra ccfals 


cclt:	
	tsx
	cpd 2,x  
	bgt cctrue 
	bra ccfals 


ccle:	
	tsx
	cpd 2,x 
	bge cctrue 
	bra ccfals 


ccgt:	
	tsx
	cpd 2,x 
	blt cctrue 
	bra ccfals 


ccge:	
	tsx
	cpd 2,x 
	ble cctrue 
	bra ccfals 


ccult:	
	tsx
	cpd 2,x 
	bhi cctrue 
	bra ccfals 


ccule:	
	tsx
	cpd 2,x 
	bhs cctrue 
	bra ccfals 


ccugt:	
	tsx
	cpd 2,x 
	blo cctrue 
	bra ccfals 


ccuge:	
	tsx
	cpd 2,x 
	bls cctrue 
	bra ccfals 


* boolean negate,  with coercion to boolean 
cclneg:	cpd #0 
	beq cclne1 
	ldd #0 
	rts 
cclne1:	ldd #1 
	rts 


* coerce to boolean type 
ccbool:
	bsr	cclneg 
	bra	cclneg 


******************************************************
* true and false returns common to all compare operations
cctrue:
	ldd #1 
	bra		ccret	to common return

ccfals:	
	clra 
	clrb 
	bra		ccret	to common return

******************************************************
* relic ???
_Xstktop:
* Put stack pointer in reg D	 
	tsx 
	xgdx 
	rts
	
******************************************************
* boolean

* inclusive or primary and calling environ stacktop 
ccior:
	tsx
	oraa	2,x
	orab	3,x
	bra		ccret
 
* exclusive or primary and calling environ stacktop
ccxor:
	tsx			get copy of stack ptr
	eora	2,x	form result 
	eorb	3,x
	bra 	ccret
	 
* and primary and calling environ stacktop
ccand:
	tsx
	anda	2,x
	andb	3,x
	bra		ccret
	
******************************************************
* misc

* sign extend low byte primary into high byte primary
ccsex:
	clra
	tstb
	bpl	*+3
	coma
	rts
	

******************************************************
* shift 

* entry : D contains shift count, stack + 2 is operand
* exit  : D contains shifted operand, stack is restored
*
* Uses y reg.
* No checking for negative shift count.

* First, move shift count from d to x and move operand
* from stack to d.
ccasr:
	xgdx
	tsy
	ldd		2,y
ccasr1:
	cpx		#0
	ble		ccret
	asra
	rorb
	dex
	bra ccasr1
	

* left
ccasl:
	xgdx
	tsy
	ldd		2,y
ccasl1:
	cpx		#0
	ble		ccret
	aslb
	rola
	dex
	bra ccasl1
	
******************************************************
* A return routine common to shift and bitwise logical operations
* Move ret adr down the stack on top of operand
* Assert that on entry to this routine,
* the stack ptr is still as it was on entry to the routine that
* jumped here.
* Must preserve reg D since it has the result.
* Uses reg y.
ccret:
	pulx			capture return address
	tsy				set up y as stack top ptr
	stx		,y		store ret adr on top of stack
	rts
	
******************************************************
* Two's complement negate the primary register
ccneg:
	coma		one's complement
	comb
	addd	#1	plus one
	rts

******************************************************
* Mult 16 bit times 16 bit yielding 16 bit.
* Overflow is possible, not checked.
* Signed and unsigned, same entry point.
* 

* entry : D contains one operand, 
*			@ stackptr is return adr
*			@ stackptr + 2 is operand
* exit  : D contains 16 bit operand,
*			stackptr is entry stackptr + 4 ( stack is restored
*			to as it was before caller pushed operand.)
*
cctmpd	equ		0
cctmpx	equ		2
ccrslt	equ		6


ccsmul:
ccmul:
* shuffle stack
	tsx
	ldx		2,x
	pshx			x op	
	pshb			d op
	psha
* stack is now
*	d op
*	x op
*	return address
*	word for result
* do multiply
	tsx
	ldaa	cctmpx+1,x	lo d times lo x
	mul
	std		ccrslt,x
	ldd		cctmpd+1,x	lo d times hi x
	mul
	addb	ccrslt,x	add hi byte of partial result 
	stab	ccrslt,x
	ldaa	cctmpd,x	hi d times lo x
	ldab	cctmpx+1,x
	mul
	addb	ccrslt,x	add hi byte of partial result
	stab	ccrslt,x
* restore stack, get result in d
	pulx
	pulx
	puly	ret adr
	pula	result
	pulb
	pshy
	rts


******************************************************
* Divide 16 bit times 16 bit yielding 16 bit.
* Underflow is possible, not checked.
* Signed and unsigned, same entry point.
 

* entry : D contains divisor, 
*			@ stackptr is return adr
*			@ stackptr + 2 is dividend
* exit  : D contains 16 bit quotient,
*			remainder not returned.
*			stackptr is entry stackptr + 4 ( stack is restored
*			to as it was before caller pushed operand.)

