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/*
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 *	mpvecadd(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *sum)
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 *
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 *		sum[0:alen] = a[0:alen-1] + b[0:blen-1]
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 *
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 *	prereq: alen >= blen, sum has room for alen+1 digits
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 */
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TEXT	mpvecadd(SB),$0
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	MOVL	alen+4(FP),DX
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	MOVL	blen+12(FP),CX
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	MOVL	a+0(FP),SI
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	MOVL	b+8(FP),BX
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	SUBL	CX,DX
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	MOVL	sum+16(FP),DI
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	XORL	BP,BP			/* this also sets carry to 0 */
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	/* skip addition if b is zero */
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	TESTL	CX,CX
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	JZ	_add1
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	/* sum[0:blen-1],carry = a[0:blen-1] + b[0:blen-1] */
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_addloop1:
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	MOVL	(SI)(BP*4), AX
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	ADCL	(BX)(BP*4), AX
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	MOVL	AX,(DI)(BP*4)
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	INCL	BP
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	LOOP	_addloop1
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_add1:
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	/* jump if alen > blen */
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	INCL	DX
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	MOVL	DX,CX
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	LOOP	_addloop2
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	/* sum[alen] = carry */
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_addend:
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	ADCL	$0, CX
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	MOVL	CX, (DI)(BP*4)
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	RET
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	/* sum[blen:alen-1],carry = a[blen:alen-1] + 0 */
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_addloop2:
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	MOVL	(SI)(BP*4),AX
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	ADCL	$0,AX
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	MOVL	AX,(DI)(BP*4)
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	INCL	BP
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	LOOP	_addloop2
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	JMP	_addend
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