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Diffstat (limited to 'newlib/libm/machine/spu/headers/atanf.h')
| -rw-r--r-- | newlib/libm/machine/spu/headers/atanf.h | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/newlib/libm/machine/spu/headers/atanf.h b/newlib/libm/machine/spu/headers/atanf.h new file mode 100644 index 000000000..ec01c1ec8 --- /dev/null +++ b/newlib/libm/machine/spu/headers/atanf.h @@ -0,0 +1,112 @@ +/* + (C) Copyright 2001,2006, + International Business Machines Corporation, + Sony Computer Entertainment, Incorporated, + Toshiba Corporation, + + 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 names of the copyright holders nor the names of their + 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. +*/ +#ifndef _ATANF_H_ +#define _ATANF_H_ 1 + +#ifndef M_PI_2 +#define M_PI_2 1.5707963267949f +#endif /* M_PI_2 */ + +/* + * FUNCTION + * float _atanf(float x) + * + * DESCRIPTION + * _atanf computes the arc tangent of the value x; that is the value + * whose tangent is x. + * + * _atanf returns the arc tangent in radians and the value is + * mathematically defined to be in the range -PI/2 to PI/2. + * + * The arc tangent function is computed using a polynomial approximation + * (B. Carlson, M. Goldstein, Los Alamos Scientific Laboratiry, 1955). + * __8__ + * \ + * \ + * atanf(x) = / Ci*x^(2*i+1) + * /____ + * i=0 + * + * for x in the range -1 to 1. The remaining regions are defined to be: + * + * [1, infinity] : PI/2 + atanf(-1/x) + * [-infinity, -1] : -PI/2 + atanf(-1/x) + */ + +static __inline float _atanf(float x) +{ + float xabs; + float bias; + float x2, x3, x4, x8, x9; + float hi, lo; + float result; + + bias = 0.0f; + xabs = (x < 0.0f) ? -x : x; + + if (xabs >= 1.0f) { + bias = M_PI_2; + if (x < 0.0f) { + bias = -bias; + } + x = -1.0f / x; + } + /* Instruction counts can be reduced if the polynomial was + * computed entirely from nested (dependent) fma's. However, + * to reduce the number of pipeline stalls, the polygon is evaluated + * in two halves(hi and lo). + */ + bias += x; + + x2 = x * x; + x3 = x2 * x; + x4 = x2 * x2; + x8 = x4 * x4; + x9 = x8 * x; + hi = 0.0028662257f * x2 - 0.0161657367f; + hi = hi * x2 + 0.0429096138f; + hi = hi * x2 - 0.0752896400f; + hi = hi * x2 + 0.1065626393f; + lo = -0.1420889944f * x2 + 0.1999355085f; + lo = lo * x2 - 0.3333314528f; + lo = lo * x3 + bias; + + result = hi * x9 + lo; + + return (result); +} + +#endif /* _ATANF_H_ */ + + + |