idigitmultadd.s

Arithmetic for integers of almost unlimited size for C and C++. Developed and copyrighted by Ra

; Thomas Pfahler, Nov 21 1997
; DigitType  DigitMultAdd (prod, a,   b,   carry)
;                          $26,  $25, $24, $23
;      DigitType *prod, a, b, carry;
;{
;      *prod=LOW(a*b + carry);
;      return HIGH(a*b + carry);
;} 

	.CODE
	.EXPORT DigitMultAdd
DigitMultAdd
	.PROC
	.CALLINFO FRAME=0,NO_CALLS
	.ENTRY
	
	stw 		%r25,-16(0,%r30)
	fldws 		-16(0,%r30),%fr9L	; a -> %fr9L
	stw 		%r24,-16(0,%r30)
	fldws 		-16(0,%r30),%fr9R	; b -> %fr9R
	xmpyu 		%fr9L,%fr9R,%fr8	; a*b -> %fr8
	fstws 		%fr8R,-16(0,%r30)
	ldw 		-16(0,%r30),%r19	; lo(prod) -> %r19
	addl 		%r19,%r23,%r28		; lo(prod) + c -> %r28
	stw 		%r28,0(0,%r26)		; store res.
	
	fstws 		%fr8L,-16(0,%r30)
	ldw 		-16(0,%r30),%r25	; hi(prod) -> %r25
	comclr,<<= 	%r23,%r28,0		; c = res < c
	addi,tr 	1,%r25,%r28		; either %r28 = %r25 + c ...
	bv		0(%r2)
	 copy 		%r25,%r28		; or     %r28 = %r25
	 
	.EXIT
	.PROCEND