diff options
Diffstat (limited to 'newlib/libm/machine/spu/headers/tanhf4.h')
| -rw-r--r-- | newlib/libm/machine/spu/headers/tanhf4.h | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/newlib/libm/machine/spu/headers/tanhf4.h b/newlib/libm/machine/spu/headers/tanhf4.h new file mode 100644 index 000000000..696ccc160 --- /dev/null +++ b/newlib/libm/machine/spu/headers/tanhf4.h @@ -0,0 +1,147 @@ +/* -------------------------------------------------------------- */ +/* (C)Copyright 2006,2007, */ +/* International Business Machines 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 name of IBM Corporation nor the names of its */ +/* contributors may be used to endorse or promote products */ +/* derived from this software without specific prior written */ +/* permission. */ +/* 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 IBM Corporation nor the names of its */ +/* 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. */ +/* -------------------------------------------------------------- */ +/* PROLOG END TAG zYx */ +#ifdef __SPU__ +#ifndef _TANHF4_H_ +#define _TANHF4_H_ 1 + +#include <spu_intrinsics.h> + +#include "expf4.h" +#include "divf4.h" + +#include "tanhd2.h" + +/* + * FUNCTION + * vector float _tanhf4(vector float x) + * + * DESCRIPTION + * The _tanhf4 function computes the hyperbolic tangent for each + * element of the input vector. + * + * We use the following to approximate tanh: + * + * |x| <= .25: Taylor Series + * |x| > .25: tanh(x) = (exp(2x) - 1)/(exp(2x) + 1) + * + * + * SPECIAL CASES: + * - tanh(+/- 0) = +/-0 + * - tanh(+/- infinity) = +/- 1 + * + */ + +static __inline vector float _tanhf4(vector float x) +{ + vector float signbit = spu_splats(-0.0f); + vector float onef = spu_splats(1.0f); + vector float twof = spu_splats(2.0f); + vector float xabs; + vector float x2; + vector unsigned int gttaylor; + vector float e; + vector float tresult; + vector float eresult; + vector float result; + + xabs = spu_andc(x, signbit); + + /* + * This is where we switch from Taylor Series + * to exponential formula. + */ + gttaylor = spu_cmpgt(xabs, spu_splats(0.25f)); + + + /* + * Taylor Series Approximation + */ + x2 = spu_mul(x,x); + tresult = spu_madd(x2, spu_splats((float)TANH_TAY06), spu_splats((float)TANH_TAY05)); + tresult = spu_madd(x2, tresult, spu_splats((float)TANH_TAY04)); + tresult = spu_madd(x2, tresult, spu_splats((float)TANH_TAY03)); + tresult = spu_madd(x2, tresult, spu_splats((float)TANH_TAY02)); + tresult = spu_madd(x2, tresult, spu_splats((float)TANH_TAY01)); + tresult = spu_mul(xabs, tresult); + + + /* + * Exponential Formula + * Our expf4 function gives a more accurate result in general + * with xabs instead of x for x<0. We correct for sign later. + */ + e = _expf4(spu_mul(xabs, twof)); + eresult = _divf4(spu_sub(e, onef), spu_add(e, onef)); + + + /* + * Select Taylor or exp result. + */ + result = spu_sel(tresult, eresult, gttaylor); + + /* + * Correct for accumulated truncation error when + * tanh(x) should return 1. + * Note that this also handles the special case of + * x = +/- infinity. + */ + result = spu_sel(result, onef, spu_cmpgt(xabs, spu_splats(9.125f))); + + /* + * Antisymmetric function - preserve sign bit of x + * in the result. + */ + result = spu_sel(result, x, (vec_uint4)signbit); + + return result; +} + +#endif /* _TANHF4_H_ */ +#endif /* __SPU__ */ |