* ccsdiv
* Not implemented yet.  
* What follows is 6809 code.
* To Be Done: convert all labels to start with cc

*|	signed divide
*|	calling: (left / right)
*|		push left
*|		ldd right
*|		jsr sdiv
*|	result in d, arg popped.
*|
*	left=6
*	right=2
*	sign=1
*	count=0
*	return=4
*	CARRY=1
*.globl sdiv,div,ASSERTFAIL
*.globl prabs
*sdiv:	leas	-4(s)
*	std	right(s)
*	bne	nozero
*	swi2
*	.byte	ASSERTFAIL
*nozero:	jsr	prabs
*div:	clr	count(s)	| prescale divisor
*	inc	count(s)
*mscl:	inc	count(s)
*	aslb
*	rola
*	bpl	mscl
*	std	right(s)
*	ldd	left(s)
*	clr	left(s)
*	clr	left+1(s)
*div1:	subd	right(s)	| check subtract
*	bcc	div2
*	addd	right(s)
*	andcc	#~CARRY
*	bra	div3
*div2:	orcc	#CARRY
*div3:	rol	left+1(s)	| roll in carry
*	rol	left(s)
*	lsr	right(s)
*	ror	right+1(s)
*	dec	count(s)
*	bne	div1
*	ldd	left(s)
*	tst	sign(s)		| sign fiddle
*	beq	nochg
*	nega
*	negb
*	sbca	#0
*nochg:	std	right(s)	| move return addr
*	ldd	return(s)
*	std	left(s)
*	ldd	right(s)
*	leas	6(s)
*	rts
*

*|	prabs.  converts both args to unsigned, and
*|	remembers result sign as sign a eor sign b
*|	used only by divide support
*|	result d contains right, sign is non-zero
*|	if result (from divide) should be negative.
*|
*|
*.globl prabs
*	left=8.
*	right=4.
*	sign=3.
*prabs:	clr	sign(s)
*	ldd	left(s)
*	bge	tryr
*	nega
*	negb
*	sbca	#0
*	std	left(s)
*	inc	sign(s)
*tryr:	ldd	right(s)
*	bge	done
*	nega
*	negb
*	sbca	#0
*	dec	sign(s)
*	std	right(s)
*done:	rts
*

******************************************************
* Signed modulo. 16 bit modulo 16 bit yielding 16 bit.
* Underflow is possible, not checked.

 

* entry : D contains divisor, 
*			@ stackptr is return adr
*			@ stackptr + 2 is dividend
* exit  : D contains 16 bit remainder,
*			quotient not returned.
*			stackptr is entry stackptr + 4 ( stack is restored
*			to as it was before caller pushed operand.)

* ccsmod
* Not implemented yet.
* What follows is 6809 code.
* To Be Done: convert all labels to start with cc

*|	signed mod
*|	calling: (left / right)
*|		push left
*|		ldd right
*|		jsr smod
*|	result in d, arg popped.
*|
*	left=6
*	right=2
*	sign=1
*	count=0
*	return=4
*	CARRY=1
*.globl smod,mod,ASSERTFAIL
*.globl mrabs
*smod:	leas	-4(s)
*	std	right(s)
*	bne	nozero
*	swi2
*	.byte	ASSERTFAIL
*nozero:	jsr	mrabs
*mod:	clr	count(s)	| prescale divisor
*	inc	count(s)
*mscl:	inc	count(s)
*	aslb
*	rola
*	bpl	mscl
*	std	right(s)
*	ldd	left(s)
*	clr	left(s)
*	clr	left+1(s)
*mod1:	subd	right(s)	| check subtract
*	bcc	mod2
*	addd	right(s)
*	andcc	#~CARRY
*	bra	mod3
*mod2:	orcc	#CARRY
*mod3:	rol	left+1(s)	| roll in carry
*	rol	left(s)
*	lsr	right(s)
*	ror	right+1(s)
*	dec	count(s)
*	bne	mod1
*	tst	sign(s)		| sign fiddle
*	beq	nochg
*	nega
*	negb
*	sbca	#0
*nochg:	std	right(s)	| move return addr
*	ldd	return(s)
*	std	left(s)
*	ldd	right(s)
*	leas	6(s)
*	rts

*|	mrabs.  converts both args to unsigned, and
*|	remembers result sign as the sign of the left
*|	argument.  (for signed modulo)
*|	result d contains right, sign is non-zero
*|	if result (from mod) should be negative.
*|
*|
*.globl mrabs
*	left=8.
*	right=4.
*	sign=3.
*mrabs:	clr	sign(s)
*	ldd	left(s)
*	bge	tryr
*	nega
*	negb
*	sbca	#0
*	std	left(s)
*	inc	sign(s)
*tryr:	ldd	right(s)
*	bge	done
*	nega
*	negb
*	sbca	#0
*	std	right(s)
*done:	rts
*


******************************************************
* Case statement support

* Case table is of the form:
* 	FDB char_value, label
* 	FDB char_value, label
* 	FDB label,0
* That is, it consist of word pairs.
* The first word of a pair is the switch value.
* The second word of a pair is the label to jump to.
* The last pair is special -- the second word is zero
* and the first word is the label for the default case,
* if there is one, else it is the label on the code
* following the switch.
* Note that this form is different than that for v2 SmallC.
 
* TBD document the calling parameters
* entry : D contains switch value, 
*			@ stackptr is address of jump table
* exit  : exit is a jump 
*			stackptr is entry stackptr + 2 ( stack is restored
*			to as it was before caller pushed switch value.)

* cccase
* Not implemented yet.
* v2 code is readily available but table format differs.
* 6809 version was lost.


******************************************************
* Unknown use, relics ???
_etext
*	.bss 
_eend
*	.data 
*_brkend:	.wval	_eend 
_edata	




******************************************************
	OPT	l



#endasm