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/* Copyright (c) 2002, Reiner Patommel
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */
/* ---------------------------------------------------------------------------
atan2.S
Contributors:
Created by Reiner Patommel 08 December 2002
-*- Mode: Asm -*-
*
* Accuracy: better than +/-2.5*10^-7 over full range
*
* ----------------------------------------------------------------------------
* A = atan2(float A, float B) = atan2(float y, float x)
* --------------------------------------------------------------------------*/
/* $Id: atan2.S,v 1.4 2003/09/30 23:05:19 troth Exp $ */
#if !defined(DOXYGEN)
#include "gasava.inc"
#include "fplib.inc"
#include "macros.inc"
#define y3 r25 /* rA3 */
#define x3 r21 /* rB3 */
#define flags r17
#define FP_PI 0x40490FDB /* PI */
#define FP_PI_2 0x3FC90FDB /* PI/2 */
TEXT_SEG(fplib, atan2)
FUNCTION(atan2)
GLOBAL(atan2)
TST x3 ; x == 0?
BREQ .L_NS ; --> north/south: return ERANGE or +/-PI/2
TST y3 ; y == 0?
BREQ .L_EW ; --> east/west: return ERANGE or 0 or PI
RJMP .L_calc ; --> calculate atan2
.L_NS: ; here x == 0
TST y3 ; y == 0?
BREQ .L_ERANGE ; return argument range error
BST y3, 7 ; keep sign of y
FPLOAD (rA, FP_PI_2) ; A = PI/2
BLD rA3, 7 ; get sign again
RET ; return +/-PI/2 depending on sign
.L_EW: ; here y == 0
TST x3 ; x == 0?
BREQ .L_ERANGE ; return argument range error
BRPL .L_EW_ZERO ; --> return 0
FPLOAD (rA, FP_PI) ; A = PI
RET ; return PI
.L_EW_ZERO:
FPCLR (rA) ; A = 0
RET ; return 0
.L_ERANGE: ; here x ==0 and y == 0
XJMP _U(__fp_nanERANGE) ; return argument range error
.L_calc: ; here x != 0 and y != 0
PUSH flags
CLR flags
SBRC y3, 7
ORI flags, 0x01 ; keep sign of y
SBRC x3, 7
ORI flags, 0x02 ; keep sign of x
XCALL _U(__divsf3) ; A = y/x
XCALL _U(atan) ; A = atan(y/x)
SBRS flags, 1 ; if x > 0
RJMP 1f ; return atan(y/x)
FPLOAD (rB, FP_PI); ; here x < 0 --> load PI
SBRC flags, 0 ; if y < 0 return atan(y/x) - PI
ORI rB3, 0x80 ; if y > 0 return atan(y/x) + PI
XCALL _U(__addsf3)
1: POP flags ; clean-up
RET
ENDFUNC
#endif /* not DOXYGEN */
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