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2231 - 1 
;-----------------------------------------------------------------------------;
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; Fast integer squareroot routines for avr-gcc project          (C)ChaN, 2008
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; http://elm-chan.org/docs/avrlib/sqrt32.S
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;-----------------------------------------------------------------------------;
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; uint16_t isqrt32 (uint32_t n);
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; uint8_t isqrt16 (uint16_t n);
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; uint16_t ihypot (int16_t x, int16_t y);
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;-----------------------------------------------------------------------------:
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; 32bit integer squareroot
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;-----------------------------------------------------------------------------;
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;   uint16_t isqrt32 (
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;     uint32_t n
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;   );
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;
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; Return Value:
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;   Squareroot of n.
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;
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; Size  = 53 words
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; Clock = 532..548 cycles
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; Stack = 0 byte
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.global isqrt32
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.func isqrt32
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isqrt32:
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	clr	r0
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	clr	r18
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	clr	r19
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	clr	r20
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	ldi	r21, 1
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	clr	r27
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	clr	r30
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	clr	r31
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	ldi	r26, 16
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1:	lsl	r22
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	rol	r23
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	rol	r24
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	rol	r25
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	rol	r0
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	rol	r18
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	rol	r19
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	rol	r20
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	lsl	r22
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	rol	r23
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	rol	r24
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	rol	r25
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	rol	r0
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	rol	r18
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	rol	r19
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	rol	r20
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	brpl	2f
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	add	r0, r21
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	adc	r18, r27
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	adc	r19, r30
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	adc	r20, r31
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	rjmp	3f
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2:	sub	r0, r21
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	sbc	r18, r27
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	sbc	r19, r30
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	sbc	r20, r31
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3:	lsl	r21
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	rol	r27
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	rol	r30
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	andi	r21, 0b11111000
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	ori	r21, 0b00000101
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	sbrc	r20, 7
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	subi	r21, 2
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	dec	r26
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	brne	1b
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	lsr	r30
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	ror	r27
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	ror	r21
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	lsr	r30
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	ror	r27
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	ror	r21
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	mov	r24, r21
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	mov	r25, r27
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	ret
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.endfunc
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;-----------------------------------------------------------------------------:
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; 16bit integer squareroot
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;-----------------------------------------------------------------------------;
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;   uint8_t isqrt16 (
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;     uint16_t n
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;   );
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;
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; Return Value:
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;   Squareroot of n.
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;
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; Size  = 33 words
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; Clock = 181..189 cycles
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; Stack = 0 byte
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.global isqrt16
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.func isqrt16
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isqrt16:
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	clr	r18
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	clr	r19
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	ldi	r20, 1
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	clr	r21
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	ldi	r22, 8
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1:	lsl	r24
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	rol	r25
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	rol	r18
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	rol	r19
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	lsl	r24
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	rol	r25
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	rol	r18
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	rol	r19
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	brpl	2f
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	add	r18, r20
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	adc	r19, r21
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	rjmp	3f
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2:	sub	r18, r20
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	sbc	r19, r21
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3:	lsl	r20
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	rol	r21
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	andi	r20, 0b11111000
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	ori	r20, 0b00000101
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	sbrc	r19, 7
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	subi	r20, 2
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	dec	r22
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	brne	1b
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	lsr	r21
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	ror	r20
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	lsr	r21
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	ror	r20
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	mov	r24, r20
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	ret
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.endfunc
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;-----------------------------------------------------------------------------:
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; 16bit integer hypot (megaAVR is required)
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;-----------------------------------------------------------------------------;
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;   uint16_t ihypot (
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;     int16_t x,
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;     int16_t y
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;   );
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;
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; Return Value:
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;   Squareroot of (x*x + y*y)
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;
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; Size  = 42 words
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; Clock = 581..597 cycles
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; Stack = 0 byte
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.global ihypot
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.func ihypot
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ihypot:
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	clr	r26
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	sbrs	r25, 7
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	rjmp	1f
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	com	r24
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	com	r25
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	adc	r24, r26
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	adc	r25, r26
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1:	sbrs	r23, 7
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	rjmp	2f
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	com	r22
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	com	r23
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	adc	r22, r26
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	adc	r23, r26
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2:	mul	r22, r22
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	movw	r18, r0
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	mul	r23, r23
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	movw	r20, r0
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	mul	r22, r23
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	add	r19, r0
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	adc	r20, r1
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	adc	r21, r26
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	add	r19, r0
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	adc	r20, r1
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	adc	r21, r26
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	mul	r24, r24
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	movw	r30, r0
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	mul	r25, r25
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	add	r18, r30
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	adc	r19, r31
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	adc	r20, r0
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	adc	r21, r1
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	mul	r24, r25
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	add	r19, r0
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	adc	r20, r1
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	adc	r21, r26
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	add	r19, r0
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	adc	r20, r1
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	adc	r21, r26
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	movw	r24, r20
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	movw	r22, r18
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	clr	r1
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	rjmp	isqrt32
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.endfunc
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